The human microcephaly is in keeping with the previously reported mouse knockout model for Lmnb1 in which cerebral cortical size was markedly reduced.17 However, in both the Lmnb1−/− and Lmnb2−/− mice, (where brain size was not reduced at birth), there were neuronal migration defects resulting in abnormal layering of the cerebral cortex,18 suggesting potential discordance with the human phenotype and neuroimaging findings. This evidence concerns the gene LMNB1 and microcephaly.