Dynamics of Sox2 expression during rat germ cell development and its relationship with emergence of spermatogonia

1.The gonocytes represent a specific phase of male gem cell development that precedes spermatogonial stem cell differentiation. Here, we describe the expression of Sox2, an OCT4 partner, during rat germ cell development. Our hypothesis is that SOX2 has a cytoplasmic role during gonocyte-to-spermatogonia transition. Male rat embryos and testes were submitted to the analysis of Sox2 expression. Sox2 was detected in germ cells from 14 days post-conception (dpc) to 8dpp. SOX2 was present in 14dpc and 15dpc embryos and absent at 17 and 19dpc; however, it did not show direct correlation with mRNA. SOX2 labelling was detected after birth and its expression increased from 1dpp to 5dpp. SOX2 was localized in the cytoplasm and showed a granulated pattern similar to P-bodies. Indeed, GW182/SOX2 and LIN28/SOX2 double-labelling showed that SOX2 partially co-localized with the P-bodies components GW182 and LIN28. At 8dpp SOX2 was detected in the nucleus and/or in the cytoplasm of spermatogonia, whereas at 25dpp it was detected in the nucleus of rare spermatogonia. This suggests that SOX2 localization changes during gonocytes to spermatogonia transition.