Figure 1: Organization of the human dystrophin (a) and utrophin (b) genes and corresponding protein products. Top panels show specific exons (yellow boxes with exon numbers) and intronic regions (black line) flanking transcription start sites of the different gene internal promoters (arrows) (Source: Pubmed: ENSG00000198947 for DMD gene; ENSG00000152818 for utrophin gene). Alternatively spliced first exons giving rise to distinct full-length forms of dystrophin (B: Brain; M: Muscle; P: Purkinje cells) and utrophin (Utrn-A; Utrn-B) are depicted (adapted from [30]). The different dystrophin (a) and utrophin-gene (b) protein products derived from distinct internal promoters are shown below the corresponding genes, as indicated. The main structural domains are represented, including the specific NH2-terminus domain (N, different colors schematize distinct NH2-terminal sequences), the central rod domain (green bar), the cysteine-rich domain (CYS, blue), and the COOH-terminus (red). All gene regions and protein domains are not to scale.