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Berry BJ, Akanda N, Smith AST, Long CJ, Schnepper MT, Guo X, Hickman JJ. Morphological and functional characterization of human induced pluripotent stem cell-derived neurons (iCell Neurons) in defined culture systems. Biotechnol Prog 2015; 31:1613-22. [PMID: 26317319 DOI: 10.1002/btpr.2160] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 08/20/2015] [Indexed: 01/09/2023]
Abstract
Pre-clinical testing of drug candidates in animal models is expensive, time-consuming, and often fails to predict drug effects in humans. Industry and academia alike are working to build human-based in vitro test beds and advanced high throughput screening systems to improve the translation of preclinical results to human drug trials. Human neurons derived from induced pluripotent stems cells (hiPSCs) are readily available for use within these test-beds and high throughput screens, but there remains a need to robustly evaluate cellular behavior prior to their incorporation in such systems. This study reports on the characterization of one source of commercially available hiPSC-derived neurons, iCell(®) Neurons, for their long-term viability and functional performance to assess their suitability for integration within advanced in vitro platforms. The purity, morphology, survival, identity, and functional maturation of the cells utilizing different culture substrates and medium combinations were evaluated over 28 days in vitro (DIV). Patch-clamp electrophysiological data demonstrated increased capacity for repetitive firing of action potentials across all culture conditions. Significant differences in cellular maturity, morphology, and functional performance were observed in the different conditions, highlighting the importance of evaluating different surface types and growth medium compositions for application in specific in vitro protocols.
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Affiliation(s)
- Bonnie J Berry
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826
| | - Nesar Akanda
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826
| | - Alec S T Smith
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826
| | - Christopher J Long
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826
| | - Mark T Schnepper
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826
| | - Xiufang Guo
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826
| | - James J Hickman
- NanoScience Technology Center, University of Central Florida, 12424 Research Parkway, Suite 400, Orlando, FL, 32826
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Watrin F, Manent JB, Cardoso C, Represa A. Causes and consequences of gray matter heterotopia. CNS Neurosci Ther 2014; 21:112-22. [PMID: 25180909 DOI: 10.1111/cns.12322] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 07/30/2014] [Accepted: 08/06/2014] [Indexed: 12/17/2022] Open
Abstract
The objective of this article is to review the pathophysiological bases of gray matter heterotopia and to appreciate their involvement in brain cortical development and functional consequences, namely epilepsy. The development of the cerebral cortex results from complex sequential processes including cell proliferation, cell migration, cortical organization, and formation of neuronal networks. Disruption of these steps yields different types of cortical malformations including gray matter heterotopia, characterized by the ectopic position of neurons along the ventricular walls or in the deep white matter. Cortical malformations are major causes of epilepsy, being responsible for up to 40% of drug-resistant epilepsy, and the cognitive level of affected patients varies from normal to severely impaired. This review reports data from human patients and animal models highlighting the genetic causes for these disorders affecting not only neuronal migration but also the proliferation of cortical progenitors. Therefore, gray matter heterotopias should not be considered as solely due to an abnormal neuronal migration and classifying them as such may be too restrictive. The review will also summarize literature data indicating that besides ectopic neurons, neighbor cortical areas also play a consistent role in epileptogenesis, supporting the notion that plastic changes secondary to the initial malformation are instrumental in the pathophysiology of epilepsy in affected patients.
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Affiliation(s)
- Françoise Watrin
- INSERM, INMED, Marseille, France; Aix-Marseille University, UMR 901, Marseille, France
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Bando SY, Silva FN, Costa LDF, Silva AV, Pimentel-Silva LR, Castro LHM, Wen HT, Amaro E, Moreira-Filho CA. Complex network analysis of CA3 transcriptome reveals pathogenic and compensatory pathways in refractory temporal lobe epilepsy. PLoS One 2013; 8:e79913. [PMID: 24278214 PMCID: PMC3836787 DOI: 10.1371/journal.pone.0079913] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 09/25/2013] [Indexed: 12/21/2022] Open
Abstract
We previously described - studying transcriptional signatures of hippocampal CA3 explants - that febrile (FS) and afebrile (NFS) forms of refractory mesial temporal lobe epilepsy constitute two distinct genomic phenotypes. That network analysis was based on a limited number (hundreds) of differentially expressed genes (DE networks) among a large set of valid transcripts (close to two tens of thousands). Here we developed a methodology for complex network visualization (3D) and analysis that allows the categorization of network nodes according to distinct hierarchical levels of gene-gene connections (node degree) and of interconnection between node neighbors (concentric node degree). Hubs are highly connected nodes, VIPs have low node degree but connect only with hubs, and high-hubs have VIP status and high overall number of connections. Studying the whole set of CA3 valid transcripts we: i) obtained complete transcriptional networks (CO) for FS and NFS phenotypic groups; ii) examined how CO and DE networks are related; iii) characterized genomic and molecular mechanisms underlying FS and NFS phenotypes, identifying potential novel targets for therapeutic interventions. We found that: i) DE hubs and VIPs are evenly distributed inside the CO networks; ii) most DE hubs and VIPs are related to synaptic transmission and neuronal excitability whereas most CO hubs, VIPs and high hubs are related to neuronal differentiation, homeostasis and neuroprotection, indicating compensatory mechanisms. Complex network visualization and analysis is a useful tool for systems biology approaches to multifactorial diseases. Network centrality observed for hubs, VIPs and high hubs of CO networks, is consistent with the network disease model, where a group of nodes whose perturbation leads to a disease phenotype occupies a central position in the network. Conceivably, the chance for exerting therapeutic effects through the modulation of particular genes will be higher if these genes are highly interconnected in transcriptional networks.
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Affiliation(s)
- Silvia Yumi Bando
- Department of Pediatrics, Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, São Paulo, Brazil
| | | | | | - Alexandre V. Silva
- Department of Biosciences, Universidade Federal de São Paulo, Santos, São Paulo, Brazil
| | | | - Luiz HM. Castro
- Clinical Neurology Division, Hospital das Clínicas da FMUSP, São Paulo, São Paulo, Brazil
| | - Hung-Tzu Wen
- Epilepsy Surgery Group, Hospital das Clínicas da FMUSP, São Paulo, São Paulo, Brazil
| | - Edson Amaro
- Department of Radiology, Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, São Paulo, Brazil
| | - Carlos Alberto Moreira-Filho
- Department of Pediatrics, Faculdade de Medicina da Universidade de São Paulo (FMUSP), São Paulo, São Paulo, Brazil
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Abstract
Cortical dysplasia of various types, reflecting abnormalities of brain development, have been closely associated with epileptic activities. Yet, there remains considerable discussion about if/how these structural lesions give rise to seizure phenomenology. Animal models have been used to investigate the cause-effect relationships between aberrant cortical structure and epilepsy. In this article, we discuss three such models: (1) the Eker rat model of tuberous sclerosis, in which a gene mutation gives rise to cortical disorganization and cytologically abnormal cellular elements; (2) the p35 knockout mouse, in which the genetic dysfunction gives rise to compromised cortical organization and lamination, but in which the cellular elements appear normal; and (3) the methylazoxymethanol-exposed rat, in which time-specific chemical DNA disruption leads to abnormal patterns of cell formation and migration, resulting in heterotopic neuronal clusters. Integrating data from studies of these animal models with related clinical observations, we propose that the neuropathologic features of these cortical dysplastic lesions are insufficient to determine the seizure-initiating process. Rather, it is their interaction with a more subtly disrupted cortical "surround" that constitutes the circuitry underlying epileptiform activities as well as seizure propensity and ictogenesis.
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Affiliation(s)
- Philip A Schwartzkroin
- Department of Neurological Surgery, University of California-Davis, One Shields Ave., Davis, CA 95616, U.S.A.
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5
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Imai H, Yamamoto T, Terashima T, Sugioka K. Characterization of heterotopic cell clusters in the hippocampus of the rat after prenatal treatment of methylazoxymethanol acetate. Congenit Anom (Kyoto) 2012; 52:87-96. [PMID: 22639994 DOI: 10.1111/j.1741-4520.2012.00358.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Prenatal exposure of methylazoxymethanol acetate, a DNA methylating agent, to pregnant rats on embryonic day 15 is known to produce hippocampal malformation and laminar disorganization of the cerebral cortex. However, there are few studies to demonstrate developmental processes of abnormal structures in the hippocampus. In the present study, we examined complete serial sections of rat brains on postnatal day 0 to 2, which pretreated with methylazoxymethanol acetate on embryonic day 15. At birth, massive cellular clusters were found under the white matter of the cerebral cortex and then, a part of these clusters entered into the hippocampal CA1 sector on postnatal day 2. These ectopic cellular clusters in the CA1 were immunoreactive to anti-calbindin antibody, suggesting that the origin of these cellular clusters is equivalent to that of the cortical layer II/III neurons. Next, we injected FluoroGold into the lateral septal nucleus to examine hippocampo-septal projection. FluoroGold-labeled neurons were scattered in the ectopic cellular cluster, implying that CA1 pyramidal neurons project normally to the lateral septal nucleus. In conclusion, a majority of neurons found in the ectopic cellular cluster caused by prenatal methylazoxymethanol treatment is derived from cortical neurons, and some intrinsic pyramidal neurons in the CA1 of hippocampus are scattered throughout the ectopic cellular cluster.
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Affiliation(s)
- Hideaki Imai
- Division of Developmental Neurobiology, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, Japan
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Karlsson A, Lindquist C, Malmgren K, Asztely F. Altered spontaneous synaptic inhibition in an animal model of cerebral heterotopias. Brain Res 2011; 1383:54-61. [PMID: 21281607 DOI: 10.1016/j.brainres.2011.01.080] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 01/21/2011] [Accepted: 01/21/2011] [Indexed: 11/27/2022]
Abstract
We have investigated spontaneous synaptic transmission in hippocampal nodular heterotopias in rats exposed to methylazoxymethanol (MAM) in utero. Pregnant Wistar rats were injected with MAM at E16. Acute hippocampal slices were prepared from the rat pups P14 to P40. Whole-cell voltage-clamp recordings were made from visually identified neurons using IR-DIC video microscopy. Synaptic events were recorded from either heterotopic neurons in the CA1 region or "slice-matched" normotopic CA1 pyramidal neurons. Both the spontaneous inhibitory (sIPSC) and excitatory synaptic transmission (sEPSC) to the same neurons were recorded. We found a profound reduction in the frequency of sIPSCs in the heterotopic neurons vs. normotopic neurons. No significant differences in the frequency of sEPSCs were found. We also found a profound reduction in the frequency of spontaneous IPSCs in normotopic neurons following application of the GABA reuptake blocker, NO-711, even in the presence of a GABA(B) receptor antagonist (CGP 55845). Preferentially blocking extrasynaptic GABA(A) receptors caused an increased frequency of sIPSCs in the heterotopic neurons. Our data suggest that there is a predominant change in inhibitory synaptic transmission, as measured by changes in sIPSCs, with no change in excitatory synaptic transmission to heterotopic neurons in hippocampus of rats exposed to MAM in utero. We suggest that this change is caused by an increase in the extracellular concentration of GABA but is not mediated via activation of presynaptic GABA(B) receptors. Rather, we propose that the increased extracellular GABA concentration in the heterotopias dampens the activity in inhibitory neurons via activation of extrasynaptic GABA(A) receptors.
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Affiliation(s)
- Anna Karlsson
- Epilepsy Research Group, Section of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, Sahlgrenska Academy, Göteborg University, SE 413 45 Göteborg, Sweden
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7
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Regeneration of 5-HT fibers in hippocampal heterotopia of methylazoxymethanol-induced micrencephalic rats after neonatal 5,7-DHT injection. Anat Sci Int 2009; 85:38-45. [DOI: 10.1007/s12565-009-0052-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Accepted: 06/08/2009] [Indexed: 11/25/2022]
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Najm IM, Tilelli CQ, Oghlakian R. Pathophysiological mechanisms of focal cortical dysplasia: a critical review of human tissue studies and animal models. Epilepsia 2007; 48 Suppl 2:21-32. [PMID: 17571350 DOI: 10.1111/j.1528-1167.2007.01064.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Cortical dysplasia (CD, also known as malformations of cortical development) are the pathological substrates in a large percentage of patients with pharmacoresistant epilepsy who may be amenable to surgical treatment. Therefore, research on the mechanisms of dysplastic lesion formation and epileptogenicity is of paramount importance for the prevention, detection, and treatment of CD-induced epilepsy. The purpose of this review is to discuss and critically evaluate the current state and results of human tissue experimentation (focusing on reported results of studies done on neocortical dysplastic tissue resected from patients with pharmacoresistant epilepsy), and to discuss some of the concerns related to research that uses surgically resected epileptic human tissue. The use of better animal models of CD as a tool toward the better understanding of the mechanisms of pathogenesis, epileptogenesis, and epileptogenicity of dysplastic lesions will be reviewed from the perspective of their usefulness in a model of translational research that should ultimately result in better diagnostic and therapeutic techniques of CD.
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Affiliation(s)
- Imad M Najm
- Cleveland Clinic Epilepsy Center Head, Section of Adult Epilepsy and Clinical Neurophysiology, 9500 Euclid Avenue, S51, Cleveland, OH 44195, USA.
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Zsombok A, Jacobs KM. Postsynaptic currents prior to onset of epileptiform activity in rat microgyria. J Neurophysiol 2007; 98:178-86. [PMID: 17475719 DOI: 10.1152/jn.00106.2007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Structural malformations of the cortex, arising as a result of genetic mutation or injury during development are associated with dyslexia, epilepsy, and other neurological deficits. We have used a rat model of a microgyral malformation to examine mechanisms of epileptogenesis. Our previous studies showed that the frequency of miniature excitatory postsynaptic currents (mEPSCs) recorded in neocortical layer V pyramidal neurons is increased in malformed cortex at a time when field potential epileptiform events can be evoked. Here we show that the increase occurs at an age before onset of cortical epileptiform activity and at a time when the frequency of mEPSCs in control layer V pyramidal neurons is stable. An increase in the frequency of spontaneous (s)EPSCs in layer V pyramidal neurons of malformed cortex occurs earlier than that for mEPSCs, suggesting that there may additionally be alterations in intrinsic properties that increase the excitability of the cortical afferents. Frequencies of EPSC bursts and late evoked activity were also increased in malformed cortex. These results suggest that a hyperinnervation of layer V pyramidal neurons by excitatory afferents occurs as an active process likely contributing to subsequent development of field epileptiform events.
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Affiliation(s)
- A Zsombok
- Dept of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA 23298, USA
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10
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Zhou X, Qyang Y, Kelsoe JR, Masliah E, Geyer MA. Impaired postnatal development of hippocampal dentate gyrus in Sp4 null mutant mice. GENES BRAIN AND BEHAVIOR 2007; 6:269-76. [PMID: 16899055 DOI: 10.1111/j.1601-183x.2006.00256.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Sp4, a member of the Sp1 family of transcription factors, is expressed restrictively in the developing nervous system and abundantly in the hippocampus. Previously, we demonstrated that hypomorphic Sp4 mice display hippocampal vacuolization and concomitant deficits in memory and sensorimotor gating. Here, we report further analyses of Sp4 functions during postnatal development of the dentate gyrus in Sp4 null mutant mice. A reduced cell proliferation restrictively in hippocampus, but not cerebellum, was observed in the first week of postnatal development of Sp4 null mutant mice. The dendritic growth and arborization of dentate granule cells was decreased in hippocampal cultures in vitro from mutant neonatal mice. The adult Sp4 null mutant mice displayed decreased dentate granule cell density with reduced width of both dentate gyrus and the molecular layer. The abnormality of the molecular layer was indicated by a reduced level of synaptophysin expression in the mutant mice. The Sp4 transcription factor therefore appears to predominantly regulate the development of dentate granule cells.
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Affiliation(s)
- X Zhou
- Department of Psychiatry, University of California at San Diego, La Jolla, CA 92093-0804, USA.
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11
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Harrington EP, Möddel G, Najm IM, Baraban SC. Altered glutamate receptor - transporter expression and spontaneous seizures in rats exposed to methylazoxymethanol in utero. Epilepsia 2007; 48:158-68. [PMID: 17241223 DOI: 10.1111/j.1528-1167.2006.00838.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Brain malformations are a common cause of intractable epilepsy and cognitive dysfunction in children. Prenatal exposure to the teratogen methylazoxymethanol (MAM) is a rodent model of brain malformation featuring loss of lamination, clusters of displaced hippocampal cells, and pharmaco-resistance to antiepileptic drugs. In a normotopic hippocampus, expression of postsynaptic glutamate receptors and the transporters regulating neurotransmitter reuptake are critical factors modulating excitation and synaptic communication. Alterations in this system can have profound effects on overall excitability, cognitive function, and seizure thresholds. METHODS Immunohistochemical techniques were used to analyze the expression of N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5 methylisoxazole-4-proprionic acid (AMPA) receptor subunits in rats exposed to MAM in utero (25 mg/kg, intraperitoneal injection). We also examined the expression of several glutamate transporters (EAAC1, vGLUT1, and vGLUT2). A video-electroencephalographic (video-EEG) system was used for long-term monitoring of adult MAM-exposed rats. RESULTS Heterotopic hippocampal neurons exhibited striking reductions in GluR1 and EAAC1 expression; vGlut2 expression was prominent in these regions. Spontaneous electrographic seizures were verified in two animals. CONCLUSIONS We conclude that glutamate receptor subunit and transporter expression are altered in animals exposed to MAM in utero. Further studies in the MAM model may provide greater insight into the potential disruptions in excitatory synaptic neurotransmission that can occur in a malformed brain.
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Affiliation(s)
- Emily P Harrington
- Epilepsy Research Laboratory, Department of Neurological Surgery, University of California, San Francisco, California 94143, USA
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12
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Bassanini S, Hallene K, Battaglia G, Finardi A, Santaguida S, Cipolla M, Janigro D. Early cerebrovascular and parenchymal events following prenatal exposure to the putative neurotoxin methylazoxymethanol. Neurobiol Dis 2007; 26:481-95. [PMID: 17398107 PMCID: PMC3041024 DOI: 10.1016/j.nbd.2007.02.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Revised: 01/31/2007] [Accepted: 02/21/2007] [Indexed: 01/19/2023] Open
Abstract
One of the most common causes of neurological disabilities are malformations of cortical development (MCD). A useful animal model of MCD consists of prenatal exposure to methylazoxymethanol (MAM), resulting in a postnatal phenotype characterized by cytological aberrations reminiscent of human MCD. Although postnatal effects of MAM are likely a consequence of prenatal events, little is known on how the developing brain reacts to MAM. General assumption is the effects of prenatally administered MAM are short lived (24 h) and neuroblast-specific. MAM persisted for several days after exposure in utero in both maternal serum and fetal brain, but at levels lower than predicted by a neurotoxic action. MAM levels and time course were consistent with a different mechanism of indirect neuronal toxicity. The most prominent acute effects of MAM were cortical swelling associated with mild cortical disorganization and neurodegeneration occurring in absence of massive neuronal cell death. Delayed or aborted vasculogenesis was demonstrated by MAM's ability to hinder vessel formation. In vitro, MAM reduced synthesis and release of VEGF by endothelial cells. Decreased expression of VEGF, AQP1, and lectin-B was consistent with a vascular target in prenatal brain. The effects of MAM on cerebral blood vessels persisted postnatally, as indicated by capillary hypodensity in heterotopic areas of adult rat brain. In conclusion, these results show that MAM does not act only as a neurotoxin per se, but may additionally cause a short-lived toxic effect secondary to cerebrovascular dysfunction, possibly due to a direct anti-angiogenic effect of MAM itself.
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Affiliation(s)
- Stefania Bassanini
- Department of Cerebrovascular Research, Cleveland, OH, USA
- Department of Experimental Neurophysiology, Lab of Molecular Neuroanatomy, Neurological Institute “C. Besta”, Milano, Italy
| | - Kerri Hallene
- Department of Cerebrovascular Research, Cleveland, OH, USA
| | - Giorgio Battaglia
- Department of Experimental Neurophysiology, Lab of Molecular Neuroanatomy, Neurological Institute “C. Besta”, Milano, Italy
| | - Adele Finardi
- Department of Experimental Neurophysiology, Lab of Molecular Neuroanatomy, Neurological Institute “C. Besta”, Milano, Italy
| | | | - Marilyn Cipolla
- The University of Vermont College of Medicine, Burlington, VT, USA
| | - Damir Janigro
- Department of Cerebrovascular Research, Cleveland, OH, USA
- Department of Cell Biology, The Cleveland Clinic Foundation, Cleveland, OH, USA
- Department of Molecular Medicine, Cleveland, OH, USA
- Corresponding author. Molecular Medicine, Cleveland Clinic Foundation, NB-20 LRI, 9500 Euclid Ave, Cleveland, OH 44195, USA. Fax: +1 216 445 1466. (D. Janigro)
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Rosen GD, Bai J, Wang Y, Fiondella CG, Threlkeld SW, LoTurco JJ, Galaburda AM. Disruption of neuronal migration by RNAi of Dyx1c1 results in neocortical and hippocampal malformations. Cereb Cortex 2007; 17:2562-72. [PMID: 17218481 PMCID: PMC3742088 DOI: 10.1093/cercor/bhl162] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The brains of individuals with developmental dyslexia have neocortical neuronal migration abnormalities including molecular layer heterotopias, laminar dysplasias, and periventricular nodular heterotopias (PNH). RNA interference (RNAi) of Dyx1c1, a candidate dyslexia susceptibility gene, disrupts neuronal migration in developing embryonic neocortex. Using in utero electroporation, we cotransfected cells in the rat neocortical ventricular zone (VZ) at E14/15 with short hairpin RNA vectors targeting Dyx1c1 along with either plasmids encoding enhanced green fluorescent protein or plasmids encoding monomeric red fluorescent protein only. RNAi of Dyx1c1 resulted in pockets of unmigrated neurons resembling PNH. The pattern of migration of transfected neurons was bimodal, with approximately 20% of the neurons migrating a short distance from the VZ and another 40% that migrated past their expected lamina. Approximately 25% of the transfected brains had hippocampal pyramidal cell migration anomalies. Molecular layer ectopias, which were not related to injection site artifacts, were also seen in 25% of the animals. These results support the hypothesis that targeted disruption of the candidate dyslexia susceptibility gene, Dyx1c1, results in neuronal migration disorders similar to those seen in the brains of dyslexics.
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Affiliation(s)
- Glenn D Rosen
- Dyslexia Research Laboratory and Charles A Dana Research Institute, Department of Neurology, Division of Behavioral Neurology, Beth Israel Deaconess Medical Center, Boston, MA 02215, USA.
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14
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Luther JA, Birren SJ. Nerve growth factor decreases potassium currents and alters repetitive firing in rat sympathetic neurons. J Neurophysiol 2006; 96:946-58. [PMID: 16707716 DOI: 10.1152/jn.01078.2005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The sympathetic nervous system is an essential regulator of the cardiovascular system and interactions with target tissue regulate sympathetic neuronal properties. The heart produces nerve growth factor (NGF), which promotes sympathetic noradrenergic innervation of cardiac tissue and affects sympathetic synaptic strength. Neurotrophins, including NGF, are important modulators of synaptic plasticity and membrane electrical properties. Here we show that acute application of NGF causes a change in the repetitive firing pattern of cultured sympathetic neurons of the rat superior cervical ganglion. Neurons fire fewer action potentials in NGF, but with increased frequency, demonstrating an NGF-dependent change from a tonic to a phasic firing pattern. Additionally, NGF decreases the spike time variance, making spikes more tightly time locked to stimulus onset. NGF causes a decrease in the amplitude of both calcium-dependent and -independent potassium currents, and inhibition of calcium-dependent potassium currents using CdCl(2) reproduces some, but not all, of the firing properties induced by NGF. This study suggests that NGF release from cardiac tissue may act to modulate the repetitive firing properties of sympathetic neurons to tune their output to meet the physiological needs of the organism.
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Affiliation(s)
- Jason A Luther
- Department of Biology, National Center for Behavioral Genomics, Brandeis University, Waltham, Massachusetts 02454, USA
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Paredes M, Pleasure SJ, Baraban SC. Embryonic and early postnatal abnormalities contributing to the development of hippocampal malformations in a rodent model of dysplasia. J Comp Neurol 2006; 495:133-48. [PMID: 16432901 PMCID: PMC2827607 DOI: 10.1002/cne.20871] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
While there are many recent examples of single gene deletions that lead to defects in cortical development, most human cases of cortical disorganization can be attributed to a combination of environmental and genetic factors. Elucidating the cellular or developmental basis of teratogenic exposures in experimental animals is an important approach to understanding how environmental insults at particular developmental junctures can lead to complex brain malformations. Rats with prenatal exposure to methylazoxymethanol (MAM) reproduce many anatomical features seen in epilepsy patients. Previous studies have shown that heterotopic clusters of neocortically derived neurons exhibit hyperexcitable firing activity and may be a source of heightened seizure susceptibility; however, the events that lead to the formation of these abnormal cell clusters is unclear. Here we used a panel of molecular markers and birthdating studies to show that in MAM-exposed rats the abnormal cell clusters (heterotopia) first appear postnatally in the hippocampus (P1-2) and that their appearance is preceded by a distinct sequence of perturbations in neocortical development: 1) disruption of the radial glial scaffolding with premature astroglial differentiation, and 2) thickening of the marginal zone with redistribution of Cajal-Retzius neurons to deeper layers. These initial events are followed by disruption of the cortical plate and appearance of subventricular zone nodules. Finally, we observed the erosion of neocortical subventricular zone nodules into the hippocampus around parturition followed by migration of nodules to hippocampus. We conclude that prenatal MAM exposure disrupts critical developmental processes and prenatal neocortical structures, ultimately resulting in neocortical disorganization and hippocampal malformations.
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Affiliation(s)
- Mercedes Paredes
- Epilepsy Research Laboratory, Department of Neurological Surgery, University of California, San Francisco
| | - Samuel J. Pleasure
- Department of Neurology, University of California, San Francisco
- Correspondence to either: SC Baraban, Box 0520, Department of Neurological Surgery, 513 Parnassus Avenue, UCSF, San Francisco, CA 94143. Phone: (415) 476-9473; Fax: (415) or SJ Pleasure, Box 0435, Department of Neurology, 513 Parnassus Avenue, UCSF, San Francisco, CA 94143. Phone: (415) 502-5683; Fax: (415) 476-5229;
| | - Scott C. Baraban
- Epilepsy Research Laboratory, Department of Neurological Surgery, University of California, San Francisco
- Correspondence to either: SC Baraban, Box 0520, Department of Neurological Surgery, 513 Parnassus Avenue, UCSF, San Francisco, CA 94143. Phone: (415) 476-9473; Fax: (415) or SJ Pleasure, Box 0435, Department of Neurology, 513 Parnassus Avenue, UCSF, San Francisco, CA 94143. Phone: (415) 502-5683; Fax: (415) 476-5229;
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Tschuluun N, Wenzel JH, Katleba K, Schwartzkroin PA. Initiation and spread of epileptiform discharges in the methylazoxymethanol acetate rat model of cortical dysplasia: functional and structural connectivity between CA1 heterotopia and hippocampus/neocortex. Neuroscience 2005; 133:327-42. [PMID: 15893654 DOI: 10.1016/j.neuroscience.2005.02.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2004] [Revised: 02/11/2005] [Accepted: 02/11/2005] [Indexed: 10/25/2022]
Abstract
Neuronal migration disorders (NMDs) are often associated with medically intractable epilepsy. In utero injection of methylazoxymethanol acetate into pregnant rats gives rise to dysplastic cell clusters ("heterotopia") in hippocampus (and nearby regions), providing an animal model of NMD. In the present study, we have examined the structural and functional integration of hippocampal heterotopic cells into circuits that link the heterotopia with surrounding "normal" brain. Bi-directional morphological connectivity between the heterotopia and hippocampus/neocortex was demonstrated using the neurotracer, biotinylated dextran amine. Single cell recordings in hippocampal slices showed that heterotopia neurons form functional connections with the surrounding hippocampus and neocortex. However, simultaneous field recordings from the CA1 heterotopia, normotopic hippocampus, and neocortex indicated that epileptiform discharges (spontaneous events seen in slices bathed with high [K+]o and bicuculline) were rarely initiated in the heterotopia (although the heterotopia was capable of generating epileptiform discharges independently of normal brain regions). Further, in most of the experiments, the aberrant connectivity provided by CA1 heterotopia failed to function as a "bridge" for epileptiform discharges to propagate directly from low-threshold hippocampus to neocortex. These data do not support the hypothesis that NMDs (heterotopic cell populations) serve as a focus and/or trigger for epileptiform activity, and/or facilitate propagation of epileptiform events.
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Affiliation(s)
- N Tschuluun
- Department of Neurological Surgery, University of California, Davis, Medical Neuroscience Building, Room 612G, 1515 Newton Court, Davis, CA 95616, USA
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Calcagnotto ME, Baraban SC. Prolonged NMDA-mediated responses, altered ifenprodil sensitivity, and epileptiform-like events in the malformed hippocampus of methylazoxymethanol exposed rats. J Neurophysiol 2005; 94:153-62. [PMID: 15772235 DOI: 10.1152/jn.01155.2004] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cortical malformations are often associated with refractory epilepsy and cognitive deficit. Clinical and experimental studies have demonstrated an important role for glutamate-mediated synaptic transmission in these conditions. Using whole cell voltage-clamp techniques, we examined evoked glutamate-mediated excitatory postsynaptic currents (eEPSCs) and responses to exogenously applied glutamate on hippocampal heterotopic cells in an animal model of malformation i.e., rats exposed to methylazoxymethanol (MAM) in utero. Analysis revealed that the late N-methyl-D-aspartate (NMDA) receptor-mediated eEPSC component was significantly increased on heterotopic cells compared with age-matched normotopic pyramidal cells. At a holding potential of +40 mV, heterotopic cells also exhibited eEPSCs with a slower decay-time constant. No differences in the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) component of eEPSCs were detected. In 23% of heterotopic pyramidal cells, electrical stimulation evoked prolonged burst-like responses. Focal application of glutamate (10 mM) targeted to different sites near the heterotopia also evoked epileptiform-like bursts on heterotopic cells. Ifenprodil (10 microM), an NR2B subunit antagonist, only slightly reduced the NMDA receptor (NMDAR)-mediated component and amplitude of eEPSCs on heterotopic cells (MAM) but significantly decreased the late component and peak amplitude of eEPSCs in normotopic cells (control). Our data demonstrate a functional alteration in the NMDA-mediated component of excitatory synaptic transmission in heterotopic cells and suggest that this alteration may be attributable, at least in part, to changes in composition and function of the NMDAR subunit. Changes in NMDAR function may directly contribute to the hyperexcitability and cognitive deficits reported in animal models and patients with brain malformations.
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Affiliation(s)
- Maria Elisa Calcagnotto
- Epilepsy Research Laboratory, Department of Neurological Surgery, University of California, San Francisco, USA
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Heterotopic neurons with altered inhibitory synaptic function in an animal model of malformation-associated epilepsy. J Neurosci 2002. [PMID: 12196583 DOI: 10.1523/jneurosci.22-17-07596.2002] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Children with brain malformations often exhibit an intractable form of epilepsy. Although alterations in cellular physiology and abnormal histology associated with brain malformations has been studied extensively, synaptic function in malformed brain regions remains poorly understood. We used an animal model, rats exposed to methylazoxymethanol (MAM) in utero, featuring loss of lamination and distinct nodular heterotopia to examine inhibitory synaptic function in the malformed brain. Previous in vitro and in vivo studies demonstrated an enhanced susceptibility to seizure activity and neuronal hyperexcitability in these animals. Here we demonstrate that inhibitory synaptic function is enhanced in rats exposed to MAM in utero. Using in vitro hippocampal slices and whole-cell voltage-clamp recordings from visualized neurons, we observed a dramatic prolongation of GABAergic IPSCs onto heterotopic neurons. Spontaneous IPSC decay time constants were increased by 195% and evoked IPSC decay time constants by 220% compared with age-matched control CA1 pyramidal cells; no change in IPSC amplitude or rise time was observed. GABA transport inhibitors (tiagabine and NO-711) prolonged evoked IPSC decay kinetics of control CA1 pyramidal cells (or normotopic cells) but had no effect on heterotopic neurons. Immunohistochemical staining for GABA transporters (GAT-1 and GAT-3) revealed a low level of expression in heterotopic cell regions, suggesting a reduced ability for GABA reuptake at these synapses. Together, our data demonstrate that GABA-mediated synaptic function at heterotopic synapses is altered and suggests that inhibitory systems are enhanced in the malformed brain.
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