Germ granules are cytoplasmic condensates that segregate asymmetrically in early embryos to specify germ cell fate. In this Issue, Madeline Cassani and Geraldine Seydoux show that germ granules in Caenorhabditis elegans embryos contain two types of condensates, P granules and germline P-bodies. Each contain different cargoes: P granules enrich maternal mRNAs, including the Nanos homolog nos-2, and germline P-bodies enrich mRNA regulators, including components typically found in P-bodies. They discover that the intrinsically disordered proteins MEG-1 and MEG-2 are key components of germline P-bodies. In the absence of MEG-1/2, canonical P-body markers such as CGH-1 (DDX6) and EDC-3 are no longer maintained at high levels in the germline founder cell and translational activation of nos-2 is reduced, even though nos-2 still enriches in P granules. The germline founder cell divides precociously in meg-1meg-2 mutants and its descendants express a muscle marker and fail to form germ cells. Together, these data suggest that germline P-bodies are the key condensates in germ granules that promote germ cell fate.
