Trichohyalin-like proteins have evolutionarily conserved roles in the morphogenesis of skin appendages.
S100 fused-type proteins (SFTPs) such as filaggrin, trichohyalin, and cornulin are differentially expressed in cornifying keratinocytes of the epidermis and various skin appendages. To determine evolutionarily conserved, and thus presumably important, features of SFTPs, we characterized nonmammalian SFTPs and compared their amino acid sequences and expression patterns with those of mammalian SFTPs. We identified an ortholog of cornulin and a previously unknown SFTP, termed scaffoldin, in reptiles and birds, whereas filaggrin was confined to mammals. In contrast to mammalian SFTPs, both cornulin and scaffoldin of the chicken are expressed in the embryonic periderm. However, scaffoldin resembles mammalian trichohyalin with regard to its expression in the filiform papillae of the tongue and in the epithelium underneath the forming tips of the claws. Furthermore, scaffoldin is expressed in the epithelial sheath around growing feathers, reminiscent of trichohyalin expression in the inner root sheath of hair. The results of this study show that SFTP-positive epithelia function as scaffolds for the growth of diverse skin appendages such as claws, nails, hair, and feathers, indicating a common evolutionary origin.
Department of Dermatology, Medical University of Vienna, Vienna, Austria.
Veronika
V
Mlitz
Department of Dermatology, Medical University of Vienna, Vienna, Austria.
Bettina
B
Strasser
Department of Dermatology, Medical University of Vienna, Vienna, Austria.
Karin
K
Jaeger
Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, Vienna, Austria.
Marcela
M
Hermann
Department of Dermatology, Medical University of Vienna, Vienna, Austria.
Minoo
M
Ghannadan
Department of Dermatology, Medical University of Vienna, Vienna, Austria.
Maria
M
Buchberger
Dipartimento di Scienze Biologiche, Geologiche ed Ambientali (BiGeA), Università di Bologna, Bologna, Italy.
Lorenzo
L
Alibardi
Department of Dermatology, Medical University of Vienna, Vienna, Austria.
Erwin
E
Tschachler
Department of Dermatology, Medical University of Vienna, Vienna, Austria. Electronic address: leopold.eckhart@meduniwien.ac.at.
Leopold
L
Eckhart
D000818:Animals; D030161:Avian Proteins / Q000378:metabolism*; D002642:Chick Embryo; D004848:Epithelium / Q000196:embryology / Q000378:metabolism*; D005241:Feathers / Q000378:metabolism; D000091344:Filaggrin Proteins; D005786:Gene Expression Regulation; D018507:Gene Expression Regulation, Developmental; D016678:Genome; D006197:Hair / Q000378:metabolism; D006724:Hoof and Claw / Q000378:metabolism; D006801:Humans; D007381:Intermediate Filament Proteins / Q000737:chemistry; D008116:Lizards; D008565:Membrane Proteins / Q000737:chemistry*; D009262:Nails / Q000378:metabolism; D009363:Neoplasm Proteins / Q000737:chemistry*; D010802:Phylogeny; D012867:Skin / Q000196:embryology
D030161:Avian Proteins; C418764:CRNN protein, human; C000717249:FLG protein, human; D000091344:Filaggrin Proteins; D007381:Intermediate Filament Proteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; C016159:trichohyalin