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Neumann AM, Britsch S. Molecular Genetics of Acquired Temporal Lobe Epilepsy. Biomolecules 2024; 14:669. [PMID: 38927072 PMCID: PMC11202058 DOI: 10.3390/biom14060669] [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: 05/07/2024] [Revised: 06/02/2024] [Accepted: 06/03/2024] [Indexed: 06/28/2024] Open
Abstract
An epilepsy diagnosis reduces a patient's quality of life tremendously, and it is a fate shared by over 50 million people worldwide. Temporal lobe epilepsy (TLE) is largely considered a nongenetic or acquired form of epilepsy that develops in consequence of neuronal trauma by injury, malformations, inflammation, or a prolonged (febrile) seizure. Although extensive research has been conducted to understand the process of epileptogenesis, a therapeutic approach to stop its manifestation or to reliably cure the disease has yet to be developed. In this review, we briefly summarize the current literature predominately based on data from excitotoxic rodent models on the cellular events proposed to drive epileptogenesis and thoroughly discuss the major molecular pathways involved, with a focus on neurogenesis-related processes and transcription factors. Furthermore, recent investigations emphasized the role of the genetic background for the acquisition of epilepsy, including variants of neurodevelopmental genes. Mutations in associated transcription factors may have the potential to innately increase the vulnerability of the hippocampus to develop epilepsy following an injury-an emerging perspective on the epileptogenic process in acquired forms of epilepsy.
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Affiliation(s)
| | - Stefan Britsch
- Institute of Molecular and Cellular Anatomy, Ulm University, 89081 Ulm, Germany;
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2
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Jiang S, Liu B, Lin K, Li L, Li R, Tan S, Zhang X, Jiang L, Ni H, Wang Y, Ding H, Hu J, Qian H, Ge R. Impacted spike frequency adaptation associated with reduction of KCNQ2/3 exacerbates seizure activity in temporal lobe epilepsy. Hippocampus 2024; 34:58-72. [PMID: 38049972 DOI: 10.1002/hipo.23587] [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: 01/09/2022] [Revised: 09/21/2023] [Accepted: 10/28/2023] [Indexed: 12/06/2023]
Abstract
Numerous epilepsy-related genes have been identified in recent decades by unbiased genome-wide screens. However, the available druggable targets for temporal lobe epilepsy (TLE) remain limited. Furthermore, a substantial pool of candidate genes potentially applicable to TLE therapy awaits further validation. In this study, we reveal the significant role of KCNQ2 and KCNQ3, two M-type potassium channel genes, in the onset of seizures in TLE. Our investigation began with a quantitative analysis of two publicly available TLE patient databases to establish a correlation between seizure onset and the downregulated expression of KCNQ2/3. We then replicated these pathological changes in a pilocarpine seizure mouse model and observed a decrease in spike frequency adaptation due to the affected M-currents in dentate gyrus granule neurons. In addition, we performed a small-scale simulation of the dentate gyrus network and confirmed that the impaired spike frequency adaptation of granule cells facilitated epileptiform activity throughout the network. This, in turn, resulted in prolonged seizure duration and reduced interictal intervals. Our findings shed light on an underlying mechanism contributing to ictogenesis in the TLE hippocampus and suggest a promising target for the development of antiepileptic drugs.
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Affiliation(s)
- Shicheng Jiang
- Department of Pathophysiology, Bengbu Medical College, Bengbu, Anhui, China
- Laboratory of Brain and Psychiatric Disease, Bengbu Medical College, Bengbu, Anhui, China
| | - Bei Liu
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Kaiwen Lin
- Department of Pathophysiology, Bengbu Medical College, Bengbu, Anhui, China
- Laboratory of Brain and Psychiatric Disease, Bengbu Medical College, Bengbu, Anhui, China
| | - Lianjun Li
- Department of Pathophysiology, Bengbu Medical College, Bengbu, Anhui, China
- Laboratory of Brain and Psychiatric Disease, Bengbu Medical College, Bengbu, Anhui, China
| | - Rongrong Li
- Department of Pathophysiology, Bengbu Medical College, Bengbu, Anhui, China
- Laboratory of Brain and Psychiatric Disease, Bengbu Medical College, Bengbu, Anhui, China
| | - Shuo Tan
- Department of Pathophysiology, Bengbu Medical College, Bengbu, Anhui, China
- Laboratory of Brain and Psychiatric Disease, Bengbu Medical College, Bengbu, Anhui, China
| | - Xinyu Zhang
- Department of Pathophysiology, Bengbu Medical College, Bengbu, Anhui, China
- Laboratory of Brain and Psychiatric Disease, Bengbu Medical College, Bengbu, Anhui, China
| | - Lei Jiang
- Department of General Surgery, The Second Affiliated Hospital of Bengbu Medical College, Bengbu, Anhui, China
| | - Hong Ni
- Department of Pathophysiology, Bengbu Medical College, Bengbu, Anhui, China
- Laboratory of Brain and Psychiatric Disease, Bengbu Medical College, Bengbu, Anhui, China
| | - Yuanyuan Wang
- Department of Pathophysiology, Bengbu Medical College, Bengbu, Anhui, China
- Laboratory of Brain and Psychiatric Disease, Bengbu Medical College, Bengbu, Anhui, China
| | - Haihu Ding
- Department of Pathophysiology, Bengbu Medical College, Bengbu, Anhui, China
- Key Laboratory of Cardiovascular and Cerebrovascular Diseases, Bengbu Medical College, Bengbu, Anhui, China
| | - Jing Hu
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Hao Qian
- Sichuan Provincial Key Laboratory for Human Disease Gene Study, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, China
| | - Rongjing Ge
- Department of Pathophysiology, Bengbu Medical College, Bengbu, Anhui, China
- Laboratory of Brain and Psychiatric Disease, Bengbu Medical College, Bengbu, Anhui, China
- Key Laboratory of Cardiovascular and Cerebrovascular Diseases, Bengbu Medical College, Bengbu, Anhui, China
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Chen L, Xu J, Zhu L, Xu P, Chang L, Han Y, Wu Q. Disrupted in Schizophrenia 1 Reverse Ectopic Migration of Neural Precursors in Mouse Hilus After Pilocarpine-Induced Status Epilepticus. Mol Neurobiol 2023; 60:6689-6703. [PMID: 37479851 DOI: 10.1007/s12035-023-03507-4] [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: 02/16/2023] [Accepted: 07/12/2023] [Indexed: 07/23/2023]
Abstract
Neural precursors in the subgranular zone (SGZ) can be stimulated by status epilepticus (SE) and ectopically migrate to the hilus. These mislocated cells serve as "potential pacemakers" of spontaneous recurrent seizures, and targeting them could potentially reverse the seizure process. Disrupted-in-Schizophrenia 1 (DISC1) regulates hippocampal neurogenesis after seizures both in vitro and in vivo. Our previous study found that DISC1 was colocalized with neural precursors in the hilus after SE. However, its molecular mechanism and pathways contribute to the ectopic migration of neural precursors to the hilus induced by SE awaits exploration. Here, we showed that both Reelin-ApoER2/EphB2 and Reelin-Integrin β1/Integrin α5 axes may participate in the modulation of neurogenesis after SE. Especially, DISC1, as a protective role, might partly reversed the ectopic progenitor migration via EphB2 pathway. Our findings demonstrated that DISC1 played a protective role in the ectopic migration of neural precursors induced by SE insults and DISC1 could be an attractive new target for the treatment of epilepsy.
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Affiliation(s)
- Lu Chen
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan, 650032, People's Republic of China
| | - Jing Xu
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan, 650032, People's Republic of China
| | - Lin Zhu
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan, 650032, People's Republic of China
| | - Puying Xu
- Department of Neurology, Northeast Yunnan Hospital, Mengquan Avenue, Zhaoyang District, Zhaotong, Yunnan, 657000, People's Republic of China
| | - Lvhua Chang
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan, 650032, People's Republic of China
| | - Yanbing Han
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan, 650032, People's Republic of China.
| | - Qian Wu
- Department of Neurology, First Affiliated Hospital, Kunming Medical University, 295 Xi Chang Road, Kunming, Yunnan, 650032, People's Republic of China.
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Kasahara Y, Nakashima H, Nakashima K. Seizure-induced hilar ectopic granule cells in the adult dentate gyrus. Front Neurosci 2023; 17:1150283. [PMID: 36937666 PMCID: PMC10017466 DOI: 10.3389/fnins.2023.1150283] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 02/13/2023] [Indexed: 03/06/2023] Open
Abstract
Epilepsy is a chronic neurological disorder characterized by hypersynchronous spontaneous recurrent seizures, and affects approximately 50 million people worldwide. Cumulative evidence has revealed that epileptogenic insult temporarily increases neurogenesis in the hippocampus; however, a fraction of the newly generated neurons are integrated abnormally into the existing neural circuits. The abnormal neurogenesis, including ectopic localization of newborn neurons in the hilus, formation of abnormal basal dendrites, and disorganization of the apical dendrites, rewires hippocampal neural networks and leads to the development of spontaneous seizures. The central roles of hilar ectopic granule cells in regulating hippocampal excitability have been suggested. In this review, we introduce recent findings about the migration of newborn granule cells to the dentate hilus after seizures and the roles of seizure-induced ectopic granule cells in the epileptic brain. In addition, we delineate possible intrinsic and extrinsic mechanisms underlying this abnormality. Finally, we suggest that the regulation of seizure-induced ectopic cells can be a promising target for epilepsy therapy and provide perspectives on future research directions.
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Leifeld J, Förster E, Reiss G, Hamad MIK. Considering the Role of Extracellular Matrix Molecules, in Particular Reelin, in Granule Cell Dispersion Related to Temporal Lobe Epilepsy. Front Cell Dev Biol 2022; 10:917575. [PMID: 35733853 PMCID: PMC9207388 DOI: 10.3389/fcell.2022.917575] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 05/23/2022] [Indexed: 11/13/2022] Open
Abstract
The extracellular matrix (ECM) of the nervous system can be considered as a dynamically adaptable compartment between neuronal cells, in particular neurons and glial cells, that participates in physiological functions of the nervous system. It is mainly composed of carbohydrates and proteins that are secreted by the different kinds of cell types found in the nervous system, in particular neurons and glial cells, but also other cell types, such as pericytes of capillaries, ependymocytes and meningeal cells. ECM molecules participate in developmental processes, synaptic plasticity, neurodegeneration and regenerative processes. As an example, the ECM of the hippocampal formation is involved in degenerative and adaptive processes related to epilepsy. The role of various components of the ECM has been explored extensively. In particular, the ECM protein reelin, well known for orchestrating the formation of neuronal layer formation in the cerebral cortex, is also considered as a player involved in the occurrence of postnatal granule cell dispersion (GCD), a morphologically peculiar feature frequently observed in hippocampal tissue from epileptic patients. Possible causes and consequences of GCD have been studied in various in vivo and in vitro models. The present review discusses different interpretations of GCD and different views on the role of ECM protein reelin in the formation of this morphological peculiarity.
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Affiliation(s)
- Jennifer Leifeld
- Department of Neuroanatomy and Molecular Brain Research, Medical Faculty, Ruhr University Bochum, Bochum, Germany
- Department of Biochemistry I—Receptor Biochemistry, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Bochum, Germany
- *Correspondence: Jennifer Leifeld, ; Eckart Förster,
| | - Eckart Förster
- Department of Neuroanatomy and Molecular Brain Research, Medical Faculty, Ruhr University Bochum, Bochum, Germany
- *Correspondence: Jennifer Leifeld, ; Eckart Förster,
| | - Gebhard Reiss
- Institute for Anatomy and Clinical Morphology, School of Medicine, Faculty of Health, Witten/ Herdecke University, Witten, Germany
| | - Mohammad I. K. Hamad
- Institute for Anatomy and Clinical Morphology, School of Medicine, Faculty of Health, Witten/ Herdecke University, Witten, Germany
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Disrupted in schizophrenia 1 regulates ectopic neurogenesis in the mouse hilus after pilocarpine-induced status epilepticus. Neuroscience 2022; 494:69-81. [DOI: 10.1016/j.neuroscience.2022.05.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 05/01/2022] [Accepted: 05/06/2022] [Indexed: 11/20/2022]
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7
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Lybrand ZR, Goswami S, Zhu J, Jarzabek V, Merlock N, Aktar M, Smith C, Zhang L, Varma P, Cho KO, Ge S, Hsieh J. A critical period of neuronal activity results in aberrant neurogenesis rewiring hippocampal circuitry in a mouse model of epilepsy. Nat Commun 2021; 12:1423. [PMID: 33658509 PMCID: PMC7930276 DOI: 10.1038/s41467-021-21649-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 02/04/2021] [Indexed: 01/31/2023] Open
Abstract
In the mammalian hippocampus, adult-born granule cells (abGCs) contribute to the function of the dentate gyrus (DG). Disruption of the DG circuitry causes spontaneous recurrent seizures (SRS), which can lead to epilepsy. Although abGCs contribute to local inhibitory feedback circuitry, whether they are involved in epileptogenesis remains elusive. Here, we identify a critical window of activity associated with the aberrant maturation of abGCs characterized by abnormal dendrite morphology, ectopic migration, and SRS. Importantly, in a mouse model of temporal lobe epilepsy, silencing aberrant abGCs during this critical period reduces abnormal dendrite morphology, cell migration, and SRS. Using mono-synaptic tracers, we show silencing aberrant abGCs decreases recurrent CA3 back-projections and restores proper cortical connections to the hippocampus. Furthermore, we show that GABA-mediated amplification of intracellular calcium regulates the early critical period of activity. Our results demonstrate that aberrant neurogenesis rewires hippocampal circuitry aggravating epilepsy in mice.
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Affiliation(s)
- Zane R Lybrand
- Department of Biology, The University of Texas at San Antonio, San Antonio, TX, USA
- Brain Health Consortium, The University of Texas at San Antonio, San Antonio, TX, USA
- Department of Biology, Texas Woman's University, Denton, TX, USA
| | - Sonal Goswami
- Department of Biology, The University of Texas at San Antonio, San Antonio, TX, USA
- Brain Health Consortium, The University of Texas at San Antonio, San Antonio, TX, USA
| | - Jingfei Zhu
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Veronica Jarzabek
- Department of Biology, The University of Texas at San Antonio, San Antonio, TX, USA
- Brain Health Consortium, The University of Texas at San Antonio, San Antonio, TX, USA
| | - Nikolas Merlock
- Department of Biology, The University of Texas at San Antonio, San Antonio, TX, USA
- Brain Health Consortium, The University of Texas at San Antonio, San Antonio, TX, USA
| | - Mahafuza Aktar
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Courtney Smith
- Department of Biology, The University of Texas at San Antonio, San Antonio, TX, USA
- Brain Health Consortium, The University of Texas at San Antonio, San Antonio, TX, USA
| | - Ling Zhang
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, USA
| | - Parul Varma
- Department of Biology, The University of Texas at San Antonio, San Antonio, TX, USA
- Brain Health Consortium, The University of Texas at San Antonio, San Antonio, TX, USA
| | - Kyung-Ok Cho
- Department of Pharmacology, Catholic Neuroscience Institute, College of Medicine, The Catholic University of Korea, Seoul, South Korea
- Department of Biomedicine & Health Sciences, Institute of Aging and Metabolic Diseases, College of Medicine, The Catholic University of Korea, Seoul, South Korea
| | - Shaoyu Ge
- Department of Neurobiology & Behavior, Stony Brook University, Stony Brook, NY, USA
| | - Jenny Hsieh
- Department of Biology, The University of Texas at San Antonio, San Antonio, TX, USA.
- Brain Health Consortium, The University of Texas at San Antonio, San Antonio, TX, USA.
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Abstract
Chronic alcohol consumption results in alcohol use disorder (AUD). Interestingly, however, sudden alcohol withdrawal (AW) after chronic alcohol exposure also leads to a devastating series of symptoms, referred to as alcohol withdrawal syndromes. One key feature of AW syndromes is to produce phenotypes that are opposite to AUD. For example, while the brain is characterized by a hypoactive state in the presence of alcohol, AW induces a hyperactive state, which is manifested as seizure expression. In this review, we discuss the idea that hippocampal neurogenesis and neural circuits play a key role in neuroadaptation and establishment of allostatic states in response to alcohol exposure and AW. The intrinsic properties of dentate granule cells (DGCs), and their contribution to the formation of a potent feedback inhibitory loop, endow the dentate gyrus with a "gate" function, which can limit the entry of excessive excitatory signals from the cortex into the hippocampus. We discuss the possibility that alcohol exposure and withdrawal disrupts structural development and circuitry integration of hippocampal newborn neurons, and that this altered neurogenesis impairs the gate function of the hippocampus. Failure of this gate function is expected to alter the ratio of excitatory to inhibitory (E/I) signals in the hippocampus and to induce seizure expression during AW. Recent functional studies have shown that specific activation and inhibition of hippocampal newborn DGCs are both necessary and sufficient for the expression of AW-associated seizures, further supporting the concept that neurogenesis-induced neuroadaptation is a critical target to understand and treat AUD and AW-associated seizures.
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Affiliation(s)
- Sreetama Basu
- Department of Neurosciences, Cleveland Clinic, Cleveland, OH, USA
| | - Hoonkyo Suh
- Department of Neurosciences, Cleveland Clinic, Cleveland, OH, USA
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Impaired postnatal development of the hippocampus of Krushinsky-Molodkina rats genetically prone to audiogenic seizures. Epilepsy Behav 2020; 113:107526. [PMID: 33161330 DOI: 10.1016/j.yebeh.2020.107526] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2020] [Revised: 09/10/2020] [Accepted: 09/13/2020] [Indexed: 11/22/2022]
Abstract
The hippocampus plays an important role in epilepsy progression even if it is not involved in seizure generalization. We hypothesized that abnormal development of the hippocampus may underlie epileptogenesis. Here we analyzed postnatal development of the hippocampus of Krushinsky-Molodkina (KM) rats, which are the animal model of reflex audiogenic epilepsy. KM rats are genetically prone to audiogenic seizures that are expressed in age-dependent manner. The study was performed on seizure-naïve KM rats at several days of postnatal development (P15, P30, P60, P120). Wistar rats of the corresponding ages were used as a control. We showed that at early stages (P15, P30), the hippocampus of KM rats was characterized by significantly smaller cell population, but the number of proliferated cells was increased in comparison with control Wistar rats. Only at P60 proliferation and the total number of the hippocampal cells reached a level equal to Wistar rats. These data suggest delayed postnatal development of the hippocampus of KM rats. Analysis of apoptosis demonstrated significantly increased number of TUNEL-positive cells in the dentate gyrus (DG) of KM rats at P30 that was accompanied with expression of p53, Bcl-2 and cleaved caspases 3 and 9. Additionally, at all analyzed stages in the hilus of KM rats, the number of new-born glutamatergic cells was significantly increased that suggests formation of hilar ectopic granular cells. Our data suggest that in the case of hereditary epilepsy aberrant neurogenesis may be genetically determined.
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Littlejohn EL, Scott D, Saatman KE. Insulin-like growth factor-1 overexpression increases long-term survival of posttrauma-born hippocampal neurons while inhibiting ectopic migration following traumatic brain injury. Acta Neuropathol Commun 2020; 8:46. [PMID: 32276671 PMCID: PMC7147070 DOI: 10.1186/s40478-020-00925-6] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 03/29/2020] [Indexed: 01/29/2023] Open
Abstract
Cellular damage associated with traumatic brain injury (TBI) manifests in motor and cognitive dysfunction following injury. Experimental models of TBI reveal cell death in the granule cell layer (GCL) of the hippocampal dentate gyrus acutely after injury. Adult-born neurons residing in the neurogenic niche of the GCL, the subgranular zone, are particularly vulnerable. Injury-induced proliferation of neural progenitors in the subgranular zone supports recovery of the immature neuron population, but their development and localization may be altered, potentially affecting long-term survival. Here we show that increasing hippocampal levels of insulin-like growth factor-1 (IGF1) is sufficient to promote end-stage maturity of posttrauma-born neurons and improve cognition following TBI. Mice with conditional overexpression of astrocyte-specific IGF1 and wild-type mice received controlled cortical impact or sham injury and bromo-2'-deoxyuridine injections for 7d after injury to label proliferating cells. IGF1 overexpression increased the number of GCL neurons born acutely after trauma that survived 6 weeks to maturity (NeuN+BrdU+), and enhanced their outward migration into the GCL while significantly reducing the proportion localized ectopically to the hilus and molecular layer. IGF1 selectively affected neurons, without increasing the persistence of posttrauma-proliferated glia in the dentate gyrus. IGF1 overexpressing animals performed better during radial arm water maze reversal testing, a neurogenesis-dependent cognitive test. These findings demonstrate the ability of IGF1 to promote the long-term survival and appropriate localization of granule neurons born acutely after a TBI, and suggest these new neurons contribute to improved cognitive function.
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Affiliation(s)
- Erica L. Littlejohn
- grid.266539.d0000 0004 1936 8438Spinal Cord and Brain Injury Research Center, Department of Physiology, University of Kentucky, B473 Biomedical & Biological Sciences Research Building (BBSRB), 741 South Limestone St, Lexington, KY 40536-0509 USA ,grid.267309.90000 0001 0629 5880Department of Cellular and Integrative Physiology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3901 USA
| | - Danielle Scott
- grid.266539.d0000 0004 1936 8438Spinal Cord and Brain Injury Research Center, Department of Physiology, University of Kentucky, B473 Biomedical & Biological Sciences Research Building (BBSRB), 741 South Limestone St, Lexington, KY 40536-0509 USA
| | - Kathryn E. Saatman
- grid.266539.d0000 0004 1936 8438Spinal Cord and Brain Injury Research Center, Department of Physiology, University of Kentucky, B473 Biomedical & Biological Sciences Research Building (BBSRB), 741 South Limestone St, Lexington, KY 40536-0509 USA ,grid.266539.d0000 0004 1936 8438Department of Physiology, College of Medicine, University of Kentucky, Lexington, KY 40536 USA
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Corrubia L, Santhakumar V. Born to Be Wild: A Case for Targeting Ectopic Adult Born Granule Cells for Seizure Control. Epilepsy Curr 2019; 20:57-60. [PMID: 32037879 PMCID: PMC7020538 DOI: 10.1177/1535759719891438] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Altered Synaptic Drive Onto Birthdated Dentate Granule Cells in Experimental Temporal Lobe Epilepsy Althaus AL, Moore SJ, Zhang H, Du Plummer X, Murphy GG, Parent JM. J Neurosci. 2019;39(38):7604-7614. doi:10.1523/JNEUROSCI.0654-18.2019. Dysregulated adult hippocampal neurogenesis occurs in many temporal lobe epilepsy (TLE) models. Most dentate granule cells (DGCs) generated in response to an epileptic insult develop features that promote increased excitability, including ectopic location, persistent hilar basal dendrites (HBDs), and mossy fiber sprouting. However, some appear to integrate normally and even exhibit reduced excitability compared to other DGCs. To examine the relationship between DGC birthdate, morphology, and network integration in a model of TLE, we retrovirally birth-dated either early-born (postnatal day 7) or adult-born (postnatal day 60) DGCs. Male rats underwent pilocarpine-induced status epilepticus (SE) or sham treatment at postnatal day 56. Three to six months after SE or sham treatment, we used whole-cell patch clamp and fluorescence microscopy to record spontaneous excitatory and inhibitory currents from birth-dated DGCs. We found that both adult-born and early-born populations of DGCs recorded from epileptic rats received increased excitatory input compared with age-matched controls. Interestingly, when adult-born populations were separated into normally integrated (normotopic) and aberrant (ectopic or HBD containing) subpopulations, only the aberrant populations exhibited a relative increase in excitatory input (amplitude, frequency, and charge transfer). The ratio of excitatory to inhibitory input was most dramatically upregulated for ectopically localized DGCs. These data provide definitive physiological evidence that aberrant integration of post-SE, adult-born DGCs contributes to increased synaptic drive and supports the idea that ectopic DGCs serve as putative hub cells to promote seizures. Significance Statement: Adult DGC neurogenesis is altered in rodent models of TLE. Some of the new neurons show abnormal morphology and integration, but whether adult-generated DGCs contribute to the development of epilepsy is controversial. We examined the synaptic inputs of age-defined populations of DGCs using electrophysiological recordings and fluorescent retroviral reporter birth-dating. Dentate granule cells generated neonatally were compared with those generated in adulthood, and adult-born neurons with normal versus aberrant morphology or integration were examined. We found that adult-born, ectopically located DGCs exhibit the most pro-excitatory physiological changes, implicating this population in seizure generation or progression. Targeting Seizure-Induced Neurogenesis in a Clinically Relevant Time Period Leads to Transient But Not Persistent Seizure Reduction Varma P, Brulet R, Zhang L, Hsieh J. J Neurosci. 2019;39(35):7019-7028. doi:10.1523/JNEUROSCI.0920-19.2019. Mesial temporal lobe epilepsy (mTLE), the most common form of medically refractory epilepsy in adults, is usually associated with hippocampal pathophysiology. Using rodent models of mTLE, many studies including work from our laboratory have shown that new neurons born around the onset of severe acute seizures known as status epilepticus (SE) are crucial for the process of epileptogenesis and targeting seizure-induced neurogenesis either genetically or pharmacologically can impact the frequency of chronic seizures. However, these studies are limited in their clinical relevance as none of them determines the potential of blocking new neurons generated after the epileptogenic insult to alleviate the development of chronic seizures. Therefore, using a pilocarpine-induced SE model of mTLE in mice of either sex, we show that >4 weeks of continuous and concurrent ablation of seizure-induced neurogenesis after SE can reduce the formation of spontaneous recurrent seizures by 65%. We also found that blocking post-SE neurogenesis does not lead to long-term seizure reduction as the effect was observed only transiently for 10 days with >4 weeks of continuous and concurrent ablation of seizure-induced neurogenesis. Thus, these findings provide evidence that seizure-induced neurogenesis when adequately reduced in a clinically relevant time period has the potential to transiently suppress recurrent seizures, but additional mechanisms need to be targeted to permanently prevent epilepsy development. Significance Statement: Consistent with morphological and electrophysiological studies suggesting aberrant adult-generated neurons contribute to epilepsy development, ablation of seizure-induced new neurons at the time of the initial insult reduces the frequency of recurrent seizures. In this study, we show that continuous targeting of post-insult new neurons in a therapeutically relevant time period reduces chronic seizures; however, this effect does not persist suggesting possible additional mechanisms.
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12
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Abstract
Compelling evidence indicates that hippocampal dentate granule cells are generated throughout human life and into old age. While animal studies demonstrate that these new neurons are important for memory function, animal research also implicates these cells in the pathogenesis of temporal lobe epilepsy. Several recent preclinical studies in rodents now suggest that targeting these new neurons can have disease-modifying effects in epilepsy.
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Affiliation(s)
- Steve C Danzer
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Department of Anesthesia, University of Cincinnati, Cincinnati, OH, USA.,Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Center for Pediatric Neuroscience, Cincinnati Children's Hospital, Cincinnati, OH, USA
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13
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Impact of mTOR hyperactive neurons on the morphology and physiology of adjacent neurons: Do PTEN KO cells make bad neighbors? Exp Neurol 2019; 321:113029. [PMID: 31377403 DOI: 10.1016/j.expneurol.2019.113029] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 07/23/2019] [Accepted: 07/31/2019] [Indexed: 01/18/2023]
Abstract
Hyperactivation of the mechanistic target of rapamycin (mTOR) pathway is associated with epilepsy, autism and brain growth abnormalities in humans. mTOR hyperactivation often results from developmental somatic mutations, producing genetic lesions and associated dysfunction in relatively restricted populations of neurons. Disrupted brain regions, such as those observed in focal cortical dysplasia, can contain a mix of normal and mutant cells. Mutant cells exhibit robust anatomical and physiological changes. Less clear, however, is whether adjacent, initially normal cells are affected by the presence of abnormal cells. To explore this question, we used a conditional, inducible mouse model approach to delete the mTOR negative regulator phosphatase and tensin homolog (PTEN) from <1% to >30% of hippocampal dentate granule cells. We then examined the morphology of PTEN-expressing granule cells located in the same dentate gyri as the knockout (KO) cells. Despite the development of spontaneous seizures in higher KO animals, and disease worsening with increasing age, the morphology and physiology of PTEN-expressing cells was only modestly affected. PTEN-expressing cells had smaller somas than cells from control animals, but other parameters were largely unchanged. These findings contrast with the behavior of PTEN KO cells, which show increasing dendritic extent with greater KO cell load. Together, the findings indicate that genetically normal neurons can exhibit relatively stable morphology and intrinsic physiology in the presence of nearby pathological neurons and systemic disease.
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14
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Altered Synaptic Drive onto Birthdated Dentate Granule Cells in Experimental Temporal Lobe Epilepsy. J Neurosci 2019; 39:7604-7614. [PMID: 31270158 DOI: 10.1523/jneurosci.0654-18.2019] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 06/24/2019] [Accepted: 06/27/2019] [Indexed: 12/29/2022] Open
Abstract
Dysregulated adult hippocampal neurogenesis occurs in many temporal lobe epilepsy (TLE) models. Most dentate granule cells (DGCs) generated in response to an epileptic insult develop features that promote increased excitability, including ectopic location, persistent hilar basal dendrites (HBDs), and mossy fiber sprouting. However, some appear to integrate normally and even exhibit reduced excitability compared to other DGCs. To examine the relationship between DGC birthdate, morphology, and network integration in a model of TLE, we retrovirally birthdated either early-born [EB; postnatal day (P)7] or adult-born (AB; P60) DGCs. Male rats underwent pilocarpine-induced status epilepticus (SE) or sham treatment at P56. Three to six months after SE or sham treatment, we used whole-cell patch-clamp and fluorescence microscopy to record spontaneous excitatory and inhibitory currents from birthdated DGCs. We found that both AB and EB populations of DGCs recorded from epileptic rats received increased excitatory input compared with age-matched controls. Interestingly, when AB populations were separated into normally integrated (normotopic) and aberrant (ectopic or HBD-containing) subpopulations, only the aberrant populations exhibited a relative increase in excitatory input (amplitude, frequency, and charge transfer). The ratio of excitatory-to-inhibitory input was most dramatically upregulated for ectopically localized DGCs. These data provide definitive physiological evidence that aberrant integration of post-SE, AB DGCs contributes to increased synaptic drive and support the idea that ectopic DGCs serve as putative hub cells to promote seizures.SIGNIFICANCE STATEMENT Adult dentate granule cell (DGC) neurogenesis is altered in rodent models of temporal lobe epilepsy (TLE). Some of the new neurons show abnormal morphology and integration, but whether adult-generated DGCs contribute to the development of epilepsy is controversial. We examined the synaptic inputs of age-defined populations of DGCs using electrophysiological recordings and fluorescent retroviral reporter birthdating. DGCs generated neonatally were compared with those generated in adulthood, and adult-born (AB) neurons with normal versus aberrant morphology or integration were examined. We found that AB, ectopically located DGCs exhibit the most pro-excitatory physiological changes, implicating this population in seizure generation or progression.
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15
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Restrained Dendritic Growth of Adult-Born Granule Cells Innervated by Transplanted Fetal GABAergic Interneurons in Mice with Temporal Lobe Epilepsy. eNeuro 2019; 6:ENEURO.0110-18.2019. [PMID: 31043461 PMCID: PMC6497906 DOI: 10.1523/eneuro.0110-18.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 03/11/2019] [Accepted: 03/15/2019] [Indexed: 12/16/2022] Open
Abstract
The dentate gyrus (DG) is a region of the adult rodent brain that undergoes continuous neurogenesis. Seizures and loss or dysfunction of GABAergic synapses onto adult-born dentate granule cells (GCs) alter their dendritic growth and migration, resulting in dysmorphic and hyperexcitable GCs. Additionally, transplants of fetal GABAergic interneurons in the DG of mice with temporal lobe epilepsy (TLE) result in seizure suppression, but it is unknown whether increasing interneurons with these transplants restores GABAergic innervation to adult-born GCs. Here, we address this question by birth-dating GCs with retrovirus at different times up to 12 weeks after pilocarpine-induced TLE in adult mice. Channelrhodopsin 2 (ChR2)-enhanced yellow fluorescent protein (EYFP)-expressing medial-ganglionic eminence (MGE)-derived GABAergic interneurons from embryonic day (E)13.5 mouse embryos were transplanted into the DG of the TLE mice and GCs with transplant-derived inhibitory post-synaptic currents (IPSCs) were identified by patch-clamp electrophysiology and optogenetic interrogation. Putative synaptic sites between GCs and GABAergic transplants were also confirmed by intracellular biocytin staining, immunohistochemistry, and confocal imaging. 3D reconstructions of dendritic arbors and quantitative morphometric analyses were carried out in >150 adult-born GCs. GABAergic inputs from transplanted interneurons correlated with markedly shorter GC dendrites, compared to GCs that were not innervated by the transplants. Moreover, these effects were confined to distal dendritic branches and a short time window of six to eight weeks. The effects were independent of seizures as they were also observed in naïve mice with MGE transplants. These findings are consistent with the hypothesis that increased inhibitory currents over a smaller dendritic arbor in adult-born GCs may reduce their excitability and lead to seizure suppression.
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16
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Beamer EH, Jurado-Arjona J, Jimenez-Mateos EM, Morgan J, Reschke CR, Kenny A, de Leo G, Olivos-Oré LA, Arribas-Blázquez M, Madden SF, Merchán-Rubira J, Delanty N, Farrell MA, O'Brien DF, Avila J, Diaz-Hernandez M, Miras-Portugal MT, Artalejo AR, Hernandez F, Henshall DC, Engel T. MicroRNA-22 Controls Aberrant Neurogenesis and Changes in Neuronal Morphology After Status Epilepticus. Front Mol Neurosci 2018; 11:442. [PMID: 30618601 PMCID: PMC6298134 DOI: 10.3389/fnmol.2018.00442] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 11/16/2018] [Indexed: 12/12/2022] Open
Abstract
Prolonged seizures (status epilepticus, SE) may drive hippocampal dysfunction and epileptogenesis, at least partly, through an elevation in neurogenesis, dysregulation of migration and aberrant dendritic arborization of newly-formed neurons. MicroRNA-22 was recently found to protect against the development of epileptic foci, but the mechanisms remain incompletely understood. Here, we investigated the contribution of microRNA-22 to SE-induced aberrant adult neurogenesis. SE was induced by intraamygdala microinjection of kainic acid (KA) to model unilateral hippocampal neuropathology in mice. MicroRNA-22 expression was suppressed using specific oligonucleotide inhibitors (antagomir-22) and newly-formed neurons were visualized using the thymidine analog iodo-deoxyuridine (IdU) and a green fluorescent protein (GFP)-expressing retrovirus to visualize the dendritic tree and synaptic spines. Using this approach, we quantified differences in the rate of neurogenesis and migration, the structure of the apical dendritic tree and density and morphology of dendritic spines in newly-formed neurons.SE resulted in an increased rate of hippocampal neurogenesis, including within the undamaged contralateral dentate gyrus (DG). Newly-formed neurons underwent aberrant migration, both within the granule cell layer and into ectopic sites. Inhibition of microRNA-22 exacerbated these changes. The dendritic diameter and the density and average volume of dendritic spines were unaffected by SE, but these parameters were all elevated in mice in which microRNA-22 was suppressed. MicroRNA-22 inhibition also reduced the length and complexity of the dendritic tree, independently of SE. These data indicate that microRNA-22 is an important regulator of morphogenesis of newly-formed neurons in adults and plays a role in supressing aberrant neurogenesis associated with SE.
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Affiliation(s)
- Edward H Beamer
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Jeronimo Jurado-Arjona
- Institute of Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany.,Department of Molecular Biology, Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid (UAM), Centro Investigación Biomédica en Red Enfermedades Neurodegenerativa (CIBERNED), Madrid, Spain
| | - Eva M Jimenez-Mateos
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - James Morgan
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Cristina R Reschke
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland.,FutureNeuro Research Centre, RCSI, Dublin, Ireland
| | - Aidan Kenny
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Gioacchino de Leo
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Luis A Olivos-Oré
- Department of Pharmacology and Toxicology, Veterinary Faculty, Instituto Universitario de Investigación en Neuroquímica, Universidad Complutense de Madrid, Madrid, Spain
| | - Marina Arribas-Blázquez
- Department of Pharmacology and Toxicology, Veterinary Faculty, Instituto Universitario de Investigación en Neuroquímica, Universidad Complutense de Madrid, Madrid, Spain
| | - Stephen F Madden
- Data Science Centre, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Jesús Merchán-Rubira
- Department of Molecular Biology, Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid (UAM), Centro Investigación Biomédica en Red Enfermedades Neurodegenerativa (CIBERNED), Madrid, Spain
| | - Norman Delanty
- FutureNeuro Research Centre, RCSI, Dublin, Ireland.,Beaumont Hospital, Dublin, Ireland
| | | | | | - Jesus Avila
- Department of Molecular Biology, Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid (UAM), Centro Investigación Biomédica en Red Enfermedades Neurodegenerativa (CIBERNED), Madrid, Spain
| | - Miguel Diaz-Hernandez
- Department of Biochemistry and Molecular Biology, Veterinary Faculty, Universidad Complutense de Madrid, Madrid, Spain
| | - M Teresa Miras-Portugal
- Department of Biochemistry and Molecular Biology, Veterinary Faculty, Universidad Complutense de Madrid, Madrid, Spain
| | - Antonio R Artalejo
- Department of Pharmacology and Toxicology, Veterinary Faculty, Instituto Universitario de Investigación en Neuroquímica, Universidad Complutense de Madrid, Madrid, Spain
| | - Felix Hernandez
- Department of Molecular Biology, Centro de Biología Molecular "Severo Ochoa", Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid (UAM), Centro Investigación Biomédica en Red Enfermedades Neurodegenerativa (CIBERNED), Madrid, Spain
| | - David C Henshall
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland.,FutureNeuro Research Centre, RCSI, Dublin, Ireland
| | - Tobias Engel
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland.,FutureNeuro Research Centre, RCSI, Dublin, Ireland
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17
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Danzer SC. Contributions of Adult-Generated Granule Cells to Hippocampal Pathology in Temporal Lobe Epilepsy: A Neuronal Bestiary. Brain Plast 2018; 3:169-181. [PMID: 30151341 PMCID: PMC6091048 DOI: 10.3233/bpl-170056] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Hippocampal neurogenesis continues throughout life in mammals – including humans. During the development of temporal lobe epilepsy, newly-generated hippocampal granule cells integrate abnormally into the brain. Abnormalities include ectopic localization of newborn cells, de novo formation of abnormal basal dendrites, and disruptions of the apical dendritic tree. Changes in granule cell position and dendritic structure fundamentally alter the types of inputs these cells are able to receive, as well as the relative proportions of remaining inputs. Dendritic abnormalities also create new pathways for recurrent excitation in the hippocampus. These abnormalities are hypothesized to contribute to the development of epilepsy, and may underlie cognitive disorders associated with the disease as well. To test this hypothesis, investigators have used pharmacological and genetic strategies in animal models to alter neurogenesis rates, or ablate the newborn cells outright. While findings are mixed and many unanswered questions remain, numerous studies now demonstrate that ablating newborn granule cells can have disease modifying effects in epilepsy. Taken together, findings provide a strong rationale for continued work to elucidate the role of newborn granule cells in epilepsy: both to understand basic mechanisms underlying the disease, and as a potential novel therapy for epilepsy.
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Affiliation(s)
- Steve C Danzer
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Departments of Anesthesia and Pediatrics, University of Cincinnati, Cincinnati, OH, USA
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18
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Wang Y, Ji T, Nelson AD, Glanowska K, Murphy GG, Jenkins PM, Parent JM. Critical roles of αII spectrin in brain development and epileptic encephalopathy. J Clin Invest 2018; 128:760-773. [PMID: 29337302 DOI: 10.1172/jci95743] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2017] [Accepted: 11/28/2017] [Indexed: 12/26/2022] Open
Abstract
The nonerythrocytic α-spectrin-1 (SPTAN1) gene encodes the cytoskeletal protein αII spectrin. Mutations in SPTAN1 cause early infantile epileptic encephalopathy type 5 (EIEE5); however, the role of αII spectrin in neurodevelopment and EIEE5 pathogenesis is unknown. Prior work suggests that αII spectrin is absent in the axon initial segment (AIS) and contributes to a diffusion barrier in the distal axon. Here, we have shown that αII spectrin is expressed ubiquitously in rodent and human somatodendritic and axonal domains. CRISPR-mediated deletion of Sptan1 in embryonic rat forebrain by in utero electroporation caused altered dendritic and axonal development, loss of the AIS, and decreased inhibitory innervation. Overexpression of human EIEE5 mutant SPTAN1 in embryonic rat forebrain and mouse hippocampal neurons led to similar developmental defects that were also observed in EIEE5 patient-derived neurons. Additionally, patient-derived neurons displayed aggregation of spectrin complexes. Taken together, these findings implicate αII spectrin in critical aspects of dendritic and axonal development and synaptogenesis, and support a dominant-negative mechanism of SPTAN1 mutations in EIEE5.
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Affiliation(s)
| | | | | | | | - Geoffrey G Murphy
- Molecular and Behavioral Neuroscience Institute.,Department of Molecular and Integrative Physiology, and
| | - Paul M Jenkins
- Department of Pharmacology.,Department of Psychiatry, University of Michigan, Ann Arbor, Michigan, USA
| | - Jack M Parent
- Department of Neurology.,Ann Arbor VA Healthcare System, Ann Arbor, Michigan, USA
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19
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Bosch C, Masachs N, Exposito-Alonso D, Martínez A, Teixeira CM, Fernaud I, Pujadas L, Ulloa F, Comella JX, DeFelipe J, Merchán-Pérez A, Soriano E. Reelin Regulates the Maturation of Dendritic Spines, Synaptogenesis and Glial Ensheathment of Newborn Granule Cells. Cereb Cortex 2018; 26:4282-4298. [PMID: 27624722 PMCID: PMC5066826 DOI: 10.1093/cercor/bhw216] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 06/20/2016] [Indexed: 02/02/2023] Open
Abstract
Significance Statement The extracellular protein Reelin has an important role in neurological diseases, including epilepsy, Alzheimer's disease and psychiatric diseases, targeting hippocampal circuits. Here we address the role of Reelin in the development of synaptic contacts in adult-generated granule cells (GCs), a neuronal population that is crucial for learning and memory and implicated in neurological and psychiatric diseases. We found that the Reelin pathway controls the shapes, sizes, and types of dendritic spines, the complexity of multisynaptic innervations and the degree of the perisynaptic astroglial ensheathment that controls synaptic homeostasis. These findings show a pivotal role of Reelin in GC synaptogenesis and provide a foundation for structural circuit alterations caused by Reelin deregulation that may occur in neurological and psychiatric disorders.
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Affiliation(s)
- Carles Bosch
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology, Parc Científic de Barcelona and Institute of Neurosciences, University of Barcelona, Barcelona 08028, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid 28031, Spain.,Institut de Recerca de l'Hospital Universitari de la Vall d'Hebron (VHIR), Barcelona 08023, Spain
| | - Nuria Masachs
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology, Parc Científic de Barcelona and Institute of Neurosciences, University of Barcelona, Barcelona 08028, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid 28031, Spain
| | - David Exposito-Alonso
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology, Parc Científic de Barcelona and Institute of Neurosciences, University of Barcelona, Barcelona 08028, Spain
| | - Albert Martínez
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology, Parc Científic de Barcelona and Institute of Neurosciences, University of Barcelona, Barcelona 08028, Spain
| | - Cátia M Teixeira
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology, Parc Científic de Barcelona and Institute of Neurosciences, University of Barcelona, Barcelona 08028, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid 28031, Spain
| | - Isabel Fernaud
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid 28031, Spain.,Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Campus de Montegancedo, Madrid 28223, Spain.,Instituto Cajal (Consejo Superior de Investigaciones Científicas), Madrid 28002, Spain
| | - Lluís Pujadas
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology, Parc Científic de Barcelona and Institute of Neurosciences, University of Barcelona, Barcelona 08028, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid 28031, Spain.,Institut de Recerca de l'Hospital Universitari de la Vall d'Hebron (VHIR), Barcelona 08023, Spain
| | - Fausto Ulloa
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology, Parc Científic de Barcelona and Institute of Neurosciences, University of Barcelona, Barcelona 08028, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid 28031, Spain
| | - Joan X Comella
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid 28031, Spain.,Institut de Recerca de l'Hospital Universitari de la Vall d'Hebron (VHIR), Barcelona 08023, Spain.,Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, Bellaterra 08193, Spain
| | - Javier DeFelipe
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid 28031, Spain.,Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Campus de Montegancedo, Madrid 28223, Spain.,Instituto Cajal (Consejo Superior de Investigaciones Científicas), Madrid 28002, Spain
| | - Angel Merchán-Pérez
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid 28031, Spain.,Laboratorio Cajal de Circuitos Corticales, Centro de Tecnología Biomédica, Universidad Politécnica de Madrid, Campus de Montegancedo, Madrid 28223, Spain.,Departamento de Arquitectura y Tecnología de Sistemas Informáticos, Escuela Técnica Superior de Ingenieros Informáticos, Universidad Politécnica de Madrid, Madrid 28660, Spain
| | - Eduardo Soriano
- Developmental Neurobiology and Regeneration Unit, Department of Cell Biology, Parc Científic de Barcelona and Institute of Neurosciences, University of Barcelona, Barcelona 08028, Spain.,Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III, Madrid 28031, Spain.,Institut de Recerca de l'Hospital Universitari de la Vall d'Hebron (VHIR), Barcelona 08023, Spain.,Institució Catalana de Recerca i Estudis Avançats Academia, Barcelona 08010, Spain
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20
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Hosford BE, Rowley S, Liska JP, Danzer SC. Ablation of peri-insult generated granule cells after epilepsy onset halts disease progression. Sci Rep 2017; 7:18015. [PMID: 29269775 PMCID: PMC5740143 DOI: 10.1038/s41598-017-18237-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 12/08/2017] [Indexed: 11/15/2022] Open
Abstract
Aberrant integration of newborn hippocampal granule cells is hypothesized to contribute to the development of temporal lobe epilepsy. To test this hypothesis, we used a diphtheria toxin receptor expression system to selectively ablate these cells from the epileptic mouse brain. Epileptogenesis was initiated using the pilocarpine status epilepticus model in male and female mice. Continuous EEG monitoring was begun 2–3 months after pilocarpine treatment. Four weeks into the EEG recording period, at a time when spontaneous seizures were frequent, mice were treated with diphtheria toxin to ablate peri-insult generated newborn granule cells, which were born in the weeks just before and after pilocarpine treatment. EEG monitoring continued for another month after cell ablation. Ablation halted epilepsy progression relative to untreated epileptic mice; the latter showing a significant and dramatic 300% increase in seizure frequency. This increase was prevented in treated mice. Ablation did not, however, cause an immediate reduction in seizures, suggesting that peri-insult generated cells mediate epileptogenesis, but that seizures per se are initiated elsewhere in the circuit. These findings demonstrate that targeted ablation of newborn granule cells can produce a striking improvement in disease course, and that the treatment can be effective when applied months after disease onset.
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Affiliation(s)
- Bethany E Hosford
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA.,Neuroscience Graduate Program, University of Cincinnati, Cincinnati, OH, 45267, USA
| | - Shane Rowley
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA
| | - John P Liska
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA
| | - Steve C Danzer
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA. .,Departments of Anesthesia and Pediatrics, University of Cincinnati, Cincinnati, OH, 45267, USA. .,Neuroscience Graduate Program, University of Cincinnati, Cincinnati, OH, 45267, USA.
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21
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Beining M, Mongiat LA, Schwarzacher SW, Cuntz H, Jedlicka P. T2N as a new tool for robust electrophysiological modeling demonstrated for mature and adult-born dentate granule cells. eLife 2017; 6:e26517. [PMID: 29165247 PMCID: PMC5737656 DOI: 10.7554/elife.26517] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 11/21/2017] [Indexed: 12/18/2022] Open
Abstract
Compartmental models are the theoretical tool of choice for understanding single neuron computations. However, many models are incomplete, built ad hoc and require tuning for each novel condition rendering them of limited usability. Here, we present T2N, a powerful interface to control NEURON with Matlab and TREES toolbox, which supports generating models stable over a broad range of reconstructed and synthetic morphologies. We illustrate this for a novel, highly detailed active model of dentate granule cells (GCs) replicating a wide palette of experiments from various labs. By implementing known differences in ion channel composition and morphology, our model reproduces data from mouse or rat, mature or adult-born GCs as well as pharmacological interventions and epileptic conditions. This work sets a new benchmark for detailed compartmental modeling. T2N is suitable for creating robust models useful for large-scale networks that could lead to novel predictions. We discuss possible T2N application in degeneracy studies.
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Affiliation(s)
- Marcel Beining
- Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck SocietyFrankfurtGermany
- Frankfurt Institute for Advanced StudiesFrankfurtGermany
- Institute of Clinical Neuroanatomy, Neuroscience CenterGoethe UniversityFrankfurtGermany
- Faculty of BiosciencesGoethe UniversityFrankfurtGermany
| | - Lucas Alberto Mongiat
- Instituto de Investigación en Biodiversidad y MedioambienteUniversidad Nacional del Comahue-CONICETSan Carlos de BarilocheArgentina
| | | | - Hermann Cuntz
- Ernst Strüngmann Institute (ESI) for Neuroscience in Cooperation with Max Planck SocietyFrankfurtGermany
- Frankfurt Institute for Advanced StudiesFrankfurtGermany
| | - Peter Jedlicka
- Institute of Clinical Neuroanatomy, Neuroscience CenterGoethe UniversityFrankfurtGermany
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22
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Santos VR, Pun RYK, Arafa SR, LaSarge CL, Rowley S, Khademi S, Bouley T, Holland KD, Garcia-Cairasco N, Danzer SC. PTEN deletion increases hippocampal granule cell excitability in male and female mice. Neurobiol Dis 2017; 108:339-351. [PMID: 28855130 DOI: 10.1016/j.nbd.2017.08.014] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 08/10/2017] [Accepted: 08/26/2017] [Indexed: 02/06/2023] Open
Abstract
Deletion of the mTOR pathway inhibitor PTEN from postnatally-generated hippocampal dentate granule cells causes epilepsy. Here, we conducted field potential, whole cell recording and single cell morphology studies to begin to elucidate the mechanisms by which granule cell-specific PTEN-loss produces disease. Cells from both male and female mice were recorded to identify sex-specific effects. PTEN knockout granule cells showed altered intrinsic excitability, evident as a tendency to fire in bursts. PTEN knockout granule cells also exhibited increased frequency of spontaneous excitatory synaptic currents (sEPSCs) and decreased frequency of inhibitory currents (sIPSCs), further indicative of a shift towards hyperexcitability. Morphological studies of PTEN knockout granule cells revealed larger dendritic trees, more dendritic branches and an impairment of dendrite self-avoidance. Finally, cells from both female control and female knockout mice received more sEPSCs and more sIPSCs than corresponding male cells. Despite the difference, the net effect produced statistically equivalent EPSC/IPSC ratios. Consistent with this latter observation, extracellularly evoked responses in hippocampal slices were similar between male and female knockouts. Both groups of knockouts were abnormal relative to controls. Together, these studies reveal a host of physiological and morphological changes among PTEN knockout cells likely to underlie epileptogenic activity. SIGNIFICANCE STATEMENT Hyperactivation of the mTOR pathway is associated with numerous neurological diseases, including autism and epilepsy. Here, we demonstrate that deletion of the mTOR negative regulator, PTEN, from a subset of hippocampal dentate granule impairs dendritic patterning, increases excitatory input and decreases inhibitory input. We further demonstrate that while granule cells from female mice receive more excitatory and inhibitory input than males, PTEN deletion produces mostly similar changes in both sexes. Together, these studies provide new insights into how the relatively small number (≈200,000) of PTEN knockout granule cells instigates the development of the profound epilepsy syndrome evident in both male and female animals in this model.
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Affiliation(s)
- Victor R Santos
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, United States; Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Raymund Y K Pun
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, United States
| | - Salwa R Arafa
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, United States; University of Cincinnati, College of Pharmacy, Cincinnati, OH 45267, United States
| | - Candi L LaSarge
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, United States
| | - Shane Rowley
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, United States
| | - Shadi Khademi
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, United States
| | - Tom Bouley
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, United States
| | - Katherine D Holland
- Division of Neurology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, United States
| | - Norberto Garcia-Cairasco
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil
| | - Steve C Danzer
- Department of Anesthesia, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, United States; Department of Pediatrics, University of Cincinnati, Cincinnati, OH 45267, United States.
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Thodeson DM, Brulet R, Hsieh J. Neural stem cells and epilepsy: functional roles and disease-in-a-dish models. Cell Tissue Res 2017; 371:47-54. [PMID: 28831605 DOI: 10.1007/s00441-017-2675-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Accepted: 07/20/2017] [Indexed: 01/07/2023]
Abstract
Epilepsy is a disorder of the central nervous system characterized by spontaneous recurrent seizures. Although current therapies exist to control the number and severity of clinical seizures, there are no pharmacological cures or disease-modifying treatments available. Use of transgenic mouse models has allowed an understanding of neural stem cells in their relation to epileptogenesis in mesial temporal lobe epilepsy. Further, with the significant discovery of factors necessary to reprogram adult somatic cell types into pluripotent stem cells, it has become possible to study monogenic epilepsy-in-a-dish using patient-derived neurons. This discovery along with some of the newest technological advances in recapitulating brain development in a dish has brought us closer than ever to a platform in which to study and understand the mechanisms of this disease. These technologies will be critical in understanding the mechanism of epileptogenesis and ultimately lead to improved therapies and precision medicine for patients with epilepsy.
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Affiliation(s)
- Drew M Thodeson
- Departments of Pediatrics and Neurology and Neurotherapeutics, Division of Child Neurology, UT Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Rebecca Brulet
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, 75390, USA
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, Dallas, TX, 75390, USA
- Hamon Center for Regenerative Science and Medicine, UT Southwestern Medical Center, Dallas, TX, 75390, USA
| | - Jenny Hsieh
- Department of Molecular Biology, UT Southwestern Medical Center, Dallas, TX, 75390, USA.
- Department of Neurology and Neurotherapeutics, UT Southwestern Medical Center, Dallas, TX, 75390, USA.
- Hamon Center for Regenerative Science and Medicine, UT Southwestern Medical Center, Dallas, TX, 75390, USA.
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Ablation of Newly Generated Hippocampal Granule Cells Has Disease-Modifying Effects in Epilepsy. J Neurosci 2017; 36:11013-11023. [PMID: 27798182 DOI: 10.1523/jneurosci.1371-16.2016] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 08/21/2016] [Indexed: 12/30/2022] Open
Abstract
Hippocampal granule cells generated in the weeks before and after an epileptogenic brain injury can integrate abnormally into the dentate gyrus, potentially mediating temporal lobe epileptogenesis. Previous studies have demonstrated that inhibiting granule cell production before an epileptogenic brain insult can mitigate epileptogenesis. Here, we extend upon these findings by ablating newly generated cells after the epileptogenic insult using a conditional, inducible diphtheria-toxin receptor expression strategy in mice. Diphtheria-toxin receptor expression was induced among granule cells born up to 5 weeks before pilocarpine-induced status epilepticus and these cells were then eliminated beginning 3 d after the epileptogenic injury. This treatment produced a 50% reduction in seizure frequency, but also a 20% increase in seizure duration, when the animals were examined 2 months later. These findings provide the first proof-of-concept data demonstrating that granule cell ablation therapy applied at a clinically relevant time point after injury can have disease-modifying effects in epilepsy. SIGNIFICANCE STATEMENT These findings support the long-standing hypothesis that newly generated dentate granule cells are pro-epileptogenic and contribute to the occurrence of seizures. This work also provides the first evidence that ablation of newly generated granule cells can be an effective therapy when begun at a clinically relevant time point after an epileptogenic insult. The present study also demonstrates that granule cell ablation, while reducing seizure frequency, paradoxically increases seizure duration. This paradoxical effect may reflect a disruption of homeostatic mechanisms that normally act to reduce seizure duration, but only when seizures occur frequently.
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Mendonça FN, Santos LEC, Rodrigues AM, Gomes da Silva S, Arida RM, da Silveira GA, Scorza FA, Almeida ACG. Physical Exercise Restores the Generation of Newborn Neurons in an Animal Model of Chronic Epilepsy. Front Neurosci 2017; 11:98. [PMID: 28298884 PMCID: PMC5331057 DOI: 10.3389/fnins.2017.00098] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 02/14/2017] [Indexed: 01/10/2023] Open
Abstract
Neurogenesis impairment is associated with the chronic phase of the epilepsy in humans and also observed in animal models. Recent studies with animal models have shown that physical exercise is capable of improving neurogenesis in adult subjects, alleviating cognitive impairment and depression. Here, we show that there is a reduction in the generation of newborn granule cells in the dentate gyrus of adult rats subjected to a chronic model of epilepsy during the postnatal period of brain development. We also show that the physical exercise was capable to restore the number of newborn granule cells in this animals to the level observed in the control group. Notably, a larger number of newborn granule cells exhibiting morphological characteristics indicative of correct targeting into the hippocampal circuitry and the absence of basal dendrite projections was also observed in the epileptic animals subjected to physical exercise compared to the epileptic animals. The results described here could represent a positive interference of the physical exercise on the neurogenesis process in subjects with chronic epilepsy. The results may also help to reinterpret the benefits of the physical exercise in alleviating symptoms of depression and cognitive dysfunction.
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Affiliation(s)
- Fabricio N Mendonça
- Laboratório de Neurociência Experimental e Computacional, Departamento de Engenharia de Biossistemas, Universidade Federal de São João del-Rei São João del-Rei, Brazil
| | - Luiz E C Santos
- Laboratório de Neurociência Experimental e Computacional, Departamento de Engenharia de Biossistemas, Universidade Federal de São João del-Rei São João del-Rei, Brazil
| | - Antônio M Rodrigues
- Laboratório de Neurociência Experimental e Computacional, Departamento de Engenharia de Biossistemas, Universidade Federal de São João del-Rei São João del-Rei, Brazil
| | - Sérgio Gomes da Silva
- Instituto do Cérebro, Hospital Israelita Albert EinsteinSão Paulo, Brazil; Núcleo de Pesquisas Tecnológicas, Universidade de Mogi das CruzesMogi das Cruzes, Brazil
| | - Ricardo M Arida
- Departamento de Fisiologia, Escola Paulista de Medicina, Universidade Federal de São Paulo (UNIFESP) São Paulo, Brazil
| | - Gilcélio A da Silveira
- Laboratório de Neurociência Experimental e Computacional, Departamento de Engenharia de Biossistemas, Universidade Federal de São João del-Rei São João del-Rei, Brazil
| | - Fulvio A Scorza
- Laboratório de Neurociência Experimental e Computacional, Departamento de Engenharia de Biossistemas, Universidade Federal de São João del-ReiSão João del-Rei, Brazil; Disciplina de Neurologia Experimental, Escola Paulista de Medicina, Universidade Federal de São Paulo (UNIFESP)São Paulo, Brazil
| | - Antônio-Carlos G Almeida
- Laboratório de Neurociência Experimental e Computacional, Departamento de Engenharia de Biossistemas, Universidade Federal de São João del-Rei São João del-Rei, Brazil
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26
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Kelly T, Beck H. Functional properties of granule cells with hilar basal dendrites in the epileptic dentate gyrus. Epilepsia 2016; 58:160-171. [PMID: 27888509 DOI: 10.1111/epi.13605] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/10/2016] [Indexed: 01/24/2023]
Abstract
OBJECTIVE The maturation of adult-born granule cells and their functional integration into the network is thought to play a key role in the proper functioning of the dentate gyrus. In temporal lobe epilepsy, adult-born granule cells in the dentate gyrus develop abnormally and possess a hilar basal dendrite (HBD). Although morphological studies have shown that these HBDs have synapses, little is known about the functional properties of these HBDs or the intrinsic and network properties of the granule cells that possess these aberrant dendrites. METHODS We performed patch-clamp recordings of granule cells within the granule cell layer "normotopic" from sham-control and status epilepticus (SE) animals. Normotopic granule cells from SE animals possessed an HBD (SE+ HBD+ cells) or not (SE+ HBD- cells). Apical and basal dendrites were stimulated using multiphoton uncaging of glutamate. Two-photon Ca2+ imaging was used to measure Ca2+ transients associated with back-propagating action potentials (bAPs). RESULTS Near-synchronous synaptic input integrated linearly in apical dendrites from sham-control animals and was not significantly different in apical dendrites of SE+ HBD- cells. The majority of HBDs integrated input linearly, similar to apical dendrites. However, 2 of 11 HBDs were capable of supralinear integration mediated by a dendritic spike. Furthermore, the bAP-evoked Ca2+ transients were relatively well maintained along HBDs, compared with apical dendrites. This further suggests an enhanced electrogenesis in HBDs. In addition, the output of granule cells from epileptic tissue was enhanced, with both SE+ HBD- and SE+ HBD+ cells displaying increased high-frequency (>100 Hz) burst-firing. Finally, both SE+ HBD- and SE+ HBD+ cells received recurrent excitatory input that was capable of generating APs, especially in the absence of feedback inhibition. SIGNIFICANCE Taken together, these data suggest that the enhanced excitability of HBDs combined with the altered intrinsic and network properties of granule cells collude to promote excitability and synchrony in the epileptic dentate gyrus.
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Affiliation(s)
- Tony Kelly
- Laboratory for Experimental Epileptology and Cognition Research, Department of Epileptology, University of Bonn, Bonn, Germany
| | - Heinz Beck
- Laboratory for Experimental Epileptology and Cognition Research, Department of Epileptology, University of Bonn, Bonn, Germany.,German Center for Neurodegenerative Diseases (DZNE), Bonn, Germany
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Shao H, Yang Y, Qi AP, Hong P, Zhu GX, Cao XY, Ji WG, Zhu ZR. Gastrodin Reduces the Severity of Status Epilepticus in the Rat Pilocarpine Model of Temporal Lobe Epilepsy by Inhibiting Nav1.6 Sodium Currents. Neurochem Res 2016; 42:360-374. [PMID: 27743286 DOI: 10.1007/s11064-016-2079-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 09/27/2016] [Accepted: 10/04/2016] [Indexed: 01/06/2023]
Abstract
Temporal lobe epilepsy (TLE) is one of the most refractory types of adult epilepsy, and treatment options remain unsatisfactory. Gastrodin (GAS), a phenolic glucoside used in Chinese herbal medicine and derived from Gastrodia elata Blume, has been shown to have remarkable anticonvulsant effects on various models of epilepsy in vivo. However, the mechanisms of GAS as an anticonvulsant drug remain to be established. By utilizing a combination of behavioral surveys, immunofluorescence and electrophysiological recordings, the present study characterized the anticonvulsant effect of GAS in a pilocarpine-induced status epilepticus (SE) rat model of TLE and explored the underlying cellular mechanisms. We found that GAS pretreatment effectively reduced the severity of SE in the acute phase of TLE. Moreover, GAS protected medial entorhinal cortex (mEC) layer III neurons from neuronal death and terminated the SE-induced bursting discharge of mEC layer II neurons from SE-experienced rats. Furthermore, the current study revealed that GAS prevented the pilocarpine-induced enhancement of Nav1.6 currents (persistent (INaP) and resurgent (INaR) currents), which were reported to play a critical role in the generation of bursting spikes. Consistent with this result, GAS treatment reversed the expression of Nav1.6 protein in SE-experienced EC neurons. These results suggest that the inhibition of Nav1.6 sodium currents may be the underlying mechanism of GAS's anticonvulsant properties.
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Affiliation(s)
- Hui Shao
- Department of Developmental Neuropsychology, School of Psychology, Third Military Medical University, Gaotanyan Street 30, Chongqing, 400038, China
- Department of Physiology, Third Military Medical University, Chongqing, China
- The Fifth Camp of Cadet Brigade, Third Military Medical University, Chongqing, China
| | - Yang Yang
- Department of Developmental Neuropsychology, School of Psychology, Third Military Medical University, Gaotanyan Street 30, Chongqing, 400038, China
| | - Ai-Ping Qi
- Department of Developmental Neuropsychology, School of Psychology, Third Military Medical University, Gaotanyan Street 30, Chongqing, 400038, China
| | - Pian Hong
- Department of Developmental Neuropsychology, School of Psychology, Third Military Medical University, Gaotanyan Street 30, Chongqing, 400038, China
| | - Guang-Xi Zhu
- Department of Developmental Neuropsychology, School of Psychology, Third Military Medical University, Gaotanyan Street 30, Chongqing, 400038, China
| | - Xin-Yu Cao
- The Fifth Camp of Cadet Brigade, Third Military Medical University, Chongqing, China
| | - Wei-Gang Ji
- Department of Chemistry, Faculty of Pharmacy, Third Military Medical University, Chongqing, China
| | - Zhi-Ru Zhu
- Department of Developmental Neuropsychology, School of Psychology, Third Military Medical University, Gaotanyan Street 30, Chongqing, 400038, China.
- Department of Physiology, Third Military Medical University, Chongqing, China.
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Impact of rapamycin on status epilepticus induced hippocampal pathology and weight gain. Exp Neurol 2016; 280:1-12. [PMID: 26995324 DOI: 10.1016/j.expneurol.2016.03.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Revised: 03/11/2016] [Accepted: 03/14/2016] [Indexed: 02/07/2023]
Abstract
Growing evidence implicates the dentate gyrus in temporal lobe epilepsy (TLE). Dentate granule cells limit the amount of excitatory signaling through the hippocampus and exhibit striking neuroplastic changes that may impair this function during epileptogenesis. Furthermore, aberrant integration of newly-generated granule cells underlies the majority of dentate restructuring. Recently, attention has focused on the mammalian target of rapamycin (mTOR) signaling pathway as a potential mediator of epileptogenic change. Systemic administration of the mTOR inhibitor rapamycin has promising therapeutic potential, as it has been shown to reduce seizure frequency and seizure severity in rodent models. Here, we tested whether mTOR signaling facilitates abnormal development of granule cells during epileptogenesis. We also examined dentate inflammation and mossy cell death in the dentate hilus. To determine if mTOR activation is necessary for abnormal granule cell development, transgenic mice that harbored fluorescently-labeled adult-born granule cells were treated with rapamycin following pilocarpine-induced status epilepticus. Systemic rapamycin effectively blocked phosphorylation of S6 protein (a readout of mTOR activity) and reduced granule cell mossy fiber axon sprouting. However, the accumulation of ectopic granule cells and granule cells with aberrant basal dendrites was not significantly reduced. Mossy cell death and reactive astrocytosis were also unaffected. These data suggest that anti-epileptogenic effects of mTOR inhibition may be mediated by mechanisms other than inhibition of these common dentate pathologies. Consistent with this conclusion, rapamycin prevented pathological weight gain in epileptic mice, suggesting that rapamycin might act on central circuits or even peripheral tissues controlling weight gain in epilepsy.
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29
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Scharfman HE, Myers CE. Corruption of the dentate gyrus by "dominant" granule cells: Implications for dentate gyrus function in health and disease. Neurobiol Learn Mem 2016; 129:69-82. [PMID: 26391451 PMCID: PMC4792754 DOI: 10.1016/j.nlm.2015.09.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 09/02/2015] [Accepted: 09/06/2015] [Indexed: 12/31/2022]
Abstract
The dentate gyrus (DG) and area CA3 of the hippocampus are highly organized lamellar structures which have been implicated in specific cognitive functions such as pattern separation and pattern completion. Here we describe how the anatomical organization and physiology of the DG and CA3 are consistent with structures that perform pattern separation and completion. We then raise a new idea related to the complex circuitry of the DG and CA3 where CA3 pyramidal cell 'backprojections' play a potentially important role in the sparse firing of granule cells (GCs), considered important in pattern separation. We also propose that GC axons, the mossy fibers, already known for their highly specialized structure, have a dynamic function that imparts variance--'mossy fiber variance'--which is important to pattern separation and completion. Computational modeling is used to show that when a subset of GCs become 'dominant,' one consequence is loss of variance in the activity of mossy fiber axons and a reduction in pattern separation and completion in the model. Empirical data are then provided using an example of 'dominant' GCs--subsets of GCs that develop abnormally and have increased excitability. Notably, these abnormal GCs have been identified in animal models of disease where DG-dependent behaviors are impaired. Together these data provide insight into pattern separation and completion, and suggest that behavioral impairment could arise from dominance of a subset of GCs in the DG-CA3 network.
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Affiliation(s)
- Helen E Scharfman
- The Nathan S. Kline Institute for Psychiatric Research, 140 Old Orangeburg Rd., Orangeburg, NY 10962, United States; Departments of Child & Adolescent Psychiatry, Physiology & Neuroscience, and Psychiatry, New York University Langone Medical Center, United States.
| | - Catherine E Myers
- VA New Jersey Health Care System, VA Medical Center, NeuroBehavioral Research Lab (Mail Stop 15a), 385 Tremont Avenue, East Orange, NJ 07018, United States; Department of Pharmacology, Physiology & Neuroscience, Rutgers-New Jersey Medical School, United States
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30
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Korn MJ, Mandle QJ, Parent JM. Conditional Disabled-1 Deletion in Mice Alters Hippocampal Neurogenesis and Reduces Seizure Threshold. Front Neurosci 2016; 10:63. [PMID: 26941603 PMCID: PMC4766299 DOI: 10.3389/fnins.2016.00063] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 02/10/2016] [Indexed: 11/13/2022] Open
Abstract
Many animal models of temporal lobe epilepsy (TLE) exhibit altered neurogenesis arising from progenitors within the dentate gyrus subgranular zone (SGZ). Aberrant integration of new neurons into the existing circuit is thought to contribute to epileptogenesis. In particular, adult-born neurons that exhibit ectopic migration and hilar basal dendrites (HBDs) are suggested to be pro-epileptogenic. Loss of reelin signaling may contribute to these morphological changes in patients with epilepsy. We previously demonstrated that conditional deletion of the reelin adaptor protein, disabled-1 (Dab1), from postnatal mouse SGZ progenitors generated dentate granule cells (DGCs) with abnormal dendritic development and ectopic placement. To determine whether the early postnatal loss of reelin signaling is epileptogenic, we conditionally deleted Dab1 in neural progenitors and their progeny on postnatal days 7–8 and performed chronic video-EEG recordings 8–10 weeks later. Dab1-deficient mice did not have spontaneous seizures but exhibited interictal epileptiform abnormalities and a significantly reduced latency to pilocarpine-induced status epilepticus. After chemoconvulsant treatment, over 90% of mice deficient for Dab1 developed generalized motor convulsions with tonic-clonic movements, rearing, and falling compared to <20% of wild-type mice. Recombination efficiency, measured by Cre reporter expression, inversely correlated with time to the first sustained seizure. These pro-epileptogenic changes were associated with decreased neurogenesis and increased numbers of hilar ectopic DGCs. Interestingly, neurons co-expressing the Cre reporter comprised a fraction of these hilar ectopic DGCs cells, suggesting a non-cell autonomous effect for the loss of reelin signaling. We also noted a dispersion of the CA1 pyramidal layer, likely due to hypomorphic effects of the conditional Dab1 allele, but this abnormality did not correlate with seizure susceptibility. These findings suggest that the misplacement or reduction of postnatally-generated DGCs contributes to aberrant circuit development and hyperexcitability, but aberrant neurogenesis after conditional Dab1 deletion alone is not sufficient to produce spontaneous seizures.
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Affiliation(s)
- Matthew J Korn
- Department of Neurology, University of Michigan Medical Center Ann Arbor, MI, USA
| | - Quinton J Mandle
- Department of Neurology, University of Michigan Medical Center Ann Arbor, MI, USA
| | - Jack M Parent
- Department of Neurology, University of Michigan Medical CenterAnn Arbor, MI, USA; VA Ann Arbor Healthcare SystemAnn Arbor, MI, USA
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31
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Llorens-Martín M, Rábano A, Ávila J. The Ever-Changing Morphology of Hippocampal Granule Neurons in Physiology and Pathology. Front Neurosci 2016; 9:526. [PMID: 26834550 PMCID: PMC4717329 DOI: 10.3389/fnins.2015.00526] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 12/29/2015] [Indexed: 11/29/2022] Open
Abstract
Newborn neurons are continuously added to the hippocampal dentate gyrus throughout adulthood. In this review, we analyze the maturational stages that newborn granule neurons go through, with a focus on their unique morphological features during each stage under both physiological and pathological circumstances. In addition, the influence of deleterious (such as schizophrenia, stress, Alzheimer's disease, seizures, stroke, inflammation, dietary deficiencies, or the consumption of drugs of abuse or toxic substances) and neuroprotective (physical exercise and environmental enrichment) stimuli on the maturation of these cells will be examined. Finally, the regulation of this process by proteins involved in neurodegenerative and neurological disorders such as Glycogen synthase kinase 3β, Disrupted in Schizophrenia 1 (DISC-1), Glucocorticoid receptor, pro-inflammatory mediators, Presenilin-1, Amyloid precursor protein, Cyclin-dependent kinase 5 (CDK5), among others, will be evaluated. Given the recently acquired relevance of the dendritic branch as a functional synaptic unit required for memory storage, a full understanding of the morphological alterations observed in newborn neurons may have important consequences for the prevention and treatment of the cognitive and affective alterations that evolve in conjunction with impaired adult hippocampal neurogenesis.
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Affiliation(s)
- María Llorens-Martín
- Molecular Neurobiology, Function of Microtubular Proteins, Centro de Biología Molecular Severo Ochoa (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid)Madrid, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (Instituto de Salud Carlos III)Madrid, Spain
| | - Alberto Rábano
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (Instituto de Salud Carlos III)Madrid, Spain; Neuropathology Department, CIEN FoundationMadrid, Spain
| | - Jesús Ávila
- Molecular Neurobiology, Function of Microtubular Proteins, Centro de Biología Molecular Severo Ochoa (Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid)Madrid, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (Instituto de Salud Carlos III)Madrid, Spain
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32
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Zsurka G, Kunz WS. Mitochondrial dysfunction and seizures: the neuronal energy crisis. Lancet Neurol 2015; 14:956-66. [PMID: 26293567 DOI: 10.1016/s1474-4422(15)00148-9] [Citation(s) in RCA: 151] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Revised: 06/19/2015] [Accepted: 06/24/2015] [Indexed: 12/21/2022]
Abstract
Seizures are often the key manifestation of neurological diseases caused by pathogenic mutations in 169 of the genes that have so far been identified to affect mitochondrial function. Mitochondria are the main producers of ATP needed for normal electrical activities of neurons and synaptic transmission. Additionally, they have a central role in neurotransmitter synthesis, calcium homoeostasis, redox signalling, production and modulation of reactive oxygen species, and neuronal death. Hypotheses link mitochondrial failure to seizure generation through changes in calcium homoeostasis, oxidation of ion channels and neurotransmitter transporters by reactive oxygen species, a decrease in neuronal plasma membrane potential, and reduced network inhibition due to interneuronal dysfunction. Seizures, irrespective of their origin, represent an excessive acute energy demand in the brain. Accordingly, secondary mitochondrial dysfunction has been described in various epileptic disorders, including disorders that are mainly of non-mitochondrial origin. An understanding of the reciprocal relation between mitochondrial dysfunction and epilepsy is crucial to select appropriate anticonvulsant treatment and has the potential to open up new therapeutic approaches in the subset of epileptic disorders caused by mitochondrial dysfunction.
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Affiliation(s)
- Gábor Zsurka
- Division of Neurochemistry, Department of Epileptology, and Life & Brain Center, University of Bonn, Bonn, Germany
| | - Wolfram S Kunz
- Division of Neurochemistry, Department of Epileptology, and Life & Brain Center, University of Bonn, Bonn, Germany.
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33
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Singh SP, LaSarge CL, An A, McAuliffe JJ, Danzer SC. Clonal Analysis of Newborn Hippocampal Dentate Granule Cell Proliferation and Development in Temporal Lobe Epilepsy. eNeuro 2015; 2:ENEURO.0087-15.2015. [PMID: 26756038 PMCID: PMC4706641 DOI: 10.1523/eneuro.0087-15.2015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 11/23/2015] [Accepted: 12/01/2015] [Indexed: 11/21/2022] Open
Abstract
Hippocampal dentate granule cells are among the few neuronal cell types generated throughout adult life in mammals. In the normal brain, new granule cells are generated from progenitors in the subgranular zone and integrate in a typical fashion. During the development of epilepsy, granule cell integration is profoundly altered. The new cells migrate to ectopic locations and develop misoriented "basal" dendrites. Although it has been established that these abnormal cells are newly generated, it is not known whether they arise ubiquitously throughout the progenitor cell pool or are derived from a smaller number of "bad actor" progenitors. To explore this question, we conducted a clonal analysis study in mice expressing the Brainbow fluorescent protein reporter construct in dentate granule cell progenitors. Mice were examined 2 months after pilocarpine-induced status epilepticus, a treatment that leads to the development of epilepsy. Brain sections were rendered translucent so that entire hippocampi could be reconstructed and all fluorescently labeled cells identified. Our findings reveal that a small number of progenitors produce the majority of ectopic cells following status epilepticus, indicating that either the affected progenitors or their local microenvironments have become pathological. By contrast, granule cells with "basal" dendrites were equally distributed among clonal groups. This indicates that these progenitors can produce normal cells and suggests that global factors sporadically disrupt the dendritic development of some new cells. Together, these findings strongly predict that distinct mechanisms regulate different aspects of granule cell pathology in epilepsy.
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Affiliation(s)
- Shatrunjai P. Singh
- Department of Anesthesia, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio 45229
- Molecular and Developmental Biology Program, University of Cincinnati, Cincinnati, Ohio 45237
| | - Candi L. LaSarge
- Department of Anesthesia, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio 45229
| | - Amen An
- Department of Anesthesia, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio 45229
- Department of Neuroscience, McMicken College of Arts and Sciences, University of Cincinnati, Cincinnati, Ohio 45221
| | - John J. McAuliffe
- Department of Anesthesia, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio 45229
| | - Steve C. Danzer
- Department of Anesthesia, Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio 45229
- Molecular and Developmental Biology Program, University of Cincinnati, Cincinnati, Ohio 45237
- Departments of Anesthesia and Pediatrics, University of Cincinnati, Cincinnati, Ohio 45267
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34
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Gao F, Song X, Zhu D, Wang X, Hao A, Nadler JV, Zhan RZ. Dendritic morphology, synaptic transmission, and activity of mature granule cells born following pilocarpine-induced status epilepticus in the rat. Front Cell Neurosci 2015; 9:384. [PMID: 26500490 PMCID: PMC4596052 DOI: 10.3389/fncel.2015.00384] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2015] [Accepted: 09/14/2015] [Indexed: 01/23/2023] Open
Abstract
To understand the potential role of enhanced hippocampal neurogenesis after pilocarpine-induced status epilepticus (SE) in the development of epilepsy, we quantitatively analyzed the geometry of apical dendrites, synaptic transmission, and activation levels of normotopically distributed mature newborn granule cells in the rat. SE in male Sprague-Dawley rats (between 6 and 7 weeks old) lasting for more than 2 h was induced by an intraperitoneal injection of pilocarpine. The complexity, spine density, miniature post-synaptic currents, and activity-regulated cytoskeleton-associated protein (Arc) expression of granule cells born 5 days after SE were studied between 10 and 17 weeks after CAG-GFP retroviral vector-mediated labeling. Mature granule cells born after SE had dendritic complexity similar to that of granule cells born naturally, but with denser mushroom-like spines in dendritic segments located in the outer molecular layer. Miniature inhibitory post-synaptic currents (mIPSCs) were similar between the controls and rats subjected to SE; however, smaller miniature excitatory post-synaptic current (mEPSC) amplitude with a trend toward less frequent was found in mature granule cells born after SE. After maturation, granule cells born after SE did not show denser Arc expression in the resting condition or 2 h after being activated by pentylenetetrazol-induced transient seizure activity than vicinal GFP-unlabeled granule cells. Thus our results suggest that normotopic granule cells born after pilocarpine-induced SE are no more active when mature than age-matched, naturally born granule cells.
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Affiliation(s)
- Fei Gao
- Department of Physiology, Shandong University School of Medicine Jinan, China
| | - Xueying Song
- Department of Physiology, Shandong University School of Medicine Jinan, China
| | - Dexiao Zhu
- Department of Physiology, Shandong University School of Medicine Jinan, China
| | - Xiaochen Wang
- Department of Physiology, Shandong University School of Medicine Jinan, China
| | - Aijun Hao
- Department of Histology and Embryology, Shandong University School of Medicine Jinan, China
| | - J Victor Nadler
- Departments of Pharmacology and Neurobiology, Duke University Medical Center Durham, NC, USA
| | - Ren-Zhi Zhan
- Department of Physiology, Shandong University School of Medicine Jinan, China
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