Expression of the Sox9, Foxl2, Vasa, and TRPV4 genes in the ovaries and testes of the Morelet's crocodile, Crocodylus moreletii.

The Sox9 gene is important for determining sex in vertebrates, as well as for maintaining testis morphology and fertility during adult life. In the same way, Vasa is an important gene for the maintenance of the germinal lineage and has been highly conserved throughout evolution, as it is expressed in germ cells of both vertebrates and invertebrates. In the particular case of crocodiles, the expression of Sox9 during gonadal morphogenesis and in the testes of 3-month-old Alligator mississippiensis has been studied. However, it is interesting to carry out studies on other species of crocodiles in relation to their particular mechanism for sex determination influenced by temperature. In this work, we investigated the expression of the Sox9, Vasa, Foxl2, and TRPV4 genes in the ovaries and testes of 5-year-old juvenile crocodiles from Crocodylus moreletii. As expected, Sox9 expression was found in males, but surprisingly, it was also found in females. For the first time, the expression of Vasa was reported in spermatogonia, oogonia, and oocytes of 5-year-old crocodiles. Foxl2 is important for the development and maintenance of the ovary during adult life in vertebrates; moreover, Foxl2 protein and transcripts are both highly expressed in the ovaries compared to the testes. A possible upstream regulator of the Sox9 gene in reptiles has not yet been discovered; as such, the expression of the TRPV4 ion channel was evaluated. The TRPV4 ion channel was expressed in the cytoplasm of Sertoli and follicular cells and was therefore proposed as a possible regulator of SOX9.