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Nat Neurosci. 2011 Nov 20;15(1):48-56. doi: 10.1038/nn.2970.

UNC-33 (CRMP) and ankyrin organize microtubules and localize kinesin to polarize axon-dendrite sorting.

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Laboratory of Neural Circuits and Behavior, Howard Hughes Medical Institute, The Rockefeller University, New York, New York, USA.


The polarized distribution of neuronal proteins to axons and dendrites relies on microtubule-binding proteins such as CRMP, directed motors such as the kinesin UNC-104 (Kif1A) and diffusion barriers such as ankyrin. The causative relationships among these molecules are unknown. We show here that Caenorhabditis elegans CRMP (UNC-33) acts early in neuronal development, together with ankyrin (UNC-44), to organize microtubule asymmetry and axon-dendrite sorting. In unc-33 and unc-44 mutants, axonal proteins were mislocalized to dendrites and vice versa, suggesting bidirectional failures of axon-dendrite identity. unc-44 directed UNC-33 localization to axons, where it was enriched in a region that resembled the axon initial segment. unc-33 and unc-44 were both required to establish the asymmetric dynamics of axonal and dendritic microtubules; in their absence, microtubules were disorganized, the axonal kinesin UNC-104 invaded dendrites, and inappropriate UNC-104 activity randomized axonal protein sorting. We suggest that UNC-44 and UNC-33 direct polarized sorting through their global effects on neuronal microtubule organization.

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