This study presents a simple method for evaluating the cortex contractility of
Dictyostelium cells. This assay is based on the artificially-induced actomyosin-mediated contraction of the cortex cytoskeleton. Simultaneous application of Triton X-100 and ATP to
Dictyostelium cells induced rapid shrinkage of cell mass after cell lysis. This cellular contraction was dependent on ATP in the medium, and mutant cells lacking myosin II did not show significant contraction. Microscopic measurements of artificially-induced contraction such as this require only a small amount of cell suspension and can provide significant information on the contractile properties of the cortex in target cells. As one example analysis, the magnitude and velocity of the contraction in strains that exogenously expressed
Tetrahymena actin or a chimeric actin of
Dictyostelium and
Tetrahymena were measured. The results revealed certain dominant negative effects of these actin variants with respect to the endogenous
Dictyostelium actin. This simple method is thus considered to be a useful tool for the rapid assessment of phenotypes in various cytoskeleton-related mutants either in early-stage studies or in genetic manipulations intending to alter the cellular contractility in
Dictyostelium.
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