For the severe blistering skin disease epidermolysis bullosa, we have previously described several trans-splicing strategies where we replaced either 5′ or 3′ regions of a transcript, in order to correct EB-associated mutations in PLEC, KRT14, COL17A1 and COL7A1 at pre-mRNA level [9,10,15,16,17,18]. The gene discussed is COL7A1; the disease is epidermolysis bullosa.