Stage-dependent and alternative splicing of sGnRH messengers in rainbow trout testis during spermatogenesis

The gonadotropin releasing hormone (GnRH) has long been considered as a neu ropeptide involved in the control of the reproductive cycle. However, the p resence of GnRH and its receptors in various tissues, including ovary and t estis, suggests a role as autocrine/paracrine factor. In the present study, we report the expression of the sGnRH-1 and sGnRH-2 genes encoding salmon GnRH in rainbow trout testis throughout testicular development and spermato genesis. We demonstrate that both sGnRH mRNA are expressed prior of sexual differentiation. In adult, northern blot analysis indicates that sGnRH-2 tr anscripts are expressed in the testis at higher levels than sGnRH-1 messeng ers. Moreover, we observed that the expression of sGnRH-2, and not sGnRH-1, messengers was stage-dependent. sGnRH-2 mRNA expression decreases at the o nset and progressively rebounds at the end of spermatogenesis. In addition, we demonstrate that a complex stage-dependent and differential splicing of the sGnRH-2 messengers occurs throughout spermatogenesis. We isolated five transcripts corresponding to sGnRH-2 messengers. Two of them may encode a novel and shortened GnRH-associated peptide containing 18 residues instead of 46. Our data provide new insight in the putative role of GnRH and GAP pe ptides as autocrine/paracrine factors of spermatogenesis. Mol. Reprod. Dev. 59:1-10, 2001. (C) 2001 Wiley-Liss, Inc.