Search

Dermokine is a chiefly skin-specific secreted glycoprotein localized in the upper epidermis, and its family consists of three splice variants in mice and five in humans. To investigate the pathophysiological impact of dermokine, we generated mice deficient for two (βγ) or all dermokine isoforms (αβγ). Both variants, especially dermokine αβγ-deficient mice exhibited scale and wrinkle formation resembling ichthyosis accompanied by transepidermal water imbalance at the neonatal stage. Several dermokine αβγ-deficient mice died by postnatal day 21 when reared under low humidity. Moreover, the cornified envelope was vulnerable, and skin barrier lipid ceramides were reduced in the epidermis of dermokine αβγ-deficient mice. cDNA microarray and quantitative reverse transcriptase-PCR assays of the epidermis revealed the upregulation of small proline-rich protein and late cornified envelope family members, as well as antimicrobial peptides in the dermokine αβγ-deficient mice. These barrier gene signatures were similar to that seen in psoriasis, whereas recent studies demonstrated that congenital ichthyosis has gene profiles resembling psoriasis. In line with these findings, adult dermokine αβγ-deficient mice exhibited aggravated phenotypes in psoriasis-like dermatitis models but not in allergic dermatitis models. Dermokine may play a regulatory role in inflammatory dyskeratotic diseases, such as congenital ichthyosis and psoriasis, in the crosstalk between barrier dysfunction and inflammation., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

The extracellular matrix protein 1 (ECM1) is a secreted glycoprotein, which plays an important role in the structural and functional biology of the skin as demonstrated by the identification of loss-of-function mutations in ECM1 as cause of the genodermatosis lipoid proteinosis, characterized by reduplication of the skin basement membrane and hyalinization of the underlying dermis. To search for binding partner(s) of ECM1, we tested the in vitro binding activity of ECM1a, a major isoform of four ECM1 splice variants, to different skin extracellular matrix proteins (such as laminin 332, collagen type IV, and fibronectin) and polysaccharides (such as hyaluronan, heparin, and chondroitin sulfate A) with solid-phase binding assay. We demonstrated that ECM1a utilizes different regions to bind to a variety of extracellular matrix components. Ultrastructurally, ECM1 is a basement membrane protein in human skin and is part of network-like suprastructures containing perlecan, collagen type IV, and laminin 332 as constituents. Furthermore, ECM1a enhanced the binding of collagen IV to laminin 332 dose-dependently, showing its involvement in the dermal-epidermal junction and interstitial dermis and making the functional link to the pathophysiology of lipoid proteinosis. To our knowledge, this is previously unreported.

Adamantiades-Behcet's disease (ABD) is a chronic inflammatory multisystem disorder. Although the precise etiology is unclear, high prevalence of human leukocyte antigen (HLA)-B51 predisposition and predominantly involved T-helper type 1 cells (Th1)-type proinflammatory cytokines and extrinsic Streptococcal infection suggest a substantial association with an immunogenetic basis and strengthens the hypothesis that IL-12, a potent inducer of Th-1 immune reaction, is a putative candidate in its pathogenesis. These clinicopathological findings led us to examine interleukin 12 p40 (IL-12B) promoter polymorphism, for which the 4-base pair (bp) heterozygous insertion has been shown to affect the gene transcription and subsequent protein production. We analyzed IL-12B promoter genotypes in 194 Japanese subjects (92 with ABD and 102 normal controls) by PCR-based restriction enzyme digestion. The frequency of the insertion heterozygosity was significantly higher in patients than in controls (49/92, 53.3% vs 39/102, 38.2%, respectively). Comparing these with HLA haplotype data, this trend was more significant in HLA-B51-negative patients (29/42, 69.0% vs 20/50, 40.0%; P = 0.005). As assessed by semiquantitative reverse transcription-PCR and ELISA, stimulation with Streptococcal antigens specifically increased expression of IL-12 p40 mRNA and protein, in conjunction with IL-12 p70 induction, in peripheral blood mononuclear cells from heterozygous patients. Our results provide evidence for anti-bacterial host response toward Th1-immunity mediated by IL-12 in patients with ABD, and the possible insight into the genetic susceptibility that is independent of HLA background.

Kindler syndrome (OMIM 173650) is a rare autosomal recessive disorder characterized by trauma-induced blister formation (especially in childhood) and photosensitivity. Other features include mucocutaneous scarring and progressive poikiloderma. There is also an increased risk of skin and mucous membrane malignancy. The disorder was recently mapped to 20p12.3 and pathogenic mutations were identified in a new gene, KIND1. This gene encodes a 677 amino acid protein, kindlin-1, a component of focal contacts in keratinocytes. In this study, we identified four new recurrent mutations in KIND1 in 16 individuals with Kindler syndrome from 13 families of Pakistani (676insC), UK Caucasian (E304X), Omani (W616X), or Italian (958-1G > A) origins. Haplotype analysis demonstrated common ancestral mutant alleles for each mutation, apart from one of the six Pakistani families in which the mutation 676insC (which occurs in a repeat of seven cytosines) was present on a different genetic background. All mutations were homozygous, apart from the three UK Caucasian cases that were all compound heterozygotes (second allele mutations: L302X, 1161delA, 1909delA). All mutations were associated with markedly reduced or absent skin immunostaining with an antikindlin-1 antibody. These loss-of-function KIND1 mutations demonstrate the importance of kindlin-1 in maintaining epithelial integrity, although the mechanism linking this mutant protein to photosensitivity and poikiloderma remains to be determined. Delineation of these recurrent mutations is also relevant to optimizing mutation detection strategies in Kindler syndrome patients from particular ethnic backgrounds.

The autosomal recessive disorder lipoid proteinosis results from mutations in extracellular matrix protein 1 (ECM1), a glycoprotein expressed in several tissues (including skin) and composed of two alternatively spliced isoforms, ECM1a and ECM1b, the latter lacking exon 7 of this 10-exon gene (ECM1). To date, mutations that either affect ECM1a alone or perturb both ECM1 transcripts have been demonstrated in six cases. However, lipoid proteinosis is clinically heterogeneous with affected individuals displaying differing degrees of skin scarring and infiltration, variable signs of hoarseness and respiratory distress, and in some cases neurological abnormalities such as temporal lobe epilepsy. In this study, we sequenced ECM1 in 10 further unrelated patients with lipoid proteinosis to extend genotype-phenotype correlation and to add to the mutation database. We identified seven new homozygous nonsense or frameshift mutations: R53X (exon 3); 243delG (exon 4); 507delT (exon 6); 735delTG (exon 7); 785delA (exon 7); 892delC (exon 7) and 1190insC (exon 8), as well as two new compound heterozygous mutations: W160X/F167I (exon 6) and 542insAA/R243X (exons 6/7), none of which were found in controls. The mutation 507delT occurred in two unrelated subjects on different ECM1 haplotypes and may therefore represent a recurrent mutation in lipoid proteinosis. Taken with the previously documented mutations in ECM1, this study supports the view that exons 6 and 7 are the most common sites for ECM1 mutations in lipoid proteinosis. Clinically, it appears that mutations outside exon 7 are usually associated with a slightly more severe mucocutaneous lipoid proteinosis phenotype, but neurological features do not show any specific genotype-phenotype correlation.

X-linked ichthyosis is caused by steroid sulfatase deficiency which results from abnormalities in its coding gene. The majority of X-linked ichthyosis patients ( approximately 90%) have complete or partial deletions of the steroid sulfatase gene. In this study, we examined the mutations of the steroid sulfatase gene in two unrelated X-linked ichthyosis patients without complete deletion of the gene. Polymerase chain reaction-single-strand conformation polymorphism and direct sequencing analyses showed that each patient has a different single base pair substitution within exon 8 encoding the C-terminal half of the steroid sulfatase polypeptide. Both mutations resulted in the transversion of functional amino acids: a G-->C substitution at nucleotide 1344, causing a predicted change of a glycine to an arginine, and a C-->T substitution at nucleotide 1371, causing a change from a glutamine to a stop codon. In vitro steroid sulfatase cDNA expression using site-directed mutagenesis revealed that these mutations are in fact pathogenic and reflect the levels of steroid sulfatase enzyme activities in each of the X-linked ichthyosis patients.

Activator protein-2 is an important transcription factor for the activation of a number of genes. Here we report the induction of activator protein-2 in response to inflammatory cytokines such as interleukin-6 in keratinocytes. Immunoblotting and semiquantitative reverse transcriptase-polymerase chain reaction assays using normal human keratinocytes revealed that interleukin-6 caused a time- and concentration-dependent induction of activator protein-2 mRNA and protein. The increase of activator protein-2 mRNA was detected at 30 min after stimulation and that of activator protein-2 protein was at 2 h. Their levels were lower than the control levels at 24 h. The interleukin-6-dependent induction of activator protein-2 mRNA was completely blocked by adding actinomycin D, whereas it was approximately 50% affected by cycloheximide. Co-incubation with neutralizing antibodies against various inflammatory cytokines resulted in inhibition of the interleukin-6-dependent activator protein-2 induction at varying degrees, indicating an involvement of various cytokines in the activator protein-2 induction. The activator protein-2 induction was observed in keratinocytes derived from lesional skins with psoriasis or squamous cell carcinoma, and the high levels of activator protein-2 were histochemically detected in these lesions. Furthermore, a gel mobility shift assay using the nuclear extracts from interleukin-6-treated cells showed that interleukin-6 induced the functional activator protein-2 protein for the gene activation. These findings suggest a possible regulation mechanism of activator protein-2 through a complex cytokine system, which is conceivably the initial reaction leading to skin inflammation, and resultant keratinocyte growth and carcinogenesis.