A Nanos3-containing protein complex activates RNA translation in primordial germ cells in vivo

Maintaining the germline fate requires tight post transcriptional control of RNA function. Here, we investigate how primordial germ cell identity is maintained in zebrafish and reveal that a complex formed by the conserved RNA binding proteins Nanos3 and Dead End1 plays a novel role in activating translation in vivo. Using transcriptomics and in vivo imaging-based analyses, we show that this complex controls the localization and translational activation of both nanos3 and dead end1 RNAs, establishing a positive feedback loop crucial for regulating their protein expression. These findings uncover a previously unknown layer of control over germline development, where a complex containing Nanos3, a protein associated with inhibiting RNA translation, acts as an activator by interacting with the eIF3 complex to activate translation and maintain specific RNAs at the periphery of phase separated germ cell granules. Disrupting the physical interaction between Nanos3 and Dead End1 leads to transdifferentiation of germ cells into somatic lineages. Overall, our findings identify a self-sustaining mechanism of translational activation in vivo, positioning the Nanos3 and Dead End1 complex as a central effector of germline fate.