In growing Dictyostelium discoideum, PIP3 is unnecessary for migration toward folate and actively inhibits chemotaxis and pseudopod formation by promoting macropinocytosis.

The actin cytoskeleton is necessary for cell viability and plays crucial roles in cell motility, endocytosis, growth, and cytokinesis. Hence visualization of dynamic changes in F-actin distribution in vivo is of central importance in cell biology. This has been accomplished by the development of fluorescent protein fusions to actin itself or to various actin-binding proteins, actin cross-linking proteins, and their respective actin-binding domains (ABDs). Although these protein fusions have been shown to bind to F-actin in vivo, we show that the fluorescent protein used for visualization changes the subset of F-actin labeled by an F-actin ABD probe. Further, different amino acid linkers between the fluorescent protein and ABD induced a similar change in localization. Although different linkers and fluorescent proteins can alter the subset of actin bound by a particular ABD, in most cases, the fusion protein did not label all of a cell's F-actin all of the time. Even LimEΔcoil and GFP-actin, which have been used extensively for cytoskeletal visualization, were highly variable in the subsets of actin that they labeled. Lifeact, conversely, clearly labeled cortical F-actin as well as F-actin in the anterior pseudopods of motile cells and in macropinocytotic cups. We conclude that Lifeact most accurately labels F-actin and is the best currently available probe for visualization of dynamic changes in F-actin networks.

With the current state of technology, use of Acoustic Tweezers (ATω) is limited to manipulation of single or few particles in single experimental setup. This article presents a state of the art system using Acoustic Lens (AL) as a Micro-Acoustic Trap (µAT) for microparticle assembly in 3D. In this investigation 2 micron sized polystyrene beads were used. Acoustic pressure generated by AL drives the particles towards the center of the acoustic focal plane, which leads to the formation of a free floating monolayer of latex particles. Transducer is driven at 89 MHz as both continuous wave (CW) and at mixed with pulsed (PL) frequency of 2Hz. The system was driven at drive amplitudes of 0.5 V, 1 V and 1.5 V. The most tightly packed monolayer of latex particles was observed at drive amplitude of 1.5 V. A loosely formed random close pack disc like structure was observed at 1 V whereas at 0.5 V drive amplitude particles were gently driven towards the center of the Acoustic Focal Plane (AFP) but no assemble was observed. This methodology was further extended for manipulating live Dictyostelium discoideum (Amoebas). At high drive amplitude of 2V, one can not only segregate non-adherent cells from adherent ones or move them to a region of interest but also can compress them and shrink their size. It was also observed that the cells having weaker cell membrane get distorted or membrane is rupture under a continuous stream of acoustic waves.

Dysregulated cell movement can lead to developmental abnormalities, neoplasia, and immune system disorders, and there are a variety of contexts in which xenobiotics (and biologic) effects on this movement are of interest. Many toxins and toxicants have been shown to disrupt controlled cell movement. Identification of compounds that affect cell movement is crucial to drug discovery. Drug components may have unexpected consequences with respect to cell motility, which would exclude these compounds in drug development. Finally, the development of drugs that target chemotactic pathways may be useful in the treatment of tumors, which often reprogram chemotactic pathways to become metastatic. The effects of these agents on cell movement can be measured using several different in vitro chemotactic assays. This review details the procedures of three in vitro measurements of chemotaxis: the Boyden chamber, the under-agarose assay, and the automated, real-time, ECIS/Taxis assay, and discusses the inferences that can be drawn from the results of such studies.

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