BAG3 cardiomyopathy is likely of a loss-of-function nature because truncation mutations in BAG3 are frequently found in DCM patients, and a cardiac-specific Bag3-knockout mouse manifests DCM phenotypes (Chami et al., 2014; Dominguez et al., 2018; Fang et al., 2017; Franaszczyk et al., 2014). Here, BAG3 is linked to familial dilated cardiomyopathy.