Fig. 7. Model for the roles of the endocytic pathway in pole plasm assembly. The polarization of the oocyte by the Grk signal promotes the rearrangement of the MT array and initial accumulation of endosomal proteins to the oocyte posterior (arrow 1). The endocytic activity maintains MT polarity (arrow 2), which is required for osk RNA localization to the oocyte posterior. Long Osk, translated from the localized osk message, recruits endosomal proteins and upregulates endocytic activity at the oocyte posterior (arrow 3). The stimulated endocytic pathway in turn regulates the F-actin reorganization that is essential to anchor the pole plasm components to the oocyte cortex (arrow 4). The close association of endosomal proteins with osk RNP in developing oocytes (see Fig. 3) suggests that the endocytic pathway might also play a role in the targeting of osk RNP to the oocyte posterior (the arrow with a broken line).