Implication of nanos2-3'UTR in the expression and function of nanos2.

Translational control of gene expression is an important component of the regulation of cellular differentiation and development. To elucidate the function of the 3'untranslated region (UTR) of the nanos2 gene in mice, we compared the phenotypes of lacZ knock-in mice with or without a native nanos2 3'UTR and found that this region of the nanos2 gene has a potential role during translational regulation in germ cells. The nanos2-3'UTR functions to repress the translation of mRNA in oocytes, but enhances the production of protein in the male gonads. To further understand the significance of the nanos2 3'UTR in vivo, we generated the mouse line nanos2pA/pA, which lacks this region endogenously. In nanos2(-/pA) mice, the number of germ cell-depleted seminiferous tubules was increased when compared with that of nanos2pA/pA mice, indicating a dose-dependent defect in spermatogenesis. These results suggest that the level of nanos2 protein is critical for normal spermatogenesis, and that this pathway may be regulated through the nanos2-3'UTR. We found that the defects in nanos2pA/pA and nanos2(-/pA) mice were caused by apoptosis of gonocytes in the embryonic gonads and gonocyte/spermatogonia in neonatal testes. In addition, it was noted that the nanos2 expression was restricted to a particular subset of spermatogonia after birth, which indicates that nanos2 plays a role in the maintenance and differentiation of gonocytes/spermatogonia in neonatal testes.