STIM1 and heart disorder: In addition, Stim1-Ser88Gly (Figure 2A), a mutation recently discovered in a patient with heart disease (Harris et al., 2017) (see discussion), is less robustly phosphorylated than Stim1-WT in vitro and in cells (Figure 2C,D and E), suggesting that Fam20C phosphorylates Stim1-Ser88.