o:1421 Transglutaminase Activity is conserved in Stratified Epithelia and Skin Appendages of Mammals and Birds en The cross-linking of structural proteins is critical for establishing the mechanical stability of the epithelial compartments of the skin and skin appendages. The introduction of isopeptide bonds between glutamine and lysine residues depends on catalysis by transglutaminases and represents the main protein cross-linking mechanism besides the formation of disulfide bonds. Here, we used a fluorescent labeling protocol to localize the activity of transglutaminases on thin sections of the integument and its appendages in mammals and birds. In human tissues, transglutaminase activity was detected in the granular layer of the epidermis, suprabasal layers of the gingival epithelium, the duct of sweat glands, hair follicles and the nail matrix. In the skin appendages of chickens, transglutaminase activity was present in the claw matrix, the feather follicle sheath, the feather sheath and in differentiating keratinocytes of feather barb ridges. During chicken embryogenesis, active transglutaminase was found in the cornifying epidermis, the periderm and the subperiderm. Transglutaminase activity was also detected in the filiform papillae on the tongue of mice and in conical papillae on the tongue of chickens. In summary, our study reveals that transglutaminase activities are widely distributed in integumentary structures and suggests that transglutamination contributes to the cornification of hard skin appendages such as nails and feathers. Evolutionary Origin; Cell-Death; In-Vitro; Proteins; Hair; Differentiation; Keratinocytes; Localization; Expression; Mutations 1552099 10.3390/ijms24032193 2023-03-14T13:41:50.833Z 44 yes 46 Attila Placido Sachslehner Medical University of Vienna 0000-0003-1447-9254 Marta Surbek Medical University of Vienna person Bahar Golabi Medical University of Vienna person Miriam Geiselhofer Medical University of Vienna person Karin Jäger Medical University of Vienna person Claudia Hess University of Veterinary Medicine, Vienna person 0000-0002-3535-5157 Ulrike Kuchler Medical University of Vienna person Reinhard Gruber Medical University of Vienna person Leopold Eckhart Medical University of Vienna person 0000-0002-5645-2036 application/pdf 7012180 https://phaidra.vetmeduni.ac.at/o:1421 no yes 16 70 1552253 International Journal of Molecular Sciences 12 24 3 MDPI 2023