- A lab compared cell motility on substrates of different stiffness. On very stiff substrates, cells with reduced intermediate filaments migrated similarly to controls. On softer, deformable substrates, the same cells frequently lost coherence during movement and showed shorter net displacement. Actin polymerization at the leading edge was comparable across conditions. Which conclusion is most consistent with these results?
Answer: Intermediate filaments become particularly important for maintaining mechanical stability during migration when external support from the environment is reduced.
This question assesses understanding of the cytoskeleton's role in cell motility. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, facilitates cell movement through structural and dynamic functions. In the vignette, reduced intermediate filaments impair motility on soft substrates but not stiff ones, with comparable actin polymerization. Choice D is correct because it accurately describes their importance for stability with reduced external support. Choice B is incorrect because it wrongly focuses on actin polymerization control. When evaluating cytoskeletal function, consider both structural support and dynamic changes essential for cellular processes. Test substrate stiffness to uncover environment-dependent roles.
- Amoeboid cells were treated with a compound that selectively disrupts intermediate filaments while leaving actin filaments and microtubules intact. On a flat substrate, cells could still form actin-rich protrusions but frequently ruptured or fragmented when squeezing through narrow pores in a transwell assay. Which conclusion about intermediate filaments is most consistent with the observed role in cell motility?
Answer: Intermediate filaments provide mechanical resilience during deformation in confined migration, supporting cell integrity rather than directly generating protrusive force.
This question assesses understanding of the cytoskeleton's role in cell motility. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, facilitates cell movement through structural and dynamic functions. In the vignette, disrupting intermediate filaments causes rupture in narrow pores despite intact protrusions on flat surfaces. Choice A is correct because it accurately describes their role in mechanical resilience during confined migration. Choice B is incorrect because it wrongly claims they drive leading-edge protrusion. When evaluating cytoskeletal function, consider both structural support and dynamic changes essential for cellular processes. Compare behaviors across substrates to highlight mechanical roles.
- Researchers observed that disrupting intermediate filaments did not strongly affect 2D crawling speed but increased the variability of cell shape and reduced the fraction of cells completing migration through a dense 3D matrix. Actin-rich protrusions were still visible at the front. Which statement best describes the role of intermediate filaments in cell motility across environments?
Answer: Intermediate filaments are especially important for maintaining structural integrity and successful translocation in mechanically challenging 3D environments.
This question assesses understanding of the cytoskeleton's role in cell motility. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, facilitates cell movement through structural and dynamic functions. In the vignette, disrupting intermediate filaments affects 3D matrix completion more than 2D speed, with visible actin protrusions. Choice C is correct because it accurately describes their importance for integrity in challenging 3D environments. Choice B is incorrect because it wrongly claims they engine protrusion in all settings. When evaluating cytoskeletal function, consider both structural support and dynamic changes essential for cellular processes. Contrast 2D and 3D to reveal context-specific contributions.
- Migrating fibroblasts were imaged as they moved toward a wound edge. A fluorescent probe for newly polymerized actin showed transient enrichment at the cell front, while total actin signal remained relatively constant. When researchers stabilized F-actin (reducing both polymerization and depolymerization dynamics), cells formed broad protrusions that persisted but advanced slowly, and directional changes were reduced. Which statement best describes the role of actin filament dynamics in cell motility under these conditions?
Answer: Dynamic actin turnover supports efficient protrusion–retraction cycles and steering, so reducing turnover slows net migration despite visible protrusions.
This question assesses understanding of the cytoskeleton's role in cell motility. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, facilitates cell movement through structural and dynamic functions. In the vignette, stabilizing F-actin reduces dynamics, leading to persistent but slow protrusions and fewer directional changes in migrating fibroblasts. Choice B is correct because it accurately describes how dynamic actin turnover supports protrusion-retraction cycles and steering for efficient migration. Choice A is incorrect because it wrongly suggests stabilization accelerates migration without needing turnover. When evaluating cytoskeletal function, consider both structural support and dynamic changes essential for cellular processes. Focus on how altering filament dynamics impacts overall cell behavior in wound-healing contexts.
- Researchers examined amoeboid cells migrating through microchannels that force a narrow, elongated shape. Imaging revealed actin-rich protrusions at the front and a dense actin network at the rear during squeezing events. When a drug that reduces actin filament turnover was applied, cells could still enter channels but frequently stalled mid-channel and showed prolonged rear attachments. In contrast, a low dose of a myosin II inhibitor reduced rear contraction but did not prevent initial protrusion into the channel. Based on the vignette, which conclusion about cytoskeletal dynamics is most consistent?
Answer: Efficient confinement migration requires actin turnover and contractile remodeling to release rear adhesions and prevent stalling.
This question assesses understanding of actin dynamics in confined cell migration. The cytoskeleton must undergo continuous remodeling to enable cells to navigate through narrow spaces. In the vignette, reducing actin turnover caused cells to stall mid-channel with prolonged rear attachments, while myosin II inhibition affected rear contraction but not initial entry. Choice B is correct because it accurately describes how efficient confinement migration requires actin turnover and contractile remodeling to release rear adhesions and prevent stalling. Choice A is incorrect because microtubules are not the dominant force source for passage through constrictions - actin and myosin II-based contractility are key. When analyzing confined migration, remember that both actin polymerization at the front and turnover/contraction at the rear are essential for continuous forward movement.
- Cells migrating toward a chemoattractant were analyzed for coordination between cytoskeletal systems. In control cells, microtubules were biased toward the front and actin-rich protrusions were more stable on the side facing the gradient. After partial microtubule disruption, actin-based protrusions still formed but appeared around the perimeter and frequently collapsed; cells advanced in short bursts with poor net directionality. No gross loss of cell viability was noted. Based on the vignette, which conclusion about cytoskeletal coordination is most consistent?
Answer: Microtubules help spatially bias and stabilize actin-driven protrusions during chemotaxis, improving directional migration without being the sole source of protrusive force.
This question assesses understanding of cytoskeletal coordination during chemotactic migration. Effective directed migration requires cooperation between microtubules and actin, with microtubules helping to stabilize and bias actin-based protrusions. In the vignette, partial microtubule disruption led to unstable, randomly distributed protrusions and poor directionality despite continued actin activity. Choice A is correct because it accurately describes how microtubules help spatially bias and stabilize actin-driven protrusions during chemotaxis without being the sole source of protrusive force. Choice C is incorrect because microtubules do not directly push membranes - protrusion is primarily actin-driven. When analyzing chemotaxis, consider that microtubules provide spatial organization and stability to actin-based structures, enabling persistent directional movement.
- To probe actin turnover during amoeboid migration, investigators performed a pulse-labeling experiment that selectively marked newly polymerized actin near the leading edge. In motile cells, labeled actin intensity at the front peaked quickly and then declined as the cell advanced, consistent with turnover. When a compound that slows actin depolymerization was added, labeled actin persisted longer at the front, but cells showed reduced net displacement and frequent pauses. Which statement best describes the role of actin depolymerization in cell motility, based on this experimental finding?
Answer: Actin depolymerization contributes to efficient movement by enabling remodeling and recycling that supports repeated protrusion cycles and net advance.
This question assesses understanding of actin turnover dynamics in cell motility. Efficient cell movement requires not just actin polymerization but also depolymerization to enable continuous remodeling. In the vignette, slowing actin depolymerization caused labeled actin to persist at the front but reduced net displacement and caused frequent pauses. Choice B is correct because it accurately describes how actin depolymerization contributes to efficient movement by enabling remodeling and recycling that supports repeated protrusion cycles. Choice A is incorrect because persistent filaments alone cannot sustain productive movement - turnover is essential for adaptation and continued advance. When evaluating actin dynamics, remember that the balance between polymerization and depolymerization enables the flexibility needed for sustained motility.
- Researchers tracked the movement of recycling endosomes in migrating cells and found they moved along linear tracks toward the leading edge. When microtubules were stabilized (reduced dynamics but preserved tracks), endosome movement remained largely intact, but cells were slower to change direction in response to a new chemoattractant source. Which conclusion is most consistent with these observations?
Answer: Microtubule tracks can support transport even when stabilized, but microtubule dynamics help cells rapidly reorient polarity during directional changes.
This question assesses understanding of the cytoskeleton's role in cell motility. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, facilitates cell movement through structural and dynamic functions. In the vignette, stabilizing microtubules preserves tracks but slows directional changes in response to new attractants. Choice D is correct because it accurately describes how microtubule dynamics aid polarity reorientation. Choice B is incorrect because it wrongly claims stabilization abolishes transport. When evaluating cytoskeletal function, consider both structural support and dynamic changes essential for cellular processes. Differentiate between track stability and dynamic turnover in transport assays.
- Researchers compared two amoeboid cell lines: Line 1 shows rapid cycles of protrusion and retraction; Line 2 shows fewer protrusions but similar total actin content. Live imaging revealed that Line 2 has slower actin filament turnover at the leading edge (both assembly and disassembly rates are reduced). In a uniform environment (no gradient), Line 2 travels a shorter net distance over time. Based on the vignette, which conclusion about cytoskeletal dynamics is most consistent?
Answer: Reduced actin turnover decreases exploratory protrusions and limits effective translocation, even if total actin levels are unchanged.
This question assesses understanding of the cytoskeleton's role in cell motility. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, facilitates cell movement through structural and dynamic functions. In the vignette, two amoeboid cell lines differ in protrusion frequency and actin turnover, with slower turnover in Line 2 leading to shorter net distance traveled. Choice C is correct because it accurately describes how reduced actin turnover limits exploratory protrusions and effective translocation. Choice B is incorrect because it wrongly suggests reduced turnover increases contractile force and speed. When evaluating cytoskeletal function, consider both structural support and dynamic changes essential for cellular processes. Compare filament dynamics across cell types to understand motility efficiency in uniform environments.
- Migrating epithelial cells were imaged while a fluorescently labeled vesicle marker tracked delivery of membrane components to the leading edge. When microtubules were selectively destabilized, vesicles accumulated near the cell center and leading-edge expansion slowed, even though cortical actin still exhibited transient polymerization. Which conclusion about microtubules in cell migration is most consistent with the findings?
Answer: Microtubules support migration by facilitating intracellular transport to the leading edge, enabling sustained protrusion and membrane remodeling.
This question assesses understanding of the cytoskeleton's role in cell motility. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, facilitates cell movement through structural and dynamic functions. In the vignette, destabilizing microtubules causes vesicle accumulation centrally and slows leading-edge expansion despite actin polymerization. Choice D is correct because it accurately describes microtubules' role in transport for sustained protrusion. Choice B is incorrect because it wrongly claims microtubules provide primary protrusive force. When evaluating cytoskeletal function, consider both structural support and dynamic changes essential for cellular processes. Track vesicle delivery to understand microtubule contributions to migration.
- To test how leading-edge actin contributes to amoeboid motility, investigators briefly applied a localized actin polymerization inhibitor to only one side of a migrating cell (left edge) while leaving the opposite side untreated. Within minutes, the cell's protrusions became biased toward the untreated side and the cell's trajectory curved away from the inhibited region, despite no change in overall cell viability.
Which statement best describes the role of actin polymerization in this cell's motility?
Answer: Actin polymerization provides a spatially controllable protrusive force, so locally reducing polymerization shifts protrusion formation and redirects migration.
This question assesses understanding of how localized actin polymerization controls directional cell movement. The cytoskeleton generates spatially regulated protrusive forces through localized actin polymerization at the cell periphery. In the vignette, inhibiting polymerization on one side causes the cell to redirect movement toward the untreated side, demonstrating spatial control of protrusion formation. Choice D is correct because it accurately describes how actin polymerization provides controllable protrusive force that determines migration direction. Choice C is incorrect because it misattributes actin's role to rear retraction only, contradicting the observed effect on leading-edge protrusions. When analyzing directional cell motility, recognize that localized regulation of actin polymerization at the leading edge is a primary mechanism for steering cell movement.
- Cells migrating in a 3D matrix were observed to pause and then rapidly reorient when encountering obstacles. When microtubule dynamics were suppressed (microtubules remained present but less dynamic), cells could still move forward but reoriented more slowly after collisions. Which conclusion is most consistent with the role of microtubule dynamics in motility?
Answer: Microtubule dynamics contribute to rapid reorganization of cell polarity and trafficking during directional changes rather than being the sole driver of forward movement.
This question assesses understanding of the cytoskeleton's role in cell motility. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, facilitates cell movement through structural and dynamic functions. In the vignette, suppressing microtubule dynamics slows reorientation after obstacles in 3D migration. Choice D is correct because it accurately describes dynamics' contribution to polarity reorganization. Choice B is incorrect because it wrongly deems dynamics irrelevant. When evaluating cytoskeletal function, consider both structural support and dynamic changes essential for cellular processes. Test dynamic suppression in obstacle assays to reveal adaptive roles.
- A lab quantified migration persistence (straightness of path) in cells treated with either an actin filament stabilizer or a microtubule stabilizer. Actin stabilization reduced the rate of new protrusion formation and decreased persistence due to frequent pauses and reorientation. Microtubule stabilization preserved a single front but reduced the ability to rapidly change direction when the chemoattractant gradient was rotated.
What outcome would be expected if the cell must repeatedly reorient toward a changing gradient and microtubule dynamics are inhibited by stabilization?
Answer: Delayed turning because microtubule remodeling contributes to reorganizing polarity and intracellular positioning during reorientation.
This question assesses understanding of the cytoskeleton's role in cell motility. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, facilitates cell movement through structural and dynamic functions. In the vignette, cells reorienting to changing gradients require microtubule dynamics for rapid polarity reorganization. Choice B is correct because it explains delayed turning due to inhibited microtubule remodeling needed for reorientation. Choice A is incorrect because stable microtubules would hinder rather than enable rapid repolarization. When evaluating cytoskeletal function, consider both structural support and dynamic changes essential for cellular processes. Consider how stabilization affects adaptability in dynamic environments.
- In migrating neurons, mitochondria accumulate near the leading process where ATP demand is high. A lab disrupted microtubules and observed that mitochondria became dispersed and leading-edge advance slowed, even though actin polymerization events were still detectable at the cortex. Which outcome would be expected if microtubule-based transport is inhibited during migration?
Answer: Reduced delivery of organelles and cargo to the front would impair sustained migration, even if actin polymerization can still initiate protrusions.
This question assesses understanding of the cytoskeleton's role in cell motility. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, facilitates cell movement through structural and dynamic functions. In the vignette, disrupting microtubules disperses mitochondria and slows leading-edge advance despite actin events. Choice C is correct because it accurately describes how impaired transport reduces sustained migration. Choice B is incorrect because it wrongly suggests speed increases by freeing actin monomers. When evaluating cytoskeletal function, consider both structural support and dynamic changes essential for cellular processes. Monitor organelle positioning to assess transport's impact on motility.
- In an assay of amoeboid motility, cells were treated with a drug that caps actin filament barbed ends, reducing the rate of new filament elongation at the leading edge. Imaging showed diminished lamellipodial extension and reduced chemotactic accuracy, while overall ATP levels were unchanged. Which outcome would be expected if barbed-end elongation is inhibited during chemotaxis?
Answer: Cells show reduced protrusion and impaired directional movement because forward extension relies on rapid actin elongation at the leading edge.
This question assesses understanding of the cytoskeleton's role in cell motility. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, facilitates cell movement through structural and dynamic functions. In the vignette, capping actin barbed ends reduces elongation, leading to diminished lamellipodia and reduced chemotactic accuracy. Choice A is correct because it accurately describes how inhibited elongation impairs protrusion and directional movement. Choice B is incorrect because it wrongly suggests capping increases protrusion by recruiting monomers. When evaluating cytoskeletal function, consider both structural support and dynamic changes essential for cellular processes. Evaluate how end-specific inhibitors affect filament growth in chemotaxis assays.
- Researchers studied amoeboid movement in a neutrophil-like cell line in a microfluidic device containing a shallow gradient of chemoattractant. Cells normally extended a pseudopod toward the gradient and translocated the cell body forward. Acute addition of an actin depolymerization inhibitor caused cells to form an initial protrusion but then stall, with the leading edge remaining rigid and the cell failing to squeeze forward through narrow constrictions. In contrast, mild enhancement of actin filament disassembly increased the frequency of protrusion cycles but reduced net displacement due to frequent loss of polarity.
Flow summary:
Chemoattractant → pseudopod extension → cell body translocation
What outcome would be expected if actin filament turnover is strongly inhibited during amoeboid migration?
Answer: Reduced ability to move through constrictions because dynamic remodeling is needed for repeated protrusion and shape changes.
This question assesses understanding of the cytoskeleton's role in cell motility. The cytoskeleton, composed of actin filaments, microtubules, and intermediate filaments, facilitates cell movement through structural and dynamic functions. In the vignette, neutrophil-like cells in amoeboid migration require actin dynamics for pseudopod extension and translocation through constrictions. Choice B is correct because it explains how inhibiting turnover reduces dynamic remodeling needed for shape changes and movement in confined spaces. Choice A is incorrect because stable filaments would hinder flexibility rather than increase displacement. When evaluating cytoskeletal function, consider both structural support and dynamic changes essential for cellular processes. Focus on how environmental constraints like constrictions highlight the need for filament turnover.
- In a scratch-wound assay, researchers observed that cells at the wound edge formed broad lamellipodia and migrated directionally. When treated with a drug that preferentially disrupts microtubule-based transport (without fully depolymerizing microtubules), cells still produced lamellipodia but showed delayed accumulation of adhesion proteins near the front and reduced persistence of forward movement. Actin-rich protrusions repeatedly formed and retracted without consistent net advance. What outcome would be expected if microtubule-dependent transport is inhibited, consistent with the observations?
Answer: Cells exhibit less persistent migration because delivery of polarity and adhesion components to the leading edge is impaired, despite ongoing actin protrusion.
This question assesses understanding of microtubule-based transport in directed cell migration. Microtubules serve as tracks for delivering adhesion and polarity components to appropriate cellular locations. In the vignette, disrupting microtubule transport delayed adhesion protein accumulation at the front and reduced migration persistence despite continued lamellipodial formation. Choice A is correct because it accurately describes how cells exhibit less persistent migration when delivery of polarity and adhesion components is impaired, despite ongoing actin protrusion. Choice C is incorrect because lamellipodia formation is driven by actin polymerization, not microtubules. When analyzing migration persistence, consider that while actin drives protrusion, microtubule-based transport delivers the molecular machinery needed to stabilize and maintain directional movement.
- To probe how actin contributes to amoeboid movement, researchers measured membrane protrusion rate at the leading edge and overall cell translocation. They found that brief bursts of rapid protrusion preceded movement, but sustained protrusion without subsequent retraction did not correlate with long-range displacement. A perturbation that increased actin polymerization but also reduced actin disassembly produced larger protrusions yet decreased net migration distance over time.
Based on the vignette, which conclusion about actin dynamics is most consistent with the observed effect on motility?
Answer: Effective migration requires coordinated actin polymerization and depolymerization, so reducing disassembly can impair net displacement despite larger protrusions.
This question assesses understanding of how balanced actin polymerization and depolymerization enable effective cell migration. The cytoskeleton requires coordinated assembly and disassembly cycles for productive long-range movement, not just protrusion formation. In the vignette, increasing polymerization while reducing disassembly creates larger protrusions but decreases net migration, demonstrating that both processes are essential. Choice B is correct because it recognizes that effective migration requires coordination between polymerization and depolymerization, and disrupting this balance impairs movement despite larger protrusions. Choice A is incorrect because it assumes polymerization alone determines migration distance, ignoring the importance of turnover revealed by the experiment. When evaluating cytoskeletal contributions to cell motility, consider that productive movement requires not just protrusion formation but also timely retraction and recycling of components.
- Fibroblasts migrating on a 2D substrate were exposed to a localized chemoattractant gradient. Investigators observed that vesicles containing a membrane adhesion receptor accumulated near the front of the cell before an increase in directional persistence (straighter trajectories). When cells were treated with a microtubule-depolymerizing drug, vesicle accumulation at the front was reduced and cells formed protrusions but frequently changed direction. Total cellular actin levels were unchanged by the treatment. What outcome would be expected if microtubule function is inhibited, based on the vignette?
Answer: Directional persistence decreases because long-range vesicle delivery to the front is impaired, even if actin-based protrusions still occur.
This question assesses understanding of microtubule function in directed cell migration and vesicle transport. Microtubules serve as tracks for long-range intracellular transport, delivering vesicles and cargo to specific cellular locations. In the vignette, microtubule disruption prevented vesicle accumulation at the cell front and reduced directional persistence despite continued actin-based protrusions. Choice D is correct because it accurately describes how directional persistence decreases when long-range vesicle delivery via microtubules is impaired, even though actin-based protrusions continue. Choice C is incorrect because it wrongly attributes long-range transport to actin filaments rather than microtubules. When analyzing cell motility, remember that while actin drives protrusion, microtubules coordinate directional persistence through polarized transport of cellular components.
- In time-lapse imaging of amoeboid migration, researchers quantified two variables at the leading edge: (i) rate of actin filament assembly and (ii) lifetime of protrusions before retraction. They found that the fastest cells combined high assembly rates with short protrusion lifetimes, whereas slower cells had lower assembly rates and longer-lived protrusions. A perturbation that reduced assembly rate without directly affecting retraction increased protrusion lifetime but decreased net speed.
Based on the vignette, which conclusion about cytoskeletal dynamics is most consistent?
Answer: High net speed can require rapid protrusion turnover, not simply persistence, consistent with a dynamic actin network at the front.
This question assesses understanding of the relationship between actin assembly rates, protrusion dynamics, and migration speed. The cytoskeleton's effectiveness in driving motility depends on both the rate of filament assembly and the turnover of structures. In the vignette, fastest cells combine high assembly rates with short protrusion lifetimes, suggesting rapid cycling is advantageous, while reducing assembly rate decreases speed despite longer protrusions. Choice B is correct because it recognizes that high speed requires rapid turnover enabled by dynamic actin networks, not just persistent structures. Choice A is incorrect because it assumes longer-lived protrusions necessarily increase speed, contradicting the observation that fastest cells have short-lived protrusions. When analyzing cell migration efficiency, consider that optimal motility often requires balancing rapid assembly with timely disassembly to enable continuous forward progress.
