NPPA and familial dilated cardiomyopathy: Consistent with their increased disease severity, KI:KO hearts expressed higher transcript levels of two biomarkers of hemodynamic stress and heart failure, atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP)26 (Fig. 1j), thus supporting both ERRα- and ErbB2-dependent contributions to the observed DCM.