Proliferation and migration of gonocytes, the precursors of spermatogonial stem cells, to the germline niche in the basal membrane of the seminiferous tubules, are two crucial events that take place between postnatal d 0.5 (P0.5) and P5.0 in the mouse and involve a selection of the cells that are committed to the germline stem cells lineage. Here we show that from embryonic d 18.0 (E18) and up to P5, the gonocytes express platelet-derived growth factor (PDGF) receptor β-subtype (PDGFR-β) and that during the same time period, the Sertoli cells express PDGF-B and PDGF-D, both ligands for PDGFR-β. Inhibition of the PDGFR-β tyrosine kinase activity during the first five postnatal days provokes a profound reduction of gonocyte number through inhibition of their proliferation and induction of apoptosis. Moreover,wefound that PDGFR-β ligands are chemotactic for gonocytes. These data suggest that PDGFR-β activation has the remarkable capability to drive the selection, survival, and migration of the gonocytes from the center of the seminiferous tubules to the testicular germline niche on the basal membrane.
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