Background Junctional epidermolysis bullosa (JEB), a group of hereditary skin fragility disorders, is associated with a wide variety of phenotypes, although all forms are characterised by trauma induced skin blistering and tissue separation at the dermal–epidermal junction zone. A subgroup, coined JEB-other, is associated with mutations in the COL17A1 gene encoding collagen XVII or, more rarely, with mutations in the laminin 332 genes LAMA3, LAMB3, or LAMC2. The objective of this study is comprehensive genotype–phenotype analysis in JEB-other patients with COL17A1 mutations and elucidation of disease mechanisms underlying different skin phenotypes.
Methods and results COL17A1 mutations and their clinical and cellular consequences were systematically analysed in 43 patients with JEB-other. Cell culture, RT-PCR, and protein biochemistry were applied to assess the effects of splice site mutations—that is, the nature and amounts of transcripts and polypeptides synthesised and their association with the phenotypic outcome. 34 distinct COL17A1 mutations were disclosed, 12 of them novel. mRNA and protein analyses demonstrated that patients with only about 12–14% of the physiological collagen XVII levels had mild cutaneous involvement and a long life span.
Conclusions In contrast to complete null phenotypes, presence of minor amounts of collagen XVII protein in JEB skin is associated with mild phenotypic manifestations. The data have significant implications for design of molecular therapies for JEB, since they suggest that already a low extent of collagen XVII restoration will improve skin stability and alleviate symptoms.
- genetic screening/counselling
- gene therapy
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Funding This work was supported by the Network Epidermolysis bullosa grant from the Federal Ministry for Education and Research (BMBF), the CRC850/B6 grant from the German Research Foundation DFG, the Excellence Initiative of the German Federal and State Governments and Freiburg Institute for Advanced Studies, School of Life Sciences, and by the K Kriezis scholarship from the National and Kapodistrian University of Athens to DK.
Competing interests None.
Patient consent Obtained.
Ethics approval This study was conducted with the approval of the University of Freiburg, Germany.
Provenance and peer review Not commissioned; externally peer reviewed.