DWORF Gene Therapy for DMD

The goal of this project is to test adeno-associated virus (AAV)-mediated gene therapy with the Dwarf open reading frame (DWORF). Abnormal cytosolic calcium overloading is a critical pathogenic mechanism in Duchenne muscular dystrophy (DMD). DWORF is a micropeptide that enhances cytosolic calcium uptake by sarco/endoplasmic reticulum (SR) calcium ATPase (SERCA). We hypothesize that AAV-mediated DWORF expression can increase SR calcium uptake and attenuate muscle disease in the mouse model of DMD. We further hypothesize that the combined DWORF/microdystrophin gene therapy will lead to better therapy than either micro-dystrophin or DWORF therapy alone. In this funding period, we tested whether AAV DWORF therapy can attenuate Duchenne cardiomyopathy, a leading cause of morbidity and mortality in DMD patients. We first showed that DWORF expression was significantly reduced at both the transcript level and the protein level in the heart of mdx mice, the most used mouse DMD model. We then delivered an AAV.DWORF vector by tail vein injection to mdx mice. We found that AAV.DWORF vector significantly increased DWORF expression but did not alter the expression of other calcium-regulating proteins. Importantly, we found AAV DWORF expression significantly enhanced SR calcium uptake, reduced myocardial fibrosis, improved cardiac electrophysiology, and enhanced heart hemodynamics. Unexpectedly, the left ventricular relaxation time constant Tau was not altered, suggesting AAV DWORF expression may impair atrium-ventricle coupling. In summary, our results suggest that AAV DWORF holds promise to treat DMD cardiomyopathy. Disruption of atrium-ventricle coupling suggests DWORF overexpression may have potential risks. Given the importance of toxicity in gene therapy, we will determine whether AAV-mediated DWORF expression is a real safety concern in the next funding period.