cqvip:Background: Mutations in COL17A1, coding for type XVII collagen, cause juncti onal epidermolysis bullosa with an ultrastructural plane of cleavage through the lamina lucida of the epidermal basement membrane. Objectives: To identify the C OL17A1mutations in a child with reduced type XVII collagen expression and intrae pidermal blister formation. Patient and methods: Protein expression and level of tissue separationwere studied by immunofluorescence and electron microscopy. Th e mutations were identified by analysing the patient’s DNA and mRNA. Results: Immunofluorescence microscopy performed on nonlesional skin demonstrated absence of the type XVII collagen endodomain and presence, although reduced, of the she d ectodomain. Electron microscopy showed that the plane of cleavage was through the basal cells, not through the lamina lucida. Two heterozygous mutations were identified in COL17A1: a new 3- acceptor splice-site mutation in intron 21 (1 877- 2A→ C), and a deletion in exon 48 (3432delT). The splice-sitemutation in intron 21 results in alternative transcripts of which two are in-frame,with deletions of the first nine codons of exon 22 and the entire exon 22, respectiv ely. By Western blot analysis, a type XVII collagen molecule was detected that w as slightly smaller than normal. Conclusions: Occasionally mutations in the COL1 7A1 gene may result in split levels suggesting epidermolysis bullosa simplex rat her than junctional epidermolysis bullosa.
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