  During migration, amoeboid cells perform a cycle of quasi-periodic repetitive
events (motility cycle). the cell length and the strain energy exchanged with
the substrate oscillate in time with an average frequency, f, on top of which
are imposed smaller random fluctuations. the fact that a considerable portion
of the changes in cell shape are due to periodic repetitive events enables the
use of conditional statistics methods to analyze the network of biochemical
processes involved in cell motility. taking advan- tage of this cyclic nature,
we apply Principal Component analysis (PCa) and phase- average statistics to
analyze the dominant modes of shape change and their association to the
activity and localization of molecular motors. We analyze time-lapse measure-
ments of cell shape, traction forces and fluorescence from green fluorescent
protein (GfP) reporters for f-actin in Dictyostelium cells undergoing guided
chemotactic migration. using wild-type cells (wt) as reference, we investigated
the contractile and actin crosslinking functions of myosin II by studying
myosin II heavy chain null mutant cells (mhcA-) and myosin II essential light
chain null cells (mlcE-).
