This project aims to further study the regulation of human aldosterone synthase (CYP11B2) using human genetics, cell culture and transgenic mouse approaches. The proposed studies will extend the applicants' ongoing collaborative project that has defined transcriptional regulatory elements in the proximal 5' flanking region of CYP11B2. The phenotypic effects of allelism in or near CYP11B2 will be determined, including possible effects on aldosterone excretion, heart size, blood pressure and risk of myocardial infarction. Other polymorphisms in the CYP11B2-CYP11B1 region will be identified, linkage disequilibrium with already identified alleles determined, and their functional effects on aldosterone production and CYP11B2 expression defined. CYP11B2 expression in extra-adrenal tissues will be studied, including determining whether CYP11B2 is expressed within the human heart. Cis-acting elements regulating expression of CYP11B2 reporter constructs in rodent cardiac myocytes and/or human umbilical vein endothelial cells will be identified. Possible locus control regions affecting expression of CYP11B2 will be identified by determining if tissue-specific DNAse I hypersensitivity sites exist in chromatin surrounding CYP11B2, and functioning of putative locus control regions will be confirmed by producing appropriate strains of transgenic mice. Calcium signaling pathways regulating expression of CYP11B2 will be elucidated by defining the specific CaM Kinase(s) that regulate CYP11B2 transcription by transfecting plasmids and transducing recombinant retrovirus containing constitutively active CaM kinase mutants (types I, II, and IV) into H295R adrenocortical cells. Expression of the CaM kinase(s) in normal human adrenals will be examined using in situ hybridization and immunohistochemistry. These studies should provide insight into mechanisms underlying a genetic risk factor for cardiovascular disease.
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