A complete genomic screen for multiple sclerosis underscores a role for the major histocompatability complex. The Multiple Sclerosis Genetics Group

A whole genome screen for linkage disequilibrium in multiple sclerosis confirms disease associations with regions previously linked to susceptibility

Linkage analysis in multiplex families has provisionally identified several genomic regions where genes influencing susceptibility to multiple sclerosis are likely to be located. It is anticipated that association mapping will provide a higher degree of resolution, but this more powerful approach is limited by the substantial genotyping effort required. Here, we describe the first use of DNA pooling to screen the whole genome for association in multiple sclerosis based on a 0.5 cM map of microsatellite markers and using four DNA pools derived from cases (n = 216), controls (n = 219) and trio families (n = 745 affected individuals and their 1490 parents). The 10 markers showing the greatest evidence for association with multiple sclerosis that emerge from this analysis include three from the HLA region on chromosome 6p (D6S1615, D6S2444 and TNFa), providing a positive control for the method, four from regions previously identified by linkage analysis in UK multiplex families (two mapping to chromosome 17q GCT6E11 and D17S1535; one to chromosome 1p GGAA30B06; and one to 19q D19S585), and three from novel sites with respect to linkage analysis (D1S1590 at 1q; D2S2739 at 2p; and D4S416 at 4q). Our results thus provide further supporting evidence for the candidature of 6p, 17q, 19q and 1p as regions encoding susceptibililty genes for multiple sclerosis. The protocol used in this UK-based study is now being extended to 18 additional sites in Europe in order to search for susceptibility genes shared between populations of common ancestry, as well as those that exert ethnically more restricted effects.

Multiple sclerosis and anesthetic implications

PURPOSE OF REVIEW

Multiple sclerosis remains prevalent among young women in the United States of America. It is a disease of the central nervous system that possesses many anesthetic implications. Anesthesia providers need to understand this disorder and its multiple anesthetic ramifications.

RECENT FINDINGS

Recent work has provided more insight into the etiology of multiple sclerosis, its pathogenesis, diagnosis and natural history. A number of new medications have also been added to the therapeutic armamentarium. Optimal anesthetic care entails a thorough preoperative evaluation, medication history and neurologic examination, intraoperative awareness of conditions that may precipitate attacks and lead to potentially life-threatening complications, as well as postoperative attention to respiratory and other risks. Recommendations for management are based on information from small retrospective studies and anecdotal reports.

SUMMARY

In summary, our aim is to provide an updated view of multiple sclerosis from the perspective of perioperative care, emphasizing interactions between the disease, surgery and anesthesia.

Chromosome 19q13 and multiple sclerosis susceptibility in Finland: a linkage and two-stage association study

Several studies have previously provided some albeit weak evidence for linkage or association between chromosome 19q13 and multiple sclerosis (MS) susceptibility. We performed a two-stage association analysis with 19 markers spanning 7 Mb/5.5 cM of 19q13. In stage 1 analysis (135 MS families) allelic and haplotypic associations were found with markers within or close to the ApoE-ApoC subregion. These observations were taken as a hypothesis, which was tested in stage 2 in 125 families. However, none of the initial associations were replicated suggesting that they were most likely due to chance. Linkage analysis was performed in 27 Finnish multiplex families using 10 microsatellites spanning 23 Mb/24 cM of 19q13. DNA was available from 72 MS patients and 150 unaffected relatives. Parametric and non-parametric linkage analyses did not provide evidence for linkage when all families were tested. After stratifying the families according to HLA-DR15 there was weak evidence for linkage to the 19q13.1 subregion in DR15 negative families (LOD(max)=1.8). Taken together these results do not support a major role of chromosome 19q13.2-q13.3 in MS susceptibility among Finnish MS patients, whereas conclusions on the 19q13.1 subregion are less clear and this region requires further study.

Gene-microarray analysis of multiple sclerosis lesions yields new targets validated in autoimmune encephalomyelitis

Microarray analysis of multiple sclerosis (MS) lesions obtained at autopsy revealed increased transcripts of genes encoding inflammatory cytokines, particularly interleukin-6 and -17, interferon-gamma and associated downstream pathways. Comparison of two poles of MS pathology--acute lesions with inflammation versus 'silent' lesions without inflammation--revealed differentially transcribed genes. Some products of these genes were chosen as targets for therapy of experimental autoimmune encephalomyelitis (EAE) in mice. Granulocyte colony-stimulating factor is upregulated in acute, but not in chronic, MS lesions, and the effect on ameliorating EAE is more pronounced in the acute phase, in contrast to knocking out the immunoglobulin Fc receptor common gamma chain where the effect is greatest on chronic disease. These results in EAE corroborate the microarray studies on MS lesions. Large-scale analysis of transcripts in MS lesions elucidates new aspects of pathology and opens possibilities for therapy.

Genetic analysis of multiple sclerosis

The increased recurrence risk within families indicates a role for genetic factors in the etiology of multiple sclerosis. Genes may influence susceptibility to the development of multiple sclerosis and the subsequent course of the disease. To date, associations have only been demonstrated consistently with class II major histocompatibility complex (MHC) alleles. The relatively low yield from additional candidate gene studies is only modestly advanced by several whole-genome linkage analyses, and by the first in a series of planned whole-genome linkage disequilibrium screens for allelic associations. The aims of linkage and association are to narrow the search for chromosomal regions encoding genes for multiple sclerosis and, with information from the human gene project, suggest new positional candidates. In time, it is expected that these genes will include some that confer susceptibility to the general process of autoimmunity, others that are specific for multiple sclerosis in all populations, some that act only in defined ethic groups, and those that determine particular phenotypes or shape the clinical course. These genetic analyses are predicated on the assumption that multiple sclerosis is one disease; a major part of future studies will be to resolve the question of disease heterogeneity in multiple sclerosis. When eventually in place, the potential of this genetic knowledge for improved understanding of the pathogenesis of multiple sclerosis and designing novel treatments is considerable.

Multiple sclerosis in the tropics: genetic association to STR's loci spanning the HLA and TNF

Clear evidence has been presented correlating gene polymorphisms at 6p21.3-21.4 (containing HLA and TNF) and the predisposition to acquire multiple sclerosis (MS). In a previous study, we found that polymorphisms at HLA DQAI were associated with being or not being predisposed to MS in individuals inhabiting the tropics, where the prevalence of MS is significantly lower than in subtropical areas. Here, we tested the hypothesis that polymorphisms at D6S276, D6S265, D6S273 and D6S291 microsatellite loci are in strong linkage disequilibrium with a major genetic factor predisposing to MS. These microsatellites span the 6p21.3 region with intervals of 5 cM establishing particular landmarks for the HLA and TNF loci. Thirty-five MS patients and 35 controls, age, sex, social, ethnically and geographically matched healthy individuals, were studied. After testing the fit of gene frequencies to the normal distribution and performing the correlation for multiple comparisons, we found significant differences among the case and the control frequencies for the allele 202 belonging to the marker D6S276 (Pc=0.00455) and for the allele 114 belonging to the marker D6S265 (Pc=0.0084). For these two alleles at different loci, we found higher frequencies in the cases than in the controls. A nonsignificant p value was found in testing the existence of linkage disequilibrium among the studied loci in the cases and in the controls. In conclusion, the current study adds evidence to the established association among polymorphisms of genes located at 6p21.3-21.4 and MS. Furthermore, because of the distribution of the tested microsatellite loci, the more probable critical region could be correlated with the TNF neighborhood.

Microchimerism in autoimmunity and transplantation: potential relevance to multiple sclerosis

Microchimerism (MC) is the stable presence of small numbers of non-host cells and appears to be commonly present in parous women. There are several methods of detecting microchimerism and each has advantages for different types of studies, but the risk of contamination and the differing levels of sensitivity lead to difficulties in estimating the proportion of individuals that are microchimeric. Recent observations of an increased frequency of microchimerism in women with scleroderma and Hashimoto's thyroiditis suggest that microchimerism may increase the risk of developing autoimmune disease. Inferences regarding autoimmunity are drawn from the immunological effects of organ and bone-marrow transplantation. Potential research questions regarding microchimerism, human leukocyte antigen (HLA) similarity, and autoimmune diseases in the context of multiple sclerosis (MS) are discussed.

APOE genotypes and disease severity in multiple sclerosis

Apolipoprotein E (opoE) is involved in the transport of lipids necessary for membrane repair and is encoded by a gene on chromosome 19q13, a region positive for linkage in two multiple sclerosis (MS) genome-wide screens. The APOE epsilon4 allele confers susceptibility to both familial and sporadic Alzheimer's disease (AD). Carriage of epsilon4 is associated with defective dendritic remodeling in AD, and with unfavorable clinical outcome in head trauma and cerebrovascular disease. According to the results of previous studies, APOE epsilon4 does not increase the risk of developing MS, but it may influence disease progression and ultimate disability. From a total cohort of over 900 MS patients, we compared APOE epsilon2-4 genotypes in, roughly, the cohort's least disabled and most disabled septiles. 'Benign MS' (n=124) was defined as an Expanded Disability Status Scale (EDSS) score of 3.0 or less, despite at least 10 years of disease duration, and 'severe MS' (n=140) as the attainment of an EDSS score of 6.0 within 8 years of disease onset. We found no significant differences in genotype or phenotype frequencies between the benign-MS and severe-MS septiles; however, the risk conferred by epsilon4 rose progressively upon comparison of carriage rates in more narrowly defined anti-podal quantiles.

Sharing of a conserved haplotype suggests a susceptibility gene for multiple sclerosis at chromosome 17p11

Multiple sclerosis (MS) is a chronic inflammatory disease resulting in demyelination in the central nervous system (CNS). Increasing evidence supports that genetic factors confer susceptibility to MS. One locus, the HLA complex (6p21), has been identified as important in MS, but no other loci have been clearly implicated, neither by a candidate gene approach, nor by a genomic screen strategy. Here, we studied a genetically isolated population in the northern-most part of Sweden, which demonstrates a high incidence of MS, using haplotype sharing analysis. Genealogical analysis demonstrated that 22 MS patients originate from a single common ancestral couple in the eighteenth century. Five affected individuals from four nuclear families were selected for an initial genomic screen with 390 microsatellite markers. Seven shared haplotypes in six different chromosomal regions were observed. After genotyping for these haplotypes with the same and additional markers in 15 MS patients and healthy relatives, some portion of a conserved haplotype spanning 10 cM at 17p11 was found to be shared by 12 of 15 affected individuals. The statistical analysis revealed a significant excess of transmission of alleles of three markers to affected individuals (P<0.05) by the transmission/disequilibrium test (TDT). An identical four-marker haplotype was shared by six of 15 patients (40%; P<0.01). Surprisingly, DR-typing revealed no significant sharing of the HLA region. In conclusion, our data suggests a novel susceptibility gene for MS in chromosome 17p11.

Association between the phenylethanolamine N-methyltransferase gene and multiple sclerosis

Phenylethanolamine N-methyltransferase (PNMT), the terminal enzyme of the catecholamine biosynthesis pathway, catalyzes the conversion of norepinephrine (NE) to epinephrine (EPI). PNMT is a candidate gene for multiple sclerosis (MS) for two reasons. PNMT is known to map to a region identified in two genome screens for MS and it directly regulates the amounts of NE and EPI, both of which play a significant role in the modulation of the innate immune response. The frequencies of two promoter polymorphisms of the PNMT gene showed genetic association in a case-control study of 108 patients with MS and 774 ethnically and age-matched control subjects. In subjects with MS, significant differences in the frequency of the GG genotype at the G-387A marker and the AA genotype at the G-182A marker were observed. Additionally, when both markers were combined and evaluated, highly significant differences between the polymorphism distributions in patients with MS and control subjects were detected. The data suggest that these promoter polymorphisms of the PNMT gene, both independently and cumulatively, show association with MS.

Association of polymorphisms in the apolipoprotein E region with susceptibility to and progression of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disorder of the central nervous system, with a complex etiology that includes a strong genetic component. The contribution of the major histocompatibility complex (MHC) has been established in numerous genetic linkage and association studies. In addition to the MHC, the chromosome 19q13 region surrounding the apolipoprotein E (APOE) gene has shown consistent evidence of involvement in MS when family-based analyses were conducted. Furthermore, several clinical reports have suggested that the APOE-4 allele may be associated with more-severe disease and faster progression of disability. To thoroughly examine the role of APOE in MS, we genotyped its functional alleles, as well as seven single-nucleotide polymorphisms (SNPs) located primarily within 13 kb of APOE, in a data set of 398 families. Using family-based association analysis, we found statistically significant evidence that an SNP haplotype near APOE is associated with MS susceptibility (P=.005). An analysis of disease progression in 614 patients with MS from 379 families indicated that APOE-4 carriers are more likely to be affected with severe disease (P=.03), whereas a higher proportion of APOE-2 carriers exhibit a mild disease course (P=.02).

The Siblings With Ischemic Stroke Study (SWISS) protocol

BACKGROUND

Family history and twins studies suggest an inherited component to ischemic stroke risk. Candidate gene association studies have been performed but have limited capacity to identify novel risk factor genes. The Siblings With Ischemic Stroke Study (SWISS) aims to conduct a genome-wide scan in sibling pairs concordant or discordant for ischemic stroke to identify novel genetic risk factors through linkage analysis.

METHODS

Screening at multiple clinical centers identifies patients (probands) with radiographically confirmed ischemic stroke and a family history of at least 1 living full sibling with stroke. After giving informed consent, without violating privacy among other family members, the proband invites siblings concordant and discordant for stroke to participate. Siblings then contact the study coordinating center. The diagnosis of ischemic stroke in potentially concordant siblings is confirmed by systematic centralized review of medical records. The stroke-free status of potentially discordant siblings is confirmed by validated structured telephone interview. Blood samples for DNA analysis are taken from concordant sibling pairs and, if applicable, from 1 discordant sibling. Epstein-Barr virus-transformed lymphoblastoid cell lines are created, and a scan of the human genome is planned.

DISCUSSION

Conducting adequately powered genomics studies of stroke in humans is challenging because of the heterogeneity of the stroke phenotype and the difficulty of obtaining DNA samples from clinically well-characterized members of a cohort of stroke pedigrees. The multicentered design of this study is intended to efficiently assemble a cohort of ischemic stroke pedigrees without invoking community consent or using cold-calling of pedigree members.

No evidence to support CTLA-4 as a susceptibility gene in MS families: the Canadian Collaborative Study

Two polymorphisms of the CTLA-4 gene were genotyped in 232 sibling pairs affected with multiple sclerosis (MS) from 185 families. The CTLA-4 polymorphisms genotyped were a 3' untranslated (AT)(n) microsatellite and an alanine/threonine RFLP of exon 1. There was no evidence observed for linkage by either identity-by-descent (ibd) or identity-by-state (ibs) methods. A transmission disequilibrium test (TDT) was performed and no preferential transmission of alleles was observed. Upon stratification of patients, there was no preferential transmission observed based upon gender, by presence or absence of HLA*DRB1*15, by ethnicity or by clinical course of the disease. CTLA-4 does not appear to be a major MS susceptibility locus in Canadian multiplex families.

Single nucleotide polymorphisms in MHC2TA, the gene encoding the MHC class II transactivator (CIITA)

The MHC class II transactivator (CIITA) is the master regulator for HLA-D (DP, DQ, DR) gene expression. In this report the coding and promoter regions of the CIITA gene, MHC2TA, were evaluated for polymorphisms in 50 normal Caucasian individuals. Allele frequencies were obtained for four separate single nucleotide (nt) polymorphisms (SNPs) identified in the MHC2TA coding region: nt 1614 (C-->G), nt 2509 (G-->A), nt 2536 (T-->G), and nt 2791 (G-->A). MHC2TA sequence analysis of 100 chromosomes from these 50 individuals revealed a SNP in MHC2TA promoter (p) III at nt (-)155 (A-->G), but none in CIITA pI or pIV. In addition, we demonstrate the presence of splice variant at a previously undiscovered intron, accounting for a three nt (TAG) insertion at position 474 that was originally described in association with one of the disease-causing CIITA cDNA mutations in bare lymphocyte syndrome.

Identification of susceptibility genes for experimental autoimmune encephalomyelitis that overcome the effect of protective alleles at the eae2 locus

We have previously identified a locus on mouse chromosome 15 (eae2) that regulates susceptibility to experimental autoimmune encephalomyelitis in a cross between the susceptible strain B10.RIII and the resistant strain RIIIS/J. In an effort to verify the protective effect from having two RIIIS/J alleles at eae2, the resistant locus was bred into the susceptible strain in homozygous form. However, the expected effect was not as clear as in the original study. This might be due to an epistatic effect conferred by several unidentified genes in the genome of the resistant strain or due to the environment by genotype interactions, possibly overcoming the effect of protective alleles at eae2. To further the genetic understanding in this disease, a genome-wide linkage screening approach was employed on an F(2) intercross that carried the protective allele at eae2in homozygous form while the rest of the genome segregated between the B10.RIII and RIIIS/J strains as in the original investigation. In the present study we find one region on chromosome 7, not previously identified in this strain combination, that affects the disease at significant logarithm of the odds score and six regions showing suggestive evidence for linkage to disease phenotypes.

Transgenic models of autoimmune disease

Transgenic and knockout mouse models have been invaluable for the elucidation of basic mechanisms in autoimmunity and have contributed new experimental models of human autoimmune diseases. Transgenic models of self tolerance have helped to change our view of this state from a process mediated purely by thymic deletion to a more complex process encompassing deletion, peripheral anergy, down-regulation of receptors and modulation by regulatory cells. Experiments in which the genes for the candidate target antigens in autoimmune disease are over-expressed or under-expressed have helped to clarify the targets of attack. Several examples of T cell receptor transgenic mice have been described in which T cells carry the receptor derived from a human or mouse autoimmune T cell clone. Such mice allow the characterization of T cell specificities contributing to disease and of the additional factors and checkpoints influencing disease development. In addition, the expression of disease associated HLA alleles in 'humanised' transgenic lines allows the mapping of HLA-restricted T cell epitopes and investigation of the mechanisms underlying these genetic associations. These approaches are leading to the generation of new disease models, offering hope for the design and testing of novel immunotherapeutic strategies.

Cognitive impairments in multiple sclerosis: a review

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). Cognitive impairment (CI) may develop at any time during the course of the disease in the presence or absence of neurological disability. On the basis of comprehensive neuropsychological studies, there is now a consensus among investigators that 45 percent to 65 percent of MS patients suffer from some degree and form of cognitive difficulty. Features of CI include bradyphrenia; impaired attention, concentration and abstract reasoning; reduced manual speed and dexterity; deficits in memory retrieval; and language deficits in both the relapsing-remitting and progressive forms of MS. Impairments in all cognitive domains may result from the diffuse spread of microscopic pathology, although a preferential lobar distribution of plaques can present with a predominant deficit in the corresponding cognitive function. Nevertheless, the severity of CI best correlates with total microscopic and macroscopic disease burden of the brain as defined by recently developed magnetic resonance imaging (MRI) sequences. A disruption of connecting intercortical and subcortical pathways is likely to be the main cause of metabolic and functional abnormalities in neurons. However a direct toxic effect of soluble inflammatory products may also compromise neuronal function and survival. Early treatment of MS with interferons and copaxone can prevent or delay the onset of both neurological and cognitive disabilities by reducing the inflammatory activity and damage in the CNS. Until more powerful neuroprotective agents become available, simple neuropsychological screening and cognitive rehabilitation for memory and language impairments will remain important components in the care of MS patients.

Microarray analysis of gene expression in multiple sclerosis and EAE identifies 5-lipoxygenase as a component of inflammatory lesions

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system characterized by lesions that are areas of blood-brain barrier breakdown, inflammation and myelin damage. To identify genes that contribute to lesion pathology, we have compared gene expression in MS lesions and in brains of mice with experimental allergic encephalomyelitis (EAE) with that in normal white matter. Gene expression was analyzed by cDNA microarrays consisting of 2798 human genes. One of the genes found to be upregulated in both MS lesions and EAE brains was 5-lipoxygenase (5-LO), a key enzyme in the biosynthesis of the proinflammatory leukotrienes. The presence of 5-LO in MS lesions was confirmed by immunohistochemistry and indicated that 5-LO was primarily contained within macrophages. Although these findings are not specific for MS, they identify a potentially important component of pro-inflammatory activity in the demyelinating process in MS and suggest a possible target for anti-inflammatory therapy in MS.

Linkage analysis suggests a region of importance for multiple sclerosis in 3p14-13

Four genomic screens for linkage in multiple sclerosis (MS) have been reported. They confirmed the established role of the human leucocyte antigen (HLA) complex genes in MS and, in addition, suggested the importance of a few other chromosomal segments. Here we report evidence for the importance of 3p14-13 region identified by suggestive linkage in genomic screens from Canada and the United Kingdom. When studying 146 Nordic MS multiplex families, mostly affected sib-pairs, with eight microsatellite markers, spanning a 36-cM region, we observed a two-point non-parametric linkage (NPL) score of 2.39 (P = 0.007) by the GENEHUNTER package for marker D3S1285 and a multipoint NPL score of 1.20 in the same region. Association studies in Swedish MS patients revealed modest allelic associations of uncertain significance not supported by transmission analysis. Analysis of the trinucleotide repeat sequence of the SCA7 gene in Swedish index cases did not reveal expansions. We conclude that support was obtained for the location of a gene or genes with importance for MS susceptibility in 3p14-13 region.

Multiple sclerosis in sibling pairs: an analysis of 250 families

OBJECTIVES

To assess the potential contribution of genetic factors to clinical phenotype in multiple sclerosis.

METHODS

Using a cohort of 262 pairs of coaffected siblings from 250 families with multiple sclerosis, intersibling concordance analysis was used to explore underlying genetic mechanisms in disease pathogenesis by assessing parameters of disease course, clinical presentation, age and year of onset, and measures of disability and handicap.

RESULTS

Adjusted intraclass correlation coefficients were not significant for either age of onset or for year of first symptom. One third of sibling pairs were concordant for presenting symptom (81/262), a result that was non-significant. However, course type was identical in 50% of the sibling pairs (kappa=0.17 (95% confidence interval (95% CI) 0.08 to 0.26)) indicating a significant result. Severity of the disease at assessment, using the Kurtzke and CAMBS scales, demonstrated that whereas there was no agreement for relapse rate in the previous year within the sibship, there was significant concordance for measures of disability (kappa=0.11 (95% CI 0.04 to 0.19)), progression (kappa=0.09 (95% CI 0.01 to 0.18)) and handicap (kappa=0.08 (95% CI 0.02 to 0.14)).

CONCLUSIONS

Within a sibship, the clinical presentation tends to be different. However, once established, concordance is more likely to be seen for the ultimate course, leading in the end to similar disability and handicap scores. These results are consistent with the hypothesis that genes influence both disease susceptibility and evolution in multiple sclerosis.

Malignant glioma cells use MHC class II transactivator (CIITA) promoters III and IV to direct IFN-gamma-inducible CIITA expression and can function as nonprofessional antigen presenting cells in endocytic processing and CD4(+) T-cell activation

Malignant gliomas (MGs), lethal human central nervous system (CNS) neoplasms, contain tumor infiltrating lymphocytes (TIL). Although MHC class II molecules are frequently detected on MG cells, suggesting that they may be capable of antigen (Ag) presentation to CD4(+) T cells, deficiencies in CD4(+) T-cell activation are associated with these nonimmunogenic tumors. We evaluated regulation of the MHC class II transactivator (CIITA), the key intermediate that controls class II expression, in MG cells and tested whether MG cells could process native Ag. After interferon-gamma (IFN-gamma) stimulation, MG cells upregulated CIITA and class II molecules. IFN-gamma-inducible CIITA expression in MG cells, as well as primary human astrocytes, was directed by two CIITA promoters, pIV, the promoter for IFN-gamma-inducible CIITA expression in nonprofessional antigen-presenting cells (APC), and pIII, the promoter that directs constitutive CIITA expression in B cells. Both pIII and pIV directed CIITA transcription in vivo in MGs and ex vivo in IFN-gamma-activated primary MG cultures. We also demonstrate for the first time that MG cells can process native Ag for presentation to CD4(+) MHC class II-restricted Th1 cells, indicating that MG cells can serve as nonprofessional APC. CIITA may be a key target to modulate MHC class II expression, which could augment immunogenicity, Ag presentation, and CD4(+) T-cell activation in MG therapy.

The influence of the proinflammatory cytokine, osteopontin, on autoimmune demyelinating disease

Multiple sclerosis is a demyelinating disease, characterized by inflammation in the brain and spinal cord, possibly due to autoimmunity. Large-scale sequencing of cDNA libraries, derived from plaques dissected from brains of patients with multiple sclerosis (MS), indicated an abundance of transcripts for osteopontin (OPN). Microarray analysis of spinal cords from rats paralyzed by experimental autoimmune encephalomyelitis (EAE), a model of MS, also revealed increased OPN transcripts. Osteopontin-deficient mice were resistant to progressive EAE and had frequent remissions, and myelin-reactive T cells in OPN-/- mice produced more interleukin 10 and less interferon-gamma than in OPN+/+ mice. Osteopontin thus appears to regulate T helper cell-1 (TH1)-mediated demyelinating disease, and it may offer a potential target in blocking development of progressive MS.

Genomewide scans of complex human diseases: true linkage is hard to find

Many "complex" human diseases, which involve multiple genetic and environmental determinants, have increased in incidence during the past 2 decades. During the same time period, considerable effort and expense have been expended in whole-genome screens aimed at detection of genetic loci contributing to the susceptibility to complex human diseases. However, the success of positional cloning attempts based on whole-genome screens has been limited, and many of the fundamental questions relating to the genetic epidemiology of complex human disease remain unanswered. Both to review the success of the positional cloning paradigm as applied to complex human disease and to investigate the characteristics of the whole-genome scans undertaken to date, we created a database of 101 studies of complex human disease, which were found by a systematic Medline search (current as of December 2000). We compared these studies, concerning 31 different human complex diseases, with regard to design, methods, and results. The "significance" categorizations proposed by Lander and Kruglyak were used as criteria for the "success" of a study. Most (66.3% [n=67]) of the studies did not show "significant" linkage when the criteria of Lander and Kruglyak (1995) were used, and the results of studies of the same disease were often inconsistent. Our analyses suggest that no single study design consistently produces more-significant results. Multivariate analysis suggests that the only factors independently associated with increased study success are (a) an increase in the number of individuals studied and (b) study of a sample drawn from only one ethnic group. Positional cloning based on whole-genome screens in complex human disease has proved more difficult than originally had been envisioned; detection of linkage and positional cloning of specific disease-susceptibility loci remains elusive.

Genetic variation in the transforming growth factor beta1 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.

A pathogenic role for myelin-specific CD8(+) T cells in a model for multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system (CNS) characterized by plaques of infiltrating CD4(+) and CD8(+) T cells. Studies of MS and experimental autoimmune encephalomyelitis (EAE), an animal model of MS, focus on the contribution of CD4(+) myelin-specific T cells. The role of CD8(+) myelin-specific T cells in mediating EAE or MS has not been described previously. Here, we demonstrate that myelin-specific CD8(+) T cells induce severe CNS autoimmunity in mice. The pathology and clinical symptoms in CD8(+) T cell-mediated CNS autoimmunity demonstrate similarities to MS not seen in myelin-specific CD4(+) T cell-mediated EAE. These data suggest that myelin-specific CD8(+) T cells could function as effector cells in the pathogenesis of MS.

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

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) of unknown etiology. Nitric oxide (NO) is a free radical that participates in a variety of biological processes. It is an important mediator in the immune response. Several studies indicate involvement of NO in the pathogenesis of MS. We studied five markers within the three NO synthase genes with regards to susceptibility and disease course in 156 affected sib-pairs and in 96 "benign" and 96 "severe" definite MS patients and 148 controls. We found no significant association or evidence for linkage in our data sets.

The T cell regulator gene SH2D2A contributes to the genetic susceptibility of multiple sclerosis

The T cell specific adapter protein (TSAd) encoded by the SH2D2A gene is involved in the control of T cell activation. The gene is located in the 1q21 region, which has been implicated in susceptibility to experimental allergic encephalomyelitis in the mouse. We therefore evaluated whether a polymorphic GA repeat (GA(13)-GA(33)) within the promoter region of the SH2D2A gene shows association to multiple sclerosis (MS). The frequency of the short alleles GA(13-16) was increased among 313 Norwegian MS patients compared to 277 healthy controls (0.332 vs 0.249, OR 1.5, Pc = 0.03). Transmission disequilibrium analysis in 146 Scandinavian families with at least two affected sibs showed increased transmission of GA(16) to MS patients. No linkage or association of MS to four genetic markers flanking the SH2D2A gene was observed. After activation of naive CD4(+) T cells, T cells homozygous for MS associated short alleles displayed lower level of TSAd ex vivo than T cells carrying at least one long allele, which were not associated to MS. Since the SH2D2A protein modulates T cell activation, this may be a mechanism for how short SH2D2A alleles confer susceptibility to develop MS.

A genome screen for multiple sclerosis in Sardinian multiplex families

The prevalence of multiple sclerosis in Sardinia is significantly higher than in neighbouring Mediterranean countries, suggesting that the isolated growth of the population has concentrated genetic factors which increase susceptibility to the disease. The distinct HLA association of multiple sclerosis in Sardinia supports this interpretation. We have performed a whole genome screen for linkage in 49 Sardinian multiplex families using 327 markers. Non parametric linkage analysis of these data reveal suggestive linkage in the region of Chr 1q31, Chr 10q23 and Chr 11p15.

Peripheral blood cell bulk cultures are not suitable for the analysis of the genetic control of T-cell cytokine function

Recently evidence has been provided for a genetic control of T-cell dependent cytokine production by HLA-class II. Candidate genes in multiple sclerosis, a T-cell mediated autoimmune disease, are the disease-associated DR2, DQ6, Dw2 haplotype. Previous observations by us and others imply a HLA-DR2 dependent propensity of antigen-specific T-cell lines to produce increased amounts of TNF-alpha/beta. Here, we tested a possible association between HLA or disease status with cytokine production employing the simple and widely used method of bulk cultures. Peripheral blood cells of 48 patients and 68 healthy individuals were analyzed. We observed no significant differences of the cytokine production in relation to disease status or any HLA polymorphism. Our data indicate that, in contrast to monoclonal T-cell cultures, bulk cultures are not suitable to detect immunogenetic control of T-cell function.

In vivo gene expression revealed by cDNA arrays: the pattern in relapsing-remitting multiple sclerosis patients compared with normal subjects

OBJECTIVES

To use DNA arrays to identify differences in gene expression associated with relapsing-remitting (RR) MS.

METHODS

Total RNA was isolated from monocyte depleted peripheral blood mononuclear cells of 15 RR MS patients and 15 age- and sex-matched controls. The RNA was reverse transcribed to radiolabeled cDNA and the resultant cDNA was used to probe a DNA array containing over 4000 named human genes. The binding of radiolabeled cDNA to the probes on the array was measured by phosphorimager.

RESULTS

Of more than 4000 genes tested, only 34 were significantly different in RR-MS patients from controls. Of these, 25 were significantly increased and 9 significantly decreased in the RR MS patients. Twelve of these genes have inflammatory and/or immunological functions that could be relevant to the MS disease process. The potentially relevant genes that were elevated (15% to 28%) were P protein, LCK, cAMP responsive element modulator, IL-7 receptor, matrix metalloproteinase-19, M130 antigen, and peptidyl-prolyl isomerase. Those that were significantly decreased (15% to 35%) were SAS transmembrane 4 superfamily protein, STRL22 (C-C chemokine receptor 6), AFX protein, DNA fragmentation factor-45 and immunoglobulin gamma 3 (Gm marker).

CONCLUSIONS

The RR-MS disease effect was relatively restricted and most of the mRNAs tested were not different from the normal controls. However, there were significant differences identified in the expression of a subset of mRNAs, including 13 with inflammatory/immune functions that could be relevant to MS. The systematic use of DNA arrays can provide insight into the dynamic cellular pathways involved in MS pathogenesis and its phenotypic heterogeneity.

A genome screen for multiple sclerosis in Italian families

We have screened the whole genome for linkage in 40 Italian multiplex families with multiple sclerosis using 322 markers. The GENEHUNTER-PLUS program was used to analyse these data and revealed eight regions of potential linkage where the lod score exceeds the nominal 5% significance level (0.7). No region of linkage with genome-wide significance was identified and none of the markers showed evidence of statistically significant transmission disequilibrium. Overall these results have refined the linkage data relating to this disease in Italians modestly supporting some previously identified areas of interest and helping to exclude others.

Analysis of an interferon-gamma gene dinucleotide-repeat polymorphism in Nordic multiple sclerosis patients

The proinflammatory cytokine interferon (IFN)-gamma has been shown to influence the course of multiple sclerosis (MS). The IFN-gamma (IFNG) contains a multiallelic dinucleotide repeat in intron 1. To investigate whether alleles at this locus influence susceptibility to MS, we performed linkage and familial association analyses on 100 sibling pairs from four Nordic countries, and case-control association analysis on 220 intermediately disabled sporadic MS patients and 266 controls. To determine the effect of the polymorphism on disease outcome, we compared genotype frequencies in the most and least disabled octiles of a total cohort of 913 cases. We also measured IFN-gamma mRNA levels in unstimulated peripheral blood mononuclear cells from 46 MS patients and 27 controls grouped according to IFNG intron 1 genotype. Both nonparametric linkage analysis and transmission disequilibrium testing of the 100 sibling pairs produced negative results. Genotype frequencies for intermediate-MS patients did not differ significantly from those for controls; nor did genotype frequencies in the benign-MS octile differ significantly from those in the severe-MS octle. Comparison of IFN-gamma mRNA levels in genotype-conditioned subgroups revealed no significant differences. Thus, alleles at the IFNG intron 1 dinucleotide repeat appear to affect neither MS susceptibility and severity nor IFN-gamma mRNA expression in vivo.

Linkage analysis in multiple sclerosis of chromosomal regions syntenic to experimental autoimmune disease loci

Multiple sclerosis is a demyelinating disorder of the central nervous system with a putative autoimmune aetiology in which several genes are thought to be involved. Four published genomic screens have confirmed that a gene influencing MS resides within or close to the HLA class II region in 6p21. Still, this locus is likely to confer only a part of the genetic susceptibility in MS. Further, all four studies identified a number of other regions with possible linkage. We have investigated eight chromosomal intervals syntenic to loci of importance for experimental autoimmune model diseases in the rat in 74 Swedish MS families. Possible linkage (a non-parametric linkage NPL score of 1.16 by GENEHUNTER computer package) was observed with markers in 12p13.3, a region syntenic to the rat Oia2 locus which is importance for oil induced arthritis (OIA). Four markers in the T cell receptor beta chain gene region in 7q35 showed possible linkage (highest NPL score of 1.16). This locus is syntenic to the rat Cia3 locus (collagen induced arthritis). These two loci at least partially overlap with chromosomal regions showing indicative evidence for linkage in the previous MS genomic screens. Indeed, both Oia2 and Cia3 were recently found to be linked also with experimental autoimmune encephalomyelitis, a commonly used model for MS. Markers in 2p12, 3p25, 10q11.23, 17q21-25, 19q13.1, and 22q12-13 failed to provide evidence for linkage. We conclude that evidence is amounting that 12p13-12 and 7q34-36 may harbour genes with an importance for MS. The synteny with experimental loci may eventually facilitate their identification.

Molecular mimicry and antigen-specific T cell responses in multiple sclerosis and chronic CNS Lyme disease

The concept of molecular mimicry provides and elegant framework as to how cross-reactivity between antigens from a foreign agent with self proteins may trigger autoimmune diseases. While it was previously thought that sequence and structural homology between foreign and self proteins or the sharing of T cell receptor (TCR) and MHC-binding motifs are required for molecular mimicry to occur, we have shown that even completely unrelated peptide sequences may lead to cross-recognition by T cells. The use of synthetic combinatorial peptide libraries in the positional scanning format (PS-SCL) together with novel biometric prediction approaches has allowed us to describe the recognition profiles of individual autoreactive T cell clones (TCC) with unprecedented accuracy. Through studies of myelin-specific TCC as well as clones from the nervous system of patients suffering from chronic central nervous (CNS) Lyme disease it has become clear that at least some T cells are more degenerate than previously anticipated. These data will not only help us to redefine what constitutes specific T cell recognition, but also allow us to study in more detail the biological role of molecular mimicry. A recent clinical trial with an altered peptide ligand (APL) of one of the candidate myelin basic protein (MBP) epitopes in MS (amino acids 83-99) has shown that such a modified MBP peptide may not only have therapeutic efficacy, but also bears the potential to exacerbate disease. Thus, we provide firm evidence that the basic principles of cross-recognition and their pathogenetic significance are relevant in MS.

Structural basis of molecular mimicry

Infectious agents are thought to play an important role in the development of autoimmune diseases. Sequence similarity between infectious agents and self-proteins (molecular mimicry) has been proposed as a mechanism for the induction of autoimmunity [1]. However, it has been difficult to identify microbial peptides that activate autoreactive T cells using conventional sequence alignments. This chapter reviews progress made in the identification of such microbial peptides based on the analysis of structural features that are important for TCR recognition of MHC-bound peptides [2].

Sequence variation in the transforming growth factor-beta1 (TGFB1) gene and multiple sclerosis susceptibility

Genome screenings in multiple sclerosis (MS) have identified multiple susceptibility regions supporting a polygenic model for this disease. Evidence for linkage was consistently observed at ch.19q13 suggesting the presence of an MS gene(s) in this region. Several interesting candidate genes are encoded within this region, including transforming growth factor-beta 1 (TGFB1) and interleukin-11 (IL11). Both are multifunctional cytokines with significant and well-characterized immunomodulatory properties. We performed a comprehensive evaluation of common polymorphisms within the TGFB1 and IL11 loci and three closely flanking microsatellite markers (D19S421, CEA, D19S908) in 161 stringently ascertained and clinically characterized MS multiplex families using tests of both linkage (lod score, sib-pair analysis) and association (pedigree disequilibrium test or PDT). Patients and families were stratified by HLA-DR2 status to search for two-locus interactions. Suggestive evidence for linkage and association to CEA (lod score = 1.25, theta = 0.20, p = 0.015, respectively), located 0.4 cM from TGFB1, was observed in DR2 positive families only. Distinct clinical phenotypes were also examined and an association between a TGFB1 haplotype and a mild disease course was present (p = 0.008), raising the possibility that TGFB1 or a nearby locus may influence disease expression.

Lessons from studies of antigen-specific T cell responses in Multiple Sclerosis

Multiple Sclerosis (MS) is considered a T cell-mediated autoimmune disease of central nervous system myelin. Based on elegant experiments in an animal model of MS, experimental allergic encephalomyelitis (EAE), a number of myelin proteins and peptides derived from these can induce inflammatory demyelinating lesions. Recent studies with transgenic mice expressing human HLA-DR molecules and a myelin basic protein (MBP)-specific T cell receptor as well as data from a phase II clinical trial with an altered peptide ligand based on MBP peptide (83-99) provide convincing evidence that the pathogenetic concepts which largely stem from the above EAE studies are valid in MS, too.

HW, Bridges Jr. SL, Pisetsky DS, Ward R, Kastner DL, Wilder RL, Pincus T, Callahan LF, Flemming D, Wener MH, Gregersen PK. A genomewide screen in multiplex rheumatoid arthritis families suggests genetic overlap with other autoimmune diseases

Rheumatoid arthritis (RA) is an autoimmune/inflammatory disorder with a complex genetic component. We report the first major genomewide screen of multiplex families with RA gathered in the United States. The North American Rheumatoid Arthritis Consortium, using well-defined clinical criteria, has collected 257 families containing 301 affected sibling pairs with RA. A genome screen for allele sharing was performed, using 379 microsatellite markers. A nonparametric analysis using SIBPAL confirmed linkage of the HLA locus to RA (P < .00005), with lambdaHLA = 1.79. However, the analysis also revealed a number of non-HLA loci on chromosomes 1 (D1S235), 4 (D4S1647), 12 (D12S373), 16 (D16S403), and 17 (D17S1301), with evidence for linkage at a significance level of P<.005. Analysis of X-linked markers using the MLOD method from ASPEX also suggests linkage to the telomeric marker DXS6807. Stratifying the families into white or seropositive subgroups revealed some additional markers that showed improvement in significance over the full data set. Several of the regions that showed evidence for nominal significance (P < .05) in our data set had previously been implicated in RA (D16S516 and D17S1301) or in other diseases of an autoimmune nature, including systemic lupus erythematosus (D1S235), inflammatory bowel disease (D4S1647, D5S1462, and D16S516), multiple sclerosis (D12S1052), and ankylosing spondylitis (D16S516). Therefore, genes in the HLA complex play a major role in RA susceptibility, but several other regions also contribute significantly to overall genetic risk.

Multiple sclerosis: current pathophysiological concepts

Multiple sclerosis (MS) is an often disabling disease primarily affecting young adults that exhibits extraordinary clinical, radiological, and pathological heterogeneity. We review the following: (a) known environmental and genetic factors that contribute to MS susceptibility; (b) current knowledge regarding fundamental pathophysiological processes in MS, including immune cell recruitment and entry into the central nervous system (CNS), formation of the plaque, and orchestration of the immune response; (c) descriptive and qualitative distinct pathological patterns in MS and their implications; (d) the evidence supporting the causative role of direct toxins, cell-mediated and humorally mediated immune mechanisms, and the concept of a "primary oligodendrogliopathy" in demyelination and axonal injury; (e) the potential benefits of inflammation; (f) the prospects for remyelination; and (g) therapeutic implications and approaches suggested by putative pathophysiological mechanisms.

Multiple sclerosis: genomic rewards

A large body of immunologic, epidemiologic, and genetic data indicate that tissue injury in multiple sclerosis (MS) results from an abnormal immune response to one or more myelin antigens that develops in genetically susceptible individuals after exposure to an as-yet undefined causal agent. The genetic component of MS etiology is believed to result from the action of several genes of moderate effect. The incomplete penetrance of MS susceptibility alleles probably reflects interactions with other genes, post transcriptional regulatory mechanisms, and significant nutritional and environmental influences. Equally significant, it is also likely that genetic heterogeneity exists, meaning that specific genes influence susceptibility and pathogenesis in some affects but not in others. Results in multiplex MS families confirm the genetic importance of the MHC region in conferring susceptibility of MS. Susceptibility may be mediated by the class II genes themselves (DR, DQ or both), related to the known function of these molecules in the normal immune response, e.g. antigen binding and presentation and T cell repertoire determination. The possibility that other genes in the MHC or the telomeric region of the MHC are responsible for the observed genetic effect cannot be excluded. The data also indicate that although the MHC region plays a significant role in MS susceptibility, much of the genetic effect in MS remains to be explained. Some loci may be involved in the initial pathogenic events, while others could influence the development and progression of the disease. The past few years have seen real progress in the development of laboratory and analytical approaches to study non-Mendelian complex genetic disorders and in defining the pathological basis of demyelination, setting the stage for the final characterization of the genes involved in MS susceptibility and pathogenesis. Their identification and characterization is likely to define the basic etiology of the disease, improve risk assessment and influence therapeutics.

Analysis of interleukin-4 receptor alpha chain variants in multiple sclerosis

A recent candidate gene study employing microsatellite markers suggested a possible linkage of multiple sclerosis (MS) with the interleukin-4 receptor (IL4R) gene. Consequently, we investigated the association of different IL4R variants with MS in 341 German MS patients and 305 healthy controls. Analysis of the first 100 MS patients for six IL4R variants showed an increased frequency of the R551 variant in MS patients versus healthy controls and carriage of the same IL4R variant was weakly associated with myelin oligodendrocyte glycoprotein (MOG) autoantibody production. However, further analysis of all 341 MS patients did not confirm the finding that this IL4R variant represents a general genetic risk factor for MS but revealed an increased frequency of the R551 variant in MS patients with primary progressive MS (PPMS, n=48) as compared to patients with relapsing remitting MS or secondary progressive MS (RR/SPMS n=284; P=0.005 for genotype differences) and to 305 healthy controls (P=0.001 for genotype differences). This association was statistically independent of the presence of the well-known MS susceptibility allele HLA-DRB1*15. After correction for multiple comparisons only the genotype differences between PPMS patients and healthy controls remained statistically significant. These results indicate, that the IL4R variant R551 may influence the genetic predisposition for PPMS but does not represent a general genetic risk factor for MS.

A meta-analysis of genomic screens in multiple sclerosis. The Transatlantic Multiple Sclerosis Genetics Cooperative

We combined the raw genotyping data from three large multiple sclerosis genome screens and performed a global meta-analysis in order to compare and summarize the linkage results from the different studies. In alphabetical order, the screens provided data from 442 markers typed in 52 multiplex families with a total of 133 affected individuals (the American screen), 314 markers typed in 128 families with 264 affecteds (the British screen) and 257 markers typed in 61 families with a total of 139 affected subjects (the Canadian screen). Multipoint analysis of these data was performed using the GENEHUNTER program. The highest non-parametric linkage (NPL) score in the meta-analysis was observed on chromosome 17q11 (NPL score 2.58), although this score falls short of genome-wide significance. A total of eight regions had NPL scores greater than 2.0. One of the regions with an NPL score greater than 2.0 was the HLA region on chromosome 6p21 (NPL=2.2). This region is known, from association studies, to be involved in MS susceptibility, but the modest linkage result observed here suggests the encoded susceptibility effect is not large compared with the high familial recurrence in MS (lambda approximately 20). Overall, our linkage results suggest that MS is likely to be multigenic in its genetic susceptibility.

Association between the ancestral haplotype HLA A30B18DR3 and multiple sclerosis in central Sardinia

Association and linkage studies have established the importance of the major histocompatibility complex (MHC) in the susceptibility for multiple sclerosis (MS). We carried out a case-control study to investigate the ancestral haplotype A30B18DR3 and MS in the Nuoro population of Sardinia, which is isolated and genetically distinct from other populations in the Mediterranean basin and characterized by genetic homogeneity, high level of inbreeding, low migration, high prevalence of MS, high frequency of the relevant haplotype, and high past malaria prevalence. Cases and controls were serologically typed for the currently recognized HLA-A, B, and DR antigens. We used a log-linear approach to fit a wide class of models. We tested our hypothesis comparing different models via a likelihood ratio test. We overcame the complication due to unknown gametic phase using expectation-maximization (EM) algorithm as the estimation method. We estimated confidence intervals for odds ratio by using a profile likelihood approach. We found that: (1) the ancestral haplotype A30B18DR3 was associated to MS after allowing for a possible stratification in cases and controls; (2) DR3 allele was conditional independent on disease status, given A30B18 haplotype; (3) there was a tendency for ORs for the high-risk haplotypes to be higher in the high malaria strata; however, this indication did not achieve statistical significance (P = 0.11).

Mice lacking myeloperoxidase are more susceptible to experimental autoimmune encephalomyelitis

EAE is a demyelinating disease which serves as an animal model for multiple sclerosis (MS). Myeloperoxidase (MPO) has been implicated in MS through its presence in invading macrophages, and by association of a -463G/A promoter polymorphism with increased risk. Also, MPO at 17q23.1 is within a region identified in genome scans as a MS susceptibility locus. We here examine the incidence of EAE in MPO knockout (KO) mice. MPO is detected in invading macrophages in the CNS of wild-type mice, yet unexpectedly, MPO-KO mice have significantly increased incidence of EAE: Ninety percent of MPO-KO mice developed complete hind limb paralysis as compared to 33% of wildtype (WT) littermates (P<0.0001). This is the first evidence that MPO plays a significant role in EAE, consistent with its postulated role in MS.