title: Ectopic Atoh1 expression drives Merkel cell production in embryonic, postnatal and adult mouse epidermis.
abstract: Merkel cells are mechanosensitive skin cells whose production requires the basic helix-loop-helix transcription factor Atoh1. We induced ectopic Atoh1 expression in the skin of transgenic mice to determine whether Atoh1 was sufficient to create additional Merkel cells. In embryos, ectopic Atoh1 expression drove ectopic expression of the Merkel cell marker keratin 8 (K8) throughout the epidermis. Epidermal Atoh1 induction in adolescent mice similarly drove widespread K8 expression in glabrous skin of the paws, but in the whisker pads and body skin ectopic K8+ cells were confined to hair follicles and absent from interfollicular regions. Ectopic K8+ cells acquired several characteristics of mature Merkel cells in a time frame similar to that seen during postnatal development of normal Merkel cells. Although ectopic K8+ cell numbers decreased over time, small numbers of these cells remained in deep regions of body skin hair follicles at 3 months post-induction. In adult mice, greater numbers of ectopic K8+ cells were created by Atoh1 induction during anagen versus telogen and following disruption of Notch signaling by conditional deletion of Rbpj in the epidermis. Our data demonstrate that Atoh1 expression is sufficient to produce new Merkel cells in the epidermis, that epidermal cell competency to respond to Atoh1 varies by skin location, developmental age and hair cycle stage, and that the Notch pathway plays a key role in limiting epidermal cell competency to respond to Atoh1 expression.
authors.affiliation: Department of Dermatology, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Ostrowski
authors.affiliation: Center for Neurosciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Wright
authors.affiliation: Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA.
authors.forename: Alexa M
authors.initials: AM
authors.lastname: Bolock
authors.affiliation: Richard King Mellon Institute for Pediatric Research, Department of Pediatrics, University of Pittsburgh, Pittsburgh, PA 15224, USA.
authors.forename: Xuehui
authors.initials: X
authors.lastname: Geng
authors.affiliation: Richard King Mellon Institute for Pediatric Research, Department of Pediatrics, University of Pittsburgh, Pittsburgh, PA 15224, USA stephen.maricich@chp.edu.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Maricich
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000502:physiology; D002460:Cell Line; D019070:Cell Lineage; D004318:Doxycycline / Q000737:chemistry; D000078404:Epidermal Cells; D004817:Epidermis / Q000196:embryology* / Q000378:metabolism*; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D006197:Hair / Q000196:embryology; D018859:Hair Follicle / Q000378:metabolism; D015603:Keratinocytes / Q000166:cytology; D018862:Merkel Cells / Q000166:cytology*; D051379:Mice; D008822:Mice, Transgenic; D015398:Signal Transduction; D012867:Skin / Q000196:embryology; D013629:Tamoxifen / Q000737:chemistry; D019076:Transgenes; D014738:Vibrissae / Q000378:metabolism
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D004318:Doxycycline; D013629:Tamoxifen; C500943:Atoh1 protein, mouse
keywords: Mouse; Sensation; Stem cell; Touch