title: Γ-tubulin controls neuronal microtubule polarity independently of Golgi outposts.
abstract: Neurons have highly polarized arrangements of microtubules, but it is incompletely understood how microtubule polarity is controlled in either axons or dendrites. To explore whether microtubule nucleation by γ-tubulin might contribute to polarity, we analyzed neuronal microtubules in Drosophila containing gain- or loss-of-function alleles of γ-tubulin. Both increased and decreased activity of γ-tubulin, the core microtubule nucleation protein, altered microtubule polarity in axons and dendrites, suggesting a close link between regulation of nucleation and polarity. To test whether nucleation might locally regulate polarity in axons and dendrites, we examined the distribution of γ-tubulin. Consistent with local nucleation, tagged and endogenous γ-tubulins were found in specific positions in dendrites and axons. Because the Golgi complex can house nucleation sites, we explored whether microtubule nucleation might occur at dendritic Golgi outposts. However, distinct Golgi outposts were not present in all dendrites that required regulated nucleation for polarity. Moreover, when we dragged the Golgi out of dendrites with an activated kinesin, γ-tubulin remained in dendrites. We conclude that regulated microtubule nucleation controls neuronal microtubule polarity but that the Golgi complex is not directly involved in housing nucleation sites.
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Nguyen
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802.
authors.forename: Christie J
authors.initials: CJ
authors.lastname: McCracken
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802.
authors.forename: E S
authors.initials: ES
authors.lastname: Milner
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Goetschius
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802.
authors.forename: Alexis T
authors.initials: AT
authors.lastname: Weiner
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802.
authors.forename: Melissa K
authors.initials: MK
authors.lastname: Long
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802.
authors.forename: Nick L
authors.initials: NL
authors.lastname: Michael
authors.affiliation: Division of Cell Biology, MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, United Kingdom.
authors.forename: Sean
authors.initials: S
authors.lastname: Munro
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802 mur22@psu.edu.
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Rolls
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D016764:Cell Polarity; D002478:Cells, Cultured; D003712:Dendrites / Q000378:metabolism; D004330:Drosophila; D029721:Drosophila Proteins / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D021381:Protein Transport; D014404:Tubulin / Q000502:physiology*
chemical_list: D029721:Drosophila Proteins; D014404:Tubulin