Abstract 18575: The Transcriptional Cofactor Eyes Absent 4 is a Critical Regulator for Maintaining Normal Cardiac Function
Introduction: E193, a human mutation in the transcription cofactor Eyes absent 4 (EYA4) causes hearing impairment followed by terminal heart failure, defining an important role for Eya4 in maintaining normal cardiac function.
METHODS AND RESULTS: First, in-vitro experiments show that overexpression of Eya4 and the mutant isoform alter the expression of p27kip1 on both, transcript and protein levels. Next, we generated transgenic mice with cardiomyocyte-specific Eya4 or E193 overexpression to elucidate the in vivo function of Eya4 upon cardiac physiology. Luciferase and CHIP assays revealed that Eya4 and E193 bind to and regulate p27 expression in a contradictory manner, as already seen in vitro. Activity and phoshorylation of the downstream molecules CK2α and HDAC2 were significantly elevated in Eya4 mice, whereas they were significantly reduced in E193 animals compared to WT littermates. MRI and hemodynamic analysis indicate that a constitutive overexpression of Eya4 results in the age-dependent development of hypertrophy already under baseline conditions with no obvious functional effects, whereas E193 overexpressing animals develop onset of dilative cardiomyopathy as seen in human patients carrying the E193 mutation. Morphometric analysis proved ventricular hypertrophy or dilation of the LV associated with a thinning of the myocardial wall, interstitial fibrosis of myocardial tissue and alterations in cell size. Re-activation of fetal genes also occured in both TG models, characteristic for cardiac disease. Both cardiac phenotypes were aggravated upon pressure overload.
Finally, we identified a new human heterozygous truncating Eya4 mutation, E215, which leads to similar clinical features of disease and a stable myocardial expression of the mutant protein.
Conclusion: Our results implicate that Eya4 plays a critical role in regulating normal cardiac physiology and function via Six1/p27/CK2α/HDAC2 and that an imbalance within the Eya4/Six1 transcriptional complex leads to an age dependent onset of cardiomyopthy and heart failure.
Author Disclosures: T. Williams: None. M. Hundertmark: None. P. Nordbeck: None. S. Voll: None. A. Arias-Loza: None. I. Elsner: None. D. Oppelt: None. S. Olivares: None. J. Schoenberger: None. O. Ritter: None.
- © 2014 by American Heart Association, Inc.