Polycomb Limits the Neurogenic Competence of Neural Precursor Cells to Promote Astrogenic Fate Transition

During neocortical development, neural precursor cells (NPCs, or neural stem cells) produce neurons first and astrocytes later. Although the timing of the fate switch from neurogenic to astrogenic is critical for determining the number of neurons, the mechanisms are not fully understood. Here, we show that the polycomb group complex (PcG) restricts neurogenic competence of NPCs and promotes the transition of NPC fate from neurogenic to astrogenic. Inactivation of PcG by knockout of the Ring1B or Ezh2 gene or Eed knockdown prolonged the neurogenic phase of NPCs and delayed the onset of the astrogenic phase. Moreover, PcG was found to repress the promoter of the proneural gene neurogenin1 in a developmental-stage-dependent manner. These results demonstrate a role of PcG: the temporal regulation of NPC fate.