Self Organization in Cells - How to Use Proteins to Solve a Geometry Problem

Eric Cytrynbaum
Thu, May 17, 2012
PIMS, University of British Columbia
Mathematical Cell Biology Summer Course

Fragments of fish pigment cells can form and center aggregates of
pigment granules by dynein-motor-driven transport along a
self-organized radial array of microtubules (MTs). I will present a
quantitative model that describes pigment aggregation and MT-aster
self-organization and the subsequent centering of both structures.
The model is based on the observations that MTs are immobile and
treadmill, while dynein-motor-covered granules have the ability to
nucleate MTs. From assumptions based on experimental observations,
I'll derive partial integro-differential equations describing the
coupled granule-MT interaction. Analysis explains the mechanism of
aster self-organization as a positive feedback loop between motor
aggregation at the MT minus ends and MT nucleation by motors.
Furthermore, the centering mechanism is explained as a global
geometric bias in the cell established by spontaneously-nucleated
microtubules. Numerical simulations lend additional support to the
analysis. The model sheds light on role of polymer dynamics and
polymer-motor interactions in cytoskeletal organization.