Germline proliferation and its control.

The C. elegans germ line proliferates from one primordial germ cell (PGC) set aside in the early embryo to over a thousand cells in the adult. Most germline proliferation is controlled by the somatic distal tip cell, which provides a stem cell niche at the distal end of the adult gonad. The distal tip cell signals to the germ line via the Notch signaling pathway, which in turn controls a network of RNA regulators. The FBF-1 and FBF-2 RNA-binding proteins promote continued mitoses in germ cells located close to the distal tip cell, while the GLD-1, GLD-2, GLD-3, and NOS-3 RNA regulators promote entry into meiosis as germ cells leave the stem cell niche. In addition to these key regulators, many other genes affect germline proliferation.