Increased myofilament Ca2+ sensitivity, as observed in three Mybpc3 cardiomyopathy mouse models (Mybpc3 KO and KI) developed by us and others (Cazorla et al., 2006; Pohlmann et al., 2007; Vignier et al., 2009; Fraysse et al., 2012; Barefield et al., 2014), and in other animal models of HCM (Knollmann et al., 2001; Robinson et al., 2007; Iorga et al., 2008), could be an underlying cause of diastolic dysfunction. The gene discussed is MYBPC3; the disease is cardiomyopathy.