Mass dedifferentiation

Germline stem cells (GSCs) on their way to differentiation can change their minds and return to pluripotency, according to Toshie Kai and Allan Spradling (Carnegie Institution of Washington, Baltimore, MD). Such a return is a long-sought goal for those hoping to create pluripotent cells for transplantation.

GSCs in the adult fly reside in a niche where they receive Dpp signals telling them to remain undifferentiated. Upon division, one daughter escapes the niche (and the realm of Dpp) and expresses Bam. The freed cell thus differentiates into a cyst–a set of up to 16 cells interconnected by incomplete cytokinesis and a cytoskeletal structure called the fusome.

Kai and Spradling show that these steps toward differentiation can be undone with Dpp. They overexpressed Dpp in flies to form many GSCs, then induced a transient...