Recent findings indicate that mammalian Sonic hedgehog (Shh) signal transduction occurs within primary cilia, although the cell biological mechanisms underlying both Shh signaling and ciliogenesis have not been fully elucidated. We show that an uncharacterized TBC domain-containing protein, Broad-minded (Bromi), is required for high-level Shh responses in the mouse neural tube. We find that Bromi controls ciliary morphology and proper Gli2 localization within the cilium. By use of a zebrafish model, we further show that Bromi is required for proper association between the ciliary membrane and axoneme. Bromi physically interacts with cell cycle-related kinase (CCRK), whose Chlamydomonas homolog regulates flagellar length. Biochemical and genetic interaction data indicate that Bromi promotes CCRK stability and function. We propose that Bromi and CCRK control the structure of the primary cilium by coordinating assembly of the axoneme and ciliary membrane, allowing Gli proteins to be properly activated in response to Shh signaling.
Bibliographical noteFunding Information:
We thank members of K. Anderson and L. Niswander's laboratories for help with the mutagenesis screen, K. Anderson, M. Scott, A. Joyner, T. Caspary, G. Pazour, R. Fisher, X. Sun, and BayGenomics for contributing mouse lines, cell lines, and reagents, J. Goodhouse, M. Bisher, J. Levorse, S. Kyin, Y. Lin, and J. Schottenfeld for technical assistance, and R. Burdine and T. Caspary for comments on the manuscript. Monoclonal antibodies against Shh, FoxA2/Hnf3β, Nkx2.2, Nkx6.1, HB9/Mnr2, Pax6, and Pax7 were obtained from the Developmental Studies Hybridoma Bank developed under the auspices of the NICHD and maintained by the University of Iowa, Department of Biological Sciences, Iowa City, Iowa. This work was supported by New Jersey Commission on Spinal Cord Research (NJCSCR) grant 07-3069-SCR-E-0 and U.S. National Institutes of Health grant R01 HD050761. H.W.K. was supported by a postdoctoral fellowship from the NJCSCR.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Biochemistry, Genetics and Molecular Biology(all)
- Developmental Biology
- Cell Biology