Duchene muscular dystrophy (DMD) is an X-linked neuromuscular disorder that affects about one in every 5000 live male births. DMD is caused by mutations in the gene that codes for dystrophin, which is required for muscle membrane stabilization. The loss of functional dystrophin causes muscle degradation that leads to weakness, loss of ambulation, cardiac and respiratory complications, and eventually, premature death. Therapies to treat DMD have advanced in the past decade, with treatments in clinical trials and four exon-skipping drugs receiving conditional Food and Drug Administration approval. However, to date, no treatment has provided long-term correction. Gene editing has emerged as a promising approach to treating DMD. There is a wide range of tools, including meganucleases, zinc finger nucleases, transcription activator-like effector nucleases, and, most notably, RNA-guided enzymes from the bacterial adaptive immune system clustered regularly interspaced short palindromic repeats (CRISPR). Although challenges in using CRISPR for gene therapy in humans still abound, including safety and efficiency of delivery, the future for CRISPR gene editing for DMD is promising. This review will summarize the progress in CRISPR gene editing for DMD including key summaries of current approaches, delivery methodologies, and the challenges that gene editing still faces as well as prospective solutions.

The CRISPR-Cas9 system is a revolutionary tool in genetic engineering, offering unprecedented precision and efficiency in genome editing. Cas9, an enzyme derived from bacteria, is guided by RNA to edit DNA sequences within cells precisely. However, while CRISPR-Cas9 presents notable benefits and encouraging outcomes as a molecular tool and a potential therapeutic agent, the process of producing and purifying recombinant Cas9 protein remains a formidable hurdle. In this study, we systematically investigated the expression of recombinant SpCas9-His in four distinct Escherichia coli (E. coli) strains (Rosetta2, BL21(DE3), BL21(DE3)-pLysS, and BL21(DE3)-Star). Through optimization of culture conditions, including temperature and post-induction time, the BL21(DE3)-pLysS strain demonstrated efficient SpCas9 protein expression. This study also presents a detailed protocol for the purification of recombinant SpCas9, along with detailed troubleshooting tips. Results indicate successful SpCas9 protein expression using E. coli BL21(DE3)-pLysS at 0.5 mM IPTG concentration. Furthermore, the findings suggest potential avenues for further enhancements, paving the way for large-scale Cas9 production. This research contributes valuable insights into optimizing E. coli strains and culture conditions for enhanced Cas9 expression, offering a step forward in the development of efficient genome editing tools and therapeutic proteins.