Cardiomyopathy Gene-Edited Cell Lines for Drug Discovery

Cardiomyopathy encompasses a group of myocardial diseases that impair heart function. According to the World Health Organization (WHO), cardiovascular diseases remain the leading cause of death globally, with cardiomyopathy contributing significantly to heart failure and sudden cardiac death. The global prevalence of hypertrophic cardiomyopathy (HCM) is estimated at 1 in 500 individuals, while dilated cardiomyopathy (DCM) affects approximately 1 in 2500. The National Cancer Institute (NCI) does not directly track cardiomyopathy, but the condition is a major cause of morbidity and mortality, with 5-year survival rates for advanced heart failure below 50%.

Key risk factors include genetic mutations (sarcomere genes), hypertension, viral myocarditis, alcohol abuse, and chemotherapeutic agents (e.g., doxorubicin). The clinical impact is profound, with cardiomyopathy being the most common indication for heart transplantation.

Cardiomyopathy is ideal for mechanistic studies due to its well-defined genetic etiology, especially in familial cases. Over 50 genes have been implicated, with clear genotype-phenotype correlations. Public datasets such as ClinVar and the Human Gene Mutation Database (HGMD) provide extensive variant information. Open questions include the role of modifier genes, environmental triggers, and the transition from hypertrophy to heart failure. Gene-edited cell models allow precise dissection of these mechanisms.

Cardiomyopathy arises from disruptions in sarcomere structure and function, leading to impaired contractility and energy metabolism. Key pathways include:

• • Sarcomere Contraction Pathway: Mutations in MYH7, MYBPC3, TNNT2, and TNNI3 alter actin-myosin cross-bridge cycling, reducing force generation.
• • Calcium Handling Pathway: Disrupted calcium homeostasis via SERCA2a, RYR2, and PLN leads to diastolic dysfunction and arrhythmias.
• • Energy Metabolism Pathway: Impaired mitochondrial oxidative phosphorylation and fatty acid oxidation reduce ATP production, contributing to heart failure.
• • Fibrosis and Remodeling Pathway: Activation of TGF-beta signaling and matrix metalloproteinases leads to myocardial fibrosis and ventricular dilation.

Data based on ClinVar and published cohort studies.

Key signaling networks in cardiomyopathy include:

• • MAPK/ERK Pathway: Hyperactivation due to sarcomere mutations leads to hypertrophy and fibrosis.
• • PI3K/AKT Pathway: Impaired signaling reduces cell survival and metabolic efficiency.
• • TGF-beta Pathway: Promotes fibroblast activation and extracellular matrix deposition.
• • Wnt/beta-catenin Pathway: Dysregulation contributes to cardiac remodeling and fibrosis.
• • Calcineurin/NFAT Pathway: Activated by calcium overload, driving hypertrophic gene expression.

Organoids (cardiac microtissues) offer 3D architecture, cell-cell interactions, and more physiologically relevant contractile function compared to 2D monolayers.

Animal models are essential for studying cardiomyopathy in vivo:

• • Genetically Engineered Mouse Models (GEMMs): Knock-in of MYH7 R403Q or MYBPC3 deletion recapitulates HCM/DCM phenotypes.
• • Induced Models: Doxorubicin administration or transverse aortic constriction (TAC) induces cardiomyopathy in mice.
• • Patient-Derived Xenografts (PDX): Limited use due to cardiac tissue complexity; more common for cardiac tumors.
• • Zebrafish Models: Transparent embryos allow real-time imaging of cardiac development and function.

CRISPR-Cas9 technology enables the creation of isogenic cell lines with precise genetic modifications. For cardiomyopathy, common models include:

• • MYH7 Knock-In (R403Q): Models hypertrophic cardiomyopathy.
• • MYBPC3 Knockout: Models dilated cardiomyopathy with haploinsufficiency.
• • TNNT2 Knock-In (R92W): Models troponin T-related cardiomyopathy.
• • LMNA Knockout: Models lamin A/C-related DCM.

Commercially available, sequence-verified models accelerate research by providing consistent, validated tools for drug screening and mechanistic studies. These models are available from commercial sources and can be customized for specific mutations.

Knockout and knock-in lines are used to validate the role of candidate genes in cardiomyopathy. For example:

• • MYBPC3 knockout iPSC-CMs show reduced contractility and sarcomere disarray, confirming its role in DCM.
• • TNNT2 R92W knock-in iPSC-CMs exhibit calcium handling defects and arrhythmias.
• • LMNA knockout lines reveal nuclear envelope instability and apoptosis.

Isogenic pairs (e.g., MYH7 wild-type vs. R403Q) are used to screen for compounds that reverse hypertrophic phenotypes. Examples include:

• • Testing MYK-461 (mavacamten) in MYH7 mutant lines.
• • Screening for calcium channel blockers in TNNT2 mutant lines.
• • Modeling resistance to doxorubicin in LMNA knockout lines.

CRISPR-based screens identify synthetic lethal partners and biomarkers. For instance:

• • Genome-wide CRISPR screens in MYBPC3 knockout lines identify genes whose loss exacerbates or rescues the phenotype.
• • Secretome analysis of gene-edited cells reveals novel biomarkers like NT-proBNP and troponin isoforms.