1
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Du Z, Chen X, Zhu P, Lv Q, Yong J, Gu J. Knocking down SOX2 overcomes the resistance of prostate cancer to castration via notch signaling. Mol Biol Rep 2023; 50:9007-9017. [PMID: 37716921 DOI: 10.1007/s11033-023-08757-y] [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: 03/07/2023] [Accepted: 08/16/2023] [Indexed: 09/18/2023]
Abstract
BACKGROUND Castration-resistant prostate cancer (CRPC) is a terminal type of advanced cancer resistant to androgen deprivation therapy (ADT). Due to the poor therapeutic response of CRPC, novel treatment strategies are urgently required. This study aimed to clarify the regulatory roles of the SOX2/Notch axis in CRPC. METHODS For the evaluation of the SOX2, Notch, and Hey1 expression in the prostate cancer (PCa) and CRPC tissues, we conducted immunohistochemistry (IHC) analyses. RT-PCR, Western blotting, and immunofluorescence were performed to evaluate SOX2 and Notch expression in enzalutamide-resistant LNCaP cells (Enza-R). CCK-8, Transwell, Wound healing, and Western blotting assays were used to assess the viability, invasion, migration, cell cycle, and drug-resistant in Enza-R cells. RESULTS Compared to the PCa tissues, CRPC tissues exhibited significantly elevated SOX2, Notch1, and Hey1 expression. SOX2-positive patients were more likely to develop bone metastases than SOX2-negative ones. Significant activation of the signaling associated with SOX2 and Notch was detected in Enza-R cells. The suppression of SOX2 clearly inactivated the Notch signaling and inhibited malignant behaviors, including proliferation, invasion, migration, and drug resistance in Enza-R cells. Theγsecretase inhibitor, GSI-IX, abrogated the enzalutamide resistance by inhibiting Notch signaling in vitro in vitro. Also, GSI-IX alone had a significant anti-tumor effect in Enza-R cells. CONCLUSION We demonstrated that SOX2/Notch signaling was responsible for Enzalutamide resistance in CRPC. Targeting SOX2/Notch signaling might represent a new choice for the treatment and therapy of CRPC.
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Affiliation(s)
- Zhongbo Du
- Department of Clinical Medicine, North Sichuan Medical College, Nanchong, China.
- Department of Urology, Affiliated Hospital of North Sichuan Medical College, Nanchong, China.
| | - Xiaobin Chen
- Department of Clinical Medicine, North Sichuan Medical College, Nanchong, China
- Department of Urology, Affiliated Hospital of North Sichuan Medical College, Nanchong, China
| | - Pingyu Zhu
- Department of Clinical Medicine, North Sichuan Medical College, Nanchong, China
- Department of Urology, Affiliated Hospital of North Sichuan Medical College, Nanchong, China
| | - Qi Lv
- Department of Operation, Affiliated Hospital of North Sichuan Medical College, Nanchong, China
| | - Jun Yong
- Department of Urology, Affiliated Hospital of North Sichuan Medical College, Nanchong, China
| | - Junqing Gu
- Department of Urology, Affiliated Hospital of North Sichuan Medical College, Nanchong, China.
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2
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Heuermann ML, Matos S, Hamilton D, Cox BC. Regenerated hair cells in the neonatal cochlea are innervated and the majority co-express markers of both inner and outer hair cells. Front Cell Neurosci 2022; 16:841864. [PMID: 36187289 PMCID: PMC9524252 DOI: 10.3389/fncel.2022.841864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 08/29/2022] [Indexed: 11/30/2022] Open
Abstract
After a damaging insult, hair cells can spontaneously regenerate from cochlear supporting cells within the first week of life. While the regenerated cells express several markers of immature hair cells and have stereocilia bundles, their capacity to differentiate into inner or outer hair cells, and ability to form new synaptic connections has not been well-described. In addition, while multiple supporting cell subtypes have been implicated as the source of the regenerated hair cells, it is unclear if certain subtypes have a greater propensity to form one hair cell type over another. To investigate this, we used two CreER mouse models to fate-map either the supporting cells located near the inner hair cells (inner phalangeal and border cells) or outer hair cells (Deiters’, inner pillar, and outer pillar cells) along with immunostaining for markers that specify the two hair cell types. We found that supporting cells fate-mapped by both CreER lines responded early to hair cell damage by expressing Atoh1, and are capable of producing regenerated hair cells that express terminal differentiation markers of both inner and outer hair cells. The majority of regenerated hair cells were innervated by neuronal fibers and contained synapses. Unexpectedly, we also found that the majority of the laterally positioned regenerated hair cells aberrantly expressed both the outer hair cell gene, oncomodulin, and the inner hair cell gene, vesicular glutamate transporter 3 (VGlut3). While this work demonstrates that regenerated cells can express markers of both inner and outer hair cells after damage, VGlut3 expression appears to lack the tight control present during embryogenesis, which leads to its inappropriate expression in regenerated cells.
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Affiliation(s)
- Mitchell L. Heuermann
- Department of Otolaryngology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Sophia Matos
- Department of Otolaryngology, Southern Illinois University School of Medicine, Springfield, IL, United States
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Deborah Hamilton
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, United States
| | - Brandon C. Cox
- Department of Otolaryngology, Southern Illinois University School of Medicine, Springfield, IL, United States
- Department of Pharmacology, Southern Illinois University School of Medicine, Springfield, IL, United States
- *Correspondence: Brandon C. Cox,
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3
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Menendez L, Trecek T, Gopalakrishnan S, Tao L, Markowitz AL, Yu HV, Wang X, Llamas J, Huang C, Lee J, Kalluri R, Ichida J, Segil N. Generation of inner ear hair cells by direct lineage conversion of primary somatic cells. eLife 2020; 9:e55249. [PMID: 32602462 PMCID: PMC7326493 DOI: 10.7554/elife.55249] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 05/27/2020] [Indexed: 02/06/2023] Open
Abstract
The mechanoreceptive sensory hair cells in the inner ear are selectively vulnerable to numerous genetic and environmental insults. In mammals, hair cells lack regenerative capacity, and their death leads to permanent hearing loss and vestibular dysfunction. Their paucity and inaccessibility has limited the search for otoprotective and regenerative strategies. Growing hair cells in vitro would provide a route to overcome this experimental bottleneck. We report a combination of four transcription factors (Six1, Atoh1, Pou4f3, and Gfi1) that can convert mouse embryonic fibroblasts, adult tail-tip fibroblasts and postnatal supporting cells into induced hair cell-like cells (iHCs). iHCs exhibit hair cell-like morphology, transcriptomic and epigenetic profiles, electrophysiological properties, mechanosensory channel expression, and vulnerability to ototoxin in a high-content phenotypic screening system. Thus, direct reprogramming provides a platform to identify causes and treatments for hair cell loss, and may help identify future gene therapy approaches for restoring hearing.
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Affiliation(s)
- Louise Menendez
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
- Zilkha Neurogenetic Institute, University of Southern CaliforniaLos AngelesUnited States
| | - Talon Trecek
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
| | - Suhasni Gopalakrishnan
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
- Zilkha Neurogenetic Institute, University of Southern CaliforniaLos AngelesUnited States
| | - Litao Tao
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
| | - Alexander L Markowitz
- Zilkha Neurogenetic Institute, University of Southern CaliforniaLos AngelesUnited States
- USC Caruso Department of Otolaryngology – Head and Neck Surgery, University of Southern CaliforniaLos AngelesUnited States
| | - Haoze V Yu
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
| | - Xizi Wang
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
| | - Juan Llamas
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
| | | | - James Lee
- DRVision TechnologiesBellevueUnited States
| | - Radha Kalluri
- Zilkha Neurogenetic Institute, University of Southern CaliforniaLos AngelesUnited States
- USC Caruso Department of Otolaryngology – Head and Neck Surgery, University of Southern CaliforniaLos AngelesUnited States
| | - Justin Ichida
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
- Zilkha Neurogenetic Institute, University of Southern CaliforniaLos AngelesUnited States
| | - Neil Segil
- Department of Stem Cell and Regenerative Medicine, University of Southern CaliforniaLos AngelesUnited States
- Eli and Edythe Broad Center, University of Southern CaliforniaLos AngelesUnited States
- USC Caruso Department of Otolaryngology – Head and Neck Surgery, University of Southern CaliforniaLos AngelesUnited States
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4
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Brown R, Groves AK. Hear, Hear for Notch: Control of Cell Fates in the Inner Ear by Notch Signaling. Biomolecules 2020; 10:biom10030370. [PMID: 32121147 PMCID: PMC7175228 DOI: 10.3390/biom10030370] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 02/24/2020] [Accepted: 02/26/2020] [Indexed: 02/08/2023] Open
Abstract
The vertebrate inner ear is responsible for detecting sound, gravity, and head motion. These mechanical forces are detected by mechanosensitive hair cells, arranged in a series of sensory patches in the vestibular and cochlear regions of the ear. Hair cells form synapses with neurons of the VIIIth cranial ganglion, which convey sound and balance information to the brain. They are surrounded by supporting cells, which nourish and protect the hair cells, and which can serve as a source of stem cells to regenerate hair cells after damage in non-mammalian vertebrates. The Notch signaling pathway plays many roles in the development of the inner ear, from the earliest formation of future inner ear ectoderm on the side of the embryonic head, to regulating the production of supporting cells, hair cells, and the neurons that innervate them. Notch signaling is re-deployed in non-mammalian vertebrates during hair cell regeneration, and attempts have been made to manipulate the Notch pathway to promote hair cell regeneration in mammals. In this review, we summarize the different modes of Notch signaling in inner ear development and regeneration, and describe how they interact with other signaling pathways to orchestrate the fine-grained cellular patterns of the ear.
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Affiliation(s)
- Rogers Brown
- Program in Developmental Biology; Baylor College of Medicine, Houston, TX 77030, USA;
| | - Andrew K. Groves
- Program in Developmental Biology; Baylor College of Medicine, Houston, TX 77030, USA;
- Department of Neuroscience; Baylor College of Medicine, Houston, TX 77030, USA
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Correspondence: ; Tel.: +1-713-798-8743
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5
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Skip is essential for Notch signaling to induce Sox2 in cerebral arteriovenous malformations. Cell Signal 2020; 68:109537. [PMID: 31927035 DOI: 10.1016/j.cellsig.2020.109537] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 01/08/2020] [Accepted: 01/09/2020] [Indexed: 11/24/2022]
Abstract
Notch signaling and Sry-box (Sox) family transcriptional factors both play critical roles in endothelial cell (EC) differentiation in vascularization. Recent studies have shown that excessive Notch signaling induces Sox2 to cause cerebral arteriovenous malformations (AVMs). Here, we examine human pulmonary AVMs and find no induction of Sox2. Results of epigenetic studies also show less alteration of Sox2-DNA binding in pulmonary AVMs than in cerebral AVMs. We identify high expression of ski-interacting protein (Skip) in brain ECs, a Notch-associated chromatin-modifying protein that is lacking in lung ECs. Knockdown of Skip abolished Notch-induction of Sox2 in brain ECs, while restoration of Skip in lung ECs enabled Notch-mediated Sox2 induction. The results suggest that Skip is a key factor for induction of Sox2 in cerebral AVMs.
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6
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Wu X, Yao J, Wang L, Zhang D, Zhang L, Reynolds EX, Yu T, Boström KI, Yao Y. Crosstalk between BMP and Notch Induces Sox2 in Cerebral Endothelial Cells. Cells 2019; 8:E549. [PMID: 31174355 PMCID: PMC6628192 DOI: 10.3390/cells8060549] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 05/31/2019] [Accepted: 06/05/2019] [Indexed: 12/26/2022] Open
Abstract
Bone morphogenetic protein (BMP) and Notch signaling are critical for endothelial cell (EC) differentiation in vascular development. Recent studies have shown that excess BMP activity induces Notch signaling in cerebral ECs resulting in arteriovenous malformation (AVMs). However, it is unclear how the crosstalk between BMP and Notch signaling affects cerebral EC differentiation at the gene regulatory level. Here, we report that BMP6 activates the activin receptor-like kinase (ALK) 3, a BMP type 1 receptor, to induce Notch1 receptor and Jagged1 and Jagged2 ligands. We show that increased expression of the Notch components alters the transcriptional regulatory complex in the SRY-Box 2 (Sox2) promoter region so as to induce its expression in cerebral ECs. Together, our results identify Sox2 as a direct target of BMP and Notch signaling and provide information on how altered BMP and Notch signaling affects the endothelial transcriptional landscape.
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Affiliation(s)
- Xiuju Wu
- Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1679, USA.
| | - Jiayi Yao
- Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1679, USA.
| | - Lumin Wang
- Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1679, USA.
- Department of cell Biology and Genetics, School of Basic Medical Sciences, Xi'an Jiaotong University Health Science Center, Xi'an, 710061, China.
| | - Daoqin Zhang
- Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1679, USA.
| | - Li Zhang
- Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1679, USA.
| | - Eric X Reynolds
- Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1679, USA.
| | - Tongtong Yu
- Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1679, USA.
- Department of Cardiology, Shengjing Hospital of China Medical University, Shenyang 110004, China.
| | - Kristina I Boström
- Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1679, USA.
- The Molecular Biology Institute at UCLA, Los Angeles, CA 90095-1570, USA.
| | - Yucheng Yao
- Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1679, USA.
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7
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Seo EJ, Kim DK, Jang IH, Choi EJ, Shin SH, Lee SI, Kwon SM, Kim KH, Suh DS, Kim JH. Hypoxia-NOTCH1-SOX2 signaling is important for maintaining cancer stem cells in ovarian cancer. Oncotarget 2018; 7:55624-55638. [PMID: 27489349 PMCID: PMC5342441 DOI: 10.18632/oncotarget.10954] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 07/18/2016] [Indexed: 12/18/2022] Open
Abstract
Hypoxia and NOTCH signaling have been reported to be associated with the self-renewal and drug resistance of cancer stem cells (CSCs). However, the molecular mechanisms by which hypoxia and NOTCH signaling stimulate the self-renewal and drug resistance of ovarian CSCs are poorly understood. In the present study, we identified SOX2 as a key transcription factor for CSC-like characteristics in the downstream of hypoxia-induced NOTCH signaling in epithelial ovarian cancer cells. Hypoxic treatment or overexpression of intracellular domain of NOTCH1 (NICD1) in ovarian cancer cells increased sphere formation, drug resistance, and expression of CSC-associated genes such as SOX2, ALDH, and ABC transporters. Hypoxic treatment increased the expression of NICD1, and hypoxic treatment or NICD1 overexpression increased SOX2 promoter activity, which was inhibited by deletion of HIF-1 or CSL binding sites. Furthermore, DAPT treatment decreased the effect of hypoxic treatment, and SOX2 knockdown decreased the effect of hypoxic treatment and NICD overexpression on sphere formation and drug resistance in established ovarian cancer cell lines and primary ovarian cancer cells. These results suggest that hypoxia-NOTCH1-SOX2 signaling axis is important for activation of ovarian CSCs, which may provide a novel opportunity for developing therapeutics to eradicate CSCs in ovarian cancer patients.
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Affiliation(s)
- Eun Jin Seo
- Department of Physiology, School of Medicine, Pusan National University, Yangsan 50612, Gyeongsangnam-do, Republic of Korea
| | - Dae Kyoung Kim
- Department of Physiology, School of Medicine, Pusan National University, Yangsan 50612, Gyeongsangnam-do, Republic of Korea
| | - Il Ho Jang
- Department of Physiology, School of Medicine, Pusan National University, Yangsan 50612, Gyeongsangnam-do, Republic of Korea
| | - Eun Jung Choi
- Department of Physiology, School of Medicine, Pusan National University, Yangsan 50612, Gyeongsangnam-do, Republic of Korea
| | - Sang Hun Shin
- Department of Physiology, School of Medicine, Pusan National University, Yangsan 50612, Gyeongsangnam-do, Republic of Korea
| | - Su In Lee
- Department of Physiology, School of Medicine, Pusan National University, Yangsan 50612, Gyeongsangnam-do, Republic of Korea
| | - Sang-Mo Kwon
- Department of Physiology, School of Medicine, Pusan National University, Yangsan 50612, Gyeongsangnam-do, Republic of Korea
| | - Ki-Hyung Kim
- Department of Obstetrics and Gynecology, School of Medicine, Pusan National University, Yangsan 50612, Gyeongsangnam-do, Republic of Korea
| | - Dong-Soo Suh
- Department of Obstetrics and Gynecology, School of Medicine, Pusan National University, Yangsan 50612, Gyeongsangnam-do, Republic of Korea
| | - Jae Ho Kim
- Department of Physiology, School of Medicine, Pusan National University, Yangsan 50612, Gyeongsangnam-do, Republic of Korea.,Research Institute of Convergence Biomedical Science and Technology, Pusan National University Yangsan Hospital, Yangsan 50612, Gyeongsangnam-do, Republic of Korea
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8
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Zeb2 recruits HDAC-NuRD to inhibit Notch and controls Schwann cell differentiation and remyelination. Nat Neurosci 2016; 19:1060-72. [PMID: 27294509 PMCID: PMC4961522 DOI: 10.1038/nn.4322] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 05/10/2016] [Indexed: 12/12/2022]
Abstract
The mechanisms that coordinate and balance a complex network of opposing regulators to control Schwann cell (SC) differentiation remain elusive. Here we demonstrate that zinc-finger E-box binding-homeobox 2 (Zeb2/Sip1) transcription factor is a critical intrinsic timer that controls the onset of Schwann cell (SC) differentiation by recruiting HDAC1/2-NuRD co-repressor complexes. Zeb2 deletion arrests SCs at an undifferentiated state during peripheral nerve development and inhibits remyelination after injury. Zeb2 antagonizes inhibitory effectors including Notch and Sox2. Importantly, genome-wide transcriptome analysis reveals a Zeb2 target gene, encoding the Notch effector Hey2, as a potent inhibitor for SC differentiation. Strikingly, a genetic Zeb2 variant, which is associated with Mowat-Wilson syndrome, disrupts the interaction with HDAC1/2-NuRD and abolishes Zeb2 activity for SC differentiation. Therefore, Zeb2 controls SC maturation by recruiting HDAC1/2-NuRD complexes and inhibiting a novel Notch-Hey2 signaling axis, pointing to the critical role of HDAC1/2-NuRD activity in peripheral neuropathies caused by ZEB2 mutations.
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9
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Stojanova ZP, Kwan T, Segil N. Epigenetic regulation of Atoh1 guides hair cell development in the mammalian cochlea. Development 2016; 142:3529-36. [PMID: 26487780 DOI: 10.1242/dev.126763] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
In the developing cochlea, sensory hair cell differentiation depends on the regulated expression of the bHLH transcription factor Atoh1. In mammals, if hair cells die they do not regenerate, leading to permanent deafness. By contrast, in non-mammalian vertebrates robust regeneration occurs through upregulation of Atoh1 in the surviving supporting cells that surround hair cells, leading to functional recovery. Investigation of crucial transcriptional events in the developing organ of Corti, including those involving Atoh1, has been hampered by limited accessibility to purified populations of the small number of cells present in the inner ear. We used µChIP and qPCR assays of FACS-purified cells to track changes in the epigenetic status of the Atoh1 locus during sensory epithelia development in the mouse. Dynamic changes in the histone modifications H3K4me3/H3K27me3, H3K9ac and H3K9me3 reveal a progression from poised, to active, to repressive marks, correlating with the onset of Atoh1 expression and its subsequent silencing during the perinatal (P1 to P6) period. Inhibition of acetylation blocked the increase in Atoh1 mRNA in nascent hair cells, as well as ongoing hair cell differentiation during embryonic organ of Corti development ex vivo. These results reveal an epigenetic mechanism of Atoh1 regulation underlying hair cell differentiation and subsequent maturation. Interestingly, the H3K4me3/H3K27me3 bivalent chromatin structure observed in progenitors persists at the Atoh1 locus in perinatal supporting cells, suggesting an explanation for the latent capacity of these cells to transdifferentiate into hair cells, and highlighting their potential as therapeutic targets in hair cell regeneration.
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Affiliation(s)
- Zlatka P Stojanova
- Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine of the University of Southern California, Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at USC, 1425 San Pablo St., Los Angeles, CA 90033, USA
| | - Tao Kwan
- Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine of the University of Southern California, Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at USC, 1425 San Pablo St., Los Angeles, CA 90033, USA
| | - Neil Segil
- Department of Stem Cell Biology and Regenerative Medicine, Keck School of Medicine of the University of Southern California, Eli and Edythe Broad Center for Regenerative Medicine and Stem Cell Research at USC, 1425 San Pablo St., Los Angeles, CA 90033, USA Caruso Department of Otolaryngology, Keck School of Medicine of the University of Southern California, Suite 5100, 1450 San Pablo Street, Los Angeles, CA 90033, USA
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10
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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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11
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Tateya T, Sakamoto S, Imayoshi I, Kageyama R. In vivo overactivation of the Notch signaling pathway in the developing cochlear epithelium. Hear Res 2015. [DOI: 10.1016/j.heares.2015.07.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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12
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Sox2-CreER mice are useful for fate mapping of mature, but not neonatal, cochlear supporting cells in hair cell regeneration studies. Sci Rep 2015; 5:11621. [PMID: 26108463 PMCID: PMC4479870 DOI: 10.1038/srep11621] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 06/01/2015] [Indexed: 01/06/2023] Open
Abstract
Studies of hair cell regeneration in the postnatal cochlea rely on fate mapping of supporting cells. Here we characterized a Sox2-CreER knock-in mouse line with two independent reporter mouse strains at neonatal and mature ages. Regardless of induction age, reporter expression was robust, with CreER activity being readily detectable in >85% of supporting cells within the organ of Corti. When induced at postnatal day (P) 28, Sox2-CreER activity was exclusive to supporting cells demonstrating its utility for fate mapping studies beyond this age. However, when induced at P1, Sox2-CreER activity was also detected in >50% of cochlear hair cells, suggesting that Sox2-CreER may not be useful to fate map a supporting cell origin of regenerated hair cells if induced at neonatal ages. Given that this model is currently in use by several investigators for fate mapping purposes, and may be adopted by others in the future, our finding that current protocols are effective for restricting CreER activity to supporting cells at mature but not neonatal ages is both significant and timely.
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13
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Maass JC, Gu R, Basch ML, Waldhaus J, Lopez EM, Xia A, Oghalai JS, Heller S, Groves AK. Changes in the regulation of the Notch signaling pathway are temporally correlated with regenerative failure in the mouse cochlea. Front Cell Neurosci 2015; 9:110. [PMID: 25873862 PMCID: PMC4379755 DOI: 10.3389/fncel.2015.00110] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 03/10/2015] [Indexed: 12/20/2022] Open
Abstract
Sensorineural hearing loss is most commonly caused by the death of hair cells in the organ of Corti, and once lost, mammalian hair cells do not regenerate. In contrast, other vertebrates such as birds can regenerate hair cells by stimulating division and differentiation of neighboring supporting cells. We currently know little of the genetic networks which become active in supporting cells when hair cells die and that are activated in experimental models of hair cell regeneration. Several studies have shown that neonatal mammalian cochlear supporting cells are able to trans-differentiate into hair cells when cultured in conditions in which the Notch signaling pathway is blocked. We now show that the ability of cochlear supporting cells to trans-differentiate declines precipitously after birth, such that supporting cells from six-day-old mouse cochlea are entirely unresponsive to a blockade of the Notch pathway. We show that this trend is seen regardless of whether the Notch pathway is blocked with gamma secretase inhibitors, or by antibodies against the Notch1 receptor, suggesting that the action of gamma secretase inhibitors on neonatal supporting cells is likely to be by inhibiting Notch receptor cleavage. The loss of responsiveness to inhibition of the Notch pathway in the first postnatal week is due in part to a down-regulation of Notch receptors and ligands, and we show that this down-regulation persists in the adult animal, even under conditions of noise damage. Our data suggest that the Notch pathway is used to establish the repeating pattern of hair cells and supporting cells in the organ of Corti, but is not required to maintain this cellular mosaic once the production of hair cells and supporting cells is completed. Our results have implications for the proposed used of Notch pathway inhibitors in hearing restoration therapies.
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Affiliation(s)
- Juan C Maass
- Department of Neuroscience, Baylor College of Medicine Houston, TX, USA ; Department of Otolaryngology, Hospital Clínico Universidad de Chile Santiago, Chile ; Interdisciplinary Program of Physiology and Biophysics, ICBM Universidad de Chile Santiago, Chile ; Department of Otolaryngology, Clínica Alemana de Santiago, Facultad de Medicina Clínica Alemana-Universidad del Desarrollo Santiago, Chile
| | - Rende Gu
- Department of Neuroscience, Baylor College of Medicine Houston, TX, USA
| | - Martin L Basch
- Department of Neuroscience, Baylor College of Medicine Houston, TX, USA
| | - Joerg Waldhaus
- Department of Otolaryngology - Head and Neck Surgery, Stanford University School of Medicine Palo Alto, CA, USA
| | | | - Anping Xia
- Department of Otolaryngology - Head and Neck Surgery, Stanford University School of Medicine Palo Alto, CA, USA
| | - John S Oghalai
- Department of Otolaryngology - Head and Neck Surgery, Stanford University School of Medicine Palo Alto, CA, USA
| | - Stefan Heller
- Department of Otolaryngology - Head and Neck Surgery, Stanford University School of Medicine Palo Alto, CA, USA
| | - Andrew K Groves
- Department of Neuroscience, Baylor College of Medicine Houston, TX, USA ; Department of Molecular and Human Genetics, Baylor College of Medicine Houston, TX, USA ; Program in Developmental Biology, Baylor College of Medicine Houston, TX, USA
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14
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Auditory hair cell-specific deletion of p27Kip1 in postnatal mice promotes cell-autonomous generation of new hair cells and normal hearing. J Neurosci 2015; 34:15751-63. [PMID: 25411503 DOI: 10.1523/jneurosci.3200-14.2014] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Hearing in mammals relies upon the transduction of sound by hair cells (HCs) in the organ of Corti within the cochlea of the inner ear. Sensorineural hearing loss is a widespread and permanent disability due largely to a lack of HC regeneration in mammals. Recent studies suggest that targeting the retinoblastoma (Rb)/E2F pathway can elicit proliferation of auditory HCs. However, previous attempts to induce HC proliferation in this manner have resulted in abnormal cochlear morphology, HC death, and hearing loss. Here we show that cochlear HCs readily proliferate and survive following neonatal, HC-specific, conditional knock-out of p27(Kip1) (p27CKO), a tumor suppressor upstream of Rb. Indeed, HC-specific p27CKO results in proliferation of these cells without the upregulation of the supporting cell or progenitor cell proteins, Prox1 or Sox2, suggesting that they remain HCs. Furthermore, p27CKO leads to a significant addition of postnatally derived HCs that express characteristic synaptic and stereociliary markers and survive to adulthood, although a portion of the newly derived inner HCs exhibit cytocauds and lack VGlut3 expression. Despite this, p27CKO mice exhibit normal hearing as measured by evoked auditory brainstem responses, which suggests that the newly generated HCs may contribute to, or at least do not greatly detract from, function. These results show that p27(Kip1) actively maintains HC quiescence in postnatal mice, and suggest that inhibition of p27(Kip1) in residual HCs represents a potential strategy for cell-autonomous auditory HC regeneration.
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15
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Savoy-Burke G, Gilels FA, Pan W, Pratt D, Que J, Gan L, White PM, Kiernan AE. Activated notch causes deafness by promoting a supporting cell phenotype in developing auditory hair cells. PLoS One 2014; 9:e108160. [PMID: 25264928 PMCID: PMC4180070 DOI: 10.1371/journal.pone.0108160] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 08/25/2014] [Indexed: 01/10/2023] Open
Abstract
Purpose To determine whether activated Notch can promote a supporting cell fate during sensory cell differentiation in the inner ear. Methods An activated form of the Notch1 receptor (NICD) was expressed in early differentiating hair cells using a Gfi1-Cre mouse allele. To determine the effects of activated Notch on developing hair cells, Gfi1-NICD animals and their littermate controls were assessed at 5 weeks for hearing by measuring auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). The differentiation of NICD-expressing hair cells was assessed at postnatal day (P) 6, 11 and 20, using histological and molecular markers for hair cells, as well as supporting cells/progenitor cells. We also examined whether the effects of Notch were mediated by SOX2, a gene expressed in supporting cells and a likely downstream target of Notch, by crossing an inducible form of SOX2 to the Gfi1-Cre. Results Activation of Notch1 in developing auditory hair cells causes profound deafness. The NICD-expressing hair cells switch off a number of hair cell markers and lose their characteristic morphology. Instead, NICD-expressing hair cells adopt a morphology resembling supporting cells and upregulate a number of supporting cell markers. These effects do not appear to be mediated by SOX2, because although expression of SOX2 caused some hearing impairment, the SOX2-expressing hair cells did not downregulate hair cell markers nor exhibit a supporting cell-like phenotype. Conclusions Our data show that Notch signaling inhibits hair cell differentiation and promotes a supporting cell-like phenotype, and that these effects are unlikely to be mediated by SOX2.
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Affiliation(s)
- Grace Savoy-Burke
- Department of Ophthalmology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Felicia A. Gilels
- Department of Neurobiology and Anatomy, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Wei Pan
- Department of Ophthalmology, University of Rochester Medical Center, Rochester, New York, United States of America
- Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Diana Pratt
- Department of Ophthalmology, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Jianwen Que
- Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Lin Gan
- Department of Ophthalmology, University of Rochester Medical Center, Rochester, New York, United States of America
- Department of Neurobiology and Anatomy, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Patricia M. White
- Department of Neurobiology and Anatomy, University of Rochester Medical Center, Rochester, New York, United States of America
| | - Amy E. Kiernan
- Department of Ophthalmology, University of Rochester Medical Center, Rochester, New York, United States of America
- Department of Biomedical Genetics, University of Rochester Medical Center, Rochester, New York, United States of America
- * E-mail:
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16
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Raft S, Groves AK. Segregating neural and mechanosensory fates in the developing ear: patterning, signaling, and transcriptional control. Cell Tissue Res 2014; 359:315-32. [PMID: 24902666 DOI: 10.1007/s00441-014-1917-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Accepted: 05/08/2014] [Indexed: 12/21/2022]
Abstract
The vertebrate inner ear is composed of multiple sensory receptor epithelia, each of which is specialized for detection of sound, gravity, or angular acceleration. Each receptor epithelium contains mechanosensitive hair cells, which are connected to the brainstem by bipolar sensory neurons. Hair cells and their associated neurons are derived from the embryonic rudiment of the inner ear epithelium, but the precise spatial and temporal patterns of their generation, as well as the signals that coordinate these events, have only recently begun to be understood. Gene expression, lineage tracing, and mutant analyses suggest that both neurons and hair cells are generated from a common domain of neural and sensory competence in the embryonic inner ear rudiment. Members of the Shh, Wnt, and FGF families, together with retinoic acid signals, regulate transcription factor genes within the inner ear rudiment to establish the axial identity of the ear and regionalize neurogenic activity. Close-range signaling, such as that of the Notch pathway, specifies the fate of sensory regions and individual cell types. We also describe positive and negative interactions between basic helix-loop-helix and SoxB family transcription factors that specify either neuronal or sensory fates in a context-dependent manner. Finally, we review recent work on inner ear development in zebrafish, which demonstrates that the relative timing of neurogenesis and sensory epithelial formation is not phylogenetically constrained.
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Affiliation(s)
- Steven Raft
- Section on Sensory Cell Regeneration and Development, National Institute on Deafness and Other Communication Disorders National Institutes of Health, 35 Convent Drive, Bethesda, MD, 20892, USA,
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17
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Ectopic expression of activated notch or SOX2 reveals similar and unique roles in the development of the sensory cell progenitors in the mammalian inner ear. J Neurosci 2013; 33:16146-57. [PMID: 24107947 DOI: 10.1523/jneurosci.3150-12.2013] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Hearing impairment or vestibular dysfunction in humans often results from a permanent loss of critical cell types in the sensory regions of the inner ear, including hair cells, supporting cells, or cochleovestibular neurons. These important cell types arise from a common sensory or neurosensory progenitor, although little is known about how these progenitors are specified. Studies have shown that Notch signaling and the transcription factor Sox2 are required for the development of these lineages. Previously we and others demonstrated that ectopic activation of Notch can direct nonsensory cells to adopt a sensory fate, indicating a role for Notch in early specification events. Here, we explore the relationship between Notch and SOX2 by ectopically activating these factors in nonsensory regions of the mouse cochlea, and demonstrate that, similar to Notch, SOX2 can specify sensory progenitors, consistent with a role downstream of Notch signaling. However, we also show that Notch has a unique role in promoting the proliferation of the sensory progenitors. We further demonstrate that Notch can only induce ectopic sensory regions within a certain time window of development, and that the ectopic hair cells display specialized stereocilia bundles similar to endogenous hair cells. These results demonstrate that Notch and SOX2 can both drive the sensory program in nonsensory cells, indicating these factors may be useful in cell replacement strategies in the inner ear.
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18
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Liu Z, Liu Z, Walters BJ, Owen T, Kopan R, Zuo J. In vivo visualization of Notch1 proteolysis reveals the heterogeneity of Notch1 signaling activity in the mouse cochlea. PLoS One 2013; 8:e64903. [PMID: 23741415 PMCID: PMC3669271 DOI: 10.1371/journal.pone.0064903] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Accepted: 04/19/2013] [Indexed: 11/18/2022] Open
Abstract
Mechanosensory hair cells (HCs) and surrounding supporting cells (SCs) in the mouse cochlea are important for hearing and are derived from the same prosensory progenitors. Notch1 signaling plays dual but contrasting and age-dependent roles in mouse cochlear development: early lateral induction and subsequent lateral inhibition. However, it has been difficult to directly visualize mouse cochlear cells experiencing various levels of Notch1 activity at single cell resolution. Here, we characterized two knock-in mouse lines, Notch1Cre (Low)/+ and Notch1Cre (High)/+, with different Cre recombinase activities, that can detect Notch1 receptor proteolysis or Notch1 activity at high and low thresholds, respectively. Using both lines together with a highly sensitive Cre reporter line, we showed that Notch1 activity is nearly undetectable during lateral induction but increases to medium and high levels during lateral inhibition. Furthermore, we found that within the neonatal organ of Corti, the vast majority of cells that experience Notch1 activity were SCs not HCs, suggesting that HCs kept undetectable Notch1 activity during the entire lineage development. Furthermore, among SC subtypes, ∼85–99% of Deiters’ and outer pillar cells but only ∼19–38% of inner pillar cells experience medium and high levels of Notch1 activity. Our results demonstrate that Notch1 activity is highly heterogeneous: 1) between lateral induction and inhibition; 2) between HC and SC lineages; 3) among different SC subtypes; 4) among different cells within each SC subtype. Such heterogeneity should elucidate how the development of the cochclear sensory epithelium is precisely controlled and how HC regeneration can be best achieved in postnatal cochleae.
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Affiliation(s)
- Zhiyong Liu
- Department of Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
- Integrated Program in Biomedical Sciences, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
| | - Zhenyi Liu
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Division of Dermatology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Bradley J. Walters
- Department of Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
| | - Thomas Owen
- Department of Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
- University of Bath, Bath, United Kingdom
| | - Raphael Kopan
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, Missouri, United States of America
- Division of Dermatology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Jian Zuo
- Department of Developmental Neurobiology, St. Jude Children’s Research Hospital, Memphis, Tennessee, United States of America
- * E-mail:
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19
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Kiernan AE. Notch signaling during cell fate determination in the inner ear. Semin Cell Dev Biol 2013; 24:470-9. [PMID: 23578865 DOI: 10.1016/j.semcdb.2013.04.002] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 03/27/2013] [Accepted: 04/02/2013] [Indexed: 01/05/2023]
Abstract
In the inner ear, Notch signaling has been proposed to specify the sensory regions, as well as regulate the differentiation of hair cells and supporting cell within those regions. In addition, Notch plays an important role in otic neurogenesis, by determining which cells differentiate as neurons, sensory cells and non-sensory cells. Here, I review the evidence for the complex and myriad roles Notch participates in during inner ear development. A particular challenge for those studying ear development and Notch is to decipher how activation of a single pathway can lead to different outcomes within the ear, which may include changes in the intrinsic properties of the cell, Notch modulation, and potential non-canonical pathways.
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Affiliation(s)
- Amy E Kiernan
- Department of Ophthalmology, University of Rochester, Rochester, NY 14642, United States.
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20
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Regulation of p27Kip1 by Sox2 maintains quiescence of inner pillar cells in the murine auditory sensory epithelium. J Neurosci 2012; 32:10530-40. [PMID: 22855803 DOI: 10.1523/jneurosci.0686-12.2012] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Sox2 plays critical roles in cell fate specification during development and in stem cell formation; however, its role in postmitotic cells is largely unknown. Sox2 is highly expressed in supporting cells (SCs) of the postnatal mammalian auditory sensory epithelium, which unlike non-mammalian vertebrates remains quiescent even after sensory hair cell damage. Here, we induced the ablation of Sox2, specifically in SCs at three different postnatal ages (neonatal, juvenile and adult) in mice. In neonatal mice, Sox2-null inner pillar cells (IPCs, a subtype of SCs) proliferated and generated daughter cells, while other SC subtypes remained quiescent. Furthermore, p27(Kip1), a cell cycle inhibitor, was absent in Sox2-null IPCs. Similarly, upon direct deletion of p27(Kip1), p27(Kip1)-null IPCs also proliferated but retained Sox2 expression. Interestingly, cell cycle control of IPCs by Sox2-mediated expression of p27(Kip1) gradually declined with age. In addition, deletion of Sox2 or p27(Kip1) did not cause a cell fate change. Finally, chromatin immunoprecipitation with Sox2 antibodies and luciferase reporter assays with the p27(Kip1) promoter support that Sox2 directly activates p27(Kip1) transcription in postmitotic IPCs. Hence, in contrast to the well known activity of Sox2 in promoting proliferation and cell fate determination, our data demonstrate that Sox2 plays a novel role as a key upstream regulator of p27(Kip1) to maintain the quiescent state of postmitotic IPCs. Our studies suggest that manipulating Sox2 or p27(Kip1) expression is an effective approach to inducing proliferation of neonatal auditory IPCs, an initial but necessary step toward restoring hearing in mammals.
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21
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Age-dependent in vivo conversion of mouse cochlear pillar and Deiters' cells to immature hair cells by Atoh1 ectopic expression. J Neurosci 2012; 32:6600-10. [PMID: 22573682 DOI: 10.1523/jneurosci.0818-12.2012] [Citation(s) in RCA: 156] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Unlike nonmammalian vertebrates, mammals cannot convert inner ear cochlear supporting cells (SCs) into sensory hair cells (HCs) after damage, thus causing permanent deafness. Here, we achieved in vivo conversion of two SC subtypes, pillar cells (PCs) and Deiters' cells (DCs), into HCs by inducing targeted expression of Atoh1 at neonatal and juvenile ages using novel mouse models. The conversion only occurred in ∼10% of PCs and DCs with ectopic Atoh1 expression and started with reactivation of endogenous Atoh1 followed by expression of 11 HC and synaptic markers, a process that took approximately 3 weeks in vivo. These new HCs resided in the outer HC region, formed stereocilia, contained mechanoelectrical transduction channels, and survived for >2 months in vivo; however, they surprisingly lacked prestin and oncomodulin expression and mature HC morphology. In contrast, adult PCs and DCs no longer responded to ectopic Atoh1 expression, even after outer HC damage. Finally, permanent Atoh1 expression in endogenous HCs did not affect prestin expression but caused cell loss of mature HCs. Together, our results demonstrate that in vivo conversion of PCs and DCs into immature HCs by Atoh1 is age dependent and resembles normal HC development. Therefore, combined expression of Atoh1 with additional factors holds therapeutic promise to convert PCs and DCs into functional HCs in vivo for regenerative purposes.
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22
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Cox BC, Liu Z, Lagarde MMM, Zuo J. Conditional gene expression in the mouse inner ear using Cre-loxP. J Assoc Res Otolaryngol 2012; 13:295-322. [PMID: 22526732 PMCID: PMC3346893 DOI: 10.1007/s10162-012-0324-5] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 03/19/2012] [Indexed: 10/28/2022] Open
Abstract
In recent years, there has been significant progress in the use of Cre-loxP technology for conditional gene expression in the inner ear. Here, we introduce the basic concepts of this powerful technology, emphasizing the differences between Cre and CreER. We describe the creation and Cre expression pattern of each Cre and CreER mouse line that has been reported to have expression in auditory and vestibular organs. We compare the Cre expression patterns between Atoh1-CreER(TM) and Atoh1-CreER(T2) and report a new line, Fgfr3-iCreER(T2), which displays inducible Cre activity in cochlear supporting cells. We also explain how results can vary when transgenic vs. knock-in Cre/CreER alleles are used to alter gene expression. We discuss practical issues that arise when using the Cre-loxP system, such as the use of proper controls, Cre efficiency, reporter expression efficiency, and Cre leakiness. Finally, we introduce other methods for conditional gene expression, including Flp recombinase and the tetracycline-inducible system, which can be combined with Cre-loxP mouse models to investigate conditional expression of more than one gene.
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Affiliation(s)
- Brandon C. Cox
- Department of Developmental Neurobiology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105 USA
| | - Zhiyong Liu
- Department of Developmental Neurobiology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105 USA
| | - Marcia M. Mellado Lagarde
- Department of Developmental Neurobiology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105 USA
| | - Jian Zuo
- Department of Developmental Neurobiology, St. Jude Children’s Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105 USA
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