A large diversity of epigenetic factors, such as microRNAs and histones modifications, are known to be capable of regulating gene expression without altering DNA sequence itself. In particular, miR-1 is considered the first essential microRNA in cardiac development. In this study, miR-1 potential
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A large diversity of epigenetic factors, such as microRNAs and histones modifications, are known to be capable of regulating gene expression without altering DNA sequence itself. In particular, miR-1 is considered the first essential microRNA in cardiac development. In this study, miR-1 potential role in early cardiac chamber differentiation was analyzed through specific signaling pathways. For this, we performed in chick embryos functional experiments by means of miR-1 microinjections into the posterior cardiac precursors—of both primitive endocardial tubes—committed to sinoatrial region fates. Subsequently, embryos were subjected to whole mount in situ hybridization, immunohistochemistry and RT-qPCR analysis. As a relevant novelty, our results revealed that miR-1 increased
Amhc1,
Tbx5 and
Gata4, while this microRNA diminished
Mef2c and
Cripto expressions during early differentiation of the cardiac sinoatrial region. Furthermore, we observed in this developmental context that miR-1 upregulated
CrabpII and
Rarß and downregulated
CrabpI, which are three crucial factors in the retinoic acid signaling pathway. Interestingly, we also noticed that miR-1 directly interacted with
Hdac4 and
Calm1/
Calmodulin, as well as with
Erk2/
Mapk1, which are three key factors actively involved in
Mef2c regulation. Our study shows, for the first time, a key role of miR-1 as an epigenetic regulator in the early differentiation of the cardiac sinoatrial region through orchestrating opposite actions between retinoic acid and
Mef2c, fundamental to properly assign cardiac cells to their respective heart chambers. A better understanding of those molecular mechanisms modulated by miR-1 will definitely help in fields applied to therapy and cardiac regeneration and repair.
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