Abstract 13033: Titin Mutations in IPS Cells Define Sarcomere Insufficiency as a Cause of Dilated Cardiomyopathy (Best of Basic Science Abstract)
Introduction: Dilated cardiomyopathy (DCM) is one of the most common cardiovascular disorders with a prevalence of 1:250 patients. Patients with DCM develop left ventricular dilation, systolic dysfunction, and ultimately heart failure. While DCM can occur due to acquired cardiovascular conditions, our group recently identified mutations in the giant sarcomere protein titin (TTN) as the most common genetic cause of DCM, occurring in 15-20% of familial or sporadic cases. Truncation mutations in the A-band of TTN are enriched in DCM cases, while truncation mutations in the I-band are less pathogenic and are commonly found in normal patients. How some mutations in TTN lead to DCM remains unclear.
Hypothesis: We tested whether myocytes derived from induced pluripotent stem cells (iPS-CMs) with mutations in TTN in the A-band and I-band could recapitulate features of DCM by single myocyte and cardiac microtissue (iPS-CMT) assays.
Methods & Results: We engineered a panel of patient-specific iPSc’s with two truncation mutations in the A-band and a missense mutation, W976R, in the Z/I junction of TTN. TTN mutant iPS-CMTs had impaired baseline contractility and impaired response to both mechanical and adrenergic stress. In addition, isogenic iPSc lines with TTN truncation mutations in the A- and I-bands also had similarly reduced contractile function. By combining functional analyses with RNAseq, we determine that TTN truncations in the I-band are less pathogenic because I-band exons are spliced out in the adult left ventricle but are expressed in iPS-CMs. Finally, we demonstrate that mutant TTN protein in iPS-CMs leads to sarcomere insufficiency and growth factor and cell signaling deficiencies.
Conclusion: iPS-CMs and iPS-CMTs with TTN mutations derived from patient-specific and CRISPR/CAS9-edited iPScs recapitulate contractility and adaptation deficiencies often identified in patients with dilated cardiomyopathy. TTN truncation mutations in the A-band may cause DCM by impaired sarcomerogenesis while I-band truncations are spliced out and are tolerated. Sarcomere abnormalities lead to failure to activate growth factor and cell signaling pathways. The iPS-CMT assay can be a powerful strategy to determine the pathogenicity of DCM mutations.
Author Disclosures: J. Hinson: None. A. Chopra: None. S. Swist: None. C. Benson: None. C. Sheng: None. N. Nafissi: None. W. Polacheck: None. N. Hubner: None. W. Linke: None. S. Cook: None. C. Chen: Ownership Interest; Modest; Innolign Biomedical. J. Seidman: None. C. Seidman: None.
- © 2015 by American Heart Association, Inc.