Fig. 2. Transgenes used to identify the Mef2c skeletal muscle control region. Regions of Mef2c 5' flanking DNA used in lacZ transgenes are shown. (Top) The region containing endogenous skeletal-muscle specific promoter activity is indicated in yellow. The position of the Hand2 neural crest enhancer (NCE), which was used as an internal control for lacZ expression with construct 1, is shown. (Bottom) +1 indicates the transcriptional start site for skeletal muscle-specific transcripts. The minimal skeletal muscle regulatory region is indicated in pale blue. The location of the MEF2 binding site at -64 bp and the E-box at -38 bp are indicated in the enlarged construct 7. x, mutation; >, sense orientation; <, antisense orientation; < >, sense or antisense orientation. A minimum of two transgenic F0 embryos were analyzed for each construct. Multiple independent stable transgenic lines were also generated with constructs 7 and 11; they showed the same expression patterns seen in F0 transgenic mice. Broken lines indicate deleted regions.
