The goals of this project are to identify genomic determinants of lipoprotein metabolism with emphasis on those that play roles in atherosclerosis, and to elucidate their functional consequences. Mutations will be linked to specific phenotypic disorders of lipoprotein metabolism by cosegregation analysis. In kindreds where no linkage can be established with candidate genes, chromosomal loci will be pursued by the techniques of """"""""reverse genetics"""""""". Mutations will be sought both in the structural genes for proteins with functional roles in lipoprotein metabolism and in their regulatory elements, so as to detect both dysfunctional proteins and disorders involving over- or under-expression. Major emphases will be on mutations of apo B and apo E, which impair receptor-ligand function, defects of apo C-II, which impair hydrolysis of triglycerides, defects at the loci for Lp(a) and cholesterol 7-alpha- hydroxylase, and regulatory mutations that result in deficiency of high density lipoproteins. The kinetic behavior of isotopically labeled apolipoprotein B in subspecies of autologous triglyceride-rich lipoproteins separated by affinity chromatographic techniques will be studied, after injection into patients with defined mutations causing dyslipoproteinemia. The data will be analyzed by multicompartmental analysis to elucidate interconversions among the species and to relate abnormalities in apo B transport to genotype. In other kinetic studies, the metabolism of truncated mutant forms of apo B will also be studied by isotopic techniques. This project will help to identify genomic determinants that can then serve as detectable risk factors. Studies in kindreds will also afford the opportunity to study the interaction of the more common genomic determinants as compound genetic states. The elucidation of resulting abnormalities in apoprotein metabolism may provide insights leading to new therapeutic approaches. Also, the identification of a number of mutations in apolipoproteins will contribute to the mapping of functional domains of proteins. This project will serve as a resource of genomic material for other researchers at large who are investigating disorders of lipoprotein metabolism or the genomic determinants of premature atheroslerosis in kindreds.
