NFATc3 and NFATc4 Are Required for Cardiac Development and Mitochondrial Function

Abstract

Activation of the nuclear factor of activated T-cell (NFAT) family of transcription factors is associated with changes in gene expression and myocyte function in adult cardiac and skeletal muscle. However, the role of NFATs in normal embryonic heart development is not well characterized. In this report, the function of NFATc3 and NFATc4 in embryonic heart development was examined in mice with targeted disruption of both nfatc3 and nfatc4 genes. The nfatc3-/-nfatc4-/- mice demonstrate embryonic lethality after embryonic day 10.5 and have thin ventricles, pericardial effusion, and a reduction in ventricular myocyte proliferation. Cardiac mitochondria are swollen with abnormal cristae, indicative of metabolic failure, but hallmarks of apoptosis are not evident. Furthermore, enzymatic activity of complex II and IV of the respiratory chain and mitochondrial oxidative activity are reduced in nfatc3-/-nfatc4-/- cardiomyocytes. Cardiac-specific expression of constitutively active NFATc4 in nfatc3-/-nfatc4-/- embryos prolongs embryonic viability to embryonic day 12 and preserves ventricular myocyte proliferation, compact zone density, and trabecular formation. The rescued embryos also maintain cardiac mitochondrial ultrastructure and complex II enzyme activity. Together, these data support the hypothesis that loss of NFAT activity in the heart results in a deficiency in mitochondrial energy metabolism required for cardiac morphogenesis and function.

Calcineurin signaling in avian cardiovascular development

“…Cyclosporin treatment of avian embryos during heart looping results in thinning of the ventricular myocardium and heart failure evident in blood pooling and pericardial effusion. A similar phenotype was observed in mouse embryos lacking both NFATc3 and NFATc4 that die at midgestation as a result of deficiencies in cardiomyocyte proliferation and metabolism (Bushdid et al, 2003). Together, these studies support a critical role for calcineurin signaling and NFAT activation in the maturation of cardiomyoctes at E3-E4 in avian embryos and E10.5-E11.5 in mice.…”

“…Avian embryos treated with CsA from E2 to E3 exhibit thinning of the myocardium and reduced trabeculae similar to mouse embryos lacking NFATc3 and NFATc4 (Bushdid et al, 2003). These mice were originally described as having embryonic lethal vascular patterning defects, but a subsequent study demonstrated prolonged embryonic viability with cardiomyocyte-specific restoration of NFAT function (Graef et al, 2001a;Bushdid et al, 2003). The dependence of vascular development on cardiac function also has been demonstrated in mice deficient in Ncadherin or the sodium/calcium exchanger Ncx1 (Wakimoto et al, 2000;Luo et al, 2001).…”

“…Thus, the inhibitory effect of CsA at this stage does not appear to be a primary defect in blood vessel development but rather is a likely secondary effect of compromised cardiac function. Avian embryos treated with CsA from E2 to E3 exhibit thinning of the myocardium and reduced trabeculae similar to mouse embryos lacking NFATc3 and NFATc4 (Bushdid et al, 2003). These mice were originally described as having embryonic lethal vascular patterning defects, but a subsequent study demonstrated prolonged embryonic viability with cardiomyocyte-specific restoration of NFAT function (Graef et al, 2001a;Bushdid et al, 2003).…”

“…Loss of NFATc1 results in embryonic lethality due to defects in cardiac valvuloseptal development (de la Pompa et al, 1998;Ranger et al, 1998). Embryos lacking both NFATc3 and NFATc4 have embryonic lethal cardiac metabolic defects and exhibit abnormalities in vascular maturation (Graef et al, 2001a;Bushdid et al, 2003). Together these studies demonstrate that calcineurin signaling and NFAT activation are required for cardiovascular development and embryonic viability.…”

Myocardium defects and ventricular hypoplasia in mice homozygous null for the Forkhead Box m1 transcription factor

“…Disruption of this transcriptional network results in a variety of human diseases including congenital heart disease, dilated cardiomyopathy, and cardiac hypertrophy (Frey and Olson, 2003;Olson, 2004;Clark et al, 2006). Central to the regulation of these developmental processes are the cardiac transcription factors GATA4 (Watt et al, 2004), NKX2.5 (Cripps and Olson, 2002), Hand (McFadden et al, 2005), nuclear factors of activated T-cell (NFAT) c3 and c4 (Molkentin, 2000;Graef et al, 2001;Bushdid et al, 2003), Foxp4 and FOG2 (Svensson et al, 2000;Lin et al, 2004), and T-box transcription factors TBX1 and TBX5 (Plageman and Yutzey, 2005), all of which have been shown to regulate cardiomyocyte proliferation, cardiacspecific gene expression, and proper patterning of the developing heart.…”