A whole genome association study in multiple sclerosis patients from north Portugal

Tumor necrosis factor-alpha polymorphism and susceptibility to multiple sclerosis in the Iranian population

BACKGROUND

Multiple sclerosis (MS) is an immune-mediated disease of polygenic etiology. Tumor necrosis factor-α (TNF-α) microsatellite as a proinflammatory cytokine is believed to play an important role in the etiology of this disease.

OBJECTIVES

The aim of this study was to investigate the association of TNF-α microsatellite sequence variation in patients with MS and its risk factor in the southern Iranian population.

PATIENTS AND METHODS

This polymorphism was investigated in an Iranian population of 163 native southern people [81 patients with MS according to the poser criteria and 82 healthy controls (HC) with the same age, sex, social, ethnical and geographical features (Hormozgan and Fars provinces)]. All the controls were nonimmunological, neurological patients. All the cases and controls were chosen randomly and genotyped for polymorphism of TNF-α microsatellite.

RESULTS

The frequencies of TNF-α*11 (0.25, P < 0.005) and TNF-α*10 (P < 0.005) alleles increased in patients with MS compared with controls, showing a significant difference among the studied population.

CONCLUSIONS

The current study adds evidence to the association of TNF-α gene polymorphism and MS in this southern south Iranian population which is consistent with the genetic analysis of MS in Europeans (GAMES) project reports and these two alleles reported in this study may be one of the genetic risk factor for MS. Furthermore, this data can be used to build the Iranian gene bank for future studies.

Multiple sclerosis genetics

Multiple sclerosis (MS) clusters with the so-called complex genetic diseases, a group of common disorders characterized by modest disease risk heritability and multifaceted gene-environment interactions. The major histocompatibility complex (MHC) is the only genomic region consistently associated with MS, and susceptible MHC haplotypes have been identified. Although the MHC does not account for all genetic contribution to MS, the other genetic contributors have been elusive. Microarray gene-expression studies, which also have not identified a major MS locus, have, however, been promising in elucidating some of the possible pathways involved in the disease. Yet, microarray studies thus far have been unable to separate the genetic causes of MS from the expression consequences of MS. The use of new methodologies and technologies to refine the phenotype, such as brain spectroscopy, PET and functional magnetic resonance imaging combined with novel computational tools and a better understanding of the human genome architecture, may help resolve the genetic causes of MS.

The role of HLA-DRB1 alleles on susceptibility and outcome of a Portuguese Multiple Sclerosis population

BACKGROUND

The association between susceptibility to multiple sclerosis (MS) and HLA-DRB1*15 has been reported in various European populations.

OBJECTIVE

To investigate the relationship between MS, HLA-DRB1*15 and other DRB1 alleles in a Portuguese population and their association with clinical course of MS.

METHODS

The HLA-DRB1 alleles were analyzed by PCR-SSP in 248 MS patients and 282 healthy controls. In order to relate HLA-DRB1 alleles to disease aggressiveness, patients with relapsing remitting MS and secondary progressive MS were subdivided into 3 groups: 'benign' MS patients who maintain an Extended Disability Status Scale (EDSS) score of <or=3 at least 10 years after disease onset; non-benign MS patients with EDSS>3 after the same period and 'aggressive' MS those with EDSS>or=6 within 15 years of disease onset.

RESULTS

As expected, a higher frequency of HLA-DRB1*15 was found in MS patients (29.8% vs 19.9%, odds ratio (OR)=1.72, 95% CI=1.15-2.56, p=0.008). The HLA-DRB1*03 allele was positively associated with MS in the overall patient population (22.6% vs 15.6%, OR=1.58, 95% CI=1.02-2.45). Concerning disease aggressiveness, HLA-DRB1*15 occurred more frequently in the group with benign disease (42.6% vs 19.9%, OR=2.99, 95% CI=1.56-5.72) and in the group with non-benign disease (34.1% vs 19.9%, OR=2.09, 95% CI=1.05-4.16) compared with controls. When time to reach an EDSS=3 or EDSS=6 was considered as end point, HLA-DRB1*15 negative patients were found to have a worse prognosis.

CONCLUSIONS

In this population of Portuguese MS patients, the HLA-DRB1*15 allele is established as a genetic marker for susceptibility to MS and is also associated with a better outcome.

Games Collaborative Group, Ban M, Booth D, Heard R, Stewart G, Goris A, Vandenbroeck K, Dubois B, Laaksonen M, Ilonen J, Alizadeh M, Edan G, Babron MC, Brassat D, Clanet M, Cournu-Rebeix I, Fontaine B, Semana G, Goedde R, Epplen J, Weber A, Infante-Duarte C, Zipp F, Rajda C, Bencsik K, Vécsei L, Heggarty S, Graham C, Hawkins S, Liguori M, Momigliano-Richiardi P, Caputo D, Grimaldi LME, Leone M, Massacesi L, Milanese C, Salvetti M, Savettieri G, Trojano M, Bielecki B, Mycko MP, Selmaj K, Santos M, Maciel P, Pereira C, Silva A, Silva BM, Coraddu F, Marrosu MG, Akesson E, Hillert J, Datta P, Oturai A, Harbo HF, Spurkland A, Goertsches R, Villoslada P, Eraksoy M, Hensiek A, Compston A, Setakis E, Gray J, Yeo TW, Sawcer S. Linkage disequilibrium screening for multiple sclerosis implicates JAG1 and POU2AF1 as susceptibility genes in Europeans

By combining all the data available from the Genetic Analysis of Multiple sclerosis in EuropeanS (GAMES) project, we have been able to identify 17 microsatellite markers showing consistent evidence for apparent association. As might be expected five of these markers map within the Major Histocompatibility Complex (MHC) and are in LD with HLA-DRB1. Individual genotyping of the 12 non-MHC markers confirmed association for three of them--D11S1986, D19S552 and D20S894. Association mapping across the candidate genes implicated by these markers in 937 UK trio families revealed modestly associated haplotypes in JAG1 (p=0.019) on chromosome 20p12.2 and POU2AF1 (p=0.003) on chromosome 11q23.1.

SELPLG and SELP single-nucleotide polymorphisms in multiple sclerosis

P-Selectin (SELP) and P-selectin glycoprotein ligand-1 (SELPLG) constitute a receptor/ligand complex involved in the recruitment of activated lymphocytes, a critical event in the pathogenesis of multiple sclerosis (MS). In order to determine whether genetic variation in these pivotal molecules influences susceptibility to MS, we genotyped 214 Italian patients compared with 220 Italian controls for three single-nucleotide polymorphisms (SNPs): SELPLG Met62Ile, SELP C-2123G and SELP Thr715Pro. No significant differences in both SELP SNPs were found between patients and controls, whereas a decreased frequency of the Met62Ile SNP was found in patients versus controls in the Italian population (P = 0.025). To confirm these preliminary findings, the Met62Ile SNP was analysed in 938 UK trio families. This SNP did not show evidence for association with susceptibility to MS in the larger UK cohort. Therefore, none of the SNPs investigated is associated with MS, although this analysis does not conclusively exclude SELPLG and SELP as genetic risk factors for MS as much variation remains untested.

Mapping gene activity in complex disorders: Integration of expression and genomic scans for multiple sclerosis

Genetic predisposition contributes to the pathogenesis of most common diseases. Genetic studies have been extremely successful in the identification of genes responsible for a number of Mendelian disorders. However, with a few exceptions, genes predisposing to diseases with complex inheritance remain unknown despite multiple efforts. In this article we collected detailed information for all genome-wide genetic screens performed to date in multiple sclerosis (MS) and in its animal model experimental autoimmune encephalomyelitis (EAE), and integrated these results with those from all high throughput gene expression studies in humans and mice. We analyzed a total of 55 studies. We found that differentially expressed genes (DEG) are not uniformly distributed in the genome, but rather appear in clusters. Furthermore, these clusters significantly differ from the known heterogeneous organization characteristic of eukaryotic gene distributions. We also identified regions of susceptibility that overlapped with clusters of DEG leading to the prioritization of candidate genes. Integration of genomic and transcriptional information is a powerful tool to dissect genetic susceptibility in complex multifactorial disorders like MS.