Involucrin–claudin-6 tail deletion mutant (CΔ206) transgenic mice: a model of delayed epidermal permeability barrier formation and repair

Abstract

SUMMARY Preterm birth is a major global health problem that results in a large number of infant deaths, many of which are attributable to the complications of an immature epidermal permeability barrier (EPB), for which there is currently no effective therapeutic option. The mammalian EPB is formed during development and is essential for survival as it maintains thermoregulation and hydration, and provides a defense against infection. Using transgenic mouse technology, we have demonstrated the importance of claudin (Cldn)-containing tight junctions (TJs) in epidermal differentiation and, in particular, that epidermal suprabasal overexpression of Cldn6 results in an EPB-deficient phenotype that phenocopies the dysfunctional EPB of premature human infants. In this study, we used the same approach to target a Cldn6 tail deletion mutant to the epidermis of mice [involucrin (Inv)-Cldn6-CΔ206 transgenic mice]. The Inv-Cldn6-CΔ206 transgenic mice displayed a developmental delay in EPB formation, as shown by the expression of keratins and Cldns, and by X-Gal penetration assays. Trans-epidermal water loss measurements and immunolocalization studies indicated that the epidermal differentiation program was also perturbed in postnatal Inv-Cldn6-CΔ206 transgenic mice resulting in a delayed maturation. Notably, however, expression/localization of epidermal differentiation and maturation markers, including Cldns, indicated that the transgenic epidermis matured and normalized by postnatal day 10, which is 3 days after the wild-type epidermis. Our results suggest that activation of the extracellular signal-regulated kinase 1/2 (Erk1/2) pathway and Cldn1 phosphorylation are associated with the repair and maturation of the skin barrier processes. These studies provide additional support for the crucial role of Cldns in epidermal differentiation, maturation and the formation of the EPB, and describe a novel animal model for evaluating postnatal epidermal maturation and therapies that may accelerate the process.

Time- and dose-dependent claudin contribution to biological functions: Lessons from claudin-1 in skin

“…7 Studies using the other claudin-6 mutated transgenic mouse also highlighted the importance of specific claudins' characteristics to in vivo phenotype. 8,9 However, even in the epidermis, how claudin orchestrates its many effects is poorly understood. Recently, the crystal structures of claudin-4, -15, and -19 were reported; these studies suggested the structural basis for the molecules that create the TJ paracellular barriers and channels, and other claudin functions.…”

Suprabasin-null mice retain skin barrier function and show high contact hypersensitivity to nickel upon oral nickel loading

“…Another group of investigators also reported that SBSN deficiency is one of the factors related to AD pathogenesis 4 . Similarly to knockout mice for the other epidermal differentiationassociated proteins [24][25][26][27] , Sbsn -/mice were viable and healthy, without apparent growth restriction. Sbsn -/mice did not show any of the crucial features of typical (extrinsic) AD, including skin barrier dysfunction and high transcutaneous responses.…”

CLDN6: From Traditional Barrier Function to Emerging Roles in Cancers

“…Preterm birth is a major global health problem that causes a large number of infant deaths, many of which can be attributed to complications of immature EPB [42]. An integral EPB in premature birth is crucial for maintaining temperature stability, preventing microbial infection through the skin.…”

“…The skin of 2-week-old mice overexpressing a shorter deletion in the cytoplasmic tail domain of Cldn6 (Inv-Cldn6-C∆196) have striking histological abnormalities compared with the wild-type, as evidenced by epidermal hyperplasia and hyperkeratosis, which is similar to the skin of Inv-Cldn6 and Inv-Cldn6-C∆187 mice [45]. Mice expressing Cldn6 with a shorter tail deletion (Inv-Cldn6-C∆206) possess a distinct developmental defect in epidermal differentiation resulting in EPB formation delays [42]. The above mutants of CLDN6 lead to its cytoplasmic localization while affecting the expression and localization of other CLDNs, such as CLDN5, 8, 10, 11, 12, and 18, emphasizing the importance of the CLDN6 tail domain for membrane targeting and suggesting that the CLDN6 tail domain is essential for CLDNs homeostasis and EPB formation.…”