Multiple sclerosis (MS) is a common complex neurodegenerative disease of the central nervous system. It develops with autoimmune inflammation and demyelination. Genome-wide association studies (GWASs) serve as a powerful tool for investigating the genetic architecture of MS and are generally used to identify the genetic factors of disease susceptibility, clinical phenotypes, and treatment response. This review considers the main achievements and challenges of using GWAS to identify the genes involved in MS. It also describes hypothesis-driven studies with extensive genome coverage of the selected regions, complementary to GWASs. To date, over 100 MS risk loci have been identified by the combination of both approaches; 40 of them were found in at least two GWASs and meet genome-wide significance threshold (p ≤ 5 × 10(-8)) in at least one GWAS, whereas the threshold for the rest of GWASs was set in our review at p < 1 × 10(-5). Yet, MS risk loci identified to date explain only a part of the total heritability, and the reasons of "missing heritability" are discussed. The functions of MS-associated genes are described briefly; the majority of them encode immune-response proteins involved in the main stages of MS pathogenesis.

Multiple sclerosis (MS) is an autoimmune neuro-inflammatory disease arising from complex interactions of genetic, epigenetic, and environmental factors. Variations in genes of some microRNAs—key post-transcriptional regulators of many genes—can influence microRNAs expression/function and contribute to MS via expression changes of protein-coding target mRNA genes. We performed an association study of polymorphous variants of MIR146A rs2910164, MIR196A2 rs11614913, MIR499A rs3746444 MIR223 rs1044165 and their combinations with MS risk and severity. 561 unrelated patients with bout-onset MS and 441 healthy volunteers were enrolled in the study. We observed associations of MS risk with allele MIR223*T and combination (MIR223*T + MIR146A*G/G) carriage in the entire groups and in women at Bonferroni-corrected significance level (pcorr < 0.05). Besides, MIR146A*G/G association with MS was observed in women with nominal significance (pf = 0.025). No MS associations were found in men. A more severe MS course (MSSS value > 3.5) was associated with the carriage of MIR499A*C/T and, less reliably, of MIR499A*C (pcorr = 0.006 and pcorr = 0.024, respectively) and with the carriage of combinations (MIR499A*C/T + MIR196A2*C) and (MIR499A*C + MIR196A2*C) (pcorr = 0.00078 and pcorr = 0.0059, respectively). These associations also showed gender specificity, as they were not significant in men and substantially reinforced in women. The strongest association with MS severity was observed in women for combination (MIR499A*C/T + MIR196A2*C): pcorr = 4.43 × 10−6 and OR = 3.23 (CI: 1.99–5.26).

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We pinpointed the involvement of several GWAS-identified MS risk loci in GA therapy efficacy. These findings may be aggregated to predict the optimal GA response in MS patients.

Risk of the development of multiple sclerosis (MS) is known to be increased in individuals bearing distinct class II human leukocyte antigen (HLA) variants, whereas some of them may have a protective effect. Here we analyzed distribution of a highly polymorphous HLA-DRB1 locus in more than one thousand relapsing-remitting MS patients and healthy individuals of Russian ethnicity. Carriage of HLA-DRB1 * 15 and HLA-DRB1 * 03 alleles was associated with MS risk, whereas carriage of HLA-DRB1 * 01 and HLA-DRB1 * 11 was found to be protective. Analysis of genotypes revealed the compensatory effect of risk and resistance alleles in trans. We have identified previously unknown MBP 153−161 peptide located at the C-terminus of MBP protein and MBP 90−98 peptide that bound to recombinant HLA-DRB1 * 01:01 protein with affinity comparable to that of classical antigenic peptide 306-318 from the hemagglutinin (HA) of the influenza virus demonstrating the ability of HLA-DRB1 * 01:01 to present newly identified MBP 153−161 and MBP 90−98 peptides. Measurements of kinetic parameters of MBP and HA peptides binding to HLA-DRB1 * 01:01 catalyzed by HLA-DM revealed a significantly lower rate of CLIP exchange for MBP 153−161 and MBP 90−98 peptides as opposed to HA peptide. Analysis of the binding of chimeric MBP-HA peptides demonstrated that the observed difference between MBP 153−161 , MBP 90−98 , and HA peptide epitopes is caused by the lack of anchor residues in the C-terminal part of the MBP peptides resulting in a moderate occupation of P6/7 and P9 pockets of HLA-DRB1 * 01:01 by MBP 153−161 and MBP 90−98 peptides in contrast to HA 308−316 peptide. This leads to the P1 and Mamedov et al. HLA-DR1 Discriminates Antigens Kinetically P4 docking failure and rapid peptide dissociation and release of empty HLA-DM-HLA-DR complex. We would like to propose that protective properties of the HLA-DRB1 * 01 allele could be directly linked to the ability of HLA-DRB1 * 01:01 to kinetically discriminate between antigenic exogenous peptides and endogenous MBP derived peptides.

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