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The dystrophin whose defect is responsible for Duchenne and Becker muscular dystrophies is present in muscle, brain and cerebellum. We describe here the detection of dystrophin in human cultured skin fibroblasts, L809 cells and murine 3T6 cell line. Dystrophin transcripts initiated at the muscle specific first exon can also be amplified by cDNA-PCR from various fibroblastic cells. The expression of the dystrophin gene in fibroblasts could account for some abnormalities observed in patients fibroblast cultures.

ABSTRACTGene therapy for heart diseases requires availability of an efficient vector for gene transfer into myocardium. Recombinant adenovirus expressing the Escherichia coli -galactosidase (-Gal) gene was shown to infect rat cardiocytes efficiently in vivo. However, a time course of gene expression showed that transgene expression was maximal during the first week following injection, then declined and disappeared by day 21. An immunosuppressive treatment prolonged -Gal expression for at least 21 days. On the contrary, a preimmunization of the animals by two intraperitoneal injections of the vector led to a decreased transgene expression 48 hr after intramyocardial injection and to a barely detectable expression at the sixth day. Appearance of adenovirus neutralizing antibodies in preimmunized animals could have contributed to such a refractoriness to further adenoviral infection. Finally, a neonatal intrathymic injection of the vector was able to induce long-term LacZexpression for more than 2 months after heart injection, although neutralizing as well as anti--Gal antibodies were detected in sera of the animals. These results indicate that an immune response against first-generation replication-defective adenoviral vectors is a major cause of transient transgene expression, a cellular response being most probably responsible for ablation of transgene expression in immunocompetent animals.

A transcript generated by the distal part of the Duchenne Muscular Dystrophy (DMD) gene was initially detected in cells where the full size 14-kilobase (kb) messenger RNA is not found at a significant level. This transcript, approximately 4.5 kb long, corresponds to the cysteine-rich and carboxyl-terminal domains of dystrophin. It begins with a novel 80- to 100-nucleotide exon containing an ATG start site for a new coding sequence of 17 nucleotides in-frame with the consecutive dystrophin cDNA sequence from exon 63. This result suggests the existence of a third promoter that would be localized about 8 kilobases upstream from exon 63 of the DMD gene. The distal transcript is widely distributed but is absent in adult skeletal and myometrial muscle. It is much more abundant in fetal tissues. With an antibody directed against the dystrophin carboxyl terminus, the protein corresponding to this transcript was detected as a 70- to 75-kDa entity on Western blots. It was found in all tissues analyzed except in skeletal muscle. It was not found in lymphoblastoid cells from a Duchenne patient with a complete deletion of the dystrophin gene. The role and subcellular localization of this protein is not known. It may explain extramuscular symptoms exhibited by some Duchenne patients.