The frequency of palatal anomalies in Saethre-Chotzen syndrome

TWIST1, a gene associated with Saethre-Chotzen syndrome, regulates extraocular muscle organization in mouse

Heterozygous loss of function mutations in TWIST1 cause Saethre-Chotzen syndrome, which is characterized by craniosynostosis, facial asymmetry, ptosis, strabismus, and distinctive ear appearance. Individuals with syndromic craniosynostosis have high rates of strabismus and ptosis, but the underlying pathology is unknown. Some individuals with syndromic craniosynostosis have been noted to have absence of individual extraocular muscles or abnormal insertions of the extraocular muscles on the globe. Using conditional knock-out alleles for Twist1 in cranial mesenchyme, we test the hypothesis that Twist1 is required for extraocular muscle organization and position, attachment to the globe, and/or innervation by the cranial nerves. We examined the extraocular muscles in conditional Twist1 knock-out animals using Twist2-cre and Pdgfrb-cre drivers. Both are expressed in cranial mesoderm and neural crest. Conditional inactivation of Twist1 using these drivers leads to disorganized extraocular muscles that cannot be reliably identified as specific muscles. Tendons do not form normally at the insertion and origin of these dysplastic muscles. Knock-out of Twist1 expression in tendon precursors, using scleraxis-cre, however, does not alter EOM organization. Furthermore, developing motor neurons, which do not express Twist1, display abnormal axonal trajectories in the orbit in the presence of dysplastic extraocular muscles. Strabismus in individuals with TWIST1 mutations may therefore be caused by abnormalities in extraocular muscle development and secondary abnormalities in innervation and tendon formation.

Three-dimensional analysis of the palatal morphology in growing patients with Apert syndrome and Crouzon syndrome

Patients with Apert syndrome or Crouzon syndrome present with severe defects in oral-maxillofacial growth and development. In this study, we conducted a quantitative three-dimensional (3D) analysis of the palatal morphology of patients with Apert syndrome and Crouzon syndrome. Four patients with Apert syndrome (average age, 11.0 ± 0.8 years) and five with Crouzon syndrome (average age, 10.1 ± 1.6 years) were investigated. The participants' maxillary dental casts were scanned and analyzed using 3D imaging. Palatal width, depth, cross-sectional area, and palatal angle (PW, PD, PCA, and PA, respectively) were measured, and standard scores were calculated based on sex- and age-matched Japanese standard values; the actual palatal surface areas (PSA) and palatal volumes (PV) were also measured. Our results show that patients with Apert syndrome and Crouzon syndrome had a very narrow PW (standard score: -3.79 and - 0.47, respectively). 3D analysis revealed that patients with Apert syndrome had a significantly shallower PD (standard score: -1.35) than those with Crouzon syndrome (standard score: 2.47), resulting in a smaller PCA (standard score: -5.13), PSA (5.49 cm² ), and PV (1.11 cm³ ) and larger PA (standard score: -0.12) than those in patients with Crouzon syndrome. This might be due to the former having a narrower and shallower palate caused by the predominant swelling of the palatal mucosa. These findings improve our understanding of the differences in palatal morphology between Apert syndrome and Crouzon syndrome patients.

Facial Dysmorphology in Saethre-Chotzen Syndrome

PURPOSE

Classic features of Saethre-Chotzen syndrome (SCS) described in the literature include a prominent nasal bridge, eyelid ptosis, telorbitism, maxillary hypoplasia, and mandibular prognathism. The purpose of this study was to evaluate objectively the bony features of SCS.

METHODS

Preoperative computer tomography scans of 15 SCS patients, 23 normal controls, 13 bicoronal nonsyndromic, and 7 unicoronal nonsyndromic craniosynostosis patients were included for analysis. Unaffected controls and nonsyndromic patients were age- and sex-matched to SCS patients. Morphometric cephalometrics were analyzed using three-dimensional computer tomography reconstructions. Mann-Whitney U were used to compare facial measurements between SCS and normal and nonsyndromic craniosynostosis controls.

RESULTS

Telorbitism was present in bicoronal SCS patients only (P = 0.04) but absent in the unicoronal and bicoronal/metopic cohorts. The angle of the nasal bone relative to the sella was not different between SCS and controls (P = 0.536), although the angle of the nasal bone relative to the forehead was decreased in SCS by 15.5° (P < 0.001). Saethre-Chotzen syndrome had a 2.6° maxillary retrusion relative to controls (P = 0.03). In addition, SCS patients aged 4 to 7 months had a wider (39.34 versus 35.04, P = 0.017) and anteroposteriorly foreshortened (32.12 versus 35.06, P = 0.039) maxilla. There was no difference in mandibular prognathism among SCS patients as measured by the sella-nasion-B point angle compared to controls (P = 0.705).

CONCLUSIONS

Despite classic descriptions, on morphometric analysis SCS patients did not demonstrate consistency across all suture subtypes in terms of telorbitism, a broad nasal bridge, or mandibular prognathism. Rather, SCS subtypes of SCS based on suture pathology more closely resemble nonsyndromic patients.

Lateral and Frontal Cephalometric Measurements in a Cohort With Saethre-Chotzen Syndrome

OBJECTIVE

Descriptions of the craniofacial morphology in Saethre-Chotzen syndrome (SCS) are primarily based on case reports or visual assessments of affected families. The aim of this study was to compare cephalometric measurements of the craniofacial skeleton in a cohort of individuals with SCS and age- and sex-matched individuals without craniofacial anomalies.

DESIGN

Retrospective case series.

PATIENTS

Eight girls and 4 boys with SCS (age range, 7.0-19.2 years).

METHODS

Cephalometric measurements were performed using lateral and frontal cephalograms.

RESULTS

Most of the individuals with Saethre-Chotzen syndrome exhibited lower values for SNA, SNB, s-n and s-ar, while their NSL/NL, NSL/ML, NL/ML, and n-s-ba values were higher than the respective mean reference values for healthy individuals. In comparison with age- and sex-matched individuals without craniofacial anomalies, the individuals with SCS showed higher values for the maxillary and mandibular angular measurements, as well as for the menton midline angle.

CONCLUSIONS

This sample of 12 unrelated individuals with SCS is the largest collected to date for cephalometric measurements. We found that the syndrome is associated with bimaxillary retrognathism, posterior maxillary and mandibular inclination, neutral sagittal relation as well as a tendency toward an open vertical skeletal relation, a short and flattened skull base, and facial asymmetry, as compared to individuals without the syndrome.

Language Development, Hearing Loss, and Intracranial Hypertension in Children With TWIST1-Confirmed Saethre-Chotzen Syndrome

Saethre-Chotzen syndrome (SCS) is an autosomal dominant condition defined by mutations affecting the TWIST1 gene on chromosome 7p21.1. Previous research has identified an elevated prevalence of intracranial hypertension and hearing impairment associated with this syndrome. This study aimed to investigate the influence of hearing history and presence of intracranial hypertension on language development in children with SCS.A retrospective study note analysis was performed for all patients with a confirmed TWIST1 gene abnormality who attended the Oxford Craniofacial Unit and underwent a language assessment over a 22-year period. Intracranial pressure monitoring, hearing status, and language outcomes were examined in detail.Thirty patients with genetically confirmed SCS and language assessment data were identified. Twenty-eight patients underwent surgical intervention; 10 presented with intracranial hypertension (5 prior to, and 5 after primary surgical intervention). Language data coinciding with the presentation of intracranial hypertension were available for 8 children. About 44% of children with intracranial hypertension presented with concurrent receptive and expressive language delay (n = 4/8). For both children (n = 2) with longitudinal language data available, the onset of intracranial hypertension reflected a concurrent decline in language skills. Audiometric data were available for 25 children, 80% (n = 20/25) had a history of hearing loss. About 50% of these had confirmed conductive hearing loss with middle ear effusion and the other 50% had presumed conductive hearing loss with middle ear effusion. About 100% of the children with available hearing data in our study had evidence of middle ear effusion in at least 1 ear. Results also indicated that 43% (n = 13/30) of the children presented with receptive and/or expressive language delay during childhood.Given the importance of hearing for language development and the preliminary findings of a potential decline in language skills in children during periods of intracranial hypertension, regular follow-up of hearing, language, and intracranial hypertension are indicated in children with SCS.

Intercellular Genetic Interaction Between Irf6 and Twist1 during Craniofacial Development

Interferon Regulatory Factor 6 (IRF6) and TWIST1 are transcription factors necessary for craniofacial development. Human genetic studies showed that mutations in IRF6 lead to cleft lip and palate and mandibular abnormalities. In the mouse, we found that loss of Irf6 causes craniosynostosis and mandibular hypoplasia. Similarly, mutations in TWIST1 cause craniosynostosis, mandibular hypoplasia and cleft palate. Based on this phenotypic overlap, we asked if Irf6 and Twist1 interact genetically during craniofacial formation. While single heterozygous mice are normal, double heterozygous embryos (Irf6^+/−; Twist1^+/−) can have severe mandibular hypoplasia that leads to agnathia and cleft palate at birth. Analysis of spatiotemporal expression showed that Irf6 and Twist1 are found in different cell types. Consistent with the intercellular interaction, we found reduced expression of Endothelin1 (EDN1) in mandible and transcription factors that are critical for mandibular patterning including DLX5, DLX6 and HAND2, were also reduced in mesenchymal cells. Treatment of mandibular explants with exogenous EDN1 peptides partially rescued abnormalities in Meckel’s cartilage. In addition, partial rescue was observed when double heterozygous embryos also carried a null allele of p53. Considering that variants in IRF6 and TWIST1 contribute to human craniofacial defects, this gene-gene interaction may have implications on craniofacial disorders.

Craniosynostosis and Resynostosis: Models, Imaging, and Dental Implications

Craniosynostosis occurs in approximately 1 in 2,000 children and results from the premature fusion of ≥1 cranial sutures. If left untreated, craniosynostosis can cause numerous complications as related to an increase in intracranial pressure or as a direct result from cranial deformities, or both. More than 100 known mutations may cause syndromic craniosynostosis, but the majority of cases are nonsyndromic, occurring as isolated defects. Most cases of craniosynostosis require complex cranial vault reconstruction that is associated with a high risk of morbidity. While the first operation typically has few complications, bone rapidly regrows in up to 40% of children who undergo it. This resynostosis typically requires additional surgical intervention, which can be associated with a high incidence of life-threatening complications. This article reviews work related to the dental and maxillofacial implications of craniosynostosis and discusses clinically relevant animal models related to craniosynostosis and resynostosis. In addition, information is provided on the imaging modalities used to study cranial defects in animals and humans.

DLX4 is associated with orofacial clefting and abnormal jaw development

Cleft lip and/or palate (CL/P) are common structural birth defects in humans. We used exome sequencing to study a patient with bilateral CL/P and identified a single nucleotide deletion in the patient and her similarly affected son—c.546_546delG, predicting p.Gln183Argfs*57 in the Distal-less 4 (DLX4) gene. The sequence variant was absent from databases, predicted to be deleterious and was verified by Sanger sequencing. In mammals, there are three Dlx homeobox clusters with closely located gene pairs (Dlx1/Dlx2, Dlx3/Dlx4, Dlx5/Dlx6). In situ hybridization showed that Dlx4 was expressed in the mesenchyme of the murine palatal shelves at E12.5, prior to palate closure. Wild-type human DLX4, but not mutant DLX4_c.546delG, could activate two murine Dlx conserved regulatory elements, implying that the mutation caused haploinsufficiency. We showed that reduced DLX4 expression after short interfering RNA treatment in a human cell line resulted in significant up-regulation of DLX3, DLX5 and DLX6, with reduced expression of DLX2 and significant up-regulation of BMP4, although the increased BMP4 expression was demonstrated only in HeLa cells. We used antisense morpholino oligonucleotides to target the orthologous Danio rerio gene, dlx4b, and found reduced cranial size and abnormal cartilaginous elements. We sequenced DLX4 in 155 patients with non-syndromic CL/P and CP, but observed no sequence variants. From the published literature, Dlx1/Dlx2 double homozygous null mice and Dlx5 homozygous null mice both have clefts of the secondary palate. This first finding of a DLX4 mutation in a family with CL/P establishes DLX4 as a potential cause of human clefts.

Double uvula in a fifty-six-year-old woman

Introduction:

Deformities of the uvula are considered as the dark area of otorhinolaryngology practice. This little and plain part of the human organism has various functions and its abnormalities might cause serious disabilities.

Case Presentation:

In our case report, we present a unique deformity of the uvula in a 56-year-old woman.

Discussion:

The aim of this report was to present a very rare condition, unique case “polyuvula”, and to review the literature regarding other uvula abnormalities.

Hand1 phosphoregulation within the distal arch neural crest is essential for craniofacial morphogenesis

In this study we examine the consequences of altering Hand1 phosphoregulation in the developing neural crest cells (NCCs) of mice. Whereas Hand1 deletion in NCCs reveals a nonessential role for Hand1 in craniofacial development and embryonic survival, altering Hand1 phosphoregulation, and consequently Hand1 dimerization affinities, in NCCs results in severe mid-facial clefting and neonatal death. Hand1 phosphorylation mutants exhibit a non-cell-autonomous increase in pharyngeal arch cell death accompanied by alterations in Fgf8 and Shh pathway expression. Together, our data indicate that the extreme distal pharyngeal arch expression domain of Hand1 defines a novel bHLH-dependent activity, and that disruption of established Hand1 dimer phosphoregulation within this domain disrupts normal craniofacial patterning.

Analysis of Snail1 function and regulation by Twist1 in palatal fusion

Palatal fusion is a tightly controlled process which comprises multiple cellular events, including cell movement and differentiation. Midline epithelial seam (MES) degradation is essential to palatal fusion. In this study, we analyzed the function of Snail1 during the degradation of the MES. We also analyzed the mechanism regulating the expression of the Snail1 gene in palatal shelves. Palatal explants treated with Snail1 siRNA did not degrade the MES and E-cadherin was not repressed leading to failure of palatal fusion. Transforming growth factor beta 3 (Tgfβ3) regulated Snail1 mRNA, as Snail1 expression decreased in response to Tgfβ3 neutralizing antibody and a PI-3 kinase (PI3K) inhibitor. Twist1, in collaboration with E2A factors, regulated the expression of Snail1. Twist1/E47 dimers bond to the Snail1 promoter to activate expression. Without E47, Twist1 repressed Snail1 expression. These results support the hypothesis that Tgfβ3 may signal through Twist1 and then Snail1 to downregulate E-cadherin expression during palatal fusion.

Impact of genetics on the diagnosis and clinical management of syndromic craniosynostoses

PURPOSE

More than 60 different mutations have been identified to be causal in syndromic forms of craniosynostosis. The majority of these mutations occur in the fibroblast growth factor receptor 2 gene (FGFR2). The clinical management of syndromic craniosynostosis varies based on the particular causal mutation. Additionally, the diagnosis of a patient with syndromic craniosynostosis is based on the clinical presentation, signs, and symptoms. The understanding of the hallmark features of particular syndromic forms of craniosynostosis leads to efficient diagnosis, management, and long-term prognosis of patients with syndromic craniosynostoses.

METHODS

A comprehensive literature review was done with respect to the major forms of syndromic craniosynostosis and additional less common FGFR-related forms of syndromic craniosynostosis. Additionally, information and data gathered from studies performed in our own investigative lab (lab of Dr. Muenke) were further analyzed and reviewed. A literature review was also performed with regard to the genetic workup and diagnosis of patients with craniosynostosis.

RESULTS

Patients with Apert syndrome (craniosynostosis syndrome due to mutations in FGFR2) are most severely affected in terms of intellectual disability, developmental delay, central nervous system anomalies, and limb anomalies. All patients with FGFR-related syndromic craniosynostosis have some degree of hearing loss that requires thorough initial evaluations and subsequent follow-up.

CONCLUSIONS

Patients with syndromic craniosynostosis require management and treatment of issues involving multiple organ systems which span beyond craniosynostosis. Thus, effective care of these patients requires a multidisciplinary approach.

Palatal and oral manifestations of Muenke syndrome (FGFR3-related craniosynostosis)

Although Muenke syndrome is the most common syndromic form of craniosynostosis, the frequency of oral and palatal anomalies including high-arched palate, cleft lip with or without cleft palate has not been documented in a patient series of Muenke syndrome to date. Further, to our knowledge, cleft lip and palate has not been reported yet in a patient with Muenke syndrome (a previous patient with isolated cleft palate has been reported). This study sought to evaluate the frequency of palatal anomalies in patients with Muenke syndrome through both a retrospective investigation and literature review. A total of 21 patients who met criteria for this study were included in the retrospective review. Fifteen patients (71%) had a structural anomaly of the palate. Cleft lip and palate was present in 1 patient (5%). Other palatal findings included high-arched hard palate in 14 patients (67%). Individuals with Muenke syndrome have the lowest incidence of cleft palate among the most common craniosynostosis syndromes. However, high-arched palate in Muenke syndrome is common and may warrant clinical attention, as these individuals are more susceptible to recurrent chronic otitis media with effusion, dental malocclusion, and hearing loss.

Regulation of Epithelial-Mesenchymal Transition in Palatal Fusion

During palatal fusion, the midline epithelial seam between the palatal shelves degrades to achieve mesenchymal confluence. Morphological and molecular evidence support the theory that the epithelial-mesenchymal transition is one mechanism that regulates palatal fusion. It appears that transforming growth factor (TGF)-β signaling plays a role in palatal EMT. TGFβ3 is the main inducer in palatal fusion and activates both Smad-dependent and -independent signaling pathways, including the key EMT transcription factors, Lef1, Twist, and Snail1, in the MEE prior to the palatal EMT program. The roles and interactions among these transcription factors will be discussed.