Fig. 2. ALPK3 is required for sarcomere organization and calcium handling.

a, ALPK3 gene structure, schematic of ALPK3^mut gene targeting and graphic of cardiac differentiation. b, Representative immunofluorescence micrograph of WT and ALPK3^mut hPSC CMs stained for MYOM1 (green), α-actinin (purple) and DAPI (blue); scale bar, 30 μm. c, Representative line scans of Fluo-4 AM calcium handling in WT and ALPK3^mut hPSC CMs. d, Representative calcium transient trace of WT and ALPK3^mut hPSC CMs. e, Percentage of irregular calcium transients in WT and ALPK3^mut hPSC CMs. **P = 0.01. f, Peak systolic Fluo-4 AM fluorescence for WT and ALPK3^mut hPSC CMs. *P = 0.026. g, Time constant (tau) of diastolic calcium reuptake in WT and ALPK3^mut hPSC CMs. **P = 0.003. For the calcium handling data (e–g), n = 80 and 74 cardiomyocytes for WT and ALPK3^mut over eight and seven independent replicates, respectively. Data are shown as the mean ± s.e.m. Two-tailed Student’s t-test.

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