Dataset Information

A functional SNP in the regulatory region of the decay-accelerating factor gene associates with extraocular muscle pareses in myasthenia gravis.

ABSTRACT: Complement activation in myasthenia gravis (MG) may damage muscle endplate and complement regulatory proteins such as decay-accelerating factor (DAF) or CD55 may be protective. We hypothesize that the increased prevalence of severe extraocular muscle (EOM) dysfunction among African MG subjects reported earlier may result from altered DAF expression. To test this hypothesis, we screened the DAF gene sequences relevant to the classical complement pathway and found an association between myasthenics with EOM paresis and the DAF regulatory region c.-198C>G SNP (odds ratio=8.6; P=0.0003). This single nucleotide polymorphism (SNP) results in a twofold activation of a DAF 5'-flanking region luciferase reporter transfected into three different cell lines. Direct matching of the surrounding SNP sequence within the DAF regulatory region with the known transcription factor-binding sites suggests a loss of an Sp1-binding site. This was supported by the observation that the c.-198C>G SNP did not show the normal lipopolysaccharide-induced DAF transcriptional upregulation in lymphoblasts from four patients. Our findings suggest that at critical periods during autoimmune MG, this SNP may result in inadequate DAF upregulation with consequent complement-mediated EOM damage. Susceptible individuals may benefit from anti-complement therapy in addition to immunosuppression.

SUBMITTER: Heckmann JM

PROVIDER: S-EPMC2834500 | biostudies-literature | 2010 Jan

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

A functional SNP in the regulatory region of the decay-accelerating factor gene associates with extraocular muscle pareses in myasthenia gravis.

Heckmann J M JM Uwimpuhwe H H Ballo R R Kaur M M Bajic V B VB Prince S S

Genes and immunity 20090813 1

Complement activation in myasthenia gravis (MG) may damage muscle endplate and complement regulatory proteins such as decay-accelerating factor (DAF) or CD55 may be protective. We hypothesize that the increased prevalence of severe extraocular muscle (EOM) dysfunction among African MG subjects reported earlier may result from altered DAF expression. To test this hypothesis, we screened the DAF gene sequences relevant to the classical complement pathway and found an association between myasthenic ...[more]

PMID: 19675582

Similar Datasets

Project description:gene expression profile in diaphragm (DIA), extensor digitorum longus (EDL) and extraocular (EOM) muscles of rats with actively induced experimentally acquired MG (EAMG) using Affymetrix rat RAE230 gene chip. Experiment Overall Design: Total RNA was obtained with TRIzol (Invitrogen Carlsbad, CA) following the manufacturers recommended protocol. Tissues from 3 animals were combined into each RNA sample to decrease inter-subject variability. RNA pellets were cleaned by RNasey kits and resuspended at 1 Î¼g RNA/Î¼l DEPC-treated water and 5 ug was used in a reverse transcription reaction (SuperScript II; Life Technologies, Rockville, MD) to generate first strand cDNA. Double strand cDNA was synthesized and used in an in vitro transcription (IVT) reaction to generate biotinylated cRNA. Fragmented cRNA (15 ug) was used in a 300 ul hybridization cocktail containing herring sperm DNA and BSA as carrier molecules, spiked IVT controls, and buffering agents. A 200 ul aliquot of this cocktail was used for hybridization to Affymetrix rat REA230 (Santa Clara, CA) microarrays for 16 hrs at 45o C. The manufacturerâs standard post-hybridization wash, double-stain, and scanning protocols used an Affymetrix GeneChip Fluidics Station 400 and a Hewlett Packard Gene Array scanner. Experiment Overall Design: Microarray data analysis Experiment Overall Design: Raw data from microarray scans were analyzed with Affymetrix GCOS 2.0. GCOS evaluates sets of perfect match (PM) and mismatch (MM) probe sequences to obtain both hybridization signal values and present/absent calls for each transcript. Microarrays were scaled to the same target intensity and pairwise comparisons were made between experimental and control samples. Comparisons the one-sided Wilcoxonâs signed rank test to estimate âincrease/no change/ decreaseâ difference calls for each pair-wise comparison. Transcripts defined as differentially regulated met the criteria of: (a) consistent increase/decrease call across 7 out of 9 replicate comparisons, based upon Wilcoxonâs signed rank test (algorithm assesses probe pair saturation, calculates a p value and determines increase, decrease, or no change calls) and (b) the average fold difference â¥ 2.0. Data were visualized as a hierarchical dendrogram generayed on computer (Genespring software,ver 7.2; Silicon Genetics, Redwood city, CA). Annotation was done according to Affymetrix NetAffyx Gene Ontology database.

Project description:BackgroundCoexistence of thyroid-associated ophthalmopathy (TAO) and ocular myasthenia gravis (OMG) is very rare. Little is known about the orbital histopathology associated with this condition. The authors reported a case of TAO coexisting with OMG and explored the histopathologic changes in extraocular muscles.Case presentationA 32-year-old man complaint of bilateral proptosis for 2?years. The patient was documented with a history of OMG and was treated with blepharoplasty to correct ptosis 3?years prior to presentation. Physical examination revealed right upper eyelid retraction resulting from the eyelid surgery. Computed tomographic scan demonstrated bilateral enlargement of the extraocular muscles. Thyroid function test confirmed hyperthyroid status. The patient was diagnosed with TAO (clinical activity score?=?2/7) coexisting with OMG. Orbital decompression surgery reduced proptosis but resulted in new onset of left upper eyelid retraction because of the increased motor impulses to sustain eyelid elevation. Extraocular muscles were sampled during surgery and subjected to histopathologic stain. The stain results were analyzed against samples from age-, gender- matched TAO and control (non-TAO non-OMG) subjects. The measurement of myofiber size and glycosaminoglycan/collagen-occupied area was repeated in 3 randomly chosen fields of each slide. The variation of myofiber size was larger in the TAO?+?OMG (289.9?±?142.5??m2) samples than the TAO (544.1?±?160.6??m2) and control (157.0?±?47.7??m2) samples. Glycosaminoglycan was more abundant in the TAO?+?OMG (48.8?±?12.2%) samples than the TAO (28.4?±?3.6%) and control (3.3?±?0.8%) samples. Collagen fibers accumulated in the TAO (60.5?±?6.4%) samples but not in the TAO?+?OMG (36.1?±?4.3%) and control (33.9?±?2.7%) samples. Typical OMG changes were observed in the TAO?+?OMG samples but not in the TAO and control samples. These changes included central nuclei, aggregation of mitochondria and fiber type grouping. The histopathologic findings of TAO?+?OMG were summarized as inhomogeneously enlarged muscle fibers and predominantly endomysial accumulation of glycosaminoglycan.ConclusionThis study highlights the possibility of TAO coexisting with OMG and demonstrates the histopathologic features in this rare condition.

Project description:ObjectiveTo find out if the failure in immunotolerance of myasthenia gravis (MG) is a possible aspect of deduction in Breg cells and to characterize B cell subsets in MG.MethodsFlow cytometry detection and enzyme-linked immunosorbent assays in peripheral blood films of 10 MG patients and 10 healthy controls (HCs) were performed after isolation of B cells. The CD19+CD5+CD1d+ Breg cells percentages were measured to complement a B cell phenotype assay and frequencies of B cell subsets. The clinical outcome measures and immunological variables of patients with MG were compared with HCs.ResultsPatients with MG had relatively lowered percentages of CD19+CD5+CD1d+ Breg cells as compared to HCs. The production of interleukin (IL)-10 and transforming growth factor (TGF)-?1 was relatively lesser in patients with MG than HCs, which were linked with more severe of MG disease status according to Myasthenia Gravis Foundation of America (MGFA) clinical classification. The reduction of cytokine production was more significant for IL-10 than TGF-?1 when compared to HCs.ConclusionIt has been observed that the reduced number of B cells is able to produce IL-10 in MG patients but lesser than compared to HCs. The Bregs reduction mainly was regarded by the severity of disease status, which was highly significant and also by disease duration which was statistically significant as well. The findings of the measurement of B cell phenotype assay and frequencies of B cell subsets between MGs and HCs give us new ideas to develop B cell-mediated therapies of MG such as (1) isolated B cells of MGs could be cultured with steroids, e.g., dexamethasone in vitro to see if it induces the CD19+CD5+CD1d+ Breg cells, (2) it may observe whether induced CD19+CD5+CD1d+ Bregs have higher production of IL-10 and TGF-?1, as both are linked with disease severity, and (3) after completion in vitro steps, through further research in vivo to observe whether it improves the function of MG disease status.

Project description:Myasthenia gravis (MG) is an autoimmune disease affecting the neuromuscular junction, whose clinical hallmark is muscle weakness and early fatigability. Azathioprine (AZA) is commonly used in Myasthenia Gravis therapy. AZA is a purine antagonist, which inhibits the cell cycle in the resting and DNA synthesis phases. It is usually used as an immunosuppressant to block T- and B-cell proliferation. AZA, bioconverted to 6-mercaptopurine by glutathione S-transferase (GST), can be metabolized either through the hypoxanthine phosphoribosyl transferase pathway to active 6-thioguanine nucleotides (6-TGN) or through the thiopurine S-methyltransferase (TPMT) pathway to inactive methyl-thiopurine metabolites. The incorporation of active 6-TGNs into DNA, causing breaks in DNA strands resulting in interference with RNA production and thereby protein synthesis, is responsible for the drug effect. The response to AZA is determined by which metabolic pathway is being favored. While balanced use of both HPRT and TPMT pathways results in responsiveness to AZA, hyperactivity of TPMT skews the balance towards the TPMT pathway and results in unresponsiveness to AZA with no pharmacological effect. In contrast, low TPMT activity skews the balance towards the HPRT pathway, resulting in increasing side-effects due to the accumulation of 6-TGNs. Current treatments for MG therapy are often inadequate because less than 40% of patients achieve complete remission with available drugs. This reflects the lack of drugs acting on target sites for which there is strong evidence of pathogenicity and the inability to identify responder patients. No criteria for responsiveness are available, exposing patients to unpredictable failures and unpredictable side effects. These individuals are at particular risk for adverse drug reaction (ADRs) or therapeutic failure. Genetic profiling with the Affymetrix drug metabolizing enzymes and transports genotyping array offers the ability to determine 1,931 variants and 225 genes involved in drug metabolism and disposition. Accordingly, the study of well-known drug-metabolizing genes can be involved in the specific metabolic pathway of a drug, which is more likely to define genotype-phenotype association and thereby genotype profiles relevant to drug response that can be applied as predictive biomarkers for pharmacological treatment.

Dataset Information

A functional SNP in the regulatory region of the decay-accelerating factor gene associates with extraocular muscle pareses in myasthenia gravis.

Publications

A functional SNP in the regulatory region of the decay-accelerating factor gene associates with extraocular muscle pareses in myasthenia gravis.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets