Genetic basis of familial neurohypophyseal diabetes insipidus.

Familial neurohypophyseal diabetes insipidus (FNDI) is an autosomal dominant (adFNDI) or X-linked recessive (xrFNDI) disorder characterized by the development in early childhood of an irreversible deficiency of arginine vasopressin (AVP) secretion. Autopsy data in adFNDI reveal selective destruction of the posterior pituitary magnocellular neurons that normally produce the hormone. These abnormalities are due to a variety of mutations in the gene that encodes the AVP-neurophysin II precursor. Each one predicts a change in the primary structure of the preprohormone, and all but one are of a type known or reasonably presumed to impair the folding and cellular trafficking of the preprohormone. This pattern and the uniform clinical characteristics of adFNDI suggest that the disease is due to the production of a mutant precursor that is toxic for magnocellular neurons, because it cannot be folded, processed, or otherwise disposed of efficiently. Although the gene responsible for xrFNDI has not yet been cloned, the striking clinical similarities between adFNDI and xrFNDI suggest that similar pathophysiologic mechanisms may be involved.