A three generation family study of cleft lip with or without cleft palate

Syndromale und nichtsyndromale orofaziale Spalten

Orofaziale Spalten sind die zweithäufigste angeborene Fehlbildung. Die beiden häufigen Untergruppen sind die Formen der Lippen-Kiefer-Gaumen-Spalte (LKGS) und der reinen Gaumenspalte (GS). Beide können im Zuge zahlreicher Syndrome auftreten, LKGS sind häufiger nichtsyndromal (ca. 70 %) als GS (ca. 50 %). Nichtsyndromale Spalten sind multifaktoriell und bergen relativ geringe Wiederholungsrisiken für Angehörige. Manche syndromalen Spaltformen beruhen auf Chromosomenaberrationen, die meisten sind jedoch monogen. Das autosomal-dominante Van-der-Woude-Syndrom ist eine wichtige Differenzialdiagnose zu nichtsyndromalen Spaltformen, die sich nur durch Unterlippengrübchen von diesen unterscheidet, aber höhere Risiken für eine Spaltbildung bei Nachkommen birgt. Die Pränataldiagnostik orofazialer Spalten erfolgt sonographisch. Erfahrene Untersucher können LKGS in der 20. Schwangerschaftswoche diagnostizieren; die Detektion von GS ist schwieriger.

Dental materials for cleft palate repair

Numerous bone and soft tissue grafting techniques are followed to repair cleft of lip and palate (CLP) defects. In addition to the gold standard surgical interventions involving the use of autogenous grafts, various allogenic and xenogenic graft materials are available for bone regeneration. In an attempt to discover minimally invasive and cost effective treatments for cleft repair, an exceptional growth in synthetic biomedical graft materials have occurred. This study gives an overview of the use of dental materials to repair cleft of lip and palate (CLP). The eligibility criteria for this review were case studies, clinical trials and retrospective studies on the use of various types of dental materials in surgical repair of cleft palate defects. Any data available on the surgical interventions to repair alveolar or palatal cleft, with natural or synthetic graft materials was included in this review. Those datasets with long term clinical follow-up results were referred to as particularly relevant. The results provide encouraging evidence in favor of dental and other related biomedical materials to fill the gaps in clefts of lip and palate. The review presents the various bones and soft tissue replacement strategies currently used, tested or explored for the repair of cleft defects. There was little available data on the use of synthetic materials in cleft repair which was a limitation of this study. In conclusion although clinical trials on the use of synthetic materials are currently underway the uses of autologous implants are the preferred treatment methods to date.

Risk prediction models for oral clefts allowing for phenotypic heterogeneity

Oral clefts are common birth defects that have a major impact on the affected individual, their family and society. World-wide, the incidence of oral clefts is 1/700 live births, making them the most common craniofacial birth defects. The successful prediction of oral clefts may help identify sub-population at high risk, and promote new diagnostic and therapeutic strategies. Nevertheless, developing a clinically useful oral clefts risk prediction model remains a great challenge. Compelling evidences suggest the etiologies of oral clefts are highly heterogeneous, and the development of a risk prediction model with consideration of phenotypic heterogeneity may potentially improve the accuracy of a risk prediction model. In this study, we applied a previously developed statistical method to investigate the risk prediction on sub-phenotypes of oral clefts. Our results suggested subtypes of cleft lip (CL) and palate have similar genetic etiologies (AUC = 0.572) with subtypes of CL only (AUC = 0.589), while the subtypes of cleft palate only (CPO) have heterogeneous underlying mechanisms (AUCs for soft CPO and hard CPO are 0.617 and 0.623, respectively). This highlighted the potential that the hard and soft forms of CPO have their own mechanisms despite sharing some of the genetic risk factors. Comparing with conventional methods for risk prediction modeling, our method considers phenotypic heterogeneity of a disease, which potentially improves the accuracy for predicting each sub-phenotype of oral clefts.

Asymmetry in family history implicates nonstandard genetic mechanisms: application to the genetics of breast cancer

Genome-wide association studies typically target inherited autosomal variants, but less studied genetic mechanisms can play a role in complex disease. Sex-linked variants aside, three genetic phenomena can induce differential risk in maternal versus paternal lineages of affected individuals: 1. maternal effects, reflecting the maternal genome's influence on prenatal development; 2. mitochondrial variants, which are inherited maternally; 3. autosomal genes, whose effects depend on parent of origin. We algebraically show that small asymmetries in family histories of affected individuals may reflect much larger genetic risks acting via those mechanisms. We apply these ideas to a study of sisters of women with breast cancer. Among 5,091 distinct families of women reporting that exactly one grandmother had breast cancer, risk was skewed toward maternal grandmothers (p<0.0001), especially if the granddaughter was diagnosed between age 45 and 54. Maternal genetic effects, mitochondrial variants, or variant genes with parent-of-origin effects may influence risk of perimenopausal breast cancer.

Dermatoglyphic evaluation in subjects and parents of cleft lip with and without cleft palate

Objectives : Dermatoglyphic patterns make good material for genetic studies because they remain stable throughout life. Given that the primary palate, lip, and dermal ridges develop during the same period of intrauterine life, the genetic message contained in the genome can be deciphered during this period and is reflected by dermatoglyphics. This study was undertaken to compare the dermatoglyphic patterns in subjects with clefts and controls and both their parents to study the genetic etiology. Methods : A total of 294 subjects (48 cleft subjects and 50 healthy controls with both their parents) were selected. Finger and palm prints of all were recorded using the ink method. Results :  Increased frequency of loops and arches and low mean total ridge count was observed in cleft subjects. Increased frequency of loops and arches with decreased frequency of whorls, mean total ridge count, and atd angle of right hand was found in parents of cleft group as compared with the parents of the controls. Conclusion : Dermatoglyphic patterns have considerable variances. They can be used to study genetic etiology and as an educational tool for genetic counseling.

The evolution of human genetic studies of cleft lip and cleft palate

Orofacial clefts (OFCs)--primarily cleft lip and cleft palate--are among the most common birth defects in all populations worldwide, and have notable population, ethnicity, and gender differences in birth prevalence. Interest in these birth defects goes back centuries, as does formal scientific interest; scientists often used OFCs as examples or evidence during paradigm shifts in human genetics, and have also used virtually every new method of human genetic analysis to deepen our understanding of OFC. This review traces the evolution of human genetic investigations of OFC, highlights the specific insights gained about OFC through the years, and culminates in a review of recent key OFC genetic findings resulting from the powerful tools of the genomics era. Notably, OFC represents a major success for genome-wide approaches, and the field is poised for further breakthroughs in the near future.

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.

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/or palate with monogenic autosomal recessive transmission in Pyrenees shepherd dogs

OBJECTIVE

To document the genetic background of Pyrenees shepherd dogs as it relates to the incidence of cleft lip and/or cleft palate, to describe the phenotype, and to determine possible candidate genes.

DESIGN

Pedigree analysis was performed and blood samples were taken from five affected pups, their siblings, and parents. Seven candidate genes were selected and linkage analysis was performed. Further methods used included sequencing and histology.

RESULTS

In 37 litters consisting of 163 pups, we found 47 affected pups in a total population of 2104. The male:female ratio was 1:0.96. Affected pups showed isolated cleft lip and/or cleft palate; no attendant disorders have been reported. Despite a high degree of relationship, two affected pups displayed a cleft palate (- H S H -) and a cleft lip with or without cleft palate (L A -) cleft formation. Histology of affected pups showed that the medial edge epithelium remained intact and did not undergo an epithelial-mesenchymal transformation. There was no evidence for linkage between the trait and TGFb3 or Msx1. Subsequent sequencing excluded the coding sequence of Fst as well.

CONCLUSION

Pedigree analysis showed that cleft palate is not genetically distinct from cleft lip with or without cleft palate but is inherited in this breed as a monogenic autosomal recessive trait. Linkage analysis and sequencing excluded TGFb3, Msx1, and Fst as candidate genes. Histology of affected pups showed that the medial edge epithelium is still intact.

Human genetic factors in nonsyndromic cleft lip and palate: an update

Nonsyndromic cleft lip and/or palate (or orofacial cleft, OFC) is a malformation characterized by an incomplete separation between nasal and oral cavities without any associated anomalies. The last point defines the distinction between syndromic and nonsyndromic OFC. Nonsyndromic OFC is one of the most common malformations among live births and is composed of two separate entities: cleft lip with or without cleft palate (CL+/-P) and cleft palate isolated (CPI). Because of the complex etiology of nonsyndromic OFC, which is due to the differences between CL+/-P and CPI, and the heterogeneity of each group, caused by the number of genes involved, the type of inheritance, and the interaction with environmental factors, we reviewed those genes and available loci in the literature whose involvement in the onset of nonsyndromic OFC has more sound scientific evidence. Genetic studies on human populations have demonstrated that CL+/-P and CPI have distinct genetic backgrounds and, therefore, environmental factors probably disclose only these malformations. In CL+/-P several loci, OFC from 1 to 10 have been identified. The first locus, OFC1, has been mapped to chromosome 6p24. Other CL+/-P loci have been mapped to 2p13 (OFC2), 19q13.2 (OFC3) and 4q (OFC4). OFC5-8 are identified by mutations in the MSX1, IRF6, PVRL1, and TP73L gene, respectively. OFC9 maps to 13q33.1-q34, whereas OFC10 is associated with haploinsufficiency of the SUMO1 gene. In addition, MTHFR, TGF-beta3, and RARalpha play a role in cleft onset. In CPI one gene has been identified (TBX22) at present, but others are probably involved. Greater efforts are necessary in order to have a complete picture of the main factors involved in lip and palate formation. These elements will permit us to better understand and better treat patients affected by OFC.

Genetik der nichtsyndromalen Lippen-Kiefer-Gaumen-Spalten

Die Lippen-Kiefer-Gaumen-Spalte (LKG) stellt eine der häufigsten angeborenen Fehlbildungen dar. Etwa 50–60% der LKG-Fälle sind nichtsyndromal und in der Regel genetisch komplex vererbt. Assoziations- und Kopplungsanalysen ergaben eine Reihe von Kandidatengenen bzw. -regionen, wobei bislang nur wenige Befunde in unabhängigen Stichproben unterstützt werden konnten. Zur Anwendung in der medizinischen Routine eignen sich die bisherigen Erkenntnisse über genetische Faktoren noch nicht. Die langfristig zu erwartende Identifizierung aller ursächlichen Gene und exogenen Faktoren wird ein umfassendes Verständnis der pathophysiologischen Ursachen ermöglichen und zur Entwicklung neuer Präventionsstrategien beitragen.

Linkage analysis between BCL3 and nearby genes on 19q13.2 and non-syndromic cleft lip with or without cleft palate in multigenerational Japanese families

OBJECTIVE

To investigate the linkage between candidate genes on chromosome 19 and cleft lip with or without cleft palate in Japanese using a parametric method.

MATERIALS AND METHODS

After informed consent was obtained, blood samples were drawn from 90 individuals in 14 families, 30 of whom were affected, and genomic DNAs were extracted. PCR-amplified products using four microsatellite markers, D19S178, BCL3, APOC2[007/008] and APOC2[AC1/AC2] located in 19q13.2, were separated by 8% polyacrylamide gel electrophoresis. Linkage analysis was carried out using the MLINK and LINKMAP programs, and logarithm of odds (LOD) scores were calculated for each family.

RESULTS

Before undertaking linkage analysis, we analyzed 74 healthy Japanese subjects and found racial differences in that the observed number of alleles and their heterozygosity were lower in Japanese than in Caucasians, and that both populations tended to show a different allele distribution. In 14 families, two-point maximum LOD score (Zmax) for BCL3 was 0.341 and multi-point Zmax was less than -2 excluding linkage. But in 9 families with left and bilateral CL/P, two-point Zmax for APOC2[AC1/AC2] was 1.701 and multi-point Zmax at APOC2 locus was 1.909.

CONCLUSION

The LOD score was relatively high but provided no evidence of linkage for CL/P to BCL3 and nearby genes in Japanese subjects.

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.

Multiplex relative risk and estimation of the number of loci underlying an inherited disease

Knowledge of the number of causative loci is necessary to estimate the power of mapping studies of complex diseases. In the present article, we reexamine a theory developed by Risch and its implications for estimating the number L of causative loci affecting a complex inherited disease. We first show that methods based on Risch's analysis can produce estimates of L that are inconsistent with the observed population prevalence of the disease. We demonstrate this point by showing that the maximum-likelihood estimate for L produced by the method of Farrall and Holder for cleft lip/cleft palate data is not consistent with the prevalence under the multiplicative model. We show how to incorporate disease prevalence and develop a maximum-likelihood method for estimating L that uses the entire distribution of numbers of affected individuals in families containing an affected individual. This method avoids the potential inconsistencies of the Risch method and has greater precision. We apply our method to data on cleft lip/cleft palate and schizophrenia.

Epidemiological and genetic study of 121 cases of oral clefts in Kuwait

AIM

The aim of the study was to ascertain some epidemiological factors such as sex and consanguinity that may be associated with cleft lip with or without cleft palate (CL +/- CP) in Kuwait as well as to conduct genetic segregation analysis of these families.

SETTING AND SAMPLE POPULATION

A total of 113 families ascertained through 121 CL +/- CP and CP surgical probands in Kuwait. The frequencies of cleft types and the epidemiological variables were calculated using SPSS version 5.0 software. Chi-square for goodness-of-fit test was used to test the significance of the associated epidemiological variables to facial clefts. Genetic segregation analysis was performed on 76 families with extended pedigrees and included only those with non-syndromic CL +/- CP (NS CL +/- CP). Major locus segregation analysis was used to fit models to the observed family patterns under Class A regressive models as implemented by REGD routine in S.A.G.E. release 4.0. A test for heterogeneity was also conducted to complete data set in addition to two subsets: Arabs and nomads.

RESULTS

Of the 121 patients, 34(28.1%) had CP, 30(24.8%) had CL and 57 (47.1%) had CL + CP. The male to female ratio was 0.89 for CP, 1.14 for CL, 1.35 for CL + CP and 1.2 for all the clefts. The percentage of consanguineous families among those with a positive family history (60%) was not significantly different from that of the general population (54.3%), whereas for all the families with clefts the percent consanguineous was significantly lower (38%). No evidence of heterogeneity in the results between the Arab and nomad subsets was observed. The results for the major locus segregation analysis were inconclusive.

CONCLUSION

No definite association was observed between consanguinity and the occurrence of facial clefts in Kuwait. General transmission models in the full data set showed no evidence of heterogeneity in the results between the Arab and nomad subsets.

Facial clefting in an Arab town in Israel

To study the prevalence of cleft palate and cleft lip with or without cleft palate in an Israeli Arab town, questionnaires were sent to the parents of 1375 pupils in grades 1 and 2 in all seven primary schools in the town of Taibe, and 1281 responded. The information requested included data about siblings and members of the parental generation to give a total of 16 174, and the presence of consanguinity and history of exposure to medication, radiation, smoking or alcohol during pregnancy. There were four affected individuals among the index cases, of whom two had cleft palate only and two cleft lip with cleft palate, giving prevalence rates for each of these of 1.56/1000. Adding to these the number of affected siblings gave a total of 10 affected individuals; two with cleft palate only (0.39/1000) and eight with cleft lip with or without cleft palate (1.56/1000). Among the parental generation, of 16 reported affected individuals, two had cleft palate only (0.18/1000) and 14 cleft lip with or without cleft palate (1.26/1000). The overall prevalence rate for all 26 affected individuals was 1.6/1000; four of these had cleft palate only (0.24/1000) and 22 had cleft lip with or without cleft palate (1.36/1000). There were no cases whose mothers had been exposed to medication, radiation, smoking or alcohol during pregnancy. The effect of consanguinity was not significant (P < 0.92). This study shows that the prevalence of facial clefting in an Israeli Arab community is consistent with that in the general population worldwide.

The impact of molecular genetics on oral health paradigms

As a result of our increased understanding of the human genome, and the functional interrelationships of gene products with each other and with the environment, it is becoming increasingly evident that many human diseases are influenced by heritable alterations in the structure or function of genes. Significant advances in research methods and newly emerging partnerships between private and public sector interests are creating new possibilities for utilization of genetic information for the diagnosis and treatment of human diseases. The availability and application of genetic information to the understanding of normal and abnormal human growth and development are fundamentally changing the way we approach the study of human diseases. As a result, the issues and principles of medical genetics are coming to bear across all disciplines of health care. In this review, we discuss some of the potential applications of human molecular genetics for the diagnosis and treatment of oral diseases. This discussion is presented in the context of the ongoing technological advances and conceptual changes that are occurring in the field of medical genetics. To realize the promise of this new molecular genetics, we must be prepared to foresee the possibilities and to incorporate these newly emergent technologies into the evolving discipline of dentistry. By using examples of human conditions, we illustrate the broad application of this emerging technology to the study of simple as well as complex genetic diseases. Throughout this paper, we will use the following terminology: Penetrance--In a population, defined as the proportion of individuals possessing a disease-causing genotype who express the disease phenotype. When this proportion is less than 100%, the disease is said to have reduced or incomplete penetrance. Polymerase chain reaction (PCR)--A technique for amplifying a large number of copies of a specific DNA sequence flanked by two oligonucleotide primers. The DNA is alternately heated and cooled in the presence of DNA polymerase and free nucleotides, so that the specified DNA segment is denatured, hybridized with primers, and extended by DNA polymerase. MIM--Mendelian Inheritance in Man catalogue number from V. McKusick's Mendelian Inheritance in man (OMIM, 1998).

A population-based study of survival and childbearing among female subjects with birth defects and the risk of recurrence in their children

BACKGROUND AND METHODS

Persons with birth defects are at high risk for death during the perinatal period and infancy. Less is known about the later survival or reproduction of such persons. We studied a cohort that comprised 8192 women and adolescent girls with registered birth defects and 451,241 women and adolescent girls with no birth defects, all of whom were born in Norway from 1967 through 1982. The rate of survival was determined through 1992, and the rate of childbearing was determined through October 1997. We also estimated the risk of birth defects in the children of these subjects.

RESULTS

Among the subjects with birth defects, 80 percent survived to 15 years of age, as compared with 98 percent of those with no birth defects. Among the surviving subjects, 53 percent of those with birth defects gave birth to at least one infant by the age of 30 years, as compared with 67 percent of those with no birth defects. The subjects with birth defects were one third less likely to give birth by the age of 30 than those with no birth defects. The children of the subjects with birth defects had a significantly higher risk of birth defects than the children of those with no birth defects (relative risk, 1.6; 95 percent confidence interval, 1.3 to 2.1). This increased risk was confined entirely to the specific defect carried by the mother, with the relative risk of recurrence varying from 5.5 to 82 according to the defect. In contrast, there was no increase in the risk of having an infant with a different type of defect.

CONCLUSIONS

Women and girls with birth defects have decreased survival as compared with those with no birth defects, especially in the first years of life, and are less likely to have children. In addition, they have an increased risk of having children with the same defect.

Survey of genetic counselors and clinical geneticists regarding recurrence risks for families with nonsyndromic cleft lip with or without cleft palate

Nonsyndromic cleft lip with or without cleft palate (CL/P) is a common congenital malformation affecting about 1/1,000 caucasian infants. Although the familial clustering of CL/P has been studied thoroughly, estimation of recurrence risk for genetic counseling purposes can be difficult. A survey was mailed to 912 board-certified genetic counselors, 542 non-board-certified genetic counselors, and 776 board-certified clinical geneticists to investigate the recurrence risks they would assign to three example families with CL/P. Responses were received from 155 (17%) board-certified genetic counselors, 36 (6.6%) non-board-certified genetic counselors, and 100 (18.5%) board-certified clinical geneticists. No major differences were found in their responses, suggesting that for these three families, geneticists would provide similar estimates of risk, regardless of their amount of experience with oral clefts patients, where they are currently employed, or their board certification status.

Genetics of nonsyndromic oral clefts revisited

Nonsyndromic oral clefts are among the most common birth defects, affecting approximately 1 in 1000 Caucasian newborns. In recent decades, many investigators have used genetic and epidemiologic methods to identify etiologic factors, but results have often been inconclusive or contradictory. Etiologic heterogeneity is undoubtedly a major component in these birth defects, and there may not be a single answer to this problem. Here, we describe the main features of published studies pointing out their strengths and limitations. Additionally, we give insight into current methods for detecting the presence of interaction between genetic markers and environmental exposures in the etiology of oral clefts.

Analysis of the recurrence patterns for nonsyndromic cleft lip with or without cleft palate in the families of 3,073 Danish probands

The identification of several putative susceptibility loci for nonsyndromic cleft lip with or without cleft palate (CL +/- P) has sparked a renewed interest in the genetics of this condition. However, prior to undertaking linkage studies for complex traits such as CL +/- P it is desirable to have some understanding of the number and nature of the loci involved in disease susceptibility. The ability to obtain valid estimates of these parameters is contingent on the availability of family data which are unbiased by factors that distort the true familial recurrence pattern. In an effort to obtain such data, 2 centralized data repositories (the Danish Central Person Registry and the Danish Facial Cleft Database), were linked and used to estimate the risks to first, second, and third-degree relatives of 3,073 CL +/- P probands born in Denmark from 1952 to 1987. Analyses of these data excluded single locus and additive multilocus inheritance of CL +/- P, and provided evidence that CL +/- P is most likely determined by the effects of multiple interacting loci. Under a multiplicative model, no single locus can account for more than a threefold increase in the risk to first-degree relatives of CL +/- P probands. These data provide further evidence that nonparametric linkage methods (ex. affected relative pair studies) are likely to represent a more realistic approach for identifying CL +/- P susceptibility loci, than are traditional pedigree-based methods. However, at least 100 and more realistically several hundred (300-500) affected sib pairs are likely to be required to detect linkage to CL +/- P susceptibility loci.

Absence of an environmental effect on the recurrence of facial-cleft defects

BACKGROUND

The rate of recurrence of a broad range of birth defects may decrease among women who change residence after the birth of their first infant. The aim of the present study was to determine the effect of changing residence on the recurrence of congenital facial-cleft defects.

METHODS

We identified 4189 women who had infants with facial-cleft defects by linking a data base comprising the records of children with facial clefts born between 1952 and 1987 with the Central Person Registry in Denmark. Among the 4189 mothers, 1902 each had additional children after the first child with a facial-cleft defect. A total of 2692 younger siblings were identified. We compared the proportion of infants with facial-cleft defects among the younger siblings between mothers who had changed municipalities or sexual partners and those who had not.

RESULTS

Changing the municipality of residence did not decrease the frequency with which facial-cleft defects recurred in younger siblings. Among the 907 infants of mothers who changed municipalities but not partners, 29 (3.2 percent) had facial-cleft defects, as compared with 48 (3.4 percent) of 1425 infants of mothers who changed neither municipality nor partner (relative risk, 0.9; 95 percent confidence interval, 0.6 to 1.5). However, a change of partner reduced the recurrence risk significantly. Among 236 infants of mothers who changed partners, 1 (0.4 percent) had a facial-cleft defect, as compared with 77 (3.3 percent) of 2350 infants of mothers who did not change partners (relative risk, 0.1; 95 percent confidence interval, 0.02 to 0.9).

CONCLUSIONS

Recurrence of facial-cleft defects is not linked to the residence of the mother, but having a different partner reduced a woman's risk of having a second child with this defect.

Correlates of genetic risk for non-syndromic cleft lip with or without cleft palate

Multivariate analysis was used to determine which characteristics: sex of the proband, sibling sex, severity of the proband's defect or family history, are the best predictors of recurrence risk among siblings of individuals with non-syndromic cleft lip with or without cleft palate (CL +/- P). Sibling recurrence risks are not significantly related to the sex of the proband. Severity of the proband's defect, classified by the extent of the lip defect (unilateral versus bilateral), was found to be a significant predictor of sibling recurrence, whereas involvement of the palate in the proband's defect was not. A positive family history of clefting (i.e. at least one affected first-degree relative in addition to the proband) and the sex of the sibling were also found to be significant predictors of sibling recurrence. The associations between sibling risk and family history, and sibling risk and bilaterality of the proband's defect appear to be mildly confounded. After adjusting for the effects of family history, the risk to siblings of probands with bilateral lip defects is twice the risk to siblings of probands with unilateral defects (O.R. = 2.00; 95% C.I. 1.25-3.19). A positive family history of clefting increases the risk to siblings by greater than 4-fold (O.R. = 4.49; 95% C.I. 2.74-7.35), after adjusting for the extent of the proband's lip defect. These results provide a rational strategy for identifying subsets of the 'at risk' population which have markedly different recurrence risks. This information is important for genetic counseling, since it allows for more precise estimation of sibling recurrence risks in individual cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Association between alleles of the transforming growth factor-alpha locus and the occurrence of cleft lip

DNA samples from 100 patients with cleft lip with or without cleft palate (CL/P) were compared with those of 98 unaffected control individuals with respect to transforming growth factor alpha (TGFA) genotypes. Among the Caucasians in this population (83 CL/P, 84 controls), there was a significant difference in the restriction fragment length polymorphisms (RFLPs) observed after digestion with TaqI (chi 2 = 4.68, P = 0.03). The frequency of the C2 allele in the Caucasian CL/P population was 0.169, whereas that in the control group was 0.089. When the data for Caucasians, African-Americans, and Asians were examined jointly, the chi 2 value for the pooled sample was 5.08 (P = 0.02). This confirms the hypothesis of Ardinger et al. [1989, Am J Hum Genet, 45:348-353] that TFGA itself or a closely linked gene contributes to the development of CL/P in humans.

Mode of inheritance of nonsyndromic cleft lip with or without cleft palate: a reanalysis

Nonsyndromic cleft lip with or without cleft palate (CL +/- P) is traditionally recognized as a multifactorial threshold trait (MFT). Recently, however, evidence for the involvement of a major gene in the etiology of CL +/- P has been reported. To assess the potential for major-gene involvement in the etiology of this trait, familial recurrence patterns from several family studies of CL +/- P were reanalyzed. The recurrence patterns in first-degree relatives of CL +/- P probands were found to be compatible with the expectations for either an MFT or a generalized single-major-locus (gSML) trait. The use of multiple thresholds based on proband sex, defect bilaterality, or palatal involvement did not help to discriminate between these models. However, the pattern of recurrence among MZ twins and more remote relatives of CL +/- P probands is not consistent with gSML inheritance but is compatible with either an MFT model or a model specifying multiple interacting loci. For such a model, no single locus can account for more than a sixfold increase in risk to first-degree relatives. These findings have important implications with regard to the feasibility of detecting linkage to loci conferring susceptibility to CL +/- P.

Familial recurrence-pattern analysis of cleft lip with or without cleft palate

Cleft lip with or without cleft palate (CL/P) is a common congenital malformation with an incidence in European white populations of about 1/1,000. The familial clustering of CL/P has been extensively characterized, and epidemiological studies have proposed monogenic models (with reduced penetrance), multifactorial/threshold models, and mixed major-gene/multifactorial models to explain its inheritance. The recognition of an association between two RFLPs at the transforming growth factor alpha (TGFA) locus and CL/P supports a major-gene component to the etiology of CL/P. Risch has shown that the recurrence risk ratio lambda R (risk to relatives, vs. population prevalence) is a useful pointer to the mode of inheritance. Here we further develop the use of lambda R to analyze recurrence-risk data for CL/P. Recurrence risks for first-, second-, and third-degree relatives equate well with oligogenic models with as few as four loci. A monogenic/additive model is strongly rejected. The limited available twin data are also consistent with this model. A "major gene" interacting epistatically with an oligogenic background is shown to be a plausible alternative. Power calculations for a linkage study to map the CL/P major-risk locus suggest that a sample of 50 affected sib pairs will be adequate, but linkage to minor-risk loci will require very much larger samples.

Clustering of malformations in the families of South American oral cleft neonates

The relatives of 741 newborn children with non-syndromic cleft lip with or without cleft palate (CL +/- P), of 115 with isolated cleft palate (CP), and of equal numbers of appropriate controls were screened for the presence of the same or different malformations. The main findings were as follows. (1) The frequency of familial cases of CL +/- P (17.3%) was much higher than the prevalence of this malformation among the relatives of controls (0.5%). (2) The sibs of CL +/- P subjects showed a higher prevalence of this condition than their parents (2.9% v 1.6%). (3) The degree of genetic determination of this condition should be high (70 to 74%), and the data in general favour a multifactorial model of inheritance, with different thresholds between sexes. However, the action of dominant genes cannot be excluded since selection or dominant genes or both could be postulated to explain the parent/sib difference. (4) The frequency of other malformations was also significantly raised in the families of CL +/- P probands, as compared to controls (12.1% v 6.2%). (5) The prevalence of these other malformations was higher among sibs (1.6%) than parents (0.7%) of CL +/- P babies. (6) A general susceptibility to malformations and different exposure to selective agents may explain these latter findings. (7) None of the comparisons involving CP children yielded significant results.

Linkage of an autosomal dominant clefting syndrome (Van der Woude) to loci on chromosome Iq

Van der Woude syndrome (VWS) is an autosomal dominant disorder in which affected individuals have one or more of the following manifestations: cleft lip, cleft palate, hypodontia, or paramedian lower-lip pits. VWS is a well-characterized example of a single-gene abnormality that disturbs normal craniofacial morphogenesis. As a first step in identifying genes involved in human development, we used a candidate-gene-and-region approach to look for a linkage to VWS. Six families with 3 or more generations of affected individuals were studied. Evidence for linkage (theta = 0.02, lod score = 9.09) was found between the renin (REN) gene on 1q and VWS. Other linked loci included CR1, D1S58, and D1S53. The genes for laminin B2 (LAMB2), a basement-membrane protein, and for decay-accelerating factor (DAF) were studied as possible candidate genes on 1q. Recombinants between VWS and both LAMB2 and DAF excluded these genes from a causal role in the etiology of VWS for the families studied in this report. Multipoint linkage analysis indicated that the VWS locus was flanked by REN and D1S65 at a lod score of 10.83. This tight linkage with renin and other nearby loci provides a first step in identifying the molecular abnormality underlying this disturbance of human development.

Dominantly inherited cleft lip and palate in two families

Two families with non-syndromic cleft lip and cleft palate are described. The linear pattern of inheritance through several generations is difficult to explain by conventional multifactorial models. The pedigrees strengthen the suggestion that a dominantly inherited mutation exists with a major influence on clefting of the lip and palate alone.

Theoretical recurrence risks for cleft lip derived from a population of consecutive newborns

Theoretical recurrence risks for cleft lip with or without cleft palate (CL(P)) were calculated from heritability estimates derived from a population of 203 newborns with CL(P) in a total of 220,927 consecutive births in north-east Italy. Birth prevalence of CL(P) and the frequency of CL(P) in relatives of probands were estimated after exclusion of cases with CL(P) resulting from a known cause or pathogenesis. The method allowed estimation of the theoretical recurrence risk for any family by considering the total number of affected and unaffected first, second, and third degree relatives. The lower value of the theoretical risk compared to the empirical risk, obtained from retrospective data of selected families, was the result of methodological differences.

Cleft lip with or without cleft palate: identification of sporadic cases with a high level of genetic predisposition

Previous studies have suggested that asymmetry for certain bilaterally represented features may be an indicator of genetic predisposition to cleft lip with or without cleft palate and may therefore be of value in the individual assessment of recurrence risk, particularly for sporadic cases. An asymmetry score has been devised that may be of use in identifying those with a high level of genetic predisposition. Stepwise logistic regression selected nine variables that together correctly classified 85% of familial cleft patients and unrelated non-cleft controls. Applying the same regression equation to sporadic cases, 26% fell into the range occupied by the majority of familial patients, suggesting that these had a high level of genetic predisposition.

Difficulties in obtaining a sample of young adult cleft lip and palate subjects and their relatives

Families of individuals aged 15-24 yr born with cleft lip, with or without cleft palate, and suitable control families were required for a study of inherited predisposition to the malformation. Cleft patients were identified through hospital discharge listings, but the overall yield of participating patients was only 8% of the cases listed. An attempt to recruit control subjects by the same method, using patients who had been hospitalized for dissection tonsillectomy, yielded only 4% of those identified as suitable in the discharge listings. The results highlight the value of specialized, regularly updated disease registers in the recruitment of subjects for research purposes.

Genetic analysis of cleft lip with or without cleft palate in Chinese kindreds

Cleft lip with or without cleft palate (CL +/- P) affects 1 in 500-1,000 newborns worldwide; the cause remains unclear. For CL +/- P, Asians are at higher risk than Caucasians or Blacks. This report presents the results of a genetic analysis of 163 CL +/- P proband families ascertained in Shanghai, China. Based on statistical tests of several predictions from the classical multifactorial/threshold model, no evidence could be found to support it. Further, goodness-of-fit (PGOODFIT) tests of this model were also unsupportive, there being more families with two or more affected sibs than expected. Classical segregation analysis for Mendelian inheritance showed a maximum likelihood estimate of the segregation ratio of 0.187 +/- 0.068. This value was not significantly less than 0.25 (recessive inheritance) but was significantly less than 0.50 (dominant inheritance). Sex ratio data from these Chinese families suggest that manifestation of the putative single major gene is sex influenced. The apparent reduced penetrance is likewise to be expected if manifestation of CL +/- P also depends on in utero exposure to deleterious environmental agents, as demonstrated in a variety of human and animal model studies.

Cleft lip with or without cleft palate: reanalysis of a three-generation family study from England

The study population consists of 424 three-generation families originally ascertained through nonsyndromic cleft lip with or without cleft palate (CL +/- P) surgical probands by Carter et al [J Med Genet 19:246-261, 1982] in London, England. Carter et al proposed that the multifactorial threshold model (MF/T) could explain the data. The goal of our study was to test that hypothesis, plus alternatives, rigorously. Two approaches were used: 1) Carter et al had proposed that these data were consistent with the predictions of the MF/T as presented by Carter [Br Med Bull 25:52-57, 1969]. However, we tested those predictions using standard chi 2 tests and found statistically significant departures from the predictions in these families. 2) Complex segregation analysis under the mixed model was performed. Again, the MF/T model could be rejected, as could a model of a major locus alone. The best-fitting model included both major locus and multifactorial components. When the data were analyzed in two parts based on the proband's phenotype (CL vs CL + P) there was some evidence of heterogeneity in that there was a significant proportion of sporadic cases in the families of CL probands but not in the families of CL + P probands. Our results provide no support for the MF/T model. The results from segregation analyses of CL +/- P in these families were most consistent with autosomal major gene inheritance plus multifactorial contributions.

An epidemiological and genetic study of facial clefting in France. II Segregation analysis

Familial transmission of cleft lip with or without cleft palate (CL(P] and isolated cleft palate (CP) was studied in two French samples of 458 CL(P) and 156 CP nuclear families, using the recently implemented unified model. In neither case could discrimination be achieved between polygenic inheritance and monogenic inheritance with a high proportion of sporadic cases. In this type of disorder with a complex genetic basis the information furnished by such an approach, which only considers the affected status, is discussed. Future investigations on the joint familial transmission of the disease and different marker systems may help to identify the genes involved in these developmental anomalies.

Genetic analysis of cleft lip with or without cleft palate in Danish kindreds

The present study population consists of 2,532 families ascertained through non-syndromic cleft lip with or without cleft palate (CL +/- P) surgical probands born in Denmark between 1941 and 1971. Three samples were derived for analyses of the trait "clefted (CL +/- P) or not." Sample 1 consists of the 26 largest multigenerational families with four or more affected members. Both samples 2-MG and 2-N consist of nuclear families with at least two children and at least one proband among the children. Sample 2-MG contains 846 nuclear families derived from the kindreds with three or more generations. Sample 2-N contains a further 1,181 kindreds with only two generations, nuclear family information available. Four methods of analysis were used: 1) Pedigree analysis was performed on each of the multigenerational kindreds of Sample 1. Results were consistent with autosomal recessive inheritance in eight families and codominant inheritance in three families. These simple genetic hypotheses could not be distinguished in the remaining 15 families. 2) The goodness-of-fit of the multifactorial threshold (MF/T) model was tested in Samples 2-MG and 2-N. The MF/T model was rejected in both samples. 3) Classical segregation analysis was performed on Samples 2-MG and 2-N. Results were consistent with a possible recessive major gene for CL +/- P in Sample 2-MG, but not in Sample 2-N, and with significant admixture of sporadic cases in both samples. 4) Complex segregation analysis under the mixed model was performed on Samples 2-MG and 2-N. In Sample 2-MG, results were consistent with either the general mixed model or with an hypothesis of no major gene. In Sample 2-N, four hypotheses were equally likely: the mixed model with no polygenic component, the mixed model with the major gene component, the mixed model with no sib environmental correlation, and major gene alone. Three conclusions may be drawn: 1) The data provide no support for the MF/T model. 2) The data are consistent with the possibility of a major gene in a portion of the kindreds. 3) The data provide evidence for genetic heterogeneity for CL +/- P.

Additional data on spontaneous abortion and facial cleft malformations

Examination of fetal wastage data for a large collection of CL +/- P and CP sibships reported previously (Bear 1978) does not indicate the frequency of recognized abortion to be higher in the sibships of CL + P vs CL index cases, female vs male CL +/- P index cases, bilateral vs unilateral CL +/- P index cases, female bilateral CL +/- P index cases vs male unilateral CL +/- P index cases, or male vs female CP index cases. These observations fail to confirm those reported by Dronamraju (Dronamraju et al. 1982, Dronamraju & Bixler 1983a, b), and provide no evidence of a positive relation between degree of liability to facial cleft malformation and fetal mortality.

Fetal mortality in oral cleft families(IV): the "doubling effect"

Fetal mortality data from Lancaster, Penn., Chicago, Ill. and Minneapolis, Minn. are presented which support the authors' earlier findings in Indiana and Montreal that a positive relationship exists between the degree of liability to malformation and the incidence of fetal deaths in probands' sibships. Altogether, the study involved 189 CL sibships, 690 CLP sibships, and 3,416 pregnancies. On the basis of these data, which are derived from families of several different backgrounds of European ancestry, it is generalized that, as we proceed from CL sibships to CLP sibships, there is a doubling effect on fetal mortality. The consistency of this finding in several population samples is impressive. The implications of this observation are discussed with reference to genetic counseling.

A family study of isolated cleft palate

A family study was based on 245 boy and 329 girl patients treated surgically for non-syndromic cleft palate between 1920 and 1929; 86 and 81 respectively were traced and had had children. These 167 were the probands for the family study and were interviewed in their homes. None was born to a consanguineous marriage. Altogether they had had 384 children of whom 11 had cleft palate (2.9 +/- 0.9%). They had 398 sibs of whom five had cleft palate, 117 grandchildren of whom one was affected, and 517 nephews and nieces of whom one was affected. This is the largest series yet available on which to base an estimate of the risks to children of patients with non-syndromic cleft palate. The risk is probably increased where a parent or sib of the proband is affected and increased to a lesser degree where a second or third degree relative is affected. The family patterns in these and other studies suggest that the aetiology of cleft palate is heterogeneous, with some families showing modified dominant inheritance. This is in contrast to cleft lip (+/- cleft palate) where the data are consistent with a multifactorial threshold model.