700C Poster - 11. Cell division and cell growth
Saturday April 09, 1:30 PM - 3:30 PM

Authors:
Katie Rollins; J. Todd Blankenship

Affiliation: University of Denver

Keywords:
a. mitosis; j. endoplasmic reticulum

Mitotic spindles are often observed to be found in close association with the endoplasmic reticulum – however, the purpose of this association is less clear. The syncytial stage of fly embryogenesis is a period of rapid mitotic divisions, with the blastoderm stage marked by four rounds of divisions in a membrane-less syncytium near the cell cortex. These rapid divisions demonstrate major remodeling events of various membranous organelles, such as the nuclear envelope, the endoplasmic reticulum, and the deformation of the plasma membrane into cytokinetic-like furrows. Work from our lab, as well as others, has shown the contribution of multiple Rab-directed pathways to these processes, but relatively little work has examined how transformations in the ER contribute to successful mitoses. Here, we demonstrate that Rab1 controls ER to Golgi trafficking and is highly active within the Drosophila syncytium. Interestingly disrupting Rab1 results in severe mitotic failures, suggesting a role for the ER in permitting appropriate spindle function. In Rab1 knockdown embryos the endoplasmic reticulum accumulates in large spindle associated aggregates. This aggregation appears to be dynein-dependent, and disrupting the aggregation rescues mitotic function. We will also report on the mechanisms by which the over-accumulated ER affects the integrity of the spindle.