The transgene contains the following elements: a 2.2 kb DNA fragment containing the promoter, exon 1 and (part of) intron 1 of the human skeletal muscle actin alpha 1 gene, the a isoform cDNA of the mouse peroxisome proliferative activated receptor gamma coactivator 1 alpha gene, and bovine growth hormone poly(A) signal sequences. The a splice variant incorporates alternative 5' exon 1a. Six mouse lines were established and lines B, D, and E were studied. (J:84880)