Deep intronic founder mutations identified in the ERCC4/XPF gene are potential therapeutic targets for a high-frequency form of xeroderma pigmentosum.

Xeroderma pigmentosum (XP) is a genodermatosis defined by cutaneous photosensitivity with an increased risk of skin tumors because of DNA repair deficiency. The worldwide prevalence of XP is ~1 to 4 in million, with higher incidence in some countries and regions including Japan (1 in 22,000) and North Africa due to founder mutations and a high degree of consanguinity. Among XP, the complementation group F (XP-F), is a rare form (1% of worldwide XP); however, this is underdiagnosed, because the ERCC4/XPF gene is essential for fetal development and most of previously reported ERCC4/XPF pathogenic variants are hypomorphs causing relatively mild phenotypes. From the largest Japanese XP cohort study, we report 17 XP-F cases bearing two pathogenic variants, both identified in deep intronic regions of the ERCC4/XPF gene. The first variant, located in intron 1, is a Japanese founder mutation, which additionally accounts for ~10% of the entire Japanese XP cases (MAF = 0.00196), causing an aberrant pre-mRNA splicing due to a miss-binding of U1snRNA. The second mutation located in intron eight induces an alternative polyadenylation. Both mutations cause a reduction of the ERCC4/XPF gene expression, resulting in XP clinical manifestations. Most cases developed early-onset skin cancers, indicating that these variants need critical attention. We further demonstrate that antisense oligonucleotides designed for the mutations can restore the XPF protein expression and DNA repair capacity in the patients' cells. Collectively, these pathogenic variants can be potential therapeutic targets for XP.

Fibulin-4 Accelerates Amyloid Formation by Binding with a Keratin 5 Peptide Fragment.

Keratins are the major amyloid fibril component in localized cutaneous amyloidosis. We analyzed the amyloid components in the skin of patients with localized cutaneous amyloidosis by immunohistochemical staining using antisera against extracellular matrix proteins and keratin 5 (K5). Fibulin-4 and K5 colocalized in the amyloid deposits. Using 14 synthetic peptides, we screened for amyloidogenic sequences in the C-terminal region of K5, including the α-helical rod domain and the tail domain. Two peptides stained with thioflavin T possessed a ß-sheet structure and formed amyloid-like fibrils. Among the amyloidogenic peptides, a peptide KT5-6 (YQELMNTKLALDVEIATYRKLLEGE) derived from the α-helical rod domain of K5 specifically bound to fibulin-4. In addition, amyloid formation of KT5-6 was accelerated by fibulin-4. These results suggest that degraded fragments of K5 containing the KT5-6 sequence form amyloid fibrils with fibulin-4. The data further suggest that degraded fragments of K5 and fibulin-4 have the potential to initiate cutaneous amyloidosis.

Clinical practice guidelines for pseudoxanthoma elasticum (2017): Clinical Practice Guidelines for Pseudoxanthoma Elasticum Drafting Committee

Pseudoxanthoma elasticum (PXE) is a progressive hereditary disease that affects tissues such as the skin, retina, blood vessels, and gastrointestinal tracts. Therefore, comprehensive medical care across clinical departments specialized in specific organs is needed to provide the best clinical practices to PXE patients. The Japanese version of clinical guidelines developed by the Japanese Dermatological Association was published in 2017, and aimed to promote equal accessibility of PXE-related medical care. Here, the English version of Japanese guideline is reported, and is intended to be worldwide reference for medical care of PXE.

Fibroblast growth factor 2 accelerates the epithelial-mesenchymal transition in keratinocytes during wound healing process.

In the wound healing process, the morphology of keratinocytes at the wound edge temporarily changes to a spindle morphology, which is thought to occur due to an epithelial-mesenchymal transition (EMT). Fibroblast growth factor (FGF) 2, also called basic FGF, has the potential to accelerate wound closure by activating vascular endothelial cells and fibroblasts. We examined the effects of FGF2 on keratinocyte morphology and EMT in wounded skin. Histological examination of murine wounds treated with FGF2 revealed that wound edge keratinocytes formed thickened and multilayered epithelia. In addition, we detected wound edge keratinocytes migrating individually toward the wound center. These migrating keratinocytes exhibited not only spindle morphology but also down-regulated E-cadherin and up-regulated vimentin expression, which is characteristic of EMT. In FGF2-treated wounds, a PCR array revealed the upregulation of genes related to EMT, including transforming growth factor (TGF) signaling. Further, FGF2-treated wound edge keratinocytes expressed EMT-associated transcription factors, including Snai2, and showed translocation of ß-catenin from the cell membrane to the cytoplasm/nucleus. However, in vitro examination of keratinocytes revealed that FGF2 alone did not activate EMT in keratinocytes, but that FGF2 might promote EMT in combination with TGFß1. These findings suggest that FGF2 treatment of wounds could promote keratinocyte EMT, accelerating wound closure.

Coexistence of keloids and pilomatricoma in a patient with Rubinstein-Taybi syndrome.

Rubinstein-Taybi syndrome (RTS) is an autosomaldominant hereditary disease, which contains many skeletal and organ anomalies as well as mental retardation. Although high incidence of keloids in RTS is known, it is difficult to find a detailed report on the clinical features of keloids. In the following letter, we report an RTS patient fulfilling diagnostic criteria whosuffered from both keloids and pilomatricoma. We also performed a literature search, which identified the possible involvement of the Wnt/ß-catenin signaling pathway in the pathogenesis of these two skin lesions.

Calcification in dermal fibroblasts from a patient with GGCX syndrome accompanied by upregulation of osteogenic molecules.

Gamma-glutamyl carboxylase (GGCX) gene mutation causes GGCX syndrome (OMIM: 137167), which is characterized by pseudoxanthoma elasticum (PXE)-like symptoms and coagulation impairment. Here, we present a 55-year-old male with a novel homozygous deletion mutation, c.2,221delT, p.S741LfsX100, in the GGCX gene. Histopathological examination revealed calcium deposits in elastic fibers and vessel walls, and collagen accumulation in the mid-dermis. Studies of dermal fibroblasts from the patient (GGCX dermal fibroblasts) demonstrated that the mutated GGCX protein was larger, but its expression level and intracellular distribution were indistinguishable from those of the wild-type GGCX protein. Immunostaining and an enzyme-linked immunosorbent assay showed an increase in undercarboxylated matrix gamma-carboxyglutamic acid protein (ucMGP), a representative substrate of GGCX and a potent calcification inhibitor, indicating that mutated GGCX was enzymatically inactive. Under osteogenic conditions, calcium deposition was exclusively observed in GGCX dermal fibroblasts. Furthermore, GGCX dermal fibroblast cultures contained 23- and 7.7-fold more alkaline phosphatase (ALP)-positive cells than normal dermal fibroblast cultures (n = 3), without and with osteogenic induction, respectively. Expression and activity of ALP were higher in GGCX dermal fibroblasts than in normal dermal fibroblasts upon osteogenic induction. mRNA levels of other osteogenic markers were also higher in GGCX dermal fibroblasts than in normal dermal fibroblasts, which including bone morphogenetic protein 6, runt-related transcription factor 2, and periostin (POSTN) without osteogenic induction; and osterix, collagen type I alpha 2, and POSTN with osteogenic induction. Together, these data indicate that GGCX dermal fibroblasts trans-differentiate into the osteogenic lineage. This study proposes another mechanism underlying aberrant calcification in patients with GGCX syndrome.

Depletion of Epidermal Langerhans Cells in the Skin Lesions of Pellagra Patients.

Pellagra is a nutrient deficiency disease caused by insufficient niacin levels. Recent studies have shown that numbers of epidermal Langerhans cells decreased in other diseases caused by nutritional deficiencies, including necrolytic migratory erythema and acrodermatitis enteropathica. Epidermal Langerhans cells are capable of modulating or even halting the inflammatory reaction. The aim of this study was to examine changes in the number of Langerhans cells and other dendritic cells, and maturation of epidermal Langerhans cells in the lesional and adjacent non-lesional skin in pellagra patients. Seven pellagra patients and 10 healthy individuals who served as controls were included. The number and distribution of dendritic cells and other cutaneous cells were examined by immunohistochemistry. Epidermal Langerhans cells decreased considerably in the skin lesions of pellagra patients, whereas other dendritic cells did not change. The decrease in the number of Langerhans cells was positively correlated with the histological severity of skin lesions. As the number of Langerhans cells was not reduced in the undisturbed neighboring skin, the depletion of epidermal Langerhans cells did not precede skin damage but was a cause of prolonged severe inflammation.

Analysis of clinical symptoms and ABCC6 mutations in 76 Japanese patients with pseudoxanthoma elasticum.

Pseudoxanthoma elasticum (PXE) is a hereditary disease, causing calcification and degeneration of elastic fibers, which affects the skin, eye, cardiovascular systems and gastrointestinal tract. PXE is caused by mutations in the ABCC6 gene. Neither detailed nor large-scale analyses have been accomplished in Japanese patients with PXE. We, therefore, investigated clinical symptoms and ABCC6 gene mutations in 76 Japanese patients. Japanese PXE patients (n = 76) had a significantly lower incidence of vascular lesions than 505 PXE patients in the Leiden Open Variation Database (LOVD) (38.7% vs 65.1%, respectively; P = 1.34E-06); however, the incidences of the skin, eye, cardiac and gastrointestinal lesion symptoms were not significantly different. Symptom severity scores for skin, eye and vascular lesions, calculated using the Phenodex™ system, were significantly lower in Japanese PXE patients than in LOVD PXE patients. Genetic analysis revealed three nonsense, four frame-shift, one exon deletion and 13 missense mutations in ABCC6 in 73 patients; however, we were unable to detect pathogenic mutations in three patients. Frequent mutations differed between Japanese and LOVD PXE patients. In Japanese PXE patients, the top five mutations accounted for more than 60% of all pathogenic changes, suggesting the presence of founder effects. Consistent with previous reports, no obvious correlations between genotypes and phenotypes were identified in this study. In conclusion, we consider that the milder clinical phenotypes, observed even in older Japanese PXE patients, could be attributed to environmental factors such as dietary habits and lifestyle, as well as genetic background.