The mouse creatine kinase, muscle (Ckm) regulatory sequences, including 3,300 bp of 5' flanking sequence, exon 1, intron 1 and a truncated exon 2 ending just upstream of the translation initiation codon, drives expression in muscle of a cDNA containing exons 63 through 79 of the mouse dystrophin, muscular dystrophy (Dmd) gene. This represents the non-muscle Dp71 dystrophin mRNA isoform that begins at the unique Dp71 exon containing the 5' non-coding region and N-terminal coding sequence; the protein it encodes (sometimes called apo-dystrophin 1) contains only the cysteine-rich and C-terminal dystrophin associated protein complex (DAPC) interacting domains. Immunoblot analysis demonstrates expression of the Dp71 protein isoform in skeletal and cardiac muscle of transgenic, but not of control, mice. Immunohistochemical analysis shows its expression in skeletal muscle at a level similar to that of endogenous muscle dystrophin in control mice and demonstrates its correct localization to the sarcolemmal membrane and concentration at the neuromuscular junction (NMJ). (J:21841)