title: Haplotype-specific linkage disequilibrium patterns define the genetic topography of the human MHC.
abstract: Detailed knowledge of linkage disequilibrium (LD) is regarded as a prerequisite for population-based disease gene mapping. Variable patterns across the human genome are now recognized, both between regions and populations. Here, we demonstrate that LD may also vary within a genomic region in a haplotype-specific manner. In 864 Caucasian unrelated individuals, we describe haplotype-specific LD patterns across the human MHC by the construction of gene-specific allelic haplotypes at 25 loci between HLA-A and Tapasin. Strong and extensive LD is found across both common and rare haplotypes, suggesting that haplotype structure is influenced by factors other than genetic drift, including both selection and differential haplotype recombination. Knowledge of haplotype-specific LD in the HLA may explain the apparent discrepant data from previous studies of global LD, help delineate key areas in mapping HLA-associated diseases and, together with recombination data, provide valuable information about a population's demographic history and the selective pressures operating on it.
authors.affiliation: Gastroenterology Unit, University of Oxford, Gibson Laboratories, Radcliffe Infirmary, Woodstock Road, Oxford, OX2 6HE, UK. tariq.ahmad@ndm.ox.ac.uk
authors.forename: Tariq
authors.initials: T
authors.lastname: Ahmad
authors.forename: Matt
authors.initials: M
authors.lastname: Neville
authors.forename: Sara E
authors.initials: SE
authors.lastname: Marshall
authors.forename: Alessandro
authors.initials: A
authors.lastname: Armuzzi
authors.forename: Kim
authors.initials: K
authors.lastname: Mulcahy-Hawes
authors.forename: Jonathan
authors.initials: J
authors.lastname: Crawshaw
authors.forename: Hiroe
authors.initials: H
authors.lastname: Sato
authors.forename: Khoon-Lin
authors.initials: KL
authors.lastname: Ling
authors.forename: Martin
authors.initials: M
authors.lastname: Barnardo
authors.forename: Sue
authors.initials: S
authors.lastname: Goldthorpe
authors.forename: Robert
authors.initials: R
authors.lastname: Walton
authors.forename: Mike
authors.initials: M
authors.lastname: Bunce
authors.forename: Derek P
authors.initials: DP
authors.lastname: Jewell
authors.forename: Ken I
authors.initials: KI
authors.lastname: Welsh
mesh_terms: D000483:Alleles; D017920:Antiporters / Q000235:genetics; D002874:Chromosome Mapping; D005838:Genotype; D015234:HLA-A Antigens / Q000235:genetics; D006239:Haplotypes; D006801:Humans; D007136:Immunoglobulins / Q000235:genetics; D015810:Linkage Disequilibrium / Q000235:genetics; D008285:Major Histocompatibility Complex / Q000235:genetics*; D026901:Membrane Transport Proteins; D008957:Models, Genetic; D011110:Polymorphism, Genetic; D011995:Recombination, Genetic
chemical_list: D017920:Antiporters; D015234:HLA-A Antigens; D007136:Immunoglobulins; D026901:Membrane Transport Proteins; C107762:tapasin