Genetics of cleft lip and cleft palate

Orofacial clefts are common birth defects and can occur as isolated, nonsyndromic events or as part of Mendelian syndromes. There is substantial phenotypic diversity in individuals with these birth defects and their family members: from subclinical phenotypes to associated syndromic features that is mirrored by the many genes that contribute to the etiology of these disorders. Identification of these genes and loci has been the result of decades of research using multiple genetic approaches. Significant progress has been made recently due to advances in sequencing and genotyping technologies, primarily through the use of whole exome sequencing and genome-wide association studies. Future progress will hinge on identifying functional variants, investigation of pathway and other interactions, and inclusion of phenotypic and ethnic diversity in studies.

Mutations of PVRL1, encoding a cell-cell adhesion molecule/herpesvirus receptor, in cleft lip/palate-ectodermal dysplasia

Cleft lip, with or without cleft palate (CL/P), is one of the most common birth defects, occurring in 0.4 to 2.0 per 1,000 infants born alive. Approximately 70% of CL/P cases are non-syndromic (MIM 119530), but CL/P also occurs in many single-gene syndromes, each affecting a protein critical for orofacial development. Here we describe positional cloning of the gene responsible for an autosomal recessive CL/P-ectodermal dysplasia (ED) syndrome (CLPED1; previously ED4; ref. 2), which we identify as PVRL1, encoding nectin-1, an immunoglobulin (Ig)-related transmembrane cell-cell adhesion molecule that is part of the NAP cell adhesion system. Nectin-1 is also the principal cell surface receptor for alpha-herpesviruses (HveC; ref. 7), and the high frequency of CLPED1 on Margarita Island in the Caribbean Sea might result from resistance of heterozygotes to infection by these viruses.

p63-Associated Disorders

Heterozygous mutations in the transcription factor gene p63 are causative for several syndromes, with ectodermal dysplasia, orofacial clefting and limb malformations as the key characteristics. Different combinations of these features are seen in five different syndromes, of which ectrodactyly, ectodermal dysplasia and cleft lip/palate syndrome (EEC) is the most common one. Mutations in p63 can also cause non-syndromic single malformations, such as split hand foot malformation (SHFM4) and isolated cleft lip (NSCL). In this article we will present an overview of diseases caused by mutations in the p63 gene and review the known pathogenic p63 gene mutations.

Development of the upper lip: morphogenetic and molecular mechanisms

The vertebrate upper lip forms from initially freely projecting maxillary, medial nasal, and lateral nasal prominences at the rostral and lateral boundaries of the primitive oral cavity. These facial prominences arise during early embryogenesis from ventrally migrating neural crest cells in combination with the head ectoderm and mesoderm and undergo directed growth and expansion around the nasal pits to actively fuse with each other. Initial fusion is between lateral and medial nasal processes and is followed by fusion between maxillary and medial nasal processes. Fusion between these prominences involves active epithelial filopodial and adhering interactions as well as programmed cell death. Slight defects in growth and patterning of the facial mesenchyme or epithelial fusion result in cleft lip with or without cleft palate, the most common and disfiguring craniofacial birth defect. Recent studies of craniofacial development in animal models have identified components of several major signaling pathways, including Bmp, Fgf, Shh, and Wnt signaling, that are critical for proper midfacial morphogenesis and/or lip fusion. There is also accumulating evidence that these signaling pathways cross-regulate genetically as well as crosstalk intracellularly to control cell proliferation and tissue patterning. This review will summarize the current understanding of the basic morphogenetic processes and molecular mechanisms underlying upper lip development and discuss the complex interactions of the various signaling pathways and challenges for understanding cleft lip pathogenesis.

Unilateral cleft lip repair: an anatomical subunit approximation technique

BACKGROUND

A technique of unilateral cleft lip repair is described. The repair draws from a variety of previously described repairs and adheres to a concept of anatomical subunits of the lip. Cases from within the spectrum of the deformity have been chosen from a series of 144 consecutive cases to demonstrate the applicability of the technique in all forms of unilateral cleft lip.

METHODS

Incisions cross the lip perpendicular to the cutaneous roll at the cleft side peak of Cupid's bow of the medial lip and at the base of the philtral column of the lateral lip. Above this level, incisions ascend the lip to allow for approximation along a line symmetrical with the non-cleft-side philtral column. Incisions then ascend superolaterally bordering the lip columellar crease to the point of closure in the nostril sill. A Rose-Thompson lengthening effect occurs just above the level of the cutaneous roll. If necessary, a small triangle positioned just above the cutaneous roll is often used. Any central vermilion deficiency is augmented by a laterally based triangular vermilion flap from the lateral lip element.

RESULTS

Since January of 2000, this technique has been used in 144 consecutive unilateral cleft lip repairs. The inferior triangle is small (average, 1.24 mm; range, 0 to 2 mm). The technique can be applied to all degrees of unilateral cleft lip.

CONCLUSIONS

A technique of unilateral cleft lip repair is described. The repair allows for a repair line that ascends the lip at the seams of anatomical subunits.

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.

Development of a method for rating nasolabial appearance in patients with clefts of the lip and palate

Comparison of the outcome of treatment of patients with clefts of the lip and palate can yield valuable pointers for discriminating between beneficial and harmful procedures. The development of a standardized rating scheme to assess the facial appearance of these patients is described. The rating scheme can be used in conjunction with conventional cephalometric analysis and dental arch evaluation. A method is described in which the nasolabial area is masked, thus reducing the influence of the surrounding facial features since it is shown that judges are influenced by general facial attractiveness. An ordinal scale has been evaluated in which four features of the nose and lip are assessed separately and in total by a panel of judges. The nasolabial profile, the nasal symmetry, the nasal form, and vermilion border were assessed using a 5-point scale. Acceptable pooled levels of reliability and reproducibility were obtained. This standardized rating system may be used to differentiate treatment outcome in patients from different treatment centers.

A preliminary study of facial growth and morphology in unoperated male unilateral cleft lip and palate subjects over 13 years of age

This paper investigates the effects of surgery on facial growth and morphology in Sri Lankan males with unilateral cleft lip and palate who were over 13 years of age at the time of study with cephalometry and dental study models. Three separate subgroups were analyzed: those who had totally unrepaired cleft lip and palate, those who received lip repair in infancy but not palatal repair, and those who had lip and palate repair in infancy. Twenty-three healthy noncleft Sri Lankan males over 13 years formed a control group from the same racial background. The results show that subjects who had no surgery had a potential for normal maxillary growth. Subjects who have had lip repair in early infancy show relatively normal maxillary growth, but maxillary hypoplasia is common when the palate has also been repaired early.

Presurgical columellar elongation and primary retrograde nasal reconstruction in one-stage bilateral cleft lip and nose repair

We present a new combined approach to primary bilateral cleft lip, nose, and alveolus repair using presurgical nasoalveolar molding combined with a one-stage lip, nose, and alveolus repair. Presurgical alveolar molding is used to bring the protruding premaxilla back into proper alignment with the lateral segments in the maxillary arch. Presurgical nasal molding produces tissue expansion of the short columella and nasal lining. A coordinated surgical approach involves a one-stage repair of the lip, nose, and alveolus. The nasal repair uses a retrograde approach in which the prolabial flap and columella are reflected over the nasal dorsum by continuing the dissection behind the prolabium up the membranous septum and over the septal angle. Tissues are dissected out from between the tip cartilages, and the domes are sutured together in the midline. This method joins a new class of bilateral cleft repairs that place the primary emphasis on correction of the deformity of the nasal tip cartilages.

A study of facial growth in patients with unilateral cleft lip and palate treated by the Oslo CLP Team

Lateral and frontal cephalometric analysis of a mixed longitudinal survey of 257 individuals with complete unilateral cleft lip and palate from the Oslo CLP Growth Archive is described. All subjects were treated and followed up by the Oslo CLP Team according to strictly defined protocols for treatment and documentation. Craniofacial form for this sample is generally similar to that reported for Caucasian children treated for this condition elsewhere.

Validation of a vision-based, three-dimensional facial imaging system

OBJECTIVE

The aim of this study was to assess the accuracy of a newly developed three-dimensional (3D) imaging system in recording facial morphology.

METHODS

Twenty-one infants with cleft lip each had a full-face alginate impression taken at the time of primary lip repair, and a stone cast was constructed from each impression. Five anthropometric points were marked on each cast. Each cast was digitized, and the 3D co-ordinates of the five points were obtained using a co-ordinate measuring machine (CMM, Ferranti) of documented accuracy (9.53 microm). Each cast was scanned in four positions using a computerized stereophotogrammetry (C3D) system. The five points were located on the 3D images, and their 3D co-ordinates were extracted by three operators. The co-ordinate systems produced by C3D were aligned, via translation and rotation, to match the CMM co-ordinate system using partial ordinary procrustes analysis. The displacements of the adjusted C3D co-ordinates from the reference co-ordinates were then measured. Three different types of errors were identified: operator, system, and registration errors.

RESULTS

Operator error was within 0.2 mm of the true co-ordinates of the landmarks. C3D was accurate within 0.4 mm. The average displacement of points over the 21 casts at four positions for the three operators was 0.79 mm (median 0.68).

CONCLUSIONS

The presented 3D imaging system is reliable in recording facial deformity and could be utilized in recording cleft deformities and measuring the changes following surgery

Methods of assessment of cleft-related facial deformity: a review

OBJECTIVE

To review the stimulus media, measurements and scoring system, rater's characteristics, and facial region used in assessment of the appearance of cleft-related deformity.

METHODS

A review of the literature was conducted using MedLine from January 1966 to June 2003. Key orthodontic journals and The Cleft Palate-Craniofacial Journal were hand searched as well.

RESULTS

Most studies used a static two-dimensional means of assessment. Direct clinical assessment, three-dimensional media, or both have been used to a lesser extent. Only one study utilized all three assessment media. Three studies, however, attempted to compare the direct clinical assessment with that obtained using two-dimensional media. Most of the studies demonstrated that appearance of the cleft-related deformity could be measured by a variety of judges. The reliability and validity of the three different media as methods of assessment have received limited attention. The facial area assessed has varied from the full face, nasolabial area, or specific features of the lip or nose.

CONCLUSIONS

Wide variation exists in the study design related to assessment of cleft-related deformity. An internationally agreed objective method of assessment for this facial deformity is required. A three-dimensional, rather than a two-dimensional, means of assessment should be adopted.

Anthropometric and anthroposcopic findings of the nasal and facial region in cleft patients before and after primary lip and palate repair

Two populations were studied and compared to determine the effects of cleft lip and palate surgery on the nose and face. In the first, three anthropometric measurements, two nasal and one facial, were taken before primary lip repair from infants with complete unilateral cleft lip and palate (UCLP) and with bilateral cleft lip and palate (BCLP). In the second, ten measurements were taken from the nose and face of patients surgically treated for UCLP and BCLP. The high frequency of noses disproportionately wide in relation to their height in both cleft types before primary lip repair greatly decreased after surgery. Among the residual deformities after surgery for UCLP, nostril floor width asymmetry was the most frequent, followed by columella length asymmetry, flat nasal bridge, wide soft nose, flat nasal tip, and small nasal tip protrusion. In the BCLP patients, nostril floor width asymmetry was also the most common stigma, followed by flat nasal tip, wide soft nose, columella length asymmetry, flat nasal bridge and bilaterally angled alae, and small nasal tip protrusion. A subnormally flat upper face inclination was observed in UCLP and BCLP patients. Quantitative determination of these nasal stigmata in cleft lip and palate patients who have undergone primary lip repair provides valuable information for surgical correction of the cleft soft-tissue deformities.

Primary repair of bilateral cleft lip and nasal deformity

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. List five principles that guide synchronous repair of bilateral complete cleft lip and nasal deformity. 2. Explain how different growth rates for the principal nasolabial features are applied during primary repair. 3. Describe two approaches for positioning the alar cartilages to form the columella. 4. Discuss the influences on referral patterns for a newborn with bilateral cleft lip. --Traditional repair of bilateral cleft lip focused on labial closure but accentuated the nasal deformities, which were addressed later. By the end of the past century, single-staged labial closure had replaced the old multistaged procedures and the technical emphasis had begun to shift from secondary to primary nasal correction. Now, presurgical maxillary orthopedics sets the bony foundation for synchronous nasolabial repair and for closure of the alveolar clefts. The study of normal nasolabial growth and the typical stigmata of the conventional methods provides the necessary foreknowledge to guide surgical sculpture in three dimensions and to anticipate the fourth dimension. The convergence of several forces are changing referral lines for children born with bilateral cleft lip. These include affirmation of centers of excellence, surgeons' self-regulation, prenatal diagnosis, economics of health-care delivery, and increasing parental sophistication. These pressures are not necessarily in conflict. Care by a subspecialized plastic surgeon and experienced team is in the best interests of the child and the third-party payer.

Secondary alveolar bone grafting in clefts of the lip and palate

A short review of the literature is presented outlining the role of alveolar bone grafting in cleft patients. An analysis of a series of 47 secondary alveolar bone grafts in 34 patients is presented. The age range was 7-24 years. At the time of evaluation, 30 canines were in final occlusion and good alveolar bone levels were present in 83% of patients. Of the 13 bilateral cases (26 clefts), 14 canines were in final occlusion and all cases had good alveolar bone levels. No major complications were encountered. The graft was completely resorbed in 3 cases (6.4%) only.

Study models of 5 year old children as predictors of surgical outcome in unilateral cleft lip and palate

This study examined features of dental occlusion in patients born with a unilateral cleft lip and palate (UCLP). The intention was to develop a 'Goslon type' index for 5 year old children. The Goslon ranking system was used on longitudinal study models taken at 5 and 10 years of age of the same patients. All patients had UCLP and this had been repaired using a Millard type lip repair and a Veau Wardill or Von Langenbeck palatal closure. There was good intra-examiner agreement for ascribing 5 and 10 year old models to one of five categories (excellent-very poor). Inter-examiner agreement on both sets of models was at worst moderate. Two of the examiners identified up to 93 per cent of 5 year old models which either remained in the same category or deteriorated by 10 years of age. At worse the results demonstrated 70 per cent of cases of 5 years of age remained in the same category or deteriorated by 10 years of age. Consensus agreement has produced five categories of outcome for these 5 year old models. This new index is to be subjected to further validation. This study has therefore provided, for the first time, a mechanism for assessing the results of CLP surgery earlier than indices already available.

A randomised prospective clinical trial into the effect of infant orthopaedics on maxillary arch dimensions in unilateral cleft lip and palate (Dutchcleft)

Aim of the study was to evaluate the effect of infant orthopaedics (IO) on maxillary dimensions in infants with unilateral cleft lip and palate (UCLP). The study design was a prospective two-arm randomised controlled trial in parallel with three participating academic Cleft Palate Centres. Treatment was assigned by means of a computerised balanced allocation method. One group (IO+) wore passive maxillary plates during the first year of life, the other group (IO-) did not. Maxillary casts, made at birth, and at 15, 24, 48, 78 wk were digitised three-dimensionally. Before lip closure alveolar, midpalatal and posterior cleft width reduced significantly more in IO(+) than in IO(-). After lip closure, the alveolar cleft width reduced significantly more in IO(-). Until soft palate closure the slope of the palatal vault flattened significantly by IO. It is concluded that IO only has a temporary effect on maxillary arch dimensions that does not last beyond surgical soft palate closure. Therefore, infant orthopaedics as a tool to improve maxillary arch form could be abandoned. However, other outcome variables like facial and dental appearance, speech outcome, and cost-effectiveness need to be investigated further in order to assess the comprehensive effect of infant orthopaedics.

Van der Woude syndrome: a review. Cardinal signs, epidemiology, associated features, differential diagnosis, expressivity, genetic counselling and treatment

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.

Variation in IRF6 contributes to nonsyndromic cleft lip and palate

Nonsyndromic cleft lip with or without cleft palate (NSCLP) is a common craniofacial birth defect which results in lifelong medical and social consequences. While there have been a number of attempts to identify the genes responsible for this disorder, the results have not been consistent among populations and no single gene has been identified as playing a major susceptibility role. Van der Woude syndrome, a disorder characterized by lower-lip pits with or without cleft lip/palate, results in many cases from mutations in the interferon regulatory factor 6 (IRF6) gene. Recently, Zucchero et al. [2004: N Engl J Med 351:769-780] detected an association between SNPs in IRF6 and NSCLP in a number of different populations. A subsequent study by Scapoli et al. [2005: Am J Hum Genet 76:180-183] confirmed this association in an Italian population. We examined the same SNPs as Scapoli et al. [2005] in our large, well-characterized sample of NSCLP families and trios, and also detected an altered transmission of IRF6 alleles. This additional confirmation further strengthens the IRF6 association and suggests that IRF6 plays a role in NSCLP susceptibility.

Structural brain abnormalities in adult males with clefts of the lip and/or palate

PURPOSE

To evaluate brain morphology of adult males with nonsyndromic clefts of the lip and/or palate (NSCLP) in comparison to a matched healthy control group.

METHODS

Brain structure was measured using quantitative analysis of magnetic resonance images.

RESULTS

Subjects with NSCLP had significant abnormalities in brain morphology consisting of abnormally enlarged anterior regions of the cerebrum, and decreased volumes of the posterior cerebrum and cerebellum. Overall, the most severely affected region was the left temporal lobe. Furthermore, these structural abnormalities were directly related to cognitive dysfunction.

CONCLUSIONS

These findings highlight the important relationship and interplay between face and brain development.

C677T variant form at the MTHFR gene and CL/P: a risk factor for mothers?

Maternal folic acid supplementation in early pregnancy has been suggested to play a role in the prevention of nonsyndromic orofacial cleft, i.e., cleft lip with or without cleft palate (CL/P). Moreover, some authors demonstrated association of the C-->T mutation (C677T), converting an alanine to a valine residue in 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, with other congenital anomalies such as neural tube defects (NTDs). Because of MTHFR's involvement in the metabolism of folate, we investigated 64 CL/P patients and their parents for C677T MTHFR mutation. No linkage disequilibrium was found using the transmission disequilibrium test (TDT). However, a significantly higher mutation frequency was detected in mothers of CL/P patients compared to controls. The odds ratios calculated for mothers having CT or TT genotype, compared to the normal CC genotype, were 2.75 (95% confidence interval 1.30-5.57) and 2.51 (1.00-6.14), respectively. These results support the involvement of the folate pathway in the etiology of CL/P, and indicate an effect of the maternal genotype, rather than influence of the embryo's genotype.

Repair of bilateral cleft lip: review, revisions, and reflections

Rarely does the appearance of a child with a repaired bilateral cleft lip compare favorably with that of a child with a repaired unilateral cleft lip. However, there has been a major change in operative strategy during the past decade, and as a result, the typical bilateral cleft nasolabial stigmata are no longer so obvious. The senior author restates the principles for correction of bilateral cleft lip and nasal deformity, and underscores the essential role of preoperative premaxillary positioning. He reviews his method of single-stage closure of the cleft primary palate, including three-dimensional adjustments based on predicted four-dimensional changes. Operative modifications are described for variations of bilateral cleft lip. The authors emphasize the surgeon's obligation for periodic assessment. In a consecutive series of 50 patients with repaired bilateral complete cleft lip/palate, the revision-rate was 33% as compared with 12.5% if the secondary palate is intact. No revisions were necessary for philtral size or columellar length. The authors propose that nasolabial appearance and speech are the priorities in habilitation of the child with bilateral cleft lip/palate rather than the traditional emphasis on maxillary growth.

The orbicularis oris muscle: a functional approach to its repair in the cleft lip

Using electrical stimulation the different muscular components of the orbicularis oris muscle are defined at the time of operation for repair of the cleft. By wide dissection and differential re-arrangement, these muscular components can then be brought into their normal position. Not only is a better cosmetic and functional result achieved immediately but it is suggested that some common growth deformities will be avoided.

Three-dimensional nasal changes following nasoalveolar molding in patients with unilateral cleft lip and palate: geometric morphometrics

OBJECTIVE

To evaluate three-dimensional changes in nasal morphology in patients with unilateral cleft lip and palate treated with presurgical nasoalveolar molding (NAM) to correct naso-labio-alveolar deformity.

DESIGN

This was a prospective, longitudinal study. Digital stereophotogrammetry was used to capture three-dimensional facial images, and x, y, and z coordinates of 28 nasal landmarks were digitized.

SAMPLE

Ten patients with unilateral cleft lip and palate.

MAIN OUTCOME MEASURES

Nasal form changes between T1 (age: 28 +/- 2 days, pre-NAM) and T2 (age: 140 +/- 2 days, post-NAM), using conventional measurements and finite-element scaling analysis.

RESULTS

Overall nasal changes were statistically different (p < .01), but no linear or curvilinear changes were found. Specifically, relative size increases were found on the noncleft side, involving the upper nose (30%), alar depth (20%), alar dome (30%), columella height (30%), and lateral wall of the nostril (17%). On the cleft side, the following showed a size increase: upper nose (8%), alar dome (5%), columella height (30%), and lateral wall of the nostril (30%). The cleft-side alar curvature, however, showed a large decrease in size (80%), but no changes on the noncleft side were found. Corresponding shape changes and angular changes were also found.

CONCLUSIONS

Using NAM, bilateral nasal symmetry in patients with unilateral cleft lip and palate was improved before surgical repair. Furthermore, slight overcorrection of the alar dome on the cleft side using pressure exerted by the nasal stent is indicated to maintain the NAM result.