Daisuke Sawamura

Extracellular cleavage of collagen XVII is essential for correct cutaneous basement membrane formation

In skin, basal keratinocytes in the epidermis are tightly attached to the underlying dermis by the basement membrane (BM). The correct expression of hemidesmosomal and extracellular matrix (ECM) proteins is essential for BM formation, and the null-expression of one molecule may induce blistering diseases associated with immature BM formation in humans. However, little is known about the significance of post-translational processing of hemidesmosomal or ECM proteins in BM formation. Here we show that the C-terminal cleavage of hemidesmosomal transmembrane collagen XVII (COL17) is essential for correct BM formation. The homozygous p.R1303Q mutation in COL17 induces BM duplication and blistering in humans. Although laminin 332, a major ECM protein, interacts with COL17 around p.R1303, the mutation leaves the binding of both molecules unchanged. Instead, the mutation hampers the physiological C-terminal cleavage of COL17 in the ECM. Consequently, non-cleaved COL17 ectodomain remnants induce the aberrant deposition of laminin 332 in the ECM, which is thought to be the major pathogenesis of the BM duplication that results from this mutation. As an example of impaired cleavage of COL17, this study shows that regulated processing of hemidesmosomal proteins is essential for correct BM organization in skin.

Atopic diathesis in hypohidrotic/anhidrotic ectodermal dysplasia.

Recently, patients with hypohidrotic/anhidrotic ectodermal dysplasia (H/AED) have been reported to have a higher prevalence of symptoms suggestive of atopic disorders than the general population. To better understand atopic diathesis in H/AED, 6 cases of clinically or genetically diagnosed H/AED were examined. The following criteria were evaluated with patient consent: sweating, blood test results, histopathology and filaggrin staining. Five of 6 H/AED cases displayed atopic dermatitis-like manifestations, and 3 of these 5 cases experienced periorbital lesions. H/AED patients tended to present with atopic dermatitis-like eruptions with characteristics potentially indicative of periorbital lesions. Atopic diathesis in H/AED appeared not to be associated with filaggrin. We could speculate that hypohidrosis or anhidrosis itself might impair skin barrier function and contribute to atopic diathesis.

Two Japanese familial cases of punctate palmoplantar keratoderma caused by a novel AAGAB mutation, c.191_194delCAAA

o Japanese familial cases of punctate lmoplantar keratoderma caused by a vel AAGAB mutation, c.191_194delCAAA the pressure-bearing areas of the plantar skin [1,2]. Recently, two consecutive studies identified that PPPK1 was caused by mutations in the AAGAB gene, encoding alphaand gamma-adaptin binding protein p34 (p34) [1,2]. Subsequently, several AAGAB mutations were reported in PPPK1 families from Europe, the Middle East, and Asia [1–8]. Here, we describe two Japanese PPPK1 pedigrees harboring the same, novel AAGAB mutation. This work was conducted in accordance with the Declaration of Helsinki ywords: lmoplantar keratoderma;

Oral lichen planus with antibodies to desmogleins 1 and 3

Lichen planus (LP) is a chronic inflammatory disorder involving the skin or mucous membranes. Previous studies have demonstrated that some LP patients showed positive enzyme‐linked immunosorbent assay (ELISA) for desmoglein (DSG) antibodies. We report a case with intractable painful oral lesions. ELISA indices for DSG1 and 3 antibodies were increased by 49 and 36, respectively. Histopathological analysis revealed irregular acanthosis and band‐like infiltration of lymphocytes at the dermal–epidermal interface. Direct immunofluorescence revealed negative deposits of immunoglobulin G and C3 in intracellular spaces of the epidermis. Indirect immunofluorescence of normal skin also did not detect any antibodies. Consequently, we made a final diagnosis of oral LP. The previous two LP cases with positive ELISA for DSG antibodies and our case manifested the erosive form, the most advanced oral LP. Therefore, it is a possibility that severe damage of keratinocytes may induce generation of DSG antibodies. However, negative results of immunofluorescence and no relation between disease severity and titers of antibodies make the possibility unlikely. We should measure titers of DSG antibodies in LP patients and accumulate data to establish a valid conclusion.

Case of pachydermoperiostosis with solute carrier organic anion transporter family, member 2A1 (SLCO2A1) mutations

1 Kere J, Srivastava AK, Montonen O et al. X-linked anhidrotic (hypohidrotic) ectodermal dysplasia is caused by mutation in a novel transmembrane protein. Nat Genet 1996; 13: 409–416. 2 Gunadi , Miura K, Ohta M et al. Two novel mutations in the ED1 gene in Japanese families with X-linked hypohidrotic ectodermal dysplasia. Pediatr Res 2009; 65: 453–457. 3 Koguchi-Yoshioka H, Wataya-Kaneda M, Yutani M et al. Atopic diathesis in hypohidrotic/anhidrotic ectodermal dysplasia. Acta Derm Venereol 2015; 95: 476–479. 4 Dietz J, Kaercher T, Schneider AT et al. Early respiratory and ocular involvement in X-linked hypohidrotic ectodermal dysplasia. Eur J Pediatr 2013; 172: 1023–1031.

Functional analysis of the nuclear localization signal of the POU transcription factor Skn‑1a in epidermal keratinocytes

POU domain proteins are a family of critical regulators of development and differentiation due to their transcriptional activity in the nucleus. Skn‑1a, a member of the POU domain protein family, appears to be expressed predominantly in epidermal keratinocytes and is thought to play a critical role in keratinocyte differentiation and proliferation. In this study, we examined the mechanisms involved in the nuclear localization of Skn‑1a. We transiently expressed enhanced green fluorescent protein (EGFP) reporter constructs encoding EGFP fusions with Skn‑1a deletion and mutation proteins in normal human epidermal keratinocytes (NHEKs). The experiments clearly demonstrated that Skn‑1a contained a functional nuclear localization signal (NLS) domain, and that the smallest domain necessary for Skn‑1a nuclear transport was the GRKRKKR sequence located within amino acids 279‑285. Previous studies have shown that the phosphorylation of specific amino acids neighboring the NLS may regulate nuclear transport and that the amino acid residues threonine (Thr) and serine (Ser) have the potential to undergo phosphorylation. We examined whether the amino acids Thr286 and Ser287, which reside adjacent to the NLS at the carboxy‑terminal side, play a role in Skn‑1a nuclear localization. For this purpose, we generated three EGFP‑Skn‑1a mutation constructs, in which Thr286, Ser287, or both Thr286 and Ser287 residues were replaced with alanine, respectively. The results showed that the Thr286 and Ser287 residues were involved in the regulation of nuclear localization as well as epidermal differentiation. These results suggested that the epidermal differentiation signaling pathway, involving kinase and phosphatase activation, may regulate the NLS activity of Skn‑1a in keratinocytes. Collectively, these data contribute to understanding the mechanisms of nuclear translocation of POU domain proteins and epidermal differentiation.

Squamous cell carcinoma on the lip arising from discoid lupus erythematosus: a case report and review of Japanese patients

Squamous cell carcinoma (SCC) is a rare but well-recognized complication of longstanding discoid lupus erythematosus (DLE). Although few epidemiological studies concerning DLE-related SCCs in Japan exist, it has been estimated that the incidence of SCC arising in DLE lesions reaches 3.3%, which is similar to that reported for Caucasians (2.3% to 3.3%) [1,xa02]. SCC is relatively rare in Japan, and its incidence of 2.5/100,000 person-years [3] is much lower than that in Caucasians (22.65/100,000 [...]

A Palindromic Motif in the -2084 to -2078 Upstream Region is Essential for ABCA12 Promoter Function in Cultured Human Keratinocytes

ATP-binding cassette transporter family A member 12 (ABCA12) is a keratinocyte transmembrane lipid transporter that plays a critical role in preserving the skin permeability barrier. Biallelic loss of function of the ABCA12 gene is causative of some forms of recessive congenital ichthyosis, an intractable disease marked by dry, thickened and scaly skin on the whole body. Genetic diagnosis is essential, although the results may occasionally be inconclusive, because some patients with low ABCA12 expression have one mutant allele and one apparently intact allele. Aside from aberrant splicing or deletion mutations, one possible explanation for such discrepancy is loss of promoter function. This study aims to elucidate the promoter region of ABCA12 and to locate the essential elements therein, thus providing the necessary information for genetic diagnostic screening of congenital ichthyosis. Close examination of the 2980-bp upstream regions of the ABCA12 gene revealed that a palindromic motif (tgagtca) at −2084 to −2078 is essential for the promoter function, and a short fragment of −2200/−1934 alone has potent promoter activity. Identification of the key promoter element of ABCA12 in this study may provide relevant information for genetic diagnosis of recessive congenital ichthyosis.

Mycosis fungoides bullosa associated with bullous pemphigoid

recent primary infection, whereas the presence of a highavidity antibody indicates a past or recurrent infection. Moreover, during active infections, HHV-6 and HHV7 may cross-react. An IgM response to HHV-7 primary infection, therefore, may also be directed to HHV-6 with a reciprocal rising in antibody titer to both viruses. In neonates, maternal IgGs, which may persist to up to six months of age, interfere with the diagnosis of both HHV-6 and HHV-7 infections. Therefore, in the presence of symptoms compatible with primary HHV-6 infection during the first months, such as seizures accompanied by a cutaneous rash, the diagnosis may need, in addition to the detection of specific IgM, quantitative PCR testing. After primary infection, HHV-6 and HHV-7 remain latent in the body mostly in the salivary glands. Serologic assays cannot be sufficient to diagnose viral reactivations, and direct methods like PCR are preferred. Among the latter, however, the detection of the viral genome is not synonymous of active infection and only bona fide quantitative methods, which measure the HHV-6 and HHV-7 viral load in tissues, blood cells and, particularly, plasma and serum, are diagnostic, also permitting the follow-up of the active infection and suggesting a causal link. In addition, in diseases such as pityriasis rosea, which are most probably associated with the active replication of either or both HHV-6 and HHV-7, quantitative PCR assays may detect only one virus depending on the particular phase of the disease. In pityriasis rosea, HHV-7 behavior is unique. It replicates before HHV-6, but its replication tends to cease in the advanced phases. Another issue that involves quantitative methods is the possibility of chromosomal integration (ci) of HHV-6 that complicates the interpretation of a high viral load. In fact, subjects carrying ciHHV-6 present with high levels of HHV DNA in plasma, which, however, persist over time. In these cases, comparisons of the effects of viral loads on multiple fluids and tissues, together with methods that detect the expression of HHV-6 genes associated with a productive infection and measures of lytic antigens in blood cells, may help to distinguish an active infection from a ciHHV-6 state. Lastly, immunohistochemistry can detect viral antigens expressed only during a given moment in the virus replication cycle, thereby indicating the status of the infection.

Anti-laminin γ1 pemphigoid associated with ulcerative colitis and psoriasis vulgaris showing autoantibodies to laminin γ1, type XVII collagen and laminin-332.

Anti-laminin γ1 pemphigoid is a novel autoimmune subepidermal bullous disease characterized by the presence of circulating immunoglobulin (Ig) G autoantibodies to laminin γ1, a common constituent at various basement membrane zones (BMZs). Although an association between various subepidermal blistering diseases and inflammatory bowel disease (IBD) has been reported, there have been no previous reports on an association between anti-laminin γ1 pemphigoid and IBD. Here, we demonstrate a case of anti-laminin [...]