GSE107694
Purification of GFRa1+ and GFRa1- spermatogonial stem cells reveals a niche-dependent mechanism for fate determination
Undifferentiated spermatogonia comprise a pool of stem cells and progenitor cells that show heterogeneous expression of markers, including the cell surface receptor GFRa1. Technical challenges in isolation of GFRa1+ versus GFRa1- undifferentiated spermatogonia have precluded the comparative molecular characterization of these subpopulations and their functional evaluation as stem cells. Here, we develop a method to purify these subpopulations by FACS and show that GFRa1+ and GFRa1- undifferentiated spermatogonia both demonstrate elevated transplantation activity while differing principally in receptor tyrosine kinase signaling and cell cycle. We identify the cell surface molecule MCAM as differentially expressed in these populations and show that antibodies to MCAM allow isolation of highly enriched populations of GFRa1+ and GFRa1- spermatogonia from adult, wild-type mice. In germ cell culture, GFRa1- cells upregulate MCAM expression in response to GDNF/FGF stimulation. In transplanted hosts, GFRa1- spermatogonia yield GFRa1+ spermatogonia and restore spermatogenesis, albeit at lower rates than their GFRa1+ counterparts. Together, these data provide support for a model of a stem cell pool in which the GFRa1+ and GFRa1- cells are closely related, but show key cell-intrinsic differences and can interconvert between the two states based, in part, on access to niche factors. Overall design: RNA-Seq transcriptional analysis of three stem cell and progenitor populations isolated from the testis of adult Tert-Tomato reporter mice and gonocytes isolated from day 6 (P6) neonates.