EMBRYONIC POLARITY AND THE SOMA-GERMLINE DICHOTOMY
Multicellular organisms consist of two general cell types: somatic cells, which form the individual body, and germ cells, which are used for reproduction. Because the germline is the only lineage to contribute its genetic material to the next generation, it is often referred to as an immortal and totipotent lineage, capable of "outliving" its somatic host and regenerating an entire organism. These characteristics are essential for reproduction and species survival, yet the molecular mechanisms that distinguish germ cells from somatic cells are still largely unknown.
My laboratory is using genetic and molecular approaches to characterize these mechanisms in the nematode Caenorhabditis elegans. We have identified one mechanism that distinguishes germline from soma in embryos: global repression of mRNA transcription in the earliest precursors to the germline. This silencing prevents nascent germ cells from adopting somatic fates. Since our findings in C. elegans, transcriptional silencing in early germ cells has been observed in other species. A repressed genome, therefore, may be essential to preserve the unique developmental potential of the germline.