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PURPOSE: Hearing loss (HL) is often monogenic. The clinical importance of genetic testing in HL may further increase when gene therapy products become available. Diagnoses are, however, complicated by a high genetic and allelic heterogeneity, particularly of autosomal dominant (AD) HL. This work aimed to characterize the mutational spectrum of AD HL in Austria. METHODS: In an ongoing prospective study, 27 consecutive index patients clinically diagnosed with non-syndromic AD HL, including 18 previously unpublished cases, were analyzed using whole-exome sequencing (WES) and gene panels. Novel variants were characterized using literature and bioinformatic means. Two additional Austrian medical centers provided AD HL mutational data obtained with in-house pipelines. Other Austrian cases of AD HL were gathered from literature. RESULTS: The solve rate (variants graded as likely pathogenic (LP) or pathogenic (P)) within our cohort amounted to 59.26% (16/27). MYO6 variants were the most common cause. One third of LP/P variants were truncating variants in haploinsufficiency genes. Ten novel variants in HL genes were identified, including six graded as LP or P. In one cohort case and one external case, the analysis uncovered previously unrecognized syndromic presentations. CONCLUSION: More than half of AD HL cases analyzed at our center were solved with WES. Our data demonstrate the importance of genetic testing, especially for the diagnosis of syndromic presentations, enhance the molecular knowledge of genetic HL, and support other laboratories in the interpretation of variants.
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Secuenciación del Exoma , Mutación , Humanos , Austria , Masculino , Femenino , Estudios Prospectivos , Adulto , Niño , Adolescente , Preescolar , Persona de Mediana Edad , Adulto Joven , Pruebas Genéticas/métodos , Genes Dominantes , Anciano , Pérdida Auditiva/genética , Pérdida Auditiva Sensorineural/genética , Pérdida Auditiva Sensorineural/diagnóstico , LactanteRESUMEN
Loss-of-function variants in AP3D1 have been linked to Hermansky-Pudlak syndrome (HPS) 10, a severe multisystem disorder characterized by oculocutaneous albinism, immunodeficiency, neurodevelopmental delay, hearing loss (HL), and neurological abnormalities, fatal in early childhood. Here, we report a consanguineous family who presented with presumably isolated autosomal recessive (AR) HL. Whole-exome sequencing was performed on all core family members, and selected patients were screened using array-based copy-number analysis and karyotyping. Candidate variants were validated by Sanger sequencing and assessed in silico. A homozygous, likely pathogenic p.V711I missense variant in AP3D1 segregated with the HL. The family was characterized by thorough medical and laboratory examination. The HL was consistent across patients and accompanied by neurological manifestations in two brothers. The sole female patient was diagnosed with premature ovarian failure. Further findings, including mild neutropenia and reduced NK-cell cytotoxicity in some as well as brain alterations in all homozygous patients, were reminiscent of HPS10, though milder and lacking the characteristic albinism. Previously unrecognized, milder, isolated HL was identified in all heterozygous carriers. A protein model indicates that the variant interferes with protein-protein interactions. These results suggest that a missense variant alters inner-ear-specific functions leading to HL with mild HPS10-like symptoms of variable penetrance. Milder HL in heterozygous carriers may point towards semi-dominant inheritance of this trait. Since all previously reported HPS10 cases were pediatric, it is unknown whether the observed primary ovarian insufficiency recapitulates the subfertility in Ap3d1-deficient mice.
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Sordera , Pérdida Auditiva Sensorineural , Síndrome de Hermanski-Pudlak , Masculino , Humanos , Preescolar , Femenino , Animales , Ratones , Síndrome de Hermanski-Pudlak/diagnóstico , Síndrome de Hermanski-Pudlak/patología , Mutación Missense , Pérdida Auditiva Sensorineural/genética , Proteínas Portadoras , Homocigoto , Complejo 3 de Proteína Adaptadora , Subunidades delta de Complexo de Proteína Adaptadora , Subunidades beta de Complejo de Proteína AdaptadoraRESUMEN
Cell fate transitions depend on balanced rewiring of transcription and translation programs to mediate ordered developmental progression. Components of the nonsense-mediated mRNA decay (NMD) pathway have been implicated in regulating embryonic stem cell (ESC) differentiation, but the exact mechanism is unclear. Here we show that NMD controls expression levels of the translation initiation factor Eif4a2 and its premature termination codon-encoding isoform (Eif4a2PTC ). NMD deficiency leads to translation of the truncated eIF4A2PTC protein. eIF4A2PTC elicits increased mTORC1 activity and translation rates and causes differentiation delays. This establishes a previously unknown feedback loop between NMD and translation initiation. Furthermore, our results show a clear hierarchy in the severity of target deregulation and differentiation phenotypes between NMD effector KOs (Smg5 KO > Smg6 KO > Smg7 KO), which highlights heterodimer-independent functions for SMG5 and SMG7. Together, our findings expose an intricate link between mRNA homeostasis and mTORC1 activity that must be maintained for normal dynamics of cell state transitions.
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Proteínas Portadoras , Degradación de ARNm Mediada por Codón sin Sentido , Proteínas Portadoras/genética , Expresión Génica , Células HeLa , Humanos , Diana Mecanicista del Complejo 1 de la Rapamicina/genética , Diana Mecanicista del Complejo 1 de la Rapamicina/metabolismoRESUMEN
OBJECTIVE: Identification of variations in tumour suppressor genes encoding the tetrameric succinate dehydrogenase (SDHx) mitochondrial enzyme complex may lead to personalised therapeutic concepts for the orphan disease, familial paraganglioma (PGL) type 1-5. We undertook to determine the causative variation in a family suffering from idiopathic early-onset (22 ± 2 years) head and neck PGL by PCR and Sanger sequencing. DESIGN: Prospective genetic study. SETTING: Tertiary Referral Otolaryngology Centre. PARTICIPANTS: Twelve family members. MAIN OUTCOME MEASURES: Main outcomes were clinical analysis and SDH genotyping RESULTS AND CONCLUSIONS: A novel heterozygous c.298delA frameshift variation in exon 3 of SDH subunit D (SDHD) was associated with a paternal transmission pattern of PGL in affected family members available to the study. Family history over five generations in adulthood indicated a variable penetrance for PGL inheritance in older generations. The c.298delA variant would cause translation of a 34-residue C-terminus distal to lysine residue 99 in the predicted transmembrane domain II of the full-length sequence p.(Thr100LeufsTer35) and would affect the translation products of all protein-coding SDHD isoforms containing transmembrane topologies required for positional integration in the inner mitochondrial membrane and complex formation. These results underly the importance of genetic screening for PGL also in cases of unclear inheritance, and variation carriers should benefit from screening and lifelong follow-up.
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Neoplasias de Cabeza y Cuello/genética , Paraganglioma/genética , Succinato Deshidrogenasa/genética , Adulto , Edad de Inicio , Anciano de 80 o más Años , Austria , Exones , Femenino , Mutación del Sistema de Lectura , Pruebas Genéticas , Neoplasias de Cabeza y Cuello/diagnóstico por imagen , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Paraganglioma/diagnóstico por imagen , Linaje , Penetrancia , Fenotipo , Estudios Prospectivos , Adulto JovenRESUMEN
INTRODUCTION: Genetic hearing loss (HL) is often monogenic. Whereas more than half of autosomal recessive (AR) cases in Austria are caused by mutations in a single gene, no disproportionately frequent contributing genetic factor has been identified in cases of autosomal dominant (AD) HL. The genetic characterization of HL continues to improve diagnosis, genetic counseling, and lays a foundation for the development of personalized medicine approaches. METHODS: Diagnostic HL panel screening was performed in an Austrian multiplex family with AD HL, and segregation was tested with polymerase chain reaction and Sanger sequencing. In an independent approach, 18 unrelated patients with AD HL were screened for causative variants in all known HL genes to date and segregation was tested if additional family members were available. The pathogenicity of novel variants was assessed based on previous literature and bioinformatic tools such as prediction software and protein modeling. RESULTS: In six of the 19 families under study, candidate pathogenic variants were identified in MYO6, including three novel variants (p.Gln441Pro, p.Ser612Tyr, and p.Gln650ValfsTer7). Some patients carried more than one likely pathogenic variant in known deafness genes. CONCLUSION: These results suggest a potential high prevalence of MYO6 variants in Austrian cases of AD HL. The presence of multiple rare HL variants in some patients highlights the relevance of considering multiple-hit diagnoses for genetic counseling and targeted therapy design.
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Sordera , Pérdida Auditiva , Austria/epidemiología , Humanos , Mutación , Linaje , PrevalenciaRESUMEN
Nanophthalmos-4 is a rare autosomal dominant disorder caused by two known variations in TMEM98. An Austrian Caucasian pedigree was identified suffering from nanophthalmos and late onset angle-closure glaucoma and premature loss of visual acuity. Whole exome sequencing identified segregation of a c.602G > C transversion in TMEM98 (p.Arg201Pro) as potentially causative. A protein homology model generated showed a TMEM98 structure comprising α4, α5/6, α7 and α8 antiparallel helix bundles and two predicted transmembrane domains in α1 and α7 that have been confirmed in vitro. Both p.Arg201Pro and the two missense variations representing proline insertions identified previously to cause nanophthalmos-4 (p.Ala193Pro and p.His196Pro) are located in the charge polarized helix α8 (p.183-p210). Stability of the C-terminal alpha helical structure of TMEM98 is therefore essential to prevent the development of human nanophthalmos-4. Precise molecular diagnosis could lead to the development of tailored therapies for patients with orphan ocular disease.
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Glaucoma de Ángulo Cerrado/genética , Hiperopía/genética , Proteínas de la Membrana/genética , Microftalmía/genética , Mutación Missense , Trastornos de la Visión/genética , Agudeza Visual/fisiología , Adulto , Anciano de 80 o más Años , Sustitución de Aminoácidos , Arginina , Femenino , Cirugía Filtrante , Glaucoma de Ángulo Cerrado/fisiopatología , Glaucoma de Ángulo Cerrado/cirugía , Humanos , Hiperopía/fisiopatología , Hiperopía/cirugía , Implantación de Lentes Intraoculares , Masculino , Microftalmía/fisiopatología , Microftalmía/cirugía , Microscopía Acústica , Persona de Mediana Edad , Linaje , Facoemulsificación , Prolina , Conformación Proteica en Hélice alfa/genética , Microscopía con Lámpara de Hendidura , Trastornos de la Visión/fisiopatología , Secuenciación del ExomaRESUMEN
Background: Hereditary hearing loss is a disorder with high genetic and allelic heterogeneity. Diagnostic screening of candidate genes commonly yields novel variants of unknown clinical significance. TBC1D24 is a pleiotropic gene associated with recessive DOORS syndrome, epileptic encephalopathy, myoclonic epilepsy, and both recessive and dominant hearing impairment. Genotype-phenotype correlations have not been established to date but could facilitate diagnostic variant assessment and elucidation of pathomechanisms. Methods and Results: Whole-exome and gene panel screening identified a novel (c.919A>C; p.Asn307His) causative variant in TBC1D24 in two unrelated Caucasian families with Autosomal dominant (AD) nonsyndromic late-onset hearing loss. Protein modeling on the Drosophila TBC1D24 ortholog Skywalker crystal structure showed close interhelix proximity (6.8Å) between the highly conserved residue p.Asn307 in α18 and the position of the single known pathogenic dominant variation (p.Ser178Leu) in α11 that causes a form of deafness with similar clinical characteristics. Conclusion: Genetic variants affecting two polar hydrophilic residues in neighboring helices of TBC1D24 cause AD nonsyndromic late-onset hearing loss. The spatial proximity of the affected residues suggests the first genotype-phenotype association in TBC1D24-related disorders. Three conserved residues in α18 contribute to the formation of a functionally relevant cationic phosphoinositide binding pocket that regulates synaptic vesicle trafficking which may be involved in the molecular mechanism of disease.
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OBJECTIVES: Hereditary hemorrhagic telangiectasia (HHT) is a rare autosomal dominant genetic disorder characterized by pathogenic blood vessel development and maintenance. HHT type 1 (HHT1) and type 2 (HHT2) are caused by variants in endoglin (ENG) and activin receptor-like kinase-1 (ACVRL1), respectively. The aim of this study was to identify the spectrum of pathogenic variants in ENG and ACVRL1 in Austrian HHT families. METHODS: In this prospective study, eight Austrian HHT families were screened for variants in ENG and ACVRL1 by polymerase chain reaction amplification and sequencing of DNA isolated from peripheral blood. RESULTS: Heterozygous variants were identified in all families under study. HHT1 was caused by a novel c.816+1G>A splice donor variant, a novel c.1479C>A nonsense (p.Cys493X) variant and a published c.1306C>T nonsense (p.Gln436X) variant in ENG. Variants found in ACVRL1 were novel c.200G>C (p.Arg67Pro) and known c.772G>A (p.Gly258Ser) missense variants in highly conserved residues, a known heterozygous c.100dupT frameshift (p.Cys34Leufs*4) and the known c.1204G>A missense (p.Gly402Ser) and c.1435C>T nonsense (p.Arg479X) variants as causes of HHT2. CONCLUSION: Novel and published variants in ENG (37.5%) and ACVRL1 (62.5%) were exclusively identified as the cause of HHT in an Austrian patient cohort. Identification of novel causative genetics variants should facilitate the development of tailored therapeutical applications in the future treatment of autosomal dominant HHT.
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BACKGROUND: Non-syndromic autosomal dominant hearing impairment is characteristically postlingual in onset. Genetic diagnostics are essential for genetic counselling, disease prognosis and understanding of the molecular mechanisms of disease. To date, 36 causative genes have been identified, many in only individual families. Gene selection for genetic screening by traditional methods and genetic diagnosis in autosomal dominant patients has therefore been fraught with difficulty. Whole-exome sequencing provides a powerful tool to analyze all protein-coding genomic regions in parallel, thus allowing the comprehensive screening of all known genes and associated alterations. METHODS: In this study, a previously undiagnosed late-onset progressive autosomal dominant hearing loss in an Austrian family was investigated by means of whole-exome sequencing. Results were confirmed by Sanger sequencing. RESULTS: A previously described c.151C>T missense (p.Pro51Ser) mutation in the LCCL (limulus factor C, cochlin, late gestation lung protein Lgl1) domain of the cochlin gene (COCH) was identified as causative and segregated with disease in five members of the family. Molecular diagnostics led to the decision to perform cochlear implantation in an index patient who subsequently showed excellent postoperative auditory performance. The c.151C>T mutation was not found in 18 screened Austrian families with autosomal dominant hearing loss but was represented alongside other known pathogenic mutant COCH alleles in the Genome Aggregation Database (gnomAD) in European populations. A combined allele frequency of 0.000128 implies an orphan disease frequency for COCH-induced hearing loss of 1:3900 in Europe. CONCLUSIONS: Exome sequencing successfully resolved the genetic diagnosis in a family suffering from autosomal dominant hearing impairment and allowed prediction of purported auditory outcome after cochlear implantation in an index patient. Personalized treatment approaches based on the molecular mechanisms of disease may become increasingly important in the future.
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Secuenciación del Exoma , Pérdida Auditiva Sensorineural , Austria , Europa (Continente) , Exoma , Proteínas de la Matriz Extracelular , Femenino , Pérdida Auditiva Sensorineural/genética , Pérdida Auditiva Sensorineural/rehabilitación , Humanos , Masculino , Mutación , Linaje , Secuenciación del Exoma/métodosRESUMEN
Bi-allelic variations in the gap junction protein beta-2 (GJB2) gene cause up to 50% of cases of newborn hearing loss. Heterozygous pathogenic GJB2 variations are also fivefold overrepresented in idiopathic patient groups compared to the normal-hearing population. Whether hearing loss in this group is due to unidentified additional variations within GJB2 or variations in other deafness genes is unknown in most cases. Whole-exome sequencing offers an effective approach in the search for causative variations in patients with Mendelian diseases. In this prospective genetic cohort study, we initially investigated a family of Turkish origin suffering from congenital autosomal recessive hearing loss. An index patient and his normal-hearing father, both bearing a single heterozygous pathogenic c.262G>T (p.Ala88Ser) GJB2 transversion as well as the normal-hearing mother were investigated by means of whole-exome sequencing. Subsequently the genetic screening was extended to a hearing-impaired cohort of 24 families of Turkish origin. A homozygous missense c.5492G>T transversion (p.Gly1831Val) in the Myosin 15a gene, previously linked to deafness, was identified as causative in the index family. This very rare variant is not listed in any population in the Genome Aggregation Database. Subsequent screening of index patients from additional families of Turkish origin with recessive hearing loss identified the c.5492G>T variation in an additional family. Whole-exome sequencing may effectively identify the causes of idiopathic hearing loss in patients bearing heterozygous GJB2 variations.
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Conexinas/genética , Pérdida Auditiva Sensorineural , Adulto , Austria/epidemiología , Conexina 26 , Femenino , Pruebas Genéticas/métodos , Pérdida Auditiva Sensorineural/diagnóstico , Pérdida Auditiva Sensorineural/epidemiología , Pérdida Auditiva Sensorineural/genética , Humanos , Recién Nacido , Masculino , Mutación , Estudios Prospectivos , Turquía , Secuenciación del Exoma/métodosRESUMEN
BACKGROUND: Heterozygous mutations in GJB2 (MIM: 121011) encoding the gap junction protein connexin 26 are overrepresented in patient groups suffering from nonsyndromic sensorineural hearing impairment (HI) implying the involvement of additional genetic factors. Mutations in SLC26A4 (MIM: 605646), encoding the protein pendrin can cause both Pendred syndrome and autosomal recessive, nonsyndromic HI locus 4 type sensorineural HI (MIM: 600791). OBJECTIVES: Aim of this study was to investigate the role of SLC26A4 coding mutations in a nonsyndromic hearing impairment (NSHI) patient group bearing heterozygous GJB2 35delG mutations. DESIGN: We analyzed the 20 coding exons of SLC26A4 in a group of patients (nâ=â15) bearing heterozygous 35delG mutations and exclusively suffering from congenital HI. RESULTS: In a case of bilateral congenital hearing loss we identified a rare, novel SLC26A4 exon 2 splice donor mutation (c.164+1delG) predicted to truncate pendrin in the first cytoplasmic domain, as a compound heterozygote with the pathogenic missense mutation c.1061T>C (p.354F>S; rs111033243). CONCLUSIONS: Screening for SLC26A4 mutations may identify the genetic causes of hearing loss in patients bearing heterozygous mutations in GJB2. HYPOTHESIS: SLC26A4 coding mutations are genetic causes for nonsyndromic HI in patients bearing heterozygous GJB2 35delG mutations.
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Pérdida Auditiva Bilateral/genética , Pérdida Auditiva Sensorineural/genética , Proteínas de Transporte de Membrana/genética , Adulto , Niño , Preescolar , Conexina 26 , Conexinas/genética , Exones , Femenino , Heterocigoto , Humanos , Lactante , Masculino , Persona de Mediana Edad , Mutación , Transportadores de Sulfato , Adulto JovenRESUMEN
CONCLUSION: Alterations within a novel putative Exon 1a within the gap junction beta 2 (GJB2) gene may play a role in the development of genetic hearing impairment in Austria. OBJECTIVES: Mutations in the GJB2 gene are the most common cause of hereditary sensorineural deafness. Genome-wide screening for alternative transcriptional start sites in the human genome has revealed the presence of an additional GJB2 exon (E1a). This study tested the hypothesis of whether alternative GJB2 transcription involving E1a may play a role in the development of congenital sensorineural deafness in Austria. METHODS: GJB2 E1a and flanking regions were sequenced in randomized normal hearing control subjects and three different patient groups with non-syndromic hearing impairment (NSHI), and bioinformatic analysis was performed. Statistical analysis of disease association was carried out using the Cochran-Armitage test for trend. RESULTS: A single change 2410 bp proximal to the translational start site (c.-2410T > C, rs7994748, NM_004004.5:c.-23 + 792T > C) was found to be significantly associated with the common c.35delG GJB2 mutation (p = .009). c.35delG in combination with c.-2410CC occurred at a 6.9-fold increased frequency compared to the control group. Additionally, one patient with idiopathic congenital hearing loss was found to be homozygous c.-2410CC.
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Conexinas/genética , Pérdida Auditiva Sensorineural/genética , Empalme Alternativo , Austria , Secuencia de Bases , Estudios de Casos y Controles , Conexina 26 , Exones , Frecuencia de los Genes , Pruebas Genéticas , Pérdida Auditiva Sensorineural/congénito , Pérdida Auditiva Sensorineural/diagnóstico , Heterocigoto , Humanos , Tamizaje Masivo , Polimorfismo GenéticoRESUMEN
The objective of this study was to investigate the relevance of routine assessment of c.-259C>T in the Austrian newborn screening program. Homozygous and compound heterozygous mutations in the coding region of the human gene encoding gap junction protein GJB2 (Connexin 26) cause up to 50 % of neonatal autosomal recessive non-syndromic hearing impairment identified in Caucasian newborn screening programs. More recently, a null mutation in the GC box of the GJB2 basal promoter c.-259C>T has been described which causes hearing impairment by completely suppressing GJB2 promoter activity. We determined the occurrence of c.-259C>T in cases of non-syndromic hearing impairment lacking known pathogenic alterations in GJB2 (n = 43), a non-syndromic hearing impaired patient group (n = 15) bearing the heterozygous GJB2 mutations c.35delG, c.[79G>A];[341A>G] (p. [V27I];[E114G]), c.109G>A (p.V37I), c.154G>C (p.V52L), c.262G>T (p.A88S), c.269T>C (p.L90P) and c.551G>C (p.R184P) and in a normal hearing group lacking alterations in GJB2 (n = 50). In the analyzed groups, no occurrence of c.-259C>T was found. The c.-259C>T mutation, previously described as -3438C>T, is not a common cause of non-syndromic hearing impairment alone or together with heterozygous pathogenic GJB2 mutations that are statistically overrepresented in non-syndromic hearing impaired patient groups. Screening of newborns for c.-259C>T is therefore unlikely to be commonly found in Austrian NSHI patients but could make a significant contribution to non-syndromic hearing impairment in other populations.
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Conexinas/genética , ADN/genética , Pérdida Auditiva/genética , Mutación , Austria/epidemiología , Conexina 26 , Conexinas/metabolismo , Femenino , Pérdida Auditiva/epidemiología , Humanos , Recién Nacido , Masculino , Reacción en Cadena de la Polimerasa , Prevalencia , Regiones Promotoras GenéticasRESUMEN
OBJECTIVES: Similar to other zona pellucida mutations in the alpha-tectorin (TECTA) gene, the p.Y1870C alteration in DFNA8/12 causes prelingual, nonsyndromic, autosomal dominant hearing loss. Here we investigated the effect of p.Y1870C on reverse transduction by audiometric studies in the family. METHODS: Pure tone audiometry, brainstem evoked response audiometry, the Freiburger test for speech understanding and transient evoked and distortion product otoacoustic emissions were assessed in three available affected members bearing p.Y1870C. RESULTS: Pure tone audiometry showed U-shaped curves with moderate to severe degrees of hearing impairment confirmed by brainstem evoked response audiometry. Transient evoked and distortion product otoacoustic emissions were completely absent in all affected family members whereas word recognition scores were up to 95%. CONCLUSIONS: Although the missense p.Y1870C TECTA mutation leads to complete failure of the cochlear amplifier in humans, very high speech perception scores can be achieved with appropriate therapy.
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Potenciales Evocados Auditivos del Tronco Encefálico/genética , Proteínas de la Matriz Extracelular/genética , Pérdida Auditiva Sensorineural/diagnóstico , Emisiones Otoacústicas Espontáneas/genética , Adulto , Audiometría de Tonos Puros/métodos , Austria , Femenino , Proteínas Ligadas a GPI/genética , Pérdida Auditiva Sensorineural/genética , Heterocigoto , Humanos , Masculino , Persona de Mediana Edad , Mutación Missense , Linaje , Percepción del Habla , Adulto JovenRESUMEN
HYPOTHESIS: Additional genetic changes in the regulatory region of the human GJB2 gene encoding the gap junction protein (Connexin 26) may contribute to sensorineural hearing loss. BACKGROUND: Mutations in GJB2 cause up to 50% of autosomal recessive nonsyndromic hearing impairment (NSHI). METHODS: In the present study, we screened the putative 5' GJB2 regulatory region for novel alterations. RESULTS: In idiopathic familial cases of NSHI lacking known pathogenic alterations in GJB2, we identified a TâC transition (refSNP: rs117685390) in a putative transcription factor binding sequence 228 bp proximal to the transcriptional start site at a homozygous frequency of 0.125 (n = 40), significantly overrepresented in comparison to the homozygous allele frequencies of 0.043 in the normal-hearing Caucasian population (n = 211; p < 0.001). In a NSHI family, inheritance of the rs117685390 C allele segregated on independent chromosomes with NSHI in conjunction with heterozygous inheritance of c.35delG, the most common Caucasian mutation in the GJB2 coding region. In a patient group (n = 32) bearing heterozygous pathogenic c.35delG mutations, - rs117685390 C allele homozygosity was also highly overrepresented (0.25; p < 0.001) and not exclusively linked to the c.35delG mutation in cis in patients homozygous for c.35delG. However, in the majority of NSHI homozygous c.35delG chromosomes examined (91/94), c.35delG homozygosity was linked to the rs117685390 C allele in cis. CONCLUSION: These results suggest that the rs117685390 C allele could represent a biomarker for the development of NSHI in Caucasian populations and may be included in risk assessment for the development of NSHI.
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Conexinas/genética , Pérdida Auditiva/genética , Polimorfismo de Nucleótido Simple , Adulto , Alelos , Conexina 26 , Femenino , Frecuencia de los Genes , Estudios de Asociación Genética , Predisposición Genética a la Enfermedad , Genotipo , Pérdida Auditiva Sensorineural/genética , Homocigoto , Humanos , Masculino , MutaciónRESUMEN
Epigenetic mechanisms serve as key regulatory elements during vertebrate embryogenesis. Histone acetylation levels, controlled by the opposing action of histone acetyl transferases (HATs) and histone deacetylases (HDACs), influence the accessibility of DNA to transcription factors and thereby dynamically regulate transcriptional programs. HDACs execute important functions in the control of proliferation, differentiation, and the establishment of cell identities during embryonic development. To investigate the global role of the HDAC family during neural tube development, we employed Trichostatin A (TSA) to locally block enzymatic HDAC activity in chick embryos in ovo. We found that TSA treatment induces neural tube defects at the level of the posterior neuropore, ranging from slight undulations to a complete failure of neural tube closure. This phenotype is accompanied by morphological changes in neuroepithelial cells and induction of apoptosis. As a molecular consequence of HDAC inhibition, we observed a timely deregulated cadherin switching in the dorsal neural tube, illustrated by induction of Cadherin 6B as well as reciprocal downregulation of N-Cadherin expression. Concomitantly, several neural crest specific markers, including Bmp4, Pax3, Sox9 and Sox10 are induced, causing a premature loss of epithelial characteristics. Our findings provide evidence that HDAC function is crucial to control the regulatory circuits operating during trunk neural crest development and neural tube closure.
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Inhibidores de Histona Desacetilasas/toxicidad , Ácidos Hidroxámicos/toxicidad , Cresta Neural/efectos de los fármacos , Defectos del Tubo Neural/inducido químicamente , Animales , Apoptosis/efectos de los fármacos , Proteína Morfogenética Ósea 4/genética , Proteína Morfogenética Ósea 4/metabolismo , Cadherinas/genética , Cadherinas/metabolismo , Embrión de Pollo , Cresta Neural/embriología , Tubo Neural/efectos de los fármacos , Tubo Neural/embriología , Células Neuroepiteliales/efectos de los fármacos , Células Neuroepiteliales/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
Histone deacetylases (HDACs) are a family of enzymes which regulate the acetylation state of nucleosomal histones, as well as non-histone proteins. By altering local chromatin architecture, HDACs play important roles in shaping cell differentiation and morphogenesis. Expression of class I HDACs during early chick development has so far not been analyzed. Here, we report the expression profile of chick class I HDACs from the onset of gastrulation (HH2) to day 4 of development and compare it to relevant stages during mouse development. Visualized by in situ hybridization to whole mount embryos and tissue sections, we found tissue-specific overlapping temporal and spatial expression domains for all four class I HDACs in chick and mouse, although species-specific differences could be identified. All class I HDACs in both species are highly expressed in the developing brain. In particular, HDAC1 is expressed at sites of anterior and posterior neural tube closure most obvious in the hot spot-like expression of HDAC1 in HH12 chicken embryos. A significant species-specific spatio-temporal expression pattern was observed for HDAC8. Whereas HDAC8 is exclusively found in fore- and midbrain regions during early mouse embryogenesis, the chick ortholog shows an expanded expression pattern, suggesting a more diversified role of HDAC8 in the chick system. Our results present a basis for further functional analysis of class I HDACs in chick development.
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Encéfalo/embriología , Desarrollo Embrionario , Histona Desacetilasas/genética , Acetilación , Animales , Western Blotting , Encéfalo/enzimología , Diferenciación Celular , Embrión de Pollo , Cromatina/química , Embrión de Mamíferos , Embrión no Mamífero , Gastrulación , Regulación del Desarrollo de la Expresión Génica , Histona Desacetilasas/metabolismo , Histonas/genética , Histonas/metabolismo , Hibridación in Situ , Ratones , Tubo Neural/embriología , Nucleosomas/genética , Nucleosomas/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
OBJECTIVES/HYPOTHESIS: Analysis of association between genotype and phenotype. STUDY DESIGN: Prospective genetic study in a family. METHODS: Auditory investigations, computer tomography, and genetic sequencing of the fibroblast growth factor 3 (FGF3) gene were performed on a Somali family presenting with autosomal recessive, hearing impairment, microdontia, and outer ear morphologies ranging from normal auricle development to microtia assessed as type 1 Weerda dysplasia in affected individuals. RESULTS: Computed tomography imaging identified differential inter- and intraindividual malformations of the inner ear including labyrinth aplasia, development of a common cavity to the presence of a cochlear with 1.5 windings (Mondini malformation) in affected individuals, symptoms similar to those described as labyrinth aplasia, microtia, and microdontia (LAMM) syndrome, caused by mutations in FGF3. Genetic sequencing revealed the presence of a novel p.R95W missense mutation in FGF3 segregating with pathology. The p.R95W mutation substitutes a positively charged arginine for a polar tryptophan in the highly conserved RYLAM consensus of the beta 6 sheet of FGF3 that interacts with FGFR2. CONCLUSIONS: These findings describe, for the first time, variable inner ear malformations and outer ear dysplasia in the presence of constant microdontia, associated with homozygous inheritance of the p.R95W mutation in FGF3, mirroring phenotypes observed in mouse models ablating FGF3/FGFR2 signaling.
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Anomalías Múltiples/genética , Oído Externo/anomalías , Oído Interno/anomalías , Factor 3 de Crecimiento de Fibroblastos/genética , Mutación Missense , Anomalías Dentarias/genética , Femenino , Pérdida Auditiva Sensorineural/congénito , Pérdida Auditiva Sensorineural/genética , Humanos , Masculino , LinajeRESUMEN
OBJECTIVE: To analyze the prevalence and importance of the maternally inherited A1555G mutation in the 12S rRNA gene in the Austrian population. STUDY DESIGN: Investigation for mutations of genetically affected familial and sporadic cases of hearing impairment (HI), including analyses of audiometric data. SETTING: Teaching hospital, tertiary referral center. PATIENTS: Forty-five familial and 77 sporadic cases of nonsyndromic HI in an Austrian Caucasian ethnic group. MAIN OUTCOME MEASURE(S): Pure-tone audiometric data and screening by restriction fragment length polymorphism analysis after exclusion of GJB2 (Connexin 26) caused hearing loss. RESULTS: In the investigated hearing-impaired population, the mutation A1555G in the mitochondrial 12S rRNA gene was not detected. CONCLUSION: The A1555G mutation in the mitochondrial DNA 12S rRNA is not a major cause of HI in the Austrian Caucasian population.
Asunto(s)
Pérdida Auditiva/epidemiología , Pérdida Auditiva/genética , ARN Ribosómico/genética , Audiometría de Tonos Puros , Austria/epidemiología , Conexina 26 , Conexina 30 , Conexinas/genética , ADN/genética , ADN Mitocondrial/genética , Frecuencia de los Genes , Humanos , Mutación/fisiología , Polimorfismo de Longitud del Fragmento de RestricciónRESUMEN
OBJECTIVE:: To analyze the prevalence and importance of the maternally inherited A1555G mutation in the 12S rRNA gene in the Austrian population. STUDY DESIGN:: Investigation for mutations of genetically affected familial and sporadic cases of hearing impairment (HI), including analyses of audiometric data. SETTING:: Teaching hospital, tertiary referral center. PATIENTS:: Forty-five familial and 77 sporadic cases of nonsyndromic HI in an Austrian Caucasian ethnic group. MAIN OUTCOME MEASURE(S):: Pure-tone audiometric data and screening by restriction fragment length polymorphism analysis after exclusion of GJB2 (Connexin 26) caused hearing loss. RESULTS:: In the investigated hearing-impaired population, the mutation A1555G in the mitochondrial 12S rRNA gene was not detected. CONCLUSION:: The A1555G mutation in the mitochondrial DNA 12S rRNA is not a major cause of HI in the Austrian Caucasian population.