Key result
Inhibition of RhoA using C3 exoenzyme or siRNA significantly decreased activated endothelial and mesenchymal cell numbers, demonstrating its functional requirement during TGFbeta-mediated EMT.
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RhoA is functionally required for epithelial-mesenchymal transition in the embryonic chick heart and acts downstream of TGFbeta signaling.
Endothelia in the atrioventricular canal (AVC) of the embryonic heart undergo an epithelial-mesenchymal transition (EMT) and migrate into the underlying extracellular matrix. We explore here whether RhoA mediates this EMT. RhoA was detected in all cells of the chick heart during the stages studied. Expression was elevated when EMT was actively occurring. Explants treated with C3 exoenzyme in collagen gel cultures showed a significant decrease in mesenchymal cell numbers. siRNA was used to inhibit RhoA mRNA, and both activated endothelial and mesenchymal cells decreased significantly with treatment. Loss of RhoA produced a reduction of RhoB, cyclin-b2, and beta-catenin messages showing that these genes are regulated downstream of RhoA. In contrast, runx-2 was not reduced. Inhibition of TGFbeta3 or TGFbeta2 activity caused a large reduction of RhoA message. These data place RhoA in TGFbeta regulated pathways for both endothelial activation and mesenchymal invasion and demonstrate a functional requirement during EMT.
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Tavares et al. (2006) studied Epithelial-mesenchymal transition in embryonic heart. RhoA inhibition (C3 exoenzyme or siRNA) was evaluated on Mesenchymal cell numbers and endothelial activation. Inhibition of RhoA using C3 exoenzyme or siRNA significantly decreased activated endothelial and mesenchymal cell numbers, demonstrating its functional requirement during TGFbeta-mediated EMT.
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