Shirley Heggarty

IFNG polymorphisms are associated with gender differences in susceptibility to multiple sclerosis

Interferon-gamma (IFNγ) treatment is deleterious in multiple sclerosis (MS). MS occurs twice as frequently in women as in men. IFNγ expression varies by gender. We studied a population-based sample of US MS patients and ethnicity-matched controls and independent Northern Irish and Belgian hospital-based patients and controls for association with MS, stratified by gender, of an intron 1 microsatellite [I1(761)*CAn], a single nucleotide polymorphism 3′ of IFNG [3′(325)*G → A] and three flanking microsatellite markers spanning a 118 kb region around IFNG. Men carriers of the 3′(325)*A allele have increased susceptibility to MS compared to noncarriers in the USA (P=0.044; OR: 2.58, 95% CI: 0.97–8.08) and Northern Ireland (P=0.019; OR: 2.37, 95% CI: 1.10–5.13). There is a nonsignificant trend in the same direction in Belgian men (P=0.299; OR: 1.50, 95% CI: 0.71–3.26). Men carriers of I1(761)*CA13, which is in strong linkage disequilibrium with the 3′(325)*A, have increased susceptibility (P=0.050; OR: 2.22, 95% CI: 0.98–5.40), while men carriers of I1(761)*CA12 have decreased susceptibility (P=0.022; OR: 0.46, 95% CI: 0.23–0.90) to MS in the USA. Similar associations were reported in Sardinia between the I1(761)*CA12 allele and reduced risk of MS in men. Flanking markers were not associated with MS susceptibility. Polymorphisms of IFNG may contribute to differences in susceptibility to MS between men and women.

Association of Functional Heme Oxygenase‐1 Gene Promoter Polymorphism with Renal Transplantation Outcomes

Heme oxygenase‐1 (HO‐1) is a cytoprotective molecule and increased expression in experimental transplant models correlates with reduced graft injury. A functional dinucleotide repeat (GT)n polymorphism, within the HO‐1 promoter, regulates gene expression; a short number of repeats (S‐allele <25) increases transcription. The role of this HO‐1 gene promoter polymorphism on renal transplant outcomes was assessed. DNA from 707 donor/recipient pairs (n = 1414) of first deceased donor renal transplants (99% Caucasian) was genotyped. Graft survival was not significantly impacted by carriage of an S‐allele by the donor (hazard ratio 0.89, 95% CI 0.71–1.11; p = 0.28) or recipient (hazard ratio 1.19, 95% CI 0.95–1.48; p = 0.13). Similarly neither donor nor recipient genotype influenced recipient survival (hazard ratio 0.89, 95% CI 0.67–1.18; p = 0.41, and hazard ratio 1.22, 95% CI 0.93–1.62; p = 0.16). The hazard ratios changed only minimally in multivariate analysis including significant survival factors. Genotype did not alter the incidence of acute rejection or chronic allograft nephropathy. There is no evidence of a protective effect for the S‐allele of the HO‐1 gene promoter polymorphism on graft or recipient survival in clinical renal transplantation.

ZnT3 mRNA levels are reduced in Alzheimer's disease post-mortem brain.

BackgroundZnT3 is a membrane Zn2+ transporter that is responsible for concentrating Zn2+ into neuronal presynaptic vesicles. Zn2+ homeostasis in the brain is relevant to Alzheimers disease (AD) because Zn2+ released during neurotransmission may bind to Aβ peptides, accelerating the assembly of Aβ into oligomers which have been shown to impair synaptic function.ResultsWe quantified ZnT3 mRNA levels in Braak-staged human post mortem (pm) brain tissue from medial temporal gyrus, superior occipital gyrus, superior parietal gyrus, superior frontal gyrus and cerebellum from individuals with AD (n = 28), and matched controls (n = 5) using quantitative real-time PCR. ZnT3 mRNA levels were significantly decreased in all four cortical regions examined in the AD patients, to 45-60% of control levels. This reduction was already apparent at Braak stage 4 in most cortical regions examined. Quantification of neuronal and glial-specific markers in the same samples (neuron-specific enolase, NSE; and glial fibrillary acidic protein, GFAP) indicated that loss of cortical ZnT3 expression was more pronounced, and occurred prior to, significant loss of NSE expression in the tissue. Significant increases in cortical GFAP expression were apparent as the disease progressed. No gene expression changes were observed in the cerebellum, which is relatively spared of AD neuropathology.ConclusionsThis first study to quantify ZnT3 mRNA levels in human pm brain tissue from individuals with AD and controls has revealed a significant loss of ZnT3 expression in cortical regions, suggesting that neuronal cells in particular show reduced expression of ZnT3 mRNA in the disease. This suggests that altered neuronal Zn2+ handling may be an early event in AD pathogenesis.

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.

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

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

Polymorphisms in the interleukin-4 and IL-4 receptor genes and multiple sclerosis: a study in Spanish-Basque, Northern Irish and Belgian populations.

Cytokine gene polymorphisms are known to influence susceptibility and disease course of many autoimmune diseases. Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system white matter characterized by inflammation, demyelination and axonal damage. We analysed both the well‐known intronic variable number of tandem repeat (VNTR) and +33 C/T single‐nucleotide polymorphisms (SNP) in the IL‐4 gene, as well as the functional Q551R SNP in the IL4‐R gene in a cohort of three distinct populations comprising sporadic cases and controls from the northern Spanish Basque Country and Northern Ireland, as well as family trios from Belgium. The IL‐4 +33 TT genotype was decreased in primary progressive (PP) versus relapsing‐remitting (RR) patients in the Northern Irish population (OR = 0.14; 95% CI = 0.018–1.09). Two‐marker haplotype distribution of the VNTR and +33 C/T SNP in PP patients differed from that seen in RR patients in Northern Ireland (P = 0.03). The R allele of the Q551R SNP was significantly under‐transmitted in the Belgian trio families (P = 0.003), although this effect was not seen in the Northern Irish and Basque data sets. We did not identify IL‐4–IL4‐R gene–gene interaction in determining susceptibility or clinical parameters of MS. Disease or genetic heterogeneity or both may be responsible for the observed lack of reproduction in different populations. Our data reinforce recent findings for a role of IL4‐R in susceptibility to MS.

Genetic polymorphisms, their allele combinations and IFN-β treatment response in Irish multiple sclerosis patients

INTRODUCTION IFN-beta is widely used as first-line immunomodulatory treatment for multiple sclerosis. Response to treatment is variable (30-50% of patients are nonresponders) and requires a long treatment duration for accurate assessment to be possible. Information about genetic variations that predict responsiveness would allow appropriate treatment selection early after diagnosis, improve patient care, with time saving consequences and more efficient use of resources. MATERIALS & METHODS We analyzed 61 SNPs in 34 candidate genes as possible determinants of IFN-beta response in Irish multiple sclerosis patients. Particular emphasis was placed on the exploration of combinations of allelic variants associated with response to therapy by means of a Markov chain Monte Carlo-based approach (APSampler). RESULTS The most significant allelic combinations, which differed in frequency between responders and nonresponders, included JAK2-IL10RB-GBP1-PIAS1 (permutation p-value was p(perm) = 0.0008), followed by JAK2-IL10-CASP3 (p(perm) = 0.001). DISCUSSION The genetic mechanism of response to IFN-beta is complex and as yet poorly understood. Data mining algorithms may help in uncovering hidden allele combinations involved in drug response versus nonresponse.

Mapping candidate non-MHC susceptibility regions to multiple sclerosis

Understanding the genetic basis of multiple sclerosis (MS) remains a major challenge, despite decades of intensive research. In order to identify candidate non-MHC susceptibility regions to MS, the results of whole genome screens for linkage or association and follow-up studies in 18 different populations were superimposed together in a combined genomic map. Analysis of this map led to the prediction of at least 38 potential susceptibility regions, each showing linkage and/or association in several populations. Among these, 17 regions were the most reproducibly reported in these studies, thus representing top predicted candidates for MS. This non-formal approach to meta-analysis demonstrated the ability to verify results and retrieve lost information in an association study. Assessment of the map in a Northern Irish refined screen (n=415 cases, n=490 controls) revealed association in 15 regions (P<0.05), including 10 promising candidates on chromosomes 1p13, 2p13, 2q14, 3p23, 7q21, 13q14, 15q13, 17p13, 18q21 and 20p12 (P<0.0025). Seven of these regions were previously overlooked in the Northern Irish whole genome association study. Collating results from numerous studies, this draft map represents a tool that should facilitate the analysis of the genetic backgrounds of MS in many populations.

Study of polymorphisms in the interleukin-4 and IL-4 receptor genes in a population of Brazilian patients with multiple sclerosis

This study aimed to investigate in a population of Brazilian patients with multiple sclerosis (MS) single-nucleotide polymorphisms (SNP) in the promoter region of IL4 (*33C-T) and receptor IL4R (*Q551R A-G) genes proposed to interfere with disease progression. No significant differences were observed in either of the SNPs investigated between healthy controls (n=135) and MS patients (n=129). However, the IL4+33 TT genotype was significantly (p=0.039) higher in African descendants MS (AF-MS= 9.09%) than in Caucasian MS (CA-MS= 1.35%). It was also observed a significant (p=0.016) increase for the IL4R* Q551R CC genotype in AF-MS compared to those of Caucasian ethnicity (AF-MS= 21.62%; CA-MS= 4.35%). These results suggest that IL4+33 and IL4R*Q551 polymorphisms may have a disease-promoting role of TH2 mediators in African MS descendants. Additionally neither IL4 nor IL4R genes are susceptibility factors for Brazilian MS but may be able to modify ethnicity-dependent disease risk and penetrance of susceptibility factors.