ENU-induced A to T transversion at base pair 52,123,209 (v38) on chromosome 1, or base pair 3,772 in the GenBank genomic region NC_000067 encoding Stat1. The mutation corresponds to residue 523 in the mRNA sequence NM_001205313 within exon 4 of 25 total exons. The mutation results in an asparagine to isoleucine substitution at amino acid 75 (N75I) in the STAT1 protein.