The A>G mutation in the 927th base of the 3rd exon suggested a silent Leu 309 Leu (TAG-TAC) mutation, while the A>G mutation at the 814th base of the 2nd exon resulted in an amino acid substitution (Met 272 Val, i.e., from GAT to GGT) in the AVPR2. A hemizygous Met 272 Val mutation was also found in some male family members with symptoms of diabetes insipidus, such as subjects II-2 and 6; III-5; and IV-1. Here, AVPR2 is linked to diabetes insipidus.