Joshua D. Lee

Nuclear Receptor NR1H3 in Familial Multiple Sclerosis

Multiple sclerosis (MS) is an inflammatory disease characterized by myelin loss and neuronal dysfunction. Despite the aggregation observed in some families, pathogenic mutations have remained elusive. In this study, we describe the identification of NR1H3 p.Arg415Gln in seven MS patients from two multi-incident families presenting severe and progressive disease, with an average age at onset of 34 years. Additionally, association analysis of common variants in NR1H3 identified rs2279238 conferring a 1.35-fold increased risk of developing progressive MS. The p.Arg415Gln position is highly conserved in orthologs and paralogs, and disrupts NR1H3 heterodimerization and transcriptional activation of target genes. Protein expression analysis revealed that mutant NR1H3 (LXRA) alters gene expression profiles, suggesting a disruption in transcriptional regulation as one of the mechanisms underlying MS pathogenesis. Our study indicates that pharmacological activation of LXRA or its targets may lead to effective treatments for the highly debilitating and currently untreatable progressive phase of MS.

Multiple sclerosis in the Iranian immigrant population of BC, Canada: prevalence and risk factors

Background: There is a well-documented increase in the risk of multiple sclerosis (MS) when migrating from a region of low prevalence to one of high prevalence. Objective: We present here an investigation of MS prevalence and candidate environmental and genetic risk factors among Iranian immigrants to British Columbia (BC), Canada. Methods: MS cases of Iranian ancestry were ascertained from a population-based Canadian study. We collected blood samples for genetic and serological analyses, and administered a personal history questionnaire to the cases. Results: The crude prevalence of MS in this population of Iranian ancestry was 287/100,000 (95% CI: 229 – 356/100,000). MS cases were more likely to have a history of infectious mononucleosis (odds ratio (OR) = 7.5; p = 0.005) and smoking (OR = 17.0; p < 0.0001), as compared to healthy controls from previous studies in Iran. Cases were also more likely than controls to have been born between April and September (OR = 2.1; p = 0.019). Conclusion: The prevalence of MS among Iranian immigrants to Canada is greater than the overall prevalence of MS in Iran by a factor of at least four, and is similar to that recently observed among Iranian immigrants in other western nations. No major genetic susceptibility variants were identified, suggesting the environment in Canada may be what is increasing the risk of MS in this population.

Analysis of CYP27B1 in multiple sclerosis

The analysis of genetic variability in CYP27B1 and its effect on risk of multiple sclerosis (MS) has yielded conflicting results. Here we describe a study to genetically characterize CYP27B1 and elucidate its role on MS risk in the Canadian population. Sequencing CYP27B1 failed to identify mutations known to cause loss of enzymatic activity, however genotyping of p.R389H in cases and controls identified the mutation in one multi-incident family (allele frequency=0.03%) in which the p.R389H mutation segregates with disease in five family members diagnosed with MS, thus providing additional support for CYP27B1 p.R389H in the pathogenicity of MS.

Genetic variants in IL2RA and IL7R affect multiple sclerosis disease risk and progression.

Multiple sclerosis (MS) is a common demyelinating neurodegenerative disease with a strong genetic component. Previous studies have associated genetic variants in IL2RA and IL7R in the pathophysiology of the disease. In this study, we describe the association between IL2RA (rs2104286) and IL7R (rs6897932) in the Canadian population. Genotyping 1,978 MS patients and 830 controls failed to identify any significant association between these variants and disease risk. However, stratified analysis for family history of disease and disease course identified a trend towards association for IL2RA in patients without a family history (p = 0.05; odds ratio = 0.77) and a significant association between IL7R and patients who developed progressive MS (PrMS) (p = 0.002; odds ratio = 0.73). Although not statistically significant, the effect of IL2RA (rs2104286) in patients without a family history of MS indicates that the genetic components for familial and sporadic disease are perhaps distinct. This data suggests that the onset of sporadic disease is likely determined by a large number of variants of small effect, whereas MS in patients with a family history of disease is caused by a few deleterious variants. In addition, the significant association between PrMS and rs6897932 indicates that IL7R may not be disease-causing but a determinant of disease course. Further characterization of the effect of IL2RA and IL7R genetic variants in defined MS subtypes is warranted to evaluate the effect of these genes on specific clinical outcomes and to further elucidate the mechanisms of disease onset and progression.

Analysis of CH25H in multiple sclerosis and neuromyelitis optica

Oxysterols produced by CH25H during cholesterol metabolism have been shown to play an important role in the immune response. In this study we report the genetic characterization of CH25H in patients diagnosed with multiples sclerosis (MS) or neuromyelitis optica (NMO), for the identification of genetic variants affecting disease susceptibility and course. Exome analysis in 212 MS and 14 NMO patients identified a rare CH25H p.Q17H mutation in two NMO patients of Asian ancestry. In addition, association analysis of common CH25H variants identified a nominally significant association with MS patients presenting a clinical course consistent with primary progressive disease.

Colony stimulation factor 1 receptor (CSF1R) is not a common cause of multiple sclerosis

Hereditary diffuse leukoencephalopathy with spheroids (HDLS) is a rare autosomal dominant disorder characterized by cerebral white-matter degeneration. The onset of disease is typically in the fourth decade of life, and involves psychiatric, neurological and somatic symptoms leading to progressive cognitive and motor dysfunction [1,2]. In MRI, HDLS initially appears as patchy asymmetrical abnormalities in cerebral white matter that become confluent and symmetrical as the disease progresses [3]. A definite diagnosis of HDLS relies on widespread loss of myelin sheaths and axonal degeneration, neuronal spheroids, gliosis and accumulation of lipid-laden macrophages at pathological examination [1]. Missense, frame-shift and splice-site mutations in colony stimulation factor 1 receptor (CSF1R) have recently been identified as the cause of HDLS [4]. Although the pathological presentation was consistent with HDLS, the clinical presentation was found to include multiple sclerosis (MS), Parkinson’s disease, Alzheimer’s disease, or frontotemporal dementia. Interestingly, a recent study identified three patients diagnosed with MS harboring CSF1R mutations [5]. Multiple sclerosis is an inflammatory disease of the CNS characterized by myelin loss, varying degrees of axonal injury, and progressive neurological dysfunction. Due to the clinical and pathological overlap between MS and HDLS, the clinical diagnosis of MS in patients with CSF1R mutations [4,5], and the biological role of CSF1R in the inflammatory response, the question of whether mutations in CSF1R are implicated in the pathological mechanisms necessary to trigger the onset of MS was evaluated (methods are provided as supplemental information; Data S1). Genetic characterization of the entire coding sequence of CSF1R in 95 probands diagnosed with MS did not identify any of the previously reported pathogenic variants for HDLS [4,5]. Similarly, novel coding substitutions, frame shifts or splice-site mutations were not observed. Detailed information for 12 previously reported CSF1R coding variants identified in this study (five missense and seven silent) is provided in Table 1. Minor allele frequencies for these variants were consistent with those previously reported in healthy controls, suggesting they are unlikely to have an effect on MS risk. The identification of CSFR1 pathogenic mutations in HDLS [4] suggested the possibility that this gene could be implicated in other more common whitematter disorders, including MS. Additional support for this hypothesis was provided by the identification of CSF1R mutations in patients clinically diagnosed with MS [5]. However, despite the clinical and pathological overlap between HDLS and MS, sequencing of CSF1R in MS patients failed to identify any of the previously described HDLS mutations or novel mutations with potentially pathogenic effects. Although the presence of CSF1R mutations could not be confirmed in a relatively small sample of MS patients, further studies in larger cohorts of MS patients, as well as other degenerative white-matter diseases, are warranted. In conclusion, our study indicates that pathogenic mutations in CSF1R are an unlikely cause of MS in the Canadian population.

Incidence of Multiple Sclerosis and Related Disorders in Asian Populations of British Columbia.

BACKGROUND Global variation in the incidence of multiple sclerosis (MS) is generally ascribed to differences in genetic and environmental risk factors. Here we investigate temporal trends in the incidence of MS and related disorders in British Columbia, Canada, from 1986 to 2010, focusing particularly on the Asian ethnic subpopulation. METHODS A longitudinal database was screened to identify newly diagnosed cases of MS and related disorders, including neuromyelitis optica and clinically isolated syndromes. Age-standardized, sex-specific mean annual incidence was calculated for the Asian and non-Asian population of British Columbia for 5-year intervals from 1986 to 2010. Temporal changes and cohort differences in incidence rates and demographic characteristics were evaluated. RESULTS During this period, the incidence of MS and related disorders in the non-Asian population remained relatively unchanged, from 10.41 (95% confidence interval [CI]: 9.87-10.97) to 9.91 (95% CI: 9.46-10.39) per 100,000 (p=0.167). In contrast, incidence in the Asian population doubled during the same period. This increase was driven by a precipitous rise in the incidence of MS in females from 0.71 (95% CI: 0.01-1.50) to 2.08 (95% CI: 1.43-2.91) per 100,000 (p=0.004), including both Canadian-born and immigrant Asians. The incidence of neuromyelitis optica did not change significantly during this period. CONCLUSIONS The incidence of MS may be increasing among females in the Asian ethnic population of British Columbia.

Progressive multiple sclerosis does not associate with rs996343 and rs2046748

A genome-wide association study in a small case-control series of patients with progressive multiple sclerosis (PrMS; primary progressive (PPMS) and secondary progressive (SPMS)) identified an intergenic variant (rs996343) with a putative role in disease course.1 Nominally significant associations were also identified in dipeptidyl-peptidase 6 (DPP6), which after further genetic characterization nominated rs2046748 as a determinant of MS course.2 To further define the effect of rs996343 and rs2046748 on disease progression, we genotyped a series of multiple sclerosis (MS) patients and unrelated healthy controls from Canada. Genetic analyses were performed in MS patients and unrelated healthy controls of European ancestry collected through the longitudinal Canadian Collaborative Project on the Genetic Susceptibility to Multiple Sclerosis (CCPGSMS).3 The ethical review boards at the University of British Columbia approved the study, and all participants provided informed consent. All patients were diagnosed with MS according to Poser or McDonald criteria.4,5 A total of 1984 MS patients and 843 controls were characterized in this study. Detailed clinical course was available for 1634 patients (82.4%); the majority presented a clinical course consistent with relapsing–remitting MS (RRMS) (n=891; 54.5%), and the remainder presented with PPMS (n=408; 25.0%) or SPMS (n=335; 20.5%). Detailed demographics for each group are provided in Supplementary Material, Table 1. Genotyping of rs996343 and rs2046748 was performed using TaqMan probes as previously described.6 Allelic and genotypic associations were examined by the Chi-squared test. All variants were consistent with Hardy-Weinberg equilibrium. Power analysis estimates for rs996343, assuming an additive model with a disease frequency of 0.001, a genotype relative risk of 0.7, and the minor allele frequency (MAF=0.41) observed in healthy controls, indicates that our study has over 99% power to identify a positive association, at the significance level of 0.05, in the entire MS cohort or for patients presenting with RRMS, 99% for PrMS, 95% for PPMS and 92% for SPMS disease course. Applying the same model to rs2046748, assuming a MAF of 0.11 and a genotype relative risk of 1.82 we estimated over 99% power of detecting positive associations for the entire MS cohort, or for RRMS and PrMS patients, 98% for PPMS and 97% for SPMS. Association analysis of rs996343 and rs2046748 in 1984 MS patients and 843 controls from Canada did not identify a significant association between genotypic or allelic frequencies and susceptibility to MS for either variant. Similarly, significant associations for rs996343 or rs2046748 were not observed between healthy controls and RRMS, PPMS, SPMS or PrMS patients (Supplementary Material, Table 1). Likewise, differences between RRMS and PrMS were not identified (data not shown). Despite the large number of patients with MS and controls examined in this study, our data does not support a role for rs996343 and rs2046748 in the susceptibility to disease in the Canadian population. Moreover, the analysis of disease subtypes is also not supportive of the previously suggested effect on MS progression.1,2 It should be noted that not all of the replication groups from the original studies resulted in a significant association between the nominated variants and disease progression; these discrepancies were attributed to either a false positive signal in the discovery group or differences in population-specific allelic frequencies. The lack of support provided by our study indicates that the former hypothesis is more likely correct, suggesting that rs996343 and rs2046748 do not affect the development of PrMS. However, additional studies in Southern European populations are warranted. Therapeutic strategies for MS are currently ineffective to treat the progressive phase of the disease. The reason for this failure can probably be attributed to targeting the immune system, which is likely to play a minor role in the accumulation of the neuronal and synaptic damage observed in the pathophysiology of PrMS.7 Comprehensive genetic studies in large cohorts of well-characterized patients with PrMS are necessary for the identification of variants, genes, and molecular pathways implicated in the onset of this progressive phase. Unraveling the etiology of PPMS and SPMS is paramount for the development of effective therapeutics to treat the underlying molecular causes of PrMS. 517280 MSJ0010.1177/1352458513517280Multiple Sclerosis JournalBernales et al. research-article2013

Editorial Note to:Nuclear Receptor NR1H3 in Familial Multiple Sclerosis

(Neuron 90, 948–954; June 1, 2016) In this issue, we, the editors of Neuron, are publishing a Matters Arising in connection to the paper listed above, which Neuron published in June by Wang, Vilariño-G€ uell, and colleagues. In the original report, Wang et al. (2016a) reported that a missense variant of NR1H3 p.Arg415Gln (rs61731956) is associated with multiple sclerosis (MS) in patients from two unrelated families where several members are affected with the disease. The two Matters Arising articles, one from Chris Cotsapas, on behalf of the International Multiple Sclerosis Genetics Consortium, and a second from EricMinikel and Daniel MacArthur from the Broad Institute, argue against these conclusions. They suggest that the statistical estimates in the Wang study are weak and report that the proposed pathogenic allele is found in several unaffected individuals in large datasets of cases and controls that their groups have acquired.