The general research program of our laboratory is focused on the cellular and genetic aspects of atherosclerosis. Atherosclerosis is the primary cause of heart attack and stroke, which account for approximately 50% of all deaths and are the leading cause of disability in the United States. Genetic studies involving twin, siblings and families have demonstrated the heritability of atherosclerosis, but the underlying genetic factors remain to be identified. Current research projects involve generation of new genetic crosses to identify quantitative trait loci (QTL) for atherosclerosis and associated traits in mice, evaluation of major QTLs for atherosclerosis by constructing congenic strains, and identification of genes underlying the major QTLs for atherosclerosis.

We perform linkage analysis using mouse crosses to identify genes that are involved in the development of atherosclerosis. Linkage analysis is a genetic approach for mapping chromosomal regions of genes that contribute to such a complex trait as atherosclerotic lesions. A large number of F2 (intercross) or N2 (backcross) progeny derived from atherosclerosis-susceptible and -resistant inbred mouse strains are analyzed for parental phenotypes (traits). Chromosomal regions harboring the genes that determine the traits are identified with polymorphic markers that are capable of recognizing DNA sequence differences of the parental strains. This approach often leads to identification of new genes and new pathways involved in physiological or pathological processes. We have identified several major QTLs such as Ath29, CAth1 and Bglu3 that influence atherosclerotic lesion size, plasma lipid and glucose levels or body weight. We are dissecting these QTLs through construction and analysis of congenic strains. A congenic strain contains a small contiguous portion of the genome of one parental strain on the background of the other strain. Since in a congenic strain other QTLs have been eliminated, it can be used to assess the contribution of an individual QTL to a trait. More importantly, once a congenic strain is constructed to contain a QTL, the strain can be used for identification of individual candidate genes in the congenic region.

We use the candidate gene approach to identify the genes underlying major QTLs for atherosclerosis. We take advantage of increasingly data-rich databases for the mouse as well as sophisticated tools for data analysis to make assessment of the likelihood of various candidate genes residing in QTL regions. All genes within the confidence region of a QTL are perused for sequence differences in both coding and regulatory regions between parental strains by searching various databases. Sequence variations that lead to amino acid substitutions in the gene products or a frameshift in the coding region are likely to have functional significance and subject to sequence analysis for reconfirmation. Once the sequence difference of a candidate gene has been confirmed in two parental stains, we then test whether the polymorphism/mutation of a candidate gene is associated with variation in the trait in mouse strains. To obtain definitive proof for the involvement of a candidate gene in atherosclerosis, the phenotype is tested in knockout or transgenic mice. Other functional studies involving use of siRNA or pharmaceutical compounds are also used in our studies.

Selected References

Pei H, Wang Y, Miyoshi T, Zhang Z, Matsumoto AH, Helm GA, Tellides G, Shi W. (2006) "Direct evidence for a crucial role of the arterial wall in control of atherosclerosis susceptibility." Circulation. Nov 114(22):2382-9. Epub 2006 Nov 13. [PubMed]

Su Z, Li Y, James JC, Matsumoto AH, Helm GA, Lusis AJ, Shi W. (2006) "Genetic linkage of hyperglycemia, body weight and serum amyloid-P in an intercross between C57BL/6 and C3H apolipoprotein E-deficient mice." Hum Mol Genet. May 15(10):1650-8. Epub 2006 Apr 4. [PubMed]

Su Z, Li Y, James JC, McDuffie M, Matsumoto AH, Helm GA, Weber JL, Lusis AJ, ShiW. (2006) "Quantitative trait locus analysis of atherosclerosis in an intercross between C57BL/6 and C3H mice carrying the mutant apolipoprotein E gene." Genetics. 172:1799-807. Epub 2005 Dec 30. [PubMed]

Miyoshi T, Yuan Z, Shi W. (2007) "Association of a Vcam1 mutation with atherosclerosis susceptibility in diet-induced models of atherosclerosis." Atherosclerosis. Jun [Epub ahead of print] [PubMed]