Xenbase Image ID: 138136

FIG. 3. Scheme illustrating cell-cycle dynamics in neural progenitors. The neuroepithelium is composed of a single layer of rapidly dividing NSCs and progenitors. As the cells adjacent to the lumen continue to proliferate, the neural progenitors migrate and form a second layer around the neural tube. This layer becomes progressively thicker and is called the mantle zone (MZ), whereas the germinal neuroepithelium is known as the ventricular zone (VZ), subsequently called the ependyma. Cells in the MZ differentiate into both neurons and glia. In the germinal neuroepithelium, neural progenitors undergo different phases of the cell cycle. The nucleus of proliferating cells undergoes a process of interkinetic nuclear migration that corresponds to each phase of the cycle. The nuclei move away from the apical surface during G1. DNA replication (S phase) takes place in the basal VZ. During G2, the nuclei migrate away from the apical ventricular zone where they undergo mitosis (M). After one cycle is completed, the cells choose either to re-enter the cell cycle or to exit and differentiate. Quiescent cells are found in the MZ. Progression through the cell cycle depends on the cyclin/CDK complexes. During G1, phosphorylation of the retinoblastoma complex (Rb) by cyclins D releases the transcription factor E2F and induces the expression of cyclins E. DNA synthesis during the S phase is followed by the verification of DNA integrity. The progression through mitosis depends on the cyclin B/CDK1 complex. The CDK inhibitors (CKI) p27/Kip1 and p21/Cip1 stop the progression through the cycle and favor exit from the cell cycle (G0). Image published in: Juraver-Geslin HA and Durand BC (2015) Copyright © 2015. Image reproduced with permission of the Publisher, John Wiley & Sons. Larger Image Printer Friendly View

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