title: p19(Ink4d) and p21(Cip1) collaborate to maintain the postmitotic state of auditory hair cells, their codeletion leading to DNA damage and p53-mediated apoptosis.
abstract: Sensory hair cells of the auditory organ are generated during embryogenesis and remain postmitotic throughout life. Previous work has shown that inactivation of the cyclin-dependent kinase inhibitor (CKI) p19(Ink4d) leads to progressive hearing loss attributable to inappropriate DNA replication and subsequent apoptosis of hair cells. Here we show the synergistic action of another CKI, p21(Cip1), on cell cycle reactivation. The codeletion of p19(Ink4d) and p21(Cip1) triggered profuse S-phase entry of auditory hair cells during a restricted period in early postnatal life, leading to the transient appearance of supernumerary hair cells. In addition, we show that aberrant cell cycle reentry leads to activation of a DNA damage response pathway in these cells, followed by p53-mediated apoptosis. The majority of hair cells were absent in adult cochleas. These data, together with the demonstration of changing expression patterns of multiple CKIs in auditory hair cells during the stages of early postnatal maturation, show that the maintenance of the postmitotic state is an active, tissue-specific process, cooperatively regulated by several CKIs, and is critical for the lifelong survival of these sensory cells.
authors.affiliation: Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland.
authors.forename: Heidi
authors.initials: H
authors.lastname: Laine
authors.forename: Angelika
authors.initials: A
authors.lastname: Doetzlhofer
authors.forename: Johanna
authors.initials: J
authors.lastname: Mantela
authors.forename: Jukka
authors.initials: J
authors.lastname: Ylikoski
authors.forename: Marikki
authors.initials: M
authors.lastname: Laiho
authors.forename: Martine F
authors.initials: MF
authors.lastname: Roussel
authors.forename: Neil
authors.initials: N
authors.lastname: Segil
authors.forename: Ulla
authors.initials: U
authors.lastname: Pirvola
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000833:Animals, Suckling; D017209:Apoptosis / Q000502:physiology*; D002452:Cell Count; D003051:Cochlea / Q000254:growth & development / Q000473:pathology*; D003433:Crosses, Genetic; D050756:Cyclin-Dependent Kinase Inhibitor Proteins / Q000096:biosynthesis / Q000235:genetics; D050764:Cyclin-Dependent Kinase Inhibitor p19 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D004249:DNA Damage; D004260:DNA Repair / Q000235:genetics; D018450:Disease Progression; D018816:Genes, cdc; D006198:Hair Cells, Auditory / Q000378:metabolism / Q000473:pathology*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008938:Mitosis; D009928:Organ Specificity; D009925:Organ of Corti / Q000473:pathology; D016196:S Phase; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000502:physiology
chemical_list: C493957:Cdkn1a protein, mouse; C493975:Cdkn2d protein, mouse; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D050764:Cyclin-Dependent Kinase Inhibitor p19; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016159:Tumor Suppressor Protein p53