Orexin-A and -B are known to stimulate food intake in mammals. However, the critical roles of orexins in birds are not fully understood, since orexins have no stimulatory effect on food intake in the chicken. To understand the physiological role(s) of orexins in birds, we have cloned chicken orexin receptor (cOXR) cDNA by RT-PCR, and analysed the tIssue distribution of OXR mRNA in the chicken. The cOXR cDNA is 1869 bp long and encodes 501 amino acids. The cloned cDNA for cOXR corresponds to the type 2 OXR in mammals, and shows approximately 80% similarity to those of mammals at the amino acid level. Expression analysis by RNase protection assay revealed OXR mRNA was distributed widely in brain regions, and expression in the cerebrum, hypothalamus and optic tectum were abundant. In peripheral tIssues, OXR mRNA was expressed in the pituitary gland, adrenal gland and testis, but no mRNA expression was observed in other tIssues examined. Furthermore, we found that the amount of cOXR mRNA was different between testis and ovary, while prepro-orexin mRNA is equally expressed in the gonads of both sexes in the chicken. These data indicate that the orexins have neuroendocrine actions in chickens, which are mediated through hypothalamic receptors as has been observed in mammals. In addition, orexin may have specific role(s) in the regulation of gonadal function in which sex-dependent mechanisms could be involved.
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T Ohkubo, A Tsukada, and K Shamoto
T Ohkubo, M Araki, M Tanaka, S Sudo, and K Nakashima
ABSTRACT
The gene and 5′ flanking promoter region for yellowtail (Seriola quinqueradiata) GH (yGH) have been cloned, sequenced and characterized. The yGH gene spans approximately 4·6 kb and consists of six exons and five introns, as has been observed with rainbow trout, Atlantic salmon and tilapia GH genes. This result suggests that the structure of six exons and five introns is a dominant form in fish GH genes. A typical TATA box exists 26 bp upstream from the transcription start site, and Pit-1/GHF-1 (Pit-1) binding site-homologous regions were found in the promoter region of the yGH gene. In a gel shift assay, however, a single shifted band was detected with the fragments containing a region from −128 to −90 of the yGH 5′ flanking region when they were incubated with yellowtail pituitary nuclear extracts. The bound fragments contained an octamer base sequence similar, but not identical, to mammalian consensus Pit-1 binding element. A consensus octamer sequence is also proposed in this report for the binding of teleost and avian Pit-1 transcription factors.
