Involvement of the transcriptional coactivator NCOA7 during initial stages of gametogenesis of gametogenesis in European sea bass (Dicentrarchus labrax)

Trabajo presentado en el 6th International Workshop on the Biology of Fish Gametes, celebrado en Vodňany (República Checa), del 4 al 7 de septiembre de 2017Recent studies in European sea bass using a hemigonadectomy approach and transcriptomic analyses have revealed several genes potentially involved in the onset of puberty in female gonads. One of these genes is ncoa7 that encodes a nuclear receptor co-activator that, in mammals, increases the transcriptional activity of the estrogen receptor (Esr). This study is aimed at the molecular and functional characterization of the ncoa7 gene and its role during gametogenesis. We have cloned the complete cDNA of sea bass ncoa7 and studied its expression in different male and female tissues showing high expression in brain and gonads. Functional analyses using HEK293 cells co-transfected with Ncoa7 together with the estrogen, androgen and progesterone receptors, and exposed to E2, Testosterone or 17,20ß-P, showed that Ncoa7 is able to increase the transcriptional activity of all the different receptors, suggesting that can control different processes in early gametogenesis. Quantification of the expression of ncoa7, esr1, esr2a and esr2b in the ovary and testis of adult sea bass during a whole reproductive cycle showed different expression patterns among stages. In females, an increase of ncoa7 expression is observed during vitellogenesis coinciding with an increase of esr2b expression and E2 levels in the ovary, reinforcing the hypothesis that Ncoa7 is involved in the onset of puberty in female sea bass. In males, the highest expression of ncoa7 was observed in immature testes overlapping with the highest expression of esr1 and high levels of E2 in plasma. In addition, Ncoa7 and Esr1 colocalized in type A spermatogonia of immature testis, and further co-immunoprecipitation studies demonstrated that Ncoa7 was bound to Esr1 in these gonads. Finally, treatment of immature testis with E2 increased proliferation of type A spermatogonia as found by phospho-Histone H3 (Ser10) immunocytochemistry, what together with the previous results suggest that both factors may be involved in spermatogonia proliferation.Funded by AGL2015-67477-C2-1-R, Aquagenomics (CSD2007-00002), PROMETEOII-214/051.Peer reviewe