What is the clinical evidence from this study?

Study design: Other. Population: Dilated cardiomyopathy. Intervention: AAVMYO-ABE vs. PBS. Primary outcome: RBM20 localization and cardiac ejection fraction.

June 22, 2023Nature Communications47 citationsOpen Access

Striated muscle-specific base editing enables correction of mutations causing dilated cardiomyopathy

MGMarkus GroschGerman Centre for Cardiovascular Research LSLaura SchraftEuropean Molecular Biology Laboratory ACAdrian ChanHeidelberg University

Key Result

AAVMYO-delivered base editors repaired >70% of cardiomyocytes in Rbm20 mutant mice, restoring RBM20 localization in 75% of cells and returning cardiac ejection fraction to wild-type levels.

Structured PICO

Does AAVMYO-delivered adenine base editing improve molecular and physiological phenotypes in Rbm20-mutant dilated cardiomyopathy models?

Population

Juvenile P635L and R636Q Rbm20 knock-in mice treated at 4 weeks of age and followed for up to 12 weeks to assess the efficacy of AAVMYO-mediated base editing.

Intervention

Adenine base editors (ABEs, e.g., 8e-NRCH, SpRY) delivered via the synthetic AAV9 variant AAVMYO.

Comparator

PBS/saline injection (in vivo) or unedited cells (in vitro).

Outcome

Correction of Rbm20 mutation, restoration of RBM20 localization, splicing of target genes (e.g., TTN), and recovery of cardiac ejection fraction and volume.surrogate

Striated muscle-specific base editing via AAVMYO effectively corrects pathogenic Rbm20 mutations in vivo, rescuing the dilated cardiomyopathy phenotype and highlighting its potential as a gene therapy.

Limitations

WGS sensitivity limits detection of low-frequency random mutations in a subset of cells
Potential for bystander edits depending on the specific adenine deaminase used

Abstract

Dilated cardiomyopathy is the second most common cause for heart failure with no cure except a high-risk heart transplantation. Approximately 30% of patients harbor heritable mutations which are amenable to CRISPR-based gene therapy. However, challenges related to delivery of the editing complex and off-target concerns hamper the broad applicability of CRISPR agents in the heart. We employ a combination of the viral vector AAVMYO with superior targeting specificity of heart muscle tissue and CRISPR base editors to repair patient mutations in the cardiac splice factor Rbm20, which cause aggressive dilated cardiomyopathy. Using optimized conditions, we repair >70% of cardiomyocytes in two Rbm20 knock-in mouse models that we have generated to serve as an in vivo platform of our editing strategy. Treatment of juvenile mice restores the localization defect of RBM20 in 75% of cells and splicing of RBM20 targets including TTN. Three months after injection, cardiac dilation and ejection fraction reach wild-type levels. Single-nuclei RNA sequencing uncovers restoration of the transcriptional profile across all major cardiac cell types and whole-genome sequencing reveals no evidence for aberrant off-target editing. Our study highlights the potential of base editors combined with AAVMYO to achieve gene repair for treatment of hereditary cardiac diseases.

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