C. elegans germline stem cells and their niche

C. elegans germline stem cells are a particularly simple system for analysis of stem cell regulation. Their well-defined mesenchymal niche consists of a single cell, the Distal Tip Cell, which uses Notch signaling to maintain a pool of germline stem cells. Downstream of Notch signaling a post-transcriptional regulatory network dictates self-renewal or differentiation. The major self-renewal hub of that network is FBF, a conserved RNAbinding protein and conserved stem cell regulator. FBF represses mRNAs encoding key regulators of germline differentiation (entry into the meiotic cell cycle, sperm or oocyte specification) as well as established regulators of somatic differentiation. Transcriptional and post-transcriptional mechanisms also control totipotency in the C. elegans germline. The key C. elegans GSC regulators are conserved broadly, making this system a paradigm for stem cell regulation.