Around 30% of the genetic liability for multiple sclerosis can be explained by common genetic variants identified in current genome-wide association study (GWAS) arrays, a study in Scientific Reports reveals. The results highlight the potential importance of rare variants in susceptibility to this complex neurodegenerative disorder.
Multiple sclerosis (MS) is an inflammatory disease of the central nervous system, and is the most common neurological disorder affecting young adults. Both genetic and environmental factors are thought to contribute to the onset and progression of the disease. A large genetic region called the major histocompatibility complex (MHC) makes the single strongest contribution to MS susceptibility reported to date, but loci with smaller effects have also been identified in GWAS.
To investigate in more detail the role of common GWAS variants in MS susceptibility, Corey Watson, Sreeram Ramagopalan and colleagues used publically available genotype data from a large UK case-control cohort to carry out a comprehensive assessment of the contribution of common GWAS variants to variance in liability to MS. They used an approach that analyzes contributions made by all genotyped single nucleotide polymorphisms (SNPs, or single-letter variations in DNA), rather than just those risk loci that reach genome-wide significance. The authors found that variants identified by current GWAS arrays account for about 30% of MS heritability, with SNPs on chromosome 6 alone accounting for around 8%, reflecting the major contribution of the MHC. The unaccounted for proportion probably reflects the imperfect links within the genome between causal variants and common variants identified in GWAS, the authors suggest.