Fig 1: Profile of myofilament creatine kinase (MM-CK) in mutant Tnnt2-I79N and Mybpc3 hypertrophic cardiomyopathy (HCM) mouse hearts. Mice that carry the human c.772G>A MYBPC3 mutation at the homozygous state (Mybpc3-KI) and WT controls were generated in a Black Swiss background as described previously (Vignier, Schlossarek et al. 2009) and used at an age of 12–16 weeks. Transgenic mice expressing mutant or the WT troponin T (Tnnt2-I79N and -WT) were generated as described previously (Miller, Szczesna et al. 2001) in a mixed genetic background and used at an age of 12–16 weeks. A. Western blot with a creatine kinase (CK) specific antibody (Santa Cruz, sc-15,164) and an antibody against α-actinin (Sigma, A7811) to correct for loading following methods described in Sequeira and colleagues (Sequeira, Najafi et al. 2015). The CK antibody was diluted to a final working concentration of 2.0 μg/mL by a 500× dilution of the stock solution (1 mg/mL), while the α-actinin antibody was diluted to a final working concentration of 0.4 μg/mL by a 2500× dilution of the stock solution (1 mg/mL). B. Creatine kinase activity was evaluated at 37 °C using a colorimetric test kit (Abcam, ab65339), with signal saturation after 30 min. An unpaired t-test was used to compare I79N or Mybpc3 to their respective wild-type controls. The significance level was set to *p < 0.05. The data is presented as mean ± SEM and is normalized relative to controls (set to 100). A total of N = 5 mouse hearts with three to four intrinsic replicates (total of n = 16 replicates, where n is experimental repetitions) were used per each sample group.