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(Circulation. 2007;115:2925-2930.)
© 2007 American Heart Association, Inc.

Heart Failure

Loss of Mdm4 Results in p53-Dependent Dilated Cardiomyopathy

Shunbin Xiong, PhD; Carolyn S. Van Pelt, DVM, PhD; Ana C. Elizondo-Fraire, MD; Belen Fernandez-Garcia, MS; Guillermina Lozano, PhD

From the Department of Cancer Genetics (S.X., A.C.E.-F., G.L.), and Department of Veterinary Medicine & Surgery (C.S.V.P.), The University of Texas, M.D. Anderson Cancer Center, Houston, and Instituto de Biomedicina (B.F.-G.), Universidad de Leon, Campus de Vegazana, Leon, Spain.

Correspondence to Guillermina Lozano, PhD, Department of Cancer Genetics, The University of Texas, M.D. Anderson Cancer Center, Houston, TX 77030. E-mail gglozano{at}mdanderson.org

Received January 12, 2007; accepted March 9, 2007.

Background— Although several loci for familial dilated cardiomyopathy (DCM) have been mapped, the origin of a large percentage of DCM remains unclear. Mdm2, a p53-negative regulator, protects cardiomyocytes from ischemic and reperfusion-induced cell death. Mdm4, a homolog of Mdm2, inhibits p53 activity in numerous cell types. It is unknown whether Mdm4 plays a role in the inhibition of p53 in fully differentiated tissues such as adult cardiomyocytes and whether this role is associated with DCM.

Methods and Results— The conditional knockout of Mdm4 in the heart by use of cardiomyocyte-specific Cre (MyHC-Cre) allele does not result in any developmental defects. With time, however, mice with deletion of Mdm4 in the adult heart developed DCM and had a median survival of 234 days. More interestingly, the onset of DCM occurs significantly earlier in male mice than in female mice, which mimics human DCM disease. DCM in Mdm4 mutant mice was caused by loss of cardiomyocytes by apoptosis, and it was p53-dose dependent.

Conclusion— Activity of p53 was inhibited by Mdm4 even in the fully differentiated cardiomyocyte. Elevated apoptosis mediated by the p53 pathway in cardiomyocytes may be a mechanism for DCM.

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