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

Genetic analysis of the influence of neuroantigen-complete Freund's adjuvant emulsion structures on the sexual dimorphism and susceptibility to experimental allergic encephalomyelitis

The induction of organ-specific autoimmune diseases, such as experimental allergic encephalomyelitis (EAE) the principal animal model of multiple sclerosis (MS), relies on the use of complete Freund's adjuvant (CFA) emulsions. In this study we report that the physical structure of the particles comprising neuroantigen-CFA emulsions significantly influences the genetic control of the incidence and sexual dimorphism seen in EAE. Immunization of (B10.S/SgMcdJ x SJL/J) F(2) mice segregating the quantitative trait loci (QTL) controlling EAE in susceptible SJL/J and resistant B10.S/SgMcdJ mice with emulsions consisting of particles where the Mycobacterium tuberculosis and neuroantigens are localized on the phase surfaces led to severe EAE in 98.8% of the mice, overriding all sex-specific and non-sex-specific genetic checkpoints. In contrast, F(2) mice immunized with emulsions where the bacterial products and encephalitogens are buried inside the water/oil vesicles exhibited a significant reduction in disease incidence (7.5%) and a sexual dimorphism (5% male versus 10% female). A genome scan identified QTL on chromosomes 7 and 11 controlling the sexual dimorphism as a function of the physical structure of the emulsion. The chromosome 11 QTL co-localizes with eae6b, and with Il12b and heptatitis A virus cellular receptor 2 (Havcr2, formerly known as Timd3), both of which are candidate genes for this QTL. Sequence analysis of the SJL/J and B10.S/SgMcdJ alleles indicates that both gene products are structurally monomorphic. Expression analysis also excluded both as candidates for this sex-specific QTL. These results reinforce the importance of gene-environment interactions in initiating and propagating autoimmune disease of the central nervous system, particularly in the context of susceptibility to MS and disease heterogeneity.

Intercellular adhesion molecule-1: a protective haplotype against multiple sclerosis

Intercellular adhesion molecule-1 (ICAM-1) and its receptors are adhesion molecules that play a key role in the transmigration of inflammatory cells through the blood-brain barrier, one of the earliest events in multiple sclerosis (MS), which leads to demyelination in the central nervous system. To investigate the role of genes encoding ICAM-1 and its receptors, we used a strategy of genetic linkage and association in 439 case-parent MS families of French origin, well characterized according to HLA status and severity. We demonstrate that the genes encoding ICAM-1 receptors do not influence MS susceptibility or severity. ICAM-1 had a modest, but significant effect on MS genetic susceptibility, independent of HLA and disease severity. We observed a rare, and an as yet unreported, ICAM-1 gene haplotype defined by amino acids K469 and R241 that was never transmitted to patients suggesting a protective effect against MS in our population.

A genome-wide screen for linkage disequilibrium in Australian HLA-DRB1*1501 positive multiple sclerosis patients

The association of multiple sclerosis with alleles/haplotypes from the HLA region on chromosome 6p21 is well established although the remainder of the genome remains relatively unexplored. We have completed a genome-wide screen for linkage disequilibrium in a cohort of Australian multiple sclerosis patients positive for HLA-DRB1*1501. A total of 4346 microsatellite markers provided through the "Genetic Analysis of Multiple sclerosis in EuropeanS" (GAMES) collaborative were analysed in DNA separately pooled from cases (n=217) and controls (n=187). Associations were found in four genomic regions (12q15, 16p13, 18p11 and 19q13) previously identified in linkage genome screens. Three additional regions of novel association were also identified (11q12, 11q23 and 14q21). Further analysis of these regions is required to establish whether the associations observed are due to epistatic interaction with the HLA locus.

A whole genome association study in Finnish multiple sclerosis patients with 3669 markers

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system with complex genetic background. In the present study, based in the Finnish population, we typed a large number of microsatellite markers in separately pooled DNA samples from 195 MS patients and 205 controls. A total of 108 markers showed evidence of association. Five genomic regions containing two or more of these markers within a 1-Mb interval were identified, 1q43, 2p16, 4p15, 4q34 and 6p21 (the MHC region). Substantial overlap with previously published linkage genome screens is also seen.

A whole genome screen for association with multiple sclerosis in Portuguese patients

Multiple sclerosis (MS) is common in Europe affecting up to 1:500 people. In an effort to identify genes influencing susceptibility to the disease, we have performed a population-based whole genome screen for association. In this study, 6000 microsatellite markers were typed in separately pooled DNA samples from MS patients (n=188) and matched controls (n=188). Interpretable data was obtained from 4661 of these markers. Refining analysis of the most promising markers identified 10 showing potential evidence for association.

A genomic screen of Spanish multiple sclerosis patients reveals multiple loci associated with the disease

In order to identify the genomic regions that might confer susceptibility to multiple sclerosis (MS) in the Spanish population, we have performed a genome-wide screen for association in patients with MS using pooled DNA from 200 clinical cases and 200 healthy controls. The pools were typed using 5546 microsatellites. The typing was repeated for the most promising 1269 markers after which 191 potentially associated markers were identified. Eleven of these markers map to the MHC region, and 14 to non-MHC regions identified in previous linkage screens. Our results provide support for the presence of multiple coding regions that contain MS susceptibility genes of small or moderate effect.

A meta-analysis of whole genome linkage screens in multiple sclerosis

Linkage studies in complex diseases like multiple sclerosis, where the effects attributable to individual loci are modest, are critically dependent upon the number of families included. We have combined the raw genotyping data from all published genome linkage screens in multiple sclerosis and thereby performed a linkage analysis including 719 families studied with a weighted average of 359 microsatellite markers per family (range 257-453) providing an average marker separation of 10.2 cM. Linkage with genome-wide significance is confirmed in the HLA region on chromosome 6p21. In addition, two novel regions suggestive of linkage are seen (17q21 and 22q13). Our simulations would imply that the number of peaks with NPL scores >/=2.1 exceeds the number expected by chance alone.

A genome-wide German screen for linkage disequilibrium in multiple sclerosis

We report on a genome-wide screen for association with multiple sclerosis (MS) in the German population performed using 6000 microsatellite markers. These markers were typed in four DNA pools consisting of 234 MS patients (cases), 209 unrelated controls, 68 index patients from trio families and their 136 parents (related controls). Stringent analysis identified 11 markers showing apparent evidence for association. Five from regions previously identified in linkage studies and two from the MHC region on chromosome 6p21. These MHC markers are known to be in linkage disequilibrium with HLA class II alleles influencing susceptibility to MS. The identification of these markers serves as an important positive control.

Refining the linkage analysis on chromosome 10 in 449 sib-pairs with multiple sclerosis

Genome-wide screens for linkage in multiplex families with multiple sclerosis (MS) from United Kingdom, Sardinia, Italy and the Nordic countries (Denmark, Finland, Norway and Sweden) have each shown suggestive or potential linkage on chromosome 10. The partially overlapping regions identified by these studies encompass around 60 cM of the chromosome. In order to explore this region further, we typed 13 microsatellite markers in the same 449 families originally studied in the individual screens. This additional genotyping increased the information extraction in the region from 52% to 79% and revealed increased support for linkage (MLS 2.5) peaking at 10p15.

A whole genome association study in Icelandic multiple sclerosis patients with 4804 markers

Multiple sclerosis (MS) is a demyelinating disorder of the central nervous system (CNS) with a complex genetic background. Here we use a genome-wide association strategy with 4804 microsatellite markers successfully typed in separately pooled DNA from 200 patients and 200 controls. A total of 91 markers showed evidence of association. When compared to our in-house physical map of the genome, six 2-Mb regions containing at least two of these markers were detected. Of those, three regions have one or more markers among the 20 most strongly associated: chromosomes 3q25, 6p21.3 (the MHC region) and 19q13.

Updated results of the United Kingdom linkage-based genome screen in multiple sclerosis

In 1996, we reported the results of a linkage genome screen based on 129 UK multiple sclerosis multiplex families, together with follow-up typing of interesting regions in a second set of families. We have now completed screening the remainder of the genome in this second set of United Kingdom families by typing 242 microsatellite markers. These data have been analysed together with those previously published, resulting in the largest currently available whole genome linkage dataset from a single population in multiple sclerosis. Four new regions of potential linkage (chromosomes 10p, 11p, 19p, 20p) not previously described were identified. In the combined analysis of all 226 families, a total of five regions of suggestive linkage are seen (chromosomes 1p, 6p, 14q, 17q, Xq), where only one would have been expected to occur by chance alone.

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

Genetic factors are known to influence susceptibility to multiple sclerosis (MS) but the genes involved are largely undefined. Here, we report an association study based on 200 patients and 200 controls from the Porto region in Portugal. A total of 3974 markers were successfully typed from which we have identified 46 markers showing evidence of association. When compared to a physical map three regions were found with two of these markers less than 1.5 Mb apart: chromosomes 6p21.3 (the MHC region), 6q14.1 and 7q34.

Genetic analysis of multiple sclerosis

Multiple sclerosis (MS) is a complex disease with a significant genetic contribution. Similar to other complex diseases, the genetic risk for MS results from a combination of many genetic variants which individually confer only modest effects. Here we review the results of the complementary genetic approaches of linkage and association in MS, highlighting the challenges of identifying loci of modest effect. We describe meta-analytical approaches that provide additional statistical power necessary for detecting such loci and further apply this approach to evaluate the association of a CTLA-4 variant with MS. Lastly, we review recent important advances in our understanding of the patterns of genetic variation in the human genome and speculate about how these advances will aid in future studies of the genetic causes of MS.

Searching for needles in haystacks-the genetics of multiple sclerosis and other common neurological diseases

Recent years have witnessed considerable advances in our understanding of monogenic neurodegenerative diseases, such as hereditary motor sensory neuropathy and Huntington's Chorea. Progress has been slower in the genetic dissection of other more common neurological diseases with a complex mode of inheritance. The identification of relevant genes in some, such as Alzheimer's disease (AD) or Parkinson's disease (PD), has been facilitated by characteristic pathological findings and autosomal dominant inheritance in a proportion of early onset families. Attempts to identify relevant genes for multiple sclerosis have highlighted the role of the major histocompatibility complex, but so far failed to unequivocally implicate other immunologic or structural candidate genes. Six linkage-based whole genome screens have been completed in multiple sclerosis and several regions of interest have been identified. As technology and progress in the human genome project advance, it has become clear that future studies of common neurological diseases will depend critically on the availability of large sample sizes and will have to address issues of disease heterogeneity.

Polymorphisms of apolipoprotein E and Japanese patients with multiple sclerosis

The relation between apolipoprotein (APOE) gene polymorphisms and disease progression of multiple sclerosis (MS) is controversial. The present study was designed to investigate the relation between APOE gene polymorphisms and Japanese patients with MS. We analysed the frequencies of APOE gene polymorphisms in 135 MS patients and 134 healthy controls, using PCR-RFLP. The results showed no significant differences in the distribution of APOE gene polymorphisms between MS patients and controls. With regard to disease progression, there was no association between APOE gene polymorphisms and epsilon4 allele positivity and disease progression index (EDSS/ years). Furthermore, in patients with more than 10 years of disease onset, there were no significant differences between the frequencies of epsilon4 allele and patients with EDSS of more than 6. Although the low rate of epsilon4 allele in Japan should be taken into consideration, our results showed no relation between APOE gene polymorphisms and Japanese patients with MS.

A human leucocyte antigen-DR1 transgene confers susceptibility to experimental allergic encephalomyelitis elicited by an epitope of myelin basic protein

Much evidence now indicates that human leucocyte antigen (HLA) class I and class II transgenic (Tg) mice can be of value in analysing HLA-restricted presentation of T-cell epitopes relevant to experimental models of autoimmune diseases. One area where this has been applied is the characterization of myelin epitopes presented by HLA class II molecules in experimental model of multiple sclerosis (experimental allergic encephalomyelitis (EAE)). As a first step towards humanized disease models in HLA Tg mice, we have analysed immune response of lymph node cells of HLA-DR1 Tg mice immunized with the human myelin basic protein (MBP) peptides 13-33, 87-106 and 139-154 bound by HLA-DR1. We report here that HLA-DR1 Tg mice display a hierarchy of response in vivo and in vitro to MBP epitopes depending on the binding affinity to DRB*0101 molecule. In fact, the 13-33 epitope induced a strong T helper 1 (Th1) response accompanied by high T-cell precursor frequency and caused mild EAE, while the two other epitopes gave poor (139-154) or no disease (87-106), and these data correlate with in vitro Th1 response. These data could prove a useful tool in understanding the role played by different MBP epitopes in EAE.

Identification of 11 novel and common single nucleotide polymorphisms in the interleukin-7 receptor-alpha gene and their associations with multiple sclerosis

We have investigated the interleukin-7 receptor (IL-7R) alpha-chain gene as a positional and functional candidate gene for susceptibility to multiple sclerosis (MS), in view of its chromosomal location on 5p14-p12, a region that has shown suggestive linkage in MS genome screens, and its role in T- and B-cell proliferation and reactivity. Amplification and DNA sequencing of the IL-7Ralpha gene in pooled and individual samples identified 13 single nucleotide polymorphisms (SNPs), 11 of which are novel, including three in the promoter region, three in exons encoding amino-acid changes (ACC(Thr)66ATC(Ile), ATC(Ile)244ACC(Thr), ATC(Ile)336GTC(Val)), four in introns and one in the 3' untranslated region. Four IL-7R haplotypes were identified for nine SNPs, showing linkage disequilibrium across the gene, and allowing haplotype frequency determination from just three of the nine SNPs. Genotyping of the -504 polymorphism in 101 MS and 90 controls showed a suggestive (P=0.1) association of the T allele with MS; however, this was not supported by transmission disequilibrium testing in 186 MS trio families (P=0.8). There were trends towards an increase of the GTG+ haplotype (odds ratio=1.45), and under-representation of the TTA+ haplotype (OR=0.65) in DRB1*1501-positive MS cases, suggesting that larger sample sizes and comparison in more defined MS patient groups may support an association with the IL-7R gene. These polymorphisms would also be useful for studying genetic associations with other immunologic diseases.

Diverse targets for intervention during inflammatory and neurodegenerative phases of multiple sclerosis

Multiple sclerosis (MS) is an autoimmune central nervous system (CNS) demyelinating disease that causes relapsing and chronic neurologic impairment. Recent observations have altered certain traditional concepts regarding MS pathogenesis. A greater diversity of cell types and molecules involved in MS is now evident. While remyelination can occur during the early inflammatory phase when damage may be reversible, it is impaired in the later stages, which involve axonal death. These observations have important therapeutic implications.

cDNA microarray analysis in multiple sclerosis lesions: detection of genes associated with disease activity

cDNA microarray analysis of the regions of pathologically proven different activity of multiple sclerosis lesions was performed. Major differences in gene expression (DGE) occurred between the lesion margin and lesion centre in active lesions studied (57 and 69 genes differentially expressed, respectively), whereas the margins and centres of silent lesions showed markedly reduced heterogeneity (only 11 and two genes differentially expressed, respectively). To compare differences between chronic active and silent lesions, we performed DGE comparison of the pooled data from both types of lesions. The major DGE occurred at the lesion margin, 156 (26; 5%), the greater number representing upregulated genes at the margin of active lesions (15%). Fourteen genes were found to be significantly upregulated in marginal versus central zones in active lesions examined. These genes comprised predominantly inflammation/immune-related factors. We also performed DGE analysis of pooled genes upregulated at the margin of active lesions and found that among the 50 genes showing differences, nine out of 14 were identified in the previous analysis of overlapping differentially expressed genes. Thus this microarray analysis has identified a novel set of genes associated with lesion activity in multiple sclerosis, many of them not previously linked with the disease.

PDS is a new susceptibility gene to autoimmune thyroid diseases: association and linkage study

Autoimmune thyroid disease (AITD), including Graves' disease (GD), Hashimoto thyroiditis (HT), and primary idiopathic myxedema, is caused by multiple genetic and environmental factors. Genes involved in immune response and/or thyroid physiology appear to influence susceptibility to disease. The PDS gene (7q31), responsible for Pendred syndrome (congenital sensorineural hearing loss and goiter), encodes a transmembrane protein known as pendrin. Pendrin is an apical porter of iodide in the thyroid. To evaluate the contribution of PDS gene in the genetic susceptibility of AITD, we examined four microsatellite markers in the gene region. Two hundred thirty-three unrelated patients (GD,141; HT, 54; primary idiopathic myxedema, 38), 15 multiplex AITD families (104 individuals/46 patients) and 154 normal controls were genotyped. Analysis of case-control data showed a significant association of D7S496 and D7S2459 with GD (P = 10(-3)) and HT (P = 1.07 10(-24)), respectively. The family-based association test showed significant association and linkage between AITDs and alleles 121 bp of D7S496 and 173 bp of D7S501. Results obtained by transmission disequilibrium test are in good agreement with those obtained by the family-based association test. Indeed, evidence for linkage and association of allele 121 bp of D7S496 with AITD was confirmed (P = 0.0114). Multipoint nonparametric linkage analysis using MERLIN showed intriguing evidence for linkage with marker D7S496 in families with only GD patients [Z = 2.12, LOD = 0.81, P = 0.026]. Single-point and multipoint parametric LOD score linkage analysis was also performed. Again, the highest multipoint parametric LOD score was found for marker D7S496 (LOD = 1.23; P = 0.0086) in families segregating for GD under a dominant model. This work suggests that the PDS gene should be considered a new susceptibility gene to AITDs with varying contributions in each pathology.

Linkage disequilibrium between the MBP tetranucleotide repeat and multiple sclerosis is restricted to a geographically defined subpopulation in Finland

We have previously found evidence for linkage as well as allelic and haplotype association between the myelin basic protein (MBP) gene and multiple sclerosis (MS). These findings have, however, not been reproduced in other populations. Here, we have analyzed association between MBP and MS in a new set of 349 Finnish triad families. Families with a parent born in the Southern Ostrobothnian region in western Finland (Bothnia families, n=98) were analyzed as a separate group since our previous studies included a high proportion of patients and families from this high-incidence region. Other families (n=251) were collected at five hospitals in southern, eastern, and northern Finland. The MBP short tandem repeat was genotyped, and haplotype patterns were verified by sequencing. In the Bothnia families, the previously detected associations with the 1.27 kb allele and haplotype 1.27-B10 were confirmed (P=0.01 and 0.02, respectively), whereas in the other families there was not even a trend toward association. These results demonstrate a geographic/genealogical restriction in the association between MS and the MBP short tandem repeat, highlight the importance of genealogical information in genetic studies of complex traits, and may provide an explanation why the association has not been found in many other populations.

HLA-DR2 dose effect on susceptibility to multiple sclerosis and influence on disease course

Models of disease susceptibility in multiple sclerosis (MS) often assume a dominant action for the HLA-DRB1*1501 allele and its associated haplotype (DRB1*1501-DQB1*0602 or DR2). A robust and phenotypically well-characterized MS data set was used to explore this model in more detail. A dose effect of HLA-DR2 haplotypes on MS susceptibility was revealed. This observation suggests that, in addition to the role of HLA-DR2 in MS, two copies of a susceptibility haplotype further increase disease risk. Second, we report that DR2 haplotypes modify disease expression. There is a paucity of benign MS and an increase of severe MS in individuals homozygous for DR2. Concepts of the molecular mechanisms that underlie linkage and association of the human leukocyte antigen (HLA) region to MS need to be revised to accommodate these data.

Fine mapping of autistic disorder to chromosome 15q11-q13 by use of phenotypic subtypes

Autistic disorder (AutD) is a complex genetic disease. Available evidence suggests that several genes contribute to the underlying genetic risk for the development of AutD. However, both etiologic heterogeneity and genetic heterogeneity confound the discovery of AutD-susceptibility genes. Chromosome 15q11-q13 has been identified as a strong candidate region on the basis of both the frequent occurrence of chromosomal abnormalities in that region and numerous suggestive linkage and association findings. Ordered-subset analysis (OSA) is a novel statistical method to identify a homogeneous subset of families that contribute to overall linkage at a given chromosomal location and thus to potentially help in the fine mapping and localization of the susceptibility gene within a chromosomal area. For the present analysis, a factor that represents insistence on sameness (IS)--derived from a principal-component factor analysis using data on 221 patients with AutD from the repetitive behaviors/stereotyped patterns domain in the Autism Diagnostic Interview-Revised--was used as a covariate in OSA. Analysis of families sharing high scores on the IS factor increased linkage evidence for the 15q11-q13 region, at the GABRB3 locus, from a LOD score of 1.45 to a LOD score of 4.71. These results narrow our region of interest on chromosome 15 to an area surrounding the gamma-aminobutyric acid-receptor subunit genes, in AutD, and support the hypothesis that the analysis of phenotypic homogeneous subtypes may be a powerful tool for the mapping of disease-susceptibility genes in complex traits.

Genetic polymorphisms of osteopontin in association with multiple sclerosis in Japanese patients

Osteopontin (OPN) exhibits pleiotropic functions and abundant transcripts for OPN are present in brains of patients with multiple sclerosis (MS). The aim of this study was to investigate the role of OPN genes in the pathogenesis of MS. Polymorphisms at the 8090th, 9250th and 9583rd positions in OPN were detected by PCR-RFLP from DNAs of 116 MS Japanese patients and 124 healthy controls. The C/C genotype at the 8090th position in exon 6 was more prevalent in MS than in control (p<0.0001), and C allele was more prevalent in MS than in control (p<0.0001, OR=2.57, 95% CI=1.65-4.00). For the 9583rd position polymorphism in exon 7, patients with G/G genotype (age; 32.1+/-12.5 years, mean+/-S.D.) showed a later disease onset than G/A (age; 25.9+/-7.8 years, p=0.01) and A/A (age; 25.2+/-8.9 years, p=0.01) genotypes. There were no significant correlations between OPN gene polymorphisms and disease progression. Our results suggest that the 8090th polymorphism might be associated with susceptibility to MS, while the 9583rd polymorphism might be associated with age of onset of MS.

Genetic and functional studies in multiple sclerosis patients from Martinique attest for a specific and direct role of the HLA-DR locus in the syndrome

Among candidate genes involved in multiple sclerosis (MS) genetic susceptibility, MHC genes and particularly HLA-DRB1*1501-DQB1*0602 haplotype play a major role. Based on the strong linkage disequilibrium observed in Caucasians between DRB1*1501 and DQB1*0602 alleles, it is still impossible to draw a firm conclusion about the DRB1 or DQB1 locus involvement. In order to address this issue a strategy associating a genetic and a functional approach was conducted in a population of-non-Caucasian MS patients. We observed that in Martinicans (55 MS and 100 controls), the DRB1*15 and DRB1*07 alleles were positively associated with the disease. However in Martinicans the most common DRB1*15 subtype was *1503 and not *1501. Moreover, in Martinicans, the frequency of DQB1*0602, found in association with other DRB1 alleles than DRB1*15 (42% of DQB1*0602 haplotypes), was not increased in DRB1*15-negative MS patients, suggesting a neutral role of DQB1*0602 in MS genetics. In a second step, we demonstrated the capability of the DRB1*1503 allele associated with MS in Martinicans to present the immunodominant autoantigen MBP 85-99 peptide to a DRB1*1501 restricted MBP specific T cell line. Interestingly, structural features of DRB1*1501 or DRB1*1503 molecules are in good fit with the hypothesis that *1501 and *1503 molecules may act similarly in MS development by presenting the same immunodominant MBP peptide. On the whole, our results show a prominent role of the DRB1 locus (DRB1*1501 and/or DRB1*1503 alleles) in the immunodominant MBP 85-99 peptide presentation to genetically different MS patients and suggest a neutral role of the DQB1 encoded molecule in MS susceptibility.

20. Immunologic neuromuscular disorders

Immune-mediated disorders of each of the structural subdivisions of the nervous and neuromuscular system have been described. Despite the immune privilege of the central nervous system, and to a lesser extent the peripheral nervous system, immune dysregulation is not uncommon. Environmental, genetic, and immunologic factors have been postulated to be involved in the development of these disorders. Major immune-mediated neurologic diseases of the central nervous system include multiple sclerosis and acute disseminated encephalomyelitis. Immune-mediated diseases of the peripheral nervous system include myasthenia gravis, Guillain-Barré syndrome, chronic inflammatory demyelinating polyneuropathy, idiopathic polymyositis, dermatomyositis, and inclusion body myositis. Some of these disorders, such as myasthenia gravis and certain forms of acute inflammatory demyelinating polyneuropathy, are clearly autoimmune in nature, whereas the immune system plays an important role in pathogenesis in others. Understanding the immune mechanisms of disease and uncovering potential therapeutic targets are essential for the design of new treatments. The epidemiology, pathogenesis, diagnostic criteria, and current therapeutic approaches to the major neuroimmunologic diseases are reviewed.

Novel quantitative trait loci controlling development of experimental autoimmune encephalomyelitis and proportion of lymphocyte subpopulations

The B10.RIII mouse strain (H-2(r)) develops chronic experimental autoimmune encephalomyelitis (EAE) upon immunization with the myelin basic protein 89-101 peptide. EAE was induced and studied in a backcross between B10.RIII and the EAE-resistant RIIIS/J strain (H-2(r)), and a complete genome scan with microsatellite markers was performed. Five loci were significantly linked to different traits and clinical subtypes of EAE on chromosomes 1, 5, 11, 15, and 16, three of the loci having sex specificity. The quantitative trait locus on chromosome 15 partly overlapped with the Eae2 locus, previously identified in crosses between the B10.RIII and RIIIS/J mouse strains. The loci on chromosomes 11 and 16 overlapped with Eae loci identified in other mouse crosses. By analyzing the backcross animals for lymphocyte phenotypes, the proportion of B and T cells in addition to the levels of CD4(+)CD8(-) and CD4(-)CD8(+) T cells and the CD4(+)/CD8(+) ratio in spleen were linked to different loci on chromosomes 1, 2, 3, 5, 6, 11, and 15. On chromosome 16, we found significant linkage to spleen cell proliferation. Several linkages overlapped with the quantitative trait loci for disease phenotypes. The identification of subphenotypes that are linked to the same loci as disease traits could be most useful in the search for candidate genes and biological pathways involved in the pathological process.

New loci regulating rat myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis

Myelin oligodendrocyte glycoprotein-induced experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease in rats that closely mimics many clinical and histopathological aspects of multiple sclerosis. Non-MHC quantitative trait loci regulating myelin oligodendrocyte glycoprotein-induced EAE have previously been identified in the EAE-permissive strain, DA, on rat chromosomes 4, 10, 15, and 18. To find any additional gene loci in another well-known EAE-permissive strain and thereby to assess any genetic heterogeneity in the regulation of the disease, we have performed a genome-wide linkage analysis in a reciprocal (LEW.1AV1 x PVG.1AV1) male/female F(2) population (n = 185). We examined reciprocal crosses, but no parent-of-origin effect was detected. The parental rat strains share the RT1(av1) MHC haplotype; thus, non-MHC genes control differences in EAE susceptibility. We identified Eae16 on chromosome 8 and Eae17 on chromosome 13, significantly linked to EAE phenotypes. Two loci, on chromosomes 1 and 17, respectively showed suggestive linkage to clinical and histopathological EAE phenotypes. Eae16 and Eae17 differ from those found in previously studied strain combinations, thus demonstrating genetic heterogeneity of EAE. Furthermore, we detected a locus-specific parent-of-origin effect with suggestive linkage in Eae17. Further genetic and functional dissection of these loci may disclose critical disease-regulating molecular mechanisms.

Mutations in the gene for toll-like receptor 4 and multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system with heterogeneous pathological features, disease courses and genetical backgrounds. In this study we determined whether genetic variants of toll-like receptor (TLR) 4, which confer substantial differences in the inflammation elicited by bacterial lipopolysaccharide, are related to the development of MS. We found no differences in the frequencies of the cosegregating TLR4 Asp299Gly and Thr399Ile polymorphisms between Austrian MS patients (11.6%) and age-matched controls (13.7%). Furthermore, we could not detect any influence of these mutations on clinical parameters and serum levels of soluble adhesion molecules of MS patients. Our data indicate that these TLR4 polymorphisms have no influence on the incidence, progression and inflammatory parameters of MS.

CTLA4 is associated with susceptibility to multiple sclerosis

We comprehensively screened CTLA4 for novel genetic variations in patients with MS. We studied genetic variations by association methods in a population-based sample of 122 sporadic patients with MS and 244 age-, gender- and ethnicity-matched controls, and by linkage and family-based association methods in 395 individuals from 59 American multiplex pedigrees with 141 affected individuals. Being homozygous for AT(8) (common) allele of the 3'(514) microsatellite (OR: 1.69; CI: 0.99-2.86) and for the common 5'(318)*C/E1(49)*A/3'(514*AT(8) haplotype (OR: 1.96; CI: 1.13-3.39) was associated with increased susceptibility to MS in Olmsted County. The genotype frequencies of other individual polymorphisms were not significantly different between cases and controls. A pooled analysis of association studies revealed an odds ratio of 1.28 (95% CI: 1.01-1.63; p=0.043) for 5'(-318)*C homozygotes and 1.28 (95% CI: 1.08-1.51; p=0.005) for the 3'(514)*AT(8) allele. We did not detect linkage with MS susceptibility in multiplex families. We did not find a strong association with age at onset, disease course or severity. CTLA-4 is associated with susceptibility to MS.

A genome screen for linkage in Australian sibling-pairs with multiple sclerosis

The role of genetic factors in determining susceptibility to multiple sclerosis is well established but, despite the global distribution of the disease, systematic efforts to locate susceptibility genes have concentrated exclusively on populations from the Northern Hemisphere. We performed a genome wide screen of linkage in the Australian population using a panel of 397 microsatellite markers in 54 affected sibling-pairs. Multipoint linkage analysis revealed four regions of suggestive linkage (on chromosomes 2p13, 4q26-28, 6q26 and Xp11) and 18 additional regions of potential linkage (at 1q43-44, 3q13-24, 4q24, 4q31-34, 5q11-13, 6q27, 7q33-35, 8p23-21, 9q21, 13q31-32, 16p13, 16p11, 16q23-24, 17p13, 18p11, 20p12-11, Xp21-11 and Xq23-28). Our results contribute to the available data adding new provisional regions of linkage as well as increasing support for areas previously implicated in genetic susceptibility to multiple sclerosis.

Linkage disequilibrium analysis of chromosome 12q14-15 in multiple sclerosis: delineation of a 118-kb interval around interferon-gamma (IFNG) that is involved in male versus female differential susceptibility

We have recently reported the association of a polymorphic intronic CA-repeat in the interferon-gamma gene (IFNG) with gender bias in susceptibility to multiple sclerosis (MS) in a Sardinian population. This association could refer to a functional polymorphism within IFNG or could be due to linkage disequilibrium between the IFNG marker and a neighbouring susceptibility locus. Within the average reach of linkage disequilibrium, various other candidate genes are located. Among these the most striking ones are the genes coding for the cytokines interleukin-22 (IL-22) and interleukin-26 (IL-26) that constitute together with IFNG a cytokine cluster on chromosome 12q14. To determine more precisely the location of this gender-associated susceptibility locus, we have now performed a more extensive linkage disequilibrium screen of this region using nine additional microsatellite markers. This locus appeared to be confined to a 118-kb interval that is bordered by the markers D12S313 and D12S2511, in which IFNG itself remains the main candidate gene. Haplotype analysis confirmed that this MS-associated locus protects males from developing MS according to a recessive or allele-dosage model. Our results indicate that the well-documented gender differences in susceptibility to MS are at least partially caused by genetic factors in the region surrounding IFNG.

An examination of the association between beta2 adrenergic receptor polymorphisms and multiple sclerosis

In multiple sclerosis (MS), beta-adrenergic receptor densities on peripheral blood mononuclear cells are enhanced, while the astrocytes present in plaques lack beta2 adrenergic receptor (beta2AR) expression. This differentially altered expression suggests that beta2ARs may influence the pathogenesis of MS. In the present study, we investigated the association of polymorphisms of the beta2AR gene with the occurrence of MS. Our results showed no significant differences in the distribution of the polymorphisms between MS patients overall and control subjects. Furthermore, no association was observed between the presence of beta2AR gene polymorphisms and clinical characteristics, such as age at disease onset and disease severity. While a trend towards an increase of the Gly allele frequency in codon 16 was observed in the secondary-progressive MS, this result was not significantly different from that observed in relapsing-remitting MS patients or control subjects. Together, our findings suggest that the presence of beta2AR gene polymorphisms may be inconclusive in the susceptibility to MS or in the clinical characteristics of Japanese patients with MS and, therefore, need further studies.

Multiple sclerosis: deeper understanding of its pathogenesis reveals new targets for therapy

Recent technological breakthroughs allowing for large-scale analysis of gene transcripts and large-scale monitoring of the immune response with protein chips are revealing new participants in the pathogenesis of multiple sclerosis. Some of these participants may be useful targets for therapy.

Interleukin-10 polymorphisms in Spanish multiple sclerosis patients

Interleukin-10 (IL-10) is an anti-inflammatory cytokine that may be an important regulator in multiple sclerosis (MS) pathogenesis. IL-10 gene contains three single nucleotide polymorphisms (SNPs) and two polymorphic microsatellites in the 5'-flanking region. Our aim was to ascertain if any of these polymorphic markers is associated or linked to MS among Spanish patients. We have genotyped 300 patients and 357 ethnically matched controls for the microsatellites, and most of them also for the promoter SNPs. We included in this study the parents of 63 patients in order to perform a TDT analysis as well. IL-10G12 allele was significantly increased in MS patients (17% versus 11% in controls; p=0.004; p(c)<0.05). No other allele showed a significant difference between patients and controls, and the TDT analysis yielded negative results. The data indicate that IL-10 is not a major susceptibility locus in MS, but in our population it might, however, have a minor role.

Insights into the immunopathogenesis of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). Significant progress has been made in our understanding of the etiology of MS. MS is widely believed to be an autoimmune disease that results from aberrant immune responses to CNS antigens. T cells are considered to be crucial in orchestrating an immunopathological cascade that results in damage to the myelin sheath. This review summarizes the currently available data supporting the idea that myelin reactive T cells are actively involved in the immunopathogenesis of MS. Some of the therapeutic strategies for MS are discussed with a focus on immunotherapies that aim to specifically target the myelin reactive T cells.

Phenotypic analysis of mice deficient in the major myelin protein MOBP, and evidence for a novel Mobp isoform

Myelin-associated oligodendrocytic basic protein (MOBP) is a recently identified major component of central nervous system (CNS) myelin. We previously reported a detailed characterization of the genomic region encompassing the Mobp gene, elucidating the complex series of transcript splicing responsible for the generation of its diverse family of protein isoforms. These basic, positively charged polypeptides display spatial and temporal expression patterns consistent with a potential role in the compaction and maintenance of the myelin sheath. MOBP isoforms have also been localized to the nucleus and the microtubular network of oligodendrocytes; transcript corresponding to one isoform is present during embryonic development. Recent reports have identified a role for this protein family in the pathogenesis of multiple sclerosis, but a clear function for the wild-type protein has remained unclear. We report a detailed analysis of a targeted mutation of Mobp, which results in the deletion of the translational start site and most of the coding sequence of MOBP, and the deletion of the entire coding sequence corresponding to a novel, putative MOBP isoform. Our analyses clearly demonstrate that MOBP-deficient mice develop normally, generate intact compact CNS myelin, and demonstrate no obvious clinical phenotype. Furthermore, in contrast with another recent study, we find that Mobp null mice demonstrate no significant influence on the axonal diameter of myelinated axons. Although MOBP is not essential for myelination, it appears that its absence is not simply compensated for by increased expression of the "classic" myelin basic protein (MBP).

An examination of the Apo-1/Fas promoter Mva I polymorphism in Japanese patients with multiple sclerosis

BACKGROUND

The Apo-1/Fas (CD95) molecule is an apoptosis-signaling cell surface receptor belonging to the tumor necrosis factor (TNF) receptor family. Both Fas and Fas ligand (FasL) are expressed in activated mature T cells, and prolonged cell activation induces susceptibility to Fas-mediated apoptosis. The Apo-1/Fas gene is located in a chromosomal region that shows linkage in multiple sclerosis (MS) genome screens, and studies indicate that there is aberrant expression of the Apo-1/Fas molecule in MS.

METHODS

Mva I polymorphism on the Apo-1/Fas promoter gene was detected by PCR-RFLP from the DNA of 114 Japanese patients with conventional MS and 121 healthy controls. We investigated the association of the Mva I polymorphism in Japanese MS patients using a case-control association study design.

RESULTS

We found no evidence that the polymorphism contributes to susceptibility to MS. Furthermore, there was no association between Apo-1/Fas gene polymorphisms and clinical course (relapsing-remitting course or secondary-progressive course). No significant association was observed between Apo-1/Fas gene polymorphisms and the age at disease onset.

CONCLUSIONS

Overall, our findings suggest that Apo-1/Fas promoter gene polymorphisms are not conclusively related to susceptibility to MS or the clinical characteristics of Japanese patients with MS.

Investigation of bax, bcl-2, bcl-x and p53 gene polymorphisms in multiple sclerosis

Clinical course, outcome, radiological features, severity, and histopathology are heterogenous in multiple sclerosis (MS). Since MS is considered to be a polygenic disease, the genetic background may at least partly be responsible for this variability. Some MS cases are histopathologically characterized by a dramatic oligodendrocyte loss that is in part caused by apoptosis. A dysregulated apoptotic elimination of self-reactive T cells may also contribute to disease susceptibility. To analyze genetic differences in the apoptosis regulating factors bcl-2, bax, bcl-x and p53 we investigated polymorphisms of these genes in 105 patients with a relapsing remitting disease course and 99 controls by PCR-SSCP and direct sequencing. We identified so far unpublished sequence alterations in the promotor region of the bxl-x gene, in exon 7 of the p53 gene, and in exon 1 of the bax gene. No differences were observed between MS patients and controls. Additional known polymorphisms were found in intron 3 of the bax gene and in exon 6 of the p53 gene. No significant differences in the frequency of gene sequence variations were found between MS patients and controls. The apoptosis genes studied here therefore appear less likely to be important effector genes in MS.

Myelin oligodendrocyte gene polymorphisms and childhood multiple sclerosis

Myelin oligodendrocyte glycoprotein (MOG) is a quantitatively minor glycoprotein of the CNS localized preferentially on the outermost myelin lamellae and the oligodendrocyte plasma membrane. In several animal models, MOG displays highly immunogenic properties by inducing a severe multiple sclerosis-like disease, characterized by inflammatory demyelinating lesions. Immunologic findings implicate MOG as a target autoantigen in multiple sclerosis. We have performed a molecular study on the MOG gene by sequencing the promotor and the entire coding region, as well as the exon-intron boundaries, in 75 children with multiple sclerosis. A total of five unknown polymorphic sites in the promotor region not affecting any of the putative cis-acting transcriptional regulation motifs as well as nine additional base changes in four different exons each with similar distribution in patients and controls (n = 100) were detected. Exon 2 coding for the Ig-like domain revealed two rare heterozygous missense mutations, possibly altering favorable conformational epitopes (P43H; R66P). P43 is part of the encephalitogenic epitope MOG(35-55). A putative C1q binding site in the C"-D loop of the Ig superfamily motif encompasses R66. In conclusion, the polymorphisms observed do not provide evidence to support a significant role for MOG in multiple sclerosis susceptibility.

A genome-wide screen for linkage in Nordic sib-pairs with multiple sclerosis

Genetic factors influence susceptibility to multiple sclerosis but the responsible genes remain largely undefined, association with MHC class II alleles being the only established genetic feature of the disease. The Nordic countries have a high prevalence of multiple sclerosis, and to further explore the genetic background of the disease, we have carried out a genome-wide screen for linkage in 136 sibling-pairs with multiple sclerosis from Denmark, Finland, Norway and Sweden by typing 399 microsatellite markers. Seventeen regions where the lod score exceeds the nominal 5% significance threshold (0.7) were identified-1q11-24, 2q24-32, 3p26.3, 3q21.1, 4q12, 6p25.3, 6p21-22, 6q21, 9q34.3, 10p15, 10p12-13, 11p15.5, 12q21.3, 16p13.3, 17q25.3, 22q12-13 and Xp22.3. Although none of these regions reaches the level of genome-wide significance, the number observed exceeds the 10 that would be expected by chance alone. Our results significantly add to the growing body of linkage data relating to multiple sclerosis.

Genetics of multiple sclerosis: linkage and association studies

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system caused by an interplay of environmental and genetic factors. The only genetic region that has been clearly demonstrated by linkage and association studies to contribute to MS genetic susceptibility is the human leukocyte antigen (HLA) system. The majority of HLA population studies in MS have focused on Caucasians of Northern European descent, where the predisposition to disease has been consistently associated with the class II DRB1*1501-DQA1*0102-DQB1*0602 haplotype. A positive association with DR4 was detected in Sardinians and in other Mediterranean populations. Moreover DR1, DR7, DR11 have been found to be protective in several populations. Systematic searches aimed at identifying non-HLA susceptibility genes were undertaken in several populations by means of linkage studies with microsatellite markers distributed across the whole genome. The conclusion of these studies was that there is no major MS locus, and genetic susceptibility to the disease is most likely explained by the presence of different genes each conferring a small contribution to the overall familial aggregation. The involvement of several candidate genes was tested by association studies, utilizing either a population-based (case control) or a family-based (transmission disequilibrium test) approach. Candidate genes were selected mainly on the basis of their involvement in the autoimmune pathogenesis and include immunorelevant molecules such as cytokines, cytokine receptors, immunoglobulin, T cell receptor subunits and myelin antigens. With the notable exception of HLA, association studies met only modest success. This failure may result from the small size of the tested samples and the small number of markers considered for each gene. New tools for large scale screening are needed to identify genetic determinants with a low phenotypic effect. Large collaborative studies are planned to screen several thousands of patients with MS with several thousands of genetic markers. The tests are increasingly based on the DNA pooling procedure.

Primary progressive multiple sclerosis: increasing clarity but many unanswered questions

Heterogeneity in the clinical course of multiple sclerosis (MS) is well recognised and patients following a primary progressive course, 10-15% of the MS population, have a distinct clinical and paraclinical phenotype. This review examines recent advances in our understanding of this subgroup of patients and examines the new criteria to be applied in diagnosis. It also highlights developments in genetic, immunological, magnetic resonance and pathological aspects of the disease, whilst also outlining the results of recent therapeutic trials.

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.

Multiple sclerosis complexity in selected populations: the challenge of Sardinia, insular Italy

Several lines of evidence indicate a genetic contribution to multiple sclerosis (MS) both in terms of predisposition to the disease and of immunological mechanisms which are known to play crucial roles in MS pathogenesis. The presence of high- and low-risk areas for MS in neighbouring regions supports the theory that MS predisposition is influenced by a complex interaction of genetic and environmental factors. Therefore, the use of genetically homogeneous and geographically isolated populations becomes an increasing requirement to reduce biasing biological variables. Sardinians fulfil these conditions well because of their different phylogeny from Europeans and the unique selective pressures which shaped their genome. Sardinians display amongst the highest MS prevalence rates world-wide and increasing MS incidence rates over time. Also, MS in Sardinia is linked to distinct human leucocyte antigen (HLA) alleles and associated to different patterns of cytokine production from lymphoid cells of different HLA subtypes. In this context, recent findings and future perspectives on the peculiarities of Sardinian MS concerning genetic, immunological and epidemiological aspects are presented. So far, our results indicate that variations at the level of territorial distribution and HLA-association are present which render MS heterogeneous even in this ethnically homogeneous population.