PCR and immunocytochemical analyses of dystrophin-positive fibers in Duchenne muscular dystrophy.

Immunocytochemical studies on serial sections of muscles from 19 patients with Duchenne muscular dystrophy (DMD) were done using seven kinds of antidystrophin antibodies that span dystrophin. Fifteen of the patients were screened for intragenic deletions by the multiplex polymerase chain reaction (PCR); 7 were also tested, using Southern blots. Dystrophin-positive fibers were detected in 10 of the 19 patients, occurring with a frequency of 0.06-75.7%, as clusters or as single fibers in certain muscle bundles. In 7 of the 10 patients, the fibers stained with all antibodies from the N- through the C-terminal region. However, in one patient, there were dystrophin-positive fibers that stained with an N-terminal antibody (DYS-3) and an antibody specific to the rod region (DYS-1), but not with C-terminal antibody (DYS-2). In 2 patients, there were two kinds of fibers: one that did not stain with DYS-1 or DYS-2 and another that stained with all the antibodies used. Single-fiber PCR analysis in 2 patients showed that the genotype of dystrophin-positive fibers differed from that of dystrophin-negative fibers. These results suggest that the majority of dystrophin-positive fibers are of the same clonal origin, but that some are derived from plural reverse mutations, each with a different translation-frame-repairing modality and somatic mosaicism.