Inhibition of Notch activity promotes nonmitotic regeneration of hair cells in the adult mouse utricles.
The capacity of adult mammals to regenerate sensory hair cells is not well defined. To explore early steps in this process, we examined reactivation of a transiently expressed developmental gene, Atoh1, in adult mouse utricles after neomycin-induced hair cell death in culture. Using an adenoviral reporter for Atoh1 enhancer, we found that Atoh1 transcription is activated in some hair cell progenitors (supporting cells) 3 d after neomycin treatment. By 18 d after neomycin, the number of cells with Atoh1 transcriptional activity increased significantly, but few cells acquired hair cell features (i.e., accumulated ATOH1 or myosin VIIa protein or developed stereocilia). Treatment with DAPT, an inhibitor of γ-secretase, reduced notch pathway activity, enhanced Atoh1 transcriptional activity, and dramatically increased the number of Atoh1-expressing cells with hair cell features, but only in the striolar/juxtastriolar region. Similar effects were seen with TAPI-1, an inhibitor of another enzyme required for notch activity (TACE). Division of supporting cells was rare in any control or DAPT-treated utricles. This study shows that mature mammals have a natural capacity to initiate vestibular hair cell regeneration and suggests that regional notch activity is a significant inhibitor of direct transdifferentiation of supporting cells into hair cells following damage.
Department of Otolaryngology-Head and Neck Surgery, Sunnybrook Health Sciences Center, University of Toronto, Toronto, Ontario M4N 3M5, Canada.
Vincent
V
Lin
Justin S
JS
Golub
Tot Bui
TB
Nguyen
Clifford R
CR
Hume
Elizabeth C
EC
Oesterle
Jennifer S
JS
Stone
D051722:ADAM Proteins / Q000494:pharmacology; D000072198:ADAM17 Protein; D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics; D064026:Calbindins; D002147:Calmodulin / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D004151:Dipeptides / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics; D006198:Hair Cells, Auditory / Q000187:drug effects; D006877:Hydroxamic Acids / Q000494:pharmacology; D007211:Indoles; D051379:Mice; D009355:Neomycin / Q000633:toxicity; D009416:Nerve Regeneration / Q000187:drug effects / Q000502:physiology*; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009924:Organ Culture Techniques; D011500:Protein Synthesis Inhibitors / Q000633:toxicity; D051880:Receptors, Notch / Q000378:metabolism*; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D012444:Saccule and Utricle / Q000166:cytology* / Q000293:injuries; D013997:Time Factors; D014161:Transduction, Genetic / Q000379:methods; D024723:Ventricular Myosins / Q000378:metabolism
D051722:ADAM Proteins; D000072198:ADAM17 Protein; D053829:Amyloid Precursor Protein Secretases; D051792:Basic Helix-Loop-Helix Proteins; D064026:Calbindins; D002147:Calmodulin; D004151:Dipeptides; D049452:Green Fluorescent Proteins; D006877:Hydroxamic Acids; D007211:Indoles; D009355:Neomycin; D011500:Protein Synthesis Inhibitors; D051880:Receptors, Notch; D064030:S100 Calcium Binding Protein G; D024723:Ventricular Myosins; C500943:Atoh1 protein, mouse; C092152:N-((2-(hydroxyaminocarbonyl)methyl)-4-methylpentanoyl)-3-(2'-naphthyl)alanylalanine, 2-aminoethylamide; C007293:DAPI; C000606463:Adam17 protein, mouse