Spermatogenesis is a complex process involving cell division and differentiation of Spermatogonial Stem Cells (SSCs), mediated by coordinated expression of a number of genes. The study of SSC biology was challenging due to the unavailability of proper SSC markers and their culture methods. In recent years, these hurdles have been somewhat overcome. A number of markers for undifferentiated spermatogonia are known to be involved in the process of SSC self-renewal. Oct-4 is one such marker expressed from Primordial Germ Cells (PGCs) of prenatal stages till undifferentiated spermatogonia of postnatal adult testes. Though, expressed by undifferentiated spermatogonia, its role in the process of their self-renewal, proliferation and differentiation is not clearly understood. In the current study, using shRNA mediated gene silencing approach, we show that Oct-4 silencing in undifferentiated type A spermatogonia leads to phenotypic differentiation of these cells to type A1-A4 spermatogonia, marked by the increased c-KIT expression, and decreased proliferation, marked by decreased PCNA expression. The study also demonstrates that Oct-4 silencing causes down-regulation of Plzf, Gfra-1, c-Ret, Bcl6b and Etv5 mRNA and protein. Therefore the current study suggests that Oct-4 does play an important role in deciding the fate of undifferentiated spermatogonia by controlling their proliferation and differentiation. In conclusion, the present study may provide useful insights into understanding the involvement of Oct-4 in proliferation and differentiation of undifferentiated spermatogonia in mice.