A Brief Analysis on Clinical Severity of Mandibulofacial Dysostosis Guion-Almeida Type

OBJECTIVE

Genetic variants in EFTUD2 were proven to influence variable phenotypic expressivity in mandibulofacial dysostosis Guion-Almeida type (MFDGA) or mandibulofacial dysostosis with microcephaly (MFDM). Yet, the association between the severity of clinical findings with variants within the EFTUD2 gene has not been established. Thus, we aim to elucidate a possible genotype-phenotype correlation in MFDM.

METHODS

Forty articles comprising 156 patients were evaluated. The genotype-phenotype correlation was analyzed using a chi-square or Fisher's exact test.

RESULTS

The proportion of patients with MFDM was higher in Caucasian relative to Asian populations. Although, in general, there was no apparent genotype-phenotype correlation in patients with MFDM, Asians tended to have more severe clinical manifestations than Caucasians. In addition, cardiac abnormality presented in patients with intronic variants located in canonical splice sites was a predisposing factor in affecting MFDM severity.

CONCLUSION

Altogether, this article provides the pathogenic variants observed in EFTUD2 and possible genotype-phenotype relationships in this disease.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

The transcription of the main gene associated with Treacher-Collins syndrome (TCOF1) is regulated by G-quadruplexes and cellular nucleic acid binding protein (CNBP)

Treacle ribosome biogenesis factor 1 (TCOF1) is responsible for about 80% of mandibular dysostosis (MD) cases. We have formerly identified a correlation between TCOF1 and CNBP (CCHC-type zinc finger nucleic acid binding protein) expression in human mesenchymal cells. Given the established role of CNBP in gene regulation during rostral development, we explored the potential for CNBP to modulate TCOF1 transcription. Computational analysis for CNBP binding sites (CNBP-BSs) in the TCOF1 promoter revealed several putative binding sites, two of which (Hs791 and Hs2160) overlap with putative G-quadruplex (G4) sequences (PQSs). We validated the folding of these PQSs measuring circular dichroism and fluorescence of appropriate synthetic oligonucleotides. In vitro studies confirmed binding of purified CNBP to the target PQSs (both folded as G4 and unfolded) with Kd values in the nM range. ChIP assays conducted in HeLa cells chromatin detected the CNBP binding to TCOF1 promoter. Transient transfections of HEK293 cells revealed that Hs2160 cloned upstream SV40 promoter increased transcription of downstream firefly luciferase reporter gene. We also detected a CNBP-BS and PQS (Dr2393) in the zebrafish TCOF1 orthologue promoter (nolc1). Disrupting this G4 in zebrafish embryos by microinjecting DNA antisense oligonucleotides complementary to Dr2393 reduced the transcription of nolc1 and recapitulated the craniofacial anomalies characteristic of Treacher Collins Syndrome. Both cnbp overexpression and Morpholino-mediated knockdown in zebrafish induced nolc1 transcription. These results suggest that CNBP modulates the transcriptional expression of TCOF1 through a mechanism involving G-quadruplex folding/unfolding, and that this regulation is active in vertebrates as distantly related as bony fish and humans. These findings may have implications for understanding and treating MD.

A novel intronic TCOF1 pathogenic variant in a Chinese family with Treacher Collins syndrome

BACKGROUND

Treacher Collins syndrome (TCS; OMIM 154500) is a craniofacial developmental disorder.

METHODS

To investigate the genetic features of a four-generation Chinese family with TCS, clinical examinations, hearing tests, computed tomography, whole-exome sequencing (WES), Sanger sequencing, reverse transcription (RT)-PCR, and the Minigene assay were performed.

RESULTS

The probands, an 11-year-old male and his cousin exhibited typical clinical manifestations of TCS including conductive hearing loss, downward slanting palpebral fissures, and mandibular hypoplasia. Computed tomography revealed bilateral fusion of the anterior and posterior stapedial crura and malformation of the long crura of the incus. WES of both patients revealed a novel heterozygous intronic variant, i.e., c.4342 + 5_4342 + 8delGTGA (NM_001371623.1) in TCOF1. Minigene expression analysis revealed that the c.4342 + 5_4342 + 8delGTGA variant in TCOF1 caused a partial deletion of exon 24 (c.4115_4342del: p.Gly1373_Arg1448del), which was predicted to yield a truncated protein. The deletion was further confirmed via RT-PCR and sequencing of DNA from proband blood cells. A heterozygous variant in the POLR1C gene (NM_203290; exon6; c.525delG) was found almost co-segregated with the TCOF1 pathogenic variant.

CONCLUSIONS

In conclusion, we identified a heterozygous TCOF1 splicing variant c.4342 + 5_4342 + 8delGTGA (splicing) in a Chinese TSC family with ossicular chain malformations and facial anomalies. Our findings broadened the spectrum of TCS variants and will facilitate diagnostics and prognostic predictions.

[Diagnosis of a Chinese pedigree affected with Treacher-Collins syndrome due to a novel variant of TCOF1 gene through whole exome sequencing]

OBJECTIVE

To explore the genetic etiology for a Chinese pedigree affected with Treacher-Collins syndrome (TCS) through whole exome sequencing (WES).

METHODS

A TCS pedigree which was diagnosed at the Women and Children's Hospital Affiliated to Qingdao University on February 5, 2020 was selected as the study subject. Following collection of clinical data, WES was carried out. Candidate variant was validated through Sanger sequencing and bioinformatic analysis.

RESULTS

The WES results showed that the proband has harbored a heterozygous c.3337C>T variant of the TCOF1 gene, and Sanger sequencing confirmed that his mother and brother also carried the same variant. Based on guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was predicted as pathogenic (PVS1+PM2_Supporting+PP4).

CONCLUSION

The heterozygous c.3337C>T variant of the TCOF1 gene probably underlay the pathogenesis of TCS in this pedigree.

Two novel pathogenic variants in the TCOF1 found in two Chinese cases of Treacher Collins syndrome

BACKGROUND

Treacher Collins Ι syndrome (TCS1, OMIM:154500) is an autosomal dominant disease with a series of clinical manifestations such as craniofacial dysplasia including eye and ear abnormalities, small jaw deformity, cleft lip, as well as repeated respiratory tract infection and conductive hearing loss. Two cases of Treacher Collins syndrome with TCOF1(OMIM:606847) gene variations were reported in the article, with clinical characteristics, gene variants and the etiology.

METHODS

The clinical data of two patients with Treacher Collins syndrome caused by TCOF1 gene variation were retrospectively analyzed. The whole exome sequencing (WES) was performed to detect the pathogenic variants of TCOF1 gene in the patients, and the verification of variants were confirmed by Sanger sequencing.

RESULTS

Proband 1 presented with bilateral craniofacial deformities, conductive hearing loss and recurrent respiratory tract infection. Proband 2 showed bilateral craniofacial malformations with cleft palate, which harbored similar manifestations in her family. She died soon after birth due to dyspnea and feeding difficulties. WES identified two novel pathogenic variants of TCOF1 gene in two probands, each with one variant. According to the American College of Medical Genetics and Genomics, the heterozygous variation NM_001371623.1: c.877del (p. Ala293Profs*34) of TCOF1 gene was detected in Proband 1, which was evaluated as a likely pathogenic (LP) and de novo variant. Another variant found in Proband 2 was NM_001135243.1: c.1660_1661del (p. D554Qfs*3) heterozygous variation, which was evaluated as a pathogenic variation and the variant inherited from the mother. To date, the two variants have not been reported before.

CONCLUSION

Our study found two novel pathogenic variants of TCOF1 gene and clarified the etiology of Treacher Collins syndrome. We also enriched the phenotypic spectrum of Treacher Collins syndrome and TCOF1 gene variation spectrum in the Chinese population, and provided the basis for clinical diagnosis, treatment and genetic counseling.

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.

Children with Rare Nager Syndrome-Literature Review, Clinical and Physiotherapeutic Management

Nager syndrome is a rare human developmental disorder characterized by craniofacial defects including the downward slanting of the palpebral fissures, cleft palate, limb deformities, mandibular hypoplasia, hypoplasia or absence of thumbs, microretrognathia, and ankylosis of the temporomandibular joint. The prevalence is very rare and the literature describes only about a hundred cases of Nager syndrome. There is evidence of autosomal dominant and autosomal recessive inheritance for Nager syndrome, suggesting genetic heterogeneity. The majority of the described causes of Nager syndrome include pathogenic variants in the SF3B4 gene, which encodes a component of the spliceosome; therefore, the syndrome belongs to the spliceosomopathy group of diseases. The diagnosis is made on the basis of physical and radiological examination and detection of mutations in the SF3B4 gene. Due to the diversity of defects associated with Nager syndrome, patients require multidisciplinary, complex, and long-lasting treatment. Usually, it starts from birth until the age of twenty years. The surgical procedures vary over a patient's lifetime and are related to the needed function. First, breathing and feeding must be facilitated; then, oral and facial clefts should be addressed, followed by correcting eyelid deformities and cheekbone reconstruction. In later age, a surgery of the nose and external ear is performed. Speech and hearing disorders require specialized logopedic treatment. A defect of the thumb is treated by transplanting a tendon and muscle or transferring the position of the index finger. In addition to surgery, in order to maximize a patient's benefit and to reduce functional insufficiency, complementary treatments such as rehabilitation and physiotherapy are recommended. In our study, we describe eight patients of different ages with various cases of Nager syndrome. The aim of our work was to present the actual genetic knowledge on this disease and its treatment procedures.

Prenatal diagnosis of Treacher Collins syndrome: A case report and literature review

Treacher Collins syndrome (TCS) should be suspected if the triad of micrognathia, glossoptosis, and posterior cleft palate, and deformed external ears are observed during prenatal ultrasonography, excepting Pierre Robin sequence. Visualization of the fetal zygomatic bone and down-slanting palpebral fissures are conducive to differentiation. Molecular genetics testing can establish a definite diagnosis. A 28-year-old pregnant Chinese woman was referred for systematic ultrasound examination at 24 weeks. Two-dimensional and three-dimensional ultrasound showed polyhydramnios, micrognathia, absence of nasal bone, microtia, secondary cleft palate, mandibular hypoplasia, glossoptosis, and normal limbs and vertebrae. Pierre Robin sequence was misdiagnosed with the triad of micrognathia, glossoptosis, and posterior cleft palate. Final diagnosis of TCS was confirmed by whole-exome sequencing. Visualization of the fetal zygomatic bone and down-slanting palpebral fissures can facilitate a differential diagnosis between Pierre Robin sequence and TCS, with the triad of micrognathia, glossoptosis, and posterior cleft palate.

First and second branchial arch involvement in mandibulofacial dysostosis Guion-Almeida type

BACKGROUND

Mandibulofacial dysostosis Guion-Almeida Type (MFDGA; OMIM#610536) is a rare autosomal dominant genetic disorder caused by heterozygous pathogenic variants in the EFTUD2 gene. Mandibulofacial dysostoses are characterised by the core triad malar hypoplasia, maxillary hypoplasia and dysplastic ears, all derived by the impaired development of the first and second branchial arches. Differential diagnosis is often challenging. The early genetic diagnosis is extremely useful, not only for the correct management of cranial malformations, but also for the early diagnosis and treatment of the comorbidities associated to the disease, which greatly benefit from early treatment.

Clinical and molecular study of Egyptian patients with Treacher Collins syndrome

Treacher Collins syndrome (TCS) is a rare disorder of craniofacial development following different patterns of inheritance. To date, mutations in four genes ( TCOF1, POLR1D, POLR1C , and POLR1B ) have been found to cause the condition. The molecular defect remains unidentified in a significant proportion of patients. In the current study, whole exome sequencing including analysis of copy number variants was applied for genetic testing of eight Egyptian patients with typical TCS phenotype, representing the first molecular analysis of TCS patients in Egypt as well as in Arab countries. Five heterozygous frameshift mutations were reported, including four variants in the TCOF1 gene (c.3676_3694delinsCTCTGG, c.3984_3985delGA, c.4366_4369delGAAA, and c.3388delC) and one variant in the POLR1D gene (c.60dupA). Four variants were novel extending the disease mutation spectrum. In three affected individuals, no variants of interest were identified in genes associated with TCS or clinically overlapping conditions. Additionally, no relevant variant was detected in genes encoding other subunits of RNA polymerase (pol) I. Molecular analysis is important to provide accurate genetic counseling. It would also contribute to reduced disease incidence. Further studies should be designed to investigate other possible etiologies when no pathogenic variants were revealed in either of the known genes.

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

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

POLR1A variants underlie phenotypic heterogeneity in craniofacial, neural, and cardiac anomalies

Heterozygous pathogenic variants in POLR1A, which encodes the largest subunit of RNA Polymerase I, were previously identified as the cause of acrofacial dysostosis, Cincinnati-type. The predominant phenotypes observed in the cohort of 3 individuals were craniofacial anomalies reminiscent of Treacher Collins syndrome. We subsequently identified 17 additional individuals with 12 unique heterozygous variants in POLR1A and observed numerous additional phenotypes including neurodevelopmental abnormalities and structural cardiac defects, in combination with highly prevalent craniofacial anomalies and variable limb defects. To understand the pathogenesis of this pleiotropy, we modeled an allelic series of POLR1A variants in vitro and in vivo. In vitro assessments demonstrate variable effects of individual pathogenic variants on ribosomal RNA synthesis and nucleolar morphology, which supports the possibility of variant-specific phenotypic effects in affected individuals. To further explore variant-specific effects in vivo, we used CRISPR-Cas9 gene editing to recapitulate two human variants in mice. Additionally, spatiotemporal requirements for Polr1a in developmental lineages contributing to congenital anomalies in affected individuals were examined via conditional mutagenesis in neural crest cells (face and heart), the second heart field (cardiac outflow tract and right ventricle), and forebrain precursors in mice. Consistent with its ubiquitous role in the essential function of ribosome biogenesis, we observed that loss of Polr1a in any of these lineages causes cell-autonomous apoptosis resulting in embryonic malformations. Altogether, our work greatly expands the phenotype of human POLR1A-related disorders and demonstrates variant-specific effects that provide insights into the underlying pathogenesis of ribosomopathies.

A systematic review on Treacher Collins syndrome: Correlation between molecular genetic findings and clinical severity

Treacher Collins syndrome (TCS, OMIM: 154500) is a rare congenital craniofacial disorder that is caused by variants in the genes TCOF1, POLR1D, POLR1C, and POLR1B. Studies on the association between phenotypic variability and their relative variants are very limited. This systematic review summarized the 53 literatures from PubMed and Scopus to explore the potential TCS genotype-phenotype correlations with statistical analysis. Studies reporting both complete molecular genetics and clinical data were included. We identified that the molecular anomaly within TCOF1 (88.71%) accounted for most TCS cases. The only true hot spot for TCOF1 was detected in exon 24, with recurrent c.4369_4373delAAGAA variant is identified. While the hot spot for POLR1D, POLR1C, and POLR1B were identified in exons 3, 8, and 15, respectively. Our result suggested that the higher severity level was likely to be observed in Asian patients harboring TCOF1 variants rather than POLR1. Moreover, common 5-bp deletions tended to have a higher severity degree in comparison to any variants within exon 24 of TCOF1. In summary, this report suggested the relationship between genetic and clinical data in TCS. Our findings could be used as a reference for clinical diagnosis and further biological studies.

A clinically-relevant residue of POLR1D is required for Drosophila development

BACKGROUND

POLR1D is a subunit of RNA Polymerases I and III, which synthesize ribosomal RNAs. Dysregulation of these polymerases cause several types of diseases, including ribosomopathies. The craniofacial disorder Treacher Collins Syndrome (TCS) is a ribosomopathy caused by mutations in several subunits of RNA Polymerase I, including POLR1D. Here, we characterized the effect of a missense mutation in POLR1D and RNAi knockdown of POLR1D on Drosophila development.

RESULTS

We found that a missense mutation in Drosophila POLR1D (G30R) reduced larval rRNA levels, slowed larval growth, and arrested larval development. Remarkably, the G30R substitution is at an orthologous glycine in POLR1D that is mutated in a TCS patient (G52E). We showed that the G52E mutation in human POLR1D, and the comparable substitution (G30E) in Drosophila POLR1D, reduced their ability to heterodimerize with POLR1C in vitro. We also found that POLR1D is required early in the development of Drosophila neural cells. Furthermore, an RNAi screen revealed that POLR1D is also required for development of non-neural Drosophila cells, suggesting the possibility of defects in other cell types.

CONCLUSIONS

These results establish a role for POLR1D in Drosophila development, and present Drosophila as an attractive model to evaluate the molecular defects of TCS mutations in POLR1D.

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.

[Analysis of pathogenic gene variant in two children with Treacher-Collins syndrome]

OBJECTIVE

To explore the clinical and genetic characteristics of two children with a clinical diagnosis of Treacher Collins syndrome (TCS).

METHODS

Whole-exome sequencing was used to screen potential variants in the two children. Confirmation of suspected variants was performed through Sanger sequencing, multiplex ligation dependent probe amplification and real-time PCR in probands and their parents.

RESULTS

A heterozygous deletion variant, c.4357_4360delGAAA, was detected in case one, while was de novo and verified by Sanger sequencing. The variant was classified as pathogenic (PVS1 +PM2+PM6) according to ACMG guideline. The heterozygous deletion of exon 1-7 was seen in the same gene in case 2, which MLPA verified as heterozygous deletion of exon 1-6. This deletion was inherited from the father with a normal phenotype, and the father's TCOF1 gene was suspected to be chimeric heterozygous deletion of exon 1-6 verified by MLPA.

CONCLUSION

The identified variants in the TCOF1 gene probably underlie the two cases of TCS. There was no apparent correlation between genotype and phenotype. In addition, it shows a high interfamilial variability ranging from normal to full presentation of TCS. Genetic detection provided clinical diagnosis and genetic counselling for TCS patients.

[Clinical case analysis and literature review of mandibulofacial dysostosis with microcephaly syndrome]

Objective:To explore the clinical diagnosis, otological treatment and molecular etiology in a rare syndromic hearing loss case characterized by mandibulofacial dysostosis with microcephaly（MFDM）. Methods: The proband underwent detailed history collection, systematic physical examination and phenotypic analysis, as well as audiological examination, chest X-ray, temporal bone CT and brain MRI and other imaging examinations. The blood DNA of the proband and his parents was extracted and tested by the whole exom sequencing. The EFTUD2-related-MFDM literatures published by the end of 2020 were searched and sifted in PubMed and CNKI databases,the clinical characteristics of MFDM were summarized. Results:In this study, the patient presented with hypoplasia of auricle, micrognathia, microcephaly, developmental retardation, severe sensorineural hearing loss in both ears, and developmental malformation of middle and inner ear. Genetic analysis revealed a de novo deletion c.623_624delAT in EFTUD2 gene. According to the clinical features and genetic test results, the patient was diagnosed as MFDM. In order to solve the problem of hearing loss, the patient was further performed bilateral cochlear implantation, and part of the electrodes responded well during and after operation. Conclusion:This is the first domestic reported case of MFDM caused by EFTUD2 gene mutation. The key problem of cochlear implantation for this kind of patient is to avoid damaging the malformed facial nerve during the operation.The effect of speech rehabilitation after cochlear implant operation is related to many factors such as intelligence development of the patients.

The Role of Splicing Factor SF3B4 in Congenital Diseases and Tumors

In eukaryotes, spliceosomes catalyze the splicing of pre-mRNA to mature mRNA. As the core subunit of U2 spliceosome, splicing factor SF3b4 plays not only a crucial role in the splicing process, but also a role in transcription, translation, and cell signal transduction, and participates in the regulation of cell cycle, cell differentiation, and immune deficiency. In recent years, more and more research studies on SF3b4-related diseases, such as Nager syndrome and cancer, have been conducted. It has been found that SF3b4 mutations led to abnormal cell growth and were involved in the development and occurrence of these diseases. In this review, the diseases, mainly congenital diseases and tumors, in which SF3B4 is involved and the pathogenesis of them were summarized, aiming to provide a better understanding of the roles of SF3B4 in the prevention, diagnosis, and treatment of diseases in the future.

Treacher Collins Syndrome: Genetics, Clinical Features and Management

Treacher Collins syndrome (TCS) is associated with abnormal differentiation of the first and second pharyngeal arches, occurring during fetal development. Features of TCS include microtia with conductive hearing loss, slanting palpebral fissures with possibly coloboma of the lateral part of lower eyelids, midface hypoplasia, micrognathia as well as sporadically cleft palate and choanal atresia or stenosis. TCS occurs in the general population at a frequency of 1 in 50,000 live births. Four subtypes of Treacher Collins syndrome exist. TCS can be caused by pathogenic variants in the TCOF1, POLR1D, POLR1C and POLR1B genes. Genetically, the TCOF1 gene contains 27 exons which encodes the Treacle protein. In TCOF1, over 200 pathogenic variants have been identified, of which most are deletions leading to a frame-shift, that result in the formation of a termination codon. In the presented article, we review the genetics and phenotype of TCS as well as the management and surgical procedures utilized for treatment.

Treacher Collins Syndrome: A Case Report

Treacher collins syndrome (TCS) or Franceschetti syndrome is an autosomal dominant inherited disorder with variable expressivity. It affects mainly craniofacial structure that derives from 1st and 2nd branchial arches approximately between the 20th day and 12th week of intrauterine life. This syndrome has different clinical types. Most common features are antimongoloid slanting of the palpebral fissures, hypoplasia of zygoma, maxilla & mandible with various eye and ear abnormalities. Here we present a case of an 11 days old female neonate, who was ill looking, dyspnoeic having significant facial profile, multiple congenital anomalies and dolicocephaly; admitted in the department of Neonatology, Mymensingh Medical College Hospital (MMCH), Mymensingh, Bangladesh on 7th August 2020. After taking all the diagnostic assistance of the multidisciplinary approach mainly on the basis of clinical features and radiology we diagnosed the case as TCS. We managed the patient by maintaining temperature, giving nutritional support and injectable antibiotic, took consultation from Otolaryngology department then we discharged the baby with proper counseling, advised regarding further follow up and to consult with paediatric surgeon and cardiologist.

A novel nonsense mutation in the TCOF1 gene in one Chinese newborn with Treacher Collins syndrome

OBJECTIVE

The purpose of this study is that analyze the clinical characters of Treacher Collins syndrome (TCS) with the de nove TCOF1 mutation and emphasize the genetic research result.

METHODS

Genomic DNA from the proband and his parents were extracted from 200 to 400 μl of peripheral blood samples. A 4000 pathgenic genes diagnostic screening panel developed by our laboratory group was used for gene mutation screening. The panel covered the TCOF1 (NM_001135243.1), POLR1C (NM_203,290) and POLR1D (NM_015,972) genes associating with TCS.

RESULTS

We reported a case of typical, complete syndrome with a nonsense mutation c.1622G > A (p.W541*) in exon 11 of TCOF1, who presents bilateral external ears abnormalities, atresia of external auditory canals, antimongoloid slant of the eyes, bilateral partial coloboma of the lateral part of the lower lids, a large and protruding nose, macrostomia, cleft palate and hair displacement anterior to the auricle.

CONCLUSIONS

Our report expands the spectrum of known pathogenic TCOF1 variants associated with TCS in humans.TCOF1 deficiency may cause a severe neonatal presentation with birth defects.

Molecules, Mechanisms, and Disorders of Self-Domestication: Keys for Understanding Emotional and Social Communication from an Evolutionary Perspective

The neural crest hypothesis states that the phenotypic features of the domestication syndrome are due to a reduced number or disruption of neural crest cells (NCCs) migration, as these cells differentiate at their final destinations and proliferate into different tissues whose activity is reduced by domestication. Comparing the phenotypic characteristics of modern and prehistoric man, it is clear that during their recent evolutionary past, humans also went through a process of self-domestication with a simultaneous prolongation of the period of socialization. This has led to the development of social abilities and skills, especially language, as well as neoteny. Disorders of neural crest cell development and migration lead to many different conditions such as Waardenburg syndrome, Hirschsprung disease, fetal alcohol syndrome, DiGeorge and Treacher-Collins syndrome, for which the mechanisms are already relatively well-known. However, for others, such as Williams-Beuren syndrome and schizophrenia that have the characteristics of hyperdomestication, and autism spectrum disorders, and 7dupASD syndrome that have the characteristics of hypodomestication, much less is known. Thus, deciphering the biological determinants of disordered self-domestication has great potential for elucidating the normal and disturbed ontogenesis of humans, as well as for the understanding of evolution of mammals in general.

Disease modeling of core pre-mRNA splicing factor haploinsufficiency

The craniofacial disorder mandibulofacial dysostosis Guion-Almeida type is caused by haploinsufficiency of the U5 snRNP gene EFTUD2/SNU114. However, it is unclear how reduced expression of this core pre-mRNA splicing factor leads to craniofacial defects. Here we use a CRISPR-Cas9 nickase strategy to generate a human EFTUD2-knockdown cell line and show that reduced expression of EFTUD2 leads to diminished proliferative ability of these cells, increased sensitivity to endoplasmic reticulum (ER) stress and the mis-expression of several genes involved in the ER stress response. RNA-Seq analysis of the EFTUD2-knockdown cell line revealed transcriptome-wide changes in gene expression, with an enrichment for genes associated with processes involved in craniofacial development. Additionally, our RNA-Seq data identified widespread mis-splicing in EFTUD2-knockdown cells. Analysis of the functional and physical characteristics of mis-spliced pre-mRNAs highlighted conserved properties, including length and splice site strengths, of retained introns and skipped exons in our disease model. We also identified enriched processes associated with the affected genes, including cell death, cell and organ morphology and embryonic development. Together, these data support a model in which EFTUD2 haploinsufficiency leads to the mis-splicing of a distinct subset of pre-mRNAs with a widespread effect on gene expression, including altering the expression of ER stress response genes and genes involved in the development of the craniofacial region. The increased burden of unfolded proteins in the ER resulting from mis-splicing would exceed the capacity of the defective ER stress response, inducing apoptosis in cranial neural crest cells that would result in craniofacial abnormalities during development.

A Novel Human Pluripotent Stem Cell-Derived Neural Crest Model of Treacher Collins Syndrome Shows Defects in Cell Death and Migration

The neural crest (NC) is a transient multipotent cell population present during embryonic development. The NC can give rise to multiple cell types and is involved in a number of different diseases. Therefore, the development of new strategies to model NC in vitro enables investigations into the mechanisms involved in NC development and disease. In this study, we report a simple and efficient protocol to differentiate human pluripotent stem cells (HPSC) into NC using a chemically defined media, with basic fibroblast growth factor 2 (FGF2) and the transforming growth factor-β inhibitor SB-431542. The cell population generated expresses a range of NC markers, including P75, TWIST1, SOX10, and TFAP2A. NC purification was achieved in vitro through serial passaging of the population, recreating the developmental stages of NC differentiation. The generated NC cells are highly proliferative, capable of differentiating to their derivatives in vitro and engraft in vivo to NC specific locations. In addition, these cells could be frozen for storage and thawed with no loss of NC properties, nor the ability to generate cellular derivatives. We assessed the potential of the derived NC population to model the neurocristopathy, Treacher Collins Syndrome (TCS), using small interfering RNA (siRNA) knockdown of TCOF1 and by creating different TCOF1+/- HPSC lines through CRISPR/Cas9 technology. The NC cells derived from TCOF1+/- HPSC recapitulate the phenotype of the reported TCS murine model. We also report for the first time an impairment of migration in TCOF1+/- NC and mesenchymal stem cells. In conclusion, the developed protocol permits the generation of the large number of NC cells required for developmental studies, disease modeling, and for drug discovery platforms in vitro.

[Analysis of TCOF1 mutation in a Chinese patient with Treacher-Collins syndrome]

OBJECTIVE

To detect potential mutation of TCOF1 gene in a Chinese family affected with Treacher-Collins syndrome.

METHODS

Clinical data of the patient was collected. The analysis included history taking, clinical examination and genetic testing. All coding regions of the TCOF1 gene were subjected to PCR amplification and Sanger sequencing.

RESULTS

A novel mutation c.2261ins G (p.E95X) of the TCOF1 gene was discovered in the patient. The same mutation was not found in his parents and 100 healthy controls.

CONCLUSION

The c.2261insG (p.E95X) mutation of the TCOF1 gene probably underlies the disease in the patient. Genetic testing can facilitate diagnosis and genetic counseling for families affected with TCS.

Mutations in the Neuroblastoma Amplified Sequence gene in a family affected by Acrofrontofacionasal Dysostosis type 1

Acrofrontofacionasal Dysostosis type 1 (AFFND1) is an extremely rare, autosomal recessive syndrome, comprising facial and skeletal abnormalities, short stature and intellectual disability. We analyzed an Indian family with two affected siblings by exome sequencing and identified a novel homozygous truncating mutation in the Neuroblastoma-Amplified Sequence (NBAS) gene in the patients' genome. Mutations in the NBAS gene have recently been associated with different phenotypes mainly involving skeletal formation, liver and cognitive development. The NBAS protein has been implicated in two key cellular processes, namely the non-sense mediated decay and the Golgi-to-Endoplasmic Reticulum retrograde traffic. Both functions were impaired in HEK293T cells overexpressing the truncated NBAS protein, as assessed by Real-Time PCR, Western blot analysis, co-immunoprecipitation, and immunofluorescence analysis. We examined the expression of NBAS protein in mouse embryos at various developmental stages by immunohistochemistry, and detected expression in developing chondrogenic and osteogenic structures of the skeleton as well as in the cortex, hippocampus and cerebellum, which is compatible with a role in bone and brain development. Functional genetics in the zebrafish model showed that depletion of endogenous z-nbas in fish embryos results in defective morphogenesis of chondrogenic cranial skeletal elements. Overall, our data point to a conserved function of NBAS in skeletal morphogenesis during development, support the hypothesis of a causative role of the mutated NBAS gene in the pathogenesis of AFFND1 and extend the spectrum of phenotypes associated with defects in this gene.

Mandibulofacial dysostosis with microcephaly: A case presenting with seizures

We report a case of mandibulofacial dysostosis with microcephaly presenting with seizures. The proband, a 6-year-old Korean boy, had microcephaly, malar and mandibular hypoplasia, and deafness. He showed developmental delay and had suffered recurrent seizures beginning at 21months of age. Electroencephalography revealed occasional spike discharges from the right frontal area. Head magnetic resonance imaging revealed dilatation of the lateral ventricles and a small frontal lobe volume. Whole exome sequencing revealed a de novo frame shift mutation, c.2698_2701 del, of EFTUD2. The epileptic focus was consistent with the reduced frontal lobe volume on head magnetic resonance imaging. Seizures are thus a main feature of mandibulofacial dysostosis with microcephaly, which results from an embryonic development defect due to the EFTUD2 mutation.

Altered mRNA Splicing, Chondrocyte Gene Expression and Abnormal Skeletal Development due to SF3B4 Mutations in Rodriguez Acrofacial Dysostosis

The acrofacial dysostoses (AFD) are a genetically heterogeneous group of inherited disorders with craniofacial and limb abnormalities. Rodriguez syndrome is a severe, usually perinatal lethal AFD, characterized by severe retrognathia, oligodactyly and lower limb abnormalities. Rodriguez syndrome has been proposed to be a severe form of Nager syndrome, a non-lethal AFD that results from mutations in SF3B4, a component of the U2 small nuclear ribonucleoprotein particle (U2 snRNP). Furthermore, a case with a phenotype intermediate between Rodriguez and Nager syndromes has been shown to have an SF3B4 mutation. We identified heterozygosity for SF3B4 mutations in Rodriguez syndrome, confirming that the phenotype is a dominant disorder that is allelic with Nager syndrome. The mutations led to reduced SF3B4 synthesis and defects in mRNA splicing, primarily exon skipping. The mutations also led to reduced expression in growth plate chondrocytes of target genes, including the DLX5, DLX6, SOX9, and SOX6 transcription factor genes, which are known to be important for skeletal development. These data provide mechanistic insight toward understanding how SF3B4 mutations lead to the skeletal abnormalities observed in the acrofacial dysostoses.

The acrofacial dysostoses (AFD) are inherited disorders with abnormalities of the facial and limb bones. Rodriguez syndrome is a severe type of AFD that is usually lethal in the immediate perinatal period. Rodriguez syndrome has been proposed to be a severe form of Nager syndrome, a non-lethal AFD that results from mutations in SF3B4, a component of mRNA splicing machinery needed for proper maturation of primary transcripts. Furthermore, a case with a phenotype intermediate between Rodriguez and Nager syndromes has been shown to have an SF3B4 mutation. We found that mutations in SF3B4 produce Rodriguez syndrome, further demonstrating that it is allelic with Nager syndrome. The consequences of the mutations include abnormal splicing and reduced expression in growth plate chondrocytes of genes that are important for proper development of the skeleton, providing mechanistic insight toward understanding how SF3B4 mutations lead to the skeletal abnormalities observed in the acrofacial dysostoses.

Elevated plasma dihydroorotate in Miller syndrome: Biochemical, diagnostic and clinical implications, and treatment with uridine

BACKGROUND

Miller syndrome (post-axial acrofacial dysostosis) arises from gene mutations for the mitochondrial enzyme dihydroorotate dehydrogenase (DHODH). Nonetheless, despite demonstrated loss of enzyme activity dihydroorotate (DHO) has not been shown to accumulate, but paradoxically urine orotate has been reported to be raised, confusing the metabolic diagnosis.

METHODS

We analysed plasma and urine from a 4-year-old male Miller syndrome patient. DHODH mutations were determined by PCR and Sanger sequencing. Analysis of DHO and orotic acid (OA) in urine, plasma and blood-spot cards was performed using liquid chromatography-tandem mass spectrometry. In vitro stability of DHO in distilled water and control urine was assessed for up to 60h. The patient received a 3-month trial of oral uridine for behavioural problems.

RESULTS

The patient had early liver complications that are atypical of Miller syndrome. DHODH genotyping demonstrated compound-heterozygosity for frameshift and missense mutations. DHO was grossly raised in urine and plasma, and was detectable in dried spots of blood and plasma. OA was raised in urine but undetectable in plasma. DHO did not spontaneously degrade to OA. Uridine therapy did not appear to resolve behavioural problems during treatment, but it lowered plasma DHO.

CONCLUSION

This case with grossly raised plasma DHO represents the first biochemical confirmation of functional DHODH deficiency. DHO was also easily detectable in dried plasma and blood spots. We concluded that DHO oxidation to OA must occur enzymatically during renal secretion. This case resolved the biochemical conundrum in previous reports of Miller syndrome patients, and opened the possibility of rapid biochemical screening.

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.

[The research progress of Treacher Collins syndrome]

Treacher Collins syndrome (TCS, OMIM 154500), also known as Franceschetti-Klein syndrome, is a rare disorder that affects the first and second branchial arches. The estimated incidence is 1/50 000 live births. Mutations in TCOF1 (78%-93%) and POLR1C or POLR1D (8%) cause the disease. Most of TCS cases are inherited in a dominant pattern, while a small proportion are inherited in a recessive pattern. TCS has a variable phenotype with typical clinical characteristics including downward-slant of palpebral fissure, malar hypoplasia, mandibular hypoplasia and microtia. TCS management is a multidisciplinary affair, as interventions range from reconstructive to psychosocial. For hearing rehabilitation, TCS patients may have the choices of BAHA, ponto, vibrant soundbridge or bonebridge implantation. In this review, we summarize the TCS clinical malformations, diagnosis, genetics, management and auditory rehabilitation.

Phenotype analysis of Polish patients with mandibulofacial dysostosis type Guion-Almeida associated with esophageal atresia and choanal atresia caused by EFTUD2 gene mutations

We present the phenotype of three unrelated Polish patients with MFD type Guion-Almeida confirmed by EFTUD2 mutations. In all of our patients, dysmorphic craniofacial features, microcephaly, thumb abnormalities, psychomotor and speech delay were described. In addition, among other major defects, esophageal atresia (EA) in one patient and choanal atresia in two of them were present. Three different mutations in EFTUD2 gene were found in presented patients. Our observations confirm the clinical heterogeneity of mandibulofacial dysostosis type Guion-Almeida and its connection with major congenital defects such as esophageal atresia and choanal atresia.

Dysostosis mandibulo-facialis (Franceschetti-Zwahlen) in four generations

Description of a family five members of which, in four generations show the syndrome mentioned in the title. The mode of inheritance is dominant, with a rather strong penetrance and a great variability in the expressivity. The importance of genetic counseling is stressed.

Confirmation of genetic homogeneity of syndactyly type IV and triphalangeal thumb-polysyndactyly syndrome in a Chinese family and review of the literature

Syndactyly type IV (SD4) is inherited in an autosomal dominant fashion and characterized by complete cutaneous syndactyly of all fingers accompanied with polydactyly. Triphalangeal thumb-polysyndactyly syndrome (TPTPS) consists of a triphalangeal thumb, polydactyly, and syndactyly and is transmitted in an autosomal dominant manner with variable expression. Genomic duplications of the long-range limb-specific cis-regulator (ZRS) cause SD4 and TPTPS. Here, we report two individuals from a Chinese family with syndactyly. One individual had overlapping clinical symptoms of TPTPS and SD4, while the other had a typical SD4 with postaxial polydactyly of the toe. Results of quantitative PCR suggested that the duplication of ZRS involved all affected individuals, and array comparative genomic hybridization detected its size as 115.3 kb.

CONCLUSION

This work confirms the genetic homogeneity of SD4 and TPTPS. Our result expands the spectrum of ZRS duplications. TPTPS and SD4 should be considered as a continuum of phenotypes.

Facial dysostoses: Etiology, pathogenesis and management

Approximately 1% of all live births exhibit a minor or major congenital anomaly. Of these approximately one-third display craniofacial abnormalities which are a significant cause of infant mortality and dramatically affect national health care budgets. To date, more than 700 distinct craniofacial syndromes have been described and in this review, we discuss the etiology, pathogenesis and management of facial dysostoses with a particular emphasis on Treacher Collins, Nager and Miller syndromes. As we continue to develop and improve medical and surgical care for the management of individual conditions, it is essential at the same time to better characterize their etiology and pathogenesis. Here we describe recent advances in our understanding of the development of facial dysostosis with a view towards early in utero identification and intervention which could minimize the manifestation of anomalies prior to birth. The ultimate management for any craniofacial anomaly however, would be prevention and we discuss this possibility in relation to facial dysostosis.

A novel mutation in the TCOF1 gene found in two Chinese cases of Treacher Collins syndrome

OBJECTIVE

To analyze the clinical features, hearing rehabilitation and family related gene mutations in the Chinese cases of Treacher Collins syndrome (TCS). The purpose of this study is to emphasize the genetic research result correlating with the clinical assessment of TCS in Chinese families.

METHODS

Six patients with tentative diagnosis and family members of two patients were analyzed in this study. The analysis included medical histories, clinical analysis, hearing tests and genetic tests. The TCOF1, POLR1C and POLR1D genes were sequenced to identify the pathogenic mutation responsible for the development of TCS.

RESULTS

The two TCS cases exhibited high phenotypic variability. One novel heterozygous mutation (c.4420 C>T) in the TCOF1 gene was identified. The mutations were found in the TCS patients but not in any of their unaffected family members or the 200 unrelated control subjects.

CONCLUSIONS

A novel TCOF1 c.4420 C>T mutation can be a cause of TCS in Chinese. We think that genetic studies to assess patients with mandibulofacial dysostosis may assist in making TCS diagnosis and providing consultant for their families.

Informed consent for whole genome sequencing: a qualitative analysis of participant expectations and perceptions of risks, benefits, and harms

Scientific evidence on the extent to which ethical concerns about privacy, confidentiality, and return of results for whole genome sequencing (WGS) are effectively conveyed by informed consent (IC) is lacking. The aim of this study was to learn, via qualitative interviews, about participant expectations and perceptions of risks, benefits, and harms of WGS. Participants in two families with Miller syndrome consented for WGS were interviewed about their experiences of the IC process and their perceptions of risks, benefits, and harms of WGS. Interviews were transcribed and analyzed for common themes. IC documents are included in the Supplementary Materials. Participants expressed minimal concerns about privacy and confidentiality with regard to both their participation and sharing of their WGS data in restricted access databases. Participants expressed strong preferences about how results should be returned, requesting both flexibility of the results return process and options for the types of results to be returned. Participant concerns about risks to privacy and confidentiality from broad sharing of WGS data are likely to be strongly influenced by social and medical context. In these families with a rare Mendelian syndrome, the perceived benefits of participation strongly trumped concerns about risks. Individual preferences, for results return, even within a family, varied widely. This underscores the need to develop a framework for results return that allows explicitly for participant preferences and enables modifications to preferences over time. Web-based tools that facilitate participant management of their individual research results could accommodate such a framework.

Haploinsufficiency of SF3B4, a component of the pre-mRNA spliceosomal complex, causes Nager syndrome

Nager syndrome, first described more than 60 years ago, is the archetype of a class of disorders called the acrofacial dysostoses, which are characterized by craniofacial and limb malformations. Despite intensive efforts, no gene for Nager syndrome has yet been identified. In an international collaboration, FORGE Canada and the National Institutes of Health Centers for Mendelian Genomics used exome sequencing as a discovery tool and found that mutations in SF3B4, a component of the U2 pre-mRNA spliceosomal complex, cause Nager syndrome. After Sanger sequencing of SF3B4 in a validation cohort, 20 of 35 (57%) families affected by Nager syndrome had 1 of 18 different mutations, nearly all of which were frameshifts. These results suggest that most cases of Nager syndrome are caused by haploinsufficiency of SF3B4. Our findings add Nager syndrome to a growing list of disorders caused by mutations in genes that encode major components of the spliceosome and also highlight the synergistic potential of international collaboration when exome sequencing is applied in the search for genes responsible for rare Mendelian phenotypes.

[Clinical and genetic analysis of a patient with Treacher Collins syndrome in TCOF1 gene]

OBJECTIVE

To analyze the clinical and genetic features of a patient with Treacher Collins syndrome (TCS), and identify the mutation in TCOF1 gene.

METHOD

The medical history was taken, and general physical examinations and otological examinations were conducted in this patient. Genomic DNA was extracted from this patient and his parents and complete TCOF1 gene coding exons were amplified by specific PCR primers. Direct sequencing was carried out to identify the mutations. The raw data was analyzed with GeneTool software and molecular biological website.

RESULT

We detected a heterozygous c. 1639 delAG mutation in exon 11 of TCOF1, which resulted in a truncated protein lacking normal function. This mutation is a novel mutation and the second case identified in exon 11 of in TCS.

CONCLUSION

TCS patient reported in this study has unique clinical phenotype. TCOF1 gene mutation is the specific risk factor.

[Hereditary deafness in Kirov oblast: estimation of the incidence rate and DNA diagnosis in children]

Genetic analysis of hereditary deafness (HD) has been performed in the city of Kirov and ten rural districts of Kirov oblast (administrative region). The analysis employed the methods used in audiology, medical genetic counseling, and DNA diagnosis. Deafness has been established to be hereditary in 143 children from 100 unrelated families. The incidence rates of isolated and syndromic HDs in the period studied (1995-2001) have been estimated at 1.25 and 0.36 per 1000 newborns, respectively, the total incidence rate of all HD forms being 1.61 per 1000 newborns (1 case per 621 newborns). DNA analysis for the detection of seven frequent mutations in the genes GJB2 (the 35delG, 167delT, 235delC, and M34T mutations), GJB6 (the del(GJB6-D13S1854) and del(GJB6-D13S1830) mutations), and TMC1 (the R34X mutation) has been performed in families with isolated neurosensory deafness. Molecular genetic analysis has detected mutations in 51 children (48.6%); in 54 children (51.4%), no mutations have been found. The following genotypes have been identified in children with HD: 35delG/35delG in 32 probands (30.5%), 35delG/+ in 16 probands (15.2%), 35delG/235delC in 1 proband (0.95%), M34T/+ in 1 proband (0.95%), and M34T/35delG in 1 proband (0.95%). The 167delT mutation has not been found. The frequency of the 35delG mutation in the GJB2 gene has been estimated to be 39.05%. In the group with a family history of HD, mutations have been found in 66.7% of patients; in the group without a family history of HD, in 37.5% of patients. No mutation has been found in the GJB6 or TMC1 gene. Molecular genetic analysis has been performed in a family with clinically diagnosed Treacher Collins-Franceschetti syndrome. Sequencing has been used to find the 748-69C>T polymorphism in intron 6 (in the homozygous state) and the 3635C>G mutation in exon 23 leading to the substitution of glycine for alanine at position 1176 of the amino acid sequence (Ala1176Gly, in the heterozygous state), which have not been described before.

Mammalian neurogenesis requires Treacle-Plk1 for precise control of spindle orientation, mitotic progression, and maintenance of neural progenitor cells

The cerebral cortex is a specialized region of the brain that processes cognitive, motor, somatosensory, auditory, and visual functions. Its characteristic architecture and size is dependent upon the number of neurons generated during embryogenesis and has been postulated to be governed by symmetric versus asymmetric cell divisions, which mediate the balance between progenitor cell maintenance and neuron differentiation, respectively. The mechanistic importance of spindle orientation remains controversial, hence there is considerable interest in understanding how neural progenitor cell mitosis is controlled during neurogenesis. We discovered that Treacle, which is encoded by the Tcof1 gene, is a novel centrosome- and kinetochore-associated protein that is critical for spindle fidelity and mitotic progression. Tcof1/Treacle loss-of-function disrupts spindle orientation and cell cycle progression, which perturbs the maintenance, proliferation, and localization of neural progenitors during cortical neurogenesis. Consistent with this, Tcof1(+/-) mice exhibit reduced brain size as a consequence of defects in neural progenitor maintenance. We determined that Treacle elicits its effect via a direct interaction with Polo-like kinase1 (Plk1), and furthermore we discovered novel in vivo roles for Plk1 in governing mitotic progression and spindle orientation in the developing mammalian cortex. Increased asymmetric cell division, however, did not promote increased neuronal differentiation. Collectively our research has therefore identified Treacle and Plk1 as novel in vivo regulators of spindle fidelity, mitotic progression, and proliferation in the maintenance and localization of neural progenitor cells. Together, Treacle and Plk1 are critically required for proper cortical neurogenesis, which has important implications in the regulation of mammalian brain size and the pathogenesis of congenital neurodevelopmental disorders such as microcephaly.

Haploinsufficiency of a spliceosomal GTPase encoded by EFTUD2 causes mandibulofacial dysostosis with microcephaly

Mandibulofacial dysostosis with microcephaly (MFDM) is a rare sporadic syndrome comprising craniofacial malformations, microcephaly, developmental delay, and a recognizable dysmorphic appearance. Major sequelae, including choanal atresia, sensorineural hearing loss, and cleft palate, each occur in a significant proportion of affected individuals. We present detailed clinical findings in 12 unrelated individuals with MFDM; these 12 individuals compose the largest reported cohort to date. To define the etiology of MFDM, we employed whole-exome sequencing of four unrelated affected individuals and identified heterozygous mutations or deletions of EFTUD2 in all four. Validation studies of eight additional individuals with MFDM demonstrated causative EFTUD2 mutations in all affected individuals tested. A range of EFTUD2-mutation types, including null alleles and frameshifts, is seen in MFDM, consistent with haploinsufficiency; segregation is de novo in all cases assessed to date. U5-116kD, the protein encoded by EFTUD2, is a highly conserved spliceosomal GTPase with a central regulatory role in catalytic splicing and post-splicing-complex disassembly. MFDM is the first multiple-malformation syndrome attributed to a defect of the major spliceosome. Our findings significantly extend the range of reported spliceosomal phenotypes in humans and pave the way for further investigation in related conditions such as Treacher Collins syndrome.

Finding disease variants in Mendelian disorders by using sequence data: methods and applications

Many sequencing studies are now underway to identify the genetic causes for both Mendelian and complex traits. Via exome-sequencing, genes harboring variants implicated in several Mendelian traits have already been identified. The underlying methodology in these studies is a multistep algorithm based on filtering variants identified in a small number of affected individuals and depends on whether they are novel (not yet seen in public resources such as dbSNP), shared among affected individuals, and other external functional information on the variants. Although intuitive, these filter-based methods are nonoptimal and do not provide any measure of statistical uncertainty. We describe here a formal statistical approach that has several distinct advantages: (1) it provides fast computation of approximate p values for individual genes, (2) it adjusts for the background variation in each gene, (3) it allows for incorporation of functional or linkage-based information, and (4) it accommodates designs based on both affected relative pairs and unrelated affected individuals. We show via simulations that the proposed approach can be used in conjunction with the existing filter-based methods to achieve a substantially better ranking of a gene relevant for disease when compared to currently used filter-based approaches, this is especially so in the presence of disease locus heterogeneity. We revisit recent studies on three Mendelian diseases and show that the proposed approach results in the implicated gene being ranked first in all studies, and approximate p values of 10(-6) for the Miller Syndrome gene, 1.0 × 10(-4) for the Freeman-Sheldon Syndrome gene, and 3.5 × 10(-5) for the Kabuki Syndrome gene.

Mandibulofacial syndrome with growth and mental retardation, microcephaly, ear anomalies with skin tags, and cleft palate in a mother and her son: autosomal dominant or X-linked syndrome?

We report on a Brazilian mother and her son affected with mandibulofacial dysostosis, growth and mental retardation, microcephaly, first branchial arch anomalies, and cleft palate. To date only three males and one female, all sporadic cases, with a similar condition have been reported. This article describes the first familial case with this rare condition indicating autosomal dominant or X-linked inheritance.