Mouse numb is an essential gene involved in cortical neurogenesis

During neurogenesis of the mammalian neocortex, neural progenitor cells div ide to generate daughter cells that either become neurons or remain as prog enitor cells. The mouse numb (m-numb) gene encodes a membrane-associated pr otein that is asymmetrically localized to the apical cell membrane of divid ing cortical progenitor cells and may be segregated to only the apical daug hter cell that has been suggested to remain as a progenitor cell. To examin e m-numb function during neural development, we generated a loss-of-functio n mutant allele of m-numb. Mice homozygous for this mutation exhibit severe defects in cranial neural tube closure and precocious neuron production in the forebrain and die around embryonic day 11.5 (E11.5). These findings su ggest that m-numb is an essential gene that plays a role in promoting proge nitor cell fate during cortical neurogenesis.