BME PhD Preliminary Exam Announcement for Fahmida Sultana Laboni (T. Kim, advisor)

Everyone is invited to attend the public presentation beginning at 2:00 PM.

Research Title: Morphological Transition, Blebbing and cytokinesis of Cell Driven by the Contraction of Cortical Actomyosin Networks

Date: 11/13/2024

Time: 2:00 PM

Location: LYNN G155 

Thesis Committee Members:

• Major Professor: Dr. Taeyoon Kim
• Committee Members:

• Dr. Tamara L. Kinzer-Ursem
• Dr. Elsje Pienaar
• Dr. Adrian Buganza Tepole

Abstract: Cells are highly dynamic, undergoing significant changes during processes such as apoptosis, migration, and cytokinesis. Cells leverage actomyosin contractility to generate forces that produce diverse morphological changes, from membrane blebs to the furrow ingression required for cytokinesis. These transformations involve not only cortical reorganization but also the interaction of actin filaments with membrane linkers, which anchor the cortex to the cell membrane. However, the mechanisms by which these shared molecular components produce distinct morphological outcomes remain unclear. Additionally, the rapid, transient nature of bleb formation and cytokinesis poses challenges to understand the mechanisms solely through experimental methods. This study addresses this gap by using a suite of agent-based 3D computational models to examine the molecular mechanisms underlying bleb formation, cortical flow, and cytokinesis. Our computational model simulations reveal diverse cell shape changes driven by actin network dynamics. Specifically, bleb formation is initiated by F-actin fragmentation, triggered by mechanical forces within the network. We found that network tension dynamics, membrane-coupling strength, actin cross-linking protein (ACP) density, and motor protein concentration are key factors influencing bleb initiation and morphology. Simulations of the actin cytoskeleton model without a membrane show that cortical flow and bundle formation are significantly impacted by cytoskeletal properties. A minimum percolation threshold within the network is necessary to initiate cortical flow, while ACP density regulates bundle stability, and motor density determines flow speed. Using our cell-like actin cytoskeleton model, we expect to uncover the underlying mechanics of cell bleb formation and cytokinetic furrow ingression driven by cortical flow and membrane dynamics.