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Zine A, Fritzsch B. Early Steps towards Hearing: Placodes and Sensory Development. Int J Mol Sci 2023; 24:6994. [PMID: 37108158 PMCID: PMC10139157 DOI: 10.3390/ijms24086994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 04/03/2023] [Accepted: 04/06/2023] [Indexed: 04/29/2023] Open
Abstract
Sensorineural hearing loss is the most prevalent sensory deficit in humans. Most cases of hearing loss are due to the degeneration of key structures of the sensory pathway in the cochlea, such as the sensory hair cells, the primary auditory neurons, and their synaptic connection to the hair cells. Different cell-based strategies to replace damaged inner ear neurosensory tissue aiming at the restoration of regeneration or functional recovery are currently the subject of intensive research. Most of these cell-based treatment approaches require experimental in vitro models that rely on a fine understanding of the earliest morphogenetic steps that underlie the in vivo development of the inner ear since its initial induction from a common otic-epibranchial territory. This knowledge will be applied to various proposed experimental cell replacement strategies to either address the feasibility or identify novel therapeutic options for sensorineural hearing loss. In this review, we describe how ear and epibranchial placode development can be recapitulated by focusing on the cellular transformations that occur as the inner ear is converted from a thickening of the surface ectoderm next to the hindbrain known as the otic placode to an otocyst embedded in the head mesenchyme. Finally, we will highlight otic and epibranchial placode development and morphogenetic events towards progenitors of the inner ear and their neurosensory cell derivatives.
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Affiliation(s)
- Azel Zine
- LBN, Laboratory of Bioengineering and Nanoscience, University of Montpellier, 34193 Montpellier, France
| | - Bernd Fritzsch
- Department of Biology, CLAS, University of Iowa, Iowa City, IA 52242, USA
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2
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Scheibinger M, Janesick A, Benkafadar N, Ellwanger DC, Jan TA, Heller S. Cell-type identity of the avian utricle. Cell Rep 2022; 40:111432. [PMID: 36170825 PMCID: PMC9588199 DOI: 10.1016/j.celrep.2022.111432] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 07/18/2022] [Accepted: 09/08/2022] [Indexed: 11/30/2022] Open
Abstract
The avian utricle, a vestibular organ of the inner ear, displays turnover of sensory hair cells throughout life. This is in sharp contrast to the mammalian utricle, which shows limited regenerative capacity. Here, we use single-cell RNA sequencing to identify distinct marker genes for the different sensory hair cell subtypes of the chicken utricle, which we validated in situ. We provide markers for spatially distinct supporting cell populations and identify two transitional cell populations of dedifferentiating supporting cells and developing hair cells. Trajectory reconstruction resulted in an inventory of gene expression dynamics of natural hair cell generation in the avian utricle. Scheibinger et al. provide a single-cell transcriptomic atlas of the chicken utricle, a vestibular organ. Hair cell and supporting cell subtypes are defined by marker genes, and trajectories of gene expression dynamics during hair cell turnover are shown. This resource provides a baseline to study inner ear damage and regeneration.
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Affiliation(s)
- Mirko Scheibinger
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Amanda Janesick
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Nesrine Benkafadar
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Daniel C Ellwanger
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Taha A Jan
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Stefan Heller
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Institute for Stem Cell Biology and Regenerative Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA.
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3
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Kelley MW. Cochlear Development; New Tools and Approaches. Front Cell Dev Biol 2022; 10:884240. [PMID: 35813214 PMCID: PMC9260282 DOI: 10.3389/fcell.2022.884240] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2022] [Accepted: 05/19/2022] [Indexed: 12/21/2022] Open
Abstract
The sensory epithelium of the mammalian cochlea, the organ of Corti, is comprised of at least seven unique cell types including two functionally distinct types of mechanosensory hair cells. All of the cell types within the organ of Corti are believed to develop from a population of precursor cells referred to as prosensory cells. Results from previous studies have begun to identify the developmental processes, lineage restrictions and signaling networks that mediate the specification of many of these cell types, however, the small size of the organ and the limited number of each cell type has hampered progress. Recent technical advances, in particular relating to the ability to capture and characterize gene expression at the single cell level, have opened new avenues for understanding cellular specification in the organ of Corti. This review will cover our current understanding of cellular specification in the cochlea, discuss the most commonly used methods for single cell RNA sequencing and describe how results from a recent study using single cell sequencing provided new insights regarding cellular specification.
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4
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Filova I, Bohuslavova R, Tavakoli M, Yamoah EN, Fritzsch B, Pavlinkova G. Early Deletion of Neurod1 Alters Neuronal Lineage Potential and Diminishes Neurogenesis in the Inner Ear. Front Cell Dev Biol 2022; 10:845461. [PMID: 35252209 PMCID: PMC8894106 DOI: 10.3389/fcell.2022.845461] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Accepted: 01/25/2022] [Indexed: 11/13/2022] Open
Abstract
Neuronal development in the inner ear is initiated by expression of the proneural basic Helix-Loop-Helix (bHLH) transcription factor Neurogenin1 that specifies neuronal precursors in the otocyst. The initial specification of the neuroblasts within the otic epithelium is followed by the expression of an additional bHLH factor, Neurod1. Although NEUROD1 is essential for inner ear neuronal development, the different aspects of the temporal and spatial requirements of NEUROD1 for the inner ear and, mainly, for auditory neuron development are not fully understood. In this study, using Foxg1Cre for the early elimination of Neurod1 in the mouse otocyst, we showed that Neurod1 deletion results in a massive reduction of differentiating neurons in the otic ganglion at E10.5, and in the diminished vestibular and rudimental spiral ganglia at E13.5. Attenuated neuronal development was associated with reduced and disorganized sensory epithelia, formation of ectopic hair cells, and the shortened cochlea in the inner ear. Central projections of inner ear neurons with conditional Neurod1 deletion are reduced, unsegregated, disorganized, and interconnecting the vestibular and auditory systems. In line with decreased afferent input from auditory neurons, the volume of cochlear nuclei was reduced by 60% in Neurod1 mutant mice. Finally, our data demonstrate that early elimination of Neurod1 affects the neuronal lineage potential and alters the generation of inner ear neurons and cochlear afferents with a profound effect on the first auditory nuclei, the cochlear nuclei.
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Affiliation(s)
- Iva Filova
- Laboratory of Molecular Pathogenesis, Institute of Biotechnology CAS, Vestec, Czechia
| | - Romana Bohuslavova
- Laboratory of Molecular Pathogenesis, Institute of Biotechnology CAS, Vestec, Czechia
| | - Mitra Tavakoli
- Laboratory of Molecular Pathogenesis, Institute of Biotechnology CAS, Vestec, Czechia
| | - Ebenezer N. Yamoah
- Department of Physiology and Cell Biology, Institute for Neuroscience, University of Nevada, Reno, NV, United States
| | - Bernd Fritzsch
- Department of Biology, University of Iowa, Iowa City, IA, United States
| | - Gabriela Pavlinkova
- Laboratory of Molecular Pathogenesis, Institute of Biotechnology CAS, Vestec, Czechia
- *Correspondence: Gabriela Pavlinkova,
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5
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Elliott KL, Pavlínková G, Chizhikov VV, Yamoah EN, Fritzsch B. Development in the Mammalian Auditory System Depends on Transcription Factors. Int J Mol Sci 2021; 22:ijms22084189. [PMID: 33919542 PMCID: PMC8074135 DOI: 10.3390/ijms22084189] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2021] [Revised: 04/15/2021] [Accepted: 04/16/2021] [Indexed: 12/16/2022] Open
Abstract
We review the molecular basis of several transcription factors (Eya1, Sox2), including the three related genes coding basic helix–loop–helix (bHLH; see abbreviations) proteins (Neurog1, Neurod1, Atoh1) during the development of spiral ganglia, cochlear nuclei, and cochlear hair cells. Neuronal development requires Neurog1, followed by its downstream target Neurod1, to cross-regulate Atoh1 expression. In contrast, hair cells and cochlear nuclei critically depend on Atoh1 and require Neurod1 expression for interactions with Atoh1. Upregulation of Atoh1 following Neurod1 loss changes some vestibular neurons’ fate into “hair cells”, highlighting the significant interplay between the bHLH genes. Further work showed that replacing Atoh1 by Neurog1 rescues some hair cells from complete absence observed in Atoh1 null mutants, suggesting that bHLH genes can partially replace one another. The inhibition of Atoh1 by Neurod1 is essential for proper neuronal cell fate, and in the absence of Neurod1, Atoh1 is upregulated, resulting in the formation of “intraganglionic” HCs. Additional genes, such as Eya1/Six1, Sox2, Pax2, Gata3, Fgfr2b, Foxg1, and Lmx1a/b, play a role in the auditory system. Finally, both Lmx1a and Lmx1b genes are essential for the cochlear organ of Corti, spiral ganglion neuron, and cochlear nuclei formation. We integrate the mammalian auditory system development to provide comprehensive insights beyond the limited perception driven by singular investigations of cochlear neurons, cochlear hair cells, and cochlear nuclei. A detailed analysis of gene expression is needed to understand better how upstream regulators facilitate gene interactions and mammalian auditory system development.
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Affiliation(s)
- Karen L. Elliott
- Department of Biology, University of Iowa, Iowa City, IA 52242, USA;
| | - Gabriela Pavlínková
- Institute of Biotechnology of the Czech Academy of Sciences, 25250 Vestec, Czechia;
| | - Victor V. Chizhikov
- Department of Anatomy and Neurobiology, The University of Tennessee Health Science Center, Memphis, TN 38163, USA;
| | - Ebenezer N. Yamoah
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, NV 89557, USA;
| | - Bernd Fritzsch
- Department of Biology, University of Iowa, Iowa City, IA 52242, USA;
- Correspondence:
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6
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Vermeiren S, Bellefroid EJ, Desiderio S. Vertebrate Sensory Ganglia: Common and Divergent Features of the Transcriptional Programs Generating Their Functional Specialization. Front Cell Dev Biol 2020; 8:587699. [PMID: 33195244 PMCID: PMC7649826 DOI: 10.3389/fcell.2020.587699] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Accepted: 09/08/2020] [Indexed: 12/13/2022] Open
Abstract
Sensory fibers of the peripheral nervous system carry sensation from specific sense structures or use different tissues and organs as receptive fields, and convey this information to the central nervous system. In the head of vertebrates, each cranial sensory ganglia and associated nerves perform specific functions. Sensory ganglia are composed of different types of specialized neurons in which two broad categories can be distinguished, somatosensory neurons relaying all sensations that are felt and visceral sensory neurons sensing the internal milieu and controlling body homeostasis. While in the trunk somatosensory neurons composing the dorsal root ganglia are derived exclusively from neural crest cells, somato- and visceral sensory neurons of cranial sensory ganglia have a dual origin, with contributions from both neural crest and placodes. As most studies on sensory neurogenesis have focused on dorsal root ganglia, our understanding of the molecular mechanisms underlying the embryonic development of the different cranial sensory ganglia remains today rudimentary. However, using single-cell RNA sequencing, recent studies have made significant advances in the characterization of the neuronal diversity of most sensory ganglia. Here we summarize the general anatomy, function and neuronal diversity of cranial sensory ganglia. We then provide an overview of our current knowledge of the transcriptional networks controlling neurogenesis and neuronal diversification in the developing sensory system, focusing on cranial sensory ganglia, highlighting specific aspects of their development and comparing it to that of trunk sensory ganglia.
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Affiliation(s)
- Simon Vermeiren
- ULB Neuroscience Institute, Université Libre de Bruxelles, Gosselies, Belgium
| | - Eric J Bellefroid
- ULB Neuroscience Institute, Université Libre de Bruxelles, Gosselies, Belgium
| | - Simon Desiderio
- Institute for Neurosciences of Montpellier, INSERM U1051, University of Montpellier, Montpellier, France
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7
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Pisciottano F, Cinalli AR, Stopiello JM, Castagna VC, Elgoyhen AB, Rubinstein M, Gómez-Casati ME, Franchini LF. Inner Ear Genes Underwent Positive Selection and Adaptation in the Mammalian Lineage. Mol Biol Evol 2020; 36:1653-1670. [PMID: 31137036 DOI: 10.1093/molbev/msz077] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
The mammalian inner ear possesses functional and morphological innovations that contribute to its unique hearing capacities. The genetic bases underlying the evolution of this mammalian landmark are poorly understood. We propose that the emergence of morphological and functional innovations in the mammalian inner ear could have been driven by adaptive molecular evolution. In this work, we performed a meta-analysis of available inner ear gene expression data sets in order to identify genes that show signatures of adaptive evolution in the mammalian lineage. We analyzed ∼1,300 inner ear expressed genes and found that 13% show signatures of positive selection in the mammalian lineage. Several of these genes are known to play an important function in the inner ear. In addition, we identified that a significant proportion of genes showing signatures of adaptive evolution in mammals have not been previously reported to participate in inner ear development and/or physiology. We focused our analysis in two of these genes: STRIP2 and ABLIM2 by generating null mutant mice and analyzed their auditory function. We found that mice lacking Strip2 displayed a decrease in neural response amplitudes. In addition, we observed a reduction in the number of afferent synapses, suggesting a potential cochlear neuropathy. Thus, this study shows the usefulness of pursuing a high-throughput evolutionary approach followed by functional studies to track down genes that are important for inner ear function. Moreover, this approach sheds light on the genetic bases underlying the evolution of the mammalian inner ear.
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Affiliation(s)
- Francisco Pisciottano
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Alejandro R Cinalli
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Juan Matías Stopiello
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Valeria C Castagna
- Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires,Argentina
| | - Ana Belén Elgoyhen
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
| | - Marcelo Rubinstein
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Facultad de Ciencias Exactas y Naturales (FCEN), Universidad de Buenos Aires, Buenos Aires,Argentina
| | - María Eugenia Gómez-Casati
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina.,Instituto de Farmacología, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires,Argentina
| | - Lucía F Franchini
- Instituto de Investigaciones en Ingeniería Genética y Biología Molecular (INGEBI), Buenos Aires, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires, Argentina
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8
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Li Y, Liu H, Giffen KP, Chen L, Beisel KW, He DZZ. Transcriptomes of cochlear inner and outer hair cells from adult mice. Sci Data 2018; 5:180199. [PMID: 30277483 PMCID: PMC6167952 DOI: 10.1038/sdata.2018.199] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 08/02/2018] [Indexed: 01/09/2023] Open
Abstract
Inner hair cells (IHCs) and outer hair cells (OHCs) are the two anatomically and functionally distinct types of mechanosensitive receptor cells in the mammalian cochlea. The molecular mechanisms defining their morphological and functional specializations are largely unclear. As a first step to uncover the underlying mechanisms, we examined the transcriptomes of IHCs and OHCs isolated from adult CBA/J mouse cochleae. One thousand IHCs and OHCs were separately collected using the suction pipette technique. RNA sequencing of IHCs and OHCs was performed and their transcriptomes were analyzed. The results were validated by comparing some IHC and OHC preferentially expressed genes between present study and published microarray-based data as well as by real-time qPCR. Antibody-based immunocytochemistry was used to validate preferential expression of SLC7A14 and DNM3 in IHCs and OHCs. These data are expected to serve as a highly valuable resource for unraveling the molecular mechanisms underlying different biological properties of IHCs and OHCs as well as to provide a road map for future characterization of genes expressed in IHCs and OHCs.
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Affiliation(s)
- Yi Li
- Department of Otorhinolaryngology, Beijing Tongren Hospital, Beijing Capital Medical University, Beijing 100730, China
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68170, USA
| | - Huizhan Liu
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68170, USA
| | - Kimberlee P. Giffen
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68170, USA
| | - Lei Chen
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68170, USA
- Chongqing Academy of Animal Science, Chongqing 402460, China
| | - Kirk W. Beisel
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68170, USA
| | - David Z. Z. He
- Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, Nebraska 68170, USA
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9
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Spatiotemporal coordination of cellular differentiation and tissue morphogenesis in organ of Corti development. Med Mol Morphol 2018. [PMID: 29536272 DOI: 10.1007/s00795-018-0185-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The organ of Corti, an acoustic sensory organ, is a specifically differentiated epithelium of the cochlear duct, which is a part of the membranous labyrinth in the inner ear. Cells in the organ of Corti are generally classified into two kinds; hair cells, which transduce the mechanical stimuli of sound to the cell membrane electrical potential differences, and supporting cells. These cells emerge from homogeneous prosensory epithelium through cell fate determination and differentiation. In the organ of Corti organogenesis, cell differentiation and the rearrangement of their position proceed in parallel, resulting in a characteristic alignment of mature hair cells and supporting cells. Recently, studies have focused on the signaling molecules and transcription factors that regulate cell fate determination and differentiation processes. In comparison, less is known about the mechanism of the formation of the tissue architecture; however, this is important in the morphogenesis of the organ of Corti. Thus, this review will introduce previous findings that focus on how cell fate determination, cell differentiation, and whole tissue morphogenesis proceed in a spatiotemporally and finely coordinated manner. This overview provides an insight into the regulatory mechanisms of the coordination in the developing organ of Corti.
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10
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Ebeid M, Sripal P, Pecka J, Beisel KW, Kwan K, Soukup GA. Transcriptome-wide comparison of the impact of Atoh1 and miR-183 family on pluripotent stem cells and multipotent otic progenitor cells. PLoS One 2017; 12:e0180855. [PMID: 28686713 PMCID: PMC5501616 DOI: 10.1371/journal.pone.0180855] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2017] [Accepted: 06/05/2017] [Indexed: 11/18/2022] Open
Abstract
Over 5% of the global population suffers from disabling hearing loss caused by multiple factors including aging, noise exposure, genetic predisposition, or use of ototoxic drugs. Sensorineural hearing loss is often caused by the loss of sensory hair cells (HCs) of the inner ear. A barrier to hearing restoration after HC loss is the limited ability of mammalian auditory HCs to spontaneously regenerate. Understanding the molecular mechanisms orchestrating HC development is expected to facilitate cell replacement therapies. Multiple events are known to be essential for proper HC development including the expression of Atoh1 transcription factor and the miR-183 family. We have developed a series of vectors expressing the miR-183 family and/or Atoh1 that was used to transfect two different developmental cell models: pluripotent mouse embryonic stem cells (mESCs) and immortalized multipotent otic progenitor (iMOP) cells representing an advanced developmental stage. Transcriptome profiling of transfected cells show that the impact of Atoh1 is contextually dependent with more HC-specific effects on iMOP cells. miR-183 family expression in combination with Atoh1 not only appears to fine tune gene expression in favor of HC fate, but is also required for the expression of some HC-specific genes. Overall, the work provides novel insight into the combined role of Atoh1 and the miR-183 family during HC development that may ultimately inform strategies to promote HC regeneration or maintenance.
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Affiliation(s)
- Michael Ebeid
- Department of Biomedical Sciences, Creighton University, Omaha, Nebraska, United States of America
| | - Prashanth Sripal
- Department of Biomedical Sciences, Creighton University, Omaha, Nebraska, United States of America
| | - Jason Pecka
- Department of Biomedical Sciences, Creighton University, Omaha, Nebraska, United States of America
| | - Kirk W. Beisel
- Department of Biomedical Sciences, Creighton University, Omaha, Nebraska, United States of America
| | - Kelvin Kwan
- Department of Cell Biology and Neuroscience, W. M. Keck Center for Collaborative Neuroscience, Rutgers University, Piscataway, New Jersey, United States of America
| | - Garrett A. Soukup
- Department of Biomedical Sciences, Creighton University, Omaha, Nebraska, United States of America
- * E-mail:
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11
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Żak M, van Oort T, Hendriksen FG, Garcia MI, Vassart G, Grolman W. LGR4 and LGR5 Regulate Hair Cell Differentiation in the Sensory Epithelium of the Developing Mouse Cochlea. Front Cell Neurosci 2016; 10:186. [PMID: 27559308 PMCID: PMC4988241 DOI: 10.3389/fncel.2016.00186] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 07/19/2016] [Indexed: 02/06/2023] Open
Abstract
In the developing cochlea, Wnt/β-catenin signaling positively regulates the proliferation of precursors and promotes the formation of hair cells by up-regulating Atoh1 expression. Not much, however, is known about the regulation of Wnt/β-catenin activity in the cochlea. In multiple tissues, the activity of Wnt/β-catenin signaling is modulated by an interaction between LGR receptors and their ligands from the R-spondin family. The deficiency in Lgr4 and Lgr5 genes leads to developmental malformations and lethality. Using the Lgr5 knock-in mouse line we show that loss of LGR5 function increases Wnt/β-catenin activity in the embryonic cochlea, resulting in a mild overproduction of inner and outer hair cells (OHC). Supernumerary hair cells are likely formed due to an up-regulation of the “pro-hair cell” transcription factors Atoh1, Nhlh1, and Pou4f3. Using a hypomorphic Lgr4 mouse model we showed a mild overproduction of OHCs in the heterozygous and homozygous Lgr4 mice. The loss of LGR4 function prolonged the proliferation in the mid-basal turn of E13 cochleae, causing an increase in the number of SOX2-positive precursor cells within the pro-sensory domain. The premature differentiation of hair cells progressed in a medial to lateral gradient in Lgr4 deficient embryos. No significant up-regulation of Atoh1 was observed following Lgr4 deletion. Altogether, our findings suggest that LGR4 and LGR5 play an important role in the regulation of hair cell differentiation in the embryonic cochlea.
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Affiliation(s)
- Magdalena Żak
- Department of Otorhinolaryngology and Head and Neck Surgery, Brain Center Rudolf Magnus, University Medical Center Utrecht Utrecht, Netherlands
| | - Thijs van Oort
- Department of Otorhinolaryngology and Head and Neck Surgery, Brain Center Rudolf Magnus, University Medical Center Utrecht Utrecht, Netherlands
| | - Ferry G Hendriksen
- Department of Otorhinolaryngology and Head and Neck Surgery, Brain Center Rudolf Magnus, University Medical Center Utrecht Utrecht, Netherlands
| | - Marie-Isabelle Garcia
- Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Faculty of Medicine, Université Libre de Bruxelles Brussels, Belgium
| | - Gilbert Vassart
- Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Faculty of Medicine, Université Libre de Bruxelles Brussels, Belgium
| | - Wilko Grolman
- Department of Otorhinolaryngology and Head and Neck Surgery, Brain Center Rudolf Magnus, University Medical Center Utrecht Utrecht, Netherlands
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12
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Basch ML, Brown RM, Jen H, Groves AK. Where hearing starts: the development of the mammalian cochlea. J Anat 2016; 228:233-54. [PMID: 26052920 PMCID: PMC4718162 DOI: 10.1111/joa.12314] [Citation(s) in RCA: 81] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/14/2015] [Indexed: 12/11/2022] Open
Abstract
The mammalian cochlea is a remarkable sensory organ, capable of perceiving sound over a range of 10(12) in pressure, and discriminating both infrasonic and ultrasonic frequencies in different species. The sensory hair cells of the mammalian cochlea are exquisitely sensitive, responding to atomic-level deflections at speeds on the order of tens of microseconds. The number and placement of hair cells are precisely determined during inner ear development, and a large number of developmental processes sculpt the shape, size and morphology of these cells along the length of the cochlear duct to make them optimally responsive to different sound frequencies. In this review, we briefly discuss the evolutionary origins of the mammalian cochlea, and then describe the successive developmental processes that lead to its induction, cell cycle exit, cellular patterning and the establishment of topologically distinct frequency responses along its length.
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Affiliation(s)
- Martin L. Basch
- Department of NeuroscienceBaylor College of MedicineHoustonTXUSA
| | - Rogers M. Brown
- Program in Developmental BiologyBaylor College of MedicineHoustonTXUSA
| | - Hsin‐I Jen
- Program in Developmental BiologyBaylor College of MedicineHoustonTXUSA
| | - Andrew K. Groves
- Department of NeuroscienceBaylor College of MedicineHoustonTXUSA
- Program in Developmental BiologyBaylor College of MedicineHoustonTXUSA
- Department of Molecular and Human GeneticsBaylor College of MedicineHoustonTXUSA
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13
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Campbell DP, Chrysostomou E, Doetzlhofer A. Canonical Notch signaling plays an instructive role in auditory supporting cell development. Sci Rep 2016; 6:19484. [PMID: 26786414 PMCID: PMC4726253 DOI: 10.1038/srep19484] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Accepted: 12/14/2015] [Indexed: 02/07/2023] Open
Abstract
The auditory sensory epithelium, composed of mechano-sensory hair cells (HCs) and highly specialized glial-like supporting cells (SCs), is critical for our ability to detect sound. SCs provide structural and functional support to HCs and play an essential role in cochlear development, homeostasis and repair. Despite their importance, however, surprisingly little is known about the molecular mechanisms guiding SC differentiation. Here, we provide evidence that in addition to its well-characterized inhibitory function, canonical Notch signaling plays a positive, instructive role in the differentiation of SCs. Using γ-secretase inhibitor DAPT to acutely block canonical Notch signaling, we identified a cohort of Notch-regulated SC-specific genes, with diverse functions in cell signaling, cell differentiation, neuronal innervation and synaptogenesis. We validated the newly identified Notch-regulated genes in vivo using genetic gain (Emx2Cre/+; Rosa26N1ICD/+) and loss-of-function approaches (Emx2Cre/+; Rosa26DnMAML1/+). Furthermore, we demonstrate that Notch over-activation in the differentiating murine cochlea (Emx2Cre/+; Rosa26N1ICD/+) actively promotes a SC-specific gene expression program. Finally, we show that outer SCs –so called Deiters’ cells are selectively lost by prolonged reduction (Emx2Cre/+; Rosa26DnMAML1/+/+) or abolishment of canonical Notch signaling (Fgfr3-iCreER; Rbpj−/Δ), indicating a critical role for Notch signaling in Deiters’ cell development.
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Affiliation(s)
- Dean P Campbell
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine Baltimore, MD 21205, USA.,Center for Sensory Biology, Johns Hopkins University, School of Medicine Baltimore, MD 21205, USA
| | - Elena Chrysostomou
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine Baltimore, MD 21205, USA.,Center for Sensory Biology, Johns Hopkins University, School of Medicine Baltimore, MD 21205, USA
| | - Angelika Doetzlhofer
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine Baltimore, MD 21205, USA.,Center for Sensory Biology, Johns Hopkins University, School of Medicine Baltimore, MD 21205, USA
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14
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Fritzsch B, Pan N, Jahan I, Elliott KL. Inner ear development: building a spiral ganglion and an organ of Corti out of unspecified ectoderm. Cell Tissue Res 2015; 361:7-24. [PMID: 25381571 PMCID: PMC4426086 DOI: 10.1007/s00441-014-2031-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Accepted: 10/09/2014] [Indexed: 01/21/2023]
Abstract
The mammalian inner ear develops from a placodal thickening into a complex labyrinth of ducts with five sensory organs specialized to detect position and movement in space. The mammalian ear also develops a spiraled cochlear duct containing the auditory organ, the organ of Corti (OC), specialized to translate sound into hearing. Development of the OC from a uniform sheet of ectoderm requires unparalleled precision in the topological developmental engineering of four different general cell types, namely sensory neurons, hair cells, supporting cells, and general otic epithelium, into a mosaic of ten distinctly recognizable cell types in and around the OC, each with a unique distribution. Moreover, the OC receives unique innervation by ear-derived spiral ganglion afferents and brainstem-derived motor neurons as efferents and requires neural-crest-derived Schwann cells to form myelin and neural-crest-derived cells to induce the stria vascularis. This transformation of a sheet of cells into a complicated interdigitating set of cells necessitates the orchestrated expression of multiple transcription factors that enable the cellular transformation from ectoderm into neurosensory cells forming the spiral ganglion neurons (SGNs), while simultaneously transforming the flat epithelium into a tube, the cochlear duct, housing the OC. In addition to the cellular and conformational changes forming the cochlear duct with the OC, changes in the surrounding periotic mesenchyme form passageways for sound to stimulate the OC. We review molecular developmental data, generated predominantly in mice, in order to integrate the well-described expression changes of transcription factors and their actions, as revealed in mutants, in the formation of SGNs and OC in the correct position and orientation with suitable innervation. Understanding the molecular basis of these developmental changes leading to the formation of the mammalian OC and highlighting the gaps in our knowledge might guide in vivo attempts to regenerate this most complicated cellular mosaic of the mammalian body for the reconstitution of hearing in a rapidly growing population of aging people suffering from hearing loss.
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Affiliation(s)
- Bernd Fritzsch
- College of Liberal Arts and Sciences, Department of Biology, University of Iowa, 143 BB, 123 Jefferson Avenue, Iowa City, IA 52242, USA,
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15
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Characterization of the transcriptome of nascent hair cells and identification of direct targets of the Atoh1 transcription factor. J Neurosci 2015; 35:5870-83. [PMID: 25855195 DOI: 10.1523/jneurosci.5083-14.2015] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Hair cells are sensory receptors for the auditory and vestibular system in vertebrates. The transcription factor Atoh1 is both necessary and sufficient for the differentiation of hair cells, and is strongly upregulated during hair-cell regeneration in nonmammalian vertebrates. To identify genes involved in hair cell development and function, we performed RNA-seq profiling of purified Atoh1-expressing hair cells from the neonatal mouse cochlea. We identified >600 enriched transcripts in cochlear hair cells, of which 90% have not been previously shown to be expressed in hair cells. We identified 233 of these hair cell genes as candidates to be directly regulated by Atoh1 based on the presence of Atoh1 binding sites in their regulatory regions and by analyzing Atoh1 ChIP-seq datasets from the cerebellum and small intestine. We confirmed 10 of these genes as being direct Atoh1 targets in the cochlea by ChIP-PCR. The identification of candidate Atoh1 target genes is a first step in identifying gene regulatory networks for hair-cell development and may inform future studies on the potential role of Atoh1 in mammalian hair cell regeneration.
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16
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Fritzsch B, Jahan I, Pan N, Elliott KL. Evolving gene regulatory networks into cellular networks guiding adaptive behavior: an outline how single cells could have evolved into a centralized neurosensory system. Cell Tissue Res 2014; 359:295-313. [PMID: 25416504 DOI: 10.1007/s00441-014-2043-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Accepted: 10/20/2014] [Indexed: 12/18/2022]
Abstract
Understanding the evolution of the neurosensory system of man, able to reflect on its own origin, is one of the major goals of comparative neurobiology. Details of the origin of neurosensory cells, their aggregation into central nervous systems and associated sensory organs and their localized patterning leading to remarkably different cell types aggregated into variably sized parts of the central nervous system have begun to emerge. Insights at the cellular and molecular level have begun to shed some light on the evolution of neurosensory cells, partially covered in this review. Molecular evidence suggests that high mobility group (HMG) proteins of pre-metazoans evolved into the definitive Sox [SRY (sex determining region Y)-box] genes used for neurosensory precursor specification in metazoans. Likewise, pre-metazoan basic helix-loop-helix (bHLH) genes evolved in metazoans into the group A bHLH genes dedicated to neurosensory differentiation in bilaterians. Available evidence suggests that the Sox and bHLH genes evolved a cross-regulatory network able to synchronize expansion of precursor populations and their subsequent differentiation into novel parts of the brain or sensory organs. Molecular evidence suggests metazoans evolved patterning gene networks early, which were not dedicated to neuronal development. Only later in evolution were these patterning gene networks tied into the increasing complexity of diffusible factors, many of which were already present in pre-metazoans, to drive local patterning events. It appears that the evolving molecular basis of neurosensory cell development may have led, in interaction with differentially expressed patterning genes, to local network modifications guiding unique specializations of neurosensory cells into sensory organs and various areas of the central nervous system.
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Affiliation(s)
- Bernd Fritzsch
- Department of Biology, University of Iowa, CLAS, 143 BB, Iowa City, IA, 52242, USA,
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17
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Korrapati S, Roux I, Glowatzki E, Doetzlhofer A. Notch signaling limits supporting cell plasticity in the hair cell-damaged early postnatal murine cochlea. PLoS One 2013; 8:e73276. [PMID: 24023676 PMCID: PMC3758270 DOI: 10.1371/journal.pone.0073276] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Accepted: 07/18/2013] [Indexed: 12/02/2022] Open
Abstract
In mammals, auditory hair cells are generated only during embryonic development and loss or damage to hair cells is permanent. However, in non-mammalian vertebrate species, such as birds, neighboring glia-like supporting cells regenerate auditory hair cells by both mitotic and non-mitotic mechanisms. Based on work in intact cochlear tissue, it is thought that Notch signaling might restrict supporting cell plasticity in the mammalian cochlea. However, it is unresolved how Notch signaling functions in the hair cell-damaged cochlea and the molecular and cellular changes induced in supporting cells in response to hair cell trauma are poorly understood. Here we show that gentamicin-induced hair cell loss in early postnatal mouse cochlear tissue induces rapid morphological changes in supporting cells, which facilitate the sealing of gaps left by dying hair cells. Moreover, we provide evidence that Notch signaling is active in the hair cell damaged cochlea and identify Hes1, Hey1, Hey2, HeyL, and Sox2 as targets and potential Notch effectors of this hair cell-independent mechanism of Notch signaling. Using Cre/loxP based labeling system we demonstrate that inhibition of Notch signaling with a γ- secretase inhibitor (GSI) results in the trans-differentiation of supporting cells into hair cell-like cells. Moreover, we show that these hair cell-like cells, generated by supporting cells have molecular, cellular, and basic electrophysiological properties similar to immature hair cells rather than supporting cells. Lastly, we show that the vast majority of these newly generated hair cell-like cells express the outer hair cell specific motor protein prestin.
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Affiliation(s)
- Soumya Korrapati
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Hearing and Balance, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
| | - Isabelle Roux
- Department of Otolaryngology, Head and Neck Surgery, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Hearing and Balance, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
| | - Elisabeth Glowatzki
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Department of Otolaryngology, Head and Neck Surgery, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Hearing and Balance, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
| | - Angelika Doetzlhofer
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Department of Otolaryngology, Head and Neck Surgery, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- Center for Hearing and Balance, Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
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18
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Pan N, Kopecky B, Jahan I, Fritzsch B. Understanding the evolution and development of neurosensory transcription factors of the ear to enhance therapeutic translation. Cell Tissue Res 2012; 349:415-32. [PMID: 22688958 DOI: 10.1007/s00441-012-1454-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2012] [Accepted: 05/18/2012] [Indexed: 01/08/2023]
Abstract
Reconstructing a functional organ of Corti is the ultimate target towards curing hearing loss. Despite the impressive technical gains made over the last few years, many complications remain ahead for the two main restoration avenues: in vitro transformation of pluripotent cells into hair cell-like cells and adenovirus-mediated gene therapy. Most notably, both approaches require a more complete understanding of the molecular networks that ensure specific cell types form in the correct places to allow proper function of the restored organ of Corti. Important to this understanding are the basic helix-loop-helix (bHLH) transcription factors (TFs) that are highly diverse and serve to increase functional complexity but their evolutionary implementation in the inner ear neurosensory development is less conspicuous. To this end, we review the evolutionary and developmentally dynamic interactions of the three bHLH TFs that have been identified as the main players in neurosensory evolution and development, Neurog1, Neurod1 and Atoh1. These three TFs belong to the neurogenin/atonal family and evolved from a molecular precursor that likely regulated single sensory cell development in the ectoderm of metazoan ancestors but are now also expressed in other parts of the body, including the brain. They interact extensively via intracellular and intercellular cross-regulation to establish the two main neurosensory cell types of the ear, the hair cells and sensory neurons. Furthermore, the level and duration of their expression affect the specification of hair cell subtypes (inner hair cells vs. outer hair cells). We propose that appropriate manipulation of these TFs through their characterized binding sites may offer a solution by itself, or in conjunction with the two other approaches currently pursued by others, to restore the organ of Corti.
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Affiliation(s)
- Ning Pan
- Department of Biology, University of Iowa, College of Liberal Arts and Sciences, Iowa City, IA 52242, USA
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19
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Kim WY. NeuroD1 is an upstream regulator of NSCL1. Biochem Biophys Res Commun 2012; 419:27-31. [PMID: 22310718 DOI: 10.1016/j.bbrc.2012.01.100] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Accepted: 01/21/2012] [Indexed: 10/14/2022]
Abstract
Cell fate determination and differentiation during neurogenesis and myogenesis involve the sequential expression of several basic helix-loop-helix (bHLH) transcription factors. The expression of NeuroD1/2 and the expression of NSCL(Nhlh)1/2 are closely related in many developing peripheral and central neuronal cells, suggesting an epistatic relationship between these two bHLH transcription factor families during neurogenesis. To investigate this relationship, a murine neuroblastoma cell culture system and single/double knock-out (KO) mice of NeuroD1 and NeuroD2 were utilized for the gain-of-function and loss-of-function approaches, respectively. Both NeuroD1 and NeuroD2 were able to induce the transcription of NSCL1 in vitro; however, they were not able to activate NSCL2 transcription. The DNA-binding ability of NeuroD1 was essential for NSCL1 induction. To examine the epistatic relationship in vivo, we examined the expression of NSCL1 and NSCL2 in NeuroD1 and NeuroD2 KO mice and NeuroD1/2 compound KO mice by in situ hybridization, RT-PCR and Northern blotting. The expression of NSCL1 was lower in the NeuroD1 KO mice and was not further decreased in the double KO mice. However, the expression of NSCL2 did not change in either the single KO or double KO mice. These results demonstrate that NeuroD1 is an upstream regulator of the NSCL1 gene but not the NSCL2 gene in mice. In addition, NeuroD2 is not involved in this regulatory pathway in vivo.
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Affiliation(s)
- Woo-Young Kim
- Department of Molecular, Cellular and Developmental Biology, University of Colorado, CO 80309, USA.
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20
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Suzuki H, Ahn HW, Chu T, Bowden W, Gassei K, Orwig K, Rajkovic A. SOHLH1 and SOHLH2 coordinate spermatogonial differentiation. Dev Biol 2011; 361:301-12. [PMID: 22056784 DOI: 10.1016/j.ydbio.2011.10.027] [Citation(s) in RCA: 153] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2011] [Revised: 10/12/2011] [Accepted: 10/20/2011] [Indexed: 12/19/2022]
Abstract
Spermatogonial self-renewal and differentiation are essential for male fertility and reproduction. We discovered that germ cell specific genes Sohlh1 and Sohlh2, encode basic helix-loop-helix (bHLH) transcriptional regulators that are essential in spermatogonial differentiation. Sohlh1 and Sohlh2 individual mouse knockouts show remarkably similar phenotypes. Here we show that SOHLH1 and SOHLH2 proteins are co-expressed in the entire spermatogonial population except in the GFRA1(+) spermatogonia, which includes spermatogonial stem cells (SSCs). SOHLH1 and SOHLH2 are expressed in both KIT negative and KIT positive spermatogonia, and overlap Ngn3/EGFP and SOX3 expression. SOHLH1 and SOHLH2 heterodimerize with each other in vivo, as well as homodimerize. The Sohlh1/Sohlh2 double mutant phenocopies single mutants, i.e., spermatogonia continue to proliferate but do not differentiate properly. Further analysis revealed that GFRA1(+) population was increased, while meiosis commenced prematurely in both single and double knockouts. Sohlh1 and Sohlh2 double deficiency has a synergistic effect on gene expression patterns as compared to the single knockouts. SOHLH proteins affect spermatogonial development by directly regulating Gfra1, Sox3 and Kit gene expression. SOHLH1 and SOHLH2 suppress genes involved in SSC maintenance, and induce genes important for spermatogonial differentiation.
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Affiliation(s)
- Hitomi Suzuki
- Magee-Womens Research Institute, Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA 15213, USA
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21
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Yang T, Kersigo J, Jahan I, Pan N, Fritzsch B. The molecular basis of making spiral ganglion neurons and connecting them to hair cells of the organ of Corti. Hear Res 2011; 278:21-33. [PMID: 21414397 DOI: 10.1016/j.heares.2011.03.002] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2010] [Revised: 03/01/2011] [Accepted: 03/07/2011] [Indexed: 11/28/2022]
Abstract
The bipolar spiral ganglion neurons apparently delaminate from the growing cochlear duct and migrate to Rosenthal's canal. They project radial fibers to innervate the organ of Corti (type I neurons to inner hair cells, type II neurons to outer hair cells) and also project tonotopically to the cochlear nuclei. The early differentiation of these neurons requires transcription factors to regulate migration, pathfinding and survival. Neurog1 null mice lack formation of neurons. Neurod1 null mice show massive neuronal death combined with aberrant central and peripheral projections. Prox1 protein is necessary for proper type II neuron process navigation, which is also affected by the neurotrophins Bdnf and Ntf3. Neurotrophin null mutants show specific patterns of neuronal loss along the cochlea but remaining neurons compensate by expanding their target area. All neurotrophin mutants have reduced radial fiber growth proportional to the degree of loss of neurotrophin alleles. This suggests a simple dose response effect of neurotrophin concentration. Keeping overall concentration constant, but misexpressing one neurotrophin under regulatory control of another one results in exuberant fiber growth not only of vestibular fibers to the cochlea but also of spiral ganglion neurons to outer hair cells suggesting different effectiveness of neurotrophins for spiral ganglion neurite growth. Finally, we report here for the first time that losing all neurons in double null mutants affects extension of the cochlear duct and leads to formation of extra rows of outer hair cells in the apex, possibly by disrupting the interaction of the spiral ganglion with the elongating cochlea.
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Affiliation(s)
- Tian Yang
- Department of Biology, College of Liberal Arts and Sciences, University of Iowa, 143 BB, Iowa City, IA 52242, USA
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22
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Fritzsch B, Eberl DF, Beisel KW. The role of bHLH genes in ear development and evolution: revisiting a 10-year-old hypothesis. Cell Mol Life Sci 2010; 67:3089-99. [PMID: 20495996 PMCID: PMC3665285 DOI: 10.1007/s00018-010-0403-x] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 04/12/2010] [Accepted: 05/06/2010] [Indexed: 10/19/2022]
Abstract
In mouse ear development, two bHLH genes, Atoh1 and Neurog1, are essential for hair cell and sensory neuron differentiation. Evolution converted the original simple atonal-dependent neurosensory cell formation program of diploblasts into the derived developmental program of vertebrates that generates two neurosensory cell types, the sensory neuron and the sensory hair cell. This transformation was achieved through gene multiplication in ancestral triploblasts resulting in the expansion of the atonal bHLH gene family. Novel genes of the Neurogenin and NeuroD families are upregulated prior to the expression of Atoh1. Recent data suggest that NeuroD and Neurogenin were lost or their function in neuronal specification reduced in flies, thus changing our perception of the evolution of these genes. This sequence of expression changes was accompanied by modification of the E-box binding sites of these genes to regulate different downstream genes and to form inhibitory loops among each other, thus fine-tuning expression transitions.
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Affiliation(s)
- Bernd Fritzsch
- Department of Biology, College of Liberal Arts and Sciences, University of Iowa, 143 BB, Iowa City, IA 52242, USA.
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Jahan I, Pan N, Kersigo J, Fritzsch B. Neurod1 suppresses hair cell differentiation in ear ganglia and regulates hair cell subtype development in the cochlea. PLoS One 2010; 5:e11661. [PMID: 20661473 PMCID: PMC2908541 DOI: 10.1371/journal.pone.0011661] [Citation(s) in RCA: 111] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2010] [Accepted: 06/23/2010] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND At least five bHLH genes regulate cell fate determination and differentiation of sensory neurons, hair cells and supporting cells in the mammalian inner ear. Cross-regulation of Atoh1 and Neurog1 results in hair cell changes in Neurog1 null mice although the nature and mechanism of the cross-regulation has not yet been determined. Neurod1, regulated by both Neurog1 and Atoh1, could be the mediator of this cross-regulation. METHODOLOGY/PRINCIPAL FINDINGS We used Tg(Pax2-Cre) to conditionally delete Neurod1 in the inner ear. Our data demonstrate for the first time that the absence of Neurod1 results in formation of hair cells within the inner ear sensory ganglia. Three cell types, neural crest derived Schwann cells and mesenchyme derived fibroblasts (neither expresses Neurod1) and inner ear derived neurons (which express Neurod1) constitute inner ear ganglia. The most parsimonious explanation is that Neurod1 suppresses the alternative fate of sensory neurons to develop as hair cells. In the absence of Neurod1, Atoh1 is expressed and differentiates cells within the ganglion into hair cells. We followed up on this effect in ganglia by demonstrating that Neurod1 also regulates differentiation of subtypes of hair cells in the organ of Corti. We show that in Neurod1 conditional null mice there is a premature expression of several genes in the apex of the developing cochlea and outer hair cells are transformed into inner hair cells. CONCLUSIONS/SIGNIFICANCE Our data suggest that the long noted cross-regulation of Atoh1 expression by Neurog1 might actually be mediated in large part by Neurod1. We suggest that Neurod1 is regulated by both Neurog1 and Atoh1 and provides a negative feedback for either gene. Through this and other feedback, Neurod1 suppresses alternate fates of neurons to differentiate as hair cells and regulates hair cell subtypes.
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Affiliation(s)
- Israt Jahan
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Ning Pan
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Jennifer Kersigo
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
| | - Bernd Fritzsch
- Department of Biology, University of Iowa, Iowa City, Iowa, United States of America
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Jahan I, Kersigo J, Pan N, Fritzsch B. Neurod1 regulates survival and formation of connections in mouse ear and brain. Cell Tissue Res 2010; 341:95-110. [PMID: 20512592 DOI: 10.1007/s00441-010-0984-6] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Accepted: 04/15/2010] [Indexed: 12/11/2022]
Abstract
The developing sensory neurons of the mammalian ear require two sequentially activated bHLH genes, Neurog1 and Neurod1, for their development. Neurons never develop in Neurog1 null mice, and most neurons die in Neurod1 null mutants, a gene upregulated by Neurog1. The surviving neurons of Neurod1 null mice are incompletely characterized in postnatal mice because of the early lethality of mutants and the possible compromising effect of the absence of insulin on peripheral neuropathies. Using Tg(Pax2-cre), we have generated a conditional deletion of floxed Neurod1 for the ear; this mouse is viable and allows us to investigate ear innervation defects of Neurod1 absence only in the ear. We have compared the defects in embryos and show an ear phenotype in conditional Neurod1 null mice comparable with the systemic Neurod1 null mouse. By studying postnatal animals, we show that Neurod1 not only is necessary for the survival of most spiral and many vestibular neurons, but is also essential for a segregated central projection of vestibular and cochlear afferents. In the absence of Neurod1 in the ear, vestibular and cochlear afferents enter the cochlear nucleus as a single mixed nerve. Neurites coming from vestibular and cochlear sensory epithelia project centrally to both cochlear and vestibular nuclei, in addition to their designated target projections. The peripheral innervation of the remaining sensory neurons is disorganized and shows collaterals of single neurons projecting to multiple endorgans, displaying no tonotopic organization of the organ of Corti or the cochlear nucleus. Pending elucidation of the molecular details for these Neurod1 functions, these data demonstrate that Neurod1 is not only a major factor for the survival of neurons but is crucial for the development of normal ear connections, both in the ear and in the central nervous system.
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Affiliation(s)
- Israt Jahan
- Department of Biology, College of Liberal Arts and Sciences, University of Iowa, Iowa City, IA 52242, USA
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25
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Trang SH, Joyner DE, Damron TA, Aboulafia AJ, Randall RL. Potential for functional redundancy in EGF and TGFalpha signaling in desmoid cells: a cDNA microarray analysis. Growth Factors 2010; 28:10-23. [PMID: 20092031 DOI: 10.3109/08977190903299387] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Genes that replace or duplicate the function of other genes are considered functionally redundant. In this cDNA microarray study, using an Agilent microarray platform and GeneSifter analysis software, we evaluated (1) the degree of downstream transcriptional redundancy and (2) the level of genetic uniqueness apparent in desmoid tumor cells stimulated in vitro for 3 h or for 24 h with 100 ng/ml of exogenous recombinant human EGF (rhEGF) or with recombinant human transforming growth factor alpha (rhTGFalpha). Our intent was to identify genes costimulated, or genes unique to, desmoid cells stimulated in vitro with rhEGF and rhTGFalpha. This experimental approach demonstrated a 55% transcriptional redundancy in the number of desmoid genes significantly upregulated or downregulated following 3 h of stimulation with rhEGF or with rhTGFalpha, and a 65% transcriptional redundancy following 24 h of growth factor stimulation. Approximately 150 genes costimulated by rhEGF and rhTGFalpha were identified. This study suggests that EGF and TGFalpha retain some level of functional redundancy, possibly resulting from their divergence from a common ancestral gene.
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Affiliation(s)
- Sylvia H Trang
- SARC Laboratory, Sarcoma Services, Department of Orthopaedics and Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, USA
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Ruschke K, Ebelt H, Klöting N, Boettger T, Raum K, Blüher M, Braun T. Defective peripheral nerve development is linked to abnormal architecture and metabolic activity of adipose tissue in Nscl-2 mutant mice. PLoS One 2009; 4:e5516. [PMID: 19436734 PMCID: PMC2677458 DOI: 10.1371/journal.pone.0005516] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2009] [Accepted: 04/16/2009] [Indexed: 12/25/2022] Open
Abstract
Background In mammals the interplay between the peripheral nervous system (PNS) and adipose tissue is widely unexplored. We have employed mice, which develop an adult onset of obesity due to the lack the neuronal specific transcription factor Nscl-2 to investigate the interplay between the nervous system and white adipose tissue (WAT). Methodology Changes in the architecture and innervation of WAT were compared between wildtype, Nscl2−/−, ob/ob and Nscl2−/−//ob/ob mice using morphological methods, immunohistochemistry and flow cytometry. Metabolic alterations in mutant mice and in isolated cells were investigated under basal and stimulated conditions. Principal Findings We found that Nscl-2 mutant mice show a massive reduction of innervation of white epididymal and paired subcutaneous inguinal fat tissue including sensory and autonomic nerves as demonstrated by peripherin and neurofilament staining. Reduction of innervation went along with defects in the formation of the microvasculature, accumulation of cells of the macrophage/preadipocyte lineage, a bimodal distribution of the size of fat cells, and metabolic defects of isolated adipocytes. Despite a relative insulin resistance of white adipose tissue and isolated Nscl-2 mutant adipocytes the serum level of insulin in Nscl-2 mutant mice was only slightly increased. Conclusions We conclude that the reduction of the innervation and vascularization of WAT in Nscl-2 mutant mice leads to the increase of preadipocyte/macrophage-like cells, a bimodal distribution of the size of adipocytes in WAT and an altered metabolic activity of adipocytes.
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Affiliation(s)
- Karen Ruschke
- Institute of Physiological Chemistry, University of Halle-Wittenberg, Halle, Germany
- Department of Medicine, University of Leipzig, Leipzig, Germany
- Max-Planck-Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Henning Ebelt
- Institute of Physiological Chemistry, University of Halle-Wittenberg, Halle, Germany
| | - Nora Klöting
- Department of Medicine, University of Leipzig, Leipzig, Germany
| | - Thomas Boettger
- Max-Planck-Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Kay Raum
- Julius Wolff Institute and Center for Musculoskeletal Surgery, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Matthias Blüher
- Department of Medicine, University of Leipzig, Leipzig, Germany
| | - Thomas Braun
- Institute of Physiological Chemistry, University of Halle-Wittenberg, Halle, Germany
- Max-Planck-Institute for Heart and Lung Research, Bad Nauheim, Germany
- * E-mail:
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Basic helix-loop-helix transcription factors cooperate to specify a cortical projection neuron identity. Mol Cell Biol 2007; 28:1456-69. [PMID: 18160702 DOI: 10.1128/mcb.01510-07] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Several transcription factors are essential determinants of a cortical projection neuron identity, but their mode of action (instructive versus permissive) and downstream genetic cascades remain poorly defined. Here, we demonstrate that the proneural basic helix-loop-helix (bHLH) gene Ngn2 instructs a partial cortical identity when misexpressed in ventral telencephalic progenitors, inducing ectopic marker expression in a defined temporal sequence, including early (24 h; Nscl2), intermediate (48 h; BhlhB5), and late (72 h; NeuroD, NeuroD2, Math2, and Tbr1) target genes. Strikingly, cortical gene expression was much more rapidly induced by Ngn2 in the dorsal telencephalon (within 12 to 24 h). We identify the bHLH gene Math3 as a dorsally restricted Ngn2 transcriptional target and cofactor, which synergizes with Ngn2 to accelerate target gene transcription in the cortex. Using a novel in vivo luciferase assay, we show that Ngn2 generates only approximately 60% of the transcriptional drive in ventral versus dorsal telencephalic domains, an activity that is augmented by Math3, providing a mechanistic basis for regional differences in Ngn2 function. Cortical bHLH genes thus cooperate to control transcriptional strength, thereby temporally coordinating downstream gene expression.
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Schmid T, Krüger M, Braun T. NSCL-1 and -2 control the formation of precerebellar nuclei by orchestrating the migration of neuronal precursor cells. J Neurochem 2007; 102:2061-2072. [PMID: 17573818 DOI: 10.1111/j.1471-4159.2007.04694.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
During embryonic development post-mitotic neurons of the precerebellar neuroepithelium, migrate from the rhombic lip to the ventral part of the neural tube to form the precerebellar nuclei of the pons and medulla oblongata. In this study, we show that neural basic helix-loop-helix transcription factors NSCL-1 and -2 are expressed in all cells of the anterior extramural migration stream (aes), which forms the precerebellar nuclei. The combined inactivation of NSCL-1 and -2 led to a complete absence of the pontine nuclei and a strong reduction in the reticulotegmental nuclei. We demonstrate that NSCL-1/2 were required for a sustained expression of the netrin receptor and cell guidance molecule Dcc in the aes. Unc5H3, a second netrin receptor, which serves as a stop signal for migratory cells was up-regulated in NSCL-1/2 deficient cells, which ceased migration and accumulated ectopically. Furthermore, we observed a massive increase of apoptosis in cells of the aes in the absence of NSCL-1/2, which together with the arrest of migration might explain the virtually complete loss of aes-derived structures in NSCL-1/2 mutant mice. We conclude that NSCL-1/2 maintain migration and survival of cells in the aes.
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Affiliation(s)
- Thomas Schmid
- Max-Planck-Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Marcus Krüger
- Max-Planck-Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Thomas Braun
- Max-Planck-Institute for Heart and Lung Research, Bad Nauheim, Germany
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