Mouse genetic models of cleft lip with or without cleft palate

Nonsyndromic cleft lip and palate (CLP) is among the most common human birth defects. Transmission patterns suggest that the causes are "multifactorial" combinations of genetic and nongenetic factors, mostly distinct from those causing cleft secondary palate (CP). The major etiological factors are largely unknown, and the embryological mechanisms are not well understood. In contrast to CP or neural tube defects (NTD), CLP is uncommon in mouse mutants. Fourteen known mutants or strains express CLP, often as part of a severe syndrome, whereas nonsyndromic CLP is found in two conditional mutants and in two multifactorial models based on a hypomorphic variant with an epigenetic factor. This pattern suggests that human nonsyndromic CLP is likely caused by regulatory and hypomorphic gene variants, and may also involve epigenetics. The developmental pathogenic mechanism varies among mutants and includes deficiencies of growth of the medial, lateral or maxillary facial prominences, defects in the fusion process itself, and shifted midline position of the medial prominences. Several CLP mutants also have NTD, suggesting potential genetic overlap of the traits in humans. The mutants may reflect two interacting sets of genetic signaling pathways: Bmp4, Bmpr1a, Sp8, and Wnt9b may be in one set, and Tcfap2a and Sox11 may be in another. Combining the results of chromosomal linkage studies of unidentified human CLP genes with insights from the mouse models, the following previously unexamined genes are identified as strong candidate genes for causative roles in human nonsyndromic CLP: BMP4, BMPR1B, TFAP2A, SOX4, WNT9B, WNT3, and SP8.     

Cleft lip and palate: understanding genetic and environmental influences

Clefts of the lip and/or palate (CLP) are common birth defects of complex aetiology. CLP can occur in isolation or as part of a broad range of chromosomal, Mendelian or teratogenic syndromes. Although there has been marked progress in identifying genetic and environmental triggers for syndromic CLP, the aetiology of the more common non-syndromic (isolated) forms remains poorly characterized. Recently, using a combination of epidemiology, careful phenotyping, genome-wide association studies and analysis of animal models, several distinct genetic and environmental risk factors have been identified and confirmed for non-syndromic CLP. These findings have advanced our understanding of developmental biology and created new opportunities for clinical translational research.     

Genetik der nichtsyndromalen Lippen-Kiefer-Gaumen-Spalten

Nonsyndromic cleft lip with or without cleft palate (CL/P) represents one of the most common birth defects. Around 50–60% of all CL/P cases are nonsyndromic and have a complex genetic background. Association and linkage studies in the past have resulted in numerous candidate genes and regions. However, researchers have been able to replicate only some of these findings in independent samples, and the current knowledge of genetic risk factors cannot yet be used in the daily clinical routine. Knowledge of the genetic and exogenous factors contributing to clefting will lead to a comprehensive understanding of the underlying pathophysiology and will make development of new prevention strategies possible.     

Familial risk of oral clefts by morphological type and severity: population based cohort study of first degree relatives

Objective To estimate the relative risk of recurrence of oral cleft in first degree relatives in relation to cleft morphology.Design Population based cohort study.Setting Data from the medical birth registry of Norway linked with clinical data on virtually all cleft patients treated in Norway over a 35 year period.Participants 2.1 million children born in Norway between 1967 and 2001, 4138 of whom were treated for an oral cleft.Main outcome measure Relative risk of recurrence of isolated clefts from parent to child and between full siblings, for anatomic subgroups of clefts.Results Among first degree relatives, the relative risk of recurrence of cleft was 32 (95% confidence interval 24.6 to 40.3) for any cleft lip and 56 (37.2 to 84.8) for cleft palate only (P difference=0.02). The risk of clefts among children of affected mothers and affected fathers was similar. Risks of recurrence were also similar for parent-offspring and sibling-sibling pairs. The “crossover” risk between any cleft lip and cleft palate only was 3.0 (1.3 to 6.7). The severity of the primary case was unrelated to the risk of recurrence.Conclusions The stronger family recurrence of cleft palate only suggests a larger genetic component for cleft palate only than for any cleft lip. The weaker risk of crossover between the two types of cleft indicates relatively distinct causes. The similarity of mother-offspring, father-offspring, and sibling-sibling risks is consistent with genetic risk that works chiefly through fetal genes. Anatomical severity does not affect the recurrence risk in first degree relatives, which argues against a multifactorial threshold model of causation.     

Periconceptional multivitamin intake during early pregnancy, genetic variation of acetyl-N-transferase 1 (NAT1), and risk for orofacial clefts

BACKGROUND: Periconceptional supplementation of multivitamins that include folic acid have been shown to prevent several birth defects, including neural tube defects and orofacial clefts. We investigated whether polymorphic variants of fetal acetyl-N-transferase 1 (NAT1), an enzyme involved in the catabolism of folates, differentially interacted with maternal multivitamin use during early pregnancy to alter the risk of delivering an infant with an orofacial cleft malformation. METHODS: Using a large population-based case-control study, we genotyped 421 California infants born with an isolated cleft and 299 controls for two NAT1 polymorphisms. RESULTS: Compared to the homozygous wild-type genotypes, odds ratios for isolated cleft lip with/without cleft palate were slightly increased among infants who were homozygous for the variant alleles of NAT1 1088 and 1095. For isolated cleft palate, no similar associations with these two NAT1 variants were observed. For NAT1 1088 genotypes, we did not observe any differential risks for clefts related to maternal multivitamin intake. For NAT1 1095 genotypes, however, we found a two-fold higher risk for isolated cleft lip with/without cleft palate among infants who were homozygous for the variant allele and whose mothers did not take multivitamins during early pregnancy. CONCLUSIONS: We found evidence suggestive of an interaction between the NAT1 1095 polymorphism and lack of maternal multivitamin use that increased risks of isolated cleft lip with/without cleft palate.     

National estimates and race/ethnic-specific variation of selected birth defects in the United States, 1999-2001

BACKGROUND: In the United States, birth defects affect approximately 3% of all births, are a leading cause of infant mortality, and contribute substantially to childhood morbidity. METHODS: Population-based data from the National Birth Defects Prevention Network were combined to estimate the prevalence of 21 selected defects for 1999-2001, stratified by surveillance system type. National prevalence was estimated for each defect by pooling data from 11 states with active case-finding, and adjusting for the racial/ethnic distribution of US live births. We also assessed racial/ethnic variation of the selected birth defects. RESULTS: National birth defect prevalence estimates ranged from 0.82 per 10,000 live births for truncus arteriosus to 13.65 per 10,000 live births for Down syndrome. Compared with infants of non-Hispanic (NH) white mothers, infants of NH black mothers had a significantly higher birth prevalence of tetralogy of Fallot, lower limb reduction defects, and trisomy 18, and a significantly lower birth prevalence of cleft palate, cleft lip with or without cleft palate, esophageal atresia/tracheoesophageal fistula, gastroschisis, and Down syndrome. Infants of Hispanic mothers, compared with infants of NH white mothers, had a significantly higher birth prevalence of anencephalus, spina bifida, encephalocele, gastroschisis, and Down syndrome, and a significantly lower birth prevalence of tetralogy of Fallot, hypoplastic left heart syndrome, cleft palate without cleft lip, and esophageal atresia/tracheoesophageal fistula. CONCLUSIONS: This study can be used to evaluate individual state surveillance data, and to help plan for public health care and educational needs. It also provides valuable data on racial/ethnic patterns of selected major birth defects.     

Prevention and avoidance of congenital malformations

Many congenital abnormalities do not have either a Mendelian pattern of inheritance or an identifiable chromosome abnormality and are described as 'multifactorial' as it is assumed they are determined by several genes, each with added effects and modified to a greater or lesser extent by environmental factors. They include spina bifida and anencephaly, cleft lip or cleft palate or both, congenital heart defect and congenital dislocation of the hip, and they constitute a major community health problem. Developments in genetics, biochemistry and cytogenetics have presented new approaches to the prevention and avoidance of congenital abnormalities. The approaches available for the avoidance of congenital malformations include the avoidance of harmful environmental factors, the screening of the newborn and early treatment, genetic counselling and antenatal monitoring with selective termination. The prevention of neural-tube defects in 'high risk' mothers can be achieved by periconceptional vitamin supplementation. In Northern Ireland, of 438 fully supplemented women, only 4 (0.98%) infants or fetuses among 407 infants and fetuses examined had a neural-tube defect, whereas of 356 unsupplemented women, 16 (4.7%) infants or fetuses among 337 infants or fetuses examined had a neural-tube defect.     

Socioeconomic measures,orofacial clefts,and conotruncal heart defects in California

OBJECTIVE : To examine the association of multiple measures of socioeconomic status (SES) with risks of orofacial clefts and conotruncal heart defects. DESIGN : Data were from a recent population‐based case‐control study conducted in California that included 608 patients with orofacial clefts, 277 patients with conotruncal heart defects, and 617 nonmalformed controls. RESULTS : The odds ratio for the worst versus best score on a household‐level SES index was strongest for cleft lip with or without palate, at 1.7 (95% confidence interval, 0.9–3.4); the odds ratios for this comparison were closer to 1 and less precise for the other defect groups. An index based on neighborhood‐level SES was also not associated with increased risk of the studied defects. CONCLUSIONS : This detailed analysis of SES and selected birth defects did not suggest worse SES was associated with increased risk of the studied defects, with the possible exception of cleft lip with or without cleft palate. Birth Defects Research (Part A), 2009. © 2009 Wiley‐Liss, Inc.     

Variation of morphophysiological and genetic demographic traits in children with congenital cleft lip and palate

Medical records and questionnaire data have been used to analyze morphophysiological (the birth weight and length) and genetic demographic (maternal age and marriage structure) traits in a sample of children with orofacial malformations (OMs, cleft palate and/or cleft lip) living in Krasnodar Territory, Russia. The sample of children with malformations (including premature infants) differs from the control group in lower birth weight and length and a lower proportion of children with morphophysiological values close to the population average ones, as well as a higher family exogamy level estimated on the basis of marriage structure in the parental and preceding generations. The risk of congenital cleft palate and/or cleft lip is considerably increased is the maternal age is older than 35 years or, to a lower degree, if it is younger than 20 years.     

唇腭裂患儿下调表达的miRNA相关研究

目的:唇腭裂是口腔颌面部最常见的先天性畸形,危害严重。mi RNA在细胞分化,生物发育及疾病发生发展过程中发挥巨大作用,越来越多的受到科研人员的关注。本课题对唇腭裂患儿下调表达的mi RNA与唇腭裂相关性进行验证研究,为mi RNA应用在唇腭裂防治中奠定一定的基础。方法:通过芯片分析方法检测唇腭裂患儿表达下调的mi RNA,利用MIRDB、TARGETSCAN-VERT和RNA22-HSA这三个生物信息学软件对唇腭裂患儿表达下调的mi RNA进行靶基因预测分析,验证候选mi RNA与唇腭裂具有相关性。结果:得出唇腭裂患儿中出现差异表达下调的mi RNA有hsa-mi R-3119,hsa-mi R-3915等73个,其中hsa-mi R-3611对应的靶基因GABRB3和hsa-mi R-764对应的靶基因F13A1有文献报道与唇腭裂具有相关性。结论:hsa-mi R-3611,hsa-mi R-764可能与唇腭裂的发生存在关联。     

Beyond Mendel: an evolving view of human genetic disease transmission

Methodological and conceptual advances in human genetics have led to the identification of an impressive number of human disease genes. This wealth of information has also revealed that the traditional distinction between Mendelian and complex disorders might sometimes be blurred. Genetic and mutational data on an increasing number of disorders have illustrated how phenotypic effects can result from the combined action of alleles in many genes. In this review, we discuss how an improved understanding of the genetic basis of multilocus inheritance is catalysing the transition from a segmented view of human genetic disease to a conceptual continuum between Mendelian and complex traits.     

Birth prevalence of cleft lip and palate in British Columbia between 1952 and 1986: stability of rates.

We examined the birth prevalence of cleft lip with or without cleft palate and of isolated cleft palate in British Columbia between 1952 and 1986 using the data of the BC Health Surveillance Registry. The rates fluctuated over the study period, but linear trend analysis showed no increase or decrease for cleft lip with or without cleft palate; however, there was a significant increase for isolated cleft palate, attributed to improved ascertainment around 1963-66. Given the possible effects of newer agents used in both silviculture and agriculture, as well as the general concern over drugs and other environmental agents, such a long-term monitoring program is important. Furthermore, if significant clustering occurs, good background data are essential for comparison. The general public''s perception is that the rates of birth defects are increasing. Our findings should give some reassurance with respect to orofacial clefts.     

Recurrent cleft lip and palate in siblings of a patient with malabsorption syndrome, probably caused by hypovitaminosis a associated with folic acid and vitamin B(2) deficiencies

We present a woman with metabolic disorders secondary to malabsorption and renal disease who gave birth to a stillborn male fetus with left unilateral cleft lip and palate and a live born infant with left unilateral cleft lip and palate. We discuss potential cofactors that could be implicated in the abnormal embryonic process.     

A familial tetraphocomelia syndrome involving limb deformities,cleft lip,cleft palate,and associated anomalies —A new syndrome

Summary This paper reports a rare malformation syndrome which is observed in two sibs (brother and sister) of a family. It consists of nearly symmetric reductive defects of the limbs, flexon contractures of various joints, cleft lip and cleft palate, multiple minor abnormalities including capillary hemangioma of the forehead, hypoplastic cartilages of ears and nose, micrognathia, intrauterine growth retardation, and possibly mental retardation. Chromosomes of both parents and propositi are normal. Genetic data suggest autosomal recessive inheritance.     

Hereditary syndrome of ectrodactyly, congenital heart defect and cleft lip and palate

A case of a family of he proband suffering from ektrodaktyly, together with heart defect, cleft lip and palate is reported. The parents came to the genetic counselling center to get the genetic prognosis for a next child. All together 3 cases demonstrating different types of radial defects were registered in this pedigree. The authors discuss possible causes of clinical polymorphism and accent the complications of giving genetic prognosis in such cases.     

Meta-analysis of 13 genome scans reveals multiple cleft lip/palate genes with novel loci on 9q21 and 2q32-35

Isolated or nonsyndromic cleft lip with or without cleft palate (CL/P) is a common birth defect with a complex etiology. A 10-cM genome scan of 388 extended multiplex families with CL/P from seven diverse populations (2,551 genotyped individuals) revealed CL/P genes in six chromosomal regions, including a novel region at 9q21 (heterogeneity LOD score [HLOD]=6.6). In addition, meta-analyses with the addition of results from 186 more families (six populations; 1,033 genotyped individuals) showed genomewide significance for 10 more regions, including another novel region at 2q32-35 (P=.0004). These are the first genomewide significant linkage results ever reported for CL/P, and they represent an unprecedented demonstration of the power of linkage analysis to detect multiple genes simultaneously for a complex disorder.     

Meta-analysis Reveals Genome-Wide Significance at 15q13 for Nonsyndromic Clefting of Both the Lip and the Palate,and Functional Analyses Implicate GREM1 As a Plausible Causative Gene

Nonsyndromic orofacial clefts are common birth defects with multifactorial etiology. The most common type is cleft lip, which occurs with or without cleft palate (nsCLP and nsCLO, respectively). Although genetic components play an important role in nsCLP, the genetic factors that predispose to palate involvement are largely unknown. In this study, we carried out a meta-analysis on genetic and clinical data from three large cohorts and identified strong association between a region on chromosome 15q13 and nsCLP (P = 8.13×10⁻¹⁴ for rs1258763; relative risk (RR): 1.46, 95% confidence interval (CI): 1.32–1.61)) but not nsCLO (P = 0.27; RR: 1.09 (0.94–1.27)). The 5 kb region of strongest association maps downstream of Gremlin-1 (GREM1), which encodes a secreted antagonist of the BMP4 pathway. We show during mouse embryogenesis, Grem1 is expressed in the developing lip and soft palate but not in the hard palate. This is consistent with genotype-phenotype correlations between rs1258763 and a specific nsCLP subphenotype, since a more than two-fold increase in risk was observed in patients displaying clefts of both the lip and soft palate but who had an intact hard palate (RR: 3.76, CI: 1.47–9.61, P_diff<0.05). While we did not find lip or palate defects in Grem1-deficient mice, wild type embryonic palatal shelves developed divergent shapes when cultured in the presence of ectopic Grem1 protein (P = 0.0014). The present study identified a non-coding region at 15q13 as the second, genome-wide significant locus specific for nsCLP, after 13q31. Moreover, our data suggest that the closely located GREM1 gene contributes to a rare clinical nsCLP entity. This entity specifically involves abnormalities of the lip and soft palate, which develop at different time-points and in separate anatomical regions.     

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.     

干扰素调节因子-6基因与非综合征性唇腭裂的关系

先天性唇腭裂常分为综合征性唇腭裂和非综合征性唇腭裂两大类,其中非综合征性唇腭裂（nonsyndromic cleft lip with orwithout cleft palate,NSCL/P）约占先天性唇腭裂的70%-80%。国内外学者在对NSCL/P相关基因进行研究后发现,干扰素调节因子6（Interferon Regulatory Factor 6,IRF6）是迄今发现最有价值的并且与NSCL/P致病有相关性的热点基因之一,但是仍有部分学者通过实验研究后得出了相反的结论,故IRF6基因与NSCL/P之间的相关性说法不一,存在较大的争论,究竟前者是通过何种遗传方式作用于后者、仍然不十分清楚,且需要大样本的研究来证实。本文就IRF6基因与NSCL/P的关系做一综述,为研究两者的关系提供系统性参考。