No linkage or association of the nitric oxide synthase genes to multiple sclerosis

Endothelial nitric oxide synthase (NOS3) rs2070744 polymorphism and risk for multiple sclerosis

The possible role of oxidative stress and nitric oxide (NO) in the pathogenesis of multiple sclerosis (MS) has been suggested by several neuropathological, biochemical, and experimental data. Because the single-nucleotide polymorphism (SNP) rs2070744 in the endothelial nitric oxide synthase (eNOS or NOS3) gene (chromosome 7q36.1) showed association with the risk for MS in Iranians, we attempted to replicate the possible association between this SNP and the risk for MS in the Caucasian Spanish population. The frequencies of NOS3rs2070744 genotypes and allelic variants in 300 patients diagnosed with MS and 380 healthy controls were assessed with a TaqMan-based qPCR assay. The possible influence of the genotype frequency on age at onset of MS, the severity of MS, clinical evolutive subtypes of MS, and HLA-DRB1*1501 genotype were also analyzed. The frequencies of rs2070744 genotypes and allelic variants were not associated with the risk of developing MS and were not influenced by gender, age at onset and severity of MS, the clinical subtype of MS or the HLA-DRB1*1501 genotype. This study found a lack of association between NOS3 rs2070744 SNP and the risk for MS in Caucasian Spanish people.

Molecular Analysis of rs2070744 and rs1799983 Polymorphisms of NOS3 Gene in Iranian Patients With Multiple Sclerosis

Introduction

Multiple Sclerosis (MS) is a disease of central nervous system that mainly causes lesions or plaques in the spinal cord and brain. The purpose of this study was to analyze the relation between c.-813C>T (rs2070744) and c.894G>T (rs1799983) polymorphisms of NOS3 gene and MS in Iranian patients.

Methods

A total of 78 patients with MS and 80 healthy controls were screened for NOS3 (rs2070744 and rs1799983) Single Nucleotide Polymorphisms (SNPs) by tetra-primer multiplex ARMS-PCR and PCR-RFLP.

Results

Genotype frequencies of the c.-813C>T polymorphism in patients compared to controls were as follows: 53.8% to 80.0% for TT genotype, 41.0% to 18.8% for TC genotype, and 5.1% versus 1.2% for CC genotype (P=0.001). The frequencies of GG genotype was 57.7% and 78.8% and for GT genotype of c.894G>T polymorphism in patients compared to control subjects was 42.3% and 21.2%, respectively (P=0.004).

Conclusion

Our results indicate that the studied NOS3 polymorphisms may be associated with MS in Iranian patients.

Association analysis of nitric oxide synthases: NOS1, NOS2A and NOS3 genes, with multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a chronic inflammatory autoimmune disorder of the central nervous system.

AIM

To explore the genetic basis of three nitric oxide synthase (NOS) genes: NOS1, NOS2A and NOS3, with susceptibility to MS.

SUBJECTS AND METHODS

A total of 122 MS patients and 118 healthy controls screened for NOS1 (rs2682826, rs41279104), NOS2A (CCTTT)n/(TAAA)n and NOS3 (rs1800783, rs1800779, rs2070744, 27bpVNTR) markers, using TaqMan®SNP Genotyping Assays and fragment analysis were enrolled in this study. QRT-PCR and ELISA were used to analyse the expression of NOS3 mRNA and Nitric Oxide (NO) levels.

RESULTS

Two NOS3 markers were associated with susceptibility to MS and early disease development. The NOS3 rs1800779 G-allele (p = 0.04) and GG-genotype (p = 0.02) showed association with susceptibility to MS. Short NOS2 (CCTTT)n (p = 0.03) and short/long repeat (p = 0.04) genotypes also showed associations with MS. These associations were intensified by sub-division of patients into Kuwaiti Arabs and Persians (p < 0.05). The NOS3-27 bp-VNTR a-allele was associated with early MS disease onset ≤26 years (p = 0.04). The NOS3-27 bp-VNTR a/b-genotype resulted in 23% lower NO production and the NOS3-rs1800779 AA-genotype resulted in lower NOS3 expression. Haplotypes obtained from NOS2A and NOS3 showed increased susceptibility to MS. NOS1 showed no significant association with MS.

CONCLUSION

This study provides evidence for the association between selected NOS2 and NOS3 markers and MS susceptibility.

Genetic variation in nitric oxide synthase 2A (NOS2A) and risk for multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disorder of the central nervous system with a strong genetic component. Variation in the major histocompatibility complex on chromosome 6p21, specifically the HLA-DRB1*15 haplotype, is the strongest genetic factor for MS, yet it is estimated to account for only a portion of risk for the disease. Previous evidence has implicated the nitric oxide synthase gene (NOS2A) encoding inducible NOS on chromosome 17q11 as a potential MS susceptibility gene. To determine whether variation in the NOS2A gene contributes to MS risk, we investigated a total of 50 polymorphisms within or flanking the locus for evidence of association using a comprehensive analytical strategy. A total of 6265 members from 1858 well-characterized MS families were utilized. No evidence for overtransmission of any individual single-nucleotide polymorphism allele or haplotype to the MS-affected individuals was observed. Furthermore, different transmission rates were not observed in either DRB1*15-positive or DRB1*15-negative family subgroups, or when extreme clinical outcomes characterizing disease progression were examined. The very largest study of NOS2A variation in MS, to date, excludes even a modest role for this locus in susceptibility.

Preliminary evidences of a NOS2A protective effect from Relapsing–Remitting Multiple Sclerosis

The gene encoding the inducible form of Nitric Oxide Synthase (NOS2A) has been considered with interest in the evaluation of the genetic predisposition to Multiple Sclerosis (MS). The aim of the present study was to address the possible contribution of two microsatellites repeats of the NOS2A promoter region - (CCTTT)(n) and (AAAT)(n) - to MS susceptibility. One hundred and thirteen Italian patients with clinically definite RRMS and 237 age and sex matched healthy controls from Calabria (South Italy) were studied. The distribution analysis of the markers frequencies showed that the (CCTTT)(14) allele was found in 11.5% of the RRMS patients and in 25.3% of the healthy subjects, with a statistically significant difference (chi(2)=8.843, p=0.003). This data seems to confer a significant protection against MS (OR=0.348; 95% CI=0.174-0.693, corrected for age and gender). No association with MS susceptibility was observed for the bi-allelic (AAAT)(n) microsatellite. In conclusion, we found that the NOS2A (CCTTT)(14) allele was detected more frequently in the control group than in the RRMS patients, thus confirming the scientific interest on this marker.

An investigation of NOS2A promoter polymorphisms in Australian multiple sclerosis patients

As with other major autoimmune diseases, susceptibility to multiple sclerosis (MS) is believed to result from the complex interaction of a number of genes, each with modest effect. Extensive research of experimental autoimmune encephalomyelitis in mice and several direct MS studies have implicated NOS2A, which encodes the inducible form of nitric oxide synthase, and the genetic region encoding NOS2A, 17q11.2, has been identified in a number of genome wide screens as being potentially associated with MS. We investigated four single nucleotide polymorphisms in the proximal promoter region of NOS2A, in a case-control group of 100 Australian MS patients and 100 controls and in 203 MS patients and their unaffected parents. We found a trend toward excess transmission of the -277A allele (tag for the AGCC haplotype) to HLA-DRB1*1501-positive MS patients (P (uncorrected)=0.05). We initially discovered a trend toward over-representation of the AGCC haplotype in HLA-DRB1*1501-positive compared to HLA-DRB1*1501-negative MS patients in the case-control cohort. However, when combined with the probands from the transmission disequilibrium analysis, this trend was nullified. Nonetheless, despite the lack of significant evidence of association for the NOS2A promoter polymorphisms with MS, the gene remains an interesting candidate for MS susceptibility, particularly with regard to the HLA-DRB1*1501 haplotype.

Linkage and association with the NOS2A locus on chromosome 17q11 in multiple sclerosis

A large body of research supports a multifactorial cause in multiple sclerosis (MS), with an underlying genetic susceptibility likely acting in concert with undefined environmental exposures. Here, we used a highly efficient multilocus genotyping assay to study single nucleotide polymorphisms representing variation in 34 genes from inflammatory pathways in a well-characterized MS familial data set. Evidence of transmission distortion was present for several polymorphisms. Results for the NOS2A locus (exon 10 C/T, D346D) on chromosome 17q11 remained significant after correction for multiple testing and were reproduced in a second independent African American MS data set. In addition, linkage to a NOS2A promoter region polymorphism, (CCTTT)(n), was present in a third data set of multicase MS families. Our results provide strong evidence for linkage and association to a new candidate disease gene on chromosome 17q11 in MS and suggest that variation within NOS2A or a nearby locus contributes to disease susceptibility.

Investigation of an inducible nitric oxide synthase gene (NOS2A) polymorphism in a multiple sclerosis population

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) affecting most commonly the Caucasian population. Nitric oxide (NO) is a biological signaling and effector molecule and is especially important during inflammation. Inducible nitric oxide synthase (iNOS) is one of the three enzymes responsible for generating NO. It has been reported that there is an excessive production of NO in MS concordant with an increased expression of iNOS in MS lesions. This study investigated the role of a bi-allelic tetranucleotide polymorphism located in the promoter region of the human iNOS (NOS2A) gene in MS susceptibility. A group of MS patients (n = 101) were genotyped and compared to an age- and sex-matched group of healthy controls (n = 101). The MS group was subdivided into three subtypes, namely relapsing-remitting MS (RR-MS), secondary-progressive MS (SP-MS) and primary-progressive MS (PP-MS). Results of a chi-squared analysis and a Fisher's exact test revealed that allele and genotype distributions between cases and controls were not significantly different for the total population (chi(2) = 3.4, P(genotype) = 0.15; chi(2) = 3.4, P(allele) = 0.082) and for each subtype of MS (P > 0.05). This suggests that there is no direct association of this iNOS gene variant with MS susceptibility.

Two genome-wide linkage disequilibrium screens in Scandinavian multiple sclerosis patients

We report the first two genome-wide screens for linkage disequilibrium between putative multiple sclerosis (MS) susceptibility genes and genetic markers performed in the genetically homogenous Scandinavian population, using 6000 microsatellite markers and DNA pools of approximately 200 MS cases and 200 controls in each screen. Usable data were achieved from the same 3331 markers in both screens. Nine markers from eight genomic regions (1p33, 3q13, 6p21, 6q14, 7p22, 9p21, 9q21 and Xq22) were identified as potentially associated with MS in both screens.

Analysis of nitric oxide synthase genes in cluster headache

The aetiology of cluster headache is still not yet completely understood, but the potential relevance of genetic factors has been recognized during recent years. Nitric oxide (NO) plays a critical role in the regulation of vasodilation, neurotransmission, inflammation and many other events throughout the body. NO also appears to be an important mediator of vascular headache pathophysiology. In this study we have performed an association analysis of five polymorphic microsatellite markers in the three different NO synthase (NOS) genes; nNOS (NOS1), iNOS (NOS2A) and eNOS (NOS3). Ninety-one cluster headache patients diagnosed according to International Headache Society criteria and 111 matched controls were studied. Phenotype and allele frequencies were similarly distributed in patients and controls except for an iNOS (NOS2A) pentanucleotide repeat allele which was significantly more common in controls. We observed a higher phenotype frequency of this allele in our control group compared with rates in control groups of other studies, whereas the frequency in our patients was similar to that in controls from previous reports. Thus, we conclude that it is unlikely that genetic variations within the NOS genes contribute greatly to cluster headache susceptibility.