Date of Award

1-1-2015

Document Type

Dissertation

Degree Name

Ph.D.

Department

Biological Sciences

First Advisor

James Todd Blankenship

Keywords

Drosophila, Furrow formation, Rab8

Abstract

One of the most fundamental changes in cell morphology is the formation of a plasma membrane furrow. The Drosophila embryo undergoes several cycles of rapid furrow ingression during early development, which culminates in the formation of an epithelial sheet. Previous studies have demonstrated the requirement for intracellular trafficking pathways in furrow ingression; however, the pathways that link compartmental behaviors with cortical furrow ingression events have remained unclear. This research shows that Rab8, a small GTPase associated with late exocytic trafficking events, demonstrates striking dynamic behaviors in vivo; transitioning from punctate structures to a stable association with the cortex during furrow formation. Active, GTP-locked Rab8 is primarily associated with dynamic membrane compartments and the cortical array, while inactive, GDP-locked Rab8 forms large cytoplasmic aggregates. After early furrow initiation, Rab8 transitions to a cortical location that coincides with known regions of directed plasma membrane addition, with Sec5, a subunit of the exocyst and RalA, a small GTPase implicated in directed membrane trafficking.

Disruption of Rab8 function results in a complete failure of furrow formation in the early embryo, due to a failure of proper F-actin cytoskeletal dynamics and localization, which ultimately results in the failure to create an epithelial sheet. Additionally, an intact microtubule network is required for proper Rab8 dynamics during early furrow formation, but is dispensable once a Rab8 cortical array has formed. These studies suggest that active, membrane-bound Rab8 populations prefigure and initiate furrow ingression, and direct membrane trafficking behaviors in vivo in the Drosophila embryo. The work presented here demonstrates a novel role regarding the function of Rab8 and the Rab family of proteins' requirement in complex developmental processes. By elucidating new mechanisms of furrow formation, and ultimately cell division, this work will help to enhance the general knowledge of potential therapeutic targets in such diseases as cancer, developmental defects and other scenarios in which polarized membrane addition is required for the formation of discreet cell and tissue types.

Provenance

Recieved from ProQuest

Rights holder

Lauren MacKenzie Mavor

File size

100 p.

File format

application/pdf

Language

en

Discipline

Biology, Cellular biology, Developmental biology

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