Multiplatform modeling of atrial fibrillation identifies phospholamban as a central regulator of cardiac rhythm

Abstract

Atrial fibrillation (AF) is a common and genetically inheritable form of cardiac arrhythmia; however, it is currently not known how these genetic predispositions contribute to the initiation and/or maintenance of AF-associated phenotypes. One major barrier to progress is the lack of experimental systems enabling to rapidly explore gene function on rhythm parameters in models with human atrial and whole organ relevance. Here, we assembled a multi-model platform enabling 1) the high-throughput characterization of gene function on action potential duration and rhythm parameters using human iPSC-derived atrial-like cardiomyocytes and the Drosophila heart model, and 2) the validation of the findings using computational models of human adult atrial myocytes and tissue. As proof of concept, we screened 20 AF-associated genes and identified Phospholamban loss of function as a top conserved hit that shortens action potential duration and increases the incidence arrhythmia phenotypes upon stress. Mechanistically, our study reveals that Phospholamban regulates rhythm homeostasis by functionally interacting with L-type calcium channels and NCX. In summary, our study illustrates how a multi-model system approach paves the way for the discovery and molecular delineation of gene regulatory networks controlling atrial rhythm with application to AF.

The nutrient sensor CRTC & Sarcalumenin / Thinman represent a new pathway in cardiac hypertrophy

“…8B ). We have previously shown that SI tracks with intracellularly recorded action potentials (AP) and can be used as a surrogate for AP duration (APD) in this single cell layer heart tube (34). Reductions in Tmn/SRL expression would be expected to cause decreased SR Ca 2+ buffering and an increase in cytosolic Ca 2+ levels (see Model Fig.8 ) resulting in prolonged APD/SI.…”

“…4 A,B ). In addition, all three CRTC s were also expressed in 25 day hIPSC-cardiomyocytes (iPSC-CMs), but CRTC1 was expressed at very low levels compared to CRTC 2 & 3, which were expressed at levels 5-6 times higher ( Supplemental Table 7 ) (34). Consistent with this, siRNA KD of CRTC 2 or 3 in hiPSC-CMs caused significant action potential broadening while KD of the predominantly neuronal form, CRTC 1, had no effect ( Fig.…”

“…Transgenic UAS-RNAi fly lines were obtained from the Vienna Drosophila Stock Center; the Bloomington Drosophila Stock Center; and the Kyoto Stock Center. The following Gal4 drivers were used: (cardiac) TinCΔ4-Gal4 (34) and Hand4.2-Gal4 (41); (pericardial cell) DOT-Gal4 (#BL6903) and SNS- Gal4 (#BL76160), (neurons) ELAV-Gal4 (#BL8765), (fat body) CG-Gal4 (#BL7011) and LSP2-Gal4 (#BL6357), and (muscle) MEF2-Gal4 (#BL50742, all BL are from Bloomington Stock Center, Bloomington, IN, USA). The following UAS-RNAi lines were used: CRTC (#V100974), Pp2B (#V103144), Calmodulin (#V102004), CRTC-Flag (#V318324), NFAT (#V107032, all #V from Vienna Stock Center, Biocenter 1, 1030 Wien, At.).…”