The functions of the neurophysin and glycopeptide portions of the vasopressin precursor peptide are poorly understood. Mutations in the highly conserved neurophysin sequence produce defects in vasopressin expression. Two different mutations in the neurophysin sequence have been reported in the dominantly inherited syndrome of human familial diabetes insipidus. In the Brattleboro rat, an animal model of recessive central diabetes insipidus, a frameshift mutation alters the neurophysin and glycopeptide amino acid sequences and disrupts the stop codon, but it is unclear how these defects result in diabetes insipidus. Site- directed mutagenesis and three different gene transfer techniques will be used to study the role of these vasopressin-related peptides in vasopressin expression. 1) Permanently transfected cell lines will be used to study the effects that deletion, frameshift, and point mutations in the neurophysin and glycopeptide regions of the vasopressin gene have on the translation and secretion of vasopressin. 2) Using a Herpes vector, the normal vasopressin gene and mutated constructs will be transfected into hypothalamic cells of the Brattleboro rat to confirm, in vivo, the results of the cell culture studies and to test the hypothesis that correction of the frameshift mutation is sufficient to correct the diabetes insipidus. 3) Mouse lines transgenic for mutated rat vasopressin gene constructs will be developed for each of the mutations reported in the human autosomal dominant form of inherited diabetes insipidus and will be used to study the relationship between these mutations, neuronal degeneration, and loss of vasopressin secretion. Results of these experiments will provide a better understanding of the role of neurophysin and glycopeptide in the regulation of vasopressin expression and may also provide a model of neuronal degeneration due to mutation in a naturally occurring neuropeptide. The sponsor, Dr. Majzoub, is a recognized leader in the molecular biology of vasopressin and has experience in the proposed techniques. Dr. Geller, who developed the techniques of herpes vector gene transfer, is a member of Dr. Majzoub's division. Our laboratory has an ongoing collaboration with Dr. Gordon, a leader in the development and use of transgenic methods. The proposed studies are a continuation of my long interest in the three peptides encoded by the vasopressin gene and will provide me with additional training in molecular biology which will be important in my transition to an independent investigator in endocrinology.
| Grant, F D; Ahmadi, A; Hosley, C M et al. (1998) Two novel mutations of the vasopressin gene associated with familial diabetes insipidus and identification of an asymptomatic carrier infant. J Clin Endocrinol Metab 83:3958-64 |
