ATF3 expression in cardiomyocytes and myofibroblasts following transverse aortic constriction displays distinct phenotypes

Figures

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  Fig. 1. ATF3 expression in cardyomyocytes promotes heart growth following TAC operation. A. mRNA was extracted from ventricles and the expression level of ATF3 was analyzed by qRT-PCR normalized with HSP90 as housekeeping gene. ATF3 transcription at eight weeks following TAC and control. B. Schematic representation for cardiac specific KO. αMHC-CRE transgenic mouse strain was crossed with ATF3-flox mouse strain (ATF3-flox). CRE is expressed shortly before birth resulting in Exon B excision (loxP sites are indicated) specifically in cardiomyocytes. CRE expressing mice harboring two alleles of ATF3-flox are designated ATF3-cKO. C. Eight weeks following TAC procedure (10–12 weeks old male mice), mice were subjected to MRI. Ejection fraction (EF) was calculated as described in the methods. D. Mice were sacrificed eight weeks following TAC. The hearts were excised and the ventricles weight to body weight ratio is shown (VW/BW). E. mRNA was extracted from ventricles and the expression level of ATF3 was analyzed by qRT-PCR normalized with HSP90 as housekeeping gene.

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  Fig. 2. Hypertrophic and Fibrosis gene markers in ATF3-cKO mice. mRNA was extracted from ventricles and the expression levels were measured by qRT-PCR normalized with HSP90 as housekeeping gene. A. Hypertrophic gene markers ANP, BNP and Acta1. B. Fibrosis gene markers Col1α1, Col3α1, TGFβ3, Acta2, CTGF were analyzed. Expression levels are presented as relative values (compared to ATF3-Flox control mice, defined as 1). All results represent the mean ± SE *** P ≤ 0.05, control vs. TAC; †P ≤ 0.05, difference between genotypes. Each dot or triangle represents one mouse. n.s. indicates no statistical difference.

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  Fig. 3. ATF3 expression in myofibroblasts promotes hypertrophic gene program following TAC. A. Schematic representation for fibroblasts specific KO. Periostin-CRE-ER transgenic mouse strain was crossed with ATF3-flox mouse strain (ATF3-flox). CRE-ER is expressed in activated fibroblasts cells. Tamoxifen (red circle) injection is used to facilitate the translocation of CRE-ER into the nucleus resulting in Exon B excision (loxP sites are indicated) specifically in fibroblasts. CRE-ER expressing mice harboring two alleles of ATF3-flox are designated ATF3-fKO. B. RNA-sequencing data analysis for Periostin expression in the hearts of mice at different time points following TAC [16]. C. Eight weeks following TAC (10–12 weeks old male mice), mice were subjected to echocardiography and fractional shortening was calculated as described in the methods. D. Mice were sacrificed eight weeks following TAC. The hearts were excised and the ventricles weight to body weight ratio is shown (VW/BW). E. mRNA was extracted from ventricles and the expression level of ATF3 was analyzed by qRT-PCR. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of…

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  Fig. 4. Hypertrophic and Fibrosis gene markers in ATF3-fKO mice. mRNA was extracted from ventricles and the expression level were measured by qRT-PCR. A. Hypertrophic gene markers ANP, BNP and Acta1 B. Fibrosis gene markers Col1α1, Col3α1, TGFβ3, Acta2, CTGF were analyzed. Expression levels are presented as relative values (compared to ATF3-Flox control mice, defined as 1). All results represent the mean ± SE *** P ≤ 0.05, control vs. TAC; †P ≤ 0.05, difference between genotypes. Each dot or triangle represents one mouse. n.s. indicates no statistical difference.

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  Fig. 5. Schematic representation of the main conclusions. Pressure overload stress results in elevation of ATF3 expression in the heart. ATF3 in cardiomyocytes is responsible for cardiac growth and fibrosis gene markers while ATF3 expression in myofibroblasts promotes hypertrophic gene program.