MOLECULAR-CLONING AND CHARACTERIZATION OF A CDNA-ENCODING CANINE TYPE-VII COLLAGEN NONCOLLAGENOUS (NC1) DOMAIN, THE TARGET ANTIGEN OF AUTOIMMUNE-DISEASE EPIDERMOLYSIS-BULLOSA ACQUISITA (EBA)

Type VII collagen, the major component of anchoring fibrils, serves as tight adhesion of skin basement membrane zone (BMZ) through its amino -terminal non-collagenous (NCl) domain. The NCl domain is targeted by autoantibodies of an acquired blistering skin disease termed epidermol ysis bullosa acquisita (EBA) naturally occurring in humans and dogs. W e cloned the full-length canine type VII collagen NCl domain cDNA and delineated its molecular and immunological characteristics. The canine NCl domain cDNA consists of 3759 nucleotides encoding for 1253 amino acids, with a molecular mass of approx. 134 kDa and a 17 amino acid si gnal peptide. The expression of canine type VII collagen was confirmed by Northern blot analysis and by a rabbit antibody raised against a 1 7 amino acid peptide deduced from canine NCl sequence. Comparison of c anine NCl with the corresponding human sequence indicated 86.7% and 87 .6% identity at the nucleotide and deduced amino acid levels respectiv ely. The protein homology reached greater than 95% within two immunodo minant epitope areas. Furthermore, human EBA autoantibodies and a rabb it anti-human NCl cross-reacted with canine skin BMZ and the newly syn thesized canine type VII collagen. The molecular and immunological ide ntities between human and canine NCl domains suggest that NCl may be c ritical for the EBA development. (C) 1998 Elsevier Science B.V. All ri ghts reserved.