Association study of transforming growth factor alpha (TGF alpha) TaqI polymorphism and oral clefts: indication of gene-environment interaction in a population-based sample of infants with birth defects

Preliminary study of environmental risk and protective factors during pregnancy for cleft lip with or without palate in the Korean population

Objective

To investigate which types of environmental exposure during pregnancy are risk and protective factors for cleft lip with or without cleft palate (CL/P).

Methods

This case-control study included 278 orthodontic patients with CL/P (CL/P group) and 51 without CL/P (non-CL/P group). Demographic and environmental exposure data were collected using questionnaires completed by the parents. Statistical analyses were performed to identify the potential risk and protective factors for CL/P.

Results

The two groups did not show significant difference in (1) body weight at birth and number of previous births; (2) fathers' ages at birth and occupation; (3) parents' chronic diseases, alcohol consumption, and exposure to harmful substances; and (4) mothers' smoking, secondhand smoking, and vitamin and calcium intake. Most patients with CL/P were born at normal term (≥ 37 weeks, 93.2%) with normal body weight (2.9-3.7 kg, 63.7%) and as either the first or second child (90.3%). In the CL/P group, the percentages of mothers who were very young or old (≤ 19 years, ≥ 40 years) and with physical labor in their occupation were low (1.8% and 2.2%, respectively). Compared with the non-CL/P group, the CL/P group showed a lower percentage of maternal folic acid intake (68.6% vs. 20.9%, odds ratio [OR] = 0.121; P < 0.001) and higher percentages of mothers' drug intake and fathers' smoking habits (3.9% vs. 16.2%, OR = 4.73, P < 0.05; 39.2% vs. 61.2%, OR = 2.44, P < 0.01).

Conclusions

The findings of this study may explain the association between environmental factors and CL/P risk.

Epigenetic implications in maternal diabetes and metabolic syndrome-associated risk of orofacial clefts

Orofacial clefts (OFCs) are one of the most common types of structural birth defects. The etiologies are complicated, involving with genetic, epigenetic, and environmental factors. Studies have found that maternal diabetes and metabolic syndrome are associated with a higher risk of OFCs in offspring. Metabolic syndrome is a clustering of several disease risk factors, including hyperglycemia, dyslipidemia, obesity, and hypertension. Metabolic disease during pregnancy can increase risk of adverse outcomes and significantly influence fetal development, including orofacial formation and fusion. An altered metabolic state may contribute to developmental disorders or congenital defects including OFCs, potentially through epigenetic modulations, such as histone modification, DNA methylation, and noncoding RNA expression to alter activities of critical morphogenetic signaling or related developmental genes. This review summarizes the currently available evidence and underlying mechanisms of how the maternal metabolic syndrome is associated with OFCs in mostly human and some animal studies. It may provide a better understanding of the interactions between intrauterine metabolic status and fetal orofacial development which might be applied toward prevention and treatments of OFCs.

Maternal Cigarette Smoking and Cleft Lip and Palate: A Systematic Review and Meta-Analysis

A systematic review and meta-analysis to determine the association between active maternal smoking and cleft lip and palate etiology.

Medline, Embase, Web of Science and the Cochrane Library from inception to November, 2020.

Observational studies of cigarette smoking habits in pregnant women. Outcomes included cleft lip and/or palate, cleft lip  ±  palate and cleft palate only.

Publication bias analyses were performed and the Newcastle Ottawa scales were used to assess study quality. Fixed or random effect models were used in the meta-analysis, dependent on risk of statistical heterogeneity.

Forty-five studies were eligible for inclusion of which 11 were cohort and 34 were case-control studies. Sixteen studies were of sufficient standard for inclusion in the meta-analysis. The summary odds ratio for the association between smoking and cleft lip and/or palate was 1.42 (95%CI 1.27-1.59) with a population attributable fraction of 4% (95%CI 3%-5%). There was limited evidence to show a dose-response effect of smoking.

This review reports a moderate association between maternal smoking and orofacial cleft but the overall quality of the conventional observational studies included was poor. There is a need for high quality and novel research strategies to further define the role of smoking in the etiology of cleft lip and palate.

Bilateral Cleft Lip Repair: Lessons from History

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Describe the bilateral cleft lip and nasal deformity and associated anatomical variations. 2. Understand the history and evolution of the bilateral cleft lip repair. 3. Understand the key principles of the surgical repair.

SUMMARY

This article describes characteristics of the bilateral cleft lip and nasal deformity and its management, including presurgical orthopedics, operative techniques, and postsurgical care.

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.

Environmental mechanisms of orofacial clefts

Orofacial clefts (OFCs) are among the most common birth defects and impart a significant burden on afflicted individuals and their families. It is increasingly understood that many nonsyndromic OFCs are a consequence of extrinsic factors, genetic susceptibilities, and interactions of the two. Therefore, understanding the environmental mechanisms of OFCs is important in the prevention of future cases. This review examines the molecular mechanisms associated with environmental factors that either protect against or increase the risk of OFCs. We focus on essential metabolic pathways, environmental signaling mechanisms, detoxification pathways, behavioral risk factors, and biological hazards that may disrupt orofacial development.

Association of MEOX2 polymorphism with nonsyndromic cleft palate only in a Vietnamese population

To evaluate the association between the single nucleotide polymorphism (SNP) rs227493 in the MEOX2 gene and nonsyndromic cleft palate only, this research was conducted as a case-control study by comparing a nonsyndromic cleft palate only group with an independent, healthy, and unaffected control group who were both examined by specialists. Based on clinical examination and medical records, we analyzed a total of 570 DNA samples, including 277 cases and 293 controls, which were extracted from dry blood spot samples collected from both the Odonto and Maxillofacial Hospital in Ho Chi Minh City and Nguyen Dinh Chieu Hospital in Ben Tre province, respectively. The standard procedures of genotyping the specific SNP (rs2237493) for MEOX2 were performed on a StepOne Realtime PCR system with TaqMan SNP Genotyping Assays. Significant statistical differences were observed in allelic frequencies (allele T and allele G) between the non-syndromic cleft palate only and control groups in female subjects, with an allelic odds ratio of 1.455 (95% confidence interval: 1.026-2.064) and P < 0.05. These study findings suggest that nonsyndromic isolated cleft palate might be influenced by variation of MEOX2, especially SNP rs2237493 in Vietnamese females.

Transforming Growth Factor Alpha Taq I Polymorphisms and Nonsyndromic Cleft Lip and/or Palate Risk: A Meta-Analysis

BACKGROUND

A series of epidemiological studies were conducted to investigate the association between transforming growth factor alpha ( TGFA) polymorphism and nonsyndromic cleft lip and/or palate (CL/P) risk, but the findings remain conflicting. The present meta-analysis summarizes the association between the TGFA Taq I polymorphisms and nonsyndromic CL/P risk.

METHODS

We searched PubMed, EMBASE, Web of Science, and Chinese Biomedical Literature databases from their inception to May 1, 2015. Fixed-effects or random-effects models were used to calculate the pooled odds ratio for two genetic comparisons (heterozygous mutation versus wild type, homozygous mutation versus wild type). All of the statistical tests were conducted by STATA 10.0 (StataCorp, College Station, TX).

RESULTS

A total of 26 case-control studies were identified for this meta-analysis. There was evidence of a significant association between the TGFA Taq I polymorphism and nonsyndromic CL/P risk in the overall population. The TGFA polymorphism was associated with nonsyndromic CL/P susceptibility in Asian populations under any of genetic models. However, in subgroup analysis, we did not find a significant association of TGFA gene polymorphisms with a reduced cancer risk in White and other populations and (recessive model, odds ratio = 2.37, 95% confidence intervals = 0.92-6.07; odds ratio = 3.45, 95% confidence intervals = 1.07-11.09, respectively).

CONCLUSION

Our study indicates that the TGFA gene polymorphism might be associated with nonsyndromic CL/P susceptibility. However, these findings still need to be confirmed by single, large, well-designed prospective studies.

Oral Clefts, Maternal Smoking, and TGFA: A Meta-Analysis of Gene-Environment Interaction

Objective

A meta-analysis was performed to examine the association among maternal cigarette smoking, infant genotype at the Taq1 site in the transforming growth factor α (TGFA) locus, and risk of nonsyndromic oral clefts, both cleft palate (CP) and cleft lip with or without cleft palate (CL/P).

Design

Five published case-control studies were included in the meta-analyis. Pooled Mantel-Haenszel odds ratios (OR) and 95% confidence intervals (CIs) were computed. Gene-environment interaction was also assessed by using the pooled data in a case-only analysis and polytomous logistic regression.

Results

Among nonsmoking mothers, there was no evidence of any increased risk for CP if the infant carried the TGFA Taq1 C2 allele. If the mother reported smoking, however, there was an overall increased risk for CP if the infant carried the C2 allele (ORsmokers = 1.95; 95% CI = 1.22 to 3.10). TGFA genotype did not increase risk to CL/P, regardless of maternal smoking status. Polytomous logistic regression revealed a significant overall smoking effect for CL/P (OR = 1.64, 95% CI = 1.33 to 2.02) and CP (OR = 1.42, 95% CI = 1.06 to 1.90).

Conclusions

While maternal smoking was a consistent risk factor for both CL/P and CP across all studies, the suggestive evidence for gene-environment interaction between the infant's genotype at the Taq1 marker in TGFA and maternal smoking was limited to CP. Furthermore, evidence for such gene-environment interaction was strongest in a case-control study drawn from a birth defect registry where infants with non-cleft defects served as controls.

Association Study of Transforming Growth Factor Alpha TaqI Polymorphism and the Risk of Cleft Lip and/or Palate in an Iranian Population

BACKGROUND

The aim of this study is to evaluate the association of TGFA TaqI polymorphism with nonsyndromic cleft lip and/or palate (NSCLP) in an Iranian population.

METHODS

In this case-control study, 113 children with NSCLP and 209 controls were included. Genotyping of the TaqI polymorphism was performed by polymerase chain reaction and restriction fragment length polymorphism methods. A p-value of <0.05 was considered statistically significant.

RESULTS

For the TGFA TaqI polymorphism, the distributions of genotypes in the NSCLP (p = 0.810) and control group (p = 0.422) were in Hardy-Weinberg equilibrium. There was no statistically significant difference in the genotype distribution (p = 0.059) and allele frequency (p = 0.065) of the TGFA TaqI polymorphism in the NSCLP and control groups.

CONCLUSION

TGFA TaqI polymorphism was not associated with the risk of NSCLP in Iranian children. Birth Defects Research 109:1386-1389, 2017.© 2017 Wiley Periodicals, Inc.

Maternal active smoking and risk of oral clefts: a meta-analysis

OBJECTIVE

To assess the association between maternal active cigarette smoking and the risk of oral clefts in the offspring.

STUDY DESIGN

Oral clefts are divided into three subgroups: total clefts, cleft lip with or without cleft palate (CL ± P), and cleft palate only (CP). Data from studies on different levels of smoking were gathered to examine the dose-response effect.

RESULTS

The present meta-analysis included 29 case-control and cohort studies through Cochrane, PubMed, and Ovid Medline searches. A modest but statistically significant association was found between maternal active smoking and CL ± P (odds ratio [OR] 1.368; 95% confidence interval [CI] 1.259-1.486) as well as CP (OR 1.241; 95% CI 1.117-1.378). Half the studies showed positive dose-response effect for each subgroup (test for linear trend, P < .05).

CONCLUSIONS

There is a moderate risk for having a child with a CL ± P or CP in women who smoke during pregnancy. We could not confirm whether there was a positive dose-response effect between maternal smoking and clefts.

Histone acetylation is involved in TCDD‑induced cleft palate formation in fetal mice

The aim of the present was to evaluate the effects of DNA methylation and histone acetylation on 2,3,7,8-tetrachlo-rodibenzo-p-dioxin (TCDD)-induced cleft palate in fetal mice. Pregnant mice (n=10) were randomly divided into two groups: i) TCDD group, mice were treated with 28 µg/kg TCDD on gestation day (GD) 10 by oral gavage; ii) control group, mice were treated with an equal volume of corn oil. On GD 16.5, the fetal mice were evaluated for the presence of a cleft palate. An additional 36 pregnant mice were divided into the control and TCDD groups, and palate samples were collected on GD 13.5, GD 14.5 and GD 15.5, respectively. Transforming growth factor-β3 (TGF-β3) mRNA expression, TGF-β3 promoter methylation, histone acetyltransferase (HAT) activity and histone H3 (H3) acetylation in the palates were evaluated in the two groups. The incidence of a cleft palate in the TCDD group was 93.55%, and no cases of cleft palate were identified in the control group. On GD 13.5 and GD 14.5, TGF-β3 mRNA expression, HAT activity and acetylated H3 levels were significantly increased in the TCDD group compared with the control. Methylated bands were not observed in the TCDD or control groups. In conclusion, at the critical period of palate fusion (GD 13.5–14.5), TCDD significantly increased TGF-β3 gene expression, HAT activity and H3 acetylation. Therefore, histone acetylation may be involved in TCDD-induced cleft palate formation in fetal mice.

Allowing for population stratification in case-only studies of gene-environment interaction, using genomic control

Gene-environment interactions (G × E) have attracted considerable research interest in the past owing to their scientific and public health implications, but powerful statistical methods are required to successfully track down G × E, particularly at a genome-wide level. Previously, a case-only (CO) design has been proposed as a means to identify G × E with greater efficiency than traditional case-control or cohort studies. However, as with genotype-phenotype association studies themselves, hidden population stratification (PS) can impact the validity of G × E studies using a CO design. Since this problem has been subject to little research to date, we used comprehensive simulation to systematically assess the type I error rate, power and effect size bias of CO studies of G × E in the presence of PS. Three types of PS were considered, namely genetic-only (PSG), environment-only (PSE), and joint genetic and environmental stratification (PSGE). Our results reveal that the type I error rate of an unadjusted Wald test, appropriate for the CO design, would be close to its nominal level (0.05 in our study) as long as PS involves only one interaction partner (i.e., either PSG or PSE). In contrast, if the study population is stratified with respect to both G and E (i.e., if there is PSGE), then the type I error rate is seriously inflated and estimates of the underlying G × E interaction are biased. Comparison of CO to a family-based case-parents design confirmed that the latter is more robust against PSGE, as expected. However, case-parent trios may be particularly unsuitable for G × E studies in view of the fact that they require genotype data from parents and that many diseases with an environmental component are likely to be of late onset. An alternative approach to adjusting for PS is principal component analysis (PCA), which has been widely used for this very purpose in past genome-wide association studies (GWAS). However, resolving genetic PS properly by PCA requires genetic data at the population level, the availability of which would conflict with the basic idea of the CO design. Therefore, we explored three modified Wald test statistics, inspired by the genomic control (GC) approach to GWAS, as an alternative means to allow for PSGE. The modified statistics were benchmarked against a stratified Wald test assuming known population affiliation, which should provide maximum power under PS. Our results confirm that GC is capable of successfully and efficiently correcting the PS-induced inflation of the type I error rate in CO studies of G × E.

Detecting gene-environment interactions in human birth defects: Study designs and statistical methods

BACKGROUND

The National Birth Defects Prevention Study (NBDPS) contains a wealth of information on affected and unaffected family triads, and thus provides numerous opportunities to study gene-environment interactions (G×E) in the etiology of birth defect outcomes. Depending on the research objective, several analytic options exist to estimate G×E effects that use varying combinations of individuals drawn from available triads.

METHODS

In this study, we discuss important considerations in the collection of genetic data and environmental exposures.

RESULTS

We will also present several population- and family-based approaches that can be applied to data from the NBDPS including case-control, case-only, family-based trio, and maternal versus fetal effects. For each, we describe the data requirements, applicable statistical methods, advantages, and disadvantages.

CONCLUSION

A range of approaches can be used to evaluate potentially important G×E effects in the NBDPS. Investigators should be aware of the limitations inherent to each approach when choosing a study design and interpreting results.

Genetic Effect of Transforming Growth Factor Alpha Gene Variants on the Risk of Nonsyndromic Cleft Lip with or without Palate in Korean Populations

Objective

To identify the contribution of TGFA gene variants to the risk of nonsyndromic cleft lip with or without palate (NS-CL±P).

Design

The samples were from 142 Korean NS-CL±P families and 119 control parents having nonaffected children. Minor allele frequency, heterozygosity, and χ2 test for Hardy-Weinberg equilibrium were calculated for each of 10 selected single-nucleotide polymorphisms (SNPs). Ten SNPs were used to examine the association of case-parent trios with the transmission disequilibrium test (TDT) and conditional logistic regression models (CLRMs). Both allelic and genotypic TDTs for individual SNPs and sliding windows of haplotypes consisting of two to five SNPs were tested using family- and haplotype-based association test programs. Genotypic odd ratios (GORs) were obtained from CLRMs using STATA software. The parent-of-origin effect was evaluated for 10 SNPs, and a comparison between 218 case parents and 119 control parents was performed to investigate paternal and maternal ORs.

Results

Family-based TDT and haplotype analysis exhibited no statistical significance, but a relatively meaningful association was shown with rs3771497 (all P < .05; two SNPs, rs3771497 and rs3755377; five SNPs, rs3771497, rs3755377, rs3771485, rs11466212, and rs3771475). G/G homozygotes at rs3771497 have a significant decreased risk of NS-CL±P (GOR = 0.30, P < .01). No SNPs showed parent-of-origin effects. However, in the comparison between case parents and control parents, a single-marker analysis of maternal line showed a significant association with NS-CL±P in rs3771497 ( P < .001, recessive model).

Conclusion

The association of the TGFA gene with NS-CL±P in Korean populations was not clearly found. However, the etiologic effect of the TGFA gene on NS-CL±P patients should be investigated in terms of maternal genotype influence.

Classification, epidemiology, and genetics of orofacial clefts

Orofacial clefts (OFCs) include a broad range of facial conditions that differ in cause and disease burden. In the published literature, there is substantial ambiguity in both terminology and classification of OFCs. This article discusses the terminology and classification of OFCs and the epidemiology of OFCs. Demographic, environmental, and genetic risk factors for OFCs are described, including suggestions for family counseling. This article enables clinicians to counsel families regarding the occurrence and recurrence of OFCs. Although much of the information is detailed, it is intended to be accessible to all health professionals for use in their clinical practices.

The interaction between aggrecan gene VNTR polymorphism and obesity in predicting incident symptomatic lumbar disc herniation

An association between aggrecan gene variable number of tandem repeats polymorphism (VNTR) and symptomatic lumbar disc herniation (LDH) has been reported in Chinese Han of Northern China, and obesity had previously been suspected of causing severe LDH. However, the interaction between aggrecan VNTR and obesity in symptomatic LDH has not been well studied. To examine the interaction between aggrecan VNTR and obesity in the susceptibility of symptomatic LDH, 259 participants participated in this study and donated a blood sample. The disease group comprised 61 patients already diagnosed with symptomatic LDH. The control group consisted of 198 healthy blood donors without symptoms of LDH who were not diagnosed with LDH. The aggrecan gene VNTR region was analyzed using polymerase chain reaction. The data indicated that between the two groups, participants carrying one or two alleles ≤25 repeats who were non-obese people showed a 1.057-fold increase in risk for symptomatic LDH (p = 0.895, changing the number of repeat alleles to <25 repeats alone did not demonstrably change the risk of LDH), and participants carrying two alleles >25 repeats who were obese people showed an 1.061-fold higher risk (p = 0.885, adding obesity to the mix alone did not demonstrably increase the risk of LDH), while participants carrying one or two alleles ≤25 repeats who were obese people showed a 4.667-fold increase in risk for symptomatic LDH (p = 0.0003, adding obesity plus changing the repeat allele number significantly increased the risk of LDH by 4.667). Overall, the findings suggest an underlying interaction between aggrecan VNTR and obesity in symptomatic LDH.

Association between polymorphism of TGFA Taq I and cleft lip and/or palate: a meta-analysis

Background

Cleft lip and palate (CL/P) is one of the most common malformations in humans. Transforming growth factor alpha (TGFA) is a well characterized mammalian growth factor which might contribute to the development of CL/P. This meta-analysis aimed to summarize the association between the TGFA Taq I polymorphisms and CL/P.

Methods

We retrieved the relevant articles from PubMed, EMBASE, ISI Web of Science and SCOPUS databases. Studies were selected using specific inclusion and exclusion criteria. The odds ratios (ORs) and their 95% confidence intervals (95% CIs) were calculated to assess the association between TGFA Taq I polymorphism and CL/P risk. Meta-analyses were performed on the total data set and separately for the major ethnic groups, disease type and source of control. All analyses were performed using the Stata software.

Results

Twenty articles were included in the present analysis. There is a significant association between the TGFA Taq I polymorphism and CL/P (C1C2 vs C1C1: OR = 1.67, 95% CI = 1.23-2.25, C2C2 + C1C2 vs C1C1C1: OR = 1.52, 95% CI = 1.15-2.01; C2 vs C1:OR = 1.41, 95% CI = 1.12-1.78). Stratified analyses suggested that the TGFA Taq I polymorphism was significantly associated with CL/P in Caucasians (C1C2 vs C1C1: OR = 1.95, 95% CI = 1.34-2.86; C2C2 + C1C2 vs C1C1: OR = 1.68, 95% CI = 1.18-2.38; C2 vs V1: OR = 1.52, 95% CI = 1.14 -2.02).

Conclusion

TGFA Taq I polymorphism may be associated with the risk of CL/P.

Racial segregation and maternal smoking during pregnancy: a multilevel analysis using the racial segregation interaction index

Drawing from both the place stratification and ethnic enclave perspectives, we use multilevel modeling to investigate the relationships between women's race/ethnicity (i.e., non-Hispanic white, non-Hispanic black, Asian, and Hispanic) and maternal smoking during pregnancy, and examine if these relationships are moderated by racial segregation in the continental United States. The results show that increased interaction with whites is associated with increased probability of maternal smoking during pregnancy, and racial segregation moderates the relationships between race/ethnicity and maternal smoking. Specifically, living in a less racially segregated area is related to a lower probability of smoking during pregnancy for black women, but it could double and almost triple the probability of smoking for Asian women and Hispanic women, respectively. Our findings provide empirical evidence for both the place stratification and ethnic enclave perspectives.

Evidence of gene-environment interaction for two genes on chromosome 4 and environmental tobacco smoke in controlling the risk of nonsyndromic cleft palate

Nonsyndromic cleft palate (CP) is one of the most common human birth defects and both genetic and environmental risk factors contribute to its etiology. We conducted a genome-wide association study (GWAS) using 550 CP case-parent trios ascertained in an international consortium. Stratified analysis among trios with different ancestries was performed to test for GxE interactions with common maternal exposures using conditional logistic regression models. While no single nucleotide polymorphism (SNP) achieved genome-wide significance when considered alone, markers in SLC2A9 and the neighboring WDR1 on chromosome 4p16.1 gave suggestive evidence of gene-environment interaction with environmental tobacco smoke (ETS) among 259 Asian trios when the models included a term for GxE interaction. Multiple SNPs in these two genes were associated with increased risk of nonsyndromic CP if the mother was exposed to ETS during the peri-conceptual period (3 months prior to conception through the first trimester). When maternal ETS was considered, fifteen of 135 SNPs mapping to SLC2A9 and 9 of 59 SNPs in WDR1 gave P values approaching genome-wide significance (10(-6)<P<10(-4)) in a test for GxETS interaction. SNPs rs3733585 and rs12508991 in SLC2A9 yielded P = 2.26×10(-7) in a test for GxETS interaction. SNPs rs6820756 and rs7699512 in WDR1 also yielded P = 1.79×10(-7) and P = 1.98×10(-7) in a 1 df test for GxE interaction. Although further replication studies are critical to confirming these findings, these results illustrate how genetic associations for nonsyndromic CP can be missed if potential GxE interaction is not taken into account, and this study suggest SLC2A9 and WDR1 should be considered as candidate genes for CP.

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.

Oral cleft prevention program (OCPP)

Background

Oral clefts are one of the most common birth defects with significant medical, psychosocial, and economic ramifications. Oral clefts have a complex etiology with genetic and environmental risk factors. There are suggestive results for decreased risks of cleft occurrence and recurrence with folic acid supplements taken at preconception and during pregnancy with a stronger evidence for higher than lower doses in preventing recurrence. Yet previous studies have suffered from considerable design limitations particularly non-randomization into treatment. There is also well-documented effectiveness for folic acid in preventing neural tube defect occurrence at 0.4 mg and recurrence with 4 mg. Given the substantial burden of clefting on the individual and the family and the supportive data for the effectiveness of folic acid supplementation as well as its low cost, a randomized clinical trial of the effectiveness of high versus low dose folic acid for prevention of cleft recurrence is warranted.

Methods/design

This study will assess the effect of 4 mg and 0.4 mg doses of folic acid, taken on a daily basis during preconception and up to 3 months of pregnancy by women who are at risk of having a child with nonsyndromic cleft lip with/without palate (NSCL/P), on the recurrence of NSCL/P. The total sample will include about 6,000 women (that either have NSCL/P or that have at least one child with NSCL/P) randomly assigned to the 4 mg and the 0.4 mg folic acid study groups. The study will also compare the recurrence rates of NSCL/P in the total sample of subjects, as well as the two study groups (4mg, 0.4 mg) to that of a historical control group.

The study has been approved by IRBs (ethics committees) of all involved sites. Results will be disseminated through publications and presentations at scientific meetings.

Discussion

The costs related to oral clefts are high, including long term psychological and socio-economic effects. This study provides an opportunity for huge savings in not only money but the overall quality of life. This may help establish more specific clinical guidelines for oral cleft prevention so that the intervention can be better tailored for at-risk women.

ClinicalTrials.gov Identifier

NCT00397917

Genetics and management of the patient with orofacial cleft

Cleft lip or palate (CL/P) is a common facial defect present in 1 : 700 live births and results in substantial burden to patients. There are more than 500 CL/P syndromes described, the causes of which may be single-gene mutations, chromosomopathies, and exposure to teratogens. Part of the most prevalent syndromic CL/P has known etiology. Nonsyndromic CL/P, on the other hand, is a complex disorder, whose etiology is still poorly understood. Recent genome-wide association studies have contributed to the elucidation of the genetic causes, by raising reproducible susceptibility genetic variants; their etiopathogenic roles, however, are difficult to predict, as in the case of the chromosomal region 8q24, the most corroborated locus predisposing to nonsyndromic CL/P. Knowing the genetic causes of CL/P will directly impact the genetic counseling, by estimating precise recurrence risks, and the patient management, since the patient, followup may be partially influenced by their genetic background. This paper focuses on the genetic causes of important syndromic CL/P forms (van der Woude syndrome, 22q11 deletion syndrome, and Robin sequence-associated syndromes) and depicts the recent findings in nonsyndromic CL/P research, addressing issues in the conduct of the geneticist.

A comprehensive review of the genetic basis of cleft lip and palate

Cleft lip and palate (CLP) are birth defects that affect the upper lip and the roof of the mouth. CLP has a multifactorial etiology, comprising both genetic and environmental factors. In this review we discuss the recent data on the etiology of cleft lip and palate. We conducted a search of the MEDLINE database (Entrez PubMed) from January 1986 to December 2010 using the key words: ‘cleft lip,’ ‘cleft palate,’ ‘etiology,’ and ‘genetics.’ The etiology of CLP seems complex, with genetics playing a major role. Several genes causing syndromic CLP have been discovered. Three of them—T-box transcription factor-22 (TBX22), poliovirus receptor-like-1 (PVRL1), and interferon regulatory factor-6 (IRF6)—are responsible for causing X-linked cleft palate, cleft lip/palate–ectodermal dysplasia syndrome, and Van der Woude and popliteal pterygium syndromes, respectively; they are also implicated in nonsyndromic CLP. The nature and functions of these genes vary widely, illustrating the high vulnerability within the craniofacial developmental pathways. The etiological complexity of nonsyndromic cleft lip and palate is also exemplified by the large number of candidate genes and loci. To conclude, although the etiology of nonsyndromic CLP is still largely unknown, mutations in candidate genes have been identified in a small proportion of cases. Determining the relative risk of CLP on the basis of genetic background and environmental influence (including smoking, alcohol use, and dietary factors) will be useful for genetic counseling and the development of future preventive measures.

Developmental epigenetics of the murine secondary palate

Orofacial clefts occur with a frequency of 1 to 2 per 1000 live births. Cleft palate, which accounts for 30% of orofacial clefts, is caused by the failure of the secondary palatal processes--medially directed, oral projections of the paired embryonic maxillary processes--to fuse. Both gene mutations and environmental effects contribute to the complex etiology of this disorder. Although much progress has been made in identifying genes whose mutations are associated with cleft palate, little is known about the mechanisms by which the environment adversely influences gene expression during secondary palate development. An increasing body of evidence, however, implicates epigenetic processes as playing a role in adversely influencing orofacial development. Epigenetics refers to inherited changes in phenotype or gene expression caused by processes other than changes in the underlying DNA sequence. Such processes include, but are not limited to, DNA methylation, microRNA effects, and histone modifications that alter chromatin conformation. In this review, we describe our current understanding of the possible role epigenetics may play during development of the secondary palate. Specifically, we present the salient features of the embryonic palatal methylome and profile the expression of numerous microRNAs that regulate protein-encoding genes crucial to normal orofacial ontogeny.

Genetic basis of susceptibility to teratogen induced birth defects

Birth defects remain the leading cause of infant death in US. The field of teratology has been focused on the causes and underlying mechanisms of birth defects for decades, yet our understanding of these critical issues remain unacceptably vague. Conclusions from years of animal and human studies made it clear that the vast majority of birth defects have multifactorial origins, with contributions from environmental and genetic factors. The environment comprises not only of the physical, biological, and chemical external environment surrounding the pregnant woman, but it also includes the internal environment of the woman's body that interact with the developing embryo in a complex fashion. The importance of maternal and embryonic genetic factors consisting of countless genetic variants/mutations that exist within every individual contribute to birth defect susceptibility is only now being more fully appreciated. This great complexity of the genome and its diversity within individuals and populations seems to be the principal reason why the same teratogenic exposure can induce severe malformation in one embryo, while fail to do so to other exposed embryos. As the interaction between genetic and environmental factors has long been recognized as the first "Principle of Teratology" by Wilson and Warkany [1965. Teratology: Principles and techniques. Chicago: University of Chicago Press], it is only recently that the appropriate investigative tools have been developed with which to fully investigate this fundamental principle. The introduction of high throughput technologies like whole genome sequencing or genome-wide association studies are promising to deliver an enormous amount of new data that will shed light on the genomic factors that contribute susceptibility to environmental teratogens. In this review, we attempt to summarize the epidemiological and experimental literature concerning birth defects whose phenotypic expression can be clearly related to the interactions between several select environmental factors and those genetic pathways in which they are most likely to have significant modifying effects. © 2011 Wiley-Liss, Inc.

Addressing the challenges of cleft lip and palate research in India

The Indian sub-continent remains one of the most populous areas of the world with an estimated population of 1.1 billion in India alone. This yields an estimated 24.5 million births per year and the birth prevalence of clefts is somewhere between 27,000 and 33,000 clefts per year. Inequalities exist, both in access to and quality of cleft care with distinct differences in urban versus rural access and over the years the accumulation of unrepaired clefts of the lip and palate make this a significant health care problem in India. In recent years the situation has been significantly improved through the intervention of Non Governmental Organisations such as SmileTrain and Transforming Faces Worldwide participating in primary surgical repair programmes. The cause of clefts is multi factorial with both genetic and environmental input and intensive research efforts have yielded significant advances in recent years facilitated by molecular technologies in the genetic field. India has tremendous potential to contribute by virtue of improving research expertise and a population that has genetic, cultural and socio-economic diversity. In 2008, the World Health Organisation (WHO) has recognised that non-communicable diseases, including birth defects cause significant infant mortality and childhood morbidity and have included cleft lip and palate in their Global Burden of Disease (GBD) initiative. This will fuel the interest of India in birth defects registration and international efforts aimed at improving quality of care and ultimately prevention of non-syndromic clefts of the lip and palate.

Maternal smoking in pregnancy and birth defects: a systematic review based on 173 687 malformed cases and 11.7 million controls

BACKGROUND

There is uncertainty over whether maternal smoking is associated with birth defects. We conducted the first ever comprehensive systematic review to establish which specific malformations are associated with smoking.

METHODS

Observational studies published 1959–2010 were identified (Medline), and included if they reported the odds ratio (OR) for having a non-chromosomal birth defect among women who smoked during pregnancy compared with non-smokers. ORs adjusted for potential confounders were extracted (e.g. maternal age and alcohol), otherwise unadjusted estimates were used. One hundred and seventy-two articles were used in the meta-analyses: a total of 173 687 malformed cases and 11 674 332 unaffected controls.

RESULTS

Significant positive associations with maternal smoking were found for: cardiovascular/heart defects [OR 1.09, 95% confidence interval (CI) 1.02–1.17]; musculoskeletal defects (OR 1.16, 95% CI 1.05–1.27); limb reduction defects (OR 1.26, 95% CI 1.15–1.39); missing/extra digits (OR 1.18, 95% CI 0.99–1.41); clubfoot (OR 1.28, 95% CI 1.10–1.47); craniosynostosis (OR 1.33, 95% CI 1.03–1.73); facial defects (OR 1.19, 95% CI 1.06–1.35); eye defects (OR 1.25, 95% CI 1.11–1.40); orofacial clefts (OR 1.28, 95% CI 1.20–1.36); gastrointestinal defects (OR 1.27, 95% CI 1.18–1.36); gastroschisis (OR 1.50, 95% CI 1.28–1.76); anal atresia (OR 1.20, 95% CI 1.06–1.36); hernia (OR 1.40, 95% CI 1.23–1.59); and undescended testes (OR 1.13, 95% CI 1.02–1.25). There was a reduced risk for hypospadias (OR 0.90, 95% CI 0.85–0.95) and skin defects (OR 0.82, 0.75–0.89). For all defects combined the OR was 1.01 (0.96–1.07), due to including defects with a reduced risk and those with no association (including chromosomal defects).

CONCLUSIONS

Birth defects that are positively associated with maternal smoking should now be included in public health educational materials to encourage more women to quit before or during pregnancy.

Evidence for gene-environment interaction in a genome wide study of nonsyndromic cleft palate

Nonsyndromic cleft palate (CP) is a common birth defect with a complex and heterogeneous etiology involving both genetic and environmental risk factors. We conducted a genome-wide association study (GWAS) using 550 case-parent trios, ascertained through a CP case collected in an international consortium. Family-based association tests of single nucleotide polymorphisms (SNP) and three common maternal exposures (maternal smoking, alcohol consumption, and multivitamin supplementation) were used in a combined 2 df test for gene (G) and gene-environment (G × E) interaction simultaneously, plus a separate 1 df test for G × E interaction alone. Conditional logistic regression models were used to estimate effects on risk to exposed and unexposed children. While no SNP achieved genome-wide significance when considered alone, markers in several genes attained or approached genome-wide significance when G × E interaction was included. Among these, MLLT3 and SMC2 on chromosome 9 showed multiple SNPs resulting in an increased risk if the mother consumed alcohol during the peri-conceptual period (3 months prior to conception through the first trimester). TBK1 on chr. 12 and ZNF236 on chr. 18 showed multiple SNPs associated with higher risk of CP in the presence of maternal smoking. Additional evidence of reduced risk due to G × E interaction in the presence of multivitamin supplementation was observed for SNPs in BAALC on chr. 8. These results emphasize the need to consider G × E interaction when searching for genes influencing risk to complex and heterogeneous disorders, such as nonsyndromic CP.

Maxillary dental anomalies in children with cleft lip and palate: a controlled study

OBJECTIVE

To evaluate the prevalence of dental abnormalities of the primary and permanent maxillary dentitions in children affected by unilateral (UCLP) and bilateral (BCLP) cleft of the lip and palate.

METHODS

One hundred and fifty-six Caucasian patients (64 females and 92 males) affected by non-syndromic UCLP or BLCP were selected. A control sample of 1000 subjects (482 males and 518 females) without CLP was selected. All comparisons were carried out by means of z-tests on proportions.

RESULTS

The prevalence rate for missing primary lateral incisors in UCLP subjects was 8.1% and it was 27.9% for the permanent lateral incisors. In BLCP subjects, the prevalence rates were 17% for the primary lateral incisors and 60% for the permanent lateral incisors. The second premolar was absent in 5.4% of UCLP subjects and in 8.8% in the BCLP sample. The statistical analysis revealed significant differences for the prevalence rates of all dental anomalies compared with the control group except for second premolar agenesis.

CONCLUSIONS

In both UCLP and BCLP subjects the most prevalent missing teeth were the lateral incisors. The dental anomalies occurred predominantly in the cleft area, thus suggesting that the effect of the cleft disturbance is more local than general on the dentition.

The interaction between aggrecan gene VNTR polymorphism and cigarette smoking in predicting incident symptomatic intervertebral disc degeneration

An association between the aggrecan variable number of tandem repeat (VNTR) polymorphism and the disc degeneration has been previously reported in Finnish men, and smoking had previously been suspected of causing disc degeneration. However, the interaction between aggrecan gene VNTR polymorphism and smoking in symptomatic intervertebral disc degeneration (IDD) has not been well studied. To examine the interaction between aggrecan gene VNTR and smoking in the susceptibility of symptomatic IDD of Chinese Han in northern China, intervertebral discs of 132 participants were evaluated on magnetic resonance imaging, using decreased signal intensity. After harvesting the blood samples, the aggrecan gene VNTR region was analyzed using polymerase chain reaction (PCR). The data indicated that between the two groups, participants carrying one or two alleles ≤25 repeats who did not smoke showed a 1.102-fold increased risk for symptomatic IDD (p= 0.855; 95% confidence interval 0.389-3.119), and participants carrying two alleles >25 repeats who smoked more than 1 pack-year showed a 1.013-fold higher risk (p = 0.982; 95% confidence interval 0.333-3.084), whereas participants carrying one or two alleles ≤25 repeats who smoked more than 1 pack-year showed a 4.5-fold increased risk for symptomatic IDD (p = 0.005; 95% confidence interval 1.589-12.743). Overall, we observed an underlying additive and multiplicative interaction between the aggrecan gene VNTR polymorphism and smoking in symptomatic IDD.

MTHFR, TGFB3, and TGFA polymorphisms and their association with the risk of non-syndromic cleft lip and cleft palate in China

Our previous results indicated a moderate association between the methylenetetrahydrofolate reductase (MTHFR) gene 677C-T variant and an increased risk of non-syndromic cleft lip with or without cleft palate (nsCL/P) among the northern but not southern population in China, suggesting possible genetic heterogeneity in the etiology of nsCL/P between these two populations. It remains unknown whether the transforming growth factor alpha (TGFA) gene TaqI polymorphism and transforming growth factor beta 3 (TGFB3) gene CA repeats influence the risk of nsCL/P differently between the northern and southern Chinese populations. In this study of 188 Chinese case-parent triads, we found an independent association between the TGFB3 variant and risk of nsCL/P (OR = 2.10, 95% CI: 1.25-3.54 for heterozygotes; OR = 1.78, 95% CI: 0.83-3.83 for homozygotes). The MTHFR variant was associated with an increased risk of nsCL/P among children in the north (OR = 3.11, 95% CI: 1.18-8.23 for heterozygotes; OR = 3.36, 95%CI: 1.14-9.93 for homozygotes) and appear to interact marginally with the TGFB3 variant in the occurrence of nsCL/P among southern subjects (OR = 0.26, 95% CI: 0.06-1.07). No association was found between the TGFA variant and risk of nsCL/P in our data. Our results suggest that the TGFB3 gene variant may be an important genetic risk factor for nsCL/P occurrence in Chinese children, and we found no evidence of heterogeneity between northern and southern Chinese populations in the associations between TGFB3 and TGFA variants and risk of nsCL/P, but these results warrant further investigation.

A possible association of periodontal infectious diseases in pregnant women with isolated orofacial clefts in their children: A population-based case-control study

BACKGROUND

The aim of the study was to check the association of maternal periodontal infectious disease (MPID) during pregnancy and the possible risk for birth outcomes, mainly structural birth defects: congenital abnormalities (CAs) in their children.

METHODS

The population-based data set of the Hungarian Case-Control Surveillance System of Congenital Abnormalities, 1980-1996, was evaluated. The occurrence of medically recorded MPID in the prenatal maternity logbook was compared in 22,843 cases with different CAs and 38,151 matched controls without defects.

RESULTS

Twenty-one case mothers who had offspring with a CA (case group) and 17 pregnant women who delivered newborn infants without a CA (control group) had an MPID. However, of 21 cases, 6 had isolated cleft lip +/- palate (OR with 95% CI: 10.7, 4.2-27.3), and 2 were affected with isolated cleft palate (7.9, 1.8-34.2). Of these 8 cases, 6 had mothers with the exposure of MPID in the critical period of these orofacial clefts, 7 mothers were visited at home, and 6 were smokers during pregnancy.

CONCLUSIONS

The unexpected findings of the study showed a strong association of MPID during pregnancy with a higher risk of isolated orofacial clefts in their children.

Smoking cessation during pregnancy: a systematic literature review

ISSUES

Second-hand smoke presents a health risk for a large group of entirely helpless nonsmokers: unborn children. Reliable data on women continuing to smoke during pregnancy are essential for effective preventive and interventional programs. The aim of this review is therefore to identify this risk group compared with spontaneous quitters of smoking.

APPROACH

This systematic literature review is based solely on empirical original papers derived from samples of pregnant women smoking at the beginning of pregnancy. In accordance with the QUOROM Statement all population or clinic-based samples were included. Collectives from intervention studies were not included. All studies were from developed nations and published between January 1997 and March 2008.

KEY FINDINGS

A total of 19 studies were identified. The rate of quitters was between 4.0% and 69.7% for population-based studies, and 26.5% and 47.0% for clinic-based studies. A smoking partner, a large number of children, a high rate of tobacco consumption, as well as deficiencies in prenatal care were predictors of smoking during pregnancy.

IMPLICATIONS

This study identifies risk factors and correlates and indicates common obstacles for women to quit smoking during pregnancy.

CONCLUSION

The risk groups that can be defined based on our results are a key target population for preventive measures.

Cleft lip and palate

Clefts of the lip and palate are generally divided into two groups, isolated cleft palate and cleft lip with or without cleft palate, representing a heterogeneous group of disorders affecting the lips and oral cavity. These defects arise in about 1.7 per 1000 liveborn babies, with ethnic and geographic variation. Effects on speech, hearing, appearance, and psychology can lead to longlasting adverse outcomes for health and social integration. Typically, children with these disorders need multidisciplinary care from birth to adulthood and have higher morbidity and mortality throughout life than do unaffected individuals. This Seminar describes embryological developmental processes, epidemiology, known environmental and genetic risk factors, and their interaction. Although access to care has increased in recent years, especially in developing countries, quality of care still varies substantially. Prevention is the ultimate objective for clefts of the lip and palate, and a prerequisite of this aim is to elucidate causes of the disorders. Technological advances and international collaborations have yielded some successes.

Cleft lip and palate genetics and application in early embryological development

The development of the head involves the interaction of several cell populations and coordination of cell signalling pathways, which when disrupted can cause defects such as facial clefts. This review concentrates on genetic contributions to facial clefts with and without cleft palate (CP). An overview of early palatal development with emphasis on muscle and bone development is blended with the effects of environmental insults and known genetic mutations that impact human palatal development. An extensive table of known genes in syndromic and non-syndromic CP, with or without cleft lip (CL), is provided. We have also included some genes that have been identified in environmental risk factors for CP/L. We include primary and review references on this topic.

Importance of gene-environment interactions in the etiology of selected birth defects

It is generally understood that both genetic and environmental factors contribute to the highly complex etiology of structural birth defects, including neural tube defects, oral clefts and congenital heart defects, by disrupting highly regulated embryonic developmental processes. The intrauterine environment of the developing embryo/fetus is determined by maternal factors such as health/disease status, lifestyle, medication, exposure to environmental teratogens, as well as the maternal genotype. Certain genetic characteristics of the embryo/fetus also predispose it to developmental abnormalities. Epidemiologic and animal studies conducted over the last few decades have suggested that the interplay between genes and environmental factors underlies the etiological heterogeneity of these defects. It is now widely believed that the study of gene-environment interactions will lead to better understanding of the biological mechanisms and pathological processes that contribute to the development of complex birth defects. It is only through such an understanding that more efficient measures will be developed to prevent these severe, costly and often deadly defects. In this review, we attempt to summarize the complex clinical and experimental literature on current hypotheses of interactions between several select environmental factors and those genetic pathways in which they are most likely to have significant modifying effects. These include maternal folate nutritional status, maternal diabetes/obesity-related conditions, and maternal exposure to selected medications and environmental contaminants. Our goal is to highlight the potential gene-environment interactions affecting early embryogenesis that deserve comprehensive study.

Why carry out a longitudinal birth survey?

In spite of technological progress throughout the world, ill health, both physical and mental, is widespread - but much of this is preventable. With rapid globalization, populations in both industrialised and developing countries are being exposed to various stresses and to new environmental factors, such as those related to climate change and to an increasing range of chemicals of unknown effect. There is substantial evidence that exposures to environmental risk factors in pregnancy and childhood have a major influence on health and development even into adulthood and future generations. In this paper we discuss the importance of longitudinal studies in identifying the processes underlying health and developmental problems and thus, by using the strengths of birth cohort studies, identifying preventative and other strategies which will protect public health from adverse environmental influences.

Evidence that TGFA influences risk to cleft lip with/without cleft palate through unconventional genetic mechanisms

This study examined the association between markers in transforming growth factor alpha (TGFA) and isolated, non-syndromic cleft lip with/without palate (CL/P) using a case-parent trio design, considering parent-of-origin effects. We also tested for gene-environmental interaction with common maternal exposures, and for gene-gene interaction using markers in TGFA and another recognized causal gene, IRF6. CL/P case-parent trios from four populations (76 from Maryland, 146 from Taiwan, 35 from Singapore, and 40 from Korea) were genotyped for 17 single nucleotide polymorphisms (SNPs) in TGFA. The transmission disequilibrium test was used to test individual SNPs, and the parent-of-origin likelihood ratio test (PO-LRT) was used to assess parent-of-origin effects. We also screened for possible gene-environment interaction using PBAT, and tested for gene-gene interaction using conditional logistic regression models. When all trios were combined, four SNPs showed significant excess maternal transmission, two of which gave significant PO-LRT values [rs3821261: P = 0.004 and OR(imprinting) = 4.17; and rs3771475: P = 0.027 and OR(imprinting) = 2.44]. Haplotype analysis of these two SNPS also supported excess maternal transmission. We saw intriguing but suggestive evidence of G x E interaction for several SNPs in TGFA when either individual SNPs or haplotypes of adjacent SNPs were considered. Thus, TGFA appears to influence risk of CL/P through unconventional means with an apparent parent-of-origin effect (excess maternal transmission) and possible interaction with maternal exposures.