Sox9 and Vasa Gene Expression During Gonadal Differentiation in Larvae of the Urodele Amphibian Ambystoma mexicanum

The study of genes involved in sexual differentiation, as Vasa and Sox9 , is of great importance, as they serve as specific markers for the germline and the male differentiation pathway, respectively. This study characterized using immunofluorescence the expression of the Vasa and Sox9 genes and laminin during gonadal differentiation in larvae at stages (S) 50, 53, 55, 57 and in 3 months‐old urodele amphibian Ambystoma mexicanum . At S50 and S53, laminin delineated the gonad‐mesonephros complex and the medullary and cortical regions of the differentiating gonad; Sox9 was detected in somatic cell nuclei and Vasa was expressed in the cytoplasm of germ cells. During gonadal differentiation at S55 and S57, laminin delimited the ovarian cavity and, in the testes, surrounded the testicular cords; Sox9 and Vasa maintained the expression patterns observed at earlier stages. In 3 months‐old ovaries, laminin was detected surrounding the follicles, Sox9 expression was absent and Vasa was expressed in the peripheral cytoplasm of oocytes; in the testes, laminin surrounded the testicular cords, Sox9 was expressed in Sertoli cell nuclei and Vasa was detected in spermatogonia. These results suggest that, in A. mexicanum , Sox9 and Vasa are conserved genes that likely perform functions analogous to those observed in other vertebrates.