Titin-dependent transient ventricular defects result in adult atrial arrhythmia and impaired contractility

ABSTRACT: Atrial fibrillation (AF), the most common arrhythmia, is occasionally associated with cardiac developmental defects, but causal relationships are poorly defined. Importantly, functional compensation for developmental defects may mask increased risk of arrhythmia in adults. Here, we deleted 9 amino acids (Δ9) within a highly conserved A-band region of titin, a giant protein that serves as a molecular spring in cardiomyocytes, in both zebrafish and human induced pluripotent stem cell-derived atrial cardiomyocytes (hiPSC-aCMs). We find that the cardiac morphology of ttnaΔ9/Δ9 homozygous zebrafish embryos is perturbed and accompanied by reduced functional output, but ventricular function recovers within a few days of embryonic development, with most embryos reaching adulthood. Despite normal ventricular function, ttnaΔ9/Δ9 adults exhibit AF and atrial cardiomyopathy, with a striking absence of fibrosis, and these findings are recapitulated in TTNΔ9/Δ9-hiPSC-aCMs. Electrophysiological and proteomics analyses reveal atrial action potential shortening and increased expression and function of the cardiac potassium channel Kv7.1 and the slow delayed rectifier potassium current (IKs). Pharmacological suppression of IKs in both models prevents AF and improves atrial contractility. Collectively, these findings reveal how a small internal deletion in a large structural protein causes developmental abnormalities that functionally recover but increase the risk of adult cardiac disease via ion channel remodeling. The observed rescue with targeted antiarrhythmic therapy may have broader implications for the treatment of patients who harbor disease-causing rare variants in sarcomeric proteins.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Danio Rerio (zebrafish) (brachydanio Rerio)

TISSUE(S): Heart

SUBMITTER: Ziwei Zhang  

LAB HEAD: Yu Gao

PROVIDER: PXD038300 | Pride | 2024-08-09

REPOSITORIES: Pride