Vasa expression in spermatogenic cells during the reproductive-cycle phases of Podarcis sicula (Reptilia, Lacertidae).

The vasa gene encodes a DEAD-box ATP-dependent RNA helicase that regulates the translation of multiple mRNAs involved in germ line differentiation. This protein has been deeply studied in many animals, but few data are available to date on reptiles. In this work, we sequenced a portion of Podarcis sicula vasa gene (Ps-vasa), developed a specific antibody and verified its specificity. Using anti-Ps-Vasa and confocal microscopy, we studied Vasa expression in male germ cells during the reproductive cycle of P. sicula: during full gonadal activity (spring), during regression of gonadal activity (summer) and during slow autumnal recrudescence. We also analyzed Vasa expression in young testes when the walls of the seminiferous tubules were forming. The aim was to verify if Vasa is involved in the process of male germ cell differentiation in all phases of the reproductive cycle. In adult testes, during full gonadal activity and during recrudescence, Vasa staining was detected from spermatogonia to spermatids. Vasa spots were also observed in the nucleus of germ cells supporting its function in different cellular compartments. No Vasa staining was observed in mature spermatozoa during the spring and mid-late November. The seminiferous epithelium analyzed in the summer appeared reduced with only spermatogonia, all Vasa-immunostained, some in division to replace germ cells. In immature testes, the seminiferous epithelium contained only spermatogonia and spermatocytes. The clear immunostaining in their cytoplasm revealed that Vasa is already expressed in juvenile male gonads, suggesting a role in the differentiation process since P. sicula early developmental stages.