The Role of Thrombospondins in Atherothrombosis

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In the post-genomic era, high through put genome-wide scans and SNP association studies hold the promise of identifying new genes as significant risk factors for coronary artery disease (CAD) and myocardial infarction (MI). Such information raises a new challenge: how does an identified gene product influence disease? This was the challenge that emerged from GeneQuest I. This large-scale SNP case-control study in patients with familial, premature CAD/MI identified three gene that exhibited a significant association with MI. All three were members of the thrombospondin (TSP) gene family. The remarkable clustering of genes within a single family strongly implicates the TSP family in cardiovascular pathology, and this link is further bolstered by the replication of the TSP-2 and TSP-4 associations with MI in separate clinical studies and our own preliminary data showing that each of the three TSP SNP set displays distinct functions. This project will focus on TSP-4 and TSP-2. In TSP-4, the SNP leads to a A387 P substitution, occurs at high frequency (34% in the Caucasian population), and increases the risk of MI by almost 2-fold. In TSP-2, the SNP is a t3943g substitution in the 3'-untranslated region, occurs with high frequent (10%) and is protective (approximately 3-fold reduction in MI). The hypothesis to be tested is: the SNPs in TSP-4 and TSP-2 alter protein (TSP-4) or mRNA (TSP-2) structure, which affects the function and/or expression of the TSPs. Such alterations affect the responses of vascular cells, creating a pro- or anti-atherogenic environment in the vessel wall. To test this hypotheses, we will: 1) examine the influence of the TSP-4 and TSP-2 SNPs at a molecular and cellular level; 2) explore murine atherosclerosis and vascular injury models in which expression of the TSPs has been altered; 3) examine normal and atherosclerotic human vessels for SNP-dependent changes in mRNA and protein; 4) determine if the SNP variants induce different gene profiles consistent with their atherogenic effects; and 5) exploit the GeneBank of cardiology patients to establish additional associations of the TSPs with MI. The aggregate of these studies should provide a rigorous test of the hypothesis, extend our knowledge of the TSPs in cardiovascular disease; provide insights into their structure and function; and define general approaches to examine oathozenic mechanisms of other gene products that are linked to CAD and MI.