A potential dysregulation of NaV1.5, caused by human CaM mutations, has previously been investigated for a handful of LQTS-causing CaM variants (D96V, D130G, F142L, E141G) (Yin et al., 2014; Boczek et al., 2016; Rocchetti et al., 2017; Tarasov et al., 2023). Here, CALM2 is linked to familial long QT syndrome.