Mus musculus domesticus strain:C57BL/6J Transcriptome or Gene expression. Mus musculus domesticus strain:C57BL/6J

The maintenance of cycling cell lineages relies on undifferentiated subpopulations consisting of stem and progenitor pools. Features that delineate these cell types are undefined for many lineages including spermatogenesis which is supported by an undifferentiated spermatogonial population. Here, we generated a transgenic mouse line in which spermatogonial stem cells are marked by expression of an Id4-Gfp transgene. We found that Id4-Gfp+ cells exist primarily as a subset of the type Asingle pool and their frequency is greatest in neonatal development then decreases in proportion during establishment of the spermatogenic lineage, eventually comprising ~2% of the undifferentiated spermatogonial population in adulthood. RNA-sequencing analysis revealed that expression of 11 and 25 genes is unique for the Id4-Gfp+/stem cell and Id4-Gfp-/progenitor fractions, respectively. Collectively, these findings provide the first definitive evidence that stem cells exist as a rare subset of the Asingle pool and reveal transcriptome features distinguishing stem cell and progenitor states within the mammalian male germline.