ENU-induced T to C transition at base pair 53,488,587 (v38) on chromosome 9, or base pair 48,230 in the GenBank genomic region NC_000075. The mutation corresponds to residue 4,731 in the mRNA sequence NM_007499 within exon 29 of 64 total exons. The mutation results in a leucine to proline substitution at amino acid 1,531 (L1531P) in the ATM protein.