Autosomal dominant neurohypophyseal diabetes insipidus (ADNDI) is an inherited endocrine disorder caused by a progressive and specific degeneration of the magnocellular neurons that produce the hormone, vasopressin. The genetic locus of ADNDI is the gene that encodes arginine vasopressin (AVP) and the AVP binding protein, neurophysin II (NPII), and three distinct classes of mutations that cause the disease have been defined. The overall goals of this grant are to investigate the molecular basis for this disease, specifically addressing the basis of dominant inheritance and the molecular and cellular mechanisms by which the mutations cause neurodegeneration. The hypothesis is that dominant negative mutations in the AVP-NPII gene cause ADNDI, and that the mutant alleles encode an AVP-NPII precursor that is misprocessed, accumulates, and causes degeneration of the magnocellular neurons.
Specific aim 1 of the proposal is to test the hypothesis that mutant AVP-NPII alleles exert dominant negative effects. This will be tested by creation of transgenic mouse models via introduction of mutant human AVP-NPII genes. If features of ADNDI do not occur in these transgenic animals, the alternative hypothesis, that ADNDI mutations cause the disease by eliminating one of the two functional AVP-NPII alleles, will be tested in another mouse model by deleting one normal AVP-NPII allele using homologous recombination.
Specific aim 2 is to test the hypothesis that mutations that cause ADNDI alter the preproAVP-NPII precursor to disrupt proper processing and allow a toxic accumulation of misprocessed precursor. The hypothalami of the mouse models for ADNDI will be evaluated by histology, immunohistochemistry and electron microscopy to investigate for magnocellular neuron degeneration. Expression of cloned mutant and normal human AVP-NPII cDNAs in PC12 cells and in vitro transcription, translation, and processing by microsomal membranes will be employed to allow detailed study of altered cell biology and biochemistry in the presence of ADNDI mutations. These experiments will define the genetic, molecular, and cellular pathophysiology of ADNDI and contribute to knowledge of other degenerative neurological diseases.
| DiMeglio, L A; Gagliardi, P C; Browning, J E et al. (2001) A missense mutation encoding cys(67) --> gly in neurophysin ii is associated with early onset autosomal dominant neurohypophyseal diabetes insipidus. Mol Genet Metab 72:39-44 |
