PTEN and TRP53 Independently Suppress Nanog Expression in Spermatogonial Stem Cells

Mammalian spermatogonial stem cells are a special type of adult stem cells because they can contribute to the next generation. Knockout studies have indicated a role for TRP53 and PTEN in insulating male germ cells from pluripotency, but the mechanism by which this is achieved is largely unknown. To get more insight in these processes, an RNAi experiment was performed on the mouse spermatogonial stem cell line GSDG1. Lipofectamine-mediated transfection of siRNAs directed against Trp53 and Pten resulted in decreased expression levels as determined by quantitative RT-PCR and immunoblotting. The effects of knockdown were examined by determining the expression levels of genes that are involved in reprogramming and pluripotency of cells, specifically Nanog, Eras, c-Myc, Klf4, Oct4, and Sox2. Additionally, the effects of TRP53 or PTEN knockdown on Plzf and Ddx4 expression were measured, which are highly expressed in spermatogonial stem cells and differentiating male germ cells, respectively. The main finding of this study is that knockdown of Trp53 and Pten independently resulted in significantly higher expression levels of the pluripotency-associated gene Nanog, and we hypothesize that TRP53 and PTEN mediated repression is important for the insulation of male germ cells from pluripotency.