Fig. 3.

Schematic representation of stages of neuronal polarization. At stage 1, neurites are not discernable and the neuron primarily has an actin-based cytoskeleton. At stage 2, microtubule-based neurites extend from the cell body of the neuron. The neurites are equipotent in terms of their capacity for axon specification. At stage 3, a single process has been specified as an axon. The axon continues to grow, while growth stalls at the other neurites (minor processes). At this stage, PAR3–PKMζ appear to segregate from PAR3–aPKCι. While PAR3–PKMζ is present in minor processes, PAR3–aPKCι localizes to the axon. At stage 4, minor processes start to grow and arborize into dendrites. Eventually, the neuron acquires its complex, fully mature phenotype (not shown)