Acta Dermato-Venereologica 99-7CompleteContent | Page 25

699 SHORT COMMUNICATION Whole Exome Sequencing Identified a Novel Mutation of the RHBDF2 Gene in a Chinese Family of Tylosis with Esophageal Cancer Le QU 1 , Sha SHA 2 , Qian-Lei ZOU 1 , Xing-Hua GAO 1 , Ting XIAO 1 , Hong-Duo CHEN 1 * and Chundi HE 1 * Department of Dermatology, and 2 Department of Geriatrics, The First Hospital of China Medical University, 155 North Nanjing Street Shenyang 110001, China. *E-mails: [email protected]; [email protected] 1 Accepted Apr 2, 2019; E-published Apr 2, 2019 Tylosis with esophageal cancer (TOC) is an extremely rare autosomal dominant disorder characterized by early- onset palmar and plantar hyperkeratosis, oral leukoplakia, and a high risk of esophageal cancer (1, 2). The mutation of inactive rhomboid protease RHBDF2 gene has been reported as the underlying cause of TOC (3). Up till now, there are only 3 studies on RHBDF2 gene mutations in TOC reported (3–5). Here for the first time, we identified a novel c.589C>A mutation of RHBDF2 gene from a Chinese family with TOC by whole exome sequencing. We found that the mutation in the RHBDF2 gene altered RHBDF2 protein localization in tylotic skin. We also found that both sporadic and tylotic esophageal cancer types present different expression of the RHBDF2 com- pared to the normal controls. Reads that aligned to exon regions were collected for mutation identification and subsequent analysis. SAMtools mpileup and BCFtools were used to do variant calling and identify SNP and indels. The data that mapped to the targeted region chr17q25 had a mean depth of 144.01-fold, and 99.95% of the targeted bases were covered. Finally, 4 variants in 3 genes, including RHBDF2 gene: c.502C>A and c.589C>A; ITGB4 gene: c.2207G>T; and CDK3 gene: c.803A>G, with the greatest likelihood of relevance were checked by Sanger sequencing. Only the heterozygous mutation c.589C>A in exon 6 of the RHBDF2 gene co-segregated with the phenotype and was observed neither in unaffected family members nor in 100 unrelated Chinese controls (Fig. 1g). Using DNAMAN software (Lynnon BioSoft, Canada), we con- firmed that mutation c.589C>A lead to the amino acid alteration https://www.medicaljournals.se/acta/content/abstract/10.2340/00015555-3189 1 CASE REPORT The Chinese family of interest has 65 indi- viduals spanning 4 generations, of which 12 were affected (Fig. 1a). The proband (III18) is a 51-year-old man who has been affected by palmar (Fig. 1b) and plantar (Fig. 1c, d) hyperkeratosis since he was 9 years. He was diagnosed with oral leukoplakia (Fig. 1e) and esophageal cancer (Fig. f) at the age of 48. Other 7 family members (I1, II4, II5, III7, III9, III11 and III18) affected by the palmar and plantar hyperkeratosis have also been di- agnosed with esophageal cancer. Four family members (III20, IV7, IV8 and IV16) were affected by the palmar and plantar hyperke- ratosis, without esophageal cancer diagnosis so far. For complete details see Appendix S1 1 . Written informed consent was obtained from all subjects and the Institutional Review Board and the Ethics Committee of The First Hospital of China Medical University provi- ded approval for this study. Peripheral blood samples were collected from the TOC (tylosis with esophageal cancer) family members and 100 unrelated healthy individuals of Chinese origin as controls. Three affected (III11, III18 and IV16) and one unaffected individuals (III5) were subjected to the whole exome sequencing. Genomic DNAs were isolated and randomly fragmented. Whole exome sequencing was performed on all samples using Agilent SureSelect All Exon V6 kit and paired-end 150 bp sequencing on the Illumina NovaSeq platform. Sequencing reads were aligned to the GRCh37 reference genome using Burrows Wheeler Aligner (BWA). Fig. 1. (a) Family pedigree. (b) Clinical images of the proband’s palmar, (c) plantar and (e) oral leukokeratosis. (d) Skin biopsy from the proband’s plantar, and (f) mucosa biopsy from the proband’s esophageal cancer tissue. Scale bars represent 100 μm. (g) c.589C>A mutation in the exon 6 of RHBDF2 gene from normal controls and affected members of the family. This is an open access article under the CC BY-NC license. www.medicaljournals.se/acta Journal Compilation © 2019 Acta Dermato-Venereologica. doi: 10.2340/00015555-3189 Acta Derm Venereol 2019; 99: 699–700