MTHFR 1298A>C is a risk factor for autism spectrum disorder in the Korean population

Short report on a distinct electroencephalogram endophenotype for MTHFR gene variation co-occurring in autism spectrum disorder

Anecdotal reports link a distinct, bilateral, parieto-temporally generated 4.5-Hz rhythm on an electroencephalogram to a methylenetetrahydrofolate reductase gene variant co-occurring in autism spectrum disorder, but the validation of its precision is needed. The electroencephalograms of children with autism spectrum disorder showing the distinct bilateral parieto-temporally generated 4.5-Hz rhythm and their clinical chart report on polymerase chain reaction screening for methylenetetrahydrofolate reductase gene variants, 677C>T and 1298A>C, were retrieved from an outpatient clinic between February 2019 and April 2024. Twenty-five cases were identified. Patients were between 2 and 12 (7 ± 3) years old from Asian (n = 16, 64%), European (n = 5, 20%), African (n = 1, 4%) and mixed (n = 3, 12%) ethnicities. Twenty patients (80%) were positive for 677 C>Theterozygous (n = 3, 15%), 1298A>Cheterozygous (n = 8, 40%) or both (n = 9, 45%). The polymerase chain reaction testing detected neither variant in 5 (20%) patients. Therefore, the electroencephalogram-endophenotype showed 80% precision in identifying methylenetetrahydrofolate reductase gene variant within the sample. This preliminary data support the precision of the proposed distinct, bilateral, parieto-temporally generated 4.5-Hz rhythm in identifying methylenetetrahydrofolate reductase gene variants and its potential clinical applications as a valuable, non-invasive and objective measure within the population.Lay abstractMethylenetetrahydrofolate reductase mutations refer to genetic variations in the methylenetetrahydrofolate reductase enzyme, which plays an important role in folate metabolism. Folate is essential for neural development and signalling. Children with autism spectrum disorder have atypical neural signals compared with control. This study used a non-invasive method to identify a distinct neural signal that may be useful in future screening for methylenetetrahydrofolate reductase mutation in children with autism spectrum disorder. Given that the underlying causes of autism spectrum disorder have multiple genetic factors and often require subjective assessment, this study introduces a potential non-invasive screening method for methylenetetrahydrofolate reductase gene mutation. This method could provide valuable biomarkers for screening and personalised treatments, offering hope for improved risk stratification and bespoke nutritional support and supplements to mitigate the impact on affected individuals and their descendants.

Comprehensive systematic review and meta-analysis of the association between common genetic variants and autism spectrum disorder

BACKGROUND

Autism spectrum disorder (ASD) is neurodevelopmental disorder characterized by stereotyped behavior and deficits in communication and social interactions. To date, numerous studies have investigated the associations between genetic variants and ASD risk. However, the results of these published studies lack a clear consensus. In the present study, we performed a systematic review on the association between genetic variants and ASD risk. Meanwhile, we conducted a meta-analysis on available data to identify the association between the single nucleotide polymorphisms (SNPs) of candidate genes and ASD risk.

METHODS

We systematically searched public databases including English and Chinese from their inception to August 1, 2022. Two independent reviewers extracted data and assessed study quality. Odds ratio and 95 % confidence interval were used as effect indexes to evaluate the association between the SNPs of candidate genes and the risk of ASD. Heterogeneity was explored through subgroup, sensitivity, and meta-regression analyses. Publication bias was assessed by using Egger's and Begg's tests for funnel plot asymmetry. In addition, TSA analysis were performed to confirm the study findings.

RESULTS

We summarized 84 SNPs of 32 candidate genes from 81 articles included in the study. Subsequently, we analyzed 16 SNPs of eight genes by calculating pooled ORs, and identified eight significant SNPs of contactin associated protein 2 (CNTNAP2), methylentetrahydrofolate reductase (MTHFR), oxytocin receptor (OXTR), and vitamin D receptor (VDR). Results showed that seven SNPs, including the CNTNAP2 rs2710102 (homozygote, heterozygote, dominant and allelic models) and rs7794745 (heterozygote and dominant models), MTHFR C677T (homozygote, heterozygote, dominant, recessive and allelic models) and A1298C (dominant and allelic models), OXTR rs2254298 (homozygote and recessive models), VDR rs731236 (homozygote, dominant, recessive and allelic models) and rs2228570 (homozygote and recessive models), were showed to be correlated with an increased ASD risk. By contrast, the VDR rs7975232 was correlated with a decreased the risk of ASD under the homozygote and allelic models.

CONCLUSION

Our study summarized research evidence on the genetic variants of ASD and provides a broad and detailed overview of ASD risk genes. The C677T and A1298C polymorphisms of MTHFR, rs2710102 and rs7794745 polymorphisms of CNTNAP2, rs2254298 polymorphism of OXTR, and rs731236 and rs2228570 polymorphisms of VDR were genetic risk factors. The rs7975232 polymorphism of VDR was a genetic protective factor for ASD. Our study provides novel clues to clinicians and healthcare decision-makers to predict ASD susceptibility.

The potential use of folate and its derivatives in treating psychiatric disorders: A systematic review

OBJECTIVES

To examine the strengths and limitations of existing data to provide guidance for the use of folate supplements as treatment, with or without other psychotropic medications, in various psychiatric disorders. To identify area for further research in terms of the biosynthesis of mechanism of folate and genetic variants in metabolic pathway in human.

METHODS

A systematic review of published literature following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, to assess whether folate supplements are beneficial in certain psychiatric disorders (depression, bipolar disorder, schizophrenia, autism spectrum disorder, and attention deficit hyperactivity disorder). Methodology of this review is registered with Prospero (Registration number CRD 42021266605).

DATA SOURCES

Eligible studies were identified using a systematic search of four electronic databases: Embase, Pubmed, PsycINFO, and Cochrane. The search strategy covered the time period from 1974 to August 16th, 2021. Therefore, this review examines randomized control trials or open-label trials completed during this period.

RESULTS

We identified 23 studies of folate supplements in various psychiatric disorders for critical review. Of these, 9 studies investigated the efficacy of folate supplements in major depressive disorders, 5 studies in schizophrenia, 6 studies in autism spectrum disorder, 2 studies in bipolar affective disorder and 1 study in attention deficit hyperactive disorder. The most consistent finding association of oral levomefolic acid or 5-methylfolate with improvement in clinical outcomes in mental health conditions as mentioned above, especially in major depressive disorder (including postpartum and post-menopausal depression), schizophrenia, autism spectrum disorder, attention deficit hyperactivity disorder and bipolar affective disorder. Folate supplements were well tolerated.

LIMITATION

Our results are not representative of all types of studies such as case reports or case series studies, nor are they representative of the studies conducted in languages that are not in English or not translated in English.

CONCLUSION

Increasing evidence from clinical trials consistently demonstrate folate supplements, especially levomefolic acid or 5-methylfolate, may improve clinical outcomes for certain psychiatric diseases, especially as an adjunct pharmacotherapy with minimal side effects.

Genetics and Epigenetics of One-Carbon Metabolism Pathway in Autism Spectrum Disorder: A Sex-Specific Brain Epigenome?

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition affecting behavior and communication, presenting with extremely different clinical phenotypes and features. ASD etiology is composite and multifaceted with several causes and risk factors responsible for different individual disease pathophysiological processes and clinical phenotypes. From a genetic and epigenetic side, several candidate genes have been reported as potentially linked to ASD, which can be detected in about 10–25% of patients. Folate gene polymorphisms have been previously associated with other psychiatric and neurodegenerative diseases, mainly focused on gene variants in the DHFR gene (5q14.1; rs70991108, 19bp ins/del), MTHFR gene (1p36.22; rs1801133, C677T and rs1801131, A1298C), and CBS gene (21q22.3; rs876657421, 844ins68). Of note, their roles have been scarcely investigated from a sex/gender viewpoint, though ASD is characterized by a strong sex gap in onset-risk and progression. The aim of the present review is to point out the molecular mechanisms related to intracellular folate recycling affecting in turn remethylation and transsulfuration pathways having potential effects on ASD. Brain epigenome during fetal life necessarily reflects the sex-dependent different imprint of the genome-environment interactions which effects are difficult to decrypt. We here will focus on the DHFR, MTHFR and CBS gene-triad by dissecting their roles in a sex-oriented view, primarily to bring new perspectives in ASD epigenetics.

Association of MTHFR 677C > T and 1298A > C polymorphisms with susceptibility to attention deficit and hyperactivity disorder

Background: The associations of MTHFR polymorphisms with risk of attention deficit and hyperactivity disorder (ADHD) are poorly elucidated. This study was performed to evaluate the association of MTHFR polymorphisms with ADHD risk in Iranian children.Methods: This case-control study included 214 children with ADHD and 220 healthy subjects. The MTHFR 677C > T and 1298A > C polymorphisms were genotyped by an ABI PRISMs 7500 real-time PCR System. The odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of the association.Results: The MTHFR 1298A > C polymorphism CC genotype (OR= 1.526, 95% CI 1.004-2.320, p = 0.048) and C allele (OR= 1.336, 95% CI 0.1023-1.745, p = 0.034) were associated with an increased risk of ADHD. There was no significant association between MTHFR 677C > T polymorphism and increased risk of ADHD.Conclusions: Our results revealed that the MTHFR 1298A > C polymorphism but not the MTHFR 677 C > T is associated with increased risk of ADHD in Iranian children.

Association between MTHFR C677T/A1298C and susceptibility to autism spectrum disorders: a meta-analysis

BACKGROUND

Autism spectrum disorder (ASD) is becoming increasingly prevalent of late. Methylenetetrahydrofolate reductase (MTHFR) has a significant role in folate metabolism. Owing to the inconsistencies and inconclusiveness on the association between MTHFR single nucleotide polymorphism (SNP) and ASD susceptibilities, a meta-analysis was conducted to settle the inconsistencies.

METHODS

For this meta-analysis, a total of 15 manuscripts published up to January 26, 2020, were selected from PubMed, Google Scholar, Medline, WangFang, and CNKI databases using search terms "MTHFR" OR "methylenetetrahydrofolate reductase" AND "ASD" OR "Autism Spectrum Disorders" OR "Autism" AND "polymorphism" OR "susceptibility" OR "C677T" OR "A1298C".

RESULTS

The findings of the meta-analysis indicated that MTHFR C677T polymorphism is remarkably associated with ASD in the five genetic models, viz., allelic, dominant, recessive, heterozygote, and homozygote. However, the MTHFR A1298C polymorphism was not found to be significantly related to ASD in the five genetic models. Subgroup analyses revealed significant associations of ASD with the MTHFR (C677T and A1298C) polymorphism. Sensitivity analysis showed that this meta-analysis was stable and reliable. No publication bias was identified in the associations between MTHFRC677T polymorphisms and ASD in the five genetic models, except for the one with regard to the associations between MTHFRA1298C polymorphisms and ASD in the five genetic models.

CONCLUSION

This meta-analysis showed that MTHFR C677T polymorphism is a susceptibility factor for ASD, and MTHFR A1298C polymorphism is not associated with ASD susceptibility.

Methylenetetrahydrofolate Reductase Gene Variants Confer Potential Vulnerability to Autism Spectrum Disorder in a Saudi Community

PURPOSE

Several interacting genes or single nucleotide polymorphisms (SNPs) are vulnerable to the risk of autism spectrum disorder (ASD). Here we explored associations between SNPs in the methylenetetrahydrofolate reductase (MTHFR) gene or combined genotypes and the risk of ASD in a Saudi community.

SUBJECTS AND METHODS

ASD severity symptoms were assessed according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) criteria and scores on the childhood autism rating scale (CARS). Genomic DNA from buccal cells was analyzed for 112 cases and 104 healthy controls using TaqMan genotyping assays of 677C>T rs1801133 and 1298A>C rs1801131 SNPs in the MTHFR gene. SNPStats software was utilized to determine the best interactive model of inheritance of genotypic data.

RESULTS

Controls were consistent with Hardy-Weinberg equilibrium in the examined SNPs. Our data showed associations between the 677C>T and 1298A>C SNPs and ASD risk (odds ratio [OR]= 5.2; 95% confidence interval [CI], 3.1-9.8 and OR= 22.2; 95% CI, 7.9-62.3, respectively). Genotype associations of 677C>T and 1298A>C were identified in cases compared with controls (P= 0.0012 and P= 0.0008, respectively). The examined SNPs were significantly associated with ASD cases having ≥37 scores (codominant and recessive models; P= 0.001 and P= 0.0005, respectively). Six combined genotypes-C/C-A/A (42.9%), C/T-A/A (17.9%), C/T-C/C (14.5%), C/T-A/C (10.9%), T/T-C/C (10.9%), and T/T-A/A (3.6%)-were found in ASD cases. Global haplotype analysis showed a significant difference in haplotype distribution between cases and controls (P= 0.00057). The two SNPs were found to be in relatively strong linkage disequilibrium (D`= 0.63, r 2= 0.260).

CONCLUSION

Our findings suggest that the 677C>T and 1298A>C SNPs add to each other for potential vulnerability to increase the risk of ASD, particularly if they can be confirmed in larger cohorts along with other genetic/environmental factors. Our study could create reference data for future genetic association studies in the Saudi population and for use by government and health experts to develop regional health management programs.

Association of MTHFR 677C>T and 1298A>C polymorphisms with susceptibility to autism: A systematic review and meta-analysis

Several studies have investigated association of MTHFR 677C > T and 1298A > C polymorphisms with risk of autism, but they have reported controversial and inconclusive results. The present meta-analysis was designed to evaluate association of MTHFR 677C > T and 1298A > C polymorphisms with risk of autism. A comprehensive literature search was done in PubMed, EMBASE, and CNKI databases to identify all eligible publications up to April 01, 2019. Finally, 25 case-control studies including 18 studies on MTHFR 677C > T and 7 studies on MTHFR 1298A > C polymorphism were selected. Overall, a significant association was found between MTHFR 677C > T and an increased risk of autism under all five genetic models (T vs. C: OR = 1.483, 95% CI 1.188-1.850, p ≤ 0.001; TT vs. CC: OR = 1.834, 95% CI 1.155-2.913, p = 0.010; TC vs. CC: OR = 1.512, 95% CI 1.101-2.078, p = 0.011; TT + TC vs. CC: OR = 1.632, 95% CI 1.261-2.113, p ≤ 0.001; and TT vs. TC + CC: OR = 1.427, 95% CI 1.002-2.032, p = 0.049). However, no significant association was found between MTHFR 1298A > C and autism risk. Stratified analyses showed that MTHFR 677C > T and 1298A > C polymorphisms are involved in genetic susceptibility of autism by ethnicity. Results of this meta-analysis indicated that MTHFR 677C > T polymorphism may be associated with increased risk of autism in overall and by ethnicity, while MTHFR 1298A > C was reported to be significantly associated with the risk of autism only in Caucasians. MTHFR polymorphisms could be used as a diagnostic marker for autism with respect to ethnicity background.

Methylenetetrahydrofolate reductase and psychiatric diseases

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme for the critical process of one-carbon metabolism involving folate and homocysteine metabolisms. It is known that some polymorphism of MTHFR would result in reduction of MTHFR enzyme activity as well as DNA methylation process, later shown to have significant impacts in various psychiatric diseases. However, it is unclear whether the polymorphism of MTHFR could be an independent or an add-on risk factor for specific psychiatric symptoms, such as anxiety, depression, positive, or negative symptoms of schizophrenia, or acts as risk factor for specific psychiatric disorders, such as schizophrenia, major depression, autisms, and bipolar disorders. It is also understudied on whether folate supplements could be an effective treatment for psychiatric patients with defect MTHFR activity. In this review, we not only gathered the most recent discoveries on MTHFR polymorphism and related DNA methylation in various psychiatric disorders, but also highlighted the potential relationships between MTHFR activity and implication of folate-related function in specific mental diseases.

Linking genetics to epigenetics: The role of folate and folate-related pathways in neurodevelopmental disorders

There is growing evidence that epigenetic dysregulation plays a role in neurodevelopmental disorders. In humans, folate is one of the main donors of the methyl group required for the synthesis of S-adenosylmethionine, which in turn is needed for DNA and histone methylation as key neurodevelopment processes. Folate deficiency during pregnancy has been correlated with neural tube defects and with a higher incidence of neurocognitive and/or neurobehavioral deficits. A similar outcome may be exerted by gene polymorphisms in folate or folate-related pathways. This has been documented by numerous case/control association studies performed on neurodevelopmental disorders such as autism spectrum disorder and attention deficit hyperactivity disorder. In this regard, the folate cycle represents a "perfect model" of how genetics influences epigenetics. Gene variants in folate and folate-related pathways can be considered risk factors for neurodevelopmental disorders and should therefore be assessed by genetic testing in pregnant women. High-risk women should be considered for folate supplementation during pregnancy. Here, we review all published case/control association studies on gene polymorphisms in folate and folate-related pathways performed on neurodevelopmental disorders, provide an overview of neurodevelopment and DNA methylation changes occurring at this time, and describe the biological basis of neurodevelopmental disorders and recent evidence of their epigenetic dysregulation.

Genetics and epigenetics of autism: A Review

Autism is a developmental disorder that starts before age 3 years, and children with autism have impairment in both social interaction and communication, and have restricted, repetitive, and stereotyped patterns of behavior, interests, and activities. There is a strong heritable component of autism and autism spectrum disorder (ASD) as studies have shown that parents who have a child with ASD have a 2-18% chance of having a second child with ASD. The prevalence of autism and ASD have been increasing during the last 3 decades and much research has been carried out to understand the etiology, so as to develop novel preventive and treatment strategies. This review aims at summarizing the latest research studies related to autism and ASD, focusing not only on the genetics but also some epigenetic findings of autism/ASD. Some promising areas of research using transgenic/knockout animals and some ideas related to potential novel treatment and prevention strategies will be discussed.

The Molecular and Cellular Effect of Homocysteine Metabolism Imbalance on Human Health

Homocysteine (Hcy) is a sulfur-containing non-proteinogenic amino acid derived in methionine metabolism. The increased level of Hcy in plasma, hyperhomocysteinemia, is considered to be an independent risk factor for cardio and cerebrovascular diseases. However, it is still not clear if Hcy is a marker or a causative agent of diseases. More and more research data suggest that Hcy is an important indicator for overall health status. This review represents the current understanding of molecular mechanism of Hcy metabolism and its link to hyperhomocysteinemia-related pathologies in humans. The aberrant Hcy metabolism could lead to the redox imbalance and oxidative stress resulting in elevated protein, nucleic acid and carbohydrate oxidation and lipoperoxidation, products known to be involved in cytotoxicity. Additionally, we examine the role of Hcy in thiolation of proteins, which results in their molecular and functional modifications. We also highlight the relationship between the imbalance in Hcy metabolism and pathogenesis of diseases, such as cardiovascular diseases, neurological and psychiatric disorders, chronic kidney disease, bone tissue damages, gastrointestinal disorders, cancer, and congenital defects.

Association of methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism with autism: evidence of genetic susceptibility

Autism (MIM 209850) is a heterogeneous neurodevelopmental disease that manifests within the first 3 years of life. Numerous articles reported that dysfunctional folate-methionine pathway enzymes may play an important role in the pathophysiology of autism. Methylenetetrahydrofolate reductase (MTHFR) is a critical enzyme of this pathway and MTHFR C677T polymorphism reported as risk factor for autism in several case control studies. However, controversial reports were also published. Hence the present meta-analysis was designed to investigate the relationship of the MTHFR C677T polymorphism with the risk of autism. Electronic databases were searched for case control studies with following search terms - 'MTHFR', 'C677T', in combination with 'Autism'. Pooled OR with its corresponding 95 % CI was calculated and used as association measure to investigate the association between MTHFR C677T polymorphism and risk of autism. Total of thirteen studies were found suitable for the inclusion in the present meta-analysis, which comprises 1978 cases and 7257 controls. Meta-analysis using all four genetic models showed significant association between C677T polymorphism and autism (ORTvs.C = 1.48; 95 % CI: 1.18-1.86; P = 0.0007; ORTT + CT vs. CC = 1.70, 95 % CI = 0.96-2.9, p = 0.05; ORTT vs. CC = 1.84, 95 % CI = 1.12-3.02, p = 0.02; ORCT vs.CC = 1.60, 95 % CI = 1.2-2.1, p = 0.003; ORTT vs.CT+CC = 1.5, 95 % CI = 1.02-2.2, p = 0.03). In total 13 studies, 9 studies were from Caucasian population and 4 studies were from Asian population. The association between C677T polymorphism and autism was significant in Caucasian (ORTvs.C = 1.43; 95 % CI = 1.1-1.87; p = 0.009) and Asian population (ORTvs.C = 1.68; 95 % CI = 1.02-2.77; p = 0.04) using allele contrast model. In conclusion, present meta-analysis strongly suggested a significant association of the MTHFR C677T polymorphism with autism.

A comprehensive meta-analysis of common genetic variants in autism spectrum conditions

Background

Autism spectrum conditions (ASC) are a group of neurodevelopmental conditions characterized by difficulties in social interaction and communication alongside repetitive and stereotyped behaviours. ASC are heritable, and common genetic variants contribute substantial phenotypic variability. More than 600 genes have been implicated in ASC to date. However, a comprehensive investigation of candidate gene association studies in ASC is lacking.

Methods

In this study, we systematically reviewed the literature for association studies for 552 genes associated with ASC. We identified 58 common genetic variants in 27 genes that have been investigated in three or more independent cohorts and conducted a meta-analysis for 55 of these variants. We investigated publication bias and sensitivity and performed stratified analyses for a subset of these variants.

Results

We identified 15 variants nominally significant for the mean effect size, 8 of which had P values below a threshold of significance of 0.01. Of these 15 variants, 11 were re-investigated for effect sizes and significance in the larger Psychiatric Genomics Consortium dataset, and none of them were significant. Effect direction for 8 of the 11 variants were concordant between both the datasets, although the correlation between the effect sizes from the two datasets was poor and non-significant.

Conclusions

This is the first study to comprehensively examine common variants in candidate genes for ASC through meta-analysis. While for majority of the variants, the total sample size was above 500 cases and 500 controls, the total sample size was not large enough to accurately identify common variants that contribute to the aetiology of ASC.

Electronic supplementary material

The online version of this article (doi:10.1186/s13229-015-0041-0) contains supplementary material, which is available to authorized users.

MTHFR Gene C677T Polymorphism in Autism Spectrum Disorders

Aim. Autism is a subgroup of autism spectrum disorders, classified as a heterogeneous neurodevelopmental disorder and symptoms occur in the first three years of life. The etiology of autism is largely unknown, but it has been accepted that genetic and environmental factors may both be responsible for the disease. Recent studies have revealed that the genes involved in the folate/homocysteine pathway may be risk factors for autistic children. In particular, C677T polymorphism in the MTHFR gene as a possible risk factor for autism is still controversial. We aimed to investigate the possible effect of C677T polymorphism in a Turkish cohort. Methods. Autism patients were diagnosed by child psychiatrists according to DSM-IV and DSM-V criteria. A total of 98 children diagnosed as autistic and 70 age and sex-matched children who are nonautistic were tested for C677T polymorphism. This polymorphism was studied by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods. Results. MTHFR 677T-allele frequency was found to be higher in autistic children compared with nonautistic children (29% versus 24%), but it was not found statistically significant. Conclusions. We conclude that other MTHFR polymorphisms such as A1298C or other folate/homocysteine pathway genes may be studied to show their possible role in autism.