When eNOS was overexpressed in transgenic mice, the numbers of spermatocytes and spermatids in eNOS-Tg cryptorchid testes significantly decreased compared with those in wild-type cryptorchid testes from day 3, This suggested accelerated testicular germ cell apoptosis induced by experimental cryptorchidism (Ishikawa et al., 2005). Here, NOS3 is linked to cryptorchidism.