A blockage of proliferation and a trigger of ATM-P53 mediated cell death of cerebellar neuroprogenitors cause microcephaly, cerebellar atrophy, and ataxia in Nbs1-CNSΔ mice (Frappart et al., 2005; Assaf et al., 2008; Dar et al., 2011; Galron et al., 2011; Zhou et al., 2012). Here, NBN is linked to microcephaly.