Transcription factor NFATc1's signaling pathway and role in cardiomyocyte function

Atrial fibrillation (AF) is the most common sustained arrhythmia. It affects as many as 6.1 million people in the United States and increases their risk of stroke by 4-5 times. AF is evidently a very serious condition, but the scientific community does not yet fully understand its underlying mechanism. Tristani et al. have identified a family in which multiple members have early-onset AF. These members have also been found to have the M527L point mutation in their NFATc1 gene. This information leads us to believe that NFATc1 may be linked to AF. This study aimed to uncover components of NFATc1's downstream signaling pathway and examine its role in cardiomyocyte (CM) function. This knowledge could lend insight into NFATc1's potential role in AF's mechanism. A CRISPR-Cas9 system was used to knock out the NFATc1 gene in human induced pluripotent stem cells (iPSCs). The iPSCs were then differentiated into CMs. RNA sequencing and western blotting were performed on these cells to analyze expression of genes and proteins suspected to be downstream of NFATc1. The action potential duration to 50% repolarization (APD50) of these cells was also calculated. Results showed that NFATc1 knockout (KO) cardiomyocytes displayed significantly reduced expression of NKX2-5. This suggests that NFATc1 may drive NKX2-5 expression in iPSC-derived cardiomyocytes. Despite the lack of NFATc1, KO CMs had similar APD50 values as their wildtype counterparts. This may be because other proteins in the cells have the same function as NFATc1, and fulfill that role even in the absence of NFATc1.