Transcriptome analysis of conditionally immortalized atrial myocytes: identification of a novel atrium-enriched protein involved in sarcomere assembly and maintenance. (14th October 2021)

• Record Type: Journal Article
• Authors: Van Gorp, P R R; Zhang, J; Liu, J; Tsonaka, R; Mei, H; Dekker, S O; Bart, C I; Schalij, M J; De Coster, T; Atsma, D A; Pijnappels, D A; De Vries, A A F
• Is Part Of: European heart journal. Volume 42(2021)Supplement 1
• Publication Date: 2021-10-14
• Subjects: Cardiovascular Development and Anatomy; Cardiology -- Periodicals; Heart -- Diseases -- Periodicals; 616.12005
• DOI: 10.1093/eurheartj/ehab724.3181
• Languages: English
• ISSNs: 0195-668X

Abstract

Abstract: Background: Heart development relies on the tight spatiotemporal control of cardiac gene expression. Genes involved in these processes have been identified using mainly (transgenic) animals models and pluripotent stem cell-derived cardiomyocytes (CMs). Recently, the repertoire of cardiomyocyte differentiation models has been expanded with iAM-1, a monoclonal cell line of conditionally immortalized neonatal rat atrial myocytes (NRAMs) which allows toggling between proliferative and differentiated (i.e. excitable and contractile) phenotypes in a synchronized and homogenous manner. Purpose: To identify and characterize (lowly expressed) genes with an as-of-yet uncharacterized role in cardiomyocyte differentiation, dedifferentiation and proliferation by exploiting the unique properties of conditionally immortalized NRAMs (iAMs). Methods and results: RNA sequencing was performed during a full cycle of iAM-1 differentiation and subsequent dedifferentiation, identifying ±13, 000 transcripts, of which the dynamic expressional changes during cardiomyogenic differentiation in most cases opposed those during dedifferentiation. Among the genes whose expression increased during differentiation and decreased during dedifferentiation were many genes with a known (lineage-specific) role in cardiac muscle formation, thereby confirming the relevance of iAMs as cardiomyogenic differentiation model. Filtering for cardiomyocyte-enriched low abundancy transcripts, resulted in the identification of an uncharacterized protein, which is highly conserved among Nephrozoa and up- and downregulated during cardiomyocyte differentiation and dedifferentiation, respectively. In neonatal and adult rats, this protein is muscle-specific, highly atrium-enriched and localized around the C-zone of cardiac sarcomeres. Lentiviral shRNA-mediated knockdown resulted in loss of sarcomeric organization in both NRAMs and iAMs. Neither knockdown nor overexpression of this protein affected the electrophysiological properties of differentiated iAM monolayers. Conclusions: iAM-1 cells offer a relevant model to identify and characterize novel (low abundancy) genes involved in cardiomyocyte (de)differentiation as exemplified by the identification a novel uncharacterized protein that is muscle-specific, highly atrium-enriched, localized around the C-zone of cardiac sarcomeres and plays a specific role in atrial sarcomerigenesis. FUNDunding Acknowledgement: Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Netherlands Organisation for Health Research and Development (ZonMw) Leiden Regenerative Medicine Platform Holding project with number (LRMPH)