Duchenne Muscular Dystrophy (DMD)
The 14-kb mRNA transcribed from the gene is mainly expressed in the skeletal and cardiac muscles, but some is also expressed in the brain. Many different types of mutations can occur to give DMD, however all mutations are a loss-of-function mutation resulting in little or no gene product. The three common types of mutations in the dystrophin gene are large deletions of at least one exon, small point mutations and large duplications of at least one exon. Large deletions of exons occurs in 60-70% of cases, point mutations occur in 15-30% of cases and large duplications occur in 10% of cases (4). The vast majority of large deletions detected in DMD are found in two hotspots. The major hotspot spans exons 45–53 and if mutated it removes some of the rod domain of the dystrophin protein, while the minor hotspot spans exons 2–20 and mutation partially or completely removes the actin-binding sites of the protein as well as some of the rod