Tbx18 Orchestrates Cytostructural Transdifferentiation of Cardiomyocytes to Pacemaker Cells by Recruiting the Epithelial–Mesenchymal Transition Program

• Type of Material: Article
• Authors: D. Brian Foster, Johns Hopkins University; Jin-mo Gu, Emory University; Elizabeth H. Kim, Cedars-Sinai Medical Center; David W. Wolfson, Emory University; Robert O'Meally, Johns Hopkins University; Robert N. Cole, Johns Hopkins University; Hee Cheol Cho, Johns Hopkins University
• Language: English
• Date: 2022-10-07
• Publisher: ACS Publications
• Publication Version: Final Published Version
• Copyright Statement: © 2022 The Authors. Published by American Chemical Society
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): https://doi.org/10.1021%2Facs.jproteome.2c00133
• Title of Journal or Parent Work: Journal of Proteome Research
• Volume: 21
• Issue: 10
• Start Page: 2277
• End Page: 2292
• Grant/Funding Information: D.B.F. was supported by AHA 12SDG12060056, AHA 18TPA34170575, and NIH R01HL134821. J.-m.G. was supported by NSF 1609831 to H.C.C. H.C.C. was supported by R01HL111646-01A1.
• Keywords: network; heart; systems biology; proteomics; epithelial−mesenchymal transition; pacemaker; cardiomyocytes
• Research Categories: Biology, Cell; Health Sciences, Medicine and Surgery

Abstract

Previously, we reported that heterologous expression of an embryonic transcription factor, Tbx18, reprograms ventricular cardiomyocytes into induced pacemaker cells (Tbx18-iPMs), though the key pathways are unknown. Here, we have used a tandem mass tag proteomic approach to characterize the impact of Tbx18 on neonatal rat ventricular myocytes. Tbx18 expression triggered vast proteome remodeling. Tbx18-iPMs exhibited increased expression of known pacemaker ion channels, including Hcn4 and Cx45 as well as upregulation of the mechanosensitive ion channels Piezo1, Trpp2 (PKD2), and TrpM7. Metabolic pathways were broadly downregulated, as were ion channels associated with ventricular excitation–contraction coupling. Tbx18-iPMs also exhibited extensive intracellular cytoskeletal and extracellular matrix remodeling, including 96 differentially expressed proteins associated with the epithelial-to-mesenchymal transition (EMT). RNAseq extended coverage of low abundance transcription factors, revealing upregulation of EMT-inducing Snai1, Snai2, Twist1, Twist2, and Zeb2. Finally, network diffusion mapping of >200 transcriptional regulators indicates EMT and heart development factors occupy adjacent network neighborhoods downstream of Tbx18 but upstream of metabolic control factors. In conclusion, transdifferentiation of cardiac myocytes into pacemaker cells entails massive electrogenic, metabolic, and cytostructural remodeling. Structural changes exhibit hallmarks of the EMT. The results aid ongoing efforts to maximize the yield and phenotypic stability of engineered biological pacemakers.