Developmentally, these phenotypes are thought to arise in part through extensive neuroepithelial apoptosis (Kobayashi et al., 2004; McKinnon, 2012), and consistent with these observations in humans, neural stem cell-specific conditional deletion of Nbs1 and Mre11 in mouse embryos results in microcephaly (Frappart et al., 2005). This evidence concerns the gene MRE11 and microcephaly.