p57KIP2 regulates radial glia and intermediate precursor cell cycle dynamics and lower layer neurogenesis in developing cerebral cortex

Abstract

SUMMARYDuring cerebral cortex development, precise control of precursor cell cycle length and cell cycle exit is required for balanced precursor pool expansion and layer-specific neurogenesis. Here, we defined the roles of cyclin-dependent kinase inhibitor (CKI) p57 KIP2 , an important regulator of G1 phase, using deletion mutant mice. Mutant mice displayed macroencephaly associated with cortical hyperplasia during late embryogenesis and postnatal development. Embryonically, proliferation of radial glial cells (RGC) and intermediate precursors (IPC) was increased, expanding both populations, with greater effect on IPCs. Furthermore, cell cycle re-entry was increased during early corticogenesis, whereas cell cycle exit was augmented at middle stage. Consequently, neurogenesis was reduced early, whereas it was enhanced during later development. In agreement, the timetable of early neurogenesis, indicated by birthdating analysis, was delayed. Cell cycle dynamics analyses in mutants indicated that p57 KIP2 regulates cell cycle length in both RGCs and IPCs. By contrast, related CKI p27 KIP1 controlled IPC proliferation exclusively. Furthermore, p57KIP2 deficiency markedly increased RGC and IPC divisions at E14.5, whereas p27 KIP1 increased IPC proliferation at E16.5. Consequently, loss of p57 KIP2 increased primarily layer 5-6 neuron production, whereas loss of p27 KIP1 increased neurons specifically in layers 2-5. In conclusion, our observations suggest that p57 KIP2 and p27 KIP1 control neuronal output for distinct cortical layers by regulating different stages of precursor proliferation, and support a model in which IPCs contribute to both lower and upper layer neuron generation.

Hbp1 regulates the timing of neuronal differentiation during cortical development by controlling cell cycle progression

“…2B), indicating that overexpression of Hbp1 caused an attenuation of cell proliferation or premature cell cycle exit. We then carried out a calculation of cell cycle kinetics by BrdU/EdU double-labeling protocol [modified from a previously described IdU/BrdU double-labeling method (Martynoga et al, 2005;Mairet-Coello et al, 2012)] and estimated the cell cycle length. Cells transfected with pEF-Hbp1 showed a slightly longer cell cycle length compared with control ( Fig.…”

“…To estimate the cell cycle length, we conducted a dual-pulse-labeling of DNA synthesis using 5-bromo-2′-deoxyuridine (BrdU; Sigma-Aldrich) and 5-ethynyl-2′-deoxyuridine (EdU; Molecular Probes), referring to the previous methods (Martynoga et al, 2005;Mairet-Coello et al, 2012). Previous reports used EdU first, followed by BrdU, but here we administered BrdU first, followed by EdU.…”

Mcl1 regulates the terminal mitosis of neural precursor cells in the mammalian brain through p27Kip1

“…Kip2 or p27 Kip1 increases NPC proliferation, expanding the pool of NPCs and resulting in a larger brain (Caviness et al, 2003;Goto et al, 2004;Mairet-Coello et al, 2012;Nguyen et al, 2006a;Tury et al, 2011). By contrast, overexpression of either CKI induces premature NPC terminal mitosis and differentiation, reducing the size of the NPC pool and consequently the size of the brain Tarui et al, 2005;Tury et al, 2011;Tury et al, 2012).…”

“…Kip1 is more highly expressed in IPCs and regulates the terminal mitosis and differentiation of neurons primarily destined for cortical layers II-V (Goto et al, 2004;Mairet-Coello et al, 2012;Mitsuhashi et al, 2001;Tarui et al, 2005). Since gain-of-function of either p57…”

How to keep proliferative neural stem/progenitor cells

“…15,16 It is well known that neuronal progenitor cell fate can be affected by cell cycle regulators including cyclins, [17][18][19] Cdks 20 and their inhibitors. [21][22][23][24] In the developing central nervous system (CNS), mRNA of cyclin D2 shows a unique localization, to the surface of the neural tube, not seen for other cyclins. 25,26 Because of this unique localization pattern, cyclin D2 was initially thought to be expressed in postmitotic neurons 25,26 but recent work identified that the mRNA and protein localized at the tip of the AP (i.e., endfoot).…”