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 epidermal differentiation markers in the  skin. 5-μm paraffin sections were  stained using the HRP procedure (No.  21 line). (A–C) Expression of K14 in  the chimera homozygote (A), wild-type control (B), and K16 homozygote  (C). K14 is properly expressed in the  basal layer of the epidermis and the  outer root sheath in the two controls.  However, in the K16 homozygote (C),  the expression is now detected primarily suprabasally. (D–F) Expression of  K10 in the chimera homozygote (D),  wild-type control (E), and K16 homozygote (F). K10 is properly localized to the suprabasal layers of the epidermis in all three samples. Expansion  of K10 expression in F is due to the increased thickness of the suprabasal layers. (G–I) Filaggrin expression in the  chimera homozygote (G), wild-type  control (H), and K16 homozygote (I).  Filaggrin is expressed in the granular  layer of the epidermis in both G and H.  In the K16 homozygote (I) some areas  of agranulosis are observed (large asterisk) along with ectopic spinous layer  expression (arrows). Arrowheads, dermal–epidermal junction. hf, hair follicle. Small asterisks, melanin granules in  hair follicle profiles. Bar, 100 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2132878&req=5

Figure 5: Immunolocalization of epidermal differentiation markers in the skin. 5-μm paraffin sections were stained using the HRP procedure (No. 21 line). (A–C) Expression of K14 in the chimera homozygote (A), wild-type control (B), and K16 homozygote (C). K14 is properly expressed in the basal layer of the epidermis and the outer root sheath in the two controls. However, in the K16 homozygote (C), the expression is now detected primarily suprabasally. (D–F) Expression of K10 in the chimera homozygote (D), wild-type control (E), and K16 homozygote (F). K10 is properly localized to the suprabasal layers of the epidermis in all three samples. Expansion of K10 expression in F is due to the increased thickness of the suprabasal layers. (G–I) Filaggrin expression in the chimera homozygote (G), wild-type control (H), and K16 homozygote (I). Filaggrin is expressed in the granular layer of the epidermis in both G and H. In the K16 homozygote (I) some areas of agranulosis are observed (large asterisk) along with ectopic spinous layer expression (arrows). Arrowheads, dermal–epidermal junction. hf, hair follicle. Small asterisks, melanin granules in hair follicle profiles. Bar, 100 μm.

Mentions: K14, which is expressed in the basal layer of stratified epithelia, including the outer root sheath of hair follicles (16) was restricted to that location in both the chimera homozygote and the control sample (Fig. 5, A and B). In contrast, K14 was reduced in the basal layer and extended strongly in the suprabasal layers of the phenotypic sample (Fig. 5 C). This pattern of K14 localization is reminiscent of both hyperproliferative and wounded epidermis (17, 69). The expression of K10, an early marker of epidermal keratinocyte differentiation (21, 68), was detected in the suprabasal layers of all three samples (Fig. 5, D–F) with the only difference being that the area of K10 expression was thickened in the phenotypic sample due to the increased number of suprabasal layers. In contrast to the seemingly normal expression of K10, filaggrin expression in the phenotypic sample was abnormal (Fig. 5 I). Areas of the epidermis featured an expansion of filaggrin expression (compare to the thin layer of granular staining seen in the homozygous chimera and control samples; Fig. 5, G and H). In addition, there are some areas of the epidermis where the signal appeared decreased or even absent. These data suggest that there are deviations in the program of terminal differentiation executed in the phenotypic epidermis.


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 epidermal differentiation markers in the  skin. 5-μm paraffin sections were  stained using the HRP procedure (No.  21 line). (A–C) Expression of K14 in  the chimera homozygote (A), wild-type control (B), and K16 homozygote  (C). K14 is properly expressed in the  basal layer of the epidermis and the  outer root sheath in the two controls.  However, in the K16 homozygote (C),  the expression is now detected primarily suprabasally. (D–F) Expression of  K10 in the chimera homozygote (D),  wild-type control (E), and K16 homozygote (F). K10 is properly localized to the suprabasal layers of the epidermis in all three samples. Expansion  of K10 expression in F is due to the increased thickness of the suprabasal layers. (G–I) Filaggrin expression in the  chimera homozygote (G), wild-type  control (H), and K16 homozygote (I).  Filaggrin is expressed in the granular  layer of the epidermis in both G and H.  In the K16 homozygote (I) some areas  of agranulosis are observed (large asterisk) along with ectopic spinous layer  expression (arrows). Arrowheads, dermal–epidermal junction. hf, hair follicle. Small asterisks, melanin granules in  hair follicle profiles. Bar, 100 μm.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 5: Immunolocalization of epidermal differentiation markers in the skin. 5-μm paraffin sections were stained using the HRP procedure (No. 21 line). (A–C) Expression of K14 in the chimera homozygote (A), wild-type control (B), and K16 homozygote (C). K14 is properly expressed in the basal layer of the epidermis and the outer root sheath in the two controls. However, in the K16 homozygote (C), the expression is now detected primarily suprabasally. (D–F) Expression of K10 in the chimera homozygote (D), wild-type control (E), and K16 homozygote (F). K10 is properly localized to the suprabasal layers of the epidermis in all three samples. Expansion of K10 expression in F is due to the increased thickness of the suprabasal layers. (G–I) Filaggrin expression in the chimera homozygote (G), wild-type control (H), and K16 homozygote (I). Filaggrin is expressed in the granular layer of the epidermis in both G and H. In the K16 homozygote (I) some areas of agranulosis are observed (large asterisk) along with ectopic spinous layer expression (arrows). Arrowheads, dermal–epidermal junction. hf, hair follicle. Small asterisks, melanin granules in hair follicle profiles. Bar, 100 μm.
Mentions: K14, which is expressed in the basal layer of stratified epithelia, including the outer root sheath of hair follicles (16) was restricted to that location in both the chimera homozygote and the control sample (Fig. 5, A and B). In contrast, K14 was reduced in the basal layer and extended strongly in the suprabasal layers of the phenotypic sample (Fig. 5 C). This pattern of K14 localization is reminiscent of both hyperproliferative and wounded epidermis (17, 69). The expression of K10, an early marker of epidermal keratinocyte differentiation (21, 68), was detected in the suprabasal layers of all three samples (Fig. 5, D–F) with the only difference being that the area of K10 expression was thickened in the phenotypic sample due to the increased number of suprabasal layers. In contrast to the seemingly normal expression of K10, filaggrin expression in the phenotypic sample was abnormal (Fig. 5 I). Areas of the epidermis featured an expansion of filaggrin expression (compare to the thin layer of granular staining seen in the homozygous chimera and control samples; Fig. 5, G and H). In addition, there are some areas of the epidermis where the signal appeared decreased or even absent. These data suggest that there are deviations in the program of terminal differentiation executed in the phenotypic epidermis.

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