CSB Seminar: Thinking of cells as composites of materials: a way to understand shaping of the early Drosophila embryo by cytoskeletal networks

“Thinking of cells as composites of materials: a way to understand shaping of the early Drosophila embryo by cytoskeletal networks”

Tony Harris and Medha Sharma 

Cell and Systems Biology 

Abstract:

A major question in biology is how cells form and function through the coordinated activities of their molecular components.  Tony will describe how this question can be approached by thinking of cells as composites of materials.  What signals and components form each material?  What are the chemical and physical properties of each material?  How do the materials affect each other for chemical and physical change at the cellular scale?  These points will be discussed in relation to the cell cortex, a layer of actin networks and additional factors beneath the plasma membrane.  Tony will review how the activities and interactions of cortical domains produce dome-like compartments for dividing nuclei of the syncytial Drosophila embryo.  Medha will discuss her PhD research focused on a central aspect of this cortical reorganization—how a smooth boundary can form between rough-edged cortical domains.  Across the syncytial embryo surface, smooth interfaces form between expanding Arp2/3-based actin caps and surrounding actomyosin networks, demarcating the circumferences of nascent dome-like compartments.  The smoothening of the actomyosin interfaces requires Arp2/3 in vivo.  To dissect the physical basis of this requirement, Medha reconstituted the interacting networks using node-based models.  When actomyosin networks were simulated with clearances instead of Arp2/3 networks, rough boundaries persisted with low levels of myosin contractility.  With addition of expanding Arp2/3 networks, network-network interfaces failed to smoothen, but accumulated myosin nodes and tension.  After incorporating actomyosin mechanosensitivity, Arp2/3 network growth induced local contractility and smoothening of the interfaces, effects also evident in vivo.  In this way, a smooth structure can emerge from the lateral interaction of irregular starting materials, an early step of budding a dome-like compartment from a much larger cell.

Friday, April 30th, 2021 at 11:00am

https://utoronto.zoom.us/j/94049486250

Host: Tony Harris (tony.harris@utoronto.ca)