1. Keratin expression in epidermis and its appendages
Keratin expression in epidermis and its appendages. (Left) The hair follicle and its program of keratin gene expression. Permanent segments are the sebaceous glands (K5/K14 positive), upper outer root sheath (including the bulge, K5/K14 positive), and mesenchymally derived dermal papilla (vimentin-positive); all are established during embryonic follicle morphogenesis. The lower portion cycles throughout postnatal life by a process involving transient stimulation of bulge stem cells by dermal papilla. Matrix cells express little keratin; they are transit amplifying cells that differentiate upward in concentric rings of cells, giving rise to precortex cortex and medulla (hair shaft), Ha and Hb keratin positive, and surrounded by inner root sheath cells (K1/K10 expressing) and outer root sheath cells (K5/K14 positive). (Right) Schematic outlining the basic features of terminal differentiation in epidermis and the program of keratin gene expression. Outermost layer of cells is skin surface. As epidermal cells leave the basal layer and commit to terminally differentiate, they switch from expressing K5 and K14 to K1 and K10. Later in differentiation, they express K2e additionally. Palmoplantar skin is distinct in that it expresses K9 suprabasally in addition to the other differentiation-specific keratins. During wounding and in hyperproliferative disorders, K6 and K16 are expressed transiently in the suprabasal layers.
Source: Disorders of Intermediate Filaments and Their Associated Proteins, The Online Metabolic and Molecular Bases of Inherited Disease
Citation: Valle D, Beaudet AL, Vogelstein B, Kinzler KW, Antonarakis SE, Ballabio A, Gibson K, Mitchell G. The Online Metabolic and Molecular Bases of Inherited Disease; 2014 Available at: Accessed: October 03, 2017
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