Cell-cell signaling, microtubules, and the loss of symmetry in the drosophila oocyte

The Drosophila oocyte, although often thought of as an undifferentiated cell, is in fact highly polarized, and the subcellular organization of the oocyte is critical for subsequent development of the embryo. Recent results show that cell-cell signaling between the germline and the somatic components of the egg chamber establish the dorsal-ventral and anterior-posterior axes of the egg and consequently of the embryo (Gonzalez-Reyes et al., 1995; Roth et al., 1995). Most interestingly, the same signaling pathway, composed of an oocyte-bound ligand, encoded by the transforming growth factor a (TGFa) homolog gurken, and a somatically expressed receptor, encoded by the Drosophila epidermal growth factor receptor torpedo (DER/fop), is used to establish both the anterior-posterior and dorsal-ventral axes. Following signaling between the oocyte and the follicle cells, polarization of the cytoskeletal network in the oocyte establishes anterior-posterior polarity in the oocyte and leads to localization of the dorsalizing signal to the anterior and future dorsal corner of the oocyte. Building an Egg The Drosophila egg cell contains positional information required by the embryo to specify the anterior-posterior and dorsal-ventral body axes (reviewed by Morisato and Minireview