title: Increased level of linkage disequilibrium in rural compared with urban communities: a factor to consider in association-study design.
abstract: Few studies have investigated genetic differentiation within nonisolate European populations, despite the initiation of large national sample collections such as U.K. Biobank. Here, we used short tandem repeat markers to explore fine-scale genetic structure and to examine the extent of linkage disequilibrium (LD) within national subpopulations. We studied 955 unrelated individuals of local ancestry from nine Scottish rural regions and the urban center of Edinburgh, as well as 96 unrelated individuals from the general U.K. population. Despite little overall differentiation on the basis of allele frequencies, there were clear differences among subpopulations in the extent of pairwise LD, measured between a subset of X-linked markers, that reflected presumed differences in the depths of the underlying genealogies within these subpopulations. Therefore, there are strategic advantages in studying rural subpopulations, in terms of increased power and reduced cost, that are lost by sampling across regions or within urban populations. Similar rural-urban contrasts are likely to exist in many other populations with stable rural subpopulations, which could influence the design of genetic association studies and national biobank data collections.
authors.affiliation: Medical Research Council Human Genetics Unit, Western General Hospital, Edinburgh, United Kingdom. v.vitart@hgu.mrc.ac.uk
authors.forename: Veronique
authors.initials: V
authors.lastname: Vitart
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Carothers
authors.forename: Caroline
authors.initials: C
authors.lastname: Hayward
authors.forename: Peter
authors.initials: P
authors.lastname: Teague
authors.forename: Nicholas D
authors.initials: ND
authors.lastname: Hastie
authors.forename: Harry
authors.initials: H
authors.lastname: Campbell
authors.forename: Alan F
authors.initials: AF
authors.lastname: Wright
mesh_terms: D005828:Genetics, Population; D006801:Humans; D015810:Linkage Disequilibrium; D008297:Male; D012107:Research Design; D012424:Rural Population; D012606:Scotland; D020080:Tandem Repeat Sequences; D014505:Urban Population