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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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Light microscopy of  the skin of control and transgenic mice. 5-μm paraffin sections from mice were counterstained with hematoxylin and  eosin (H & E) or were subjected  to immunostaining using the  HRP procedure (No. 6 line). (A,  D, G, and J) H & E–stained section of trunk skin from 7 d mice  are shown. The epidermides of a  homozygote chimera (A), a control wild-type (D) and a K16  heterozygote (G) have a comparable thickness and similar hair  follicle profiles. The epidermis  of the K16 homozygote (J) is  significantly thickened compared with the others and there  is a reduction in the number of  hair follicles. Some of the follicles are also incorrectly oriented  (large arrowhead). (B, E, H, and  K) Immunohistochemical detection of the transgene in skin section from 7 d chimera homozygote (B), control wild-type (E),  K16 heterozygote (H), and K16  homozygote (K). The LL001 antibody was used to detect the  chimera transgene (B) and the  1275 antibody to detect the K16  transgene (E, H, K). The chimera transgene expression is  correctly restricted to the outer  root sheath of hair follicles and  the basal layer of the epidermis.  Control skin (E) shows no expression of human K16 (small  asterisk, melanin granules in hair  follicle profiles) while the K16  heterozygote (H) features the  correct regulation of the transgene. The K16 homozygote (K),  however, shows K16 expression  throughout all layers of the epidermis. (C) H & E staining of 7 d  ventral skin from a K16 homozygote that features blistering. Note the large blister (asterisks) that occurs within the suprabasal layers of the epidermis. (F) H & E of ventral skin from the same mouse that features  parakeratosis. The arrows indicate parakeratotic nuclei and the asterisk denotes a Munro microabcess, a common feature of psoriasis. C  and F also illustrate the presence of a large dermal infiltrate suggesting an inflammatory response. (I and L) H & E staining of 41 d dorsal skin from a wild-type control (I) and K16 homozygote (L), (No. 10 line). Note that at this age the epidermides of the two mice are of  comparable thickness. hf, hair follicle; sg, sebaceous gland. Arrowheads, indicate the dermal–epidermal junction. Bar, 100 μm.
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Figure 3: Light microscopy of the skin of control and transgenic mice. 5-μm paraffin sections from mice were counterstained with hematoxylin and eosin (H & E) or were subjected to immunostaining using the HRP procedure (No. 6 line). (A, D, G, and J) H & E–stained section of trunk skin from 7 d mice are shown. The epidermides of a homozygote chimera (A), a control wild-type (D) and a K16 heterozygote (G) have a comparable thickness and similar hair follicle profiles. The epidermis of the K16 homozygote (J) is significantly thickened compared with the others and there is a reduction in the number of hair follicles. Some of the follicles are also incorrectly oriented (large arrowhead). (B, E, H, and K) Immunohistochemical detection of the transgene in skin section from 7 d chimera homozygote (B), control wild-type (E), K16 heterozygote (H), and K16 homozygote (K). The LL001 antibody was used to detect the chimera transgene (B) and the 1275 antibody to detect the K16 transgene (E, H, K). The chimera transgene expression is correctly restricted to the outer root sheath of hair follicles and the basal layer of the epidermis. Control skin (E) shows no expression of human K16 (small asterisk, melanin granules in hair follicle profiles) while the K16 heterozygote (H) features the correct regulation of the transgene. The K16 homozygote (K), however, shows K16 expression throughout all layers of the epidermis. (C) H & E staining of 7 d ventral skin from a K16 homozygote that features blistering. Note the large blister (asterisks) that occurs within the suprabasal layers of the epidermis. (F) H & E of ventral skin from the same mouse that features parakeratosis. The arrows indicate parakeratotic nuclei and the asterisk denotes a Munro microabcess, a common feature of psoriasis. C and F also illustrate the presence of a large dermal infiltrate suggesting an inflammatory response. (I and L) H & E staining of 41 d dorsal skin from a wild-type control (I) and K16 homozygote (L), (No. 10 line). Note that at this age the epidermides of the two mice are of comparable thickness. hf, hair follicle; sg, sebaceous gland. Arrowheads, indicate the dermal–epidermal junction. Bar, 100 μm.

Mentions: To examine the histological changes in the phenotypic mice, trunk skin from non-transgenic, heterozygous, and homozygous 7-d-old littermates from a K16 phenotypic line was obtained and examined by light microscopy (Fig. 3, D, G, and J, respectively). Trunk skin was also obtained from a 7-d-old homozygous mouse from the No. B1 chimera control line (Fig. 3 A). The epidermis from the K16 transgenic homozygote was significantly thickened when compared with control epidermis (compare Fig. 3, J and A; D and G). This acanthosis involves an expansion of both the spinous and granular layers. Many of the cells in the spinous layer are hypertrophic (see EM data below). In addition, the stratum corneum of the epidermis is also thickened (hyperkeratosis). As previously mentioned, blistering occurs in two of the K16 transgenic lines. The blistering occurred in the suprabasal layers of the epidermis (Fig. 3 C) and was extensive along the ventral surface around the limbs of the animals. In addition, ventral skin from phenotypic mice featured areas of parakeratosis (Fig. 3 F) and the presence of Munro microabcesses, a common feature of psoriasis (11). In both the blistered and parakeratotic epidermis, there was the presence of a large dermal infiltrate suggesting an inflammatory response. The other major morphological aberration of the phenotypic skin was a marked reduction in the number of hair follicles. Many of the remaining follicles were misoriented and did not extend deeply into the hypodermis (Fig. 3 J) suggesting that there might a partial impairment of follicle morphogenesis. None of these differences were seen in either the control or heterozygote littermates or in the homozygote chimera control.


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)

Light microscopy of  the skin of control and transgenic mice. 5-μm paraffin sections from mice were counterstained with hematoxylin and  eosin (H & E) or were subjected  to immunostaining using the  HRP procedure (No. 6 line). (A,  D, G, and J) H & E–stained section of trunk skin from 7 d mice  are shown. The epidermides of a  homozygote chimera (A), a control wild-type (D) and a K16  heterozygote (G) have a comparable thickness and similar hair  follicle profiles. The epidermis  of the K16 homozygote (J) is  significantly thickened compared with the others and there  is a reduction in the number of  hair follicles. Some of the follicles are also incorrectly oriented  (large arrowhead). (B, E, H, and  K) Immunohistochemical detection of the transgene in skin section from 7 d chimera homozygote (B), control wild-type (E),  K16 heterozygote (H), and K16  homozygote (K). The LL001 antibody was used to detect the  chimera transgene (B) and the  1275 antibody to detect the K16  transgene (E, H, K). The chimera transgene expression is  correctly restricted to the outer  root sheath of hair follicles and  the basal layer of the epidermis.  Control skin (E) shows no expression of human K16 (small  asterisk, melanin granules in hair  follicle profiles) while the K16  heterozygote (H) features the  correct regulation of the transgene. The K16 homozygote (K),  however, shows K16 expression  throughout all layers of the epidermis. (C) H & E staining of 7 d  ventral skin from a K16 homozygote that features blistering. Note the large blister (asterisks) that occurs within the suprabasal layers of the epidermis. (F) H & E of ventral skin from the same mouse that features  parakeratosis. The arrows indicate parakeratotic nuclei and the asterisk denotes a Munro microabcess, a common feature of psoriasis. C  and F also illustrate the presence of a large dermal infiltrate suggesting an inflammatory response. (I and L) H & E staining of 41 d dorsal skin from a wild-type control (I) and K16 homozygote (L), (No. 10 line). Note that at this age the epidermides of the two mice are of  comparable thickness. hf, hair follicle; sg, sebaceous gland. Arrowheads, indicate the dermal–epidermal junction. Bar, 100 μm.
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Figure 3: Light microscopy of the skin of control and transgenic mice. 5-μm paraffin sections from mice were counterstained with hematoxylin and eosin (H & E) or were subjected to immunostaining using the HRP procedure (No. 6 line). (A, D, G, and J) H & E–stained section of trunk skin from 7 d mice are shown. The epidermides of a homozygote chimera (A), a control wild-type (D) and a K16 heterozygote (G) have a comparable thickness and similar hair follicle profiles. The epidermis of the K16 homozygote (J) is significantly thickened compared with the others and there is a reduction in the number of hair follicles. Some of the follicles are also incorrectly oriented (large arrowhead). (B, E, H, and K) Immunohistochemical detection of the transgene in skin section from 7 d chimera homozygote (B), control wild-type (E), K16 heterozygote (H), and K16 homozygote (K). The LL001 antibody was used to detect the chimera transgene (B) and the 1275 antibody to detect the K16 transgene (E, H, K). The chimera transgene expression is correctly restricted to the outer root sheath of hair follicles and the basal layer of the epidermis. Control skin (E) shows no expression of human K16 (small asterisk, melanin granules in hair follicle profiles) while the K16 heterozygote (H) features the correct regulation of the transgene. The K16 homozygote (K), however, shows K16 expression throughout all layers of the epidermis. (C) H & E staining of 7 d ventral skin from a K16 homozygote that features blistering. Note the large blister (asterisks) that occurs within the suprabasal layers of the epidermis. (F) H & E of ventral skin from the same mouse that features parakeratosis. The arrows indicate parakeratotic nuclei and the asterisk denotes a Munro microabcess, a common feature of psoriasis. C and F also illustrate the presence of a large dermal infiltrate suggesting an inflammatory response. (I and L) H & E staining of 41 d dorsal skin from a wild-type control (I) and K16 homozygote (L), (No. 10 line). Note that at this age the epidermides of the two mice are of comparable thickness. hf, hair follicle; sg, sebaceous gland. Arrowheads, indicate the dermal–epidermal junction. Bar, 100 μm.
Mentions: To examine the histological changes in the phenotypic mice, trunk skin from non-transgenic, heterozygous, and homozygous 7-d-old littermates from a K16 phenotypic line was obtained and examined by light microscopy (Fig. 3, D, G, and J, respectively). Trunk skin was also obtained from a 7-d-old homozygous mouse from the No. B1 chimera control line (Fig. 3 A). The epidermis from the K16 transgenic homozygote was significantly thickened when compared with control epidermis (compare Fig. 3, J and A; D and G). This acanthosis involves an expansion of both the spinous and granular layers. Many of the cells in the spinous layer are hypertrophic (see EM data below). In addition, the stratum corneum of the epidermis is also thickened (hyperkeratosis). As previously mentioned, blistering occurs in two of the K16 transgenic lines. The blistering occurred in the suprabasal layers of the epidermis (Fig. 3 C) and was extensive along the ventral surface around the limbs of the animals. In addition, ventral skin from phenotypic mice featured areas of parakeratosis (Fig. 3 F) and the presence of Munro microabcesses, a common feature of psoriasis (11). In both the blistered and parakeratotic epidermis, there was the presence of a large dermal infiltrate suggesting an inflammatory response. The other major morphological aberration of the phenotypic skin was a marked reduction in the number of hair follicles. Many of the remaining follicles were misoriented and did not extend deeply into the hypodermis (Fig. 3 J) suggesting that there might a partial impairment of follicle morphogenesis. None of these differences were seen in either the control or heterozygote littermates or in the homozygote chimera control.

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