Neuroepithelial cells

Neuroepithelial cells are the "stem cells" of the nervous system, deriving from actual stem cells in several different stages of neural development. These neural stem cells then differentiate further into multiple types of cells, like neurons, astrocytes and other glial cells. They appear during embryonic development of the neural tube as well as in adult neurogenesis in specific areas of the central nervous system. They are also associated with several neurodegenerative diseases. These cells have often been called neuroblasts in an effort to delineate them as precursors to neurons and glial cells.

During the third week of embryonic growth the brain begins to develop in the early fetus in a process called induction. Neuroepithelial cells of the ectoderm begin multiplying rapidly and fold in forming the neural plate, which invaginates during the fourth week of embryonic growth and forms the neural tube. The formation of the neural tube polarizes the neuroepithelial cells by orienting the apical side of the cell to face inward, which later becomes the ventricular zone, and the basal side is oriented outward, which contacts the pial, or outer surface of the developing brain. As part of this polarity, neuroepithelial cells express prominin-1 in the apical plasma membrane as well as tight junctions to maintain the cell polarity.Integrin α6 anchors the neuroepithelial cells to the basal lamina. The neural tube begins as a single layer of pseudostratified epithelial cells, but rapid proliferation of neuroepithelial cells creates additional layers and eventually three distinct regions of growth. As these additional layers form the apical-basal polarity must be downregulated. Further proliferation of the cells in these regions gives rise to three distinct areas of the brain: the forebrain, midbrain, and hindbrain. The neural plate itself eventually gives rise to the spinal cord.

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