Association of a CA repeat polymorphism upstream of the Fas ligand gene with multiple sclerosis

[The association of the FAS/APO-1 (rs2234767) gene polymorphism with the risk and rapid progression of multiple sclerosis]

AIM

To evaluate the association of the FAS/APO-1 (rs2234767) gene polymorphism with the risk of multiple sclerosis and its progression dynamics.

MATERIAL AND METHODS

A case-control study included 100 patients with recurrent multiple sclerosis (MS), Russians from the Altai Territory, and 100 healthy volunteers. Real-time polymerase chain reaction was used to genotype the 1377G>A polymorphism in the promoter of the FAS/APO-1 (rs2234767) gene. Association of this polymorphism with the risk of multiple sclerosis and its progression was evaluated.

RESULTS

The G/А genotype and the А-allele were associated with the increased risk of multiple sclerosis. The G/А genotype and the А-allele were associated with the risk of high progression rate of the disease. The G/G genotype and the G-allele had a protective effect.

CONCLUSION

Predisposition to MS as well as to high progression rate are associated with the FAS/APO-1*G/А gene in Russians living in the Altai Territory. Further research is required to make the conclusion.

The role of T cell apoptosis in nervous system autoimmunity

Fas is a transmembrane receptor involved in the death program of several cell lines, including T lymphocytes. Deleterious mutations hitting genes involved in the Fas pathway cause the autoimmune lymphoprolipherative syndrome (ALPS). Moreover, defective Fas function is involved in the development of common autoimmune diseases, including autoimmune syndromes hitting the nervous system, such as multiple sclerosis (MS) and chronic inflammatory demyelinating polyneuropathy (CIDP). In this review, we first explore some peculiar aspects of Fas mediated apoptosis in the central versus peripheral nervous system (CNS, PNS); thereafter, we analyze what is currently known on the role of T cell apoptosis in both MS and CIDP, which, in this regard, may be seen as two faces of the same coin. In fact, we show that, in both diseases, defective Fas mediated apoptosis plays a crucial role favoring disease development and its chronic evolution.

An evolutionary analysis of RAC2 identifies haplotypes associated with human autoimmune diseases

The human RAC2 gene encodes a small GTP-binding protein with a pivotal role in immune activation and in the induction of peripheral immune tolerance through restimulation-induced cell death (RICD). Different human pathogens target the protein product of RAC2, suggesting that the gene may be subject to natural selection, and that variants in RAC2 may affect immunological phenotypes in humans. We scanned the genomic region encompassing the entire transcription unit for the presence of putative noncoding regulatory elements conserved across mammals. This information was used to select two RAC2 gene regions and analyze their intraspecific genetic diversity. Results suggest that a region covering the 3' untranslated region has been a target of multiallelic balancing selection (or diversifying selection), and three major RAC2 haplogroups occur in human populations. Haplotypes belonging to one of these clades are associated with increased susceptibility to multiple sclerosis (P = 0.022) and earlier onset of disease symptoms (P = 0.025). This same haplogroup is significantly more common in patients with Crohn's disease compared with healthy controls (P = 0.048). These data reinforce recent evidences that susceptibility alleles/haplotypes are shared among multiple autoimmune disorders and support a causal "role for RAC2" variants in the pathogenesis of autoimmune diseases. Other genes with a role in RICD have previously been associated with autoimmunity in humans, suggesting that this pathway and RAC2 may represent novel therapeutic targets in autoimmune disorders.

Association analysis of chromosome 1 migraine candidate genes

BACKGROUND

Migraine with aura (MA) is a subtype of typical migraine. Migraine with aura (MA) also encompasses a rare severe subtype Familial Hemiplegic Migraine (FHM) with several known genetic loci. The type 2 FHM (FHM-2) susceptibility locus maps to chromosome 1q23 and mutations in the ATP1A2 gene at this site have recently been implicated. We have previously provided evidence of linkage of typical migraine (predominantly MA) to microsatellite markers on chromosome 1, in the 1q31 and 1q23 regions. In this study, we have undertaken a large genomic investigation involving candidate genes that lie within the chromosome 1q23 and 1q31 regions using an association analysis approach.

METHODS

We have genotyped a large population of case-controls (243 unrelated Caucasian migraineurs versus 243 controls) examining a set of 5 single nucleotide polymorphisms (SNPs) and the Fas Ligand dinucleotide repeat marker, located within the chromosome 1q23 and 1q31 regions.

RESULTS

Several genes have been studied including membrane protein (ATP 1 subtype A4 and FasL), cytoplasmic glycoprotein (CASQ 1) genes and potassium (KCN J9 and KCN J10) and calcium (CACNA1E) channel genes in 243 migraineurs (including 85% MA and 15% of migraine without aura (MO)) and 243 matched controls. After correction for multiple testing, chi-square results showed non-significant P values (P > 0.008) across all SNPs (and a CA repeat) tested in these different genes, however results with the KCN J10 marker gave interesting results (P = 0.02) that may be worth exploring further in other populations.

CONCLUSION

These results do not show a significant role for the tested candidate gene variants and also do not support the hypothesis that a common chromosome 1 defective gene influences both FHM and the more common forms of migraine.

CD95 polymorphisms are associated with susceptibility to MS in women

CD95/CD95L interaction results in activation-induced apoptosis thereby regulating clonal expansion of T cells outside the thymus. Genetic defects in this system result in autoimmune lymphoproliferation in mice and men. CD95-induced cell death may be defective in MS. We studied the association of CD95 and CD95L polymorphisms with MS in 221 unique patients representing 79% ascertainment in Olmsted County, MN, and 442 gender-, age- and ethnicity-matched controls. Being a homozygote for the G allele of CD95 5'(-670)*A-->G SNP (p=0.034; OR: 1.59, 95% CI: 1.06-2.38) and for the C allele of CD95 E7(74)*C-->T SNP (p=0.007; OR: 1.73, 95% CI: 1.17-2.56) increased susceptibility to MS exclusively in women. There was strong but incomplete linkage disequilibrium between the two markers (p<0.001; D'=0.546). Homozygosity for 5'(-670)*A or E7(74)*C explained 28% of risk of MS in women but 0% of the risk in men in Olmsted County, MN. Our results agree with the previously published studies and highlight that the association of the polymorphisms is restricted to women with MS. We did not find an association between CD95L and susceptibility to MS nor CD95 or CD95L and age of onset, disease course and disease severity.

Cellular FLICE-inhibitory protein: an attractive therapeutic target?

Cellular FLIP (c-FLIP), also known as FLICE-inhibitory protein, has been identified as an inhibitor of apoptosis triggered by engagement of death receptors (DRs) such as Fas or TRAIL (TNF-related apoptosis-inducing ligand). cFLIP is recruited to DR signalling complexes, where it prevents caspase activation. Animal models have indicated that c-FLIP plays an important role in T cell proliferation and heart development. Abnormal c-FLIP expression has been identified in various diseases such as multiple sclerosis (MS), Alzheimer's disease (AD), diabetes mellitus, rheumatoid arthritis (RA) and various cancers. This review focuses on recent insights into c-FLIP dysregulation associated with human diseases and addresses the possibilities of using c-FLIP as a therapeutic target.

Fas ligand gene polymorphisms are not associated with Hashimoto's thyroiditis and Graves' disease

Hashimoto's thyroiditis and Graves' disease represent the two most common autoimmune thyroid disorders. Whereas in Hashimoto's thyroiditis FasL expression causes thyrocytes to undergo apoptosis, additional anti-apoptotic molecules appear to protect these cells in Graves' disease. Mutations of the FasL gene were observed in systemic lupus erythematosus. Given its functional relevance for the pathogenesis of thyroid autoimmunity we wondered whether variants of the FasL gene play a role in Hashimoto's thyroiditis and Graves' disease. We genotyped families with at least one offspring affected by Hashimoto's thyroiditis (n = 86) and Graves' disease (n = 90) for two FasL gene polymorphisms (C -843 T in the promoter, A IVS2nt-124 G in intron 2). Extended transmission disequilibrium (ETDT) and chi(2) testing were performed. Neither polymorphism alone nor the promoter/intron 2 haplotypes (p = 0.91) were associated with Hashimoto's thyroiditis. No association with Graves' disease was observed for the promoter polymorphism (p = 0.91) and the intron 2 "A" allele (57.1%; p = 0.36) or the promoter/intron 2 haplotypes (p = 0.31). Moreover, intron 2 genotyping revealed no difference between an additional 251 patients with Graves' disease and 197 healthy controls (p = 0.37). Italian and German families did not differ for the studied polymorphisms. In conclusion, our data do not suggest common genetic FasL variants to significantly contribute to the pathogenesis of either Hashimoto's thyroiditis or Graves' disease.

The FAS-670 polymorphism influences susceptibility to multiple sclerosis

Several studies have reported a defective Fas function in patients with multiple sclerosis (MS). We were interested whether this could result from a genetically altered Fas regulation. We examined the FAS-670 polymorphism in 382 patients with MS and 206 controls, and found that the carriership of allele FAS-670*G was significantly less frequent in patients than in controls. We found no association between the carriership of FAS-670*G and clinical features. For a subgroup of patients, longitudinal MRI data were available. We observed similar brain and lesion volumes in carriers and noncarriers of FAS-670*G. These data suggest that FAS-670*G decreases the risk of developing MS, but does not affect the course of disease.