miRNA contributions to pediatric-onset multiple sclerosis inferred from GWAS.

ObjectiveOnset of multiple sclerosis (MS) occurs in childhood for approximately 5% of cases (pediatric MS, or ped-MS). Epigenetic influences are strongly implicated in MS pathogenesis in adults, including the contribution from microRNAs (miRNAs), small noncoding RNAs that affect gene expression by binding target gene mRNAs. Few studies have specifically examined miRNAs in ped-MS, but individuals developing MS at an early age may carry a relatively high burden of genetic risk factors, and miRNA dysregulation may therefore play a larger role in the development of ped-MS than in adult-onset MS. This study aimed to look for evidence of miRNA involvement in ped-MS pathogenesis.MethodsGWAS results from 486 ped-MS cases and 1362 controls from the U.S. Pediatric MS Network and Kaiser Permanente Northern California membership were investigated for miRNA-specific signals. First, enrichment of miRNA-target gene network signals was evaluated using MIGWAS software. Second, SNPs in miRNA genes and in target gene binding sites (miR-SNPs) were tested for association with ped-MS, and pathway analysis was performed on associated target genes.ResultsMIGWAS analysis showed that miRNA-target gene signals were enriched in GWAS (P = 0.038) and identified 39 candidate biomarker miRNA-target gene pairs, including immune and neuronal signaling genes. The miR-SNP analysis implicated dysregulation of miRNA binding to target genes in five pathways, mainly involved in immune signaling.InterpretationEvidence from GWAS suggests that miRNAs play a role in ped-MS pathogenesis by affecting immune signaling and other pathways. Candidate biomarker miRNA-target gene pairs should be further studied for diagnostic, prognostic, and/or therapeutic utility

Associations between the gut microbiota and host immune markers in pediatric multiple sclerosis and controls.

BackgroundAs little is known of association(s) between gut microbiota profiles and host immunological markers, we explored these in children with and without multiple sclerosis (MS).MethodsChildren ≤18 years provided stool and blood. MS cases were within 2-years of onset. Fecal 16S rRNA gene profiles were generated on an Illumina Miseq platform. Peripheral blood mononuclear cells were isolated, and Treg (CD4+CD25hiCD127lowFoxP3+) frequency and CD4+ T-cell intracellular cytokine production evaluated by flow cytometry. Associations between microbiota diversity, phylum-level abundances and immune markers were explored using Pearson's correlation and adjusted linear regression.ResultsTwenty-four children (15 relapsing-remitting, nine controls), averaging 12.6 years were included. Seven were on a disease-modifying drug (DMD) at sample collection. Although immune markers (e.g. Th2, Th17, Tregs) did not differ between cases and controls (p > 0.05), divergent gut microbiota associations occurred; richness correlated positively with Th17 for cases (r = +0.665, p = 0.018), not controls (r = -0.644, p = 0.061). Bacteroidetes inversely associated with Th17 for cases (r = -0.719, p = 0.008), not controls (r = +0.320, p = 0.401). Fusobacteria correlated with Tregs for controls (r = +0.829, p = 0.006), not cases (r = -0.069, p = 0.808).ConclusionsOur observations motivate further exploration to understand disruption of the microbiota-immune balance so early in the MS course

Longitudinal evaluation of cognitive functioning in pediatric multiple sclerosis: report from the US Pediatric Multiple Sclerosis Network

BackgroundApproximately one-third of those with pediatric-onset multiple sclerosis (MS) experience cognitive impairment. Less is known concerning their change in cognitive functioning over time.ObjectiveChanges in cognitive function over time were measured in the largest pediatric cohort to date through the US Network of Pediatric MS Centers.MethodsA total of 67 individuals with pediatric MS (n=62) or clinically isolated syndrome (CIS, n=5), ranging from 8-17 years of age (mean age ± standard deviation (SD)=14.37 ± 2.02) completed initial and follow-up neuropsychological testing after an average of 1.64 ± 0.63 years apart. The nine tests administered measure general intellect, attention and working memory, verbal memory, visuomotor integration, language, and executive functioning.ResultsRate of impairment (having one-third or more scores in the impaired range) was 37% at baseline and 33% at follow-up. Tests commonly impaired were measures of visuomotor integration, speeded processing, and attention. Most tested did not decline over two years. There was no clear pattern of change on any specific measure.ConclusionFindings suggest that, over short timeframes, stable or even improved performances on measures of cognitive ability can occur. Pediatric MS may instead prevent expected age-related cognitive gains

Genetic predictors of relapse rate in pediatric MS

BackgroundGenetic ancestry, sex, and individual alleles have been associated with multiple sclerosis (MS) susceptibility.ObjectiveTo determine whether established risk factors for disease onset are associated with relapse rate in pediatric MS.MethodsWhole-genome genotyping was performed for 181 MS or high-risk clinically isolated syndrome patients from two pediatric MS centers. Relapses and disease-modifying therapies were recorded as part of continued follow-up. Participants were characterized for 25-hydroxyvitamin D serum status. Ancestral estimates (STRUCTURE v2.3.1), human leukocyte antigen (HLA)-DRB1*15 carrier status (direct sequencing), sex, and a genetic risk score (GRS) of 110 non-HLA susceptibility single-nucleotide polymorphisms (SNPs) were evaluated for association with relapse rate with Cox and negative binomial regression models.ResultsOver 622 patient-years, 408 relapses were captured. Girls had greater relapse rate than boys (incident rate ratio (IRR) = 1.40, 95% confidence interval (CI) = 1.04-1.87, p = 0.026). Participants were genetically diverse; ~40% (N = 75) had <50% European ancestry. HLA-DRB1*15 status modified the association of vitamin D status (pixn = 0.022) with relapse rate (per 10 ng/mL, in DRB1*15+ hazard ratio (HR) = 0.72, 95% CI = 0.58-0.88, p = 0.002; in DRB1*15- HR = 0.96, 95% CI = 0.83-1.12, p = 0.64). Neither European ancestry nor GRS was associated with relapse rate.ConclusionWe demonstrate that HLA-DRB1*15 modifies the association of vitamin D status with relapse rate. Our findings emphasize the need to pursue disease-modifying effects of MS genes in the context of environmental factors

Examining the contributions of environmental quality to pediatric multiple sclerosis

BackgroundMultiple sclerosis (MS) is a presumed autoimmune disease caused by genetic and environmental factors. It is hypothesized that environmental exposures (such as air and water quality) trigger the innate immune response thereby activating a pro-inflammatory cascade.ObjectiveTo examine potential environmental factors in pediatric MS using geographic information systems (GIS).MethodsPediatric MS cases and healthy controls were identified as part of an ongoing multicenter case-control study. Subjects' geographic locations were mapped by county centroid to compare to an Environmental Quality Index (EQI). The EQI examines 5 individual environmental components (air, land, water, social, built factors). A composite EQI score and individual scores were compared between cases and controls, stratified by median proximity to enrollment centers (residence <20 or ≥20 miles from the recruiting center), using logistic regression.ResultsOf the 287 MS cases and 445 controls, 46% and 49% respectively live in areas where the total EQI is the highest (worst environmental quality). Total EQI was not significantly associated with the odds for MS (p = 0.90 < 20 miles from center; p = 0.43 ≥ 20 miles); however, worsening air quality significantly impacted the odds for MS in those living near a referral center (OR = 2.83; 95%CI 1.5, 5.4) and those who reside ≥ 20 miles from a referral center (OR = 1.61; 95%CI 1.2, 2.3).ConclusionAmong environmental factors, air quality may contribute to the odds of developing MS in a pediatric population. Future studies will examine specific air constituents and other location-based air exposures and explore potential mechanisms for immune activation by these exposures