Genetics

This blog post reviews a multi-ancestry evaluation of commonly used SNP “tags” for key multiple sclerosis–associated HLA alleles (HLA-DRB115:01*, HLA-DRB115:03*, HLA-DQB106:02*) and the protective allele HLA-A02:01*, using HLA-typed samples from the 1000 Genomes Project. It explains how population-specific linkage disequilibrium can cause tag SNPs validated in European cohorts to perform poorly in African, East Asian, South Asian, or admixed American populations, leading to misclassification and inconsistent genetic association results. The post highlights practical outcomes—such as a robust tag for HLA-A02:01* across African and European groups—while underscoring the study’s central recommendation: tag SNPs in the MHC must be empirically validated in the specific ancestry context where they will be applied.