What's new in estrogen receptor action in the female reproductive tract

in Journal of Molecular Endocrinology

Estrogen receptor alpha (ERα) is a critical player in development and function of the female reproductive system. Perturbations in ERα response can affect wide-ranging aspects of health in humans as well as in livestock and wildlife. Because of its long-known and broad impact, ERα mechanisms of action continue to be the focus on cutting-edge research efforts. Consequently, novel insights have greatly advanced understanding of every aspect of estrogen signaling. In this review, we attempt to briefly outline the current understanding of ERα mediated mechanisms in the context of the female reproductive system.

Abstract

Estrogen receptor alpha (ERα) is a critical player in development and function of the female reproductive system. Perturbations in ERα response can affect wide-ranging aspects of health in humans as well as in livestock and wildlife. Because of its long-known and broad impact, ERα mechanisms of action continue to be the focus on cutting-edge research efforts. Consequently, novel insights have greatly advanced understanding of every aspect of estrogen signaling. In this review, we attempt to briefly outline the current understanding of ERα mediated mechanisms in the context of the female reproductive system.

Estrogen receptor

The vast majority of estrogen's activities are mediated by the estrogen receptor (ER), a member of the nuclear receptor family of hormone activated transcription factors. Our understanding of the physiological role of estrogen action has been greatly advanced by the generation of experimental mouse and rat models with knockout of receptors or coactivators either globally or in specific tissues and cells, or with knock-in expression of mutated forms of these molecules. These models, used in combination with microarray, RNA next generation sequencing (RNA-seq), and chromatin immunoprecipitation next generation sequencing (ChIP-seq) methods, allow comprehensive mapping of interaction of ERs with the chromatin landscape to impact genomic response. Together, these models and techniques have led to better understanding of the molecular details of ER roles in biological processes.

Estrogen receptor alpha (ERα) cDNA was the first described and cloned estrogen receptor (termed ESR1 (ERα)) (Walter et al. 1985). A second ER gene, termed ESR2 (ERβ), was discovered in 1996 (Kuiper et al. 1996). ERα and ERβ are not isoforms but rather distinct receptors encoded by two separate genes on different chromosomes. ERα is found on chromosome 6 in humans and chromosome 10 in mice. ERβ is found on chromosome 14 in humans and chromosome 12 in mice. The ERα proteins are 595 and 599 amino acids in length in humans and mice respectively with an approximate molecular weight of 66 kDa (Fig. 1) (Heldring et al. 2007, Le Romancer et al. 2011, Gibson & Saunders 2012).

Figure 1
Figure 1

Structures of ERα and ERβ protein with functional domains. Estrogen receptors ERα and ERβ share a conserved domain structure. The A/B domain, at the amino terminus (N) of the protein contains AF-1. The C domain binds to DNA motifs called EREs. The D domain is called the hinge region, and contributes to DNA binding specificity and nuclear localization of the ERs. The E domain is called the ligand binding domain because it interacts with estrogen, through an arrangement of 11 α helices (H1, and H3 through H12). H12 in this region of the receptor is critical to mediating transcriptional activation via AF-2. At the carboxy terminus (C) is the F domain. The % homology shared between ERα and ERβ in the C and E domains is shown.

Citation: Journal of Molecular Endocrinology 56, 2; 10.1530/JME-15-0254

The ESR2 encodes a receptor of 549 amino acids in rodents and 530 amino acids in humans, each with an approximate molecular weight of 60–63 kDa (Fig. 1) (Gibson & Saunders 2012). Therefore, ERβ is slightly smaller than ERα, and most of these differences lie within the smaller N-terminus.

Receptor structure

The estrogen receptors are composed of five functional domains (Fig. 1), an N-terminal domain (NTD) or A/B domain, the DNA-binding (DBD or C) domain, a hinge (D) region, LBD (LBD or E), and a C-terminal F domain (Laudet & Gronemeyer 2001, Aagaard et al. 2011, Hilser & Thompson 2011, Brelivet et al. 2012, Helsen et al. 2012).

NTD or A/B domain

Crystallography of the ER NTD or A/B domain has been largely unsuccessful because this portion of the receptor is unstructured and fluctuates in aqueous solutions. However, evidence suggests that intramolecular interactions between the A/B and other receptor domains are likely to induce a more structured NTD (McEwan 2004, Aagaard et al. 2011, Hilser & Thompson 2011), as evidenced from recent cryogenic Electron Microscopy (cryo-EM) studies (Yi et al. 2015). Current models of ER signaling incorporate the flexibility of intrinsically disordered (ID) regions of the receptor, including the NTD, into a mechanism of allosteric interaction and coordination of ligand, DNA motif and ER domain functions (Aagaard et al. 2011, Hilser & Thompson 2011). The NTD contains the transcriptional activation function-1 (AF-1) domain and provides for cell- and promoter-specific activity of the receptor as well as a site for interaction with coreceptor proteins (Table 1). More recent description of full-length ERα structure derived using cryo-EM indicates A/B domain is positioned near the LBD and facilitates recruitment of the steroid receptor transcriptional coactivator, SRC-3 (Yi et al. 2015). Posttranslational modifications, such as phosphorylation, of the A/B domain can dramatically affect the overall behavior of the receptor and are thought to be an important mechanism for the modulation of AF-1 functions (Le Romancer et al. 2011).

Table 1

ER coregulator complexes. Adapted, with permission, from Binder AK, Winuthayanon W, Hewitt SC, Couse JF & Korach KS (2015) Steroid receptors in the uterus and ovary. In Knobil and Neill's Physiology of Reproduction, 4th Edn, pp 1099–1193. Eds TM Plant & AJ Zeleznik. Elsevier

ComplexFunctionsCommentsReferences
Src1, Src2, Src3Interact with Helix12 of agonist bound ER, interact with SWI/SNF, histone modifiersHsia et al. (2010) and Johnson & O'Malley (2012)
Mediator‘Bridges’ ER and transcriptional ‘machinery’ (RNA Pol II) to control transcriptionMade up of >20 subunits, MED 1–31, arranged in three modules (head, middle, tail)Malik & Roeder (2010) and Conaway & Conaway (2011)
SWI/SNFRegulate access to enhancer sequences via chromatin remodeling, ATPase activityMade up of 9+ subunits, examples include BRG1, BRM, BAF subunitsRoberts & Orkin (2004)
Histone modifiersModify histones to increase or decrease transcriptionAcetyl transferase (HAT; e.g., p300/CBP), deacetyase (HDAC; e.g., NCoR), methyl transferase (e.g., PMRT/CARM), de-methylaseBarnes et al. (2005) and Wu & Zhang (2009)
26S proteasome‘Clears’ transcriptional modulatory proteins to facilitate subsequent transcription, transcriptional terminationStructure made up of 20S catalytic core particles (CP), 19S regulatory particles (RP)Keppler et al. (2011) and Kim et al. (2011a,b)

DNA-binding or C domain

The C domain of the ER recognizes and binds to the cis-acting enhancer sequences, called estrogen responsive elements (EREs) (Helsen et al. 2012). The C domain contains two zinc fingers, each composed of four cysteine residues that chelate a single Zn2 ion. Crystallography studies indicate a highly conserved structure consisting of dual α-helices positioned perpendicular to each other (Aagaard et al. 2011, Hilser & Thompson 2011, Helsen et al. 2012). Amino acids in the C-terminal ‘knuckle’ of the first zinc finger form the proximal box (‘P-box’) of the DNA binding domain and confer DNA sequence recognition specificity to the receptor for binding DNA sequences; hence, the proximal zinc finger is often referred as forming the ‘recognition helix. ’ Amino acids at the N-terminal ‘knuckle’ of the second zinc finger form the distal box (‘D-box’) and are more specifically involved in differentiating the ‘spacer’ sequence within the ERE as well as providing a secondary interface for receptor dimerization.

The consensus motif (ERE) that ER binds is composed of a six-base pair (bp) palindromic sequence arranged as an inverted repeat and separated by a three-bp spacer, GGTCAnnnTGACC. The inverted-repeat arrangement of the ERE dictates that the ER homodimerizes in a ‘head-to-head’ position when bound to DNA. Structural analysis has revealed the importance of the 10–30 amino acid carboxy terminal extension (CTE) of the DBD in DNA interaction (Aagaard et al. 2011, Hilser & Thompson 2011, Helsen et al. 2012). Although this CTE region is variable between steroid receptors, it is crucial for DNA binding, particularly for sequence selectivity of DNA binding, by extending the interaction surfaces between the receptor and the DNA.

Hinge region or D domain

The above described CTE extends into the hinge region, which also contains a nuclear localization signal, and influences cellular compartmentalization of ER, as well as sites of post-translation modifications (Kim et al. 2006). Current mechanisms suggest this non-conserved and ID domain is important for intra-molecular allosteric interactions involving the N-terminal and LBD. This type of flexible structural interaction works to allow rapid response to diverse modulators governing changes in biological environments (Kumar & McEwan 2012).

LBD or E domain

The LBD or E domain of the ER is a highly structured multifunctional region that primarily serves to specifically bind estrogen and provide for hormone-dependent transcriptional activity through an activation function 2 (AF-2) domain located close to the C-terminus of the E domain. A strong receptor dimerization interface, sites for interaction with heat shock proteins, and nuclear localization signals are also within the E domain (Laudet & Gronemeyer 2001, Kumar & McEwan 2012). Structural studies indicate that the LBD is composed of 11 α-helices (H1, and H3 through H12) arranged in a three-layer α-helical sandwich to create a hydrophobic ligand-binding pocket near the C-terminus of the receptor (Huang et al. 2010). Receptor binding to an estrogen agonist leads to rearrangement of the LBD such that H11 is repositioned and H12 rotates back toward the core of the domain to form a ‘lid’ over the binding pocket. This agonist-induced repositioning of H12 leads to the formation of a hydrophobic cleft, or ‘NR box,’ by helices 3, 4, and 5 on the receptor surface, constituting the AF-2, which serves to recruit coactivators (Table 1) to the receptor complex. In contrast, estrogen antagonists are unable to induce a similar repositioning of H12, leading to a receptor formation that is incompatible with coactivator recruitment and is therefore less likely to activate transcription. The LBDs of ERα and ERβ exhibit ∼60% homology (Fig. 1) but bind the endogenous estrogen, estradiol (E2), with similar affinity (ERα, 0.1 nM; ERβ, 0.4 nM) (Le Romancer et al. 2011, Gibson & Saunders 2012) indicating only a small portion of the LBD sequence governs the specificity of ligand binding. However, given the divergence in homology, it is not surprising that ERα and ERβ exhibit measurable differences in their affinity for other endogenous steroids and xenoestrogens (Le Romancer et al. 2011, Gibson & Saunders 2012). Natural and synthetic steroidal and non-steroidal ER agonists and antagonists have been described, some of which show specificity or preference for one or the other ER subtype, illustrating differences between the LBDs of ERα and ERβ and provide for conceptual pharmacological tools to discern the overall function of each ER. The most widely used ER sub-type selective ligands currently in use are propylpyrazole (PPT), an ERα selective agonist, and diarylpropionitrate (DPN), an agonist showing preference, but not exclusive selectivity, towards ERβ (Stauffer et al. 2000, Meyers et al. 2001).

F domain

Among the sex steroid receptors, only ERs possess a well-defined F domain (Fig. 1). This region is relatively unstructured with little known function, although some data indicate a role in coactivator recruitment, dimerization and receptor stability (Katzenellenbogen et al. 2000, Koide et al. 2007, Yang et al. 2008, Kumar et al. 2011, Arao et al. 2013).

Coregulatory complexes

All steroid receptors interact with coregulatory molecules, coactivators, and corepressors (Hsia et al. 2010, George et al. 2011). The primary coactivator interaction for steroid receptors is with a family of p160/SRC (steroid receptor coactivator) 1, 2, and 3 coactivators (Lonard & O'Malley 2005, Bulynko & O'Malley 2011, Johnson & O'Malley 2012). SRC1 (NCOA1), SRC2 (GRIP1 and TIF2), and SRC3 (pCIP, RAC3, ACTR, TRAM, and A1B1) interact with helix 12 of ERs via ‘LXXLL’ motifs in their nuclear receptor interacting domains, which are leucine rich regions with ‘X’ designating any amino acid (Johnson & O'Malley 2012). SRCs also contain activation domains that recruit secondary molecules such as p300, and a bHLH-PAS motif within the N-terminal region, which can interact with other transcription factors (Johnson & O'Malley 2012). ERs and SRCs function as a nexus interacting with massive multimeric complexes, including the SWI/SNF chromatin remodeler, mediator complex, or proteasomes (Table 1) (Bulynko & O'Malley 2011). These interactions coordinate the specific functions necessary to allow appropriate gene and cell selective access to chromatin, via modifications of histones or members of coregulatory complexes (O'Malley et al. 2012). In this way, coactivators dynamically mediate and coordinate processes necessary to accomplish transcription, including initiation, elongation, termination, and clearing or turnover of the transcriptional modulators.

Mechanisms of estrogen response

Our understanding of the mechanisms by which estrogens influence cell function and behavior has expanded profoundly since initial models of ligand-dependent activation, which is now referred to as the ‘classical’ or ligand dependent direct DNA binding model of receptor function (Fig. 2). In the years since, numerous discoveries primarily in cell-based systems have been made that illuminate the complexity of ER signaling in cells and tissues. The entrée into the ‘omics’ era has facilitated massive expansion for the study of transcriptional regulation and chromatin remodeling. In addition, several alternative receptor signaling mechanisms that diverge from the classic model have become apparent, including ‘tethering’ of the ER to heterologous DNA-bound transcription factors to provide for regulation of genes that lack ERE sequences (Fig. 2); plasma membrane estrogen signaling, often referred to as ‘nongenomic’ steroid actions and ligand-independent ‘cross-talk’ with intracellular and second messenger systems that provide for ER activation in the absence of the cognate steroid ligand (Fig. 2). These modes of ER responses as currently understood are discussed below.

Figure 2
Figure 2

Ligand-dependent and ligand-independent nuclear receptor mechanisms. The direct ‘classic’ model of ER action involves direct interaction between ER bound to estrogen (triangles) and ERE; the tethered pathway utilizes indirect ‘tethering’ of ER to genes via interactions with other transcription factors (TF). ‘Nongenomic’ signaling is initiated by membrane-localized receptors modulating extranuclear second messenger (SM) signaling pathways. Ligand-independent responses occur as a result of transduction of membrane receptor signaling, such as growth factors (GF), to nuclear ER. Adapted, with permission, from Heldring N, Pike A, Andersson S, Matthews J, Cheng G, Hartman J, Tujague M, Ström A, Treuter E, Warner M & Gustafsson JA (2007) Estrogen receptors: how do they signal and what are their targets. Physiological Reviews87 905–931. Copyright 2007 The American Physiological Society (APS). All rights reserved.

Citation: Journal of Molecular Endocrinology 56, 2; 10.1530/JME-15-0254

Ligand-dependent actions: direct or classical

In the classic model of estrogen response (Figs 2 and 3) estrogen ligands diffuse across the plasma and nuclear membranes to bind ER, primarily localized to the nucleus, resulting in a conformational change in the receptor, transforming it to an ‘activated’ state that interacts with chromatin via ERE motifs and transcriptional mediators. ERs seem to be preferentially recruited to open regions of chromatin (Biddie et al. 2010). Studies using MCF7 breast cancer cells indicate that FoxA1 acts as a pioneering factor, providing accessible regions in the chromatin that recruit ERα (Fig. 3) (Carroll et al. 2005, Carroll & Brown 2006, Fu et al. 2011, Zaret & Carroll 2011). The ligand–ERE-bound receptor complex then engages coactivator molecules as described above (Johnson & O'Malley 2012) leading to modulation of transcription rates of responding genes. This classic steroid receptor mechanism is dependent on the functions of both AF-1 and AF-2 domains of the receptor, which synergize via the recruitment of coactivator proteins, most notably the p160 family members (Johnson & O'Malley 2012). Depending on the cell and target gene promoter context, the DNA-bound receptor complex may positively or negatively affect expression of the downstream target gene. Initially, study of ER mediated gene regulation was carried out on a gene-by gene basis using a handful of known hormone regulated transcripts. Now, after numerous comprehensive analyses of hormonally regulated transcriptional profiles, using microarray and more recently RNA-seq, thousands of ER targets have been found in various cell lines and tissues.

Figure 3
Figure 3

Model of chromatin dynamics in ER mediated transcription. FoxA1 interacts with chromatin, providing access for ER to nearby EREs. ER then interacts with transcriptional coactivators and chromatin modifying enzymes to open up transcription start sites (TSS) for RNA polymerase II (PolII), allowing initiation of transcription. Adapted, with permission, from Wall EH, Hewitt SC, Case LK, Lin CY, Korach KS & Teuscher C (2014) The role of genetics in estrogen responses: a critical piece of an intricate puzzle. FASEB Journal28 5042–5054.

Citation: Journal of Molecular Endocrinology 56, 2; 10.1530/JME-15-0254

Indirect/tethered actions (ERE independent)

In in vitro reporter gene systems, ligand-activated ER can modulate the expression of genes that lack a conspicuous ERE within their promoter (Kushner et al. 2000, Safe & Kim 2004, 2008). This mechanism of ERE-independent steroid receptor activation is postulated to involve a ‘tethering’ of the ligand-activated receptor to transcription factors that are directly bound to DNA via their respective response elements (Fig. 2). However, the ERαEAAE/EAAE mouse, which is mutated in the ERα DBD and lacks ERE binding, does not exhibit estrogen response in vivo, indicating the tethering mechanism, at least on its own, is unable to mediate hormonal responses (Ahlbory-Dieker et al. 2009, Hewitt et al. 2014) and is likely complimentary to the direct DNA stimulated responses.

Non-genomic actions

Rapid effects of E2 have been described, including a rapid activation of endothelial nitric oxide synthase in endothelial cells (Levin 2011) and potentiation of nerve conductance (Takeo & Sakuma 1995, Kim et al. 2011a,b). Because these estrogen effects occur within minutes, they have been thought not to involve direct ER activation of gene transcription, they are often collectively referred to as representing ‘non-genomic’ pathways of estrogen action. Questions remain concerning whether the membrane-associated receptors mediating these events are identical or variant forms of the ER or instead distinct receptors altogether.

One potential mediator of rapid membrane localized hormone response is the G protein coupled ER (GPER, originally referred to as GPR30), which is activated by E2 (Prossnitz & Barton 2011). Gper null mice lack reproductive phenotypes (Langer et al. 2010), although effects on the degrees of uterine responses elicited by E2 have been observed with G15, a GPER selective antagonist, suggesting a potential role for GPER in modulating ERα mediated responsiveness (Gao et al. 2011).

Ligand independent actions: membrane receptor cross-talk

Peptide growth factors are able to activate ERα-mediated gene expression via mitogen-activated protein kinase activation of ERα in the absence of E2 (Fig. 2). Likewise, growth factors are able to mimic the effects of E2 in the rodent uterus via E2 independent activation of ERα (Curtis & Korach 1999, Fox et al. 2009). In some cases, the MAP kinase protein ERK is corecruited to chromatin with ERα (Madak-Erdogan et al. 2011). Ligand-independent activation of estrogen receptors is believed to rely largely on cellular kinase pathways that alter the phosphorylation state of the receptor and/or its associated proteins (e.g., coactivators, heat shock proteins) (Fig. 2).

Uterine response to E2

Utilizing animal models to follow and manipulate estrogen responsiveness is one way to understand and describe mechanisms of estrogen responses. The reproductive function of the mouse has been especially well studied and characterized in this manner.

Treatment of ovariectomized mice with estrogens (e.g., E2 or diethylstilbestrol – DES) has long served as an experimental model to mimic the uterine events that occur during the estrous phase of the rodent cycle or immediately after the preovulatory E2 surge. Morphological and biochemical changes occur in the rodent uterus after estrogen stimulation following an established biphasic temporal pattern (Hewitt et al. 2003). Estrogen-stimulated changes in the rodent uterus that occur early, within the first 6 h after treatment, include increases in nuclear ER occupancy, water imbibition, vascular permeability and hyperemia, prostaglandin release, glucose metabolism, eosinophil infiltration, gene expression (e.g., c-fos), lipid and protein synthesis. ERα ChIP-Seq profiles from in vivo studies of uterine tissues show that in the unstimulated state the receptor pre-occupies chromatin sites in the absence of hormone and that E2 treatment increases ERα recruitment (Hewitt et al. 2012). The above processes are followed by responses that peak after 24–72 h and include dramatic increases in RNA and DNA synthesis, epithelial proliferation, and differentiation of epithelial cells toward a more columnar secretory phenotype, dramatic increases in uterine weight, and continued gene expression.

Changes in uterine gene expression

The dramatic physiological changes that occur in the uterus in response to steroid hormones are presumably the ultimate effects of equally dramatic changes in gene expression among the uterine cells. It is unlikely that the E2–ER complex is directly involved in mediating the whole genomic response in the uterus but more plausibly serves to stimulate a cascade of downstream signaling pathways that act to amplify the estrogen action. However, early investigations of the genomic response to estrogens in the rodent uterus discovered a handful of genes that are directly regulated via the classic ER mode of action, including progesterone receptor (Pgr) and lactoferrin or lactotransferrin (Ltf). Microarray analysis has significantly advanced understanding of genomic response of the rodent uterus to E2. Numerous studies have used microarray techniques to map the global gene expression patterns after estrogen exposure in the uterus and largely demonstrate that the biphasic uterine response to estrogens, so well characterized by physiological indicators above, is mirrored by the global changes in gene expression (Andrade et al. 2002, Fertuck et al. 2003, Hewitt et al. 2003, Watanabe et al. 2003, Ho Hong et al. 2004, Moggs et al. 2004, Hewitt et al. 2005, Hong et al. 2006). The clearly defined patterns of early and late response genes found in mouse uterine tissues are completely lacking in ERα–null (αERKO, Ex3αERKO) uteri (Hewitt et al. 2003, 2010a,b). The identified genes fall into functional groups, including signal transduction, gene transcription, metabolism, protein synthesis and processing, immune function, and cell cycle. The expression levels of a striking number of genes are actively repressed by estrogen in the mouse uterus, and these effects were absent in ERα-null uteri or are relieved by cotreatment with ER antagonists in the presence of ERα, indicating that ERα is also actively involved in transcriptional repression as part of mediating the physiological responses (Hewitt et al. 2003, 2010a,b).

Whole transcriptome analyses are now routinely incorporated into studies of disruptions in signaling pathways underlying uterine phenotypes of mouse models such as those described in Table 2. Thus, microarray comparisons have now become just one of many tools employed for investigation of uterine functions.

Table 2

Uterine phenotypes in mice null or mutated for estrogen receptors or estrogen signaling. Adapted, with permission, from Binder AK, Winuthayanon W, Hewitt SC, Couse JF & Korach KS (2015) Steroid receptors in the uterus and ovary. In Knobil and Neill's Physiology of Reproduction, 4th Edn, pp 1099–1193. Eds TM Plant & AJ Zeleznik. Elsevier

Mutated or null for sex steroid receptors and signalingUterine phenotypesReferences
Esr1/− (homozygous null alleles for ERα: αERKO and Ex3αERKO)Normal uterine development but exhibits hypoplastic uteri

Insensitive to the proliferative and differentiating effects of endogenous, growth factors and exogenous E2

Implantation defect

aLack decidualization

Infertile
Lubahn et al. (1993), Curtis et al. (1999), Dupont et al. (2000), Curtis Hewitt et al. (2002), Hewitt et al. (2010a,b), Antonson et al. (2012)
NERKI+/− (one mutated allele of two-point mutation in ERα DBD and one WT allele)Normal uterine development but exhibits hyperplastic uteri

Hypersensitive to estrogen

Infertile
Jakacka et al. (2002)
KIKO (ERAA/−) (one mutated allele of two-point mutation in DNA binding domain of ERα and one ERαKO allele)Normal uterine development

Insensitive to the proliferative effects of exogenous E2 treatment

ERAA binds HRE and induces genes that are normally progesterone responsive

Infertile
O'Brien et al. (2006) and Hewitt et al. (2010a,b)
ERαEAAE/EAAE (homozygous animal of four-point mutation of DBD ERα)Normal uterine development but exhibits hypoplastic uteri

Loss of E2-induced uterine transcripts

Infertile
Ahlbory-Dieker et al. (2009)
ERαAF-1° (deletion of amino acids 2–128 on ERα)Normal uterine development and architecture

Blunted E2 response

Infertile
Billon-Gales et al. (2009) and Abot et al. (2013)
ERαAF-2° (deletion of amino acids 543–549 on ERα)Normal uterine development but exhibits hypoplastic uteri

Insensitive to E2 treatment

Infertile
Billon-Gales et al. (2011)
ENERKI (ERαG525L) (homozygous animal of one point mutation in LBD of ERα)Normal uterine development but exhibits hypoplastic uteri

Insensitive to E2 treatment

IGF1 induced slight uterine epithelial proliferation compared to control littermates (non-homogenous pattern)

Infertile
Sinkevicius et al. (2008)
AF2ERKI/KI (homozygous knock-in of two-point mutation in LBD of ERα)Normal uterine development but exhibits hypoplastic uteri

Insensitive to E2 treatment

ER antagonists and partial agonist (ICI 182,780 and TAM) induced uterine epithelial proliferation

Growth factor did not induce the uterine epithelial cell proliferation

Infertile
Arao et al. (2011)
ERα Epi-cKO (epithelial cell specific deletion of ERα using Wnt7aCre+; Esr1f/f mouse model)Normal uterine development

Sensitive to E2- and growth factor-induced epithelial cell proliferation

Lack full uterine growth response to E2

Selective loss of E2-target gene response

Implantation and decidualization defects

Infertile
Winuthayanon et al. (2010 2014) and Pawar et al. (2015)
Esr1d/d (uterine deletion of ERα using PgrCre+; Esr1f/f mouse model)Normal uterine development

Hypoplastic uteri

Defective decidual response
Pawar et al. (2015)
Esr2−/− (homozygous null alleles for ERβ: βERKO, Ex3βERKO, and bERβSTL−/L−)Exhibit grossly normal uterine development and function

Sensitive to E2 treatment

Some Esr2−/− lines reported elevated uterine epithelial proliferation after E treatment compared with WT

Some are complete sterile (due to ovarian phenotype)
Krege et al. (1998), Dupont et al. (2000), Wada-Hiraike et al. (2006) and Antal et al. (2008)
αβERKO (homozygous null for both ERα and Erβ)Normal uterine development but exhibit hypoplastic uteri, similar to those of Esr1−/−. Insensitive to E2, infertileCouse et al. (1999) and Dupont et al. (2000)
Cyp19a1−/− (homozygous null aromatase: ArKO)Normal uterine development but exhibits hypoplastic uteri

Sensitive to E2-induced epithelial cell proliferation

Infertile
Fisher et al. (1998) and Toda et al. (2001)
Esr1C541A palmitoylation deficient mutantsC451A-ERα normal uterine development, E2 growth response

Nuclear-only ERα [NOER] hypoplastic ERα-null like uterus
Adlanmerini et al. (2014) and Pedram et al. (2014)

αERKO females have a similar uterine phenotype to the newer Ex3αERKO except for maintaining decidualization response, which may due to the splice variants in the original αERKO that retains ER activities.

ERβSTL−/L− females are the only line of ERβ knockout animals that reported to be completely sterile.

Chip-seq

Evaluation of sites of transcription factor interaction with chromatin, by enriching a DNA binding protein, such as ERα, that has been crosslinked in situ to chromatin, with immunoprecipitation (ChIP), followed by hybridizing the associated DNA to a chip tiled with promoter region sequences (ChIP–Chip) or by ‘next generation’ massively parallel sequencing (ChIP-seq), have been developed and widely utilized to study sites of ER interaction (Farnham 2009, Park 2009, Biddie et al. 2010, Green & Han 2011, Martens et al. 2011, Meyer et al. 2012). Initial studies focused on ERα binding in MCF7 breast cancer cells, and several similar studies followed, which are summarized and compared in several review articles (Deblois & Giguere 2008, Cheung & Kraus 2010, Gao & Dahlman-Wright 2011, Tang et al. 2011, Gilfillan et al. 2012). These articles reported that most sites were distal from transcriptional start sites (TSS), or were in intronic regions, rather than adjacent to TSS, as models of ER regulation of target transcripts had hypothesized. These comprehensive maps of cis-acting transcriptional regulators have been dubbed ‘cistromes.’ The initial ERα cistrome-associated sequences were evaluated for enrichment of transcription factor motifs and confirmed binding to the experimentally defined ‘ERE’ sequence. In the case of the MCF7 tumor cells, enrichment of motifs for forkhead binding factors (Fox) was apparent as mentioned in the earlier section. Owing to the abundant expression of the FoxA1 member of the Fox family, a potential role for FoxA1 in estrogen response was pursued with an arsenal of bioinformatic, Next Gen sequencing and biological studies that demonstrated FoxA1's role as ‘pioneer,’ creating accessible regions of the chromatin that were subsequently targeted by ERα (Lupien et al. 2009, Zaret & Carroll 2011).

ChIP-seq analysis is examining the ERα binding sites in mouse uterine tissue indicated that, much like the MCF7 breast cancer study, most ERα sites were not proximal to TSS (Hewitt et al. 2012). ERs bind to thousands of sites within the cellular chromatin, and not all potential EREs in every cell bind ER. Rather, it is apparent that chromatin exhibits ‘pre-opened’ regions destined to recruit ER (Grontved & Hager 2012). For ER in MCF7 and FoxA1 can establish ER accessible regions. The accessible chromatin regions are colocalized within nuclear ‘hubs,’ which seem to optimize frequency of interaction with ER (Grontved & Hager 2012). ChIP-seq is also used to locate other molecules involved in chromatin remodeling and transcriptional regulation, and to examine activating or repressive histone modifications or ‘marks.’ These maps of relative locations and dynamics of ER and chromatin components greatly enhance our understanding of hormone response mechanisms (Deblois & Giguere 2008, Green & Han 2011, Martens et al. 2011, Gilfillan et al. 2012, Meyer et al. 2012).

Uterine phenotypes in mouse models of disrupted estrogen signaling

Mouse models of disrupted ER signaling have proven invaluable to experimental investigation of estrogen actions and the contribution of each ER form to these functions (Table 2). In addition to the ER-null models are lines of mice that lack the capacity to synthesize E2 due to disruption of the Cyp19 gene (Fisher et al. 1998, Toda et al. 2001). Below we will describe how these different mouse models have helped to delineate the biological role of ER mechanisms in estrogen hormone action.

ERα null patients and mice

Only one male patient and one female patient with ERα mutation have been described (Smith et al. 1994, Quaynor et al. 2013). The male patient's mutation is a true null since no ERα protein is expressed due to the mutation generating a premature stop codon in the A/B domain. The female patient has a single point mutation in her ERα LBD that results in decreased activity by reducing the receptors affinity for coactivator proteins more than 200-fold.

There are currently numerous reported lines of ERα-null mice and additional lines of mice with mutations in functional domains of ERα. Three separate lines of ERα-null mice were generated: the αERKO, first described by Lubahn et al. (1993), the ERαKO (or Ex3αERKO), described by Dupont et al. (2000) and by Hewitt et al. (2010a,b), and ERα−/− described by Antonson et al. (2012). Homologous recombination was employed to disrupt ERα (αERKO), or cre-mediated recombination was used to completely excise exon 3, which encodes the ER DNA binding domain (Dupont et al. 2000, Hewitt et al. 2010a,b, Antonson et al. 2012) of the murine Esr1 (ERα) gene (ERαKO, Ex3αERKO, and ERα−/−). The uterine estrogenic response in αERKO females differs from the latter two lines, but the overall spectrum of phenotypes are the same, as αERKO animals have minimal level of truncated ERα protein produced from a splice variant, which preserves some residual biological functions (Couse et al. 1995), but all ERα null female mice are infertile. Recently, an ERα null rat has been derived using zinc finger nuclease (ZFN) genome editing. All phenotypes in the ERα null rats examined thus far were previously seen in the ERα null mice, including infertility due to hypoplastic uteri, polycystic ovaries, and ovulation defects (Rumi et al. 2014). The female patient with homozygous ERα mutation also has cystic ovaries and a small uterus despite elevated circulating serum E2 (Quaynor et al. 2013).

The essential role of ERα in uterine response to estrogen is indicated by the loss of early phase effects of water imbibition and hyperemia as well as the late-phase effects of increased DNA synthesis and epithelial proliferation in ERα-null uteri (Couse et al. 1995, Korach et al. 1996, Hewitt et al. 2010a,b). The αERKO model was the first test of a prevailing hypothesis that early uterine effects were non-receptor mediated (Lubahn et al. 1993). Lack of these early responses of water imbibition, hyperemia, and eosinophil infiltration in αERKO indicated that ERα was involved in some manner and these responses clearly require the estrogen receptor. Additionally, ovariectomized mice normally exhibit a three- to four-fold increase in uterine weight after three daily treatments with E2 or DES, whereas no such response is observed in the uteri of ERα-null females (Lubahn et al. 1993, Korach 1994, Hewitt et al. 2010a,b). Uteri of mice that lack ERα just in uterine epithelial cells (Wnt7aCre+; Esr1f/f, called ERα Epi-cKO) have an initial proliferative response to estrogen, but full uterine response is impaired, as the growth after 3 days of estrogen treatment is significantly less than expected (Winuthayanon et al. 2010). The total lack of response to estrogens in ERα-null uteri as well as a lack of late biological response in epithelial ERα knockout uteri provide strong evidence that ERα is required to mediate the full biochemical and biological uterine response to estrogens (Hewitt et al. 2010a,b, Winuthayanon et al. 2010, 2014).

Numerous studies have demonstrated some of the molecular mechanisms of E2-induced uterine epithelial cell proliferative responses in animal models. The transcription factor CCAAT enhancer binding protein beta (C/EBPβ) is involved in hormone-induced uterine proliferation (Mantena et al. 2006). Maximum uterine expression of C/EBPβ is induced 1 h after E2 treatment in both epithelial and stromal cells (Mantena et al. 2006, Ramathal et al. 2010). ICI 182,786 (ER antagonist) strongly inhibited E2-induced Cebpb transcript in the uterus suggesting an ER-dependent expression of C/EBPβ (Bagchi et al. 2006). In addition, loss of epithelial ERα in the uterus did not alter E2-induced Cebpb expression, indicating that Cebpb expression is independent of epithelial ER (Winuthayanon et al. 2010), and suggesting the stimulation was through a paracrine mechanism via stromal ERα. This points to the action of estrogen through ERα as the major mediator of C/EBPβ expression in the uterus. Indeed, the deletion of C/EBPβ (C/EBPβ−/−) leads to a lack of the E-induced uterine proliferative response (Mantena et al. 2006) as reflected by the absence of mitotic activity, S-phase activity and an increase in apoptotic activity in the uterine epithelial cells (Ramathal et al. 2010). In addition to a blunted uterine growth response to hormones, the C/EBPβ−/− females also exhibit complete infertility (Bagchi et al. 2006), due to implantation and decidualization defects (Mantena et al. 2006).

Pan et al. (2006) demonstrated that the uterine expression of minichromosome maintenance proteins (MCMs), a complex required for DNA synthesis initiation, is induced after E2 treatment, specifically MCM2 and MCM3. MCM2 activity is crucial and required for DNA synthesis in uterine epithelial cells (Ray & Pollard 2012). Further study demonstrated E2-mediated induction of the transcription factor KLF4, which then targets the Mcm2 promoter (Ray & Pollard 2012).

Mice lacking ERβ

ERβ-null mice have provided insight into the importance of ERβ to female fertility and studies to date indicate ERβ plays a particularly important role in ovarian function. Four different lines of ERβ-null mice have been described. The βERKO mouse, made using homologous recombination was first described by Krege et al. (1998), and the ERβKO or Ex3βERKO, was described by Dupont et al. (2000), and by Binder et al. (2013). Cre-mediated recombination was employed in both lines to disrupt exon 3 (Dupont et al. 2000, Binder et al. 2013) of the murine Esr2 (ERβ) gene. As described to date, the reproductive, endocrine, and ovarian phenotypes of both lines are indistinguishable, with both exhibiting female subfertility. Shughrue et al. (2002) reported the third line of ERβKO animals, however, no uterine or ovarian phenotypes were reported (Shughrue et al. 2002). Recently, ERβKOSTL−/L− animals, which contain LoxP sites flanking exon 3 of Esr2, were generated using the Cre/loxP recombination system (Antal et al. 2008). Interestingly, female mice from this recently described ERβKOSTL−/L− colony were reported to be sterile due to an ovarian defect while Ex3βERKO (Binder et al. 2013) are subfertile, due to ovulatory defects.

Mice lacking ER α and β

The two reported lines of compound ER-null mice are the αβERKO, described by Couse et al. (1999), and the ERαβKO, described by Dupont et al. (2000). Both were generated by cross breeding animals heterozygous for the respective individual ER-null mice and as described to date, exhibit comparable reproductive, endocrine, and ovarian phenotypes. The most striking phenotype is the unique trans-differentiation of the ovarian granulosa cells to sertoli-like cells in follicles of αβERKO females which is age dependent. To date, no manipulation of the individual αERKO or βERKO mouse lines can reproduce this novel phenotype. This model clearly uncovered that both ER signaling systems are required to maintain the proper differentiation state of the adult granulosa cells.

Mice lacking Cyp19

Estrogens are produced by aromatase cytochrome P450, the product of Cyp19 gene. Female mice with disruption of circulating estrogen production exhibit altered reproduction (Fisher et al. 1998, Honda et al. 1998, Toda et al. 2001). There are three animal models of Cyp19-null mice (called ArKO). Fisher et al. (1998) reported the first mouse line in 1998, which disrupted exon 9 of Cyp19 gene, as the region is highly conserved. Later, Honda et al. (1998) reported a mouse line with targeted disruption of exons 1 and 2 of the Cyp19 gene. Subsequently, Toda et al. (2001) generated the most recent mouse line of Cyp19-null in 2001 with a targeted disruption of exon 9 of the Cyp19 gene. These ArKO female phenotypes are indistinguishable (Fisher et al. 1998, Honda et al. 1998, Toda et al. 2001), with similarity to the αβERKO mice with a clear metabolic syndrome (Couse et al. 1999) and infertility due to ovarian dysfunction marked by cystic follicles and a failure to respond to exogenous gonadotropins. Interestingly, the phenotype of the original ArKO mice (Fisher et al. 1998) were also shown to exhibit the same age related ovarian phenotype (Britt et al. 2002) as the αβERKO mice, indicating that hormone mediated ER action is required.

Female reproductive phenotypes in mice with disrupted estrogen signaling

Females within each respective model exhibit a similar phenotypic syndrome. Female mice lacking ERα or aromatase are infertile due to dysfunction of numerous physiological systems, including the ovary and uterus, whereas ERβ-null females exhibit reduction or loss of fecundity that is largely attributable to ovarian dysfunction. A level of caution is warranted when making phenotypic comparisons between the ER-null and Cyp19-null models because sensitivity to maternally derived estrogens may provide a more normal developmental environment during gestation in Cyp19-null mice and sensitivity to dietary estrogens during adulthood is able to abate several phenotypes in Cyp19-null mice (Britt et al. 2002).

The reported uterine phenotypes of these models are summarized in Table 2. All lines of ER-null females exhibit uteri that possess the expected tissue compartments, myometrium, endometrial stroma, and epithelium (Couse & Korach 1999, Hewitt et al. 2010a,b). However, in females lacking functional ERα or Cyp19, uteri are overtly hypoplastic and exhibit severely reduced weights relative to wild-type littermates (Fisher et al. 1998, Couse & Korach 1999, Britt et al. 2001, Toda et al. 2001), whereas ERβ-null uteri are grossly normal and normally responsive to ovarian-derived steroids (Couse & Korach 1999). The uterus of ERα-null females is severely hypotrophic, poorly organized, and possesses a paucity of glandular structures (Korach et al. 1996, Hewitt et al. 2010a,b). The luminal and glandular epithelial cells in ERα-null uteri are severely immature with fewer glands present in the adults (Nanjappa et al. 2015) and consistently exhibit a cuboidal morphology, vs the tall columnar morphology and basal location of the nucleus of an ‘estrogenized’ epithelium in WT uteri. Therefore, fetal, neonatal, and perinatal development of the female reproductive tract in mice is largely independent of ERα- and ERβ-mediated actions, but estrogen responsiveness and sexual maturation of the adult uterus are ablated after the loss of functional ERα. The totality of the ERα-null phenotype and lack of any overt uterine abnormalities in ERβ-null females suggest that ERβ has little meaningful function in mediating estrogen actions in the uterus. Moreover, ERαβ-null also demonstrated a similar uterine phenotype as ERα-null (Walker & Korach 2004). Weihua et al. (2000) reported that ERβ-null females exhibited a slightly aberrant uterine growth response after estrogen replacement; however, the uterine bioassay was conducted in immature intact, not ovariectomized adult, animals. In addition, Wada-Hiraike et al. (2006) showed that in immature females, loss of ERβ leads to increased uterine epithelial proliferation induced by E2 compared with WT uteri. Although ERβ-null females are subfertile, when pregnancies are established they are sustained to term (Krege et al. 1998), indicating uterine competence. More recent findings suggest that loss of ERβ leads to complete sterility due to a defect in ovarian function (Dupont et al. 2000, Antal et al. 2008).

Mice with uterine specific deletion of ERα

Selectively deleting ERα in the uterus postpubertally, using the Cre/LoxP recombination system, by crossing PgrCre+ with Esr1f/f animals (Esr1d/d), leads to a hypoplastic uterus that lacks a decidual response (Pawar et al. 2015). Our laboratory has described uterine epithelial cell selective deletion of ERα, using the Cre/LoxP recombination system, by crossing Wnt7aCre+ (Huang et al. 2012) with Esr1f/f animals (Hewitt et al. 2010a,b) (ERα Epi-cKO). The expression of ERα in the uterine luminal and glandular epithelium of these animals was ablated, while the ERα expression in the stromal cells and other uterine cells remains intact (Winuthayanon et al. 2010). The epithelial ERα was ablated not only in the uterus in this mouse line (Winuthayanon et al. 2010), but also in the oviduct (Winuthayanon et al. 2015). As expected, based on findings in the global ERα knockouts, loss of uterine epithelial ERα has no effect on female reproductive tract development. Uterine histological analysis showed a similar uterine morphology as WT control (Winuthayanon et al. 2010). The ERα Epi-cKO uteri are sensitive to 24 h treatment of E2, as the uterine epithelial proliferation is preserved. However, ERα Epi-cKO uteri lack a complete uterine response to E2, following a 3-day uterine bioassay, which demonstrated a blunted growth response and increased apoptotic activity in ERα Epi-cKO compared with the control uteri. Additionally, a lack of ERα expression in the uterine epithelial cells contributes to complete infertility, due to oviduct, and uterine implantation and decidulaization defects (Winuthayanon et al. 2010, Pawar et al. 2015, Winuthayanon et al. 2015). This suggests that uterine epithelial ERα is dispensable for early uterine proliferative responses but crucial for a complete adult biological response induced by E2, as well as for establishing pregnancy.

Mice with mutated DNA binding domains of ERα

To date, there are two mouse lines with mutations that are designed to disrupt the DNA binding function of the ERα that have been ‘knocked-in’ (KI) at the ERα gene locus. The first line was generated by replacing critical P-box amino acids E207 and G208 with alanines (ERαAA). This line was named ‘non-genomic ER knock-in’ (NERKI), as these mutations were intended to restrict ERα signaling to the non-genomic and tethered mechanisms. Female NERKI+/− animals that have one mutated allele and one WT allele (Jakacka et al. 2002) were infertile, exhibiting a highly novel hyperplastic uterine phenotype, so NERKI+/− males were crossed with ERα null heterozygous (WT/KO) females to produce mice with one NERKI mutated allele and one deleted Esr1 allele, called ERα KIKO or ERαAA/− as described by O'Brien et al. (2006). The second line of DNA-binding domain knock-in animals were created through mutation of four amino acids in the first zinc finger of the Esr1 gene, substituting Y at position 201 with E, and in the critical P box, K at position 210 with A, K at position 214 with A, and R at position 215 with E as described by Ahlbory-Dieker et al. (2009; called ERαEAAE/EAAE).

The NERKI+/− females have normal uterine development but exhibit hyperplastic uteri, and are hypersensitive to estrogen (Jakacka et al. 2002). These NERKI+/− are infertile and exhibit a uterine abnormality of enlarged hyperplastic endometrial glands despite possessing normal levels of circulating sex steroids.

ERαAA/− females have normal uterine development. Initially, O'Brien et al. (2006) reported that ERαAA/− females, with mutation of the DNA binding domain, maintained proliferative responses induced by E2. However, in subsequent studies, no uterine proliferation was observed (Hewitt et al. 2009, 2010). Ahlbory-Dieker et al. (2009) showed that, unlike the NERKI+/−, females heterozygous for the ERαEAAE mutation are fertile. The homozygous ERαEAAE/EAAE females have normal reproductive tract development but uteri are severely hypoplastic, similar to global ERα-null uteri. Additionally, ERαEAAE/EAAE uteri do not respond to E treatment, as normally estrogen-responsive uterine and liver genes are not regulated in ERαEAAE/EAAE (Ahlbory-Dieker et al. 2009, Hewitt et al. 2014). The females from these two mouse lines with point mutations in the DNA binding domain of ERα are infertile. Thus the physiological function of the DNA binding domain of ERα is crucial for female reproduction. ERα ChIP-seq analysis of the ERαAA/− uterus revealed that the DBD mutation, rather than completely disrupting DNA binding instead altered the motif specificity, so that ERαAA could bind HRE motifs normally occupied by progesterone receptor (Pgr or PR). Additionally, this HRE binding lead to E2 regulation of uterine transcripts that are normally progesterone responsive (Hewitt et al. 2014). This novel ERαAA binding activity may also explain the hyperplastic phenotype of the heterozygous ERαAA/+ females where the normally activated uterine HRE sites are occupied by the mutant ERαAA and thus blocking the dampening activity of uterine PR at those sites. Adding to this abnormal regulation is the expression of ERαAA in all uterine cells at all times, whereas, the PR is restricted at times, to epithelial cells and is dynamically induced in the stromal cells during the estrous cycle. Additionally, the phenotype also indicates the specificity of the action at the HRE requires the proper activity of the PR to elicit the dampening action.

Mice with mutated AF-1 or AF-2 domains of ERα

As discussed in the Receptor structure section, AF-1 and AF-2 are important for ER transcriptional activity (Fig. 1). Amino acids 2–128 were deleted from exon 1 of Esr1, which removes the AF-1 domain, and knocked into a mouse line (called ERαAF-1°) (Billon-Gales et al. 2009). There are three reported mouse lines with mutation in the AF-2 domain of ERα. One with a single point mutation in ERα of G at position 525 to L in the ligand binding domain (LBD), called ‘estrogen-nonresponsive ERα knock-in or ENERKI’ (ERαG525L) (Sinkevicius et al. 2008). Amino acids 543–549 were deleted from the LBD of ERα, removing helix 12 and thus AF-2 functionality, to create a second mouse line (called ERαAF-2°) (Billon-Gales et al. 2011). Two point mutations in the AF-2 of the LBD of ERα were knocked into a mouse (L543A and L544A, called AF2ERKI/KI animals) (Arao et al. 2011). ERαAF-1°, ERαG525L, ERαAF-2°, and AF2ERKI/KI females are all sterile (Sinkevicius et al. 2008, Billon-Gales et al. 2009, Arao et al. 2011, Billon-Gales et al. 2011).

ERαAF-1° females exhibited minimal uterine wet weight gain compared with ER+/+ uteri after treatment with E2 pellets for two consecutive weeks, while ERαAF-2° females did not respond (Billon-Gales et al. 2009, 2011, Abot et al. 2013). This indicates that the ERα AF-2 functional domain contributes to minimal uterine weight increase induced by E2 in the absence of AF-1. Both lines of AF-2 mutated animals (ERαG525L and AF2ERKI/KI) display severely hypoplastic uteri, and lack uterine growth response to E2 treatment (Sinkevicius et al. 2008, Arao et al. 2011, Billon-Gales et al. 2011). Interestingly, uterine wet weight can be increased by using the synthetic ERα agonist PPT in ERαG525L or by using the ER antagonists ICI 182,780 or tamoxifen in AF2ERKI/KI females (Sinkevicius et al. 2008, Arao et al. 2011). The ability of the antagonists to mediate responses seems to be due to a unique conformation of the LBD of the AF2ER that leads to AF-1-dependent transcriptional activity (Arao et al. 2011, 2013). Arao et al. (2011) also demonstrated that the uterine response to ICI or tamoxifen includes increased DNA synthesis in the uterine epithelial cells of AF2ERKI/KI. The growth factor IGF-1 induced minimal uterine epithelial proliferation in ERαG525L, and was not seen in AF2ERKI/KI uteri (Sinkevicius et al. 2008, Arao et al. 2011). Together, these findings indicated that both AF-1 and AF-2 activation domains of ERα contribute to a normal regulation of the complete biological response of uterine growth and reproductive functions. As the AF domains mediate ER-coregulator interaction (Table 1), this emphasizes the importance of effective ERα coactivator protein recruitment for successful uterine E2 response. Similarly, mice lacking sufficient SRC-1 coactivator (SRC1−/−), exhibit measurably diminished uterine response to E2 (Xu et al. 1998).

Mice with altered localization of ERα

A mutated mouse ERα that remains sequestered outside the nucleus (ERαH2NES), is unable to mediate transcriptional responses in a cell based assay, but maintains estrogen induced MAPK phosphorylation (Burns et al. 2011). Targeting steroid receptors to the membrane involves palmitoylation, which is facilitated by HSP27 (Levin 2011). The palmitoylation promotes interaction with caveolin-1, which then results in localization of the receptor in membrane caveolin rafts. Two laboratories have mutated the palmitoylation site of the mouse ERα, and created knock in mouse models to study the effect of disabling this mechanism in vivo (Adlanmerini et al. 2014, Pedram et al. 2014). Both mouse lines have ovarian defects, but differ in several aspects (Table 2). Both involved knocking in an ERα with the same mutation of cysteine 451 to alanine. The first, C451A-ERα, exhibits normal uterine development and E2 induced growth response (Adlanmerini et al. 2014), whereas the nuclear-only ERα (NOER) has a hypoplastic ERα-null like uterus that fails to respond to E2 (Pedram et al. 2014). Both models have elevation in LH, but only the NOER has elevated E2. These mixed results remain to be reconciled to definitively illustrate the role of membrane associated ERα in these physiological systems.

Conclusion

Female reproduction is a complex staged series of physiological responses occurring in multiple organ systems activated by estrogen and estrogen receptors. Cell based studies have uncovered that cellular signaling mechanisms for ER are multifaceted regarding gene regulation. Because of the complexity with what is known about female reproduction and fertility, the mechanisms and activities cannot be clearly studied or tested in cell based systems. The development of gene targeting has allowed the evaluation of the physiological roles of estrogen action and ER functionality under natural biological conditions. It is now apparent from the experimental and clinical reports outlined in this review that the primary mediator of female reproduction is ERα. What functional aspects of the ERα action are required will be forthcoming with the continued use of new technologies and experimental approaches, which will lead to a better understanding for the potential origins of infertility, reproductive tract disease and development of reproductive therapeutics.

Declaration of interest

The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of this review.

Funding

Research support for studies reported in this review was provided by the Division of Intramural Research of the NIEHS/NIH 1ZIAES070065 to K S K.

References

  • AagaardMMSiersbaekRMandrupS2011Molecular basis for gene-specific transactivation by nuclear receptors. Biochimica et Biophysic Acta1812824835. (doi:10.1016/j.bbadis.2010.12.018).

    • Search Google Scholar
    • Export Citation
  • AbotAFontaineCRaymond-LetronIFlouriotGAdlanmeriniMBuscatoMOttoCBergesHLaurellHGourdyP2013The AF-1 activation function of estrogen receptor α is necessary and sufficient for uterine epithelial cell proliferation in vivo. Endocrinology15422222233. (doi:10.1210/en.2012-2059).

    • Search Google Scholar
    • Export Citation
  • AdlanmeriniMSolinhacRAbotAFabreARaymond-LetronIGuihotALBoudouFSautierLVessieresEKimSH2014Mutation of the palmitoylation site of estrogen receptor α in vivo reveals tissue-specific roles for membrane versus nuclear actions. PNAS111E283E290. (doi:10.1073/pnas.1322057111).

    • Search Google Scholar
    • Export Citation
  • Ahlbory-DiekerDLStrideBDLederGSchkoldowJTrolenbergSSeidelHOttoCSommerAParkerMGSchutzG2009DNA binding by estrogen receptor-α is essential for the transcriptional response to estrogen in the liver and the uterus. Molecular Endocrinology2315441555. (doi:10.1210/me.2009-0045).

    • Search Google Scholar
    • Export Citation
  • AndradePMSilvaIBorraRCde LimaGRBaracatEC2002Estrogen regulation of uterine genes in vivo detected by complementary DNA array. Hormone and Metabolic Research34238244. (doi:10.1055/s-2002-32136).

    • Search Google Scholar
    • Export Citation
  • AntalMCKrustAChambonPMarkM2008Sterility and absence of histopathological defects in nonreproductive organs of a mouse ER β-null mutant. PNAS10524332438. (doi:10.1073/pnas.0712029105).

    • Search Google Scholar
    • Export Citation
  • AntonsonPOmotoYHumirePGustafssonJA2012Generation of ERα-floxed and knockout mice using the Cre/LoxP system. Biochemical and Biophysical Research Communications424710716. (doi:10.1016/j.bbrc.2012.07.016).

    • Search Google Scholar
    • Export Citation
  • AraoYHamiltonKJRayMKScottGMishinaYKorachKS2011Estrogen receptor α AF-2 mutation results in antagonist reversal and reveals tissue selective function of estrogen receptor modulators. PNAS1081498614991. (doi:10.1073/pnas.1109180108).

    • Search Google Scholar
    • Export Citation
  • AraoYHamiltonKJCoonsLAKorachKS2013Estrogen receptor α L543A, L544A mutation changes antagonists to agonists which correlates with the ligand binding domain dimerization associated with DNA binding activity. Journal of Biological Chemistry2882110521116. (doi:10.1074/jbc.M113.463455).

    • Search Google Scholar
    • Export Citation
  • BagchiMKMantenaSRKannanABagchiIC2006Role of C/EBP β in steroid-induced cell proliferation and differentiaion in the uterus: Functional implications for establishment of early pregnancy. Placenta27A13A13.

    • Search Google Scholar
    • Export Citation
  • BarnesPJAdcockIMItoK2005Histone acetylation and deacetylation: importance in inflammatory lung diseases. European Respiratory Journal25552563. (doi:10.1183/09031936.05.00117504).

    • Search Google Scholar
    • Export Citation
  • BiddieSCJohnSHagerGL2010Genome-wide mechanisms of nuclear receptor action. Trends in endocrinology and metabolism2139. (doi:10.1016/j.tem.2009.08.006).

    • Search Google Scholar
    • Export Citation
  • Billon-GalesAFontaineCFilipeCDouin-EchinardVFouqueMJFlouriotGGourdyPLenfantFLaurellHKrustA2009The transactivating function 1 of estrogen receptor α is dispensable for the vasculoprotective actions of 17 β-estradiol. PNAS10620532058. (doi:10.1073/pnas.0808742106).

    • Search Google Scholar
    • Export Citation
  • Billon-GalesAKrustAFontaineCAbotAFlouriotGToutainCBergesHGadeauAPLenfantFGourdyP2011Activation function 2 (AF2) of estrogen receptor-α is required for the atheroprotective action of estradiol but not to accelerate endothelial healing. PNAS1081331113316. (doi:10.1073/pnas.1105632108).

    • Search Google Scholar
    • Export Citation
  • BinderAKRodriguezKFHamiltonKJStocktonPSReedCEKorachKS2013The absence of ER-β results in altered gene expression in ovarian granulosa cells isolated from in vivo preovulatory follicles. Endocrinology15421742187. (doi:10.1210/en.2012-2256).

    • Search Google Scholar
    • Export Citation
  • Binder AK Winuthayanon W Hewitt SC Couse JF & Korach KS. 2015 Steroid receptors in the uterus and ovary. In Knobil and Neill's Physiology of Reproduction pp 1099–1193. Eds TM Plant AJ Zeleznik: Elsevier

  • BrelivetYRochelNMorasD2012Structural analysis of nuclear receptors: From isolated domains to integral proteins. Molecular and Cellular Endocrinology348466473. (doi:10.1016/j.mce.2011.08.015).

    • Search Google Scholar
    • Export Citation
  • BrittKLDrummondAEDysonMWrefordNGJonesMESimpsonERFindlayJK2001The ovarian phenotype of the aromatase knockout (ArKO) mouse. Journal of Steroid Biochemistry and Molecular Biology79181185. (doi:10.1016/S0960-0760(01)00158-3).

    • Search Google Scholar
    • Export Citation
  • BrittKLKerrJO'DonnellLJonesMEDrummondAEDavisSRSimpsonERFindlayJK2002Estrogen regulates development of the somatic cell phenotype in the eutherian ovary. FASEB Journal1613891397. (doi:10.1096/fj.01-0992com).

    • Search Google Scholar
    • Export Citation
  • BulynkoYAO'MalleyBW2011Nuclear receptor coactivators: structural and functional biochemistry. Biochemistry50313328. (doi:10.1021/bi101762x).

    • Search Google Scholar
    • Export Citation
  • BurnsKALiYAraoYPetrovichRMKorachKS2011Selective mutations in estrogen receptor α D-domain alters nuclear translocation and non-estrogen response element gene regulatory mechanisms. Journal of Biological Chemistry2861264012649. (doi:10.1074/jbc.M110.187773).

    • Search Google Scholar
    • Export Citation
  • CarrollJSBrownM2006Estrogen receptor target gene: an evolving concept. Molecular Endocrinology2017071714. (doi:10.1210/me.2005-0334).

    • Search Google Scholar
    • Export Citation
  • CarrollJSLiuXSBrodskyASLiWMeyerCASzaryAJEeckhouteJShaoWHestermannEVGeistlingerTR2005Chromosome-wide mapping of estrogen receptor binding reveals long-range regulation requiring the forkhead protein FoxA1. Cell1223343. (doi:10.1016/j.cell.2005.05.008).

    • Search Google Scholar
    • Export Citation
  • CheungEKrausWL2010Genomic analyses of hormone signaling and gene regulation. Annual Review of Physiology72191218. (doi:10.1146/annurev-physiol-021909-135840).

    • Search Google Scholar
    • Export Citation
  • ConawayRCConawayJW2011Function and regulation of the Mediator complex. Current Opinion in Genetics & Development21225230. (doi:10.1016/j.gde.2011.01.013).

    • Search Google Scholar
    • Export Citation
  • CouseJFKorachKS1999Estrogen receptor null mice: what have we learned and where will they lead us?Endocrine Reviews20358417. (doi:10.1210/edrv.20.3.0370).

    • Search Google Scholar
    • Export Citation
  • CouseJFCurtisSWWashburnTFLindzeyJGoldingTSLubahnDBSmithiesOKorachKS1995Analysis of transcription and estrogen insensitivity in the female mouse after targeted disruption of the estrogen receptor gene. Molecular Endocrinology914411454. (doi:10.1210/mend.9.11.8584021).

    • Search Google Scholar
    • Export Citation
  • CouseJFHewittSCBunchDOSarMWalkerVRDavisBJKorachKS1999Postnatal sex reversal of the ovaries in mice lacking estrogen receptors α and β. Science28623282331. (doi:10.1126/science.286.5448.2328).

    • Search Google Scholar
    • Export Citation
  • Curtis SH & Korach KS. 1999 Steroid receptor knockout models: Phenotypes and responses illustrate interactions between receptor signaling pathways in vivo. In Hormones and Signaling pp 357-380. Ed BW O'Malley. San Diego CA USA: Academic Press

  • CurtisSWClarkJMyersPKorachKS1999Disruption of estrogen signaling does not prevent progesterone action in the estrogen receptor α knockout mouse uterus. PNAS9636463651. (doi:10.1073/pnas.96.7.3646).

    • Search Google Scholar
    • Export Citation
  • Curtis HewittSGouldingEHEddyEMKorachKS2002Studies using the estrogen receptor α knockout uterus demonstrate that implantation but not decidualization-associated signaling is estrogen dependent. Biology of Reproduction6712681277. (doi:10.1095/biolreprod67.4.1268).

    • Search Google Scholar
    • Export Citation
  • DebloisGGiguereV2008Nuclear receptor location analyses in mammalian genomes: from gene regulation to regulatory networks. Molecular Endocrinology2219992011. (doi:10.1210/me.2007-0546).

    • Search Google Scholar
    • Export Citation
  • DupontSKrustAGansmullerADierichAChambonPMarkM2000Effect of single and compound knockouts of estrogen receptors α (ERα) and β (ERβ) on mouse reproductive phenotypes. Development12742774291.

    • Search Google Scholar
    • Export Citation
  • FarnhamPJ2009Insights from genomic profiling of transcription factors. Nature Reviews. Genetics10605616. (doi:10.1038/nrg2636).

  • FertuckKCEckelJEGenningsCZacharewskiTR2003Identification of temporal patterns of gene expression in the uteri of immature, ovariectomized mice following exposure to ethynylestradiol. Physiological Genomics15127141. (doi:10.1152/physiolgenomics.00058.2003).

    • Search Google Scholar
    • Export Citation
  • FisherCRGravesKHParlowAFSimpsonER1998Characterization of mice deficient in aromatase (ArKO) because of targeted disruption of the cyp19 gene. PNAS9569656970. (doi:10.1073/pnas.95.12.6965).

    • Search Google Scholar
    • Export Citation
  • FoxEMAndradeJShupnikMA2009Novel actions of estrogen to promote proliferation: integration of cytoplasmic and nuclear pathways. Steroids74622627. (doi:10.1016/j.steroids.2008.10.014).

    • Search Google Scholar
    • Export Citation
  • FuXHuangCSchiffR2011More on FOX News: FOXA1 on the horizon of estrogen receptor function and endocrine response. Breast Cancer Research13307. (doi:10.1186/bcr2849).

    • Search Google Scholar
    • Export Citation
  • GaoHDahlman-WrightK2011The gene regulatory networks controlled by estrogens. Molecular and Cellular Endocrinology3348390. (doi:10.1016/j.mce.2010.09.002).

    • Search Google Scholar
    • Export Citation
  • GaoFMaXOstmannABDasSK2011GPR30 activation opposes estrogen-dependent uterine growth via inhibition of stromal ERK1/2 and estrogen receptor α (ERα) phosphorylation signals. Endocrinology15214341447. (doi:10.1210/en.2010-1368).

    • Search Google Scholar
    • Export Citation
  • GeorgeCLLightmanSLBiddieSC2011Transcription factor interactions in genomic nuclear receptor function. Epigenomics3471485. (doi:10.2217/epi.11.66).

    • Search Google Scholar
    • Export Citation
  • GibsonDASaundersPT2012Estrogen dependent signaling in reproductive tissues - a role for estrogen receptors and estrogen related receptors. Molecular and Cellular Endocrinology348361372. (doi:10.1016/j.mce.2011.09.026).

    • Search Google Scholar
    • Export Citation
  • GilfillanSFioritoEHurtadoA2012Functional genomic methods to study estrogen receptor activity. Journal of Mammary Gland Biology and Neoplasia17147153. (doi:10.1007/s10911-012-9254-4).

    • Search Google Scholar
    • Export Citation
  • GreenCDHanJD2011Epigenetic regulation by nuclear receptors. Epigenomics35972. (doi:10.2217/epi.10.75).

  • GrontvedLHagerGL2012Impact of chromatin structure on PR signaling: transition from local to global analysis. Molecular and Cellular Endocrinology3573036. (doi:10.1016/j.mce.2011.09.006).

    • Search Google Scholar
    • Export Citation
  • HeldringNPikeAAnderssonSMatthewsJChengGHartmanJTujagueMStromATreuterEWarnerM2007Estrogen receptors: how do they signal and what are their targets. Physiological Reviews87905931. (doi:10.1152/physrev.00026.2006).

    • Search Google Scholar
    • Export Citation
  • HelsenCKerkhofsSClinckemalieLSpansLLaurentMBoonenSVanderschuerenDClaessensF2012Structural basis for nuclear hormone receptor DNA binding. Molecular and Cellular Endocrinology348411417. (doi:10.1016/j.mce.2011.07.025).

    • Search Google Scholar
    • Export Citation
  • HewittSCDerooBJHansenKCollinsJGrissomSAfshariCAKorachKS2003Estrogen receptor-dependent genomic responses in the uterus mirror the biphasic physiological response to estrogen. Molecular Endocrinology1720702083. (doi:10.1210/me.2003-0146).

    • Search Google Scholar
    • Export Citation
  • HewittSCCollinsJGrissomSDerooBKorachKS2005Global uterine genomics in vivo: microarray evaluation of the estrogen receptor α-growth factor cross-talk mechanism. Molecular Endocrinology19657668. (doi:10.1210/me.2004-0142).

    • Search Google Scholar
    • Export Citation
  • HewittSCO'BrienJEJamesonJLKisslingGEKorachKS2009Selective disruption of ER α DNA-binding activity alters uterine responsiveness to estradiol. Molecular Endocrinology2321112116. (doi:10.1210/me.2009-0356).

    • Search Google Scholar
    • Export Citation
  • HewittSCKisslingGEFieselmanKEJayesFLGerrishKEKorachKS2010aBiological and biochemical consequences of global deletion of exon 3 from the ER α gene. FASEB Journal2446604667. (doi:10.1096/fj.10-163428).

    • Search Google Scholar
    • Export Citation
  • HewittSCLiYLiLKorachKS2010bEstrogen-mediated regulation of Igf1 transcription and uterine growth involves direct binding of estrogen receptor α to estrogen-responsive elements. Journal of Biological Chemistry28526762685. (doi:10.1074/jbc.M109.043471).

    • Search Google Scholar
    • Export Citation
  • HewittSCLiLGrimmSAChenYLiuLLiYBushelPRFargoDKorachKS2012Research resource: whole-genome estrogen receptor α binding in mouse uterine tissue revealed by ChIP-Seq. Molecular Endocrinology26887898. (doi:10.1210/me.2011-1311).

    • Search Google Scholar
    • Export Citation
  • HewittSCLiLGrimmSAWinuthayanonWHamiltonKJPocketteBRubelCAPedersenLCFargoDLanzRB2014Novel DNA motif binding activity observed in vivo with an estrogen receptor α mutant mouse. Molecular Endocrinology28899911. (doi:10.1210/me.2014-1051).

    • Search Google Scholar
    • Export Citation
  • HilserVJThompsonEB2011Structural dynamics, intrinsic disorder, and allostery in nuclear receptors as transcription factors. Journal of Biological Chemistry2863967539682. (doi:10.1074/jbc.R111.278929).

    • Search Google Scholar
    • Export Citation
  • HongSHNahHYLeeJYGyeMCKimCHKimMK2004Analysis of estrogen-regulated genes in mouse uterus using cDNA microarray and laser capture microdissection. Journal of Endocrinology181157167. (doi:10.1677/joe.0.1810157).

    • Search Google Scholar
    • Export Citation
  • HondaSHaradaNItoSTakagiYMaedaS1998Disruption of sexual behavior in male aromatase-deficient mice lacking exons 1 and 2 of the cyp19 gene. Biochemical and Biophysical Research Communications252445449. (doi:10.1006/bbrc.1998.9672).

    • Search Google Scholar
    • Export Citation
  • HongEJParkSHChoiKCLeungPCJeungEB2006Identification of estrogen-regulated genes by microarray analysis of the uterus of immature rats exposed to endocrine disrupting chemicals. Reproductive Biology and Endocrinology449. (doi:10.1186/1477-7827-4-49).

    • Search Google Scholar
    • Export Citation
  • HsiaEYGoodsonMLZouJXPrivalskyMLChenHW2010Nuclear receptor coregulators as a new paradigm for therapeutic targeting. Advanced Drug Delivery Reviews6212271237. (doi:10.1016/j.addr.2010.09.016).

    • Search Google Scholar
    • Export Citation
  • HuangPXChandraVRastinejadF2010Structural overview of the nuclear receptor superfamily: insights into physiology and therapeutics. Annual Review of Physiology72247272. (doi:10.1146/annurev-physiol-021909-135917).

    • Search Google Scholar
    • Export Citation
  • HuangCCOrvisGDWangYBehringerRR2012Stromal-to-epithelial transition during postpartum endometrial regeneration. PLoS ONE7e44285. (doi:10.1371/journal.pone.0044285).

    • Search Google Scholar
    • Export Citation
  • JakackaMItoMMartinsonFIshikawaTLeeEJJamesonJL2002An estrogen receptor (ER)α deoxyribonucleic acid-binding domain knock-in mutation provides evidence for nonclassical ER pathway signaling in vivo. Molecular Endocrinology1621882201. (doi:10.1210/me.2001-0174).

    • Search Google Scholar
    • Export Citation
  • JohnsonABO'MalleyBW2012Steroid receptor coactivators 1, 2, and 3: Critical regulators of nuclear receptor activity and steroid receptor modulator (SRM)-based cancer therapy. Molecular and Cellular Endocrinology348430439. (doi:10.1016/j.mce.2011.04.021).

    • Search Google Scholar
    • Export Citation
  • KatzenellenbogenBSChoiIHDelage-MourrouxREdigerTRMartiniPGMontanoMSunJWeisKKatzenellenbogenJA2000Molecular mechanisms of estrogen action: selective ligands and receptor pharmacology. Journal of Steroid Biochemistry and Molecular Biology74279285. (doi:10.1016/S0960-0760(00)00104-7).

    • Search Google Scholar
    • Export Citation
  • KepplerBRArcherTKKinyamuHK2011Emerging roles of the 26S proteasome in nuclear hormone receptor-regulated transcription. Biochimica et Biophysica Acta1809109118. (doi:10.1016/j.bbagrm.2010.08.005).

    • Search Google Scholar
    • Export Citation
  • KimMYWooEMChongYTHomenkoDRKrausWL2006Acetylation of estrogen receptor α by p300 at lysines 266 and 268 enhances the deoxyribonucleic acid binding and transactivation activities of the receptor. Molecular Endocrinology2014791493. (doi:10.1210/me.2005-0531).

    • Search Google Scholar
    • Export Citation
  • KimHMYuYChengY2011aStructure characterization of the 26S proteasome. Biochimica et Biophysica Acta18096779. (doi:10.1016/j.bbagrm.2010.08.008).

    • Search Google Scholar
    • Export Citation
  • KimHKuSYSungJJKimSHChoiYMKimJGMoonSY2011bAssociation between hormone therapy and nerve conduction study parameters in postmenopausal women. Climacteric14488491. (doi:10.3109/13697137.2011.553972).

    • Search Google Scholar
    • Export Citation
  • KoideAZhaoCNaganumaMAbramsJDeighton-CollinsSSkafarDFKoideS2007Identification of regions within the F domain of the human estrogen receptor α that are important for modulating transactivation and protein-protein interactions. Molecular Endocrinology21829842. (doi:10.1210/me.2006-0203).

    • Search Google Scholar
    • Export Citation
  • KorachKS1994Insights from the study of animals lacking functional estrogen receptor. Science26615241527. (doi:10.1126/science.7985022).

    • Search Google Scholar
    • Export Citation
  • KorachKSCouseJFCurtisSWWashburnTFLindzeyJKimbroKSEddyEMMigliaccioSSnedekerSMLubahnDB1996Estrogen receptor gene disruption: molecular characterization and experimental and clinical phenotypes. Recent Progress in Hormone Research51159186; discussion 186–158.

    • Search Google Scholar
    • Export Citation
  • KregeJHHodginJBCouseJFEnmarkEWarnerMMahlerJFSarMKorachKSGustafssonJASmithiesO1998Generation and reproductive phenotypes of mice lacking estrogen receptor β. PNAS951567715682. (doi:10.1073/pnas.95.26.15677).

    • Search Google Scholar
    • Export Citation
  • KuiperGGEnmarkEPelto-HuikkoMNilssonSGustafssonJA1996Cloning of a novel receptor expressed in rat prostate and ovary. PNAS9359255930. (doi:10.1073/pnas.93.12.5925).

    • Search Google Scholar
    • Export Citation
  • KumarRMcEwanIJ2012Allosteric Modulators of steroid hormone receptors: structural dynamics and gene regulation. Endocrine Reviews33271299. (doi:10.1210/er.2011-1033).

    • Search Google Scholar
    • Export Citation
  • KumarRZakharovMNKhanSHMikiRJangHToraldoGSinghRBhasinSJasujaR2011The dynamic structure of the estrogen receptor. Journal of Amino Acids2011812540. (doi:10.4061/2011/812540).

    • Search Google Scholar
    • Export Citation
  • KushnerPJAgardDAGreeneGLScanlanTSShiauAKUhtRMWebbP2000Estrogen receptor pathways to AP-1. Journal of Steroid Biochemistry and Molecular Biology74311317. (doi:10.1016/S0960-0760(00)00108-4).

    • Search Google Scholar
    • Export Citation
  • LangerGBaderBMeoliLIsenseeJDelbeckMNoppingerPROttoC2010A critical review of fundamental controversies in the field of GPR30 research. Steroids75603610. (doi:10.1016/j.steroids.2009.12.006).

    • Search Google Scholar
    • Export Citation
  • Laudet V & Gronemeyer H 2001 The Nuclear Receptor FactsBook. Cambridge MA USA: Academic Press

  • Le RomancerMPoulardCCohenPSentisSRenoirJMCorboL2011Cracking the estrogen receptor's posttranslational code in breast tumors. Endocrine Reviews32597622. (doi:10.1210/er.2010-0016).

    • Search Google Scholar
    • Export Citation
  • LevinER2011Minireview: extranuclear steroid receptors: roles in modulation of cell functions. Molecular Endocrinology25377384. (doi:10.1210/me.2010-0284).

    • Search Google Scholar
    • Export Citation
  • LonardDMO'MalleyBW2005Expanding functional diversity of the coactivators. Trends in Biochemical Sciences30126132. (doi:10.1016/j.tibs.2005.01.001).

    • Search Google Scholar
    • Export Citation
  • LubahnDBMoyerJSGoldingTSCouseJFKorachKSSmithiesO1993Alteration of reproductive function but not prenatal sexual development after insertional disruption of the mouse estrogen receptor gene. PNAS901116211166. (doi:10.1073/pnas.90.23.11162).

    • Search Google Scholar
    • Export Citation
  • LupienMEeckhouteJMeyerCAKrumSARhodesDRLiuXSBrownM2009Coactivator function defines the active estrogen receptor α cistrome. Molecular and Cellular Biology2934133423. (doi:10.1128/MCB.00020-09).

    • Search Google Scholar
    • Export Citation
  • Madak-ErdoganZLupienMStossiFBrownMKatzenellenbogenBS2011Genomic collaboration of estrogen receptor α and extracellular signal-regulated kinase 2 in regulating gene and proliferation programs. Molecular and Cellular Biology31226236. (doi:10.1128/MCB.00821-10).

    • Search Google Scholar
    • Export Citation
  • MalikSRoederRG2010The metazoan mediator co-activator complex as an integrative hub for transcriptional regulation. Nature Reviews. Genetics11761772. (doi:10.1038/nrg2901).

    • Search Google Scholar
    • Export Citation
  • MantenaSRKannanACheonYPLiQJohnsonPFBagchiICBagchiMK2006C/EBPβ is a critical mediator of steroid hormone-regulated cell proliferation and differentiation in the uterine epithelium and stroma. PNAS10318701875. (doi:10.1073/pnas.0507261103).

    • Search Google Scholar
    • Export Citation
  • MartensJHRaoNAStunnenbergHG2011Genome-wide interplay of nuclear receptors with the epigenome. Biochimica et Biophysica Acta1812818823. (doi:10.1016/j.bbadis.2010.10.005).

    • Search Google Scholar
    • Export Citation
  • McEwanIJ2004Molecular mechanisms of androgen receptor-mediated gene regulation: structure-function analysis of the AF-1 domain. Endocrine-Related Cancer11281293. (doi:10.1677/erc.0.0110281).

    • Search Google Scholar
    • Export Citation
  • MeyerCATangQLiuXS2012Minireview: applications of next-generation sequencing on studies of nuclear receptor regulation and function. Molecular Endocrinology2616511659. (doi:10.1210/me.2012-1150).

    • Search Google Scholar
    • Export Citation
  • MeyersMJSunJCarlsonKEMarrinerGAKatzenellenbogenBSKatzenellenbogenJA2001Estrogen receptor-β potency-selective ligands: Structure- activity relationship studies of diarylpropionitriles and their acetylene and polar analogues. Journal of Medicinal Chemistry4442304251. (doi:10.1021/jm010254a).

    • Search Google Scholar
    • Export Citation
  • MoggsJGTinwellHSpurwayTChangHSPateILimFLMooreDJSoamesAStuckeyRCurrieR2004Phenotypic anchoring of gene expression changes during estrogen-induced uterine growth. Environmental Health Perspectives11215891606. (doi:10.1289/ehp.7345).

    • Search Google Scholar
    • Export Citation
  • NanjappaMKMedranoTIMarchAGCookePS2015Neonatal uterine and vaginal cell proliferation and adenogenesis are independent of estrogen receptor 1 (ESR1) in the mouse. Biology of Reproduction9278. (doi:10.1095/biolreprod.114.125724).

    • Search Google Scholar
    • Export Citation
  • O'BrienJEPetersonTJTongMHLeeEJPfaffLEHewittSCKorachKSWeissJJamesonJL2006Estrogen-induced proliferation of uterine epithelial cells is independent of estrogen receptor α binding to classical estrogen response elements. Journal of Biological Chemistry2812668326692. (doi:10.1074/jbc.M601522200).

    • Search Google Scholar
    • Export Citation
  • O'MalleyBWMalovannayaAQinJ2012Minireview: nuclear receptor and coregulator proteomics–2012 and beyond. Molecular Endocrinology2616461650. (doi:10.1210/me.2012-1114).

    • Search Google Scholar
    • Export Citation
  • PanHDengYPollardJW2006Progesterone blocks estrogen-induced DNA synthesis through the inhibition of replication licensing. PNAS1031402114026. (doi:10.1073/pnas.0601271103).

    • Search Google Scholar
    • Export Citation
  • ParkPJ2009ChIP-seq: advantages and challenges of a maturing technology. Nature Reviews. Genetics10669680. (doi:10.1038/nrg2641).

  • PawarSLawsMJBagchiICBagchiMK2015Uterine epithelial estrogen receptor-α controls decidualization via a paracrine mechanism. Molecular Endocrinology2913621374. (doi:10.1210/me.2015-1142).

    • Search Google Scholar
    • Export Citation
  • PedramARazandiMLewisMHammesSLevinER2014Membrane-localized estrogen receptor α is required for normal organ development and function. Developmental Cell29482490. (doi:10.1016/j.devcel.2014.04.016).

    • Search Google Scholar
    • Export Citation
  • ProssnitzERBartonM2011The G-protein-coupled estrogen receptor GPER in health and disease. Nature Reviews. Endocrinology7715726. (doi:10.1038/nrendo.2011.122).

    • Search Google Scholar
    • Export Citation
  • QuaynorSDStradtmanEWJrKimHGShenYChorichLPSchreihoferDALaymanLC2013Delayed puberty and estrogen resistance in a woman with estrogen receptor α variant. New England Journal of Medicine369164171. (doi:10.1056/NEJMoa1303611).

    • Search Google Scholar
    • Export Citation
  • RamathalCBagchiICBagchiMK2010Lack of CCAAT enhancer binding protein β (C/EBPβ) in uterine epithelial cells impairs estrogen-induced DNA replication, induces DNA damage response pathways, and promotes apoptosis. Molecular and Cellular Biology3016071619. (doi:10.1128/MCB.00872-09).

    • Search Google Scholar
    • Export Citation
  • RaySPollardJW2012KLF15 negatively regulates estrogen-induced epithelial cell proliferation by inhibition of DNA replication licensing. PNAS109E1334E1343. (doi:10.1073/pnas.1118515109).

    • Search Google Scholar
    • Export Citation
  • RobertsCWOrkinSH2004The SWI/SNF complex – chromatin and cancer. Nature Reviews. Cancer4133142. (doi:10.1038/nrc1273).

  • RumiMADhakalPKubotaKChakrabortyDLeiTLarsonMAWolfeMWRobyKFVivianJLSoaresMJ2014Generation of Esr1-knockout rats using zinc finger nuclease-mediated genome editing. Biology of Reproduction15519911999. (doi:10.1210/en.2013-2150).

    • Search Google Scholar
    • Export Citation
  • SafeSKimK2004Nuclear receptor-mediated transactivation through interaction with Sp proteins. Progress in Nucleic Acid Research and Molecular Biology77136. (doi:10.1016/S0079-6603(04)77001-4).

    • Search Google Scholar
    • Export Citation
  • SafeSKimK2008Non-classical genomic estrogen receptor (ER)/specificity protein and ER/activating protein-1 signaling pathways. Journal of Molecular Endocrinology41263275. (doi:10.1677/JME-08-0103).

    • Search Google Scholar
    • Export Citation
  • ShughruePJAskewGRDellovadeTLMerchenthalerI2002Estrogen-binding sites and their functional capacity in estrogen receptor double knockout mouse brain. Endocrinology14316431650. (doi:10.1210/endo.143.5.8772).

    • Search Google Scholar
    • Export Citation
  • SinkeviciusKWBurdetteJEWoloszynKHewittSCHamiltonKSuggSLTempleKAWondisfordFEKorachKSWoodruffTK2008An estrogen receptor-α knock-in mutation provides evidence of ligand-independent signaling and allows modulation of ligand-induced pathways in vivo. Endocrinology14929702979. (doi:10.1210/en.2007-1526).

    • Search Google Scholar
    • Export Citation
  • SmithEPBoydJFrankGRTakahashiHCohenRMSpeckerBWilliamsTCLubahnDBKorachKS1994Estrogen resistance caused by a mutation in the estrogen-receptor gene in a man. New England Journal of Medicine33110561061. (doi:10.1056/NEJM199410203311604).

    • Search Google Scholar
    • Export Citation
  • StaufferSRColettaCJTedescoRNishiguchiGCarlsonKSunJKatzenellenbogenBSKatzenellenbogenJA2000Pyrazole ligands: structure-affinity/activity relationships and estrogen receptor-α-selective agonists. Journal of Medicinal Chemistry4349344947. (doi:10.1021/jm000170m).

    • Search Google Scholar
    • Export Citation
  • TakeoTSakumaY1995Diametrically opposite effects of estrogen on the excitability of female rat medial and lateral preoptic neurons with axons to the midbrain locomotor region. Neuroscience Research227380. (doi:10.1016/0168-0102(95)00885-W).

    • Search Google Scholar
    • Export Citation
  • TangQChenYMeyerCGeistlingerTLupienMWangQLiuTZhangYBrownMLiuXS2011A comprehensive view of nuclear receptor cancer cistromes. Cancer Research7169406947. (doi:10.1158/0008-5472.CAN-11-2091).

    • Search Google Scholar
    • Export Citation
  • TodaKTakedaKOkadaTAkiraSSaibaraTKanameTYamamuraKOnishiSShizutaY2001Targeted disruption of the aromatase P450 gene (Cyp19) in mice and their ovarian and uterine responses to 17β-oestradiol. Journal of Endocrinology17099111. (doi:10.1677/joe.0.1700099).

    • Search Google Scholar
    • Export Citation
  • Wada-HiraikeOHiraikeHOkinagaHImamovOBarrosRPMoraniAOmotoYWarnerMGustafssonJA2006Role of estrogen receptor β in uterine stroma and epithelium: insights from estrogen receptor β−/− mice. PNAS1031835018355. (doi:10.1073/pnas.0608861103).

    • Search Google Scholar
    • Export Citation
  • WalkerVRKorachKS2004Estrogen receptor knockout mice as a model for endocrine research. ILAR Journal45455461. (doi:10.1093/ilar.45.4.455).

    • Search Google Scholar
    • Export Citation
  • WallEHHewittSCCaseLKLinCYKorachKSTeuscherC2014The role of genetics in estrogen responses: a critical piece of an intricate puzzle. FASEB Journal2850425054. (doi:10.1096/fj.14-260307).

    • Search Google Scholar
    • Export Citation
  • WalterPGreenSGreeneGKrustABornertJMJeltschJMStaubAJensenEScraceGWaterfieldM1985Cloning of the human estrogen receptor cDNA. PNAS8278897893. (doi:10.1073/pnas.82.23.7889).

    • Search Google Scholar
    • Export Citation
  • WatanabeHSuzukiAKobayashiMTakahashiEItamotoMLubahnDBHandaHIguchiT2003Analysis of temporal changes in the expression of estrogen-regulated genes in the uterus. Journal of Molecular Endocrinology30347358. (doi:10.1677/jme.0.0300347).

    • Search Google Scholar
    • Export Citation
  • WeihuaZSajiSMakinenSChengGJensenEVWarnerMGustafssonJA2000Estrogen receptor (ER) β, a modulator of ERα in the uterus. PNAS9759365941. (doi:10.1073/pnas.97.11.5936).

    • Search Google Scholar
    • Export Citation
  • WinuthayanonWHewittSCOrvisGDBehringerRRKorachKS2010Uterine epithelial estrogen receptor α is dispensable for proliferation but essential for complete biological and biochemical responses. PNAS1071927219277. (doi:10.1073/pnas.1013226107).

    • Search Google Scholar
    • Export Citation
  • WinuthayanonWHewittSCKorachKS2014Uterine epithelial cell estrogen receptor α-dependent and -independent genomic profiles that underlie estrogen responses in mice. Biology of Reproduction91110. (doi:10.1095/biolreprod.114.120170).

    • Search Google Scholar
    • Export Citation
  • WinuthayanonWBernhardtMLPadilla-BanksEMyersPHEdinMLHewittSCKorachKSWilliamsCJ2015Oviductal estrogen receptor α signaling prevents protease-mediated embryo death. eLife4e10453. (doi:10.7554/eLife.10453).

    • Search Google Scholar
    • Export Citation
  • WuSCZhangY2009Minireview: role of protein methylation and demethylation in nuclear hormone signaling. Molecular Endocrinology2313231334. (doi:10.1210/me.2009-0131).

    • Search Google Scholar
    • Export Citation
  • XuJQiuYDeMayoFJTsaiSYTsaiMJO'MalleyBW1998Partial hormone resistance in mice with disruption of the steroid receptor coactivator-1 (SRC-1) gene. Science27919221925. (doi:10.1126/science.279.5358.1922).

    • Search Google Scholar
    • Export Citation
  • YangJSingletonDWShaughnessyEAKhanSA2008The F-domain of estrogen receptor-α inhibits ligand induced receptor dimerization. Molecular and Cellular Endocrinology29594100. (doi:10.1016/j.mce.2008.08.001).

    • Search Google Scholar
    • Export Citation
  • YiPWangZFengQPintilieGDFouldsCELanzRBLudtkeSJSchmidMFChiuWO'MalleyBW2015Structure of a biologically active estrogen receptor-coactivator complex on DNA. Molecular Cell5710471058. (doi:10.1016/j.molcel.2015.01.025).

    • Search Google Scholar
    • Export Citation
  • ZaretKSCarrollJS2011Pioneer transcription factors: establishing competence for gene expression. Genes and Development2522272241. (doi:10.1101/gad.176826.111).

    • Search Google Scholar
    • Export Citation

If the inline PDF is not rendering correctly, you can download the PDF file here.

 

      Society for Endocrinology

Sept 2018 onwards Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 1652 767 34
PDF Downloads 435 230 15
  • AagaardMMSiersbaekRMandrupS2011Molecular basis for gene-specific transactivation by nuclear receptors. Biochimica et Biophysic Acta1812824835. (doi:10.1016/j.bbadis.2010.12.018).

    • Search Google Scholar
    • Export Citation
  • AbotAFontaineCRaymond-LetronIFlouriotGAdlanmeriniMBuscatoMOttoCBergesHLaurellHGourdyP2013The AF-1 activation function of estrogen receptor α is necessary and sufficient for uterine epithelial cell proliferation in vivo. Endocrinology15422222233. (doi:10.1210/en.2012-2059).

    • Search Google Scholar
    • Export Citation
  • AdlanmeriniMSolinhacRAbotAFabreARaymond-LetronIGuihotALBoudouFSautierLVessieresEKimSH2014Mutation of the palmitoylation site of estrogen receptor α in vivo reveals tissue-specific roles for membrane versus nuclear actions. PNAS111E283E290. (doi:10.1073/pnas.1322057111).

    • Search Google Scholar
    • Export Citation
  • Ahlbory-DiekerDLStrideBDLederGSchkoldowJTrolenbergSSeidelHOttoCSommerAParkerMGSchutzG2009DNA binding by estrogen receptor-α is essential for the transcriptional response to estrogen in the liver and the uterus. Molecular Endocrinology2315441555. (doi:10.1210/me.2009-0045).

    • Search Google Scholar
    • Export Citation
  • AndradePMSilvaIBorraRCde LimaGRBaracatEC2002Estrogen regulation of uterine genes in vivo detected by complementary DNA array. Hormone and Metabolic Research34238244. (doi:10.1055/s-2002-32136).

    • Search Google Scholar
    • Export Citation
  • AntalMCKrustAChambonPMarkM2008Sterility and absence of histopathological defects in nonreproductive organs of a mouse ER β-null mutant. PNAS10524332438. (doi:10.1073/pnas.0712029105).

    • Search Google Scholar
    • Export Citation
  • AntonsonPOmotoYHumirePGustafssonJA2012Generation of ERα-floxed and knockout mice using the Cre/LoxP system. Biochemical and Biophysical Research Communications424710716. (doi:10.1016/j.bbrc.2012.07.016).

    • Search Google Scholar
    • Export Citation
  • AraoYHamiltonKJRayMKScottGMishinaYKorachKS2011Estrogen receptor α AF-2 mutation results in antagonist reversal and reveals tissue selective function of estrogen receptor modulators. PNAS1081498614991. (doi:10.1073/pnas.1109180108).

    • Search Google Scholar
    • Export Citation
  • AraoYHamiltonKJCoonsLAKorachKS2013Estrogen receptor α L543A, L544A mutation changes antagonists to agonists which correlates with the ligand binding domain dimerization associated with DNA binding activity. Journal of Biological Chemistry2882110521116. (doi:10.1074/jbc.M113.463455).

    • Search Google Scholar
    • Export Citation
  • BagchiMKMantenaSRKannanABagchiIC2006Role of C/EBP β in steroid-induced cell proliferation and differentiaion in the uterus: Functional implications for establishment of early pregnancy. Placenta27A13A13.

    • Search Google Scholar
    • Export Citation
  • BarnesPJAdcockIMItoK2005Histone acetylation and deacetylation: importance in inflammatory lung diseases. European Respiratory Journal25552563. (doi:10.1183/09031936.05.00117504).

    • Search Google Scholar
    • Export Citation
  • BiddieSCJohnSHagerGL2010Genome-wide mechanisms of nuclear receptor action. Trends in endocrinology and metabolism2139. (doi:10.1016/j.tem.2009.08.006).

    • Search Google Scholar
    • Export Citation
  • Billon-GalesAFontaineCFilipeCDouin-EchinardVFouqueMJFlouriotGGourdyPLenfantFLaurellHKrustA2009The transactivating function 1 of estrogen receptor α is dispensable for the vasculoprotective actions of 17 β-estradiol. PNAS10620532058. (doi:10.1073/pnas.0808742106).

    • Search Google Scholar
    • Export Citation
  • Billon-GalesAKrustAFontaineCAbotAFlouriotGToutainCBergesHGadeauAPLenfantFGourdyP2011Activation function 2 (AF2) of estrogen receptor-α is required for the atheroprotective action of estradiol but not to accelerate endothelial healing. PNAS1081331113316. (doi:10.1073/pnas.1105632108).

    • Search Google Scholar
    • Export Citation
  • BinderAKRodriguezKFHamiltonKJStocktonPSReedCEKorachKS2013The absence of ER-β results in altered gene expression in ovarian granulosa cells isolated from in vivo preovulatory follicles. Endocrinology15421742187. (doi:10.1210/en.2012-2256).

    • Search Google Scholar
    • Export Citation
  • Binder AK Winuthayanon W Hewitt SC Couse JF & Korach KS. 2015 Steroid receptors in the uterus and ovary. In Knobil and Neill's Physiology of Reproduction pp 1099–1193. Eds TM Plant AJ Zeleznik: Elsevier

  • BrelivetYRochelNMorasD2012Structural analysis of nuclear receptors: From isolated domains to integral proteins. Molecular and Cellular Endocrinology348466473. (doi:10.1016/j.mce.2011.08.015).

    • Search Google Scholar
    • Export Citation
  • BrittKLDrummondAEDysonMWrefordNGJonesMESimpsonERFindlayJK2001The ovarian phenotype of the aromatase knockout (ArKO) mouse. Journal of Steroid Biochemistry and Molecular Biology79181185. (doi:10.1016/S0960-0760(01)00158-3).

    • Search Google Scholar
    • Export Citation
  • BrittKLKerrJO'DonnellLJonesMEDrummondAEDavisSRSimpsonERFindlayJK2002Estrogen regulates development of the somatic cell phenotype in the eutherian ovary. FASEB Journal1613891397. (doi:10.1096/fj.01-0992com).

    • Search Google Scholar
    • Export Citation
  • BulynkoYAO'MalleyBW2011Nuclear receptor coactivators: structural and functional biochemistry. Biochemistry50313328. (doi:10.1021/bi101762x).

    • Search Google Scholar
    • Export Citation
  • BurnsKALiYAraoYPetrovichRMKorachKS2011Selective mutations in estrogen receptor α D-domain alters nuclear translocation and non-estrogen response element gene regulatory mechanisms. Journal of Biological Chemistry2861264012649. (doi:10.1074/jbc.M110.187773).

    • Search Google Scholar
    • Export Citation
  • CarrollJSBrownM2006Estrogen receptor target gene: an evolving concept. Molecular Endocrinology2017071714. (doi:10.1210/me.2005-0334).

    • Search Google Scholar
    • Export Citation
  • CarrollJSLiuXSBrodskyASLiWMeyerCASzaryAJEeckhouteJShaoWHestermannEVGeistlingerTR2005Chromosome-wide mapping of estrogen receptor binding reveals long-range regulation requiring the forkhead protein FoxA1. Cell1223343. (doi:10.1016/j.cell.2005.05.008).

    • Search Google Scholar
    • Export Citation
  • CheungEKrausWL2010Genomic analyses of hormone signaling and gene regulation. Annual Review of Physiology72191218. (doi:10.1146/annurev-physiol-021909-135840).

    • Search Google Scholar
    • Export Citation
  • ConawayRCConawayJW2011Function and regulation of the Mediator complex. Current Opinion in Genetics & Development21225230. (doi:10.1016/j.gde.2011.01.013).

    • Search Google Scholar
    • Export Citation
  • CouseJFKorachKS1999Estrogen receptor null mice: what have we learned and where will they lead us?Endocrine Reviews20358417. (doi:10.1210/edrv.20.3.0370).

    • Search Google Scholar
    • Export Citation
  • CouseJFCurtisSWWashburnTFLindzeyJGoldingTSLubahnDBSmithiesOKorachKS1995Analysis of transcription and estrogen insensitivity in the female mouse after targeted disruption of the estrogen receptor gene. Molecular Endocrinology914411454. (doi:10.1210/mend.9.11.8584021).

    • Search Google Scholar
    • Export Citation
  • CouseJFHewittSCBunchDOSarMWalkerVRDavisBJKorachKS1999Postnatal sex reversal of the ovaries in mice lacking estrogen receptors α and β. Science28623282331. (doi:10.1126/science.286.5448.2328).

    • Search Google Scholar
    • Export Citation
  • Curtis SH & Korach KS. 1999 Steroid receptor knockout models: Phenotypes and responses illustrate interactions between receptor signaling pathways in vivo. In Hormones and Signaling pp 357-380. Ed BW O'Malley. San Diego CA USA: Academic Press

  • CurtisSWClarkJMyersPKorachKS1999Disruption of estrogen signaling does not prevent progesterone action in the estrogen receptor α knockout mouse uterus. PNAS9636463651. (doi:10.1073/pnas.96.7.3646).

    • Search Google Scholar
    • Export Citation
  • Curtis HewittSGouldingEHEddyEMKorachKS2002Studies using the estrogen receptor α knockout uterus demonstrate that implantation but not decidualization-associated signaling is estrogen dependent. Biology of Reproduction6712681277. (doi:10.1095/biolreprod67.4.1268).

    • Search Google Scholar
    • Export Citation
  • DebloisGGiguereV2008Nuclear receptor location analyses in mammalian genomes: from gene regulation to regulatory networks. Molecular Endocrinology2219992011. (doi:10.1210/me.2007-0546).

    • Search Google Scholar
    • Export Citation
  • DupontSKrustAGansmullerADierichAChambonPMarkM2000Effect of single and compound knockouts of estrogen receptors α (ERα) and β (ERβ) on mouse reproductive phenotypes. Development12742774291.

    • Search Google Scholar
    • Export Citation
  • FarnhamPJ2009Insights from genomic profiling of transcription factors. Nature Reviews. Genetics10605616. (doi:10.1038/nrg2636).

  • FertuckKCEckelJEGenningsCZacharewskiTR2003Identification of temporal patterns of gene expression in the uteri of immature, ovariectomized mice following exposure to ethynylestradiol. Physiological Genomics15127141. (doi:10.1152/physiolgenomics.00058.2003).

    • Search Google Scholar
    • Export Citation
  • FisherCRGravesKHParlowAFSimpsonER1998Characterization of mice deficient in aromatase (ArKO) because of targeted disruption of the cyp19 gene. PNAS9569656970. (doi:10.1073/pnas.95.12.6965).

    • Search Google Scholar
    • Export Citation
  • FoxEMAndradeJShupnikMA2009Novel actions of estrogen to promote proliferation: integration of cytoplasmic and nuclear pathways. Steroids74622627. (doi:10.1016/j.steroids.2008.10.014).

    • Search Google Scholar
    • Export Citation
  • FuXHuangCSchiffR2011More on FOX News: FOXA1 on the horizon of estrogen receptor function and endocrine response. Breast Cancer Research13307. (doi:10.1186/bcr2849).

    • Search Google Scholar
    • Export Citation
  • GaoHDahlman-WrightK2011The gene regulatory networks controlled by estrogens. Molecular and Cellular Endocrinology3348390. (doi:10.1016/j.mce.2010.09.002).

    • Search Google Scholar
    • Export Citation
  • GaoFMaXOstmannABDasSK2011GPR30 activation opposes estrogen-dependent uterine growth via inhibition of stromal ERK1/2 and estrogen receptor α (ERα) phosphorylation signals. Endocrinology15214341447. (doi:10.1210/en.2010-1368).

    • Search Google Scholar
    • Export Citation
  • GeorgeCLLightmanSLBiddieSC2011Transcription factor interactions in genomic nuclear receptor function. Epigenomics3471485. (doi:10.2217/epi.11.66).

    • Search Google Scholar
    • Export Citation
  • GibsonDASaundersPT2012Estrogen dependent signaling in reproductive tissues - a role for estrogen receptors and estrogen related receptors. Molecular and Cellular Endocrinology348361372. (doi:10.1016/j.mce.2011.09.026).

    • Search Google Scholar
    • Export Citation
  • GilfillanSFioritoEHurtadoA2012Functional genomic methods to study estrogen receptor activity. Journal of Mammary Gland Biology and Neoplasia17147153. (doi:10.1007/s10911-012-9254-4).

    • Search Google Scholar
    • Export Citation
  • GreenCDHanJD2011Epigenetic regulation by nuclear receptors. Epigenomics35972. (doi:10.2217/epi.10.75).

  • GrontvedLHagerGL2012Impact of chromatin structure on PR signaling: transition from local to global analysis. Molecular and Cellular Endocrinology3573036. (doi:10.1016/j.mce.2011.09.006).

    • Search Google Scholar
    • Export Citation
  • HeldringNPikeAAnderssonSMatthewsJChengGHartmanJTujagueMStromATreuterEWarnerM2007Estrogen receptors: how do they signal and what are their targets. Physiological Reviews87905931. (doi:10.1152/physrev.00026.2006).

    • Search Google Scholar
    • Export Citation
  • HelsenCKerkhofsSClinckemalieLSpansLLaurentMBoonenSVanderschuerenDClaessensF2012Structural basis for nuclear hormone receptor DNA binding. Molecular and Cellular Endocrinology348411417. (doi:10.1016/j.mce.2011.07.025).

    • Search Google Scholar
    • Export Citation
  • HewittSCDerooBJHansenKCollinsJGrissomSAfshariCAKorachKS2003Estrogen receptor-dependent genomic responses in the uterus mirror the biphasic physiological response to estrogen. Molecular Endocrinology1720702083. (doi:10.1210/me.2003-0146).

    • Search Google Scholar
    • Export Citation
  • HewittSCCollinsJGrissomSDerooBKorachKS2005Global uterine genomics in vivo: microarray evaluation of the estrogen receptor α-growth factor cross-talk mechanism. Molecular Endocrinology19657668. (doi:10.1210/me.2004-0142).

    • Search Google Scholar
    • Export Citation
  • HewittSCO'BrienJEJamesonJLKisslingGEKorachKS2009Selective disruption of ER α DNA-binding activity alters uterine responsiveness to estradiol. Molecular Endocrinology2321112116. (doi:10.1210/me.2009-0356).

    • Search Google Scholar
    • Export Citation
  • HewittSCKisslingGEFieselmanKEJayesFLGerrishKEKorachKS2010aBiological and biochemical consequences of global deletion of exon 3 from the ER α gene. FASEB Journal2446604667. (doi:10.1096/fj.10-163428).

    • Search Google Scholar
    • Export Citation
  • HewittSCLiYLiLKorachKS2010bEstrogen-mediated regulation of Igf1 transcription and uterine growth involves direct binding of estrogen receptor α to estrogen-responsive elements. Journal of Biological Chemistry28526762685. (doi:10.1074/jbc.M109.043471).

    • Search Google Scholar
    • Export Citation
  • HewittSCLiLGrimmSAChenYLiuLLiYBushelPRFargoDKorachKS2012Research resource: whole-genome estrogen receptor α binding in mouse uterine tissue revealed by ChIP-Seq. Molecular Endocrinology26887898. (doi:10.1210/me.2011-1311).

    • Search Google Scholar
    • Export Citation
  • HewittSCLiLGrimmSAWinuthayanonWHamiltonKJPocketteBRubelCAPedersenLCFargoDLanzRB2014Novel DNA motif binding activity observed in vivo with an estrogen receptor α mutant mouse. Molecular Endocrinology28899911. (doi:10.1210/me.2014-1051).

    • Search Google Scholar
    • Export Citation
  • HilserVJThompsonEB2011Structural dynamics, intrinsic disorder, and allostery in nuclear receptors as transcription factors. Journal of Biological Chemistry2863967539682. (doi:10.1074/jbc.R111.278929).

    • Search Google Scholar
    • Export Citation
  • HongSHNahHYLeeJYGyeMCKimCHKimMK2004Analysis of estrogen-regulated genes in mouse uterus using cDNA microarray and laser capture microdissection. Journal of Endocrinology181157167. (doi:10.1677/joe.0.1810157).

    • Search Google Scholar
    • Export Citation
  • HondaSHaradaNItoSTakagiYMaedaS1998Disruption of sexual behavior in male aromatase-deficient mice lacking exons 1 and 2 of the cyp19 gene. Biochemical and Biophysical Research Communications252445449. (doi:10.1006/bbrc.1998.9672).

    • Search Google Scholar
    • Export Citation
  • HongEJParkSHChoiKCLeungPCJeungEB2006Identification of estrogen-regulated genes by microarray analysis of the uterus of immature rats exposed to endocrine disrupting chemicals. Reproductive Biology and Endocrinology449. (doi:10.1186/1477-7827-4-49).

    • Search Google Scholar
    • Export Citation
  • HsiaEYGoodsonMLZouJXPrivalskyMLChenHW2010Nuclear receptor coregulators as a new paradigm for therapeutic targeting. Advanced Drug Delivery Reviews6212271237. (doi:10.1016/j.addr.2010.09.016).

    • Search Google Scholar
    • Export Citation
  • HuangPXChandraVRastinejadF2010Structural overview of the nuclear receptor superfamily: insights into physiology and therapeutics. Annual Review of Physiology72247272. (doi:10.1146/annurev-physiol-021909-135917).

    • Search Google Scholar
    • Export Citation
  • HuangCCOrvisGDWangYBehringerRR2012Stromal-to-epithelial transition during postpartum endometrial regeneration. PLoS ONE7e44285. (doi:10.1371/journal.pone.0044285).

    • Search Google Scholar
    • Export Citation
  • JakackaMItoMMartinsonFIshikawaTLeeEJJamesonJL2002An estrogen receptor (ER)α deoxyribonucleic acid-binding domain knock-in mutation provides evidence for nonclassical ER pathway signaling in vivo. Molecular Endocrinology1621882201. (doi:10.1210/me.2001-0174).

    • Search Google Scholar
    • Export Citation
  • JohnsonABO'MalleyBW2012Steroid receptor coactivators 1, 2, and 3: Critical regulators of nuclear receptor activity and steroid receptor modulator (SRM)-based cancer therapy. Molecular and Cellular Endocrinology348430439. (doi:10.1016/j.mce.2011.04.021).

    • Search Google Scholar
    • Export Citation
  • KatzenellenbogenBSChoiIHDelage-MourrouxREdigerTRMartiniPGMontanoMSunJWeisKKatzenellenbogenJA2000Molecular mechanisms of estrogen action: selective ligands and receptor pharmacology. Journal of Steroid Biochemistry and Molecular Biology74279285. (doi:10.1016/S0960-0760(00)00104-7).

    • Search Google Scholar
    • Export Citation
  • KepplerBRArcherTKKinyamuHK2011Emerging roles of the 26S proteasome in nuclear hormone receptor-regulated transcription. Biochimica et Biophysica Acta1809109118. (doi:10.1016/j.bbagrm.2010.08.005).

    • Search Google Scholar
    • Export Citation
  • KimMYWooEMChongYTHomenkoDRKrausWL2006Acetylation of estrogen receptor α by p300 at lysines 266 and 268 enhances the deoxyribonucleic acid binding and transactivation activities of the receptor. Molecular Endocrinology2014791493. (doi:10.1210/me.2005-0531).

    • Search Google Scholar
    • Export Citation
  • KimHMYuYChengY2011aStructure characterization of the 26S proteasome. Biochimica et Biophysica Acta18096779. (doi:10.1016/j.bbagrm.2010.08.008).

    • Search Google Scholar
    • Export Citation
  • KimHKuSYSungJJKimSHChoiYMKimJGMoonSY2011bAssociation between hormone therapy and nerve conduction study parameters in postmenopausal women. Climacteric14488491. (doi:10.3109/13697137.2011.553972).

    • Search Google Scholar
    • Export Citation
  • KoideAZhaoCNaganumaMAbramsJDeighton-CollinsSSkafarDFKoideS2007Identification of regions within the F domain of the human estrogen receptor α that are important for modulating transactivation and protein-protein interactions. Molecular Endocrinology21829842. (doi:10.1210/me.2006-0203).

    • Search Google Scholar
    • Export Citation
  • KorachKS1994Insights from the study of animals lacking functional estrogen receptor. Science26615241527. (doi:10.1126/science.7985022).

    • Search Google Scholar
    • Export Citation
  • KorachKSCouseJFCurtisSWWashburnTFLindzeyJKimbroKSEddyEMMigliaccioSSnedekerSMLubahnDB1996Estrogen receptor gene disruption: molecular characterization and experimental and clinical phenotypes. Recent Progress in Hormone Research51159186; discussion 186–158.

    • Search Google Scholar
    • Export Citation
  • KregeJHHodginJBCouseJFEnmarkEWarnerMMahlerJFSarMKorachKSGustafssonJASmithiesO1998Generation and reproductive phenotypes of mice lacking estrogen receptor β. PNAS951567715682. (doi:10.1073/pnas.95.26.15677).

    • Search Google Scholar
    • Export Citation
  • KuiperGGEnmarkEPelto-HuikkoMNilssonSGustafssonJA1996Cloning of a novel receptor expressed in rat prostate and ovary. PNAS9359255930. (doi:10.1073/pnas.93.12.5925).

    • Search Google Scholar
    • Export Citation
  • KumarRMcEwanIJ2012Allosteric Modulators of steroid hormone receptors: structural dynamics and gene regulation. Endocrine Reviews33271299. (doi:10.1210/er.2011-1033).

    • Search Google Scholar
    • Export Citation
  • KumarRZakharovMNKhanSHMikiRJangHToraldoGSinghRBhasinSJasujaR2011The dynamic structure of the estrogen receptor. Journal of Amino Acids2011812540. (doi:10.4061/2011/812540).

    • Search Google Scholar
    • Export Citation
  • KushnerPJAgardDAGreeneGLScanlanTSShiauAKUhtRMWebbP2000Estrogen receptor pathways to AP-1. Journal of Steroid Biochemistry and Molecular Biology74311317. (doi:10.1016/S0960-0760(00)00108-4).

    • Search Google Scholar
    • Export Citation
  • LangerGBaderBMeoliLIsenseeJDelbeckMNoppingerPROttoC2010A critical review of fundamental controversies in the field of GPR30 research. Steroids75603610. (doi:10.1016/j.steroids.2009.12.006).

    • Search Google Scholar
    • Export Citation
  • Laudet V & Gronemeyer H 2001 The Nuclear Receptor FactsBook. Cambridge MA USA: Academic Press

  • Le RomancerMPoulardCCohenPSentisSRenoirJMCorboL2011Cracking the estrogen receptor's posttranslational code in breast tumors. Endocrine Reviews32597622. (doi:10.1210/er.2010-0016).

    • Search Google Scholar
    • Export Citation
  • LevinER2011Minireview: extranuclear steroid receptors: roles in modulation of cell functions. Molecular Endocrinology25377384. (doi:10.1210/me.2010-0284).

    • Search Google Scholar
    • Export Citation
  • LonardDMO'MalleyBW2005Expanding functional diversity of the coactivators. Trends in Biochemical Sciences30126132. (doi:10.1016/j.tibs.2005.01.001).

    • Search Google Scholar
    • Export Citation
  • LubahnDBMoyerJSGoldingTSCouseJFKorachKSSmithiesO1993Alteration of reproductive function but not prenatal sexual development after insertional disruption of the mouse estrogen receptor gene. PNAS901116211166. (doi:10.1073/pnas.90.23.11162).

    • Search Google Scholar
    • Export Citation
  • LupienMEeckhouteJMeyerCAKrumSARhodesDRLiuXSBrownM2009Coactivator function defines the active estrogen receptor α cistrome. Molecular and Cellular Biology2934133423. (doi:10.1128/MCB.00020-09).

    • Search Google Scholar
    • Export Citation
  • Madak-ErdoganZLupienMStossiFBrownMKatzenellenbogenBS2011Genomic collaboration of estrogen receptor α and extracellular signal-regulated kinase 2 in regulating gene and proliferation programs. Molecular and Cellular Biology31226236. (doi:10.1128/MCB.00821-10).

    • Search Google Scholar
    • Export Citation
  • MalikSRoederRG2010The metazoan mediator co-activator complex as an integrative hub for transcriptional regulation. Nature Reviews. Genetics11761772. (doi:10.1038/nrg2901).

    • Search Google Scholar
    • Export Citation
  • MantenaSRKannanACheonYPLiQJohnsonPFBagchiICBagchiMK2006C/EBPβ is a critical mediator of steroid hormone-regulated cell proliferation and differentiation in the uterine epithelium and stroma. PNAS10318701875. (doi:10.1073/pnas.0507261103).

    • Search Google Scholar
    • Export Citation
  • MartensJHRaoNAStunnenbergHG2011Genome-wide interplay of nuclear receptors with the epigenome. Biochimica et Biophysica Acta1812818823. (doi:10.1016/j.bbadis.2010.10.005).

    • Search Google Scholar
    • Export Citation
  • McEwanIJ2004Molecular mechanisms of androgen receptor-mediated gene regulation: structure-function analysis of the AF-1 domain. Endocrine-Related Cancer11281293. (doi:10.1677/erc.0.0110281).

    • Search Google Scholar
    • Export Citation
  • MeyerCATangQLiuXS2012Minireview: applications of next-generation sequencing on studies of nuclear receptor regulation and function. Molecular Endocrinology2616511659. (doi:10.1210/me.2012-1150).

    • Search Google Scholar
    • Export Citation
  • MeyersMJSunJCarlsonKEMarrinerGAKatzenellenbogenBSKatzenellenbogenJA2001Estrogen receptor-β potency-selective ligands: Structure- activity relationship studies of diarylpropionitriles and their acetylene and polar analogues. Journal of Medicinal Chemistry4442304251. (doi:10.1021/jm010254a).

    • Search Google Scholar
    • Export Citation
  • MoggsJGTinwellHSpurwayTChangHSPateILimFLMooreDJSoamesAStuckeyRCurrieR2004Phenotypic anchoring of gene expression changes during estrogen-induced uterine growth. Environmental Health Perspectives11215891606. (doi:10.1289/ehp.7345).

    • Search Google Scholar
    • Export Citation
  • NanjappaMKMedranoTIMarchAGCookePS2015Neonatal uterine and vaginal cell proliferation and adenogenesis are independent of estrogen receptor 1 (ESR1) in the mouse. Biology of Reproduction9278. (doi:10.1095/biolreprod.114.125724).

    • Search Google Scholar
    • Export Citation
  • O'BrienJEPetersonTJTongMHLeeEJPfaffLEHewittSCKorachKSWeissJJamesonJL2006Estrogen-induced proliferation of uterine epithelial cells is independent of estrogen receptor α binding to classical estrogen response elements. Journal of Biological Chemistry2812668326692. (doi:10.1074/jbc.M601522200).

    • Search Google Scholar
    • Export Citation
  • O'MalleyBWMalovannayaAQinJ2012Minireview: nuclear receptor and coregulator proteomics–2012 and beyond. Molecular Endocrinology2616461650. (doi:10.1210/me.2012-1114).

    • Search Google Scholar
    • Export Citation
  • PanHDengYPollardJW2006Progesterone blocks estrogen-induced DNA synthesis through the inhibition of replication licensing. PNAS1031402114026. (doi:10.1073/pnas.0601271103).

    • Search Google Scholar
    • Export Citation
  • ParkPJ2009ChIP-seq: advantages and challenges of a maturing technology. Nature Reviews. Genetics10669680. (doi:10.1038/nrg2641).

  • PawarSLawsMJBagchiICBagchiMK2015Uterine epithelial estrogen receptor-α controls decidualization via a paracrine mechanism. Molecular Endocrinology2913621374. (doi:10.1210/me.2015-1142).

    • Search Google Scholar
    • Export Citation
  • PedramARazandiMLewisMHammesSLevinER2014Membrane-localized estrogen receptor α is required for normal organ development and function. Developmental Cell29482490. (doi:10.1016/j.devcel.2014.04.016).

    • Search Google Scholar
    • Export Citation
  • ProssnitzERBartonM2011The G-protein-coupled estrogen receptor GPER in health and disease. Nature Reviews. Endocrinology7715726. (doi:10.1038/nrendo.2011.122).

    • Search Google Scholar
    • Export Citation
  • QuaynorSDStradtmanEWJrKimHGShenYChorichLPSchreihoferDALaymanLC2013Delayed puberty and estrogen resistance in a woman with estrogen receptor α variant. New England Journal of Medicine369164171. (doi:10.1056/NEJMoa1303611).

    • Search Google Scholar
    • Export Citation
  • RamathalCBagchiICBagchi