Masahiro Hayashi

Dyschromatosis symmetrica hereditaria.

Dyschromatosis symmetrica hereditaria (DSH) is a rare pigmentary genodermatosis, which is acquired by autosomal dominant inheritance with high penetrance. Most cases of this condition have been reported from East Asian countries, including Japan, China and Taiwan. Its symptoms are mixed hyper‐ and hypopigmented macules on the dorsal aspect of the hands and feet and freckle‐like macules on the face. The gene responsible for DSH has been identified as adenosine deaminase acting on RNA1 (ADAR1). The ADAR1 protein catalyzes the transformation of adenosine to inosine in dsRNA substrates (so‐called A‐to‐I editing) and is involved in various activities, such as viral inactivation, structural change of the protein and the resultant cell survival. However, its function in the skin and role in the development of DSH are still unknown. To date, more than 100 mutations of ADAR1 have been reported in patients with DSH, and the catalytic domain deaminase is believed to be crucial to the activities of this gene. Some complications of DSH have been reported and, intriguingly, several patients have been reported to develop neurological symptoms, such as dystonia and mental deterioration. Because ADAR1 plays various important roles in human tissue, we believe that a clarification of the pathogenesis of DSH will promote the understanding of the physiological functions of ADAR1, which will have significant scientific implications.

Detection of HPV-DNA, p53 alterations, and methylation in penile squamous cell carcinoma in Japanese men

Penile carcinoma is a rare disease, accordingly there are few studies on molecular changes, and these results also vary greatly. A total of 26 penile squamous cell carcinomas in Japanese men were studied with respect to HPV, p53 alterations, and methylation of gene promoter region. HPV‐DNA was detected in three of 26 patients (11.5%). Overexpression of p53 was observed in 13 of 26 patients (50%), and p53 gene mutations were detected in four of 26 patients (15.4%). The frequency of methylation was as follows: DAPK, 26.9% (7/26); FHIT, 88.4% (23/26); MGMT, 19.2% (5/26); p14, 3.8% (1/26); p16, 23.1% (6/26); RAR‐β, 23.1% (6/26); RASSF1A, 11.5% (3/26); and RUNX3, 42.3% (11/26). As for correlation between HPV and p53 alterations, and methylation status, mutations of the p53 gene were detected only in HPV‐negative patients, and methylation was more frequently found in HPV‐negative than in HPV‐positive patients. The present results suggest that the majority of penile squamous cell carcinomas in Japanese men are unrelated to HPV, and gene alterations accumulate more frequently in HPV‐unrelated penile carcinomas.

Microsatellite instability in esophageal squamous cell carcinoma is not associated with hMLH1 promoter hypermethylation

To test whether a subset of esophageal squamous cell carcinomas (SCC) develop through a deficiency in DNA mismatch repair, we examined microsatellite instability (MSI) using 11 microsatellite markers including BAT‐26, hMLH1 protein expression by immunohistochemistry, and methylation status of the hMLH1 promoter by methylation‐specific polymerase chain reaction (MSP). p53 mutations were also investigated. Microsatellite instability at one or more loci was observed in 40% (12/30) of esophageal SCC tumor samples, although only one of these tumors was categorized as high‐frequency MSI (MSI‐H) and none showed BAT‐26 instability. While immunohistochemistry revealed decreased hMLH1 protein expression in 27% (8/30) of the tumors, hMLH1 promoter hypermethylation was not observed. Absence of hMLH1 protein expression was relatively common in well‐differentiated (keratinizing‐type) esophageal SCC, but was not associated with hMLH1 promoter hypermethylation. p53 mutation was detected in 37% (11/30) and loss of heterozygosity (LOH) in 90% (27/30) of esophageal SCC samples. Our results suggested that most esophageal SCC develop through defects in tumor suppressor genes (i.e. the suppressor pathway), and that MSI in esophageal SCC probably represent random replication errors rather than being associated with DNA mismatch repair deficiency.

Whole-exome sequencing identifies ADAM10 mutations as a cause of reticulate acropigmentation of Kitamura, a clinical entity distinct from Dowling-Degos disease

Reticulate acropigmentation of Kitamura (RAK) is a rare genetic disorder of cutaneous pigmentation with an autosomal dominant pattern of inheritance and a high penetration rate. The characteristic skin lesions are reticulate, slightly depressed pigmented macules mainly affecting the dorsa of the hands and feet, which first appear before puberty and subsequently expand to the proximal limb and the trunk. To identify mutations that cause RAK, we performed exome sequencing of four family members in a pedigree with RAK. Fifty-three SNV/Indels were considered as candidate mutations after some condition narrowing. We confirmed the mutation status in each candidate gene of four other members in the same pedigree to find the gene that matched the mutation status and phenotype of each member. A mutation in ADAM10 encoding a zinc metalloprotease, a disintegrin and metalloprotease domain-containing protein 10 (ADAM10), was identified in the RAK family. ADAM10 is known to be involved in the ectodomain shedding of various substrates in the skin. Sanger sequencing of four additional unrelated RAK patients revealed four additional ADAM10 mutations. We identified a total of three truncating mutations, a splice site mutation and a missense mutation in ADAM10. We searched for mutations in the KRT5 gene, a causative gene for the similar pigmentation disorder Dowling-Degos disease (DDD), in all the patients and found no KRT5 mutation. These results reveal that mutations in ADAM10 are a cause of RAK and that RAK is an independent clinical entity distinct from DDD.

Frequent epigenetic silencing of the FHIT gene in penile squamous cell carcinomas

Methylation of normally unmethylated CpG-rich islands in or near the promoter region has been associated with transcriptional inactivation of tumor-suppressor and tumor-related genes in human cancers. However, so far, only a few studies have searched for DNA methylation in penile carcinoma (PC). On the other hand, human papillomavirus (HPV) has been reported to be associated with the pathogenesis of PC. To elucidate the methylation status of PC and HPV infection, the methylation status of eight genes (DAPK, FHIT, MGMT, p14, p16, RAR-β, RASSF1A, and RUNX3), the incidences of the HPV status, and the expression of Fhit protein were examined in 25 PCs. The frequencies of methylation were: 28% for DAPK, 92% for FHIT, 20% for MGMT, 4% for p14, 24% for p16, 24% for RAR-β, 12% for RASSF1A, and 44% for RUNX3. Negative expression of Fhit protein was observed in 22 of the 25 cancers (88%). Among those 22, 20 showed methylation of the FHIT gene. HPV-DNA was detected in three of the 25 cancers (12%). Methylation of FHIT gene was frequently found than HPV infection, therefore methylation of the FHIT gene is suggested to play an important role in the pathogenesis of penile squamous cell carcinoma.

Genetic analysis of cutaneous squamous cell carcinomas arising from different areas

Although cutaneous squamous cell carcinomas (SCC) occur most frequently in sun‐exposed areas of the skin, they can also arise in non‐sun‐exposed areas. Some risk factors for cutaneous SCC, such as ultraviolet (UV) light, are well known. However, the major factor for carcinogenesis may depend on the site of the tumor as well as the ethnicity of the patient. In this study we examined 41 Japanese cutaneous SCC cases, focusing on the area of appearance and the presence of genetic alteration, with 27 cases from sun‐exposed areas, 10 from non‐sun‐exposed areas (excluding genital areas), and four from burn scars from sun‐exposed areas. Squamous cell carcinomas arising in sun‐exposed areas showed less frequent p53 gene mutations compared to SCC arising in non‐sun‐exposed areas. Ultraviolet light‐specific mutations were found in only two cases of SCC from sun‐exposed areas. Human papilloma virus (HPV) DNA was detected in two cases (7.4%) of the sun‐exposed areas and none of the non‐sun‐exposed or scar areas. The frequency of loss of heterozygosity on D5S178 in non‐sun‐exposed SCC was significantly higher than in sun‐exposed SCC. Furthermore, the incidence of fractional allelic loss (FAL) was significantly higher in non‐sun‐exposed SCC than in sun‐exposed SCC. Our findings suggest that sun‐exposed SCC in Japan may be relatively less involved with p53 mutation, and that non‐sun‐exposed SCC acquire more genetic alterations than sun‐exposed SCC.

Retrodental synovial cyst which disappeared after posterior C1-C2 fusion: A case report

Synovial cysts of the cervical spine are extremely rare. We describe an 8-year-old boy with atlantoaxial subluxation and hypoplasia of the dens. Magnetic resonance imaging showed a round lesion, posterior to the odontoid process. This mass was characterized by a low signal intensity on T1-weighted images, and high signal intensity on T2-weighted images. The retrodental synovial cyst disappeared after posterior atlantoaxial arthrodesis.

Absence of BAT-26 instability in gastric intestinal metaplasia

BAT‐26 instability, a sensitive marker for the high‐frequency microsatellite instability (MSI‐H) phenotype, was analyzed in samples of gastric cancer and in adjacent intestinal metaplastic mucosae. Although all MSI‐H gastric cancer samples showed BAT‐26 instability, as assessed using 12 dinucleotide microsatellite markers, BAT‐26 instability was not found in the adjacent intestinal metaplastic mucosa in any of the samples.

Dystrophic epidermolysis bullosa pruriginosa of elderly onset

A 71‐year‐old man with no family history of skin diseases presented with a 4u2003month history of recalcitrant pruritic papules and nodules on the lower extremities. He had prurigo‐like eruptions with tense bullae on the extensor aspect of his lower extremities with multiple adjacent milia. Toenail dystrophy was observed. Mucous membranes were not affected. Skin biopsy from the shin showed a subepidermal blister with milium. Electron microscopy from lesional and perilesional skin of the leg showed scanty, hypoplastic anchoring fibrils. We detected a heterozygous mutation in the COL7A1 gene, a G‐to‐A substitution in exon 87 (c.6859G>A; p.Gly2287Arg). Thus, the clinicopathological and molecular findings supported a diagnosis of dystrophic epidermolysis bullosa pruriginosa. Assessment of other relatives was not feasible. To the best of our knowledge, this is the oldest clinical onset of this unusual variant of dystrophic epidermolysis bullosa reported to date. Why the onset of skin fragility should have occurred so late is not known, but the case serves as a reminder that this particular mechanobullous disease can have a delayed presentation.

Oculocutaneous albinism type 3: A Japanese girl with novel mutations in TYRP1 gene

BACKGROUNDnOculocutaneous albinism (OCA) type 3 caused by mutations of the TYRP1 gene is an autosomal recessive disorder of pigmentation characterized by reduced biosynthesis of melanin pigment in the skin, hair, and eye. The clinical phenotype has been reported as mild in Caucasian OCA3 patients.nnnOBJECTIVEnWe had the opportunity to examine a Japanese girl with OCA3 and investigated activity of TYRP1 protein derived from the mutant allele detected in the patient.nnnMETHODSnMutation search for OCA responsible genes was done. A mutant allele with a missense mutation was analyzed using melanocyte cultures (b cells) established from a mouse model of OCA3.nnnRESULTSnCompound heterozygous mutations, p.C30R and p.367fsX384, were detected in the Japanese girl. Then we revealed that the missense mutation, p.C30R, was functionally incapable of melanin synthesis with in vitro experiments.nnnCONCLUSIONnThis is the first report of the occurrence of OCA3 in Japanese population.