Heart failure is a leading cause of morbidity and mortality in Western society. The cardiovascular
transcription factor CHF1/Hey2 has been linked to experimental
heart failure in mice, but the mechanisms by which it regulates myocardial function remain incompletely understood. The objective of this study was to determine how CHF1/Hey2 affects development of
heart failure through examination of contractility in a myocardial knockout mouse model. We generated myocardial-specific knockout mice. At baseline, cardiac function was normal, but, after aortic banding, the conditional knockout mice demonstrated a greater increase in ventricular weight-to-
body weight ratio compared with control mice (5.526 vs. 4.664 mg/g) and a significantly decreased ejection fraction (47.8 vs. 72.0% control). Isolated cardiac myocytes from these mice showed decreased
calcium transients and fractional shortening after electrical stimulation. To determine the molecular basis for these alterations in excitation-contraction coupling, we first measured total sarcoplasmic reticulum
calcium stores and
calcium-dependent force generation in isolated muscle fibers, which were normal, suggesting a defect in
calcium cycling. Analysis of gene expression demonstrated normal expression of most genes known to be involved in myocardial
calcium cycling, with the exception of the
ryanodine receptor binding protein FKBP12.6, which was expressed at increased levels in the conditional knockout hearts. Treatment of the isolated knockout myocytes with
FK506, which inhibits the association of
FKBP12.6 with the
ryanodine receptor, restored contractile function. These findings demonstrate that conditional deletion of CHF1/Hey2 in the myocardium leads to abnormalities in
calcium handling mediated by
FKBP12.6 that predispose to pressure overload-induced
heart failure.