Retinoic acid dependent spermatogonial differentiation in mice

Spermatogonial differentiation is a developmental process that is essential for spermatogenesis, but the molecular and cellular changes that germ cells must undergo to transition from undifferentiated spermatogonia to differentiating spermatogonia remain largely undefined. Retinoic acid (RA) is necessary and sufficient for spermatogonial differentiation. Using the postnatal mouse testis, we examine the transcriptome changes that accompany spermatogonial differentiation. Spermatogenesis was synchronized by administration of potent and selective RA synthesis inhibitor; as a result, testes contained only undifferentiated spermatogonia. Then, the inhibitor was discontinued, and mice were given a single dose of exogenous RA to initiate spermatogonial differentiation. We measured transcriptomes in FACS-enriched germ cells either before RA administration, when the cells correspond to Aal spermatogonia (and a minor contribution of spermatogonial stem cells) or at two points after RA administration, when the cells correspond to A1 or A3 differentiating spermatogonia. The results of this study reveal the full transcriptome changes accompanying spermatogonial differentiation in the mouse. WIN 18,446 treatment through P10 blocked normal spermatogonial differentiation and thus testes at P11 were filled with STRA8-/KIT- undifferentiated stem and progenitor spermatogonia. At P11, a single injection of exogenous RA induced all spermatogonia (save for the spermatogonial stem cells, or SSCs) to differentiate. RA is extremely labile (half-life in mice <0.5 hr), and thus is not expected to persist in the testis past P12. Twenty-four hrs later in these ‘RA-sufficient’ testes, nearly all spermatogonia were STRA8+/KIT+ type A1 differentiating spermatogonia that continued differentiating (A3). This study is paired with GSE194376.