Late cornified envelope (LCE) proteins: distinct expression patterns of LCE2 and LCE3 members suggest nonredundant roles in human epidermis and other epithelia.

BACKGROUND: Deletion of the late cornified envelope (LCE) proteins LCE3B and LCE3C is a strong and widely replicated psoriasis risk factor. It is amenable to biological analysis because it precludes the expression of two epidermis-specific proteins, rather than being a single-nucleotide polymorphism of uncertain significance. The biology of the 18-member LCE family of highly homologous proteins has remained largely unexplored so far. OBJECTIVES: To analyse LCE3 expression at the protein level in human epithelia, as a starting point for functional analyses of these proteins in health and disease. METHODS: We generated the first pan-LCE3 monoclonal antibody and provide a detailed analysis of its specificity towards individual LCE members. LCE2 and LCE3 expression in human tissues and in reconstructed human skin models was studied using immunohistochemical analyses and quantitative polymerase chain reaction. RESULTS: Our study reveals that LCE2 and LCE3 proteins are differentially expressed in human epidermis, and colocalize only in the upper stratum granulosum layer. Using an in vitro reconstructed human skin model that mimics epidermal morphogenesis, we found that LCE3 proteins are expressed at an early time point during epidermal differentiation in the suprabasal layers, while LCE2 proteins are found only in the uppermost granular layer and stratum corneum. CONCLUSIONS: Based on the localization of LCE2 and LCE3 in human epidermis we conclude that members of the LCE protein family are likely to have distinct functions in epidermal biology. This finding may contribute to understanding why LCE3B/C deletion increases psoriasis risk.

Paediatric-onset psoriasis is associated with ERAP1 and IL23R loci, LCE3C_LCE3B deletion and HLA-C*06.

BACKGROUND: Recent genome-wide association studies have identified several genetic risk factors for psoriasis, but data on their association with age at onset are lacking. OBJECTIVES: To compare the association between known risk alleles and psoriasis in well-defined cohorts with paediatric- and adult-onset psoriasis. METHODS: Based on previous studies we selected seven genes and loci associated with psoriasis. Patients with paediatric-onset (< 18 years) and adult-onset psoriasis (≥ 18 years) and controls were genotyped. Genotype frequencies were compared between controls (n = 450) and all cases (n = 217), and between controls and cases stratified for confirmed age at onset (paediatric onset n = 80, adult onset n = 85). RESULTS: Paediatric-onset psoriasis showed a significant association with single nucleotide polymorphisms in the ERAP1 (P = 0.042) and IL23R loci (P = 0.042), LCE3C_LCE3B-del (P = 0.003) and HLA-C*06 (P = 1.72 × 10(-19)) when compared with the control group. A significant association of these four genes was also demonstrated when all psoriasis cases were compared with controls. In adult-onset psoriasis a significant association was found for HLA-C*06 (P = 5.11 × 10(-6)) and for LCE3C_LCE3B-del (P = 0.042). No associations were found for the IFIH1, IL12B and TRAF3IP2 loci. CONCLUSIONS: Notwithstanding the small cohort sizes, we demonstrated an association with established and recently discovered genetic risk factors in paediatric-onset psoriasis including genes involved in epidermal barrier function and adaptive immunity. Our data suggest that heritable factors may play a more important role in paediatric-onset psoriasis than in adult-onset psoriasis.

Expression profile of cornified envelope structural proteins and keratinocyte differentiation-regulating proteins during skin barrier repair.

BACKGROUND: Recent studies have emphasized the importance of heritable and acquired skin barrier abnormalities in common inflammatory diseases such as psoriasis and atopic dermatitis (AD). To date, no comprehensive studies on the effect of experimental barrier disruption on cornified envelope protein expression have been performed. OBJECTIVES: To analyse the effect of experimental skin barrier disruption on the expression of cornified envelope structural proteins and keratinocyte differentiation-regulating proteins. METHODS: We examined mRNA (day 1, 3 and 7) and protein (day 1, 2, 4 and 9) expression levels of structural proteins and regulatory molecules after sodium dodecyl sulphate (SDS) application on normal skin, and tape stripping of uninvolved epidermis of patients with psoriasis and AD and healthy controls. RESULTS: Upon tape stripping, several structural molecules were significantly downregulated (at the mRNA level as well as the protein level), including LCE5A, LCE2B, FLG, FLG2 and LOR, whereas others were upregulated: IVL, SPRR1, SPRR2, HRNR and most notably LCE3A. The epidermal crosslinking enzymes TGM1, TGM3 and TGM5 were all upregulated, whereas proteases involved in the desquamation process (CTSV, KLK5 and KLK7) were downregulated or unaffected. Most results were similar in SDS-instigated irritant contact dermatitis. There was no significant difference in response between normal epidermis and nonlesional skin of patients with psoriasis and AD. CONCLUSIONS: Skin barrier disruption induces a temporary barrier repair response composed of increased expression of several cornification-related proteins, and decreased expression of some structural and desquamation-related proteins.