Differential DNA methylation and gene expression in stem cell-derived cardiomyocytes from patients with and without a history of clozapine-induced myocarditis

Clozapine is an effective antipsychotic medication for the management of treatment-resistant schizophrenia. However, the use of clozapine is limited due to severe and sometimes fatal adverse events, including cardiac inflammation (myocarditis). To date, studies of clozapine dosing and genetic studies have not identified robust risk markers. Our study aimed to identify potential epigenetic markers for clozapine-induced myocarditis using genome-wide profiling of DNA methylation and RNA sequencing in a novel in vitro model using patient-derived cells. Induced pluripotent stem cells (iPSCs) from treatment-resistant schizophrenia patients with (case) and without (control) a history of clozapine-induced myocarditis were differentiated into beating cardiomyocytes (iPSC-CMs). These cells were exposed to clozapine at a physiologically relevant concentration (2.8 µmol/L) for 24 h. Before and after clozapine treatment, RNA from the iPSC-CMs was sequenced (RNA-seq), and DNA was assessed for methylation using the EPIC array. Our analysis revealed that hypermethylation at the promoter regions of <i>GSTM1</i> and <i>ZNF559</i> is associated with reduced gene expression in cases relative to controls, regardless of clozapine exposure. Additionally, hypermethylation in the gene bodies of <i>AKAP7</i> and <i>HLA-DRB1</i> was associated with increased expression in cases relative to controls. Conversely, hypomethylation in the gene bodies of <i>GAL3ST3</i> and <i>PDPR</i> correlated with lowered gene expression in cases relative to controls. These findings highlight a potential involvement of DNA methylation in gene expression regulation and its putative impact on clozapine-induced myocarditis. Additional studies are warranted to validate our findings and further elucidate a potential mechanism.