Functional improvement of mutant keratin cells on addition of desmin: an alternative approach to gene therapy for dominant diseases.

A major challenge to the concept of gene therapy for dominant disorders is the silencing or repairing of the mutant allele. Supplementation therapy is an alternative approach that aims to bypass the defective gene by inducing the expression of another gene, with similar function but not susceptible to the disrupting effect of the mutant one. Epidermolysis bullosa simplex (EBS) is a genetic skin fragility disorder caused by mutations in the genes for keratins K5 or K14, the intermediate filaments present in the basal cells of the epidermis. Keratin diseases are nearly all dominant in their inheritance. In cultured keratinocytes, mutant keratin renders cells more sensitive to a variety of stress stimuli such as osmotic shock, heat shock or scratch wounding. Using a 'severe' disease cell culture model system, we demonstrate reversion towards wild-type responses to stress after transfection with human desmin, an intermediate filament protein normally expressed in muscle cells. Such a supplementation therapy approach could be widely applicable to patients with related individual mutations and would avoid some of the financial obstacles to gene therapy for rare diseases.