NBN and microcephaly: The Nbn‐CNS‐del mouse, which carries full Nbn knockout restricted to the central nervous system (CNS), recapitulates some of the neural phenotypes of the above‐mentioned syndromes such as microcephaly and dramatic cerebellar atrophy associated with ataxia [16, 17], indicating that the MRN complex is essential for cerebellar development and for the expansion of cerebellar GCPs [16, 18].