Identification by denaturing high-performance liquid chromatography of numerous polymorphisms in a candidate region for multiple sclerosis susceptibility

Genetic association analysis of candidate regions where evidence of linkage has accumulated is becoming a key issue in the study of complex diseases. A high density of markers, at least one per centimorgan, is required to imp rove the chances of observing linkage disequilibrium with disease alleles. A recently available single nucleotide polymorphism (SNP) map designed to c over the whole genome provides an average density of one marker per 2 cM. I n the present study we show that the number of markers can be approximately doubled in a selected region, thus reaching a density suitable for associa tion studies, by applying a completely automated technique for polymorphism detection, denaturing high-performance liquid chromatography (DHPLC). A sy stematic search for SNPs was performed in the region 5ptel-q13, where weak but convergent evidence for linkage with multiple sclerosis has accumulated . Screening for polymorphisms was performed on 124 sequence tagged sites (S TSs) in the 3'UTR ends of expressed sequence tags totaling about 30,000 bp, Thirty SNPs in 28 STSs were found with less than 10% overlap with the mark ers already detected in the same region. The data confirm the validity of t he approach using DHPLC on expressed gene sequences tagged by a set of stan dard commercially available primers. (C) 1999 Academic Press.