Association between 5, 10-methylenetetrahydrofolate reductase (MTHFR) polymorphisms and congenital heart disease: A meta-analysis

Environmental and Genetic Risk Factors of Congenital Anomalies: an Umbrella Review of Systematic Reviews and Meta-Analyses

BACKGROUND

The prevalence of congenital anomalies in newborns in South Korea was 272.9 per 100,000 in 2005, and 314.7 per 100,000 in 2006. In other studies, the prevalence of congenital anomalies in South Korea was equivalent to 286.9 per 10,000 livebirths in 2006, while it was estimated 446.3 per 10,000 births during the period from 2008 to 2014. Several systematic reviews and meta-analyses analyzing the factors contributing to congenital anomalies have been reported, but comprehensive umbrella reviews are lacking.

METHODS

We searched PubMed, Google Scholar, Cochrane, and EMBASE databases up to July 1, 2019, for systematic reviews and meta-analyses that investigated the effects of environmental and genetic factors on any type of congenital anomalies. We categorized 8 subgroups of congenital anomalies classified according to the 10th revision of the International Statistical Classification of Diseases (ICD-10). Two researchers independently searched the literature, retrieved the data, and evaluated the quality of each study.

RESULTS

We reviewed 66 systematic reviews and meta-analyses that investigated the association between non-genetic or genetic risk factors and congenital anomalies. Overall, 269 associations and 128 associations were considered for environmental and genetic risk factors, respectively. Congenital anomalies based on congenital heart diseases, cleft lip and palate, and others were associated with environmental risk factors based on maternal exposure to environmental exposures (air pollution, toxic chemicals), parental smoking, maternal history (infectious diseases during pregnancy, pregestational and gestational diabetes mellitus, and gestational diabetes mellitus), maternal obesity, maternal drug intake, pregnancy through artificial reproductive technologies, and socioeconomic factors. The association of maternal alcohol or coffee consumption with congenital anomalies was not significant, and maternal folic acid supplementation had a preventive effect on congenital heart defects. Genes or genetic loci associated with congenital anomalies included MTHFR, MTRR and MTR, GATA4, NKX2-5, SRD5A2, CFTR, and 1p22 and 20q12 anomalies.

CONCLUSION

This study provides a wide perspective on the distribution of environmental and genetic risk factors of congenital anomalies, thus suggesting future studies and providing health policy implications.

Angiotensin-converting enzyme insertion/deletion (ACE I/D) gene polymorphism in Egyptian children with congenital heart disease

BACKGROUND

Congenital heart diseases (CHDs) are the leading cause of infant deaths worldwide. The relationship between angiotensin-converting enzyme (ACE) gene polymorphism and CHDs is not clear. The aim of this work is to assess the presence of an association between ACE I/D polymorphism and CHD in Egyptian population.

SUBJECTS AND METHODS

Seventy CHD cases and 70 controls were incorporated in this study. DNA was isolated from their peripheral blood, and then ACE I/D gene polymorphism was tested by polymerase chain reaction (PCR).

RESULTS

There was no significant difference among the frequencies of the DD, II, and DI genotypes in patients and controls (26 [37.1%], 37 [53.3%], and 4 [5.7%], 5 [6.7%]), 40 (57.2%), 28 (40%), respectively (p value = 1 and OR [95% CI] = 1.1). There was no significant difference between D allele (DD + DI) and II genotype distribution among patients and controls (p value = 1 and OR [95% CI] = 1.2 [0.3-2.9]). Moreover, there was no difference between I allele (II + DI) and DD frequency (p value = 0.2 and OR [95% CI] = 0.6 [0.3-1.2]).

CONCLUSIONS

ACE I/D gene polymorphism might not be a risk factor of CHD in Egyptian children. Additional widespread studies are needed to affirm these data.

Rare Copy Number Variations Might Not be Involved in the Molecular Pathogenesis of PA-IVS in an Unselected Chinese Cohort

Congenital heart defect (CHD) is one of the most common birth defects in China, while pulmonary atresia with intact ventricular septum (PA-IVS) is the life-threatening form of CHD. Numerous previous studies revealed that rare copy number variants (CNVs) play important roles in CHD, but little is known about the prevalence and role of rare CNVs in PA-IVS. In this study, we conducted a genome-wide scanning of rare CNVs in an unselected cohort consisted of 54 Chinese patients with PA-IVS and 20 patients with pulmonary atresia with ventricular septal defect (PA-VSD). CNVs were identified in 6/20 PA-VSD patients (30%), and three of these CNVs (15%) were considered potentially pathogenic. Two pathogenic CNVs occurred at a known CHD locus (22q11.2) and one likely pathogenic deletion located at 13q12.12. However, no rare CNVs were detected in patients with PA-IVS. Potentially pathogenic CNVs were more enriched in PA-VSD patients than in PA-IVS patients (p = 0.018). No rare CNVs were detected in patients with PA-IVS in our study. PA/IVS might be different from PA/VSD in terms of genetics as well as anatomy.

MTHFR C677T polymorphism analysis: A simple, effective restriction enzyme-based method improving previous protocols

Background

5,10‐Methylentetrahydrofolate reductase (MTHFR) C677T polymorphism is one of the most studied genetic variations in the human genome. Polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) is one of the most used techniques to characterize the point mutations in genomic sequences because of its suitability and low cost. The most widely used method for the MTHFR C677T polymorphism characterization was developed by Frosst et al. (1995) but appears to have some technical limitations. The aim of this study was to propose a novel PCR‐RFLP method for the detection of this polymorphism.

Methods

In order to retrieve all published articles possibly describing any PCR‐RFLP methods useful to analyze MTHFR C677T polymorphism, we performed systematic queries on PubMed, using a combination of Boolean operators (AND/OR) and MeSH terms. Amplify software was used in order to design a new primer pair following the optimal standard criteria. Primer‐BLAST software was used to check primer pair's biological specificity.

Results

The analysis of previous literature showed that PCR‐RFLP method remains the most used technique. None of the 108 primer pairs described was ideal with regard to main accepted primer pair biochemical technical parameters. The new primer pair amplifies a DNA‐fragment of 513 base pair (bp) that, in the presence of the polymorphism, is cut by Hinf I enzyme in two pieces of 146 bp and 367 bp and clearly visible on 2% agarose gel. The level of expertise and the materials required are minimal and the protocol takes one day to carry out.

Conclusion

Our original PCR‐RFLP strategy, specifically designed to make the analysis optimal with respect to PCR primers and gel analysis, fits the ideal criteria compared to the widely used strategy by Frosst et al (1995) as well as any other PCR‐RFLP strategies proposed for MTHFR C677T polymorphism genotyping to date.

Methylenetetrahydrofolate Reductase C677T Gene Polymorphism as Risk Factor for Psoriasis in Saudis

Methylenetetrahydrofolate reductase (MTHFR) has been linked with the etiopathogenesis of psoriasis with inconsistent results. Methylenetetrahydrofolate reductase C677T polymorphism was evaluated in 106 Saudi psoriasis vulgaris patients and 280 matched healthy controls using PCR-RFLP (restriction fragment length plymorphism) technique. The cardiovascular risk factors were also compared in cases and controls. Allele T and genotypes CT and TT were found to be increased while allele C and genotype CC significantly decreased in psoriasis patients as compared with controls (P < .001). These results showed that the T-allele and T-containing genotypes (TT, CT) of MTHFR C677T are significantly linked with psoriasis susceptibility while C-allele and CC genotype are protective for it. Body mass index, fasting glucose, total cholesterol, low-density lipoprotein, triglycerides, and C-reactive protein, known markers for cardiovascular diseases, were found to be significantly elevated in the patient group as compared with the controls. It is concluded that the MTHFR C677T polymorphism increases psoriasis risk in Saudi patients.

Meta-Prediction of MTHFR Gene Polymorphism and Air Pollution on the Risks of Congenital Heart Defects Worldwide: A Transgenerational Analysis

Congenital heart disease (CHD) is the leading cause of death in children, and is affected by genetic and environmental factors. To investigate the association of air pollution with methylene-tetrahydrofolate reductase (MTHFR) polymorphisms and the risk of CHD, we included 58 study groups of children and parents, with 12,347 cases and 18,106 controls worldwide. Both MTHFR C677T (rs 1801133) and A1298C (rs 1801131) gene polymorphisms were risks for CHD in children with transgenerational effects from their parents. Countries with greater risks of CHD with a pooled risk ratio (RR) > 2 from MTHFR 677 polymorphisms included Germany, Portugal, China, and Egypt for children; and Brazil, Puerto Rico, Mexico, China, and Egypt for mothers. Whereas, countries with greater risk of CHD with RR > 2 from MTHFR 1298 polymorphisms included Taiwan, Turkey, and Egypt for children; and Brazil, China, and Egypt for mothers. Additionally, meta-prediction analysis revealed that the percentages of MTHFR 677TT and TT plus CT polymorphisms together were increased in countries with higher levels of air pollution, with a trend of increased CHD risks with higher levels of air pollution for children (p = 0.07). Our findings may have significant implications for inflammatory pathways in association with MTHFR polymorphisms and future intervention studies to correct for folate-related enzyme deficits resulted from MTHFR polymorphisms to prevent CHDs for future generations.

Association of Cx43 rs2071166 polymorphism with an increased risk for atrial septal defect

Atrial septal defect is one of the most common CHD. The pathogenesis of atrial septal defect still remains unknown. Cx43 is the most prevalent connexin in the mammalian heart during development. Its genetic variants can cause several CHD. The aim of our study was to investigate the association of genetic variations of the Cx43 with sporadic atrial septal defect. A total of 450 paediatric patients were recruited, including 150 cases with atrial septal defect and 300 healthy controls. The promoter region of Cx43 was analysed by sequencing after polymerase chain reaction. All data were analysed by using the Statistic Package for Social Science 19.0 software. The frequency of the single nucleotide polymorphism rs2071166 was significantly higher in atrial septal defect cases than in healthy controls. The CC genotype at rs2071166 site in Cx43 was correlated with an increased risk for atrial septal defect (p<0.0001, odds ratio=3.891, 95% confidence interval 1.948-7.772) and the C allele was positively correlated with atrial septal defect (p=0.007, odds ratio=1.567, 95% confidence interval 1.129-2.175). In conclusion, our results confirmed that rs2071166 in Cx43 may be relevant with an increased atrial septal defect risk.

A Targeted, Next-Generation Genetic Sequencing Study on Tetralogy of Fallot, Combined With Cleft Lip and Palate

Background:

Congenital heart disease (CHD), plus cleft lip and palate (CLP) are currently the most common types of structural malformation in infants. Many genes have been investigated for their involvement in CHD with CLP. Targeted next-generation sequencing can analyze large amounts of genetic information rapidly, and thus address this question.

Methods:

The authors designed a targeted, next-generation sequencing gene panel for 455 genes previously implicated in CHD or CLP. A single-subject patient served as a genetic source. Variants that affect protein-coding regions were classified into silico and filtered through databases, such as the Single-Nucleotide Polymorphism Database, Yan Huang, the Exome Sequencing Project, and the 1000 Genomes Project. The authors then predicted the function of gene mutations by PolyPhen-2, SIFT, and Mutation Taster. To confirm the related disease genes, the authors surveyed relevant literature on PubMed. Finally, the variant was verified by Sanger sequencing.

Results:

A total of 1520 mutations were successfully found in a patient using combined tetralogy of Fallot and CLP by the targeted next-generation sequencing. However, there were 6 gene mutations (ZNF528, PVRL2, methylenetetrahydrofolate reductase [MTHFR], EVC2, DAND5, CCDC39) that were not found on Single-Nucleotide Polymorphism Database, Yan Huang, Exome Sequencing Project, and 1000 Genomes Project. Four genes (ZNF528, PVRL2, EVC2, CCDC39) were all predicted to be “tolerated,” “benign,” or “polymorphic” by SIFT, PolyPhen-2, and Mutation Taster. The DAND5 gene was predicted to be “possibly damaging” and “disease causing” respectively by PolyPhen-2 and Mutation Taster, but the SIFT program predicted this mutation to be “tolerated.” Likewise, the MTHFR gene mutation was predicted to be “damaging,” “possibly damaging,” and “disease causing” respectively by SIFT, PolyPhen-2, and Mutation Taster. There is no relevant report about MTHFR gene mutation (c.G586A, p.G196S) on PubMed.

Conclusion:

Using targeted, next-generation sequencing technology, the authors identified for the first time a mutation (c.G586A, p.G196S) in the MTHFR gene as a possible cause of TOF and CLP in a patient.

Folate, vitamin B12, homocysteine and polymorphisms in folate metabolizing genes in children with congenital heart disease and their mothers

BACKGROUND/OBJECTIVES

The objective of the study was to assess the role of variations in serum folate, vitamin B12, homocysteine and the presence of genetic polymorphisms as risk factors for congenital heart disease (CHD) in children.

SUBJECTS/METHODS

A total of 32 children with CHD, and their mothers and 32 normal children and their mothers formed the study and control groups, respectively. Serum folate, vitamin B12 and homocysteine as well as genetic polymorphisms MTHFR C677→︀T, MTHFR A1298→︀C, MTR A2756→︀G and MTRR A66→︀G were assessed.

RESULTS

Low serum folate and genetic polymorphisms MTHFR C677→︀T and MTRR A66→︀G among children and their mothers and high homocysteine among mothers were noted as risk factors for CHD (P<0.05). Vitamin B12 levels were normal and showed no association. Presence of MTHFR C677→︀T and MTRR A66→︀G, both concurrently among children as well as mothers and simultaneously among mother-child pairs, showed several fold increase in the risk for CHD. On multivariate analysis, the risk factors noted for CHD were presence of MTHFR C677→︀T among children and their mothers and MTRR A66→︀G among mothers. Analyses for nutrient-gene interaction revealed significant associations between low serum folate and high serum homocysteine levels, and the presence of selected genetic polymorphisms.

CONCLUSIONS

Low serum folate, high homocysteine and presence of selected genetic polymorphisms among children and their mothers were noted as risk factors for CHD. Nutrient-gene interaction being a modifiable risk factor, the study recommends the use of peri-conceptional folate supplementation with vitamin B12 sufficiency for primary prevention of CHD.

The role of histone modification and a regulatory single-nucleotide polymorphism (rs2071166) in the Cx43 promoter in patients with TOF

Abnormal level of Cx43 expression could result in CHD. Epigenetic modification and disease-associated, non-coding SNPs might influence gene transcription and expression. Our study aimed to determine the role of histone modification and an rSNP (rs2071166) in the Cx43 promoter in patients with TOF. Our results indicate that H3K18ac bind to Cx43 promoter and that their levels are reduced in TOF patients relative to controls. The relationship between the non-coding SNP in the Cx43 gene and TOF patients was evaluated in 158 patients and 300 controls. The C allele of rs2071166 was confirmed to result in an increased risk of TOF (OR = 1.586, 95%CI 1.149–2.189). Individuals with the CC genotype at rs2071166 also showed a significant susceptibility to TOF (OR = 2.961, 95%CI 1.452–6.038). The mRNA level in TOF who were CC genotype was lower than that in patients with the AA/AC genotype. Functional analysis in cells and transgenic zebrafish models showed that rs2071166 decreased the activity of the promoter and could block the interaction between RXRα and RARE. This is the first study to illustrate that epigenetic modification and an rSNP in the Cx43 promoter region play a critical role in TOF by impacting the transcriptional activity and expression level of Cx43.

A Genetic Variant in FIGN Gene Reduces the Risk of Congenital Heart Disease in Han Chinese Populations

Congenital heart disease (CHD) is one of the most common birth anomalies worldwide. Folate deficiency is an independent risk factor for CHD. Genome-wide association studies (GWAS) revealed that human folate level could be significantly influenced by fidgetin (FIGN), methylenetetrahydrofolate reductase (MTHFR), prickle homolog 2 (PRICKLE2), synaptotagmin 9 (SYT9), gamma-aminobutyric acid B receptor 2 (GABBR2), and alkaline phosphatase (ALPL) genes. The association between the above-mentioned six variants and CHD was examined in the two independent case-control studies in a total of 868 CHD patients and 931 healthy controls. Our results showed that the G > C (rs2119289) variant in intron 4 of FIGN led to a significant reduction of CHD susceptibility in both the separate and combined case-control studies (allele distribution P < 0.001, genotype distribution P < 0.001). Specifically, by analyzing the combined samples, we observed that the risks of CHD in individuals carrying the heterozygous G/C and homozygous C/C genotypes were reduced by 45% (adjusted OR 0.55, 95% CI 0.47-0.67) and 66% (adjusted OR 0.34, 95% CI 0.23-0.50), respectively, in comparison with individuals carrying the wild-type G/G genotype. Our findings have demonstrated that the C allele of variant rs2119289 of FIGN gene is an important genetic marker for decreased CHD risk. Considering that the rs2119289 of FIGN gene is related to the appropriate folate level, FIGN might play an important role in CHD by upregulating plasma folate concentration during embryo heart development. This work provides a new insight for risk assessment of CHD.

Advances in molecular genetics for pulmonary atresia

Genetic and environmental factors may be similar in certain CHD. It has been widely accepted that it is the cumulative effect of these risk factors that results in disease. Pulmonary atresia is a rare type of complex cyanotic CHD with a poor prognosis. Understanding the molecular mechanism of pulmonary atresia is essential for future diagnosis, prevention, and therapeutic approaches. In this article, we reviewed several related copy number variants and related genetic mutations, which were identified in patients with pulmonary atresia, including pulmonary atresia with ventricular septal defect and pulmonary atresia with intact ventricular septum.

Genetics of Congenital Heart Disease: Past and Present

Congenital heart disease is the most common congenital anomaly, representing an important cause of infant morbidity and mortality. Congenital heart disease represents a group of heart anomalies that include septal defects, valve defects, and outflow tract anomalies. The exact genetic, epigenetic, or environmental basis of congenital heart disease remains poorly understood, although the exact mechanism is likely multifactorial. However, the development of new technologies including copy number variants, single-nucleotide polymorphism, next-generation sequencing are accelerating the detection of genetic causes of heart anomalies. Recent studies suggest a role of small non-coding RNAs, micro RNA, in congenital heart disease. The recently described epigenetic factors have also been found to contribute to cardiac morphogenesis. In this review, we present past and recent genetic discoveries in congenital heart disease.

Evaluation of High Resolution Melting for MTHFR C677T Genotyping in Congenital Heart Disease

Background

High resolution melting (HRM) is a simple, flexible and low-cost mutation screening technique. The methylenetetrahydrofolate reductase (MTHFR) gene encoding a critical enzyme, potentially affects susceptibility to some congenital defects like congenital heart disease (CHD). We evaluate the performance of HRM for genotyping of the MTHFR gene C677T locus in CHD cases and healthy controls of Chinese Han population.

Methods

A total of 315 blood samples from 147 CHD patients (male72, female 75) and 168 healthy controls (male 92, female 76) were enrolled in the study. HRM was utilized to genotype MTHFR C677T locus of all the samples. The results were compared to that of PCR-RFLP and Sanger sequencing. The association of the MTHFR C677T genotypes and the risk of CHD was analyzed using odds ratio with their 95% confidence interval (CIs) from unconditional logistic regression.

Results

All the samples were successfully genotyped by HRM within 1 hour and 30 minutes while at least 6 hours were needed for PCR-RFLP and sequencing. The genotypes of MTHFR C677T CC, CT, and TT were 9.52%, 49.66%, and 40.82% in CHD group but 29.17%, 50% and 20.83% in control group, which were identical using both methods of HRM and PCR-RFLP, demonstrating the sensitivity and specificity of HRM were all 100%.

Conclusion

MTHFR C677T is a potential risk factor for CHD in our local residents of Shandong province in China. HRM is a fast, sensitive, specific and reliable method for clinical application of genotyping.

Association between glutathione S-transferase P1 Ile (105) Val gene polymorphism and chronic obstructive pulmonary disease: A meta-analysis based on seventeen case-control studies

INTRODUCTION

Previous studies have shown that glutathione S-transferase P1 (GSTP1) was associated with chronic obstructive pulmonary disease (COPD). However, the association between GSTP1 Ile (105) Val gene polymorphism and COPD remains controversial. To drive a more precise estimation, we performed a meta-analysis based on published case-control studies.

METHODS

An electronic search of PubMed, EMBASE, Cochrane library, Web of Science and China Knowledge Resource Integrated (CNKI) Database for papers on GSTP1 Ile (105) Val gene polymorphism and COPD risk was performed. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association in the homozygote model, heterozygote model, dominant model, recessive model and an additive mode. Statistical heterogeneity, test of publication bias and sensitivity analysis was performed. The software STATA (Version 13.0) was used data analysis.

RESULTS

Overall, seventeen studies with 1892 cases and 2012 controls were included in this meta-analysis. The GSTP1 Ile (105) Val polymorphism showed pooled odds ratios for the homozygote comparison (OR = 1.501, 95%CI [0.862, 2.614]), heterozygote comparison (OR = 0.924, 95%CI [0.733, 1.165]), dominant model (OR = 1.003, 95%CI [0.756, 1.331]), recessive model (OR = 1.510, 95%CI [0.934, 2.439]), and an additive model (OR = 1.072, 95%CI [0.822, 1.398]).

CONCLUSIONS

In conclusion, the current meta-analysis, based on the most updated information, showed no significant association between GSTP1 Ile (105) Val gene polymorphism and COPD risk in any genetic models. The results of subgroup analysis also showed no significant association between GSTP1 Ile (105) Val gene polymorphism and COPD risk in Asian population and Caucasian population. Further studies involving large populations and careful control with age, sex, ethnicity, and cigarette smoking are greatly needed.