[Show abstract][Hide abstract] ABSTRACT: The ability to differentiate human ESCs (hESCs) to defined lineages in a totally controlled manner is fundamental to developing cell-based therapies and studying human developmental mechanisms. We report a novel, scaleable, and widely applicable system for deriving and propagating neural stem cells from hESCs without the use of animal products, proprietary formulations, or genetic manipulation. This system provides a definitive platform for studying human neural development and has potential therapeutic implications.
[Show abstract][Hide abstract] ABSTRACT: We have genotyped 14,436 nonsynonymous SNPs (nsSNPs) and 897 major histocompatibility complex (MHC) tag SNPs from 1,000 independent cases of ankylosing spondylitis ( AS), autoimmune thyroid disease (AITD), multiple sclerosis ( MS) and breast cancer ( BC). Comparing these data against a common control dataset derived from 1,500 randomly selected healthy British individuals, we report initial association and independent replication in a North American sample of two new loci related to ankylosing spondylitis, ARTS1 and IL23R, and confirmation of the previously reported association of AITD with TSHR and FCRL3. These findings, enabled in part by increased statistical power resulting from the expansion of the control reference group to include individuals from the other disease groups, highlight notable new possibilities for autoimmune regulation and suggest that IL23R may be a common susceptibility factor for the major `seronegative' diseases.
[Show abstract][Hide abstract] ABSTRACT: By combining all the data available from the Genetic Analysis of Multiple sclerosis in EuropeanS (GAMES) project, we have been able to identify 17 microsatellite markers showing consistent evidence for apparent association. As might be expected five of these markers map within the Major Histocompatibility Complex (MHC) and are in LD with HLA-DRB1. Individual genotyping of the 12 non-MHC markers confirmed association for three of them--D11S1986, D19S552 and D20S894. Association mapping across the candidate genes implicated by these markers in 937 UK trio families revealed modestly associated haplotypes in JAG1 (p=0.019) on chromosome 20p12.2 and POU2AF1 (p=0.003) on chromosome 11q23.1.
Journal of Neuroimmunology 11/2006; 179(1-2):108-16. · 3.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Variation in major histocompatibility complex genes on chromosome 6p21.3, specifically the human leukocyte antigen HLA-DR2 or DRB1*1501-DQB1*0602 extended haplotype, confers risk for multiple sclerosis (MS). Previous studies of DRB1 variation and both MS susceptibility and phenotypic expression have lacked statistical power to detect modest genotypic influences, and have demonstrated conflicting results. Results derived from analyses of 1339 MS families indicate DRB1 variation influences MS susceptibility in a complex manner. DRB1*15 was strongly associated in families (P=7.8x10(-31)), and a dominant DRB1*15 dose effect was confirmed (OR=7.5, 95% CI=4.4-13.0, P<0.0001). A modest dose effect was also detected for DRB1*03; however, in contrast to DRB1*15, this risk was recessive (OR=1.8, 95% CI=1.1-2.9, P=0.03). Strong evidence for under-transmission of DRB1*14 (P=5.7x10(-6)) even after accounting for DRB1*15 (P=0.03) was present, confirming a protective effect. In addition, a high risk DRB1*15 genotype bearing DRB1*08 was identified (OR=7.7, 95% CI=4.1-14.4, P<0.0001), providing additional evidence for trans DRB1 allelic interactions in MS. Further, a significant DRB1*15 association observed in primary progressive MS families (P=0.0004), similar to relapsing-remitting MS families, suggests that DRB1-related mechanisms are contributing to both phenotypes. In contrast, results obtained from 2201 MS cases argue convincingly that DRB1*15 genotypes do not modulate age of onset, or significantly influence disease severity measured using expanded disease disability score and disease duration. These results contribute substantially to our understanding of the DRB1 locus and MS, and underscore the importance of using large sample sizes to detect modest genetic effects, particularly in studies of genotype-phenotype relationships.
Human Molecular Genetics 09/2006; 15(18):2813-24. · 7.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: CD24 is expressed on a broad range of cells in the immune and central nervous systems and appears to be required for development of experimental autoimmune encephalomyelitis in mice. Association of a CD24 Ala/Val coding polymorphism with susceptibility to and progression of multiple sclerosis was recently reported. We typed this coding polymorphism in a combined cohort of 1,180 cases and 1,168 unrelated and family-based controls from Belgium and the UK, but were unable to confirm either association. Since the CD24 gene is part of a segmental duplication, special care is required for the identification and genotyping of single nucleotide polymorphisms.
Journal of Neuroimmunology 07/2006; 175(1-2):200-2. · 3.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In an effort to accelerate the identification of susceptibility genes in diabetic nephropathy, the first genome-wide fluorescence-based DNA microsatellite (n=6000) association screen was performed, using pools of genomic DNA derived from Irish patients with (cases; n=200) and without (controls; n=200) type 1 diabetic nephropathy. Allele image profiles were generated for 5353 (89.2%) microsatellite markers for both case and control pools. Allele counts (estimated from allele image profiles) were compared in case versus control groups, and empirical P values were generated. Markers then were ranked on the basis of their empirical P values (lowest to highest). Repeat PCR amplification and electrophoresis of pooled samples were performed systematically on ranked markers until the 50 most associated markers with consistent results were identified. DNA samples that composed the pools then were genotyped individually for these markers. Two markers on chromosome 10, D10S558 (Pcorrected=0.005) and D10S1435 (Pcorrected=0.016), revealed statistically significant associations with diabetic nephropathy. An additional four markers (D6S281, D4S2937, D2S291, and D17S515) also are worthy of further investigation. Relevant functional candidate genes have been identified in the vicinity of these markers, demonstrating the feasibility of low-resolution genome-wide microsatellite association screening to identify possible candidate genes for diabetic nephropathy.
Journal of the American Society of Nephrology 04/2006; 17(3):831-6. · 8.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The 620W allele of PTPN22 has been associated with susceptibility to several different forms of chronic inflammatory disease, including Type 1 diabetes (T1D), rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), and autoimmune thyroiditis (AIT). We set out to explore its possible role in two other inflammatory diseases: multiple sclerosis (MS) and Crohn's disease (CD). In our cohort of 496 MS trios from the United Kingdom, we observed reduced transmission of the PTPN22 620W allele. The CD sample consisted of 169 trios as well as 249 cases of CD with their 207 matched control subjects collected in the province of Québec, Canada; there was also no evidence of association between the PTPN22 620W allele and susceptibility for CD. Pooled analyses combining our data with published data assessed a total of 1496 cases of MS and 1019 cases of CD but demonstrated no evidence of association with either disease. Given the modest odds ratios of known risk alleles for inflammatory diseases, these analyses do not exclude a role for the PTPN22 allele in susceptibility to CD or MS, but they do suggest that such a putative role would probably be more modest than that reported so far in T1D, RA, SLE, and AIT.
European Journal of HumanGenetics 04/2006; 14(3):317-21. · 4.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: There is a need for more standardized methods of maintenance and propagation of human embryonic stem cell (hESC) cultures. Enzymatic passaging currently represents the most widely used method for expansion of hESCs. Although rapid and straightforward, this technique results in variable-sized cell clusters and significant cellular trauma, which may apply selective pressure in long-term culture. Mechanical passaging has the potential advantages of defined colony fragment sizes, reduced cellular trauma, and the possibility of selecting undifferentiated colonies for transfer. However, manual dissection of individual colonies is a prohibitively time-consuming process unsuitable for maintaining large numbers of hESCs without the use of additional chemical means. In this study we report an efficient automated method for mechanically passaging hESCs. We have used this method exclusively to maintain hESCs in long-term undifferentiated culture without the use of enzymatic digestion for longer than 100 days. This automated technique can thus be used routinely to culture hESCs in the laboratory.
[Show abstract][Hide abstract] ABSTRACT: Microglia exist under physiological conditions in a resting state but become activated after neuronal injury. Recent studies have highlighted the reciprocal role of neurons in controlling both the number and activity of microglia. In this study, microglia derived from newborn rat cortices were cultured and activated by interferon-gamma (IFNgamma) treatment, then exposed to recombinant Sema3A or conditioned medium derived from stressed embryonic cortical neurons. We found that activation of microglia by IFNgamma induced differential upregulation of the semaphorin receptors Plexin-A1 and Neuropilin-1. This result was confirmed by Northern blotting, reverse transcription-PCR, and Western blotting. Furthermore, recombinant Sema3A induced apoptosis of microglia when added to the in vitro culture, and a similar result was obtained on activated microglia when Sema3A was produced by stressed neurons. Using an in vivo model of microglia activation by striatal injection of lipopolysaccharide demonstrated a corresponding upregulation of Plexin-A1 and Neuropilin-1 in activated microglia and enhanced production of Sema3A by stressed adult neurons. These results suggest a novel semaphorin-mediated mechanism of neuroprotection whereby stressed neurons can protect themselves from further damage by activated microglia.
Journal of Neuroscience 03/2006; 26(6):1730-8. · 6.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Variation in the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) gene plays a significant role in determining susceptibility to autoimmune thyroid disease and type 1 diabetes. Its role in multiple sclerosis is more controversial. In order to explore this logical candidate more thoroughly, we genotyped 771 multiple sclerosis trio families from the United Kingdom for the 3' untranslated region variable number tandem repeat, the CT60 single nucleotide polymorphism (SNP) and five haplotype-tagging SNPs. No individual marker or common haplotype showed evidence of association with disease. These data suggest that any effect of CTLA-4 on multiple sclerosis susceptibility is likely to be very small.
Journal of Neuroimmunology 03/2006; 171(1-2):193-7. · 3.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: P-Selectin (SELP) and P-selectin glycoprotein ligand-1 (SELPLG) constitute a receptor/ligand complex involved in the recruitment of activated lymphocytes, a critical event in the pathogenesis of multiple sclerosis (MS). In order to determine whether genetic variation in these pivotal molecules influences susceptibility to MS, we genotyped 214 Italian patients compared with 220 Italian controls for three single-nucleotide polymorphisms (SNPs): SELPLG Met62Ile, SELP C-2123G and SELP Thr715Pro. No significant differences in both SELP SNPs were found between patients and controls, whereas a decreased frequency of the Met62Ile SNP was found in patients versus controls in the Italian population (P = 0.025). To confirm these preliminary findings, the Met62Ile SNP was analysed in 938 UK trio families. This SNP did not show evidence for association with susceptibility to MS in the larger UK cohort. Therefore, none of the SNPs investigated is associated with MS, although this analysis does not conclusively exclude SELPLG and SELP as genetic risk factors for MS as much variation remains untested.
[Show abstract][Hide abstract] ABSTRACT: Contemporary licensed treatments for multiple sclerosis fail to provide a solution for the disease because their effects are limited to a modest reduction in the frequency of new episodes. They do not reduce disability or materially influence the progressive phase of the disease. A contemporary strategy for management requires a more detailed analysis of the separate contributions to the clinical features and overall course made by inflammation, axonal injury, compensatory mechanisms, and remyelination. From this formulation emerges the need either for early and fully effective suppression of the inflammatory response, limiting the damage to all components of the axon-glial unit; or the development of strategies for axonal and myelin repair that solve the issues of controlled differentiation, delivery and timing of these cell and growth factor-based interventions.
[Show abstract][Hide abstract] ABSTRACT: The major histocompatibility complex human leukocyte antigen (HLA)-DRB1*15 (DR2) haplotype is strongly associated with risk of multiple sclerosis (MS). The primary susceptibility has been localized to only approximately 200 kb encompassing the HLA-DR and -DQ loci. Further dissection of disease association with this region is demanding because of the high levels of linkage disequilibrium (LD). Recently, evidence was obtained for the involvement of a gene, potentially encoding an immune co-receptor, in another DR2-associated inflammatory condition, sarcoidosis. The implicated gene, BTNL2, is adjacent to DR and is in strong LD with HLA-DRB1. This fact, combined with a sequence relationship between BTNL2 and myelin oligodendrocyte glycoprotein, an autoantigen associated with MS, makes the gene an attractive candidate. To determine whether BTNL2 contributes to MS, we genotyped 1136 well-characterized MS families from the UK and the USA, as well as an African-American case-control data set, making this among the largest genetic studies in MS. Family-based and case-control association studies were performed for the BTNL2 and HLA-DRB1 loci. In all family data sets, the protein-truncating allele of BTNL2, implicated in sarcoidosis, was significantly over-transmitted to cases (combined data sets: global P=2.4x10(-11)). Given that the protein-truncating allele of BTNL2 virtually always occurred with DRB1*15, an effect could only be tested in DRB1*15-negative individuals or pedigrees. However, despite adequate power to detect an independent association, no difference in transmission of BTNL2 alleles or genotypes was observed in DRB1*15-negative individuals with MS. Conditional logistic regression modeling also strongly supported the conclusion that BTNL2 does not confer additional disease risk. The association of BTNL2 with MS observed in the African-American data set was also secondary to the primary DRB1*15 association.
Human Molecular Genetics 02/2006; 15(1):155-61. · 7.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To provide a definitive linkage map for multiple sclerosis, we have genotyped the Illumina BeadArray linkage mapping panel (version 4) in a data set of 730 multiplex families of Northern European descent. After the application of stringent quality thresholds, data from 4,506 markers in 2,692 individuals were included in the analysis. Multipoint nonparametric linkage analysis revealed highly significant linkage in the major histocompatibility complex (MHC) on chromosome 6p21 (maximum LOD score [MLS] 11.66) and suggestive linkage on chromosomes 17q23 (MLS 2.45) and 5q33 (MLS 2.18). This set of markers achieved a mean information extraction of 79.3% across the genome, with a Mendelian inconsistency rate of only 0.002%. Stratification based on carriage of the multiple sclerosis-associated DRB1*1501 allele failed to identify any other region of linkage with genomewide significance. However, ordered-subset analysis suggested that there may be an additional locus on chromosome 19p13 that acts independent of the main MHC locus. These data illustrate the substantial increase in power that can be achieved with use of the latest tools emerging from the Human Genome Project and indicate that future attempts to systematically identify susceptibility genes for multiple sclerosis will have to involve large sample sizes and an association-based methodology.
The American Journal of Human Genetics 10/2005; 77(3):454-67. · 11.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Neural stem cells (NSCs) are considered to have widespread therapeutic possibilities on account of their ability to provide large numbers of cells whilst retaining multi-potentiality. Application to human demyelinating diseases requires improved understanding of the signalling requirements underlying the generation of oligodendrocytes from NSCs. During development, spinal cord oligodendrocyte precursors (OPCs) originate from the ventral, but not dorsal neuroepithelium due to the regulatory effects of the morphogen Sonic hedgehog (Shh). The developing human spinal cord shows comparable ventral-dorsal gradient of oligodendrocyte differentiation potential to the embryonic rodent spinal cord. In contrast expanded human neural precursors derived from both isolated ventral or dorsal cultures show a reduced capacity to generate oligodendrocytes, whereas comparable rodent cultures demonstrate a marked increase in oligodendrocyte formation by a hedgehog independent pathway. Inter-species difference in the capacity of neural precursors to generate oligodendrocytes emphasises the need for greater study of human derived stem cell populations.
Journal of the Neurological Sciences 07/2005; 233(1-2):179-81. · 2.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Whole genome screening is increasingly used to identify genetic risk factors for complex diseases. In this study, a genome wide linkage disequilibrium (LD) screen was performed in a cohort of Parkinson's disease (PD) patients from the UK (n = 195) using pooled DNA to facilitate efficient genotyping of 5546 microsatellite markers. Allele frequencies were compared with those found in 2 previously typed disease free control populations, and the most interesting markers were selected for multiple repeat testing among the 3 pools. Markers were then individually genotyped in our original PD cohort and one of the original control groups, and independently in a second cohort of UK PD patients (n = 179), and additional controls. Using this 2-stage approach, we have been unable to find evidence for consistent association of any markers with sporadic PD. Subgroup analysis of the most promising marker shows some evidence that microsatellite marker D1S2886 is associated with familial forms of the disease.
Journal of Neurology 06/2005; 252(5):597-602. · 3.58 Impact Factor