GSE108359
Repression of Ect2 induces cytokinesis failure and decreases heart muscle cell proliferation in congenital heart disease
Proliferation of heart muscle cells (cardiomyocytes) is the basis for heart development and regeneration. In mammals, cardiomyocytes become binucleated, which is thought to limit their proliferative capacity, but mechanisms are unknown. Here, we show the detailed mechanisms of formation of binucleated cardiomyocytes and how these mechanisms are dysregulated in congenital heart disease (CHD). Cardiomyocytes become binucleated by failing the last stage of cytokinesis, abscission. We identified the underlying molecular mechanism with single-cell transcriptional profiling, which showed repression of the cytokinesis gene Ect2, a Rho-guanine-nucleotide exchange factor. Inactivating Ect2 tripled the proportion of binucleated cardiomyocytes and reduced the number of cardiomyocytes by 34% in newborn mice, which was lethal. Cardiomyocyte-specific overexpression of Ect2 in transgenic mice decreased cytokinesis failure. We demonstrate that the Ect2 gene is regulated by the Hippo tumor suppressor pathway, and upstream of that, by ß-adrenergic receptor signaling. In neonatal mice, stimulating ß-adrenergic signaling pathway output with forskolin decreased the number of cardiomyocytes, and administration of ß-blockers increased the number of cardiomyocytes. Finally, we show that patients with tetralogy of Fallot with pulmonary stenosis (ToF/PS), a common type of CHD, develop a 2.2-fold increase in bi- and multi-nucleated cardiomyocytes. Using in vivo labeling of one ToF/PS patient with 15N-thymidine, followed by imaging mass spectrometry, we demonstrate that this increase happens after birth. Organotypic cultures of myocardium from infants with ToF/PS showed that cardiomyocyte binucleation could be reduced with ß-blockers. These results demonstrate how cardiomyocyte proliferation stops and provide the basis for new therapeutic strategies to increase cardiomyocyte proliferation in patients with CHD. Overall design: The cardiomyocytes were isolated from embryonic (E14.5) and postnatal (P5) mouse (FUCCI) hearts, then the single cardiomyocytes were collected through FACS. The cycling cardiomyocytes were identified through Azami Green-Geminin (mAG-hGem) signal. The mRNA was amplified using the antisense RNA (aRNA) amplification method.