Hormonal Regulation of Vasa-Like Messenger RNA Expression in the Ovary of the Marine Teleost Sparus aurata

The vasa gene is an important maternal regulator of primordial germ cell (PGC) development in both vertebrate and invertebrate models. It is also expressed in the mature gonads, but its role in these tissues is still unclear. In oviparous species, oogenesis is a complex process under hormonal control: estrogens, gonadotropins, and other hormones operate at different stages of oogenesis, regulating meiosis, vitellogenesis, follicle maturation, and egg release. The aim of this work is the determination of a regulative role of hormones controlling oocyte maturation on vasa mRNA expression in the sea bream ovary through a molecular biology approach. By in situ hybridization and reverse transcription-polymerase chain reaction (RT-PCR), reaction (the vasa mRNA in the sea bream ovary was found to be expressed at higher levels in the advanced stages of oocyte maturation. After in vivo hormonal treatment, the effect on ovarian vasa mRNA expression was studied through semiquantitative RT-PCR. The quantification of vasa-like mRNA expression in sea bream ovary demonstrates that estradiol (E2), growth hormone (GH), and the combination of gonadotropin-releasing hormone (GnRH) with GH are able to induce an increase in vasa mRNA expression. In contrast, the treatments with GnRH alone or E2 plus GH significantly decreased vasa mRNA expression. These data suggest a regulative interplay between the vasa gene expression and the endocrine system that controls the oogenesis in the ovary of the sea bream.