A to G transition at base pair 11,784,654 (v38) on chromosome 4, or base pair 26,498 in the GenBank genomic region NC_000070 encoding Cdh17. The mutation corresponds to residue 956 (c.956A>G) in the mRNA sequence NM_019753.4 within exon 8 of 18 total exons. The mutation results in a tyrosine to cysteine substitution at position 270 (p.Y270C) in the CDH17 protein.