title: Cardiac Myocyte De Novo DNA Methyltransferases 3a/3b Are Dispensable for Cardiac Function and Remodeling after Chronic Pressure Overload in Mice.
abstract: BACKGROUND
  Recent studies reported altered DNA methylation in failing human hearts. This may suggest a role for de novo DNA methylation in the development of heart failure. Here, we tested whether cardiomyocyte-specific loss of de novo DNA methyltransferases Dnmt3a and Dnmt3b altered cardiac function and remodeling after chronic left ventricular pressure overload.
  
  
  METHODS
  Mice with specific ablation of Dnmt3a and Dnmt3b expression in cardiomyocytes were generated by crossing floxed Dnmt3afl and Dnmt3bfl alleles with mice expressing Cre recombinase under control of the atrial myosin light chain gene promoter. The efficacy of combined Dnmt3a/3b ablation (DKO) was characterized on cardiomyocyte-specific genomic DNA and mRNA levels. Cardiac phenotyping was carried out without (sham) or with left ventricular pressure overload induced by transverse aortic constriction (TAC). Under similar conditions, cardiac genome-wide transcriptional profiling was performed and DNA methylation levels of promoters of differentially regulated genes were assessed by pyrosequencing.
  
  
  RESULTS
  DKO cardiomyocytes showed virtual absence of targeted Dnmt3a and Dnmt3b mRNA transcripts. Cardiac phenotyping revealed no significant differences between DKO and control mice under sham and TAC conditions. Transcriptome analyses identified upregulation of 44 and downregulation of 9 genes in DKO as compared with control sham mice. TAC mice showed similar changes with substantial overlap of regulated genes compared to sham. Promoters of upregulated genes were largely unmethylated in DKO compared to control mice.
  
  
  CONCLUSIONS
  The absence of cardiac pathology in the presence of the predicted molecular phenotype suggests that de novo DNA methylation in cardiomyocytes is dispensable for adaptive mechanisms after chronic cardiac pressure overload.
authors.affiliation: Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany; Universitäts-Herzzentrum Freiburg • Bad Krozingen, Klinik für Kardiologie und Angiologie II, Bad Krozingen, Germany.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Nührenberg
authors.affiliation: Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany.
authors.forename: Nils
authors.initials: N
authors.lastname: Hammann
authors.affiliation: Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany; Universitäts-Herzzentrum Freiburg • Bad Krozingen, Klinik für angeborene Herzfehler und pädiatrische Kardiologie, Hugstetter Straße 55, 79106, Freiburg, Germany.
authors.forename: Tilman
authors.initials: T
authors.lastname: Schnick
authors.affiliation: Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany; Hermann Staudinger Graduate School, University of Freiburg, Albertstraße 21, 79104, Freiburg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Preißl
authors.affiliation: Core Unit Genomics für Hochdurchsatzgenetik und-genomik an der Medizinischen Fakultät Münster, Westfälische Wilhelms-Universität Münster, Münster, Germany.
authors.forename: Anika
authors.initials: A
authors.lastname: Witten
authors.affiliation: Core Unit Genomics für Hochdurchsatzgenetik und-genomik an der Medizinischen Fakultät Münster, Westfälische Wilhelms-Universität Münster, Münster, Germany.
authors.forename: Monika
authors.initials: M
authors.lastname: Stoll
authors.affiliation: Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Gilsbach
authors.affiliation: Universitäts-Herzzentrum Freiburg • Bad Krozingen, Klinik für Kardiologie und Angiologie II, Bad Krozingen, Germany.
authors.forename: Franz-Josef
authors.initials: FJ
authors.lastname: Neumann
authors.affiliation: Institute of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany; BIOSS Centre for Biological Signalling Studies, University of Freiburg, Schänzlestr. 18, 79104, Freiburg, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Hein
mesh_terms: D000818:Animals; D004247:DNA / Q000235:genetics; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000235:genetics*; D019175:DNA Methylation / Q000235:genetics; D000090205:DNA Methyltransferase 3A; D006321:Heart / Q000502:physiology*; D006333:Heart Failure / Q000235:genetics / Q000503:physiopathology; D008297:Male; D051379:Mice; D032383:Myocytes, Cardiac / Q000201:enzymology* / Q000502:physiology*; D011312:Pressure; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D059467:Transcriptome / Q000235:genetics; D020257:Ventricular Remodeling / Q000235:genetics / Q000502:physiology*; D000097584:DNA Methyltransferase 3B
chemical_list: D004247:DNA; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D012333:RNA, Messenger; D000097584:DNA Methyltransferase 3B; C000717967:DNMT3A protein, human; C000715535:Dnmt3a protein, mouse