title: The APOA1/C3/A4/A5 gene cluster, lipid metabolism and cardiovascular disease risk.
abstract: OBJECTIVE
  APOA1/C3/A4/A5 are key components modulating lipoprotein metabolism and cardiovascular disease risk. This review examines the evidence regarding linkage disequilibrium and haplotype structure within the A1/C3/A4/A5 cluster, and assesses its association with plasma lipids and cardiovascular disease risk. In addition, we use genomic information from several species to draw inferences about the location of functional variants within this cluster.
  
  
  RESULTS
  The close physical distance of these genes and the interrelated functions of these apolipoproteins have encumbered attempts to determine the role of individual variants on lipid metabolism. Therefore, current research aims to define linkage disequilibrium and haplotype structure within this cluster. Functional variants in regulatory regions are most interesting as they are potentially amenable to therapy. Comparative genomics can contribute to the identification of such functional variants.
  
  
  CONCLUSIONS
  Genetic variability at the APOA1/C3/A4/A5 cluster has been examined in relation to lipid metabolism and cardiovascular disease risk. However, the findings are inconsistent. This is partly due to the classic approach of studying single and mostly nonfunctional polymorphisms. Moreover, allelic expression may depend on the concurrent presence of environmental factors. Association studies using haplotypes should increase the power to detect true associations and interactions. We hypothesize that phenotypes observed in association with transcriptional regulatory variants can be readily modified by environmental factors. Therefore, studies focusing on regulatory variants may be more fruitful to locate/define future therapeutic targets.
authors.affiliation: Nutrition and Genomics Laboratory, Jean Mayer--US Department of Agriculture, Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts 02111, USA. chao.lai@tufts.edu
authors.forename: Chao-Qiang
authors.initials: CQ
authors.lastname: Lai
authors.forename: Laurence D
authors.initials: LD
authors.lastname: Parnell
authors.forename: Jose M
authors.initials: JM
authors.lastname: Ordovas
mesh_terms: D016632:Apolipoprotein A-I / Q000235:genetics; D000072040:Apolipoprotein A-V; D053305:Apolipoprotein C-III; D001053:Apolipoproteins / Q000235:genetics*; D001054:Apolipoproteins A / Q000235:genetics; D001056:Apolipoproteins C / Q000235:genetics; D002318:Cardiovascular Diseases / Q000209:etiology / Q000235:genetics* / Q000378:metabolism; D005786:Gene Expression Regulation; D020022:Genetic Predisposition to Disease; D023281:Genomics; D006239:Haplotypes; D006801:Humans; D015810:Linkage Disequilibrium; D050356:Lipid Metabolism; D008055:Lipids / Q000097:blood; D005810:Multigene Family / Q000235:genetics*; D012307:Risk Factors
chemical_list: C437704:APOA5 protein, human; D016632:Apolipoprotein A-I; D000072040:Apolipoprotein A-V; D053305:Apolipoprotein C-III; D001053:Apolipoproteins; D001054:Apolipoproteins A; D001056:Apolipoproteins C; D008055:Lipids; C022205:apolipoprotein A-IV