TAp63 Is Important for Cardiac Differentiation of Embryonic Stem Cells and Heart Development

To investigate the effects of rapamycin on cardiac differentiation, murine embryonic stem cells (ESCs) were induced into cardiomyocytes by 10−4 M ascorbic acid (AA), 20 nM rapamycin alone or 0.01% solvent DMSO. We found that rapamycin alone was insufficient to initiate cardiomyogenesis. Then, the ESCs were treated with AA and rapamycin (20 nM) or AA and DMSO (0.01%) as a control. Compared with control, mouse ESCs (mESCs) treated with rapamycin (20 nM) and AA yielded a significantly higher percentage of cardiomyocytes, as confirmed by the percentage of beating embryonic bodies (EBs), the immunofluorescence and FACS analysis. Rapamycin significantly increased the expression of a panel of cardiac markers including Gata4, α-Mhc, β-Mhc, and Tnnt2. Additionally, rapamycin enhanced the expression of mesodermal and cardiac transcription factors such as Mesp1, Brachyury T, Eomes, Isl1, Gata4, Nkx2.5, Tbx5, and Mef2c. Mechanistic studies showed that rapamycin inhibits Wnt/β-catenin and Notch signaling but promotes the expression of fibroblast growth factor (Fgf8), Fgf10, and Nodal at early stage, and bone morphogenetic protein 2 (Bmp 2) at later stages. Sequential treatment of rapamycin showed that rapamycin promotes cardiac differentiation at the early and later stages. Interestingly, another mammalian target of rapamycin (mTOR) inhibitor Ku0063794 (1 µM) had similar effects on cardiomyogenesis. In conclusion, our results highlight a practical approach to generate cardiomyocytes from mESCs by rapamycin.

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Abstract 361: Neuregulin Transcriptional Programming of Embryonic Endothelial Progenitor Cells and Embryonic Stem Cells

Circulation Research ◽

10.1161/res.111.suppl_1.a361 ◽

2012 ◽

Vol 111 (suppl_1) ◽

Author(s):

Jijun Hao ◽

Cristi L Galindo ◽

Radwan N Safa ◽

Truc-Linh Tran ◽

Douglas B Sawyer

Keyword(s):

Stem Cells ◽

Embryonic Stem Cells ◽

Heart Development ◽

Progenitor Cell ◽

Critical Role ◽

Embryonic Stem ◽

Mapk Signaling ◽

P Value ◽

Type I ◽

Endothelial Progenitor

Jijun Hao, Cristi L. Galindo, Radwan N. Safa, Truc-Linh Tran, Douglas B. Sawyer Neuregulin-1 (NRG-1) plays a critical role in heart development by signaling through type I receptor tyrosine kinases in the erbB family (erbB2, erbB3 and erbB4). Mice with disrupted expression of NRG-1, ErbB2, ErbB3 or ErbB4 die in utero with failure of cardiac development. We have previously shown that NRG-1 has distinct effects on two embryonic progenitor cell populations that express ErbB2 and ErbB3 receptors. In an embryonic endothelial progenitor cell line (eEPCs) NRG-1 treatment induces phosphorylation of Akt, GSK-3β, and Erk1/2, and protects eEPCs against serum deprivation-induced apoptosis. In embryonic stem cells (ESCs) we find that NRG-1 treatment from day 0∼2 induces cardiomyocyte formation by day 8 in culture, and when ErbB3 is knocked down in the ESCs, NRG-1 fails to promote cardiomyogenesis. To understand early molecular events that might regulate these distinct effects, we analyzed global transcriptional changes induced by NRG-1 in both eEPCs and ESCs using microarrays. There were only 244 significantly differential (p value < 0.05, fold-change > 1.5) genes detected in NRG-1-treated ESCs, while NRG-1 induced differential expression of 1,547 transcripts in eEPCs. Based on functional analysis, the most significantly over-represented function (Fishers Exact Test, p value with FDR < 0.05) in ESCs was “cell morphogenesis during differentiation”. In eEPCs, genes regulated via Ras/MAPK signaling were altered, as were those downstream of the Akt-PI3K pathway and calcium signaling. For both cell lines, the most statistically significant transcription factor identified as a regulator of the genes altered in response to NRG-1 was SRF, consistent with a role for NRG-1 in heart development and regeneration. Based on the results of this study, we constructed a putative signaling pathway whereby NRG mediates cardiomyogenesis in pluripotent stem cells that correlates with phenotypic observations.

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