title: Hedgehog signaling, keratin 6 induction, and sebaceous gland morphogenesis: implications for pachyonychia congenita and related conditions.
abstract: Keratins 6a and b (K6a, K6b) belong to a subset of keratin genes with constitutive expression in epithelial appendages, and inducible expression in additional epithelia, when subjected to environmental challenges or disease. Mutations in K6a or K6b cause a broad spectrum of epithelial lesions that differentially affect nail, hair, and glands in humans. Some lesions reflect a loss of the structural support function shared by K6, other keratins, and intermediate filament proteins. The formation of sebaceous gland-derived epithelial cysts does not fit this paradigm, raising the question of the unique functions of different K6 isoforms in this setting. Here, we exploit a mouse model of constitutively expressed Gli2, a Hedgehog (Hh) signal effector, to show that K6a expression correlates with duct fate in sebaceous glands (SGs). Whether in the setting of Gli2 transgenic mice skin, which develops a prominent SG duct and additional pairs of highly branched SGs, or in wild-type mouse skin, K6a expression consistently coincides with Hh signaling in ductal tissue. Gli2 expression modestly transactivates a K6a promoter-driven reporter in heterologous systems. Our findings thus identify K6 as a marker of duct fate in SGs, partly in response to Hh signaling, with implications for the pathological expansion of SGs that arises in the context of certain keratin-based diseases and related disorders.
authors.affiliation: Department of Biological Chemistry, Johns Hopkins University School of Medicine, 725 N. Wolfe St., Baltimore, MD 21205, USA.
authors.forename: Li-Hong
authors.initials: LH
authors.lastname: Gu
authors.forename: Pierre A
authors.initials: PA
authors.lastname: Coulombe
mesh_terms: D000818:Animals; D005455:Fluorescent Antibody Technique; D015870:Gene Expression; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D053553:Keratin-6 / Q000378:metabolism*; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D053549:Pachyonychia Congenita / Q000503:physiopathology*; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012627:Sebaceous Glands / Q000254:growth & development / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014162:Transfection; D000075746:Zinc Finger Protein Gli2
chemical_list: C000618551:Gli2 protein, mouse; D053823:Hedgehog Proteins; D053553:Keratin-6; C507567:Krt6a protein, mouse; D051741:Kruppel-Like Transcription Factors; D000075746:Zinc Finger Protein Gli2