title: Microtubules have opposite orientation in axons and dendrites of Drosophila neurons.
abstract: In vertebrate neurons, axons have a uniform arrangement of microtubules with plus ends distal to the cell body (plus-end-out), and dendrites have equal numbers of plus- and minus-end-out microtubules. To determine whether microtubule orientation is a conserved feature of axons and dendrites, we analyzed microtubule orientation in invertebrate neurons. Using microtubule plus end dynamics, we mapped microtubule orientation in Drosophila sensory neurons, interneurons, and motor neurons. As expected, all axonal microtubules have plus-end-out orientation. However, in proximal dendrites of all classes of neuron, approximately 90% of dendritic microtubules were oriented with minus ends distal to the cell body. This result suggests that minus-end-out, rather than mixed orientation, microtubules are the signature of the dendritic microtubule cytoskeleton. Surprisingly, our map of microtubule orientation predicts that there are no tracks for direct cargo transport between the cell body and dendrites in unipolar neurons. We confirm this prediction, and validate the completeness of our map, by imaging endosome movements in motor neurons. As predicted by our map, endosomes travel smoothly between the cell body and axon, but they cannot move directly between the cell body and dendrites.
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Michelle C
authors.initials: MC
authors.lastname: Stone
authors.forename: Fabrice
authors.initials: F
authors.lastname: Roegiers
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Rolls
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001369:Axons / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D003712:Dendrites / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006579:Heterozygote; D008164:Luminescent Proteins / Q000378:metabolism; D008870:Microtubules / Q000378:metabolism*; D008954:Models, Biological; D009474:Neurons / Q000378:metabolism*; D019076:Transgenes; D000097573:Red Fluorescent Protein
chemical_list: D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D000097573:Red Fluorescent Protein