Prevention of early-onset cardiomyopathy in Dmd exon 52-54 deletion mice by CRISPR-Cas9-mediated exon skipping.

Duchenne muscular dystrophy (DMD) is a disease with a life-threatening trajectory resulting from mutations in the dystrophin gene, leading to degeneration of skeletal muscle and fibrosis of cardiac muscle. The overwhelming majority of mutations are multiexonic deletions. We previously established a dystrophic mouse model with deletion of exons 52-54 in Dmd that develops an early-onset cardiac phenotype similar to DMD patients. Here we employed CRISPR-Cas9 delivered intravenously by adeno-associated virus (AAV) vectors to restore functional dystrophin expression via excision or skipping of exon 55. Exon skipping with a solitary guide significantly improved editing outcomes and dystrophin recovery over dual guide excision. Some improvements to genomic and transcript editing levels were observed when the guide dose was enhanced, but dystrophin restoration did not improve considerably. Editing and dystrophin recovery were restricted primarily to cardiac tissue. Remarkably, our exon skipping approach completely prevented onset of the cardiac phenotype in treated mice up to 12 weeks. Thus, our results demonstrate that intravenous delivery of a single-cut CRISPR-Cas9-mediated exon skipping therapy can prevent heart dysfunction in DMD in vivo.

Advances in CRISPR/Cas9 Genome Editing for the Treatment of Muscular Dystrophies.

Muscular dystrophies (MDs) comprise a diverse group of inherited disorders characterized by progressive muscle loss and weakness. Given the genetic etiology underlying MDs, researchers have explored the potential of clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) genome editing as a therapeutic intervention, resulting in significant advances. Here, we review recent progress on the use of CRISPR/Cas9 genome editing as a potential therapy for MDs. Significant strides have been made in this realm, made possible through innovative techniques such as precision genetic editing by modified forms of CRISPR/Cas9. These approaches have shown varying degrees of success in animal models of MD, including Duchenne MD, congenital muscular dystrophy type 1A, and myotonic dystrophy type 1. Even so, there are several challenges facing the development of CRISPR/Cas9-based MD therapies, including the targeting of satellite cells, improved editing efficiency in skeletal and cardiac muscle tissue, delivery vehicle enhancements, and the host immunogenic response. Although more work is needed to advance CRISPR/Cas9 genome editing past the preclinical stages, its therapeutic potential for MD is extremely promising and justifies concentrated efforts to move into clinical trials.

Targeted genome editing in vivo corrects a Dmd duplication restoring wild-type dystrophin expression.

Tandem duplication mutations are increasingly found to be the direct cause of many rare heritable diseases, accounting for up to 10% of cases. Unfortunately, animal models recapitulating such mutations are scarce, limiting our ability to study them and develop genome editing therapies. Here, we describe the generation of a novel duplication mouse model, harboring a multi-exonic tandem duplication in the Dmd gene which recapitulates a human mutation. Duplication correction of this mouse was achieved by implementing a single-guide RNA (sgRNA) CRISPR/Cas9 approach. This strategy precisely removed a duplication mutation in vivo, restored full-length dystrophin expression, and was accompanied by improvements in both histopathological and clinical phenotypes. We conclude that CRISPR/Cas9 represents a powerful tool to accurately model and treat tandem duplication mutations. Our findings will open new avenues of research for exploring the study and therapeutics of duplication disorders.

Twitter Activity Is Associated With a Higher Research Citation Index for Academic Thoracic Surgeons.

BACKGROUND: Academic surgeons are encouraged to promote their work on social media. We hypothesized that thoracic surgeons who are active on Twitter have a higher research citation index (Hirsch index [h-index]) than their counterparts who are not. METHODS: Thoracic surgeons on CTSNet.org in Canada and the United States were queried for profiles with an h-index on Google Scholar and/or Research Gate in July 2018. Surgeons were categorized by whether they possessed a Twitter account (T+) or not (T-), and h-index values were compared. Within the T+ cohort a multivariate regression model was used to identify independent predictors of increased h-index among variables related to Twitter activity. RESULTS: Of 3741 surgeons queried, 19.3% (722) had a known h-index. The mean h-index for the entire cohort was 14.54 (SD, 15.73). The median h-index was 10 (range, 0-121), and the 75th percentile h-index was 20. T+ surgeons had a median h-index of 10 (range, 0-66), and T- surgeons had a median h-index of 10 (range, 0-72; P = .25). The 75th percentile h-index for T+ surgeons was 23 compared with 20 for T- surgeons (P = .24). For T+ surgeons the regression model identified the number of followers (P = .029), the number of people followed (P = .048), and the frequency of tweeting (P = .046) as independent predictors of a higher h-index. CONCLUSIONS: The median h-index for an academic thoracic surgeon in Canada and the United States is 10. Surgeons who engage in Twitter activity are more likely to have their research cited by others.