Mitochondrial expression of a short dystrophin-like product with molecularweight of 71 kDa

In the brain, Dp71 is the most abundant protein product of the DMD gene and by alternative splicing of exon 78 two isoforms can be expressed, Dp71d an d Dp71f. To explore the subcellular distribution of these Dp71 isoforms, sp ecific monoclonal antibodies were used, Dp71d (with exon 78) was found in m icrosomes, while Dp71f (without exon 78) was detected in mitochondria. To d etermine the alterations which the absence of dystrophin proteins induces, we compared the expression of Dp71d in microsomes and Dp71f in mitochondria from mdx and mdx(3CV) mice. Dp71d in microsomes of mdx was similar to that of wild-type mice and, as expected, in mdx(3CV) this protein was undetecta ble. However, in mitochondria from mdx(3CV), Dp71f was overexpressed in com parison to mitochondria from mdx mice. Because in mdx(3CV) mice all the dys trophin proteins are mutated or diminished, we concluded that the protein d etected in mitochondria is not a Dp71f but a novel product named Dp71f-like protein. (C) 2000 Academic Press.