Reproductive endocrinology of the Senegalese sole (Solea senegalensis): recent advances and applications to aquaculture

Jornada Anual de la Secció d’Aqüicultura de la Societat Catalana de Biologia, Avenços en Recerca en Aqüicultura, 12 de Juny de 2015, Barcelona.-- 2 pages
The aquaculture of Senegalese sole is hampered by the absence of methods to control reproduction, and in particular by the low amount and quality of the sperm produced by cultured males. In Senegalese sole, spermatogenesis is semi-cystic and its endocrine control is largely unknown. In recent years, we have made significant progress in the understanding of sole spermatogenesis by focusing on the mechanism of action of the major reproductive hormones, the gonadotropins follicle-stimulating hormone (Fsh) and luteinizing hormone (Lh). The isolation of the transcripts encoding the sole Fsh and Lh subunits, as well as the Fsh and Lh receptors (Fshra and Lhcgrba), allowed us to produce recombinant hormones and specific antibodies to investigate the role of Fsh and Lh during spermatogenesis. Cell-based functional assays and immunolocalization studies showed that the sole Fshra is promiscuos (i.e. activated by both Fsh and Lh), and expressed in Sertoli cells enclosing the germ cells as well as in the androgen-producing Leydig cells. By contrast, the sole Lhcgrba is Lh-specific and only present in Leydig cells and spermatids free in the tubular lumen. Both Fsh and Lh control similar steroidogenic pathways in the testis, although Fsh also regulates genes encoding Sertoli cell growth factors, and Lh specifically activates spermatid-specific genes encoding spermatozoon proteins through direct interaction with the Lhcgrba in these cells. Finally, we have developed specific enzyme-linked immunosorbent assays (ELISAs) for Fsh and Lh that are being employed to determine the plasma levels of both gonadotropins during the reproductive cycle. All these molecular tools will allow the design of novel methods based on recombinant hormones for the control of sperm production in Senegalese sole, and the establishment of biomarkers to monitor reproductive success in cultured stocks