RNA localization and the development of asymmetry during Drosophila oogenesis.

Recent work on axis formation in Drosophila has revealed that polarity arises in several distinct stages during oogenesis. One cell of a germline cyst is selected to become the oocyte, the position of the oocyte determines the posterior of the follicle, and the position of the oocyte nucleus determines the dorsal side. Each of these symmetry-breaking steps involves the asymmetric localization of a unique structure, leading to polarization of the cytoskeleton and the localization of specific mRNAs.