Cardiac-Specific Expression of ΔH2-R15 Mini-Dystrophin Normalized All Electrocardiogram Abnormalities and the End-Diastolic Volume in a 23-Month-Old Mouse Model of Duchenne Dilated Cardiomyopathy

Abstract

Heart disease is a major health threat for Duchenne/Becker muscular dystrophy patients and carriers. Expression of a 6-8 kb mini-dystrophin gene in the heart holds promise to change the disease course dramatically. However, the mini-dystrophin gene cannot be easily studied with adeno-associated virus (AAV) gene delivery because the size of the minigene exceeds AAV packaging capacity. Cardiac protection of the ΔH2-R19 minigene was previously studied using the cardiac-specific transgenic approach. Although this minigene fully normalized skeletal muscle force, it only partially corrected electrocardiogram and heart hemodynamics in dystrophin-null mdx mice that had moderate cardiomyopathy. This study evaluated the ΔH2-R15 minigene using the same transgenic approach in mdx mice that had more severe cardiomyopathy. In contrast to the ΔH2-R19 minigene, the ΔH2-R15 minigene carries dystrophin spectrin-like repeats 16 to 19 (R16-19), a region that has been suggested to protect the heart in clinical studies. Cardiac expression of the ΔH2-R15 minigene normalized all aberrant electrocardiogram changes and improved hemodynamics. Importantly, it corrected the end-diastolic volume, an important diastolic parameter not rescued by ΔH2-R19 mini-dystrophin. It is concluded that that ΔH2-R15 mini-dystrophin is a superior candidate gene for heart protection. This finding has important implications in the design of the mini/micro-dystrophin gene for Duchenne cardiomyopathy therapy.

Systemic AAV Micro-dystrophin Gene Therapy for Duchenne Muscular Dystrophy

“…In support of this, it was recently discovered that cardiac dystrophin interacts with a distinctive set of cellular proteins 155 . We also found that modification of the rod domain configuration substantially improved myocardial protection 156, 157. Heart rescue has only been studied in a few microgenes in mdx mice, and most of these studies have used the ΔR4–23/ΔC microgene 55, 59, 63, 65, 158, 159, 160.…”

Micro-utrophin Improves Cardiac and Skeletal Muscle Function of Severely Affected D2/mdx Mice

“… 23 In a more recent study, a mini-dystrophin construct optimized for the heart more effectively rescued cardiac function in aged BL10/ mdx mice. 48 These studies highlight the importance of tissue-specific mini-gene construct design. It is also important to note that a fully optimized mini-gene will only produce a mild BMD phenotype in DMD patients.…”

AAV CRISPR editing rescues cardiac and muscle function for 18 months in dystrophic mice

“…Western blot. Proteins from heart and skeletal muscle were extracted according to our published protocol (31). Dystrophin was detected with a rabbit polyclonal antibody against the C-terminal domain (catalog RB 9024, 1:500, Thermo Fisher Scientific).…”