Research Division of Biology and Pathobiology of the Skin, Department of Dermatology, Medical University of Vienna, Vienna, Austria.
Department of Medical Biochemistry, Medical University of Vienna, Vienna, Austria.
Protoplasma. 2019 Sep;256(5):1257-1265. doi: 10.1007/s00709-019-01381-3. Epub 2019 Apr 29.
Feathers are the most complex skin appendages of vertebrates. Mature feathers consist of interconnected dead keratinocytes that are filled with heavily cross-linked proteins. Although the molecular architecture determines essential functions of feathers, only few feather proteins have been characterized with regard to their amino acid sequences and evolution. Here, we identify Epidermal Differentiation protein containing DPCC Motifs (EDDM) as a cysteine-rich protein that has co-evolved with other feather proteins. The EDDM gene is located within the avian epidermal differentiation complex (EDC), a cluster of genes that has originated and diversified in amniotes. EDDM shares the exon-intron organization with EDC genes of other amniotes, including humans, and a gene encoding an EDDM-like protein is present in crocodilians, suggesting that avian EDDM arose by sequence modification of an epidermal differentiation gene present in a common ancestor of archosaurs. The EDDM protein contains multiple sequence repeats and a higher number of cysteine residues than any other protein encoded in the EDC. Immunohistochemical analysis of chicken skin and skin appendages showed expression of EDDM in barb and barbules of feathers as well as in the subperiderm on embryonic scutate scales. These results suggest that the diversification and differential expression of EDDM, besides other EDC genes, was instrumental in facilitating the evolution of the most complex molecular architecture of feathers.
羽毛是脊椎动物最复杂的皮肤附属物。成熟的羽毛由相互连接的死亡角蛋白细胞组成，这些细胞充满了高度交联的蛋白质。尽管分子结构决定了羽毛的基本功能，但只有少数羽毛蛋白的氨基酸序列和进化得到了表征。在这里，我们将含有 DPCC 基序的表皮分化蛋白（EDDM）鉴定为一种富含半胱氨酸的蛋白质，它与其他羽毛蛋白共同进化。EDDM 基因位于鸟类表皮分化复合物（EDC）内，该基因簇起源于羊膜动物并在其中多样化。EDDM 与其他羊膜动物的 EDC 基因具有相同的外显子-内含子组织，包括人类，并且在鳄鱼中存在编码 EDDM 样蛋白的基因，这表明鸟类 EDDM 是由恐龙共同祖先中存在的表皮分化基因的序列修饰产生的。EDDM 蛋白含有多个序列重复和比 EDC 中编码的任何其他蛋白更多的半胱氨酸残基。鸡皮肤和皮肤附属物的免疫组织化学分析显示，EDDM 在羽毛的羽支和羽小支以及鳞片的表皮下表达。这些结果表明，EDDM 以及其他 EDC 基因的多样化和差异表达，有助于促进羽毛最复杂的分子结构的进化。
