Myosin VI is required for asymmetric segregation of cellular components during C-elegans spermatogenesis

Background: The asymmetric division of cells and unequal allocation of cell contents is essential for correct development. This process of active segr egation is poorly understood but in many instances has been shown to depend on the cytoskeleton. Motor proteins moving along actin filaments and micro tubules are logical candidates to provide the motive force for asymmetric s orting of cell contents. The role of myosins in such processes has been sug gested, but few examples of their involvement are known. Results: Analysis of a Caenorhabditis elegans class VI myosin deletion muta nt reveals a role for this motor protein in the segregation of cell compone nts during spermatogenesis. Mutant spermatocytes cannot efficiently deliver mitochondria and endoplasmic reticulum/Golgi-derived fibrous-body membrano us organelle complexes to budding spermatids, and fail to remove actin fila ments and microtubules from the spermatids. The segregation defects are not due to a global sorting failure as nuclear inheritance is unaffected. Conclusions: C. elegans myosin VI has an important role in the unequal part itioning of both organelles and cytoskeletal components, a novel role for t his class of motor protein.