title: Two novel mutations on exon 8 and intron 65 of COL7A1 gene in two Chinese brothers result in recessive dystrophic epidermolysis bullosa.
abstract: Dystrophic epidermolysis bullosa is an inherited bullous dermatosis caused by the COL7A1 gene mutation in autosomal dominant or recessive mode. COL7A1 gene encodes type VII collagen - the main component of the anchoring fibrils at the dermal-epidermal junction. Besides the 730 mutations reported, we identified two novel COL7A1 gene mutations in a Chinese family, which caused recessive dystrophic epidermolysis bullosa (RDEB). The diagnosis was established histopathologically and ultrastructurally. After genomic DNA extraction from the peripheral blood sample of all subjects (5 pedigree members and 136 unrelated control individuals), COL7A1 gene screening was performed by polymerase chain reaction amplification and direct DNA sequencing of the whole coding exons and flanking intronic regions. Genetic analysis of the COL7A1 gene in affected individuals revealed compound heterozygotes with identical novel mutations. The maternal mutation is a 2-bp deletion at exon 8 (c.1006_1007delCA), leading to a subsequent reading frame-shift and producing a premature termination codon located 48 amino acids downstream in exon 9 (p.Q336EfsX48), consequently resulting in the truncation of 2561 amino acids downstream. This was only present in two affected brothers, but not in the other unaffected family members. The paternal mutation is a 1-bp deletion occurring at the first base of intron 65 (c.IVS5568+1delG) that deductively changes the strongly conserved GT dinucleotide at the 5' donor splice site, results in subsequent reading-through into intron 65, and creates a stop codon immediately following the amino acids encoded by exon 65 (GTAA→TAA). This is predicted to produce a truncated protein lacking of 1089 C-terminal amino acids downstream. The latter mutation was found in all family members except one of the two unaffected sisters. Both mutations were observed concurrently only in the two affected brothers. Neither mutation was discovered in 136 unrelated Chinese control individuals. This study reveals novel disease-causing mutations in the COL7A1 gene.
authors.affiliation: The Sichuan Provincial Key Laboratory for Human Disease Gene Study, Sichuan Academy of Medical Sciences & Sichuan Provincial People's Hospital, No.32, Western 2nd Section, Chengdu, Sichuan, P. R. China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Lin
authors.forename: Xue-Jun
authors.initials: XJ
authors.lastname: Chen
authors.forename: Wei
authors.initials: W
authors.lastname: Liu
authors.forename: Bo
authors.initials: B
authors.lastname: Gong
authors.forename: Jun
authors.initials: J
authors.lastname: Xie
authors.forename: Jun-Hao
authors.initials: JH
authors.lastname: Xiong
authors.forename: Jing
authors.initials: J
authors.lastname: Cheng
authors.forename: Xi-Ling
authors.initials: XL
authors.lastname: Duan
authors.forename: Zhao-Chun
authors.initials: ZC
authors.lastname: Lin
authors.forename: Lu-Lin
authors.initials: LL
authors.lastname: Huang
authors.forename: Hui-Ying
authors.initials: HY
authors.lastname: Wan
authors.forename: Xiao-Qi
authors.initials: XQ
authors.lastname: Liu
authors.forename: Lin-Hong
authors.initials: LH
authors.lastname: Song
authors.forename: Zheng-Lin
authors.initials: ZL
authors.lastname: Yang
mesh_terms: D000328:Adult; D044466:Asian People / Q000235:genetics*; D001483:Base Sequence; D024143:Collagen Type VII / Q000235:genetics*; D004252:DNA Mutational Analysis; D016108:Epidermolysis Bullosa Dystrophica / Q000235:genetics* / Q000473:pathology; D005091:Exons / Q000235:genetics*; D005808:Genes, Recessive / Q000235:genetics; D006801:Humans; D007438:Introns / Q000235:genetics*; D008297:Male; D009154:Mutation; D035781:Siblings
chemical_list: C569053:COL7A1 protein, human; D024143:Collagen Type VII