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Lessons from loricrin-deficient mice: compensatory mechanisms maintaining skin barrier function in the absence of a major cornified envelope protein.

Koch PJ, de Viragh PA, Scharer E, Bundman D, Longley MA, Bickenbach J, Kawachi Y, Suga Y, Zhou Z, Huber M, Hohl D, Kartasova T, Jarnik M, Steven AC, Roop DR - J. Cell Biol. (2000)

Bottom Line: The epidermal cornified cell envelope (CE) is a complex protein-lipid composite that replaces the plasma membrane of terminally differentiated keratinocytes.Tape stripping experiments suggested that the stratum corneum stability was reduced in newborn Lor(-/-) mice compared with wild-type controls.Isolated mutant CEs were more easily fragmented by sonication in vitro, indicating a greater susceptibility to mechanical stress.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.

ABSTRACT
The epidermal cornified cell envelope (CE) is a complex protein-lipid composite that replaces the plasma membrane of terminally differentiated keratinocytes. This lamellar structure is essential for the barrier function of the skin and has the ability to prevent the loss of water and ions and to protect from environmental hazards. The major protein of the epidermal CE is loricrin, contributing approximately 70% by mass. We have generated mice that are deficient for this protein. These mice showed a delay in the formation of the skin barrier in embryonic development. At birth, homozygous mutant mice weighed less than control littermates and showed skin abnormalities, such as congenital erythroderma with a shiny, translucent skin. Tape stripping experiments suggested that the stratum corneum stability was reduced in newborn Lor(-/-) mice compared with wild-type controls. Isolated mutant CEs were more easily fragmented by sonication in vitro, indicating a greater susceptibility to mechanical stress. Nevertheless, we did not detect impaired epidermal barrier function in these mice. Surprisingly, the skin phenotype disappeared 4-5 d after birth. At least one of the compensatory mechanisms preventing a more severe skin phenotype in newborn Lor(-/-) mice is an increase in the expression of other CE components, such as SPRRP2D and SPRRP2H, members of the family of "small proline rich proteins", and repetin, a member of the "fused gene" subgroup of the S100 gene family.

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Alterations in the expression of SPRRPs (A and C), repetin (B), and of filaggrin (D) in Lor−/− mice. RPA and Western blot analysis were done with littermates from lor+/− intercrosses. (A) RPA analysis of SPRRP expression in the back skin epidermis of E17.5 embryos, newborn, and 4-d-old pups. The genotypes of the animals are indicated above the lanes. β-Actin, cyclophilin, and desmoglein 3 (Dsg3; Koch et al. 1997) probes were used as internal standards. Note that the expression of SPRRP2D and SPRRP2H was increased at all time points examined (for details see text). (B) RPA analysis of repetin expression in the back skin of E17.5 embryos, newborn, and 4-d-old mice. Cyclophilin was used as an internal standard. The expression of repetin was increased in Lor−/− mice at all time points (see text for details). Note that the repetin probe produces two bands, most likely due to a polymorphism in the repetin gene. (C) RPA analysis of SPRRP2H expression in the back skin epidermis of E16.5 embryos. Note similar expression levels in mutant and wild-type mice. (D) Western blot analysis of protein extracts from newborn back skin with antibodies f111 and f133. The genotypes of the animals are indicated above the lanes. An additional profilaggrin band was detected in extracts from Lor−/− mice (arrows). Note that f133 indicates a reduction in the amount of mature filaggrin (Fil.) in Lor−/− mice.
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Figure 7: Alterations in the expression of SPRRPs (A and C), repetin (B), and of filaggrin (D) in Lor−/− mice. RPA and Western blot analysis were done with littermates from lor+/− intercrosses. (A) RPA analysis of SPRRP expression in the back skin epidermis of E17.5 embryos, newborn, and 4-d-old pups. The genotypes of the animals are indicated above the lanes. β-Actin, cyclophilin, and desmoglein 3 (Dsg3; Koch et al. 1997) probes were used as internal standards. Note that the expression of SPRRP2D and SPRRP2H was increased at all time points examined (for details see text). (B) RPA analysis of repetin expression in the back skin of E17.5 embryos, newborn, and 4-d-old mice. Cyclophilin was used as an internal standard. The expression of repetin was increased in Lor−/− mice at all time points (see text for details). Note that the repetin probe produces two bands, most likely due to a polymorphism in the repetin gene. (C) RPA analysis of SPRRP2H expression in the back skin epidermis of E16.5 embryos. Note similar expression levels in mutant and wild-type mice. (D) Western blot analysis of protein extracts from newborn back skin with antibodies f111 and f133. The genotypes of the animals are indicated above the lanes. An additional profilaggrin band was detected in extracts from Lor−/− mice (arrows). Note that f133 indicates a reduction in the amount of mature filaggrin (Fil.) in Lor−/− mice.

Mentions: The fast regeneration of the Lor−/− epidermis with normal TEWL shortly after birth and the disappearance of the phenotype by day 4 or 5, suggested a compensatory mechanism that was induced either in utero or immediately after birth. The fact that the CE of newborn Lor−/− mice was of normal thickness (Jarnik, M., P.A. de Viragh, D. Bundman, M. Simon, D.R. Roop, and A.C. Stevens, manuscript submitted for publication), but abnormal structure, further supported the idea that another CE component was compensating for the loss of loricrin. Therefore, we compared the expression levels of several known CE components in E16.5 and E17.5 embryos, newborn, and 4-d-old Lor−/− and Lor+/+ mice. We found an increase in the expression of repetin and two members of the SPRRPs protein family in Lor−/− epidermis at all time points examined (Fig. 7a and Fig. b), except for E16.5. At E16.5, we did not obtain detectable signals with the repetin and SPRRP2D probe, respectively. The SPRRP2H probe, however, gave reproducible signals. The expression levels of this gene were identical in Lor−/− and wild-type mice at E16.5 (Fig. 7 C).


Lessons from loricrin-deficient mice: compensatory mechanisms maintaining skin barrier function in the absence of a major cornified envelope protein.

Koch PJ, de Viragh PA, Scharer E, Bundman D, Longley MA, Bickenbach J, Kawachi Y, Suga Y, Zhou Z, Huber M, Hohl D, Kartasova T, Jarnik M, Steven AC, Roop DR - J. Cell Biol. (2000)

Alterations in the expression of SPRRPs (A and C), repetin (B), and of filaggrin (D) in Lor−/− mice. RPA and Western blot analysis were done with littermates from lor+/− intercrosses. (A) RPA analysis of SPRRP expression in the back skin epidermis of E17.5 embryos, newborn, and 4-d-old pups. The genotypes of the animals are indicated above the lanes. β-Actin, cyclophilin, and desmoglein 3 (Dsg3; Koch et al. 1997) probes were used as internal standards. Note that the expression of SPRRP2D and SPRRP2H was increased at all time points examined (for details see text). (B) RPA analysis of repetin expression in the back skin of E17.5 embryos, newborn, and 4-d-old mice. Cyclophilin was used as an internal standard. The expression of repetin was increased in Lor−/− mice at all time points (see text for details). Note that the repetin probe produces two bands, most likely due to a polymorphism in the repetin gene. (C) RPA analysis of SPRRP2H expression in the back skin epidermis of E16.5 embryos. Note similar expression levels in mutant and wild-type mice. (D) Western blot analysis of protein extracts from newborn back skin with antibodies f111 and f133. The genotypes of the animals are indicated above the lanes. An additional profilaggrin band was detected in extracts from Lor−/− mice (arrows). Note that f133 indicates a reduction in the amount of mature filaggrin (Fil.) in Lor−/− mice.
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Figure 7: Alterations in the expression of SPRRPs (A and C), repetin (B), and of filaggrin (D) in Lor−/− mice. RPA and Western blot analysis were done with littermates from lor+/− intercrosses. (A) RPA analysis of SPRRP expression in the back skin epidermis of E17.5 embryos, newborn, and 4-d-old pups. The genotypes of the animals are indicated above the lanes. β-Actin, cyclophilin, and desmoglein 3 (Dsg3; Koch et al. 1997) probes were used as internal standards. Note that the expression of SPRRP2D and SPRRP2H was increased at all time points examined (for details see text). (B) RPA analysis of repetin expression in the back skin of E17.5 embryos, newborn, and 4-d-old mice. Cyclophilin was used as an internal standard. The expression of repetin was increased in Lor−/− mice at all time points (see text for details). Note that the repetin probe produces two bands, most likely due to a polymorphism in the repetin gene. (C) RPA analysis of SPRRP2H expression in the back skin epidermis of E16.5 embryos. Note similar expression levels in mutant and wild-type mice. (D) Western blot analysis of protein extracts from newborn back skin with antibodies f111 and f133. The genotypes of the animals are indicated above the lanes. An additional profilaggrin band was detected in extracts from Lor−/− mice (arrows). Note that f133 indicates a reduction in the amount of mature filaggrin (Fil.) in Lor−/− mice.
Mentions: The fast regeneration of the Lor−/− epidermis with normal TEWL shortly after birth and the disappearance of the phenotype by day 4 or 5, suggested a compensatory mechanism that was induced either in utero or immediately after birth. The fact that the CE of newborn Lor−/− mice was of normal thickness (Jarnik, M., P.A. de Viragh, D. Bundman, M. Simon, D.R. Roop, and A.C. Stevens, manuscript submitted for publication), but abnormal structure, further supported the idea that another CE component was compensating for the loss of loricrin. Therefore, we compared the expression levels of several known CE components in E16.5 and E17.5 embryos, newborn, and 4-d-old Lor−/− and Lor+/+ mice. We found an increase in the expression of repetin and two members of the SPRRPs protein family in Lor−/− epidermis at all time points examined (Fig. 7a and Fig. b), except for E16.5. At E16.5, we did not obtain detectable signals with the repetin and SPRRP2D probe, respectively. The SPRRP2H probe, however, gave reproducible signals. The expression levels of this gene were identical in Lor−/− and wild-type mice at E16.5 (Fig. 7 C).

Bottom Line: The epidermal cornified cell envelope (CE) is a complex protein-lipid composite that replaces the plasma membrane of terminally differentiated keratinocytes.Tape stripping experiments suggested that the stratum corneum stability was reduced in newborn Lor(-/-) mice compared with wild-type controls.Isolated mutant CEs were more easily fragmented by sonication in vitro, indicating a greater susceptibility to mechanical stress.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.

ABSTRACT
The epidermal cornified cell envelope (CE) is a complex protein-lipid composite that replaces the plasma membrane of terminally differentiated keratinocytes. This lamellar structure is essential for the barrier function of the skin and has the ability to prevent the loss of water and ions and to protect from environmental hazards. The major protein of the epidermal CE is loricrin, contributing approximately 70% by mass. We have generated mice that are deficient for this protein. These mice showed a delay in the formation of the skin barrier in embryonic development. At birth, homozygous mutant mice weighed less than control littermates and showed skin abnormalities, such as congenital erythroderma with a shiny, translucent skin. Tape stripping experiments suggested that the stratum corneum stability was reduced in newborn Lor(-/-) mice compared with wild-type controls. Isolated mutant CEs were more easily fragmented by sonication in vitro, indicating a greater susceptibility to mechanical stress. Nevertheless, we did not detect impaired epidermal barrier function in these mice. Surprisingly, the skin phenotype disappeared 4-5 d after birth. At least one of the compensatory mechanisms preventing a more severe skin phenotype in newborn Lor(-/-) mice is an increase in the expression of other CE components, such as SPRRP2D and SPRRP2H, members of the family of "small proline rich proteins", and repetin, a member of the "fused gene" subgroup of the S100 gene family.

Show MeSH
Related in: MedlinePlus