Cytoskeleton Structure and Cell Motility (2A) Practice Test

Migrating neurons were imaged as they advanced a leading process on a laminin substrate. Investigators quantified delivery of adhesion receptors to the front of the cell. Under control conditions, receptor-containing vesicles moved along linear tracks toward the leading edge and accumulated in the front membrane. After treatment with a microtubule motor inhibitor, vesicle movement became largely diffusive, front membrane receptor density decreased, and cells exhibited repeated protrusion attempts without sustained forward translocation.

Which conclusion about cytoskeletal dynamics is most consistent with these findings?

To test the mechanical role of intermediate filaments during migration, researchers compared wild-type cells to cells lacking a major intermediate filament protein. Both cell types were placed in a 3D matrix with narrow pores. Wild-type cells elongated and maintained integrity while squeezing through pores. Intermediate-filament–deficient cells initiated entry into pores but frequently developed localized membrane blebs and transient ruptures, followed by abrupt retraction; their average displacement over time decreased despite normal-looking actin-rich protrusions.

Which statement best describes the role of intermediate filaments in cell motility in this context?