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

Abstract

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.