Gene mapping in isolated populations: New roles for old friends?

Population isolates are increasingly being used in attempts to map genes un derlying complex diseases. To further explore the utility of isolates for t his purpose, we explore linkage disequilibrium patterns in polymorphisms fr om two regions (VWF and NF1) in three isolated populations from Finland. At the NF1 locus, the Finnish populations have greater pairwise disequilibriu m than populations from Africa, Asia, or northern Europe. However, populati ons from 'New Finland' and 'Old Finland' do not differ in their disequilibr ium levels at either the NF1 or the VWF locus. In addition, disequilibrium patterns and haplotype diversity do not differ between a sample from the Al and Islands, Finland, and a collection of outbred Centre d'Etude du Polymor phisme Humain families. These results show that linkage disequilibrium patt erns sometimes differ among populations with different histories and foundi ng dates, but some putative isolated populations may not significantly diff er from larger admired populations. We discuss factors that should be consi dered when using isolated populations in gene-mapping studies.