COL7A1 and recessive dystrophic epidermolysis bullosa: To demonstrate the feasibility of COL7A1 editing in primary RDEB cells using the CRISPR/Cas9 approach, we designed five guide RNAs (gRNAs) in order to correct a causative null mutation in exon 2 seen in several RDEB subjects (c.189delG; p.Leu64Trpfs*40).