![]() This is the case for retinal ganglion cells and bipolar cells in the developing vertebrate retina ( Figure 1A-B) ( Hinds & Hinds 1978, Morgan et al 2006, Zolessi et al 2006). Careful examination of the morphological transition between neural progenitors and post-mitotic neurons reveal that neurons can inherit their axon and dendrite polarity directly from the apico-basal polarity of their progenitors. While migrating, post-mitotic neurons form a leading process and a trailing process which become the axon or the dendrite depending on the cell type ( Figure 1). In vivo, most neurons undergo axon-dendrite polarization during migration. Neuronal polarization can be divided in several specific steps: upon cell cycle exit, mammalian neurons usually migrate over a long distance before reaching their final destination. The current review will provide an updated model synthesizing a recent body of work suggesting that in vivo, neuronal polarity is most probably a result of a complex interaction between extracellular cues directing intrinsic cell polarity pathways. Based on existing data, Craig and Banker provided a conceptual framework for the experiments that, over the past decade, have improved our understanding on how neuronal polarity is established mostly using in vitro approaches. ![]() A seminal review published by Craig and Banker fifteen years ago in this journal ( Craig & Banker 1994) observed that “we almost nothing about the cellular mechanisms responsible for the compartmentation in neurons”. How are the axonal and dendritic compartments generated during development? This question has received a lot of attention both at the cellular and molecular levels over the past three decades. Dendrites integrate synaptic inputs triggering the generation of axon potentials at the level of the soma and propagates along the axon making presynaptic contacts onto the dendrite of target neurons. Neurons typically form a single axon and multiple dendrites which underlie the flow of information transfer in the central nervous system. Neurons are among the most polarized cell types in our body and are compartimentalized into two molecularly and functionally distinct domains: the axon and the dendrites. Its disruption is thought to underlie several pathological states including cell transformation and metastasis. Cell polarity lies at the center of many biological processes including epithelial morphogenesis, cell migration and chemotaxis.
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