Neither CASP3+ cells nor expression of p53 were observed in Emx1Cre/+-Arglu1fl/+ or Emx1Cre/+-Arglu1fl/+; COUPTFfl/+ mouse cortices (Supplementary Fig. 6A, B), suggesting that removal of Arglu1 indeed caused cell apoptosis, a possible cause that leads to microcephaly. This evidence concerns the gene TP53 and microcephaly.