OCHRE SUPPRESSOR TRANSFER-RNA RESTORED DYSTROPHIN EXPRESSION IN MDX MICE

The mdx mouse is an animal model for human Duchenne muscular dystrophy . The lack of dystrophin in mdx mice is caused by an ochre mutation in exon 23 of the dystrophin gene. This study tested the feasibility of inhibiting translational termination as an approach for genetic therap y for diseases caused by nonsense mutations. We evaluated both the in vitro and in vivo efficiencies of readthrough of ochre codons in 2 gen es with the tRNA suppressor gene. The first target was a CAT reporter gene bearing an ochre mutation at the 5' end (CATochre). The second ta rget was the dystrophin gene in mdx mice. The readthrough efficiencies were about 20 % in COS cells and 5.5 % in rat hearts. At four weeks a fter a direct injection of plasmid DNA encoding the tRNA suppressor in to mdx mice, dystrophin positive fibers were detected by sarcolemmal i mmunostaining. This is the first convincing data that a tRNA suppresso r gene might be a useful in vivo treatment for the genetic disorders c aused by nonsense mutations. (C) 1997 Elsevier Science Inc.