Journal Article

Suppression of revertant fibers in <i>mdx</i> mice by expression of a functional dystrophin

Gregory E. Crawford, Qi Long Lu, Terry A. Partridge and Jeffrey S. Chamberlain

in Human Molecular Genetics

Volume 10, issue 24, pages 2745-2750
Published in print November 2001 | ISSN: 0964-6906
Published online November 2001 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/10.24.2745
Suppression of revertant fibers in mdx mice by expression of a functional dystrophin

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Duchenne muscular dystrophy (DMD) is characterized by progressive muscle degeneration that results from the absence of dystrophin. Despite null mutations in the dystrophin gene, many DMD patients display a low percentage of dystrophin-positive fibers. These ‘revertant fibers’ are also present in the dystrophin-deficient mdx mouse and are believed to result from alternative splicing or second mutation events that bypass the mutation and restore an open reading frame. However, it is unclear what role dystrophin and the dystrophic pathology might play in revertant fiber formation and accumulation. We have analyzed the role of dystrophin expression and the dystrophic pathology in this process by monitoring revertant fibers in transgenic mdx mice that express truncated dystrophins. We found that newborn transgenic mice displayed approximately the same number of revertant fibers as newborn mdx mice, indicating that expression of a functional dystrophin does not suppress the initiation of revertant fiber formation. Surprisingly, when the transgene encoded a functional dystrophin, revertant fibers were not detected in adult or old mdx mice. In contrast, adult transgenic mice expressing a non-functional dystrophin accumulated increasing numbers of revertant fibers, similar to mdx mice, suggesting that positive selection is required for the persistence of revertant fibers. Finally, we provide evidence that the loss of revertant dystrophin in transgenic mdx muscle fibers overexpressing a functional dystrophin results from displacement of the revertant protein by the transgene-encoded dystrophin.

Journal Article.  4392 words.  Illustrated.

Subjects: Genetics and Genomics

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