Vertebrate Neurogenesis: Cell Polarity

Abstract

Abstract During development, neurons are formed from epithelial cells that, after proliferation and cell fate decisions, must undergo a series of transitions in polarity to achieve the differentiated state. The fate of neural progenitors greatly depends on the interplay between cell cycle and neuroepithelial polarity. In this respect, two main processes appear to influence neurogenesis: (a) the asymmetrical inheritance of apical or basal compartments during the last cell division and (b) the interkinetic nuclear migration through gradients of signalling molecules. After a neuron is born, the differentiation process starts with a downregulation of epithelial polarity, followed by cell detachment and migration and the final acquisition of a neuronal morphology. All these transitions are based on extremely conserved molecular mechanisms, including polarity protein complexes and small GTPases. However, some important variations have been observed in different neuronal types and experimental conditions, which might represent a tip for the neuronal type differentiation iceberg. Key concepts: Origin of neurons in the central nervous system of the vertebrates. Cellular organization of the primordium of the central nervous system. Importance of cell divisions in the development of the central nervous system. Relationship between cell polarity and the generation of neurons. Symmetrical and asymmetrical cell divisions and their role in cell fate determination in the central nervous system. Cell polarity and maintenance of neural progenitors. Cell polarity and neuronal migration. Cell polarity and neuronal differentiation. Morphological transitions that lead to neuronal differentiation. Distinction between cell polarity and orientation in neuronal differentiation.