Smad4 mediated BMP2 signal is essential for the regulation of GATA4 and Nkx2.5 by affecting the histone H3 acetylation in H9c2 cells

Cardiac competence of the paraxial head mesoderm fades concomitant with a shift towards the head skeletal muscle programme

The vertebrate head mesoderm provides the heart, the great vessels, some smooth and most head skeletal muscle, in addition to parts of the skull. It has been speculated that the ability to generate cardiac and smooth muscle is the evolutionary ground-state of the tissue. However, whether indeed the entire head mesoderm has generic cardiac competence, how long this may last, and what happens as cardiac competence fades, is not clear. Bone morphogenetic proteins (Bmps) are known to promote cardiogenesis. Using 41 different marker genes in the chicken embryo, we show that the paraxial head mesoderm that normally does not engage in cardiogenesis has the ability to respond to Bmp for a long time. However, Bmp signals are interpreted differently at different time points. Up to early head fold stages, the paraxial head mesoderm is able to read Bmps as signal to engage in the cardiac programme; the ability to upregulate smooth muscle markers is retained slightly longer. Notably, as cardiac competence fades, Bmp promotes the head skeletal muscle programme instead. The switch from cardiac to skeletal muscle competence is Wnt-independent as Wnt caudalises the head mesoderm and also suppresses Msc-inducing Bmp provided by the prechordal plate, thus suppressing both the cardiac and the head skeletal muscle programmes. Our study for the first time suggests a specific transition state in the embryo when cardiac competence is replaced by skeletal muscle competence. It sets the stage to unravel the cardiac-skeletal muscle antagonism that is known to partially collapse in heart failure.

Towards Understanding the Gene-Specific Roles of GATA Factors in Heart Development: Does GATA4 Lead the Way?

Transcription factors play crucial roles in the regulation of heart induction, formation, growth and morphogenesis. Zinc finger GATA transcription factors are among the critical regulators of these processes. GATA4, 5 and 6 genes are expressed in a partially overlapping manner in developing hearts, and GATA4 and 6 continue their expression in adult cardiac myocytes. Using different experimental models, GATA4, 5 and 6 were shown to work together not only to ensure specification of cardiac cells but also during subsequent heart development. The complex involvement of these related gene family members in those processes is demonstrated through the redundancy among them and crossregulation of each other. Our recent identification at the genome-wide level of genes specifically regulated by each of the three family members and our earlier discovery that gata4 and gata6 function upstream, while gata5 functions downstream of noncanonical Wnt signalling during cardiac differentiation, clearly demonstrate the functional differences among the cardiogenic GATA factors. Such suspected functional differences are worth exploring more widely. It appears that in the past few years, significant advances have indeed been made in providing a deeper understanding of the mechanisms by which each of these molecules function during heart development. In this review, I will therefore discuss current evidence of the role of individual cardiogenic GATA factors in the process of heart development and emphasize the emerging central role of GATA4.

Functional genetic variants of the GATA4 gene promoter in acute myocardial infarction

Coronary artery disease (CAD), including acute myocardial infarction (AMI), is a common complex disease; however, the genetic causes remain largely unknown. Recent epidemiological investigations indicated that the incidence of CAD in patients with congenital heart diseases is markedly higher than that observed in healthy controls. It was therefore hypothesized that the dysregulated expression of cardiac developmental genes may be involved in CAD development. GATA binding protein 4 (GATA4) serves essential roles in heart development and coronary vessel formation. In the present study, the GATA4 gene promoter was analyzed in patients with AMI (n=395) and in ethnically‑matched healthy controls (n=397). A total of 14 DNA variants were identified, including two single‑nucleotide polymorphisms. Three novel heterozygous DNA variants (g.31806C>T, g.31900G>C and g.32241C>T) were reported in three patients with AMI. These DNA variants significantly increased the activity of the GATA4 gene promoter. The electrophoretic mobility shift assay revealed that the DNA variant g.32241C>T influenced the binding ability of transcription factors. Taken together, the DNA variants may alter GATA4 gene promoter activity and affect GATA4 levels, thus contributing to AMI development.

Contributions of bone morphogenetic proteins in cardiac repair cells in three-dimensional in vitro models and angiogenesis

One of the main efforts in myocardial tissue engineering is towards designing cardiac tissues able to rescue the reduction in heart function once implanted at the site of myocardial infarction. To date, the efficiency of this approach in preclinical applications is limited in part by our incomplete understanding of the inflammatory environment known to be present at the site of myocardial infarct and by poor vascularization. It was recently reported that polarized macrophages known to be present at the site of myocardial infarction secrete bone morphogenetic proteins (BMPs)-2 and -4 causing changes in the expression of cardiac proteins in a 2D in vitro model. Here, these findings were extended towards cardiac tissues composed of human embryonic stem cell derived cardiomyocytes embedded in collagen gel. By preconditioning cardiac tissues with BMPs, constructs were obtained with enhanced expression of cardiac markers. Additionally, after BMP preconditioning, the resulting cardiac-tissues were able to sustain diffusion of the BMPs with the added benefit of supporting human umbilical vein endothelial cell tube formation. Here, a model is proposed of cardiac tissues preconditioned with BMPs that results in stimulation of cardiomyocyte function and diffusion of BMPs able to support angiogenesis. This platform represents a step towards the validation of more complex bioengineered constructs for in vivo applications.

Inhibition of histone acetylation by curcumin reduces alcohol-induced fetal cardiac apoptosis

Background

Prenatal alcohol exposure may cause cardiac development defects, however, the underlying mechanisms are not yet clear. In the present study we have investigated the roles of histone modification by curcumin on alcohol induced fetal cardiac abnormalities during the development.

Methods and results

Q-PCR and Western blot results showed that alcohol exposure increased gene and active forms of caspase-3 and caspase-8, while decreased gene and protein of bcl-2. ChIP assay results showed that, alcohol exposure increased the acetylation of histone H3K9 near the promoter region of caspase-3 and caspase-8, and decreased the acetylation of histone H3K9 near the promoter region of bcl-2. TUNEL assay data revealed that alcohol exposure increased the apoptosis levels in the embryonic hearts. In vitro experiments demonstrated that curcumin treatment could reverse the up-regulation of active forms of caspase-3 and caspase-8, and down-regulation of bcl-2 induced by alcohol treatment. In addition, curcumin also corrected the high level of histone H3K9 acetylation induced by alcohol. Moreover, the high apoptosis level induced by alcohol was reversed after curcumin treatment in cardiac cells.

Conclusions

These findings indicate that histone modification may play an important role in mediating alcohol induced fetal cardiac apoptosis, possibly through the up-regulation of H3K9 acetylation near the promoter regions of apoptotic genes. Curcumin treatment may correct alcohol-mediated fetal cardiac apoptosis, suggesting that curcumin may play a protective role against alcohol abuse caused cardiac damage during pregnancy.