Fig. 1. Schematic diagram of the mouse Mef2c gene. (A) The genomic structure of the mouse Mef2c gene is shown. Open boxes represent UTR. Closed boxes represent translated sequence. Skeletal muscle specific-transcripts contain exon 1 spliced directly to exon 4. Exons 2 and 3 are specific to heart and brain, respectively. The translational start site for Mef2c is located in exon 4 (ATG) and the stop codon (TGA) is located in exon 14. The contributions of exons 4-14 to the translated MEF2C protein are detailed in the black boxes below the genomic structure. Numbers above the boxes indicate the number of amino acids in each exon. The MADS/MEF2 domain is encoded by exons 4 and 5. Exons 6, 7, 9, 11 and 14 are used alternatively (see text). Exons 14a and 14b are generated by alternate splice acceptor sites that maintain the same open reading frame. However exon 14a is longer than exon 14b by 32 amino acids. (B) The skeletal muscle-specific 5'-untranslated sequence of Mef2c from the beginning of exon 1 to the translational start site (boxed) is given. The junction between exons 1 and 4 is located in the region between the arrowheads.