Abstract 4140554: Epigenetic Activation of Endothelial to Mesenchymal Transition Links Endothelial Dysfunction to Atrial Fibrillation in Lamin A/C Cardiomyopathy

Introduction: Accumulating evidence supports a bidirectional association between atrial fibrillation (AF), and endothelial cell (EC) dysfunction; however, the underlying mechanisms remain elusive. Variants in LMNA , which encodes the nuclear envelope protein Lamin A/C, have been linked with AF. It is known that LMNA variants can cause atherosclerotic changes in blood vessels and increase the risk for stroke, however, it remains unclear if endothelial dysfunction creates an arrhythmogenic substrate for AF in the atria. Hypothesis: LMNA -S143P mutation induces endothelial to mesenchymal transition ( EndMT) in ECs which creates an arrhythmogenic substrate for AF by extracellular matrix (ECM) and ion channel remodeling. Methods: We generated and co-cultured human induced pluripotent stem cell-derived endothelial cells (hiPSC-ECs) and atrial cardiomyocytes (hiPSC-aCMs) from a large family harboring a pathogenic LMNA -S143P mutation ( Fig. A-B ) and performed functional characterization by an angiogenesis assay. Analysis of action potential duration (APD) (Fig. B) was performed by optical voltage mapping. Transcriptomic and epigenetic analysis was performed by RNA-sequencing and assay for transposase accessible chromatin and sequencing (ATAC-seq). Results: LMNA -S143P hiPSC-ECs show hallmarks of EC dysfunction with reduced angiogenesis ( Fig. C ), gene expression signature of EndMT, upregulation of ECM remodeling genes and downregulation of endothelial genes ( Fig. E ). Upstream regulator analysis identified TWIST-1 as a driver of EndMT (Fig. F) . ATAC-seq showed increased open chromatin at genes related to EndMT and identified TWIST-1 as one of the most significantly enriched transcription factors ( Fig. G-I ). Upregulated ATAC peaks were associated with inflammation and fibrosis pathways ( Fig. H ). Co-culture of LMNA -S143P hiPSC-ECs with wild-type hiPSC-aCMs induced APD heterogeneity (SD=0.03, 0.2, 0.01 for WT, LMNA -S143P, CRISPR-GC respectively, p<0.05, n=6) ( Fig. D ). These changes were rescued by the CRSIPR-GC hiPSC-ECs. Conclusion: Our results suggest that epigenetic-driven EndMT due to a LMNA -S143P mutation promotes inflammatory and fibrotic remodeling in the atria and we identified TWIST1 as a potential therapeutic target.