Cytoskeleton and motility · USMLE Step 1

During directed cell migration, which cytoskeletal filament system and associated dynamics are mainly responsible for establishing cell polarity (front–rear axis)?

  1. Intermediate filaments providing structural rigidity to the whole cell
  2. Leading-edge actin protrusions with rear microtubule reorientation
  3. Microtubule polymerization at the cell cortex only
  4. A static actin cortex that does not undergo remodeling
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Correct answer: Leading-edge actin protrusions with rear microtubule reorientation

Cell polarity during migration depends on actin-driven protrusive structures at the leading edge and coordinated microtubule reorientation that helps organize intracellular trafficking and rear retraction — both cytoskeletal networks are critical.

Difficulty: Medium Question 18 of 21

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