Fig. 7
From: Micro RNAs are involved in activation of epicardium during zebrafish heart regeneration
A proposed schematic model of miR-1 and miR-133 actions in blocking the FGF-dependent transduction pathway in the cells involved in cardiac regeneration: CMs, fibroblast, EPCs and endocardial cells. In zebrafish these four types acting in concert, the regeneration in trans-differentiation and/or proliferation of existing resident cells under the induction of FGF1-2. The scheme is a comprehensive information from literature and from the present research. miR-1 is not expressed by ERK1,2 activity because of the expression of cardiac embryonal genes and relative proteins such as GATA4. When the genes of differentiation are expressed, such as MyoD, miR-1 start to be highly transcripted and act as a repressor of GATA4 translation and other embryonic key proteins. For example, in epicardial cells it may control the WT1 expression. miR-133a instead acts directly on blocking the expression of the receptor of FGF and on the expression of the PP2AC that promotes the activity of ERK. miR-133b is instead involved in the transition from endothelial to mesenchymal cells by blocking directly the expression of connective tissue growth factor (CTGF)
