Oral clefts, transforming growth factor alpha gene variants, and maternal smoking: a population-based case-control study in Denmark, 1991-1994

Birth Defects Associated with Prenatal Alcohol Exposure-A Review

Since the recognition of fetal alcohol syndrome, alcohol has been accepted as a human teratogen. However, little is known about the relation between prenatal alcohol exposure and the spectrum of associated major birth defects. The objective of this review was to summarize data on the association of major congenital abnormalities and prenatal alcohol exposure. We included all major birth defects according to ICD-10 classification. We found that the strongest evidence to date lies in the research examining herniation (gastroschisis and omphalocele), oral clefts (cleft lip with or without palate and cleft palate) and cardiac defects. There is less consistent evidence supporting the association between prenatal alcohol exposure and anomalies of gastrointestinal system, diaphragmatic hernia, genitourinary system and neural tube defects. We found no material support for PAE and choanal atresia, biliary atresia or clubfoot.

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.

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.

Maternal smoking during pregnancy and birth defects in children: a systematic review with meta-analysis

This systematic review aimed to investigate the association between maternal smoking during pregnancy and birth defects in children. We performed an electronic search of observational studies in the databases ovid MEDLINE (1950 to April 2010), LILACS and SciELO. We included 188 studies with a total of 13,564,914 participants (192,655 cases). Significant positive associations were found between maternal smoking and birth defects in the following body systems: cardiovascular (OR: 1.11; 95%CI: 1.03-1.19), digestive (OR: 1.18; 95%CI: 1.07-1.30), musculoskeletal (OR: 1.27; 95%CI: 1.16-1.39) and face and neck (OR: 1.28; 95%CI: 1.19-1.37). The strength of association between maternal smoking and birth defects measured by the OR (95%CI) is significantly related to the amount of cigarettes smoked daily (χ2 = 12.1; df = 2; p = 0.002). In conclusion, maternal smoking during pregnancy is associated with congenital malformations in children and this association is dose-dependent.

Higher risk of orofacial clefts in children born to mothers with angina pectoris: a population-based case-control study

Previously an unexpected association of maternal angina pectoris (MAP) during pregnancy with a higher risk of orofacial clefts in their children was found. There were three objectives of this study: (i) to evaluate the validity of MAP-diagnoses in the previous study and the recent history of mothers with MAP in a follow-up study; (ii) to estimate the prevalence of other congenital abnormalities in the offspring of mothers with MAP; and (iii) to analyze the possible effect of confounders for the risk of orofacial clefts. The large dataset of population-based Hungarian Case-Control Surveillance System of Congenital Abnormalities, 1980-1996 was evaluated including 22 843 cases with congenital abnormalities and 38 151 controls without any defect. Twenty-two cases (0.10%) and 12 controls (0.03%) were born to mothers with medically recorded MAP (odds ratio [OR] with 95% confidence interval [CI]: 3.7, 1.8-7.3). Of 22 cases, six had isolated cleft lip ± palate (OR with 95% CI: 13.3, 4.9-35.9) and two were affected with isolated cleft palate (OR with 95% CI: 10.5, 2.3-47.6). The diagnosis of MAP was confirmed in seven women visited at home in 2009-2010, two had recent myocardial infarction and five were smokers. There was no higher risk for other congenital abnormalities. In conclusion the higher risk of orofacial clefts was confirmed in the children of mothers with MAP and smoking may trigger the genetic predisposition of both MAP and orofacial clefts. However, the number of cases was limited and therefore further studies are needed to confirm or reject this theoretically and practically important observation.

Ethnic Variation in Oral Cleft Occurrence in Denmark 1981–2002

Objective

To examine differences in oral cleft (OC) occurrence based on maternal only and parental country of origin in Denmark from 1981 to 2002.

Methods

Data on all live births from the Danish Medical Birth Register from 1981 to 2002 were linked with the Danish Facial Cleft Database. Cleft cases were categorized into isolated and nonisolated cleft lip with or without palate (CL/P) and cleft palate only (CP). Birth prevalence was calculated as cases per 1,000 live born children by maternal country of origin, world region, and mixed parental groups.

Results

We identified 3094 OC cases among 1,319,426 live births. Danish-born women had an OC birth prevalence of 2.38 with a 95% confidence interval (CI) (2.29–2.47) and foreign-born women a significant lower prevalence of 2.01 (CI, 1.77–2.27). This difference was explained by a lower isolated CL/P birth prevalence among foreign-born women of 0.97 (CI, 0.81–1.16) versus 1.35 (CI, 1.28–1.41). No significant differences were seen for the remaining subtypes. Parents with the same foreign country of origin had a lower overall OC (1.63; CI, 1.35–1.94) and isolated CL/P (0.76; CI, 0.57–0.99) birth prevalence than Danish-born parents. This was not the case for any of the mixed parental groups. Overall and subtype prevalence rates varied according to maternal categories of world region.

Conclusion

In this study we found differences in OC occurrence among all live births in the Danish population based on maternal country of origin from 1981 to 2002. Danish-born women had higher OC and isolated CL/P birth prevalence compared with foreign-born women.

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.

Maternal alcohol consumption during pregnancy and the risk of orofacial clefts in infants: a systematic review and meta-analysis

BACKGROUND

The teratogenic effects of maternal alcohol consumption during pregnancy include anomalies of craniofacial structures derived from the cranial neural crest cells. The presence of specific craniofacial anomalies contributes to the diagnosis of fetal alcohol spectrum disorders. Cleft lip and palate [orofacial clefts (OFCs)], also derived from the cranial neural crest cells, are common congenital anomalies, but their relationship with prenatal alcohol consumption is unknown.

METHODS

To evaluate the association between maternal consumption of alcohol during pregnancy and the occurrence of OFCs in infants, we conducted a systematic review and meta-analyses of published studies. We examined the associations between any alcohol consumption, binge level drinking, and heavy and moderate levels of consumption vs. no or low levels of consumption.

RESULTS

After screening 737 publications, we identified 33 studies (23 case-control and 10 cohort studies). There was considerable heterogeneity in individual study design, quality measures and study results. Findings from random effects meta-analyses suggest no relationship between prenatal alcohol consumption and the occurrence of OFCs {pooled odds ratios for any alcohol intake and binge level drinking respectively: cleft lip with or without cleft palate 1.00 [95% confidence interval (CI) 0.86, 1.16] from 18,349 participants in 13 studies, 1.04 [95% CI 0.87, 1.24] [8763 individuals, 4 studies]; cleft palate only 1.05 [95% CI 0.92, 1.21] [21,459 individuals, 17 studies], 0.94 [95% CI 0.74, 1.21] [7730 participants, 4 studies]}.

CONCLUSIONS

While we found no association between alcohol consumption during pregnancy and OFCs in infants, the influence of study design, particularly in relation to alcohol exposure measurement and OFC ascertainment cannot be ignored.

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.

Maternal snuff use and smoking and the risk of oral cleft malformations--a population-based cohort study

Objective

To determine if maternal use of snuff (containing high levels of nicotine, low levels of nitrosamines and no combustion products) is associated with an increased risk of oral cleft malformations in the infant and whether cessation of snuff use or smoking before the antenatal booking influences the risk.

Method

A population-based cohort study was conducted on all live born infants, recorded in the Swedish Medical Birth Register from 1999 through 2009 (n = 1 086 213). Risks of oral clefts were evaluated by multivariate logistic regression analyses (using adjusted odds ratios, with 95% confidence intervals [CI]).

Results

Among 975 866 infants that had information on maternal tobacco use, 1761 cases of oral clefts were diagnosed. More than 50% of the mothers who used snuff or smoked three months prior pregnancy stopped using before the antenatal booking. Almost 8% of the mothers were smoking at the antenatal booking and 1,1% of the mothers used snuff. Compared with infants of non-tobacco users, the adjusted odds ratios (95% CI) of any oral cleft for infants of mothers who continued to use snuff or to smoke were 1.48 [1.00–2.21] and 1.19 [1.01–1.41], respectively. In contrast, in infants of mothers who stopped using snuff or stopped smoking before the antenatal booking, the corresponding risks were not increased (adjusted odds ratios [95% CI] were 0.71 [0.44–1.14] and 0.88 [0.73–1.05], respectively).

Conclusion

Maternal snuff use or smoking in early pregnancy is associated with an increased risk of oral clefts. Infants of mothers who stopped using snuff or stopped smoking before the antenatal booking had no increased risk of oral cleft malformations. Oral snuff or other sources of nicotine should not be recommended as an alternative for smoke-cessation during pregnancy.

Maternal occupational exposure to polycyclic aromatic hydrocarbons and risk of oral cleft-affected pregnancies

OBJECTIVE

To evaluate whether there is an association between maternal occupational exposure to polycyclic aromatic hydrocarbons and oral clefts in offspring. This is the first human study of polycyclic aromatic hydrocarbons and clefts of which the authors are aware.

DESIGN

Case-control study.

SETTING, PARTICIPANTS

Data for 1997 to 2002 from the National Birth Defects Prevention Study, a large population-based case-control study in the United States, were analyzed. Maternal telephone interviews yielded information on jobs held in the month before through 3 months after conception. Two industrial hygienists independently assessed occupational exposure to polycyclic aromatic hydrocarbons; all jobs rated as exposed or with rating difficulty were reviewed with a third industrial hygienist to reach consensus on all exposure parameters. Logistic regression estimated crude and adjusted odds ratios with 95% confidence intervals for cleft lip with or without cleft palate and cleft palate alone.

RESULTS

There were 2989 controls (3.5% exposed), 805 cases of cleft lip with or without cleft palate (5.8% exposed), and 439 cases of cleft palate alone (4.6% exposed). The odds of maternal occupational exposure to polycyclic aromatic hydrocarbons (any versus none) during pregnancy was increased for cleft lip with or without cleft palate cases as compared with controls (odds ratio, 1.69; 95% confidence interval, 1.18 to 2.40); the odds ratio was 1.47 (95% confidence interval 1.02 to 2.12) when adjusted for maternal education. There was a statistically significant adjusted exposure-response relationship for cleft lip with or without cleft palate (Ptrend = .02). Odd ratios for cleft palate alone were not statistically significant.

CONCLUSIONS

Maternal occupational exposure to polycyclic aromatic hydrocarbons was associated with increased risk of cleft lip with or without cleft palate in offspring.

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.

An Epidemiologic Study of Orofacial Clefts in Hamedan City, Iran: A 15-Year Study

Objective

To determine the epidemiology of cleft lip and/or palate (CL/P) in births in hospitals of Hamedan City, Iran, and to evaluate the etiologic factors that have a role in the development of these anomalies.

Design

This research was a 15-year cross-sectional study (1993 to 2008).

Participants

All infants born with CL/P during the study period comprised the study group. One thousand healthy children without cleft anomalies born in the same hospitals during the study period comprised the control group.

Results

The prevalence of CL/P was 1.016 per 1000 live births (53.4% boys and 46.6% girls). Cleft lip associated with cleft palate (CLP) was the most common type of anomaly (53.5%), followed by isolated cleft lip (CL; 28.7%) and isolated cleft palate (CP; 17.8%). Eighty-six babies (81%) had unilateral CL and 20 babies (19%) had bilateral CL. Twenty-three newborns with CL/P (17.8%) had other congenital deformities. The frequency of CL/P in parents, siblings, and relatives of newborns in study group was higher than in the control group. There was a significant difference between the study and control groups with respect to maternal drug intake, trauma, smoking, and x-ray exposure during pregnancy.

Conclusion

The birth prevalence of CL/P in Hamedan City was closer to the prevalence of CL/P in the United States and Europe than Africa and the Far East. We found that the presence of cleft in parents, siblings, and other relatives; maternal drug intake; trauma; radiation; and smoking were risk factors for cleft development in newborns.

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.

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.

Risk factors for oral clefts: a population-based case-control study in Shenyang, China

Shenyang in Northern China has one of the highest reported prevalence rates of oral clefts in the world. To explore the risk factors for oral clefts in Shenyang, we carried out a population-based case-control study. A total of 360 990 births in 2000 to 2007 were screened for oral clefts; the overall prevalence was 1.76 per 1000. The ratio of cleft lip with or without cleft palate (CL +/- P) : cleft palate only (CP) was 5.60:1. The overall male : female ratio was 2.02:1. CLP and CL were more common in males than in females with a sex ratio (SR) of 2.88:1 and 1.86:1 respectively, whereas CP was more common in females with an SR of 0.71:1. Using a multivariable conditional logistic regression model, 586 oral clefts cases were compared with 1172 control mothers. Maternal factors significantly associated with increased risk for oral clefts were history of a fever or cold (adjusted OR 2.34, 95% CI 1.06, 5.60); use of analgesic and antipyretic drugs (adjusted OR 3.10, 95% CI 1.41, 6.86); poor ventilation during heating (adjusted OR 2.25, 95% CI 1.10, 4.60); and consumption of pickled vegetables >6 per week (adjusted OR 3.86, 95% CI 1.11, 13.47) during pregnancy. Factors which appeared to be protective were meat consumption >or=4 times per week (adjusted OR 0.43, 95% CI 0.28, 0.67); and legume consumption >6 times per week (adjusted OR 0.60, 95% CI 0.41, 0.89). Differences in risk were found between the two most common phenotypes, CL +/- P and CP only. Most of the environmental factors had stronger associations with risk for CL +/- P rather than CP, whereas history of oral clefts, as well as legume consumption, were more strongly associated with the risk for CP than for CL +/- P. The findings suggest that aetiological heterogeneity may exist between CL +/- P and CP.

Genetic susceptibilities in the association between maternal exposure to tobacco smoke and the risk of nonsyndromic oral cleft

Maternal tobacco consumption is considered as a risk factor for nonsyndromic oral clefts. However, this risk is moderate and may be modulated by genetic susceptibilities, including variants of the TGFA, TGFB3 and MSX1 developmental genes and polymorphisms of genes of the CYP (1A1, 2E1) and GST (M1, T1) families involved in metabolic pathways of tobacco smoke compounds. This French case-control study (1998-2001; 240 nonsyndromic cases, 236 controls) included a case-parent design (175 triad-families) that made it possible to distinguish the direct effect of the child's genotype and maternally mediated effects. Maternal smoking during the first trimester of pregnancy was not associated with the oral cleft risk in this population, but we observed statistically significant increased risks associated with maternal exposure to environmental tobacco smoke (ETS). No variant of any of the three developmental genes was significantly associated with oral cleft. The fetal CYP1A1*2C variant allele was associated with a statistically significant decreased risk, compared with the homozygous wild-type: relative risk = 0.48, 95% confidence interval: 0.2, 1.0. Suggestive reduced risks were also observed for the maternal CYP1A1*2C allele and the fetal CYP2E1*5 allele. The GSTM1 and GSTT1 deletions appeared to play no role. Our findings suggest some interactions, with the strongest between ETS and CYP1A1 or MSX1 and between maternal smoking and CYP2E1. We did not confirm the maternal smoking-infant GSTT1 null interaction previously reported by other investigators.

Maternal smoking and oral clefts: the role of detoxification pathway genes

BACKGROUND

There is evidence for an effect of cigarette smoking on risk of oral clefts. There are also hypothetical pathways for a biologic effect involving toxic chemicals in cigarette smoke.

METHODS

We performed a combined case-control and family-triad study of babies born with oral clefts in Norway in the period 1996 to 2001, with 88% participation among cases (n = 573) and 76% participation among controls (n = 763). Mothers completed a questionnaire 4 months after birth of the baby. DNA was collected from parents and children, and assayed for genes related to detoxification of compounds of cigarette smoke (NAT1, NAT2, CYP1A1, GSTP1, GSTT1, and GSTM1).

RESULTS

For isolated cleft lip (with or without cleft palate) there was a dose-response effect of smoking in the first trimester. The odds ratio rose from 1.6 (95% confidence interval = 1.0-2.5) for passive smoking to 1.9 (0.9-4.0) for mothers who smoked more than 10 cigarettes per day. There was little evidence of an association with cleft palate. Genetic analyses used both case-control and family-triad data. In case-triads we found an association between a NAT2 haplotype and isolated cleft lip (relative risk of 1.6 with 1 copy of the allele and 2.5 with 2 copies), but with little evidence of interaction with smoking. Other genes did not show associations, and previously described interactions with smoking were not confirmed.

CONCLUSION

First-trimester smoking was clearly associated with risk of cleft lip. This effect was not modified by variants of genes related to detoxification of compounds of cigarette smoke.

Review on genetic variants and maternal smoking in the etiology of oral clefts and other birth defects

A spectrum of adverse pregnancy outcomes, including preterm birth, low birth weight, and birth defects has been linked with maternal smoking during pregnancy. This article includes a review of studies investigating interactions between genetic variants and maternal smoking in contributing to birth defects using oral clefting as a model birth defect. The primary gene-smoking studies for other major birth defects are also summarized. Gene-environment interaction studies for birth defects are still at an early stage with several mixed results, but evolving research findings have begun to document clinically and developmentally important interactions. As samples and data become increasingly available, more effort is needed in designing innovative analytical methods to study gene-environment interactions.

TGFA/TAQ I polymorphism in nonsyndromic cleft lip and palate patients from Rio Grande Do Sul, Brazil

OBJECTIVE

To test the TGFA/Taq I polymorphism in the development of nonsyndromic cleft lip and palate.

DESIGN AND SETTING

The research was based on a case-control study, including nonsyndromic cleft lip and palate patients (140 individuals) and a control sample of unaffected individuals (142) to ascertain the absence or presence of genic mutation at the TGFA locus.

INTERVENTIONS

The DNA of carriers of nonsyndromic cleft lip with or without cleft palate was obtained by buccal swab, and the DNA of the control group was extracted from peripheral blood leucocytes. TGFA/Taq I polymorphism was determined genetically by polymerase chain reaction using specific primers and fragment digestion with Taq I restriction enzyme.

RESULTS

No significant association was detected when patients and controls were compared with the genotype for TGFA/Taq I polymorphism.

CONCLUSION

Mutations in TGFA gene have no association with nonsyndromic cleft lip and palate in the sample from Rio Grande do Sul. Therefore, based on this study, it is not possible to determine the role played by TGFA in the expression of cleft lip and palate.

Utility of family history reports of major birth defects as a public health strategy

A major birth defect is an abnormality that can affect the structure or function of an organ. In the United States, major birth defects are the leading cause of infant mortality and contribute substantially to childhood disability and morbidity. Globally, these conditions lead to the death of millions of infants and children annually. Patients with 1 or more affected family members may be at increased risk for having a child with a major birth defect; thus, accurate knowledge of these conditions among family members of their patients gives the clinician the ability to provide improved risk assessment and reproductive planning. Such knowledge can also serve as motivation for patients to adhere to healthy behaviors such as folic acid use or smoking cessation. To evaluate the utility of collecting family history reports of major birth defects as a public health strategy, 6 key criteria were examined by reviewing the relevant published literature. Overall, the review showed that major birth defects satisfied several of the criteria. Additional research is needed, however, regarding the awareness of parent reports of the occurrence of these conditions among relatives and how knowledge of birth defect diagnoses and related risk factors are transmitted among relatives. Such research needs to encompass not only immediate family members but also other first-degree and second-degree relatives. In summary, routine collection of family history reports of birth defects in pediatric practice holds promise as a public health strategy to reduce the burden of morbidity, mortality, and disability associated with major birth defects.

Storage policies and use of the Danish Newborn Screening Biobank

After routine newborn screening, residual dried blood spot samples (DBSS) are stored at -20 degrees C in the Danish Newborn Screening Biobank (NBS-Biobank), which contains DBSS from virtually all newborns in Denmark since 1982--about 1.8 million samples. The purpose of the storage is: (1) diagnosis and treatment of congenital disorders including documentation, repeat testing, quality assurance, statistics and improvement of screening methods; (2) diagnostic use later in infancy after informed consent; (3) legal use after court order; (4) the possibility of research projects after approval by the Scientific Ethical Committee System in Denmark, The Danish Data Protection Agency and the NBS-Biobank Steering Committee. The operation and use of the NBS-Biobank has until recently been regulated by an executive order of 1993 from the Danish Ministry of Health. The Ethical Council, the Central Scientific Ethical Committee and the National Board of Health were also involved in the regulations. These regulations have now been replaced by detailed general operational guidelines for biobanks in Denmark according to Acts on Processing of Personal Data, Patient's Rights, Health 546/2005 and the Biomedical Research Ethics Committee System. No specific Act on biobanks per se has been made in Denmark, but the new regulations and guidelines make the operations of the Danish NBS-Biobank even more clear-cut and safe. The Danish NBS-Biobank has been used in several research projects for aetiological studies of a number of disorders, recently employing new sensitive multiplex technologies and genetic analyses utilizing whole-genome amplified DNA.

Spatial distribution of orofacial cleft defect births in Harris County, Texas, 1990 to 1994, and historical evidence for the presence of low-level radioactivity in tap water

BACKGROUND

While both ionizing and nonionizing radiation are known to impair human reproductive capacity, the role of low-level domestic radiation continues to be an unsettled issue.

OBJECTIVES

We examined the geostatistical distribution (residential longitude and latitude) of orofacial cleft birth cases adjusted for the underlying population distribution. Furthermore, we examined the cleft birth rates enumerated by zip codes for possible associations with levels of radium and radon in drinking water.

METHODS

Cleft births and unaffected live births in Harris County, Texas, from 1990 to 1994, were geocoded by residential addresses and tested for spatial clusters using the space-time clustering program SaTScan. Historical sample data on local variations in water quality facilitated the assessment of the association of orofacial cleft defect births with low-level radiation exposure.

RESULTS

A cluster of significantly greater than expected numbers of cleft defect births was identified in northwest Harris County, (relative risk = 3.0, P = 0.043), where the presence of elevated levels of radium (> 3 pCi/L) and radon (> 300 pCi/L) in the tap water has been known since the 1980s.

CONCLUSIONS

Despite the ecological design of the study, lacking individual exposure measurements for cleft birth residences, there was strong suggestive evidence of an association between elevated radiation levels in tap water and elevated cleft birth prevalence rates by zip codes. Attention of physicians is invited to environmental causes as potential risk factors for orofacial cleft. This would aid in genetic counseling and the development of future preventive measures.

Oral clefts and life style factors — A case-cohort study based on prospective Danish data

This study examines the association between oral clefts and first trimester maternal lifestyle factors based on prospective data from the Danish National Birth Cohort. The cohort includes approximately 100,000 pregnancies. In total 192 mothers gave birth to child with an oral cleft during 1997-2003. Information on risk factors such as smoking, alcohol consumption, tea, coffee, cola, and food supplements was obtained during pregnancy for these and 828 randomly selected controls. We found that first trimester maternal smoking was associated with an increased risk of oral clefts (odds ratio (OR): 1.50; 95% confidence interval (CIs): 1.05, 2.14). Although not statistically significant, we also saw associations with first trimester consumption of alcohol (OR: 1.11; CIs: 0.79, 1.55), tea (OR: 1.31; CIs: 0.93, 1.86), and drinking more than 1 l of cola per week (OR: 1.40; CIs: 0.92, 2.12). Furthermore supplementation with > or =400 mcg folic acid daily during the entire first trimester (OR: 0.75; CIs: 0.46, 1.22) suggested an inverse associated with oral clefts, similar to our results on coffee drinking. No effects were found for smaller doses of folic acid, vitamin A, B6 or B12 in this study. The present study found an association between oral clefts and smoking and, although not conclusive, supports an association of oral cleft with alcohol.

Orofacial cleft risk is increased with maternal smoking and specific detoxification-gene variants

Maternal smoking is a recognized risk factor for orofacial clefts. Maternal or fetal pharmacogenetic variants are plausible modulators of this risk. In this work, we studied 5,427 DNA samples, including 1,244 from subjects in Denmark and Iowa with facial clefting and 4,183 from parents, siblings, or unrelated population controls. We examined 25 single-nucleotide polymorphisms in 16 genes in pathways for detoxification of components of cigarette smoke, to look for evidence of gene-environment interactions. For genes identified as related to oral clefting, we studied gene-expression profiles in fetal development in the relevant tissues and time intervals. Maternal smoking was a significant risk factor for clefting and showed dosage effects, in both the Danish and Iowan data. Suggestive effects of variants in the fetal NAT2 and CYP1A1 genes were observed in both the Iowan and the Danish participants. In an expanded case set, NAT2 continued to show significant overtransmission of an allele to the fetus, with a final P value of .00003. There was an interaction between maternal smoking and fetal inheritance of a GSTT1-null deletion, seen in both the Danish (P=.03) and Iowan (P=.002) studies, with a Fisher's combined P value of <.001, which remained significant after correction for multiple comparisons. Gene-expression analysis demonstrated expression of GSTT1 in human embryonic craniofacial tissues during the relevant developmental interval. This study benefited from two large samples, involving independent populations, that provided substantial power and a framework for future studies that could identify a susceptible population for preventive health care.

Association between the transforming growth factor alpha gene and nonsyndromic oral clefts: a HuGE review

Transforming growth factor alpha (TGFA) is a well-characterized mammalian growth factor. Since the first report of an association between DNA sequence variants at the TGFA genetic locus and nonsyndromic oral clefts, 47 studies have been carried out, producing conflicting results. In this review, the author synthesizes findings from published reports on the association between the TGFA gene and clefting in humans. Bias, lack of statistical power, and genuine population diversity can explain the diverse results. In the aggregate, TGFA is probably a genetic modifier of clefting in humans, which is consistent with the oligogenic model suggested for nonsyndromic oral clefts.

Smoking habits, nicotine use, and congenital malformations

OBJECTIVE

We examined whether maternal smoking and use of nicotine substitutes during the first 12 weeks of pregnancy increased the prevalence of congenital malformations in general and of certain congenital malformations in particular.

METHODS

In the Danish National Birth Cohort (1997-2003) we identified 76,768 pregnancies (and their subsequent singleton births); 20,603 were exposed to tobacco smoking during the first 12 weeks of pregnancy. Birth outcomes were collected by linkage to the Central Population Register, the National Patients Register, and the National Birth Register. We identified congenital malformations from the Hospital Medical Birth Registry as they were recorded at birth or in the first year of follow-up.

RESULTS

Smoking mothers were younger, weighed less, consumed more alcohol, and had received less education. Children exposed to prenatal tobacco smoking had no increase in congenital malformations prevalence compared with the nonexposed children in both crude and adjusted analyses. Children born to nonsmokers, but who used nicotine substitutes, had a slightly increased relative congenital malformations prevalence ratio; relative prevalence rate ratio was 1.61 (95% confidence interval 1.01-2.58), which represents a 60% increased risk. When the analysis was restricted to musculoskeletal malformations, the relative prevalence rate ratio was 2.63 (95% confidence interval 1.53-4.52).

CONCLUSION

Our results showed no increase in congenital malformations related to prenatal tobacco smoking. However, we identified an increase of malformations risk in nonsmokers using nicotine substitutes. This finding needs to be replicated in other data sources.

LEVEL OF EVIDENCE

II-2.

Endothelial nitric oxide synthase (NOS3) genetic variants, maternal smoking, vitamin use, and risk of human orofacial clefts

Orofacial clefts have been associated with maternal cigarette smoking and lack of folic acid supplementation (which results in higher plasma homocysteine concentrations). Because endothelial nitric oxide synthase (NOS3) activity influences homocysteine concentration and because smoking compromises NOS3 activity, genetic variation in NOS3 might interact with smoking and folic acid use in clefting risk. The authors genotyped 244 infants with isolated cleft lip with or without cleft palate (CL/P), 99 with isolated cleft palate, and 588 controls from a California population-based case-control study (1987-1989 birth cohort) for two NOS3 polymorphisms: A(-922)G and G894T. Analyses of gene-only effects for each polymorphism revealed a 60% increased risk of CL/P among NOS3 A(-922)G homozygotes (odds ratio (OR) = 1.6, 95% confidence interval (CI): 1.0, 2.6). There was some evidence for higher risk of CL/P with maternal periconceptional smoking in infants with an NOS3 -922G allele (for homozygotes, OR = 2.5, 95% CI: 1.2, 5.6) but not in those with an 894T allele. For CL/P risk, odds ratios were over 4 among mothers who smoked, who did not use vitamins, and whose infants had at least one variant allele for each NOS3 polymorphism (for A(-922)G, OR = 4.6, 95% CI: 2.1, 10.2; for 894T, OR = 4.4, 95% CI: 1.8, 10.7). No similar patterns were observed for risk of cleft palate.

Changing lifestyles and oral clefts occurrence in Denmark

OBJECTIVE

The aim of this project was to assess whether any changes in the birth prevalence of cleft lip with/without cleft palate (CL[P]) occurred in Denmark during the period 1988 through 2001. In this period an official recommendation of a supplementation of folic acid to pregnant women was introduced; furthermore, smoking among pregnant women decreased considerably.

DESIGN AND SETTINGS

There are few places in which ecological studies of oral clefts are possible. Denmark provides a particularly good setting for this kind of study because of a high ascertainment and a centralized registration of subjects with cleft over the last 65 years.

PARTICIPANTS

Cleft occurrence in Denmark from 1936 to 1987 has previously been reported. Here we extend the study to include all live-born children with oral clefts born in Denmark in 1988 through 2001. Among a total of 992,727 live births, 1332 children with CL(P) were born during this period.

RESULTS AND CONCLUSIONS

The birth prevalence of CL(P) in Denmark has previously been found to be constant in the period 1962 through 1987, with a frequency of 1.4 to 1.5 per 1000 live births. This study showed a similar occurrence in 1988 through 2001 (birth prevalence = 1.44 per 1000 live births, 95% confidence interval = 1.37 to 1.52). The introduction of folic acid and the decrease in smoking prevalence among pregnant women do not seem to have reduced the birth prevalence. This may be due to noncompliance with the folic acid recommendation and/or only a weak causal association between folic acid and smoking and occurrence of CL(P).

The prevalence of smoking among pregnant and postpartum women in Israel: a national survey and review

BACKGROUND

Cigarette smoking during pregnancy is a significant health risk to the developing fetus. In order to develop and implement an appropriate preconceptional and prenatal smoking cessation program a national pregnancy risk survey was done.

METHODS

The survey was conducted through the Public Health Service's, Mother and Child Health Clinics (MCHC). The nursing staff initiated structured interviews with pregnant women and mothers of newborn infants. Questions included in the survey addressed folic acid utilization, smoking habits, onset of prenatal care and demographic characteristics.

RESULTS

Overall, of the 1613 questionnaires received with smoking data, 12.8% of the women had smoked either in the 3 months preceding their current pregnancy and/or during their pregnancy. The smoking prevalence in Jewish women, was significantly greater then that found among Arab women (17.2 and 3.0%, P<.001, OR=7.5, CI=4.2-13.4). The prevalence of smoking for the duration of the pregnancy was 8.0% among Jewish women and 1.8% among Arab women. Among Jewish women, smoking prevalence was significantly associated with education, women who had completed 12 years of education were more likely to be nonsmokers (P=.034, OR=1.8, CI=1.0-3).

CONCLUSION

Smoking in the preconceptional and prenatal period is a significant problem among Jewish women. Since less years of education is a significant risk factor, smoking cessation programs should focus on this subgroup of Jewish women.

Cancer risk in persons with oral cleft--a population-based study of 8,093 cases

The authors conducted a nationwide study of the occurrence of cancer among 8,093 Danish oral cleft cases born in 1936 through 1998 and followed in the Danish Cancer Registry from 1968 through 1998, a total of 175,863 person-years, to assess a possible association between cancer and oral clefts. Observed and expected numbers of cancers among oral cleft cases were summarized as the overall and as 52 site-specific standardized incidence ratios. The expected overall number of all cancers was 131, but 140 incident cancers were found, corresponding to a standardized incidence ratio of 1.07 (95% confidence interval (CI): 0.90, 1.26). Analyses of the 52 sites for all oral cleft cases and analyses stratified for three cleft subgroups and the two sexes revealed only a few significant associations: an increased occurrence of breast cancer among females born with cleft lip and/or cleft palate (standardized incidence ratio (SIR) = 1.52, 95% CI: 1.05, 2.14), primary brain cancer among females born with cleft palate (SIR = 3.11, 95% CI: 1.14, 6.78), and primary lung cancer among males born with both cleft lip and cleft palate (SIR = 2.49, 95% CI: 1.00, 5.14). The results do not provide evidence for an increased overall cancer risk for individuals born with oral clefts.

Smoking and the risk of oral clefts: exploring the impact of study designs

BACKGROUND

Maternal cigarette smoking is a suspected cause of oral clefts, although this association has not been firmly established. We used case-crossover, case-time-control, and bidirectional case-crossover designs to supplement findings from a case-control study of maternal smoking and oral clefts among offspring in a large birth registry.

METHODS

Data are from the Swedish Medical Birth Registry. From 1983 through 1997 there were 678 recorded cases of cleft palate and 1175 cases of cleft lip with or without palate. Maternal smoking status was ascertained in early pregnancy. Controls for the case-control study were a random sample of infants born without a cleft; controls for the case-crossover designs were nonmalformed infants born to case mothers.

RESULTS

Cleft palate was positively associated with maternal smoking in all study designs, whereas cleft lip with or without cleft palate was associated with smoking only in the case-control design. In the case-control design, the odds ratios for cleft palate were 1.2 (95% confidence interval = 1.0-1.5) for women who smoked 1 to 9 cigarettes per day and 1.4 (1.1-1.8) for women who smoked 10+ cigarettes per day. In the case-time-control analysis, the odds ratio for cleft palate with maternal smoking was 3.2 (1.3-7.4) and in the bidirectional case-crossover design, the odds ratio was 2.2 (1.1-4.1).

CONCLUSIONS

An association between smoking and cleft palate was supported by all designs, whereas that between smoking and cleft lip with or without cleft palate was not. Case-only designs are a viable option in birth registries and may yield more information than a case-control design alone.

Gene-environment interactions: a review of effects on reproduction and development

Polymorphisms in genes can lead to differences in the level of susceptibility of individuals to potentially adverse effects of environmental influences, such as chemical exposure, on prenatal development or male or female reproductive function. We have reviewed the literature in this area, with the caveat that papers involving straight gene knock-outs in experimental animals, without a clear human relevance, were largely excluded. This review represents current knowledge in this rapidly moving field, presenting both human epidemiological and animal data, where available. Among the polymorphic genes and environmental interactions discussed with respect to prenatal development are those for P-glycoprotein (multidrug resistance protein) and the avermectins; methylenetetrahydrofolate reductase (MTHFR), an enzyme in folate metabolism, and dietary folic acid; transforming growth factor alpha (TGFalpha) and cigarette smoke; and alcohol dehydrogenase (ADH) and cytochrome P-450 (CYP) 2E1 in association with alcohol consumption. Effects on male reproduction attributable to gene-environment interaction involve infertility seen as a result of either organophosphorous (OP) pesticide interaction with the polymorphic paraoxonase (PON1) gene or antiandrogenic agent interaction with the androgen receptor (AR). MTHFR, folate metabolism, and dietary folic acid are also considered in conjunction with preeclampsia and early pregnancy loss, and the effect of the interaction of glutathione S-transferase (GST) with exposure to benzene or cigarette smoke on pregnancy maintenance is explored. As a conclusion, we offer a discussion of lessons learned and suggested research needs.

Evaluation of two methods for assessing gene-environment interactions using data from the Danish case-control study of facial clefts

BACKGROUND

Epidemiological investigations have begun to consider gene-environment (GE) interactions as potential risk factors for many diseases, including several different birth defects. However, traditional methodological approaches for the analysis of case-control data tend to have low power for detection of interaction effects. A log-linear approach that can impose the assumption that the genotype and exposure of interest occur independently in the population has been proposed as a potentially more powerful method for assessing GE interactions but has not been widely applied in the published literature.

METHODS

The present analyses were undertaken to compare the results obtained when stratified analyses and a log-linear approach were used to assess potential GE interactions. The analyses were conducted using data from a population-based, case-control study conducted in Denmark and considered associations between nonsyndromic cleft lip with or without cleft palate (CL+/-P), infant genotype for variants of RAR-alpha, TGF-alpha, TGF-beta3, and MSX1, and maternal exposure to smoking, alcohol, and multivitamins.

RESULTS

Neither the stratified nor the log-linear analyses provided evidence that that risk of CL+/-P is influenced by any of the GE interactions that were evaluated, despite the potential increase in power offered by the latter approach. Further, the analyses highlight concerns regarding the power to reject the assumption of independence of the genetic and environmental factor of interest in the controls and related concerns regarding the validity of results obtained using the log-linear approach when the underlying assumption is violated.

CONCLUSIONS

The potential increase in power offered by the log-linear approach is offset by concerns regarding the validity of this approach when the independence assumption is violated.

Genetics of nonsyndromic cleft lip with or without cleft palate: is there a Mendelian sub-entity?

The mode of inheritance of nonsyndromic cleft lip with or without cleft palate (NSCLP) is still a matter of dispute. We performed segregation analysis on three data sets of families ascertained through an affected child with NSCLP. The first two data sets were selected in France and were pooled for a global analysis. No major gene effect could be evidenced in spite of a very large number of families (666 pedigrees including 719 nuclear families). The third data set was British and consisted of three-generation families including the offspring of probands. A major gene effect, as well as a strong residual multifactorial component, were highly significant and we could show that this evidence almost entirely came from the information on probands' offspring. We conclude that a mixture of monogenic and of multifactorial cases is probably the best explanation for the observations made in this study. Analyses performed in pedigrees with multiple cases closely related might allow reducing heterogeneity and help identifying those Mendelian sub-entities.

Smoking and orofacial clefts: a United Kingdom-based case-control study

OBJECTIVE

To investigate the association between smoking and orofacial clefts in the United Kingdom.

DESIGN

Case-control study in which the mother's exposure to tobacco smoke was assessed by a structured interview.

SETTING

Scotland and the Manchester and Merseyside regions of England.

PARTICIPANTS

One hundred ninety children born with oral cleft between September 1, 1997, and January 31, 2000, and 248 population controls, matched with the cases on sex, date of birth, and region.

MAIN OUTCOME MEASURE

Cleft lip with or without cleft palate and cleft palate.

RESULTS

There was a positive association between maternal smoking during the first trimester of pregnancy and both cleft lip with or without cleft palate (odds ratio 1.9, 95% confidence interval 1.1 to 3.1) and cleft palate (odds ratio 2.3, 95% confidence interval 1.3 to 4.1). There was evidence of a dose-response relationship for both types of cleft. An effect of passive smoking could not be excluded in mothers who did not smoke themselves.

CONCLUSION

The small increased risk for cleft lip with or without cleft palate in the offspring of women who smoke during pregnancy observed in this study is in line with previous evidence. In contrast to some previous studies, an increased risk was also apparent for cleft palate. In these U.K. data, there was evidence of a dose-response effect of maternal smoking for both types of cleft. The data were compatible with a modest effect of maternal passive smoking, but the study lacked statistical power to detect or exclude such an effect with confidence. It may be useful to incorporate information on the effects of maternal smoking on oral clefts into public health campaigns on the consequences of maternal smoking.

Transforming growth factor-alpha and nonsyndromic cleft lip with or without palate in Brazilian patients: results of a large case-control study

OBJECTIVE

Transforming growth factor-alpha (TGFA) was the first gene suggested to be associated with nonsyndromic cleft lip, cleft palate, or both (CL/ P). There are, however, still controversies of the effect of TGFA on the predisposition of this malformation. To contribute to a better understanding of the role of this gene in the occurrence of CL/P we undertook a case-control study including patients and controls ascertained in different regions of the country.

DESIGN

We examined the C2/TaqI variant of the TGFA gene in 536 patients with nonsyndromic CL/P and 412 controls. The TGFA genotype frequencies in patients were compared with controls using chi-square or Fisher exact test. DNA, obtained from peripheral blood or buccal swabs, was genotyped for the TaqI polymorphism of TGFA.

SETTING

The probands and corresponding controls were ascertained in different centers of Brazil, partly representing the ethnic admixture of our population.

RESULTS

The TGFA genotype distribution was very similar in patients with CL/P ascertained in the three different regions of Brazil. However, a discrete difference was observed between controls of Säo Paulo and Ceará (chi-square = 3.605; p = 0.058), with a lower value of the C2/Taq allele frequency in controls of CE (0.04). These data reinforce that this polymorphic system is heterogenous among different ethnic groups. In addition, no evidence was found for an association of TGFA with CL/P in this case-control study.

CONCLUSION

These data further suggest that TGFA is not a relevant modifier locus for the occurrence of CL/P.

Cleft palate, transforming growth factor alpha gene variants, and maternal exposures: Assessing gene-environment interactions in case-parent triads

We have previously reported a threefold risk of cleft palate only (CPO) among children homozygous for the less common allele A2 at the TaqI marker site of the transforming growth factor alpha gene (TGFA) (Jugessur et al. [2003a] Genet. Epidemiol. 24:230-239). Here we assess possible interaction between the child's TGFA TaqI A2A2 genotype and maternal cigarette smoking, alcohol consumption, use of multivitamins and folic acid. This was done by comparing the strength of genetic associations between strata of exposed and unexposed case-parent triads. We also looked for possible gene-gene interaction with the polymorphic variant C677T of the folic acid-metabolizing gene MTHFR. We analyzed a total of 88 complete CPO triads selected from a population-based study of orofacial clefts in Norway (May 1996-1998). No evidence of interaction was observed with either smoking or alcohol use. The risk associated with two copies of the A2 allele at TGFA TaqI was strong among children whose mothers did not use folic acid (relative risk=4.5, 95% confidence interval=1.3-15.7), and was only marginal among children whose mothers reported using folic acid (RR=1.4, 95% CI=0.2-12.7). Although the interaction between the child's genotypes at TGFA TaqI and MTHFR-C677T was not statistically significant, the effect of the TGFA TaqI A2A2 genotype appeared to be stronger among children with either one or two copies of the T-allele at C677T (RR=4.0, 95% CI=1.1-13.9) compared to children homozygous for the C-allele (RR=1.7, 95% CI=0.2-15.7). In conclusion, we find little evidence of interaction between the child's genotypes at TGFA TaqI and various exposures for cleft palate, with the possible exception of folic acid intake.

A genome-wide scan for loci predisposing to non-syndromic cleft lip with or without cleft palate in two large Syrian families

Non-syndromic cleft lip with/without cleft palate (CL/P) is a common, usually non-fatal birth defect of complex etiology. Several segregation analyses have demonstrated that genetic factors are important in the pathogenesis of CL/P, most likely through the interaction of several genes of modest effects. The aim of this study was to perform a genome-wide linkage analysis to identify/search for candidate gene loci for CL/P. We conducted a genome-wide search in two large, relatively isolated Syrian families, each one with a large number of cases with CL/P (18 in family 1 and 4 in family 2). A locus with a multipoint LOD score of 2.80 and a 2-point non-parametric MLS LOD of 3.0 was detected on 17p13.1. Other chromosomal regions with multipoint LOD scores > or = 1.2 (P < or = 0.01) included 3p21.2, 4q32.1, and 7q34. These data indicate the possible presence of several susceptibility loci for CL/P and identify a strong candidate locus for this common birth defect on chromosome 17p13.

Variants of developmental genes (TGFA, TGFB3, and MSX1) and their associations with orofacial clefts: a case-parent triad analysis

We selected 262 case-parent triads from a population-based study of orofacial clefts in Norway, and examined variants of developmental genes TGFA, TGFB3, and MSX1 in the etiology of orofacial clefts. One hundred seventy-four triads of cleft lip cases (CL+/-P) and 88 triads of cleft palate only cases (CPO) were analyzed. There was little evidence for an association of any of these genes with CL+/-P. The strongest association was a 1.7-fold risk with two copies of the TGFB3-CA variant (95% CI=0.9-3.0). Among CPO cases, there was a 3-fold risk with two copies of the TGFA TaqI A2 allele, and no increase with one copy. Assuming this to be a recessive effect, we estimated a 3.2-fold risk among babies homozygous for the variant (95% CI=1.1-9.2). Furthermore, there was strong evidence of gene-gene interaction. While there was only a weak association of the MSX1-CA variant with CPO, the risk was 9.7-fold (95% CI=2.9-32) among children homozygous for both the MSX1-CA A4 allele and the TGFA A2 allele. No association of CPO with the TGFA variant was seen among the other MSX1-CA genotypes. In conclusion, no strong associations were found between CL+/-P and variants at these three genes. There was a possible recessive effect of the TGFA TaqI variant on the risk of CPO, with a 3-fold risk among children homozygous for the variant. The effect of this TGFA genotype was even stronger among children homozygous for the MSX1-CA A4 allele, raising the possibility of interaction between these two genes.

Recent developments in orofacial cleft genetics

Nonsyndromic cleft of the lip and/or palate (CLP or orofacial cleft) derives from an embryopathy with consequent failure of the nasal process and/or palatal shelves fusion. This severe birth defect is one of the most common malformations among live births. Nonsyndromic CLP is composed of two separate entities: cleft lip and palate (CL+/-P) and cleft palate only (CPO). Both have a genetic background, and environmental factors probably disclose these malformations. In CL+/-P, several loci have been identified, and, in one case, a specific gene has also been found. In CPO, one gene has been identified, but many more are probably involved. Because of the complexity of the genetics of nonsyndromic CLP as a result of the difference between CL+/-P and CPO, heterogeneity of each group caused by the number of involved genes, type of inheritance, and interaction with environmental factors, we discuss the more sound results obtained with different approaches: epidemiological studies, animal models, human genetic studies, and in vitro studies.

Evidence that BCL3 plays a role in the etiology of nonsyndromic oral clefts in Brazilian families

The BCL3 gene has been considered a susceptibility locus for nonsyndromic cleft lip with or without cleft palate (NSCL/P), based on association and linkage studies in some populations. We evaluated an intragenic marker at the BCL3 gene and the microsatellite D19S178 (1.1 cM distant from the BCL3 gene) among 98 infants born with NSCL/P and their parents, using the transmission disequilibrium test (TDT) and a method for haplotype analysis. Our analysis, based on BCL3 alleles, revealed the existence of a marginal association of allele 135pb of the BCL3 gene with NSCL/P (chi(2)=3.60; P=0.058; 1 df), with a major effect in female (chi(2)=5.77; P=0.016; 1 df) and in familial cases (chi(2)=3.79; P=0.051; 1 df). However, the haplotype analysis detected no significant segregation distortion, even if the alleles of the D19S178 were grouped into two classes. These findings support previous findings that BCL3 plays a role in the etiology of NSCL/P as an allele of low penetrance or as a modifier locus. We hypothesize that there might be more than one mutation in this gene associated with NSCL/P, or alternatively, that more than one mutation has arisen associated with the 135-bp allele. Genet. Epidemiol. 23:364-374, 2002