A Metastable Atrial State Underlies The Primary Genetic Substrate for MYL4 Mutation-Associated Atrial Fibrillation

Ghazizadeh, Z., Kiviniemi, T.O., Olafsson, S., Plotnick, D., Beerens, M., Zhang, K., Gillon, L., Steinbaugh, M., Barrera, V., Ho Sui, S., Werdich, A.A., Kapur, S., Eranti, A., Gunn, J., Jalkanen, J., Airaksinen, J., Kleber, A.G., Hollmén, M., MacRae, C.A.
Circulation   141(4): 301-312 (Journal)
Registered Authors
MacRae, Calum A.
MeSH Terms
  • Animals
  • Animals, Genetically Modified/genetics
  • Animals, Genetically Modified/metabolism
  • Atrial Fibrillation*/genetics
  • Atrial Fibrillation*/metabolism
  • Atrial Fibrillation*/pathology
  • Cell Line
  • Connexin 43/genetics
  • Connexin 43/metabolism
  • Gene Knockout Techniques
  • Heart Atria/metabolism
  • Heart Atria/pathology
  • Human Embryonic Stem Cells/metabolism
  • Human Embryonic Stem Cells/pathology
  • Humans
  • Induced Pluripotent Stem Cells/metabolism
  • Induced Pluripotent Stem Cells/pathology
  • Mutation*
  • Myocytes, Cardiac*/metabolism
  • Myocytes, Cardiac*/pathology
  • Myosin Light Chains*/genetics
  • Myosin Light Chains*/metabolism
  • Zebrafish
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism
31735076 Full text @ Circulation
Background: Atrial fibrillation (AF) is the most common clinical arrhythmia and is associated with heart failure, stroke and increased mortality. The myocardial substrate for AF is poorly understood due to limited access to primary human tissue and mechanistic questions around existing in vitro or in vivo models. Methods: Using an MYH6:mCherry knock-in reporter line we developed a protocol to generate and highly purify human pluripotent stem cell-derived cardiomyocytes displaying physiological and molecular characteristics of atrial cells (hESC-atrial cells). We modeled human MYL4 mutants, one of the few definitive genetic causes of AF. To explore non cell-autonomous components of AF substrate, we also created a zebrafish Myl4 KO model, which exhibited molecular, cellular and physiologic abnormalities that parallel those in humans bearing the cognate mutations. Results: There was evidence of increased retinoic acid signaling in both hESC and zebrafish mutant models, as well as abnormal expression and localization of cytoskeletal proteins, and loss of intracellular NAD and NADH. To identify potentially druggable proximate mechanisms, we performed a chemical suppressor screen integrating multiple human cellular and zebrafish in vivo endpoints. This screen identified connexin 43 hemichannel (HC) blockade, as a robust suppressor of the abnormal phenotypes in both models of MYL4-related atrial cardiomyopathy. Immunofluorescence and co-immunoprecipitation studies revealed an interaction between MYL4 and Cx43 with altered localization of Cx43 HCs to the lateral membrane in MYL4 mutants, as well as in atrial biopsies from unselected forms of human AF. The membrane fraction from MYL4-/- hESC-atrial cells demonstrated increased phospho-Cx43 which was further accentuated by retinoic acid (RA) treatment and by the presence of risk alleles at the Pitx2 locus. Protein kinase C was induced by RA, and PKC inhibition also rescued the abnormal phenotypes in the atrial cardiomyopathy models. Conclusions: These data establish a mechanistic link between the transcriptional, metabolic and electrical pathways previously implicated in AF substrate and suggest novel avenues for the prevention or therapy of this common arrhythmia.
Genes / Markers
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Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Engineered Foreign Genes