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Long-term maintenance of dystrophin expression and resistance to injury of skeletal muscle in gene-edited mice

ABSTRACT: Duchenne Muscular Dystrophy (DMD) is a lethal muscle disease caused by mutations in the dystrophin gene. CRISPR/Cas9 genome-editing has been used to correct DMD mutations in animal models at young ages. However, the longevity and durability of CRISPR/Cas9 editing remained to be determined. To address these issues, we subjected DEx44 DMD mice to systemic delivery of AAV9 expressing CRISPR/Cas9 gene editing components to reframe exon 45 of the dystrophin gene, allowing robust dystrophin expression and maintenance of muscle structure and function. We showed that genome correction by CRISPR/Cas9 confers lifelong expression of dystrophin in mice and that corrected skeletal muscle is highly durable and resistant to myofiber necrosis and fibrosis, even in response to chronic injury. In contrast, when muscle fibers were ablated by barium chloride injection, satellite cells were unable to restore dystrophin expression due to restriction of gene editing components. Analysis of on-target and off-target gene editing in aged mice confirmed the stability of gene correction and the lack of significant off-target editing at 18 months of age. These findings demonstrate the long-term durability of CRISPR/Cas9 genome editing as a therapy for maintaining the integrity and function of DMD muscle, even under conditions of stress.

ORGANISM(S): Mus musculus

PROVIDER: GSE180771 | GEO | 2021/07/27

REPOSITORIES: GEO

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Project description:Absence of the dystrophin gene in Duchenne muscular dystrophy (DMD) results in the degeneration of skeletal and cardiac muscles. Owing to advances in respiratory medicine, cardiomyopathy has become a significant aspect of the disease. While CRISPR/Cas9 genome editing technology holds great potential as a novel therapeutic avenue for DMD, little is known about the efficacy of correction of DMD using the CRISPR/Cas9 system in mitigating the cardiomyopathy phenotype in DMD. To define the effects of CRISPR/Cas9 genome editing on structural, functional and transcriptional dysregulation in DMD-associated cardiomyopathy. We generated induced pluripotent stem cells (iPSCs) from a patient with a deletion of exon 44 of the DMD gene (ΔEx44) and his healthy brother. Here, we targeted exon 45 of the DMD gene by CRISPR/Cas9 genome editing to generate corrected DMD (cDMD) iPSC lines, wherein the DMD open reading frame was restored via reframing (RF) or exon skipping (ES). While DMD cardiomyocytes (CMs) demonstrated morphologic, structural and functional deficits compared to control CMs, CMs from both cDMD lines were similar to control CMs. Bulk RNA-sequencing of DMD CMs showed transcriptional dysregulation consistent with dilated cardiomyopathy, which was mitigated in cDMD CMs. We then corrected DMD CMs by adenoviral delivery of Cas9/gRNA and showed that postnatal correction of DMD CMs reduces their arrhythmogenic potential. Single-nucleus RNA-sequencing of hearts showed reduced transcriptional dysregulation in CMs and fibroblasts in corrected mice compared with DMD mice, consistent with reduced histopathologic changes.We show that CRISPR/Cas9-mediated correction of DMD ΔEx44 mitigates structural, functional and transcriptional dysregulation consistent with dilated cardiomyopathy irrespective of how the protein reading frame is restored. We show that these effects extend to postnatal editing in iPSC-CMs and mice. These findings provide key insights into the utility of genome editing as a novel therapeutic for DMD-associated cardiomyopathy.

Project description:Rationale – Absence of the dystrophin gene in Duchenne muscular dystrophy (DMD) results in the degeneration of skeletal and cardiac muscles. Owing to advances in respiratory medicine, cardiomyopathy has become a significant aspect of the disease. While CRISPR/Cas9 genome editing technology holds great potential as a novel therapeutic avenue for DMD, little is known about the efficacy of correction of DMD using the CRISPR/Cas9 system in mitigating the cardiomyopathy phenotype in DMD. Objective – To define the effects of CRISPR/Cas9 genome editing on structural, functional and transcriptional dysregulation in DMD-associated cardiomyopathy. Methods and Results – We generated induced pluripotent stem cells (iPSCs) from a patient with a deletion of exon 44 of the DMD gene (ΔEx44) and his healthy brother. Here, we targeted exon 45 of the DMD gene by CRISPR/Cas9 genome editing to generate corrected DMD (cDMD) iPSC lines, wherein the DMD open reading frame was restored via reframing (RF) or exon skipping (ES). While DMD cardiomyocytes (CMs) demonstrated morphologic, structural and functional deficits compared to control CMs, CMs from both cDMD lines were similar to control CMs. Bulk RNA-sequencing of DMD CMs showed transcriptional dysregulation consistent with dilated cardiomyopathy, which was mitigated in cDMD CMs. We then corrected DMD CMs by adenoviral delivery of Cas9/gRNA and showed that postnatal correction of DMD CMs reduces their arrhythmogenic potential. Single-nucleus RNA-sequencing of hearts showed reduced transcriptional dysregulation in CMs and fibroblasts in corrected mice compared with DMD mice, consistent with reduced histopathologic changes. Conclusions – We show that CRISPR/Cas9-mediated correction of DMD ΔEx44 mitigates structural, functional and transcriptional dysregulation consistent with dilated cardiomyopathy irrespective of how the protein reading frame is restored. We show that these effects extend to postnatal editing in iPSC-CMs and mice. These findings provide key insights into the utility of genome editing as a novel therapeutic for DMD-associated cardiomyopathy.

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Long-term maintenance of dystrophin expression and resistance to injury of skeletal muscle in gene-edited mice

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