TY - JOUR TI - Unrestrained growth of correctly oriented microtubules instructs axonal microtubule orientation AU - Jakobs, Maximilian AH AU - Zemel, Assaf AU - Franze, Kristian A2 - Shen, Kang A2 - Akhmanova, Anna A2 - Prokop, Andreas VL - 11 PY - 2022 DA - 2022/10/10 SP - e77608 C1 - eLife 2022;11:e77608 DO - 10.7554/eLife.77608 UR - https://doi.org/10.7554/eLife.77608 AB - In many eukaryotic cells, directed molecular transport occurs along microtubules. Within neuronal axons, transport over vast distances particularly relies on uniformly oriented microtubules, whose plus-ends point towards the distal axon tip (anterogradely polymerizing, or plus-end-out). However, axonal microtubules initially have mixed orientations, and how they orient during development is not yet fully understood. Using live imaging of primary Drosophila melanogaster neurons, we found that, in the distal part of the axon, catastrophe rates of plus-end-out microtubules were significantly reduced compared to those of minus-end-out microtubules. Physical modelling revealed that plus-end-out microtubules should therefore exhibit persistent long-term growth, while growth of minus-end-out microtubules should be limited, leading to a bias in overall axonal microtubule orientation. Using chemical and physical perturbations of microtubule growth and genetic perturbations of the anti -catastrophe factor p150, which was enriched in the distal axon tip, we confirmed that the enhanced growth of plus-end-out microtubules is critical for achieving uniform microtubule orientation. Computer simulations of axon development integrating the enhanced plus-end-out microtubule growth identified here with previously suggested mechanisms, that is, dynein-based microtubule sliding and augmin-mediated templating, correctly predicted the long-term evolution of axonal microtubule orientation as found in our experiments. Our study thus leads to a holistic explanation of how axonal microtubules orient uniformly, a prerequisite for efficient long-range transport essential for neuronal functioning. KW - axons KW - neurons KW - microtubule orientation KW - microtubule polarity JF - eLife SN - 2050-084X PB - eLife Sciences Publications, Ltd ER -