PLN and familial dilated cardiomyopathy: Based on previously published data on the development of DCM in PLN-R14 Δ/Δ mice [15,16], we decided to start PLN-ASO injections at 5 (ASO-early) or 6 (ASO-late) weeks of age when mice were shown to exhibit moderate (27.5 ± 0.2% fractional shortening (FS) vs. 36.2 ± 1.1% in age-matched wild-type (WT) controls) or severe (13.6 ± 2.3% FS) LV dysfunction with ventricular dilatation, respectively (Figure 1A and Figure S1).