Gu LH, Coulombe PA. Hedgehog signaling, keratin 6 induction, and sebaceous gland morphogenesis: implications for pachyonychia congenita and related conditions.
THE AMERICAN JOURNAL OF PATHOLOGY 2008;
173:752-61. [PMID:
18688029 DOI:
10.2353/ajpath.2008.071089]
[Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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.
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