“…To do this, we performed RNA FISH for 16 gene transcripts as multiplexed pairs in 11,135 alpha-actinin-2-mEGFP expressing cardiomyocytes at D18 and D32 (Figures S5A-S5C; Table S3). Five of these genes were chosen because of their association with known sarcomere biology at a structural, regulatory, or functional level and included MYL7, ATP2A2, TCAP, NKX2.5, and BAG3 (Judge et al, 2017;Kasahara et al, 2003;Kubalak et al, 1994;MacLennan et al, 1985;Mason et al, 1999;Sacchetto et al, 2020). The remaining 11 genes were chosen based on results in a complementary transcriptomic study (Grancharova et al, 2021), where groups of genes were identified for their ability to correctly assign cardiomyocytes to a selected time point, which included MYH7, MYH6, COL2A1, H19, VCAN, CNTN5, MEF2C, PLN, PRSS35, BMPER, and housekeeping gene HPRT1 (Bargehr et al, 2019;Bertero et al, 2019;Friedman et al, 2018;Palpant et al, 2017) (Figures 6B-6E and S5A-S5C).…”