Infants'MTHFRpolymorphisms and nonsyndromic orofacial clefts susceptibility: A meta-analysis based on 17 case-control studies

Genetic markers for non-syndromic orofacial clefts in populations of European ancestry: a meta-analysis

To date, the involvement of various genetic markers in the aetiopathogenesis of non-syndromic orofacial cleft (nsOFC) has been extensively studied. In the present study, we focused on studies performed on populations of European ancestry to systematically review the available literature to define relevant genetic risk factors for nsOFC. Eligible studies were obtained by searching Ovid Medline and Ovid Embase. We gathered the genetic markers from population-based case–control studies on nsOFC, and conducted meta-analysis on the repeatedly reported markers. Whenever possible, we performed stratified analysis based on different nsOFC phenotypes, using allelic, dominant, recessive and overdominant genetic models. Effect sizes were expressed as pooled odds ratios (ORs) with 95% confidence intervals (CIs), and p ≤ 0.05 were considered statistically significant. A total of 84 studies were eligible for this systematic review, with > 700 markers included. Of these, 43 studies were included in the meta-analysis. We analysed 47 genetic variants in 30 genes/loci, which resulted in 226 forest plots. There were statistically significant associations between at least one of the nsOFC phenotypes and 19 genetic variants in 13 genes/loci. These data suggest that IRF6, GRHL3, 8q24, VAX1, TGFA, FOXE1, ABCA4, NOG, GREM1, AXIN2, DVL2, WNT3A and WNT5A have high potential as biomarkers of nsOFC in populations of European descent. Although other meta-analyses that included European samples have been performed on a limited number of genetic variants, this study represents the first meta-analysis of all genetic markers that have been studied in connection with nsOFC in populations of European ancestry.

5,10-Methylenetetrahydrofolate reductase (MTHFR) C677T/A1298C polymorphisms in patients with nonsyndromic cleft lip and palate

Cleft lip with or without cleft palate (CL/P) is considered a multifactorial genetic disorder. Folic acid metabolism has been suggested to underlie the development of CL/P. The gene for the enzyme 5,10-methylentetrahydrofolate reductase (MTHFR) contributes to folic acid metabolism, and polymorphisms of this gene at C677T (rs1801133) and A1298C (rs1801131) are reported to alter its enzyme activity and are suggested to be involved in CL/P development. We investigated C677T and A1298C polymorphisms of the MTHFR gene in Japanese patients with nonsyndromic CL/P and cleft palate only (CPO). We examined 240 patients with CL/P, 103 fathers and 153 mothers of the patients, and 68 healthy controls. Restriction fragment length polymorphisms (RFLPs) of C677T and A1298C of MTHFR were analyzed. We determined the frequencies of the polymorphisms in the patients and controls and performed a transmission equilibrium test and haplotype analysis of both MTHFR C677T and A1298C. There were no significant differences in the frequencies of MTHFR C677T and A1298C polymorphisms between the patients and controls. We did not observe transmission equilibrium or linkage equilibrium among the cases. In this experimental condition, we did not detect an association of MTHFR C677T and/or A1298C polymorphisms with the development of CL/P in this Japanese cohort.

A meta-analysis and meta-regression of association between MTHFR A1298C polymorphism and nonsyndromic cleft lip/palate risk: An evaluation based on five genetic models

OBJECTIVE

The present meta-analysis is intended to assess the association between NSCL/P risk and methylenetetrahydrofolate reductase (MTHFR) A1298C polymorphism in case-control studies.

MATERIALS AND METHODS

The Web of Science, PubMed/Medline, Scopus, and Cochrane Library databases were searched for related articles published by April 2019. Review Manager 5.3 was applied to measure the odds ratios (ORs) with 95% confidence interval (CI) in the analyses assessing the strength of the association between A1298C polymorphism and NSCL/P risk. Results Sixteen studies were involved and analysed in this meta-analysis. Altogether, the reviewed articles included 2677 NSCL/P patients and 3669 controls. The pooled ORs of the allele, homozygote, heterozygote, dominant, and recessive models were 1.11 (95% CI: 0.94, 1.30; P=0.21), 1.14 (95% CI: 0.94, 1.37; P=0.18), 0.98 (95% CI: 0.80, 1.20; P=0.87), 1.03 (95% CI: 0.86, 1.22; P=0.79), and 1.18 (95% CI: 0.99, 1.41; P=0.07), respectively. The analysis did not identify any significant association between the polymorphism and the risk of NSCL/P in any ethnicity or source of controls.

CONCLUSIONS

This meta-analysis revealed that A1298C polymorphism is not associated with NSCL/P susceptibility, and the subgroup analyses based on ethnicity and the source of cases further confirmed this result.

Association between 20q12 rs13041247 polymorphism and risk of nonsyndromic cleft lip with or without cleft palate: a meta-analysis

BACKGROUND

Previous genome-wide association studies have identified a link between the rs13041247 single nucleotide polymorphisms (SNPs) in the chromosome 20q12 locus and the development of the congenital malformation known as nonsyndromic cleft lip with or without cleft palate (NSCL/P). The present meta-analysis was therefore designed to formally assess the relationship between rs13041247 and NSCL/P.

METHODS

We searched Embase, Web of Science, PubMed, the China National Knowledge Internet (CNKI), and the China Wanfang database in order to identify relevant published through 25 June 2019. This allowed us to identify 13 studies incorporating 4914 patients and 5981 controls for whom rs13041247 genotyping had been conducted, with STATA 12.0 then being used to conduct a meta-analysis of these pooled results. The I² statistic was used to compare heterogeneity among studies.

RESULTS

In total this analysis incorporated 13 case-control studies. No association between the rs13041247 polymorphism and NSCL/P risk was detected in individuals of Asian ethnicity (C vs T: OR = 0.847, 95% CI = 0.702-1.021; CC vs TT: OR = 0.725, 95% CI = 0.494-1.063; CC vs CT: OR = 0.837, 95% CI = 0.657-1.067; CT + TT vs CC: OR = 1.265, 95% CI = 0.951-1.684; CC + CT vs TT: OR = 0.805, 95% CI = 0.630-1.029) or Caucasian ethnicity (C vs T: OR = 0.936, 95% CI = 0.786-1.114; CC vs TT: OR = 0.988, 95% CI = 0.674-1.446; CC vs CT: OR = 1.197, 95% CI = 0.816-1.757; CT + TT vs CC: OR = 0.918, 95% CI = 0.639-1.318; CC + CT vs TT: OR = 0.855, 95% CI = 0.677-1.081). However, an overall analysis of all participants in these studies revealed the rs13041247 C allele, the CT genotype, and the CC + CT model to be linked to a reduced NSCL/P risk (C vs T: OR = 0.897, 95% CI: 0.723-1.114, P = 0.048; CT vs TT: OR = 0.839, 95% CI: 0.734-0.959, P = 0.01; CC + CT vs TT: OR = 0.824, 95% CI: 0.701-0.968, P = 0.019).

CONCLUSION

These results suggest that the rs13041247 SNP located at the 20q12 chromosomal locus is associated with NSCL/P risk in an overall pooled study population, although this association was not significant in East Asian or Caucasian populations.

Methylenetetrahydrofolate reductase C677T polymorphism is not associated with the risk of nonsyndromic cleft lip/palate: An updated meta-analysis

Both genetic and environmental factors affect the risk of orofacial clefts. The present meta-analysis aimed to evaluate the association between methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and risk of nonsyndromic cleft lip/palate (NSCL/P) in cases-control studies. The PubMed/Medline, Scopus, Web of Science, and Cochrane Library databases were searched up to April 2019 with no restrictions. The odds ratios (ORs) and 95% confidence intervals (CIs) in all analyses were calculated by Review Manager 5.3 software. The funnel plot analysis was carried out by the Comprehensive Meta-Analysis version 2.0 software. Subgroup analysis, meta-regression, and sensitivity analysis were performed for the pooled analyses. Thirty-one studies reviewed in this meta-analysis included 4710 NSCL/P patients and 7271 controls. There was no significant association between MTHFR C677T polymorphism and NSCL/P susceptibility related to allelic model (OR = 1.04; P = 0.49), homozygote model (OR = 1.11; P = 0.35), heterozygote model (OR = 0.99; P = 0.91), dominant model (OR = 1.00; P = 0.96), or recessive model (OR = 1.08; P = 0.23). There was no significant association between MTHFR C677T polymorphism and NSCL/P susceptibility based on the ethnicity or the source of cases. There was a significant linear relationship between the year of publication and log ORs for the allele model. The results of the present meta-analysis failed to show an association between MTHFR C677T polymorphism and NSCL/P susceptibility. The subgroup analyses based on the ethnicity and the source of cases further confirmed this result.

Association between methylenetetrahydrofolate reductase polymorphisms and non-syndromic cleft lip with or without palate susceptibility: an updated systematic review and meta-analysis

Methylenetetrahydrofolate reductase (MTHFR) polymorphisms are thought to be involved in the development of cleft lip with or without cleft palate (NSCL/P), but published results are contradictory. We therefore designed an updated meta-analysis to pool eligible studies and to evaluate further the possible relations between MTHFR polymorphisms (c.677C>T and c.1298A>C) and susceptibility to NSCL/P. A comprehensive search based on PubMed, Medline, Web of Science, and Embase databases was made up to February 2018. Twenty-three case-control and 10 case-parent trio studies (including 1149 cases and 1161 controls) were retrieved. Odds ratio (OR) with 95% CI were used to estimate the pooled strength of association under different genetic models. The Q test and I² test were used to estimate heterogeneity among studies, the quality of which was assessed using the Newcastle-Ottawa scale. In the MTHFR c.677C>T polymorphism group, there were significant overall results for the recessive (OR 1.231, 95%CI 1.092 to 1.387) and homozygote (OR 1.252, 95%CI 1.078 to 1.456) models. Subgroup analysis by subjects and ethnicity identified only associations in European mothers for the recessive model and the homozygote model. For the c.1298A>C group, there were no significant results for either European or Asian patients for all genetic models. The MTHFR c.677C>T polymorphism might increase susceptibility to NSCL/P in European mothers, but was negatively associated in Asian patients, and the MTHFR c.1298A>C polymorphism is not involved in the development of NSCL/P in either European or Asian patients.

Associations Between MTR A2756G, MTRR A66G, and TCN2 C776G Polymorphisms and Risk of Nonsyndromic Cleft Lip With or Without Cleft Palate: A Meta-Analysis

OBJECTIVE

We conducted a meta-analysis to investigate the associations of methionine synthase (MTR) A2756G, methionine synthase reductase (MTRR) A66G, and transcobalamin 2 (TCN2) C776G gene polymorphisms with nonsyndromic cleft lip with or without cleft palate (NSCL/P).

MATERIALS AND METHODS

The PubMed, Web of Science, Embase, and Wiley Online Library databases and the China Biomedical Literature Service System (SinoMed) were searched for relevant articles to explore the associations between the MTR A2756G, MTRR A66G, and TCN2 C776G polymorphisms and the risk of NSCL/P. We performed overall comparisons and stratified analyses according to the ethnicity, type of NSCL/P, and Hardy-Weinberg equilibrium (HWE) of the control group. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were applied to estimate the associations of these gene polymorphisms with NSCL/P risk using fixed-effects or random-effects models incorporating five genetic models.

RESULTS

Ultimately, 12 articles were included in this study. The pooled results did not reveal a significant association of the MTR A2756G polymorphism with NSCL/P risk (G vs. A: OR = 0.95, 95% CI = 0.82-1.11, p = 0.55). Similar results were observed for the MTRR A66G polymorphism (G vs. A: OR = 0.99, 95% CI = 0.82-1.18, p = 0.72) and the TCN2 C776G polymorphism (G vs. C: OR = 0.95, 95% CI = 0.86-1.06, p = 0.37).

CONCLUSION

In summary, the MTR A2756G, MTRR A66G, and TCN2 C776G polymorphisms might not be associated with NSCL/P risk.

Association Between CRISPLD2 Polymorphisms and the Risk of Nonsyndromic Clefts of the Lip and/or Palate: A Meta-analysis

OBJECTIVE

Nonsyndromic clefts of the lip and/or palate (NSCL/P) are one of the most common polygenic diseases. Recently, many studies focused on the association between CRISPLD2 polymorphisms and NSCL/P risk. However, some studies have shown opposite results. In this study, meta-analysis was used to confirm whether CRISPLD2 polymorphism was associated with NSCL/P, and the possible mechanism between CRISPLD2 and NSCL/P was explored.

METHODS

Relevant studies were conducted on PubMed, Ovid, EBSCO, CINAHL, FMRS, Web of Science, CNKI, and Wanfang databases from their inception up to June 31, 2016. Review Manager 5.0.24 was used to analyze whether CRISPLD2 polymorphism was involved in NSCL/P by pooling odds ratios (ORs) and 95% confidence intervals (CIs). Potential publication bias was evaluated by visual inspection of the funnel plot.

RESULTS

CRISPLD2 rs4783099 was associated with cleft lip and/or palate (CL/P) statistically (OR = 3.18, P < .01). Compared to genotype TT, genotypes CC and CT were correlated significantly (OR = 2.04, P = .04) with CL/P. No evidence showed an association between genetic variation at the CRISPLD2 locus and cleft palate only (CP).

CONCLUSION

The polymorphism of CRISPLD2 rs4783099 is correlated with an increased risk of CL/P.

Genetic Interactions in Nonsyndromic Orofacial Clefts in Europe—EUROCRAN Study

Background

Nonsyndromic cleft lip with or without cleft palate (nsCL±P) and nonsyndromic cleft palate (nsCP) are caused by a combination of genetic and environmental risk factors. We investigated gene-environment and gene-gene joint effects in a large multicenter study of case-parent triads.

Methods

The nsCL±P or nsCP triads were recruited in 11 European countries between 2001 and 2005. We collected DNA samples from infants and from their mothers and fathers, and mothers completed a questionnaire on exposures, including smoking and folic acid supplement use during pregnancy. We used log-linear regression to estimate relative risks (RRs) and 95% confidence intervals (CIs) for associations between nsCL±P or nsCP and variants in MTHFR, MTHFD1, TGFA, SATB2, and MSX1, stratifying by environmental or genetic factors.

Results

We obtained genotype and exposure data for 728 nsCL±P triads and 292 nsCP triads. In male infants, there was no association between the mother's homozygous MSX1 p(CA) ∗4/∗4 genotype and nsCL±P (RR, 0.98; 95% CI, 0.63–1.54), but this maternal genotype resulted in a doubling of risk for female infants (RR, 2.21; 95% CI, 1.13–4.34). There was evidence suggestive of gene-gene joint-effects between MTHFR-TGFA for nsCP but not for nsCL±P.

Conclusion

Although we chose the genes and their variants and putative joint effects based on associations previously reported in the literature, we replicated few associations. These results do not provide evidence supporting associations between these genes and oral clefts in European populations, although gene-environment and gene-gene interactions could play a role in oral cleft etiology.

Genetic polymorphism of MTHFR C677T with preterm birth and low birth weight susceptibility: a meta-analysis

PURPOSE

This study aimed at clarifying the association of maternal and neonatal methylenetetrahydrofolate reductase (MTHFR) C677T polymorphisms with preterm birth (PTB) and low birth weight (LBW) susceptibility, respectively.

MATERIALS AND METHODS

A systematic search of Embase, Medline, China Biological Medicine Database (CBM), Chinese National Knowledge Infrastructure (CNKI), and Wanfang Database was performed before June, 2016. The frequencies of maternal and neonatal MTHFR C677T genotypes in the cases and controls and other information were extracted by two independent investigators. Odds ratios (ORs) with 95% confidence intervals (CIs) were adopted to estimate the relationships between MTHFR C677T polymorphisms and PTB as well as LBW by random or fixed effect models.

RESULTS

Twenty-five studies from 20 articles concerning maternal and neonatal MTHFR C677T gene polymorphism with PTB and LBW were included in this study. Maternal MTHFR C677T polymorphism was associated with PTB risk under allele contrast (T vs. C, OR = 1.36, 95% CI 1.02-1.81), homozygote (TT vs. CC, OR = 1.70, 95% CI 1.07-2.68), and recessive (TT vs. CT + CC, OR = 1.49, 95% CI 1.00-2.22) model, but not dominant or heterozygote model. Maternal MTHFR C677T polymorphism was also associated with LBW risk under allele contrast (OR = 1.69, 95% CI 1.25-2.28), homozygote (OR = 2.26, 95% CI 1.44-3.54), dominant (OR = 1.71, 95% CI 1.19-2.47), recessive (OR = 1.79, 95% CI 1.42-2.26) model, but not heterozygote model. No associations between neonatal MTHFR C677T polymorphism and PTB or LBW were found under all genetic models.

CONCLUSIONS

Identification of maternal MTHFR C677T mutation may play a key role for primary prevention of PTB as well as LBW and screening pregnant women of high risk in developing countries.

MTR, MTRR, and MTHFR Gene Polymorphisms and Susceptibility to Nonsyndromic Cleft Lip With or Without Cleft Palate

OBJECTIVE

To examine the associations of methionine synthase (MTR), methionine synthase reductase (MTRR), and methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms with the susceptibility to nonsyndromic cleft lip with or without cleft palate (NSCL/P).

METHODS

Between May 2012 and August 2014, 147 NSCL/P patients (case group) and 129 healthy volunteers (control group) were recruited for the study. The MTR A2756G, MTRR A66G, MTHFR C677T and MTHFR A1298C polymorphisms were assessed by polymerase chain reaction-restriction fragment length polymorphism. Haplotype analyses were performed with SHEsis software. Logistic regression analysis was used to evaluate the possible risk factors for NSCL/P. Generalized multifactor dimensionality reduction (GMDR) was applied to detect gene-gene interactions.

RESULTS

MTR A2756G, MTRR A66G, and MTHFR C677T gene polymorphisms were associated with the risk of NSCL/P (all p < 0.05). Logistic regression analysis revealed that MTR A2756G, MTR RA66G, and MTHFR C667T might increase the risk of NSCL/P (odds ratio [OR] = 0.270, 95% confidence interval [95% CI] = 0.106-0.689; OR = 0.159, 95% CI = 0.069-0.368; OR = 0.343, 95% CI = 0.139-0.844). The CA haplotype in the MTHFR gene may serve as a protective factor for NSCL/P (OR = 0.658, 95% CI = 0.470-0.923), and the TA haplotype might be a risk factor (OR = 2.001, 95% CI = 1.301-3.077). GMDR revealed that the optimal models were two- and four-dimensional models with prediction accuracies of 75.73% (p = 0.001) and 77.21% (p = 0.001) and the best cross-validation consistencies of 10/10 and 10/10, respectively.

CONCLUSION

MTR A2756G, MTRR A66G, and MTHFR C677T polymorphisms may be related to NSCL/P, and interactions were detected between the MTR A2756G, MTRR A66G, and MTHFR C677T and A1298C polymorphisms.

WITHDRAWN: The MSX1 gene polymorphisms rs12532 and rs1001179 confer an increased risk of non syndromic orofacial clefts

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Non-syndromic cleft lip with or without cleft palate in Asian populations: Association analysis on three gene polymorphisms of the folate pathway

OBJECTIVE

Orofacial clefts (OFCs) are one of the most common birth defects in humans. They are the subject of a number of investigations aimed at elucidating the bases of their complex mode of inheritance involving both genetic and environmental factors. Genes belonging to the folate pathway have been among the most studied. The aim of the investigation was to replicate previous studies reporting evidence of association between polymorphisms of folate related genes and the occurrence of non-syndromic cleft lip with or without cleft palate (NSCL/P), using three independent samples of different ancestry: from Tibet, Bangladesh and Iran, respectively.

DESIGN

Specifically, the polymorphisms rs1801133 of MTHFR, rs1801198 of TCN2, and rs4920037 of CBS, were tested.

RESULTS

A decreased risk of NSCL/P was observed in patients presenting the C677T variant at MTHFR gene (relative risk for heterozygotes=0.53; 95% confidence interval [C.I.]=0.32-0.87). The investigated polymorphisms mapping at TCN2 and CBS genes did not provide any evidence of association.

CONCLUSION

Overall, these results indicate that NSCL/P risk factors differ among populations and confirm the importance of testing putative susceptibility variants in different genetic backgrounds.

Association between Maternal MTHFR Polymorphisms and Nonsyndromic Cleft Lip with or without Cleft Palate in Offspring, A Meta-Analysis Based on 15 Case-Control Studies

Background

The methylenetetrahydrofolate reductase (MTHFR) is thought to be involved in the development of nonsyndromic cleft lip with or without cleft palate (NSCL/P). However, conflicting results have been obtained when evaluating the association between maternal MTHFR C677T and A1298C polymorphisms and the risk of NSCL/P. In light of this gap, a meta-analysis of all eligible case-control studies was conducted in the present study.

Materials and Methods

A total of 15 case-control studies were ultimately identified after a comprehensive literature search and Hardy-Weinberg equilibrium (HWE) examination. Cochrane’s Q test and index of heterogeneity (I²) indicated no obvious heterogeneity among studies.

Results

Fixed or random-effects models were used to calculate the pooled odds ratios (ORs). The results showed that the TT genotype in mothers increased the likelihood of having NSCL/P offspring 1.25 times (95% CI: 1.047-1.494) more than the CC homozygotes. Meanwhile, maternal TT genotype increased the risk of producing NSCL/P offspring in recessive model (OR=1.325, 95% CI: 1.124-1.562). However, the CT heterozygote and the CT+TT dominant models had no association with NSCL/P offspring compared with the CC wild-type homozygote model. Subgroup analyses based on ethnicity indicated that maternal TT genotype increased the likelihood of having NSCL/P offspring in Whites (OR=1.308, 95% CI: 1.059-1.617) and Asians (OR=1.726, 95% CI: 1.090-2.733) in recessive model. Also, subgroup analyses based on source of control showed that mothers with the 677TT genotype had a significantly increased susceptibility of having NSCL/P children in hospital based population (HB) when compared with CC homozygotes (OR=1.248, 95% CI: 1.024-1.520) and un- der the recessive model (OR=1.324, 95% CI: 1.104-1.588). Furthermore, maternal A1298C polymorphism had no significant association with producing NSCL/P offspring (dominant model OR=0.952, 95% CI: 0.816-1.111, recessive model OR=0.766, 95% CI: 0.567-1.036).

Conclusion

MTHFR C677T polymorphism is associated with the risk of generating NSCL/P offspring, and being a 677TT homozygote is a risk factor. MTHFR A1298C polymorphism was not associated with generating NSCL/P offspring. However, further work should be performed to confirm these findings.

Lack of Association Between MTHFR, MTR, MTRR, and TCN2 Genes and Nonsyndromic CL±P in a Chinese Population: Case-Control Study and Meta-Analysis

Nonsyndromic cleft lip with or without cleft palate (NSCLP) is a common congenital deformity, often associated with folate deficiency. The genes MTHFR, MTR, MTRR, and TCN2 play key roles in folate metabolism. The risk of NSCLP associated with particular variants in the folic acid pathway differs among ethnic groups. The goal of this study was to explore whether genetic variations in these four genes, as well as gene-gene interactions, are associated with NSCLP. We investigated 7 tagSNPs for MTHFR, 18 tagSNPs for MTR, 15 tagSNPs for MTRR, and 7 tagSNPs for TCN2 selected from HapMap data in a Chinese population. These single nucleotide polymorphisms (SNPs) were examined for associations with NSCLP in 204 patients and 226 controls. We then performed a meta-analysis of association between rs1801133 and NSCLP. There was a significant difference in the allele frequency and haplotype analysis of rs4077829 and rs10802565 in MTR between the NSCLP and control groups but not a significant difference after correction with 10,000 times permutations. The allele frequency, haplotype analysis, and gene-gene interactions of other SNPs did not show a significant difference. The meta-analysis results showed that no significant differences were found for allele comparison, heterozygote comparison, homozygote comparison, dominant model comparison, or recessive model comparison. The alterations of folate metabolism related to these polymorphisms are not involved in NSCLP in the Chinese population.

Genetic epidemiology and nonsyndromic structural birth defects: from candidate genes to epigenetics

Birth defects are a leading cause of infant morbidity and mortality worldwide. The vast majority of birth defects are nonsyndromic, and although their etiologies remain mostly unknown, evidence supports the hypothesis that they result from the complex interaction of genetic, epigenetic, environmental, and lifestyle factors. Since our last review published in 2002 describing the basic tools of genetic epidemiology used to study nonsyndromic structural birth defects, many new approaches have become available and have been used with varying success. Through rapid advances in genomic technologies, investigators are now able to investigate large portions of the genome at a fraction of previous costs. With next-generation sequencing, research has progressed from assessing a small percentage of single-nucleotide polymorphisms to assessing the entire human protein-coding repertoire (exome)-an approach that is starting to uncover rare but informative mutations associated with nonsyndromic birth defects. Herein, we report on the current state of the genetic epidemiology of birth defects and comment on future challenges and opportunities. We consider issues of study design, and we discuss common variant approaches, including candidate gene studies and genome-wide association studies. We also discuss the complexities embedded in exploring interactions between genes and the environment. We complete our review by describing new and promising next-generation sequencing technologies and examining how the study of epigenetic mechanisms could become the key to unraveling the complex etiologies of nonsyndromic structural birth defects.

Contribution of transforming growth factor α polymorphisms to nonsyndromic orofacial clefts: a HuGE review and meta-analysis

We performed a meta-analysis of the association of transforming growth factor α gene (TGFA) polymorphisms with the risk of cleft lip with or without cleft palate (CL/P) or cleft palate (CP). In total, data from 29 studies were pooled for the following 3 polymorphisms: TGFA/TaqI, TGFA/BamHI, and TGFA/RasI in the TGFA gene. A fixed-effects or random-effects model was used to calculate the pooled odds ratios based on the results from the heterogeneity tests. A significantly increased CL/P or CP risk was observed in persons carrying a C2 allele at the TaqI polymorphism (odds ratio (OR) = 1.70, 95% confidence interval (CI): 1.41, 2.05) compared with those with a C1 allele (OR = 1.57, 95% CI: 1.23, 2.01). For the TGFA/BamHI polymorphism, carriers of the minor A1 allele had an estimated relative decrease in CL/P risk (OR = 0.44, 95% CI: 0.30, 0.64). These associations remained significant when only high-quality studies were included. However, no significant association was observed between the TGFA/RasI variant and CL/P risk. In summary, this meta-analysis provided a robust estimate of the positive association of the TGFA/TaqI polymorphism with both CL/P and CP and suggests that persons with an A1 allele may have a markedly decreased risk of CL/P.

Determination of Methylenetetrahydrofolate Reductase (MTHFR) gene polymorphism in Turkish patients with nonsyndromic cleft lip and palate

OBJECTIVE

To investigate the association between MTHFR C677T polymorphism and Turkish patients with nonsyndromic cleft lip and/or palate (nsCL/P) and to determine the prevalence of the Turkish population.

PATIENTS AND METHODS

Molecular analysis of gene polymorphisms were carried out using polymerase chain reactions and restriction enzyme digestions. In our study, 80 patients with nsCL/P and 125 unrelated individuals from Turkey were studied.

RESULTS

We found that MTHFR C677T polymorphism is a significant risk factor for nsCL/P in Turkey (p=0.0004). These results support the impact of MTHFR C677T polymorphism and importance of folic acid intake in the etiology of nsCL/P.

CONCLUSIONS

MTHFR gene which is localized in the relevant region of chromosome 1p36.3 not been studied Turkish patients with nsCL/P and the prevalence of our country not to be determined. We revealed statistically association between the MTHFR C677T gene polymorphism and nonsyndromic cleft lip and/or palate in the Turkish population.

Methylenetetrahydrofolate reductase C677T and A1298C polymorphisms and susceptibility to gastric adenocarcinoma in an Italian population

Objective

Several studies have reported the association between methylenetetrahydrofolate reductase (MTHFR) C677T and A1298C polymorphisms and nonsyndromic cleft lip with or without palate (NSCL/P) in Asian populations. However, findings have been conflicting. In order to investigate the association, a meta-analysis was performed.

Methods

We searched Pubmed, MedLine and EmBase database to selected eligible studies. The pooled odds ratios (ORs) with 95% confidence intervals (95%CIs) were calculated using fixed effects model or random effects model to assess the association between MTHFR polymorphisms and NSCL/P in both Asian children and mothers.

Results

Finally, nine case-control studies were included. Overall, the MTHFR C677T polymorphism and NSCL/P showed pooled ORs (95%CI) of 1.41(1.23–1.61) in Asian children, and 1.70(1.19–2.42) in Asian mothers. Subgroup analyses by geographical locations further identified the association in Eastern Asian children, Western/Central Asian children and mothers, but not in Eastern Asian mothers. However, no significant relationship between MTHFR A1298C polymorphism and NSCL/P was found in this meta-analysis.

Conclusions

The MTHFR 677T allele was associated with an increased risk of NSCL/P in Asian populations.