Actin mesh hinders microtubules

Like an iron curtain, a mesh of actin keeps microtubules in place in the fly oocyte, according to Katja Dahlgaard, Daniel St Johnston, and colleagues (University of Cambridge, UK). When the mesh comes down, microtubules are washed into a new orientation by free-flowing cytoplasm.

Microtubule orientation in the fly oocyte points transported mRNAs for polarity-inducing proteins in the right direction. The microtubule array starts off nucleated from the anterior end of the oocyte and extending toward the posterior. At late oogenesis, the array is redistributed to lay flat against the edge of the oocyte. At the same time, the cytoplasm of the oocyte begins to churn like a washing machine.

This rearrangement and churning occurs prematurely in mutants of the actin-associated proteins Cappuccino...