Ca2+ transients are prolonged in tmem161b zebrafish mutants. (A) Schematic of the GCaMP6f biosensor used to measure in vivo, cardiomyocyte-specific Ca2+ transients. (B) Ca2+ transient parameters. (C–E) Representative overlaid Ca2+ transients from the (C) atrium, (D) AVC, and (E) ventricle of tmem161b+/+ and tmem161b−/− embryos. (F–H) Ca2+ transient parameters in 3 dpf tmem161b+/+, tmem161b+/−, and tmem161b−/− embryos. (F) Transient upstroke time, showing a faster upstroke in the ventricle of tmem161b−/− embryos. (G) Normalized GCaMP6f signal amplitude, demonstrating a higher ventricular Ca2+ transient amplitude in tmem161b−/−. (H) Ca2+ recovery time, demonstrating a slower reuptake/efflux of Ca2+ in tmem161b−/− ventricles (mean ± SD; n = 12 to 23; *P < 0.05, **P ≤ 0.01, ***P ≤ 0.001; n.s., nonsignificant.
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