Generation of a new six1-null line in Xenopus tropicalis for study of development and congenital disease.

The vertebrate Six (Sine oculis homeobox) family of homeodomain transcription factors plays critical roles in the development of several organs. Six1 plays a central role in cranial placode development, including the precursor tissues of the inner ear, as well as other cranial sensory organs and the kidney. In humans, mutations in SIX1 underlie some cases of Branchio-oto-renal (BOR) syndrome, which is characterized by moderate-to-severe hearing loss. We utilized CRISPR/Cas9 technology to establish a six1 mutant line in Xenopus tropicalis that is available to the research community. We demonstrate that at larval stages, the six1-null animals show severe disruptions in gene expression of putative Six1 target genes in the otic vesicle, cranial ganglia, branchial arch, and neural tube. At tadpole stages, six1-null animals display dysmorphic Meckel's, ceratohyal, and otic capsule cartilage morphology. This mutant line will be of value for the study of the development of several organs as well as congenital syndromes that involve these tissues.

Alterações funcionais e estruturais do complexo craniofacial na síndrome branquio-óculo-facial: relato de caso / Functional and structural alterations of the craniofacial complex in the branchio-oculo-facial syndrome: case report / Alteraciones funcionales y estructurales del complejo craneofacial en el síndrome branquio-óculo-facial: relato de caso

Objetivo: Descrever características clínicas, alterações funcionais e estruturais de complexo craniofacial de sujeito com síndrome branquio-óculo-facial. Método: Paciente de 13 anos e 3 meses, respiradora oral com perda auditiva condutiva de grau moderadamente severo em ambas as orelhas, diagnosticada com síndrome branquio-óculo-facial, apresentou: fissura labiopalatina transforame bilateral completa corrigida por labioplastia e palatoplastia primárias, assimetria facial, fístula em região anterior de palato duro, atresia maxilar transversa, dentinogênese imperfeita, trespasse horizontal negativo, oclusão Classe I de Angle e mordida aberta anterior e lateral bilateralmente, desvio severo da linha média superior para a esquerda, incisivo lateral superior permanente semi-erupcionado por vestibular do canino superior decíduo do lado esquerdo, retenção prolongada do segundo molar inferior decíduo direito, apinhamento dentário inferior, hipotonia e posicionamento inadequado de língua, ausência de vedamento labial em repouso, deglutição adaptada, alteração na mobilidade de lábios, bochechas e palato mole com escape de ar nasal na fala, caracterizando disfunção velofaríngea. Sujeitos com fissura lábiopalatina podem apresentar grande variedade de alterações na produção dos fones. Paciente apresenta crescimento deficiente da maxila que, como relatado na literatura, pode alterar o desenvolvimento do terço médio da face com repercussão na oclusão dentária, fala e formato do nariz. Conclusão: As alterações clínicas funcionais e estruturais relatadas são na maioria do complexo craniofacial, demonstrando a importância da otorrinolaringologia, fonoaudiologia e odontologia na terapêutica interdisciplinar dos pacientes com a síndrome.

Introduction: Branchio-Oculo-Facial Syndrome (BOFS) is a rare autosomal disease with variable expression, dependent on genetic mutations, whose phenotype is characterized by ocular, hearing and craniofacial alterations. Purpose: describe the clinical features, the functional and structural alterations in the craniofacial complex of a subject with branchio-oculo-facial syndrome. Method: A 13-year and 3-month-old girl, with moderately severe conductive bilateral hearing loss diagnosed with BOFS, presented: bilateral cleft lip and palate treated by labioplasty and palatoplasty, facial asymmetry, anterior maxillary fistula, transverse maxillary atresia, imperfect dentinogenesis, negative horizontal trespass, Angle Class I bilateral, anterior and lateral open bite on both sides, severe left superior midline deviation, eruption by vestibular of the superior canine on the left side, prolonged retention of the second inferior molar right deciduous, lower dental crowding, hypotonia and inadequate tongue positioning, absence of labial resting at rest, adapted swallowing, alteration in mobility of lips, cheeks and palate with nasal air exhaust in speech, characterizing velopharyngeal dysfunction. There are few publications of BOFS, given its rarity. Subjects with cleft lip and palate may present a wide variety of changes in the production of headphones. Patient presents deficient growth of the maxilla which, as reported in the literature, may alter the development of the middle third of the face with repercussion in dental occlusion, speech and nose shape. Conclusion: The functional and structural clinical alterations reported are the majority of the craniofacial complex, demonstrating the importance of otorhinolaryngology, speech therapy and orthodontics in the interdisciplinary therapy of patients with BOFS.

Introducción: El síndrome branquio-oculo-facial (BOFS) es una enfermedad autosómica rara con expresión variable, dependiente de las mutaciones genéticas, caracterizada por alteraciones oculares, auriculares y craneofaciales. Propósito: describir características clínicas, alteraciones funcionales y estructurales del complejo craneofacial de un sujeto con BOFS. Método: Niña de 13 años y 3 meses de edad, con pérdida de audición conductiva moderadamente grave bilateralmente diagnosticada con SBOF, presentó: paladar y labio hendido bilateral tratado por labioplastia y palatoplastia primarias, asimetría facial, fístula maxilar anterior, atresia maxilar transversal, dentinogénesis imperfecta, traspaso horizontal negativo, clase I de Angle bilateral, mordida abierta anterior y lateral bilateralmente, desviación severa de la línea media superior izquierda, erupción vestibular del canino superior del lado izquierdo, retención prolongada del segundo molar inferior derecho deciduo, apiñamiento dental, hipotonía e inadecuada colocación de la lengua, ausencia de sello labial en reposo, deglución adaptada, alteración de movilidad de labios, mejillas y velo del paladar con escape de aire nasal y disfunción velofaríngea Hay pocas publicaciones de BOFS, dada su rareza. Los sujetos con labio y paladar hendido pueden presentar una gran variedad de cambios en la producción de auriculares. El paciente presenta crecimiento deficiente del maxilar que, según se informa en la literatura, puede alterar el desarrollo del tercio medio de la cara con repercusión en la oclusión dental, habla y la forma de la nariz. Conclusión: Alteraciones clínicas funcionales y estructurales la mayoría del complejo craniofacial. Eso demuestra la importancia de otorrinolaringología, fonoaudiología y odontología en la terapia interdisciplinaria de pacientes con SBOF.;Introdução: A Síndrome Branquio-Óculo-Facial é uma doença autossômica rara com expressão variável, dependente das mutações genéticas, cujo fenótipo caracteriza-se por alterações oculares, auriculares e craniofaciais.

A clinical and molecular analysis of branchio-oculo-facial syndrome patients in Russia revealed new mutations in TFAP2A.

Branchio-oculo-facial syndrome (BOFS, OMIM# 113620) is a rare autosomal dominant disorder characterised by branchial cleft sinus defects, ocular anomalies and facial dysmorphisms, including lip or palate cleft or pseudocleft, and is associated with mutations in the TFAP2A gene. Here, we performed clinical analysis and mutation diagnostics in seven BOFS patients in Russia. The phenotypic presentation of BOFS observed in three patients showed high heterogeneity, including variation in its main clinical manifestations (linear loci of cervical cutaneous aplasia, ocular anomalies and orofacial cleft). In certain other cases, isolated ocular anomalies, or an orofacial cleft with accessory BOFS symptoms, were observed. In five BOFS patients, conductive hearing loss was diagnosed. Direct sequencing of the coding region of the TFAP2A gene revealed missense mutations in four BOFS patients. One patient was observed to have a previously described mutation (p.Arg251Gly), while three patients from two families were found to have novel mutations: p.Arg213Ser and p.Val210Asp. These novel mutations were not present in healthy members of the same family and therefore should be classified as de novo.

Mutational analysis of EYA1, SIX1 and SIX5 genes and strategies for management of hearing loss in patients with BOR/BO syndrome.

BACKGROUND: Branchio-oto-renal (BOR) or branchio-otic (BO) syndrome is one of the most common forms of autosomal dominant syndromic hearing loss. Mutations in EYA1, SIX1 and SIX5 genes have been associated with BOR syndrome. In this study, clinical and genetic analyses were performed in patients with BOR/BO syndrome focusing on auditory manifestations and rehabilitation. METHODS: The audiologic manifestations were reviewed in 10 patients with BOR/BO syndrome. The operative findings and hearing outcome were analyzed in patients who underwent middle ear surgeries. The modality and outcome of auditory rehabilitation were evaluated. Genetic analysis was performed for EYA1, SIX1, and SIX5 genes. RESULTS: All patients presented with mixed hearing loss. Five patients underwent middle ear surgeries without successful hearing gain. Cochlear implantation performed in two patients resulted in significant hearing improvement. Genetic analysis revealed four novel EYA1 mutations and a large deletion encompassing the EYA1 gene. CONCLUSIONS: Auditory rehabilitation in BOR/BO syndrome should be individually tailored keeping in mind the high failure rate after middle ear surgeries. Successful outcome can be expected with cochlear implantations in patients with BOR/BO syndrome who cannot benefit from hearing aids. The novel EYA1 mutations may add to the genotypic and phenotypic spectrum of BOR syndrome in the East Asian population.

Structure-function analyses of the human SIX1-EYA2 complex reveal insights into metastasis and BOR syndrome.

SIX1 interacts with EYA to form a bipartite transcription factor essential for mammalian development. Loss of function of this complex causes branchio-oto-renal (BOR) syndrome, whereas re-expression of SIX1 or EYA promotes metastasis. Here we describe the 2.0-Å structure of SIX1 bound to EYA2, which suggests a new DNA-binding mechanism for SIX1 and provides a rationale for the effect of BOR syndrome mutations. The structure also reveals that SIX1 uses predominantly a single helix to interact with EYA. Substitution of a single amino acid in this helix is sufficient to disrupt SIX1-EYA interaction, SIX1-mediated epithelial-mesenchymal transition and metastasis in mouse models. Given that SIX1 and EYA are overexpressed in many tumor types, our data indicate that targeting the SIX1-EYA complex may be a potent approach to inhibit tumor progression in multiple cancer types.

A family with a complex clinical presentation characterized by arrhythmogenic right ventricular dysplasia/cardiomyopathy and features of branchio-oculo-facial syndrome.

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) is a familial form of cardiomyopathy typically caused by mutations in genes that encode an element of the cardiac desmosome. Branchio-oculo-facial syndrome (BOFS) is a craniofacial disorder caused by TFAP2A mutations. In a family segregating ARVD/C, some members also had features of BOFS. Genetic testing for ARVD/C identified a mutation in PKP2, encoding plakophilin-2, a component of the cardiac desmosome. Evaluation of dysmorphology by chromosome microarray (CMA) identified a 4.4 Mb deletion at chromosome 6p24 that included both TFAP2A and DSP, encoding desmoplakin, an additional component of the cardiac desmosome implicated in ARVD/C. A family member with both the 6p24 deletion and PKP2 mutation had more severe cardiac dysfunction. These findings suggest that this contiguous gene deletion contributes to both ARVD/C and BOFS, and that DSP haploinsufficiency may contribute to cardiomyopathy. This family provides a clinical example that underscores the need for careful evaluation in clinical scenarios where genetic heterogeneity is known to exist. Finally, it suggests that individuals with unexplained cardiomyopathy and dysmorphic facial features may benefit from CMA analysis.

Mutation screening of the EYA1, SIX1, and SIX5 genes in a large cohort of patients harboring branchio-oto-renal syndrome calls into question the pathogenic role of SIX5 mutations.

Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder characterized by branchial, ear, and renal anomalies. Over 80 mutations in EYA1 have been reported in BOR. Mutations in SIX1, a DNA binding protein that associates with EYA1, have been reported less frequently. One group has recently described four missense mutations in SIX5 in five unrelated patients with BOR. Here, we report a screening of these three genes in a cohort of 140 patients from 124 families with BOR. We identified 36 EYA1 mutations in 42 unrelated patients, 2 mutations, and 1 change of unknown significance in SIX1 in 3 unrelated patients, but no mutation in SIX5. We did not find correlation between genotype and phenotype, and observed a high phenotypic variability between and within BOR families. We show the difficulty in establishing a molecular diagnosis strategy in BOR syndrome: the screening focusing on patients with typical BOR would detect a mutation rate of 76%, but would also miss mutations in 9% of patients with atypical BOR. We detected a deletion removing three EYA1 exons in a patient who was previously reported to carry the SIX5 Thr552Met mutation. This led us to reconsider the role of SIX5 in the development of BOR.

EYA1 mutations associated with the branchio-oto-renal syndrome result in defective otic development in Xenopus laevis.

BACKGROUND INFORMATION: The BOR (branchio-oto-renal) syndrome is a dominant disorder most commonly caused by mutations in the EYA1 (Eyes Absent 1) gene. Symptoms commonly include deafness and renal anomalies. RESULTS: We have used the embryos of the frog Xenopus laevis as an animal model for early ear development to examine the effects of different EYA1 mutations. Four eya1 mRNAs encoding proteins correlated with congenital anomalies in human were injected into early stage embryos. We show that the expression of mutations associated with BOR, even in the presence of normal levels of endogenous eya1 mRNA, leads to morphologically abnormal ear development as measured by overall otic vesicle size, establishment of sensory tissue and otic innervation. The molecular consequences of mutant eya1 expression were assessed by QPCR (quantitative PCR) analysis and in situ hybridization. Embryos expressing mutant eya1 showed altered levels of multiple genes (six1, dach, neuroD, ngnr-1 and nt3) important for normal ear development. CONCLUSIONS: These studies lend support to the hypothesis that dominant-negative effects of EYA1 mutations may have a role in the pathogenesis of BOR.

[Genetic deafness]. / Surdités d'origine génétique.

OBJECTIVES: The aim of this study was to review the different types of genetic deafness. METHODS: We describe syndromic and isolated sensorineural deafness and transmission deafness. RESULTS: Genetic sensorineural syndromic deafness represents 30% of cases of genetic deafness. A frequent cause is Pendred syndrome, which associates congenital sensorineural deafness with goitre and malformations of the inner ear which can be identified on computed tomography scan. Isolated deafness which is responsible for 70% of cases of genetic deafness is then outlined. Among the different types of isolated deafness, 80% are autosomal recessive disorders. A frequent form of autosomal recessive deafness is due to mutations in the connexin 26 gene. Lastly, we detail transmission deafness dominated by aplasia. Major aplasia is characterized by a malformation of the external ear associated with malformations of the middle ear whereas, minor aplasia corresponds to a malformation of the middle ear, sometimes associated with minor external ear malformations. CONCLUSION: For each type of deafness we propose a systematic assessment.

SIX1 mutation associated with enlargement of the vestibular aqueduct in a patient with branchio-oto syndrome.

OBJECTIVES: : The objectives of this study were to identify SIX1 gene mutations in a patient with branchio-oto syndrome (BO) and to clarify the relationship between SIX1 mutation and enlargement of the vestibular aqueduct (EVA). METHODS: : A genetic study and retrospective chart review for a patient in whom EYA1 mutation had already been excluded was conducted. We studied a Japanese patient who had autosomal-dominant mixed hearing loss, a unilateral ear pit and unilateral EVA, and who was previously diagnosed as having BO. We searched for SIX1 and SLC26A4 mutations using polymerase chain reaction and direct gene sequencing. RESULTS: : The patient carried a heterozygous A-->G mutation at nucleotide 386 within exon 1 of SIX1 that resulted in substitution of a cysteine for a tyrosine at codon 129 (Y129C) of the gene product. Y129C is a previously identified SIX1 mutation and was not detected in any of our 164 control chromosomes. No SLC26A4 mutations were identified. CONCLUSION: : Y129C mutation in SIX1 may cause EVA as well as BO.

[Clinical symptoms of branchio-oto-renal syndrome in a family with a positive test for EYA1 gene].

Three families with branchio-oto-renal syndrome (BOR syndrome) were examined. In one of the families all its members with BOR syndrome had deletion of cytosine in position 759 (759delC) in DNA sequence of EYA1 gene in exone 8. Clinical characteristics of BOR syndrome in the family are given. Molecular-genetic analysis confirmed the diagnosis clinically in case of all signs of the syndrome presence among the members of the family. Rare cases of hereditary syndromes with hearing problems provide more knowledge about structure of hereditary hypoacusis forms in the population. The syndromal forms reflect a complex genetic basis of the processes of sound perception.

A comparative study of Eya1 and Eya4 protein function and its implication in branchio-oto-renal syndrome and DFNA10.

Allele variants of EYA1 and EYA4, two members of the vertebrate Eya gene family, underlie two types of inherited human deafness, branchio-oto-renal (BOR) syndrome and DFNA10, respectively. To clarify how mutations in these two genes and their encoded proteins impact the normal biology of hearing, we completed a number of functional studies using the yeast-two-hybrid system. We verified that bait constructs of the homologous region ( Eya1HR and Eya4HR) interact with Six1 prey constructs, although no interaction with Dach1 prey was demonstrable. To compare interaction affinities, we evaluated alpha-galactosidase activity after cotransformation of Eya1HR/Six1 and Eya4HR/Six1 and found that the latter interaction was weaker. By immunofluorescence staining, we showed Eya4HR localization to the cytoplasm. After coexpression of Six1, Eya4HR was translocated to the nucleus. Results with Eya1HR were similar. Translation of mutant constructs ( Eya4HR(R564X) and Eya1HR(R539X)) could not be demonstrated. Using dual Eya-containing constructs (with two wild-type alleles or wild-type and mutant alleles), we confirmed no translation of the mutant allele, even if the mutation was nontruncating. These results are consistent with clinical data and implicate haploinsufficiency as the cause of BOR syndrome and DFNA10.

Evidence of progression and fluctuation of hearing impairment in branchio-oto-renal syndrome.

We retrospectively analysed long-term serial audiometry data from patients with branchio-oto-renal (BOR) syndrome to show the features of progression and fluctuation in hearing impairment and relate the findings to age and magnetic resonance imaging (MRI) findings in the petrosal bones. Thirty-two clinically affected BOR patients from six Dutch families (A-F) were included. Audiograms were available in 24 cases, covering followup intervals of between 3 and 30 years, and suitable for individual statistical analysis in 16 cases: 14 cases also had MRI findings. Significant progression in hearing impairment was found in 10 cases, while findings of significant fluctuation were made in seven cases. These findings did not clearly correlate with MRI findings. Substantial fluctuation occurred only in cases followed at a relatively young age. Patients with an enlarged endolymphatic duct and/or sac showed significantly higher sensorineural hearing thresholds than those with either normal MRI findings or cochlear/labyrinthine hypoplasia with or without enlarged duct or sac. We conclude that progressive, fluctuant hearing loss occurred in some BOR patients; however, only young patients showed substantial threshold fluctuation. BOR patients with an enlarged endolymphatic duct and/or sac on MRI seemed to be predisposed to developing more severe hearing impairment.

Impaired interactions between mouse Eyal harboring mutations found in patients with branchio-oto-renal syndrome and Six, Dach, and G proteins.

Mutations in the EYA1 gene are responsible for branchio-oto-renal (BOR) syndrome as well as for other ocular defects. Most of the mutations are located within or in the vicinity of the EYA domain, which is highly conserved in the EYA protein family. The EYA domain is required for protein-protein interactions, which are important to the biological function of EYA proteins. To determine how EYA1 mutations cause BOR syndrome and/or ocular defects, we tested the effects of Eya1 mutations on interactions with Six. Dach, and G proteins by mammalian two-hybrid and GST-pulldown assays. Defective interactions were noted between BOR-type mutations S486P and L504R of Eya1 and Dach1, G proteins, and some Six proteins. These mutations impaired the activation of transcription from a Six-responsive gene, myogenin, with Six5. S486P and L504R showed an altered digestion pattern with trypsin, and L504R also decreased the sensitivity to V8 protease digestion and produced a peptide fragment with a different M(r). Our results suggest that defective protein-protein interactions of the mutations in the EYA domain underlie BOR syndrome and that SIX, DACH, and/or G proteins are possibly involved in the pathogenic processes.

Oto-facio-cervical (OFC) syndrome is a contiguous gene deletion syndrome involving EYA1: molecular analysis confirms allelism with BOR syndrome and further narrows the Duane syndrome critical region to 1 cM.

Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder involving hearing loss, branchial defects, ear pits and renal abnormalities. Oto-facio-cervical (OFC) syndrome is clinically similar to BOR syndrome, with clinical features in addition to those of BOR syndrome. Mutations in the EYA1 gene (localised to 8q13.3) account for nearly 70% of BOR syndrome cases exhibiting at least three of the major features. Small intragenic deletions of the 3' region of the gene have also been reported in patients with BOR syndrome. We have developed a fluorescent quantitative multiplex polymerase chain reaction for three 3' exons (7, 9 and 13) of the EYA1 gene. This dosage assay, combined with microsatellite marker analysis, has identified de novo deletions of the EYA1 gene and surrounding region in two patients with complex phenotypes involving features of BOR syndrome. One patient with OFC syndrome carried a large deletion of the EYA1 gene region, confirming that OFC syndrome is allelic with BOR syndrome. Microsatellite analysis has shown that comparison of the boundaries of this large deletion with other reported rearrangements of the region reduces the critical region for Duane syndrome (an eye movement disorder) to between markers D8S553 and D8S1797, a genetic distance of approximately 1 cM.

In-the-ear hearing aids within auricular prostheses.

We report a child with bilateral congenital microtia in whom cosmetic and auditory rehabilitation has been effected using in-the-ear hearing aids within prostheses overlying the rudimentary external auditory meati after canaloplasty. This novel method of auditory rehabilitation has not been reported before and is suitable in selected cases. The prostheses themselves were successfully secured using a prosthetic contact adhesive we have developed that offers excellent retention, little if any skin reaction, and high patient acceptability.