title: Linkage disequilibrium and haplotype diversity in the genes of the renin-angiotensin system: findings from the family blood pressure program.
abstract: Association studies of candidate genes with complex traits have generally used one or a few single nucleotide polymorphisms (SNPs), although variation in the extent of linkage disequilibrium (LD) within genes markedly influences the sensitivity and precision of association studies. The extent of LD and the underlying haplotype structure for most candidate genes are still unavailable. We sampled 193 blacks (African-Americans) and 160 whites (European-Americans) and estimated the intragenic LD and the haplotype structure in four genes of the renin-angiotensin system. We genotyped 25 SNPs, with all but one of the pairs spaced between 1 and 20 kb, thus providing resolution at small scale. The pattern of LD within a gene was very heterogeneous. Using a robust method to define haplotype blocks, blocks of limited haplotype diversity were identified at each locus; between these blocks, LD was lost owing to the history of recombination events. As anticipated, there was less LD among blacks, the number of haplotypes was substantially larger, and shorter haplotype segments were found, compared with whites. These findings have implications for candidate-gene association studies and indicate that variation between populations of European and African origin in haplotype diversity is characteristic of most genes.
authors.affiliation: Department of Preventive Medicine and Epidemiology, Loyola Stritch School of Medicine, Maywood, Illinois 60153, USA. xzhu1@lumc.edu
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Zhu
authors.forename: Denise
authors.initials: D
authors.lastname: Yan
authors.forename: Richard S
authors.initials: RS
authors.lastname: Cooper
authors.forename: Amy
authors.initials: A
authors.lastname: Luke
authors.forename: Morna A
authors.initials: MA
authors.lastname: Ikeda
authors.forename: Yen-Pei C
authors.initials: YP
authors.lastname: Chang
authors.forename: Alan
authors.initials: A
authors.lastname: Weder
authors.forename: Aravinda
authors.initials: A
authors.lastname: Chakravarti
mesh_terms: D000328:Adult; D000808:Angiotensinogen / Q000235:genetics; D044383:Black People / Q000235:genetics; D001794:Blood Pressure / Q000235:genetics*; D004792:Enzyme Precursors / Q000235:genetics; D014644:Genetic Variation / Q000235:genetics*; D005828:Genetics, Population / Q000379:methods; D006239:Haplotypes / Q000235:genetics*; D006801:Humans; D015810:Linkage Disequilibrium / Q000235:genetics*; D009679:Nuclear Family / Q000208:ethnology; D007703:Peptidyl-Dipeptidase A / Q000235:genetics; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D044140:Receptor, Angiotensin, Type 1; D011945:Receptors, Angiotensin / Q000235:genetics; D012083:Renin / Q000235:genetics; D012084:Renin-Angiotensin System / Q000235:genetics*; D012494:Sampling Studies; D044465:White People / Q000235:genetics; D001741:Black or African American
chemical_list: D004792:Enzyme Precursors; D044140:Receptor, Angiotensin, Type 1; D011945:Receptors, Angiotensin; D000808:Angiotensinogen; D007703:Peptidyl-Dipeptidase A; D012083:Renin