Riding the spermatogenic wave: profiling gene expression within neonatal germ and sertoli cells during a synchronized initial wave of spermatogenesis in mice.

Continual sperm production relies on germ cells undergoing spermatogenesis asynchronously. As a result, the testis always contains a mixed population of germ cells at different stages of their differentiation process. The heterogeneous nature of the testis makes profiling gene expression within Sertoli cells or specific populations of germ cells impossible when a wild-type testis is assessed. We recently reported a unique method for synchronizing spermatogenesis without affecting fertility by manipulating RA levels within the neonatal testis. Using this protocol, combined with the RiboTag transgenic mouse line, we have mapped the Sertoli and germ cell translatome during the initial synchronized wave of spermatogenesis. Using microarray analysis, we identified 392 and 194 germ cell and Sertoli cells transcripts, respectively, that dynamically change during spermatogonial differentiation, division, and the onset of meiosis. Functional annotation clustering revealed that transcripts enriched in germ cells were mostly associated with meiosis (21 transcripts), chromatin organization (12 transcripts), and cell cycle (3 transcripts). In addition, glycoproteins (65 transcripts), cell adhesion (15 transcripts), and cell junction (13 transcripts) transcripts were overrepresented in the Sertoli cell-enriched list. These datasets represent the first transcriptional analysis of spermatogonial differentiation, division, and meiotic onset. These data suggest that several of the genes encoding meiotic proteins are expressed and are actively being translated well before germ cells enter meiosis. In addition, this study provides novel candidate genes, Asf1b and Esyt3, that may be involved in the regulation of spermatogonial chromatin reorganization, germ-Sertoli cell interactions, and/or blood-testis barrier formation.