Phenotype correction of hemophilia A mice by spliceosome-mediated RNA trans-splicing

Conventional gene therapy of hemophilia A relies on the transfer of factor VIII (FVIII; encoded by the F8 gene) cDNA. We carried out spliceosome-mediated RNA trans -splicing (SMaRT) to repair mutant FVIII mRNA. A pre- trans -splicing molecule (PTM) corrected endogenous FVIII mRNA in F8 knockout mice with the hemophilia A phenotype, producing sufficient functional FVIII to correct the hemophilia A phenotype. This is the first description of phenotypic correction of a genetic defect by RNA repair in a knockout animal model. Our results indicate the feasibility of using SMaRT to repair RNA for the treatment of genetic diseases.