Meeting Abstract
11.2 Thursday, Jan. 3 Kisspeptin Stimulates GnRH Synthesis and Release in Atlantic Croaker KHAN, IA*; KLINE, RJ; GALIMA, MM; MOHAMED, JS; Univ. of Texas at Austin; Univ. of Texas at Austin; Univ. of Texas at Austin; Baylor College of Medicine, Houston ikhan@utmsi.utexas.edu
There is considerable evidence that kisspeptin (KiSS) stimulates gonadotropin-releasing hormone (GnRH-I) release by acting via its G protein-coupled receptor (GPR54) in mammals. However, a KiSS-like natural ligand for GPR54 has not been identified in any non-mammalian species. In this study, the cDNAs of KiSS and GPR54 were isolated from the brain of Atlantic croaker, Micropogonias undulatus. In addition, levels of GPR54 and three GnRH mRNAs were quantified in dissected brain areas by real-time quantitative RT-PCR. The expression of three GnRH mRNAs in discrete brain areas was consistent with their localization by in situ hybridization. Interestingly, GPR54 mRNA expression also was higher in anterior brain regions where GnRH neurons have been localized. Moreover, localization of GPR54 protein on GnRH neuronal elements by immunocytochemistry provides a morphological basis for GPR54-mediated actions on GnRH in fish at multiple levels of the neuroendocrine organization, including the preoptic-anterior hypothalamic area (POAH) and pituitary. The results of this study also demonstrate that mammalian KiSS stimulates both the synthesis of seabream GnRH (GnRH-I) in the POAH and its release from POAH and pituitary slices. Taken together, these data strongly suggest that the KiSS-GPR54 neuroendocrine pathway controlling GnRH may be functional also in fish. To our knowledge, this is the first report of the stimulatory effects of KiSS on both the synthesis and release of GnRH. Further, the discovery of KiSS cDNAs in Atlantic croaker and some other non-mammalian vertebrates will facilitate future investigations on KiSS-GPR54 interactions in these species. This study was supported by grants from NIH, Sid Richardson Memorial Fund and UT-Austin.
