ENU-induced C to T transition at base pair 119,538,137 (v38) on chromosome 8, or base pair 20,689 in the GenBank genomic region NC_000074. The mutation corresponds to residue 1,609 in the mRNA sequence NM_019709 within exon 9 of 24 total exons. The mutation results in a proline to serine substitution at position 341 (P341S) in the Site 1 protease (S1P) protein. (J:274663)