I have evaluated the following article for F1000 Prime:
Myosin-va and dynamic actin oppose microtubules to drive long-range organelle transport.
RD Evans, C Robinson, DA Briggs, DJ Tooth, JS Ramalho, M Cantero, L Montoliu, S Patel, EV Sviderskaya and AN Hume
Curr Biol 2014 Aug 4; 24(15):1743-50 DOI: 10.1016/j.cub.2014.06.019
These comments were originally posted at: http://f1000.com/prime/718509369
This is a fascinating paper that reports the perhaps unexpected finding that the long-range centrifugal transport of melanosomes is driven by myosin rather than kinesin motors. Considerable previous work in this area has demonstrated clearly defined roles for cytoplasmic dynein and kinesin-2 in bidirectional motility of melanosomes along microtubules. Here, the authors use unbiased monitoring of organelle positions, made possible through the use of constrained patterning, combined with some clever use of myosin mutants. The authors make some interesting points in the discussion about the potential physiological relevance of this mechanism in driving the dispersal of pigment granules between cells. From a more fundamental, mechanistic perspective, I would be fascinated to see the outcome of similar experiments in which the kinesin-2 motor was also perturbed. Clearly, there is much more to be uncovered in melanosome biology, notably in terms of the relative contributions of the different motor/filament systems to the maturation and dispersal of pigment granules.