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Višnjar T, Maver A, Writzl K, Maloku O, Bergant G, Jaklič H, Neubauer D, Fogolari F, Pečarič Meglič N, Peterlin B. Biallelic ATOH1 Gene Variant in Siblings With Pontocerebellar Hypoplasia, Developmental Delay, and Hearing Loss. Neurol Genet 2022; 8:e677. [PMID: 35518571 PMCID: PMC9067583 DOI: 10.1212/nxg.0000000000000677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 03/04/2022] [Indexed: 11/15/2022]
Abstract
Background and Objectives To report on the novel association of biallelic variant in atonal basic helix-loop-helix transcription factor 1 (ATOH1) gene and pontocerebellar hypoplasia (PCH), severe global developmental delay, intellectual disability, and hearing loss in a family with 2 affected siblings. Methods A detailed clinical assessment and exome sequencing of peripheral blood sample were performed. Segregation analysis with Sanger sequencing and structural modeling of the variant was performed to support the pathogenicity of the variant. Results A homozygous missense variant (NM_005172.1:c.481C>G) in the ATOH1 gene was identified in the proband and his affected sister. The segregation analysis subsequently confirmed its segregation with an apparently recessive PCH in this family. ATOH1 encodes for the atonal basic helix-loop-helix (bHLH) transcription factor 1, a core transcription factor in the developing cerebellum, brainstem, and dorsal spinal cord, and in the ear. The identified variant results in the p.(Arg161Gly) amino acid substitution in the evolutionarily conserved DNA-binding bHLH domain of the ATOH1 protein. Biallelic missense variants in this domain were previously reported to result in disordered cerebellar development and hearing loss in animal models. In silico homology modeling revealed that p.Arg161Gly in ATOH1 protein probably disrupts a salt bridge with DNA backbone phosphate and increases the flexibility of the bHLH helix-both of which together affect the binding capability of the bHLH domain to the DNA. Discussion Based on the sequencing results and evidence from structural modeling of the identified variant, as well as with previous reports of ATOH1 gene disruption, we conclude that ATOH1 may represent a novel candidate gene associated with the phenotype of PCH, global developmental delay, and hearing loss in humans.
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Affiliation(s)
- Tanja Višnjar
- Clinical Institute of Genomic Medicine (T.V., A.M., K.W., G.B., H.J., B.P.), University Medical Centre Ljubljana, Slovenia; Medical Faculty (K.W., D.N.), University of Ljubljana, Slovenia; Division of Paediatrics (D.N.), Department of Child, Adolescent & Developmental Neurology, University Medical Centre Ljubljana, Slovenia; Clinical Institute of Radiology (N.P.M.), University Medical Centre Ljubljana, Slovenia; and Department of Mathematics (O.M., F.F.), Informatics and Physics, University of Udine, Italy
| | - Aleš Maver
- Clinical Institute of Genomic Medicine (T.V., A.M., K.W., G.B., H.J., B.P.), University Medical Centre Ljubljana, Slovenia; Medical Faculty (K.W., D.N.), University of Ljubljana, Slovenia; Division of Paediatrics (D.N.), Department of Child, Adolescent & Developmental Neurology, University Medical Centre Ljubljana, Slovenia; Clinical Institute of Radiology (N.P.M.), University Medical Centre Ljubljana, Slovenia; and Department of Mathematics (O.M., F.F.), Informatics and Physics, University of Udine, Italy
| | - Karin Writzl
- Clinical Institute of Genomic Medicine (T.V., A.M., K.W., G.B., H.J., B.P.), University Medical Centre Ljubljana, Slovenia; Medical Faculty (K.W., D.N.), University of Ljubljana, Slovenia; Division of Paediatrics (D.N.), Department of Child, Adolescent & Developmental Neurology, University Medical Centre Ljubljana, Slovenia; Clinical Institute of Radiology (N.P.M.), University Medical Centre Ljubljana, Slovenia; and Department of Mathematics (O.M., F.F.), Informatics and Physics, University of Udine, Italy
| | - Ornela Maloku
- Clinical Institute of Genomic Medicine (T.V., A.M., K.W., G.B., H.J., B.P.), University Medical Centre Ljubljana, Slovenia; Medical Faculty (K.W., D.N.), University of Ljubljana, Slovenia; Division of Paediatrics (D.N.), Department of Child, Adolescent & Developmental Neurology, University Medical Centre Ljubljana, Slovenia; Clinical Institute of Radiology (N.P.M.), University Medical Centre Ljubljana, Slovenia; and Department of Mathematics (O.M., F.F.), Informatics and Physics, University of Udine, Italy
| | - Gaber Bergant
- Clinical Institute of Genomic Medicine (T.V., A.M., K.W., G.B., H.J., B.P.), University Medical Centre Ljubljana, Slovenia; Medical Faculty (K.W., D.N.), University of Ljubljana, Slovenia; Division of Paediatrics (D.N.), Department of Child, Adolescent & Developmental Neurology, University Medical Centre Ljubljana, Slovenia; Clinical Institute of Radiology (N.P.M.), University Medical Centre Ljubljana, Slovenia; and Department of Mathematics (O.M., F.F.), Informatics and Physics, University of Udine, Italy
| | - Helena Jaklič
- Clinical Institute of Genomic Medicine (T.V., A.M., K.W., G.B., H.J., B.P.), University Medical Centre Ljubljana, Slovenia; Medical Faculty (K.W., D.N.), University of Ljubljana, Slovenia; Division of Paediatrics (D.N.), Department of Child, Adolescent & Developmental Neurology, University Medical Centre Ljubljana, Slovenia; Clinical Institute of Radiology (N.P.M.), University Medical Centre Ljubljana, Slovenia; and Department of Mathematics (O.M., F.F.), Informatics and Physics, University of Udine, Italy
| | - David Neubauer
- Clinical Institute of Genomic Medicine (T.V., A.M., K.W., G.B., H.J., B.P.), University Medical Centre Ljubljana, Slovenia; Medical Faculty (K.W., D.N.), University of Ljubljana, Slovenia; Division of Paediatrics (D.N.), Department of Child, Adolescent & Developmental Neurology, University Medical Centre Ljubljana, Slovenia; Clinical Institute of Radiology (N.P.M.), University Medical Centre Ljubljana, Slovenia; and Department of Mathematics (O.M., F.F.), Informatics and Physics, University of Udine, Italy
| | - Federico Fogolari
- Clinical Institute of Genomic Medicine (T.V., A.M., K.W., G.B., H.J., B.P.), University Medical Centre Ljubljana, Slovenia; Medical Faculty (K.W., D.N.), University of Ljubljana, Slovenia; Division of Paediatrics (D.N.), Department of Child, Adolescent & Developmental Neurology, University Medical Centre Ljubljana, Slovenia; Clinical Institute of Radiology (N.P.M.), University Medical Centre Ljubljana, Slovenia; and Department of Mathematics (O.M., F.F.), Informatics and Physics, University of Udine, Italy
| | - Nuška Pečarič Meglič
- Clinical Institute of Genomic Medicine (T.V., A.M., K.W., G.B., H.J., B.P.), University Medical Centre Ljubljana, Slovenia; Medical Faculty (K.W., D.N.), University of Ljubljana, Slovenia; Division of Paediatrics (D.N.), Department of Child, Adolescent & Developmental Neurology, University Medical Centre Ljubljana, Slovenia; Clinical Institute of Radiology (N.P.M.), University Medical Centre Ljubljana, Slovenia; and Department of Mathematics (O.M., F.F.), Informatics and Physics, University of Udine, Italy
| | - Borut Peterlin
- Clinical Institute of Genomic Medicine (T.V., A.M., K.W., G.B., H.J., B.P.), University Medical Centre Ljubljana, Slovenia; Medical Faculty (K.W., D.N.), University of Ljubljana, Slovenia; Division of Paediatrics (D.N.), Department of Child, Adolescent & Developmental Neurology, University Medical Centre Ljubljana, Slovenia; Clinical Institute of Radiology (N.P.M.), University Medical Centre Ljubljana, Slovenia; and Department of Mathematics (O.M., F.F.), Informatics and Physics, University of Udine, Italy
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Brownstein Z, Gulsuner S, Walsh T, Martins FTA, Taiber S, Isakov O, Lee MK, Bordeynik-Cohen M, Birkan M, Chang W, Casadei S, Danial-Farran N, Abu-Rayyan A, Carlson R, Kamal L, Arnthórsson AÖ, Sokolov M, Gilony D, Lipschitz N, Frydman M, Davidov B, Macarov M, Sagi M, Vinkler C, Poran H, Sharony R, Samra N, Zvi N, Baris-Feldman H, Singer A, Handzel O, Hertzano R, Ali-Naffaa D, Ruhrman-Shahar N, Madgar O, Sofrin-Drucker E, Peleg A, Khayat M, Shohat M, Basel-Salmon L, Pras E, Lev D, Wolf M, Steingrimsson E, Shomron N, Kelley MW, Kanaan MN, Allon-Shalev S, King MC, Avraham KB. Spectrum of genes for inherited hearing loss in the Israeli Jewish population, including the novel human deafness gene ATOH1. Clin Genet 2020; 98:353-364. [PMID: 33111345 DOI: 10.1111/cge.13817] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 07/13/2020] [Accepted: 07/15/2020] [Indexed: 12/26/2022]
Abstract
Mutations in more than 150 genes are responsible for inherited hearing loss, with thousands of different, severe causal alleles that vary among populations. The Israeli Jewish population includes communities of diverse geographic origins, revealing a wide range of deafness-associated variants and enabling clinical characterization of the associated phenotypes. Our goal was to identify the genetic causes of inherited hearing loss in this population, and to determine relationships among genotype, phenotype, and ethnicity. Genomic DNA samples from informative relatives of 88 multiplex families, all of self-identified Jewish ancestry, with either non-syndromic or syndromic hearing loss, were sequenced for known and candidate deafness genes using the HEar-Seq gene panel. The genetic causes of hearing loss were identified for 60% of the families. One gene was encountered for the first time in human hearing loss: ATOH1 (Atonal), a basic helix-loop-helix transcription factor responsible for autosomal dominant progressive hearing loss in a five-generation family. Our results show that genomic sequencing with a gene panel dedicated to hearing loss is effective for genetic diagnoses in a diverse population. Comprehensive sequencing enables well-informed genetic counseling and clinical management by medical geneticists, otolaryngologists, audiologists, and speech therapists and can be integrated into newborn screening for deafness.
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Affiliation(s)
- Zippora Brownstein
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Suleyman Gulsuner
- Departments of Genome Sciences and Medicine, University of Washington, Seattle, Washington, USA
| | - Tom Walsh
- Departments of Genome Sciences and Medicine, University of Washington, Seattle, Washington, USA
| | - Fábio T A Martins
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Shahar Taiber
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Ofer Isakov
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ming K Lee
- Departments of Genome Sciences and Medicine, University of Washington, Seattle, Washington, USA
| | - Mor Bordeynik-Cohen
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - Maria Birkan
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,Raphael Recanati Genetic Institute, Rabin Medical Center-Beilinson Hospital, Tel Aviv University Felsenstein Medical Research Center, Petach Tikva, Israel
| | - Weise Chang
- Laboratory of Cochlear Development, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland, USA
| | - Silvia Casadei
- Departments of Genome Sciences and Medicine, University of Washington, Seattle, Washington, USA
| | - Nada Danial-Farran
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,Genetics Institute, Ha'Emek Medical Center, Afula, Israel.,Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Amal Abu-Rayyan
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,Department of Biological Sciences, Bethlehem University, Bethlehem, Palestine
| | - Ryan Carlson
- Departments of Genome Sciences and Medicine, University of Washington, Seattle, Washington, USA
| | - Lara Kamal
- Department of Biological Sciences, Bethlehem University, Bethlehem, Palestine
| | - Asgeir Ö Arnthórsson
- Department of Biochemistry and Molecular Biology, BioMedical Center, Faculty of Medicine, University of Iceland, Reykjavik, Iceland
| | - Meirav Sokolov
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,Department of Otolaryngology-Head and Neck Surgery, Schneider Children's Medical Center, Petach Tikva, Israel
| | - Dror Gilony
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,Department of Otolaryngology-Head and Neck Surgery, Schneider Children's Medical Center, Petach Tikva, Israel
| | - Noga Lipschitz
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,Department of Otolaryngology-Head and Neck Surgery, Sheba Medical Center, Tel Hashomer, Israel
| | - Moshe Frydman
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,Institute of Human Genetics, Sheba Medical Center, Tel Hashomer, Israel
| | - Bella Davidov
- Raphael Recanati Genetic Institute, Rabin Medical Center-Beilinson Hospital, Tel Aviv University Felsenstein Medical Research Center, Petach Tikva, Israel
| | - Michal Macarov
- Department of Human Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Michal Sagi
- Department of Human Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Chana Vinkler
- Institute of Medical Genetics, Wolfson Medical Center, Holon, Israel
| | - Hana Poran
- Institute of Human Genetics, Sheba Medical Center, Tel Hashomer, Israel
| | - Reuven Sharony
- Genetics Institute, Meir Medical Center, Kfar Saba and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | | | - Na'ama Zvi
- Department of Human Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Hagit Baris-Feldman
- Genetics Institute, Tel-Aviv Sourasky Medical Center and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Amihood Singer
- Community Genetics Department, Public Health Services, Ministry of Health, Ramat Gan, Israel
| | - Ophir Handzel
- Department of Otolaryngology Head and Neck Surgery and Maxillofacial Surgery, Tel-Aviv Sourasky Medical Center and Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ronna Hertzano
- Department of Otorhinolaryngology Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Doaa Ali-Naffaa
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,Human Genetics Institute, Lady Davis Carmel Medical Center, Haifa, Israel
| | - Noa Ruhrman-Shahar
- Raphael Recanati Genetic Institute, Rabin Medical Center-Beilinson Hospital, Tel Aviv University Felsenstein Medical Research Center, Petach Tikva, Israel
| | - Ory Madgar
- Department of Otolaryngology-Head and Neck Surgery, Sheba Medical Center, Tel Hashomer, Israel
| | - Efrat Sofrin-Drucker
- Raphael Recanati Genetic Institute, Rabin Medical Center-Beilinson Hospital, Tel Aviv University Felsenstein Medical Research Center, Petach Tikva, Israel
| | - Amir Peleg
- Human Genetics Institute, Lady Davis Carmel Medical Center, Haifa, Israel
| | - Morad Khayat
- Genetics Institute, Ha'Emek Medical Center, Afula, Israel
| | - Mordechai Shohat
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,Sheba Cancer Research Center, Sheba Medical Center, Tel Hashomer, Israel.,Institute of Medical Genetics, Maccabi HMO, Rehovot, Israel
| | - Lina Basel-Salmon
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,Raphael Recanati Genetic Institute, Rabin Medical Center-Beilinson Hospital, Tel Aviv University Felsenstein Medical Research Center, Petach Tikva, Israel
| | - Elon Pras
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,Institute of Human Genetics, Sheba Medical Center, Tel Hashomer, Israel
| | - Dorit Lev
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel.,Institute of Medical Genetics, Wolfson Medical Center, Holon, Israel
| | - Michael Wolf
- Department of Otolaryngology-Head and Neck Surgery, Sheba Medical Center, Tel Hashomer, Israel
| | - Eirikur Steingrimsson
- Department of Biochemistry and Molecular Biology, BioMedical Center, Faculty of Medicine, University of Iceland, Reykjavik, Iceland
| | - Noam Shomron
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Matthew W Kelley
- Laboratory of Cochlear Development, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland, USA
| | - Moien N Kanaan
- Department of Biological Sciences, Bethlehem University, Bethlehem, Palestine
| | - Stavit Allon-Shalev
- Genetics Institute, Ha'Emek Medical Center, Afula, Israel.,Rappaport Faculty of Medicine, Technion, Haifa, Israel
| | - Mary-Claire King
- Departments of Genome Sciences and Medicine, University of Washington, Seattle, Washington, USA
| | - Karen B Avraham
- Department of Human Molecular Genetics & Biochemistry, Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
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An Atoh1-S193A Phospho-Mutant Allele Causes Hearing Deficits and Motor Impairment. J Neurosci 2017; 37:8583-8594. [PMID: 28729444 DOI: 10.1523/jneurosci.0295-17.2017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2017] [Revised: 06/20/2017] [Accepted: 06/29/2017] [Indexed: 12/21/2022] Open
Abstract
Atonal homolog 1 (Atoh1) is a basic helix-loop-helix (bHLH) transcription factor that is essential for the genesis, survival, and maturation of a variety of neuronal and non-neuronal cell populations, including those involved in proprioception, interoception, balance, respiration, and hearing. Such diverse functions require fine regulation at the transcriptional and protein levels. Here, we show that serine 193 (S193) is phosphorylated in Atoh1's bHLH domain in vivo Knock-in mice of both sexes bearing a GFP-tagged phospho-dead S193A allele on a null background (Atoh1S193A/lacZ) exhibit mild cerebellar foliation defects, motor impairments, partial pontine nucleus migration defects, cochlear hair cell degeneration, and profound hearing loss. We also found that Atoh1 heterozygous mice of both sexes (Atoh1lacZ/+) have adult-onset deafness. These data indicate that different cell types have different degrees of vulnerability to loss of Atoh1 function and that hypomorphic Atoh1 alleles should be considered in human hearing loss.SIGNIFICANCE STATEMENT The discovery that Atonal homolog 1 (Atoh1) governs the development of the sensory hair cells in the inner ear led to therapeutic efforts to restore these cells in cases of human deafness. Because prior studies of Atoh1-heterozygous mice did not examine or report on hearing loss in mature animals, it has not been clinical practice to sequence ATOH1 in people with deafness. Here, in seeking to understand how phosphorylation of Atoh1 modulates its effects in vivo, we discovered that inner ear hair cells are much more vulnerable to loss of Atoh1 function than other Atoh1-positive cell types and that heterozygous mice actually develop hearing loss late in life. This opens up the possibility that missense mutations in ATOH1 could increase human vulnerability to loss of hair cells because of aging or trauma.
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Dvorakova M, Jahan I, Macova I, Chumak T, Bohuslavova R, Syka J, Fritzsch B, Pavlinkova G. Incomplete and delayed Sox2 deletion defines residual ear neurosensory development and maintenance. Sci Rep 2016; 6:38253. [PMID: 27917898 PMCID: PMC5137136 DOI: 10.1038/srep38253] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 11/07/2016] [Indexed: 11/09/2022] Open
Abstract
The role of Sox2 in neurosensory development is not yet fully understood. Using mice with conditional Islet1-cre mediated deletion of Sox2, we explored the function of Sox2 in neurosensory development in a model with limited cell type diversification, the inner ear. In Sox2 conditional mutants, neurons initially appear to form normally, whereas late- differentiating neurons of the cochlear apex never form. Variable numbers of hair cells differentiate in the utricle, saccule, and cochlear base but sensory epithelium formation is completely absent in the apex and all three cristae of the semicircular canal ampullae. Hair cells differentiate only in sensory epithelia known or proposed to have a lineage relationship of neurons and hair cells. All initially formed neurons lacking hair cell targets die by apoptosis days after they project toward non-existing epithelia. Therefore, late neuronal development depends directly on Sox2 for differentiation and on the survival of hair cells, possibly derived from common neurosensory precursors.
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Affiliation(s)
- Martina Dvorakova
- Institute of Biotechnology CAS, Prague, Czechia.,Faculty of Science, Charles University, Prague, Czechia
| | - Israt Jahan
- Department of Biology, University of Iowa, Iowa City, IA, USA
| | - Iva Macova
- Institute of Biotechnology CAS, Prague, Czechia.,Faculty of Science, Charles University, Prague, Czechia
| | | | | | - Josef Syka
- Institute of Experimental Medicine CAS, Prague, Czechia
| | - Bernd Fritzsch
- Department of Biology, University of Iowa, Iowa City, IA, USA
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Jahan I, Pan N, Kersigo J, Fritzsch B. Neurog1 can partially substitute for Atoh1 function in hair cell differentiation and maintenance during organ of Corti development. Development 2015. [PMID: 26209643 DOI: 10.1242/dev.123091] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Atoh1, a basic helix-loop-helix (bHLH) transcription factor (TF), is essential for the differentiation of hair cells (HCs), mechanotransducers that convert sound into auditory signals in the mammalian organ of Corti (OC). Previous work demonstrated that replacing mouse Atoh1 with the fly ortholog atonal rescues HC differentiation, indicating functional replacement by other bHLH genes. However, replacing Atoh1 with Neurog1 resulted in reduced HC differentiation compared with transient Atoh1 expression in a 'self-terminating' Atoh1 conditional null mouse (Atoh1-Cre; Atoh1(f/f)). We now show that combining Neurog1 in one allele with removal of floxed Atoh1 in a self-terminating conditional mutant (Atoh1-Cre; Atoh1(f/kiNeurog1)) mouse results in significantly more differentiated inner HCs and outer HCs that have a prolonged longevity of 9 months compared with Atoh1 self-terminating littermates. Stereocilia bundles are partially disorganized, disoriented and not HC type specific. Replacement of Atoh1 with Neurog1 maintains limited expression of Pou4f3 and Barhl1 and rescues HCs quantitatively, but not qualitatively. OC patterning and supporting cell differentiation are also partially disrupted. Diffusible factors involved in patterning are reduced (Fgf8) and factors involved in cell-cell interactions are affected (Jag1, Hes5). Despite the presence of many HCs with stereocilia these mice are deaf, possibly owing to HC and OC patterning defects. This study provides a novel approach to disrupt OC development through modulating the HC-specific intracellular TF network. The resulting disorganized OC indicates that normally differentiated HCs act as 'self-organizers' for OC development and that Atoh1 plays a crucial role to initiate HC stereocilia differentiation independently of HC viability.
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Affiliation(s)
- Israt Jahan
- Department of Biology, College of Liberal Arts & Sciences, University of Iowa, Iowa City, IA 52242, USA
| | - Ning Pan
- Department of Biology, College of Liberal Arts & Sciences, University of Iowa, Iowa City, IA 52242, USA
| | - Jennifer Kersigo
- Department of Biology, College of Liberal Arts & Sciences, University of Iowa, Iowa City, IA 52242, USA
| | - Bernd Fritzsch
- Department of Biology, College of Liberal Arts & Sciences, University of Iowa, Iowa City, IA 52242, USA
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Jahan I, Pan N, Elliott KL, Fritzsch B. The quest for restoring hearing: Understanding ear development more completely. Bioessays 2015. [PMID: 26208302 DOI: 10.1002/bies.201500044] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Neurosensory hearing loss is a growing problem of super-aged societies. Cochlear implants can restore some hearing, but rebuilding a lost hearing organ would be superior. Research has discovered many cellular and molecular steps to develop a hearing organ but translating those insights into hearing organ restoration remains unclear. For example, we cannot make various hair cell types and arrange them into their specific patterns surrounded by the right type of supporting cells in the right numbers. Our overview of the topologically highly organized and functionally diversified cellular mosaic of the mammalian hearing organ highlights what is known and unknown about its development. Following this analysis, we suggest critical steps to guide future attempts toward restoration of a functional organ of Corti. We argue that generating mutant mouse lines that mimic human pathology to fine-tune attempts toward long-term functional restoration are needed to go beyond the hope generated by restoring single hair cells in postnatal sensory epithelia.
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Affiliation(s)
- Israt Jahan
- Department of Biology, CLAS, University of Iowa, Iowa City, IA, USA
| | - Ning Pan
- Department of Biology, CLAS, University of Iowa, Iowa City, IA, USA
| | - Karen L Elliott
- Department of Biology, CLAS, University of Iowa, Iowa City, IA, USA
| | - Bernd Fritzsch
- Department of Biology, CLAS, University of Iowa, Iowa City, IA, USA
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Jahan I, Pan N, Fritzsch B. Opportunities and limits of the one gene approach: the ability of Atoh1 to differentiate and maintain hair cells depends on the molecular context. Front Cell Neurosci 2015; 9:26. [PMID: 25698932 PMCID: PMC4318345 DOI: 10.3389/fncel.2015.00026] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 01/14/2015] [Indexed: 02/03/2023] Open
Abstract
Atoh1 (Math1) was the first gene discovered in ear development that showed no hair cell (HC) differentiation when absent and could induce HC differentiation when misexpressed. These data implied that Atoh1 was both necessary and sufficient for hair cell development. However, other gene mutations also result in loss of initially forming HCs, notably null mutants for Pou4f3, Barhl1, and Gfi1. HC development and maintenance also depend on the expression of other genes (Sox2, Eya1, Gata3, Pax2) and several genes have been identified that can induce HCs when misexpressed (Jag1) or knocked out (Lmo4). In the ear Atoh1 is not only expressed in HCs but also in some supporting cells and neurons that do not differentiate into HCs. Simple removal of one gene, Neurod1, can de-repress Atoh1 and turns those neurons into HCs suggesting that Neurod1 blocks Atoh1 function in neurons. Atoh1 expression in inner pillar cells may also be blocked by too many Hes/Hey factors but conversion into HCs has only partially been achieved through Hes/Hey removal. Detailed analysis of cell cycle exit confirmed an apex to base cell cycle exit progression of HCs of the organ of Corti. In contrast, Atoh1 expression progresses from the base toward the apex with a variable delay relative to the cell cycle exit. Most HCs exit the cell cycle and are thus defined as precursors before Atoh1 is expressed. Atoh1 is a potent differentiation factor but can differentiate and maintain HCs only in the ear and when other factors are co-expressed. Upstream factors are essential to regulate Atoh1 level of expression duration while downstream, co-activated by other factors, will define the context of Atoh1 action. We suggest that these insights need to be taken into consideration and approaches beyond the simple Atoh1 expression need to be designed able to generate the radial and longitudinal variations in hair cell types for normal function of the organ of Corti.
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Affiliation(s)
- Israt Jahan
- Department of Biology, University of Iowa Iowa City, IA, USA
| | - Ning Pan
- Department of Biology, University of Iowa Iowa City, IA, USA
| | - Bernd Fritzsch
- Department of Biology, University of Iowa Iowa City, IA, USA
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Mulvaney JF, Amemiya Y, Freeman SD, Ladher RK, Dabdoub A. Molecular cloning and functional characterisation of chicken Atonal homologue 1: a comparison with human Atoh1. Biol Cell 2015; 107:41-60. [PMID: 25412697 DOI: 10.1111/boc.201400078] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 11/20/2014] [Indexed: 12/19/2022]
Abstract
BACKGROUND INFORMATION The vertebrate basic helix-loop-helix transcription factor Atoh1 is essential for maturation and survival of mechanosensory hair cells of the inner ear, neurogenesis, differentiation of the intestine, homeostasis of the colon and is implicated in cancer progression. Given that mutations in Atoh1 are detected in malignant tumours, study of functionally different Atoh1 alleles and homologues might yield useful avenues for investigation. The predicted sequence of chicken Atoh1 (cAtoh1) has large regions of dissimilarity to that of mammalian Atoh1 homologues. We hypothesise that cAtoh1 might have intrinsic functional differences to mammalian Atoh1. RESULTS In this study, we cloned and sequenced the full open reading frame of cAtoh1. In overexpression experiments, we show that this sequence is sufficient to generate a cAtoh1 protein capable of inducing hair cell markers when expressed in nonsensory regions of the developing inner ear, and that morpholino-mediated knock-down using a section of the sequence 5' to the start codon inhibits differentiation of hair cells in the chicken basilar papilla. Furthermore, we compare the behaviour of cAtoh1 and human Atoh1 (hAtoh1) in embryonic mouse cochlear explants, showing that cAtoh1 is a potent inducer of hair cell differentiation and that it can overcome Sox2-mediated repression of hair cell differentiation more effectively than hAtoh1. CONCLUSIONS cAtoh1 is both necessary and sufficient for avian mechanosensory hair cell differentiation. The non-conserved regions of the cAtoh1 coding region have functional consequences on its behaviour.
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Affiliation(s)
- Joanna F Mulvaney
- Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, ON, M4N 3M5, Canada
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