Genetic suppression of a phosphomimic myosin II identifies system-level factors that promote myosin II cleavage furrow accumulation.
Bottom Line: How myosin II localizes to the cleavage furrow in Dictyostelium and metazoan cells remains largely unknown despite significant advances in understanding its regulation.Analysis of several mutant strains revealed that different thresholds of myosin II activity are required for daughter cell symmetry than for furrow ingression dynamics.Finally, an engineered myosin II with a longer lever arm (2xELC), producing a highly mechanosensitive motor, could also partially suppress the intragenic 3xAsp.
Affiliation: Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205.Show MeSH
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Mentions: To test the role of RMD1 using loss-of-function analysis, we depleted rmd1 via small interference RNA (siRNA) using a hairpin construct (rmd1hp), which yielded ∼90–95% reduction of mRNA levels (Figure 5B, inset). Silencing of rmd1 in WT cells induced more binucleated and multinucleated cells (Figure 5, A and B) and reduced the cortical tension of cells (Figure 5C). Commensurate with the mild cytokinesis defect and reduction in cortical tension, rmd1hp cells also showed faster furrow ingression dynamics than the WT control, which had the stereotypical, near-exponential furrow ingression trajectory (Figure 5D). Of note, changes in the furrow ingression trajectory of rmd1hp cells are similar to what we observed previously for 14-3-3hp, myoII-, and several other cell mechanics mutants (e.g., Zhang and Robinson, 2005; Reichl et al., 2008; Zhou et al., 2010).
Affiliation: Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205.