ES-mediated chimera analysis revealed requirement of DDX6 for NANOS2 localization and function in mouse germ cells

In embryonic male germ cells, the RNA-binding protein NANOS2 recruits its target RNAs to processing bodies (P-bodies), where they are repressed. This process is necessary to promote male-type germ cell differentiation. However, it remains unclear whether all NANOS2 functions depend on P-bodies. To address this question, we established ES cell lines containing a germ cell-specific inducible Cre and reporter together with the floxed Ddx6 allele. We deleted the Ddx6 gene by administering tamoxifen to chimeric embryos containing germ cells derived from recombinant ES cells. DDX6-null germ cells exhibited both similar and distinct defects from those observed in NANOS2-null germ cells. These results demonstrate that NANOS2 function is carried out via both P-body-dependent and -independent mechanisms. RNA-seq analyses further supported the phenotypic differences between DDX6-null and NANOS2-null germ cells, and indicated distinct molecular cascades involved in NANOS2-mediated gene regulation.