Gonadotropin-inhibitory hormone (GnIH) receptor gene is expressed in the chicken ovary: potential role of GnIH in follicular maturation

Abstract

Gonadotropin-inhibitory hormone (GnIH), an RFamide peptide, has been found to inhibit pituitary LH secretion in avian and mammalian species. The gene encoding a putative receptor for GnIH (GnIHR) was recently identified in the chicken and Japanese quail brain and pituitary gland. GnIHR appears to be a seven-transmembrane protein belonging to a family of G-protein-coupled receptors. In the present study, we have characterized the expression of GnIHR mRNA in the chicken ovary and demonstrate that GnIHR may exert an inhibitory effect on ovarian follicular development. By RT-PCR, we detected GnIHR mRNA in the chicken testis and in the ovary, specifically both thecal and granulosa cell layers. Real-time quantitative PCR analysis revealed greater GnIHR mRNA quantity in theca cells of prehierarchial follicles compared with that of preovulatory follicles. GnIHR mRNA quantity was significantly decreased in sexually mature chicken ovaries versus ovaries of sexually immature chickens. Estradiol (E 2 ) and/or progesterone (P 4 ) treatment of sexually immature chickens significantly decreased ovarian GnIHR mRNA abundance. Treatment of prehierarchial follicular granulosa cells in vitro with chicken GnIH peptide significantly decreased basal but not FSH-stimulated cellular viability. Collectively, our results indicate that the ovarian GnIHR is likely to be involved in ovarian follicular development. A decrease in ovarian GnIHR mRNA abundance due to sexual maturation or by E 2 and/or P 4 treatment would implicate an inhibitory role for GnIHR in ovarian follicular development. Furthermore, GnIH may affect follicular maturation by decreasing the viability of prehierarchial follicular granulosa cells through binding to GnIHR.

Effects of gonadotropin-inhibitory hormone on folliculogenesis and steroidogenesis of cyclic mice

“…Because receptors for GnIH are also expressed in gonadal tissue of birds (29) and rhesus monkey (Macaca mulatta) (47), there is a potential for a highly localized autocrine or paracrine effect of GnIH on gonads. GnIH-R mRNA have been localized in the theca and granulosa cells, with significantly lower levels found in preovulatory follicles than in smaller growing follicles (30). The earlier finding showing presence of GnIH-R in the ovary together with the findings of present in vivo and in vitro study suggests intraovarian effects of GnIH in mice.…”

“…Whether these effects of GnIH on testes are exerted through suppression of pituitary gonadotropin synthesis and/or they are due to direct action of GnIH on testes is not clear. Recent studies indicate that the avian reproductive system (female and male gonads, epididymis) has the capability to synthesize and bind GnIH (29,30).…”

Apoptosis-mediated testicular alteration in Japanese quail (Coturnix coturnix japonica) in response to temporal phase relation of serotonergic and dopaminergic oscillations

“…The presence of GnIH-R has been detected in the testes and ovaries of several vertebrate species, including birds (McGuire and Bentley, 2010), and putative GnIH binding sites have been demonstrated in the granulosa cell layer by receptor fluorography in birds . GnIH-R mRNA has been localized in the theca and granulosa cells, with significantly lower levels found in preovulatory follicles than in smaller growing follicles (Maddineni et al, 2008). Singh et al (2011) has demonstrated the direct inhibitory effect of GnIH on ovarian steroidogenesis in mice.…”

Identification and association of single-nucleotide polymorphisms in gonadotropin-inhibitory hormone (GnIH) gene with egg production traits in Erlang mountainous chickens

“…Thus, variations within genes have important effects on biological traits. Previous studies on the chicken genome have shown higher GnIH expression at sexual maturity in chicken ovaries, diencephalon (Maddineni et al, 2008b), and follicular maturation (Maddineni et al, 2008a). In the chicken hypothalamus, pituitary, ovary, and oviduct, GnIH mRNA expression of broody and after brooding chickens was higher than that of laying hens (He, 2009).…”