Cilia defects are often linked to disturbed left-right asymmetry and to kidney cysts, a symptom also seen in mice and frogs that lack the conserved RNA-binding protein Bicaudal C (BicC). Now, on , Daniel Constam and colleagues identify a role for BicC in cilia biology. The authors find that disrupting BicC function in either mouse or Xenopus embryos randomises left-right asymmetry by disturbing the regular planar orientation of motile cilia and, hence, cilia-driven fluid flow. Further, the researchers find that in kidney cell lines, the BicC sterile alpha motif (SAM) domain guides the localisation of BicC to cytoplasmic structures that contain the canonical Wnt signalling component Dishevelled 2 (Dvl2), as well as RNA-processing bodies known as P-bodies. BicC interferes with Dvl2-mediated canonical Wnt signalling; such interference has been suggested to promote planar cell polarity (PCP) signalling. Thus, the authors propose, BicC might link cilia orientation with PCP signalling by modulating P-body-mediated RNA silencing or by regulating Dvl2 function.
