Multiple sclerosis: Postlinkage genetics

Abstract

Because of the relative failure of linkage analysis in multiple sclerosis, despite the investigation of more than 700 affected relative pairs, we have applied four alternative strategies to identify genes that confer susceptibility to the disease. First, we have reported two clusters of MS patients from isolated populations where 19 and 13 patients, respectively, could be shown to have common ancestry tracing back several centuries. Three and five haplotypes, respectively, were shown to be shared by affected individuals, however, these haplotypes were extended and the statistical evidence modest. Second, we have recently reported the results of a two-stage candidate gene analysis of 66 selected genes, mostly of immune function. The IL-7 receptor alpha gene and LAG-3 both had three SNP markers associated with MS. Third, we recently identified the MHC class II transactivator gene in an animal model with inflammatory properties and later confirmed it to be of importance for MS, rheumatoid arthritis and acute myocardial infarction. Finally, in collaboration with the Serono Genetics Institute, we have completed a genome-wide screen with over 100,000 markers in three sets of 300 MS patients and 300 matched controls. Eighty genes showed evidence of importance in all three populations. These strategies appear to hold some promise of success where linkage analysis has proven less successful than anticipated.