Tracing disease gene(s) in non-syndromic clefts of orofacial region: HLA haplotypic linkage by analyzing the microsatellite markers: MIB, C1_2_5, C1_4_1, and C1_2_A

BACKGROUND:

Cleft lip with or without cleft palate (CL/P) is the most frequent craniofacial malformation seen in man. The etiology of CL/P is complex involving both genetic and epigenetic (environmental) factors, and the genes play an almost deterministic role in the normal development of craniofacial structures. This study was aimed at ascertaining the association of HLA microsatellites in CL/P patients.

MATERIALS AND METHODS:

Case DNA was obtained from 76 patients (40M and 36 F, average age 7.8 years, range 1-16 years). Unaffected individuals from the same geographical area without population mixing included as controls (n=154, 76 M and 78 F, average age 8.2 years, range 2-17 years). All DNA samples were purified from peripheral blood by standard techniques.

RESULTS:

Four microsatellites were compared in this case-control study. C1_2_5 locus was the most polymorphic marker with 15 observed alleles while C1_4_1 had the least number of alleles. Three of the four markers viz MIB,C1_4_1 and C1_2_5 showed a significant association of microsatellite alleles with CL/P. Five alleles (MIB_326,332,350; C1_4_1 – 213 and C1_2_5-204) were seen with an increased frequency among the test samples, whereas two alleles (C1-4_1_217, and C1_2_5_196) had an increased frequency among the control samples. One allele (C1-4-1-209) had an increased frequency in patient group but was not observed in the controls.

CONCLUSION:

The role of HLA complex in the pathogenesis of CL/P is speculative and has not been established so far. The result of this study shows that a few alleles have an increased frequency of expression in the diseased group which suggests that these alleles may predispose the individuals to clefting. This finding may be beneficial to aid in early diagnosis and plan intervention strategies.     

Plasma zinc concentrations of mothers and the risk of nonsyndromic oral clefts in their children: a case-control study in the Philippines

BACKGROUND: Findings from animal experiments suggest a link between poor maternal zinc status and increased risk of oral clefts in offspring; however, there are few human studies on this issue. METHODS: A case-control study was conducted using 74 case mothers of children with nonsyndromic cleft lip with or without cleft palate (CL/P, n=57) or cleft palate alone (CP, n=17), and 283 control mothers of unaffected children recruited in the Philippines in early 2003. Maternal zinc status was assessed by determining plasma zinc concentrations a mean of 5 years after delivery of the index child. Odds ratios (ORs) of estimates of the relative risk of oral clefts were calculated for quartiles of maternal plasma zinc concentrations. RESULTS: The mean plasma zinc concentration of CL/P case mothers (9.6+/-1.2, SD micromol/l) was significantly lower than that in control mothers (10.1+/-1.6 micromol/l; P<0.05). Low plasma zinc concentrations (<11.0 micromol/l) were found in 88% and 94% of CL/P and CP case mothers, respectively, and in 72% of controls (P<0.05). The ORs for CL/P and CP combined, adjusted for potential confounding factors, decreased with increasing quartile of plasma zinc as follows: 1.0 (lowest quartile reference), 0.83 (95% confidence interval 0.37-1.89), 0.70 (0.31-1.68), and 0.26 (0.10-0.70) (P trend=0.008). CONCLUSIONS: Low plasma zinc concentrations were common in Filipino women of reproductive age, and higher plasma zinc concentrations were associated with a lower risk for oral clefts in their children.     

Use of special education services by children with orofacial clefts

BACKGROUND: Our objective was to evaluate the use of special education services by children with orofacial clefts (OFCs). METHODS: We linked the birth certificates of children born from 1982–2001 in five counties of metropolitan Atlanta to a population‐based birth defects surveillance system to identify children with OFCs, and to the special education files for the school years 1992–2004 to identify children who used special education services. The special education data contained exceptionalities and services rendered for each school year. Prevalence ratios (PRs) and 95% CIs were calculated. The data were stratified by race/ethnicity, maternal education, type of OFC, and the presence of associated major malformations. In addition, we assessed the age at which special education began and the amount of time spent receiving services. RESULTS: Of the 777 children with OFCs, 201 (26%) were in special education at least 1 year compared with 8% of the children who had no major birth defects, yielding a PR of 3.2 (95% CI: 2.9–3.6). The most common exceptionality or service for children with an OFC was speech and language services. Compared with children with no birth defects, children with an OFC were four times more likely to be in this exceptionality (PR 3.8; 95% CI: 3.3–4.3). After excluding children in speech and language services, children with OFCs were still more likely to use special education services (PR 2.4; 95% CI: 1.7–3.2). CONCLUSIONS: Children with OFCs used special education services more often than children without birth defects. This information can help in planning for future population needs. Birth Defects Research (Part A), 2008. © 2008 Wiley‐Liss, Inc.     

Confirmation of the role of N-acetyltransferase 2 in teratogen-induced cleft palate using transgenics and knockouts

Previous work on Dilantin- and hydrocortisone-induced cleft palate and cleft lip with or without cleft palate using congenics for the N-acetyltransferase loci (Nat1 and Nat2 are closely linked) and recombinant inbred lines implicated the Nat1,2 region in susceptibility to teratogen-induced orofacial clefting. Since Nat1 does not differ between the two strains, Nat2 appeared to be responsible. We have now tested this conclusion using transgenics and knockouts. Transgenics for human NAT1 (equivalent to mouse Nat2) and knockouts for Nat2 were tested for susceptibility to Dilantin, hydrocortisone, and 6-aminonicotinamide-induced orofacial clefting. We found that Nat2 greatly influences teratogen-induced orofacial clefting on the A/J background but not on the C57BL/6J background. The magnitude and direction of the effects depended on which teratogen was used. The Nat2 knockout did not make C57BL/6J susceptible or A/J (already with very low activity) more susceptible but significantly decreased sporadic clefting in the A/J strain. We conclude that only the A/J strain, with several loci affecting orofacial clefting, is influenced by Nat2.     

Cleft palate: A clinical review

Orofacial clefts, including cleft palates (CP), are one of the most common birth defects. CP have a multiplicity of effects on the individual and society in terms of economic costs, loss of productivity, psychosocial effects, and increased morbidity and mortality at all stages of life. Embryological development of the palate is well delineated, with developments in the last decade regarding the biomolecular processes involved. Etiology is complex, involving a number of genetic and environmental factors. Various techniques can be employed for the repair of CP, depending on whether the cleft is of the primary or secondary palate, the width of the cleft, whether lengthening of the palate is necessary, and with regard to concerns of disruption of midfacial growth. All surgical techniques have the goals of restoring functional speech, swallowing, and aesthetics. A multidisciplinary team is necessary for the long‐term pre‐ and postoperative care of CP patients to handle complications, associated anomalies, and to optimize function and quality of life. Birth Defects Research (Part C) 102:333–342, 2014. © 2014 Wiley Periodicals, Inc.     

Wnt9b is the mutated gene involved in multifactorial nonsyndromic cleft lip with or without cleft palate in A/WySn mice, as confirmed by a genetic complementation test

BACKGROUND: Nonsyndromic cleft lip (CL) with or without cleft palate (CLP) is a common human birth defect with complex genetic etiology. One of the unidentified genes maps to chromosome 17q21. A mouse strain, A/WySn, has CLP with complex genetic etiology that models the human defect, and 1 of its causative genes, clf1, maps to a region homologous to human 17q21. Extensive studies of the candidate region pointed to a novel insertion of an IAP transposon 3' from the gene Wnt9b as the clf1 mutation. Independently a recessive knockout mutation of Wnt9b (Wnt9b-) was reported to cause a lethal syndrome that includes some CLP. METHODS: A standard genetic test of allelism between clf1 and the Wnt9b- mutation was done. A total of 83 F1 embryos at gestation day 14 (GD 14) from Wnt9b-/+ males crossed with A/WySn females, and 79 BC1 GD 14 embryos from F1 Wnt9b-/clf1 males back-crossed to A/WySn females were observed for CL. Embryo genotypes at clf1 and Wnt9b were obtained from DNA markers. Genotypes for a second unlinked modifier locus from A/WySn, clf2, were similarly obtained. RESULTS: The compound mutant embryos (Wnt9b-/clf1) had high frequencies of CL: 27% in the F1 and 63% in the BC1. The clf2 modifier gene was found to have 3 alleles segregating in this study and to strongly influence the penetrance of CL in the compound mutant. CONCLUSIONS: The noncomplementation of clf1 and Wnt9b- confirms that clf1 is a mutation of the Wnt9b gene. The homologous human WNT9B gene and 3' conserved noncoding region should be examined for a role in human nonsyndromic CLP.     

Folic acid-containing supplement consumption during pregnancy and risk for oral clefts: a meta-analysis

BACKGROUND: There is equivocal evidence in the published literature that folic acid supplementation during pregnancy may protect against the common congenital anomalies cleft lip with or without cleft palate (CLP) and cleft palate alone (CP). We undertook this meta-analysis to test the hypothesis that nonsyndromic oral cleft birth prevalences are different for those whose mothers took folic acid-containing supplements and for those whose mothers did not. METHODS: Human studies published in English were identified through MEDLINE, bibliography reviews, and contacting experts in the field. Within strata of prospective and case-control studies, CLP, CP, and all clefts, respectively, were analyzed using either a fixed or random effects model, as appropriate. We assessed for publication bias using Begg and Mazumdar's rank correlation and Egger's regression-based tests. RESULTS: Five prospective studies were analyzed, yielding combined relative risks of 0.51 (95% CI: 0.32, 0.95) for CLP, 1.19 (95% CI: 0.43, 3.28) for CP, and 0.55 (95% CI: 0.32, 0.95) for all clefts. Twelve case-control studies were assessed, which resulted in combined relative risks of 0.77 (95% CI: 0.65, 0.90) for CLP, 0.80 (95% CI: 0.69, 0.93) for CP, and 0.78 (95% CI: 0.71, 0.85) for all clefts. CONCLUSIONS: In aggregate, our results support the hypothesis of a protective effect of folic acid-containing supplement intake during pregnancy on the risk for oral clefts, although this conclusion is tempered by the potential for bias and uncontrolled confounding.     

Etiology and genetic factors in clefts of lip and/or palate reported at children’s hospital,Lahore, Pakistan

The etiology of cleft lip (CL) and/or cleft palate (CP) has been extensively studied in industrialized countries and is suggested to be heterogeneous with increasing evidence that both genetic and environmental factors are operating. To evaluate this assertion in a developing country like Pakistan, a case finding cross-sectional study was completed from 1^st July 2010 to 31^st May 2011 for 100 cases of CL and/or CP referred to the Genetic Clinic of the Children’s Hospital, Lahore, Pakistan. A clinical examination followed by necessary diagnostic work-up was completed for each case. The cause of CL and/or CP was clear in 18% of the children (n = 18). Environmental causes were found in 6 children (four mothers developed hyperthermia during the 2^nd month of gestation, one mother was diabetic, and one mother was a known case of epilepsy and took sodium valproate throughout her pregnancy). Six children were suffering from known genetic malformation syndromes (each with Jarcho-Levin syndrome, Oral-Facial-Digital syndrome type XI, Oral-Duplication syndrome, Kabuki syndrome, Fronto-nasal dysplasia and Nager syndrome). Novel chromosomal aberrations were identified in 2 children. In 82% of the children (n = 82) the cause of oro-facial clefts remained unknown. Impact of gender and consanguinity on the development of CL and/or CP was also studied. Prevalence of CP was significantly more among female children as compared to that in males (P < 0.05). Associated anomalies were present in 18% of the cases, anomalies of the craniofacial region being the most common. These findings were compared with regional and international studies.     

A digenic cause of cleft lip in A-strain mice and definition of candidate genes for the two loci

BACKGROUND: Nonsyndromic cleft lip with or without cleft palate, CL(P), is a common human birth defect with a complex unknown genetic cause. The mouse model is the "A/-" strains. Our previous studies mapped two loci: clf1 on Chr11 and clf2 on Chr13--with a strong genetic maternal effect on the level of risk. Here we test the hypothesis that CL(P) is digenic and identify candidate genes for clf1 and clf2. METHODS: We observed E14 CL(P) frequencies in backcross (BC1) embryos from a new cross of A/WySn to AXB-4/Pgn and from test crosses of three new "congenic RI" lines. Using new polymorphic markers from genes and our mapping panels of segregants and RI strains, we identified the candidate genes for clf1 and clf2. We sequenced the coding region of Ptch in A/WySn cDNA. RESULTS: Seventy new BC1 CL(P) segregants (4%) were obtained, as predicted. All three new congenic RI lines homozygous for both clf1 and clf2 had A/WySn-level CL(P) frequencies (10-30%) in test crosses. The clf1 region contains 10 known genes (Arf2, Cdc27, Crhr1, Gosr2, Itgb3, Mapt, Myl4, Nsf, Wnt3, and Wnt9b). The clf2 region contains 17 known genes with human orthologs. Both regions contain additional potential genes. No causal mutation in Ptch coding sequence was found. CONCLUSIONS: In A-strain mice, nonsyndromic CL(P) is digenic, suggesting that nonsyndromic human CL(P) may also be digenic. The orthologous human genes are on 17q (clf1) and 9q, 8q and 5p (clf2), and good candidate genes are WNT3 or WNT9B (17q), and PTCH (9q) or MTRR (5p).     

Reduction in orofacial clefts following folic acid fortification of the U.S. grain supply

BACKGROUND: Folic acid fortification in the United States became mandatory January 1, 1998, to reduce the occurrence of neural tube defects (NTDs). We evaluated the impact of folic acid fortification on orofacial clefts using United States birth certificate data for 45 states and the District of Columbia. METHODS: Prevalence ratios (PRs) were calculated comparing orofacial cleft prevalence among births prefortification (1/1990-12/1996) and postfortification (10/1998-12/2002), based on fortification status at conception. The JoinPoint Regression Program and exponentially weighted moving average charts (EWMA) were used to assess the timing of any statistically significant changes in prevalence. Data were stratified by maternal race/ethnicity, age, smoking, and timing of prenatal care. RESULTS: Orofacial clefts declined following folic acid fortification (PR=0.94; 95% CI: 0.92-0.96). The EWMA chart flagged a significant decrease in the fourth quarter of 1998. The JoinPoint graph had one change in slope, with a significant quarterly percent change (-0.34) between 1996 and 2002. The decline in orofacial clefts occurred in non-Hispanic Whites but not other racial/ethnic groups, nonsmokers but not women who reported smoking during pregnancy, and women who received prenatal care in the first trimester but not women who began receiving care later in pregnancy. CONCLUSION: Folic acid fortification in the United States was associated with a small decrease in orofacial cleft prevalence, with the timing of the decline consistent with the introduction of fortification. The decline is much smaller than that observed for NTDs, but nonetheless suggests an additional benefit of this public health intervention.     

Interaction between the ADH1C polymorphism and maternal alcohol intake in the risk of nonsyndromic oral clefts: an evaluation of the contribution of child and maternal genotypes

BACKGROUND: Maternal alcohol consumption has been associated with an increased risk of nonsyndromic oral clefts in some studies. Study of gene-environment interaction may provide insight into the reasons for their discrepancies observed. We focused on a polymorphism of the ADH1C gene (third gene of the class I alcohol dehydrogenase family), involved in the metabolism of ethanol and other alcohols. METHODS: Data come from a French case-control study (1998-2001), which tested the association between maternal alcohol consumption during the first trimester of pregnancy and the risk of nonsyndromic oral clefts (240 cases, 236 controls). A case-parent study design looked at the association with an ADH1C polymorphism (Ile349Val site) and potential gene-environment interaction effects. A log-linear model was used to distinguish the direct effect of the child's genotype from the maternally mediated effects. RESULTS: An increased risk of nonsyndromic oral clefts was observed for women who reported drinking alcohol during the first trimester, compared with women who did not. The mutated ADH1C allele carried by the child seemed to have a protective effect against the risk of oral clefts (RRone copy, 0.71; 95% confidence interval [CI], 0.50-1.02; RRtwo copies, 0.63; 95% CI, 0.3-1.3). The maternal genotype played a less important role than the child's, and its action remains unclear. No significant evidence of interaction effects between the ADH1C genotype and maternal alcohol consumption was observed. CONCLUSIONS: Because the ADH1C gene is involved in the metabolic pathways of many alcohols, we propose several hypotheses about the causal pathway, including ethanol oxidation activity and, more probably, retinol oxidation.     

The common MTHFR C677T and A1298C variants are not associated with the risk of non-syndromic cleft lip/palate in northern Venezuela

Non-syndromic cleft lip with or without cleft palate （nsCL/P） is among the most common major birth defects, with complex inheritance involving multiple genes and environmental factors. Numerous studies of MTHFR, encoding methylenetetrahydrofolate reductase, which catalyzes the rate-limiting step of folic acid biosynthesis, have shown inconsistent association of two common hypomorphic allelic variants, C677T and A1298C, in nsCL/P patients and, in some cases, their mothers. We have studied the MTHFR C677T and A1298C polymorphisms in nsCL/P patients, their mothers, and population-matched controls from northern Venezuela. We found no evidence for contribution of the MTHFR C677T and A1298C variants to the risk of nsCL/P in northern Venezuela. Overall, our findings fail to support a causal role of either the MTHFR C677T or A 1298C variants in the pathogenesis of nsCL/P in northern Venezuela.     

Maternal fever during early pregnancy and the risk of oral clefts

An increased risk of birth defects after hyperthermic exposures has been confirmed in animal studies, but population studies have yielded inconsistent results. Oral clefts are a common birth defect and have been associated with these exposures in some of these studies. In this study, data from the National Birth Defects Prevention Study was used to evaluate the association of maternal report of febrile illness in early pregnancy and the risk of oral clefts. All oral cleft cases born between 1997 and 2004 were compared with nonmalformed controls born in the same geographical region during the same time period. Mothers reporting febrile illness during pregnancy were stratified by fever grade and antipyretic use. Logistic regression models were used to generate crude and adjusted odds ratios for exposure to fever and association with each oral cleft phenotype. The dataset included 5821 controls, 1567 cases of cleft lip with or without cleft palate (CL+/?P) and 835 cases of cleft palate only. A modestly increased risk was observed for isolated CL+/?P (odds ratio, 1.28; 95% confidence interval, 1.01–1.63). Stratification by fever grade (body temperature <101.5° or ≥101.5°F) did not yield significant differences in risk. Risk estimates were higher among women who reported a fever, but did not take antipyretics to control their fever, particularly for nonisolated compared with isolated oral clefts. This finding suggests that adequate control of fever may diminish the deleterious effects of fever in cases of oral cleft. Birth Defects Research (Part A), 2010. © 2010 Wiley‐Liss, Inc.