MiR–206 is Important for Proper Development of the Notochord–Somite Boundary in Xenopus laevis

MicroRNAs (miRNA) are small, non-coding sequences of RNA that regulate genes post-transcriptionally by binding specific messenger RNAs (mRNA) and blocking their translation. MiRNAs have been shown to play a major role in the transcriptional regulation of cells during embryogenesis and in diseases. MiR-206 is a microRNA that is exclusively expressed in the skeletal muscle tissue of vertebrates. Using a morpholino approach, we block the ability of miR-206 to bind to its target mRNAs during Xenopus laevis embryogenesis. We show that knockdown of miR-206 leads to a disruption in the formation and maintenance of the notochord-somite boundary. The formation of this boundary is an important step in development for it separates the dorsal mesoderm into two distinct tissues—the notochord and somites. Confocal imaging analysis reveals a large gap between the notochord and the developing somites. Scanning electron micrographs further show that this gap is comprised of excessive extracellular matrix. To understand this resultant phenotype, we used an explant system that will allow us to live image the cell behaviors associated with the formation of the notochord-somite boundary. These explants show that the notochord-somite boundary is more prominent in miR-206 morphants in comparison to controls. Together, these results show that miR-206 plays an important role in regulating early tissue morphogenesis during vertebrate development.