Immunolocalization of Scaffoldin, a Trichohyalin‐Like Protein, in the Epidermis of the Chicken Embryo

Abstract

Recent comparative genomic studies have identified a chicken gene that codes for a trichohyalin-like protein rich in arginine and glutamic acid termed scaffoldin. Immunocytochemistry and immunoelectron microscopy show that this protein is predominantly localized in periderm granules, subcellular structures present in the periderm of the embryonic epidermis of chick scales, beak, claw, and in the sheath of developing and regenerating feathers. This suggests that scaffoldin contributes to the formation of periderm granules and to the soft cornification of the embryonic epidermis before the definitive epidermis is formed. Scaffoldin is absent from the definitive and adult epidermis generated underneath the periderm in scales and in inter-follicular regions. Scaffoldin mixes with corneous beta-proteins (beta-keratins) synthesized in keratinocytes of the transitional layers formed beneath the periderm in the subunguis of the developing claws. Immunoreactivity for scaffoldin is absent in keratinocytes that accumulate corneous beta-proteins such as those of scales, claws, and barbule-barb cells of feathers. Corneous beta-proteins represent the prevalent type of proteins present in adult epidermis of claws, scales, and feathers. These observations indicate that scaffoldin is a protein of transitional epidermal cells of the avian integument and might represent an important component of periderm granules. Anat Rec, 298:479-487, 2015. V C 2014 Wiley Periodicals, Inc.

The Trichohyalin-Like Protein Scaffoldin Is Expressed in the Multilayered Periderm during Development of Avian Beak and Egg Tooth

“…In the chicken, SCFN was detected in the multilayered periderm around the egg tooth ( Figure 5D,E). It formed granules that corresponded in size and distribution to eosinophilic periderm granules [38] (Figure 5A-C), supporting the conclusion of a previous study that identified SCFN as a major component of granules in the periderm covering the embryonic epidermis [39]. A similar distribution of eosinophilic periderm granules (Figure 6A,B) and accumulation of SCFN were observed on the upper embryonic beak of quails ( Figure 6E,F).…”

Immunolocalization of a Histidine-Rich Epidermal Differentiation Protein in the Chicken Supports the Hypothesis of an Evolutionary Developmental Link between the Embryonic Subperiderm and Feather Barbs and Barbules

“…The expression pattern of EDMTFH is similar to that of EDCRP and clearly different from that of scaffoldin, another EDC-encoded protein that we have previously detected in the embryonic periderm and feather sheath [14, 41]. EDCRP has an extraordinarily high content of cysteine residues and, therefore, it likely forms multiple disulfide bonds which might contribute to the cross-linking of cytoskeletal proteins and the hardening of feathers.…”

Embryonic development of parakeratinized epithelium of the tongue in the domestic duck (Anas platyrhynchos f. domestica): LM, SEM, and TEM observations

“…The present study confirms that observation. Previously, similar mesh-like structures were recorded in the periderm during the development of the interfollicular skin, scales, claws, and feathers in reptiles and birds and were named periderm granules (Alibardi 1998 , 2002 , 2009a , b , 2014 ; Alibardi et al 2015 ). The diameter of the coarse filaments forming periderm granules varies between taxa.…”

“…The diameter of the coarse filaments forming periderm granules varies between taxa. Periderm granules in the periderm of the interfollicular skin in birds are composed of coarse filaments of 20–40 nm in diameter, while in the periderm of the scales and beak the diameter of coarse filaments is 30–50 nm (Alibardi 2002 ; Alibardi et al 2015 ). In comparison, the diameter of periderm granules in reptiles ranges between 20 and 25 nm (Alibardi 1998 ).…”