Practice question

Perinuclear positioning of Golgi ribbon relies on continuous dynein-dependent transport of Golgi stacks toward microtubule minus ends clustered at centrosome. Direct causality requires selective dynein perturbation while monitoring microtubules. Approach involves inducible expression of p150Glued CC1 fragment that competes for dynein binding to dynactin, siRNA against dynein heavy chain DYNC1H1, or pharmacologic ciliobrevin D that inhibits AAA+ ATPase without depolymerizing tubulin. Outcome assessed by immunofluorescence for cis marker GM130, medial Golgin-84, trans TGN46 shows rapid conversion of compact juxtanuclear ribbon to dispersed ministacks throughout cytoplasm, quantified by distance from nucleus and fragment number. Maintaining intact microtubules visualized by alpha-tubulin staining confirms defect due to motor loss not track loss. Depolymerizing microtubules with nocodazole also disperses Golgi but nonspecifically. Inhibiting kinesin would cause tighter perinuclear clustering opposite prediction, mutating actin tests different cytoskeleton. Thus dynein-specific inhibition leading to dispersion provides strongest mechanistic proof. Integration with cell cycle kinases, calcium signaling and mechanical cues ensures coordinated remodeling during growth, migration and differentiation.