Physicists
at Lehigh University have created a mathematical model that could benefit
researchers who study cell motion, including cancerous cell motion, tissue healing
processes, and human embryonic development.
Their
model consists of partial-differential equations that describe the behavior of
actin filaments at the cell’s leading edge. The alternate accumulation and
dissipation of actin drive the protrusion and retraction behavior of the cell
membrane of crawling cells.
Gillian
L. Ryan, a postdoctoral scientist in the physics department, and Dimitrios Vavylonis,
associate professor of physics, developed the model, which hypothesizes that
actin assembly is part of an excitable system. The protrusion of the actin
cytoskeleton near the cell membrane along the cell’s leading edge, said Ryan,
represents one of three factors that contribute to cell movement. The other two
are the adhesion by the cell to an outside surface and the contraction of the
cell’s back edge.
Ryan and
Vavylonis, along with Naoki Watanabe, a professor of life sciences at Tohoku
University in Japan, and Heather Petroccia, who earned a BS in physics from
Villanova University in 2011, published an article in Biophysical Journal.
Coordinating actin activities and cell motion
Watanabe’s laboratory used fluorescent tags to mark actin accumulation in XTC
cells from frogs. Inside the lamellipodia, which are cell extensions along the
cell edges, actin polymerizes into a dense network of filaments that protrude
from the cell membrane in a dynamic process. Image analysis of actin
fluorescence enabled Ryan to correlate the buildup and dissipation of actin
with the motion of the cell.
“Once we
had a clear quantitative analysis, this enabled us to formulate and test a
coarse-grained mathematical model that attempts to capture the basic features
of the system,” Ryan said.
A better
understanding of actin behavior might affect multiple fields. Vavylonis, Ryan
and members of their group are continuing their studies in cell biophysics by
examining the ways in which actin filaments contribute to cell division and
other cell processes.
“We hope
to better understand how actin filament assembly and disassembly generate cell
patterns and mechanical forces,” Vavylonis said.
Watanabe
is trying to apply the discovery to the medical field. “He’s looking at the
effects that different drugs can have on lamellipodia,” Vavylonis said.
Watanabe hopes to find drugs that will facilitate the activation or suppression
of lamellipodial responses, because cell motion is vital both to tissue
remodeling and the cancer cell invasion in humans.
The
project is funded by Human Frontiers Science Program, which supports
collaboration across different disciplines and in different countries.
Source: Lehigh University
