A case of pretibial dystrophic epidermolysis bullosa: decreased expression of the non-helical domain of type VII collagen molecule

Pretibial dystrophic epidermolysis bullosa: a recessively inherited COL7A1 splice site mutation affecting procollagen VII processing

Pretibial epidermolysis bullosa (PEB) is a rare form of localized epidermolysis bullosa dystrophica (EBD), a heterogeneous group of inherited, blistering diseases characterized by scarring, loss of dermal-epidermal adhesion and altered anchoring fibrils (AF). Mutations in the type VII collagen gene (COL7A1) underlie EBD and in a dominant PEB family a glycine substitution mutation has been identified. We report a 33-year-old man affected by PEB showing abnormal AF and reduced immunostaining for type VII collagen. Mutation search in the COL7A1 gene revealed a 14 bp deletion in the 115 exon-intron boundary (33563del14), which resulted in the in-frame skipping of exon 115 with elimination of 29 amino acids from the pro-alpha1(VII) polypeptide chain. As a consequence, procollagen VII failed to be processed to mature collagen VII and accumulated at the dermal-epidermal junction, as revealed by immunofluorescence staining using a NC-2 domain-specific antibody. The proband's father was a clinically unaffected heterozygous carrier of mutation 33563del14, whereas the maternal pathogenetic mutation has still not been identified. This represents the first report of a recessive deletion mutation in PEB and extends the range of EBD phenotypes associated with mutation 33563del14.

The structure of the interstitial surfaces of the epithelial basement membranes of mouse oral mucosa, gingiva and tongue

It is known that the gaps between epithelium and the underlying connective tissue usually occur between the epithelial cells and the basement membrane, resulting in exposure of the cellular surface of the lamina densa. After dithiothreitol separation, the epithelia of oral mucosa, gingiva, and tongue were mechanically peeled off from the underlying connective tissues. This treatment severed the connections between the basement membrane and the underlying connective tissue and the anchoring fibrils were pulled off from the collagen layer. In contrast, connections between the epithelial cells and basement membrane were preserved, resulting in exposure of the interstitial surfaces of the laminae densae. Scanning electron-microscopic observations of those interstitial surfaces were possible using the specimens prepared as above. The basement membranes of these three oral epithelia were morphologically the same not only by transmission but also by scanning electron microscopy. Scanning electron-microscopic observations revealed that their laminae densae were composed of fine fibrils and demonstrated three-dimensionally the projection of the anchoring fibrils from the laminae densae to the interstitial side. These findings coincide with those for epidermal basement membrane, which had already been observed with the same method.