title: Significant linkage of BMI to chromosome 10p in the U.K. population and evaluation of GAD2 as a positional candidate.
abstract: Obesity is a major health problem, and many family-based studies have suggested that it has a strong genetic basis. We performed a genome-wide quantitative trait linkage scan for loci influencing BMI in 573 pedigrees from the U.K. We identified genome-wide significant linkage (logarithm of odds = 3.74, between D10S208 and D10S196, genome-wide P=0.0186) on chromosome 10p. The size of our study population and the statistical significance of our findings provide substantial contributions to the body of evidence for a locus on chromosome 10p. We examined eight single nucleotide polymorphisms (SNPs) in GAD2, which maps to this linkage region, tagging the majority of variation in the gene, and observed marginally significant (0.01<P<0.05) associations between four common variants and BMI. However, these SNPs did not account for our evidence of linkage to BMI, and they did not replicate (in direction of effect) the previous associations. We therefore conclude that these SNPs are not the etiological variants underlying this locus. We cannot rule out the possibility that other untagged variations in GAD2 may, in part, be involved, but it is most likely that alternative gene(s) within the broad gene-rich region of linkage on 10p are responsible for variation in body mass and susceptibility to obesity.
authors.affiliation: Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Oxford, UK.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Groves
authors.forename: Eleftheria
authors.initials: E
authors.lastname: Zeggini
authors.forename: Mark
authors.initials: M
authors.lastname: Walker
authors.forename: Graham A
authors.initials: GA
authors.lastname: Hitman
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Levy
authors.forename: Stephen
authors.initials: S
authors.lastname: O'Rahilly
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Hattersley
authors.forename: Mark I
authors.initials: MI
authors.lastname: McCarthy
authors.forename: Steven
authors.initials: S
authors.lastname: Wiltshire
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D002879:Chromosomes, Human, Pair 10 / Q000235:genetics*; D005787:Gene Frequency; D008040:Genetic Linkage; D020022:Genetic Predisposition to Disease; D005968:Glutamate Decarboxylase / Q000235:genetics*; D006239:Haplotypes; D006801:Humans; D007527:Isoenzymes / Q000235:genetics*; D015810:Linkage Disequilibrium; D018895:Microsatellite Repeats; D008875:Middle Aged; D009765:Obesity / Q000235:genetics; D020641:Polymorphism, Single Nucleotide; D040641:Quantitative Trait Loci / Q000235:genetics; D006113:United Kingdom
chemical_list: D007527:Isoenzymes; D005968:Glutamate Decarboxylase; C401141:glutamate decarboxylase 2