Identification of a Novel COL17A1 Compound Heterozygous Mutation in a Chinese Girl with Non-Herlitz Junctional Epidermolysis Bullosa

Abstract

Non-Herlitz junctional epidermolysis bullosa (JEB-nH), an autosomal recessive bullous genodermatosis, is characterized by generalized skin blistering from birth onward, dental anomalies, universal alopecia and nail dystrophy. The underlying defect is mutation of the COL17A1 gene encoding the type XVII collagen, resulting in losing structure for attachment of basal epithelial cells to the matrix. In present study, we described one case of congenitally affected female child aged 10 years, with skin blistering. Dermatologic examination revealed sparse, mild blisters on the face and hand, with profound enamel pitting of the teeth. Skin biopsy from proband's bullous skin displayed subepidermal bulla formation without acantholysis. The immunofluorescence of anti-type XVII collagen antibody staining showed loss of type XVII collagen staining at the basement membrane zone. A combination of whole exome sequencing (WES) and Sanger sequencing revealed the novel heterozygous mutations (c.4324C>T;p.Q1442* and c.1834G>C;p.G612R) in COL17A1 gene, which could be associated with the observed JEB-nH. One allele had a novel nonsense mutation (c.4324C>T;p.Q1442*), resulting in nonsense-mediated mRNA decay and truncated collagen XVII; the other allele had a novel missense mutation of c.1834G>C;p.G612R in exon 22, causing a glycine-to-arginine substitution in the Gly-X-Y triple helical repeating motifs and decreasing the thermal stability of collagen XVII. Our findings indicate that the genetic test based on WES can be useful in diagnosing JEB-nH patients. The novel pathogenic mutations identified would further expand our understanding of the mutation spectrum of COL17A1 gene in association with the inherited blistering diseases.

Keywords: COL17A1 gene; mutation; non-Herlitz junctional epidermolysis bullosa; whole exome sequencing.