טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentAdler Yair
SubjectLamellipodia Dynamics in Motile Cells
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Josef Givli
Full Thesis textFull thesis text - English Version


Abstract

The lamellipodia, one of the important cell motility mechanisms, is a very thin and wide region in the cell front, which attaches to surfaces using adhesive proteins. Inside this region lies a crowded network of polymers, mainly polarized actin filaments. These actin filaments depolymerize at their rear end and polymerize at the other end which is directed towards the cell leading edge. This process affects the shape of the cell membrane and forces the lamellipodia edge to protrude in a crawl-like manner.

In this work, we study the mechanical processes underlying the lamellipodia behavior by means of a simplified theoretical model. The model accounts for the membrane dynamic shape and its coupling with the active network of actin filaments. To this end we utilize a non-linear integro-differential PDE to describe the shape evolution, together with a conservation equation for the actin dynamics along the edge of the lamellipodia. The evolution of the lamellipodia shape is simulated by solving the model equations using a characteristic-based finite differences numerical scheme. The simulated results are compared to experimental observations and show good agreement, both for the steady state configurations and for the nature of the dynamic process. Importantly, we were able to study the stability of steady state configurations, which is a central characteristic of the lamellipodia mechanism. Our results suggest that the mechanical coupling between the membrane shape and the actin network is a central feature of the lamellipodia, which dominates its dynamic behavior.