The association between maternal methylenetetrahydrofolate reductase C677T and A1298C polymorphism and birth defects and adverse pregnancy outcomes

Association between early spontaneous abortion and homocysteine metabolism

Objective

The purpose of this study is to explore the effects of homocysteine (HCY) metabolism and related factors on early spontaneous abortion.

Methods

We conducted a hospital-based case-control study and included a total of 500 cases and 1,000 controls in Shaanxi China. Pregnant women waiting for delivery in the hospital were interviewed to report their characteristics and other relevant information during pregnancy. The unconditional Logisitic regression model was applied to assess the association between early spontaneous abortion and HCY metabolism and related factors. The multiplicative model was applied to assess the effects of interaction of HCY metabolism and related factors on early spontaneous abortion. The logit test method of generalized structural equation model (GSEM) was used to construct the pathway diagram of HCY metabolism and related factors affecting early spontaneous abortion.

Results

Folic acid supplementation and adequate folic acid supplementation during periconception were the protective factors of early spontaneous abortion (OR = 0.50, 95% CI: 0.38-0.65; OR = 0.44, 95% CI: 0.35-0.54). The serum folate deficiency, higher plasma HCY in early pregnancy, the women who carried the MTHFR 677TT genotype were the risk factors of early spontaneous abortion (OR = 5.87, 95% CI: 1.53-22.50; OR = 2.94, 95% CI: 1.14-7.57; OR = 2.32, 95% CI: 1.20-4.50). The women's educational level and maternal and child health care utilization affected the occurrence of early spontaneous abortion by influencing the folic acid supplementation during periconception. The folic acid supplementation during periconception affected the occurrence of early spontaneous abortion by influencing the level of serum folate or plasma HCY in early pregnancy. The maternal MTHFR 677 gene polymorphism affected the occurrence of early spontaneous abortion by influencing the level of serum folate in early pregnancy. In terms of the risks for early spontaneous abortion, there was multiplicative interaction between higher plasma HCY in early pregnancy, serum folate deficiency in early pregnancy and maternal MTHFR 677TT genotype (OR = 1.76, 95% CI: 1.17-4.03), and there was multiplicative interaction between higher plasma HCY and serum folate deficiency in early pregnancy (OR = 3.46, 95% CI: 2.49-4.81), and there was multiplicative interaction between serum folate deficiency in early pregnancy and maternal MTHFR 677TT genotype (OR = 3.50, 95% CI: 2.78-5.18). The above interactions are all synergistic. The occurrence risk of early spontaneous abortion was significantly increased if multiple factors existed at the same time.

Conclusion

Our study is the first time to construct the pathway of HCY metabolism and related factors affecting early spontaneous abortion, and provides a comprehensively new idea to prevent and reduce the occurrence of spontaneous abortion.

Epigenetic role of LINE-1 methylation and key genes in pregnancy maintenance

Spontaneous abortion is a pregnancy complication characterized by complex and multifactorial etiology. About 5% of childbearing women are globally affected by early pregnancy loss (EPL) and most of them experience recurrence (RPL). Epigenetic mechanisms and controlled inflammation are crucial for pregnancy maintenance and genetic predispositions may increase the risk affecting the maternal-fetal crosstalk. Combined analyses of global methylation, inflammation and inherited predispositions may contribute to define pregnancy loss etiopathogenesis. LINE-1 epigenetic regulation plays crucial roles during embryo implantation, and its hypomethylation has been associated with senescence and several complex diseases. By analysing a group of 230 women who have gone through pregnancy interruption and comparing those experiencing spontaneous EPL (n = 123; RPL, 54.5%) with a group of normal pregnant who underwent to voluntary interruption (VPI, n = 107), the single statistical analysis revealed significant lower (P < 0.00001) LINE-1 methylation and higher (P < 0.0001) mean cytokine levels (CKs: IL6, IL10, IL17A, IL23) in EPL. Genotyping of the following SNPs accounted for different EPL/RPL risk odds ratio: F13A1 rs5985 (OR = 0.24; 0.06-0.90); F13B rs6003 (OR = 0.23; 0.047-1.1); FGA rs6050 (OR = 0.58; 0.33-1.0); CRP rs2808635/rs876538 (OR = 0.15; 0.014-0.81); ABO rs657152 (OR = 0.48; 0.22-1.08); TP53 rs1042522 (OR = 0.54; 0.32-0.92); MTHFR rs1801133/rs1801131 (OR = 2.03; 1.2-3.47) and FGB rs1800790 (OR = 1.97; 1.01-3.87), although Bonferroni correction did not reach significant outputs. Principal Component Analysis (PCA) and logistic regression disclosed further SNPs positive/negative associations (e.g. APOE rs7412/rs429358; FGB rs1800790; CFH rs1061170) differently arranged and sorted in four significant PCs: PC1 (F13A, methylation, CKs); PC3 (CRP, MTHFR, age, methylation); PC4 (F13B, FGA, FGB, APOE, TP53, age, methylation); PC6 (F13A, CFH, ABO, MTHFR, TP53, age), yielding further statistical power to the association models. In detail, positive EPL risk association was with PC1 (OR = 1.81; 1.33-2.45; P < 0.0001) and negative associations with PC3 (OR = 0.489; 0.37-0.66; P < 0.0001); PC4 (OR = 0.72; 0.55-0.94; P = 0.018) and PC6 (OR = 0.61; 0.46-0.81; P = 0.001). Moreover, significant inverse associations were detected between methylation and CKs levels in the whole group (rIL10 = - 0.22; rIL17A = - 0.25; rIL23 = - 0.19; rIL6 = - 0.22), and methylation with age in the whole group, EPL and RPL subgroups (r2TOT = 0.147; r2EPL = 0.136; r2 RPL = 0.248), while VPI controls lost significance (r2VPI = 0.011). This study provides a valuable multilayer approach for investigating epigenetic abnormalities in pregnancy loss suggesting genetic-driven dysregulations and anomalous epigenetic mechanisms potentially mediated by LINE-1 hypomethylation. Women with unexplained EPL might benefit of such investigations, providing new insights for predicting the pregnancy outcome and for treating at risk women with novel targeted epidrugs.

Exome sequencing identified novel variants in three Chinese patients with 5,10-methenyltetrahydrofolate synthetase deficiency

5,10-methenyltetrahydrofolate synthetase (MTHFS) deficiency is a folate metabolism disorder known as a rare autosomal recessive neurodevelopmental disorder (MIM: #618367). With central nervous system involvements, it is mainly characterized by developmental delay, epilepsy, microcephaly, hypertonia, and cranial nerves involvement. Here, we report three new cases with MTHFS deficiency from two non-consanguineous Chinese families. All patients showed white matter dysplasia and global developmental delay, of which only patient 1 and 2 manifested tonic-clonic seizures. Moreover, patient 2 had severe eczema and patient 3 had recurrent diarrhea. Both phenotypic features are firstly found in MTHFS deficiency. Trio whole-exome sequencing and sanger sequencing were used to identify four novel variants, p.Y169Tfs*17, p.S53F, c.117+1delG, and p.E61G in the MTHFS gene. The identification of four novel pathogenic variants and varied clinical features in three affected patients expands the genotype and phenotype spectrum of MTHFS deficiency. We also reviewed all cases of MTHFS deficiency that had previously been reported. The experience of diagnosis and treatment from these cases provides us a more comprehensive understanding of this rare disease.

Association of C677T and A1298C polymorphisms of the MTHFR gene with maternal risk for Down syndrome: A meta-analysis of case-control studies

BACKGROUND

Several studies around the world support the hypothesis that genetic polymorphisms involved in folate metabolism could be related to the maternal risk for Down syndrome (DS). Most of them investigated the role of MTHFR C677T and/or A1298C polymorphisms as maternal risk factors for DS, but their results are often conflicting and still inconclusive.

METHODS

We conducted a systematic review and meta-analysis to clarify the association of MTHFR C677T and/or A1298C polymorphisms with the maternal risk of DS. Our search strategy selected 42 eligible case control studies for a total of 4131 case mothers and 5452 control mothers. The Newcastle-Ottawa Scale was used to assess the methodological quality of the selected studies. To assess the confidence of statistically significant associations we applied false positive report probability test, and we performed the trial sequential analysis to minimize the type I error and random error.

RESULTS

We observed significant associations between the MTHFR C677T polymorphism and maternal risk for DS for each of the genetic models investigated (dominant, recessive, codominant, and allelic contrast). Subgroup analysis by region revelated significant association in the Asian population for all the genetic models investigated. Significant associations were also found for certain genetic models in North American, South American, and Middle Eastern populations, while no association was observed in Europeans. The MTHFR A1298C polymorphism did not show any association with the maternal risk of DS, either alone or in combination with the C677T one. The results of false positive report probability to verify the confidence of a significant association suggest that the association between the MTHFR C677T polymorphism and the maternal risk for DS is noteworthy, with high confidence in Asians.

CONCLUSION

The results of this meta-analysis support that the MTHFR C677T polymorphism, but not the A1298C one, is associated with the maternal risk for DS. Further studies are required to better characterize the contribution of gene-gene and gene-nutrient interactions as well as those of other regional or ethnic factors that could explain the observed different effect size in different populations.

The Proper Diagnosis of Thrombophilic Status in Preventing Fetal Growth Restriction

Fetal growth restriction is an important part of monitoring a pregnancy. Because guidelines or diagnostic criteria for either minor or major thrombophilia are scarce, this systematic review aims to summarize the present knowledge in the field. We performed the CRD42022376006 protocol in Prospero with a systematic literature search in PubMed and Web of Science databases and included original full-text articles (randomized control trials and clinical trials) from the last 10 years, published in English, and with the "thrombophilia AND (pregnancy OR diagnostic criteria) AND fetal growth restriction" criteria. After two researchers extracted the articles of interest, they were assessed using the Newcastle-Ottawa Scale and eight articles were included. The elements from the thrombophilia diagnostic predict IUGR, factor V Leiden mutation, MTHFR C667T mutation, protein S deficiency, antithrombin deficiency, factor VII polymorphism, and antiphospholipid antibodies, while the association of protein C, PAI-1 and certain combinations of mutations are still under debate and require the collection of more data. The present systematic review provides an extensive picture of the actual knowledge about thrombophilia diagnosis and its links with pregnancy complications, such as intrauterine growth restriction, despite its limitation in the inclusion of other actually debated disorders such as PAI-1 mutation, protein C deficiency and other thrombophilia types.

Association of MTHFR 677C>T polymorphism with pregnancy outcomes in IVF/ICSI-ET recipients with adequate synthetic folic acid supplementation

Methylenetetrahydrofolate reductase (MTHFR) genetic polymorphism rs1801133 (677C>T) will decrease the utilization of folate. Folate deficiency and its resulting homocysteine (HCY) accumulation can impair female fertility. Folic acid (FA) supplementation is necessary in pregnant women who are undergoing in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) - embryo transfer (ET), and especially in women with MTHFR rs1801133 C-to-T mutations. At present, affordable and accessible synthetic FA is mainly used. However, some studies have suggested that 5-methylenetetrahydrofolate (5-MTHF), a type of active FA, may be more suitable for women with the MTHFR 677C>T polymorphism, since it is safer and more effective. This retrospective study aimed to evaluate whether the MTHFR rs1801133 gene polymorphism is related to the pregnancy outcomes of IVF/ICSI-ET recipients after sufficient supplementation with FA instead of 5-MTHF. Data on 692 women undergoing IVF/ICSI-ET and taking adequate FA were collected. Participant characteristics were compared using the Kruskal-Wallis test and Pearson chi-square test. Logistic regressions were used to calculate the odds ratio (OR) and 95% confidence interval (95% CI), after adjusting for age, BMI, method of fertilization, method of embryo transfer and number of embryos transferred. An additive model (T/T vs. C/C), dominant model (C/T + T/T vs. C/C), and recessive model (T/T vs. C/T + C/C) were evaluated. Analysis revealed that MTHFR rs1801133 in IVF/ICSI-ET women with adequate FA supplementation was not associated with the pregnancy rate but with age (OR = 0.91, 95% CI = 0.88, 0.94, P < 0.001) and BMI (OR = 0.95, 95% CI = 0.90, 0.997, P = 0.037). In 349 clinically pregnant women, no association of the MTHFR 677C>T with pregnancy outcomes was found in the additive model, dominant model, or recessive model. Of the 273 women with positive pregnancy outcomes, 34 had a preterm delivery. MTHFR 677C>T was not associated with a preterm delivery after adjusting for age and BMI. The current results indicated that MTHFR polymorphism rs1801133 was not related to the pregnancy rate or pregnancy outcomes of women undergoing IVF/ICSI-ET with adequate synthetic FA supplementation, suggesting that simple supplementation with less expensive and readily available FA, rather than expensive 5-MTHF, appeared to be appropriate.

Genetic Background of Fetal Growth Restriction

Fetal growth restriction (FGR) is one of the most formidable challenges in present-day antenatal care. Pathological fetal growth is a well-known factor of not only in utero demise in the third trimester, but also postnatal morbidity and unfavorable developmental outcomes, including long-term sequalae such as metabolic diseases, diabetic mellitus or hypertension. In this review, the authors present the current state of knowledge about the genetic disturbances responsible for FGR diagnosis, divided into fetal, placental and maternal causes (including preeclampsia), as well as their impact on prenatal diagnostics, with particular attention on chromosomal microarray (CMA) and noninvasive prenatal testing technique (NIPT).

The association between 5, 10 - methylenetetrahydrofolate reductase and the risk of unexplained recurrent pregnancy loss in China: A Meta-analysis

BACKGROUD

To analyze the correlation between gene polymorphisms of 5,10- methylenetetrahydrofolate reductase (MTHFR) and risk of unexplained recurrent pregnancy loss (URPL) in Chinese women.

METHODS

Eligible studies were searched in Pubmed, Embase, Web of Science, Wanfang, and China National Knowledge Infrastructure (CNKI) databases. Established inclusion criteria were used to screening articles, subsequently evaluate the quality of the included studies, Stata 16.0 PM and RevMan 5.3 software were conducted for meta-analysis. The pooled odds ratio (OR) with 95% confidence interval (CI) was determined to assess the relationship between MTHFR and risk of URPL in Chinese women.

RESULTS

For MTHFR C677T, fifty studies were included, involving 6677 URPL cases and 8111 controls. The overall results showed that MTHFR C677T was significantly correlated with URPL risk, especially in the homozygous model (TT vs CC; OR 3.06; 95% CI 2.56-3.66). For MTHFR A1298C, twenty-first studies were included, involving 3439 URPL cases and 3155 controls. The results showed that MTHFR A1298C was also significantly correlated with URPL risk in recessive (CC vs AC + AA; OR 1.55; 95% CI 1.25-1.93) and homozygous (CC vs AA; OR 1.53; 95% CI 1.22-1.91) models. In addition, sub-group results showed that no significant difference between north and south China populations in the MTHFR gene polymorphisms and URPL risk. Of note, the patients carrying MTHFR C677T and MTHFR A1298C joint mutants had no synergistic effect (OR 2.71; 95% CI 0.84-8.70) on the occurrence of URPL compared with the wild-type homozygous genotype (MTHFR 677CC/ MTHFR 1298AA).

CONCLUSION

Studies included in this meta-analysis suggested that MTHFR 677T allele and 677TT genotype and MTHFR 1298CC genotype were both associated with URPL; testing MTHFR C677T gene polymorphism was a more appropriate target compared with other mutations in the prediction of URPL.

MTHFR 1298A>C Substitution is a Strong Candidate for Analysis in Recurrent Pregnancy Loss: Evidence from 14,289 Subjects

We undertook meta-analyses on MTHFR 1298A>C substitution for critically evaluating its association with recurrent pregnancy loss (RPL). MTHFR genotype data for 5888 cases and 8401 controls from 39 studies were pooled to perform this meta-analyses. Genotype data were screened, scrutinized, pooled, analysed and subjected to sensitivity analysis to carefully evaluate the association between MTHFR 1298A>C and recurrent pregnancy loss. Genetic associations were sought using dominant, recessive and co-dominant models of genetic testing with odds ratio and 95% Confidence interval (CI) as the effect measures. Further analyses were undertaken by classifying the studies into Caucasian and East Asian sub-groups. Genetic heterogeneity was tested before pooling the data across studies. For assessing publication bias, Egger's intercept test was undertaken. We found a significant association of 1298A>C substitution with increased risk of RPL in the dominant (P=0.000; OR = 1.58; 95% CI =1.25-1.99) as well as recessive (P=0.000; OR = 1.66; 95% CI =1.25-2.20) models. In sub-group analysis, we observed a significant association of the polymorphism with RPL in the Caucasian populations using dominant (P=0.000; OR = 1.98; 95% CI =1.42-2.76) and recessive (P=0.000; OR = 2.20; 95% CI =1.49-3.24) models. However, this substitution showed no association with RPL in the East Asian populations (P=0.149; OR = 1.187; 95% CI =0.94-1.50). MTHFR 1298A>C substitution shows association with the risk of recurrent pregnancy loss. The association is in a population-specific manner with the substitution being a strong risk factor only in the Caucasian populations.

Association Between Folate and Health Outcomes: An Umbrella Review of Meta-Analyses

Background: There is no study that has systematically investigated the breadth and validity of the associations of folate and multiple health outcomes. We aimed to evaluate the quantity, validity, and credibility of evidence regarding associations between folate and multiple health outcomes by using umbrella review of meta-analysis. Methods: We searched the MEDLINE, EMBASE, and Cochrane Library databases from inception to May 20, 2018, to identify potential meta-analyses that examined the association of folate with any health outcome. For each included meta-analysis, we estimated the summary effect size and their 95% confidence interval using the DerSimonian and Laird random-effects model. We used the AMSTAR 2 (A Measurement Tool to Assess Systematic Reviews) to assess methodological quality and the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation working group classification) to assess the quality of evidence for each outcome included in the umbrella review. Results: Overall, 108 articles reporting 133 meta-analyses of observational studies and 154 meta-analyses of randomized controlled trials (RCTs) were included in the study. Among them, 108 unique exposure-outcome-population triplets (referred to as unique meta-analyses hereafter) of RCTs and 87 unique meta-analyses of observational studies were reanalyzed. Beneficial effects of folate were observed in the all-cause mortality rate and in a number of chronic diseases, including several birth/pregnancy outcomes, several cancers, cardiovascular disease and metabolic-related outcomes, neurological conditions, and several other diseases. However, adverse effects of folate were observed for prostate cancer, colorectal adenomatous lesions, asthma or wheezing, and wheezing as an isolated symptom and depression. Conclusions: Current evidence allows for the conclusion that folate is associated with decreased risk of all-cause mortality and a wide range of chronic diseases. However, folate may be associated with an increased risk of prostate cancer. Further research is warranted to improve the certainty of the estimates.

Association of MTHFR 677C>T polymorphism with IUGR and placental abruption risk: A systematic review and meta-analysis

OBJECTIVE

The effects of the MTHFR 677C > T polymorphism on the intrauterine growth restriction (IUGR) and placental abruption risk have been evaluated in some studies. However, those studies results were conflicting and ambiguous. Therefore, we carried out the current meta-analysis to evaluate the association of MTHFR 677C > T polymorphism with risk of IUGR and placental abruption from all eligible studies.

METHODS

An electronic search of the PubMed, Embase, Scopus and CNKI databases was performed up to February 25, 2020.

RESULTS

A total of 25 case-control studies including eight studies with 687 cases and 2336 controls for IUGR and 17 studies with 1574 cases and 5758 controls for placental abruption were selected. The analysis results indicated that MTHFR 677C > T polymorphism was associated with an increased risk of IUGR and placental abruption in global population. When stratified by ethnicity a significant association between the MTHFR 677C > T polymorphism and IUGR risk was found in Caucasians and Africans. However, there was no a significant association between the MTHFR 677C > T polymorphism and placental abruption risk by ethnicity.

CONCLUSIONS

Our pooled data indicated that the MTHFR 677C > T polymorphism might play a role in development of IUGR and placental abruption.

The Folate Concentration and/or Folic Acid Metabolites in Plasma as Factor for COVID-19 Infection

Pregnant women appear to be more susceptible to infectious diseases than women in reproductive age. According to the California Department of Public Health pregnant women were 9.6-folds more likely to be hospitalized during the 2009 influenza outbreak when compared to non-pregnant women in reproductive age. In contrast, it was reported that of 16,749 COVID-19 patients that were hospitalized in the UK, the probability for pregnant women to require in-patient care due to infection by SARS-CoV-2 was 0.95 versus non-pregnant women. Therefore 9.6/0.95 = 10.10, which brings us to the conclusion that pregnant women are 10.10-folds less likely to be hospitalized for a SARS-CoV-2 infection than for the 2009 H1N1 pandemic. Folic acid supplementation during pregnancy could be the factor that is protecting these patients against SARS-CoV-2 infection. Two independent papers that used informatic simulation proved that folic acid reduced the replication of this virus. One of them showed that folic acid inhibits the furin protease which the virus needs in order to enter its host cell, while the other one explained that folic acid inactivates protease 3CL pro , a protein that the virus needs to replicate. Nonetheless the probability that folic acid blocks two different proteins is very low, therefore the mechanism by which folic acid has apparently protected pregnant women during the COVID-19 pandemic has not been determined.

Genetic and epigenetic MTHFR gene variants in the mothers of attention-deficit/hyperactivity disorder affected children as possible risk factors for neurodevelopmental disorders

Aim: To assess promoter methylation levels, gene expression levels and 677C>T/1298A>C genotype and allele frequencies of the MTHFR gene in 45 mothers of attention-deficit/hyperactivity disorder affected child/children (ADHDM) and compare it with age matched healthy control mothers (HCM). Materials & methods: High resolution melting analysis, quantitative real time PCR and PCR-RFLP were performed to assess methylation, gene expression and genotyping, respectively. Significance between ADHDM and HCM was assessed by linear (methylation and gene expression) and logistic regression (genotypes). Results: MTHFR gene expression levels were significantly higher in the ADHDM compared with the HCM group (adj-p < 7.7E-04). No differences in MTHFR promoter methylation level and 677C>T/1298A>C genotype frequencies were detected between ADHDM and HCM. Conclusion: We observed increased MTHFR expression levels not resulting from promoter methylation changes in ADHDM respect to HMC, potentially contributing to the ADHD condition in their children and deserving further investigation.

MTHFR and F5 genetic variations have association with preeclampsia in Pakistani patients: a case control study

BACKGROUND

To study the role of single nucleotide variants (SNVs) of genes related to preeclampsia in Pakistani pregnant women.

METHODS

After ethical approval and getting informed consent; 250 pregnant women were enrolled and equally divided into two groups (125 preeclamptic cases and 125 normotensive pregnant women). Demographic details and medical history were recorded, and 10 ml blood sample was obtained for DNA extraction. The tetra-primer amplification refractory mutation system (ARMS) assays were developed for assessing the variants of three preeclampsia related genes; F5, MTHFR and VEGFA. An association of six SNVs; F5:c.1601G > A (rs6025), F5:c.6665A > G (rs6027), MTHFR: c.665C > T (rs1801133), MTHFR: c.1286A > C (rs1801131), VEGFA: c.-2055A > C (rs699947) and VEGFA: c.*237C > T (rs3025039) with preeclampsia was determined by using different genetic models.

RESULTS

Genotyping of the SNVs revealed that patients with MTHFR:c.665C > T, have increased susceptibility to preeclampsia (CT versus CC/TT: OR = 2.79, 95% CI = 1.18-6.59; P* = 0.046 and CT/TT vs CC: OR = 2.91, 95% CI = 1.29-6.57; P* = 0.0497, in overdominant and dominant models, respectively), whereas F5:c.6665A > G, (A/G vs AA/GG: OR = 0.42, 95% CI = 0.21-0.84; P* = 0.038 in overdominant model) and MTHFR:c.1286A > C, (CC versus AA: OR = 0.36, 95% CI = 0.18-0.72; P* = 0.0392 in codominant model) have significantly decreased risk for preeclampsia. F5:c.1601G > A, VEGFA: c.-2055A > C and VEGFA: c.*237C > T variants revealed no relationship with the disease.

CONCLUSION

This is the first case control study describing the protective role of F5:c.6665A > G against preeclampsia in any world population. In addition, the present study confirmed the association and role of MTHFR gene variations in the development of preeclampsia in Pakistani patients. Further genetic studies may be required to better understand the complex genetic mechanism of SNVs in preeclampsia related genes in pregnant women.

Association of Polymorphisms in Genes Involved in One-Carbon Metabolism with MTHFR Methylation Levels

Methylenetetrahydrofolate reductase (MTHFR) is a pivotal enzyme in the one-carbon metabolism, a metabolic pathway required for DNA synthesis and methylation reactions. MTHFR hypermethylation, resulting in reduced gene expression, can contribute to several human disorders, but little is still known about the factors that regulate MTHFR methylation levels. We performed the present study to investigate if common polymorphisms in one-carbon metabolism genes contribute to MTHFR methylation levels. MTHFR methylation was assessed in peripheral blood DNA samples from 206 healthy subjects with methylation-sensitive high-resolution melting (MS-HRM); genotyping was performed for MTHFR 677C>T (rs1801133) and 1298A>C (rs1801131), MTRR 66A>G (rs1801394), MTR 2756A>G (rs1805087), SLC19A1 (RFC1) 80G>A (rs1051266), TYMS 28-bp tandem repeats (rs34743033) and 1494 6-bp ins/del (rs34489327), DNMT3A -448A>G (rs1550117), and DNMT3B -149C>T (rs2424913) polymorphisms. We observed a statistically significant effect of the DNMT3B -149C>T polymorphism on mean MTHFR methylation levels, and particularly CT and TT carriers showed increased methylation levels than CC carriers. The present study revealed an association between a functional polymorphism of DNMT3B and MTHFR methylation levels that could be of relevance in those disorders, such as inborn defects, metabolic disorders and cancer, that have been linked to impaired DNA methylation.

Molecular mechanisms of congenital heart disease in down syndrome

Down syndrome (DS), as a typical genomic aneuploidy, is a common cause of various birth defects, among which is congenital heart disease (CHD). 40-60% neonates with DS have some kinds of CHD. However, the molecular pathogenic mechanisms of DS associated CHD are still not fully understood. This review summarizes available studies on DS associated CHD from seven aspects so as to provide a crucial and updated overview of what we known so far in this domain.