Oct4-GFP expression during transformation of gonocytes into spermatogonial stem cells in the perinatal mouse testis

Background/aimIn cryptorchidism perinatal failure to switch off Oct4, a germ cell (GC) marker, may lead to carcinoma in situ. We aimed to analyze Oct4 expression during mouse gonocyte transformation into spermatogonial stem cells (SSC).Materials and methodsTestes from OG2 (Oct4-promoter driven eGFP) mice at embryonic day (E) 17 and postnatal day P0-10 underwent immunohistochemistry and immunoblotting. Antibodies against MVH, AMH, Ki67, and c-Kit were visualized by confocal microscopy. Numbers of Oct4-GFP+ GC and Oct4-GFP− GC/tubule were counted using ImageJ. Data were analyzed using nonparametric one-way ANOVA.ResultsGC from E17-P4 were Oct4-GFP+. Numbers of Oct4-GFP− GC/tubule increased from P6-10, whereas Oct4-GFP+ GC/tubule numbers remained similar between P6 and P10. Sertoli cells proliferated from E17-P10, whereas GC only proliferated from P2. Gonocytes (Oct4-GFP+/c-Kit−) central in tubules migrated to the basement membrane to become prospermatogonia (Oct4-GFP+/c-Kit−) and then SSC (Oct4-GFP+/c-Kit+) from day 4 and further developed into Oct4-GFP−/c-Kit+ at P6.ConclusionIn Oct4-GFP mice both centrally located gonocytes and prospermatogonia located at the tubular basement membrane were Oct4-GFP+/c-Kit− before further developing into SSC (Oct4-GFP+/c-Kit+). This indicates that Oct4 is important in gonocyte transformation into SSC. Understanding this process will aid GC tumor diagnostics and fertility potential in boys with UDT undergoing orchidopexy.