VDAC1 and Arrhythmia: Given that upregulation of mitochondrial Ca2+ uptake restores cardiac contraction in tremblor/ncx1h mutant embryos (Shimizu et al., 2015) and that E73 was previously reported to have an essential role in Ca2+ handling (Israelson et al., 2007; Peng et al., 2020), we suspected that E73 may be a critical residue that determines the isoform-specific rescue effect of VDAC genes on tremblor/ncx1h’s arrhythmia phenotype.