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Ma Q, Chen G, Li Y, Guo Z, Zhang X. The molecular genetics of PI3K/PTEN/AKT/mTOR pathway in the malformations of cortical development. Genes Dis 2024; 11:101021. [PMID: 39006182 PMCID: PMC11245990 DOI: 10.1016/j.gendis.2023.04.041] [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: 12/07/2022] [Revised: 04/07/2023] [Accepted: 04/30/2023] [Indexed: 07/16/2024] Open
Abstract
Malformations of cortical development (MCD) are a group of developmental disorders characterized by abnormal cortical structures caused by genetic or harmful environmental factors. Many kinds of MCD are caused by genetic variation. MCD is the common cause of intellectual disability and intractable epilepsy. With rapid advances in imaging and sequencing technologies, the diagnostic rate of MCD has been increasing, and many potential genes causing MCD have been successively identified. However, the high genetic heterogeneity of MCD makes it challenging to understand the molecular pathogenesis of MCD and to identify effective targeted drugs. Thus, in this review, we outline important events of cortical development. Then we illustrate the progress of molecular genetic studies about MCD focusing on the PI3K/PTEN/AKT/mTOR pathway. Finally, we briefly discuss the diagnostic methods, disease models, and therapeutic strategies for MCD. The information will facilitate further research on MCD. Understanding the role of the PI3K/PTEN/AKT/mTOR pathway in MCD could lead to a novel strategy for treating MCD-related diseases.
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Affiliation(s)
- Qing Ma
- NHC and CAMS Key Laboratory of Molecular Probe and Targeted Theranostics, Harbin Medical University, Harbin, Heilongjiang 150000, China
| | - Guang Chen
- Department of Urology, The Fourth Hospital of Harbin Medical University, Harbin, Heilongjiang 150000, China
| | - Ying Li
- NHC and CAMS Key Laboratory of Molecular Probe and Targeted Theranostics, Harbin Medical University, Harbin, Heilongjiang 150000, China
- Department of Child and Adolescent Health, School of Public Health, Harbin Medical University, Harbin, Heilongjiang 150000, China
| | - Zhenming Guo
- Institute for Regenerative Medicine, Shanghai East Hospital, Frontier Science Center for Stem Cell Research, School of Life Sciences and Technology, Tongji University, Shanghai 200120, China
| | - Xue Zhang
- NHC and CAMS Key Laboratory of Molecular Probe and Targeted Theranostics, Harbin Medical University, Harbin, Heilongjiang 150000, China
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Qiao E, Fulmore CA, Schaffer DV, Kumar S. Substrate stress relaxation regulates neural stem cell fate commitment. Proc Natl Acad Sci U S A 2024; 121:e2317711121. [PMID: 38968101 PMCID: PMC11252819 DOI: 10.1073/pnas.2317711121] [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: 10/12/2023] [Accepted: 05/17/2024] [Indexed: 07/07/2024] Open
Abstract
Adult neural stem cells (NSCs) reside in the dentate gyrus of the hippocampus, and their capacity to generate neurons and glia plays a role in learning and memory. In addition, neurodegenerative diseases are known to be caused by a loss of neurons and glial cells, resulting in a need to better understand stem cell fate commitment processes. We previously showed that NSC fate commitment toward a neuronal or glial lineage is strongly influenced by extracellular matrix stiffness, a property of elastic materials. However, tissues in vivo are not purely elastic and have varying degrees of viscous character. Relatively little is known about how the viscoelastic properties of the substrate impact NSC fate commitment. Here, we introduce a polyacrylamide-based cell culture platform that incorporates mismatched DNA oligonucleotide-based cross-links as well as covalent cross-links. This platform allows for tunable viscous stress relaxation properties via variation in the number of mismatched base pairs. We find that NSCs exhibit increased astrocytic differentiation as the degree of stress relaxation is increased. Furthermore, culturing NSCs on increasingly stress-relaxing substrates impacts cytoskeletal dynamics by decreasing intracellular actin flow rates and stimulating cyclic activation of the mechanosensitive protein RhoA. Additionally, inhibition of motor-clutch model components such as myosin II and focal adhesion kinase partially or completely reverts cells to lineage distributions observed on elastic substrates. Collectively, our results introduce a unique system for controlling matrix stress relaxation properties and offer insight into how NSCs integrate viscoelastic cues to direct fate commitment.
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Affiliation(s)
- Eric Qiao
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA94720
| | - Camille A. Fulmore
- Department of Molecular and Cell Biology, University of California, Berkeley, CA94720
| | - David V. Schaffer
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA94720
- Department of Molecular and Cell Biology, University of California, Berkeley, CA94720
- Department of Bioengineering, University of California, Berkeley, CA94720
| | - Sanjay Kumar
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA94720
- Department of Bioengineering, University of California, Berkeley, CA94720
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA94143
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3
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Ochi S, Manabe S, Kikkawa T, Ebrahimiazar S, Kimura R, Yoshizaki K, Osumi N. A Transcriptomic Dataset of Embryonic Murine Telencephalon. Sci Data 2024; 11:586. [PMID: 38839806 PMCID: PMC11153524 DOI: 10.1038/s41597-024-03421-x] [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: 09/28/2023] [Accepted: 05/24/2024] [Indexed: 06/07/2024] Open
Abstract
Sex bias is known in the prevalence/pathology of neurodevelopmental disorders. Sex-dependent differences of the certain brain areas are known to emerge perinatally through the exposure to sex hormones, while gene expression patterns in the rodent embryonic brain does not seem to be completely the same between male and female. To investigate potential sex differences in gene expression and cortical organization during the embryonic period in mice, we conducted a comprehensive analysis of gene expression for the telencephalon at embryonic day (E) 11.5 (a peak of neural stem cell expansion) and E14.5 (a peak of neurogenesis) using bulk RNA-seq data. As a result, our data showed the existence of notable sex differences in gene expression patterns not obviously at E11.5, but clearly at E14.5 when neurogenesis has become its peak. These data can be useful for exploring potential contribution of genes exhibiting sex differences to the divergence in brain development. Additionally, our data underscore the significance of studying the embryonic period to gain a deeper understanding of sex differences in brain development.
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Affiliation(s)
- Shohei Ochi
- Department of Developmental Neuroscience, Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan
| | - Shyu Manabe
- Department of Developmental Neuroscience, Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan
| | - Takako Kikkawa
- Department of Developmental Neuroscience, Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan
| | - Sara Ebrahimiazar
- Department of Developmental Neuroscience, Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan
| | - Ryuichi Kimura
- Department of Developmental Neuroscience, Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan
- Institute of Resource Development and Analysis, Kumamoto University, Kumamoto, 860-0811, Japan
| | - Kaichi Yoshizaki
- Department of Developmental Neuroscience, Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan
- Kobe University Graduate School of Medicine, Department of Future Medical Sciences, Division of Integrated Analysis of Bioresource and Health Care, Kobe, 650-0047, Japan
- Kobe University Hospital, Bioresource Center, Kobe, 650-0047, Japan
| | - Noriko Osumi
- Department of Developmental Neuroscience, Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan.
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4
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Xiang X, Jiang X, Lu X. Regulation of neural stem cell self-renewal, proliferation and differentiation by the RhoA guanine nucleotide exchange factor Arhgef 1. Gene 2023; 863:147306. [PMID: 36813057 DOI: 10.1016/j.gene.2023.147306] [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: 12/11/2022] [Revised: 02/01/2023] [Accepted: 02/17/2023] [Indexed: 02/22/2023]
Abstract
The role of the Arhgef1 as a RhoA-specific guanine nucleotide exchange factor has been widely investigated in the immune system. Our previous findings reveal that Arhgef 1 is highly expressed in neural stem cells (NSCs) and controls the process of neurite formation. However, the functional role of Arhgef 1 in NSCs remains poorly understood. In order to investigate the role of Arhgef 1 in NSCs, Arhgef 1 expression in NSCs was reduced by using lentivirus-mediated short hairpin RNA interference. Our results indicate that down-regulated expression of Arhgef 1 reduced the self-renewal, proliferation capacity of NSCs and affect cell fate determination. In addition, the comparative transcriptome analysis from RNA-seq data determines the mechanisms of deficits in Arhgef 1 knockdown NSCs. Altogether, our present studies show that Arhgef 1 down-regulation leads to interruption of the cell cycle procession. The importance of Arhgef 1 for regulating self-renewal, proliferation and differentiation in NSCs is reported for the first time.
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Affiliation(s)
- Xiaoliang Xiang
- Key Laboratory of Research and Utilization of Ethnomedicinal Plant Resources of Hunan Province,College of Biological and Food Engineering, Huaihua University, Huaihua 418008, China.
| | - Xia Jiang
- Key Laboratory of Research and Utilization of Ethnomedicinal Plant Resources of Hunan Province,College of Biological and Food Engineering, Huaihua University, Huaihua 418008, China
| | - Xiaomin Lu
- Department of Pathology, Hunan University of Medicine Huaihua, Hunan 418000, China
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Ochi S, Manabe S, Kikkawa T, Osumi N. Thirty Years' History since the Discovery of Pax6: From Central Nervous System Development to Neurodevelopmental Disorders. Int J Mol Sci 2022; 23:6115. [PMID: 35682795 PMCID: PMC9181425 DOI: 10.3390/ijms23116115] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 05/19/2022] [Accepted: 05/27/2022] [Indexed: 12/23/2022] Open
Abstract
Pax6 is a sequence-specific DNA binding transcription factor that positively and negatively regulates transcription and is expressed in multiple cell types in the developing and adult central nervous system (CNS). As indicated by the morphological and functional abnormalities in spontaneous Pax6 mutant rodents, Pax6 plays pivotal roles in various biological processes in the CNS. At the initial stage of CNS development, Pax6 is responsible for brain patterning along the anteroposterior and dorsoventral axes of the telencephalon. Regarding the anteroposterior axis, Pax6 is expressed inversely to Emx2 and Coup-TF1, and Pax6 mutant mice exhibit a rostral shift, resulting in an alteration of the size of certain cortical areas. Pax6 and its downstream genes play important roles in balancing the proliferation and differentiation of neural stem cells. The Pax6 gene was originally identified in mice and humans 30 years ago via genetic analyses of the eye phenotypes. The human PAX6 gene was discovered in patients who suffer from WAGR syndrome (i.e., Wilms tumor, aniridia, genital ridge defects, mental retardation). Mutations of the human PAX6 gene have also been reported to be associated with autism spectrum disorder (ASD) and intellectual disability. Rodents that lack the Pax6 gene exhibit diverse neural phenotypes, which might lead to a better understanding of human pathology and neurodevelopmental disorders. This review describes the expression and function of Pax6 during brain development, and their implications for neuropathology.
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Affiliation(s)
| | | | | | - Noriko Osumi
- Department of Developmental Neuroscience, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan; (S.O.); (S.M.); (T.K.)
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Kikkawa T, Osumi N. Multiple Functions of the Dmrt Genes in the Development of the Central Nervous System. Front Neurosci 2021; 15:789583. [PMID: 34955736 PMCID: PMC8695973 DOI: 10.3389/fnins.2021.789583] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 11/22/2021] [Indexed: 12/26/2022] Open
Abstract
The Dmrt genes encode the transcription factor containing the DM (doublesex and mab-3) domain, an intertwined zinc finger-like DNA binding module. While Dmrt genes are mainly involved in the sexual development of various species, recent studies have revealed that Dmrt genes, which belong to the DmrtA subfamily, are differentially expressed in the embryonic brain and spinal cord and are essential for the development of the central nervous system. Herein, we summarize recent studies that reveal the multiple functions of the Dmrt genes in various aspects of vertebrate neural development, including brain patterning, neurogenesis, and the specification of neurons.
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Affiliation(s)
- Takako Kikkawa
- Department of Developmental Neuroscience, United Centers for Advanced Research and Translational Medicine (ART), Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Noriko Osumi
- Department of Developmental Neuroscience, United Centers for Advanced Research and Translational Medicine (ART), Tohoku University Graduate School of Medicine, Sendai, Japan
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Teplyashina EA, Komleva YK, Lychkovskaya EV, Deikhina AS, Salmina AB. Regulation of neurogenesis and cerebral angiogenesis by cell protein proteolysis products. RUDN JOURNAL OF MEDICINE 2021. [DOI: 10.22363/2313-0245-2021-25-2-114-126] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Brain development is a unique process characterized by mechanisms defined as neuroplasticity (synaptogenesis, synapse elimination, neurogenesis, and cerebral angiogenesis). Numerous neurodevelopmental disorders brain damage, and aging are manifested by neurological deficits that are caused by aberrant neuroplasticity. The presence of stem and progenitor cells in neurogenic niches of the brain is responsible for the formation of new neurons capable of integrating into preexisting synaptic assemblies. The determining factors for the cells within the neurogenic niche are the activity of the vascular scaffold and the availability of active regulatory molecules that establish the optimal microenvironment. It has been found that regulated intramembrane proteolysis plays an important role in the control of neurogenesis in brain neurogenic niches. Molecules generated by the activity of specific proteases can stimulate or suppress the activity of neural stem and progenitor cells, their proliferation and differentiation, migration and integration of newly formed neurons into synaptic networks. Local neoangiogenesis supports the processes of neurogenesis in neurogenic niches, which is guaranteed by the multivalent action of peptides formed from transmembrane proteins. Identification of new molecules regulating the neuroplasticity (neurogenesis and angiogenesis). i. e. enzymes, substrates, and products of intramembrane proteolysis, will ensure the development of protocols for detecting the neuroplasticity markers and targets for efficient pharmacological modulation.
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Rajan A, Ostgaard CM, Lee CY. Regulation of Neural Stem Cell Competency and Commitment during Indirect Neurogenesis. Int J Mol Sci 2021; 22:12871. [PMID: 34884676 PMCID: PMC8657492 DOI: 10.3390/ijms222312871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2021] [Revised: 11/24/2021] [Accepted: 11/24/2021] [Indexed: 11/29/2022] Open
Abstract
Indirect neurogenesis, during which neural stem cells generate neurons through intermediate progenitors, drives the evolution of lissencephalic brains to gyrencephalic brains. The mechanisms that specify intermediate progenitor identity and that regulate stem cell competency to generate intermediate progenitors remain poorly understood despite their roles in indirect neurogenesis. Well-characterized lineage hierarchy and available powerful genetic tools for manipulating gene functions make fruit fly neural stem cell (neuroblast) lineages an excellent in vivo paradigm for investigating the mechanisms that regulate neurogenesis. Type II neuroblasts in fly larval brains repeatedly undergo asymmetric divisions to generate intermediate neural progenitors (INPs) that undergo limited proliferation to increase the number of neurons generated per stem cell division. Here, we review key regulatory genes and the mechanisms by which they promote the specification and generation of INPs, safeguarding the indirect generation of neurons during fly larval brain neurogenesis. Homologs of these regulators of INPs have been shown to play important roles in regulating brain development in vertebrates. Insight into the precise regulation of intermediate progenitors will likely improve our understanding of the control of indirect neurogenesis during brain development and brain evolution.
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Affiliation(s)
- Arjun Rajan
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA; (A.R.); (C.M.O.)
| | - Cyrina M. Ostgaard
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA; (A.R.); (C.M.O.)
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
| | - Cheng-Yu Lee
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA; (A.R.); (C.M.O.)
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI 48109, USA
- Division of Genetic Medicine, Department of Internal Medicine and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109, USA
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9
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Janssen R, Budd GE. Oscillating waves of Fox, Cyclin and CDK gene expression indicate unique spatiotemporal control of cell cycling during nervous system development in onychophorans. ARTHROPOD STRUCTURE & DEVELOPMENT 2021; 62:101042. [PMID: 33752095 DOI: 10.1016/j.asd.2021.101042] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Revised: 02/04/2021] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
Forkhead box (Fox) genes code for a class of transcription factors with many different fundamental functions in animal development including cell cycle control. Other important factors of cell cycle control are Cyclins and Cyclin-dependent kinases (CDKs). Here we report on the oscillating expression of three Fox genes, FoxM, FoxN14 (jumeaux) and FoxN23 (Checkpoint suppressor like-1), Cyclins and CDKs in an onychophoran, a representative of a relatively small group of animals that are closely related to the arthropods. Expression of these genes is in the form of several waves that start as dot-like domains in the center of each segment and then transform into concentric rings that run towards the periphery of the segments. This oscillating gene expression, however, occurs exclusively along the anterior-posterior body axis in the tissue ventral to the base of the appendages, a region where the central nervous system and the enigmatic ventral and preventral organs of the onychophoran develop. We suggest that the oscillating gene expression and the resulting waves of expression we report are likely correlated with cell cycle control during the development of the onychophoran nervous system. This intriguing patterning appears to be unique for onychophorans as it is not found in any of the arthropods we also investigated in this study, and is likely correlated with the slow embryonic development of onychophorans compared to arthropods.
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Affiliation(s)
- Ralf Janssen
- Uppsala University, Department of Earth Sciences, Palaeobiology, Villavägen 16, 75236 Uppsala, Sweden.
| | - Graham E Budd
- Uppsala University, Department of Earth Sciences, Palaeobiology, Villavägen 16, 75236 Uppsala, Sweden
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Wang J, Hu J, Chen X, Lei X, Feng H, Wan F, Tan L. Traditional Chinese Medicine Monomers: Novel Strategy for Endogenous Neural Stem Cells Activation After Stroke. Front Cell Neurosci 2021; 15:628115. [PMID: 33716673 PMCID: PMC7952516 DOI: 10.3389/fncel.2021.628115] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 01/19/2021] [Indexed: 01/01/2023] Open
Abstract
Stem cell therapy, which has become a potential regenerative medical treatment and a promising approach for treating brain injuries induced by different types of cerebrovascular disease, has various application methods. Activation of endogenous neural stem cells (NSCs) can enable infarcted neuron replacement and promote neural networks’ regeneration without the technical and ethical issues associated with the transplantation of exogenous stem cells. Thus, NSC activation can be a feasible strategy to treat central nervous system (CNS) injury. The potential molecular mechanisms of drug therapy for the activation of endogenous NSCs have gradually been revealed by researchers. Traditional Chinese medicine monomers (TCMs) are active components extracted from Chinese herbs, and some of them have demonstrated the potential to activate proliferation and neurogenesis of NSCs in CNS diseases. Ginsenoside Rg1, astragaloside IV (AST), icariin (ICA), salvianolic acid B (Sal B), resveratrol (RES), curcumin, artesunate (ART), and ginkgolide B (GB) have positive effects on NSCs via different signaling pathways and molecules, such as the Wingless/integrated/β-catenin (Wnt/β-catenin) signaling pathway, the sonic hedgehog (Shh) signaling pathway, brain-derived neurotrophic factor (BDNF), nuclear factor erythroid 2-related factor 2 (Nrf2), and heme oxygenase 1 (HO-1). This article may provide further motivation for researchers to take advantage of TCMs in studies on CNS injury and stem cell therapy.
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Affiliation(s)
- Ju Wang
- Department of Neurosurgery and Key Laboratory of Neurotrauma, Southwest Hospital, Third Military Medical University (Army Military Medical University), Chongqing, China
| | - Jun Hu
- Department of Neurology, Southwest Hospital, Third Military Medical University (Army Military Medical University), Chongqing, China
| | - Xuezhu Chen
- Department of Neurosurgery and Key Laboratory of Neurotrauma, Southwest Hospital, Third Military Medical University (Army Military Medical University), Chongqing, China
| | - Xuejiao Lei
- Department of Neurosurgery and Key Laboratory of Neurotrauma, Southwest Hospital, Third Military Medical University (Army Military Medical University), Chongqing, China
| | - Hua Feng
- Department of Neurosurgery and Key Laboratory of Neurotrauma, Southwest Hospital, Third Military Medical University (Army Military Medical University), Chongqing, China
| | - Feng Wan
- Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macau, China
| | - Liang Tan
- Department of Neurosurgery and Key Laboratory of Neurotrauma, Southwest Hospital, Third Military Medical University (Army Military Medical University), Chongqing, China.,Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macau, China
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11
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Oproescu AM, Han S, Schuurmans C. New Insights Into the Intricacies of Proneural Gene Regulation in the Embryonic and Adult Cerebral Cortex. Front Mol Neurosci 2021; 14:642016. [PMID: 33658912 PMCID: PMC7917194 DOI: 10.3389/fnmol.2021.642016] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 01/26/2021] [Indexed: 12/21/2022] Open
Abstract
Historically, the mammalian brain was thought to lack stem cells as no new neurons were found to be made in adulthood. That dogma changed ∼25 years ago with the identification of neural stem cells (NSCs) in the adult rodent forebrain. However, unlike rapidly self-renewing mature tissues (e.g., blood, intestinal crypts, skin), the majority of adult NSCs are quiescent, and those that become 'activated' are restricted to a few neurogenic zones that repopulate specific brain regions. Conversely, embryonic NSCs are actively proliferating and neurogenic. Investigations into the molecular control of the quiescence-to-proliferation-to-differentiation continuum in the embryonic and adult brain have identified proneural genes encoding basic-helix-loop-helix (bHLH) transcription factors (TFs) as critical regulators. These bHLH TFs initiate genetic programs that remove NSCs from quiescence and drive daughter neural progenitor cells (NPCs) to differentiate into specific neural cell subtypes, thereby contributing to the enormous cellular diversity of the adult brain. However, new insights have revealed that proneural gene activities are context-dependent and tightly regulated. Here we review how proneural bHLH TFs are regulated, with a focus on the murine cerebral cortex, drawing parallels where appropriate to other organisms and neural tissues. We discuss upstream regulatory events, post-translational modifications (phosphorylation, ubiquitinylation), protein-protein interactions, epigenetic and metabolic mechanisms that govern bHLH TF expression, stability, localization, and consequent transactivation of downstream target genes. These tight regulatory controls help to explain paradoxical findings of changes to bHLH activity in different cellular contexts.
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Affiliation(s)
- Ana-Maria Oproescu
- Sunnybrook Research Institute, Biological Sciences Platform, Toronto, ON, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Sisu Han
- Sunnybrook Research Institute, Biological Sciences Platform, Toronto, ON, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
| | - Carol Schuurmans
- Sunnybrook Research Institute, Biological Sciences Platform, Toronto, ON, Canada
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
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12
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Kawaguchi A. Neuronal Delamination and Outer Radial Glia Generation in Neocortical Development. Front Cell Dev Biol 2021; 8:623573. [PMID: 33614631 PMCID: PMC7892903 DOI: 10.3389/fcell.2020.623573] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 12/28/2020] [Indexed: 12/25/2022] Open
Abstract
During neocortical development, many neuronally differentiating cells (neurons and intermediate progenitor cells) are generated at the apical/ventricular surface by the division of neural progenitor cells (apical radial glial cells, aRGs). Neurogenic cell delamination, in which these neuronally differentiating cells retract their apical processes and depart from the apical surface, is the first step of their migration. Since the microenvironment established by the apical endfeet is crucial for maintaining neuroepithelial (NE)/aRGs, proper timing of the detachment of the apical endfeet is critical for the quantitative control of neurogenesis in cerebral development. During delamination, the microtubule-actin-AJ (adherens junction) configuration at the apical endfeet shows dynamic changes, concurrent with the constriction of the AJ ring at the apical endfeet and downregulation of cadherin expression. This process is mediated by transcriptional suppression of AJ-related molecules and multiple cascades to regulate cell adhesion and cytoskeletal architecture in a posttranscriptional manner. Recent advances have added molecules to the latter category: the interphase centrosome protein AKNA affects microtubule dynamics to destabilize the microtubule-actin-AJ complex, and the microtubule-associated protein Lzts1 inhibits microtubule assembly and activates actomyosin systems at the apical endfeet of differentiating cells. Moreover, Lzts1 induces the oblique division of aRGs, and loss of Lzts1 reduces the generation of outer radial glia (oRGs, also called basal radial glia, bRGs), another type of neural progenitor cell in the subventricular zone. These findings suggest that neurogenic cell delamination, and in some cases oRG generation, could be caused by a spectrum of interlinked mechanisms.
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Affiliation(s)
- Ayano Kawaguchi
- Department of Anatomy and Cell Biology, Nagoya University Graduate School of Medicine, Nagoya, Japan
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