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Omais S, El Atie YE, Ghanem N. Rb deficiency, neuronal survival and neurodegeneration: In search of the perfect mouse model. CURRENT RESEARCH IN NEUROBIOLOGY 2023; 4:100074. [PMID: 36699152 PMCID: PMC9869410 DOI: 10.1016/j.crneur.2023.100074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 10/26/2022] [Accepted: 01/06/2023] [Indexed: 01/14/2023] Open
Abstract
Three decades following the introduction of the first Rb knockout (KO) mouse model, the role of this critical protein in regulating brain development during embryogenesis and beyond remains a major scientific interest. Rb is a tumor suppressor gene known as the master regulator of the G1/S checkpoint and control of cell cycle progression in stem and progenitor cells, but also their differentiated progeny. Here, we review the recent literature about the various Rb conditional Knockout (cKO) and inducible Knockout (iKO) models studied thus far, highlighting how findings should always be interpreted in light of the model and context under inquiry especially when studying the role of Rb in neuronal survival. There is indeed evidence of age-specific, cell type-specific and region-specific effects following Rb KO in the embryonic and the adult mouse brain. In terms of modeling neurodegenerative processes in human diseases, we discuss cell cycle re-entry (CCE) as a candidate mechanism underlying the increased vulnerability of Rb-deficient neurons to cell death. Notably, mouse models may limit the extent to which CCE due to Rb inactivation can mimic the pathological course of these disorders, such as Alzheimer's disease. These remarks ought to be considered in future research when studying the consequences of Rb inactivation on neuronal generation and survival in rodents and their corresponding clinical significance in humans.
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Affiliation(s)
| | | | - Noël Ghanem
- Corresponding author. Department of Biology, American University of Beirut, PO Box 11-0236, Riad El Solh, 1107 2020, Beirut, Lebanon.
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2
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Abstract
The methyltransferase-like (METTL) family is a diverse group of methyltransferases that can methylate nucleotides, proteins, and small molecules. Despite this diverse array of substrates, they all share a characteristic seven-beta-strand catalytic domain, and recent evidence suggests many also share an important role in stem cell biology. The most well characterized family members METTL3 and METTL14 dimerize to form an N6-methyladenosine (m6A) RNA methyltransferase with established roles in cancer progression. However, new mouse models indicate that METTL3/METTL14 are also important for embryonic stem cell (ESC) development and postnatal hematopoietic and neural stem cell self-renewal and differentiation. METTL1, METTL5, METTL6, METTL8, and METTL17 also have recently identified roles in ESC pluripotency and differentiation, while METTL11A/11B, METTL4, METTL7A, and METTL22 have been shown to play roles in neural, mesenchymal, bone, and hematopoietic stem cell development, respectively. Additionally, a variety of other METTL family members are translational regulators, a role that could place them as important players in the transition from stem cell quiescence to differentiation. Here we will summarize what is known about the role of METTL proteins in stem cell differentiation and highlight the connection between their growing importance in development and their established roles in oncogenesis.
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Affiliation(s)
- John G Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 955 Main St., Buffalo, NY, 14203, USA
| | - James P Catlin
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 955 Main St., Buffalo, NY, 14203, USA
| | - Christine E Schaner Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, 955 Main St., Buffalo, NY, 14203, USA.
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3
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Singh G, Bloskie T, Storey KB. Tissue-specific response of the RB-E2F1 complex during mammalian hibernation. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2022; 337:1002-1009. [PMID: 35945704 DOI: 10.1002/jez.2648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 07/14/2022] [Accepted: 07/25/2022] [Indexed: 06/15/2023]
Abstract
Metabolic rate depression during prolonged bouts of torpor is characteristic of mammalian hibernation, reducing energy expenditures over the winter. Cell cycle arrest is observed in quiescent cells during dormancy, partly due to the retinoblastoma (Rb) protein at G1 /S, given cell division and proliferation are metabolic-costly processes. Rb binds to E2F transcription factors and recruits corepressors (e.g., SUV39H1) to E2F target genes, blocking their transcription and cell cycle passage. Phosphorylation by cyclin-CDK complexes at S780 or S795 abolishes Rb-mediated repression, allowing transition into S phase. The present study compares Rb-E2F1 responses between euthermic and torpid states in five organs (brain, heart, kidney, liver, skeletal muscle) of 13-lined ground squirrels (Ictidomys tridecemlineatus). Immunoblotting assessed the expression of Rb, pRb (S780, S795), E2F1, and SUV39H1. Our findings demonstrate multi-tissue upregulation of Rb and SUV39H1 during torpor, with tissue-specific changes to E2F1 and pRb (S780), suggesting Rb-E2F1 contributes to cell cycle control in hibernation.
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Affiliation(s)
- Gurjit Singh
- Department of Biology, Carleton University, Ottawa, Ontario, Canada
| | - Tighe Bloskie
- Department of Biology, Carleton University, Ottawa, Ontario, Canada
| | - Kenneth B Storey
- Department of Biology, Carleton University, Ottawa, Ontario, Canada
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4
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Evidence of cell cycle re-entry in post-mitotic, terminally differentiated feline neurons. Histochem Cell Biol 2022; 158:193-198. [PMID: 35551458 PMCID: PMC9338102 DOI: 10.1007/s00418-022-02112-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/25/2022] [Indexed: 02/08/2023]
Abstract
Parvovirus infections in dogs and cats are restricted to highly mitotically active tissues, predominantly to the epithelium of the gastrointestinal tract and, in cases of prenatal infections in cats, also to Purkinje cell neuroblasts. The evidence of parvovirus-infected mature feline neurons gave rise to reconsider the dogma of post-mitotically fixed and terminally differentiated neurons in the adult central nervous system. To elucidate the postulated capability of certain terminally differentiated feline neurons to re-enter the cell cycle, immunohistochemical double labeling using the transcription factor Sox2 and the tumor suppressor and cell cycle regulator retinoblastoma protein in its phosphorylated state (pRb) was performed. Formalin-fixed and paraffin-embedded brain tissue negative for parvovirus-antigen from 14 cats was compared to brain tissue from 13 cats with immunohistochemically confirmed cerebral parvovirus infection; the 27 cats were aged between 50 days of gestation (E50) and 5 years. Both groups revealed nuclear Sox2 and pRb immunosignals in numerous neurons, suggesting a more active state than mature neurons should have. Accordingly, parvovirus is not exclusively involved in the reactivation of the cell cycle machinery in those post-mitotic, terminally differentiated feline neurons.
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Omais S, Hilal RN, Halaby NN, Jaafar C, Ghanem N. Aging entails distinct requirements for Rb at maintaining adult neurogenesis. AGING BRAIN 2022; 2:100041. [PMID: 36908894 PMCID: PMC9997174 DOI: 10.1016/j.nbas.2022.100041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 04/13/2022] [Accepted: 04/28/2022] [Indexed: 10/18/2022] Open
Abstract
Cell cycle proteins play essential roles in regulating embryonic and adult neurogenesis in the mammalian brain. A key example is the Retinoblastoma protein (Rb) whose loss disrupts the whole neurogenic program during brain development, but only results in increased progenitor proliferation in the adult subventricular zone (SVZ) and compromised long-term neuronal survival in the adult olfactory bulb (OB). Whether this holds true of neurogenesis in the aged brain remains unknown. In this study, we find no evidence of irregular proliferation or early commitment defects in the mid-aged (12-month-old) and old-aged (20-month-old) SVZ following tamoxifen-inducible Rb knockout (Rb iKO) in mice. However, we highlight a striking defect in early maturation of Rb-deficient migrating neuroblasts along the rostral migratory stream (RMS), followed by massive decline in neuronal generation inside the aged OB. In the absence of Rb, we also show evidence of incomplete cell cycle re-entry (CCE) along with DNA damage in the young OB, while we find a similar trend towards CCE but no clear signs of DNA damage or neurodegenerative signatures (pTau or Synuclein accumulation) in the aged OB. However, such phenotype could be masked by the severe maturation defect reported above in addition to the natural decline in adult neurogenesis with age. Overall, we show that Rb is required to prevent CCE and DNA damage in adult-born OB neurons, hence maintain neuronal survival. Moreover, while loss of Rb alone is insufficient to trigger seeding of neurotoxic species, this study reveals age-dependent non-monotonic dynamics in regulating neurogenesis by Rb.
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Affiliation(s)
- Saad Omais
- Department of Biology, American University of Beirut, Lebanon
| | - Rouba N Hilal
- Department of Biology, American University of Beirut, Lebanon
| | - Nour N Halaby
- Department of Biology, American University of Beirut, Lebanon
| | - Carine Jaafar
- Department of Biology, American University of Beirut, Lebanon
| | - Noël Ghanem
- Department of Biology, American University of Beirut, Lebanon
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6
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Akagawa R, Nabeshima YI, Kawauchi T. Alternative Functions of Cell Cycle-Related and DNA Repair Proteins in Post-mitotic Neurons. Front Cell Dev Biol 2021; 9:753175. [PMID: 34746147 PMCID: PMC8564117 DOI: 10.3389/fcell.2021.753175] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 09/28/2021] [Indexed: 11/13/2022] Open
Abstract
Proper regulation of neuronal morphological changes is essential for neuronal migration, maturation, synapse formation, and high-order function. Many cytoplasmic proteins involved in the regulation of neuronal microtubules and the actin cytoskeleton have been identified. In addition, some nuclear proteins have alternative functions in neurons. While cell cycle-related proteins basically control the progression of the cell cycle in the nucleus, some of them have an extra-cell cycle-regulatory function (EXCERF), such as regulating cytoskeletal organization, after exit from the cell cycle. Our expression analyses showed that not only cell cycle regulators, including cyclin A1, cyclin D2, Cdk4/6, p21cip1, p27kip1, Ink4 family, and RAD21, but also DNA repair proteins, including BRCA2, p53, ATM, ATR, RAD17, MRE11, RAD9, and Hus1, were expressed after neurogenesis, suggesting that these proteins have alternative functions in post-mitotic neurons. In this perspective paper, we discuss the alternative functions of the nuclear proteins in neuronal development, focusing on possible cytoplasmic roles.
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Affiliation(s)
- Remi Akagawa
- Laboratory of Molecular Life Science, Institute of Biomedical Research and Innovation, Foundation for Biomedical Research and Innovation at Kobe (FBRI), Kobe, Japan
| | - Yo-Ichi Nabeshima
- Laboratory of Molecular Life Science, Institute of Biomedical Research and Innovation, Foundation for Biomedical Research and Innovation at Kobe (FBRI), Kobe, Japan
| | - Takeshi Kawauchi
- Laboratory of Molecular Life Science, Institute of Biomedical Research and Innovation, Foundation for Biomedical Research and Innovation at Kobe (FBRI), Kobe, Japan.,Department of Physiology, Keio University School of Medicine, Tokyo, Japan
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Catlin JP, Marziali LN, Rein B, Yan Z, Feltri ML, Schaner Tooley CE. Age-related neurodegeneration and cognitive impairments of NRMT1 knockout mice are preceded by misregulation of RB and abnormal neural stem cell development. Cell Death Dis 2021; 12:1014. [PMID: 34711807 PMCID: PMC8553844 DOI: 10.1038/s41419-021-04316-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 10/07/2021] [Accepted: 10/11/2021] [Indexed: 01/02/2023]
Abstract
N-terminal methylation is an important posttranslational modification that regulates protein/DNA interactions and plays a role in many cellular processes, including DNA damage repair, mitosis, and transcriptional regulation. Our generation of a constitutive knockout mouse for the N-terminal methyltransferase NRMT1 demonstrated its loss results in severe developmental abnormalities and premature aging phenotypes. As premature aging is often accompanied by neurodegeneration, we more specifically examined how NRMT1 loss affects neural pathology and cognitive behaviors. Here we find that Nrmt1-/- mice exhibit postnatal enlargement of the lateral ventricles, age-dependent striatal and hippocampal neurodegeneration, memory impairments, and hyperactivity. These morphological and behavior abnormalities are preceded by alterations in neural stem cell (NSC) development. Early expansion and differentiation of the quiescent NSC pool in Nrmt1-/- mice is followed by its subsequent depletion and many of the resulting neurons remain in the cell cycle and ultimately undergo apoptosis. These cell cycle phenotypes are reminiscent to those seen with loss of the NRMT1 target retinoblastoma protein (RB). Accordingly, we find misregulation of RB phosphorylation and degradation in Nrmt1-/- mice, and significant de-repression of RB target genes involved in cell cycle. We also identify novel de-repression of Noxa, an RB target gene that promotes apoptosis. These data identify Nα-methylation as a novel regulatory modification of RB transcriptional repression during neurogenesis and indicate that NRMT1 and RB work together to promote NSC quiescence and prevent neuronal apoptosis.
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Affiliation(s)
- James P Catlin
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14203, USA
| | - Leandro N Marziali
- Departments of Biochemistry and Neurology, Jacobs School of Medicine and Biomedical Sciences, Hunter James Kelly Research Institute, State University of New York at Buffalo, Buffalo, NY, 14203, USA
| | - Benjamin Rein
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14203, USA
| | - Zhen Yan
- Department of Physiology and Biophysics, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14203, USA
| | - M Laura Feltri
- Departments of Biochemistry and Neurology, Jacobs School of Medicine and Biomedical Sciences, Hunter James Kelly Research Institute, State University of New York at Buffalo, Buffalo, NY, 14203, USA
| | - Christine E Schaner Tooley
- Department of Biochemistry, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY, 14203, USA.
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8
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Alimoradi N, Firouzabadi N, Fatehi R. Metformin and insulin-resistant related diseases: Emphasis on the role of microRNAs. Biomed Pharmacother 2021; 139:111662. [PMID: 34243629 DOI: 10.1016/j.biopha.2021.111662] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 04/16/2021] [Accepted: 04/22/2021] [Indexed: 12/14/2022] Open
Abstract
Metformin is one of the most prescribed drugs in type II diabetes (T2DM) which has recently found new applications in the prevention and treatment of various illnesses, from metabolic disorders to cardiovascular and age-related diseases. Metformin improves insulin resistance (IR) by modulating metabolic mechanisms and mitochondrial biogenesis. Alternation of microRNAs (miRs) in the treatment of IR-related illnesses has been observed by metformin therapy. MiRs are small non-coding RNAs that play important roles in RNA silencing, targeting the 3'untranslated region (3'UTR) of most mRNAs and inhibiting the translation of related proteins. As a result, their dysregulation is associated with many diseases. Metformin may alter miRs levels in the treatment of various diseases by AMPK-dependent or AMPK-independent mechanisms. Here, we summarized the therapeutic role of metformin by modifying the aberrant expression of miRs as potential biomarkers or therapeutic targets in diseases in which IR plays a key role.
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Affiliation(s)
- Nahid Alimoradi
- Department of Pharmacology & Toxicology, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Negar Firouzabadi
- Department of Pharmacology & Toxicology, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran.
| | - Reihaneh Fatehi
- Department of Pharmacology & Toxicology, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Iran
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9
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Brain microRNAs dysregulation: Implication for missplicing and abnormal post-translational modifications of tau protein in Alzheimer’s disease and related tauopathies. Pharmacol Res 2020; 155:104729. [DOI: 10.1016/j.phrs.2020.104729] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Revised: 02/01/2020] [Accepted: 02/26/2020] [Indexed: 12/16/2022]
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10
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Xia P, Liu Y, Chen J, Cheng Z. Cell Cycle Proteins as Key Regulators of Postmitotic Cell Death. THE YALE JOURNAL OF BIOLOGY AND MEDICINE 2019; 92:641-650. [PMID: 31866779 PMCID: PMC6913832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Cell cycle progression in dividing cells, characterized by faithful replication of the genomic materials and duplication of the original cell, is fundamental for growth and reproduction of all mammalian organisms. Functional maturation of postmitotic cells, however, requires cell cycle exit and terminal differentiation. In mature postmitotic cells, many cell cycle proteins remain to be expressed, or can be induced and reactivated in pathological conditions such as traumatic injury and degenerative diseases. Interestingly, elevated levels of cell cycle proteins in postmitotic cells often do not induce proliferation, but result in aberrant cell cycle reentry and cell death. At present, the cell cycle machinery is known predominantly for regulating cell cycle progression and cell proliferation, albeit accumulating evidence indicates that cell cycle proteins may also control cell death, especially in postmitotic tissues. Herein, we provide a brief summary of these findings and hope to highlight the connection between cell cycle reentry and postmitotic cell death. In addition, we also outline the signaling pathways that have been identified in cell cycle-related cell death. Advanced understanding of the molecular mechanisms underlying cell cycle-related death is of paramount importance because this knowledge can be applied to develop protective strategies against pathologies in postmitotic tissues. Moreover, a full-scope understanding of the cell cycle machinery will allow fine tuning to favor cell proliferation over cell death, thereby potentially promoting tissue regeneration.
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Affiliation(s)
| | | | | | - Zhaokang Cheng
- To whom all correspondence should be addressed: Zhaokang Cheng, PhD, Department of Pharmaceutical Sciences, Washington State University, PBS 423, 412 E. Spokane Falls Blvd. Spokane, WA 99202-2131; Tel: 509-358-7741,
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11
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Samaridou E, Walgrave H, Salta E, Álvarez DM, Castro-López V, Loza M, Alonso MJ. Nose-to-brain delivery of enveloped RNA - cell permeating peptide nanocomplexes for the treatment of neurodegenerative diseases. Biomaterials 2019; 230:119657. [PMID: 31837821 DOI: 10.1016/j.biomaterials.2019.119657] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2019] [Revised: 11/21/2019] [Accepted: 11/27/2019] [Indexed: 12/31/2022]
Abstract
Direct nose-to-brain (N-to-B) delivery enables the rapid transport of drugs to the brain, while minimizing systemic exposure. The objective of this work was to engineer a nanocarrier intended to enhance N-to-B delivery of RNA and to explore its potential utility for the treatment of neurological disorders. Our approach involved the formation of electrostatically driven nanocomplexes between a hydrophobic derivative of octaarginine (r8), chemically conjugated with lauric acid (C12), and the RNA of interest. Subsequently, these cationic nanocomplexes were enveloped (enveloped nanocomplexes, ENCPs) with different protective polymers, i.e. polyethyleneglycol - polyglutamic acid (PEG-PGA) or hyaluronic acid (HA), intended to enhance their stability and mucodiffusion across the olfactory nasal mucosa. These rationally designed ENCPs were produced in bulk format and also using a microfluidics-based technique. This technique enabled the production of a scalable nanoformulation, exhibiting; (i) a unimodal size distribution with a tunable mean size, (ii) the capacity to highly associate (100%) and protect RNA from degradation, (iii) the ability to preserve its physicochemical properties in biorelevant media and prevent the premature RNA release. Moreover, in vitro cell culture studies showed the capacity of ENCPs to interact and be efficiently taken-up by CHO cells. Finally, in vivo experiments in a mouse model of Alzheimer's disease provided evidence of a statistically significant increase of a potentially therapeutic miRNA mimic in the hippocampus area and its further effect on two mRNA targets, following its intranasal administration. Overall, these findings stress the value of the rational design of nanocarriers towards overcoming the biological barriers associated to N-to-B RNA delivery and reveal their potential value as therapeutic strategies in Alzheimer's disease.
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Affiliation(s)
- Eleni Samaridou
- Center for Research in Molecular Medicine and Chronic Diseases, IDIS research Institute, Department of Pharmacy and Pharmaceutical Technology, School of Pharmacy, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
| | - Hannah Walgrave
- Vlaams Instituut voor Biotechnologie (VIB) Center for Brain and Disease, VIB-Leuven, Center for Human Genetics, Universitaire Ziekenhuizen and Leuven Research Institute for Neuroscience and Disease, KU-Leuven, Leuven, Belgium
| | - Evgenia Salta
- Vlaams Instituut voor Biotechnologie (VIB) Center for Brain and Disease, VIB-Leuven, Center for Human Genetics, Universitaire Ziekenhuizen and Leuven Research Institute for Neuroscience and Disease, KU-Leuven, Leuven, Belgium
| | - David Moreira Álvarez
- BioFarma Research Group, CIMUS, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Vanessa Castro-López
- Center for Research in Molecular Medicine and Chronic Diseases, IDIS research Institute, Department of Pharmacy and Pharmaceutical Technology, School of Pharmacy, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain
| | - Mabel Loza
- BioFarma Research Group, CIMUS, Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Maria José Alonso
- Center for Research in Molecular Medicine and Chronic Diseases, IDIS research Institute, Department of Pharmacy and Pharmaceutical Technology, School of Pharmacy, Universidade de Santiago de Compostela, 15782, Santiago de Compostela, Spain.
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12
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Duraikannu A, Krishnan A, Chandrasekhar A, Zochodne DW. Beyond Trophic Factors: Exploiting the Intrinsic Regenerative Properties of Adult Neurons. Front Cell Neurosci 2019; 13:128. [PMID: 31024258 PMCID: PMC6460947 DOI: 10.3389/fncel.2019.00128] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2018] [Accepted: 03/14/2019] [Indexed: 01/19/2023] Open
Abstract
Injuries and diseases of the peripheral nervous system (PNS) are common but frequently irreversible. It is often but mistakenly assumed that peripheral neuron regeneration is robust without a need to be improved or supported. However, axonal lesions, especially those involving proximal nerves rarely recover fully and injuries generally are complicated by slow and incomplete regeneration. Strategies to enhance the intrinsic growth properties of reluctant adult neurons offer an alternative approach to consider during regeneration. Since axons rarely regrow without an intimately partnered Schwann cell (SC), approaches to enhance SC plasticity carry along benefits to their axon partners. Direct targeting of molecules that inhibit growth cone plasticity can inform important regenerative strategies. A newer approach, a focus of our laboratory, exploits tumor suppressor molecules that normally dampen unconstrained growth. However several are also prominently expressed in stable adult neurons. During regeneration their ongoing expression “brakes” growth, whereas their inhibition and knockdown may enhance regrowth. Examples have included phosphatase and tensin homolog deleted on chromosome ten (PTEN), a tumor suppressor that inhibits PI3K/pAkt signaling, Rb1, the protein involved in retinoblastoma development, and adenomatous polyposis coli (APC), a tumor suppressor that inhibits β-Catenin transcriptional signaling and its translocation to the nucleus. The identification of several new targets to manipulate the plasticity of regenerating adult peripheral neurons is exciting. How they fit with canonical regeneration strategies and their feasibility require additional work. Newer forms of nonviral siRNA delivery may be approaches for molecular manipulation to improve regeneration.
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Affiliation(s)
- Arul Duraikannu
- Division of Neurology, Department of Medicine, and Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Anand Krishnan
- Division of Neurology, Department of Medicine, and Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Ambika Chandrasekhar
- Division of Neurology, Department of Medicine, and Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
| | - Douglas W Zochodne
- Division of Neurology, Department of Medicine, and Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
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13
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Dhumale P, Menon S, Chiang J, Püschel AW. The loss of the kinases SadA and SadB results in early neuronal apoptosis and a reduced number of progenitors. PLoS One 2018; 13:e0196698. [PMID: 29698519 PMCID: PMC5919486 DOI: 10.1371/journal.pone.0196698] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Accepted: 04/17/2018] [Indexed: 11/18/2022] Open
Abstract
The neurons that form the mammalian neocortex originate from progenitor cells in the ventricular (VZ) and subventricular zone (SVZ). Newborn neurons are multipolar but become bipolar during their migration from the germinal layers to the cortical plate (CP) by forming a leading process and an axon that extends in the intermediate zone (IZ). Once they settle in the CP, neurons assume a highly polarized morphology with a single axon and multiple dendrites. The AMPK-related kinases SadA and SadB are intrinsic factors that are essential for axon formation during neuronal development downstream of Lkb1. The knockout of both genes encoding Sad kinases (Sada and Sadb) results not only in a loss of axons but also a decrease in the size of the cortical plate. The defect in axon formation has been linked to a function of Sad kinases in the regulation of microtubule binding proteins. However, the causes for the reduced size of the cortical plate in the Sada-/-;Sadb-/- knockout remain to be analyzed in detail. Here we show that neuronal cell death is increased and the number of neural progenitors is decreased in the Sada-/-;Sadb-/- CP. The reduced number of progenitors is a non-cell autonomous defect since they do not express Sad kinases. These defects are restricted to the neocortex while the hippocampus remains unaffected.
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Affiliation(s)
- Pratibha Dhumale
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität, Münster, Germany
- Cells-in-Motion Cluster of Excellence, University of Münster, Münster, Germany
| | - Sindhu Menon
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität, Münster, Germany
| | - Joanna Chiang
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität, Münster, Germany
- Cells-in-Motion Cluster of Excellence, University of Münster, Münster, Germany
| | - Andreas W. Püschel
- Institut für Molekulare Zellbiologie, Westfälische Wilhelms-Universität, Münster, Germany
- Cells-in-Motion Cluster of Excellence, University of Münster, Münster, Germany
- * E-mail:
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14
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Omais S, Jaafar C, Ghanem N. "Till Death Do Us Part": A Potential Irreversible Link Between Aberrant Cell Cycle Control and Neurodegeneration in the Adult Olfactory Bulb. Front Neurosci 2018; 12:144. [PMID: 29593485 PMCID: PMC5854681 DOI: 10.3389/fnins.2018.00144] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Accepted: 02/22/2018] [Indexed: 12/13/2022] Open
Abstract
Adult neurogenesis (AN) is an ongoing developmental process that generates newborn neurons in the olfactory bulb (OB) and the hippocampus (Hi) throughout life and significantly contributes to brain plasticity. Adult neural stem and progenitor cells (aNSPCs) are relatively limited in number and fate and are spatially restricted to the subventricular zone (SVZ) and the subgranular zone (SGZ). During AN, the distinct roles played by cell cycle proteins extend beyond cell cycle control and constitute key regulatory mechanisms involved in neuronal maturation and survival. Importantly, aberrant cell cycle re-entry (CCE) in post-mitotic neurons has been strongly linked to the abnormal pathophysiology in rodent models of neurodegenerative diseases with potential implications on the etiology and progression of such diseases in humans. Here, we present an overview of AN in the SVZ-OB and olfactory epithelium (OE) in mice and humans followed by a comprehensive update of the distinct roles played by cell cycle proteins including major tumors suppressor genes in various steps during neurogenesis. We also discuss accumulating evidence underlining a strong link between abnormal cell cycle control, olfactory dysfunction and neurodegeneration in the adult and aging brain. We emphasize that: (1) CCE in post-mitotic neurons due to loss of cell cycle suppression and/or age-related insults as well as DNA damage can anticipate the development of neurodegenerative lesions and protein aggregates, (2) the age-related decline in SVZ and OE neurogenesis is associated with compensatory pro-survival mechanisms in the aging OB which are interestingly similar to those detected in Alzheimer's disease and Parkinson's disease in humans, and (3) the OB represents a well suitable model to study the early manifestation of age-related defects that may eventually progress into the formation of neurodegenerative lesions and, possibly, spread to the rest of the brain. Such findings may provide a novel approach to the modeling of neurodegenerative diseases in humans from early detection to progression and treatment as well.
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Affiliation(s)
- Saad Omais
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Carine Jaafar
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Noël Ghanem
- Department of Biology, American University of Beirut, Beirut, Lebanon
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15
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Delou JMA, Biasoli D, Borges HL. The Complex Link between Apoptosis and Autophagy: a Promising New Role for RB. AN ACAD BRAS CIENC 2018; 88:2257-2275. [PMID: 27991962 DOI: 10.1590/0001-3765201620160127] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Accepted: 06/27/2016] [Indexed: 12/14/2022] Open
Abstract
Physiological processes, as autophagy, proliferation and apoptosis are affected during carcinogenesis. Restoring cellular sensitivity to apoptotic stimuli, such as the antineoplastic cocktails, has been explored as a strategy to eliminate cancer cells. Autophagy, a physiological process of recycling organelles and macromolecules can be deviated from homeostasis to support cancer cells survival, proliferation, escape from apoptosis, and therapy resistance. The relationship between autophagy and apoptosis is complex and many stimuli can induce both processes. Most chemotherapeutic agents induce autophagy and it is not clear whether and how this chemotherapy-induced autophagy might contribute to resistance to apoptosis. Here, we review current strategies to sensitize cancer cells by interfering with autophagy. Moreover, we discuss a new link between autophagy and apoptosis: the tumor suppressor retinoblastoma protein (RB). Inactivation of RB is one of the earliest and more frequent hallmarks of cancer transformation, known to control cell cycle progression and apoptosis. Therefore, understanding RB functions in controlling cell fate is essential for an effective translation of RB status in cancer samples to the clinical outcome.
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Affiliation(s)
- João M A Delou
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 373, Ilha do Fundão, 21949-590 Rio de Janeiro, RJ, Brazil
| | - Deborah Biasoli
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 373, Ilha do Fundão, 21949-590 Rio de Janeiro, RJ, Brazil
| | - Helena L Borges
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Av. Carlos Chagas Filho, 373, Ilha do Fundão, 21949-590 Rio de Janeiro, RJ, Brazil
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16
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Oshikawa M, Okada K, Tabata H, Nagata KI, Ajioka I. Dnmt1-dependent Chk1 pathway suppression is protective against neuron division. Development 2017; 144:3303-3314. [PMID: 28928282 DOI: 10.1242/dev.154013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2017] [Accepted: 08/01/2017] [Indexed: 12/19/2022]
Abstract
Neuronal differentiation and cell-cycle exit are tightly coordinated, even in pathological situations. When pathological neurons re-enter the cell cycle and progress through the S phase, they undergo cell death instead of division. However, the mechanisms underlying mitotic resistance are mostly unknown. Here, we have found that acute inactivation of retinoblastoma (Rb) family proteins (Rb, p107 and p130) in mouse postmitotic neurons leads to cell death after S-phase progression. Checkpoint kinase 1 (Chk1) pathway activation during the S phase prevented the cell death, and allowed the division of cortical neurons that had undergone acute Rb family inactivation, oxygen-glucose deprivation (OGD) or in vivo hypoxia-ischemia. During neurogenesis, cortical neurons became protected from S-phase Chk1 pathway activation by the DNA methyltransferase Dnmt1, and underwent cell death after S-phase progression. Our results indicate that Chk1 pathway activation overrides mitotic safeguards and uncouples neuronal differentiation from mitotic resistance.
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Affiliation(s)
- Mio Oshikawa
- Center for Brain Integration Research (CBIR), Tokyo Medical and Dental University (TMDU), Tokyo 113-8510, Japan
| | - Kei Okada
- Center for Brain Integration Research (CBIR), Tokyo Medical and Dental University (TMDU), Tokyo 113-8510, Japan
| | - Hidenori Tabata
- Department of Molecular Neurobiology, Institute for Developmental Research, Aichi Human Service Center, Kasugai Aichi 480-0392, Japan
| | - Koh-Ichi Nagata
- Department of Molecular Neurobiology, Institute for Developmental Research, Aichi Human Service Center, Kasugai Aichi 480-0392, Japan
| | - Itsuki Ajioka
- Center for Brain Integration Research (CBIR), Tokyo Medical and Dental University (TMDU), Tokyo 113-8510, Japan .,The Japan Science and Technology Agency (JST), Precursory Research for Embryonic Science and Technology (PRESTO), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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17
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Tse KH, Herrup K. Re-imagining Alzheimer's disease - the diminishing importance of amyloid and a glimpse of what lies ahead. J Neurochem 2017; 143:432-444. [PMID: 28547865 DOI: 10.1111/jnc.14079] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Revised: 05/13/2017] [Accepted: 05/23/2017] [Indexed: 12/13/2022]
Abstract
Many have criticized the amyloid cascade hypothesis of Alzheimer's disease for its inconsistencies and failures to either accurately predict disease symptoms or guide the development of productive therapies. In addition to criticisms, however, we believe that the field would benefit from having alternative narratives and disease models that can either replace or function alongside of an amyloid-centric view of Alzheimer's. This review is an attempt to meet that need. We offer three experimentally verified amyloid-independent mechanisms, each of which plausibly contributes substantially to the aetiology of Alzheimer's disease: loss of DNA integrity, faulty cell cycle regulation, regression of myelination. We outline the ways in which the failure of each can contribute to AD initiation and progression, and review how, acting alone or in combination with each other, they are sufficient for explaining the full range of AD pathologies. Yet, these three alternatives represent only a few of the many non-amyloid mechanisms that can explain AD pathogenesis. Therefore instead of proposing a single 'alternative hypothesis' to the amyloid cascade theory, sporadic AD is pictured as the result of independent yet intersecting age-related pathologies that afflict the ageing human brain. This article is part of the series "Beyond Amyloid". Cover Image for this issue: doi. 10.1111/jnc.13823.
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Affiliation(s)
- Kai-Hei Tse
- Division of Life Science and the State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
| | - Karl Herrup
- Division of Life Science and the State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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18
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Molecular connections of obesity and aging: a focus on adipose protein 53 and retinoblastoma protein. Biogerontology 2017; 18:321-332. [PMID: 28357524 DOI: 10.1007/s10522-017-9698-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 03/27/2017] [Indexed: 12/13/2022]
Abstract
Obesity is an induced health problem that human beings have been facing with non-optimal treatment so far. Humans are on average getting fatter with age, and obesity and aging interact each other to shorten lifetime and decrease life quality. Obesity also causes several aging related-disorders such as cancer, strokes, cardiovascular disease, high blood pressure and type 2 diabetes. So, the molecular connections between aging and obesity are promising targets for bio-medical researches and innovative therapies of many health problems. In this review, we discuss the findings of adipose p53 and Rb-two central molecular linkages between aging and obesity-on lipid metabolism and obesity.
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19
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Fong BC, Slack RS. RB: An essential player in adult neurogenesis. NEUROGENESIS 2017; 4:e1270382. [PMID: 28229086 DOI: 10.1080/23262133.2016.1270382] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 11/30/2016] [Accepted: 12/04/2016] [Indexed: 12/16/2022]
Abstract
The fundamental mechanisms underlying adult neurogenesis remain to be fully clarified. Members of the cell cycle machinery have demonstrated key roles in regulating adult neural stem cell (NSC) quiescence and the size of the adult-born neuronal population. The retinoblastoma protein, Rb, is known to possess CNS-specific requirements that are independent from its classical role as a tumor suppressor. The recent study by Vandenbosch et al. has clarified distinct requirements for Rb during adult neurogenesis, in the restriction of proliferation, as well as long-term adult-born neuronal survival. However, Rb is no longer believed to be the main cell cycle regulator maintaining the quiescence of adult NSCs. Future studies must consider Rb as part of a larger network of regulatory effectors, including the other members of the Rb family, p107 and p130. This will help elucidate the contribution of Rb and other pocket proteins in the context of adult neurogenesis, and define its crucial role in regulating the size and fate of the neurogenic niche.
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Affiliation(s)
- Bensun C Fong
- University of Ottawa Brain and Mind Research Institute, Department of Cellular & Molecular Medicine, University of Ottawa , Ottawa, ON, Canada
| | - Ruth S Slack
- University of Ottawa Brain and Mind Research Institute, Department of Cellular & Molecular Medicine, University of Ottawa , Ottawa, ON, Canada
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20
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Jaafar C, Omais S, Al Lafi S, El Jamal N, Noubani M, Skaf L, Ghanem N. Role of Rb during Neurogenesis and Axonal Guidance in the Developing Olfactory System. Front Mol Neurosci 2016; 9:81. [PMID: 27667971 PMCID: PMC5016521 DOI: 10.3389/fnmol.2016.00081] [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] [Received: 07/13/2016] [Accepted: 08/24/2016] [Indexed: 11/19/2022] Open
Abstract
The Retinoblastoma protein, Rb, was shown to regulate distinct aspects of neurogenesis in the embryonic and adult brain besides its primary role in cell cycle control. It is still unknown, however, whether Rb is required for tissue morphogenesis and the establishment of synaptic connections between adjacent tissues during development. We have investigated here the role of Rb during development of the olfactory system (OS), which heavily relies on reciprocal interactions between the olfactory epithelium (OE) and the olfactory bulb (OB). We show that mice carrying a telencephalic-specific deletion of Rb display several neurogenic defects in the OS during late development. In the OE, loss of Rb leads to ectopic proliferation of late-born progenitors (Tuj-1+), abnormal radial migration and terminal maturation of olfactory sensory neurons (OSNs). In the OB, deletion of Rb causes severe lamination defects with loss of clear boundaries between distinct layers. Importantly, starting around E15.5 when OB glomerulogenesis is initiated, many OSNs axons that project along the olfactory nerve layer (ONL) fail to properly innervate the nascent bulb, thus resulting in partial loss of connectivity between OE-OB and gradual neuronal degeneration in both tissues peaking at birth. This deficiency correlates with deregulated expressions of two key chemo-repellant molecules, Robo2/Slit1 and Nrp2/Sema3F that control the formation of dorsal-ventral topographic map of OSNs connections with OB glomeruli. This study highlights a critical requirement for Rb during neurogenesis and the establishment of proper synaptic connections inside the OS during development.
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Affiliation(s)
- Carine Jaafar
- Department of Biology, American University of Beirut Beirut, Lebanon
| | - Saad Omais
- Department of Biology, American University of Beirut Beirut, Lebanon
| | - Sawsan Al Lafi
- Department of Biology, American University of Beirut Beirut, Lebanon
| | - Nadim El Jamal
- Department of Biology, American University of Beirut Beirut, Lebanon
| | - Mohammad Noubani
- Department of Biology, American University of Beirut Beirut, Lebanon
| | - Larissa Skaf
- Department of Biology, American University of Beirut Beirut, Lebanon
| | - Noël Ghanem
- Department of Biology, American University of Beirut Beirut, Lebanon
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21
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Vandenbosch R, Clark A, Fong BC, Omais S, Jaafar C, Dugal-Tessier D, Dhaliwal J, Lagace DC, Park DS, Ghanem N, Slack RS. RB regulates the production and the survival of newborn neurons in the embryonic and adult dentate gyrus. Hippocampus 2016; 26:1379-1392. [DOI: 10.1002/hipo.22613] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/15/2016] [Indexed: 12/22/2022]
Affiliation(s)
- Renaud Vandenbosch
- Department of Cellular and Molecular Medicine; University of Ottawa Brain and Mind Research Institute, University of Ottawa; Ottawa ON Canada
| | - Alysen Clark
- Department of Cellular and Molecular Medicine; University of Ottawa Brain and Mind Research Institute, University of Ottawa; Ottawa ON Canada
| | - Bensun C. Fong
- Department of Cellular and Molecular Medicine; University of Ottawa Brain and Mind Research Institute, University of Ottawa; Ottawa ON Canada
| | - Saad Omais
- Department of Biology; American University of Beirut; Beirut Lebanon
| | - Carine Jaafar
- Department of Biology; American University of Beirut; Beirut Lebanon
| | - Delphie Dugal-Tessier
- Department of Cellular and Molecular Medicine; University of Ottawa Brain and Mind Research Institute, University of Ottawa; Ottawa ON Canada
| | - Jagroop Dhaliwal
- Department of Cellular and Molecular Medicine; University of Ottawa Brain and Mind Research Institute, University of Ottawa; Ottawa ON Canada
| | - Diane C. Lagace
- Department of Cellular and Molecular Medicine; University of Ottawa Brain and Mind Research Institute, University of Ottawa; Ottawa ON Canada
| | - David S. Park
- Department of Cellular and Molecular Medicine; University of Ottawa Brain and Mind Research Institute, University of Ottawa; Ottawa ON Canada
| | - Noël Ghanem
- Department of Biology; American University of Beirut; Beirut Lebanon
| | - Ruth S. Slack
- Department of Cellular and Molecular Medicine; University of Ottawa Brain and Mind Research Institute, University of Ottawa; Ottawa ON Canada
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22
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Ajioka I. Biomaterial-engineering and neurobiological approaches for regenerating the injured cerebral cortex. Regen Ther 2016; 3:63-67. [PMID: 31245474 PMCID: PMC6581816 DOI: 10.1016/j.reth.2016.02.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2015] [Revised: 01/08/2016] [Accepted: 02/12/2016] [Indexed: 01/07/2023] Open
Abstract
The cerebral cortex is responsible for higher functions of the central nervous system (CNS), such as movement, sensation, and cognition. When the cerebral cortex is severely injured, these functions are irreversibly impaired. Although recent neurobiological studies reveal that the cortex has the potential for regeneration, therapies for functional recovery face some technological obstacles. Biomaterials have been used to evoke regenerative potential and promote regeneration in several tissues, including the CNS. This review presents a brief overview of new therapeutic strategies for cortical regeneration from the perspectives of neurobiology and biomaterial engineering, and discusses a promising technology for evoking the regenerative potential of the cerebral cortex.
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Affiliation(s)
- Itsuki Ajioka
- Center for Brain Integration Research (CBIR), Tokyo Medical and Dental University (TMDU), Tokyo 113-8510, Japan,The Japan Science and Technology Agency (JST), Precursory Research for Embryonic Science and Technology (PRESTO), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan,Center for Brain Integration Research, Tokyo Medical and Dental University, 1-5-45 Yushima, Tokyo 113-8510, Japan. Fax: +81 3 5803 4716.
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23
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Naser R, Vandenbosch R, Omais S, Hayek D, Jaafar C, Al Lafi S, Saliba A, Baghdadi M, Skaf L, Ghanem N. Role of the Retinoblastoma protein, Rb, during adult neurogenesis in the olfactory bulb. Sci Rep 2016; 6:20230. [PMID: 26847607 PMCID: PMC4742828 DOI: 10.1038/srep20230] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 12/23/2015] [Indexed: 12/15/2022] Open
Abstract
Adult neural stem cells (aNSCs) are relatively quiescent populations that give rise to distinct neuronal subtypes throughout life, yet, at a very low rate and restricted differentiation potential. Thus, identifying the molecular mechanisms that control their cellular expansion is critical for regeneration after brain injury. Loss of the Retinoblastoma protein, Rb, leads to several defects in cell cycle as well as neuronal differentiation and migration during brain development. Here, we investigated the role of Rb during adult neurogenesis in the olfactory bulb (OB) by inducing its temporal deletion in aNSCs and progenitors. Loss of Rb was associated with increased proliferation of adult progenitors in the subventricular zone (SVZ) and the rostral migratory stream (RMS) but did not alter self-renewal of aNSCs or neuroblasts subsequent migration and terminal differentiation. Hence, one month after their birth, Rb-null neuroblasts were able to differentiate into distinct subtypes of GABAergic OB interneurons but were gradually lost after 3 months. Similarly, Rb controlled aNSCs/progenitors proliferation in vitro without affecting their differentiation capacity. This enhanced SVZ/OB neurogenesis associated with loss of Rb was only transient and negatively affected by increased apoptosis indicating a critical requirement for Rb in the long-term survival of adult-born OB interneurons.
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Affiliation(s)
- Rayan Naser
- Department of Biology, American University of Beirut, Lebanon
| | - Renaud Vandenbosch
- Department of Cellular and Molecular Medicine, University of Ottawa, Canada
| | - Saad Omais
- Department of Biology, American University of Beirut, Lebanon
| | - Dayana Hayek
- Department of Biology, American University of Beirut, Lebanon
| | - Carine Jaafar
- Department of Biology, American University of Beirut, Lebanon
| | - Sawsan Al Lafi
- Department of Biology, American University of Beirut, Lebanon
| | - Afaf Saliba
- Department of Biology, American University of Beirut, Lebanon
| | | | - Larissa Skaf
- Department of Biology, American University of Beirut, Lebanon
| | - Noël Ghanem
- Department of Biology, American University of Beirut, Lebanon
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24
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Hradek AC, Lee HP, Siedlak SL, Torres SL, Jung W, Han AH, Lee HG. Distinct chronology of neuronal cell cycle re-entry and tau pathology in the 3xTg-AD mouse model and Alzheimer's disease patients. J Alzheimers Dis 2016; 43:57-65. [PMID: 25061053 DOI: 10.3233/jad-141083] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Cell cycle re-entry in Alzheimer's disease (AD) has emerged as an important pathological mechanism in the progression of the disease. This appearance of cell cycle related proteins has been linked to tau pathology in AD, but the causal and temporal relationship between the two is not completely clear. In this study, we found that hyperphosphorylated retinoblastoma protein (ppRb), a key regulator for G1/S transition, is correlated with a late marker for hyperphosphorylation of tau but not with other early markers for tau alteration in the 3xTg-AD mouse model. However, in AD brains, ppRb can colocalize with both early and later markers for tau alterations, and can often be found singly in many degenerating neurons, indicating the distinct development of pathology between the 3xTg-AD mouse model and human AD patients. The conclusions of this study are two-fold. First, our findings clearly demonstrate the pathological link between the aberrant cell cycle re-entry and tau pathology. Second, the chronological pattern of cell cycle re-entry with tau pathology in the 3xTg-AD mouse is different compared to AD patients suggesting the distinct pathogenic mechanism between the animal AD model and human AD patients.
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Affiliation(s)
- Alex C Hradek
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Hyun-Pil Lee
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Sandra L Siedlak
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Sandy L Torres
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Wooyoung Jung
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Ashley H Han
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Hyoung-gon Lee
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
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25
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Affiliation(s)
- Paul H Huang
- The Institute of Cancer Research, Division of Cancer Biology, Chester Beatty Laboratories, London, UK
| | - Rebecca Cook
- The Institute of Cancer Research, Division of Cancer Biology, Chester Beatty Laboratories, London, UK
- Cancer Cell Signalling, UCL Cancer Institute, University College London, London, UK
| | - Sibylle Mittnacht
- The Institute of Cancer Research, Division of Cancer Biology, Chester Beatty Laboratories, London, UK
- Cancer Cell Signalling, UCL Cancer Institute, University College London, London, UK
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26
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Krishnan A, Duraikannu A, Zochodne DW. Releasing 'brakes' to nerve regeneration: intrinsic molecular targets. Eur J Neurosci 2015; 43:297-308. [PMID: 26174154 DOI: 10.1111/ejn.13018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 07/03/2015] [Accepted: 07/06/2015] [Indexed: 02/01/2023]
Abstract
Restoring critical neuronal architecture after peripheral nerve injury is challenging. Although immediate regenerative responses to peripheral axon injury involve the synthesis of regeneration-associated proteins in neurons and Schwann cells, an unfavorable balance between growth facilitatory and growth inhibitory signaling impairs the growth continuum of injured peripheral nerves. Molecules involved with the signaling network of tumor suppressors play crucial roles in shifting the balance between growth and restraint during axon regeneration. An understanding of the molecular framework of tumor suppressor molecules in injured neurons and its impact on stage-specific regeneration events may expose therapeutic intervention points. In this review we discuss how signaling networks of the specific tumor suppressors PTEN, Rb1, p53, p27 and p21 are altered in injured peripheral nerves and how this impacts peripheral nerve regeneration. Insights into the roles and importance of these pathways may open new avenues for improving the neurological deficits associated with nerve injury.
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Affiliation(s)
- Anand Krishnan
- Division of Neurology & Neuroscience and Mental Health Institute, Department of Medicine, University of Alberta, 7-123A Clinical Sciences Building, Edmonton, AB, T6G 2G3, Canada
| | - Arul Duraikannu
- Division of Neurology & Neuroscience and Mental Health Institute, Department of Medicine, University of Alberta, 7-123A Clinical Sciences Building, Edmonton, AB, T6G 2G3, Canada
| | - Douglas W Zochodne
- Division of Neurology & Neuroscience and Mental Health Institute, Department of Medicine, University of Alberta, 7-123A Clinical Sciences Building, Edmonton, AB, T6G 2G3, Canada
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27
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Tao L, Segil N. Early transcriptional response to aminoglycoside antibiotic suggests alternate pathways leading to apoptosis in sensory hair cells in the mouse inner ear. Front Cell Neurosci 2015; 9:190. [PMID: 26052268 PMCID: PMC4439550 DOI: 10.3389/fncel.2015.00190] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 04/29/2015] [Indexed: 01/22/2023] Open
Abstract
Aminoglycoside antibiotics are “the drug of choice” for treating many bacterial infections, but their administration results in hearing loss in up to one fourth of the patients who receive them. Several biochemical pathways have been implicated in aminoglycoside antibiotic ototoxicity; however, little is known about how hair cells respond to aminoglycoside antibiotics at the transcriptome level. Here we have investigated the genome-wide response to the aminoglycoside antibiotic gentamicin. Using organotypic cultures of the perinatal organ of Corti, we performed RNA sequencing using cDNA libraries obtained from FACS-purified hair cells. Within 3 h of gentamicin treatment, the messenger RNA level of more than three thousand genes in hair cells changed significantly. Bioinformatic analysis of these changes highlighted several known signal transduction pathways, including the JNK pathway and the NF-κB pathway, in addition to genes involved in the stress response, apoptosis, cell cycle control, and DNA damage repair. In contrast, only 698 genes, mainly involved in cell cycle and metabolite biosynthetic processes, were significantly affected in the non-hair cell population. The gene expression profiles of hair cells in response to gentamicin share a considerable similarity with those previously observed in gentamicin-induced nephrotoxicity. Our findings suggest that previously observed early responses to gentamicin in hair cells in specific signaling pathways are reflected in changes in gene expression. Additionally, the observed changes in gene expression of cell cycle regulatory genes indicate a disruption of the postmitotic state, which may suggest an alternate pathway regulating gentamicin-induced apoptotic hair cell death. This work provides a more comprehensive view of aminoglycoside antibiotic ototoxicity, and thus contributes to identifying potential pathways or therapeutic targets to alleviate this important side effect of aminoglycoside antibiotics.
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Affiliation(s)
- Litao Tao
- Genetic, Molecular and Cellular Biology Program, University of Southern California Los Angeles, CA, USA ; Department of Stem Cell Biology and Regenerative Medicine, University of Southern California Los Angeles, CA, USA
| | - Neil Segil
- Genetic, Molecular and Cellular Biology Program, University of Southern California Los Angeles, CA, USA ; Department of Stem Cell Biology and Regenerative Medicine, University of Southern California Los Angeles, CA, USA ; Department of Otolaryngology, University of Southern California Los Angeles, CA, USA
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28
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Marathe S, Liu S, Brai E, Kaczarowski M, Alberi L. Notch signaling in response to excitotoxicity induces neurodegeneration via erroneous cell cycle reentry. Cell Death Differ 2015; 22:1775-84. [PMID: 25822340 DOI: 10.1038/cdd.2015.23] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Revised: 01/26/2015] [Accepted: 02/11/2015] [Indexed: 02/06/2023] Open
Abstract
Neurological disorders such as Alzheimer's disease, stroke and epilepsy are currently marred by the lack of effective treatments to prevent neuronal death. Erroneous cell cycle reentry (CCR) is hypothesized to have a causative role in neurodegeneration. We show that forcing S-phase reentry in cultured hippocampal neurons is sufficient to induce neurodegeneration. We found that kainic-acid treatment in vivo induces erroneous CCR and neuronal death through a Notch-dependent mechanism. Ablating Notch signaling in neurons provides neuroprotection against kainic acid-induced neuronal death. We further show that kainic-acid treatment activates Notch signaling, which increases the bioavailability of CyclinD1 through Akt/GSK3β pathway, leading to aberrant CCR via activation of CyclinD1-Rb-E2F1 axis. In addition, pharmacological blockade of this pathway at critical steps is sufficient to confer resistance to kainic acid-induced neurotoxicity in mice. Taken together, our results demonstrate that excitotoxicity leads to neuronal death in a Notch-dependent manner through erroneous CCR.
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Affiliation(s)
- S Marathe
- Department of Medicine, Institute of Anatomy, University of Fribourg, Fribourg, Switzerland
| | - S Liu
- Receptor Biology Section, NINDS/NIH, Bethesda, MD, USA
| | - E Brai
- Department of Medicine, Institute of Anatomy, University of Fribourg, Fribourg, Switzerland
| | - M Kaczarowski
- Department of Medicine, Institute of Anatomy, University of Fribourg, Fribourg, Switzerland
| | - L Alberi
- Department of Medicine, Institute of Anatomy, University of Fribourg, Fribourg, Switzerland
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DNA damage signaling regulates age-dependent proliferative capacity of quiescent inner ear supporting cells. Aging (Albany NY) 2015; 6:496-510. [PMID: 25063730 PMCID: PMC4100811 DOI: 10.18632/aging.100668] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Supporting cells (SCs) of the cochlear (auditory) and vestibular (balance) organs hold promise as a platform for therapeutic regeneration of the sensory hair cells. Prior data have shown proliferative restrictions of adult SCs forced to re-enter the cell cycle. By comparing juvenile and adult SCs in explant cultures, we have here studied how proliferative restrictions are linked with DNA damage signaling. Cyclin D1 overexpression, used to stimulate cell cycle re-entry, triggered higher proliferative activity of juvenile SCs. Phosphorylated form of histone H2AX (γH2AX) and p53 binding protein 1 (53BP1) were induced in a foci-like pattern in SCs of both ages as an indication of DNA double-strand break formation and activated DNA damage response. Compared to juvenile SCs, γH2AX and the repair protein Rad51 were resolved with slower kinetics in adult SCs, accompanied by increased apoptosis. Consistent with the in vitro data, in a Rb mutant mouse model in vivo, cell cycle re-entry of SCs was associated with γH2AX foci induction. In contrast to cell cycle reactivation, pharmacological stimulation of SC-to-hair-cell transdifferentiation in vitro did not trigger γH2AX. Thus, DNA damage and its prolonged resolution are critical barriers in the efforts to stimulate proliferation of the adult inner ear SCs.
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Svoboda DS, Clark A, Park DS, Slack RS. Induction of protein deletion through in utero electroporation to define deficits in neuronal migration in transgenic models. J Vis Exp 2015:51983. [PMID: 25650557 DOI: 10.3791/51983] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Genetic deletion using the Cre-Lox system in transgenic mouse lines is a powerful tool used to study protein function. However, except in very specific Cre models, deletion of a protein throughout a tissue or cell population often leads to complex phenotypes resulting from multiple interacting mechanisms. Determining whether a phenotype results from disruption of a cell autonomous mechanism, which is intrinsic to the cell in question, or from a non-cell autonomous mechanism, which would result from impairment of that cell's environment, can be difficult to discern. To gain insight into protein function in an in vivo context, in utero electroporation (IUE) enables gene deletion in a small subset of cells within the developing cortex or some other selected brain region. IUE can be used to target specific brain areas, including the dorsal telencephalon, medial telencephalon, hippocampus, or ganglionic eminence. This facilitates observation of the consequences of cell autonomous gene deletion in the context of a healthy environment. The goal of this protocol is to show how IUE can be used to analyze a defect in radial migration in a floxed transgenic mouse line, with an emphasis on distinguishing between the cell autonomous and non-cell autonomous effects of protein deletion. By comparing the phenotype resulting from gene deletion within the entire cortex versus IUE-mediated gene deletion in a limited cell population, greater insight into protein function in brain development can be obtained than by using either technique in isolation.
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Affiliation(s)
- Devon S Svoboda
- Department of Cellular and Molecular Medicine, University of Ottawa;
| | - Alysen Clark
- Department of Cellular and Molecular Medicine, University of Ottawa
| | - David S Park
- Department of Cellular and Molecular Medicine, University of Ottawa
| | - Ruth S Slack
- Department of Cellular and Molecular Medicine, University of Ottawa;
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31
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Germain ND, Chen PF, Plocik AM, Glatt-Deeley H, Brown J, Fink JJ, Bolduc KA, Robinson TM, Levine ES, Reiter LT, Graveley BR, Lalande M, Chamberlain SJ. Gene expression analysis of human induced pluripotent stem cell-derived neurons carrying copy number variants of chromosome 15q11-q13.1. Mol Autism 2014; 5:44. [PMID: 25694803 PMCID: PMC4332023 DOI: 10.1186/2040-2392-5-44] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Accepted: 08/01/2014] [Indexed: 12/15/2022] Open
Abstract
Background Duplications of the chromosome 15q11-q13.1 region are associated with an estimated 1 to 3% of all autism cases, making this copy number variation (CNV) one of the most frequent chromosome abnormalities associated with autism spectrum disorder (ASD). Several genes located within the 15q11-q13.1 duplication region including ubiquitin protein ligase E3A (UBE3A), the gene disrupted in Angelman syndrome (AS), are involved in neural function and may play important roles in the neurobehavioral phenotypes associated with chromosome 15q11-q13.1 duplication (Dup15q) syndrome. Methods We have generated induced pluripotent stem cell (iPSC) lines from five different individuals containing CNVs of 15q11-q13.1. The iPSC lines were differentiated into mature, functional neurons. Gene expression across the 15q11-q13.1 locus was compared among the five iPSC lines and corresponding iPSC-derived neurons using quantitative reverse transcription PCR (qRT-PCR). Genome-wide gene expression was compared between neurons derived from three iPSC lines using mRNA-Seq. Results Analysis of 15q11-q13.1 gene expression in neurons derived from Dup15q iPSCs reveals that gene copy number does not consistently predict expression levels in cells with interstitial duplications of 15q11-q13.1. mRNA-Seq experiments show that there is substantial overlap in the genes differentially expressed between 15q11-q13.1 deletion and duplication neurons, Finally, we demonstrate that UBE3A transcripts can be pharmacologically rescued to normal levels in iPSC-derived neurons with a 15q11-q13.1 duplication. Conclusions Chromatin structure may influence gene expression across the 15q11-q13.1 region in neurons. Genome-wide analyses suggest that common neuronal pathways may be disrupted in both the Angelman and Dup15q syndromes. These data demonstrate that our disease-specific stem cell models provide a new tool to decipher the underlying cellular and genetic disease mechanisms of ASD and may also offer a pathway to novel therapeutic intervention in Dup15q syndrome.
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Affiliation(s)
- Noelle D Germain
- Department of Genetics and Developmental Biology, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06032, USA
| | - Pin-Fang Chen
- Department of Genetics and Developmental Biology, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06032, USA
| | - Alex M Plocik
- Department of Genetics and Developmental Biology, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06032, USA
| | - Heather Glatt-Deeley
- Department of Genetics and Developmental Biology, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06032, USA
| | - Judith Brown
- Chromosome Core, Department of Molecular and Cell Biology and Department of Allied Health Sciences, University of Connecticut, 354 Mansfield Road, Storrs, CT 06269, USA
| | - James J Fink
- Department of Neuroscience, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030, USA
| | - Kaitlyn A Bolduc
- Department of Neuroscience, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030, USA
| | - Tiwanna M Robinson
- Department of Neuroscience, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030, USA
| | - Eric S Levine
- Department of Neuroscience, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030, USA
| | - Lawrence T Reiter
- Department of Neurology, University of Tennessee Health Science Center, 855 Monroe Avenue, Suite 415, Memphis, TN 38163, USA
| | - Brenton R Graveley
- Department of Genetics and Developmental Biology, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06032, USA ; University of Connecticut Institute for Systems Genomics, Farmington, CT 06030, USA
| | - Marc Lalande
- Department of Genetics and Developmental Biology, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06032, USA
| | - Stormy J Chamberlain
- Department of Genetics and Developmental Biology, University of Connecticut Health Center, 400 Farmington Avenue, Farmington, CT 06032, USA
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Christie KJ, Krishnan A, Martinez JA, Purdy K, Singh B, Eaton S, Zochodne D. Enhancing adult nerve regeneration through the knockdown of retinoblastoma protein. Nat Commun 2014; 5:3670. [PMID: 24752312 PMCID: PMC5028199 DOI: 10.1038/ncomms4670] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Accepted: 03/17/2014] [Indexed: 12/22/2022] Open
Abstract
Tumour suppressor pathways may offer novel targets capable of altering the plasticity of post-mitotic adult neurons. Here we describe a role for the retinoblastoma (Rb) protein, widely expressed in adult sensory neurons and their axons, during regeneration. In adult sensory neurons, Rb short interfering RNA (siRNA) knockdown or Rb1 deletion in vitro enhances neurite outgrowth and branching. Plasticity is achieved in part through upregulation of neuronal PPARυ; its antagonism inhibits Rb siRNA plasticity, whereas a PPARυ agonist increases growth. In an in vivo regenerative paradigm following complete peripheral nerve trunk transection, direct delivery of Rb siRNA prompts increased outgrowth of axons from proximal stumps and entrains Schwann cells to accompany them for greater distances. Similarly, Rb siRNA delivery following a nerve crush improves behavioural indices of motor and sensory recovery in mice. The overall findings indicate that inhibition of tumour suppressor molecules has a role to play in promoting adult neuron regeneration.
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Affiliation(s)
- Kimberly J Christie
- 1] Department of Clinical Neurosciences and the Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1 [2]
| | - Anand Krishnan
- 1] Department of Clinical Neurosciences and the Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1 [2]
| | - Jose A Martinez
- Department of Clinical Neurosciences and the Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
| | - Kaylynn Purdy
- Department of Clinical Neurosciences and the Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
| | - Bhagat Singh
- Department of Clinical Neurosciences and the Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
| | - Shane Eaton
- Department of Clinical Neurosciences and the Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
| | - Douglas Zochodne
- Department of Clinical Neurosciences and the Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
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Ajioka I. Coordination of proliferation and neuronal differentiation by the retinoblastoma protein family. Dev Growth Differ 2014; 56:324-34. [PMID: 24697649 DOI: 10.1111/dgd.12127] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 02/13/2014] [Accepted: 02/16/2014] [Indexed: 12/23/2022]
Abstract
Once neurons enter the post-mitotic G0 phase during central nervous system (CNS) development, they lose their proliferative potential. When neurons re-enter the cell cycle during pathological situations such as neurodegeneration, they undergo cell death after S phase progression. Thus, the regulatory networks that drive cell proliferation and maintain neuronal differentiation are highly coordinated. In this review, the coordination of cell cycle control and neuronal differentiation during development are discussed, focusing on regulation by the Rb family of tumor suppressors (including p107 and p130), and the Cip/Kip family of cyclin dependent kinase (Cdk) inhibitors. Based on recent findings suggesting roles for these families in regulating neurogenesis and neuronal differentiation, I propose that the Rb family is essential for daughter cells of neuronal progenitors to enter the post-mitotic G0 phase without affecting the initiation of neuronal differentiation in most cases, while the Cip/Kip family regulates the timing of neuronal progenitor cell cycle exit and the initiation of neuronal differentiation at least in the progenitor cells of the cerebral cortex and the retina. Rb's lack of involvement in regulating the initiation of neuronal differentiation may explain why Rb family-deficient retinoblastomas characteristically exhibit neuronal features.
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Affiliation(s)
- Itsuki Ajioka
- Center for Brain Integration Research, Tokyo Medical and Dental University, 1-5-45 Yushima, Tokyo, 113-8510, Japan
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Meng X, Wang X, Tian X, Yang Z, Li M, Zhang C. Protection of neurons from high glucose-induced injury by deletion of MAD2B. J Cell Mol Med 2014; 18:844-51. [PMID: 24444371 PMCID: PMC4119390 DOI: 10.1111/jcmm.12229] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Accepted: 12/09/2013] [Indexed: 12/19/2022] Open
Abstract
Diabetic encephalopathy may lead to cognitive deficits in diabetic patients and diminish quality of life. It has been shown that protracted hyperglycaemia is directly associated with neuronal apoptosis, which is involved in diabetic encephalopathy. The anaphase-promoting complex (APC) is essential for the survival of post-mitotic neurons. In our previous study, we found that the mitotic arrest deficient protein MAD2B, one of APC inhibitors, was expressed in neurons in central nervous system. However, whether MAD2B is involved in hyperglycaemia-induced apoptosis and thus takes part in diabetic encephalopathy is still unknown. To address this issue, we first explored the expression of MAD2B and cyclin B1 detected by immunofluorescence and Western blot. It was found that hyperglycaemia remarkably increased the expression of MAD2B and accumulation of cyclin B1 in cortices of diabetes mellitus rat model and in cultured primary neurons. To further explore the role of MAD2B in hyperglycaemia-induced neuronal injury, we depleted MAD2B expression by a specifically targeted shRNA against MAD2B. We observed that MAD2B deficiency alleviated cyclin B1 expression and apoptotic neuronal death. These results demonstrate that MAD2B expression is the main culprit for accumulation of cyclin B1 and apoptosis in neurons under high glucose. Moreover, inhibition of the expression of MAD2B prevented neurons from entering an aberrant S phase that led differentiated neurons into apoptotic cell death. These results suggest that hyperglycaemia induced neuronal apoptosis through inducing expression of MAD2B, which represents a novel mechanism of diabetic encephalopathy.
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Affiliation(s)
- Xianfang Meng
- Department of Neurobiology, School of Basic Medical Sciences, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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MiR-26b, upregulated in Alzheimer's disease, activates cell cycle entry, tau-phosphorylation, and apoptosis in postmitotic neurons. J Neurosci 2013; 33:14645-59. [PMID: 24027266 DOI: 10.1523/jneurosci.1327-13.2013] [Citation(s) in RCA: 216] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
MicroRNA (miRNA) functions in the pathogenesis of major neurodegenerative diseases such as Alzheimer's disease (AD) are only beginning to emerge. We have observed significantly elevated levels of a specific miRNA, miR-26b, in the defined pathological areas of human postmortem brains, starting from early stages of AD (Braak III). Ectopic overexpression of miR-26b in rat primary postmitotic neurons led to the DNA replication and aberrant cell cycle entry (CCE) and, in parallel, increased tau-phosphorylation, which culminated in the apoptotic cell death of neurons. Similar tau hyperphosphorylation and CCE are typical features of neurons in pre-AD brains. Sequence-specific inhibition of miR-26b in culture is neuroprotective against oxidative stress. Retinoblastoma protein (Rb1), a major tumor suppressor, appears as the key direct miR-26b target, which mediates the observed neuronal phenotypes. The downstream signaling involves upregulation of Rb1/E2F cell cycle and pro-apoptotic transcriptional targets, including cyclin E1, and corresponding downregulation of cell cycle inhibitor p27/Kip1. It further leads to nuclear export and activation of Cdk5, a major kinase implicated in tau phosphorylation, regulation of cell cycle, and death in postmitotic neurons. Therefore, upregulation of miR-26b in neurons causes pleiotropic phenotypes that are also observed in AD. Elevated levels of miR-26b may thus contribute to the AD neuronal pathology.
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36
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Pocket proteins pRb and p107 are required for cortical lamination independent of apoptosis. Dev Biol 2013; 384:101-13. [DOI: 10.1016/j.ydbio.2013.09.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Revised: 09/06/2013] [Accepted: 09/09/2013] [Indexed: 01/24/2023]
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Herrup K. Post-mitotic role of the cell cycle machinery. Curr Opin Cell Biol 2013; 25:711-6. [PMID: 24055434 DOI: 10.1016/j.ceb.2013.08.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 08/08/2013] [Indexed: 12/27/2022]
Abstract
The process of cell division is highly complex. The DNA of the genome must be accurately replicated and segregated into two precisely equal portions; the cytoskeleton must be actively rearranged; and the cellular motor forces that allow the separation of the replicated chromosomes and the splitting of the mother cell into two daughters must be kept under strict spatial and temporal regulation. Not surprisingly for a process of this complexity, there is a wide range of proteins whose location and activity must be accurately controlled to ensure both efficiency and precision. Although the demands placed on these cell cycle proteins are high, once cells such as neurons differentiate they enter a long non-mitotic phase where evolution has conspired to repurpose many of these proteins, leading them to assume new and often unrelated cellular tasks. In neurons there is a wide range of non-cycling functions for these 'cell cycle' proteins and this review covers some of the best-known examples. There is little apparent logic to the second use, but the sheer number of examples suggests that there must be a significant evolutionary advantage to this repurposing strategy.
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Affiliation(s)
- Karl Herrup
- Division of Life Science, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong; Dept. of Cell Biology and Neuroscience, Rutgers University, 604 Allison Road, Piscataway, NJ 08854, United States.
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38
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Blais A. Rb and chromatin remodeling in the maintenance of the post-mitotic state of neurons. Cell Cycle 2013; 12:1661-2. [PMID: 23708446 PMCID: PMC3713122 DOI: 10.4161/cc.25071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- Alexandre Blais
- Ottawa Institute of Systems Biology, Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, ON Canada.
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Oshikawa M, Okada K, Nakajima K, Ajioka I. Cortical excitatory neurons become protected from cell division during neurogenesis in an Rb family-dependent manner. Development 2013; 140:2310-20. [PMID: 23615279 DOI: 10.1242/dev.095653] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cell cycle dysregulation leads to abnormal proliferation and cell death in a context-specific manner. Cell cycle progression driven via the Rb pathway forces neurons to undergo S-phase, resulting in cell death associated with the progression of neuronal degeneration. Nevertheless, some Rb- and Rb family (Rb, p107 and p130)-deficient differentiating neurons can proliferate and form tumors. Here, we found in mouse that differentiating cerebral cortical excitatory neurons underwent S-phase progression but not cell division after acute Rb family inactivation in differentiating neurons. However, the differentiating neurons underwent cell division and proliferated when Rb family members were inactivated in cortical progenitors. Differentiating neurons generated from Rb(-/-); p107(-/-); p130(-/-) (Rb-TKO) progenitors, but not acutely inactivated Rb-TKO differentiating neurons, activated the DNA double-strand break (DSB) repair pathway without increasing trimethylation at lysine 20 of histone H4 (H4K20), which has a role in protection against DNA damage. The activation of the DSB repair pathway was essential for the cell division of Rb-TKO differentiating neurons. These results suggest that newly born cortical neurons from progenitors become epigenetically protected from DNA damage and cell division in an Rb family-dependent manner.
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Affiliation(s)
- Mio Oshikawa
- Center for Brain Integration Research, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
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40
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Andrusiak MG, Vandenbosch R, Dick FA, Park DS, Slack RS. LXCXE-independent chromatin remodeling by Rb/E2f mediates neuronal quiescence. Cell Cycle 2013; 12:1416-23. [PMID: 23574720 DOI: 10.4161/cc.24527] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Neuronal survival is dependent upon the retinoblastoma family members, Rb1 (Rb) and Rb2 (p130). Rb is thought to regulate gene repression, in part, through direct recruitment of chromatin modifying enzymes to its conserved LXCXE binding domain. We sought to examine the mechanisms that Rb employs to mediate cell cycle gene repression in terminally differentiated cortical neurons. Here, we report that Rb loss converts chromatin at the promoters of E2f-target genes to an activated state. We established a mouse model system in which Rb-LXCXE interactions could be induciblely disabled. Surprisingly, this had no effect on survival or gene silencing in neuronal quiescence. Absence of the Rb LXCXE-binding domain in neurons is compatible with gene repression and long-term survival, unlike Rb deficiency. Finally, we are able to show that chromatin activation following Rb deletion occurs at the level of E2fs. Blocking E2f-mediated transcription downstream of Rb loss is sufficient to maintain chromatin in an inactive state. Taken together our results suggest a model whereby Rb-E2f interactions are sufficient to maintain gene repression irrespective of LXCXE-dependent chromatin remodeling.
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Affiliation(s)
- Matthew G Andrusiak
- Department of Cellular & Molecular Medicine, University of Ottawa, Ottawa, ON, Canada
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