Isolation and characterization of the epidermolysis bullosa acquisita antigei

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Epidermolysis bullosa acquisita is an autoimmune blistering disease, clinically characterized with mild trauma inducible bulla. Histological examination revealed that bulla develops in the subepidermal region. Patients with this disease have circulating autoantibodies against basemen membrane zone. The autoantigen reactive to this autoantibodies is type VII collagen which is a major component of an anchoring fibril. To isolate cDNA which code this autoantigen and to characterize this autoantigen, we first started to screening the cDNA library which corresponds io human keratinocyte mRNA.A cDNA with an insert of -1Kb was isolated with monoclonal antibody that specifically bind to type VII collagen. Northern blot revealed -9.5Kb single band. Therefor in 1993, we re-screened the cDNA library to obtain the extended clones. The resultant cDNAs, overlapping to each other, cover almost all the N-terminal non-coolagenous domain of type VII collagen. The nucleotide sequence and the deduced amino acid sequence revealed that 1 ) this molecules has a homology to type lll repeat of fibronectin, 2) it has internal repeating unit, and 3) homoiogy between the repetitive unit is similar to those of fibronectin type III repeat. These reuslt strongly suggest that the N-terminal non-collagenous domain of type VII collagen has similar structure to fibrionectin and that it may possese similar function to this macromolecule such as bindiong to other proteins.