A new mutation of the arginine vasopressin-neurophysin II gene in a family with autosomal dominant neurohypophyseal diabetes insipidus.

Familial neurohypophyseal diabetes insipidus (FNDI) is an autosomally dominant inherited disorder with a typical onset at one to six years of age. The genetic locus of FNDI is the arginine vasopressin-neurophysin II (AVP-NPII) gene. The gene encoding the precursor hormone (prepro-AVP-neurophysin II) is located in the chromosomal region 20p13 and contains three exons. Mutations that cause FNDI have been found to occur within the signal peptide of the prepro-AVP-neurophysin II precursor, within the coding sequence for neurophysin II and the vasopressin-coding sequence. A family (four members with FNDI, two without FNDI) in three consecutive generations was investigated. Index case was a now 22-year old man with a history of severe polyuria (18 L/day) and polydipsia first recognized at about 4-5 months of age. The arginine vasopressin-neurophysin II gene was investigated by direct sequencing of PCR products amplified from each exon. Subsequently, a restriction analysis was performed to verify the sequencing results. The affected individuals were found to have a missense mutation in exon 2 at nucleotide position 1887 (G to C) of the AVP-NPII gene. Using both restriction enzyme digestion and sequence analysis, the mutation was found in all affected family members, but not in the unaffected members studied. This mutation (1887 G to C) represents a novel mutation of the AVP-NPII gene.