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Cardiac Myocyte De Novo DNA Methyltransferases 3a/3b Are Dispensable for Cardiac Function and Remodeling after Chronic Pressure Overload in Mice.

Nührenberg TG, Hammann N, Schnick T, Preißl S, Witten A, Stoll M, Gilsbach R, Neumann FJ, Hein L - PLoS ONE (2015)

Bottom Line: 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.DKO cardiomyocytes showed virtual absence of targeted Dnmt3a and Dnmt3b mRNA transcripts.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.

View Article: PubMed Central - PubMed

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.

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.

Conclusion: 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.

No MeSH data available.


Related in: MedlinePlus

General characteristics of sham and TAC-operated mice.Mice were sacrificed and (A) body weight and (B) tibia length were measured. (C) Lung weight to tibia length ratio was calculated to assess possible pulmonary congestion. (D) Heart rate was determined in short axis M-mode measurements. Sham CTL (n ≥ 9), sham DKO (n ≥ 5), TAC CTL (n ≥ 9), TAC DKO (n ≥ 9). * p < 0.05, ** p < 0.01.
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pone.0131019.g003: General characteristics of sham and TAC-operated mice.Mice were sacrificed and (A) body weight and (B) tibia length were measured. (C) Lung weight to tibia length ratio was calculated to assess possible pulmonary congestion. (D) Heart rate was determined in short axis M-mode measurements. Sham CTL (n ≥ 9), sham DKO (n ≥ 5), TAC CTL (n ≥ 9), TAC DKO (n ≥ 9). * p < 0.05, ** p < 0.01.

Mentions: The cardiac phenotype was assessed by several means in sham- and TAC-operated mice 4 weeks after the procedure. Ventricular weight to body weight (VW/BW) and ventricular weight to tibia length (VW/TL) ratios were determined for all animals (Figs 3 and 4). Pressure overload showed induction of cardiac hypertrophy by increased VW/BW- and VW/TL-ratios as well as increased cardiac myocyte cross-sectional areas (Fig 4A and 4B). This was accompanied by increased cardiac fibrosis (Fig 4C) and by features of heart failure such as impaired systolic left ventricular ejection fraction and ventricular dilatation (Fig 4D). However, ablation of Dnmt3a and Dnmt3b expression in cardiomyocytes did not lead to significant differences in any echocardiographic parameter neither in sham nor in TAC animals (Figs 4D and 5).


Cardiac Myocyte De Novo DNA Methyltransferases 3a/3b Are Dispensable for Cardiac Function and Remodeling after Chronic Pressure Overload in Mice.

Nührenberg TG, Hammann N, Schnick T, Preißl S, Witten A, Stoll M, Gilsbach R, Neumann FJ, Hein L - PLoS ONE (2015)

General characteristics of sham and TAC-operated mice.Mice were sacrificed and (A) body weight and (B) tibia length were measured. (C) Lung weight to tibia length ratio was calculated to assess possible pulmonary congestion. (D) Heart rate was determined in short axis M-mode measurements. Sham CTL (n ≥ 9), sham DKO (n ≥ 5), TAC CTL (n ≥ 9), TAC DKO (n ≥ 9). * p < 0.05, ** p < 0.01.
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Related In: Results  -  Collection

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pone.0131019.g003: General characteristics of sham and TAC-operated mice.Mice were sacrificed and (A) body weight and (B) tibia length were measured. (C) Lung weight to tibia length ratio was calculated to assess possible pulmonary congestion. (D) Heart rate was determined in short axis M-mode measurements. Sham CTL (n ≥ 9), sham DKO (n ≥ 5), TAC CTL (n ≥ 9), TAC DKO (n ≥ 9). * p < 0.05, ** p < 0.01.
Mentions: The cardiac phenotype was assessed by several means in sham- and TAC-operated mice 4 weeks after the procedure. Ventricular weight to body weight (VW/BW) and ventricular weight to tibia length (VW/TL) ratios were determined for all animals (Figs 3 and 4). Pressure overload showed induction of cardiac hypertrophy by increased VW/BW- and VW/TL-ratios as well as increased cardiac myocyte cross-sectional areas (Fig 4A and 4B). This was accompanied by increased cardiac fibrosis (Fig 4C) and by features of heart failure such as impaired systolic left ventricular ejection fraction and ventricular dilatation (Fig 4D). However, ablation of Dnmt3a and Dnmt3b expression in cardiomyocytes did not lead to significant differences in any echocardiographic parameter neither in sham nor in TAC animals (Figs 4D and 5).

Bottom Line: 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.DKO cardiomyocytes showed virtual absence of targeted Dnmt3a and Dnmt3b mRNA transcripts.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.

View Article: PubMed Central - PubMed

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.

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.

Conclusion: 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.

No MeSH data available.


Related in: MedlinePlus