Selection bias in genetic-epidemiological studies of cleft lip and palate.
(73/686)
The possible impact of selection bias in genetic and epidemiological studies of cleft lip and palate was studied, using three nationwide ascertainment sources and an autopsy study in a 10% sample of the Danish population. A total of 670 cases were identified. Two national record systems, when used together, were found suitable for ascertaining facial cleft in live births. More than 95% ascertainment was obtained by means of surgical files for cleft lip (with or without cleft palate) without associated malformations/syndromes. However, surgical files could be a poor source for studying isolated cleft palate (CP) (only a 60% and biased ascertainment), and they cannot be used to study the prevalence of associated malformations or syndromes in facial cleft cases. The male:female ratio was 0.88 in surgically treated cases of CP and was 1.5 in nonoperated CP cases, making the overall sex ratio for CP 1.1 (95% confidence limits 0.86-1.4) The sex ratio for CP without associated malformation was 1.1 (95% confidence limits 0.84-1.6). One of the major test criteria in CP multifactorial threshold models (higher CP liability among male CP relatives) must be reconsidered, if other investigations confirm that a CP sex-ratio reversal to male predominance occurs when high ascertainment is achieved. (+info)
The complex genetics of cleft lip and palate.
(74/686)
Clefts of the lip and palate are a common craniofacial anomaly, requiring complex multidisciplinary treatment and having lifelong implications for affected individuals. The aetiology of both cleft lip with or without cleft palate (CLP) and isolated cleft palate (CP) is thought to be multifactorial, with both genetic and environmental factors playing a role. In recent years, a number of significant breakthroughs have occurred with respect to the genetics of these conditions, in particular, characterization of the underlying gene defects associated with several important clefting syndromes. These include the identification of mutations in the interferon regulatory factor-6 (IRF6) gene as the cause of van der Woude syndrome and the poliovirus receptor related-1 (PVRL1) gene as being responsible for an autosomal recessive ectodermal dysplasia syndrome associated with clefting. While no specific disease-causing gene mutations have been identified in non-syndromic clefting, a number of candidate genes have been isolated through both linkage and association studies. However, it is clear that environmental factors also play a role and an important area of future research will be to unravel interactions that occur between candidate genes and environmental factors during early development of the embryo. Orthodontists are intimately involved in the therapeutic management of individuals affected by CLP and it is important that they keep abreast of current knowledge of the aetiology behind these conditions. This review aims to summarize some of the more significant advances in the genetics of CLP and highlight current thinking on the modes of inheritance and genetic loci that might be involved in this complex disorder. (+info)
Van der Woude syndrome: a review. Cardinal signs, epidemiology, associated features, differential diagnosis, expressivity, genetic counselling and treatment.
(75/686)
Congenital pits of the lower lip constitute a rare developmental malformation, transmitted by an autosomal dominant mode, with considerable heterogeneity as regards the expression of the disorder. They are present in van der Woude syndrome (VWS), in which clefts of the upper lip and/or palate are often observed. Literature related to the various parameters associated with and relevant to the disorder is extensive. The purpose of this review is to cover, synthesize and categorize the existing knowledge into distinct entities, in order to facilitate understanding of the aetiopathogenesis of the malformation, its clinical manifestations and histological features, the epidemiology of the syndromic situation and the fundamental approach to an integral differential diagnosis. Special emphasis is given to the rationale underlying the treatment modalities that have been suggested, and the necessity for appropriate genetic counselling, as the disorder shows a high affinity with clefts and a familial type of occurrence. (+info)
Maternal MTHFR interacts with the offspring's BCL3 genotypes, but not with TGFA, in increasing risk to nonsyndromic cleft lip with or without cleft palate.
(76/686)
The 677 C --> T polymorphism in the 5-10 methylenetetrahydrofolate reductase (MTHFR) gene has been associated with nonsyndromic cleft lip with or without cleft palate (CL/P) in some populations, but not others. Previous studies (ie, case-control and transmission disequilibrium tests (TDT)) in Brazilian families with CL/P have been unable to replicate this putative association. However, our group observed a lower proportion of CT heterozygotes among the mothers of CL/P probands, suggesting that the maternal genotype for this polymorphism might influence predisposition to CL/P. In order to further examine this issue, we performed a case-control study of the 677 C --> T/MTHFR polymorphism in families with CL/P ascertained in two regions of Brazil: 172 from Sao Paulo (SP) and 252 from Ceara (CE). The control samples included 243 individuals from SP and 401 from CE. TDT was carried out in 102 patients with CL/P and their parents. No evidence of an association was observed between the 677 C --> T/MTHFR polymorphism and CL/P using the case-control design, while borderline significance was obtained with the TDT (P=0.055). We have also looked for an interaction between maternal MTHFR genotypes and the propositi offspring's genotypes at two candidate susceptibility loci for CL/P, TGFA and BCL3. Interestingly, we observed an interaction between the maternal MTHFR and offspring's BCL3 genotypes (OR: 2.3; 95% CI: 1.1-4.8; P=0.03) but not with the offspring's TGFA genotypes. Therefore, our results reinforce the idea that the maternal MTHFR genotype plays a significant role in susceptibility to CL/P, but its teratogenic effect depends on the genotype of the offspring. (+info)
Tobacco smoking and oral clefts: a meta-analysis.
(77/686)
OBJECTIVE: To examine the association between maternal smoking and non-syndromic orofacial clefts in infants. METHODS: A meta-analysis of the association between maternal smoking during pregnancy was carried out using data from 24 case-control and cohort studies. FINDINGS: Consistent, moderate and statistically significant associations were found between maternal smoking and cleft lip, with or without cleft palate (relative risk 1.34, 95% confidence interval 1.25-1.44) and between maternal smoking and cleft palate (relative risk 1.22, 95% confidence interval 1.10-1.35). There was evidence of a modest dose-response effect for cleft lip with or without cleft palate. CONCLUSION: The evidence of an association between maternal tobacco smoking and orofacial clefts is strong enough to justify its use in anti-smoking campaigns. (+info)
The cleft lip and palate defects in Dancer mutant mice result from gain of function of the Tbx10 gene.
(78/686)
Cleft lip and palate (CL/P) is a common disfiguring birth defect with complex, poorly understood etiology. Mice carrying a spontaneous mutation, Dancer (Dc), exhibit CL/P in homozygotes and show significantly increased susceptibility to CL/P in heterozygotes [Deol, M. S. & Lane, P. W. (1966) J. Embryol. Exp. Morphol. 16, 543-558 and Trasler, D. G., Kemp, D. & Trasler, T. A. (1984) Teratology 29, 101-104], providing an animal model for understanding the molecular pathogenesis of CL/P. We genetically mapped Dc to within a 1-cM region near the centromere of chromosome 19. In situ hybridization analysis showed that one positional candidate gene, Tbx10, is ectopically expressed in Dc mutant embryos. Positional cloning of the Dc locus revealed an insertion of a 3.3-kb sequence containing the 5' region of the p23 gene into the first intron of Tbx10, which causes ectopic expression of a p23-Tbx10 chimeric transcript encoding a protein product identical to a normal variant of the Tbx10 protein. Furthermore, we show that ectopic expression of Tbx10 in transgenic mice recapitulates the Dc mutant phenotype, indicating that CL/Pin Dc mutant mice results from the p23 insertion-induced ectopic Tbx10 expression. These results identify gain of function of a T-box transcription factor gene as a mechanism underlying CL/P pathogenesis. (+info)
Long term follow up study of survival associated with cleft lip and palate at birth.
(79/686)
OBJECTIVE: To assess the overall and cause specific mortality of people from birth to 55 years with cleft lip and palate. DESIGN: Long term follow up study. SETTING: Danish register of deaths. PARTICIPANTS: People born with cleft lip and palate between 1943 and 1987, followed to 1998. MAIN OUTCOME MEASURES: Observed and expected numbers of deaths, summarised as overall and cause specific standardised mortality ratios. RESULTS: 5331 people with cleft lip and palate were followed for 170 421 person years. The expected number of deaths was 259, but 402 occurred, corresponding to a standardised mortality ratio of 1.4 (95% confidence interval 1.3 to 1.6) for males and 1.8 (1.5 to 2.1) for females. The increased risk of mortality was nearly constant for the three intervals at follow up: first year of life, 1-17 years, and 18-55 years. The participants had an increased risk of all major causes of death. CONCLUSIONS: People with cleft lip and palate have increased mortality up to age 55. Children born with cleft lip and palate and possibly other congenital malformations may benefit from specific preventive health measures into and throughout adulthood. (+info)
Mutations of ephrin-B1 (EFNB1), a marker of tissue boundary formation, cause craniofrontonasal syndrome.
(80/686)
Craniofrontonasal syndrome (CFNS) is an X-linked developmental disorder that shows paradoxically greater severity in heterozygous females than in hemizygous males. Females have frontonasal dysplasia and coronal craniosynostosis (fusion of the coronal sutures); in males, hypertelorism is the only typical manifestation. Here, we show that the classical female CFNS phenotype is caused by heterozygous loss-of-function mutations in EFNB1, which encodes a member of the ephrin family of transmembrane ligands for Eph receptor tyrosine kinases. In mice, the orthologous Efnb1 gene is expressed in the frontonasal neural crest and demarcates the position of the future coronal suture. Although EFNB1 is X-inactivated, we did not observe markedly skewed X-inactivation in either blood or cranial periosteum from females with CFNS, indicating that lack of ephrin-B1 does not compromise cell viability in these tissues. We propose that in heterozygous females, patchwork loss of ephrin-B1 disturbs tissue boundary formation at the developing coronal suture, whereas in males deficient in ephrin-B1, an alternative mechanism maintains the normal boundary. This is the only known mutation in the ephrin/Eph receptor signaling system in humans and provides clues to the biogenesis of craniosynostosis. (+info)