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 (vimentinpositive); 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
Source: Disorders of Intermediate Filaments and Their Associated Proteins, The Online Metabolic and Molecular Bases of Inherited Disease
program of keratin gene expression. Outermost layer of cells is skin surface. As epidermal cells leave the basal layer and commit to terminally
Valle
D, expressing
Beaudet AL,K5
Vogelstein
B, K1
Kinzler
SE, Ballabio
A, Gibson
Mitchell
G. The Palmoplantar
Online Metabolic
Molecular
differentiate, Citation:
they switch
from
and K14 to
and KW,
K10. Antonarakis
Later in differentiation,
they
expressK,K2e
additionally.
skinand
is distinct
in
Bases
of
Inherited
Disease;
2014
Available
at:
http://mhmedical.com/
Accessed:
July
31,
2017
that it expresses K9 suprabasally in addition to the other differentiation-specific keratins. During wounding and in hyperproliferative disorders, K6 and K16
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Education. All rights reserved
are expressed
transiently
in theMcGraw-Hill
suprabasal layers.