AbstractExon skipping is a disease modifying therapy that operates at the RNA level. In this strategy, oligonucleotide analog drugs are used to specifically mask specific exons and prevent them from inclusion in the mature mRNA. Of course, this also results in loss of the corresponding region from the cognate protein, which is one possible therapeutic aim. Exon skipping can also be used to restore protein expression in cases where a genetic frameshift mutation has occurred, and this how it is applied to Duchenne muscular dystrophy, DMD. DMD most commonly arises as a result of large exonic deletions that juxtapose flanking exons of incompatible reading frame in the dystrophin gene, creating a frameshift and abolishing protein expression. Loss of dystrophin protein leads to the pathology of the disease, which is severe, causing death generally in the second or third decade of life. Here, the primary aim of exon skipping is the restoration of the reading frame by skipping an exon adjacent to the patient’s original defect. However, the therapeutically expressed protein is of course edited, and missing both the region of the underlying genetic defect, as well as the therapeutically skipped exon. While restoring some protein expression is good, how removing some region from the middle of a protein effects its structure and function is unclear. Complicating this in the case of DMD is the fact that the dystrophin gene is very large, containing 79 exons. Many different underlying deletions are known, and exon skipping can be applied in many ways. It has previously been shown that many exon-skip edits result in structural perturbations of varying degrees. What has been unclear is whether and how exon editing can be done to minimize these perturbations. In this study we examine a systematic and comprehensive panel of possible exon edits in a region of the dystrophin protein, and identify for the first time, exon edits that appear to maintain structural stability similar to wildtype protein. We also identify factors that appear to be correlated with the degree of structural perturbation, such as the number of cooperative protein domains, as well as how the underlying exon structure interacts with the protein domain structure.
Structural Perturbations of Exon-Skipping Edits within the Dystrophin D20:24 Region
