Drosophila Polycomb complexes restrict neuroblast competence to generate motoneurons.

Similar to mammalian neural progenitors, Drosophila neuroblasts progressively lose competence to make early-born neurons. In neuroblast 7-1 (NB7-1), Kruppel (Kr) specifies the third-born U3 motoneuron and Kr misexpression induces ectopic U3 cells. However, competence to generate U3 cells is limited to early divisions, when the Eve(+) U motoneurons are produced, and competence is lost when NB7-1 transitions to making interneurons.