Microtubules are necessary for proper Reticulon localization during mitosis

During mitosis, the structure of the Endoplasmic Reticulum (ER) displays a dramatic reorganization and remodeling event, however the mechanism driving these changes is poorly understood. Recently, the Reticulon family of ER shaping proteins has been identified as possible factors to promote these drastic changes in ER morphology. In addition, the Reticulons and other ER shaping proteins have been directly linked to several hereditary neurodegenerative disorders. Here, we provide key insight into the cytoskeletal factors involved in the Drosophila Reticulon, Reticulon-like 1 (Rtnl1) during mitosis in the early embryo. At prometaphase, Rtnl1 localizes at the spindle poles just prior to the bulk of ER localization suggesting a role in recruitment. Using precise temporal injections of cytoskeletal inhibitors in the early syncytial Drosophila embryo, we show that microtubules, not microfilaments are necessary for proper Rtnl1 localization and function during mitosis. Lastly, we show that astral microtubules are necessary for Rtnl1 localization at the spindle poles early in mitosis. This work highlights the role of the microtubule cytoskeleton in Rtnl1 localization and ER dynamics during mitosis and sheds light on a pathway towards inheritance of this major organelle.