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Rima Rozen - One of the best experts on this subject based on the ideXlab platform.
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Effect of Hyperhomocystinemia and Hypertension on Endothelial Function in Methylenetetrahydrofolate Reductase–Deficient Mice
2016Co-Authors: Agostino Virdis, Rima Rozen, Marc Iglarz, Mario Fritsch Neves, Farhad Amiri, Rhian M. Touyz, Ernesto L. SchiffrinAbstract:Objective—We evaluated the effect of hyperhomocystinemia and angiotensin (Ang) II on vascular function and structure in Methylenetetrahydrofolate Reductase knockout mice (Mthfr/). Methods and Results—Mthfr/ and controls (Mthfr/) received Ang II (400 ng/kg per min SC) or saline (14 days). Blood pressure, similar in Mthfr/ and Mthfr/, was increased by Ang II. Acetylcholine- and bradykinin-induced relaxations were impaired in mesenteric resistance arteries (pressurized myograph) in Mthfr/ and in Ang II–infused Mthfr/ mice and additionally blunted in Ang II–infused Mthfr/ mice. The inhibition by L-NAME on acetylcholine was reduced in Mthfr/ and in Ang II–Mthfr/ and absent in Ang II–Mthfr/ mice. In these groups, vitamin C improved the response to acetylcholine and restored the inhibition by L-NAME. The media to lumen ratio of small arteries, similar in Mthfr/ and Mthfr/, was increased by Ang II. Vascular NADPH oxidase activity, similar in Mthfr/ and Mthfr/, increased after Ang II infusion. Vascular xanthine oxidase activity was also similar in Mthfr/ and Mthfr/. Superoxide production in the aorta was reduced by sepiapterin and by L-NAME, suggesting that reduced bioavailability of tetrahydrobiopterin and uncoupling of nitric oxide synthase were the origin of increased reactive oxygen species in this model. Conclusions—Mthfr/ mice show endothelial dysfunction of mesenteric vessels probably attributable to a reduced nitric oxide bioavailability caused by oxidative excess due to uncoupling of nitric oxide synthase without vascula
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mice deficient in Methylenetetrahydrofolate Reductase exhibit tissue specific distribution of folates
Journal of Nutrition, 2004Co-Authors: Haifa Ghandour, Zhoutao Chen, Jacob Selhub, Rima RozenAbstract:Methylenetetrahydrofolate Reductase (MTHFR) catalyzes the synthesis of 5-methyltetrahydrofolate (5-methylTHF), which is used for homocysteine remethylation to methionine, the precursor of S-adenosylmethi- onine (SAM). Impairment of MTHFR will increase homocysteine levels and compromise SAM-dependent methyl- ation reactions. Mild MTHFR deficiency is common in many populations due to a polymorphism at bp 677. To assess how impaired MTHFR activity affects folate metabolism in various tissues in vivo, we used affinity/HPLC with electrochemical detection to analyze the distribution of folates in plasma, liver, and brain of Mthfr-deficient mice. The most pronounced difference in total folate was observed in plasma. In Mthfr / mice, plasma total folate levels were 25% of those in wild-type (Mthfr /) mice. Only 40% of plasma folate in Mthfr / mice was comprised of 5-methylTHF, compared with at least 80% in the other 2 genotype groups. In liver and brain, there were no differences in total folate. However, the proportion of 5-methylTHF in both tissues was again markedly reduced in mice with the Mthfr / genotype. In this genotype group, 5-methylTHF is likely derived from the diet. Our study demonstrated reduced total circulatory folate and altered distribution of folate derivatives in liver and brain in Mthfr deficiency. Decreased methylfolates and increased nonmethylfolates would affect the flux of one-carbon units between methylation reactions and nucleotide synthesis. This altered flux has implications for several common disorders, including cancer and vascular disease. J. Nutr. 134: 2975-2978, 2004.
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effects of common polymorphisms on the properties of recombinant human Methylenetetrahydrofolate Reductase
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Kazuhiro Yamada, Rima Rozen, Zhoutao Chen, Rowena G MatthewsAbstract:Methylenetetrahydrofolate Reductase (MTHFR) catalyzes the conversion of Methylenetetrahydrofolate to methyltetrahydrofolate, the major methyl donor for the conversion of homocysteine to methionine. Two common polymorphisms of the human enzyme have been identified: 677C>T, which leads to the substitution of Ala-222 by valine, and 1298A>C, which leads to the replacement of Glu-429 by alanine; the former polymorphism is the most frequent genetic cause of mild hyperhomocysteinemia, a risk factor for cardiovascular disease. By using a baculovirus expression system, recombinant human MTHFR has been expressed at high levels and purified to homogeneity in quantities suitable for biochemical characterization. The Glu429Ala protein has biochemical properties that are indistinguishable from the wild-type enzyme. The Ala222Val MTHFR, however, has an enhanced propensity to dissociate into monomers and to lose its FAD cofactor on dilution; the resulting loss of activity is slowed in the presence of methyltetrahydrofolate or adenosylmethionine. This biochemical phenotype is in good agreement with predictions made on the basis of studies comparing wild-type Escherichia coli MTHFR with a mutant, Ala177Val, homologous to the Ala222Val mutant human enzyme [Guenther, B. D., et al. (1999) Nat. Struct. Biol. 6, 359–365].
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polymorphisms in the Methylenetetrahydrofolate Reductase gene clinical consequences
American Journal of Pharmacogenomics, 2001Co-Authors: Bernd Schwahn, Rima RozenAbstract:5,10-Methylenetetrahydrofolate Reductase (MTHFR) plays a key role in folate metabolism by channeling one-carbon units between nucleotide synthesis and methylation reactions. Severe enzyme deficiency leads to hyperhomocysteinemia and homocystinuria, with altered folate distribution and a phenotype that is characterized by damage to the nervous and vascular systems. Two frequent polymorphisms in the human MTHFR gene confer moderate functional impairment of MTHFR activity for homozygous mutant individuals. The C to T change at nucleotide position 677, whose functional consequences are dependent on folate status, has been extensively studied for its clinical consequences. A second polymorphism, an A to C change at nucleotide position 1298, is not as well characterized. Still equivocal are associations between MTHFR polymorphisms and vascular arteriosclerotic or thrombotic disease. Neural tube defects and pregnancy complications appear to be linked to impaired MTHFR function. Colonic cancer and acute leukemia, however, appear to be less frequent in individuals homozygous for the 677T polymorphism. MTHFR polymorphisms influence the homocysteine-lowering effect of folates and could modify the pharmacodynamics of antifolates and many other drugs whose metabolism, biochemical effects, or target structures require methylation reactions. However, only preliminary evidence exists for gene-drug interactions. This review summarizes the biochemical basis and clinical evidence for interactions between MTHFR polymorphisms and several disease entities, as well as potential interactions with drug therapies. Future investigations of MTHFR in disease should consider the influence of other variants of functionally-related genes as well as the medication regimen of the patients. Animal models for genetic deficiencies in folate metabolism will likely play a greater role in our understanding of folate-dependent disorders.
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the structure and properties of Methylenetetrahydrofolate Reductase from escherichia coli suggest how folate ameliorates human hyperhomocysteinemia
Nature Structural & Molecular Biology, 1999Co-Authors: Brian D Guenther, Christal A Sheppard, Rowena G Matthews, Rima Rozen, Pamela V Tran, Martha L LudwigAbstract:Elevated plasma homocysteine levels are associated with increased risk for cardiovascular disease and neural tube defects in humans. Folate treatment decreases homocysteine levels and dramatically reduces the incidence of neural tube defects. The flavoprotein Methylenetetrahydrofolate Reductase (MTHFR) is a likely target for these actions of folate. The most common genetic cause of mildly elevated plasma homocysteine in humans is the MTHFR polymorphism A222V (base change C677→T). The X-ray analysis of E. coli MTHFR, reported here, provides a model for the catalytic domain that is shared by all MTHFRs. This domain is a β8α8 barrel that binds FAD in a novel fashion. Ala 177, corresponding to Ala 222 in human MTHFR, is near the bottom of the barrel and distant from the FAD. The mutation A177V does not affect Km or kcat but instead increases the propensity for bacterial MTHFR to lose its essential flavin cofactor. Folate derivatives protect wild-type and mutant E. coli enzymes against flavin loss, and protect human MTHFR and the A222V mutant against thermal inactivation, suggesting a mechanism by which folate treatment reduces homocysteine levels.
Rowena G Matthews - One of the best experts on this subject based on the ideXlab platform.
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effects of common polymorphisms on the properties of recombinant human Methylenetetrahydrofolate Reductase
Proceedings of the National Academy of Sciences of the United States of America, 2001Co-Authors: Kazuhiro Yamada, Rima Rozen, Zhoutao Chen, Rowena G MatthewsAbstract:Methylenetetrahydrofolate Reductase (MTHFR) catalyzes the conversion of Methylenetetrahydrofolate to methyltetrahydrofolate, the major methyl donor for the conversion of homocysteine to methionine. Two common polymorphisms of the human enzyme have been identified: 677C>T, which leads to the substitution of Ala-222 by valine, and 1298A>C, which leads to the replacement of Glu-429 by alanine; the former polymorphism is the most frequent genetic cause of mild hyperhomocysteinemia, a risk factor for cardiovascular disease. By using a baculovirus expression system, recombinant human MTHFR has been expressed at high levels and purified to homogeneity in quantities suitable for biochemical characterization. The Glu429Ala protein has biochemical properties that are indistinguishable from the wild-type enzyme. The Ala222Val MTHFR, however, has an enhanced propensity to dissociate into monomers and to lose its FAD cofactor on dilution; the resulting loss of activity is slowed in the presence of methyltetrahydrofolate or adenosylmethionine. This biochemical phenotype is in good agreement with predictions made on the basis of studies comparing wild-type Escherichia coli MTHFR with a mutant, Ala177Val, homologous to the Ala222Val mutant human enzyme [Guenther, B. D., et al. (1999) Nat. Struct. Biol. 6, 359–365].
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the structure and properties of Methylenetetrahydrofolate Reductase from escherichia coli suggest how folate ameliorates human hyperhomocysteinemia
Nature Structural & Molecular Biology, 1999Co-Authors: Brian D Guenther, Christal A Sheppard, Rowena G Matthews, Rima Rozen, Pamela V Tran, Martha L LudwigAbstract:Elevated plasma homocysteine levels are associated with increased risk for cardiovascular disease and neural tube defects in humans. Folate treatment decreases homocysteine levels and dramatically reduces the incidence of neural tube defects. The flavoprotein Methylenetetrahydrofolate Reductase (MTHFR) is a likely target for these actions of folate. The most common genetic cause of mildly elevated plasma homocysteine in humans is the MTHFR polymorphism A222V (base change C677→T). The X-ray analysis of E. coli MTHFR, reported here, provides a model for the catalytic domain that is shared by all MTHFRs. This domain is a β8α8 barrel that binds FAD in a novel fashion. Ala 177, corresponding to Ala 222 in human MTHFR, is near the bottom of the barrel and distant from the FAD. The mutation A177V does not affect Km or kcat but instead increases the propensity for bacterial MTHFR to lose its essential flavin cofactor. Folate derivatives protect wild-type and mutant E. coli enzymes against flavin loss, and protect human MTHFR and the A222V mutant against thermal inactivation, suggesting a mechanism by which folate treatment reduces homocysteine levels.
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Methylenetetrahydrofolate Reductase and methionine synthase biochemistry and molecular biology
European Journal of Pediatrics, 1998Co-Authors: Rowena G Matthews, Christal A Sheppard, Celia W GouldingAbstract:Methylenetetrahydrofolate Reductase and cobalamin-dependent methionine synthase catalyze the penultimate and ultimate steps in the biosynthesis of methionine in prokaryotes, and are required for the regeneration of the methyl group of methionine in mammals. Defects in either of these enzymes can lead to hyperhomocysteinemia. The sequences of the human Methylenetetrahydrofolate Reductase and methionine synthase are now known, and show clear homology with their bacterial analogues. Mutations in both enzymes that are known to occur in humans and to be associated with hyperhomocysteinemia affect residues that are conserved in the bacterial enzymes. Structure/function studies on the bacterial proteins, summarized in this review, are therefore relevant to the function of the human enzymes; in particular studies on the effects of bacterial mutations analogous to those causing hyperhomocysteinemia in human may shed light on the defects associated with these mutations.
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a candidate genetic risk factor for vascular disease a common mutation in Methylenetetrahydrofolate Reductase
Nature Genetics, 1995Co-Authors: P Frosst, Henk J Blom, Renate Milos, Philippe Goyette, Christal A Sheppard, Rowena G Matthews, G J H Boers, Den M Heijer, Leo A J Kluijtmans, L P W J Van Den HeuvelAbstract:Hyperhomocysteinaemia has been identified as a risk factor for cerebrovascular, peripheral vascular and coronary heart disease1−4. Elevated levels of plasma homocysteine can result from genetic or nutrient-related disturbances in the trans-sulphuration or re-methylation pathways for homocysteine metabolism1,5−7. 5,10-Methylenetetrahydrofolate Reductase (MTHFR) catalyzes the reduction of 5,10-Methylenetetrahydrofolate to 5-methyltetra-hydrofolate, the predominant circulatory form of folate and carbon donor for the re-methylation of homocysteine to methionine. Reduced MTHFR activity with a thermolabile enzyme has been reported in patients with coronary and peripheral artery disease5,6. We have identified a common mutation in MTHFR which alters a highly-conserved amino acid; the substitution occurs at a frequency of approximately 38% of unselected chromosomes. The mutation in the heterozygous or homozygous state correlates with reduced enzyme activity and increased thermolability in lymphocyte extracts; in vitro expression of a mutagenized cDNA containing the mutation confirms its effect on thermolability of MTHFR. Finally, individuals homozygous for the mutation have significantly elevated plasma homocysteine levels. This mutation in MTHFR may represent an important genetic risk factor in vascular disease.
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human Methylenetetrahydrofolate Reductase isolation of cdna mapping and mutation identification
Nature Genetics, 1994Co-Authors: Philippe Goyette, Renate Milos, Rowena G Matthews, James S Sumner, Alessandra M V Duncan, David S Rosenblatt, Rima RozenAbstract:Methylenetetrahydrofolate Reductase (MTHFR) catalyses the reduction of Methylenetetrahydrofolate to methyltetrahydrofolate, a cofactor for homocysteine methylation to methionine. MTHFR deficiency, an autosomal recessive disorder, results in homocysteinemia. Using degenerate oligonucleotides based on porcine peptide sequence data, we isolated a 90-bp cDNA by PCR from pig liver RNA. This cDNA was used to isolate a human cDNA, the predicted amino acid sequence of which shows strong homology to porcine MTHFR and to bacterial metF genes. The human gene has been localized to chromosome 1p36.3. Two mutations were identified in MTHFR-deficient patients: a missense mutation (Arg to Gln), in a residue conserved in bacterial enzymes, and a nonsense mutation (Arg to Ter).
Henk J Blom - One of the best experts on this subject based on the ideXlab platform.
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homocysteine Methylenetetrahydrofolate Reductase and risk of schizophrenia a meta analysis
Molecular Psychiatry, 2006Co-Authors: Janwillem Muntjewerff, Henk J Blom, Rene S Kahn, Den M HeijerAbstract:Elevated plasma homocysteine concentration has been suggested as a risk factor for schizophrenia, but the results of epidemiological studies have been inconsistent. The most extensively studied genetic variant in the homocysteine metabolism is the 677C>T polymorphism in the Methylenetetrahydrofolate Reductase (MTHFR) gene, resulting in reduced enzyme activity and, subsequently, in elevated homocysteine. A meta-analysis of eight retrospective studies (812 cases and 2113 control subjects) was carried out to examine the association between homocysteine and schizophrenia. In addition, a meta-analysis of 10 studies (2265 cases and 2721 control subjects) on the homozygous (TT) genotype of the MTHFR 677C>T polymorphism was carried out to assess if this association is causal. A 5 micromol/l higher homocysteine level was associated with a 70% (95% confidence interval, CI: 27-129) higher risk of schizophrenia. The TT genotype was associated with a 36% (95% CI: 7-72) higher risk of schizophrenia compared to the CC genotype. The performed meta-analyses showed no evidence of publication bias or excessive influence attributable to any given study. In conclusion, our study provides evidence for an association of homocysteine with schizophrenia. The elevated risk of schizophrenia associated with the homozygous genotype of the MTHFR 677C>T polymorphism provides support for causality between a disturbed homocysteine metabolism and risk of schizophrenia.
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Methylenetetrahydrofolate Reductase polymorphism affects the change in homocysteine and folate concentrations resulting from low dose folic acid supplementation in women with unexplained recurrent miscarriages
Journal of Nutrition, 1998Co-Authors: W L D M Nelen, Henk J Blom, G H J Boers, Chris M G Thomas, Eric A P Steegers, T K A B EskesAbstract:To determine the effects of daily supplementation of 0.5 mg folic acid on homocysteine and folate concentrations, we investigated 49 women with a history of unexplained recurrent miscarriages. A methionine loading test (including the vitamin concentrations of concern) was used preceding and after 2 mo of folic acid intake. Subsequently, these effects were studied after stratification for C677T 5,10-Methylenetetrahydrofolate Reductase (MTHFR) polymorphism. Folic acid supplementation (for 2 mo) reduced the median fasting and delta (after-load minus fasting) total plasma homocysteine (tHcy) concentrations 27% (P T mutation of the MTHFR-gene.
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a second common mutation in the Methylenetetrahydrofolate Reductase gene an additional risk factor for neural tube defects
American Journal of Human Genetics, 1998Co-Authors: F J M Gabreels, T K A B Eskes, Erik M B Stevens, Jan A M Smeitink, Frans J M Trijbels, Lambert P Van Den Heuvel, Henk J BlomAbstract:Summary Recently, we showed that homozygosity for the common 677(C→T) mutation in the Methylenetetrahydrofolate Reductase (MTHFR) gene, causing thermolability of the enzyme, is a risk factor for neural-tube defects (NTDs). We now report on another mutation in the same gene, the 1298(A→C) mutation, which changes a glutamate into an alanine residue. This mutation destroys an Mbo II recognition site and has an allele frequency of .33. This 1298(A→C) mutation results in decreased MTHFR activity (one-way analysis of variance [ANOVA] P P P n = 86) of the NTD patients compared with 20% ( n = 403) among controls, resulting in an odds ratio of 2.04 (95% confidence interval: .9–4.7). These data suggest that the combined heterozygosity for the two MTHFR common mutations accounts for a proportion of folate-related NTDs, which is not explained by homozygosity for the 677(C→T) mutation, and can be an additional genetic risk factor for NTDs.
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thermolabile Methylenetetrahydrofolate Reductase and factor v leiden in the risk of deep vein thrombosis
Thrombosis and Haemostasis, 1998Co-Authors: Leo A J Kluijtmans, Henk J Blom, Den M Heijer, Sandra G Heil, Pieter H Reitsma, F R RosendaalAbstract:Mild hyperhomocysteinemia is an established risk factor for both arteriosclerosis and thrombosis, and may be caused by genetic and environmental factors. Methylenetetrahydrofolate Reductase (MTHFR) catalyzes the reduction of 5,10-Methylenetetrahydrofolate to 5-methyltetrahydrofolate, the cofactor for the methylation of homocysteine to methionine. Individuals with the thermolabile variant of MTHFR have decreased MTHFR activities, resulting in elevated plasma homocysteine concentrations. A homozygous 677C T transition in the MTHFR gene has recently been identified as the cause of reduced enzyme activity and thermolability of the protein. We studied the frequency of the homozygous mutant (+/+) genotype in 471 patients with deep-vein thrombosis and 474 healthy controls enrolled in The Leiden Thrombophilia Study (LETS), its interaction with factor V Leiden, and assessed the association between the MTHFR genotypes and plasma homocysteine concentration. Homozygosity for the 677C T polymorphism was observed in 47 (10%) patients, and in 47 (9.9%) controls (OR 1.01 [95% CI: 0.7-1.5]). No modified risk of the (+/+) genotype was observed in carriers of factor V Leiden. Our data suggest that, although the homozygous mutant genotype is associated with elevated plasma homocysteine concentrations, this homozygous mutation itself is not a genetic risk factor for deep-vein thrombosis, irrespective of factor V Leiden genotype.
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mutated Methylenetetrahydrofolate Reductase as a risk factor for spina bifida
The Lancet, 1995Co-Authors: F J M Trijbels, T K A B Eskes, Henk J Blom, P Frosst, L P W J Van Den Heuvel, Regine P M Steegerstheunissen, Edwin C M Mariman, Den M Heyer, Rima RozenAbstract:Abstract Periconceptional folate supplementation reduces the risk of neural-tube defects. We studied the frequency of the 677C→T mutation in the 5,10–Methylenetetrahydrofolate Reductase (MTHFR) gene in 55 patients with spina bifida and parents of such patients (70 mothers, 60 fathers), 5% of 207 controls were homozygous for the 677C→T mutation compared with 16% of mothers, 10% of fathers, and 13% of patients. The mutation was associated with decreased MTHFR activity, low plasma folate, and high plasma homocysteine and red-cell folate concentrations. The 677C→T mutation should be regarded as a genetic risk factor for spina bifida.
P Frosst - One of the best experts on this subject based on the ideXlab platform.
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gene structure of human and mouse Methylenetetrahydrofolate Reductase mthfr
Mammalian Genome, 1998Co-Authors: Philippe Goyette, P Frosst, Renate Milos, Zhoutao Chen, Aditya Pai, Pamela V Tran, Manuel Chan, Rima RozenAbstract:Methylenetetrahydrofolate Reductase (MTHFR) catalyzes the conversion of 5,10-Methylenetetrahydrofolate to 5-methyltetrahydrofolate, a co-substrate for homocysteine remethylation to methionine. A human cDNA for MTHFR, 2.2 kb in length, has been expressed and shown to result in a catalytically active enzyme of approximately 70 kDa. Fifteen mutations have been identified in the MTHFR gene: 14 rare mutations associated with severe enzymatic deficiency and 1 common variant associated with a milder deficiency. The common polymorphism has been implicated in three multifactorial diseases: occlusive vascular disease, neural tube defects, and colon cancer. The human gene has been mapped to chromosomal region 1p36.3 while the mouse gene has been localized to distal Chromosome (Chr) 4. Here we report the isolation and characterization of the human and mouse genes for MTHFR. A human genomic clone (17 kb) was found to contain the entire cDNA sequence of 2.2 kb; there were 11 exons ranging in size from 102 bp to 432 bp. Intron sizes ranged from 250 bp to 1.5 kb with one exception of 4.2 kb. The mouse genomic clones (19 kb) start 7 kb 5′ exon 1 and extend to the end of the coding sequence. The mouse amino acid sequence is approximately 90% identical to the corresponding human sequence. The exon sizes, locations of intronic boundaries, and intron sizes are also quite similar between the two species. The availability of human genomic clones has been useful in designing primers for exon amplification and mutation detection. The mouse genomic clones will be helpful in designing constructs for gene targeting and generation of mouse models for MTHFR deficiency.
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Methylenetetrahydrofolate Reductase polymorphism plasma folate homocysteine and risk of myocardial infarction in us physicians
Circulation, 1996Co-Authors: Meir J Stampfer, P Frosst, Jacob Selhub, C H Hennekens, J Horsford, M R Malinow, Walter C Willett, Rima RozenAbstract:Background Hyperhomocysteinemia appears to be an independent risk factor for coronary disease. Elevated levels of plasma total homocysteine (tHCY) can result from genetic or nutrient-related disturbances in the transsulfuration or remethylation pathways for homocysteine metabolism. The enzyme 5,10-Methylenetetrahydrofolate Reductase (MTHFR) catalyzes the reduction of 5,10-Methylenetetrahydrofolate to 5-methyltetrahydrofolate, the predominant circulatory form of folate, which serves as a methyl donor for remethylation of homocysteine to methionine. A common mutation in MTHFR recently has been identified. Methods and Results We assessed the polymorphism in MTHFR, plasma tHCY, and folate using baseline blood levels among 293 Physicians' Health Study participants who developed myocardial infarction (MI) during up to 8 years of follow-up and 290 control subjects. The frequency of the three genotypes was (−/−) (homozygous normal), 47%; (+/−) (heterozygous), 41%; and (+/+) (homozygous mutant), 12%, with a simila...
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mutated Methylenetetrahydrofolate Reductase as a risk factor for spina bifida
The Lancet, 1995Co-Authors: F J M Trijbels, T K A B Eskes, Henk J Blom, P Frosst, L P W J Van Den Heuvel, Regine P M Steegerstheunissen, Edwin C M Mariman, Den M Heyer, Rima RozenAbstract:Abstract Periconceptional folate supplementation reduces the risk of neural-tube defects. We studied the frequency of the 677C→T mutation in the 5,10–Methylenetetrahydrofolate Reductase (MTHFR) gene in 55 patients with spina bifida and parents of such patients (70 mothers, 60 fathers), 5% of 207 controls were homozygous for the 677C→T mutation compared with 16% of mothers, 10% of fathers, and 13% of patients. The mutation was associated with decreased MTHFR activity, low plasma folate, and high plasma homocysteine and red-cell folate concentrations. The 677C→T mutation should be regarded as a genetic risk factor for spina bifida.
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seven novel mutations in the Methylenetetrahydrofolate Reductase gene and genotype phenotype correlations in severe Methylenetetrahydrofolate Reductase deficiency
American Journal of Human Genetics, 1995Co-Authors: Philippe Goyette, P Frosst, David S Rosenblatt, Rima RozenAbstract:5-Methyltetrahydrofolate, the major form of folate in plasma, is a carbon donor for the remethylation of homocysteine to methionine. This form of folate is generated from 5,10-Methylenetetrahydrofolate through the action of 5,10-Methylenetetrahydrofolate Reductase (MTHFR), a cytosolic flavoprotein. Patients with an autosomal recessive severe deficiency of MTHFR have homocystinuria and a wide range of neurological and vascular disturbances. We have recently described the isolation of a cDNA for MTHFR and the identification of two mutations in patients with severe MTHFR deficiency. We report here the characterization of seven novel mutations in this gene: six missense mutations and a 5' splice-site defect that activates a cryptic splice site in the coding sequence. We also present a preliminary analysis of the relationship between genotype and phenotype for all nine mutations identified thus far in this gene. A nonsense mutation and two missense mutations (proline to leucine and threonine to methionine) in the homozygous state are associated with extremely low activity (0%-3%) and onset of symptoms within the 1st year of age. Other missense mutations (arginine to cysteine and arginine to glutamine) are associated with higher enzyme activity and later onset of symptoms.
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a candidate genetic risk factor for vascular disease a common mutation in Methylenetetrahydrofolate Reductase
Nature Genetics, 1995Co-Authors: P Frosst, Henk J Blom, Renate Milos, Philippe Goyette, Christal A Sheppard, Rowena G Matthews, G J H Boers, Den M Heijer, Leo A J Kluijtmans, L P W J Van Den HeuvelAbstract:Hyperhomocysteinaemia has been identified as a risk factor for cerebrovascular, peripheral vascular and coronary heart disease1−4. Elevated levels of plasma homocysteine can result from genetic or nutrient-related disturbances in the trans-sulphuration or re-methylation pathways for homocysteine metabolism1,5−7. 5,10-Methylenetetrahydrofolate Reductase (MTHFR) catalyzes the reduction of 5,10-Methylenetetrahydrofolate to 5-methyltetra-hydrofolate, the predominant circulatory form of folate and carbon donor for the re-methylation of homocysteine to methionine. Reduced MTHFR activity with a thermolabile enzyme has been reported in patients with coronary and peripheral artery disease5,6. We have identified a common mutation in MTHFR which alters a highly-conserved amino acid; the substitution occurs at a frequency of approximately 38% of unselected chromosomes. The mutation in the heterozygous or homozygous state correlates with reduced enzyme activity and increased thermolability in lymphocyte extracts; in vitro expression of a mutagenized cDNA containing the mutation confirms its effect on thermolability of MTHFR. Finally, individuals homozygous for the mutation have significantly elevated plasma homocysteine levels. This mutation in MTHFR may represent an important genetic risk factor in vascular disease.
Philippe Goyette - One of the best experts on this subject based on the ideXlab platform.
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gene structure of human and mouse Methylenetetrahydrofolate Reductase mthfr
Mammalian Genome, 1998Co-Authors: Philippe Goyette, P Frosst, Renate Milos, Zhoutao Chen, Aditya Pai, Pamela V Tran, Manuel Chan, Rima RozenAbstract:Methylenetetrahydrofolate Reductase (MTHFR) catalyzes the conversion of 5,10-Methylenetetrahydrofolate to 5-methyltetrahydrofolate, a co-substrate for homocysteine remethylation to methionine. A human cDNA for MTHFR, 2.2 kb in length, has been expressed and shown to result in a catalytically active enzyme of approximately 70 kDa. Fifteen mutations have been identified in the MTHFR gene: 14 rare mutations associated with severe enzymatic deficiency and 1 common variant associated with a milder deficiency. The common polymorphism has been implicated in three multifactorial diseases: occlusive vascular disease, neural tube defects, and colon cancer. The human gene has been mapped to chromosomal region 1p36.3 while the mouse gene has been localized to distal Chromosome (Chr) 4. Here we report the isolation and characterization of the human and mouse genes for MTHFR. A human genomic clone (17 kb) was found to contain the entire cDNA sequence of 2.2 kb; there were 11 exons ranging in size from 102 bp to 432 bp. Intron sizes ranged from 250 bp to 1.5 kb with one exception of 4.2 kb. The mouse genomic clones (19 kb) start 7 kb 5′ exon 1 and extend to the end of the coding sequence. The mouse amino acid sequence is approximately 90% identical to the corresponding human sequence. The exon sizes, locations of intronic boundaries, and intron sizes are also quite similar between the two species. The availability of human genomic clones has been useful in designing primers for exon amplification and mutation detection. The mouse genomic clones will be helpful in designing constructs for gene targeting and generation of mouse models for MTHFR deficiency.
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seven novel mutations in the Methylenetetrahydrofolate Reductase gene and genotype phenotype correlations in severe Methylenetetrahydrofolate Reductase deficiency
American Journal of Human Genetics, 1995Co-Authors: Philippe Goyette, P Frosst, David S Rosenblatt, Rima RozenAbstract:5-Methyltetrahydrofolate, the major form of folate in plasma, is a carbon donor for the remethylation of homocysteine to methionine. This form of folate is generated from 5,10-Methylenetetrahydrofolate through the action of 5,10-Methylenetetrahydrofolate Reductase (MTHFR), a cytosolic flavoprotein. Patients with an autosomal recessive severe deficiency of MTHFR have homocystinuria and a wide range of neurological and vascular disturbances. We have recently described the isolation of a cDNA for MTHFR and the identification of two mutations in patients with severe MTHFR deficiency. We report here the characterization of seven novel mutations in this gene: six missense mutations and a 5' splice-site defect that activates a cryptic splice site in the coding sequence. We also present a preliminary analysis of the relationship between genotype and phenotype for all nine mutations identified thus far in this gene. A nonsense mutation and two missense mutations (proline to leucine and threonine to methionine) in the homozygous state are associated with extremely low activity (0%-3%) and onset of symptoms within the 1st year of age. Other missense mutations (arginine to cysteine and arginine to glutamine) are associated with higher enzyme activity and later onset of symptoms.
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a candidate genetic risk factor for vascular disease a common mutation in Methylenetetrahydrofolate Reductase
Nature Genetics, 1995Co-Authors: P Frosst, Henk J Blom, Renate Milos, Philippe Goyette, Christal A Sheppard, Rowena G Matthews, G J H Boers, Den M Heijer, Leo A J Kluijtmans, L P W J Van Den HeuvelAbstract:Hyperhomocysteinaemia has been identified as a risk factor for cerebrovascular, peripheral vascular and coronary heart disease1−4. Elevated levels of plasma homocysteine can result from genetic or nutrient-related disturbances in the trans-sulphuration or re-methylation pathways for homocysteine metabolism1,5−7. 5,10-Methylenetetrahydrofolate Reductase (MTHFR) catalyzes the reduction of 5,10-Methylenetetrahydrofolate to 5-methyltetra-hydrofolate, the predominant circulatory form of folate and carbon donor for the re-methylation of homocysteine to methionine. Reduced MTHFR activity with a thermolabile enzyme has been reported in patients with coronary and peripheral artery disease5,6. We have identified a common mutation in MTHFR which alters a highly-conserved amino acid; the substitution occurs at a frequency of approximately 38% of unselected chromosomes. The mutation in the heterozygous or homozygous state correlates with reduced enzyme activity and increased thermolability in lymphocyte extracts; in vitro expression of a mutagenized cDNA containing the mutation confirms its effect on thermolability of MTHFR. Finally, individuals homozygous for the mutation have significantly elevated plasma homocysteine levels. This mutation in MTHFR may represent an important genetic risk factor in vascular disease.
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human Methylenetetrahydrofolate Reductase isolation of cdna mapping and mutation identification
Nature Genetics, 1994Co-Authors: Philippe Goyette, Renate Milos, Rowena G Matthews, James S Sumner, Alessandra M V Duncan, David S Rosenblatt, Rima RozenAbstract:Methylenetetrahydrofolate Reductase (MTHFR) catalyses the reduction of Methylenetetrahydrofolate to methyltetrahydrofolate, a cofactor for homocysteine methylation to methionine. MTHFR deficiency, an autosomal recessive disorder, results in homocysteinemia. Using degenerate oligonucleotides based on porcine peptide sequence data, we isolated a 90-bp cDNA by PCR from pig liver RNA. This cDNA was used to isolate a human cDNA, the predicted amino acid sequence of which shows strong homology to porcine MTHFR and to bacterial metF genes. The human gene has been localized to chromosome 1p36.3. Two mutations were identified in MTHFR-deficient patients: a missense mutation (Arg to Gln), in a residue conserved in bacterial enzymes, and a nonsense mutation (Arg to Ter).