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David W Scoville, Artiom Gruzdev and Anton M Jetten

Recent advances in high throughput RNA sequencing have revealed that, in addition to messenger RNAs (mRNAs), long non-coding RNAs (lncRNAs) play an important role in the regulation of many cell functions and of organ development. While a number of lncRNAs have been identified in pancreatic islets, their function remains largely undetermined. Here, we identify a novel long ncRNA regulated by the transcription factor GLIS3, which we refer to as GLIS3 regulated 1 (G3R1). This lncRNA was identified for its significant loss of expression in GLIS3 knockout mouse pancreatic islets. G3R1 appears to be specifically expressed in mouse pancreatic β-cells and in a β-cell line (βTC-6). ChIP-seq analysis indicated that GLIS3 and other islet-enriched transcription factors bind near the G3R1 gene, suggesting they directly regulate G3R1 transcription. Similarly, an apparent human homolog of G3R1 displays a similar expression pattern, with additional expression seen in human brain. In order to determine the function of G3R1 in mouse pancreatic β-cells, we utilized CRISPR to develop a knockout mouse where ~80% of G3R1 sequence is deleted. Phenotypic analysis of these mice did not reveal any impairment in β-cell function or glucose regulation, indicating the complexity underlying the study of lncRNA function.

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Pablo Pánico, Marcia Hiriart, Patricia Ostrosky-Wegman and Ana María Salazar

The calpain-10 (CAPN10) protease is implicated in the translocation of the glucose transporter 4 (GLUT4), which is retained in the Golgi matrix via the Tether containing a UBX domain for GLUT4 (TUG) protein. Insulin stimulation induces the proteolytic processing of TUG, which leads to the translocation of GLUT4 to the cell membrane. We tested whether TUG is a CAPN10 substrate. Proteolysis of TUG by calpains was assessed using a cell-free system containing calpain-1 and TUG. In situ proteolysis of TUG by calpains was demonstrated in 3T3-L1 adipocytes in the presence of insulin or calpain inhibitors to modulate calpain activity. Proteolysis of TUG by CAPN10 was confirmed using transient or stable silencing of CAPN10 in 3T3-L1 adipocytes. Calpains proteolyzed the C-terminus of TUG in vitro. In adipocytes, insulin-induced cleavage of TUG was correlated with the activation of calpains. Treatment with calpain inhibitors reduced TUG cleavage, resulting in impaired GLUT4 translocation without altering Akt phosphorylation. Furthermore, CAPN10 but not calpain-1 or calpain-2 colocalized with GLUT4 in the absence of insulin, and their colocalization was reduced after stimulation with insulin. Finally, we demonstrated that CAPN10 knockdown reduced the proteolysis of TUG without altering the phosphorylation of Akt or the expression of the Usp25m protease. Thus, our results provide evidence that the TUG protein is cleaved by CAPN10 to regulate GLUT4 translocation.

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Maya Elena Lee, Aisha Aderayo Tepede, Adel Mandl, Lee Scott Weinstein, Jaydira del Rivero, Sunita K Agarwal and Jenny E Blau

Gastroenteropancreatic neuroendocrine tumors (GEP NETs) comprise a heterogenous and diverse group of neoplasms arising from a common neuroendocrine cell origin. The majority of these tumors occur sporadically while ~20% manifest within the context of hereditary syndromes. Germline MEN1 mutations cause a syndrome with an increased susceptibility to multifocal primary GEP NETs. In addition, somatic MEN1 mutations also occur in these sporadic lesions. MEN1 alterations are the most frequent somatic mutation found in pancreatic neuroendocrine tumors. In this review, we explore the implication of the loss of the MEN1-encoded protein menin as a key pathogenic driver in subsets of GEP NETs with downstream consequences including upregulation of the oncogenic receptor c-MET (hepatocyte growth factor receptor). Furthermore, the review will summarize the data related to the clinical presentation, therapeutic standards, and outcomes of these tumors in both sporadic and germline MEN1 mutation-associated contexts. Finally, we present the data on c-MET expression in GEP NETs, clinical trials using c-MET inhibitors and provide an overview of the molecular mechanisms by which c-MET inhibition in these lesions represents a potential precision-medicine targeted approach.

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Leonard Y M Cheung and Karine Rizzoti

In the last 15 years, single-cell technologies have become robust and indispensable tools to investigate cell heterogeneity. Beyond transcriptomic, genomic and epigenome analyses, technologies are constantly evolving, in particular toward multi-omics, where analyses of different source materials from a single cell are combined, and spatial transcriptomics, where resolution of cellular heterogeneity can be detected in situ. While some of these techniques are still being optimized, single-cell RNAseq has commonly been used because the examination of transcriptomes allows characterization of cell identity and, therefore, unravel previously uncharacterized diversity within cell populations. Most endocrine organs have now been investigated using this technique, and this has given new insights into organ embryonic development, characterization of rare cell types, and disease mechanisms. Here, we highlight recent studies, particularly on the hypothalamus and pituitary, and examine recent findings on the pancreas and reproductive organs where many single-cell experiments have been performed.

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Yujia Pan, Weikang Yun, Bingshuai Shi, Rongjun Cui, Chi Liu, Zhong Ding, Jialin Fan, Wenqian Jiang, Jiebing Tang, Tianhu Zheng, Xiaoguang Yu and Ying Liu

miR-146b-5p is overexpressed in papillary thyroid carcinoma (PTC) and is thought to be a related diagnostic marker. Previous studies have indicated the effects of iodine on oncogenic activation. However, the effect of iodine on the proliferation of PTC cells and the associated underlying mechanisms remain unclear. We found that miR-146b-5p was downregulated and smad4 was upregulated in patients exposed to high iodine concentration by in situ hybridisation (ISH) and immunohistochemical (IHC). NaI (10−3 M) treatment downregulated miR-146b-5p and upregulated Smad4 in PTC cell lines. Luciferase assay was used to confirm that Smad4 is a target of miR-146b-5p. Furthermore, MTT assay and cell cycle analysis indicated that 10−3 M NaI suppressed cell proliferation and caused G0/G1 phase arrest. Real-time PCR and Western blotting demonstrated that 10−3 M NaI increased p21, p27, and p57 levels and reduced cyclin D1 levels in PTC cells. Our findings suggest that 10−3 M NaI increases Smad4 levels through repression of miR-146b-5p expression, curbing the proliferation in PTC.

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Kai Huang, Gezi Chen, Wenqian Fan and Linli Hu

A receptive endometrium is required in a successful embryo implantation. The ubiquitination-induced β-catenin degradation is related to the implantation failure.This study aimed to elucidate whether miR-23a-3p regulates endometrial receptivity via the modulation of β-catenin ubiquitination.The expressions of miR-23a-3p and CUL3 were detected in endometrial epithelial cells (EECs) isolated from pregnant mice and in hormone-induced EEC-like Ishikawa cells. The ubiquitination experiment was performed to explore the effect of CUL3 and miR-23a-3p on β-catenin ubiquitination level. The trophoblast attachment was detected by co-culturing JAR (choriocarcinoma cell line) spheroids with Ishikawa cell monolayers. miR-23a-3p was upregulated while CUL3 was downregulated in EECs at day 4 after pregnancy compared with day 1, as well as in hormone-induced Ishikawa cells. miR-23a-3p positively regulated the protein level of β-catenin without affecting the mRNA level. The ubiquitination and degradation of β-catenin was suppressed by miR-23a-3p, while it was promoted by CUL3. Immunoprecipitation confirmed the binding between CUL3 and β-catenin. Luciferase reporter assay confirmed the target relationship between miR-23a-3p and CUL3. The ubiquitination of β-catenin was modulated by the miR-23a-3p/CUL3 pathway. The overexpression of miR-23a-3p promoted JAR spheroid attachments in Ishikawa cells. miR-23a-3p is beneficial for the endometrial receptivity and embryo implantation, whose mechanism is partly through the modulation of CUL3/β-catenin.

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Dimitrios Doultsinos and Ian Mills

Prostate cancer is a high-incidence male cancer, which is dependent on the activity of a nuclear hormone receptor, the androgen receptor (AR). Since the AR is required for both normal prostate gland development and for prostate cancer progression, it is possible that prostate cancer evolves from perturbations in AR-dependent biological processes that sustain specialist glandular functions. The archetypal example of course is the use of prostate specific antigen (PSA), an organ-type specific component of the normal prostate secretome, as a biomarker of prostate cancer. Furthermore, localised prostate cancer is characterised by a low proliferative index and a heterogenous array of somatic mutations aligned to a multifocal disease pattern. We and others have identified a number of biological processes that are AR dependent and represent aberrations in significant glandular processes. Glands are characterised by high rates of metabolic activity including protein synthesis supported by co-dependent processes such as glycosylation, organelle biogenesis and vesicle trafficking. Impairments in anabolic metabolism and in protein folding/processing will inevitably impose proteotoxic and oxidative stress on glandular cells and, in particular, luminal epithelial cells for which secretion is their primary function. As cancer develops there is also significant metabolic dysregulation including impaired negative feedback effects on glycolytic and anabolic activity under conditions of hypoxia and heightened protein synthesis due to dysregulated PI 3-kinase/mTOR activity. In this review we will focus on the components of the AR regulome that support cancer development as well as glandular functions focussing on the unfolded protein response and on regulators of mTOR activity.

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Rebecca Roy, Caitlyn Nguyen-Ngo and Martha Lappas

Gestational diabetes mellitus (GDM) affects up to 16% of pregnant women and is associated with significant long-term health detriments for the mother and her offspring. Two central features of GDM are low-grade inflammation and maternal peripheral insulin resistance, therefore therapeutics which target these may be most effective at preventing the development of GDM. Short-chain fatty acids (SCFAs), such as butyrate and propionate, are metabolites produced from the fermentation of dietary fibre by intestinal microbiota. SCFAs possess anti-inflammatory, anti-obesity and anti-diabetic properties. Therefore, this study aimed to investigate the effect of SCFAs on inflammation and insulin signalling defects in an in vitro model of GDM. Human placenta, visceral adipose tissue (VAT) and s.c. adipose tissue (SAT) were stimulated with either the pro-inflammatory cytokine TNF or bacterial product lipopolysaccharide (LPS). The SCFAs butyrate and propionate blocked TNF- and LPS-induced mRNA expression and secretion of pro-inflammatory cytokines and chemokines in placenta, VAT and SAT. Primary human cells isolated from skeletal muscle were stimulated with TNF to assess the effect of SCFAs on inflammation-induced defects in the insulin signalling pathway. Butyrate and propionate were found to reverse TNF-induced increases in IRS-1 serine phosphorylation and decreases in glucose uptake. Butyrate and propionate exerted these effects by preventing ERK activation. Taken together, these results suggest that the SCFAs may be able to improve insulin sensitivity and prevent inflammation induced by sterile or bacterial inflammation. Future in vivo studies are warranted to investigate the efficacy and safety of SCFAs in preventing insulin resistance and inflammation associated with GDM.

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Hong Zhu, Wei Cao, Peng Zhao, Jieyu Wang, Yuying Qian and Yun Li

The excessive activation of renin-angiotensin system (RAS) is one of key pathophysiological characteristics in the development of cardiac remodelling. Angiotensin (Ang) II, as a main active peptide in RAS, induces cardiac structural disorders and dysfunction. However, the molecular mechanisms are still not fully disclosed. Present study aimed to determine the role and potential mechanisms of cardiac TIR-domain-containing adapter-inducing interferon-β (TRIF) in Ang-II-mediated cardiac remodelling in mice. In vitro and in vivo studies showed Ang II and downstream aldosterone obviously increased the expression of TRIF, accompanied with cardiac structural abnormalities and functional injuries. Specific blockage of cardiac TRIF effectively decreased Ang-II/aldosterone-induced cardiac inflammation, fibrosis, hypertrophy and dysfunction in mice. Mechanistically, the TRIF triggered the activation of EGF receptor (EGFR) signalling by nuclear factor (NF)-κB transcriptional regulation and downstream EGFR ligands. Taken together, present study supported that cardiac TRIF was a potential therapeutic target for attenuating cardiac pathophysiological remodelling. The TRIF/EGFR axis partially explained the molecular mechanism of Ang-II/aldosterone-induced cardiac inflammation, fibrosis, hypertrophy and dysfunction in mice.

Open access

Miguel Beato, Roni H G Wright and François Le Dily

Gene regulation by steroid hormones has been at the forefront in elucidating the intricacies of transcriptional regulation in eukaryotes ever since the discovery by Karlson and Clever that the insect steroid hormone ecdysone induces chromatin puffs in giant chromosomes. After the successful cloning of the hormone receptors toward the end of the past century, detailed mechanistic insight emerged in some model systems, in particular the MMTV provirus. With the arrival of next generation DNA sequencing and the omics techniques, we have gained even further insight into the global cellular response to steroid hormones that in the past decades also extended to the function of the 3D genome topology. More recently, advances in high resolution microcopy, single cell genomics and the new vision of liquid-liquid phase transitions in the context of nuclear space bring us closer than ever to unravelling the logic of gene regulation and its complex integration of global cellular signaling networks. Using the function of progesterone and its cellular receptor in breast cancer cells, we will briefly summarize the history and describe the present extent of our knowledge on how regulatory proteins deal with the chromatin structure to gain access to DNA sequences and interpret the genomic instructions that enable cells to respond selectively to external signals by reshaping their gene regulatory networks.