A novel splice site mutation of the arginine vasopressin-neurophysin II gene identified in a kindred with autosomal dominant familial neurohypophyseal diabetes insipidus

Autosomal dominant familial neurohypophyseal diabetes insipidus is an inherited deficiency of arginine vasopressin (AVP), and this is caused by mutations in the AVP-neurophysin II (AVP-NP II) gene. Most of these mutations have been located in the signal peptide or in the NP II moiety. In the present study, we have analyzed the AVP-NP II gene in a Korean family. Clinical and genetic studies were performed on three members of the family, and on a normal healthy unrelated individual. The diagnosis of neurohypophyseal diabetes insipidus was done by performing a fluid deprivation test and a vasopressin challenge. For genetic analysis, the genomic DNA was extracted and the AVP-NP II gene was amplified by polymerase chain reaction (PCR). Clinical assessment of the affected individuals confirmed the diagnosis of neurohypophyseal diabetes insipidus. Genetic analysis of the AVP-NP II gene revealed a novel deletion mutation of a single nucleotide (guanine) within the splice acceptor site of intron 2 (IVS2 +1 delG). The affected individuals were heterozygous for this mutation. We also demonstrated through RT-PCR analysis of the mutant gene that this mutation resulted in the retention of intron 2 during pre-mRNA splicing. We concluded that a novel splicing mutation in the AVP-NP II gene causes neurohypophyseal diabetes insipidus in this family.