Fig. 1. Various types of cell polarity in which the PAR-aPKC system is involved. (A) Anterior-posterior polarization of the C. elegans zygote just after fertilization. (B) Anterior-posterior polarizations (early and late) of Drosophila oocytes during oogenesis. (C) Development of apical-basal polarity of Drosophila blastoderm epithelium formed just beneath the egg membrane. (D) Apical-basal polarity observed in mammalian cultured epithelial cells. (E) Polarization of mammalian primary-cultured astrocytes to the front during directed migration. (F) Polarization of a mammalian primary-cultured neuron that specifies one of the immature neurites as an axon. Red lines and dots represent the localization of the aPKC complex, whereas blue lines indicate the PAR-1 distribution. The distribution of PAR-1 in the Drosophila embryonic ectoderm and its derivative neuroblasts, as well as in mammalian astrocytes and neurons has not been clearly described. Gray ovals represent nuclei, green lines represent microtubules.