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Wang G, Gu Y, Liu Z. Deciphering the genetic interactions between Pou4f3, Gfi1, and Rbm24 in maintaining mouse cochlear hair cell survival. eLife 2024; 12:RP90025. [PMID: 38483314 PMCID: PMC10939501 DOI: 10.7554/elife.90025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2024] Open
Abstract
Mammals harbor a limited number of sound-receptor hair cells (HCs) that cannot be regenerated after damage. Thus, investigating the underlying molecular mechanisms that maintain HC survival is crucial for preventing hearing impairment. Intriguingly, Pou4f3-/- or Gfi1-/- HCs form initially but then rapidly degenerate, whereas Rbm24-/- HCs degenerate considerably later. However, the transcriptional cascades involving Pou4f3, Gfi1, and Rbm24 remain undescribed. Here, we demonstrate that Rbm24 expression is completely repressed in Pou4f3-/- HCs but unaltered in Gfi1-/- HCs, and further that the expression of both POU4F3 and GFI1 is intact in Rbm24-/- HCs. Moreover, by using in vivo mouse transgenic reporter assays, we identify three Rbm24 enhancers to which POU4F3 binds. Lastly, through in vivo genetic testing of whether Rbm24 restoration alleviates the degeneration of Pou4f3-/- HCs, we show that ectopic Rbm24 alone cannot prevent Pou4f3-/- HCs from degenerating. Collectively, our findings provide new molecular and genetic insights into how HC survival is regulated.
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Affiliation(s)
- Guangqin Wang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of SciencesShanghaiChina
- University of Chinese Academy of SciencesBeijingChina
| | - Yunpeng Gu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of SciencesShanghaiChina
- University of Chinese Academy of SciencesBeijingChina
| | - Zhiyong Liu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of SciencesShanghaiChina
- University of Chinese Academy of SciencesBeijingChina
- Shanghai Center for Brain Science and Brain-Inspired Intelligence TechnologyShanghaiChina
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2
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Anselmi C, Fuller GK, Stolfi A, Groves AK, Manni L. Sensory cells in tunicates: insights into mechanoreceptor evolution. Front Cell Dev Biol 2024; 12:1359207. [PMID: 38550380 PMCID: PMC10973136 DOI: 10.3389/fcell.2024.1359207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Accepted: 03/04/2024] [Indexed: 04/04/2024] Open
Abstract
Tunicates, the sister group of vertebrates, offer a unique perspective for evolutionary developmental studies (Evo-Devo) due to their simple anatomical organization. Moreover, the separation of tunicates from vertebrates predated the vertebrate-specific genome duplications. As adults, they include both sessile and pelagic species, with very limited mobility requirements related mainly to water filtration. In sessile species, larvae exhibit simple swimming behaviors that are required for the selection of a suitable substrate on which to metamorphose. Despite their apparent simplicity, tunicates display a variety of mechanoreceptor structures involving both primary and secondary sensory cells (i.e., coronal sensory cells). This review encapsulates two decades of research on tunicate mechanoreception focusing on the coronal organ's sensory cells as prime candidates for understanding the evolution of vertebrate hair cells of the inner ear and the lateral line organ. The review spans anatomical, cellular and molecular levels emphasizing both similarity and differences between tunicate and vertebrate mechanoreception strategies. The evolutionary significance of mechanoreception is discussed within the broader context of Evo-Devo studies, shedding light on the intricate pathways that have shaped the sensory system in chordates.
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Affiliation(s)
- Chiara Anselmi
- Hopkins Marine Station, Institute for Stem Cell Biology and Regenerative Medicine, Stanford University, Pacific Grove, CA, United States
- Wu Tsai Neurosciences Institute, Stanford University, Stanford, CA, United States
| | - Gwynna K. Fuller
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
| | - Alberto Stolfi
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, United States
| | - Andrew K. Groves
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, United States
- Department of Neuroscience, Baylor College of Medicine, Houston, TX, United States
| | - Lucia Manni
- Dipartimento di Biologia, Università degli Studi di Padova, Padova, Italy
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Li X, Ren M, Gu Y, Zhu T, Zhang Y, Li J, Li C, Wang G, Song L, Bi Z, Liu Z. In situ regeneration of inner hair cells in the damaged cochlea by temporally regulated co-expression of Atoh1 and Tbx2. Development 2023; 150:dev201888. [PMID: 38078650 DOI: 10.1242/dev.201888] [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: 04/18/2023] [Accepted: 11/02/2023] [Indexed: 12/18/2023]
Abstract
Cochlear inner hair cells (IHCs) are primary sound receptors, and are therefore a target for developing treatments for hearing impairment. IHC regeneration in vivo has been widely attempted, although not yet in the IHC-damaged cochlea. Moreover, the extent to which new IHCs resemble wild-type IHCs remains unclear, as is the ability of new IHCs to improve hearing. Here, we have developed an in vivo mouse model wherein wild-type IHCs were pre-damaged and nonsensory supporting cells were transformed into IHCs by ectopically expressing Atoh1 transiently and Tbx2 permanently. Notably, the new IHCs expressed the functional marker vGlut3 and presented similar transcriptomic and electrophysiological properties to wild-type IHCs. Furthermore, the formation efficiency and maturity of new IHCs were higher than those previously reported, although marked hearing improvement was not achieved, at least partly due to defective mechanoelectrical transduction (MET) in new IHCs. Thus, we have successfully regenerated new IHCs resembling wild-type IHCs in many respects in the damaged cochlea. Our findings suggest that the defective MET is a critical barrier that prevents the restoration of hearing capacity and should thus facilitate future IHC regeneration studies.
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Affiliation(s)
- Xiang Li
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Minhui Ren
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yunpeng Gu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Tong Zhu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Yu Zhang
- Department of Otolaryngology-Head and Neck Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
| | - Jie Li
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Chao Li
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Guangqin Wang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lei Song
- Department of Otolaryngology-Head and Neck Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China
- Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai 200125, China
| | - Zhenghong Bi
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Zhiyong Liu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China
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Pan Y, Li S, He S, Wang G, Li C, Liu Z, Xiang M. Fgf8 P2A-3×GFP/+: A New Genetic Mouse Model for Specifically Labeling and Sorting Cochlear Inner Hair Cells. Neurosci Bull 2023; 39:1762-1774. [PMID: 37233921 PMCID: PMC10661496 DOI: 10.1007/s12264-023-01069-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2022] [Accepted: 03/08/2023] [Indexed: 05/27/2023] Open
Abstract
The cochlear auditory epithelium contains two types of sound receptors, inner hair cells (IHCs) and outer hair cells (OHCs). Mouse models for labelling juvenile and adult IHCs or OHCs exist; however, labelling for embryonic and perinatal IHCs or OHCs are lacking. Here, we generated a new knock-in Fgf8P2A-3×GFP/+ (Fgf8GFP/+) strain, in which the expression of a series of three GFP fragments is controlled by endogenous Fgf8 cis-regulatory elements. After confirming that GFP expression accurately reflects the expression of Fgf8, we successfully obtained both embryonic and neonatal IHCs with high purity, highlighting the power of Fgf8GFP/+. Furthermore, our fate-mapping analysis revealed, unexpectedly, that IHCs are also derived from inner ear progenitors expressing Insm1, which is currently regarded as an OHC marker. Thus, besides serving as a highly favorable tool for sorting early IHCs, Fgf8GFP/+ will facilitate the isolation of pure early OHCs by excluding IHCs from the entire hair cell pool.
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Affiliation(s)
- Yi Pan
- Department of Otolaryngology and Head and Neck Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China
| | - Shuting Li
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Shunji He
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Guangqin Wang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chao Li
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Zhiyong Liu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China.
- Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai, 201210, China.
| | - Mingliang Xiang
- Department of Otolaryngology and Head and Neck Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200025, China.
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Sun Y, Liu Z. Recent advances in molecular studies on cochlear development and regeneration. Curr Opin Neurobiol 2023; 81:102745. [PMID: 37356371 DOI: 10.1016/j.conb.2023.102745] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 05/06/2023] [Accepted: 05/25/2023] [Indexed: 06/27/2023]
Abstract
The auditory organ cochlea harbors two types of sound receptors, inner hair cells (IHCs) and outer hair cells (OHCs), which are innervated by spiral (auditory) ganglion neurons (SGNs). Recent transcriptomic, epigenetic, and genetic studies have started to reveal various aspects of cochlear development, including how prosensory progenitors are specified and diversified into IHCs or OHCs, as well as the heterogeneity among SGNs and how SGN subtypes are formed. Here, we primarily review advances in this line of research over the past five years and discuss a few key studies (from the past two years) to elucidate (1) how prosensory progenitors are specified; (2) the cis-regulatory control of Atoh1 expression and the synergistic interaction between Atoh1 and Pou4f3; and (3) the essential roles of Insm1 and Ikzf2 in OHC development and Tbx2 in IHC development. Moreover, we highlight the contribution of recent molecular studies on cochlear development toward the goal of regenerating IHCs and OHCs, which holds considerable potential for application in treating human deafness. Lastly, we briefly summarize the most recent progress on uncovering when and how SGN diversity is generated.
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Affiliation(s)
- Yuwei Sun
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Zhiyong Liu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, 200031, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai, 201210, China.
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Li S, He S, Lu Y, Jia S, Liu Z. Epistatic genetic interactions between Insm1 and Ikzf2 during cochlear outer hair cell development. Cell Rep 2023; 42:112504. [PMID: 37171961 DOI: 10.1016/j.celrep.2023.112504] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 03/17/2023] [Accepted: 04/27/2023] [Indexed: 05/14/2023] Open
Abstract
The cochlea harbors two types of sound receptors, outer hair cells (OHCs) and inner hair cells (IHCs). OHCs transdifferentiate into IHCs in Insm1 mutants, and OHCs in Ikzf2-deficient mice are dysfunctional and maintain partial IHC gene expression. Insm1 potentially acts as a positive but indirect regulator of Ikzf2, considering that Insm1 is expressed earlier than Ikzf2 and primarily functions as a transcriptional repressor. However, direct evidence of this possibility is lacking. Here, we report the following results: first, Insm1 overexpression in IHCs leads to ectopic Ikzf2 expression. Second, Ikzf2 expression is repressed in Insm1-deficient OHCs, and forced expression of Ikzf2 mitigates the OHC abnormality in Insm1 mutants. Last, dual ablation of Insm1 and Ikzf2 generates a similar OHC phenotype as does Insm1 ablation alone. Collectively, our findings reveal the transcriptional cascade from Insm1 to Ikzf2, which should facilitate future investigation of the molecular mechanisms underlying OHC development and regeneration.
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Affiliation(s)
- Shuting Li
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shunji He
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Ying Lu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Shiqi Jia
- The First Affiliated Hospital, Jinan University, Guangzhou 510630, China
| | - Zhiyong Liu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China.
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Abstract
Cochlear hair cells (HCs) in the inner ear are responsible for sound detection. For HC fate specification, the master transcription factor Atoh1 is both necessary and sufficient. Atoh1 expression is dynamic and tightly regulated during development, but the cis-regulatory elements mediating this regulation remain unresolved. Unexpectedly, we found that deleting the only recognized Atoh1 enhancer, defined here as Eh1, failed to impair HC development. By using the assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq), we discovered two additional Atoh1 enhancers: Eh2 and Eh3. Notably, Eh2 deletion was sufficient for impairing HC development, and concurrent deletion of Eh1 and Eh2 or all three enhancers resulted in nearly complete absence of HCs. Lastly, we showed that Atoh1 binds to all three enhancers, consistent with its autoregulatory function. Our findings reveal that the cooperative action of three distinct enhancers underpins effective Atoh1 regulation during HC development, indicating potential therapeutic approaches for HC regeneration.
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Single-cell transcriptomic landscapes of the otic neuronal lineage at multiple early embryonic ages. Cell Rep 2022; 38:110542. [PMID: 35320729 DOI: 10.1016/j.celrep.2022.110542] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Revised: 12/03/2021] [Accepted: 02/25/2022] [Indexed: 11/20/2022] Open
Abstract
Inner ear vestibular and spiral ganglion neurons (VGNs and SGNs) are known to play pivotal roles in balance control and sound detection. However, the molecular mechanisms underlying otic neurogenesis at early embryonic ages have remained unclear. Here, we use single-cell RNA sequencing to reveal the transcriptomes of mouse otic tissues at three embryonic ages, embryonic day 9.5 (E9.5), E11.5, and E13.5, covering proliferating and undifferentiated otic neuroblasts and differentiating VGNs and SGNs. We validate the high quality of our studies by using multiple assays, including genetic fate mapping analysis, and we uncover several genes upregulated in neuroblasts or differentiating VGNs and SGNs, such as Shox2, Myt1, Casz1, and Sall3. Notably, our findings suggest a general cascaded differentiation trajectory during early otic neurogenesis. The comprehensive understanding of early otic neurogenesis provided by our study holds critical implications for both basic and translational research.
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