Intracellular accumulation of collagen VII in cultured keratinocytes from a patient with dominant dystrophic epidermolysis bullosa.

Expression of collagen VII, a candidate molecule for dystrophic epidermolysis bullosa, was analyzed in cultured keratinocytes from a patient with generalized dominant dystrophic epidermolysis bullosa (DEBD) of the Pasini subtype. Double immunofluorescence revealed an increased intracellular staining of collagen VII that co-localized with protein disulfide isomerase, a marker of the rough endoplasmic reticulum. Ultrastructural analysis of cultured DEBD cells showed dilated cisternae of the rough endoplasmic reticulum and numerous residual bodies, both of which contained abundant collagen VII as detected by immunoelectron microscopy. Immunoblotting of keratinocyte extracts indicated an increased ratio of cell-associated versus secreted soluble collagen VII in DEBD cells. Collagen VII mRNA was of normal size in the DEBD cells, but present in excessive amounts. The data suggest a mutation in the collagen VII gene that leads to intracellular accumulation and degradation of this collagen, and thus to a reduced number of anchoring fibrils at the dermo-epidermal junction, and subsequently to blistering of the skin in this family.