Tbx20 regulates a genetic program essential to adult mouse cardiomyocyte function

Abstract

Human mutations in or variants of TBX20 are associated with congenital heart disease, cardiomyopathy, and arrhythmias. To investigate whether cardiac disease in patients with these conditions results from an embryonic or ongoing requirement for Tbx20 in myocardium, we ablated Tbx20 specifically in adult cardiomyocytes in mice. This ablation resulted in the onset of severe cardiomyopathy accompanied by arrhythmias, with death ensuing within 1 to 2 weeks of Tbx20 ablation. Accounting for this dramatic phenotype, we identified molecular signatures that posit Tbx20 as a central integrator of a genetic program that maintains cardiomyocyte function in the adult heart. Expression of a number of genes encoding critical transcription factors, ion channels, and cytoskeletal/myofibrillar proteins was downregulated consequent to loss of Tbx20. Genome-wide ChIP analysis of Tbx20-binding regions in the adult heart revealed that many of these genes were direct downstream targets of Tbx20 and uncovered a previously undescribed DNA-binding site for Tbx20. Bioinformatics and in vivo functional analyses revealed a cohort of transcription factors that, working with Tbx20, integrated multiple environmental signals to maintain ion channel gene expression in the adult heart. Our data provide insight into the mechanisms by which mutations in TBX20 cause adult heart disease in humans.

Astragalus polysaccharides suppress ICAM-1 and VCAM-1 expression in TNF-α-treated human vascular endothelial cells by blocking NF-κB activation

“…Immunofluorescence of NF-κB NF-κB expression in HUVECs was detected by immunofluorescence as described previously [17] . Cells were seeded onto sterilized cover slips placed in a 6-well tissue culture plate.…”

Probing chromatin landscape reveals roles of endocardial TBX20 in septation

“…Our analysis of genomic regions that were available for TF interaction through ATAC-seq in endocardial lineages and bound by TBX20 in embryonic heart revealed overrepresentation of specific TF motifs. Several of these TFs, including NKX2-5, GATA4, MEF2, and TEAD, have been previously associated with TBX20 in adult cardiomyocytes and cardiac fibroblasts (31,34). Interestingly, motifs highly enriched near TBX20-binding sites within endocardial lineages included those recognized by the AP1 family, which contains JUN, FOS, ATF, and MAF proteins.…”

“…31). Canonical T-box motifs (TBX5, Eomes; AAGTGTCA) were also enriched, though to a lesser extent (Supplemental Table 2).…”

“…In addition, we found overrepresentation of motifs for GATA family TFs MAFA, a member of the bZIP family of TFs that includes AP1 factors MEF2C, homeodomain TFs NKX2-1 and NKX2-5, and TEAD TF-binding motifs ( Figure 5B and Supplemental Table 2). NKX2-5, GATA, MEF2, and TEAD TFs have been previously identified as cofactors of TBX20 in cell lines and adult heart, indicating a high level of functional conservation (3,30,31,33,34).…”

A novel variant in TBX20 (p.D176N) identified by whole-exome sequencing in combination with a congenital heart disease related gene filter is associated with familial atrial septal defect

“…In the developing mouse embryos, tbx20 is expressed in cardiac progenitor cells, as well as in the developing myocardium and endothelial cells associated with endocardial cushions, the precursor structures for the cardiac valves and the atrioventricular septum, which implies that tbx20 is essential for proper heart development. Loss function of tbx20 in the mouse has been found in connection with various forms of congenital heart defects, including defects in septation, valvulogenesis, cardiomyopathy, and arrhythmia (Stennard et al, 2003;Stennard et al, 2005;Kirk et al, 2007;Liu et al, 2008;Posch et al, 2010a;Sotoodehnia et al, 2010;Shen et al, 2011;Zhang et al, 2011;Qiao et al, 2012).…”