Primary cilia are microtubule-based organelles that project from the surface of nearly every animal cell. Although important functions of primary cilia in morphogenesis and tissue homeostasis have been identified, the mechanisms that control the formation of primary cilia are not understood. Here we characterize a zebrafish gene, termed duboraya (dub), that is essential for ciliogenesis. Knockdown of dub in zebrafish embryos results in both defects in primary cilia formation in Kupffer's vesicle and randomization of left-right organ asymmetries. We show that, at the molecular level, the function of dub in ciliogenesis is regulated by phosphorylation, which in turn depends on Frizzled-2-mediated noncanonical Wnt signaling. We also provide evidence that, at the cellular level, dub function is essential for actin organization in the cells lining Kupffer's vesicle. Taken together, our findings identify a molecular factor that links noncanonical Wnt signaling with the control of left-right axis specification, and provide an entry point for analyzing the mechanisms that regulate primary cilia formation.
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We thank M. Schwarz for help in preparing the manuscript; M. Marti Gaudes for help with confocal microscopy and T. Matsui and A. Rojas for discussion. I.O. was initially partially supported by fellowships from The Cell Science Research Foundation and the Japan Heart Foundation. Work in the laboratory of J.C.I.B. was supported by the US National Institutes of Health and the Cellex, Biobide and G. Harold and Leila Y. Mathers charitable foundations.