Quach, Diana

Background and Objectives The genetic basis of adult-onset multiple sclerosis (MS) is well-studied, but less is known about pediatric-onset MS (pedMS), comprising approximately 5% of all MS onsets. Mendelian randomization (MR) studies have demonstrated evidence for a causal association between MS and both 25-hydroxyvitamin D [25(OH)D] serum levels and genetic variation related to vitamin D receptor (VDR) binding. The objective was to identify whether VDR binding variants (VDR-BVs) previously implicated in adult-onset MS were associated with pedMS using genetic instrumental variables (GIVs). Methods Using previously identified VDR-BVs to construct individual GIVs with two-sample MR, we investigated associations with pedMS in 725 cases and 592 controls of European ancestry from the US Network of Pediatric MS Centers. Associations between each VDR-BV and pedMS were estimated using logistic regression adjusting for the first three genome-wide principal components. A significant interaction between a VDR-BV and 25(OH)D GIV provided evidence for a causal association unbiased by pleiotropy. Results One VDR-BV, rs2531804, previously associated with adult-onset MS, was also significantly associated with pedMS after multiple testing correction. Discussion This study is the first to use VDR-BVs from previous MR studies to demonstrate causal differences in VDR binding at a locus contributing to pedMS susceptibility.

Background: Rare genetic variants are emerging as important contributors to the heritability of multiple sclerosis (MS). Whether rare variants also contribute to pediatric-onset multiple sclerosis (POMS) is unknown. Objective: To test whether genes harboring rare variants associated with adult-onset MS risk ( PRF1, PRKRA, NLRP8 , and HDAC7 ) and 52 major histocompatibility complex (MHC) genes are associated with POMS. Methods: We analyzed DNA samples from 330 POMS cases and 306 controls from the US Network of Pediatric MS Centers and Kaiser Permanente Northern California for which Illumina ExomeChip genotypes were available. Using the gene-based method “SKAT-O,” we tested the association between candidate genes and POMS risk. Results: After correction for multiple comparisons, one adult-onset MS gene ( PRF1, p = 2.70 × 10 −3 ) and two MHC genes ( BRD2, p = 5.89 × 10 −5 and AGER, p = 7.96 × 10 −5 ) were significantly associated with POMS. Results suggest these are independent of HLA-DRB1*1501. Conclusion: Findings support a role for rare coding variants in POMS susceptibility. In particular, rare minor alleles within PRF1 were more common among individuals with POMS compared to controls while the opposite was true for rare variants within significant MHC genes, BRD2 and AGER . These genes would not have been identified by common variant studies, emphasizing the merits of investigating rare genetic variation in complex diseases.

AbstractObjectiveOnset of multiple sclerosis (MS) occurs in childhood for approximately 5% of cases (pediatricMS, or ped‐MS). Epigenetic influences are strongly implicated inMSpathogenesis in adults, including the contribution from microRNAs (miRNAs), small noncodingRNAs that affect gene expression by binding target genemRNAs. Few studies have specifically examined miRNAs in ped‐MS, but individuals developingMSat an early age may carry a relatively high burden of genetic risk factors, and miRNAdysregulation may therefore play a larger role in the development of ped‐MSthan in adult‐onsetMS. This study aimed to look for evidence of miRNAinvolvement in ped‐MSpathogenesis.MethodsGWASresults from 486 ped‐MScases and 1362 controls from the U.S. PediatricMSNetwork and Kaiser Permanente Northern California membership were investigated for miRNA‐specific signals. First, enrichment of miRNA‐target gene network signals was evaluated usingMIGWASsoftware. Second,SNPs in miRNAgenes and in target gene binding sites (miR−SNPs) were tested for association with ped‐MS, and pathway analysis was performed on associated target genes.ResultsMIGWASanalysis showed that miRNA‐target gene signals were enriched inGWAS(P = 0.038) and identified 39 candidate biomarker miRNA‐target gene pairs, including immune and neuronal signaling genes. The miR‐SNPanalysis implicated dysregulation of miRNAbinding to target genes in five pathways, mainly involved in immune signaling.InterpretationEvidence fromGWASsuggests that miRNAs play a role in ped‐MSpathogenesis by affecting immune signaling and other pathways. Candidate biomarker miRNA‐target gene pairs should be further studied for diagnostic, prognostic, and/or therapeutic utility.

Background: Strong evidence supports the role of both genetic and environmental factors in pediatric-onset multiple sclerosis (POMS) etiology. Objective: We comprehensively investigated the association between established major histocompatibility complex (MHC) and non-MHC adult multiple sclerosis (MS)-associated variants and susceptibility to POMS. Methods: Cases with onset <18 years ( n = 569) and controls ( n = 16,251) were included from the United States and Sweden. Adjusted logistic regression and meta-analyses were performed for individual risk variants and a weighted genetic risk score (wGRS) for non-MHC variants. Results were compared to adult MS cases ( n = 7588). Results: HLA–DRB1*15:01 was strongly associated with POMS (odds ratio (OR) meta = 2.95, p < 2.0 × 10 −16 ). Furthermore, 28 of 104 non-MHC variants studied (23%) were associated ( p < 0.05); POMS cases carried, on average, a higher burden of these 28 variants compared to adults (OR avg = 1.24 vs 1.13, respectively), though the difference was not significant. The wGRS was strongly associated with POMS (OR meta = 2.77, 95% confidence interval: 2.33, 3.32, p < 2.0 × 10 −16 ) and higher, on average, when compared to adult cases. Additional class III risk variants in the MHC region associated with POMS were revealed after accounting for HLA–DRB1*15:01 and HLA–A*02. Conclusion: Pediatric and adult MS share many genetic variants suggesting similar biological processes are present. MHC variants beyond HLA–DRB1*15:01 and HLA–A*02 are also associated with POMS.