title: In vivo generation of immature inner hair cells in neonatal mouse cochleae by ectopic Atoh1 expression.
abstract: Regeneration of auditory hair cells (HCs) is a promising approach to restore hearing. Recent studies have demonstrated that induced pluripotent stem cells/embryonic stem cells or supporting cells (SCs) adjacent to HCs can be converted to adopt the HC fate. However, little is known about whether new HCs are characteristic of outer or inner HCs. Here, we showed in vivo conversion of 2 subtypes of SCs, inner border cells (IBs) and inner phalangeal cells (IPhs), to the inner HC (IHC) fate. This was achieved by ectopically activating Atoh1, a transcription factor necessary for HC fate, in IBs/IPhs at birth. Atoh1+ IBs/IPhs first turned on Pou4f3, another HC transcription factor, before expressing 8 HC markers. The conversion rate gradually increased from ∼ 2.4% at 1 week of age to ∼ 17.8% in adult. Interestingly, new HCs exhibited IHC characteristics such as straight line-shaped stereociliary bundles, expression of Fgf8 and otoferlin, and presence of larger outward currents than those of outer HCs. However, new HCs lacked the terminal differentiation IHC marker vGlut3, exhibited reduced density of presynaptic Cbtp2 puncta that had little postsynaptic GluR2 specialization, and displayed immature IHC outward currents. Our results demonstrate that the conversion rate of IBs/IPhs in vivo by Atoh1 ectopic expression into the IHC fate was higher and faster and the conversion was more complete than that of the 2 other SC subtypes underneath the outer HCs; however, these new IHCs are arrested before terminal differentiation. Thus, IBs/IPhs are good candidates to regenerate IHCs in vivo.
authors.affiliation: 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.
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, United States of America.
authors.forename: Jie
authors.initials: J
authors.lastname: Fang
authors.affiliation: Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, United States of America.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Dearman
authors.affiliation: Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, United States of America.
authors.forename: Lingli
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee, United States of America.
authors.forename: Jian
authors.initials: J
authors.lastname: Zuo
mesh_terms: D026922:Amino Acid Transport Systems, Acidic / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn; D051792:Basic Helix-Loop-Helix Proteins / Q000502:physiology*; D002454:Cell Differentiation; D003051:Cochlea / Q000166:cytology* / Q000378:metabolism; D004594:Electrophysiology; D051524:Fibroblast Growth Factor 8 / Q000235:genetics / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental; D006199:Hair Cells, Auditory, Inner / Q000166:cytology* / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D017403:In Situ Hybridization; D017404:In Situ Hybridization, Fluorescence; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D012038:Regeneration / Q000502:physiology*; D050821:Transcription Factor Brn-3C / Q000235:genetics / Q000378:metabolism
chemical_list: D026922:Amino Acid Transport Systems, Acidic; D051792:Basic Helix-Loop-Helix Proteins; D051524:Fibroblast Growth Factor 8; D018398:Homeodomain Proteins; D008565:Membrane Proteins; D050821:Transcription Factor Brn-3C; C500943:Atoh1 protein, mouse; C496457:Fgf8 protein, mouse; C121290:Pou4f3 protein, mouse; C516233:otoferlin protein, mouse; C504941:Slc17a8 protein, mouse