Analyzed at P0, Brca2 deletion by Emx1Cre (Emx1Cre/+;Brca2fl/fl, Brca2 cKO-E) led to significant microcephaly (Fig. 8a, b), callosal agenesis, and hippocampal hypoplasia (Supplementary Fig. 8a, b) remarkably similar to Ino80 cKO-E. Here, BRCA2 is linked to microcephaly.