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Free keywords:
REACTION-DIFFUSION SYSTEM, LIPID SIGNALING SYSTEM, HEAVY-CHAIN GENE,
DICTYOSTELIUM CELLS, SELF-ORGANIZATION, TRAVELING-WAVES, IMAGE-ANALYSIS,
DYNAMICS, CHEMOTAXIS, MODELCell Biology; Developmental Biology; Actin waves, PIP3 signals, Excitable systems, Cell polarity, Cell fusion;
Abstract:
The membrane and actin cortex of a motile cell can autonomously
differentiate into two states, one typical of the front, the other of
the tail. On the substrate-attached surface of Dictyostelium discoideum
cells, dynamic patterns of front-like and tail-like states are generated
that are well suited to monitor transitions between these states. To
image large-scale pattern dynamics independently of boundary effects, we
produced giant cells by electric-pulse-induced cell fusion. In these
cells, actin waves are coupled to the front and back of
phosphatidylinositol (3,4,5)-trisphosphate (PIP3)-rich bands that have a
finite width. These composite waves propagate across the plasma membrane
of the giant cells with undiminished velocity. After any disturbance,
the bands of PIP3 return to their intrinsic width. Upon collision, the
waves locally annihilate each other and change direction; at the cell
border they are either extinguished or reflected. Accordingly, expanding
areas of progressing PIP3 synthesis become unstable beyond a critical
radius, their center switching from a front-like to a tail-like state.
Our data suggest that PIP3 patterns in normal-sized cells are segments
of the self-organizing patterns that evolve in giant cells.
