Treacher Collins syndrome: etiology, pathogenesis and prevention

[Pathogenic genes and clinical therapeutic strategies for Treacher Collins syndrome]

Treacher Collins syndrome is a congenital craniofacial malformation with autosomal dominant inheritance as the main genetic pattern. In this condition, the biosynthesis of ribosomes in neural crest cells and neuroepithelial cells is blocked and the number of neural crest cells that migrate to the craniofacial region decreases, causing first and second branchial arch dysplasia. Definite causative genes include treacle ribosome biogenesis factor 1 (tcof1), RNA polymerase Ⅰ and Ⅲ subunit C (polr1c), and RNA polymerase Ⅰ and Ⅲ subunit D (polr1d). This paper provides a review of research of three major patho-genic genes, pathogenesis, phenotypic research, prevention, and treatment of the syndrome.

Urgent Complex Intraoperative Reintubation in a Known Difficult Airway After Endotracheal Tube Damage: A Case Report

Treacher Collins syndrome is an inherited disorder resulting in maldevelopment of the first and second branchial arches. Patients have complex orofacial anatomy often requiring airway interventions from birth. A 17-year-old boy with Treacher Collins syndrome and history of difficult ventilation and intubation presented for elective maxillofacial reconstruction. After uneventful awake nasal fiberoptic intubation, the nasotracheal tube was damaged intraoperatively. Due to the patient's unique anatomy, a fiberoptic bronchoscope and ventilating exchange catheter were utilized together to facilitate a nasotracheal tube exchange. This case demonstrates the utilization of a combination of advanced airway techniques in an urgent perioperative setting.

Autosomal recessive Treacher Collins syndrome due to POLR1C mutations: Report of a new family and review of the literature

Treacher Collins syndrome (TCS) is a frequent cause of mandibulofacial dysostosis. To date, TCS-causing mutations in three genes, namely TCOF1, POLR1D, and POLR1C have been identified. TCS is usually inherited in an autosomal dominant manner, with a high clinical variability and no phenotype-genotype correlation. Up-to now, five families have been reported with an autosomal recessive mode of inheritance due to mutations in POLR1D or POLR1C. We report here a new family with two sisters affected by mild TCS carrying compound POLR1C heterozygous mutations, and review the literature on mild forms of TCS, autosomal recessive inheritance in this syndrome and POLR1C mutations.

Difficult airway management in a patient with Treacher Collins syndrome using two-part surgery

Treacher Collins syndrome (TCS), Franceschetti-Zwahlen-Klein, or mandibulofacial dysostosis, is a rare disorder of craniofacial development (incidence of approximately 1:50.000 live births). TCS is relevant to the anaesthetist because it can cause difficulties in airway management. A case report is presented of a 24 year-old woman who was referred to our institution for facial reconstruction surgery in two stages. In both surgeries Airtraq™ was essential for airway management. By presenting this case, it is intended to show that planning, communication and teamwork are indispensable for patient safety.

Counterclockwise Craniofacial Distraction Osteogenesis for Tracheostomy-Dependent Children with Treacher Collins Syndrome

BACKGROUND

The craniofacial rotation deformity in Treacher Collins syndrome results in airway compression that is not addressed by isolated mandibular distraction osteogenesis. Our purpose is to present a surgical technique-counterclockwise craniofacial distraction osteogenesis-that improves airway morphology and occlusal rotation in tracheostomy-dependent patients with this condition.

METHODS

All patients underwent subcranial Le Fort II osteotomies with simultaneous mandibular osteotomies, followed by coordinated maxillomandibular distraction with counterclockwise rotation. We reviewed pretreatment, posttreatment, and end-treatment cephalograms. Airway changes were assessed using polysomnography, sleep endoscopy, and direct laryngoscopy. Bivariate statistics were computed to compare pretreatment and posttreatment measures.

RESULTS

Five subjects (age range, 4.5 to 12.1 years) underwent this new procedure; three had previously undergone mandibular distraction. The average palatal plane rotation was 17 degrees, the effective mandible length increase was 18 mm, and the facial plane relative to skull base rotation was 14 degrees. There was a symmetric 30 percent relapse of rotation with maintained occlusion in the first 9 months of follow-up that then stabilized. Four patients were successfully decannulated following counterclockwise craniofacial distraction osteogenesis following polysomnography. Sleep endoscopy available on two patients demonstrated resolution of the upper airway obstruction.

CONCLUSIONS

Counterclockwise craniofacial distraction osteogenesis provided greater palatal rotation than previous techniques. The resulting improvement in airway anatomy allowed for decannulation in four of five tracheotomized patients. Stability of the counterclockwise rotation is comparable to that of related orthognathic operations, despite substantially greater magnitude.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Does an ear deformity bring an adverse impact on quality of life of Treacher Collins syndrome individuals?

Treacher Collins syndrome (TCS) is an autosomal dominant disorder with variable expression in which the ear may or may not be absent or with a malformation. Individuals with TCS suffer social stigma that may affect interaction with their peers. Quality of life instruments obtained through self-perception questionnaires are stigma identification tools and can enable social adjustment of these individuals. This study aims to assess the quality of life of individuals with TCS and to gauge the impacts of ear deformity on the quality of life. Twelve volunteers with a clinical and genetic diagnosis of TCS answered the WHO quality of life questionnaire and were divided into groups with normal ears (n = 6) versus affected ears (n = 6), and their results were compared. Siviero's scale was used to stratify the quality of life scores as satisfactory, intermediate and unsatisfactory. The overall score of the normal ears group was 73.13 and 71.81 for the affected ears group, and both were classified as an intermediate quality of life, with no statistically significant differences between them. Ear deformity is not a burden to the quality of life of these individuals, who already show other deformities and overall intermediate quality of life scores.

How to make a tongue: Cellular and molecular regulation of muscle and connective tissue formation during mammalian tongue development

The vertebrate tongue is a complex muscular organ situated in the oral cavity and involved in multiple functions including mastication, taste sensation, articulation and the maintenance of oral health. Although the gross embryological contributions to tongue formation have been known for many years, it is only relatively recently that the molecular pathways regulating these processes have begun to be discovered. In particular, there is now evidence that the Hedgehog, TGF-Beta, Wnt and Notch signaling pathways all play an important role in mediating appropriate signaling interactions between the epithelial, cranial neural crest and mesodermal cell populations that are required to form the tongue. In humans, a number of congenital abnormalities that affect gross morphology of the tongue have also been described, occurring in isolation or as part of a developmental syndrome, which can greatly impact on the health and well-being of affected individuals. These anomalies can range from an absence of tongue formation (aglossia) through to diminutive (microglossia), enlarged (macroglossia) or bifid tongue. Here, we present an overview of the gross anatomy and embryology of mammalian tongue development, focusing on the molecular processes underlying formation of the musculature and connective tissues within this organ. We also survey the clinical presentation of tongue anomalies seen in human populations, whilst considering their developmental and genetic etiology.

Relationship between neural crest cell specification and rare ocular diseases

Development of the eye is closely associated with neural crest cell migration and specification. Eye development is extremely complex, as it requires the working of a combination of local factors, receptors, inductors, and signaling interactions between tissues such as the optic cup and periocular mesenchyme (POM). The POM is comprised of neural crest-derived mesenchymal progenitor cells that give rise to numerous important ocular structures including those tissues that form the optic cup and anterior segment of the eye. A number of genes are involved in the migration and specification of the POM such as PITX2, PITX3, FOXC1, FOXE3, PAX6, LMX1B, GPR48, TFAP2A, and TFAP2B. In this review, we will discuss the relevance of these genes in the development of the POM and how mutations and defects result in rare ocular diseases.

Hemifacial microsomia (oculo-auriculo-vertebral spectrum) in an individual from the Teramo Sant'Anna archaeological site (7th-12th centuries of the Common Era, Italy)

BACKGROUND

This study is based in an analysis of the skeletal remains of an adult male from the Teramo Sant'Anna archaeological site (7th-12th centuries of the Common Era, Teramo, Italy).

RESULTS AND DISCUSSION

The individual shows distinct abnormalities that principally involve asymmetric hypoplasia and dysmorphogenesis of the facial skeleton. The combination of these findings and the absence of abnormalities of the spine strongly suggest diagnosis of the congenital malformation known as hemifacial microsomia. This very heterogeneous syndrome affects primarily aural, ocular, oral and mandibular development. Despite the lack of clinical information and the absence of soft tissue, it was possible to perform a differential diagnosis for this palaeopathological case. Mastication was probably altered considering that the mandible is extremely asymmetric and lacks true condyles. The temporomandibular joints are present, but the right one is hypoplastic and abnormal in shape. There is evidence of bilateral dislocation, and the facial muscles are hypertrophic.

CONCLUSIONS

This case represents an important contribution to the palaeopathological literature because this is an uncommon condition that has not been widely documented in ancient skeletal remains.

Regulation of RNA Polymerase I Transcription in Development, Disease, and Aging

Ribosome biogenesis is a complex and highly energy-demanding process that requires the concerted action of all three nuclear RNA polymerases (Pol I-III) in eukaryotes. The three largest ribosomal RNAs (rRNAs) originate from a precursor transcript (pre-rRNA) that is encoded by multicopy genes located in the nucleolus. Transcription of these rRNA genes (rDNA) by Pol I is the key regulation step in ribosome production and is tightly controlled by an intricate network of signaling pathways and epigenetic mechanisms. In this article, we give an overview of the composition of the basal Pol I machinery and rDNA chromatin. We discuss rRNA gene regulation in response to environmental signals and developmental cues and focus on perturbations occurring in diseases linked to either excessive or limited rRNA levels. Finally, we discuss the emerging view that rDNA integrity and activity may be involved in the aging process.

Patient-Reported Quality of Life in the Highest Functioning Patients With Treacher Collins Syndrome

BACKGROUND

Treacher Collins syndrome has a wide variation of clinical presentation, including airway obstruction and hearing loss. The objective of this study was to assess patient-rated quality of life in Treacher Collins syndrome, who received multidisciplinary treatment at a specialized craniofacial hospital, and to compare their quality of life with a control sample.

METHODS

Treacher Collins patients under treatment in a multidisciplinary setting were assessed with the World Health Organization Quality of Life (WHOQOL-100) questionnaire. The Siviero scale was used to classify quality of life as unsatisfactory (scores below 25), intermediate (scores between 25 and 75), and satisfactory (scores above 75). Quality of life comparison between Treacher Collins patients and 2342 unaffected individuals from a previous database was performed using the analysis of variance test. Differences were considered significant at P < 0.05.

RESULTS

Treacher Collins patients demonstrated an overall intermediate and satisfactory (score >60%) quality of life in almost all WHOQOL-100 facets and domains. The comparison of the scores between unaffected individuals and Treacher Collins patients demonstrated a significant difference (P < 0.05) in the environment domain.

CONCLUSION

The highest functioning Treacher Collins syndrome patients under multidisciplinary treatment presented intermediate and satisfactory quality of life, consistent with quality of life scores of unaffected controls. In the environment domain, Treacher Collins patients presented even higher scores of quality of life than the control group.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Ribosomopathies: There's strength in numbers

Ribosomopathies are a group of human disorders most commonly caused by ribosomal protein haploinsufficiency or defects in ribosome biogenesis. These conditions manifest themselves as physiological defects in specific cell and tissue types. We review current molecular models to explain ribosomopathies and attempt to reconcile the tissue specificity of these disorders with the ubiquitous requirement for ribosomes in all cells. Ribosomopathies as a group are diverse in their origins and clinical manifestations; we use the well-described Diamond-Blackfan anemia (DBA) as a specific example to highlight some common features. We discuss ribosome homeostasis as an overarching principle that governs the sensitivity of specific cells and tissue types to ribosomal protein mutations. Mathematical models and experimental insights rationalize how even subtle shifts in the availability of ribosomes, such as those created by ribosome haploinsufficiency, can drive messenger RNA-specific effects on protein expression. We discuss recently identified roles played by ribosome rescue and recycling factors in regulating ribosome homeostasis.

Syndromic Hearing Loss: A Brief Review of Common Presentations and Genetics

Congenital hearing loss is one of the most common birth defects worldwide, with around 1 in 500 people experiencing some form of severe hearing loss. While over 400 different syndromes involving hearing loss have been described, it is important to be familiar with a wide range of syndromes involving hearing loss so an early diagnosis can be made and early intervention can be pursued to maximize functional hearing and speech-language development in the setting of verbal communication. This review aims to describe the presentation and genetics for some of the most frequently occurring syndromes involving hearing loss, including neurofibromatosis type 2, branchio-oto-renal syndrome, Treacher Collins syndrome, Stickler syndrome, Waardenburg syndrome, Pendred syndrome, Jervell and Lange-Nielsen syndrome, Usher syndromes, Refsum disease, Alport syndrome, MELAS, and MERRF.

Diagnosis of fetal syndromes by three- and four-dimensional ultrasound: is there any improvement?

With all of our present knowledge, high technology diagnostic equipment, electronic databases and other available supporting resources, detection of fetal syndromes is still a challenge for healthcare providers in prenatal as well as in the postnatal period. Prenatal diagnosis of fetal syndromes is not straightforward, and it is a difficult puzzle that needs to be assembled and solved. Detection of one anomaly should always raise a suspicion of the existence of more anomalies, and can be a trigger to investigate further and raise awareness of possible syndromes. Highly specialized software systems for three- and four-dimensional ultrasound (3D/4D US) enabled detailed depiction of fetal anatomy and assessment of the dynamics of fetal structural and functional development in real time. With recent advances in 3D/4D US technology, antenatal diagnosis of fetal anomalies and syndromes shifted from the 2nd to the 1st trimester of pregnancy. It is questionable what can and should be done after the prenatal diagnosis of fetal syndrome. The 3D and 4D US techniques improved detection accuracy of fetal abnormalities and syndromes from early pregnancy onwards. It is not easy to make prenatal diagnosis of fetal syndromes, so tools which help like online integrated databases are needed to increase diagnostic precision. The aim of this paper is to present the possibilities of different US techniques in the detection of some fetal syndromes prenatally.

Uncovering the pathogenesis of microtia using bioinformatics approach

OBJECTIVE

Bioinformatics is widely used in the field of cancer research, but in the research of pathogenesis of congenital malformations the situation is different. The aim of this study was to explore the underlying mechanism using bioinformatics approach.

METHODS

The data were available from Mouse Genome Informatics and Pubmed. Protein-protein interaction (PPI) network of pathogenic genes was conducted using STRING. Gene ontology and pathway enrichment analyses were also performed to pathogenic genes.

RESULTS

Total 63 genes were identified as pathogenic genes in the study. The PPI networks for pathogenic genes were constructed, which contained 62 nodes and 228 edges with PAX6, FGFR1 and CTNNB1 as the hub genes. All the genes were linked to 921 pathways in biological processes, 31 pathways in cell component, 41 pathways in molecular function, and 76 pathways in the KEGG. These genes were discovered significantly enriched in embryonic organ development, ear morphogenesis, ear development, and regulation of RNA synthesis and processing.

CONCLUSIONS

bioinformatics methods were utilized to analysis pathogenic genes involved in microtia development, including pathogenic genes identifying, PPI network construction and functional analysis. And we also predicted that several potential mechanisms might contribute to occurrence of microtia by disturbing GO terms and pathways. This approach could be useful for the study of the etiology and pathogenesis of microtia.

The airway approach to a neonate with Treacher Collins syndrome - Case report

Neonates and small infants with syndromes characterized by the presence of craniofacial abnormalities may represent great challenges regarding the management of the airway. We describe the case of a 9-day-old neonate with Treacher Collins syndrome, in which a laryngeal mask was essential to improve the airway obstruction, ventilate the patient and serve as an airway conduit for a fiberoptic intubation. By presenting this case, we intend to show that in neonates with Treacher Collins syndrome, in whom difficulties ventilation and intubation are expected, a thoughtful airway management planning is mandatory.

Treacher Collins syndrome: A case report and review of ophthalmic features

Treacher Collins syndrome is a congenital disorder with bilaterally symmetric anomalies of the structures developing from the first and second branchial arches. The ocular and orbital features are an obligatory component for the diagnosis. We presented a case of typical, complete syndrome and also reviewed the varied ophthalmological manifestations of the disease in the literature. Antimongoloid slanting of palpebral fissures and lower lid colobomas are constant features of the syndrome. However, varied ocular and lacrimal drainage anomalies are also associated. TCS is a syndrome with multiple ocular and orbital features, a knowledge of which will help in the diagnosis of incomplete forms of the syndrome.

Face off against ROS: Tcof1/Treacle safeguards neuroepithelial cells and progenitor neural crest cells from oxidative stress during craniofacial development

One-third of all congenital birth defects affect the head and face, and most craniofacial anomalies are considered to arise through defects in the development of cranial neural crest cells. Cranial neural crest cells give rise to the majority of craniofacial bones, cartilages and connective tissues. Therefore, understanding the events that control normal cranial neural crest and subsequent craniofacial development is important for elucidating the pathogenetic mechanisms of craniofacial anomalies and for the exploring potential therapeutic avenues for their prevention. Treacher Collins syndrome (TCS) is a congenital disorder characterized by severe craniofacial anomalies. An animal model of TCS, generated through mutation of Tcof1, the mouse (Mus musculus) homologue of the gene primarily mutated in association with TCS in humans, has recently revealed significant insights into the pathogenesis of TCS. Apoptotic elimination of neuroepithelial cells including neural crest cells is the primary cause of craniofacial defects in Tcof1 mutant embryos. However, our understanding of the mechanisms that induce tissue-specific apoptosis remains incomplete. In this review, we describe recent advances in our understanding of the pathogenesis TCS. Furthermore, we discuss the role of Tcof1 in normal embryonic development, the correlation between genetic and environmental factors on the severity of craniofacial abnormalities, and the prospect for prenatal prevention of craniofacial anomalies.

The Roles of RNA Polymerase I and III Subunits Polr1c and Polr1d in Craniofacial Development and in Zebrafish Models of Treacher Collins Syndrome

Ribosome biogenesis is a global process required for growth and proliferation of all cells, yet perturbation of ribosome biogenesis during human development often leads to tissue-specific defects termed ribosomopathies. Transcription of the ribosomal RNAs (rRNAs) by RNA polymerases (Pol) I and III, is considered a rate limiting step of ribosome biogenesis and mutations in the genes coding for RNA Pol I and III subunits, POLR1C and POLR1D cause Treacher Collins syndrome, a rare congenital craniofacial disorder. Our understanding of the functions of individual RNA polymerase subunits, however, remains poor. We discovered that polr1c and polr1d are dynamically expressed during zebrafish embryonic development, particularly in craniofacial tissues. Consistent with this pattern of activity, polr1c and polr1d homozygous mutant zebrafish exhibit cartilage hypoplasia and cranioskeletal anomalies characteristic of humans with Treacher Collins syndrome. Mechanistically, we discovered that polr1c and polr1d loss-of-function results in deficient ribosome biogenesis, Tp53-dependent neuroepithelial cell death and a deficiency of migrating neural crest cells, which are the primary progenitors of the craniofacial skeleton. More importantly, we show that genetic inhibition of tp53 can suppress neuroepithelial cell death and ameliorate the skeletal anomalies in polr1c and polr1d mutants, providing a potential avenue to prevent the pathogenesis of Treacher Collins syndrome. Our work therefore has uncovered tissue-specific roles for polr1c and polr1d in rRNA transcription, ribosome biogenesis, and neural crest and craniofacial development during embryogenesis. Furthermore, we have established polr1c and polr1d mutant zebrafish as models of Treacher Collins syndrome together with a unifying mechanism underlying its pathogenesis and possible prevention.

Ribosomes synthesize all proteins, and are therefore critical for cell growth and proliferation. Ribosome biogenesis, or the process of making ribosomes, is one of the most energy consuming processes within a cell, and disruptions in ribosome biogenesis can lead to congenital disorders termed ribosomopathies. Interestingly, individual ribosomopathies are characterized by tissue-specific phenotypes, which is surprising given the universal importance of ribosomes. Treacher Collins syndrome (TCS) for example, is a ribosomopathy characterized by anomalies of facial bones, palate, eyes and ears. Mutations in TCOF1, POLR1C, and POLR1D are associated with the underlying etiology of TCS. TCOF1 plays an important role in the synthesis of ribosomal RNA, one of the rate-limiting steps of ribosome biogenesis. Consequently, TCOF1 is essential for the survival and proliferation of neural crest cell progenitors, which are the precursors of craniofacial bone, cartilage and connective tissue. In contrast, the functions of POLR1C and POLR1D, which are subunits of RNA Polymerases I and III remain unknown. Here we examined the function of polr1c and polr1d during zebrafish development and discovered that these genes display dynamic spatiotemporal activity during embryogenesis with enriched expression in craniofacial tissues. Furthermore, we observed that polr1c and polr1d loss-of-function zebrafish exhibit anomalies in craniofacial cartilage development, which reflects the characteristic features of TCS. An examination of polr1c^-/- and polr1d^-/- mutants revealed that diminished ribosome biogenesis results in neuroepithelial cell death and a deficiency of migrating neural crest cells, which are the progenitors of the craniofacial skeleton. Moreover, the cell death observed in polr1c^-/- and polr1d^-/- mutants is Tp53-dependent, and inhibition of tp53 is sufficient to repress cell death and rescue cranioskeletal cartilage formation in polr1c^-/- and polr1d^-/- mutant embryos. These studies provide evidence for tissue-specific functions of polr1c and polr1d during embryonic development, while also establishing polr1c and polr1d loss-of-function zebrafish mutants as models of Treacher Collins syndrome.

Modeling craniofacial and skeletal congenital birth defects to advance therapies

Craniofacial development is an intricate process of patterning, morphogenesis, and growth that involves many tissues within the developing embryo. Genetic misregulation of these processes leads to craniofacial malformations, which comprise over one-third of all congenital birth defects. Significant advances have been made in the clinical management of craniofacial disorders, but currently very few treatments specifically target the underlying molecular causes. Here, we review recent studies in which modeling of craniofacial disorders in primary patient cells, patient-derived induced pluripotent stem cells (iPSCs), and mice have enhanced our understanding of the etiology and pathophysiology of these disorders while also advancing therapeutic avenues for their prevention.

Treacher Collins Syndrome: A Systematic Review of Evidence-Based Treatment and Recommendations

BACKGROUND

No reviews or guidelines are available on evidence-based treatment for the multidisciplinary approach in Treacher Collins syndrome. The authors' aim is to provide an evidence-based review of multidisciplinary treatment of Treacher Collins syndrome based on levels of evidence and supported with graded recommendations.

METHODS

A systematic search was performed by means of the PubMed, Web-of-Science, Embase, and Cochrane Central databases (1985 to January of 2014). Included were clinical studies (with five or more Treacher Collins syndrome patients) related to therapy, diagnosis, or risk of concomitant diseases. Level of evidence of the selected articles was rated according to the American Society of Plastic Surgeons evidence-based clinical practice guidelines. After two panelists had reviewed each abstract separately, a consensus method was used to solve any disagreements concerning article inclusion.

RESULTS

Of the 2433 identified articles, 63 studies (Level of Evidence II through V) were included. Conclusions and recommendations were extracted consecutively for the following items: upper airway; ear, hearing, and speech; the eye, eyelashes, and lacrimal system; growth, feeding, and swallowing; the nose; psychosocial factors; and craniofacial reconstruction.

CONCLUSIONS

In this systematic review, current evidence for the multidisciplinary treatment of Treacher Collins syndrome is provided, recommendations for treatment are made, and a proposed algorithm for treatment is presented. Although some topics are well supported, others, especially ocular, nasal, speech, feeding, and swallowing problems, lack sufficient evidence. In addition, craniofacial surgical reconstruction lacks a sufficient level of evidence to provide a sound basis for a full treatment protocol. Despite the rarity of the syndrome, more research is needed to compare outcomes of several surgical treatments, especially in orbitozygomatic/maxillary regions.

Prevention of Treacher Collins syndrome craniofacial anomalies in mouse models via maternal antioxidant supplementation

Craniofacial anomalies account for approximately one-third of all birth defects and are a significant cause of infant mortality. Since the majority of the bones, cartilage and connective tissues that comprise the head and face are derived from a multipotent migratory progenitor cell population called the neural crest, craniofacial disorders are typically attributed to defects in neural crest cell development. Treacher Collins syndrome (TCS) is a disorder of craniofacial development and although TCS arises primarily through autosomal dominant mutations in TCOF1, no clear genotype-phenotype correlation has been documented. Here we show that Tcof1 haploinsufficiency results in oxidative stress-induced DNA damage and neuroepithelial cell death. Consistent with this discovery, maternal treatment with antioxidants minimizes cell death in the neuroepithelium and substantially ameliorates or prevents the pathogenesis of craniofacial anomalies in Tcof1(+/-) mice. Thus maternal antioxidant dietary supplementation may provide an avenue for protection against the pathogenesis of TCS and similar neurocristopathies.

Treacher Collins syndrome: a clinical and molecular study based on a large series of patients

PURPOSE

Treacher Collins/Franceschetti syndrome (TCS; OMIM 154500) is a disorder of craniofacial development belonging to the heterogeneous group of mandibulofacial dysostoses. TCS is classically characterized by bilateral mandibular and malar hypoplasia, downward-slanting palpebral fissures, and microtia. To date, three genes have been identified in TCS:,TCOF1, POLR1D, and POLR1C.

METHODS

We report a clinical and extensive molecular study, including TCOF1, POLR1D, POLR1C, and EFTUD2 genes, in a series of 146 patients with TCS. Phenotype-genotype correlations were investigated for 19 clinical features, between TCOF1 and POLR1D, and the type of mutation or its localization in the TCOF1 gene.

RESULTS

We identified 92/146 patients (63%) with a molecular anomaly within TCOF1, 9/146 (6%) within POLR1D, and none within POLR1C. Among the atypical negative patients (with intellectual disability and/or microcephaly), we identified four patients carrying a mutation in EFTUD2 and two patients with 5q32 deletion encompassing TCOF1 and CAMK2A in particular. Congenital cardiac defects occurred more frequently among patients with TCOF1 mutation (7/92, 8%) than reported in the literature.

CONCLUSION

Even though TCOF1 and POLR1D were associated with extreme clinical variability, we found no phenotype-genotype correlation. In cases with a typical phenotype of TCS, 6/146 (4%) remained with an unidentified molecular defect.

Nasal sequelae of Treacher Collins syndrome

OBJECTIVE

This study aimed to determine external and endonasal deformity, and satisfaction with nasal functioning and appearance, in Treacher Collins syndrome.

STUDY DESIGN

A cross-sectional cohort study was conducted.

METHODS

Eleven adult patients with Treacher Collins syndrome were compared with 151 controls in terms of satisfaction with nasal functioning and appearance by means of the Nasal Appearance and Function Evaluation Questionnaire. In all patients with Treacher Collins syndrome, external nasal deformities were scored on standardized digital photographs of the nose as rated independently by three experienced physicians. Endonasal deformity was determined by standardized nasal endoscopy.

RESULTS

The patients were relatively satisfied with the various esthetic nasal subunits. The most significant functional problems were snoring (P = 0.001) and quality of phonation (P = 0.003). The main external nasal deformities were the dorsal hump (73%), external deviation (≤55%), the bifid or bulbous nasal tip (55%), and columellar septal luxation (55%). In 82% of the patients, a septal deviation was found, often associated with spurs.

CONCLUSION

Satisfaction with esthetics of the nose was fair, but these patients suffer from the functional problems of snoring and impaired quality of phonation. A structured nasal ENT physical examination with nasal endoscopy might determine aspects requiring more attention during treatment. Septorhinoplasty can be performed at an adult age if there is a considerable esthetic wish of the patient and/or nasal obstruction combined with septal deviation. Attention should be paid to dorsal hump reduction, correction of the deviated external osseous framework, septoplasty, and correction of the nasal tip shape.

LEVEL OF EVIDENCE

2b.

The incidence, embryology, and oculofacial abnormalities associated with eyelid colobomas

PURPOSE

To describe a cohort of patients with congenital eyelid coloboma, to identify associated ocular and craniofacial abnormalities, and to establish any correlation between the size and location of eyelid colobomas and the presence of such abnormalities.

METHODS

An observational case series of 55 patients with eyelid coloboma treated by a single surgeon (JROC) between 1985 and 2005.

RESULTS

Eyelid colobomas predominantly affected the upper lids (93%), and were typically unilateral (76%). About a third (29%) were an isolated finding, with the remainder associated with other ocular (62%) and/or craniofacial (53%) abnormalities. Of those with ocular abnormalities; 19 (56%) had conjunctival traction bands, 16 (47%) choristomas, and 8 (24%) an abnormal globe. Of those with craniofacial abnormalities; 13 (45%) had Goldenhar Syndrome, 10 (35%) clefting disorders, and 4 (14%) Fraser Syndrome. Clefting disorders were typically associated with more severe colobomas and a higher incidence of conjunctival traction bands, first arch syndromes with smaller colobomas and more choristomas. Overall large colobomas were significantly associated with the presence of other craniofacial defects compared with small colobomas (P<0.01, χ(2)), but coloboma size did not correspond with the presence of other ocular abnormalities.

CONCLUSIONS

Coloboma size, location, and associations in this series are consistent with our current understanding of eyelid embryogenesis. It is likely that those colobomas associated with other craniofacial and ocular abnormalities are those which result from errors earlier in embryogenesis during eyelid specification, growth, and closure, whereas isolated colobomas arise later during eyelid separation, and after codependent structures have developed.

Cleft Lip and/or Palate and Auricular Malformations

Objective

To study the relationship between cleft lip and/or palate and auricular malformations in Finnish patients with cleft.

Design

Retrospective analysis of patients with an external ear malformation and either a cleft lip with or without a cleft palate (CL±P) or an isolated cleft palate (CP).

Setting

Tertiary referral clinic.

Patients

Review of hospital records of 100 patients from the register of 8200 patients with cleft in the Cleft and Craniofacial Centre at the Helsinki University Central Hospital.

Main Outcome Measures

Proportions of variable auricular malformations among CL±P and CP patients.

Results

Microtia is the most common auricular malformation among patients with cleft and is almost equally prevalent with both CL±P and CP. The prevalence of microtia increases as the severity of CL±P increases. The combination of microtia and CL±P or CP is frequently found with both oculo-auriculo-vertebral spectrum and Treacher Collins syndrome.

Conclusions

Microtia seems to be the most common auricular malformation among patients with cleft. The prevalence of microtia seems to increase as the severity of CL±P increases, whereas in isolated CP microtia seems to occur independently.

Mouse Models of Rare Craniofacial Disorders

A rare disease is defined as a condition that affects less than 1 in 2000 individuals. Currently more than 7000 rare diseases have been documented, and most are thought to be of genetic origin. Rare diseases primarily affect children, and congenital craniofacial syndromes and disorders constitute a significant proportion of rare diseases, with over 700 having been described to date. Modeling craniofacial disorders in animal models has been instrumental in uncovering the etiology and pathogenesis of numerous conditions and in some cases has even led to potential therapeutic avenues for their prevention. In this chapter, we focus primarily on two general classes of rare disorders, ribosomopathies and ciliopathies, and the surprising finding that the disruption of fundamental, global processes can result in tissue-specific craniofacial defects. In addition, we discuss recent advances in understanding the pathogenesis of an extremely rare and specific craniofacial condition known as syngnathia, based on the first mouse models for this condition. Approximately 1% of all babies are born with a minor or major developmental anomaly, and individuals suffering from rare diseases deserve the same quality of treatment and care and attention to their disease as other patients.

Orthognathic Surgeries in Patients With Congenital Craniofacial Anomalies: Profile and Hospitalization Outcomes

OBJECTIVE

To examine the occurrence of complications in patients with congenital facial anomalies who underwent orthognathic surgeries and to identify the role of patient-related factors in occurrence of complications.

DESIGN

Retrospective analysis of hospital discharge database.

SETTING

Nationwide inpatient sample for the years 2004 to 2010. All patients with a diagnosis of cleft lip and/or palate or congenital craniofacial anomalies and who had an orthognathic surgery were selected.

INTERVENTIONS

Orthognathic surgery.

MAIN OUTCOME MEASURES

Occurrence of complications.

RESULTS

During the study period, a total of 8340 patients with congenital craniofacial anomalies underwent orthognathic surgeries. The overall complication rate was 9.1%. Six different complications (bacterial infections, hemorrhage, postoperative pneumonia, iatrogenic-induced complications such as accidental punctures/lacerations or pneumothorax, other infections, and respiratory complications) occurred in at least 1% of all patients having orthognathic surgeries. Ninety-five percent of patients were discharged routinely after surgery. Patients with high comorbid burden are at a higher risk for developing complications (P < .05).

CONCLUSIONS

The current study findings indicate that orthognathic surgeries can be safely performed in patients with congenital craniofacial anomalies. The present study results reflect the practice patterns and hospitalization outcomes across the country and could serve as benchmarks for future well-designed prospective controlled studies to examine risk factors associated with complications for not only orthognathic surgeries but also for a wider range of surgical procedures.

Mandibulofacial dysostosis (Treacher Collins syndrome): A case report and review of literature

Treacher Collins syndrome (TCS) or Franceschetti syndrome is an autosomal dominant disorder of craniofacial development with variable phenotypic expression. It presents with characteristic facial appearance enabling it to be easily recognizable. A case of a 10-year-old girl having TCS is briefly described in this article. A review of the etiology, clinical features, differential diagnosis, and treatment options are also discussed.

The Future of Prenatal Diagnosis and Screening

The future of prenatal diagnosis and screening lies in developing clinical approaches and laboratory technologies applicable to genetic analyses and therapeutic interventions during embryonic development.

Deletion of Drosophila Nopp140 induces subcellular ribosomopathies

The nucleolar and Cajal body phosphoprotein of 140 kDa (Nopp140) is considered a ribosome assembly factor, but its precise functions remain unknown. To approach this problem, we deleted the Nopp140 gene in Drosophila using FLP-FRT recombination. Genomic PCR, reverse transcriptase-PCR (RT-PCR), and immunofluorescence microscopy confirmed the loss of Nopp140, its messenger RNA (mRNA), and protein products from all tissues examined. Nopp140-/- larvae arrested in the second instar stage and most died within 8 days. While nucleoli appeared intact in Nopp140-/- cells, the C/D small nucleolar ribonucleoprotein (snoRNP) methyltransferase, fibrillarin, redistributed to the nucleoplasm in variable amounts depending on the cell type; RT-PCRs showed that 2'-O-methylation of ribosomal RNA (rRNA) in Nopp140-/- cells was reduced at select sites within both the 18S and 28S rRNAs. Ultrastructural analysis showed that Nopp140-/- cells were deficient in cytoplasmic ribosomes, but instead contained abnormal electron-dense cytoplasmic granules. Immunoblot analysis showed a loss of RpL34, and metabolic labeling showed a significant drop in protein translation, supporting the loss of functional ribosomes. Northern blots showed that pre-RNA cleavage pathways were generally unaffected by the loss of Nopp140, but that R2 retrotransposons that naturally reside within the 28S region of normally silent heterochromatic Drosophila ribosomal DNA (rDNA) genes were selectively expressed in Nopp140-/- larvae. Unlike copia elements and the related R1 retrotransposon, R2 expression appeared to be preferentially dependent on the loss of Nopp140 and not on environmental stresses. We believe the phenotypes described here define novel intracellular ribosomopathies resulting from the loss of Nopp140.

The neural crest: a versatile organ system

The neural crest is the name given to the strip of cells at the junction between neural and epidermal ectoderm in neurula-stage vertebrate embryos, which is later brought to the dorsal neural tube as the neural folds elevate. The neural crest is a heterogeneous and multipotent progenitor cell population whose cells undergo EMT then extensively and accurately migrate throughout the embryo. Neural crest cells contribute to nearly every organ system in the body, with derivatives of neuronal, glial, neuroendocrine, pigment, and also mesodermal lineages. This breadth of developmental capacity has led to the neural crest being termed the fourth germ layer. The neural crest has occupied a prominent place in developmental biology, due to its exaggerated migratory morphogenesis and its remarkably wide developmental potential. As such, neural crest cells have become an attractive model for developmental biologists for studying these processes. Problems in neural crest development cause a number of human syndromes and birth defects known collectively as neurocristopathies; these include Treacher Collins syndrome, Hirschsprung disease, and 22q11.2 deletion syndromes. Tumors in the neural crest lineage are also of clinical importance, including the aggressive melanoma and neuroblastoma types. These clinical aspects have drawn attention to the selection or creation of neural crest progenitor cells, particularly of human origin, for studying pathologies of the neural crest at the cellular level, and also for possible cell therapeutics. The versatility of the neural crest lends itself to interlinked research, spanning basic developmental biology, birth defect research, oncology, and stem/progenitor cell biology and therapy.

A syndromic form of Pierre Robin sequence is caused by 5q23 deletions encompassing FBN2 and PHAX

Pierre Robin sequence (PRS) is an aetiologically distinct subgroup of cleft palate. We aimed to define the critical genomic interval from five different 5q22-5q31 deletions associated with PRS or PRS-associated features and assess each gene within the region as a candidate for the PRS component of the phenotype. Clinical array-based comparative genome hybridisation (aCGH) data were used to define a 2.08 Mb minimum region of overlap among four de novo deletions and one mother-son inherited deletion associated with at least one component of PRS. Commonly associated anomalies were talipes equinovarus (TEV), finger contractures and crumpled ear helices. Expression analysis of the orthologous genes within the PRS critical region in embryonic mice showed that the strongest candidate genes were FBN2 and PHAX. Targeted aCGH of the critical region and sequencing of these genes in a cohort of 25 PRS patients revealed no plausible disease-causing mutations. In conclusion, deletion of ∼2 Mb on 5q23 region causes a clinically recognisable subtype of PRS. Haploinsufficiency for FBN2 accounts for the digital and auricular features. A possible critical region for TEV is distinct and telomeric to the PRS region. The molecular basis of PRS in these cases remains undetermined but haploinsufficiency for PHAX is a plausible mechanism.

Biomedical visual data analysis to build an intelligent diagnostic decision support system in medical genetics

BACKGROUND

In general, medical geneticists aim to pre-diagnose underlying syndromes based on facial features before performing cytological or molecular analyses where a genotype-phenotype interrelation is possible. However, determining correct genotype-phenotype interrelationships among many syndromes is tedious and labor-intensive, especially for extremely rare syndromes. Thus, a computer-aided system for pre-diagnosis can facilitate effective and efficient decision support, particularly when few similar cases are available, or in remote rural districts where diagnostic knowledge of syndromes is not readily available.

METHODS

The proposed methodology, visual diagnostic decision support system (visual diagnostic DSS), employs machine learning (ML) algorithms and digital image processing techniques in a hybrid approach for automated diagnosis in medical genetics. This approach uses facial features in reference images of disorders to identify visual genotype-phenotype interrelationships. Our statistical method describes facial image data as principal component features and diagnoses syndromes using these features.

RESULTS

The proposed system was trained using a real dataset of previously published face images of subjects with syndromes, which provided accurate diagnostic information. The method was tested using a leave-one-out cross-validation scheme with 15 different syndromes, each of comprised 5-9 cases, i.e., 92 cases in total. An accuracy rate of 83% was achieved using this automated diagnosis technique, which was statistically significant (p<0.01). Furthermore, the sensitivity and specificity values were 0.857 and 0.870, respectively.

CONCLUSION

Our results show that the accurate classification of syndromes is feasible using ML techniques. Thus, a large number of syndromes with characteristic facial anomaly patterns could be diagnosed with similar diagnostic DSSs to that described in the present study, i.e., visual diagnostic DSS, thereby demonstrating the benefits of using hybrid image processing and ML-based computer-aided diagnostics for identifying facial phenotypes.

Characterization of distinct classes of differential gene expression in osteoblast cultures from non-syndromic craniosynostosis bone

Craniosynostosis, the premature fusion of one or more skull sutures, occurs in approximately 1 in 2500 infants, with the majority of cases non-syndromic and of unknown etiology. Two common reasons proposed for premature suture fusion are abnormal compression forces on the skull and rare genetic abnormalities. Our goal was to evaluate whether different sub-classes of disease can be identified based on total gene expression profiles. RNA-Seq data were obtained from 31 human osteoblast cultures derived from bone biopsy samples collected between 2009 and 2011, representing 23 craniosynostosis fusions and 8 normal cranial bones or long bones. No differentiation between regions of the skull was detected, but variance component analysis of gene expression patterns nevertheless supports transcriptome-based classification of craniosynostosis. Cluster analysis showed 4 distinct groups of samples; 1 predominantly normal and 3 craniosynostosis subtypes. Similar constellations of sub-types were also observed upon re-analysis of a similar dataset of 199 calvarial osteoblast cultures. Annotation of gene function of differentially expressed transcripts strongly implicates physiological differences with respect to cell cycle and cell death, stromal cell differentiation, extracellular matrix (ECM) components, and ribosomal activity. Based on these results, we propose non-syndromic craniosynostosis cases can be classified by differences in their gene expression patterns and that these may provide targets for future clinical intervention.

Treacher Collins Syndrome: the genetics of a craniofacial disease

OBJECTIVES

The molecular underpinnings of Treacher Collins Syndrome (TCS) are diverse. This article codifies the most recent findings in this complex area of research to further current understanding of the disease process. Elucidating the genetic causes of the disorder can be useful in earlier detection and better treatment planning.

DESIGN

Articles from 1991 to 2013 were selected and reviewed by five researchers utilizing the most recent literature of the genetics and pathophysiology of TCS.

RESULTS

Mutations in TCOF1, POLR1C and POLR1D have all been implicated in causing TCS. The association of the TCOF1 gene product, Treacle, and gene products of POLR1C and POLR1D with ribosome biosynthesis suggests that a loss of function mutation in these genes disrupts ribosome biosynthesis in constituent neural crest cells and neuroepithelium leading to apoptosis. However, recent data illustrating that P53 heterozygosity is protective against TCS, and that P53 and TCOF1 hemizygous embryos do not affect ribosomal function, implicates P53 or elements downstream of P53 as playing a role in TCS pathogenesis.

CONCLUSION

Our study codified nascent findings of the molecular determinants of TCS. These findings add to a burgeoning database of TCS-associated mutations, and as such, can be used to establish TCS diagnosis and further clarify TCS pathogenesis.

Associations between speech features and phenotypic severity in Treacher Collins syndrome

BACKGROUND

Treacher Collins syndrome (TCS, OMIM 154500) is a rare congenital disorder of craniofacial development. Characteristic hypoplastic malformations of the ears, zygomatic arch, mandible and pharynx have been described in detail. However, reports on the impact of these malformations on speech are few. Exploring speech features and investigating if speech function is related to phenotypic severity are essential for optimizing follow-up and treatment.

METHODS

Articulation, nasal resonance, voice and intelligibility were examined in 19 individuals (5-74 years, median 34 years) divided into three groups comprising children 5-10 years (n = 4), adolescents 11-18 years (n = 4) and adults 29 years and older (n = 11). A speech composite score (0-6) was calculated to reflect the variability of speech deviations. TCS severity scores of phenotypic expression and total scores of Nordic Orofacial Test-Screening (NOT-S) measuring orofacial dysfunction were used in analyses of correlation with speech characteristics (speech composite scores).

RESULTS

Children and adolescents presented with significantly higher speech composite scores (median 4, range 1-6) than adults (median 1, range 0-5). Nearly all children and adolescents (6/8) displayed speech deviations of articulation, nasal resonance and voice, while only three adults were identified with multiple speech aberrations. The variability of speech dysfunction in TCS was exhibited by individual combinations of speech deviations in 13/19 participants. The speech composite scores correlated with TCS severity scores and NOT-S total scores. Speech composite scores higher than 4 were associated with cleft palate. The percent of intelligible words in connected speech was significantly lower in children and adolescents (median 77%, range 31-99) than in adults (98%, range 93-100). Intelligibility of speech among the children was markedly inconsistent and clearly affecting the understandability.

CONCLUSIONS

Multiple speech deviations were identified in children, adolescents and a subgroup of adults with TCS. Only children displayed markedly reduced intelligibility. Speech was significantly correlated with phenotypic severity of TCS and orofacial dysfunction. Follow-up and treatment of speech should still be focused on young patients, but some adults with TCS seem to require continuing speech and language pathology services.

CRISPR/Cas9 allows efficient and complete knock-in of a destabilization domain-tagged essential protein in a human cell line, allowing rapid knockdown of protein function

Although modulation of protein levels is an important tool for study of protein function, it is difficult or impossible to knockdown or knockout genes that are critical for cell growth or viability. For such genes, a conditional knockdown approach would be valuable. The FKBP protein-based destabilization domain (DD)-tagging approach, which confers instability to the tagged protein in the absence of the compound Shield-1, has been shown to provide rapid control of protein levels determined by Shield-1 concentration. Although a strategy to knock-in DD-tagged protein at the endogenous loci has been employed in certain parasite studies, partly due to the relative ease of knock-in as a result of their mostly haploid lifecycles, this strategy has not been demonstrated in diploid or hyperploid mammalian cells due to the relative difficulty of achieving complete knock-in in all alleles.

The recent advent of CRISPR/Cas9 homing endonuclease-mediated targeted genome cleavage has been shown to allow highly efficient homologous recombination at the targeted locus. We therefore assessed the feasibility of using CRISPR/Cas9 to achieve complete knock-in to DD-tag the essential gene Treacher Collins-Franceschetti syndrome 1 (TCOF1) in human 293T cells. Using a double antibiotic selection strategy to select clones with at least two knock-in alleles, we obtained numerous complete knock-in clones within three weeks of initial transfection. DD-TCOF1 expression in the knock-in cells was Shield-1 concentration-dependent, and removal of Shield-1 resulted in destabilization of DD-TCOF1 over the course of hours. We further confirmed that the tagged TCOF1 retained the nucleolar localization of the wild-type untagged protein, and that destabilization of DD-TCOF1 resulted in impaired cell growth, as expected for a gene implicated in ribosome biogenesis. CRISPR/Cas9-mediated homologous recombination to completely knock-in a DD tag likely represents a generalizable and efficient strategy to achieve rapid modulation of protein levels in mammalian cells.

Cranial neural crest: migratory cell behavior and regulatory networks

Defects of the head and neck region account for a substantial portion of all human birth disorders. The high incidence of malformations in this region may be attributed in part to the intricate means by which the facial region is assembled during embryonic development. The starting constituent for the majority of skeletal and connective tissues in the face is a pluripotent population of cells, the cranial neural crest (CNC) cells. This population of cells exhibit remarkable migratory abilities and diversity of potential cell types. This review draws on extensive research that has been done in the field, focusing specifically on findings generated in the last decade on cell behavior and the gene regulatory networks of migratory CNC cells. In the later part of this review, the importance of the CNC cells in the overall development of the craniofacial region will be illustrated with a discussion of a craniofacial birth defect, the Treacher Collins syndrome. The next decade will most likely herald in an era of greater understanding of the integrative molecular networks at different stages of the development of the CNC cells. Such new information is essential towards a better understanding the etiology and pathogenesis of the many craniofacial birth defects and will ultimately lead to new therapeutic modalities.

Genomic characterization of the mouse ribosomal DNA locus

The transcription of rRNA is critical to all living cells and is tightly controlled at the level of chromatin structure. Although the widespread adoption of genomic technologies including chromatin immunoprecipitation with massively parallel short-read sequencing (ChIP-seq) has allowed for the interrogation of chromatin structure on a genome-wide scale, until recently rDNA has not been analyzed by this technique. We extended genomic analysis of rDNA to mouse (Mus musculus), in which rDNA is similar in structure but highly divergent in sequence compared with human rDNA. Comparison of rDNA histone marks between mouse embryonic stem cells (mESCs) and more differentiated mouse cell types revealed differences between pluripotent and differentiated states. We also observed substantial divergence in rDNA histone modification patterns between mESCs and human embryonic stem cells (hESCs). Surprisingly, we found that the pluripotency factor OCT4 was bound to rDNA in similar patterns in mESCs and hESCs. Extending this analysis, we found that an additional 17 pluripotency-associated factors were bound to rDNA in mESCs, suggesting novel modes of rDNA regulation in pluripotent cells. Taken together, our results provide a detailed view of rDNA chromatin structure in an important model system and enable high-resolution comparison of rDNA regulation between mouse and human.

The emerging roles of ribosome biogenesis in craniofacial development

Neural crest cells (NCCs) are a transient, migratory cell population, which originates during neurulation at the neural folds and contributes to the majority of tissues, including the mesenchymal structures of the craniofacial skeleton. The deregulation of the complex developmental processes that guide migration, proliferation, and differentiation of NCCs may result in a wide range of pathological conditions grouped together as neurocristopathies. Recently, due to their multipotent properties neural crest stem cells have received considerable attention as a possible source for stem cell based regenerative therapies. This exciting prospect underlines the need to further explore the developmental programs that guide NCC differentiation. This review explores the particular importance of ribosome biogenesis defects in this context since a specific interface between ribosomopathies and neurocristopathies exists as evidenced by disorders such as Treacher-Collins-Franceschetti syndrome (TCS) and Diamond-Blackfan anemia (DBA).