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Jungas T, Joseph M, Fawal MA, Davy A. Population Dynamics and Neuronal Polyploidy in the Developing Neocortex. Cereb Cortex Commun 2020; 1:tgaa063. [PMID: 34296126 PMCID: PMC8152829 DOI: 10.1093/texcom/tgaa063] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 09/01/2020] [Accepted: 09/01/2020] [Indexed: 11/27/2022] Open
Abstract
The mammalian neocortex is composed of different subtypes of projection neurons that are generated sequentially during embryogenesis by differentiation of neural progenitors. While molecular mechanisms that control neuronal production in the developing neocortex have been extensively studied, the dynamics and absolute numbers of the different progenitor and neuronal populations are still poorly characterized. Here, we describe a medium throughput approach based on flow cytometry and well-known identity markers of cortical subpopulations to collect quantitative data over the course of mouse neocortex development. We collected a complete dataset in a physiological developmental context on two progenitor and two neuron populations, including relative proportions and absolute numbers. Our study reveals unexpected total numbers of Tbr2+ progenitors. In addition, we show that polyploid neurons are present throughout neocortex development.
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Affiliation(s)
- Thomas Jungas
- Centre de Biologie Intégrative (CBI), Centre de Biologie du Développement (CBD), Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
| | - Mathieu Joseph
- Centre de Biologie Intégrative (CBI), Centre de Biologie du Développement (CBD), Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
- Montreal Clinical Research Institute (IRCM), Montreal, QC H2W 1R7, Canada
- Department of Molecular Biology, University of Montreal, Montreal, QC H3T 1J4, Canada
| | - Mohamad-Ali Fawal
- Centre de Biologie Intégrative (CBI), Centre de Biologie du Développement (CBD), Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
| | - Alice Davy
- Centre de Biologie Intégrative (CBI), Centre de Biologie du Développement (CBD), Université de Toulouse, CNRS, UPS, 31062 Toulouse, France
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López-Sánchez N, Fontán-Lozano Á, Pallé A, González-Álvarez V, Rábano A, Trejo JL, Frade JM. Neuronal tetraploidization in the cerebral cortex correlates with reduced cognition in mice and precedes and recapitulates Alzheimer's-associated neuropathology. Neurobiol Aging 2017; 56:50-66. [DOI: 10.1016/j.neurobiolaging.2017.04.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2016] [Revised: 03/28/2017] [Accepted: 04/09/2017] [Indexed: 01/14/2023]
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Jungas T, Perchey RT, Fawal M, Callot C, Froment C, Burlet-Schiltz O, Besson A, Davy A. Eph-mediated tyrosine phosphorylation of citron kinase controls abscission. J Cell Biol 2016; 214:555-69. [PMID: 27551053 PMCID: PMC5004443 DOI: 10.1083/jcb.201602057] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 07/25/2016] [Indexed: 12/30/2022] Open
Abstract
Abscission is the last step of cytokinesis, allowing the physical separation of daughter cells at the end of cell division. It has been considered a cell autonomous process, yet Jungas et al. report that Ephrin/Eph signaling controls the completion of abscission. Cytokinesis is the last step of cell division, culminating in the physical separation of daughter cells at the end of mitosis. Cytokinesis is a tightly regulated process that until recently was mostly viewed as a cell-autonomous event. Here, we investigated the role of Ephrin/Eph signaling, a well-known local cell-to-cell communication pathway, in cell division. We show that activation of Eph signaling in vitro leads to multinucleation and polyploidy, and we demonstrate that this is caused by alteration of the ultimate step of cytokinesis, abscission. Control of abscission requires Eph kinase activity, and Src and citron kinase (CitK) are downstream effectors in the Eph-induced signal transduction cascade. CitK is phosphorylated on tyrosines in neural progenitors in vivo, and Src kinase directly phosphorylates CitK. We have identified the specific tyrosine residues of CitK that are phosphorylated and show that tyrosine phosphorylation of CitK impairs cytokinesis. Finally, we show that, similar to CitK, Ephrin/Eph signaling controls neuronal ploidy in the developing neocortex. Our study indicates that CitK integrates intracellular and extracellular signals provided by the local environment to coordinate completion of cytokinesis.
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Affiliation(s)
- Thomas Jungas
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, Centre National de la Recherche Scientifique, Université Paul Sabatier, 31062 Toulouse, France
| | - Renaud T Perchey
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1037, Cancer Research Center of Toulouse, 31037 Toulouse, France Centre National de la Recherche Scientifique, ERL 5294, Université de Toulouse, Université Paul Sabatier, 31037 Toulouse, France
| | - Mohamad Fawal
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, Centre National de la Recherche Scientifique, Université Paul Sabatier, 31062 Toulouse, France
| | - Caroline Callot
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1037, Cancer Research Center of Toulouse, 31037 Toulouse, France Centre National de la Recherche Scientifique, ERL 5294, Université de Toulouse, Université Paul Sabatier, 31037 Toulouse, France
| | - Carine Froment
- Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale, 31077 Toulouse, France
| | - Odile Burlet-Schiltz
- Centre National de la Recherche Scientifique, Institut de Pharmacologie et de Biologie Structurale, 31077 Toulouse, France
| | - Arnaud Besson
- Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1037, Cancer Research Center of Toulouse, 31037 Toulouse, France Centre National de la Recherche Scientifique, ERL 5294, Université de Toulouse, Université Paul Sabatier, 31037 Toulouse, France
| | - Alice Davy
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, Centre National de la Recherche Scientifique, Université Paul Sabatier, 31062 Toulouse, France
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Abstract
Neurons are usually regarded as postmitotic cells that undergo apoptosis in response to cell cycle reactivation. Nevertheless, recent evidence indicates the existence of a defined developmental program that induces DNA replication in specific populations of neurons, which remain in a tetraploid state for the rest of their adult life. Similarly, de novo neuronal tetraploidization has also been described in the adult brain as an early hallmark of neurodegeneration. The aim of this review is to integrate these recent developments in the context of cell cycle regulation and apoptotic cell death in neurons. We conclude that a variety of mechanisms exists in neuronal cells for G1/S and G2/M checkpoint regulation. These mechanisms, which are connected with the apoptotic machinery, can be modulated by environmental signals and the neuronal phenotype itself, thus resulting in a variety of outcomes ranging from cell death at the G1/S checkpoint to full proliferation of differentiated neurons.
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Key Words
- AD, Alzheimer disease
- BDNF, brain-derived neurotrophic factor
- BrdU, 5-bromo-2′-deoxyuridine
- CKI, Cdk-inhibitor
- CNS, central nervous system
- Cdk, cyclin-dependent kinase
- Cip/Kip, cyclin inhibitor protein/kinase inhibitor protein
- G0, quiescent state
- G1, growth phase 1
- G2, growth phase 2
- Ink, inhibitor of kinase
- Mcm2, minichromosome maintenance 2
- PCNA, proliferating cell nuclear antigen
- PD, Parkinson disease
- RGCs, retinal ganglion cells
- Rb, Retinoblastoma
- S-phase
- S-phase, synthesis phase.
- apoptosis
- cell cycle re-entry
- mitosis
- neuron
- p38MAPK, p38 mitogen-activated protein kinase
- p75NTR, neurotrophin receptor p75
- tetraploid
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Affiliation(s)
- José M Frade
- a Department of Molecular, Cellular and Developmental Neurobiology; Instituto Cajal; Consejo Superior de Investigaciones Científicas (IC-CSIC) ; Madrid , Spain
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Slaninová I, López-Sánchez N, Šebrlová K, Vymazal O, Frade JM, Táborská E. Introduction of macarpine as a novel cell-permeant DNA dye for live cell imaging and flow cytometry sorting. Biol Cell 2015; 108:1-18. [DOI: 10.1111/boc.201500047] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 10/15/2015] [Indexed: 01/10/2023]
Affiliation(s)
- Iva Slaninová
- Department of Biology; Faculty of Medicine; Masaryk University; Brno 62500 Czech Republic
| | | | - Kristýna Šebrlová
- Department of Biochemistry; Faculty of Medicine; Masaryk University; Brno 62500 Czech Republic
| | - Ondřej Vymazal
- Department of Biology; Faculty of Medicine; Masaryk University; Brno 62500 Czech Republic
| | - José María Frade
- Cajal Institute; IC-CSIC; Avda. Doctor Arce 37 Madrid E-28002 Spain
| | - Eva Táborská
- Department of Biochemistry; Faculty of Medicine; Masaryk University; Brno 62500 Czech Republic
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Ovejero-Benito MC, Frade JM. p27(Kip1) participates in the regulation of endoreplication in differentiating chick retinal ganglion cells. Cell Cycle 2015; 14:2311-22. [PMID: 25946375 PMCID: PMC4614947 DOI: 10.1080/15384101.2015.1044175] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Nuclear DNA duplication in the absence of cell division (i.e. endoreplication) leads to somatic polyploidy in eukaryotic cells. In contrast to some invertebrate neurons, whose nuclei may contain up to 200,000-fold the normal haploid DNA amount (C), polyploid neurons in higher vertebrates show only 4C DNA content. To explore the mechanism that prevents extra rounds of DNA synthesis in these latter cells we focused on the chick retina, where a population of tetraploid retinal ganglion cells (RGCs) has been described. We show that differentiating chick RGCs that express the neurotrophic receptors p75 and TrkB while lacking retinoblastoma protein, a feature of tetraploid RGCs, also express p27Kip1. Two different short hairpin RNAs (shRNA) that significantly downregulate p27Kip1 expression facilitated DNA synthesis and increased ploidy in isolated chick RGCs. Moreover, this forced DNA synthesis could not be prevented by Cdk4/6 inhibition, thus suggesting that it is triggered by a mechanism similar to endoreplication. In contrast, p27Kip1 deficiency in mouse RGCs does not lead to increased ploidy despite previous observations have shown ectopic DNA synthesis in RGCs from p27Kip1−/− mice. This suggests that a differential mechanism is used for the regulation of neuronal endoreplication in mammalian versus avian RGCs.
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Affiliation(s)
- María C Ovejero-Benito
- a Department of Molecular , Cellular, and Developmental Neurobiology; Cajal Institute; IC-CSIC ; Madrid , Spain
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Ovejero-Benito MC, Frade JM. Brain-derived neurotrophic factor-dependent cdk1 inhibition prevents G2/M progression in differentiating tetraploid neurons. PLoS One 2013; 8:e64890. [PMID: 23741412 PMCID: PMC3669015 DOI: 10.1371/journal.pone.0064890] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Accepted: 04/19/2013] [Indexed: 11/28/2022] Open
Abstract
Neurodegeneration is often associated with DNA synthesis in neurons, the latter usually remaining for a long time as tetraploid cells before dying by apoptosis. The molecular mechanism preventing G2/M transition in these neurons remains unknown, but it may be reminiscent of the mechanism that maintains tetraploid retinal ganglion cells (RGCs) in a G2-like state during normal development, thus preventing their death. Here we show that this latter process, known to depend on brain-derived neurotrophic factor (BDNF), requires the inhibition of cdk1 by TrkB. We demonstrate that a subpopulation of chick RGCs previously shown to become tetraploid co-expresses TrkB and cdk1 in vivo. By using an in vitro system that recapitulates differentiation and cell cycle re-entry of chick retinal neurons we show that BDNF, employed at concentrations specific for the TrkB receptor, reduces the expression of cdk1 in TrkB-positive, differentiating neurons. In this system, BDNF also inhibits the activity of both endogenous cdk1 and exogenously-expressed cdk1/cyclin B1 complex. This inhibition correlates with the phosphorylation of cdk1 at Tyr15, an effect that can be prevented with K252a, a tyrosine kinase inhibitor commonly used to prevent the activity of neurotrophins through their Trk receptors. The effect of BDNF on cdk1 activity is Tyr15-specific since BDNF cannot prevent the activity of a constitutively active form of cdk1 (Tyr15Phe) when expressed in differentiating retinal neurons. We also show that BDNF-dependent phosphorylation of cdk1 at Tyr15 could not be blocked with MK-1775, a Wee1-selective inhibitor, indicating that Tyr15 phosphorylation in cdk1 does not seem to occur through the canonical mechanism observed in proliferating cells. We conclude that the inhibition of both expression and activity of cdk1 through a BDNF-dependent mechanism contributes to the maintenance of tetraploid RGCs in a G2-like state.
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Affiliation(s)
- María C. Ovejero-Benito
- Department of Molecular, Cellular, and Developmental Neurobiology, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | - José M. Frade
- Department of Molecular, Cellular, and Developmental Neurobiology, Instituto Cajal, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- * E-mail:
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López-Sánchez N, Frade JM. Genetic evidence for p75NTR-dependent tetraploidy in cortical projection neurons from adult mice. J Neurosci 2013; 33:7488-500. [PMID: 23616554 PMCID: PMC6619587 DOI: 10.1523/jneurosci.3849-12.2013] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Revised: 02/26/2013] [Accepted: 03/21/2013] [Indexed: 11/21/2022] Open
Abstract
A subpopulation of chick retinal projection neurons becomes tetraploid during development, an event prevented by blocking antibodies against p75 neurotrophin receptor (p75(NTR)). We have used an optimized flow cytometric assay, based on the analysis of unfixed brain cell nuclei, to study whether p75(NTR)-dependent neuronal tetraploidization takes place in the cerebral cortex, giving rise to projection neurons as well. We show that 3% of neurons in both murine neocortex and chick telencephalic derivatives are tetraploid, and that in the mouse ~85% of these neurons express the immediate early genes Erg-1 and c-Fos, indicating that they are functionally active. Tetraploid cortical neurons (65-80%) express CTIP2, a transcription factor specific for subcortical projection neurons in the mouse neocortex. During the period in which these neurons are born, p75(NTR) is detected in differentiating neurons undergoing DNA replication. Accordingly, p75(NTR)-deficient mice contain a reduced proportion of both NeuN and CTIP2-positive neocortical tetraploid neurons, thus providing genetic evidence for the participation of p75(NTR) in the induction of neuronal tetraploidy in the mouse neocortex. In the striatum tetraploidy is mainly associated with long-range projection neurons as well since ~80% of tetraploid neurons in this structure express calbindin, a marker of neostriatal-matrix spiny neurons, known to establish long-range projections to the substantia nigra and globus pallidus. In contrast, only 20% of tetraploid cortical neurons express calbindin, which is mainly expressed in layers II-III, where CTIP2 is absent. We conclude that tetraploidy mainly affects long-range projection neurons, being facilitated by p75(NTR) in the neocortex.
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Affiliation(s)
- Noelia López-Sánchez
- Department of Molecular, Cellular, and Developmental Neurobiology, Cajal Institute, Consejo Superior de Investigaciones Científicas, E-28002 Madrid, Spain
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Mitosis in neurons: Roughex and APC/C maintain cell cycle exit to prevent cytokinetic and axonal defects in Drosophila photoreceptor neurons. PLoS Genet 2012; 8:e1003049. [PMID: 23209426 PMCID: PMC3510051 DOI: 10.1371/journal.pgen.1003049] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 09/11/2012] [Indexed: 02/02/2023] Open
Abstract
The mechanisms of cell cycle exit by neurons remain poorly understood. Through genetic and developmental analysis of Drosophila eye development, we found that the cyclin-dependent kinase-inhibitor Roughex maintains G1 cell cycle exit during differentiation of the R8 class of photoreceptor neurons. The roughex mutant neurons re-enter the mitotic cell cycle and progress without executing cytokinesis, unlike non-neuronal cells in the roughex mutant that perform complete cell divisions. After mitosis, the binucleated R8 neurons usually transport one daughter nucleus away from the cell body into the developing axon towards the brain in a kinesin-dependent manner resembling anterograde axonal trafficking. Similar cell cycle and photoreceptor neuron defects occurred in mutants for components of the Anaphase Promoting Complex/Cyclosome. These findings indicate a neuron-specific defect in cytokinesis and demonstrate a critical role for mitotic cyclin downregulation both to maintain cell cycle exit during neuronal differentiation and to prevent axonal defects following failed cytokinesis. Neurons generally differentiate and never divide again. One barrier to understanding the mechanisms has been the paucity of genetic mutations that result in neuronal cell cycles. Here we show that mutation in three genes lead to cell cycle re-entry by a particular class of developing photoreceptor neurons in the fly retina. Strikingly, these neurons do not complete cell division but only divide their nuclei. The binucleated neurons then typically retain one nucleus in its normal location in the cell body, while transporting the other into the growing axon like other axonal material. Our findings identify Cyclin A regulation as crucial to maintaining cell cycle exit by at least some neurons and identify a neuron-specific defect in cell division as a further barrier to neuron proliferation. Because defects in transporting axonal material have been implicated in the origin of multiple neurodegenerative diseases, our findings also suggest a possible connection between defective cell cycle regulation and neuronal cell death.
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Nerve growth factor-induced cell cycle reentry in newborn neurons is triggered by p38MAPK-dependent E2F4 phosphorylation. Mol Cell Biol 2012; 32:2722-37. [PMID: 22586272 DOI: 10.1128/mcb.00239-12] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Cumulative evidence indicates that activation of cyclin D-dependent kinase 4/6 (cdk4/6) represents a major trigger of cell cycle reentry and apoptosis in vertebrate neurons. We show here the existence of another mechanism triggering cell cycle reentry in differentiating chick retinal neurons (DCRNs), based on phosphorylation of E2F4 by p38(MAPK). We demonstrate that the activation of p75(NTR) by nerve growth factor (NGF) induces nuclear p38(MAPK) kinase activity, which leads to Thr phosphorylation and subsequent recruitment of E2F4 to the E2F-responsive cdc2 promoter. Inhibition of p38(MAPK), but not of cdk4/6, specifically prevents NGF-dependent cell cycle reentry and apoptosis in DCRNs. Moreover, a constitutively active form of chick E2F4 (Thr261Glu/Thr263Glu) stimulates G(1)/S transition and apoptosis, even after inhibition of p38(MAPK) activity. In contrast, a dominant-negative E2F4 form (Thr261Ala/Thr263Ala) prevents NGF-induced cell cycle reactivation and cell death in DCRNs. These results indicate that NGF-induced cell cycle reentry in neurons depends on the activation of a novel, cdk4/6-independent pathway that may participate in neurodegeneration.
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