DBH as a Modifying Gene in Neurodegenerative Diseases

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DESCRIPTION (provided by applicant): The applicant, Dr. Cyrus Zabetian, has spent the past three years as a postdoctoral fellow at Yale University/ VACHS. He will join the neurology faculty at the University of Washington next year where his future mentors, Drs. Thomas Bird and Gerard Schellenberg, have established a superb research program in neurogenetics. His training will include participation in laboratory meetings, seminars, structured courses, and annual scientific meetings. He will become part of a rich collaborative network of researchers with expertise in clinical and molecular neurogenetics, catecholamine biochemistry, and biostatistics. Dr. Zabetian's long-term plans are to become established as an independent laboratory investigator within five years, and remain actively involved in patient care and resident training on the neurology service. In neurodegenerative disease research, identifying genetic mechanisms underlying compensatory changes in surviving neurons promises to lead to improved strategies of diagnosis and treatment. The project proposed in this application seeks to determine if a newly discovered promoter polymorphism (C-1021T) influences regulation of the DBH gene with potential clinical consequences in Parkinson's disease (PD), and is divided into three parts. The goal of part I is to evaluate whether homozygosity for the T allele of C-1021 T, which is associated with low levels of plasma DBH enzyme, is predictive of an earlier onset and more severe symptoms of sympathetic failure in patients with PD. A group of forty subjects homozygous for either the C or T allele will be selected from a population of 400 clinic patients with PD and assessed longitudinally using indices of sympathetic function. Part II seeks to determine whether C-1021T strongly associates with DBH expression in noradrenergic tissues. Levels of DBH protein and mRNA will be compared in postmortem human adrenal medulla specimens, homozygous for either the C or T allele, using western blots and quantitative real time RT-PCR, respectively. Part III will assess whether C-1021T is directly functional. If preliminary results are favorable, two transgenic mouse lines homozygous for either the T or C allele will be created in which the proximal 2 kb of the endogenous mouse DBH promoter is replaced by homologous human sequence. Comparing plasma and tissue levels of DBH protein and catecholamines in the two lines will detect the effect of each allele on DBH expression.