Increased expression of keratin 16 causes anomalies in cytoarchitecture and keratinization in transgenic mouse skin.

Injury to epidermis and other stratified epithelia triggers profound but transient changes in the pattern of keratin expression. In postmitotic cells located at the wound edge, a strong induction of K6, K16, and K17 synthesis occurs at the expense of the keratins produced under the normal situation. The functional significance of these alterations in keratin expression is not known. Here, we report that overexpression of a wild-type human K16 gene in a tissue-specific fashion in transgenic mice causes aberrant keratinization of the hair follicle outer root sheath and proximal epidermis, and it leads to hyperproliferation and increased thickness of the living layers (acanthosis), as well as cornified layers (hyperkeratosis). The pathogenesis of lesions in transgenic mouse skin begins with a reorganization of keratin filaments in postmitotic keratinocytes, and it progresses in a transgene level-dependent fashion to include disruption of keratinocyte cytoarchitecture and structural alterations in desmosomes at the cell surface. No evidence of cell lysis could be found at the ultrastructural level. These results demonstrate that the disruption of the normal keratin profile caused by increased K16 expression interferes with the program of terminal differentiation in outer root sheath and epidermis. They further suggest that when present at sufficiently high intracellular levels, K16, along with K6 and K17, appear capable of inducing a reorganization of keratin filaments in the cytoplasm of skin epithelial cells.

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Overexpression of protein kinase C-alpha in the epidermis of transgenic mice results in striking alterations in phorbol ester-induced inflammation and COX-2, MIP-2 and TNF-alpha expression but not tumor promotion

Journal of Cell Science ◽

10.1242/jcs.112.20.3497 ◽

1999 ◽

Vol 112 (20) ◽

pp. 3497-3506

Author(s):

H.Q. Wang ◽

R.C. Smart

Keyword(s):

Protein Kinase ◽

Transgenic Mice ◽

Normal Mouse ◽

Mouse Skin ◽

Tumor Promotion ◽

Epidermal Differentiation ◽

Wild Type ◽

Outer Root Sheath ◽

Proinflammatory Mediators ◽

Cox 2

Protein kinase Calpha (PKCalpha) is one of six PKC isoforms expressed in keratinocytes of mouse epidermis. To gain an understanding of the role of epidermal PKCalpha, we have localized its expression to specific cells of normal mouse skin and examined the effect of keratin 5 (K5) promoter directed expression of PKCalpha in transgenic mice. In normal mouse skin, PKCalpha was extensively expressed in the outer root sheath (ORS) keratinocytes of the anagen hair follicle and weakly expressed in keratinocytes of interfollicular epidermis. K5-targeted expression of PKCalpha to epidermal basal keratinocytes and follicular ORS keratinocytes resulted in a tenfold increase in epidermal PKCalpha. K5-PKCalpha mice exhibited no abnormalities in keratinocyte growth and differentiation in the epidermis. However, a single topical treatment with the PKC activator, 12-O-tetradecanoylphorbol-13-acetate (TPA) resulted in a striking inflammatory response characterized by edema and extensive epidermal infiltration of neutrophils that formed intraepidermal microabscesses in the epidermis. Compared to TPA-treated wild-type mice, the epidermis of TPA-treated K5-PKCalpha mice displayed increased expression of cyclooxygenase-2 (COX-2), the neutrophil chemotactic factor macrophage inflammatory protein-2 (MIP-2) mRNA and the proinflammatory cytokine TNFalpha mRNA but not IL-6 or IL-1alpha mRNA. To determine if K5-PKCalpha mice display an altered response to TPA-promotion, 7, 12-dimethylbenz[a]anthracene-initiated K5-PKCalpha mice and wild-type mice were promoted with TPA. No differences in papilloma incidence or multiplicity were observed between K5-PKCalpha mice and wild-type littermates. These results demonstrate that the overexpression of PKCalpha in epidermis increases the expression of specific proinflammatory mediators and induces cutaneous inflammation but has little to no effect on epidermal differentiation, proliferation or TPA tumor promotion.

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Onset of re-epithelialization after skin injury correlates with a reorganization of keratin filaments in wound edge keratinocytes: defining a potential role for keratin 16.

The Journal of Cell Biology ◽

10.1083/jcb.132.3.381 ◽

1996 ◽

Vol 132 (3) ◽

pp. 381-397 ◽

Cited By ~ 270

Author(s):

R D Paladini ◽

K Takahashi ◽

N S Bravo ◽

P A Coulombe

Keyword(s):

Cultured Cells ◽

Structural Function ◽

Cell Periphery ◽

Post Injury ◽

Wound Edge ◽

Keratin 16 ◽

Skin Keratinocytes ◽

Keratin Filaments ◽

10 Nm Filaments

Injury to stratified epithelia causes a strong induction of keratins 6 (K6) and 16 (K16) in post-mitotic keratinocytes located at the wound edge. We show that induction of K6 and K16 occurs within 6 h after injury to human epidermis. Their subsequent accumulation in keratinocytes correlates with the profound reorganization of keratin filaments from a pan-cytoplasmic distribution to one in which filaments are aggregated in a juxtanuclear location, opposite to the direction of cell migration. This filament reorganization coincides with additional cytoarchitectural changes and the onset of re-epithelialization after 18 h post-injury. By following the assembly of K6 and K16 in vitro and in cultured cells, we find that relative to K5 and K14, a well-characterized keratin pair that is constitutively expressed in epidermis, K6 and K16 polymerize into short 10-nm filaments that accumulate near the nucleus, a property arising from K16. Forced expression of human K16 in skin keratinocytes of transgenic mice causes a retraction of keratin filaments from the cell periphery, often in a polarized fashion. These results imply that K16 may not have a primary structural function akin to epidermal keratins. Rather, they suggest that in the context of epidermal wound healing, the function of K16 could be to promote a reorganization of the cytoplasmic array of keratin filaments, an event that precedes the onset of keratinocyte migration into the wound site.

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Migration of Melanoblasts into the Developing Murine Hair Follicle Is Accompanied by Transient c-Kit Expression

Journal of Histochemistry & Cytochemistry ◽

10.1177/002215540205000602 ◽

2002 ◽

Vol 50 (6) ◽

pp. 751-766 ◽

Cited By ~ 78

Author(s):

Eva M. J. Peters ◽

Desmond J. Tobin ◽

Natasha Botchkareva ◽

Marcus Maurer ◽

Ralf Paus

Keyword(s):

Stem Cell ◽

Hair Follicle ◽

Stem Cell Factor ◽

Mouse Skin ◽

Dermal Papilla ◽

Hair Follicles ◽

Cell Populations ◽

Outer Root Sheath ◽

Hair Bulb ◽

Root Sheath

Disruption of the c-Kit/stem cell factor (SCF) signaling pathway interferes with the survival, migration, and differentiation of melanocytes during generation of the hair follicle pigmentary unit. We examined c-Kit, SCF, and S100 (a marker for precursor melanocytic cells) expression, as well as melanoblast/melanocyte ultrastructure, in perinatal C57BL/6 mouse skin. Before the onset of hair bulb melanogenesis (i.e., stages 0–4 of hair follicle morphogenesis), strong c-Kit immunoreactivity (IR) was seen in selected non-mela-nogenic cells in the developing hair placode and hair plug. Many of these cells were S100-IR and were ultrastructurally identified as melanoblasts with migratory appearance. During the subsequent stages (5 and 6), increasingly dendritic c-Kit-IR cells successively invaded the hair bulb, while S100-IR gradually disappeared from these cells. Towards the completion of hair follicle morphogenesis (stages 7 and 8), several distinct follicular melanocytic cell populations could be defined and consisted broadly of (a) undifferentiated, non-pigmented c-Kit-negative melanoblasts in the outer root sheath and bulge and (b) highly differentiated melanocytes adjacent to the hair follicle dermal papilla above Auber's line. Widespread epithelial SCF-IR was seen throughout hair follicle morphogenesis. These findings suggest that melanoblasts express c-Kit as a prerequisite for migration into the SCF-supplying hair follicle epithelium. In addition, differentiated c-Kit-IR melanocytes target the bulb, while non-c-Kit-IR melanoblasts invade the outer root sheath and bulge in fully developed hair follicles.

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Post Zygotic, Somatic, Deletion in KERATIN 1 V1 Domain Generates Structural Alteration of the K1/K10 Dimer, Producing a Monolateral Palmar Epidermolytic Nevus

International Journal of Molecular Sciences ◽

10.3390/ijms22136901 ◽

2021 ◽

Vol 22 (13) ◽

pp. 6901

Author(s):

Sabrina Caporali ◽

Biagio Didona ◽

Mauro Paradisi ◽

Alessandro Mauriello ◽

Elena Campione ◽

...

Keyword(s):

In Silico Analysis ◽

Peripheral Blood Lymphocytes ◽

Wild Type ◽

Keratin 16 ◽

Dermatological Disease ◽

Blaschko Lines ◽

Keratin Filaments ◽

The Right ◽

Silico Analysis ◽

Keratin 1

Palmoplantar keratodermas (PPKs) are characterized by thickness of stratum corneum and epidermal hyperkeratosis localized in palms and soles. PPKs can be epidermolytic (EPPK) or non epidermolytic (NEPPK). Specific mutations of keratin 16 (K16) and keratin 1 (K1) have been associated to EPPK, and NEPPK. Cases of mosaicism in PPKs due to somatic keratin mutations have also been described in scientific literature. We evaluated a patient presenting hyperkeratosis localized monolaterally in the right palmar area, characterized by linear yellowish hyperkeratotic lesions following the Blaschko lines. No other relatives of the patient showed any dermatological disease. Light and confocal histological analysis confirmed the presence of epidermolityic hyperkeratosis. Genetic analysis performed demonstrates the heterozygous deletion NM_006121.4:r.274_472del for a total of 198 nucleotides, in KRT1 cDNA obtained by a palmar lesional skin biopsy, corresponding to the protein mutation NP_006112.3:p.Gly71_Gly137del. DNA extracted from peripheral blood lymphocytes did not display the presence of the mutation. These results suggest a somatic mutation causing an alteration in K1 N-terminal variable domain (V1). The deleted sequence involves the ISIS subdomain, containing a lysine residue already described as fundamental for epidermal transglutaminases in the crosslinking of IF cytoskeleton. Moreover, a computational analysis of the wild-type and V1-mutated K1/K10 keratin dimers, suggests an unusual interaction between these keratin filaments. The mutation taster in silico analysis also returned a high probability for a deleterious mutation. These data demonstrate once again the importance of the head domain (V1) of K1 in the formation of a functional keratinocyte cytoskeleton. Moreover, this is a further demonstration of the presence of somatic mutations arising in later stages of the embryogenesis, generating a mosaic phenotype.

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Expression of keratin K14 in the epidermis and hair follicle: insights into complex programs of differentiation.

The Journal of Cell Biology ◽

10.1083/jcb.109.5.2295 ◽

1989 ◽

Vol 109 (5) ◽

pp. 2295-2312 ◽

Cited By ~ 130

Author(s):

P A Coulombe ◽

R Kopan ◽

E Fuchs

Keyword(s):

Mrna Expression ◽

Hair Follicle ◽

Hair Shaft ◽

Basal Cells ◽

Outer Root Sheath ◽

Root Sheath ◽

Keratin Filaments ◽

Squamous Epithelia ◽

Keratin Filament ◽

Monospecific Antisera

Keratins K14 and K5 have long been considered to be biochemical markers of the stratified squamous epithelia, including epidermis (Moll, R., W. Franke, D. Schiller, B. Geiger, and R. Krepler. 1982. Cell. 31:11-24; Nelson, W., and T.-T. Sun. 1983. J. Cell Biol. 97:244-251). When cells of most stratified squamous epithelia differentiate, they downregulate expression of mRNAs encoding these two keratins and induce expression of new sets of keratins specific for individual programs of epithelial differentiation. Frequently, as in the case of epidermis, the expression of differentiation-specific keratins also leads to a reorganization of the keratin filament network, including denser bundling of the keratin fibers. We report here the use of monospecific antisera and cRNA probes to examine the differential expression of keratin K14 in the complex tissue of human skin. Using in situ hybridizations and immunoelectron microscopy, we find that the patterns of K14 expression and filament organization in the hair follicle are strikingly different from epidermis. Some of the mitotically active outer root sheath (ORS) cells, which give rise to ORS under normal circumstances and to epidermis during wound healing, produce only low levels of K14. These cells have fewer keratin filaments than basal epidermal cells, and the filaments are organized into looser, more delicate bundles than is typical for epidermis. As these cells differentiate, they elevate their expression of K14 and produce denser bundles of keratin filaments more typical of epidermis. In contrast to basal cells of epidermis and ORS, matrix cells, which are relatively undifferentiated and which can give rise to inner root sheath, cuticle and hair shaft, show no evidence of K14, K14 mRNA expression, or keratin filament formation. As matrix cells differentiate, they produce hair-specific keratins and dense bundles of keratin filaments but they do not induce K14 expression. Collectively, the patterns of K14 and K14 mRNA expression and filament organization in mitotically active epithelial cells of the skin correlate with their relative degree of pluripotency, and this suggests a possible basis for the deviation of hair follicle programs of differentiation from those of other stratified squamous epithelia.

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Collagenase expression in transgenic mouse skin causes hyperkeratosis and acanthosis and increases susceptibility to tumorigenesis.

Molecular and Cellular Biology ◽

10.1128/mcb.15.10.5732 ◽

1995 ◽

Vol 15 (10) ◽

pp. 5732-5739 ◽

Cited By ~ 93

Author(s):

J D'Armiento ◽

T DiColandrea ◽

S S Dalal ◽

Y Okada ◽

M T Huang ◽

...

Keyword(s):

Transgenic Mice ◽

Transgenic Mouse ◽

Histological Analysis ◽

Skin Diseases ◽

Morphological Changes ◽

Mouse Skin ◽

Ultrastructural Level ◽

Epidermal Hyperplasia ◽

Scaly Skin ◽

Skin Epidermis

In a series of transgenic mice, the human tissue collagenase gene was expressed in the suprabasal layer of the skin epidermis. Visually, the mice had dry and scaly skin which upon histological analysis revealed acanthosis, hyperkeratosis, and epidermal hyperplasia. At the ultrastructural level, intercellular granular materials were absent in the transgenic skin epidermis but contact was maintained through the intact desmosomes. Despite a diversity of underlying etiologies, similar morphological hyperproliferative changes in the epidermis are observed in the human skin diseases of lamellar ichthyosis, atopic dermatitis, and psoriasis. Subsequent experiments demonstrate that when the transgenic mouse skin was treated once with an initiator (7,12-dimethyl-benz[a]anthracene) and then twice weekly with a promoter (12-O-tetradecanoylphorbol-13-acetate), there was a marked increase in tumor incidence among transgenic mice compared with that among control littermates. These experiments demonstrate that by overexpressing the highly specific proteolytic enzyme collagenase, a cascade of events leading to profound morphological changes which augment the sensitivity of the skin towards carcinogenesis is initiated in the epidermis.

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Overexpression of human keratin 16 produces a distinct skin phenotype in transgenic mouse skin

Biochemistry and Cell Biology ◽

10.1139/o95-067 ◽

1995 ◽

Vol 73 (9-10) ◽

pp. 611-618 ◽

Cited By ~ 15

Author(s):

Pierre A. Coulombe ◽

Nicola S. Bravo ◽

Rudolph D. Paladini ◽

Diem Nguyen ◽

Kenzo Takahashi

Keyword(s):

Wound Healing ◽

Transgenic Mice ◽

Transgenic Mouse ◽

Transgene Expression ◽

Germ Line ◽

Mouse Skin ◽

Transgenic Animals ◽

Skin Lesions ◽

Cellular Level ◽

Outer Root Sheath

Human cytokeratin 16 (K16; 48 kDa) is constitutively expressed in postmitotic keratinocytes in a variety of stratified epithelial tissues, but it is best known for the marked enhancement of its expression in stratified squamous epithelia showing hyperproliferation or abnormal differentiation. Of particular interest to us, K16 is strongly induced at the wound edge after injury to the epidermis, and its accumulation correlates spatially and temporally with the onset of reepithelialization. To examine the properties of K16 in its natural cellular context, we introduced a wild-type human K16 gene into the germ line of transgenic mice. Several transgenic lines were established and characterized. Under most conditions, the human K16 transgene is regulated tissue specifically in the skin of transgenic mice. Animals that feature low levels of transgene expression are indistinguishable from controls during die first 6–8 months of life. In contrast, transgenic animals expressing the transgene at higher levels develop skin lesions at 1 week after birth, coinciding with the emergence of fur. At a cellular level, alterations begin with the reorganization of keratin filaments and are first seen at the level of the hair follicle outer root sheath (ORS), where K16 expression is known to occur constitutively. The lesions then progressively spread to involve the proximal epidermis, with which the ORS is contiguous. Elevated transgene expression is associated with a marked thickening of these two epithelia, along with altered keratinocyte cytoarchitecture and aberrant keratinization but no keratinocyte lysis. The implications of this phenotype for epithelial differentiation, human genodermatoses, and wound healing in skin are discussed.Key words: cytokeratin, skin, skin disease, transgenic mouse, wound healing.

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Directed Expression of Keratin 16 to the Progenitor Basal Cells of Transgenic Mouse Skin Delays Skin Maturation

The Journal of Cell Biology ◽

10.1083/jcb.142.4.1035 ◽

1998 ◽

Vol 142 (4) ◽

pp. 1035-1051 ◽

Cited By ~ 59

Author(s):

Rudolph D. Paladini ◽

Pierre A. Coulombe

Keyword(s):

Transgenic Mice ◽

Transgenic Mouse ◽

Egf Receptor ◽

Basal Layer ◽

Mouse Skin ◽

Hair Follicles ◽

Type I ◽

Basal Cells ◽

Tail Domain ◽

Keratin 16

We previously hypothesized that the type I keratin 16 (K16) plays a role in the process of keratinocyte activation that occurs in response to skin injury (Paladini, R.D., K. Takahashi, N.S. Bravo, and P.A. Coulombe. 1996. J. Cell Biol. 132:381–397). To further examine its properties in vivo, the human K16 cDNA was constitutively expressed in the progenitor basal layer of transgenic mouse skin using the K14 gene promoter. Mice that express approximately as much K16 protein as endogenous K14 display a dramatic postnatal phenotype that consists of skin that is hyperkeratotic, scaly, and essentially devoid of fur. Histologically, the epidermis is thickened because of hyperproliferation of transgenic basal cells, whereas the hair follicles are decreased in number, poorly developed, and hypoproliferative. Microscopically, the transgenic keratinocytes are hypertrophic and feature an altered keratin filament network and decreased cell–cell adhesion. The phenotype normalizes at ∼5 wk after birth. In contrast, control mice expressing a K16-K14 chimeric protein to comparable levels are normal. The character and temporal evolution of the phenotype in the K16 transgenic mice are reminiscent of the activated EGF receptor– mediated signaling pathway in skin. In fact, tyrosine phosphorylation of the EGF receptor is increased in the newborn skin of K16 transgenic mice. We conclude that expression of K16 can significantly alter the response of skin keratinocytes to signaling cues, a distinctive property likely resulting from its unique COOH-terminal tail domain.

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