Background

Substantial progress has been made toward unraveling the genetic architecture of multiple sclerosis (MS) within populations of European ancestry, but few genetic studies have focused on Hispanic and African American populations within the United States.

Objective

We sought to test the relevance of common European MS risk variants outside of the major histocompatibility complex (n = 200) within these populations.

Methods

Genotype data were available on 2652 Hispanics (1298 with MS, 1354 controls) and 2435 African Americans (1298 with MS, 1137 controls). We conducted single variant, pathway, and cumulative genetic risk score analyses.

Results

We found less replication than statistical power suggested, particularly among African Americans. This could be due to limited correlation between the tested and causal variants within the sample or alternatively could indicate allelic and locus heterogeneity. Differences were observed between pathways enriched among the replicating versus all 200 variants. Although these differences should be examined in larger samples, a potential role exists for gene-environment or gene-gene interactions which alter phenotype differentially across racial and ethnic groups. Cumulative genetic risk scores were associated with MS within each study sample but showed limited diagnostic capability.

Conclusion

These findings provide a framework for fine-mapping efforts in multi-ethnic populations of MS.

Background and objective

Hispanics with multiple sclerosis (MS) present younger and more often with optic neuritis (ON) as compared to Whites in the western United States. Regional differences related to Hispanic genetic admixture could be responsible. We investigated the association between global genetic ancestry and ON and age at onset of MS in Hispanics.

Methods

Data were obtained for 1033 self-identified Hispanics with MS from four MS-based registries from four academic institutions across the United States January 2016-April 2017. Multivariate regression models, utilizing genetic ancestry estimates for Native American (NA), African, and European ancestry, were used to assess the relationship between genetic ancestry and ON presentation and age of MS onset, defined as age at first symptom.

Results

Genetic ancestry and ON proportions varied by region where NA ancestry and ON proportions were highest among Hispanics in the southwestern United States (40% vs. 19% overall for NA and 38% vs. 25% overall for ON). A strong inverse correlation was observed between NA and European ancestry (r = -0.83). ON presentation was associated with younger age of onset (OR: 0.98; 95% CI: 0.96-0.99; P = 7.80 × 10^-03) and increased NA ancestry (OR: 2.35 for the highest versus the lowest quartile of NA ancestry; 95% CI: 1.35-4.10; P = 2.60 × 10^-03). Younger age of onset was found to be associated with a higher proportion NA (Beta: -5.58; P = 3.49 × 10^-02) and African ancestry (Beta: -10.07; P = 1.39 × 10^-03).

Interpretation

Ethnic differences associated with genetic admixture could influence clinical presentation in Hispanics with MS; underscoring the importance of considering genetic substructure in future clinical, genetic, and epigenetic studies in Hispanics.

The Major Histocompatibility Complex (MHC) makes the largest genetic contribution to multiple sclerosis (MS) susceptibility, with 32 independent effects across the region explaining 20% of the heritability in European populations. Variation is high across populations with allele frequency differences and population-specific risk alleles identified. We sought to identify MHC-specific MS susceptibility variants and assess the effect of ancestral risk modification within 2652 Latinx and Hispanic individuals as well as 2435 Black and African American individuals. We have identified several novel susceptibility alleles which are rare in European populations including HLA-B*53:01, and we have utilized the differing linkage disequilibrium patterns inherent to these populations to identify an independent role for HLA-DRB1*15:01 and HLA-DQB1*06:02 on MS risk. We found a decrease in Native American ancestry in MS cases vs controls across the MHC, peaking near the previously identified MICB locus with a decrease of ~5.5% in Hispanics and ~0.4% in African Americans. We have identified several susceptibility variants, including within the MICB gene region, which show global ancestry risk modification and indicate ancestral differences which may be due in part to correlated environmental factors. We have also identified several susceptibility variants for which MS risk is modified by local ancestry and indicate true ancestral genetic differences; including HLA-DQB1*06:02 for which MS risk for European allele carriers is almost two times the risk for African allele carriers. These results validate the importance of investigating MS susceptibility at an ancestral level and offer insight into the epidemiology of MS phenotypic diversity.

The All of Us Research Program seeks to engage at least one million diverse participants to advance precision medicine and improve human health. We describe here the cloud-based Researcher Workbench that uses a data passport model to democratize access to analytical tools and participant information including survey, physical measurement, and electronic health record (EHR) data. We also present validation study findings for several common complex diseases to demonstrate use of this novel platform in 315,000 participants, 78% of whom are from groups historically underrepresented in biomedical research, including 49% self-reporting non-White races. Replication findings include medication usage pattern differences by race in depression and type 2 diabetes, validation of known cancer associations with smoking, and calculation of cardiovascular risk scores by reported race effects. The cloud-based Researcher Workbench represents an important advance in enabling secure access for a broad range of researchers to this large resource and analytical tools.