Crosslinking and immunoprecipitation: a new route for dead end

Germline cells are the foundation of inheritance for genetic and epigenetic information from generation to generation. The precursors of germ cells, termed primordial germ cells (PGCs), are one of the earliest cell types specified during embryogenesis. There are two modes of PGC origin. In model organisms such as Drosophila, C. elegans, zebrafish, and Xenopus, germ cells are specified by the inheritance of germ plasm, which is composed of maternal proteins and RNAs. In contrast, in mouse and possibly most mammals including humans, PGCs are induced by local signals such as BMP4 and WNT (1).