Potential role of Nanos3 in maintaining the undifferentiated spermatogonia population

In this study, we show that, in prepuberal testis, Nanos3 is expressed in undifferentiated spermatogonia and that its up-regulation causes accumulation of cells in the G1 phase, indicating that this protein is able to delay the cell cycle progression of spermatogonial cells. This is in line with the observation that the cell cycle length of the undifferentiated germ cells is longer than in differentiating spermatogonia. We also demonstrate a conserved mechanism of action of Nanos3, involving the interaction with the murine RNA-binding protein Pumilio2 and consisting of a potential translational repressor activity. According to the possible role of Nanos3 in inhibiting spermatogonia cell differentiation, we show that treatment with the differentiating factor all-trans retinoic acid induces a dramatic down-regulation of its expression. These results allow to conclude that, in the prepuberal testis, Nanos3 is important to maintain undifferentiated spermatogonia via the regulation of their cell cycle.