Moving pigment granules switch from actin to microtubules more often when they are congregating (top) than dispersing (bottom).
In the cell's transportation system, microtubules are highways for long-distance journeys, whereas actin fibers are local roads for short trips. Cargos can switch fibers, but researchers haven't been able to observe these transfers because so many filaments crisscross the cytoplasm.
To determine how often switching occurs, Slepchenko et al. combined measurements of organelle movement in fish melanophores, or pigment cells, with mathematical models. The researchers tracked pigment granules traveling toward either the cell center or the periphery on actin and microtubules, including in cells with only one filament type. The team used the...
