During dorsal closure (DC) in Drosophila embryos, actin-rich filopodia extended by the leading edge cells of two epithelial sheets make transient cell-cell contacts that allow the sheets to `zipper' together and form permanent cell-adhesion structures. Now, Susan Parkhurst and co-workers reveal that the Drosophila myosin XV homolog Sisyphus facilitates these processes (see p. 53). Sisyphus - an actin-based motor protein - contains a microtubule-binding MyTH4 domain and a cargo-binding FERM domain. The researchers show that Sisyphus is expressed at high levels in the leading edge cells and in their filopodia during the zippering phase of DC. RNAi knockdown of Sisyphus, they report, disrupts the correct alignment of cells on opposing sides of the fusing epithelial sheets and the adhesion of cells in the final zippering phase. They also identify several putative Sisyphus cargos,including DE-cadherin (which is involved in filopodia-mediated adhesion) and several microtubule-linked proteins. Overall, the researchers propose that Sisyphus regulates filopodia dynamics during DC by coordinating actin and microtubule cytoskeleton components.
Motor protein zips up dorsal closure
Motor protein zips up dorsal closure. Development 1 January 2008; 135 (1): e102. doi:
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