Abstract 3822: Different microRNA In Mouse Heart, Cardiac Stem Cells And Cardiac Stem Cells With GATA4, Indicate Different Sets Of microRNA Involved In Stem Cell Differentiation By Gene Repression
Several studies suggest that miRNA have important roles in the development of the heart and cardiac function. We hypothesized that specific miRNA are involved in the differentiation steps of cardiac stem cells to heart cells. We studied 569 unique miRNAs probes in mouse heart cells (MHtC), cardiac stem cells (CSC) and CSC with GATA4 (CSCG) . Based on Sanger miRMouse -10.1, we compared miRNAs in the following groups 1) MHtC vs. CSC, 2) CSC vs.CSCG , 3) MHtCs v CSCG. We also compared CSCs under hypoxia and normoxia. miRNAs reported in the results were confirmed by PCR As previously reported miRNA 1, 133a and 133b were highly expressed in MHt. However, we also found previously unreported, relatively high expression of miRNAs 126 –3p, 145, , 451and 499 in MHtC. MicroRNAs have not previously been reported in CSCs or CSCG. We found unique expression miRNAs 10a,10b, 31, 214 and 762 in CSCs and increased expression of miRNAs 705,709,762, and 1224 in CSCG. In MHt, miR 21 was lower compared to miR21 in CSCs . Expression of miRNA-762 was expressed significantly more in CSC-G than in CSC. Therefore, miR-762 could be the direct transcriptional target of GATA-4 in CSC and a part of the differentiation control pathway from CSC to MHtC. In addition we studied miRNA from CSCs exposed to hypoxia. Hypoxia suppressed all miRs found except miR-574 –5p, which was increased in hypoxia. The results led us to identify which genes are targeted by these miRNAs. miRNA 762 is located into the BCl-7c gene and by miRNA target predictions it was found to target activin A receptor (type IB and II-like-1) gene, bone morphogenic gene and transforming growth factor, beta receptor III (TGFβIII). Embryonic stem cells differentiate into cardiomyocytes in the presence of activin A and BMP4, therefore we suggest that the miRNA 700 family ( miR762 in particluar) in cardiac stem cells inhibits activin A and BMP4 genes, possibly through TGFβIII signaling, to maintain stem cells in the undifferentiated state. The results reveal new miRNAs in cardiac stem cells differentiation to adult heart cells and suggest their role of specific gene targeting.