title: Loss of Mdm4 results in p53-dependent dilated cardiomyopathy.
abstract: 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.
  
  
  RESULTS
  The conditional knockout of Mdm4 in the heart by use of cardiomyocyte-specific Cre (alphaMyHC-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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Cancer Genetics, The University of Texas, M.D. Anderson Cancer Center, Houston, TX 77030, USA.
authors.forename: Shunbin
authors.initials: S
authors.lastname: Xiong
authors.forename: Carolyn S
authors.initials: CS
authors.lastname: Van Pelt
authors.forename: Ana C
authors.initials: AC
authors.lastname: Elizondo-Fraire
authors.forename: Belen
authors.initials: B
authors.lastname: Fernandez-Garcia
authors.forename: Guillermina
authors.initials: G
authors.lastname: Lozano
mesh_terms: D000818:Animals; D017209:Apoptosis; D002311:Cardiomyopathy, Dilated / Q000209:etiology*; D005260:Female; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D032383:Myocytes, Cardiac / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000172:deficiency* / Q000502:physiology*; D012737:Sex Factors; D015996:Survival Rate; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors / Q000502:physiology*; D044767:Ubiquitin-Protein Ligases / Q000172:deficiency* / Q000502:physiology*
chemical_list: C461497:Mdm4 protein, mouse; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D044767:Ubiquitin-Protein Ligases