Expeditions to the pole: RNA localization in Xenopus and Drosophila

In Xenopus and Drosophila oocytes, a number of maternally synthesized RNAs encoding molecules that act in formation and patterning of embryonic tissues are localized to the vegetal and posterior poles, respectively. In Drosophila, and probably in Xenopus, localization of their RNAs within the oocyte generates the regionalized distributions of these molecules in the early embryo that are required for proper development. Studies described here have begun to reveal components of the cellular machinery that effects RNA localization. While specific aspects of localization differ among RNAs, similarities between pathways used by Xenopus and Drosophila suggest that common themes have been conserved among localization mechanisms.