Janet Schaefer-Klein

A point mutation in PTPRC is associated with the development of multiple sclerosis

Multiple sclerosis (MS) is the most common demyelinating disease of the central nervous system. It is widely accepted that a dysregulated immune response against brain resident antigens is central to its yet unknown pathogenesis. Although there is evidence that the development of MS has a genetic component, specific genetic factors are largely unknown. Here we investigated the role of a point mutation in the gene (PTPRC) encoding protein-tyrosine phosphatase, receptor-type C (also known as CD45) in the heterozygous state in the development of MS. The nucleotide transition in exon 4 of the gene locus interferes with mRNA splicing and results in altered expression of CD45 isoforms on immune cells. In three of four independent case-control studies, we demonstrated an association of the mutation with MS. We found the PTPRC mutation to be linked to and associated with the disease in three MS nuclear families. In one additional family, we found the same variant CD45 phenotype, with an as-yet-unknown origin, among the members affected with MS. Our findings suggest an association of the mutation in PTPRC with the development of MS in some families.

Association of APOE polymorphisms with disease severity in MS is limited to women

The authors studied the association of an exon 4 (E4*ε2/3/4) and three promoter polymorphisms of APOE with disease course and severity stratified by gender in 221 patients with multiple sclerosis from two overlapping population-based prevalence cohorts. Women carriers of the E4*ε2 allele took longer to attain an Expanded Disability Status Scale score of 6 (p = 0.015) and had more favorable ranked severity scores than noncarriers (p = 0.009). There was no association in men. Alleles ε3 or ε4 and promoter polymorphisms were not associated with disease course or severity.

Genetic analysis of aquaporin-4 in neuromyelitis optica.

Objective: Autoantibodies to aquaporin-4 (AQP4) are specific and pathogenic for neuromyelitis optica (NMO). Therefore, we evaluated whether AQP4 single-nucleotide polymorphisms (SNPs) are associated with susceptibility to NMO or whether mutations that potentially alter AQP4 structure or expression are present in some patients. Methods: We genotyped 8 AQP4 SNPs chosen based on their minor allele frequency, location, and novelty in 177 NMO sporadic cases, 14 NMO familial cases, and 1,363 matched controls by TaqMan-based assay. We performed bidirectional sequencing of the promoter (1 kb), exons 0–4, and flanking splice consensus sequences, and the 5′ and 3′ untranslated regions of 177 sporadic and 14 familial NMO cases. Results: One of 8 SNPs (minor allele frequency = 0.01) was associated with NMO (NC 18.8; chrom pos. 22695167: T>A): odds ratio (95% confidence interval) = 13.1 (1.4–126.7); p = 0.026. In 3 patients with NMO (2 related), we detected 2 different missense allelic mutations at Arg19 (R19I and R19T). None of the 1,363 control subjects had Arg19 mutations (p = 0.001). Conclusions: Except for one uncommon SNP, no tested SNP was associated with NMO, nor were 3 SNP haplotypes, providing no support for the hypothesis that genetic variation in AQP4 accounts for overall susceptibility to NMO. Two different allelic Arg19 missense mutations are specific to NMO and segregated with the disease in one pedigree. Although the pathobiology underlying this is not yet established, their effects on the structure of the M1 isoform N terminus or the regulatory sequence of the M23 isoform by virtue of their location support a role of AQP4 orthogonal array formation on molecular susceptibility to NMO.

Interferon gamma allelic variants: sex-biased multiple sclerosis susceptibility and gene expression.

BACKGROUND Interferon (IFN) gamma (IFNG) allelic variants are associated with susceptibility to multiple sclerosis (MS) in men but not in women. OBJECTIVES To conduct a high-density linkage disequilibrium association study of IFNG and the surrounding region for sex-associated MS susceptibility bias and to evaluate whether IFNG allelic variants associated with MS susceptibility are associated with expression. DESIGN Genotype case-control study, quantitative polymerase chain reaction (qPCR), and enzyme-linked immunosorbent assay expression analyses for IFN gamma. SETTING Three independently ascertained populations from the Mayo Clinic, Rochester, Minnesota, Queens University of Belfast, Belfast, Ireland, and University of Leuven, Leuven, Belgium. PATIENTS For linkage disequilibrium, 861 patients with MS (293 men and 568 women) and 843 controls (340 men and 503 women) derived from the US (population-based) and the Northern Ireland and Belgium (clinic-based) cohorts were studied. For expression analyses, 50 US patients were selected to enrich for homozygotes and to achieve a balance between men and women. INTERVENTIONS Twenty markers were genotyped over the 120-kilobase region harboring IFNG and the interleukin 26 gene (IL26). MAIN OUTCOME MEASURES Expression of IFN gamma was evaluated by qPCR and enzyme-linked immunosorbent assay in stimulated peripheral blood mononuclear cells. RESULTS Multiple markers were associated with MS susceptibility in men but not in women. The sex-specific susceptibility markers, of which rs2069727 was the strongest, were confined to IFNG. Carriers of rs2069727*G had higher expression than noncarriers. The effect of genotype in the qPCR experiments was also evident in men but not in women. CONCLUSIONS IFNG is associated with sex bias in MS susceptibility and with expression of IFN gamma in MS. These observations add to a growing body of literature that implicates an interaction between sex and IFN gamma expression in a variety of disease states.

Aquaporin 4 Expression and Tissue Susceptibility to Neuromyelitis Optica

IMPORTANCE To understand the predilection for optic nerve and spinal cord pathologic changes in neuromyelitis optica (NMO). OBJECTIVE TO evaluate tissue-specific expression (RNA and protein) and supramolecular aggregation of aquaporin 4 (AQP4) in mouse, rat, and human tissues. DESIGN Quantitative polymerase chain reaction, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and blue native polyacrylamide gel electrophoresis. SETTING Laboratory analysis of mouse, rat, and human tissue. PARTICIPANTS Tissues from control individuals and 1 patient with NMO obtained at autopsy. EXPOSURE Neuromyelitis optica in the patient. MAIN OUTCOMES AND MEASURES Tissue-specific messenger RNA and protein expression and supramolecular aggregation of AQP4. RESULTS The AQP4 messenger RNA and proteins were much more highly expressed in the optic nerve and spinal cord relative to other regions of the brain and to non-central nervous system tissues in all species evaluated. Large supramolecular aggregates of AQP4 were overrepresented in the optic nerve and spinal cord relative to other central nervous system tissue. There was no difference in AQP4 expression between an individual with NMO and the control samples. CONCLUSIONS AND RELEVANCE Optic nerve tissue from an individual with NMO did not differ in AQP4 expression from control samples. The relatively high levels of expression and of supramolecular aggregation in the optic nerve and spinal cord may contribute to the predilection of these structures to NMO pathologic changes.

Genetic variation in the transforming growth factor β1 gene in multiple sclerosis

Transforming growth factor beta1 (TGFbeta1) is a Th2 cytokine encoded on chromosome 19q13, a region possibly linked to multiple sclerosis (MS). TGFbeta1 exerts favorable effects on experimental allergic encephalomyelitis. We performed a comprehensive search for genetic variants in this gene in 122 population-based sporadic cases of MS. We detected six variants, including three missense variants. We tested for association of the variants with susceptibility and course of MS and for linkage and transmission disequilibrium in a family series consisting of 395 samples in 59 pedigrees. Genetic variation in TGFB1 does not appear to contribute in a major way to susceptibility to MS.

Association of IL2RA polymorphisms with susceptibility to multiple sclerosis is not explained by missense mutations in IL2RA

Genome-wide association studies have identified an association between two intronic single nucleotide polymorphisms (SNPs), rs12722489 and rs2104286, in the interleukin-2 receptor alpha-chain gene (IL2RA) and susceptibility to multiple sclerosis (MS). We studied these SNPs in association with susceptibility to and severity of MS in a population-based cohort of 220 patients from Olmsted County, Minnesota, compared with 442 matched controls. We sequenced the exons, splice sites and 5’ and 3’ untranslated regions in 27 randomly selected MS patients (powered for allele frequency ≥0.04) to search for mutations. No novel missense mutation was identified. Two patients (7.5%) had an exon 2 SNP (rs4308625) and two patients had an exon 4 SNP (rs2228149), both synonymous.