Treacher Collins syndrome: etiology, pathogenesis and prevention

Treacher Collins Syndrome Associated with Disproportionate Nervous System, Cardiovascular, Otologic Complications Among 1,114 Patients

OBJECTIVE

To compare the rates of selected nervous system, cardiovascular, and otologic abnormalities in patients with and without Treacher Collins Syndrome (TCS).

DESIGN

Retrospective TriNetX platform cohort study.

SETTING

Aggregated and deidentified electronic health record (EHR) data from across the United States.

PATIENTS, PARTICIPANTS

Patients with TCS (n = 1,114) and a propensity matched control cohort without TCS (n = 1,114 matched from n = 110,368,585).

MAIN OUTCOME MEASURED

Prevalence and relative risk (RR) of selected diagnoses in a propensity-matched cohort.

RESULTS

The RR of congenital malformations of the circulatory system in patients with TCS was 8.5 (95% CI 4.44-16.28). Patients with TCS also had higher rates of otologic abnormalities including conductive hearing loss (RR 44, 95% CI 24-83) and nervous system disorders including movement disorders (RR 2.60, 95% CI 1.27-5.50) and recurrent seizures (RR 4.2, 95% CI 2.12-8.33).

CONCLUSIONS

We found a significantly elevated risk in TCS patients within all three systems. We postulate that the nervous system effects may be the result of one of the TCS-linked genes, for which a mutation has also been associated with progressive ataxia, cerebellar atrophy, hypomyelination, and seizures. As the previously-identified causal genes influence neural crest cells that form the head and face, these cells may also populate cardiac structures, resulting in cardiovascular abnormalities. Finally, the characteristic craniofacial abnormalities identified in TCS impair hearing and are associated with increased risk of otitis media. Our findings may help researchers to hypothesize the function of the genes underlying TCS, as well as to inform the care of affected individuals.

Molecular and Clinical Heterogeneity in Hungarian Patients with Treacher Collins Syndrome-Identification of Two Novel Mutations by Next-Generation Sequencing

Treacher Collins syndrome (TCS) is a rare congenital craniofacial disorder with variable penetrance and high genetic and phenotypic heterogeneity. It is caused by pathogenic variants in the TCOF1, POLR1D, POLR1C, and POLR1B genes, and its major characteristic features are malar and mandibular hypoplasia, downward slanting of the palpebral fissures, and conductive hearing loss. In this study, five patients (two males and three females, age range from 2 to 29 years) with TCS were tested by Next-Generation Sequencing (NGS)-based sequencing and clinically characterized. Genetic analyses detected two deletions and one insertion in the TCOF1 gene and one missense variant in the POLR1D gene. Two novel mutations, c.1371_1372insT (p.Lys458*) in the TCOF1 gene and c.295 G>C (p.Gly99Arg) in the POLR1D gene, were identified. Moreover, two already known mutations, c.4369_4373del (p.Lys1457Glufs*12) and c.2103_2106del (p.Ser701Argfs*9) in the TCOF1 gene, were detected. The novel TCOF1 c.1371_1372insT mutation was associated with mild craniofacial manifestations and very rare symptoms of TCS, i.e., developmental delay and moderate intellectual disability. Although incomplete penetrance is a known phenomenon in TCS, surprisingly, the majority of our patients inherited the disease-causing variants from an asymptomatic mother. The unique feature of our study is the observation of causative mutation transmission between asymptomatic family members. Our results expanded the clinical and mutational spectrum of TCS and further confirmed the inter- and intra-familial variability of this disorder.

Treacher Collins syndrome: A comprehensive review on clinical features, diagnosis, and management

Treacher Collins syndrome is a rare genetic disorder that affects the bone development, resulting in significant craniofacial deformities. The syndrome is characterized by cleft palate, micrognathia, low-set or small ears, and sparse eyelashes. These characteristic symptoms guide for the diagnosis. However, the manifestations may resemble other diseases, which makes the clinical diagnosis difficult. Although the majority of cases are clearly diagnosed at birth, genetic counseling and imaging scans, such as x-ray or computed tomography, may help to confirm the diagnosis. The severity of the disease varies among patients, ranging from mild undiagnosed cases to severe marked deformities. Nevertheless, airway difficulty at birth represents a significant challenge for anesthesiologists since these patients have abnormal development of zygomatic arch, which may result in airway complications. Therefore, proper management requires multidisciplinary departments, including pediatrics, neurosurgery, otolaryngology, audiology, plastic surgery, and genetics. Hence, it can be inherited in an autosomal dominant manner; genetic counseling is also needed.

Potentials of ribosomopathy gene as pharmaceutical targets for cancer treatment

Ribosomopathies encompass a spectrum of disorders arising from impaired ribosome biogenesis and reduced functionality. Mutation or dysexpression of the genes that disturb any finely regulated steps of ribosome biogenesis can result in different types of ribosomopathies in clinic, collectively known as ribosomopathy genes. Emerging data suggest that ribosomopathy patients exhibit a significantly heightened susceptibility to cancer. Abnormal ribosome biogenesis and dysregulation of some ribosomopathy genes have also been found to be intimately associated with cancer development. The correlation between ribosome biogenesis or ribosomopathy and the development of malignancies has been well established. This work aims to review the recent advances in the research of ribosomopathy genes among human cancers and meanwhile, to excavate the potential role of these genes, which have not or rarely been reported in cancer, in the disease development across cancers. We plan to establish a theoretical framework between the ribosomopathy gene and cancer development, to further facilitate the potential of these genes as diagnostic biomarker as well as pharmaceutical targets for cancer treatment.

A Novel Missense Variant in the TCOF1 Gene in one Chinese Case With Treacher Collins Syndrome

The purpose of this study is to analyze the clinical characteristics of a Treacher Collins syndrome (TCS) patient carrying a de novo variant of TCOF1, and briefly analyze the correlation between genetic results and clinical features. Also, the pathogenesis and clinical treatment of TCS are reviewed.

A Chinese pedigree with TCS containing 8 members was enrolled. Phenotype of the proband was evaluated by a surgeon, then whole exome sequencing of the proband was performed. Then we verified the proband-derived variants by Sanger sequencing in the pedigree. Correlation between genotype and phenotype was analyzed.

The study was conducted in a stomatological hospital.

A Chinese pedigree with TCS containing 8 members.

To ascertain the genetic variants in the Chinese pedigree with TCS.

Blood samples were collected.

We reported a case of typical TCS with a de novo missense variant (NM_001371623.1:c.38T>G, p.(Leu13Arg)) in exon 1 of TCOF1, who presented asymmetrical facial abnormalities, including downward slanting of the palpebral fissures, sparse eyebrows, lateral tilt of the eyeballs, bilateral external ears deformities, hypoplasia of midface, reduction of the zygomatic body, bilateral orbital invagination, right external auditory canal atresia, mandibular ramus short deformity, cleft palate and the whole face was convex.

This research found a novel variant of TCS in Chinese, expanding the spectrum of TCS pathogenic variants. Genetic results combined with clinical phenotype can make a definite diagnosis and provide genetic counseling for the family.

Severity of Mandibular Dysmorphology in Treacher Collins Syndrome for Stratification of Perioperative Airway Risk

BACKGROUND

Patients with Treacher Collins syndrome (TCS) and attendant airway dysmorphology may be predisposed to airway complications in the perioperative period. However, limited data correlates severity of mandibular hypoplasia and airway status. This study aims to improve risk stratification for perioperative airway insufficiency in TCS by using a previously proposed mandibular severity index.

METHODS

Patient demographics, perioperative airway status, difficulty of intubation, and Cormack Lehane grade were collected and compared using a TCS mandibular hypoplasia severity grading scale in patients with TCS treated between 2000 and 2022.

RESULTS

Twenty-six patients underwent 222 procedures with institutional mandibular severity gradings as follows: 23% Grade I, 31% Grade II, 39% Grade III, 8% Grade IV. Our severity index was associated with intubation difficulty ( P <0.001) and difficult airway status ( P <0.001), with 72% of difficult airways found in grade III and grade IV patients. Mandibular retrusion and ramal hypoplasia subscores were positively correlated with measures of airway severity ( P <0.001), whereas the gonial angle was negatively correlated ( P <0.001). Age was negatively correlated with difficult visualization for endotracheal intubation ( P =0.02) but had no association with difficult airway status ( P =0.2).

CONCLUSIONS

This study found a positive correlation between severity of maxillomandibular dysmorphology and perioperative airway difficulty in TCS patients. Our findings suggest that severely affected patients require heightened vigilance throughout life, as difficult airways may not completely resolve with aging. Given the risk of morbidity and mortality associated with airway complications, proper identification and preparation for challenging airways is critical for TCS patients.

The application of three-dimensional printing in the management of a difficult airway due to Treacher Collins syndrome

We describe the use of three-dimensional printing to create precise airway models for a patient with Treacher Collins syndrome who presented for bimaxillary temporomandibular joint prostheses, and for whom airway management was predicted to be difficult. The model was based on pre-operative cone beam computed tomography images and printed in the 3D Lab of Hospital Universitario La Paz. Transparent models allowed clear visualisation for simulation and iterative refinement of airway management techniques and aided in risk assessment and instrument sizing. This case report emphasises the utility of this approach in complex airway scenarios.

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.

rRNA transcription is integral to phase separation and maintenance of nucleolar structure

Transcription of ribosomal RNA (rRNA) by RNA Polymerase (Pol) I in the nucleolus is necessary for ribosome biogenesis, which is intimately tied to cell growth and proliferation. Perturbation of ribosome biogenesis results in tissue specific disorders termed ribosomopathies in association with alterations in nucleolar structure. However, how rRNA transcription and ribosome biogenesis regulate nucleolar structure during normal development and in the pathogenesis of disease remains poorly understood. Here we show that homozygous null mutations in Pol I subunits required for rRNA transcription and ribosome biogenesis lead to preimplantation lethality. Moreover, we discovered that Polr1a-/-, Polr1b-/-, Polr1c-/- and Polr1d-/- mutants exhibit defects in the structure of their nucleoli, as evidenced by a decrease in number of nucleolar precursor bodies and a concomitant increase in nucleolar volume, which results in a single condensed nucleolus. Pharmacological inhibition of Pol I in preimplantation and midgestation embryos, as well as in hiPSCs, similarly results in a single condensed nucleolus or fragmented nucleoli. We find that when Pol I function and rRNA transcription is inhibited, the viscosity of the granular compartment of the nucleolus increases, which disrupts its phase separation properties, leading to a single condensed nucleolus. However, if a cell progresses through mitosis, the absence of rRNA transcription prevents reassembly of the nucleolus and manifests as fragmented nucleoli. Taken together, our data suggests that Pol I function and rRNA transcription are required for maintaining nucleolar structure and integrity during development and in the pathogenesis of disease.

The coordinated management of ribosome and translation during injury and regeneration

Diverse acute and chronic injuries induce damage responses in the gastrointestinal (GI) system, and numerous cell types in the gastrointestinal tract demonstrate remarkable resilience, adaptability, and regenerative capacity in response to stress. Metaplasias, such as columnar and secretory cell metaplasia, are well-known adaptations that these cells make, the majority of which are epidemiologically associated with an elevated cancer risk. On a number of fronts, it is now being investigated how cells respond to injury at the tissue level, where diverse cell types that differ in proliferation capacity and differentiation state cooperate and compete with one another to participate in regeneration. In addition, the cascades or series of molecular responses that cells show are just beginning to be understood. Notably, the ribosome, a ribonucleoprotein complex that is essential for translation on the endoplasmic reticulum (ER) and in the cytoplasm, is recognized as the central organelle during this process. The highly regulated management of ribosomes as key translational machinery, and their platform, rough endoplasmic reticulum, are not only essential for maintaining differentiated cell identity, but also for achieving successful cell regeneration after injury. This review will cover in depth how ribosomes, the endoplasmic reticulum, and translation are regulated and managed in response to injury (e.g., paligenosis), as well as why this is essential for the proper adaptation of a cell to stress. For this, we will first discuss how multiple gastrointestinal organs respond to stress through metaplasia. Next, we will cover how ribosomes are generated, maintained, and degraded, in addition to the factors that govern translation. Finally, we will investigate how ribosomes and translation machinery are dynamically regulated in response to injury. Our increased understanding of this overlooked cell fate decision mechanism will facilitate the discovery of novel therapeutic targets for gastrointestinal tract tumors, focusing on ribosomes and translation machinery.

Molecular etiology of defective nuclear and mitochondrial ribosome biogenesis: Clinical phenotypes and therapy

Ribosomopathies are rare congenital disorders associated with defective ribosome biogenesis due to pathogenic variations in genes that encode proteins related to ribosome function and biogenesis. Defects in ribosome biogenesis result in a nucleolar stress response involving the TP53 tumor suppressor protein and impaired protein synthesis leading to a deregulated translational output. Despite the accepted notion that ribosomes are omnipresent and essential for all cells, most ribosomopathies show tissue-specific phenotypes affecting blood cells, hair, spleen, or skin. On the other hand, defects in mitochondrial ribosome biogenesis are associated with a range of clinical manifestations affecting more than one organ. Intriguingly, the deregulated ribosomal function is also a feature in several human malignancies with a selective upregulation or downregulation of specific ribosome components. Here, we highlight the clinical conditions associated with defective ribosome biogenesis in the nucleus and mitochondria with a description of the affected genes and the implicated pathways, along with a note on the treatment strategies currently available for these disorders.

Comprehensive Serial Treatment of Treacher Collins Syndrome

OBJECTIVE

To discuss and summarize the comprehensive serial surgical treatment of Treacher Collins syndrome.

MATERIALS AND METHODS

From September 2012 to January 2020, 12 patients with Treacher Collins syndrome were treated by autologous fat graft, mandibular distraction osteogenesis, orbitozygomatic reconstruction with calvarial external lamina, orthognathic surgery combined with postoperative orthodontics, transplantation of upper eyelid orbicularis myocutaneous flap, lateral canthal ligament reduction, and other methods. The authors evaluated the postoperative improvement, summarized experiences, and reviewed literatures about the comprehensive serial treatment of Treacher Collins syndrome.

RESULTS

All patients showed significant improvement in appearance and function, and no complications were found during the follow-up period of 5 months to 3 years.

CONCLUSIONS

The deformities of Treacher Collins syndrome involves multiple craniofacial region, and only by formulating comprehensive serial treatment strategies according to the malformation characteristics of different patients can the best effect be achieved.

Comparative Research: Regulatory Mechanisms of Ribosomal Gene Transcription in Saccharomyces cerevisiae and Schizosaccharomyces pombe

Restricting ribosome biosynthesis and assembly in response to nutrient starvation is a universal phenomenon that enables cells to survive with limited intracellular resources. When cells experience starvation, nutrient signaling pathways, such as the target of rapamycin (TOR) and protein kinase A (PKA), become quiescent, leading to several transcription factors and histone modification enzymes cooperatively and rapidly repressing ribosomal genes. Fission yeast has factors for heterochromatin formation similar to mammalian cells, such as H3K9 methyltransferase and HP1 protein, which are absent in budding yeast. However, limited studies on heterochromatinization in ribosomal genes have been conducted on fission yeast. Herein, we shed light on and compare the regulatory mechanisms of ribosomal gene transcription in two species with the latest insights.

Gene-environment interactions in the pathogenesis of common craniofacial anomalies

Craniofacial anomalies often exhibit phenotype variability and non-mendelian inheritance due to their multifactorial origin, involving both genetic and environmental factors. A combination of epidemiologic studies, genome-wide association, and analysis of animal models have provided insight into the effects of gene-environment interactions on craniofacial and brain development and the pathogenesis of congenital disorders. In this chapter, we briefly summarize the etiology and pathogenesis of common craniofacial anomalies, focusing on orofacial clefts, hemifacial microsomia, and microcephaly. We then discuss how environmental risk factors interact with genes to modulate the incidence and phenotype severity of craniofacial anomalies. Identifying environmental risk factors and dissecting their interaction with different genes and modifiers is central to improved strategies for preventing craniofacial anomalies.

Dynamic regulation and requirement for ribosomal RNA transcription during mammalian development

Ribosomal RNA (rRNA) transcription by RNA polymerase I (Pol I) is a critical rate-limiting step in ribosome biogenesis, which is essential for cell survival. Despite its global function, disruptions in ribosome biogenesis cause tissue-specific birth defects called ribosomopathies, which frequently affect craniofacial development. Here, we describe a cellular and molecular mechanism underlying the susceptibility of craniofacial development to disruptions in Pol I transcription. We show that Pol I subunits are highly expressed in the neuroepithelium and neural crest cells (NCCs), which generate most of the craniofacial skeleton. High expression of Pol I subunits sustains elevated rRNA transcription in NCC progenitors, which supports their high tissue-specific levels of protein translation, but also makes NCCs particularly sensitive to rRNA synthesis defects. Consistent with this model, NCC-specific deletion of Pol I subunits Polr1a, Polr1c, and associated factor Tcof1 in mice cell-autonomously diminishes rRNA synthesis, which leads to p53 protein accumulation, resulting in NCC apoptosis and craniofacial anomalies. Furthermore, compound mutations in Pol I subunits and associated factors specifically exacerbate the craniofacial anomalies characteristic of the ribosomopathies Treacher Collins syndrome and Acrofacial Dysostosis-Cincinnati type. Mechanistically, we demonstrate that diminished rRNA synthesis causes an imbalance between rRNA and ribosomal proteins. This leads to increased binding of ribosomal proteins Rpl5 and Rpl11 to Mdm2 and concomitantly diminished binding between Mdm2 and p53. Altogether, our results demonstrate a dynamic spatiotemporal requirement for rRNA transcription during mammalian cranial NCC development and corresponding tissue-specific threshold sensitivities to disruptions in rRNA transcription in the pathogenesis of congenital craniofacial disorders.

Global ubiquitinome profiling identifies NEDD4 as a regulator of Profilin 1 and actin remodelling in neural crest cells

The ubiquitin ligase NEDD4 promotes neural crest cell (NCC) survival and stem-cell like properties to regulate craniofacial and peripheral nervous system development. However, how ubiquitination and NEDD4 control NCC development remains unknown. Here we combine quantitative analysis of the proteome, transcriptome and ubiquitinome to identify key developmental signalling pathways that are regulated by NEDD4. We report 276 NEDD4 targets in NCCs and show that loss of NEDD4 leads to a pronounced global reduction in specific ubiquitin lysine linkages. We further show that NEDD4 contributes to the regulation of the NCC actin cytoskeleton by controlling ubiquitination and turnover of Profilin 1 to modulate filamentous actin polymerization. Taken together, our data provide insights into how NEDD4-mediated ubiquitination coordinates key regulatory processes during NCC development.

Here the authors combine multi-omics approaches to uncover a role for ubiquitination and the ubiquitin ligase NEDD4 in targeting the actin binding protein Profilin 1 to regulate actin polymerisation in neural crest cells.

The transcription factor Xrp1 orchestrates both reduced translation and cell competition upon defective ribosome assembly or function

Ribosomal Protein (Rp) gene haploinsufficiency affects translation rate, can lead to protein aggregation, and causes cell elimination by competition with wild type cells in mosaic tissues. We find that the modest changes in ribosomal subunit levels observed were insufficient for these effects, which all depended on the AT-hook, bZip domain protein Xrp1. Xrp1 reduced global translation through PERK-dependent phosphorylation of eIF2α. eIF2α phosphorylation was itself sufficient to enable cell competition of otherwise wild type cells, but through Xrp1 expression, not as the downstream effector of Xrp1. Unexpectedly, many other defects reducing ribosome biogenesis or function (depletion of TAF1B, eIF2, eIF4G, eIF6, eEF2, eEF1α1, or eIF5A), also increased eIF2α phosphorylation and enabled cell competition. This was also through the Xrp1 expression that was induced in these depletions. In the absence of Xrp1, translation differences between cells were not themselves sufficient to trigger cell competition. Xrp1 is shown here to be a sequence-specific transcription factor that regulates transposable elements as well as single-copy genes. Thus, Xrp1 is the master regulator that triggers multiple consequences of ribosomal stresses and is the key instigator of cell competition.

TCOF1 upregulation in triple-negative breast cancer promotes stemness and tumour growth and correlates with poor prognosis

BACKGROUND

Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with poor prognosis. By performing multiomic profiling, we recently uncovered super-enhancer heterogeneity between breast cancer subtypes. Our data also revealed TCOF1 as a putative TNBC-specific super-enhancer-regulated gene. TCOF1 plays a critical role in craniofacial development but its function in cancer remains unclear.

METHODS

Overall survival and multivariant Cox regression analyses were conducted using the METABRIC data set. The effect of TCOF1 knockout on TNBC growth and stemness was evaluated by in vitro and in vivo assays. RNA-seq and rescue experiments were performed to explore the underlying mechanisms.

RESULTS

TCOF1 is frequently upregulated in TNBC and its elevated expression correlates with shorter overall survival. TCOF1 depletion significantly inhibits the growth and stemness of basal-like TNBC, but not of mesenchymal-like cells, highlighting the distinct molecular dependency in different TNBC subgroups. RNA-seq uncovers several stem cell molecules regulated by TCOF1. We further demonstrate that KIT is a downstream effector of TCOF1 in mediating TNBC stemness. TCOF1 expression in TNBC is regulated by the predicted super-enhancer.

CONCLUSIONS

TCOF1 depletion potently attenuates the growth and stemness of basal-like TNBC. Expression of TCOF1 may serve as a TNBC prognostic marker and a therapeutic target.

A Novel Method for Quantitative Three-Dimensional Analysis of Zygomatico-Maxillary Complex Symmetry

To develop a reliable and accurate method to quantify the symmetry of the zygomaticomaxillary complex (ZMC).

Disability in a medieval village community: A unique case of facial dysmorphism

OBJECTIVE

To identify the pathology causing the severe facial dysmorphia of a medieval individual from the site of Rigny (Indre-et-Loire, France) and to evaluate its functional repercussions on the subject's hearing and social life.

MATERIALS

An individual from Rigny for the osteological study, 69 individuals from the region for the Ct-Scan study and 48 individuals from the site for the isotopic analysis.

METHODS

Macroscopic analysis was performed using standard osteological methods. Consequences of pathology on hearing were assessed by CT-scan. Dietary behaviour was analysed by stable carbon and nitrogen isotope analysis of bone collagen.

RESULTS

The individual is a woman who was over 50 years of age at the time of her death with a severe form of Treacher-Collins syndrome that resulted in deafness. No osteological signs of maltreatment were observed and there is no evidence that this individual's diet was different from that of the rest of the community.

CONCLUSIONS

All information testifies to the integration of this individual into the village population.

SIGNIFICANCE

This study is the first archaeological description of Treacher Collins syndrome. It shows the ability of the paleopathological approach to help identify the attitudes of societies for which written sources are most often lacking.

LIMITATIONS

In the absence of palaeogenomic analysis it is not possible to identify the origin of this case.

SUGGESTIONS FOR FURTHER RESEARCH

Increase the paleopathological semiology by CT-scan in order to specify the consequences of pathologies and integrate isotopic analyses to enrich discussion about perceptions of disease.

Anesthetic Management of Treacher Collins Syndrome in an Outpatient Surgical Center

Patient: Male, 15-year-old

Final Diagnosis: Treacher Collins syndrome

Symptoms: Difficult airway management

Medication:—

Clinical Procedure: —

Specialty: Anesthesiology

Description of Total Population Hospital Admissions for Treacher Collins Syndrome in Australia

OBJECTIVE

To describe patterns and demographic characteristics of total-population hospital admissions with a diagnosis of Treacher Collins syndrome (TCS) in Australia.

DATA SOURCE

Population summary data for inpatient hospitals admissions (public and private) with a principal diagnosis of TCS (ICD10-AM-Q87.04) were obtained from the Australian Institute of Health and Welfare National Hospital Morbidity Database for a 11-year period (2002-2013).

MAIN OUTCOME MEASURES

The primary outcome was hospital separation rate (HSR), calculated by dividing the number of hospital separations by estimated resident population per year. Trends in HSR s adjusted for age and sex were investigated by negative binomial regression presented as annual percent change and the association of rates with age and sex was expressed as incidence rate ratio.

RESULTS

In 244 admissions identified, we observed an increase of 4.55% (95% confidence interval [CI] -1.78, 11.29) in HSR's over the 11-year period. Rates were higher during infancy (1.87 [95% CI 1.42, 2.42]), declining markedly with increasing age. The average length of hospital stay was 6.09 days (95% CI 5.78, 6.40) per episode, but longer for females and infants.

CONCLUSIONS

Findings indicate an increase in hospitalization rates, especially among infants and females which potentially relates to early airway intervention procedures possibly influenced by sex specific-disease severity and phenotypic variability of TCS. Awareness of the TCS phenotype and improved access to genetic testing may support more personalized and efficient care. Total-population administrative data offers a potential to better understand the health burden of rare craniofacial diseases.

Phenotype Analysis and Genetic Study of Chinese Patients With Treacher Collins Syndrome

OBJECTIVE

The aim of this study was to confirm the pathogenic variants, explore the genotype-phenotype correlation and characteristics of Chinese patients with Treacher Collins syndrome (TCS).

DESIGN

Clinical details of 3 TCS family cases and 2 sporadic cases were collected and analyzed. Whole-exome sequencing and Sanger sequencing were conducted to detect causative variants.

SETTING

Tertiary clinical care.

PATIENTS

This study included 8 patients clinically diagnosed with TCS who were from 3 familial cases and 2 sporadic cases.

MAIN OUTCOME MEASURES

When filtering the database, variants were saved as rare variants if their frequency were less than 0.005 in the 1000 Genomes Project Database, the Exome Aggregation Consortium (ExAC) browser, and the Novogene database, or they would be removed as common ones. The pathogenic variants identified were verified by polymerase chain reaction. The sequencing results were analyzed by Chromas 2.1 software.

RESULTS

Two novel pathogenic variants (NM_000356.3: c.537del and NM_000356.3: c.1965_1966dupGG) and 2 known pathogenic variants (NM_000356.3: c.1535del, NM_000356.3: c.4131_4135del) were identified within TCOF1 which are predicted to lead to premature termination codons resulting in a truncated protein. There was a known missense SNP (NM_015972.3: c.139G>A) within POLR1D. No phenotype-genotype correlation was observed. Instead, these 8 patients demonstrated the high genotypic and phenotypic heterogeneity of TCS.

CONCLUSIONS

This study expands on the pathogenic gene pool of Chinese patients with TCS. Besides the great variation among patients which is similar to international reports, Chinese patients have their own characteristics in clinical phenotype and pathogenesis mutations.

De novo TCOF1 mutation in Treacher Collins syndrome

OBJECTIVE

To analyze the genetic cause of a hearing loss child with the Treacher Collins syndrome (TCS) phenotypes of malar hypoplasia, micrognathia, antimongoloid slanting palpebral fissures and cup ears.

METHODS

Clinical analysis, hearing tests, chromosomal microarray analysis (CMA) and whole exome sequencing (WES) were performed on the family members.

RESULTS

The 6 months old boy with a range of Treacher Collins syndrome phenotypes including malar hypoplasia, micrognathia, antimongoloid slanting palpebral fissures, cup ears, and hearing loss. While CMA analyses did not detect significant deletion or duplication, WES analysis identified a novel nonsense mutation c.163C > T (p.Q55X) in exon 2 of TCOF1 gene. Sanger sequencing analysis confirmed the mutation in the patient, but not in his parents.

CONCLUSION

This article reports a novel nonsense mutation located at exon 2 in TCOF1 gene, which predicts premature protein termination of treacle, indicating that haploinsufficiency of TCOF1 gene is responsible for Treacher Collins syndrome. Our study increases the cohort of Chinese TCS patients, and expands the TCS variation spectrum.

The exon-junction complex helicase eIF4A3 controls cell fate via coordinated regulation of ribosome biogenesis and translational output

Eukaryotic initiation factor 4A-III (eIF4A3), a core helicase component of the exon junction complex, is essential for splicing, mRNA trafficking, and nonsense-mediated decay processes emerging as targets in cancer therapy. Here, we unravel eIF4A3's tumor-promoting function by demonstrating its role in ribosome biogenesis (RiBi) and p53 (de)regulation. Mechanistically, eIF4A3 resides in nucleoli within the small subunit processome and regulates rRNA processing via R-loop clearance. EIF4A3 depletion induces cell cycle arrest through impaired RiBi checkpoint-mediated p53 induction and reprogrammed translation of cell cycle regulators. Multilevel omics analysis following eIF4A3 depletion pinpoints pathways of cell death regulation and translation of alternative mouse double minute homolog 2 (MDM2) transcript isoforms that control p53. EIF4A3 expression and subnuclear localization among clinical cancer specimens correlate with the RiBi status rendering eIF4A3 an exploitable vulnerability in high-RiBi tumors. We propose a concept of eIF4A3's unexpected role in RiBi, with implications for cancer pathogenesis and treatment.

Augmented BMP4 signal impairs tongue myogenesis

Tongue muscles are derived from mesodermal cells, while signals driven by cranial neural crest cells (CNCCs) regulate tongue myogenesis via tissue-tissue interaction. Based on such mechanisms of interaction, congenital tongue defects occur in CNC-related syndromes in humans. This study utilized a pathologic model for the syndrome of congenital bony syngnathia, Wnt1-Cre;pMes-Bmp4 mouse line, to explore impacts of enhanced CNCCs-originated BMP4 signal on tongue myogenesis via tissue-tissue interaction. Our results revealed that microglossia, a clinical phenotype of congenital bony syngnathia in humans exhibited in Wnt1-Cre;pMes-Bmp4 mice due to impaired myogenesis. The augmented BMP4 signal affected the distal distribution, proliferation, and differentiation of myogenic cells as well as tendon patterning, resulting in disarrangement and atrophy of tongue muscles and the loss of the anterior digastric muscle. This study demonstrated how a CNCCs-originated ligand impaired tongue myogenesis via a non-autonomous way, which provided potential formation mechanisms for understanding tongue abnormalities in CNC-related syndromes.

Diabetes, Oxidative Stress, and DNA Damage Modulate Cranial Neural Crest Cell Development and the Phenotype Variability of Craniofacial Disorders

Craniofacial malformations are among the most common birth defects in humans and they often have significant detrimental functional, aesthetic, and social consequences. To date, more than 700 distinct craniofacial disorders have been described. However, the genetic, environmental, and developmental origins of most of these conditions remain to be determined. This gap in our knowledge is hampered in part by the tremendous phenotypic diversity evident in craniofacial syndromes but is also due to our limited understanding of the signals and mechanisms governing normal craniofacial development and variation. The principles of Mendelian inheritance have uncovered the etiology of relatively few complex craniofacial traits and consequently, the variability of craniofacial syndromes and phenotypes both within families and between families is often attributed to variable gene expression and incomplete penetrance. However, it is becoming increasingly apparent that phenotypic variation is often the result of combinatorial genetic and non-genetic factors. Major non-genetic factors include environmental effectors such as pregestational maternal diabetes, which is well-known to increase the risk of craniofacial birth defects. The hyperglycemia characteristic of diabetes causes oxidative stress which in turn can result in genotoxic stress, DNA damage, metabolic alterations, and subsequently perturbed embryogenesis. In this review we explore the importance of gene-environment associations involving diabetes, oxidative stress, and DNA damage during cranial neural crest cell development, which may underpin the phenotypic variability observed in specific craniofacial syndromes.

The Ribosomal Gene Loci-The Power behind the Throne

Nucleoli form around actively transcribed ribosomal RNA (rRNA) genes (rDNA), and the morphology and location of nucleolus-associated genomic domains (NADs) are linked to the RNA Polymerase I (Pol I) transcription status. The number of rDNA repeats (and the proportion of actively transcribed rRNA genes) is variable between cell types, individuals and disease state. Substantial changes in nucleolar morphology and size accompanied by concomitant changes in the Pol I transcription rate have long been documented during normal cell cycle progression, development and malignant transformation. This demonstrates how dynamic the nucleolar structure can be. Here, we will discuss how the structure of the rDNA loci, the nucleolus and the rate of Pol I transcription are important for dynamic regulation of global gene expression and genome stability, e.g., through the modulation of long-range genomic interactions with the suppressive NAD environment. These observations support an emerging paradigm whereby the rDNA repeats and the nucleolus play a key regulatory role in cellular homeostasis during normal development as well as disease, independent of their role in determining ribosome capacity and cellular growth rates.

Negative Pressure Pulmonary Edema Related to Laryngospasm and Upper Airway Obstruction in a Patient With Treacher Collins Syndrome

Laryngospasm is an uncommon complication of anesthesia in adults but more common in pediatric anesthesia, which could present similarly to supraglottic upper airway obstruction. The management of such airway complications is even more difficult in patients with difficult mask ventilation and intubation. Our case illustrated the management of laryngospasm and negative pressure pulmonary edema in a patient with Treacher Collins syndrome. A literature search revealed few previous similar reports. We demonstrated an algorithm to differentiate between the true laryngospasm from the supraglottic upper airway obstruction, the management of laryngospasm in patients with difficult airways, and the recognition and management of negative pressure pulmonary edema as a complication of laryngospasm.

Treacher Collins syndrome: Orthodontic treatment with mandibular distraction osteogenesis and orthognathic surgery

Interdisciplinary treatment for patients with Treacher Collins syndrome is challenging because of the rarity of the condition and the wide variety of phenotypic expression. A 23-year-old male was diagnosed with Treacher Collins syndrome with a history of severe obstructive sleep apnea. He presented with a Pruzansky-Kaban classification grade I mandible, skeletal type II pattern with a hyperdivergent mandibular plane, severe convex profile, and Class II malocclusion with a missing mandibular incisor. Improvement of facial esthetics was achieved by a combination of orthodontics, mandibular distraction osteogenesis, and 2-jaw maxillomandibular advancement surgery. Presurgical orthodontic treatment involved permanent tooth extraction to relieve severe crowding, and Class III mechanics were employed to increase overjet. Correction of mandibular hypoplasia by increasing ramal height and the mandibular length was done by intraoral mandibular distraction osteogenesis. Counterclockwise rotation of the mandibular plane angle and a Class III occlusion with negative overjet were achieved after mandibular distraction osteogenesis. A postdistraction posterior open bite was maintained with a biteplane during the consolidation period. Subsequently, 2-jaw orthognathic surgery was performed. LeFort I osteotomy was done for maxillary advancement to correct an anterior crossbite, eliminate canting, and reestablish occlusal contact at the mandibular occlusal plane. Bilateral sagittal split ramus osteotomy was done to correct the residual mandibular deviation. A genioplasty was also performed to improve chin projection. Postoperatively, the oropharyngeal airway was enlarged. The patient's facial profile and obstructive sleep apnea problem were improved as a result of advancement and counterclockwise rotation of the maxillomandibular complex.

Treacher Collins Syndrome in the United States: Examining Incidence and Inpatient Interventions

OBJECTIVE

Advancements have been made in the care of patients with Treacher Collins syndrome (TCS), but epidemiological data are lacking given its rarity. A national database provides a valuable opportunity for studying the incidence of rare craniofacial conditions. We sought to evaluate disease incidence of phenotypically severe cases and the frequency of the most common associated diagnoses and interventions.

DESIGN

The 2016 Kids' Inpatient Database (KID), Healthcare Cost and Utilization Project, Agency for Healthcare Research and Quality was the first version to include updated International Classification of Diseases-Tenth Edition (ICD-10) coding encompassing a unique code for TCS. The 2016 KID was queried for the unique code. Incidence was calculated using national estimates. Diagnosis and procedure codes were pooled and analyzed.

PATIENTS

A total of 266 discharge cases with a diagnosis code for TCS (Q75.4).

MAIN OUTCOMES

Disease incidence and the most frequent diagnosis and procedure codes.

RESULTS

The estimated incidence of children born with a diagnosis of TCS was approximately 1 in 80,000. Two of the three most common ICD-10 diagnosis codes were tracheostomy status and obstructive sleep apnea. The most common procedures performed were airway examination procedures.

CONCLUSIONS

Treacher Collins syndrome is a rare craniofacial disorder requiring complex multidisciplinary management. Phenotypically severe cases requiring inpatient management may be rarer than previous estimates suggest. Inpatient airway interventions are very common, and multidisciplinary team members should anticipate the degree of potential airway risk these patients pose.

Extracraniofacial anomalies in Treacher Collins syndrome: A multicentre study of 248 patients

Treacher Collins syndrome (TCS) is a congenital malformation of the craniofacial structures derived from the first and second pharyngeal arches. The craniofacial deformities are well described in the literature. However, little is known about whether there are associated extracraniofacial anomalies. A retrospective study was conducted using data from four craniofacial units. Medical charts were reviewed for the presence and type of extracraniofacial anomalies, as well as age at diagnosis. A possible correlation between the severity of the phenotype and the presence of extracraniofacial anomalies was assessed using the Hayashi classification. A total of 248 patients with TCS were identified; 240 were confirmed to have TCS, of whom 61 (25.4%) were diagnosed with one or more extracraniofacial anomalies. Ninety-five different extracraniofacial anomalies were found; vertebral (n=32) and cardiac (n=13) anomalies were most frequently seen, followed by reproductive system (n=11), central nervous system (n=7), and limb (n=7) anomalies. No correlations between tracts were found. Extracraniofacial anomalies were more prevalent in these patients with TCS compared to the general population (25.4% vs 0.001-2%, respectively). Furthermore, a positive trend was seen between the severity of the syndrome and the presence of extracraniofacial anomalies. A full clinical examination should be performed on any new TCS patient to detect any extracraniofacial anomalies on first encounter with the craniofacial team.

Genetic Disorders of Bone or Osteodystrophies of Jaws-A Review

Bone is a specialized form of connective tissue, which is mineralized and made up of approximately 28% type I collagen and 5% noncollagenous matrix proteins. The properties of bone are very remarkable, because it is a dynamic tissue, undergoing constant renewal in response to mechanical, nutritional, and hormonal influences. In 1978, "The International Nomenclature of Constitutional Diseases of Bone" divided bone disorders into two broad groups: osteochondrodysplasias and dysostoses. The osteochondrodysplasia group is further subdivided into two categories: dysplasias (abnormalities of bone and/or cartilage growth) and osteodystrophies (abnormalities of bone and/or cartilage texture). The dysplasias form the largest group of bone disorders, hence the loose term "skeletal dysplasia" that is often incorrectly used when referring to a condition that is in reality an osteodystrophy or dysostosis. The word "dystrophy" implies any condition of abnormal development. "Osteodystrophies," as their name implies, are disturbances in the growth of bone. It is also known as osteodystrophia. It includes bone diseases that are neither inflammatory nor neoplastic but may be genetic, metabolic, or of unknown origin. Recent studies have shown that bone influences the activity of other organs, and the bone is also influenced by other organs and systems of the body, providing new insights and evidencing the complexity and dynamic nature of bone tissue. The 1,25-dihydroxyvitamin D3, or simply vitamin D, in association with other hormones and minerals, is responsible for mediating the intestinal absorption of calcium, which influences plasma calcium levels and bone metabolism. Diagnosis of the specific osteodystrophy type is a rather complex process and various biochemical markers and radiographic findings are used, so as to facilitate this condition. For diagnosis, we must consider the possibility of lesions related to bone metabolism altered by chronic renal failure (CRI), such as the different types of osteodystrophies, and differentiate from other possible neoplastic and/or inflammatory pathologies. It is important that the dentist must be aware of patients medical history, suffering from any systemic diseases, and identify the interference of the drugs and treatments to control them, so that we can able to perform the correct diagnosis and propose the most adequate treatment and outcomes of the individuals with bone lesions.

The Role of TCOF1 Gene in Health and Disease: Beyond Treacher Collins Syndrome

The nucleoli are membrane-less nuclear substructures that govern ribosome biogenesis and participate in multiple other cellular processes such as cell cycle progression, stress sensing, and DNA damage response. The proper functioning of these organelles is ensured by specific proteins that maintain nucleolar structure and mediate key nucleolar activities. Among all nucleolar proteins, treacle encoded by TCOF1 gene emerges as one of the most crucial regulators of cellular processes. TCOF1 was initially discovered as a gene involved in the Treacher Collins syndrome, a rare genetic disorder characterized by severe craniofacial deformations. Later studies revealed that treacle regulates ribosome biogenesis, mitosis, proliferation, DNA damage response, and apoptosis. Importantly, several reports indicate that treacle is also involved in cancer development, progression, and response to therapies, and may contribute to other pathologies such as Hirschsprung disease. In this manuscript, we comprehensively review the structure, function, and the regulation of TCOF1/treacle in physiological and pathological processes.

Transversus abdominis plane block as a sole anesthetic technique for open appendectomy in patient with Treacher Collins syndrome: a case report

Patients with Treacher Collins syndrome (TCS) present serious challenges to anesthetist in securing of airway; upper airway obstruction and difficult tracheal intubation are considered complex entity in these patients. This case report describes the significance of transversus abdominis plane (TAP) block as a sole anesthetic choice in appendectomy where airway management can be avoided. A 17-year-old boy, known case of TCS, presented with acute appendicitis underwent emergency laparotomy. Surgery was successfully performed by TAP block with dexmedetomidine infusion. Open appendectomy can be performed successfully in certain circumstances under TAP block with adjunctive use of dexmedetomidine infusion where airway handling is avoided. Further studies are warranted to distinct its use as sole anesthetic choice in lower abdominal surgeries.

Targeted Next-Generation Sequencing in the Diagnosis of Facial Dysostoses

Background

Defects in the development of the first and second pharyngeal arches and their derivatives result in abnormal formation of the craniofacial complex, consequently giving rise to facial dysostoses (FDs). FDs represent a group of rare and highly heterogeneous disease entities that encompass mandibulofacial dysostoses (MFDs) with normal extremities and acrofacial dysostoses (AFDs) with limb anomalies in addition to craniofacial defects.

Methods

We examined 11 families with variable clinical symptoms of FDs, in most of which only one member was affected. We applied two custom gene panels—first comprising 37 genes related to the genetic disorders of craniofacial development such as FDs (On-Demand AmpliSeq Thermo Fisher Scientific gene panel with two primer pools) and second composed of 61 genes and 11 single nucleotide variants (SNVs) known to be involved in the development of skull malformations, mainly in the form of craniosynostoses (SureSelect Agilent Technologies). Targeted next-generation sequencing (NGS) was performed using the Ion Torrent S5 platform. To confirm the presence of each detected variant, we have analyzed a genomic region of interest using Sanger sequencing.

Results

In this paper, we summarized the results of custom targeted gene panel sequencing in the cohort of sixteen patients from 11 consecutive families affected by distinct forms of FDs. We have found three novel pathogenic variants in the TCOF1 gene—c.2145_2148dupAAAG p.(Ser717Lysfs^∗42), c.4370delA p.(Lys1457Argfs^∗118), c.83G>C p.(Arg28Pro) causing Treacher Collins syndrome type 1, two novel missense variants in the EFTUD2 gene–c.491A>G p.(Asp164Gly) and c.779T>A p.(Ile260Asn) in two female patients affected by acrofacial dysostosis Guion-Almeida type, one previously reported–c.403C>T (p.Arg135Cys), as well as one novel missense variant–c.128C>T p.(Pro43Leu) in the DHODH gene in the male patient with Miller syndrome and finally one known pathogenic variant c.574G>T p.(Glu192^∗) in the SF3B4 gene in the patient with Nager syndrome.

Conclusion

Our study confirms the efficiency and clinical utility of the targeted gene panel sequencing and shows that this strategy is suitable and efficient in the molecular screening of variable forms of FDs.

Genetics and signaling mechanisms of orofacial clefts

Craniofacial development involves several complex tissue movements including several fusion processes to form the frontonasal and maxillary structures, including the upper lip and palate. Each of these movements are controlled by many different factors that are tightly regulated by several integral morphogenetic signaling pathways. Subject to both genetic and environmental influences, interruption at nearly any stage can disrupt lip, nasal, or palate fusion and result in a cleft. Here, we discuss many of the genetic risk factors that may contribute to the presentation of orofacial clefts in patients, and several of the key signaling pathways and underlying cellular mechanisms that control lip and palate formation, as identified primarily through investigating equivalent processes in animal models, are examined.

Modeling Medical Education: The Impact of Three-Dimensional Printed Models on Medical Student Education in Plastic Surgery

PURPOSE

Trainee exposure to craniofacial pathology can be limited due to rare disease presentation, revealing a need for tools that assist in visualizing complex 3D pathologic anatomy. 3D-printed models show potential as a useful aid, allowing for physical manipulation and hands-on experience. This study investigates their educational value in teaching craniofacial pathology and surgical repair.

METHODS

Forty-four medical students randomly assigned to a control group or model group were given a PowerPoint presentation-based module on craniosynostosis and surgical repair. The model group was also provided with 3D-printed models of sagittal, metopic, and bicoronal synostosis, created using patient-specific preoperative computed tomography data. A survey using the Likert scale evaluated participants' learning experience. Pre- and postmodule scores on a 10-question multiple choice quiz were recorded.

RESULTS

The survey showed that students in the model group reported better understanding of the anatomy (4.86 ± 0.15 versus 4.26 ± 0.22; P = 0.0001) and visualization of the pathology (4.76 ± 0.23 versus 4.26 ± 0.25; P = 0.0064), gaining an improved understanding of surgical approach (4.38 ± 0.37 versus 3.83 ± 0.29; P = 0.0266), which was more effectively taught (4.24 ± 0.33 versus 3.30 ± 0.38; P = 0.0007) with the 3D-printed models. The mean pre- and post-module quiz scores between groups were similar.

CONCLUSION

3D-printed models demonstrated an improved learning experience for medical students as shown by survey. These findings suggest a potential use for 3D-printed models in medical education of craniofacial pathology and surgery.

Cranial Neural Crest Cells and Their Role in the Pathogenesis of Craniofacial Anomalies and Coronal Craniosynostosis

Craniofacial anomalies are among the most common of birth defects. The pathogenesis of craniofacial anomalies frequently involves defects in the migration, proliferation, and fate of neural crest cells destined for the craniofacial skeleton. Genetic mutations causing deficient cranial neural crest migration and proliferation can result in Treacher Collins syndrome, Pierre Robin sequence, and cleft palate. Defects in post-migratory neural crest cells can result in pre- or post-ossification defects in the developing craniofacial skeleton and craniosynostosis (premature fusion of cranial bones/cranial sutures). The coronal suture is the most frequently fused suture in craniosynostosis syndromes. It exists as a biological boundary between the neural crest-derived frontal bone and paraxial mesoderm-derived parietal bone. The objective of this review is to frame our current understanding of neural crest cells in craniofacial development, craniofacial anomalies, and the pathogenesis of coronal craniosynostosis. We will also discuss novel approaches for advancing our knowledge and developing prevention and/or treatment strategies for craniofacial tissue regeneration and craniosynostosis.

Necrotizing scleritis after strabismus surgery in Treacher Collins syndrome

Objective: To describe a case of surgically induced scleral necrosis in Treacher Collins syndrome after strabismus surgery. Methods: A 19-year-old girl underwent bilateral squint surgery. Two weeks postoperatively, she presented with subconjunctival abscess in the left eye. The surrounding conjunctiva was markedly inflamed with raised edges. Surgical debridement, microbiological evaluation and medical management were started immediately. Screening for autoimmune and vasculitic conditions did not provide any positive results. Results: On subsequent follow-up, conjunctival retraction and an area of scleral necrosis with thinning was noted. Significant healing with antibiotics and steroids was noted within one week. The integrity of the globe was well maintained and no further procedure for tectonic support was performed. Conclusion: Surgically induced scleral necrosis can be immune-mediated or following surgical site infection. Pre-existing scleral thinning due to neuroectodermal apoptosis in Treacher Collins syndrome remains a possible explanation for the accelerated necrotising scleritis in our case.

Comparison Between Treacher Collins Syndrome and Pierre Robin Sequence: A Cephalometric Study

OBJECTIVE

The aim of this study was to compare the dentoskeletal pattern of Treacher Collins syndrome (TCS) and nonsyndromic Pierre Robin sequence (PRS).

DESIGN

Retrospective.

SETTING

Single center.

PATIENTS

Eighteen patients diagnosed with TCS (Group TCS) or PRS (Group PRS) in rehabilitation treatment at a single center. Group TCS was composed of 9 patients (4 male, 5 female) with a mean age of 12.9 years (standard deviation = 4.8). Group PRS was composed of 9 patients paired by age and sex with group TCS.

MAIN OUTCOME MEASURE(S)

Cone beam computed tomography-derived cephalometric images taken before the orthodontic or the orthodontic-surgical treatment were analyzed using Dolphin Imaging (Dolphin Imaging 11.0 & Management Solutions). Variables evaluating the cranial base, the maxillary and mandibular skeletal components, maxillomandibular relationship, the vertical components and the dentoalveolar region were measured. Intergroup comparisons were performed using t tests. The significance level considered was 5%.

RESULTS

Intergroup differences in the mandible size and growth pattern were observed. Group TCS showed a smaller mandibular length (Co-Go, Co-Gn) and a higher palatal plane (SN-Palatal Plane) and mandibular plane angles (SN-Go.Gn) compared to group PRS. No differences between TCS and PRS were observed for the sagittal position of the maxilla, maxillomandibular relationship, and dental components.

CONCLUSIONS

Treacher Collins syndrome presented a decreased mandible and a more severe vertical growth pattern compared to PRS.

OROFACIAL CLEFTS AND CARDIOVASCULAR RISK AND DISEASES: THE CAUSAL RELATIONSHIP AND ASSOCIATIONS

There is a complex interplay between orofacial clefts (OFCs) or cleft of the lip and palate and cardiovascular risk factors and cardiac diseases. The presence of maternal cardiovascular risk factors serves as a potent predisposing factor to the development of OFCs during foetal development in addition to the fact that various congenital anomalies are associated with OFCs either in syndromic or non-syndrome relationship. This article narratively explores this complex interplay, which is not uncommon.

Treacle controls the nucleolar response to rDNA breaks via TOPBP1 recruitment and ATR activation

Induction of DNA double-strand breaks (DSBs) in ribosomal DNA (rDNA) repeats is associated with ATM-dependent repression of ribosomal RNA synthesis and large-scale reorganization of nucleolar architecture, but the signaling events that regulate these responses are largely elusive. Here we show that the nucleolar response to rDNA breaks is dependent on both ATM and ATR activity. We further demonstrate that ATM- and NBS1-dependent recruitment of TOPBP1 in the nucleoli is required for inhibition of ribosomal RNA synthesis and nucleolar segregation in response to rDNA breaks. Mechanistically, TOPBP1 recruitment is mediated by phosphorylation-dependent interactions between three of its BRCT domains and conserved phosphorylated Ser/Thr residues at the C-terminus of the nucleolar phosphoprotein Treacle. Our data thus reveal an important cooperation between TOPBP1 and Treacle in the signaling cascade that triggers transcriptional inhibition and nucleolar segregation in response to rDNA breaks.

Ribosome assembly coming into focus

In the past 25 years, genetic and biochemical analyses of ribosome assembly in yeast have identified most of the factors that participate in this complex pathway and have generated models for the mechanisms driving the assembly. More recently, the publication of numerous cryo-electron microscopy structures of yeast ribosome assembly intermediates has provided near-atomic resolution snapshots of ribosome precursor particles. Satisfyingly, these structural data support the genetic and biochemical models and provide additional mechanistic insight into ribosome assembly. In this Review, we discuss the mechanisms of assembly of the yeast small ribosomal subunit and large ribosomal subunit in the nucleolus, nucleus and cytoplasm. Particular emphasis is placed on concepts such as the mechanisms of RNA compaction, the functions of molecular switches and molecular mimicry, the irreversibility of assembly checkpoints and the roles of structural and functional proofreading of pre-ribosomal particles.

Three-Dimensional Upper Airway Assessment in Treacher Collins Syndrome

Objectives:

The purpose of this investigation was to assess the pharyngeal dimensions and the craniofacial morphology of individuals with Treacher Collins syndrome (TCS) when compared to vertical skeletal class II individuals. It is our hypothesis that the upper airways of individuals with TCS are reduced in view of the skeletal pattern and the maxillomandibular dysmorphologies.

Materials and Methods:

Cone-beam computed tomography scans of 26 individuals had the pharyngeal volume (V) and minimal cross-sectional area (mCSA) evaluated. Study group (TCS) was formed by 13 scans of patients with TCS (7 males and 6 females; 20.2 ± 4.7 years). Control group (CG) assembled 13 scans of nonaffected individuals with the same type of skeletal pattern (2 males and 11 females; 26.6 ± 5.4 years). Cephalometric data of maxillomandibular position, maxillomandibular dimensions, and growth pattern were assessed. Statistical analysis ( P ≤ .05) included Student t test and Pearson correlation coefficient.

Results:

Although reduced, pharyngeal V and mCSA of TCS were not statistically different from the CG. On both groups, mCSA was mostly at the oropharyngeal level. Individuals with TCS presented retrognathic chin, reduced maxillomandibular dimensions, and increased clockwise rotation of the palatal plane. Maxillary and mandibular lengths were correlated with pharyngeal V and mCSA.

Conclusions:

The pharyngeal dimensions of individuals with TCS are impacted by the micrognathia and retrognathia. In association with the skeletal pattern, the reduction of the airways, although not statistically significant, may explain the increased prevalence of airways disorder in this syndrome.

EFTUD2 gene deficiency disrupts osteoblast maturation and inhibits chondrocyte differentiation via activation of the p53 signaling pathway

Background

Mandibulofacial dysostosis with microcephaly (MFDM) is characteristic of multiple skeletal anomalies comprising craniofacial anomalies/dysplasia, microcephaly, dysplastic ears, choanal atresia, and short stature. Heterozygous loss of function variants of EFTUD2 was previously reported in MFDM; however, the mechanism underlying EFTUD2-associated skeletal dysplasia remains unclear.

Results

We identified a novel frameshift variant of EFTUD2 (c.1030_1031delTG, p.Trp344fs*2) in an MFDM Chinese patient with craniofacial dysmorphism including ear canal structures and microcephaly, mild intellectual disability, and developmental delay. We generated a zebrafish model of eftud2 deficiency, and a consistent phenotype consisting of mandibular bone dysplasia and otolith loss was observed. We also showed that EFTUD2 deficiency significantly inhibited proliferation, differentiation, and maturation in human calvarial osteoblast (HCO) and human articular chondrocyte (HC-a) cells. RNA-Seq analysis uncovered activated TP53 signaling with increased phosphorylation of the TP53 protein and upregulation of five TP53 downstream target genes (FAS, STEAP3, CASP3, P21, and SESN1) both in HCO and in eftud2−/− zebrafish. Additionally, inhibition of p53 by morpholino significantly reduced the mortality of eftud2−/− larvae.

Conclusions

Our results confirm a novel de novo variant of the EFTUD2 gene and suggest that EFTUD2 may participate in the maturation and differentiation of osteoblasts and chondrocytes, possibly via activation of the TP53 signaling pathway. Thus, mutations in this gene may lead to skeletal anomalies in vertebrates.