Revertant fibres: a possible genetic therapy for Duchenne muscular dystrophy?

The mdx mouse, an animal model used to study Duchenne muscular dystrophy (DMD), has a nonsense mutation in exon 23 of the dystrophin gene which should result in a truncated protein that cannot be correctly localized at the sarcolemma of the muscle fibres. Immunohistochemical staining with anti-dystrophin antibodies had shown that while most of the muscle tissue was dystrophin-negative, a small percentage of muscle fibres were clearly dystrophin-positive and had somehow by-passed the primary nonsense mutation. A nested PCR-based examination of dystrophin gene transcripts around the mdx mutation revealed several alternatively processed transcripts, of which four mRNA species skipped the mutation in exon 23, were in-frame and could be translated into a shorter, but still functional dystrophin protein. Specific tests for these transcripts demonstrated these were also present in normal adult and embryonic mouse muscle tissue.