Normal Molecular Weight of Type VII Collagen Produced by Recessive Dystrophic Epidermolysis Bullosa Keratinocytes

Abstract

Studies of the recessive dystrophic form of epidermolysis bullosa (RDEB) have suggested that an abnormality in type VII collagen may be involved in the pathogenesis of this disorder. Indirect immunofluorescence studies have shown that the staining for type VII collagen along the dermal-epidermal junction is markedly reduced or absent in all but rare cases of severe, generalized RDEB. These findings imply that the genetic defect may involve type VII collagen but do not exclude the possibility that the alterations demonstrated are secondary, for example, to nonspecific proteolysis of type VII collagen. To evaluate the ability of cells of affected patients to produce type VII collagen, we cultured keratinocytes from a severely affected patient and immunoprecipitated type VII collagen from the cells. Keratinocytes were metabolically labelled with 35S-methionine, and solubilized cell extracts were reacted with antibody to type VII collagen. The results indicate that the patient's keratinocytes synthesize type VII collagen and that the M(r) of the protein synthesized does not differ from that of an unaffected control. Because cultured cells from a patient severely affected with recessive dystrophic epidermolysis bullosa produce type VII collagen, the genetic defect, at least in this patient, is unlikely to reside in a major truncation of the type VII collagen molecule.