Treacher Collins Syndrome: Genetics, Clinical Features and Management

Polymerase I as a Target for Treating Neurodegenerative Disorders

Polymerase I (Pol I) is at the epicenter of ribosomal RNA (rRNA) synthesis. Pol I is a target for the treatment of cancer. Given the many cellular commonalities between cancer and neurodegeneration (i.e., different faces of the same coin), it seems rational to consider targeting Pol I or, more generally, rRNA synthesis for the treatment of disorders associated with the death of terminally differentiated neurons. Principally, ribosomes synthesize proteins, and, accordingly, Pol I can be considered the starting point for protein synthesis. Given that cellular accumulation of abnormal proteins such as α-synuclein and tau is an essential feature of neurodegenerative disorders such as Parkinson disease and fronto-temporal dementia, reduction of protein production is now considered a viable target for treatment of these and closely related neurodegenerative disorders. Abnormalities in polymerase I activity and rRNA production may also be associated with nuclear and nucleolar stress, DNA damage, and childhood-onset neuronal death, as is the case for the UBTF E210K neuroregression syndrome. Moreover, restraining the activity of Pol I may be a viable strategy to slow aging. Before starting down the road of Pol I inhibition for treating non-cancerous disorders of the nervous system, many questions must be answered. First, how much Pol I inhibition can neurons tolerate, and for how long? Should inhibition of Pol I be continuous or pulsed? Will cells compensate for Pol I inhibition by upregulating the number of active rDNAs? At present, we have no effective and safe disease modulatory treatments for Alzheimer disease, α-synucleinopathies, or tauopathies, and novel therapeutic targets and approaches must be explored.

Postoperative Upper Airway Volume Measurements Among Children With Craniofacial Abnormalities

OBJECTIVE

To measure postoperative airway volumes among patients with craniofacial abnormalities and compare them to normative values.

STUDY DESIGN

Retrospective, comparative study.

SETTING

Academic Medical Center.

METHODS

Retrospective analysis of imaging of children with craniofacial abnormalities treated at NYU Langone Health from January 2013 to February 2021. Upper airway volumes postcraniofacial surgery were measured using 3D processing software (Dolphin 3D, version 11.95). These values were compared with published normative values.

RESULTS

Twenty-one subjects were identified and compared to normative values. The postoperative oropharyngeal volumes were on average 43.7% smaller than the normative values (P < .001), and the total upper airway volumes were 31.6% smaller (P = .003). No significant differences were observed in the nasopharyngeal or hypopharyngeal volumes of the study cohort compared to the normative data. Among children ages 12 to 17 years (n = 13), the mean oropharyngeal volumes were 47.6% smaller than normal (P < .001), and the mean total upper airway volumes were 34.6% smaller than normal (P < .001). Among children ages 7 to 11 years (n = 8), the mean oropharyngeal volumes were 35.1% smaller than normal (P = .049), but no difference in mean total upper airway volume was observed.

CONCLUSION

In children with craniofacial anomalies, postoperative airway volumes remain lower than normative values. However, even a slight increase in airway volume can yield a substantial increase in flow rate. 3D airway evaluations are a valuable tool for surgical planning and analysis and can help with optimizing airway dynamics.

Atypical mandibulofacial dysostosis with microcephaly diagnosed through the identification of a novel pathogenic mutation in EFTUD2

BACKGROUND

Mandibulofacial dysostosis with microcephaly (MFDM, OMIM# 610536) is a rare monogenic disease that is caused by a mutation in the elongation factor Tu GTP binding domain containing 2 gene (EFTUD2, OMIM* 603892). It is characterized by mandibulofacial dysplasia, microcephaly, malformed ears, cleft palate, growth and intellectual disability. MFDM can be easily misdiagnosed due to its phenotypic overlap with other craniofacial dysostosis syndromes. The clinical presentation of MFDM is highly variable among patients.

METHODS

A patient with craniofacial anomalies was enrolled and evaluated by a multidisciplinary team. To make a definitive diagnosis, whole-exome sequencing was performed, followed by validation by Sanger sequencing.

RESULTS

The patient presented with extensive facial bone dysostosis, upward slanting palpebral fissures, outer and middle ear malformation, a previously unreported orbit anomaly, and spina bifida occulta. A novel, pathogenic insertion mutation (c.215_216insT: p.Tyr73Valfs*4) in EFTUD2 was identified as the likely cause of the disease.

CONCLUSIONS

We diagnosed this atypical case of MFDM by the detection of a novel pathogenetic mutation in EFTUD2. We also observed previously unreported features. These findings enrich both the genotypic and phenotypic spectrum of MFDM.

Possible germline mosaicism in a pedigree with Treacher Collins syndrome: A case report and brief review

Treacher Collins syndrome (TCS) is a rare congenital craniofacial disorder, typically inherited as an autosomal dominant condition. Here, we report on a family in which germline mosaicism for TCS was likely present. The proband was diagnosed with TCS based on the typical clinical features and a pathogenic variant TCOF1 (c.4369_4373delAAGAA, p.K1457Efs*12). The mutation was not detected in his parents' peripheral blood DNA samples, suggesting a de novo mutation had occurred in the proband. However, a year later, the proband's mother became pregnant, and the amniotic fluid puncture revealed that the fetus carried the same mutation as the proband. Prenatal ultrasound also indicated a maxillofacial dysplasia with unilateral microtia. The mother then disclosed a previous birth history in which a baby had died of respiratory distress shortly after birth, displaying a TCS-like phenotype. Around the same time, the proband's father was diagnosed with mild bilateral conductive hearing loss. Based on array data, we concluded that the father may have had germline mosaicism for TCOF1 mutation. Our findings highlight the importance of considering germline mosaicism in sporadic de novo TCOF1 mutations when providing genetic consulting, and prenatal diagnosis is important when the proband's parents become pregnant again.

Foxi3GFP and Foxi3CreER mice allow identification and lineage labeling of pharyngeal arch ectoderm and endoderm, and tooth and hair placodes

BACKGROUND

FOXI3 is a forkhead family transcription factor that is expressed in the progenitors of craniofacial placodes, epidermal placodes, and the ectoderm and endoderm of the pharyngeal arch region. Loss of Foxi3 in mice and pathogenic Foxi3 variants in dogs and humans cause a variety of craniofacial defects including absence of the inner ear, severe truncations of the jaw, loss or reduction in external and middle ear structures, and defects in teeth and hair.

RESULTS

To allow for the identification, isolation, and lineage tracing of Foxi3-expressing cells in developing mice, we targeted the Foxi3 locus to create Foxi3GFP and Foxi3CreER mice. We show that Foxi3GFP mice faithfully recapitulate the expression pattern of Foxi3 mRNA at all ages examined, and Foxi3CreER mice can trace the derivatives of pharyngeal arch ectoderm and endoderm, the pharyngeal pouches and clefts that separate each arch, and the derivatives of hair and tooth placodes.

CONCLUSIONS

Foxi3GFP and Foxi3CreER mice are new tools that will be of use in identifying and manipulating pharyngeal arch ectoderm and endoderm and hair and tooth placodes.

Conductive Hearing Loss in Children

A variety of congenital and acquired disorders result in pediatric conductive hearing loss. Malformations of the external auditory canal are invariably associated with malformations of the middle ear space and ossicles. Isolated ossicular malformations are uncommon. Syndromes associated with external and middle ear malformations are frequently associated with abnormal development of first and second pharyngeal arch derivatives. Chronic inflammatory disorders include cholesteatoma, cholesterol granuloma, and tympanosclerosis.

Craniofacial features of POLR3-related leukodystrophy caused by biallelic variants in POLR3A, POLR3B and POLR1C

BACKGROUND

RNA polymerase III-related or 4H leukodystrophy (POLR3-HLD) is an autosomal recessive hypomyelinating leukodystrophy characterized by neurological dysfunction, hypodontia and hypogonadotropic hypogonadism. The disease is caused by biallelic pathogenic variants in POLR3A, POLR3B, POLR1C or POLR3K. Craniofacial abnormalities reminiscent of Treacher Collins syndrome have been originally described in patients with POLR3-HLD caused by biallelic pathogenic variants in POLR1C. To date, no published studies have appraised in detail the craniofacial features of patients with POLR3-HLD. In this work, the specific craniofacial characteristics of patients with POLR3-HLD associated with biallelic pathogenic variants in POLR3A, POLR3B and POLR1C are described.

METHODS

The craniofacial features of 31 patients with POLR3-HLD were evaluated, and potential genotype-phenotype associations were evaluated.

RESULTS

Various craniofacial abnormalities were recognized in this patient cohort, with each individual presenting at least one craniofacial abnormality. The most frequently identified features included a flat midface (61.3%), a smooth philtrum (58.0%) and a pointed chin (51.6%). In patients with POLR3B biallelic variants, a thin upper lip was frequent. Craniofacial anomalies involving the forehead were most commonly associated with biallelic variants in POLR3A and POLR3B while a higher proportion of patients with POLR1C biallelic variants demonstrated bitemporal narrowing.

CONCLUSION

Through this study, we demonstrated that craniofacial abnormalities are common in patients with POLR3-HLD. This report describes in detail the dysmorphic features of POLR3-HLD associated with biallelic variants in POLR3A, POLR3B and POLR1C.

Auriculocondylar syndrome: Pathogenesis, clinical manifestations and surgical therapies

Auriculocondylar syndrome (ARCND) is a genetic and rare craniofacial condition caused by abnormal development of the first and second pharyngeal arches during the embryonic stage and is characterized by peculiar auricular malformations (question mark ears), mandibular condyle hypoplasia, micrognathia and other less-frequent features. GNAI3, PLCB4 and EDN1 have been identified as pathogenic genes in this syndrome so far, all of which are implicated in the EDN1-EDNRA signal pathway. Therefore, ARCND is genetically classified as ARCND1, ARCND2 and ARCND3 based on the mutations in GNAI3, PLCB4 and EDN1, respectively. ARCND is inherited in an autosomal dominant or recessive mode with significant intra- and interfamilial phenotypic variation and incomplete penetrance, rendering its diagnosis difficult and therapies individualized. To raise clinicians' awareness of the rare syndrome, we focused on the currently known pathogenesis, pathogenic genes, clinical manifestations and surgical therapies in this review.

The etiology, clinical features, and treatment options of hemifacial microsomia

The second most frequent craniomaxillofacial congenital deformity is hemifacial microsomia (HFM). Patients often accompany short mandible, ear dysplasia, facial nerve, and soft tissue dysplasia. The etiology of HFM is not fully understood. To organize the possible up-to-date information on the etiology, craniofacial phenotypes, and therapeutic alternatives in order to fully comprehend the HFM. Reviewing the potential causes, exploring the clinical features of HFM and summarizing the available treatment options. Vascular malformation, Meckel's cartilage abnormalities, and cranial neural crest cells (CNCCs) abnormalities are three potential etiology hypotheses. The commonly used clinical classification for HFM is OMENS, OMENS-plus, and SAT. Other craniofacial anomalies, like dental defects, and zygomatic deformities, are still not precisely documented in the classification. Patients with moderate phenotypes may not need any treatment from infancy through adulthood. However, patients with severe HFM require to undergo multiple surgeries to address facial asymmetries, such as mandibular distraction osteogenesis (MDO), autologous costochondral rib graft (CCG), orthodontic and orthognathic treatment, and facial soft tissue reconstruction. It is anticipated that etiology research will examine the pathogenic mechanism of HFM. A precise treatment for HFM may be possible with thoroughly documented phenotypes and a pathogenic diagnosis.

[TCOF1 Gene variation in Treacher Collins syndrome and evaluation of speech rehabilitation after bone bridge surgery]

Objective:By analyzing the clinical phenotypic characteristics and gene sequences of two patients with Treacher Collins syndrome（TCS）, the biological causes of the disease were determined. Then discuss the therapeutic effect of hearing intervention after bone bridge implantation. Methods:All clinical data of the two family members were collected, and the patients signed the informed consent. The peripheral blood of the proband and family members was extracted, DNA was extracted for whole exome sequencing, and Sanger sequencing was performed on the family members for the mutation site.TCOF1genetic mutations analysis was performed on the paitents. Then, the hearing threshold and speech recognition rate of family 2 proband were evaluated and compared under the sound field between bare ear and wearing bone bridge. Results:In the two pedigrees, the probands of both families presented with auricle deformity, zygomatic and mandibular hypoplasia, micrognathia, hypotropia of the eye fissure, and hypoplasia of the medial eyelashes. The proband of Family 1 also presents with specific features including right-sided narrow anterior nasal aperture and dental hypoplasia, which were consistent with the clinical diagnosis of Treacher Collins syndrome. Genetic testing was conducted on both families, and two heterozygous mutations were identified in the TCOF1 gene: c. 1350_1351dupGG（p. A451Gfs*43） and c. 4362_4366del（p. K1457Efs*12）, resulting in frameshift mutations in the amino acid sequence. Sanger sequencing validation of the TCOF1 gene in the parents of the proband in Family 1 did not detect any mutations. Proband 1 TCOF1 c. 1350_1351dupGG heterozygous variants have not been reported previously. The postoperative monosyllabic speech recognition rate of family 2 proband was 76%, the Categories of Auditory Performance（CAP） score was 6, and the Speech Intelligibility Rating（SIR） score was 4. Assessment using the Meaningful Auditory Integration Scale（MAIS） showed notable improvement in the patient's auditory perception, comprehension, and usage of hearing aids. Evaluation using the Glasgow Children's Benefit Inventory and quality of life assessment revealed significant improvements in the child's self care abilities, daily living and learning, social interactions, and psychological well being, as perceived by the parents. Conclusion:This study has elucidated the biological cause of Treacher Collins syndrome, enriched the spectrum of TCOF1 gene mutations in the Chinese population, and demonstrated that bone bridge implantation can improve the auditory and speech recognition rates in TCS patients.

AI-based diagnosis in mandibulofacial dysostosis with microcephaly using external ear shapes

Introduction

Mandibulo-Facial Dysostosis with Microcephaly (MFDM) is a rare disease with a broad spectrum of symptoms, characterized by zygomatic and mandibular hypoplasia, microcephaly, and ear abnormalities. Here, we aimed at describing the external ear phenotype of MFDM patients, and train an Artificial Intelligence (AI)-based model to differentiate MFDM ears from non-syndromic control ears (binary classification), and from ears of the main differential diagnoses of this condition (multi-class classification): Treacher Collins (TC), Nager (NAFD) and CHARGE syndromes.

Methods

The training set contained 1,592 ear photographs, corresponding to 550 patients. We extracted 48 patients completely independent of the training set, with only one photograph per ear per patient. After a CNN-(Convolutional Neural Network) based ear detection, the images were automatically landmarked. Generalized Procrustes Analysis was then performed, along with a dimension reduction using PCA (Principal Component Analysis). The principal components were used as inputs in an eXtreme Gradient Boosting (XGBoost) model, optimized using a 5-fold cross-validation. Finally, the model was tested on an independent validation set.

Results

We trained the model on 1,592 ear photographs, corresponding to 1,296 control ears, 105 MFDM, 33 NAFD, 70 TC and 88 CHARGE syndrome ears. The model detected MFDM with an accuracy of 0.969 [0.838-0.999] (p < 0.001) and an AUC (Area Under the Curve) of 0.975 within controls (binary classification). Balanced accuracies were 0.811 [0.648-0.920] (p = 0.002) in a first multiclass design (MFDM vs. controls and differential diagnoses) and 0.813 [0.544-0.960] (p = 0.003) in a second multiclass design (MFDM vs. differential diagnoses).

Conclusion

This is the first AI-based syndrome detection model in dysmorphology based on the external ear, opening promising clinical applications both for local care and referral, and for expert centers.

Vertebral Anomalies in Microtia Patients at a Tertiary Pediatric Care Center

OBJECTIVE

Microtia is a congenital condition known to be associated with vertebral anomalies and congenital syndromes, most prominently hemifacial microsomia. There is controversy, however, on whether to screen with spinal imaging. Additionally, microtia ear reconstruction utilizes rib harvesting that could potentially worsen pre-existing vertebral and rib anomalies, specifically scoliosis. We report on the prevalence and characteristics of vertebral anomalies among microtia patients at a tertiary pediatric center.

STUDY DESIGN

Retrospective case review with literature review.

SETTING

Tertiary pediatric referral center.

METHODS

A review of 425 children with microtia was conducted, characterized as either syndromic or nonsyndromic. Data included demographics, spinal imaging performed, indications, anomalies detected, and microtia repair.

RESULTS

Among 425 microtia patients, 24.5% were syndromic with an average age of 9.7 years. Only 18.4% of all patients had spinal imaging performed (50% syndromic vs 8.1% nonsyndromic). Overall, 10.6% had a vertebral anomaly with a 57.7% detection rate (67.3% syndromic vs 38.5% nonsyndromic). The most common anomaly was scoliosis, with a prevalence of 7.8%. Fusion defects and rib deformities were the next most prominent. Microtia repair, most commonly with an autologous rib graft, was performed in 21.6% of the cohort. However, only 19.2% had spinal imaging and 16.7% with a vertebral anomaly.

CONCLUSION

Children with microtia are at a greater risk of vertebral abnormalities. Scoliosis prevalence in isolated microtia is comparable to the general population (2%-3%) but greatly increased with genetic syndromes. Screening for vertebral anomalies should be considered when planning microtia reconstructions, especially in the syndromic population.

Obstructive Sleep Apnea in Adults with Treacher Collins Syndrome is Related with Altered Anthropometric Measurements, Increased Blood Pressure and Impaired Quality of Life

Objectives  This study aimed at evaluating the risk for obstructive sleep apnea (OSA) and its frequency in adults with Treacher Collins syndrome (TCS). The association of OSA with excessive daytime sleepiness (EDS), respiratory symptoms, and clinical variables was also assessed. Material and Methods  The subjects were prospectively screened for OSA through the Berlin Questionnaire and type I polysomnography. The Epworth Sleepiness Scale and the Respiratory Symptoms Questionnaire were used for assessing OSA-related symptoms. Quality of life was assessed by means of the Short Form 36 Health Survey. Results  The sample comprised 20 adults with TCS (55.0% female), aged 22.6 ± 5.8 years. Mean values of systemic blood pressure (113.0 ± 12.6/68.0 ± 9.5mmHg), body mass index (22.9 ± 5.9kg/m ² ), neck (34.1 ± 4.3cm), and waist circumference (80.4 ± 13.6cm) characterized the sample. A high risk for OSA was detected in 35% of the sample. Polysomnography results indicated an OSA frequency of 44.4%, with a median apnea-hypopnea index (AHI) value of 3.8 events/hour (minimum = 0.2; maximum = 77.5). Snoring (75.0%), nasal obstruction (70.0%) and EDS (20.0%) were the reported OSA-related symptoms. Quality of life median scores were 72.3 points (minimum = 45.0; maximum = 91.1). Strong positive correlations between AHI versus waist circumference and AHI versus systolic blood pressure were found. Moderate positive correlations between AHI versus body mass index and AHI versus neck circumference were detected. Negative correlation between AHI versus vitality were also observed. Conclusion  Adults with TCS are at high risk for OSA, which is associated with respiratory symptoms, altered anthropometric measurements, increased systolic pressure and impairment of quality of life.

Genetics and orofacial clefts: a clinical perspective

Orofacial clefts (OFCs) are the most common congenital craniofacial anomaly seen in humans. Most OFCs are sporadic and isolated - these are thought to be multifactorial in origin. Chromosomal and monogenic variants account for the syndromic forms and for some of the non-syndromic inherited forms. This review discusses the importance of genetic testing and the current clinical strategy to deliver a genomics service that is of direct benefit to patients and their families.

A biallelic variant in POLR2C is associated with congenital hearing loss and male infertility: Case report

BACKGROUND

DNA-directed RNA polymerase II subunit 3 (RPB3) is the third largest subunit of RNA polymerase II and is encoded by the POLR2C (OMIM:180663). A large Iranian family with congenital hearing loss and infertility is described here with genetic and clinical characterizations of five male patients.

METHODS

After doing clinical examinations, the proband was subjected to karyotyping and GJB2/6 sequencing to rule out the most evident chromosomal and gene abnormalities for male infertility and hearing loss, respectively. A custom-designed next-generation sequencing panel was also used to detect mutations in deafness-related genes. Finally, to reveal the underlying molecular cause(s) justifying hearing loss and male infertility, five male patients and 2 healthy male controls within the family were subjected to paired-end whole-exome sequencing (WES). Linkage analysis was also performed based on the data.

RESULTS

All male patients showed prelingual sensorineural hearing loss and also decreased sperm motility. Linkage analysis determined 16q21 as the most susceptible locus in which a missense variant in exon 7 of POLR2C-NM_032940.3:c.545T>C;p.(Val182Ala)-was identified as a 'likely pathogenic' variant co-segregated with phenotypes.

CONCLUSIONS

Using segregation and in silico analyses, for the first time, we suggested that the NM_032940.3:c.545T>C; p.(Val182Ala) in POLR2C is associated with hearing loss and male infertility.

Nucleolar stress: From development to cancer

The nucleolus is a large nuclear membraneless organelle responsible for ribosome biogenesis. Ribosomes are cytoplasmic macromolecular complexes comprising RNA and proteins that link amino acids together to form new proteins. The biogenesis of ribosomes is an intricate multistep process that involves the transcription of ribosomal DNA (rDNA), the processing of ribosomal RNA (rRNA), and the assembly of rRNA with ribosomal proteins to form active ribosomes. Nearly all steps necessary for ribosome production and maturation occur in the nucleolus. Nucleolar shape, size, and number are directly linked to ribosome biogenesis. Errors in the steps of ribosomal biogenesis are sensed by the nucleolus causing global alterations in nucleolar function and morphology. This phenomenon, known as nucleolar stress, can lead to molecular changes such as stabilization of p53, which in turn activates cell cycle arrest or apoptosis. In this review, we discuss recent work on the association of nucleolar stress with degenerative diseases and developmental defects. In addition, we highlight the importance of de novo nucleotide biosynthesis for the enhanced nucleolar activity of cancer cells and discuss targeting nucleotide biosynthesis as a strategy to activate nucleolar stress to specifically target cancer cells.

A Possible Incomplete Form of Treacher Collins Syndrome: A Case Report

Treacher Collins syndrome (TCS) is a rare genetic disorder that affects craniofacial development due to malformation of the first and second branchial arches. The TCOF1 gene is mainly responsible for this condition. Here, we present a case of a 13-year-old adolescent girl with complaints of maligned teeth with conductive deafness. On clinical examination, she had retrognathia, a broad nose, maligned teeth, a high arch palate, and midfacial hypoplasia. On the basis of the clinical findings, a diagnosis of a mild-variant TCS was made as eyes were not involved and supportive treatment was given to the patient. The symptoms of the disease have a varying range of severity. Early diagnosis and supportive treatments, which include multidisciplinary treatment involving pediatrics, otolaryngologists, audiologists, orthodontists, and psychologists, are very important for the management of such cases.