Cell Behavior and Actomyosin Organization in Dictyostelium During Substrate Exploration.

Abstract

ABSTRACT.The behavior of individual Dictyostelium amebae was quantitatively analyzed with the computer-assisted "Dynamic Morphology System" (Soil, Voss, Varnum-Finney and Wessels, (1988) /. Cell. Biochem.,. The same amoebae were then fixed and analyzed for filamentous (F-) actin and myosin (myosin-II, or "coventional" myosin) by fluorescence microscopy using the "agar-overlay method" (Yumura, and Fukui (1985) Nature, 314: 194-196.). This procedure provides a novel description of the behavior and morphometric changes preceding the static analysis of cytoskeletal organization in the same cell. It is demonstrated that when translocating cells make contact with an etched-smooth glass interface, 14% cross the interface, 20% either reverse direction or migrate along the interface, and the remaining 45%stay at the site. Cells contacting the interface from the smooth or etched side show equivalent behavioral responses. Upon contact with the interface, they project numerous lamellipodia and pseudopodia. While the lamellipodial projections exhibit cycles of spreading and retraction, the pseudopodia show lateral scanning motion, analogous to "substrate exploration" in fibroblasts (Albrecht-Buehler (1976) /. Cell BioL , 69: 275-286.). F-actin is localized in the lamellipodia and pseudopodia of amoebae contacting the interface. There is also discernable cortical F-actin, while conventional myosin appears to be excluded from the cortex and dispersed throughout the cytoplasm. The myosin displays a transient filamentous lattice at the base of newly forming lamellipodia. The ultrastructural study suggests that the new lamellipodia are formed on the dorsal surface and subsequently make contact with the substrate, indicating the dorsoventral sequence of polarity of the motile/sensory cellular organs. The present study demonstrates substrate exploration in Dictyostelium amoebae, and suggests its coupling to dynamic reorganization of the actomyosin cytoskeleton. The possible role of single-headed small myosin(s) (myosin-I, or minimyosin) is discussed.

Migration of isogenic cell lines quantified by dynamic multivariate analysis of single-cell motility

“…A manual version of differential imaging was previously shown in a publication by Fukui et al, and was referred to as producing "difference pictures." 53 However, we are unaware of any other algorithms/computational methods that reflect the same activity as DECCA. Originally, DECCA was developed with the intent to distinguish between two cell types that have the same migration speed, but very different membrane protrusion dynamics (to be included in future work).…”

Myosin II Is Essential for the Spatiotemporal Organization of Traction Forces during Cell Motility

“…This process is mainly driven by the coordinated turnover of filamentous actin (F-actin) and the F-actin–directed nonmuscular myosin II complex (MyoII) (Condeelis et al , 1988; Fukui et al , 1991; Iwadate and Yumura, 2008). Actin filament length is regulated by capping proteins, and the mechanical properties of F-actin are modulated by actin binding and cross-linking proteins (Wear et al , 2000; Pollard and Borisy, 2003; Iwasa and Mullins, 2007), among them MyoII.…”

How a Cell Crawls and the Role of Cortical Myosin II

“…Although we initially considered the uropod and main cell body a single motile entity, especially since there was no visible cytoplasmic barrier between the two as was the case at the interface (21), evidence has accumulated in other systems that a variety of molecules specifically localize in the uropod (12,38,45). Here we have identified several characteristics that also support the individuality of the uropod.…”

“…The main cell body was bordered by the interface and junction and appeared to behave differently from either the pseudopods or uropod. Fukui and coworkers (21) observed that the interface between pseudopod and cell body in D. discoideum amoebae stained for both Factin and myosin II, leading to the suggestion that a filamentous lattice at the interface excluded organelles and vesicles from entering pseudopods and disrupting the F-actin gel. The junction marks the transition between the main cell body and the uropod and functions as a sink for retracting pseudopods.…”