Immunoelectron microscopic analysis of basement membrane components in type VII collagen knockout skin

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Receive dystrophic epidermolysis bullosa (RDEB) is a congenital bullous disease caused by lack of type VII collagen that anchors epidermal basement membrane (lamina densa) to the dermis. Molecular relationship between the type VII collagen and the other epidermal basement membrane molecules is not fully elucidated. The purpose of this study is to elucidate the in vivo molecular ultrastructural relationship between the type VII collagen and the other basement membrane molecules using the skin of RDEB patients, which were the type VII knockout human skin. For this, the precise ultrastructural localization of basement membrane molecules including type VII collagen, BPAG2, laminin 5 were compared between the type VII collagen knockout human skin and the normal human skin. The diagnosis of RDEB confirmed by electron microscopy and the lack of expression of LH7.2 antigen, N-terminus domain of type VII collagen. Blood samples from the five patients with RDEB were processed for genomic DNA elution. COL7A1 gene that encodes type VII collagen was amplified and DNA sequences were analyzed. Among ten alleles, three mutations on four alleles were identified: 6573+1G>C, 5504delA and 5818delC. Skin samples were obtained from three RDEB patients by consent. Localizations of N and C terminus of BPAG2, and laminin 5 were observed with post-embedding immunogold electron microscopy and compared statistically with those of normal human skin. As results, the N terminus of BPAG2 was localized at the hemidesmosome and laminin 5 was localized at lamina densa. There was no significant difference in localization of these molecules between normal and RDEB skin. However, C-terminus of BPAG2 were significantly shifted from lamina densa to the epidermal side. These results indicated that type VII collagen may have some molecular interaction between BPAG2 via C-terminal domain of BPAG2, both of which were localized at lamina densa in the normal skin.