No influence on disease progression of non-HLA susceptibility genes in MS

Class II HLA (DRB1, & DQB1) alleles and IL7R (rs6897932) variants and the risk for Multiple Sclerosis in Kerala, India

BACKGROUND

Different human leukocyte antigen (HLA) variants are known to modulate the risk of multiple sclerosis. The main objective of this study was to identify HLA-DRB1 and HLA-DQB1 alleles and Non -HLA gene IL7R (rs6897932) variants associated with MS.

METHODS

Patients attending the MS clinic, diagnosed with Multiple Sclerosis as per Mc Donald diagnostic criteria were the subjects in the study. The association of the highly polymorphic HLA-DRB1 and HLA-DQB1 loci was determined by high resolution tissue typing and the genotyping of the IL7R (rs6897932) variants was performed by Sanger sequencing in MS patients (n = 81) and healthy individuals (n = 82).

RESULTS

HLA-DRB1*15:01/15:02 alleles (OR = 3.65; p< 0.0001) and HLA-DQB1*06:02 (OR=4.19, p<0.0001) were found to be positively associated while HLA-DRB1*14:04:01 (OR = 0.21; p = 0.0009) was found to be negatively associated with MS. The most significant predisposing HLA haplotype was found to be DRB1*15:01-DQB1*06:02 (OR=5.69, p<0.0001). Univariate analysis of IL7R SNP (rs6897932) showed no significant association with MS in our population whereas analysis of HLA-DRB1 alleles and IL7R (rs6897932) genotypes showed significant association between the HLA-DRB1*15:01/15:02 and the IL7R (rs6897932) CC genotype (OR = 3.58, p = 0.0002).

CONCLUSION

HLA-DRB1*15:01, 15:02 and DQB1*06:02 are the predisposing alleles while HLA-DRB1*14:04 is the protective allele for MS in our population.

Identification of an iron-responsive subtype in two children diagnosed with relapsing-remitting multiple sclerosis using whole exome sequencing

Background

Multiple sclerosis is a disorder related to demyelination of axons. Iron is an essential cofactor in myelin synthesis. Previously, we described two children (males of mixed ancestry) with relapsing-remitting multiple sclerosis (RRMS) where long-term remission was achieved by regular iron supplementation. A genetic defect in iron metabolism was postulated, suggesting that more advanced genetic studies could shed new light on disease pathophysiology related to iron.

Methods

Whole exome sequencing (WES) was performed to identify causal pathways. Blood tests were performed over a 10 year period to monitor the long-term effect of a supplementation regimen. Clinical wellbeing was assessed quarterly by a pediatric neurologist and regular feedback was obtained from the schoolteachers.

Results

WES revealed gene variants involved in iron absorption and transport, in the transmembrane protease, serine 6 (TMPRSS6) and transferrin (TF) genes; multiple genetic variants in CUBN, which encodes cubilin (a receptor involved in the absorption of vitamin B12 as well as the reabsorption of transferrin-bound iron and vitamin D in the kidneys); SLC25A37 (involved in iron transport into mitochondria) and CD163 (a scavenger receptor involved in hemorrhage resolution). Variants were also found in COQ3, involved with synthesis of Coenzyme Q10 in mitochondria. Neither of the children had the HLA-DRB1*1501 allele associated with increased genetic risk for MS, suggesting that the genetic contribution of iron-related genetic variants may be instrumental in childhood MS. In both children the RRMS has remained stable without activity over the last 10 years since initiation of nutritional supplementation and maintenance of normal iron levels, confirming the role of iron deficiency in disease pathogenesis in these patients.

Conclusion

Our findings highlight the potential value of WES to identify heritable risk factors that could affect the reabsorption of transferrin-bound iron in the kidneys causing sustained iron loss, together with inhibition of vitamin B12 absorption and vitamin D reabsorption (CUBN) and iron transport into mitochondria (SLC25A37) as the sole site of heme synthesis. This supports a model for RRMS in children with an apparent iron-deficient biochemical subtype of MS, with oligodendrocyte cell death and impaired myelination possibly caused by deficits of energy- and antioxidant capacity in mitochondria.

Interferon beta treatment of multiple sclerosis increases serum interleukin-7

BACKGROUND

Interleukin-7 (IL-7) is a non-redundant cytokine for T-cell development and survival. The IL-7 signaling pathway has been genetically and functionally associated with several autoimmune diseases including multiple sclerosis (MS).

OBJECTIVE

The objective of this paper is to elucidate the effect of the widely used immunomodulatory MS therapy interferon beta (IFNβ) on IL-7 homeostasis.

METHODS

Swedish MS patients were screened for IL-7 concentration in serum and blood cell counts. IL-7 receptor alpha chain (IL-7Rα) expression was determined by semi-quantitative real-time polymerase chain reaction (PCR) and flow cytometry.

RESULTS

IFNβ treatment led to significantly increased serum IL-7 levels (mean: 17 pg/ml) compared with healthy controls (mean: 7.6 pg/ml) and natalizumab-treated patients (mean: 5.3 pg/ml). In vitro and in vivo, peripheral blood leukocytes showed decreased IL-7Rα expression and IL-7 consumption upon IFNβ exposure, suggesting that their IL-7 responsiveness is impaired during treatment.

CONCLUSIONS

MS patients undergoing IFNβ treatment have increased serum IL-7 levels and decreased IL-7 consumption. Given IL-7's important role in T-cell immunity, this relationship may be highly relevant for IFNβ's treatment efficacy.

CD226 Gly307Ser association with neuromyelitis optica in Southern Han Chinese

BACKGROUND

Neuromyelitis optica (NMO) and multiple sclerosis (MS) are autoimmune diseases of the central nervous system with complex pathogeneses. NMO was once considered to be a severe variant of MS. There has been more evidence that a non-synonymous exchange (rs763361/Gly307Ser) in the gene for CD226 is linked to several autoimmune diseases including multiple sclerosis (MS). However, no studies have investigated the role of rs763361 in the pathogenesis of NMO.

OBJECTIVES

The goal of our study is to evaluate the role of CD226 Gly307Ser in neuromyelitis optica (NMO) in Southern Han Chinese.

METHODS

Eight-nine NMO patients, 93 relapsing-remitting multiple sclerosis (RRMS) patients, and 122 controls (CTLs) were enrolled. The rs763361 alleles of the subjects were determined by sequencing-based typing.

RESULTS

The results strongly support that the TT genotypes are associated with NMO but are not significantly correlated with susceptibility for MS.

CONCLUSIONS

CD226 Gly307Ser may correlate with risk of NMO in Southern Han Chinese.

Glutamate gene polymorphisms predict brain volumes in multiple sclerosis

Background:

Several genetic markers have been associated with multiple sclerosis (MS) susceptibility; however, uncovering the genetic aetiology of the complex phenotypic expression of MS has been more difficult so far. The most common approach in imaging genetics is based on mass-univariate linear modelling (MULM), which faces several limitations.

Objective:

Here we apply a novel multivariate statistical model, sparse reduced-rank regression (sRRR), to identify possible associations of glutamate related single nucleotide polymorphisms (SNPs) and multiple MRI-derived phenotypes in MS.

Methods:

Seven phenotypes related to brain and lesion volumes for a total number of 326 relapsing–remitting and secondary-progressive MS patients and a total of 3809 glutamate related and control SNPs were analysed with sRRR, which resulted in a ranking of SNPs in decreasing order of importance (‘selection probability’). Lasso regression and MULM were used as comparative statistical techniques to assess consistency of the most important associations over different statistical models.

Results:

Five SNPs within the NMDA-receptor-2A-subunit (GRIN2A) domain were identified by sRRR in association with normalized brain volume (NBV), normalized grey matter volume and normalized white matter volume (NMWM). The association between GRIN2A and both NBV and NWMV was confirmed in MULM and Lasso analysis.

Conclusions:

Using a novel, multivariate regression model confirmed by two other statistical approaches we show associations between GRIN2A SNPs and phenotypic variation in NBV and NWMV in this first exploratory study. Replications in independent datasets are now necessary to validate these findings.