Inhibition of microRNA suppression of Dishevelled results in Wnt pathway associated developmental defects.

MicroRNAs (miRNAs) are highly conserved, small non-coding RNAs that regulate gene expressions by binding to the 3'untranslated region (UTR) of target mRNAs and silence translation. Some miRNAs are key regulators of the Wnt signaling pathways which impact developmental processes. This study investigates miRNA regulation of different isoforms of Dishevelled (Dvl/Dsh) , a key component in the Wnt signaling pathway. The sea urchin Dvl mRNA isoforms have similar spatial distribution in early development, but one isoform is distinctively expressed in the larval ciliary band. We demonstrated that Dvl isoforms are directly suppressed by miRNAs. By blocking miRNA suppression of Dvl isoforms, we observed dose-dependent defects of spicule length, patterning of the primary mesenchyme cells (PMCs), gut morphology, and cilia. These defects likely result from increased Dvl protein levels, leading to perturbation of Wnt dependent signaling pathways and additional Dvl-mediated processes. We further demonstrated that overexpression of Dvl isoforms recapitulated some of the Dvl miRNATP-induced phenotypes. Overall, our results indicate that miRNA suppression of Dvl isoforms plays an important role in ensuring proper development and function of the PMCs and cilia.