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Directed expression of keratin 16 to the progenitor basal cells of transgenic mouse skin delays skin maturation.

Paladini RD, Coulombe PA - J. Cell Biol. (1998)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

ABSTRACT
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 approximately 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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Immunolocalization  of cell adhesion molecules in  the epidermis (No. 10 line).  8-μm frozen sections of skin  from control (A, C, E, G, I,  and K) and K16 homozygote  littermates (B, D, F, H, J, and  L) were used for the localization of cell adhesion molecules by indirect immunofluorescence. For the α6  integrin the HRP method  was used. Sections were  stained for Desmoplakin (A  and B), E-cadherin (C and  D), β-catenin (E and F),  Connexin 26 (G and H), α3  integrin (I and J), and α6 integrin (K and L). Desmoplakin staining in the  homozygote was not only  reduced at regions of cell– cell contact but was also  prevalent in the cytoplasm  of cells (asterisks, compare B  and A). E-Cadherin was absent from the basal layer of  the homozygote (asterisks in  D) and was more disorganized suprabasally compared with control (C). The  results of the β-catenin staining were similar to those  obtained with desmoplakin  with the additional fact that  staining seemed reduced in  the basal layer of the homozygote (asterisks, compare  F and E). Connexin 26,  which is normally expressed  in the hair follicle (arrow) and not the epidermis (G) in control skin, was dramatically induced suprabasally in the homozygote (H). Expression of α3 integrin extended suprabasally (asterisks) in homozygous epidermis (J) as opposed to its normal basal expression in control (I). α6 integrin expression appeared comparable between homozygous (L) and control (K) epidermis with the possible exception of  increased lateral and apical staining of basal cells in the homozygote. Arrowheads, the dermal–epidermal junction. hf, hair follicle. Bars:  (A–J) 50 μm; (K and L) 50 μm.
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Figure 8: Immunolocalization of cell adhesion molecules in the epidermis (No. 10 line). 8-μm frozen sections of skin from control (A, C, E, G, I, and K) and K16 homozygote littermates (B, D, F, H, J, and L) were used for the localization of cell adhesion molecules by indirect immunofluorescence. For the α6 integrin the HRP method was used. Sections were stained for Desmoplakin (A and B), E-cadherin (C and D), β-catenin (E and F), Connexin 26 (G and H), α3 integrin (I and J), and α6 integrin (K and L). Desmoplakin staining in the homozygote was not only reduced at regions of cell– cell contact but was also prevalent in the cytoplasm of cells (asterisks, compare B and A). E-Cadherin was absent from the basal layer of the homozygote (asterisks in D) and was more disorganized suprabasally compared with control (C). The results of the β-catenin staining were similar to those obtained with desmoplakin with the additional fact that staining seemed reduced in the basal layer of the homozygote (asterisks, compare F and E). Connexin 26, which is normally expressed in the hair follicle (arrow) and not the epidermis (G) in control skin, was dramatically induced suprabasally in the homozygote (H). Expression of α3 integrin extended suprabasally (asterisks) in homozygous epidermis (J) as opposed to its normal basal expression in control (I). α6 integrin expression appeared comparable between homozygous (L) and control (K) epidermis with the possible exception of increased lateral and apical staining of basal cells in the homozygote. Arrowheads, the dermal–epidermal junction. hf, hair follicle. Bars: (A–J) 50 μm; (K and L) 50 μm.

Mentions: Desmoplakin was examined as a marker of desmosomal adhesion. Detection was primarily at the surface of basal cells in the areas of cell–cell contact (Fig. 8 A). The intensity of staining increased on the surface of suprabasal cells coinciding with the maturation of desmosomes as keratinocytes differentiate (91). Cell–cell staining in the majority of basal and suprabasal cells from the phenotypic epidermis was reduced (Fig. 8 B) as would be expected from the EM data.


Directed expression of keratin 16 to the progenitor basal cells of transgenic mouse skin delays skin maturation.

Paladini RD, Coulombe PA - J. Cell Biol. (1998)

Immunolocalization  of cell adhesion molecules in  the epidermis (No. 10 line).  8-μm frozen sections of skin  from control (A, C, E, G, I,  and K) and K16 homozygote  littermates (B, D, F, H, J, and  L) were used for the localization of cell adhesion molecules by indirect immunofluorescence. For the α6  integrin the HRP method  was used. Sections were  stained for Desmoplakin (A  and B), E-cadherin (C and  D), β-catenin (E and F),  Connexin 26 (G and H), α3  integrin (I and J), and α6 integrin (K and L). Desmoplakin staining in the  homozygote was not only  reduced at regions of cell– cell contact but was also  prevalent in the cytoplasm  of cells (asterisks, compare B  and A). E-Cadherin was absent from the basal layer of  the homozygote (asterisks in  D) and was more disorganized suprabasally compared with control (C). The  results of the β-catenin staining were similar to those  obtained with desmoplakin  with the additional fact that  staining seemed reduced in  the basal layer of the homozygote (asterisks, compare  F and E). Connexin 26,  which is normally expressed  in the hair follicle (arrow) and not the epidermis (G) in control skin, was dramatically induced suprabasally in the homozygote (H). Expression of α3 integrin extended suprabasally (asterisks) in homozygous epidermis (J) as opposed to its normal basal expression in control (I). α6 integrin expression appeared comparable between homozygous (L) and control (K) epidermis with the possible exception of  increased lateral and apical staining of basal cells in the homozygote. Arrowheads, the dermal–epidermal junction. hf, hair follicle. Bars:  (A–J) 50 μm; (K and L) 50 μm.
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Figure 8: Immunolocalization of cell adhesion molecules in the epidermis (No. 10 line). 8-μm frozen sections of skin from control (A, C, E, G, I, and K) and K16 homozygote littermates (B, D, F, H, J, and L) were used for the localization of cell adhesion molecules by indirect immunofluorescence. For the α6 integrin the HRP method was used. Sections were stained for Desmoplakin (A and B), E-cadherin (C and D), β-catenin (E and F), Connexin 26 (G and H), α3 integrin (I and J), and α6 integrin (K and L). Desmoplakin staining in the homozygote was not only reduced at regions of cell– cell contact but was also prevalent in the cytoplasm of cells (asterisks, compare B and A). E-Cadherin was absent from the basal layer of the homozygote (asterisks in D) and was more disorganized suprabasally compared with control (C). The results of the β-catenin staining were similar to those obtained with desmoplakin with the additional fact that staining seemed reduced in the basal layer of the homozygote (asterisks, compare F and E). Connexin 26, which is normally expressed in the hair follicle (arrow) and not the epidermis (G) in control skin, was dramatically induced suprabasally in the homozygote (H). Expression of α3 integrin extended suprabasally (asterisks) in homozygous epidermis (J) as opposed to its normal basal expression in control (I). α6 integrin expression appeared comparable between homozygous (L) and control (K) epidermis with the possible exception of increased lateral and apical staining of basal cells in the homozygote. Arrowheads, the dermal–epidermal junction. hf, hair follicle. Bars: (A–J) 50 μm; (K and L) 50 μm.
Mentions: Desmoplakin was examined as a marker of desmosomal adhesion. Detection was primarily at the surface of basal cells in the areas of cell–cell contact (Fig. 8 A). The intensity of staining increased on the surface of suprabasal cells coinciding with the maturation of desmosomes as keratinocytes differentiate (91). Cell–cell staining in the majority of basal and suprabasal cells from the phenotypic epidermis was reduced (Fig. 8 B) as would be expected from the EM data.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

ABSTRACT
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 approximately 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.

Show MeSH
Related in: MedlinePlus