Medicine (RMH) - Research Publications
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ItemGenes implicated in multiple sclerosis pathogenesis from consilience of genotyping and expression profiles in relapse and remission(BMC, 2008-03-19)BACKGROUND: Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS). Although the pathogenesis of MS remains unknown, it is widely regarded as an autoimmune disease mediated by T-lymphocytes directed against myelin proteins and/or other oligodendrocyte epitopes. METHODS: In this study we investigated the gene expression profiles of peripheral blood cells from patients with RRMS during the relapse and the remission phases utilizing gene microarray technology. Dysregulated genes encoded in regions associated with MS susceptibility from genomic screens or previous transcriptomic studies were identified. The proximal promoter region polymorphisms of two genes were tested for association with disease and expression level. RESULTS: Distinct sets of dysregulated genes during the relapse and remission phases were identified including genes involved in apoptosis and inflammation. Three of these dysregulated genes have been previously implicated with MS susceptibility in genomic screens: TGFbeta1, CD58 and DBC1. TGFbeta1 has one common SNP in the proximal promoter: -508 T>C (rs1800469). Genotyping two Australian trio sets (total 620 families) found a trend for over-transmission of the T allele in MS in females (p < 0.13). Upregulation of CD58 and DBC1 in remission is consistent with their putative roles in promoting regulatory T cells and reducing cell proliferation, respectively. A fourth gene, ALOX5, is consistently found over-expressed in MS. Two common genetic variants were confirmed in the ALOX5 putative promoter: -557 T>C (rs12762303) and a 6 bp tandem repeat polymorphism (GGGCGG) between position -147 and -176; but no evidence for transmission distortion found. CONCLUSION: The dysregulation of these genes tags their metabolic pathways for further investigation for potential therapeutic intervention.
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ItemVariants of ST8SIA1 Are Associated with Risk of Developing Multiple Sclerosis(PUBLIC LIBRARY SCIENCE, 2008-07-09)Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system of unknown etiology with both genetic and environmental factors playing a role in susceptibility. To date, the HLA DR15/DQ6 haplotype within the major histocompatibility complex on chromosome 6p, is the strongest genetic risk factor associated with MS susceptibility. Additional alleles of IL7 and IL2 have been identified as risk factors for MS with small effect. Here we present two independent studies supporting an allelic association of MS with polymorphisms in the ST8SIA1 gene, located on chromosome 12p12 and encoding ST8 alpha-N-acetyl-neuraminide alpha-2,8-sialyltransferase 1. The initial association was made in a single three-generation family where a single-nucleotide polymorphism (SNP) rs4762896, was segregating together with HLA DR15/DQ6 in MS patients. A study of 274 family trios (affected child and both unaffected parents) from Australia validated the association of ST8SIA1 in individuals with MS, showing transmission disequilibrium of the paternal alleles for three additional SNPs, namely rs704219, rs2041906, and rs1558793, with p = 0.001, p = 0.01 and p = 0.01 respectively. These findings implicate ST8SIA1 as a possible novel susceptibility gene for MS.
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ItemGenome-wide association study identifies new multiple sclerosis susceptibility loci on chromosomes 12 and 20(NATURE PUBLISHING GROUP, 2009-07)To identify multiple sclerosis (MS) susceptibility loci, we conducted a genome-wide association study (GWAS) in 1,618 cases and used shared data for 3,413 controls. We performed replication in an independent set of 2,256 cases and 2,310 controls, for a total of 3,874 cases and 5,723 controls. We identified risk-associated SNPs on chromosome 12q13-14 (rs703842, P = 5.4 x 10(-11); rs10876994, P = 2.7 x 10(-10); rs12368653, P = 1.0 x 10(-7)) and upstream of CD40 on chromosome 20q13 (rs6074022, P = 1.3 x 10(-7); rs1569723, P = 2.9 x 10(-7)). Both loci are also associated with other autoimmune diseases. We also replicated several known MS associations (HLA-DR15, P = 7.0 x 10(-184); CD58, P = 9.6 x 10(-8); EVI5-RPL5, P = 2.5 x 10(-6); IL2RA, P = 7.4 x 10(-6); CLEC16A, P = 1.1 x 10(-4); IL7R, P = 1.3 x 10(-3); TYK2, P = 3.5 x 10(-3)) and observed a statistical interaction between SNPs in EVI5-RPL5 and HLA-DR15 (P = 0.001).
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ItemValidation of linear cerebral atrophy markers in multiple sclerosis(ELSEVIER SCI LTD, 2008-02)Linear measures of cerebral ventricular enlargement may act as surrogate measures of cerebral atrophy in multiple sclerosis (MS). Linear atrophy markers were measured from routine MRI scans during a population survey of 171 Tasmanian MS patients and 91 healthy controls. Thirty-five Victorian MS clinic patients were recruited as a validation cohort with 14 of these re-assessed 4 years later. In the population survey, we measured three linear brain atrophy markers: inter-caudate distance (ICD), third ventricle width (TVW) and frontal horn width (FHW). TVW (OR 2.0, p=0.001) and ICD (OR 16.1, p<0.001) differentiated between MS cases and controls. In the validation study, we correlated the intercaudate ratio (ICR=ICD/brain width) and third ventricular ratio (TVR=TVW/brain width) with brain parenchymal volume. Cross-sectionally, ICR (R=-0.453, p<0.01) and TVR (R=-0.653, p<0.01) were correlated with brain parenchymal volume. Longitudinally, brain parenchymal volume loss was inversely correlated with increased ICD (R=-0.77, p<0.01) and TVW (R=-0.71, p<0.01). This study shows that ICD measurements obtained from clinical MRI scans are valid brain atrophy measures for use in monitoring MS progression.