title: Skin fragility and impaired desmosomal adhesion in mice lacking all keratins.
abstract: Keratins perform major structural and regulatory functions in epithelia. Owing to redundancy, their respective contribution to epidermal integrity, adhesion, and cell junction formation has not been addressed in full. Unexpectedly, the constitutive deletion of type II keratins in mice was embryonic lethal ∼ E9.5 without extensive tissue damage. This prompted us to analyze keratin functions in skin where keratins are best characterized. Here, we compare the mosaic and complete deletion of all type II keratins in mouse skin, with distinct consequences on epidermal integrity, adhesion, and organismal survival. Mosaic knockout (KO) mice survived ∼ 12 days while global KO mice died perinatally because of extensive epidermal damage. Coinciding with absence of keratins, epidermal fragility, inflammation, increased epidermal thickness, and increased proliferation were noted in both strains of mice, accompanied by significantly smaller desmosomes. Decreased desmosome size was due to accumulation of desmosomal proteins in the cytoplasm, causing intercellular adhesion defects resulting in intercellular splits. Mixing different ratios of wild-type and KO keratinocytes revealed that ∼ 60% of keratin-expressing cells were sufficient to maintain epithelial sheets under stress. Our data reveal a major contribution of keratins to the maintenance of desmosomal adhesion and epidermal integrity with relevance for the treatment of epidermolysis bullosa simplex and other keratinopathies.
authors.affiliation: Translational Center for Regenerative Medicine and Institute of Biology, University of Leipzig, Leipzig, Germany.
authors.forename: Janina
authors.initials: J
authors.lastname: Bär
authors.affiliation: Translational Center for Regenerative Medicine and Institute of Biology, University of Leipzig, Leipzig, Germany.
authors.forename: Vinod
authors.initials: V
authors.lastname: Kumar
authors.affiliation: German Center for Neurodegenerative Diseases, Bonn, Germany.
authors.forename: Wera
authors.initials: W
authors.lastname: Roth
authors.affiliation: Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Aachen, Germany.
authors.forename: Nicole
authors.initials: N
authors.lastname: Schwarz
authors.affiliation: Translational Center for Regenerative Medicine and Institute of Biology, University of Leipzig, Leipzig, Germany.
authors.forename: Miriam
authors.initials: M
authors.lastname: Richter
authors.affiliation: Institute of Molecular and Cellular Anatomy, RWTH Aachen University, Aachen, Germany.
authors.forename: Rudolf E
authors.initials: RE
authors.lastname: Leube
authors.affiliation: Translational Center for Regenerative Medicine and Institute of Biology, University of Leipzig, Leipzig, Germany. Electronic address: thomas.magin@trm.uni-leipzig.de.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Magin
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D003896:Desmosomes / Q000378:metabolism*; D004195:Disease Models, Animal; D004817:Epidermis / Q000378:metabolism; D016110:Epidermolysis Bullosa Simplex / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D015603:Keratinocytes / Q000378:metabolism; D053531:Keratins, Type II / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009030:Mosaicism; D010641:Phenotype; D012867:Skin / Q000196:embryology / Q000473:pathology*
chemical_list: D053531:Keratins, Type II