Gianna Costa

Variants within the immunoregulatory CBLB gene are associated with Multiple Sclerosis

A genome-wide association scan of ∼6.6 million genotyped or imputed variants in 882 Sardinian individuals with multiple sclerosis (cases) and 872 controls suggested association of CBLB gene variants with disease, which was confirmed in 1,775 cases and 2,005 controls (rs9657904, overall P = 1.60 × 10−10, OR = 1.40). CBLB encodes a negative regulator of adaptive immune responses, and mice lacking the ortholog are prone to experimental autoimmune encephalomyelitis, the animal model of multiple sclerosis.

Multiple Sclerosis in Sardinia Is Associated and in Linkage Disequilibrium with HLA-DR3 and -DR4 Alleles

The preponderance of genetic factors in attempts to account for susceptibility to multiple sclerosis (MS), a common inflammatory and demyelinating disease of young adults, has recently been demonstrated (Ebers et al . 1995). The inheritance of MS appears to be complex and is believed to involve several genes (Ebers et al . 1996; The Multiple Sclerosis Genetics Group 1996; Sawcer et al . 1996). Methodological approaches to the study of genes conferring susceptibility to MS include association studies, which measure the frequency of a specific allele in affected and healthy populations, and linkage studies, which trace the inheritance of a gene from parents and correlate these genes to disease susceptibility.

Variation within the CLEC16A gene shows consistent disease association with both multiple sclerosis and type 1 diabetes in Sardinia

Variation within intron 19 of the CLEC16A (KIAA0350) gene region was recently found to be unequivocally associated with type 1 diabetes (T1D) in genome-wide association (GWA) studies in Northern European populations. A variant in intron 22 that is nearly independent of the intron 19 variant showed suggestive evidence of association with multiple sclerosis (MS). Here, we genotyped the rs725613 polymorphism, representative of the earlier reported associations with T1D within CLEC16A, in 1037 T1D cases, 1498 MS cases and 1706 matched controls, all from the founder, autoimmunity-prone Sardinian population. In these Sardinian samples, allele A of rs725613 is positively associated not only with T1D (odds ratio=1.15, P one-tail=5.1 × 10−3) but also, and with a comparable effect size, with MS (odds ratio=1.21, P one-tail 6.7 × 10−5). Taken together these data provide evidence of joint disease association in T1D and MS within CLEC16A and underline a shared disease pathway.

mtDNA nt13708A variant increases the risk of multiple sclerosis.

Background Mitochondrial DNA (mtDNA) polymorphism is a possible factor contributing to the maternal parent-of-origin effect in multiple sclerosis (MS) susceptibility. Methods and Findings In order to investigate the role of mtDNA variations in MS, we investigated six European MS case-control cohorts comprising >5,000 individuals. Three well matched cohorts were genotyped with seven common, potentially functional mtDNA single nucleotide polymorphisms (SNPs). A SNP, nt13708 G/A, was significantly associated with MS susceptibility in all three cohorts. The nt13708A allele was associated with an increased risk of MS (OR = 1.71, 95% CI 1.28–2.26, P = 0.0002). Subsequent sequencing of the mtDNA of 50 individuals revealed that the nt13708 itself, rather than SNPs linked to it, was responsible for the association. However, the association of nt13708 G/A with MS was not significant in MS cohorts which were not well case-control matched, indicating that the significance of association was affected by the population structure of controls. Conclusions Taken together, our finding identified the nt13708A variant as a susceptibility allele to MS, which could contribute to defining the role of the mitochondrial genome in MS pathogenesis.

HLA‐DQB1 genotype in Sardinian multiple sclerosis Evidence for a key role of DQB1 *0201 and *0302 alleles

We studied HLA-DQB1 haplotypes in 103 unrelated multiple sclerosis (UMS) patients and in 26 related (RMS) patients from 12 families from Sardinia, Italy, where the disease was associated with the HLA-DR4 allele. Using polymerase chain reaction and allele-specific oligonucleotide probes, we found in UMS an increased frequency of the DQB1 *0201 (p = 0.010) and DQB1 *0302 (p = 0.025) alleles, whereas the DQB1 *0301 allele was significantly decreased (p = 0.027). In RMS, only the DQB1 *0302 allele was increased (p = 0.047), and no difference was found in the DQB1 *0301 allele. For DQB haplotypes, an increased frequency of DQB1 *0302/*0502 (p = 0.026) and a decreased frequency of DQB1 *0201/*0601 (p = 0.009) and DQB1 *0502/*0502 (p = 0.025) was found in UMS patients, whereas RMS patients showed an increased frequency of DQB1 *0301/*0302 (p = 0.005). Because DQB1 *0201 and *0302 alleles are increased in Caucasian MS patients, where the disease is related to HLA-DR2 and where a primary association with the HLA-DR2, DQB1 *0602 allele has been reported, we conclude that Caucasian and Sardinian populations share HLA-DQB1 *0201 and *0302 alleles in genetic susceptibility to MS.

Dementia, pyramidal system involvement, and leukoencephalopathy with a presenilin 1 mutation.

The authors describe four members of a family with a novel P284S presenilin 1 mutation presenting a clinical phenotype characterized by early-onset dementia, paratetraparesis, dysarthria, dysphagia, and marked involvement of brain white matter. The distinctive clinical and MRI findings in the family studied extend the phenotypic spectrum of dementia associated with mutation of the PS1 gene.

HLA-DR,DQ and APOE genotypes and gender influence in Sardinian primary progressive MS

The authors examined the influence of APOE and human leukocyte antigen-DRB1-DQB1 polymorphisms on the course of multiple sclerosis in 871 patients, 773 with relapsing and 98 with primary progressive disease, and 348 control subjects. The risk of the primary progressive course was increased (odds ratio = 6.81, p = 0.002) in women carrying the APOE4 but not the DRB1-DQB1 predisposing genotype, suggesting in this subgroup of patients a reciprocal influence between these genes and gender in modulating clinical variability of the disease.

HLA‐DQA1 and ‐DQB1 associations with multiple sclerosis in Sardinia and French Canada Evidence for immunogenetically distinct patient groups

We analyzed the association of HLA-DQA1 and -DQB1 alleles with multiple sclerosis (MS) in a collaborative study of 116 Sardinian and 75 French Canadian MS patients by the relative predispositional effect method. In French Canadians, MS was positively associated with DQAl*0102 and DQB1*0602, but there was no positive association of either allele with Sardinian MS, which, by contrast, was positively associated with DQB1*0302 and *0201 and with DQA1*0301, whereas none of these alleles was MS-associated in French Canadians. In comparison with French Canadian results, DQA1*0102 was protective against MS in Sardinians. We suggest that DQA1*0102 has no MS predispositional role in French Canadians, but is MS-associated because it is in linkage disequilibrium with true predispositional alleles present within the DQB1*0602-bearing haplotype. Whereas DQB1 alleles encoding leucine (Leu) at residue 26 showed a strong MS association in French Canadians (relative risk = 24.71, there was no correlation with DQP Leu26 in Sardinian MS. No other DQA1 or DQB1 codons showed a positive disease correlation in both groups. Together the data suggest that the two MS patient groups are immunogenetically distinct, and it may be impossible to formulate a unifying hypothesis that explains the different MS-class II associations in these and other ethnic groups.

Genetic loci linked to Type 1 Diabetes and Multiple Sclerosis families in Sardinia

BackgroundThe Mediterranean island of Sardinia has a strikingly high incidence of the autoimmune disorders Type 1 Diabetes (T1D) and Multiple Sclerosis (MS). Furthermore, the two diseases tend to be co-inherited in the same individuals and in the same families. These observations suggest that some unknown autoimmunity variant with relevant effect size could be fairly common in this founder population and could be detected using linkage analysis.MethodsTo search for T1D and MS loci as well as any that predispose to both diseases, we performed a whole genome linkage scan, sequentially genotyping 593 microsatellite marker loci in 954 individuals distributed in 175 Sardinian families. In total, 413 patients were studied; 285 with T1D, 116 with MS and 12 with both disorders. Model-free linkage analysis was performed on the genotyped samples using the Kong and Cox logarithm of odds (LOD) score statistic.ResultsIn T1D, aside from the HLA locus, we found four regions showing a lod-score ≥1; 1p31.1, 6q26, 10q21.2 and 22q11.22. In MS we found three regions showing a lod-score ≥1; 1q42.2, 18p11.21 and 20p12.3. In the combined T1D-MS scan for shared autoimmunity loci, four regions showed a LOD >1, including 6q26, 10q21.2, 20p12.3 and 22q11.22. When we typed more markers in these intervals we obtained suggestive evidence of linkage in the T1D scan at 10q21.2 (LOD = 2.1), in the MS scan at 1q42.2 (LOD = 2.5) and at 18p11.22 (LOD = 2.6). When all T1D and MS families were analysed jointly we obtained suggestive evidence in two regions: at 10q21.1 (LOD score = 2.3) and at 20p12.3 (LOD score = 2.5).ConclusionThis suggestive evidence of linkage with T1D, MS and both diseases indicates critical chromosome intervals to be followed up in downstream association studies.

Vitamin D Responsive Elements within the HLA-DRB1 Promoter Region in Sardinian Multiple Sclerosis Associated Alleles

Vitamin D response elements (VDREs) have been found in the promoter region of the MS-associated allele HLA-DRB1*15∶01, suggesting that with low vitamin D availability VDREs are incapable of inducing *15∶01 expression allowing in early life autoreactive T-cells to escape central thymic deletion. The Italian island of Sardinia exhibits a very high frequency of MS and high solar radiation exposure. We test the contribution of VDREs analysing the promoter region of the MS-associated DRB1 *04∶05, *03∶01, *13∶01 and *15∶01 and non-MS-associated *16∶01, *01, *11, *07∶01 alleles in a cohort of Sardinians (44 MS patients and 112 healthy subjects). Sequencing of the DRB1 promoter region revealed a homozygous canonical VDRE in all *15∶01, *16∶01, *11 and in 45/73 *03∶01 and in heterozygous state in 28/73 *03∶01 and all *01 alleles. A new mutated homozygous VDRE was found in all *13∶03, *04∶05 and *07∶01 alleles. Functionality of mutated and canonical VDREs was assessed for its potential to modulate levels of DRB1 gene expression using an in vitro transactivation assay after stimulation with active vitamin D metabolite. Vitamin D failed to increase promoter activity of the *04∶05 and *03∶01 alleles carrying the new mutated VDRE, while the *16∶01 and *03∶01 alleles carrying the canonical VDRE sequence showed significantly increased transcriptional activity. The ability of VDR to bind the mutant VDRE in the DRB1 promoter was evaluated by EMSA. Efficient binding of VDR to the VDRE sequence found in the *16∶01 and in the *15∶01 allele reduced electrophoretic mobility when either an anti-VDR or an anti-RXR monoclonal antibody was added. Conversely, the Sardinian mutated VDRE sample showed very low affinity for the RXR/VDR heterodimer. These data seem to exclude a role of VDREs in the promoter region of the DRB1 gene in susceptibility to MS carried by DRB1* alleles in Sardinian patients.