Abstract 213: Single-Cell RNA Sequencing Reveals Pathways Dysregulation by a NFATc1 Mutation in Patient-Specific Cardiomyocytes Derived From Inducible Pluripotent Stem Cells

Using a family-based approach with whole exome sequencing (WES) and custom bioinformatics tools we identified a novel mutation (M527L) in the Nuclear Factor of Activated T-Cells 1 gene (NFATc1). This nonsynonymous heterozygous substitution segregates in an autosomal dominant pattern within a family with a young onset Atrial Fibrillation (AF) phenotype. Patient specific inducible pluripotent stem cell derived-cardiomyocytes (iPSC-CM) from a patient carrying this variant showed abbreviated repolarization resulting in a shorter action potential duration compared to iPSC-CM from a healthy sibling control. Unlike familial monogenic AF where the mutation occurs in an ion channel gene, NFATc1 is a transcription factor that influences expression of multiple genes. Using single-cell RNA sequencing on 30 day post-differentiation iPSC-CM, we identified four subpopulations by K-mean clustering (k=4) of single cell transcriptomes and subsequent marker expression. We then performed gene-annotation enrichment analysis of differentially expressed genes specifically in the mutant (MT) and wild-type (WT) cardiomyocyte (CM) populations, detecting several key functional and pathological cardiac pathways affected in response to the NFATc1 mutation. These included Wnt, NF-kappaB and MAPK signaling, Ca homeostasis and gene categories that have been associated with atrial fibrillation. These results suggest that NFATc1 mutation may play an important role in the pathophysiology of familial atrial fibrillation by its broad impact on gene expression and subsequent pathway regulation.