1
|
Iqbal MA, Bilen M, Liu Y, Jabre V, Fong BC, Chakroun I, Paul S, Chen J, Wade S, Kanaan M, Harper ME, Khacho M, Slack RS. The integrated stress response promotes neural stem cell survival under conditions of mitochondrial dysfunction in neurodegeneration. Aging Cell 2024:e14165. [PMID: 38757355 DOI: 10.1111/acel.14165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 02/27/2024] [Accepted: 03/18/2024] [Indexed: 05/18/2024] Open
Abstract
Impaired mitochondrial function is a hallmark of aging and a major contributor to neurodegenerative diseases. We have shown that disrupted mitochondrial dynamics typically found in aging alters the fate of neural stem cells (NSCs) leading to impairments in learning and memory. At present, little is known regarding the mechanisms by which neural stem and progenitor cells survive and adapt to mitochondrial dysfunction. Using Opa1-inducible knockout as a model of aging and neurodegeneration, we identify a decline in neurogenesis due to impaired stem cell activation and progenitor proliferation, which can be rescued by the mitigation of oxidative stress through hypoxia. Through sc-RNA-seq, we identify the ATF4 pathway as a critical mechanism underlying cellular adaptation to metabolic stress. ATF4 knockdown in Opa1-deficient NSCs accelerates cell death, while the increased expression of ATF4 enhances proliferation and survival. Using a Slc7a11 mutant, an ATF4 target, we show that ATF4-mediated glutathione production plays a critical role in maintaining NSC survival and function under stress conditions. Together, we show that the activation of the integrated stress response (ISR) pathway enables NSCs to adapt to metabolic stress due to mitochondrial dysfunction and metabolic stress and may serve as a therapeutic target to enhance NSC survival and function in aging and neurodegeneration.
Collapse
Affiliation(s)
- Mohamed Ariff Iqbal
- Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Maria Bilen
- Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Yubing Liu
- Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Vanessa Jabre
- Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Bensun C Fong
- Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Imane Chakroun
- Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Smitha Paul
- Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Jingwei Chen
- Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| | - Steven Wade
- Department of Biochemistry, Microbiology and Immunology, Center for Neuromuscular Disease (CNMD), Ottawa Institute of Systems Biology (OISB), Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Michel Kanaan
- Department of Biochemistry, Microbiology and Immunology, Ottawa Institute of Systems Biology (OISB), Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Mary-Ellen Harper
- Department of Biochemistry, Microbiology and Immunology, Ottawa Institute of Systems Biology (OISB), Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Mireille Khacho
- Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, Ontario, Canada
- Department of Biochemistry, Microbiology and Immunology, Center for Neuromuscular Disease (CNMD), Ottawa Institute of Systems Biology (OISB), Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada
| | - Ruth S Slack
- Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research Institute, University of Ottawa, Ottawa, Ontario, Canada
| |
Collapse
|
2
|
Sanidas I, Lawrence MS, Dyson NJ. Patterns in the tapestry of chromatin-bound RB. Trends Cell Biol 2024; 34:288-298. [PMID: 37648594 PMCID: PMC10899529 DOI: 10.1016/j.tcb.2023.07.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 07/27/2023] [Accepted: 07/28/2023] [Indexed: 09/01/2023]
Abstract
The retinoblastoma protein (RB)-mediated regulation of E2F is a component of a highly conserved cell cycle machine. However, RB's tumor suppressor activity, like RB's requirement in animal development, is tissue-specific, context-specific, and sometimes appears uncoupled from cell proliferation. Detailed new information about RB's genomic distribution provides a new perspective on the complexity of RB function, suggesting that some of its functional specificity results from context-specific RB association with chromatin. Here we summarize recent evidence showing that RB targets different types of chromatin regulatory elements at different cell cycle stages. RB controls traditional RB/E2F targets prior to S-phase, but, when cells proliferate, RB redistributes to cell type-specific chromatin loci. We discuss the broad implications of the new data for RB research.
Collapse
Affiliation(s)
- Ioannis Sanidas
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149, 13th Street, Charlestown, MA 02129, USA
| | - Michael S Lawrence
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149, 13th Street, Charlestown, MA 02129, USA; Broad Institute of MIT and Harvard, 415 Main Street, Cambridge, MA 02142, USA
| | - Nicholas J Dyson
- Massachusetts General Hospital Cancer Center and Harvard Medical School, Building 149, 13th Street, Charlestown, MA 02129, USA.
| |
Collapse
|
3
|
Liu Y, Bilen M, McNicoll MM, Harris RA, Fong BC, Iqbal MA, Paul S, Mayne J, Walker K, Wang J, Figeys D, Slack RS. Early postnatal defects in neurogenesis in the 3xTg mouse model of Alzheimer's disease. Cell Death Dis 2023; 14:138. [PMID: 36801910 PMCID: PMC9938901 DOI: 10.1038/s41419-023-05650-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 01/26/2023] [Accepted: 02/03/2023] [Indexed: 02/19/2023]
Abstract
Alzheimer's disease (AD) is a progressive neurodegenerative disorder leading to dementia. The hippocampus, which is one of the sites where neural stem cells reside and new neurons are born, exhibits the most significant neuronal loss in AD. A decline in adult neurogenesis has been described in several animal models of AD. However, the age at which this defect first appears remains unknown. To determine at which stage, from birth to adulthood, the neurogenic deficits are found in AD, we used the triple transgenic mouse model of AD (3xTg). We show that defects in neurogenesis are present as early as postnatal stages, well before the onset of any neuropathology or behavioral deficits. We also show that 3xTg mice have significantly fewer neural stem/progenitor cells, with reduced proliferation and decreased numbers of newborn neurons at postnatal stages, consistent with reduced volumes of hippocampal structures. To determine whether there are early changes in the molecular signatures of neural stem/progenitor cells, we perform bulk RNA-seq on cells sorted directly from the hippocampus. We show significant changes in the gene expression profiles at one month of age, including genes of the Notch and Wnt pathways. These findings reveal impairments in neurogenesis very early in the 3xTg AD model, which provides new opportunities for early diagnosis and therapeutic interventions to prevent neurodegeneration in AD.
Collapse
Affiliation(s)
- Yubing Liu
- grid.28046.380000 0001 2182 2255Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research institute, K1H 8M5 Ottawa, Canada
| | - Maria Bilen
- grid.28046.380000 0001 2182 2255Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research institute, K1H 8M5 Ottawa, Canada
| | - Marie-Michelle McNicoll
- grid.28046.380000 0001 2182 2255Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research institute, K1H 8M5 Ottawa, Canada
| | - Richard A. Harris
- grid.28046.380000 0001 2182 2255Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research institute, K1H 8M5 Ottawa, Canada
| | - Bensun C. Fong
- grid.28046.380000 0001 2182 2255Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research institute, K1H 8M5 Ottawa, Canada
| | - Mohamed Ariff Iqbal
- grid.28046.380000 0001 2182 2255Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research institute, K1H 8M5 Ottawa, Canada
| | - Smitha Paul
- grid.28046.380000 0001 2182 2255Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research institute, K1H 8M5 Ottawa, Canada
| | - Janice Mayne
- grid.28046.380000 0001 2182 2255Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, K1H 8M5 Ottawa, Canada
| | - Krystal Walker
- grid.28046.380000 0001 2182 2255Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, K1H 8M5 Ottawa, Canada
| | - Jing Wang
- grid.28046.380000 0001 2182 2255Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research institute, K1H 8M5 Ottawa, Canada ,grid.412687.e0000 0000 9606 5108Regenerative Medicine Program, Ottawa Hospital Research Institute, K1H 8L6 Ottawa, Canada
| | - Daniel Figeys
- grid.28046.380000 0001 2182 2255Ottawa Institute of Systems Biology and Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, K1H 8M5 Ottawa, Canada
| | - Ruth S. Slack
- grid.28046.380000 0001 2182 2255Department of Cellular and Molecular Medicine, University of Ottawa Brain and Mind Research institute, K1H 8M5 Ottawa, Canada
| |
Collapse
|
4
|
Gao M, Wang K, Zhao H. GABAergic neurons maturation is regulated by a delicate network. Int J Dev Neurosci 2023; 83:3-15. [PMID: 36401305 DOI: 10.1002/jdn.10242] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2022] [Revised: 10/25/2022] [Accepted: 11/13/2022] [Indexed: 11/21/2022] Open
Abstract
Gamma-aminobutyric acid-expressing (GABAergic) neurons are implicated in a variety of neuropsychiatric disorders, such as epilepsy, anxiety, autism, and other pathological processes, including cerebral ischemia injury and drug addiction. Therefore, GABAergic neuronal processes warrant further research. The development of GABAergic neurons is a tightly controlled process involving the activity of multiple transcription and growth factors. Here, we focus on the gene expression pathways and the molecular modulatory networks that are engaged during the development of GABAergic neurons with the goal of exploring regulatory mechanisms that influence GABAergic neuron fate (i.e., maturation). Overall, we hope to provide a basis for clarifying the pathogenesis of neurodegenerative disorders.
Collapse
Affiliation(s)
- Mingxing Gao
- Department of Histology and Embryology, School of Basic Medical Science, Jilin University, Changchun, Jilin, China
| | - Kaizhong Wang
- Department of Thoracic Surgery, The First Hospital of Jilin University, Changchun, Jilin, China
| | - Hui Zhao
- Department of Histology and Embryology, School of Basic Medical Science, Jilin University, Changchun, Jilin, China
| |
Collapse
|
5
|
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.
Collapse
Affiliation(s)
| | | | - Noël Ghanem
- Corresponding author. Department of Biology, American University of Beirut, PO Box 11-0236, Riad El Solh, 1107 2020, Beirut, Lebanon.
| |
Collapse
|
6
|
Fong BC, Chakroun I, Iqbal MA, Paul S, Bastasic J, O’Neil D, Yakubovich E, Bejjani AT, Ahmadi N, Carter A, Clark A, Leone G, Park DS, Ghanem N, Vandenbosch R, Slack RS. The Rb/E2F axis is a key regulator of the molecular signatures instructing the quiescent and activated adult neural stem cell state. Cell Rep 2022; 41:111578. [DOI: 10.1016/j.celrep.2022.111578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 08/11/2022] [Accepted: 10/07/2022] [Indexed: 11/06/2022] Open
|
7
|
Sanidas I, Lee H, Rumde PH, Boulay G, Morris R, Golczer G, Stanzione M, Hajizadeh S, Zhong J, Ryan MB, Corcoran RB, Drapkin BJ, Rivera MN, Dyson NJ, Lawrence MS. Chromatin-bound RB targets promoters, enhancers, and CTCF-bound loci and is redistributed by cell-cycle progression. Mol Cell 2022; 82:3333-3349.e9. [PMID: 35981542 PMCID: PMC9481721 DOI: 10.1016/j.molcel.2022.07.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 05/19/2022] [Accepted: 07/20/2022] [Indexed: 02/06/2023]
Abstract
The interaction of RB with chromatin is key to understanding its molecular functions. Here, for first time, we identify the full spectrum of chromatin-bound RB. Rather than exclusively binding promoters, as is often described, RB targets three fundamentally different types of loci (promoters, enhancers, and insulators), which are largely distinguishable by the mutually exclusive presence of E2F1, c-Jun, and CTCF. While E2F/DP facilitates RB association with promoters, AP-1 recruits RB to enhancers. Although phosphorylation in CDK sites is often portrayed as releasing RB from chromatin, we show that the cell cycle redistributes RB so that it enriches at promoters in G1 and at non-promoter sites in cycling cells. RB-bound promoters include the classic E2F-targets and are similar between lineages, but RB-bound enhancers associate with different categories of genes and vary between cell types. Thus, RB has a well-preserved role controlling E2F in G1, and it targets cell-type-specific enhancers and CTCF sites when cells enter S-phase.
Collapse
Affiliation(s)
- Ioannis Sanidas
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA
| | - Hanjun Lee
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA; Broad Institute of MIT and Harvard, 415 Main Street, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
| | - Purva H Rumde
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA
| | - Gaylor Boulay
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA; Broad Institute of MIT and Harvard, 415 Main Street, Cambridge, MA 02142, USA
| | - Robert Morris
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA
| | - Gabriel Golczer
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA
| | - Marcelo Stanzione
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA
| | - Soroush Hajizadeh
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA
| | - Jun Zhong
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA
| | - Meagan B Ryan
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA
| | - Ryan B Corcoran
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA
| | - Benjamin J Drapkin
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA; UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390, USA
| | - Miguel N Rivera
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA; Broad Institute of MIT and Harvard, 415 Main Street, Cambridge, MA 02142, USA
| | - Nicholas J Dyson
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA.
| | - Michael S Lawrence
- Massachusetts General Hospital Cancer Center, Harvard Medical School, Building 149 13th Street, Charlestown, MA 02129, USA; Broad Institute of MIT and Harvard, 415 Main Street, Cambridge, MA 02142, USA.
| |
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
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.
Collapse
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.
| |
Collapse
|
10
|
Omais S, Halaby NN, Habashy KJ, Jaafar C, Bejjani AT, Ghanem N. Histological Assessment of Cre-loxP Genetic Recombination in the Aging Subventricular Zone of Nestin-CreER T2/Rosa26YFP Mice. Methods Mol Biol 2020; 2045:187-199. [PMID: 30888667 DOI: 10.1007/7651_2019_214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The use of inducible transgenic Nestin-CreERT2 mice has proved to be an essential research tool for gene targeting and studying the molecular pathways implicated in adult neurogenesis, namely, inside the adult subgranular zone (SGZ) of the dentate gyrus and the adult subventricular zone (SVZ) lining the lateral ventricles. Several lines of Nestin-CreER-expressing mice were generated and used in adult neurogenesis research in the past two decades; however, their suitability for studying neurogenesis in aged mice remains elusive. Here, we assessed the efficiency of Cre-loxP genetic recombination in the aging SVZ using the Nestin-CreERT2/Rosa26YFP line designed by Lagace et al. (J Neurosci 27(46):12623-12629, 2007). This analysis was performed in 12-month-old (middle-aged) mice and 20-month-old (old) mice compared to 2-month-old (young adult) mice. To evaluate successful recombination, our approach relies on the histological assessment of Cre mRNA level of expression and the YFP reporter gene's expression inside the aging SVZ by combining in situ hybridization and immunohistochemistry. Using co-immunolabeling, this approach also provides the advantage of estimating the percentage of recombined progeny [(GFP+Nestin+)/Nestin+] and the rate of cell proliferation [(GFP+Ki67+)/GFP+] inside the aging SVZ niche.
Collapse
Affiliation(s)
- Saad Omais
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Nour N Halaby
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Karl John Habashy
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Carine Jaafar
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Anthony T Bejjani
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Noël Ghanem
- Department of Biology, American University of Beirut, Beirut, Lebanon.
| |
Collapse
|
11
|
Cho IJ, Lui PP, Obajdin J, Riccio F, Stroukov W, Willis TL, Spagnoli F, Watt FM. Mechanisms, Hallmarks, and Implications of Stem Cell Quiescence. Stem Cell Reports 2019; 12:1190-1200. [PMID: 31189093 PMCID: PMC6565921 DOI: 10.1016/j.stemcr.2019.05.012] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 05/14/2019] [Accepted: 05/14/2019] [Indexed: 02/08/2023] Open
Abstract
Cellular quiescence is a dormant but reversible cellular state in which cell-cycle entry and proliferation are prevented. Recent studies both in vivo and in vitro demonstrate that quiescence is actively maintained through synergistic interactions between intrinsic and extrinsic signals. Subtypes of adult mammalian stem cells can be maintained in this poised, quiescent state, and subsequently reactivated upon tissue injury to restore homeostasis. However, quiescence can become deregulated in pathological settings. In this review, we discuss the recent advances uncovering intracellular signaling pathways, transcriptional changes, and extracellular cues within the stem cell niche that control induction and exit from quiescence in tissue stem cells. We discuss the implications of quiescence as well as the pharmacological and genetic approaches that are being explored to either induce or prevent quiescence as a therapeutic strategy.
Collapse
Affiliation(s)
- Inchul J Cho
- Centre for Stem Cells and Regenerative Medicine, King's College London, Guy's Hospital, Floor 28, Tower Wing, Great Maze Pond, London SE1 9RT, UK
| | - Prudence PokWai Lui
- Centre for Stem Cells and Regenerative Medicine, King's College London, Guy's Hospital, Floor 28, Tower Wing, Great Maze Pond, London SE1 9RT, UK
| | - Jana Obajdin
- Centre for Stem Cells and Regenerative Medicine, King's College London, Guy's Hospital, Floor 28, Tower Wing, Great Maze Pond, London SE1 9RT, UK
| | - Federica Riccio
- Centre for Stem Cells and Regenerative Medicine, King's College London, Guy's Hospital, Floor 28, Tower Wing, Great Maze Pond, London SE1 9RT, UK
| | - Wladislaw Stroukov
- Centre for Stem Cells and Regenerative Medicine, King's College London, Guy's Hospital, Floor 28, Tower Wing, Great Maze Pond, London SE1 9RT, UK
| | - Thea Louise Willis
- Centre for Stem Cells and Regenerative Medicine, King's College London, Guy's Hospital, Floor 28, Tower Wing, Great Maze Pond, London SE1 9RT, UK
| | - Francesca Spagnoli
- Centre for Stem Cells and Regenerative Medicine, King's College London, Guy's Hospital, Floor 28, Tower Wing, Great Maze Pond, London SE1 9RT, UK
| | - Fiona M Watt
- Centre for Stem Cells and Regenerative Medicine, King's College London, Guy's Hospital, Floor 28, Tower Wing, Great Maze Pond, London SE1 9RT, UK.
| |
Collapse
|
12
|
Urbach A, Witte OW. Divide or Commit - Revisiting the Role of Cell Cycle Regulators in Adult Hippocampal Neurogenesis. Front Cell Dev Biol 2019; 7:55. [PMID: 31069222 PMCID: PMC6491688 DOI: 10.3389/fcell.2019.00055] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Accepted: 03/28/2019] [Indexed: 12/21/2022] Open
Abstract
The adult dentate gyrus continuously generates new neurons that endow the brain with increased plasticity, helping to cope with changing environmental and cognitive demands. The process leading to the birth of new neurons spans several precursor stages and is the result of a coordinated series of fate decisions, which are tightly controlled by extrinsic signals. Many of these signals act through modulation of cell cycle (CC) components, not only to drive proliferation, but also for linage commitment and differentiation. In this review, we provide a comprehensive overview on key CC components and regulators, with emphasis on G1 phase, and analyze their specific functions in precursor cells of the adult hippocampus. We explore their role for balancing quiescence versus self-renewal, which is essential to maintain a lifelong pool of neural stem cells while producing new neurons “on demand.” Finally, we discuss available evidence and controversies on the impact of CC/G1 length on proliferation versus differentiation decisions.
Collapse
Affiliation(s)
- Anja Urbach
- Hans Berger Department of Neurology, Jena University Hospital, Jena, Germany
| | - Otto W Witte
- Hans Berger Department of Neurology, Jena University Hospital, Jena, Germany
| |
Collapse
|
13
|
Zibara K, Ballout N, Mondello S, Karnib N, Ramadan N, Omais S, Nabbouh A, Caliz D, Clavijo A, Hu Z, Ghanem N, Gajavelli S, Kobeissy F. Combination of drug and stem cells neurotherapy: Potential interventions in neurotrauma and traumatic brain injury. Neuropharmacology 2018; 145:177-198. [PMID: 30267729 DOI: 10.1016/j.neuropharm.2018.09.032] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 09/17/2018] [Accepted: 09/21/2018] [Indexed: 12/12/2022]
Abstract
Traumatic brain injury (TBI) has been recognized as one of the major public health issues that leads to devastating neurological disability. As a consequence of primary and secondary injury phases, neuronal loss following brain trauma leads to pathophysiological alterations on the molecular and cellular levels that severely impact the neuropsycho-behavioral and motor outcomes. Thus, to mitigate the neuropathological sequelae post-TBI such as cerebral edema, inflammation and neural degeneration, several neurotherapeutic options have been investigated including drug intervention, stem cell use and combinational therapies. These treatments aim to ameliorate cellular degeneration, motor decline, cognitive and behavioral deficits. Recently, the use of neural stem cells (NSCs) coupled with selective drug therapy has emerged as an alternative treatment option for neural regeneration and behavioral rehabilitation post-neural injury. Given their neuroprotective abilities, NSC-based neurotherapy has been widely investigated and well-reported in numerous disease models, notably in trauma studies. In this review, we will elaborate on current updates in cell replacement therapy in the area of neurotrauma. In addition, we will discuss novel combination drug therapy treatments that have been investigated in conjunction with stem cells to overcome the limitations associated with stem cell transplantation. Understanding the regenerative capacities of stem cell and drug combination therapy will help improve functional recovery and brain repair post-TBI. This article is part of the Special Issue entitled "Novel Treatments for Traumatic Brain Injury".
Collapse
Affiliation(s)
- Kazem Zibara
- ER045, Laboratory of Stem Cells, PRASE, Lebanese University, Beirut, Lebanon; Biology Department, Faculty of Sciences-I, Lebanese University, Beirut, Lebanon
| | - Nissrine Ballout
- ER045, Laboratory of Stem Cells, PRASE, Lebanese University, Beirut, Lebanon
| | - Stefania Mondello
- Department of Biomedical and Dental Sciences and Morphofunctional Imaging, University of Messina, Messina, Italy
| | - Nabil Karnib
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Lebanon
| | - Naify Ramadan
- Department of Women's and Children's Health (KBH), Division of Clinical Pediatrics, Karolinska Institute, Sweden
| | - Saad Omais
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Ali Nabbouh
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Lebanon
| | - Daniela Caliz
- Lois Pope LIFE Center, Neurosurgery, University of Miami, 33136, Miami, FL, USA
| | - Angelica Clavijo
- Lois Pope LIFE Center, Neurosurgery, University of Miami, 33136, Miami, FL, USA
| | - Zhen Hu
- Lois Pope LIFE Center, Neurosurgery, University of Miami, 33136, Miami, FL, USA
| | - Noël Ghanem
- Department of Biology, American University of Beirut, Beirut, Lebanon
| | - Shyam Gajavelli
- Lois Pope LIFE Center, Neurosurgery, University of Miami, 33136, Miami, FL, USA.
| | - Firas Kobeissy
- Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, Lebanon; Program for Neurotrauma, Neuroproteomics & Biomarkers Research, Department of Emergency Medicine, University of Florida, Gainesville, FL, 32611, USA.
| |
Collapse
|
14
|
Schultz LE, Haltom JA, Almeida MP, Wierson WA, Solin SL, Weiss TJ, Helmer JA, Sandquist EJ, Shive HR, McGrail M. Epigenetic regulators Rbbp4 and Hdac1 are overexpressed in a zebrafish model of RB1 embryonal brain tumor, and are required for neural progenitor survival and proliferation. Dis Model Mech 2018; 11:11/6/dmm034124. [PMID: 29914980 PMCID: PMC6031359 DOI: 10.1242/dmm.034124] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Accepted: 05/03/2018] [Indexed: 12/11/2022] Open
Abstract
In this study, we used comparative genomics and developmental genetics to identify epigenetic regulators driving oncogenesis in a zebrafish retinoblastoma 1 (rb1) somatic-targeting model of RB1 mutant embryonal brain tumors. Zebrafish rb1 brain tumors caused by TALEN or CRISPR targeting are histologically similar to human central nervous system primitive neuroectodermal tumors (CNS-PNETs). Like the human oligoneural OLIG2+/SOX10+ CNS-PNET subtype, zebrafish rb1 tumors show elevated expression of neural progenitor transcription factors olig2, sox10, sox8b and the receptor tyrosine kinase erbb3a oncogene. Comparison of rb1 tumor and rb1/rb1 germline mutant larval transcriptomes shows that the altered oligoneural precursor signature is specific to tumor tissue. More than 170 chromatin regulators were differentially expressed in rb1 tumors, including overexpression of chromatin remodeler components histone deacetylase 1 (hdac1) and retinoblastoma binding protein 4 (rbbp4). Germline mutant analysis confirms that zebrafish rb1, rbbp4 and hdac1 are required during brain development. rb1 is necessary for neural precursor cell cycle exit and terminal differentiation, rbbp4 is required for survival of postmitotic precursors, and hdac1 maintains proliferation of the neural stem cell/progenitor pool. We present an in vivo assay using somatic CRISPR targeting plus live imaging of histone-H2A.F/Z-GFP fusion protein in developing larval brain to rapidly test the role of chromatin remodelers in neural stem and progenitor cells. Our somatic assay recapitulates germline mutant phenotypes and reveals a dynamic view of their roles in neural cell populations. Our study provides new insight into the epigenetic processes that might drive pathogenesis in RB1 brain tumors, and identifies Rbbp4 and its associated chromatin remodeling complexes as potential target pathways to induce apoptosis in RB1 mutant brain cancer cells. This article has an associated First Person interview with the first author of the paper. Summary: This study shows that chromatin remodelers that are overexpressed in a zebrafish model of RB1 mutant brain cancer are required for neural progenitor proliferation and survival, providing insight into potential mechanisms that drive tumor growth.
Collapse
Affiliation(s)
- Laura E Schultz
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
| | - Jeffrey A Haltom
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
| | - Maira P Almeida
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
| | - Wesley A Wierson
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
| | - Staci L Solin
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
| | - Trevor J Weiss
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
| | - Jordan A Helmer
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
| | - Elizabeth J Sandquist
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
| | - Heather R Shive
- Department of Population Health and Pathobiology, North Carolina State University, Raleigh, NC 27607, USA
| | - Maura McGrail
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA
| |
Collapse
|
15
|
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.
Collapse
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
| |
Collapse
|
16
|
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.
Collapse
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
| |
Collapse
|
17
|
Matsui T, Nieto-Estévez V, Kyrychenko S, Schneider JW, Hsieh J. Retinoblastoma protein controls growth, survival and neuronal migration in human cerebral organoids. Development 2017; 144:1025-1034. [PMID: 28087635 DOI: 10.1242/dev.143636] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Accepted: 12/16/2016] [Indexed: 01/22/2023]
Abstract
The tumor suppressor retinoblastoma protein (RB) regulates S-phase cell cycle entry via E2F transcription factors. Knockout (KO) mice have shown that RB plays roles in cell migration, differentiation and apoptosis, in developing and adult brain. In addition, the RB family is required for self-renewal and survival of human embryonic stem cells (hESCs). Since little is known about the role of RB in human brain development, we investigated its function in cerebral organoids differentiated from gene-edited hESCs lacking RB. We show that RB is abundantly expressed in neural stem and progenitor cells in organoids at 15 and 28 days of culture. RB loss promoted S-phase entry in DCX+ cells and increased apoptosis in Sox2+ neural stem and progenitor cells, and in DCX+ and Tuj1+ neurons. Associated with these cell cycle and pro-apoptotic effects, we observed increased CCNA2 and BAX gene expression, respectively. Moreover, we observed aberrant Tuj1+ neuronal migration in RB-KO organoids and upregulation of the gene encoding VLDLR, a receptor important in reelin signaling. Corroborating the results in RB-KO organoids in vitro, we observed ectopically localized Tuj1+ cells in RB-KO teratomas grown in vivo Taken together, these results identify crucial functions for RB in the cerebral organoid model of human brain development.
Collapse
Affiliation(s)
- Takeshi Matsui
- Department of Molecular Biology and Hamon Center for Regenerative Science and Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Vanesa Nieto-Estévez
- Department of Molecular Biology and Hamon Center for Regenerative Science and Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Sergii Kyrychenko
- Department of Internal Medicine and Hamon Center for Regenerative Science and Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jay W Schneider
- Department of Internal Medicine and Hamon Center for Regenerative Science and Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
| | - Jenny Hsieh
- Department of Molecular Biology and Hamon Center for Regenerative Science and Medicine, UT Southwestern Medical Center, Dallas, TX 75390, USA
| |
Collapse
|
18
|
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.
Collapse
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
| |
Collapse
|