Lack of maternal folic acid supplementation is associated with heart defects in Down syndrome: a report from the National Down Syndrome Project

Understanding the Genetic and Non-genetic Interconnections in the Aetiology of Isolated Congenital Heart Disease: An Updated Review: Part 1

PURPOSE OF REVIEW

Congenital heart disease (CHD) is the most frequently occurring birth defect. Majority of the earlier reviews focussed on the association of genetic factors with CHD. A few epidemiological studies provide convincing evidence for environmental factors in the causation of CHD. Although the multifactorial theory of gene-environment interaction is the prevailing explanation, explicit understanding of the biological mechanism(s) involved, remains obscure. Nonetheless, integration of all the information into one platform would enable us to better understand the collective risk implicated in CHD development.

RECENT FINDINGS

Great strides in novel genomic technologies namely, massive parallel sequencing, whole exome sequencing, multiomics studies supported by system-biology have greatly improved our understanding of the aetiology of CHD. Molecular genetic studies reveal that cardiac specific gene variants in transcription factors or signalling molecules, or structural proteins could cause CHD. Additionally, non-hereditary contributors such as exposure to teratogens, maternal nutrition, parental age and lifestyle factors also contribute to induce CHD. Moreover, DNA methylation and non-coding RNA are also correlated with CHD. Here, we inform that a complex combination of genetic, environmental and epigenetic factors interact to interfere with morphogenetic processes of cardiac development leading to CHD. It is important, not only to identify individual genetic and non-inherited risk factors but also to recognize which factors interact mutually, causing cardiac defects.

Understanding the Genetic and Non-Genetic Interconnections in the Aetiology of Syndromic Congenital Heart Disease: An Updated Review: Part 2

PURPOSE OF REVIEW

Approximately 30% of syndromic cases diagnosed with CHD, which lure us to further investigate the molecular and clinical challenges behind syndromic CHD (sCHD). The aetiology of sCHD in a majority of cases remains enigmatic due to involvement of multiple factors, namely genetic, epigenetic and environmental modifiable risk factors for the development of the disease. Here, we aim to update the role of genetic contributors including chromosomal abnormalities, copy number variations (CNVs) and single gene mutations in cardiac specific genes, maternal lifestyle conditions, environmental exposures and epigenetic modifiers in causing CHD in different genetic syndromes.

RECENT FINDINGS

The exact aetiology of sCHD is still unknown. With the advancement of next-generation technologies including WGS, WES, transcriptome, proteome and methylome study, numerous novel genes and pathways have been identified. Moreover, our recent knowledge regarding epigenetic and environmental regulation during cardiogenesis is still evolving and may solve some of the mystery behind complex sCHD. Here, we focus to understand how the complex combination of genetic, environmental and epigenetic factors interact to interfere with developmental pathways, culminating into cardiac and extracardiac defects in sCHD.

Congenital Heart Defects and Outcome in a Large Cohort of Down Syndrome: A Single-Center Experience from Turkey

OBJECTIVE

Congenital heart defects occur in approximately 50% of children with Down syndrome and they contribute considerably to morbidity and mortality. The aim of this study is to investigate the prevalence, classification, and survival of congenital heart defects in Down syndrome.

MATERIALS AND METHODS

About 1731 Down syndrome patients who underwent echocardiography between 1986 and 2022 were evaluated. The median follow-up duration was 8.7 years (range 1-35.8 years). Congenital heart defect was grouped as cyanotic and acyanotic.

RESULTS

Among the 1731 patients, 52.1% had congenital heart defects. Congenital heart defect was significantly more common in females than males. The most common cardiac defect was ventricular septal defect (35%), followed by atrial septal defect (31.8%), atrioventricular septal defect (23.4%), tetralogy of Fallot (5%), and patent ductus arteriosus (3.6%). In the follow-up, 43.2% of atrial septal defect, 17.8% of ventricular septal defect, and a total of 20% of congenital heart defects were closed spontaneously. About 34.4% of congenital heart defect was corrected by cardiac surgery/intervention. Five-year survival rate was 97.4% in patients without congenital heart defects, whereas it was 95.6% in mild congenital heart defects and 86.1% in moderate to severe congenital heart defects. There was no relationship between consanguinity, parental age, maternal disease, folic acid supplementation before/during pregnancy, gestational age, birth weight, and congenital heart defects. Neuromotor development was similar in patients with and without congenital heart defects.

CONCLUSION

We demonstrated that almost half of the patients had congenital heart defects; ventricular septal defect was the most common congenital heart defect type. This study is valuable in terms of the largest single-center study describing the classification, prognostic factors, and survival of Down syndrome patients with congenital heart defect from Turkey.

Health-Promoting Ingredients in Goat's Milk and Fermented Goat's Milk Drinks

The present study aimed to determine the content of health-promoting compounds, and fatty acids, with particular emphasis on the content of cis9trans11 C18:2 (CLA) acid, selected minerals, folates in organic and commercial goat's milk and fermented goat's milk drinks. The analyzed milk and yoghurts had various contents of particular groups of fatty acids, CLA, minerals, and folates. Raw organic goat's milk had a significantly (p < 0.05) higher content of CLA (3.26 mg/g fat) compared to commercial milk (2.88 mg/g fat and 2.54 mg/g fat). Among the analyzed fermented goat's milk drinks, the highest CLA content (4.39 mg/g fat) was determined in commercial natural yoghurts, while the lowest one was in organic natural yoghurts (3.28 mg/g fat). The highest levels of calcium (1322.9-2324.4 µg/g), phosphorus (8148.1-11,309.9 µg/g), and copper (0.072-0.104 µg/g) were found in all commercial products and those of manganese (0.067-0.209 µg/g) in organic products. The contents of the other assayed elements (magnesium, sodium, potassium, iron, and zinc) did not depend on the production method, but only on the product type, i.e., the degree of goat's milk processing. The highest folate content in the analyzed milks was found in the organic sample (3.16 µg/100 g). Organic Greek yoghurts had a several times higher content of folates, reaching 9.18 µg/100 g, compared to the other analyzed fermented products.

Cardiovascular Complications of Down Syndrome: Scoping Review and Expert Consensus

Cardiovascular disease is a leading cause of morbidity and mortality in individuals with Down syndrome. Congenital heart disease is the most common cardiovascular condition in this group, present in up to 50% of people with Down syndrome and contributing to poor outcomes. Additional factors contributing to cardiovascular outcomes include pulmonary hypertension; coexistent pulmonary, endocrine, and metabolic diseases; and risk factors for atherosclerotic disease. Moreover, disparities in the cardiovascular care of people with Down syndrome compared with the general population, which vary across different geographies and health care systems, further contribute to cardiovascular mortality; this issue is often overlooked by the wider medical community. This review focuses on the diagnosis, prevalence, and management of cardiovascular disease encountered in people with Down syndrome and summarizes available evidence in 10 key areas relating to Down syndrome and cardiac disease, from prenatal diagnosis to disparities in care in areas of differing resource availability. All specialists and nonspecialist clinicians providing care for people with Down syndrome should be aware of best clinical practice in all aspects of care of this distinct population.

Association Between Maternal Factors and Risk of Congenital Heart Disease in Offspring: A Systematic Review and Meta-Analysis

INTRODUCTION

This study aimed to summarize the evidence describing the relationship between maternal factors during gestation and risk of congenital heart disease (CHD) in offspring.

METHODS

PubMed, EMBASE, and the Cochrane Library were searched for potentially relevant reports from inception to May 2021. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) calculated by the random-effects model were used to evaluate the association between maternal factors and CHD risk.

RESULTS

There was a significant association between CHD risk and obesity in pregnancy (OR 1.29, 95% CI 1.22-1.37; P < 0.001), smoking in pregnancy (OR 1.16, 95% CI 1.07-1.25; P < 0.001), maternal diabetes (OR 2.65, 95% CI 2.20-3.19; P < 0.001), and exposure of pregnant women to organic solvents (OR 1.82, 95% CI 1.23-2.70; P = 0.003). No correlations were revealed between CHD susceptibility and advanced maternal age (OR 1.04, 95% CI 0.96-1.12; P = 0.328), underweight (OR 1.02, 95% CI 0.96-1.08; P = 0.519), alcohol intake in pregnancy (OR 1.08, 95% CI 0.95-1.22; P = 0.251), coffee intake (OR 1.18, 95% CI 0.97-1.44; P = 0.105), and exposure to irradiation (OR 1.80, 95% CI 0.85-3.80; P = 0.125).

DISCUSSION

Maternal factors including maternal obesity, smoking in pregnancy, maternal diabetes and exposure to organic solvents might predispose the offspring to CHD risk.

Willingness to Pay for Down Syndrome Screening: A systematics Review

Background:Financial ability to pay has a unique role in the accessibility of health care services, which indicates the necessity of raising enough funds by governments. However, how much households are willing to pay (WTP) for receiving a particular service? And what factors influence their WTP? The current systematic review aimed to, firstly, review studies on the WTP for Down syndrome (DS) screening, and, secondly, to identify factors that affect WTP for DS screening. Methods:We systematically searched the Scopus, PubMed, Web of Sciences (ISI), and Embase databases to identify relevant studies from their inception to June 2020; the search strategy was updated on December 2021. Initially, 157 articles were identified, and 5 were found eligible for full-text review. In event of any disagreement, a third reviewer was used. Extracted WTPs were converted to US dollars in 2018 using exchange rate parity and the present value formula to make a comparison. The quality assessment of the selected studies was done using the "Lancsar and Louvier" and Smith checklist; also, vote counting was used to assess the influence of factors. Results:Five eligible studies, published from 2005 to 2020, were fully reviewed. All final studies were scored as good quality. The extracted WTPs varied from $169 to $1118 in UK and Canada, respectively. Income and information/knowledge about screening tests were the most frequently investigated factors. Education level, detection rate, women's age, cost, and family history were significantly associated with higher levels of WTP for DS screening. Conclusion:This study demonstrated a significant gap in WTP for DS screening in various countries. Women are WTP higher costs for tests with higher screenings. Also, a unique role was identified for income, occupation, information, and family history of DS in WTP for DS screening. In addition, a positive association was found for the variable of age.

Characteristics of Dietary Supplements with Folic Acid Available on the Polish Market

One way of increasing folate status, especially in a state of increased demand (e.g., women of childbearing age), is dietary supplementation with folic acid (FA). The dietary supplements market in Poland shows a controversial situation and, for many reasons (the ease of placing them on the market, the lack of control of chemical composition), the possibility of inaccurate information provided on the supplement’s label arises. We questioned whether FA supplements available in Poland are indeed complying with regulations and if they could actually improve folate status amongst the target population groups consuming them. Almost 500 products containing FA were identified and available for sale in pharmacies, all of them including specific information provided by manufacturers on the packaging, such as the amount of FA, their intended use and daily dosage. HPLC analysis of FA content in 30 randomly purchased supplements exposed that in four of the tested products, FA content was less than 4% of the declared value (DV). Another 11 samples exposed that the difference with declared FA content varied from 25% up to 80% of the DV. The obtained results are in agreement with the ones from inspections previously conducted on the Polish dietary supplements market and indicate the urgent need to implement improvements in the notification system as well as the monitorization of these product’s authenticity.

The association between folic acid supplementation and congenital heart defects: Systematic review and meta-analysis

Introduction:

Various trial and epidemiological studies consistently documented the association between maternal folic acid supplementations and neural tube defects. However, existing literatures revealed inconclusive findings about maternal periconceptional folic acid supplementations and the risk of congenital heart defects. Thus, the current systematic review and meta-analysis was aimed to estimate the pooled association between maternal periconceptional folic acid supplementations and congenital heart defects.

Methods:

Electronic searches of PubMed, Web of Science/Scopus, Cochrane library and Google Scholar databases were conducted to access the required studies published up to March 2021. Predetermined eligibility criteria were used for study selections. Data extraction were independently done on excel. STATA version 14 software was used to calculate the pooled effect size with 95% confidence intervals (95% CI) of maternal periconceptional folic acid supplementations on congenital heart defects using the DerSimonian and Laird random effects meta-analysis (random effects model). Statistical heterogeneity was checked using the Cochran Q test (chi-squared statistic), I2 statistic, and by visual inspection of the funnel plot.

Results:

A total of 37 studies of case–control, cohort and randomized controlled trial in nature were included in the review. The finding of the present systematic review and meta-analysis indicated that periconceptional folic acid supplementation significantly decreases the risk of congenital heart defects (risk ratio (RR), 0.79; CI, 0.71, 0.89). Both Cochrane Q test statistic (χ2 = 19.33, p = 0.962) and I2 test statistic (I2 = 0.0%, p = 0.962) did not reveal statistically significant heterogeneity among included studies. In this meta-analysis, traditional funnel plot, Begg’s funnel plot, Egger’s weighted regression (p = 0.13) as well as Begg’s rank correlation statistic (p = 0.676) revealed no evidence of publication bias.

Conclusion:

The present systematic review and meta-analysis found that maternal periconception folic acid supplementation was significantly associated with the risk of congenital heart defects. The risk of congenital heart defects was significantly reduced by 21% among those children of mothers who use periconceptional folic acid supplementations in high-income countries. We recommend that a large prospective study be conducted to investigate the association between maternal periconceptional folic acid supplementation and occurrence of congenital heart defect of various types, especially in the developing countries.

Association of periconceptional folate supplements and FOLR1 and FOLR2 gene polymorphisms with risk of congenital heart disease in offspring: A hospitalbased casecontrol study

OBJECTIVES

Maternal periconceptional folic acid supplement is by far the most effective primary prevention strategy to reduce the incidence of congenital heart disease (CHD) in offspring. It was revealed that the underlying mechanisms are complex, including a combination of genetic and environmental factors. The purpose of this study is to investigate the association between periconceptional folic acid supplement, the genetic polymorphisms of maternal folic acid receptor 1 gene (FOLR1) and folic acid receptor 2 gene (FOLR2) and the impact of their interaction on the risk of CHD in offspring, and to provide epidemiological evidence for individualized folic acid dosing in hygienic counseling.

METHODS

A case-control study on 569 mothers of CHD infants and 652 mothers of health controls was performed. The interesting points were periconceptional folate supplements, single nucleotide polymorphisms (SNPs) of maternal FOLR1 gene and FOLR2 gene.

RESULTS

Mothers who took folate in the periconceptional period were observed a decreased risk of CHD [adjusted odds ratio (aOR)=0.58, 95% CI 0.35 to 0.95]. Our study also found that polymorphisms of maternal FOLR1 gene at rs2071010 (G/A vs G/G: aOR=0.67, 95% CI 0.47 to 0.96) and FOLR2 gene at rs514933 (T/C vs T/T: aOR=0.60, 95% CI 0.43 to 0.84; C/C vs T/T: aOR=0.55, 95% CI 0.33 to 0.90; the dominant model: T/C+ C/C vs T/T: aOR=0.59, 95% CI 0.43 to 0.81; and the addictive model: C/C vs T/C vs T/T: aOR=0.70, 95% CI 0.56 to 0.88) were significantly associated with lower risk of CHD [all P<0.05, false discovery rate P value (FDR_P)<0.1]. Besides, significant interaction between periconceptional folate supplements and rs2071010 G→A (aOR=0.59, 95% CI 0.41-0.86) and rs514933 T→C (aOR=0.52, 95% CI 0.37 to 0.74) on CHD risk were observed (all P<0.05, FDR_P<0.1).

CONCLUSIONS

Periconceptional folate supplements, polymorphisms of FOLR1 gene and FOLR2 gene and their interactions are significantly associated with risk of CHD. However, more studies in different ethnic populations with a larger sample and prospective designs are required to confirm our findings.

The Role of Epigenetics in Congenital Heart Disease

Congenital heart disease (CHD) is the most common birth defect among newborns worldwide and contributes to significant infant morbidity and mortality. Owing to major advances in medical and surgical management, as well as improved prenatal diagnosis, the outcomes for these children with CHD have improved tremendously so much so that there are now more adults living with CHD than children. Advances in genomic technologies have discovered the genetic causes of a significant fraction of CHD, while at the same time pointing to remarkable complexity in CHD genetics. For this reason, the complex process of cardiogenesis, which is governed by multiple interlinked and dose-dependent pathways, is a well investigated process. In addition to the sequence of the genome, the contribution of epigenetics to cardiogenesis is increasingly recognized. Significant progress has been made dissecting the epigenome of the heart and identified associations with cardiovascular diseases. The role of epigenetic regulation in cardiac development/cardiogenesis, using tissue and animal models, has been well reviewed. Here, we curate the current literature based on studies in humans, which have revealed associated and/or causative epigenetic factors implicated in CHD. We sought to summarize the current knowledge on the functional role of epigenetics in cardiogenesis as well as in distinct CHDs, with an aim to provide scientists and clinicians an overview of the abnormal cardiogenic pathways affected by epigenetic mechanisms, for a better understanding of their impact on the developing fetal heart, particularly for readers interested in CHD research.

Congenital heart disease in Down syndrome – A review of temporal changes

Background

Congenital heart disease (CHD) is a well-known co-occurring condition in Down syndrome (DS). We aimed to review the literature to evaluate the current evidence to address key questions.

Methods

A series of key questions were formulated a priori to inform the search strategy and review process. These addressed the topics of prevalence, type of CHD, severity, and screening. Using the National Library of Medicine database, PubMed, detailed literature searches were performed. The quality of available evidence was then evaluated, the existing literature was summarized, and knowledge gaps were identified.

Results

Fifty-six relevant original articles were identified which addressed at least one key question. Study details, including: research design, internal validity, external validity, and relevant results are presented. The total prevalence of CHD reported in DS ranged from 20 to 57.9%. In later decades, the prevalence remained constant at 40—55%. The types and classification of CHD varied considerably between studies. Some studies indicate a trend towards a milder phenotype, but this was not consistent. Over time, some studies observed an improved prognosis for CHD in DS. Studies investigating screening for CHD by physical examination, chest X-ray, and electrocardiogram report sensitivities of 71–95%.

Conclusion

To further improve knowledge on CHD in DS, we suggest that future studies cover a wide range of nations and regions, with a longitudinal design, and account for potential confounding factors.

Maternal B-vitamin intake and B-vitamin supplementation during pregnancy in relation to neonatal congenital heart defects: a case-control study with propensity score matching

BACKGROUND/OBJECTIVES

The effect of dietary folate intake or folic acid (FA) supplementation during pregnancy on neonatal congenital heart defects (CHDs) remains inconclusive. There are limited data about non-folate-B-vitamin intake and the risk of CHDs. Furthermore, few studies have investigated dietary B-vitamin intake and B-vitamin supplement use simultaneously in relation to the risk of CHDs. This study aimed to explore the associations between maternal folate, vitamin B₆, and vitamin B₁₂ intake (dietary intake, total intake from diet and supplements); B-vitamin supplement use during pregnancy; and the risk of CHDs using the propensity score matching (PSM) method.

METHODS

We conducted a case-control study and included 760 cases and 1600 controls in Shaanxi Province, China. Diet, supplement use and other information were collected through a questionnaire interview. By using the 1:2 ratio PSM method, 396 cases were matched with 792 controls. Conditional logistic regression was used to investigate the associations between maternal B-vitamin intake and supplement use during pregnancy and CHDs.

RESULTS

Higher maternal dietary and total intake of folate and vitamin B₁₂ were associated with reduced risk of CHDs, and the tests for linear trend were significant. Compared with non-users, maternal FA + VB₆ + VB₁₂ containing supplement use during pregnancy (OR 0.61, 95%CI 0.40-0.94), FA supplement use during pregnancy (OR 0.70, 95%CI 0.50-0.98) and in the first trimester (OR 0.62, 95%CI 0.46-0.85) were associated with a lower risk of CHDs.

CONCLUSIONS

The findings of this study suggest that a higher intake of folate and vitamin B₁₂ during pregnancy reduces the risk of CHDs.

Types and Distribution of Congenital Heart Defects in Pediatric Patients with Down's Syndrome: A Retrospective Study

Background Congenital heart disease (CHD) is common in patients with Down's syndrome (DS), rendering them at risk of significant mortality and morbidity. However, all patients with confirmed DS must undergo further investigation for a cardiac anomaly early in their lives. Objective To define frequency and patterns of CHD among children with DS in Northwest, Saudi Arabia (SA). Methods A five-year chart review study was conducted in Northwest SA between January 2015 and June 2019. We included all children referred to the pediatric cardiology clinic with a confirmed diagnosis of DS and CHD. Children were identified in the clinic's database, and charts were reviewed retrospectively.  Results Among 851 patients with CHD, 53 were identified with DS. Male patients represented 62.3%, while female patients represented 37.7%. The median patients' age at the time of diagnosis was two days, with most patients diagnosed before 28 days old (67.9%). This study found that atrial septal defect (ASD) and patent ductus arteriosus (PDA) were the most common isolated lesions (37% of isolated cases), while the most common combined lesions were ASD, ventricular septal defect (VSD), and PDA, as well as combined ASD and VSD. Female gender was significantly associated with higher percentage of VSD (p = 0.031) more than male. While male patients had significantly higher percentages of ASD and valvular anomalies than female patients (p = 0.019 and 0.033, respectively). Conclusions The patient's gender was significantly associated with some types of CHD. Both ASD and valvular lesions were more common among males, while VSD was more common among female patients, no gender differences were detected regarding the other types of CHD.

Maternal risk factors for congenital heart defects in infants with Down syndrome from Western Mexico

Atrioventricular septal defects (AVSDs) have been identified as intriguingly infrequent among Hispanics with Down syndrome (DS) born in the United States. The aim of this study was to evaluate the effect of possible maternal risk factors in the presence of congenital heart defects (CHDs) in Mexican infants with DS. A total of 231 live birth infants born with DS during 2009-2018 at the "Dr. Juan I. Menchaca" Civil Hospital of Guadalajara (Guadalajara, Mexico) were ascertained in a case-control study. Patients with DS with any major CHD were included as cases and those without major CHD as controls. Potential risk factors were analyzed using logistic regression. Of eligible infants with DS, 100 (43.3%) had ≥1 major CHDs (cases) and were compared with a control group of 131 infants (56.7%) with DS without CHDs. Prevalent CHDs were ostium secundum atrial septal defects (ASDs) (46.9%), ventricular septal defects (27.3%), and AVSDs (14%). Lack of folic acid supplementation before pregnancy had a significant risk for CHDs in infants with DS (adjusted odds ratio [aORs] = 2.9 (95% confidence interval [95% CI]: 1.0-8.6) and in the analysis by subtype of CHDs, also, for the occurrence of ASDs (aOR = 11.5, 95% CI: 1.4-94.4). Almost half of the infants with DS in our sample had CHDs, being ASD the commonest subtype and AVSD the rarest. Our ethnic background alone or in concomitance with observed nutritional disadvantages seems to contribute differences in CHD subtype rates in our DS patients.

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.

Maternal folic acid supplementation and dietary folate intake and congenital heart defects

Background

It has been reported that folic acid supplementation before and/or during pregnancy could reduce the risk of congenital heart defects (CHDs). However, the results from limited epidemiologic studies have been inconclusive. We investigated the associations between maternal folic acid supplementation, dietary folate intake, and the risk of CHDs.

Methods

A birth cohort study was conducted in 2010–2012 at the Gansu Provincial Maternity & Child Care Hospital in Lanzhou, China. After exclusion of stillbirths and multiple births, a total of 94 births were identified with congenital heart defects, and 9,993 births without any birth defects. Unconditional logistic regression was used to estimate the associations.

Results

Compared to non-users, folic acid supplement users before pregnancy had a reduced risk of overall CHDs (OR: 0.42, 95% CI: 0.21–0.86, P_trend = 0.025) after adjusted for potential confounders. A protective effect was observed for certain subtypes of CHDs (OR: 0.37, 95% CI: 0.16–0.85 for malformation of great arteries; 0.26, 0.10–0.68 for malformation of cardiac septa; 0.34, 0.13–0.93 for Atrial septal defect). A similar protective effect was also seen for multiple CHDs (OR: 0.49, 95% CI: 0.26–0.93, P_trend = 0.004). Compared with the middle quartiles of dietary folate intake, lower dietary folate intake (<149.88 μg/day) during pregnancy were associated with increased risk of overall CHDs (OR: 1.63, 95% CI: 1.01–2.62) and patent ductus arteriosus (OR: 1.85, 95% CI: 1.03–3.32). Women who were non-user folic acid supplement and lower dietary folate intake have almost 2-fold increased CHDs risk in their offspring.

Conclusions

Our study suggested that folic acid supplementation before pregnancy was associated with a reduced risk of CHDs, lower dietary folate intake during pregnancy was associated with increased risk. The observed associations varied by CHD subtypes. A synergistic effect of dietary folate intake and folic acid supplementation was also observed.

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.

Prevalence of congenital heart diseases in children with Down syndrome in Mansoura, Egypt: a retrospective descriptive study

BACKGROUND

The pattern and risk factors for congenital heart diseases (CHD) in children with Down syndrome (DS) vary over time.

OBJECTIVES

To update knowledge of the prevalence, types, trends and associated factors for CHD in children with DS in the Egyptian Delta.

DESIGN

A retrospective hospital record-based descriptive study.

SETTING

A tertiary care center in Mansoura, Egypt during a period of 14 years from 2003 up to 2016.

PATIENTS AND METHODS

We studied children with genetically proven DS. Relevant sociodemographic factors, medical history, clinical examination, karyotype and echocardiographic data were statistically analyzed.

MAIN OUTCOME MEASURES

Prevalence, types and risk factors of CHD in DS.

RESULTS

The prevalence of overall, isolated and multiple CHD in 1720 children with DS were 36.9%, 29% and 8%, respectively. Isolated defects accounted for 78.4% of all CHD. Ventricular septal defect, atrioventricular septal defect and atrial septal defect were the most frequent isolated defects. There was a downward trend in the prevalence of overall CHD (from 56.2% to 25.0%) and isolated CHD (from 56.2% to 19.8%). The logistic regression model predicted 65.7% of CHD and revealed that passive maternal smoking, lack of folic acid/multivitamin supplementation and parental consanguinity were the independent predictors of CHD in children with DS with adjusted odds ratios of 1.9, 1.8 and 1.9, respectively.

CONCLUSION

More than one-third of children with DS have CHD with ventricular septal defect, which is the most common. Avoidance of passive maternal smoking and consanguineous marriage together with maternal folic acid supplementation could contribute to further reduction of CHD in children with DS.

LIMITATIONS

Single-center study and retrospective.

The impact of folic acid supplementation on gestational and long term health: Critical temporal windows, benefits and risks

Highlights

Associations between FA supplementation in pregnancy and effects on offspring's NTDs, allergy/respiratory problems, cancer and behaviour problems as been studied.There is growing concern about the effects of excessive FA supplementation, whether in terms of doses or times of exposure.FA supplementation in the periconceptional period is protective against NTDs while in later periods it could be deleterious.A daily dose of 0.4 mg FA in the periconceptional period seems to be effective and safe.

Abstract

Maternal folic acid (FA) supplementation is one of the most popular nutritional interventions during pregnancy for its protective effect against neural tube defects (NTDs).The purposes of this review are: (a) to gather the current evidence regarding supplementation of maternal diet with FA and (b) to problematize the available literature in terms of dosages, critical temporal windows, and its potential benefits and risks.The expression (pregnancy OR fetus OR offspring OR mother) AND ("folic acid" AND supplementation) was searched on PubMed database, filtering for articles published from 2005 to 2014. Publications referring to FA supplementation during the periconceptional period or pregnancy in which there was a conclusion about the effects of isolated FA supplementation on pregnant woman, pregnancy or offspring were included. Of the initial 1182 papers, 109 fulfilled the inclusion criteria.The majority of the publications reported FA supplementation outcomes on offspring's health, with emphasis in NTDs, allergy/respiratory problems, cancer and behaviour problems. Some inconsistency is observed on the impact of FA supplementation on different outcomes, except for NTDs. It is also visible an increased concern about the impact of excessive supplementation, either in terms of doses or exposure's duration.In conclusion, there is a growing interest in FA supplementation issues. The protective effect of FA supplementation over NTDs has been confirmed, being the periconceptional period a critical window, and it is frequently suggested that allergy/respiratory outcomes arise from (excessive) FA supplementation particularly later in pregnancy. Further research on critical doses and time of exposure should be conducted.

Genotype-phenotype correlation for congenital heart disease in Down syndrome through analysis of partial trisomy 21 cases

Among Down syndrome (DS) children, 40-50% have congenital heart disease (CHD). Although trisomy 21 is not sufficient to cause CHD, three copies of at least part of chromosome 21 (Hsa21) increases the risk for CHD. In order to establish a genotype-phenotype correlation for CHD in DS, we built an integrated Hsa21 map of all described partial trisomy 21 (PT21) cases with sufficient indications regarding presence or absence of CHD (n=107), focusing on DS PT21 cases. We suggest a DS CHD candidate region on 21q22.2 (0.96Mb), being shared by most PT21 cases with CHD and containing three known protein-coding genes (DSCAM, BACE2, PLAC4) and four known non-coding RNAs (DSCAM-AS1, DSCAM-IT1, LINC00323, MIR3197). The characterization of a DS CHD candidate region provides a useful approach to identify specific genes contributing to the pathology and to orient further investigations and possibly more effective therapy in relation to the multifactorial pathogenesis of CHD.

The Complex Genetic Basis of Congenital Heart Defects

Twenty years ago, chromosomal abnormalities were the only identifiable genetic causes of a small fraction of congenital heart defects (CHD). Today, a de novo or inherited genetic abnormality can be identified as pathogenic in one-third of cases. We refer to them here as monogenic causes, insofar as the genetic abnormality has a readily detectable, large effect. What explains the other two-thirds? This review considers a complex genetic basis. That is, a combination of genetic mutations or variants that individually may have little or no detectable effect contribute to the pathogenesis of a heart defect. Genes in the embryo that act directly in cardiac developmental pathways have received the most attention, but genes in the mother that establish the gestational milieu via pathways related to metabolism and aging also have an effect. A growing body of evidence highlights the pathogenic significance of genetic interactions in the embryo and maternal effects that have a genetic basis. The investigation of CHD as guided by a complex genetic model could help estimate risk more precisely and logically lead to a means of prevention.

Is maternal smoking during pregnancy associated with an increased risk of congenital heart defects among offspring? A systematic review and meta-analysis of observational studies

OBJECTIVE

To investigate the association between maternal smoking during pregnancy and risk of congenital heart defects (CHDs) among offspring.

METHODS

PubMed, EMBASE, and Web of Science were searched for eligible studies. The outcomes of interest included risk of any CHD and nine subtypes. We summarized study characteristics and used a random-effects model in meta-analysis, and a two-stage dose-response model was utilized to assess the association between smoking consumption and risk. Statistical heterogeneity was assessed by a chi-squared test of the Cochrane Q statistic and I-squared value. Publication bias was assessed by funnel plots and Egger's test, and trim and fill method was utilized when publication bias existed.

RESULTS

Forty-three observational epidemiologic studies were included. The pooled risk ratio (RR) of any CHD was 1.11 (95% CI: 1.04, 1.18), but it exhibited substantial statistical heterogeneity (p < 0.001, I²=69.0%). In sensitivity analysis, we observed significant associations for atrial septal defect (ASD) and marginally significant associations for septal defects (SPD). The two-stage dose-response analysis showed evidence to support that higher levels of tobacco smoke was associated with an increased risk of septal defects, particularly for ASD and VSD (ventricular septal defect).

CONCLUSION

Our study presents evidence to support the cardiovascular teratogenic effect of maternal smoking during pregnancy, and their offspring may suffer from approximately a 10% relative increase in the risk of CHDs on average.

DNA Methylation Profiling at Single-Base Resolution Reveals Gestational Folic Acid Supplementation Influences the Epigenome of Mouse Offspring Cerebellum

It is becoming increasingly more evident that lifestyle, environmental factors, and maternal nutrition during gestation can influence the epigenome of the developing fetus and thus modulate the physiological outcome. Variations in the intake of maternal nutrients affecting one-carbon metabolism may influence brain development and exert long-term effects on the health of the progeny. In this study, we investigated whether supplementation with high maternal folic acid during gestation alters DNA methylation and gene expression in the cerebellum of mouse offspring. We used reduced representation bisulfite sequencing to analyze the DNA methylation profile at the single-base resolution level. The genome-wide DNA methylation analysis revealed that supplementation with higher maternal folic acid resulted in distinct methylation patterns (P < 0.05) of CpG and non-CpG sites in the cerebellum of offspring. Such variations of methylation and gene expression in the cerebellum of offspring were highly sex-specific, including several genes of the neuronal pathways. These findings demonstrate that alterations in the level of maternal folic acid during gestation can influence methylation and gene expression in the cerebellum of offspring. Such changes in the offspring epigenome may alter neurodevelopment and influence the functional outcome of neurologic and psychiatric diseases.

Association between alcohol consumption during pregnancy and risks of congenital heart defects in offspring: meta-analysis of epidemiological observational studies

Background

To explore the association between maternal alcohol consumption and/or binge drinking and congenital heart defects (CHDs), we conducted a meta-analysis for more sufficient evidence on this issue.

Methods

We searched Medline, EMBASE, and the Cochrane Library from their inceptions to December 2014 for case-control and cohort studies that assessed the association between maternal alcohol consumption and CHD risk. Study-specific relative risk estimates were calculated using random-effect or fixed-effect models.

Results

A total of 19 case-control studies and 4 cohort studies were included in the meta-analysis. We observed a null association between maternal alcohol consumption during pregnancy and the risk of CHDs. Even in the analysis of different trimesters of pregnancy, we found little association between the two.

Conclusions

This meta-analysis suggests that maternal alcohol consumption is modestly not associated with the risk of CHDs. However, further investigation is needed to confirm this conclusion.

DNA methylation abnormalities in congenital heart disease

Congenital heart defects represent the most common malformation at birth, occurring also in ∼50% of individuals with Down syndrome. Congenital heart defects are thought to have multifactorial etiology, but the main causes are largely unknown. We have explored the global methylation profile of fetal heart DNA in comparison to blood DNA from control subjects: an absolute correlation with the type of tissue was detected. Pathway analysis revealed a significant enrichment of differential methylation at genes related to muscle contraction and cardiomyopathies in the developing heart DNA. We have also searched for abnormal methylation profiles on developing heart-tissue DNA of syndromic and non-syndromic congenital heart defects. On average, 3 regions with aberrant methylation were detected per sample and 18 regions were found differentially methylated between groups. Several epimutations were detected in candidate genes involved in growth regulation, apoptosis and folate pathway. A likely pathogenic hypermethylation of several intragenic sites at the MSX1 gene, involved in outflow tract morphogenesis, was found in a fetus with isolated heart malformation. In addition, hypermethylation of the GATA4 gene was present in fetuses with Down syndrome with or without congenital heart defects, as well as in fetuses with isolated heart malformations. Expression deregulation of the abnormally methylated genes was detected. Our data indicate that epigenetic alterations of relevant genes are present in developing heart DNA in fetuses with both isolated and syndromic heart malformations. These epimutations likely contribute to the pathogenesis of the malformation by cis-acting effects on gene expression.

Lifestyle, pregnancy and epigenetic effects

Rapidly growing evidences link maternal lifestyle and prenatal factors with serious health consequences and diseases later in life. Extensive epidemiological studies have identified a number of factors such as diet, stress, gestational diabetes, exposure to tobacco and alcohol during gestation as influencing normal fetal development. In light of recent discoveries, epigenetic mechanisms such as alteration of DNA methylation, chromatin modifications and modulation of gene expression during gestation are believed to possibly account for various types of plasticity such as neural tube defects, autism spectrum disorder, congenital heart defects, oral clefts, allergies and cancer. The purpose of this article is to review a number of published studies to fill the gap in our understanding of how maternal lifestyle and intrauterine environment influence molecular modifications in the offspring, with an emphasis on epigenetic alterations. To support these associations, we highlighted laboratory studies of rodents and epidemiological studies of human based on sampling population cohorts.

Genome-Wide Association Study of Down Syndrome-Associated Atrioventricular Septal Defects

The goal of this study was to identify the contribution of common genetic variants to Down syndrome−associated atrioventricular septal defect, a severe heart abnormality. Compared with the euploid population, infants with Down syndrome, or trisomy 21, have a 2000-fold increased risk of presenting with atrioventricular septal defects. The cause of this increased risk remains elusive. Here we present data from the largest heart study conducted to date on a trisomic background by using a carefully characterized collection of individuals from extreme ends of the phenotypic spectrum. We performed a genome-wide association study using logistic regression analysis on 452 individuals with Down syndrome, consisting of 210 cases with complete atrioventricular septal defects and 242 controls with structurally normal hearts. No individual variant achieved genome-wide significance. We identified four disomic regions (1p36.3, 5p15.31, 8q22.3, and 17q22) and two trisomic regions on chromosome 21 (around PDXK and KCNJ6 genes) that merit further investigation in large replication studies. Our data show that a few common genetic variants of large effect size (odds ratio >2.0) do not account for the elevated risk of Down syndrome−associated atrioventricular septal defects. Instead, multiple variants of low-to-moderate effect sizes may contribute to this elevated risk, highlighting the complex genetic architecture of atrioventricular septal defects even in the highly susceptible Down syndrome population.

The genetics of folate metabolism and maternal risk of birth of a child with Down syndrome and associated congenital heart defects

Almost 15 years ago it was hypothesized that polymorphisms of genes encoding enzymes involved in folate metabolism could lead to aberrant methylation of peri-centromeric regions of chromosome 21, favoring its abnormal segregation during maternal meiosis. Subsequently, more than 50 small case-control studies investigated whether or not maternal polymorphisms of folate pathway genes could be risk factors for the birth of a child with Down syndrome (DS), yielding conflicting and inconclusive results. However, recent meta-analyses of those studies suggest that at least three of those polymorphisms, namely MTHFR 677C>T, MTRR 66A>G, and RFC1 80G>A, are likely to act as maternal risk factors for the birth of a child with trisomy 21, revealing also complex gene-nutrient interactions. A large-cohort study also revealed that lack of maternal folic acid supplementation at peri-conception resulted in increased risk for a DS birth due to errors occurred at maternal meiosis II in the aging oocyte, and it was shown that the methylation status of chromosome 21 peri-centromeric regions could favor recombination errors during meiosis leading to its malsegregation. In this regard, two recent case-control studies revealed association of maternal polymorphisms or haplotypes of the DNMT3B gene, coding for an enzyme required for the regulation of DNA methylation at centromeric and peri-centromeric regions of human chromosomes, with risk of having a birth with DS. Furthermore, congenital heart defects (CHD) are found in almost a half of DS births, and increasing evidence points to a possible contribution of lack of folic acid supplementation at peri-conception, maternal polymorphisms of folate pathway genes, and resulting epigenetic modifications of several genes, at the basis of their occurrence. This review summarizes available case-control studies and literature meta-analyses in order to provide a critical and up to date overview of what we currently know in this field.

Maternal Alcohol Consumption before and during Pregnancy and the Risks of Congenital Heart Defects in Offspring: A Systematic Review and Meta-analysis

OBJECTIVE

Epidemiologic studies have reported conflicting results regarding maternal alcohol consumption before and during pregnancy, and the risk of congenital heart defects (CHDs). However, a systematic review and meta-analysis of the association between maternal alcohol consumption and CHDs in offspring has not been conducted.

DESIGN

We searched MEDLINE and EMBASE for articles catalogued between their inception and February 16, 2015; we identified relevant published studies that assessed the association between maternal alcohol consumption and CHD risk. Two authors independently assessed the eligibility of the retrieved articles and extracted data from them. Study-specific relative risk estimates were pooled by random-effects or fixed-effects models.

RESULTS

From the 1527 references, a total of 19 case-control studies and four cohort studies were enrolled in this meta-analysis. The summary of 23 studies related to CHDs indicated an overall pooled relative risk of 1.13 (95% confidence interval: 0.96, 1.29) among mothers drinking before or during pregnancy. Statistically significant heterogeneity was detected (Q = 196.61, P < .001, I(2) = 88.8%) with no publication bias (Egger's test: P = .157). We conducted stratified and meta-regression analyses to identify the origin of the heterogeneity among studies.

CONCLUSION

In summary, this meta-analysis provided no positive association between maternal alcohol consumption and risk of CHDs.

Maternal folic acid supplementation and the risk of congenital heart defects in offspring: a meta-analysis of epidemiological observational studies

Epidemiological studies have reported conflicting results regarding the association between maternal folic acid supplementation and the risk of congenital heart defects (CHDs). However, a meta-analysis of the association between maternal folic acid supplementation and CHDs in offspring has not been conducted. We searched the MEDLINE and EMBASE databases for articles cataloged between their inceptions and October 10, 2014 and identified relevant published studies that assessed the association between maternal folate supplementation and the risk of CHDs. Study-specific relative risk estimates were pooled using random-effects or fixed-effects models. Out of the 1,606 articles found in our initial literature searches, a total of 1 randomized controlled trial, 1 cohort study, and 16 case-control studies were included in our final meta-analysis. The overall results of this meta-analysis provide evidence that maternal folate supplementation is associated with a significantly decreased risk of CHDs (RR = 0.72, 95% CI: 0.63–0.82). Statistically significant heterogeneity was detected (Q = 82.48, P < 0.001, I² = 79.4%). We conducted stratified and meta-regression analyses to identify the origin of the heterogeneity among the studies, and a Galbraith plot was generated to graphically assess the sources of heterogeneity. This meta-analysis provides a robust estimate of the positive association between maternal folate supplementation and a decreased risk of CHDs.

Contribution of copy-number variation to Down syndrome-associated atrioventricular septal defects

Purpose

The goal of this study was to identify the contribution of large copy number variants (CNV) to Down syndrome (DS) associated atrioventricular septal defects (AVSD), whose risk in the trisomic population is 2000-fold more compared to general disomic population.

Methods

Genome-wide CNV analysis was performed on 452 individuals with DS (210 cases with complete AVSD; 242 controls with structurally normal hearts) using Affymetrix SNP 6.0 arrays, making this the largest heart study conducted to date on a trisomic background.

Results

Large common CNVs with substantial effect sizes (OR>2.0) do not account for the increased risk observed in DS-associated AVSD. In contrast, cases had a greater burden of large rare deletions (p<0.01) and intersected more genes (p<0.007) when compared to controls. We also observed a suggestive enrichment of deletions intersecting ciliome genes in cases compared to controls.

Conclusion

Our data provide strong evidence that large rare deletions increase the risk of DS-associated AVSD, while large common CNVs do not appear to increase the risk of DS-associated AVSD. The genetic architecture of AVSD is complex and multifactorial in nature.

Folic acid supplementation in pregnancy and implications in health and disease

Maternal exposure to dietary factors during pregnancy can influence embryonic development and may modulate the phenotype of offspring through epigenetic programming. Folate is critical for nucleotide synthesis, and preconceptional intake of dietary folic acid (FA) is credited with reduced incidences of neural tube defects in infants. While fortification of grains with FA resulted in a positive public-health outcome, concern has been raised for the need for further investigation of unintended consequences and potential health hazards arising from excessive FA intakes, especially following reports that FA may exert epigenetic effects. The objective of this article is to discuss the role of FA in human health and to review the benefits, concerns and epigenetic effects of maternal FA on the basis of recent findings that are important to design future studies.

Echocardiography in children with Down syndrome

Congenital heart disease is a common problem in children with Down syndrome (DS). Echocardiography plays an important role in the detection of both structural and functional abnormalities in this group of patients. Fetal echocardiography can help in the early recognition of DS by detecting soft markers of DS, but its main role is to define the exact nature of the suspected cardiac problem in the fetus. Postnatal echocardiography is mandatory in the first month of life for all neonates with DS. It is also indicated before any cardiac surgery and for serial follow-up after cardiac surgery. In this article, we discuss the types and mechanism of cardiac abnormalities in DS children and the role of both fetal and postnatal echocardiography in the detection of these abnormalities.

Echocardiography in children with Down syndrome

Congenital heart disease is a common problem in children with Down syndrome (DS). Echocardiography plays an important role in the detection of both structural and functional abnormalities in this group of patients. Fetal echocardiography can help in the early recognition of DS by detecting soft markers of DS, but its main role is to define the exact nature of the suspected cardiac problem in the fetus. Postnatal echocardiography is mandatory in the first month of life for all neonates with DS. It is also indicated before any cardiac surgery and for serial follow-up after cardiac surgery. In this article, we discuss the types and mechanism of cardiac abnormalities in DS children and the role of both fetal and postnatal echocardiography in the detection of these abnormalities.

The MTR 2756A>G polymorphism and maternal risk of birth of a child with Down syndrome: a case-control study and a meta-analysis

Methionine synthase (MTR) is required for the conversion of homocysteine (hcy) to methionine in the one-carbon metabolic pathway. Previous studies investigating a common MTR 2756A>G polymorphism as a maternal risk factor for the birth of a child with Down syndrome (DS) are conflicting and limited by small case-control cohorts, and its contribution to circulating hcy levels is still debated. We performed a large case-control study and a meta-analysis of the literature to further address the role of MTR 2756A>G as a maternal risk factor for the birth of a child with DS. 286 mothers of a DS child (MDS) and 305 control mothers of Italian origin were included in the case-control study. Genotyping was performed by means of PCR/RFLP technique. Data on circulating levels of hcy, folates, and vitamin B12 were available for 189 MDS and 194 control mothers. The meta analysis of previous and present data involved a total of 8 studies (1,171 MDS and 1,402 control mothers). Both the case-control study and the meta-analysis showed no association of MTR 2756A>G with the maternal risk of birth of a child with DS (OR = 1.15; 95 % CI 0.85-1.55, and OR = 1.08; 95 % CI 0.93-1.25, respectively), even after stratification of the overall data available for the meta-analysis into ethnic groups. No association of the studied polymorphism with circulating levels of hcy, folates, and vitamin B12 was observed. Present data do not support a role for MTR 2756A>G as independent maternal risk factor for a DS birth.

Complex cardiac defects after ethanol exposure during discrete cardiogenic events in zebrafish: prevention with folic acid

BACKGROUND

Fetal alcohol spectrum disorder (FASD) describes a range of birth defects including various congenital heart defects (CHDs). Mechanisms of FASD-associated CHDs are not understood. Whether alcohol interferes with a single critical event or with multiple events in heart formation is not known.

RESULTS

Our zebrafish embryo experiments showed that ethanol interrupts different cardiac regulatory networks and perturbs multiple steps of cardiogenesis (specification, myocardial migration, looping, chamber morphogenesis, and endocardial cushion formation). Ethanol exposure during gastrulation until cardiac specification or during myocardial midline migration did not produce severe or persistent heart development defects. However, exposure comprising gastrulation until myocardial precursor midline fusion or during heart patterning stages produced aberrant heart looping and defective endocardial cushions. Continuous exposure during entire cardiogenesis produced complex cardiac defects leading to severely defective myocardium, endocardium, and endocardial cushions. Supplementation of retinoic acid with ethanol partially rescued early heart developmental defects, but the endocardial cushions did not form correctly. In contrast, supplementation of folic acid rescued normal heart development, including the endocardial cushions.

CONCLUSIONS

Our results indicate that ethanol exposure interrupted divergent cardiac morphogenetic events causing heart defects. Folic acid supplementation was effective in preventing a wide spectrum of ethanol-induced heart developmental defects.

DNMT3B promoter polymorphisms and maternal risk of birth of a child with Down syndrome

STUDY QUESTION

Are DNMT3B promoter polymorphisms among maternal risk factors for the birth of a child with Down syndrome (DS)?

SUMMARY ANSWER

Present results suggest that combinations of functional DNMT3B promoter polymorphisms might modulate maternal risk of birth of a child with DS.

WHAT IS KNOWN ALREADY

The DNMT3B gene codes for DNA methyltransferase 3b (DNMT3b), a protein required for genome-wide de novo methylation, for the establishment of DNA methylation patterns during development and for regulating the histone code and DNA methylation at centromeric regions. Two common functional DNMT3B promoter polymorphisms, namely -149 C > T (rs2424913) and -579 G > T (rs1569686), have been extensively investigated in cancer genetic association studies but less is known about their role in non-cancer diseases. Early in 1999, it was supposed that impaired DNA methylation of pericentromeric regions might represent a maternal risk factor for having a baby with DS.

STUDY DESIGN, SIZE AND DURATION

We aimed to investigate DNMT3B -149 C > T and -579 G > T polymorphisms as maternal risk factors for the birth of a child with DS. The study was performed on DNA samples from 172 mothers of DS individuals (135 aged <35 years when they conceived) and 157 age-matched mothers of unaffected individuals.

PARTICIPANTS/MATERIALS, SETTING AND METHODS

Genotyping was performed by means of the PCR-RFLP technique.

MAIN RESULTS AND THE ROLE OF CHANCE

The DNMT3B -579T allele [odds ratio (OR) = 0.68; 95% confidence interval (CI) = 0.48-0.94, P = 0.02], the DNMT3B -579 GT genotype (OR = 0.55; 95% CI = 0.35-0.87 , P = 0.01) and the combined DNMT3B -579 GT + TT genotype (OR = 0.55; 95% CI = 0.36-0.86 , P = 0.008) were associated with reduced risk of birth of a child with DS. A joint effect of the two polymorphisms was observed and the combined -579 GT/-149 CC genotype resulted in decreased DS risk (OR = 0.22; 95% CI = 0.08-0.64, P = 0.003). The effect remained statistically significant after Bonferroni's correction for multiple comparisons. Similar results were obtained when the analysis was restricted to women who conceived a DS child before 35 years of age.

LIMITATIONS AND REASONS FOR CAUTION

To the best of our knowledge, this is the first genetic association study aimed at evaluating DNMT3B polymorphisms as maternal risk factors for DS. Replication of the findings in other populations is required.

WIDER IMPLICATIONS OF THE FINDINGS

If confirmed in subsequent studies, DNMT3B promoter polymorphisms might be additional markers to be taken into account when evaluating the contribution of one-carbon (folate) metabolism to the maternal risk of birth of a child with DS.

Down syndrome in India--diagnosis, screening, and prenatal diagnosis

Down syndrome (DS) is the most common genetic cause of mental retardation. Clinical manifestations are variable, and children have psychomotor impairment, multiple malformations, and medical conditions. Confirmation of the diagnosis is by karyotype analysis. The cytogenetic abnormality can be classified into pure trisomy 21, translocation, or mosaicism. Risk of recurrence depends on the primary cytogenetic abnormality in the proband. Prenatal screening is by biochemical and ultrasound markers in the first and second trimester. Definitive prenatal diagnosis is by analysis of fetal chromosomes in fetal chorionic villi, amniocytes, or cord blood. A noninvasive test for trisomy 21 in maternal blood has been developed by massively parallel shotgun sequencing. Therapeutic studies in Ts65Dn mice suggest an exciting prospect of improvement of learning ability and memory deficits.

Molecular signatures of cardiac defects in Down syndrome lymphoblastoid cell lines suggest altered ciliome and Hedgehog pathways

Forty percent of people with Down syndrome exhibit heart defects, most often an atrioventricular septal defect (AVSD) and less frequently a ventricular septal defect (VSD) or atrial septal defect (ASD). Lymphoblastoid cell lines (LCLs) were established from lymphocytes of individuals with trisomy 21, the chromosomal abnormality causing Down syndrome. Gene expression profiles generated from DNA microarrays of LCLs from individuals without heart defects (CHD⁻; n = 22) were compared with those of LCLs from patients with cardiac malformations (CHD⁺; n = 21). After quantile normalization, principal component analysis revealed that AVSD carriers could be distinguished from a combined group of ASD or VSD (ASD+VSD) carriers. From 9,758 expressed genes, we identified 889 and 1,016 genes differentially expressed between CHD⁻ and AVSD and CHD⁻ and ASD+VSD, respectively, with only 119 genes in common. A specific chromosomal enrichment was found in each group of affected genes. Among the differentially expressed genes, more than 65% are expressed in human or mouse fetal heart tissues (GEO dataset). Additional LCLs from new groups of AVSD and ASD+VSD patients were analyzed by quantitative PCR; observed expression ratios were similar to microarray results. Analysis of GO categories revealed enrichment of genes from pathways regulating clathrin-mediated endocytosis in patients with AVSD and of genes involved in semaphorin-plexin-driven cardiogenesis and the formation of cytoplasmic microtubules in patients with ASD-VSD. A pathway-oriented search revealed enrichment in the ciliome for both groups and a specific enrichment in Hedgehog and Jak-stat pathways among ASD+VSD patients. These genes or related pathways are therefore potentially involved in normal cardiogenesis as well as in cardiac malformations observed in individuals with trisomy 21.