Limits...
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.

Show MeSH

Related in: MedlinePlus

Immunolocalization  of hyperproliferation markers in  the skin. Mice were injected with  BrdU 2 h before sacrifice, and  samples from dorsal trunk skin  were paraffin-embedded, sectioned, and immunostained using the HRP procedure (No. 6  line). (A–C) Trunk skin from a  7 d chimera homozygote (A), a  wild-type control (B), and a K16  homozygote (C) were stained  with an anti-BrdU antibody. The  two controls (A and B) exhibit  low labeling in the epidermis  while the hair follicles are highly  labeled. In the K16 homozygote  (C), however, the follicles show  little mitotic activity while the  epidermis is highly labeled. (D  and E) Skin from 21-d-old wild-type control (D) and a K16 homozygote (E) stained with the  anti-BrdU antibody. Note that  the control shows very little labeling in both the epidermis and  the telogen stage hair follicles. In  contrast, phenotypic epidermis  still features high mitotic activity  and, in addition, the anagen  stage hair follicles are now  highly labeled. (F–H) Trunk skin  from a 7-d-old chimera homozygote (F), a wild-type control (G),  and a K16 homozygote (H) were  stained with an anti-K17 antibody. K17 expression was restricted to the outer root sheath  of hair follicles in the two controls (F and G). In the K16 homozygote, however, K17 expression was detected in all layers of  the epidermis. Arrowheads, the  dermal–epidermal junction. hf,  hair follicle. Bar, 100 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2132878&req=5

Figure 6: Immunolocalization of hyperproliferation markers in the skin. Mice were injected with BrdU 2 h before sacrifice, and samples from dorsal trunk skin were paraffin-embedded, sectioned, and immunostained using the HRP procedure (No. 6 line). (A–C) Trunk skin from a 7 d chimera homozygote (A), a wild-type control (B), and a K16 homozygote (C) were stained with an anti-BrdU antibody. The two controls (A and B) exhibit low labeling in the epidermis while the hair follicles are highly labeled. In the K16 homozygote (C), however, the follicles show little mitotic activity while the epidermis is highly labeled. (D and E) Skin from 21-d-old wild-type control (D) and a K16 homozygote (E) stained with the anti-BrdU antibody. Note that the control shows very little labeling in both the epidermis and the telogen stage hair follicles. In contrast, phenotypic epidermis still features high mitotic activity and, in addition, the anagen stage hair follicles are now highly labeled. (F–H) Trunk skin from a 7-d-old chimera homozygote (F), a wild-type control (G), and a K16 homozygote (H) were stained with an anti-K17 antibody. K17 expression was restricted to the outer root sheath of hair follicles in the two controls (F and G). In the K16 homozygote, however, K17 expression was detected in all layers of the epidermis. Arrowheads, the dermal–epidermal junction. hf, hair follicle. Bar, 100 μm.

Mentions: To determine whether or not the epidermis of the phenotypic mice was hyperproliferative, mice were injected with BrdU 2 h before they were killed. An anti-BrdU antibody was used to detect cells that were in S phase at the time of sacrifice. The K16 transgenic phenotypic epidermis had many more BrdU-positive nuclei compared with either of the two controls (compare Fig. 6, C with A and B). Quantitatively, the phenotypic epidermis had an approximately threefold higher mitotic index than either of the two controls. The opposite effect was observed in the hair follicles. The control mouse follicles had many nuclei that were BrdU positive, whereas follicles from the K16 homozygote showed fewer positive nuclei. These data indicate that the epidermis is hyperproliferative whereas the hair follicles are hypoproliferative. At ∼3 wk, when the first hair cycle is completed (5, 20) control epidermis and hair follicles have very few BrdU-positive nuclei (Fig. 6 D). In striking contrast, there are many BrdU-positive nuclei in the hair follicles of the phenotypic mice (Fig. 6 E). This data suggests that the first hair cycle in the phenotypic mice is dramatically delayed.


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 hyperproliferation markers in  the skin. Mice were injected with  BrdU 2 h before sacrifice, and  samples from dorsal trunk skin  were paraffin-embedded, sectioned, and immunostained using the HRP procedure (No. 6  line). (A–C) Trunk skin from a  7 d chimera homozygote (A), a  wild-type control (B), and a K16  homozygote (C) were stained  with an anti-BrdU antibody. The  two controls (A and B) exhibit  low labeling in the epidermis  while the hair follicles are highly  labeled. In the K16 homozygote  (C), however, the follicles show  little mitotic activity while the  epidermis is highly labeled. (D  and E) Skin from 21-d-old wild-type control (D) and a K16 homozygote (E) stained with the  anti-BrdU antibody. Note that  the control shows very little labeling in both the epidermis and  the telogen stage hair follicles. In  contrast, phenotypic epidermis  still features high mitotic activity  and, in addition, the anagen  stage hair follicles are now  highly labeled. (F–H) Trunk skin  from a 7-d-old chimera homozygote (F), a wild-type control (G),  and a K16 homozygote (H) were  stained with an anti-K17 antibody. K17 expression was restricted to the outer root sheath  of hair follicles in the two controls (F and G). In the K16 homozygote, however, K17 expression was detected in all layers of  the epidermis. Arrowheads, the  dermal–epidermal junction. hf,  hair follicle. Bar, 100 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132878&req=5

Figure 6: Immunolocalization of hyperproliferation markers in the skin. Mice were injected with BrdU 2 h before sacrifice, and samples from dorsal trunk skin were paraffin-embedded, sectioned, and immunostained using the HRP procedure (No. 6 line). (A–C) Trunk skin from a 7 d chimera homozygote (A), a wild-type control (B), and a K16 homozygote (C) were stained with an anti-BrdU antibody. The two controls (A and B) exhibit low labeling in the epidermis while the hair follicles are highly labeled. In the K16 homozygote (C), however, the follicles show little mitotic activity while the epidermis is highly labeled. (D and E) Skin from 21-d-old wild-type control (D) and a K16 homozygote (E) stained with the anti-BrdU antibody. Note that the control shows very little labeling in both the epidermis and the telogen stage hair follicles. In contrast, phenotypic epidermis still features high mitotic activity and, in addition, the anagen stage hair follicles are now highly labeled. (F–H) Trunk skin from a 7-d-old chimera homozygote (F), a wild-type control (G), and a K16 homozygote (H) were stained with an anti-K17 antibody. K17 expression was restricted to the outer root sheath of hair follicles in the two controls (F and G). In the K16 homozygote, however, K17 expression was detected in all layers of the epidermis. Arrowheads, the dermal–epidermal junction. hf, hair follicle. Bar, 100 μm.
Mentions: To determine whether or not the epidermis of the phenotypic mice was hyperproliferative, mice were injected with BrdU 2 h before they were killed. An anti-BrdU antibody was used to detect cells that were in S phase at the time of sacrifice. The K16 transgenic phenotypic epidermis had many more BrdU-positive nuclei compared with either of the two controls (compare Fig. 6, C with A and B). Quantitatively, the phenotypic epidermis had an approximately threefold higher mitotic index than either of the two controls. The opposite effect was observed in the hair follicles. The control mouse follicles had many nuclei that were BrdU positive, whereas follicles from the K16 homozygote showed fewer positive nuclei. These data indicate that the epidermis is hyperproliferative whereas the hair follicles are hypoproliferative. At ∼3 wk, when the first hair cycle is completed (5, 20) control epidermis and hair follicles have very few BrdU-positive nuclei (Fig. 6 D). In striking contrast, there are many BrdU-positive nuclei in the hair follicles of the phenotypic mice (Fig. 6 E). This data suggests that the first hair cycle in the phenotypic mice is dramatically delayed.

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