Expression profiles of kisspeptin system genes in the hypothalamus of the european sea bass during different gonadal stages

Abstract

Kisspeptins are now considered as key players in the neuroendocrine control of reproduction in vertebrates. The European sea bass (Dicentrarchus labrax) has two kiss genes (kiss1, kiss2) and two gpr54 receptors (gpr54-1b, gpr54-2b) that have been recently cloned and characterized. In this study, the relative mRNA expression profiles of kisspeptin system genes in the hypothalamus of adult male and female fish were analyzed in relation to the reproductive status using qRT-PCR. We also analyzed the expression of gnrh-1 in the hypothalamus and gnrhr-II-1a, fshbeta and lhbeta in the pituitary in order to investigate the relationship between both kisspeptin/gnrh systems in this perciform fish. Results demonstrated that the patterns of changes in all these genes followed the profile of the gonadosomatic index increase in females, showing high expression levels at the vitellogenesis and maturation-ovulation stages. In males, the tight association between these two neuroendorcine systems and the involvement of kisspeptins in the puberty onset was not evident. To date, the reproductive function of kisspeptins in fish merits further investigation.