miR-124 regulation of the Delta/Notch signaling pathway in early sea urchin development

Song, Jia L.microRNAs play a crucial role in cell differentiation. The brain-specific miR- 124 is highly conserved in both invertebrates and vertebrates. We used the purple sea urchin, Strongylocentrotus purpuratus, to examine the function of miR-124 in development and specifically its role in regulating the Delta/Notch signaling pathway. In the sea urchin, the Delta/Notch signaling pathway activates transcription factors for specification of all non-skeletogenic mesodermal cell types. We bioinformatically identified two potential binding sites for miR-124 in the 3'UTR of sea urchin Notch. To test the direct regulation of miR-124 on Notch, we cloned the Notch 3'UTR downstream of Renilla luciferase reporter construct and identified the first seed site position +1516 in the 3'UTR as a functional miR-124 seed site. To examine the function of miR-124 in the early embryo, we microinjected the miR-124 inhibitor into newly fertilized eggs. We found that miR-124 inhibition caused ectopic misexpression of Ese, a transcription factor that controls the specification of blastocoelar cells, suggesting that miR-124 functions in restricting non-skeletogenic mesoderm blastocoelar cell specification. Furthermore, we identified miR-124 to suppress transcription factors that regulate neural specification, mesodermal specification and endodermal genes. Our data suggest that miR-124 is important for non-skeletogenic mesodermal specification and potentially regulates additional gene expressions in the sea urchin embryo.University of Delaware, Department of Biological SciencesM.S