MicroRNA expression in mouse Branchial Arches

Vertebrate branchial arches (BAs) are a developmental paradigm, undergoing coordinated differentiation and morphogenesis to form various adult derivatives. MicroRNAs can strengthen gene regulatory networks (GRNs) to promote developmental stability. To interrogate how microRNAs stabilise BA development, we generated a novel microRNA-sequencing dataset from mouse BAs. We identified global expression of 550 microRNAs, of which approximately 20% demonstrate significant differential expression across BA domains. The three most posterior BAs and the connecting outflow tract (PBA/OFT) are enriched biological processes linked to cardiovascular development. In this study we identified enriched predicted microRNA-target interactions with PBA/OFT upregulated cardiovascular genes, and validated two fundamental cardiac transcription factors (TFs), Gata6 and Tbx20, as targets of miR-92b-3p. Furthermore, we demonstrated that miR-92b-3p can downregulate endogenous GATA6 and TBX20 in human embryonic stem cells (hESCs) undergoing cardiomyocyte differentiation, consistent with conservation of these microRNA-target interactions in a cardiogenic setting. MiR-92b-3p has previously been shown to target two other cardiac TFs, Hand2 and Mef2D. Therefore, we hypothesise that miR-92b-3p acts to stabilise cardiovascular GRNs during PBA/OFT development, through acting in multiple microRNA-mediated coherent feedforward loops.