Methylenetetrahydrofolate Reductase Promoter Research Articles

Promoter methylation status of methylenetetrahydrofolate reductase (MTHFR) gene in spermatozoa of Iraqi infertile men

In the vast majority of instances, the causes of male infertility are unknown, although scientists have lately attempted to correlate epigenetics to infertility mechanisms. DNA methylation is an important biological modification that gives phenotypic diversity and adaptability. The aim of this study was whether the methylation status of the methylenetetrahydrofolate reductase (MTHFR) gene promoter in Iraqi men’s spermatozoa is correlated with male infertility. Semen samples were collected from 100 infertile and healthy fertile men. Divided into 4 groups included 25 subjects of healthy fertile men as a control group(C) and infertile groups, which divided into (3) subgroups: Asthenozoospermia (A) (n=25), Oligoasthenozoospermia (OA) (n = 25) and severe Oligoasthenoteratozoospermia (SOA) (n =25). Sperm DNAs and RNAs from all samples were isolated; followed by sperm-specific methylation detection using the EpiJET DNA Methylation Analysis Kit, which is simple digestion was performed with two restriction enzymes (MspI/HpaII). The methylation percentage (mean ± SD) of the MTHFR gene promoter was quantified in each studied group as follow:[ (C) ( 1.76±0.46) (A) (3.59±0.89), (OA) (26.10±4.14) and (SOA)( 29.13±4.88)]. The percentage of MTHFR promoter methylation infertile men was significantly higher than that in the healthy control group (p = 0.00). Methylation level was determined via receiver operator characteristic (ROC) analysis as the cut-off values of each infertile subgroup were as follows: [(A) (2.43%), (OA) (7.59%) and (SOA) (10.96%)]. According to WHO guidelines, sperm concentration, progressive motility and morphologically normal sperm were determining (WHO, 2010). The qRT-PCR was used to evaluate MTHFR gene expression in all sperm samples. The results revealed a substantial reduction in fold expression (2–∆∆Ct) in all infertile groups when compared to the control g roup, with a P-value (0.002). In this research findings suggest that epigenetic impairment (hypermethylation) of the MTHFR promoter region in sperm DNA from OA and SOA patients may increase male infertility risk.

Association of methylenetetrahydrofolate reductase (MTHFR) and cystathionine β-synthase (CBS) genes promoter methylation pattern with the risk of essential hypertension

Methylenetetrahydrofolate reductase (MTHFR) and cystathionine β-synthase (CBS) are key enzymes in the metabolism of homocysteine pathway whose dysfunction can lead to essential hypertension (EH). This study aimed to investigate the possible association of MTHFR and CBS genes promoter methylation patterns with the risk of EH. We also aimed to search differentially expressed microRNAs (miRs) and demonstrate the role of miRs in the aberrant DNA methylation in essential hypertensive patients by targeting DNA methyltransferases (DNMTs).20 essential hypertensive patients and 20 healthy controls were selected. DNA methylation levels of 10 CpG dinucleotides on MTHFR and 19 CpG dinucleotides on CBS genes promoter was measured using Bisulfite-Sequencing PCR (BSP). The GSE118578 profile was downloaded from the GEO database to identify differentially expressed miRs in hypertensive patients and R statistical software was used to analyze the data. Enrichment analysis was conducted to predict target genes using databases of Targetscan, and miRDB-MicroRNA Target Prediction Database.No significant association between MTHFR gene methylation and EH was observed. There was a significant association between one of the CpG sites of CBS gene promoter (CpG19 (+1035C)) and EH [OR = 5.3(0.895–31.393), p = 0.047]. Furthermore, we reported a list of miRs that may have an essential role in regulating DNA methylation by targeting DNMTs.Our findings showed that hypermethylation of CpG19 (+1035C) of CBS gene promoter could increase the risk of EH. Methylation status of MTHFR gene had no significant association with EH. Also, in-silico investigation showed that miRs may affect aberrant genes methylation through altering DNMTs biogenesis.

Correlation of methylation status in MTHFR promoter region with recurrent pregnancy loss

BackgroundDNA methylation is an epigenetic process for modifying transcription factors in various genes. Methylenetetrahydrofolate reductase (MTHFR) stimulates synthesis of methyl radical in the homocysteine cycle and delivers methyl groups needed in DNA methylation. Furthermore, numerous studies have linked gene polymorphisms of this enzyme with a larger risk of recurrent pregnancy loss (RPL), yet scarce information is available concerning the association between epigenetic deviations in this gene and RPL. Hypermethylation at precise DNA sequences can function as biomarkers for a diversity of diseases. We aimed by this study to evaluate the methylation status of the promoter region of MTHFR gene in women with RPL compared to healthy fertile women. It is a case–control study. Hundred RPL patients and hundred healthy fertile women with no history of RPL as controls were recruited. MTHFR C677T was assessed by polymerase chain reaction-restriction fragment length polymorphism (RFLP). Quantitative evaluation of DNA methylation was performed by high-resolution melt analysis by real-time PCR. ResultsThe median of percentage of MTHFR promoter methylation in RPL cases was 6.45 [0.74–100] vs. controls was 4.50 [0.60–91.7], P value < 0.001. In the case group, 57 hypermethylated and 43 normo-methylated among RPL patients vs. 40 hypermethylated and 60 normo-methylated among controls, P< 0.005. Frequency of T allele in C677T MTHFR gene among RPL patients was 29% vs. 23% among the control group; C allele vs. T allele: odds ratio (OR) = 1.367 (95% confidence interval (CI) 0.725–2.581). ConclusionFindings suggested a significant association between hypermethylation of the MTHFR promoter region in RPL patients compared to healthy fertile women.

Methylation patterns of methylenetetrahydrofolate reductase gene promoter in infertile males.

Errors of folate/homocysteine pathways which are critical for transferring methyl groups have been suggested to affect male fertility. We aimed to evaluate the methylation patterns of the promoter of methylenetetrahydrofolate reductase (MTHFR) gene in infertile males and to investigate the association between MTHFR promoter methylation and success of sperm retrieval. Thirty-five nonobstructive azoospermic and 46 severe oligozoospermic patients constituted the study group and were compared with 49 fertile and/or normozoospermic men. The methylation status was analysed by methylation-specific polymerase chain reaction. MTHFR promoter methylation was detected in infertile men with NOA and SO in the ratio of 48.6% and 58.7%, respectively. Methylation was also observed in 51% of controls. MTHFR promoter was methylated in 65% of men with viable spermatozoon during TESE. No association was found regarding to the profile of MTHFR promoter methylation between both NOA and SO patients and controls (p=.621). There was no relation between the methylation status of MTHFR promoter and low motility and poor morphology (p=.682 and p=.413, respectively). No association was found between MTHFR promoter methylation and presence of viable spermatozoa (p=.382). Our data indicate that the promoter methylation of MTHFR gene may not be associated with male infertility.

Epigenetic Modification in Methylene Tetrahydrofolate Reductase (MTHFR) Gene of Women with Pre-eclampsia

Genetic and epigenetic factors play significant roles in the aetio-pathogenesis of pre-eclampsia (PE). The effects may vary across racial and geographical boundaries. The role of epigenetic modification in pre-eclampsia was studied among African populations in Lagos, Nigeria.This study aimed to determine the pattern of Methylene tetrahydrofolate reductase gene (MTHFR) CpG island methylation in pre-eclampsia, and evaluate associated covariates.This study was an observational, cross-sectional, study conducted at the Lagos University Teaching Hospital and the Lagos State Island Maternity Hospital. A total of 400 pregnant women consisting of 200 pregnant women diagnosed with pre-eclampsia (study group) and 200 pregnant normotensive and apparently healthy women (control group) were recruited for the study. Demographic and clinical histories were obtained through questionnaires. The DNA Methylation status of the CpG Island in promoter region of the MTHFR gene was assessed using bisulphite conversion and methylation specific PCR method. The biochemical parameters measured in the study were: red cell folate, vitamin B12, plasma homocysteine (Hcy) and methylene tetrahydrofolate reductase enzyme level.Homozygous MTHFR CpG island hypomethylation pattern was significantly associated with pre-eclampsia (χ2 = 22.96; p = 0.000), Mean values of plasma homocysteine in PE women with homozygous hypomethylation (26.1 ± 9.1 umol/L) were significantly higher than (20.1 ± 4.2 umol/L) observed in PE subjects with homozygous hypermethylation (p = 0.008). Homozygous CpG island hypomethylated pattern of the MTHFR promoter region, was associated with the lowest median MTHFR enzyme level (72.8 ± 39.8 pmol/L) compared with heterozygous methylated pattern (91.3 ± 60.9 pmol/L; p = 0.047) and homozygous methylated pattern (82.3 ± 31.0 pmol/L; 0.047). Red cell folate and Vitamin B12 levels were not significantly associated with CpG island methylation status.Epigenetic modification plays significant role in the pathogenesis of pre-eclampsia.

The MTHFR promoter hypermethylation pattern associated with the A1298C polymorphism influences lipid parameters and glycemic control in diabetic patients

BackgroundPolymorphisms in the gene encoding methylenetetrahydrofolate reductase (MTHFR) have been investigated as risk factors for microvascular complications of diabetes; however, simultaneous analysis of these polymorphisms and the methylation pattern of the gene has never been conducted. The objective of the present study was to evaluate the simultaneous relationship between MTHFR methylation and MTHFR C6TT7 and A1298C polymorphisms with metabolic, inflammatory and oxidative stress parameters related to microvascular complications, diabetic retinopathy (DR) and diabetic nephropathy (DN) in diabetic patients.MethodsA total of 107 patients who were diagnosed in the previous 5 to 10 years were recruited and divided into groups with complications (DR and/or DN) or without complications. Methylation analysis of the gene promoter was conducted using the MSP technique, and analysis of the A1298C and C677T polymorphisms was conducted using the restriction fragment length polymorphism (RFLP) assay. Microalbuminuria was determined using urine samples, and other analytes of interest were determined in blood samples using commercial kits. The Mann–Whitney and Chi square statistical tests were used with significance considered at p < 0.05.ResultsSubjects with a hypermethylated profile and the 1298AA genotype showed the highest levels of blood glucose (p = 0.03), total cholesterol (p = 0.0001) and LDL cholesterol (p = 0.0006). The same profile was associated with higher levels of HbA1c (p = 0.025), glycemia (p = 0.04) and total cholesterol (0.004) in the control group and total cholesterol (p = 0.005) and LDL cholesterol (p = 0.002) in the complications group. Serum creatinine was higher in subjects in the hypermethylated group with the genotype 677CC only in the control group (p = 0.0020). The methylated profile in presence of 677CC + 1298AA and the 677CT/TT +1298AA haplotypes showed higher levels of total cholesterol (p = 0.0024; 0.0031) and LDL cholesterol (p = 0.0060; 0.0125) than 1298AC/CC carriers. The fasting glycemia was higher in hypermethylated profile in the presence of 677CC/1298AA haplotype (p = 0.0077).ConclusionThe hypermethylated methylation profile associated with the 1298AA genotype appeared to be connected to higher values of glycemia, total cholesterol and LDL cholesterol.

The Impact of Methylenetetrahydrofolate Reductase (MTHFR) Sperm Methylation and Variants on Semen Parameters and the Chance of Recurrent Pregnancy Loss in the Couple.

Recurrent pregnancy loss (RPL) defined as three or more consecutive spontaneous miscarriages before the 20th week of gestation is caused by different factors including genetic and epigenetic background. However the involvement of paternal background on RPL is an interesting novel argument, which is not well studied. The main focus of the present study was to investigate for the association of paternal methylenetetrahydrofolate reductase (MTHFR) epigenotypes with sperm parameters and RPL. Moreover, the frequency of two of MTHFR Single Nucleotide Polymorphisms (SNPs) in males was assessed. This is a case-control study. Methylation Specific PCR (MSP) was used to evaluate the methylation status of MTHFR promoter on sperm DNA of 25 male partners of RPL and 25 male partners of non-RPL couples. PCR-RFLP method was used to analyze 1,298 A>C (rs1801131) and 677 C>T (rs1801133) polymorphisms. No significant difference was observed in frequency of methylated MTHFR epigenotype between RPL and non-RPL males. Furthermore, methylated MTHFR epigenotype was more frequent (but not statistically significant) among men with abnormal sperm parameters compared to normal-sperm men. Among studied polymorphisms, only the mutated allele of C677T showed statistically higher prevalence among RPL males. Although our results do not establish any connection between MTHFR epigenotypes and RPL they do highlight the impact of C677T in the pathology.

MTHFR promoter hypermethylation may lead to congenital heart defects in Down syndrome.

Altered global methylation levels revealed LINE-1 methylation in young mothers of Down syndrome (DS) compared to controls suggesting the possibility of impaired DNA methylation causing abnormal segregation of chromosome 21. Methylene Tetrahydrofolate Reductase (MTHFR) is one of the major enzymes of the folate metabolism pathway. MTHFR gene polymorphism has been associated with maternal risk for DS. Studies have revealed that increased MTHFR promoter methylation results in the reduction of MTHFR protein activity further leading to increased risk of various diseases. The aim of this study is to compare the levels of MTHFR promoter methylation in all three study groups. A total of 120 subjects were recruited for the study and was divided into the following three groups: Group I (mothers of DS without Congenital Heart Defects (CHD), n = 40); Group II (mothers of DS with CHD, n = 40); and Group III (age matched control mothers, n = 40). Genomic DNA was isolated from 2 ml peripheral blood and bisulfite treatment was done to convert all unmethylated cytosines into uracil followed by PCR amplification for MTHFR promoter region and Sanger's sequencing. Results showed that there was a two fold increase in methylated promoter region of MTHFR gene in group II compared to other groups. None of the methylation pattern was observed in the control group. MTHFR promoter methylation affects folate metabolism which is known to play a role in chromosomal breakage, abnormal chromosomal segregation and genomic instability and therefore a developmental defect in the form of congenital cardiac anomaly.

Association between methylenetetrahydrofolate reductase (MTHFR) gene promoter hypermethylation and the risk of idiopathic male infertility.

Epigenetics has become a major field of reproductive medicine after the epigenetic regulation of gene expression was discovered. The aim of this study was to find out whether or not methylenetetrahydrofolate reductase (MTHFR) gene promoter hypermethylation in the spermatozoa of men who were offered assisted reproduction is associated with idiopathic male infertility. Sperm DNAs from 40 idiopathic infertile men with normozoospermia and 40 controls consisting of healthy fertile men were isolated. Following the modification of DNAs by sodium bisulphite, the methylation status of the MTHFR gene promoter was quantified by pyrosequencing. No significant differences were observed between the clinical characteristics of patients and controls. The percentage of MTHFR promoter methylation in infertile men with normozoospermia (11%) was significantly higher than that in the healthy control (4.3%) group (p=.01). A 9.5% of methylation level was determined via receiver operator characteristic (ROC) analysis as the cut-off value. There were 21 (53%) hypermethylated men among the infertile men and 2 (5%) in the control group (p=.0001). The intragroup analysis of the infertile group did not reveal any statistically significant differences in terms of overall clinical characteristics between hyper- and normo-methylated infertile men. Our results suggest that epigenetic silencing (hypermethylation) of MTHFR could result in an elevated risk of male infertility.

Increased MTHFR promoter methylation in mothers of Down syndrome individuals

Despite that advanced maternal age at conception represents the major risk factor for the birth of a child with Down syndrome (DS), most of DS babies are born from women aging less than 35 years. Studies performed in peripheral lymphocytes of those women revealed several markers of global genome instability, including an increased frequency of micronuclei, shorter telomeres and impaired global DNA methylation. Furthermore, young mothers of DS individuals (MDS) are at increased risk to develop dementia later in life, suggesting that they might be “biologically older” than mothers of euploid babies of similar age.Mutations in folate pathway genes, and particularly in the methylenetetrahydrofolate reductase (MTHFR) one, have been often associated with maternal risk for a DS birth as well as with risk of dementia in the elderly. Recent studies pointed out that also changes in MTHFR methylation levels can contribute to human disease, but nothing is known about MTHFR methylation in MDS tissues.We investigated MTHFR promoter methylation in DNA extracted from perypheral lymphocytes of 40 MDS and 44 matched control women that coinceived their children before 35 years of age, observing a significantly increased MTHFR promoter methylation in the first group (33.3±8.1% vs. 28.3±5.8%; p=0.001). In addition, the frequency of micronucleated lymphocytes was available from the women included in the study, was higher in MDS than control mothers (16.1±8.6‰ vs. 10.5±4.3‰; p=0.0004), and correlated with MTHFR promoter methylation levels (r=0.33; p=0.006).Present data suggest that MTHFR epimutations are likely to contribute to the increased genomic instability observed in cells from MDS, and could play a role in the risk of birth of a child with DS as well as in the onset of age related diseases in those women.

Genetic and epigenetic variants in the MTHFR gene are not associated with non-Hodgkin lymphoma

The methylenetetrahydrofolate reductase (MTHFR) gene codes for the MTHFR enzyme which plays a key role in the pathway of folate and methionine metabolism. Polymorphisms of genes in this pathway affect its regulation and have been linked to lymphoma. In this study we examined whether we could detect an association between two common non-synonymous MTHFR polymorphisms, 677C>T (rs1801133) and 1298A>C (rs1801131), and susceptibility to non-Hodgkin lymphoma (NHL) in an Australian case–control cohort. We found no significant differences between genotype or allele frequencies for either polymorphisms between lymphoma cases and controls. We also explored whether epigenetic modification of MTHFR, specifically DNA methylation of a CpG island in the MTHFR promoter region, is associated with NHL using blood samples from patients. No difference in methylation levels was detected between the case and control samples suggesting that although hypermethylation of MTHFR has been reported in tumour tissues, particularly in the diffuse large B-cell lymphoma subtype of NHL, methylation of this MTHFR promoter CpG island is not a suitable epigenetic biomarker for NHL diagnosis or prognosis in peripheral blood samples. Further studies into epigenetic variants could focus on genes that are robustly associated with NHL susceptibility.

DNA methylation status of the methylenetetrahydrofolate reductase gene promoter in peripheral blood of end-stage renal disease patients

End-stage renal disease (ESRD) is one of the main causes of morbidity and mortality worldwide. DNA methylation is a major epigenetic modification of the genome that has the potential to silence gene expression. Methylenetetrahydrofolate reductase (MTHFR) gene inactivation was recognized as a predisposing factor of hyperhomocysteinemia in renal patients. The current study aimed to determine the methylation status within the MTHFR promoter region in DNA isolated from peripheral blood of ESRD patients and controls and the correlation of this methylation with the clinical and biochemical characteristics in ESRD patients. Ninety-six ESRD patients and 96 healthy ethnically, age and gender matched controls were included within the study. MTHFR promoter methylation was assessed using methylation specific polymerase chain reaction. The frequency of MTHFR methylation was significantly higher in ESRD patients than in controls (P=0.003), additionally, MTHFR methylation was associated to a decrease in estimated glomerular filtration rate, serum high-density lipoprotein cholesterol level and an increase in both serum total cholesterol and low-density lipoprotein cholesterol levels. Data generated from this study suggest the possible involvement of MTHFR promoter methylation in the pathogenesis of ESRD and support a new dimension of MTHFR inactivation.

Methylenetetrahydrofolate reductase (MTHFR) polymorphisms and promoter methylation in cervical oncogenic lesions and cancer

The aim of this study was to investigate the role of methylenetetrahydrofolate reductase (MTHFR) polymorphisms and MTHFR methylation pattern in cervical lesions development among women from Romania, a country with high prevalence of human papillomavirus (HPV) cervical infections. To achieve this goal, blood samples and cervical cytology specimens (n = 77)/tumour tissue specimens (n = 23) were investigated. As control, blood and negative cytological smears (n = 50) were used. A statistically significant association was found between T allele of C677T polymorphism and cervical lesions, heterozygote women presenting a threefold increased risk (normal/cervical lesions and tumours: wild homozygote 34/41 (0.68/0.41), heterozygote 14/51 (0.28/0.51), mutant homozygote 2/8 (0.04/0.08); OR = 3.081, P = 0.0035). Using χ square test for the control group, the HPV-negative and HPV-positive patients with cervix lesions, a significant correlation between viral infection and T allele of C677T polymorphism (P = 0.0287) was found. The MTHFR promoter was methylated in all HGSIL and tumour samples, significant differences being noted between HPV-positive samples, control group and cases of cervical dysplastic lesions without HPV DNA (P < 0. 0001) and between samples from patients with high-risk (hr)HPV versus low-risk (lr)HPV (P = 0.0026). No correlations between polymorphisms and methylation were observed. In Romania, individuals carrying T allele are susceptible for cervical lesions. MTHFR promoter methylation is associated with cervical severity lesions and with hrHPV.

Methylenetetrahydrofolate reductase gene promoter hypermethylation in semen samples of infertile couples correlates with recurrent spontaneous abortion

Is the methylation status of the methylenetetrahydrofolate reductase (MTHFR) promoter region in semen samples associated with 'recurrent spontaneous abortion' (RSA)? MTHFR promoter hypermethylation is more frequent in semen samples from RSA couples than in semen samples from infertile couples with no history of RSA (NRSA) and affects the whole sperm population significantly more often. Modifications to the MTHFR gene such as polymorphisms and promoter methylations are associated with male infertility. Retrospective cohort study of semen samples from 20 RSA couples, 147 NRSA couples and 20 fertile men between 2011 and 2012. DNA from the semen samples of RSA, NRSA and fertile men were analyzed by methylation-specific PCR amplification using primers which anneal to the methylated or unmethylated cytosine-phosphodiester bond guanine (CpG) islands within the promoter region of MTHFR. The specificity of the PCR products was assessed by DNA sequencing. The methylated MTHFR epigenotype (including samples where it co-existed with unmethylated MTHFR epigenotypes) was detected in 75% of RSA men, 54% of NRSA men and 15% of fertile men. MTHFR methylation was observed in the whole sperm population in semen samples from 55% of RSA men compared with 8% in NRSA men (P < 0.05) and 0% in fertile men (P < 0.05). DNA sequencing analysis was fully concordant with the PCR results and revealed that when MTHFR methylation occurred, CpG islands within the promoter region were 100% methylated (hypermethylation of MTHFR promoter). The relatively small sample size of RSA infertile couples. The hypermethylation of the MTHFR gene promoter should be taken into consideration as a novel putative risk factor in RSA etiology. Our institution has received an FAR research grant from the University of Ferrara, Ferrara, Italy. No competing interests declared.

MTHFR promoter hypermethylation in testicular biopsies of patients with non-obstructive azoospermia: the role of epigenetics in male infertility

The causative mechanisms of male infertility are still poorly understood. Mutations in the Methylenetetrahydrofolate reductase (MTHFR) gene have been shown to be involved in male infertility; however, other mechanisms of pathogenesis, like promoter hyper-methylation, could also play a role. Therefore, in this study we compared the methylation status of the promoter region of MTHFR in male patients with non-obstructive azoospermia (NOA) and obstructive azoospermia without anomalies of spermatogenesis. DNA from peripheral blood (PB) samples of 50 patients with NOA and 50 fertile men (controls) as well as DNA from testicular biopsies of 32 patients with NOA and five patients with obstructive azoospemia, but normal spermatogenesis, were analyzed by Methylation Specific PCR amplification using primers that hybridize to the CpG island in the promoter region of MTHFR. In PB, no differences in the methylation profile of the promoter region of MTHFR were observed between patients and controls. In testis biopsies, hyper-methylation was detected in 53% of the patients with NOA compared with 0% of patients with obstructive azoospermia (P = 0.03). These results indicate that hyper-methylation in testis DNA from NOA patients is specific and not due a general methylation defect, and suggest that epigenetic silencing of MTHFR could play a role in azoospermic infertility.

Valproic acid increases expression of methylenetetrahydrofolate reductase (MTHFR) and induces lower teratogenicity in MTHFR deficiency

Valproate (VPA) treatment in pregnancy leads to congenital anomalies, possibly by disrupting folate or homocysteine metabolism. Since methylenetetrahydrofolate reductase (MTHFR) is a key enzyme of folate interconversion and homocysteine metabolism, we addressed the possibility that VPA might have different teratogenicity in Mthfr(+/+) and Mthfr(+/-) mice and that VPA might interfere with folate metabolism through MTHFR modulation. Mthfr(+/+) and Mthfr(+/-) pregnant mice were injected with VPA on gestational day 8.5; resorption rates and occurrence of neural tube defects (NTDs) were examined on gestational day 14.5. We also examined the effects of VPA on MTHFR expression in HepG2 cells and on MTHFR activity and homocysteine levels in mice. Mthfr(+/+) mice had increased resorption rates (36%) after VPA treatment, compared to saline treatment (10%), whereas resorption rates were similar in Mthfr(+/-) mice with the two treatments (25-27%). NTDs were only observed in one group (VPA-treated Mthfr(+/+)). In HepG2 cells, VPA increased MTHFR promoter activity and MTHFR mRNA and protein (2.5- and 3.7-fold, respectively). Consistent with cellular MTHFR upregulation by VPA, brain MTHFR enzyme activity was increased and plasma homocysteine was decreased in VPA-treated pregnant mice compared to saline-treated animals. These results underscore the importance of folate interconversion in VPA-induced teratogenicity, since VPA increases MTHFR expression and has lower teratogenic potential in MTHFR deficiency.