Involvement of the retinoic acid signaling pathway in sex differentiation and pubertal development in the European sea bass .

Retinoic Acid (RA) is a vitamin A derivative present in many biological processes including embryogenesis, organ development and cell differentiation. The RA signaling pathway is essential for the onset of meiosis in tetrapods, although its role in fish reproduction needs further evidence. This study reports the expression profiles of several genes involved in this pathway during sex differentiation and the first reproductive season in European sea bass () gonads. The assessed genes are representative of several steps of the pathway including retinol transport, RA synthesis, nuclear receptors, RA transport and degradation. The study includes a synteny analysis of , a tetrapod meiosis gatekeeper, in several taxa. The results show that, these genes were overexpressed during early gonad development and their expression decreased during meiosis progression in males and during vitellogenesis in females. Specifically, a decrease of , involved in RA degradation, together with an increase of and , in charge of RA-synthesis, might ensure the availability of high RA levels at the time of meiosis in males and females. Moreover, the absence of in the European sea bass genome, as well as the conserved genomic neighbourhood found in other taxa, suggest a independent signaling for RA during meiosis. Taken together, our results might help to better understand the role of RA signaling in teleost gonad development.