Two microRNAs are sufficient for embryogenesis inC. elegans

The Microprocessor, composed of Drosha and Pasha/DGCR8, is necessary for the biogenesis of canonical microRNAs (miRNAs) and essential for animal embryogenesis. However, the cause for this requirement is largely unknown: the Microprocessor may be required to produce one or few essential miRNAs, or many individually non-essential miRNAs. Additionally, Drosha and Pasha/ DGCR8 may be required for processing non-miRNA substrates. To distinguish between these possibilities, we developed a system inC. elegansto stringently deplete embryos of Microprocessor activity. Microprocessor-depleted embryos fail to undergo morphogenesis or form organs. We show that this early embryonic arrest is rescued by the addition of two miRNAs from the miR-35 and miR-51 families, resulting in morphologically normal larvae. Thus, just two canonical miRNAs are sufficient for morphogenesis and organogenesis, and the processing of these miRNAs accounts for the essential requirement for Drosha and Pasha/DGCR8 duringC. elegansembryonic development.