Abstract

Generating cardiomyocytes (CMs) from human induced pluripotent stem cells (hiPSCs) has represented a significant advance in our ability to model cardiac disease. Current differentiation protocols, however, have limited use due to their production of heterogenous cell populations, primarily consisting of ventricular-like CMs. Here we describe the creation of two chamber-specific reporter hiPSC lines by site-directed genomic integration using CRISPR-Cas9 technology. In the MYL2-tdTomato reporter, the red fluorescent tdTomato was inserted upstream of the 3′ untranslated region of the Myosin Light Chain 2 (MYL2) gene in order faithfully label hiPSC-derived ventricular-like CMs while avoiding disruption of endogenous gene expression. Similarly, in the SLN-CFP reporter, Cyan Fluorescent Protein (CFP) was integrated downstream of the coding region of the atrial-specific gene, Sarcolipin (SLN). Purification of tdTomato+ and CFP+ CMs using flow cytometry coupled with transcriptional and functional characterization validated these genetic tools for their use in the isolation of bona fide ventricular-like and atrial-like CMs, respectively. Finally, we successfully generated a double reporter system allowing for the isolation of both ventricular and atrial CM subtypes within a single hiPSC line. These tools provide a platform for chamber-specific hiPSC-derived CM purification and analysis in the context of atrial- or ventricular-specific disease and therapeutic opportunities.

Highlights

  • Generating cardiomyocytes (CMs) from human induced pluripotent stem cells has represented a significant advance in our ability to model cardiac disease

  • The donor plasmid was constructed using the P2A self-cleaving peptide-based multi-gene expression system allowing for the co-expression of the target genes and their corresponding fluorophores based on endogenous promoter activity without disruption to their biological function

  • Using single cell traction force microscopy (TFM), we identified greater contractile force generated in tdTomato+ hiPSCCMs as compare to tdTomato− human induced pluripotent stem cells (hiPSCs)-CMs (Fig. 3G)

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Summary

Introduction

Generating cardiomyocytes (CMs) from human induced pluripotent stem cells (hiPSCs) has represented a significant advance in our ability to model cardiac disease. Using CRISPR-Cas[9] technology, we successfully generated three categories of fluorescent reporter lines including ventricular (MYL-2-tandem dimer Tomato (tdTomato) only), atrial (SLN-cyan fluorescent protein (CFP) only), and a double atrial-ventricular (MYL-2-tdTomato; SLN-CFP) reporter lines by targeting fluorescent reporter constructs to these highly-conserved, chamber-specific genes. These tools provide novel insights into the morphologic, functional and biological differences in chamber-specific cardiomyocytes, and provide an effective method for purifying atrial and ventricular populations from the same hiPSC line for further analysis and high-throughput screening

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Conclusion

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