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Affiliation(s)
- Peter B Crino
- Shriners Hospitals Paediatric Research Centre, Department of Neurology, Temple University School of Medicine, Philadelphia, USA
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52
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Gorter JA, van Vliet EA, Aronica E. Status epilepticus, blood-brain barrier disruption, inflammation, and epileptogenesis. Epilepsy Behav 2015; 49:13-6. [PMID: 25958228 DOI: 10.1016/j.yebeh.2015.04.047] [Citation(s) in RCA: 133] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 04/19/2015] [Indexed: 11/15/2022]
Abstract
Over the last 15 years, attention has been focused on dysfunction of the cerebral vasculature and inflammation as important players in epileptogenic processes, with a specific emphasis on failure of the blood-brain barrier (BBB; Fig. 1) (Seiffert et al., 2004; Marchi et al., 2007; Oby and Janigro, 2006; van Vliet et al., 2014; Vezzani et al., 2011) [3-7]. Here, we discuss how the BBB is disrupted as a consequence of SE and how this BBB breakdown may be involved in epileptogenesis. This article is part of a Special Issue entitled "Status Epilepticus".
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Affiliation(s)
- Jan A Gorter
- Center for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
| | - Erwin A van Vliet
- Academic Medical Center, Department of (Neuro)Pathology, University of Amsterdam, Amsterdam, The Netherlands
| | - Eleonora Aronica
- Center for Neuroscience, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands; Academic Medical Center, Department of (Neuro)Pathology, University of Amsterdam, Amsterdam, The Netherlands; SEIN - Stichting Epilepsie Instellingen Nederland, Heemstede, The Netherlands
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53
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Katsnelson A, Buzsáki G, Swann JW. Catastrophic childhood epilepsy: a recent convergence of basic and clinical neuroscience. Sci Transl Med 2015; 6:262ps13. [PMID: 25391480 DOI: 10.1126/scitranslmed.3010531] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Advances in understanding the genetics and underlying pathology of the catastrophic childhood epilepsies are pointing toward treatments.
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Affiliation(s)
| | - Gyorgy Buzsáki
- Department of Neural Science, New York University School of Medicine, New York, NY 10003, USA
| | - John W Swann
- The Cain Foundation Laboratories, The Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Baylor College of Medicine, Houston, TX 77030, USA.
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Nakashima M, Saitsu H, Takei N, Tohyama J, Kato M, Kitaura H, Shiina M, Shirozu H, Masuda H, Watanabe K, Ohba C, Tsurusaki Y, Miyake N, Zheng Y, Sato T, Takebayashi H, Ogata K, Kameyama S, Kakita A, Matsumoto N. Somatic Mutations in the MTOR gene cause focal cortical dysplasia type IIb. Ann Neurol 2015; 78:375-86. [PMID: 26018084 DOI: 10.1002/ana.24444] [Citation(s) in RCA: 140] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 05/26/2015] [Accepted: 05/26/2015] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Focal cortical dysplasia (FCD) type IIb is a cortical malformation characterized by cortical architectural abnormalities, dysmorphic neurons, and balloon cells. It has been suggested that FCDs are caused by somatic mutations in cells in the developing brain. Here, we explore the possible involvement of somatic mutations in FCD type IIb. METHODS We collected a total of 24 blood-brain paired samples with FCD, including 13 individuals with FCD type IIb, 5 with type IIa, and 6 with type I. We performed whole-exome sequencing using paired samples from 9 of the FCD type IIb subjects. Somatic MTOR mutations were identified and further investigated using all 24 paired samples by deep sequencing of the entire gene's coding region. Somatic MTOR mutations were confirmed by droplet digital polymerase chain reaction. The effect of MTOR mutations on mammalian target of rapamycin (mTOR) kinase signaling was evaluated by immunohistochemistry and Western blotting analyses of brain samples and by in vitro transfection experiments. RESULTS We identified four lesion-specific somatic MTOR mutations in 6 of 13 (46%) individuals with FCD type IIb showing mutant allele rates of 1.11% to 9.31%. Functional analyses showed that phosphorylation of ribosomal protein S6 in FCD type IIb brain tissues with MTOR mutations was clearly elevated, compared to control samples. Transfection of any of the four MTOR mutants into HEK293T cells led to elevated phosphorylation of 4EBP, the direct target of mTOR kinase. INTERPRETATION We found low-prevalence somatic mutations in MTOR in FCD type IIb, indicating that activating somatic mutations in MTOR cause FCD type IIb.
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Affiliation(s)
- Mitsuko Nakashima
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Hirotomo Saitsu
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Nobuyuki Takei
- Department of Molecular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan
| | - Jun Tohyama
- Department of Child Neurology, Nishi-Niigata Chuo National Hospital, Niigata, Japan
| | - Mitsuhiro Kato
- Department of Pediatrics, Showa University School of Medicine, Tokyo, Japan
| | - Hiroki Kitaura
- Department of Pathology, Brain Research Institute, University of Niigata, Niigata, Japan
| | - Masaaki Shiina
- Department of Biochemistry, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Hiroshi Shirozu
- Department of Functional Neurosurgery, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
| | - Hiroshi Masuda
- Department of Functional Neurosurgery, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
| | - Keisuke Watanabe
- Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
| | - Chihiro Ohba
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Yoshinori Tsurusaki
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Noriko Miyake
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Yingjun Zheng
- Department of Pathology, Brain Research Institute, University of Niigata, Niigata, Japan
| | - Tatsuhiro Sato
- Division of Biochemistry, School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan
| | - Hirohide Takebayashi
- Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
| | - Kazuhiro Ogata
- Department of Biochemistry, Yokohama City University Graduate School of Medicine, Yokohama, Japan
| | - Shigeki Kameyama
- Department of Functional Neurosurgery, Epilepsy Center, Nishi-Niigata Chuo National Hospital, Niigata, Japan
| | - Akiyoshi Kakita
- Department of Pathology, Brain Research Institute, University of Niigata, Niigata, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
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Abstract
Focal cortical dysplasias are common malformations of cerebral cortical development and are highly associated with medically intractable epilepsy. They have been classified into neuropathological subtypes (type Ia, Ib, IIa, IIb, and III) based on the severity of cytoarchitectural disruption--tangential or radial dispersion, or loss of laminar structure--and the presence of unique cells types such as cytomegalic neurons or balloon cells. Most focal cortical dysplasias can be identified on neuroimaging and many require resective epilepsy surgery to cure refractory seizures. The pathogenesis of focal cortical dysplasias remains to be defined, although there is recent evidence to suggest that focal cortical dysplasias arise from de novo somatic mutations occurring during brain development. Some focal cortical dysplasia subtypes show a link to the mammalian target of rapamycin signaling cascade; this has now extended to other cortical malformations, including hemimegalencephaly.
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Affiliation(s)
- Peter B Crino
- Department of Neurology, Shriners Hospital Pediatric Research Center and Temple University, Philadelphia, Pennsylvania
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56
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Sarnat HB, Flores-Sarnat L. Infantile tauopathies: Hemimegalencephaly; tuberous sclerosis complex; focal cortical dysplasia 2; ganglioglioma. Brain Dev 2015; 37:553-62. [PMID: 25451314 DOI: 10.1016/j.braindev.2014.08.010] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Revised: 07/31/2014] [Accepted: 08/04/2014] [Indexed: 11/16/2022]
Abstract
Tau is a normal microtubule-associated protein; mutations to phosphorylated or acetylated forms are neurotoxic. In many dementias of adult life tauopathies cause neuronal degeneration. Four developmental disorders of the fetal and infant brain are presented, each of which exhibits up-regulation of tau. Microtubules are cytoskeletal structures that provide the strands of mitotic spindles and specify cellular polarity, growth, lineage, differentiation, migration and axonal transport of molecules. Phosphorylated tau is abnormal in immature as in mature neurons. Several malformations are demonstrated in which upregulated tau may be important in pathogenesis. All produce highly epileptogenic cortical foci. The prototype infantile tauopathy is (1) hemimegalencephaly (HME); normal tau is degraded by a mutant AKT3 or AKT1 gene as the aetiology of focal somatic mosaicism in the periventricular neuroepithelium. HME may be isolated or associated with neurocutaneous syndromes, particularly epidermal naevus syndromes, also due to somatic mutations. Other tauopathies of early life include: (2) tuberous sclerosis complex; (3) focal cortical dysplasia type 2b (FCD2b); and (4) ganglioglioma, a tumor with dysplastic neurons and neoplastic glial cells. Pathological tau in these infantile cases alters cellular growth and architecture, synaptic function and tissue organization, but does not cause neuronal loss. All infantile tauopathies are defined neuropathologically as a tetrad of (1) dysmorphic and megalocytic neurons; (2) activation of the mTOR signaling pathway; (3) post-zygotic somatic mosaicism; and (4) upregulation of phosphorylated tau. HME and FCD2b may be the same disorder with different timing of the somatic mutation in the mitotic cycles of the neuroepithelium. HME and FCD2b may be the same disorder with different timing of the somatic mutation in the mitotic cycles of the neuroepithelium. Tauopathies must be considered in infantile neurological disease and no longer restricted to adult dementias. The mTOR inhibitor everolimus, already demonstrated to be effective in TSC, also may be a potential treatment in other infantile tauopathies.
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Affiliation(s)
- Harvey B Sarnat
- Department of Paediatrics, University of Calgary Faculty of Medicine and Alberta Children's Hospital Research Foundation, Calgary, Alberta, Canada; Department of Pathology (Neuropathology), University of Calgary Faculty of Medicine and Alberta Children's Hospital Research Foundation, Calgary, Alberta, Canada; Department of Clinical Neurosciences, University of Calgary Faculty of Medicine and Alberta Children's Hospital Research Foundation, Calgary, Alberta, Canada.
| | - Laura Flores-Sarnat
- Department of Paediatrics, University of Calgary Faculty of Medicine and Alberta Children's Hospital Research Foundation, Calgary, Alberta, Canada; Department of Clinical Neurosciences, University of Calgary Faculty of Medicine and Alberta Children's Hospital Research Foundation, Calgary, Alberta, Canada
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57
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Blackmon K. Structural MRI biomarkers of shared pathogenesis in autism spectrum disorder and epilepsy. Epilepsy Behav 2015; 47:172-82. [PMID: 25812936 DOI: 10.1016/j.yebeh.2015.02.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Revised: 02/11/2015] [Accepted: 02/16/2015] [Indexed: 01/28/2023]
Abstract
Etiological factors that contribute to a high comorbidity between autism spectrum disorder (ASD) and epilepsy are the subject of much debate. Does epilepsy cause ASD or are there common underlying brain abnormalities that increase the risk of developing both disorders? This review summarizes evidence from quantitative MRI studies to suggest that abnormalities of brain structure are not necessarily the consequence of ASD and epilepsy but are antecedent to disease expression. Abnormal gray and white matter volumes are present prior to onset of ASD and evident at the time of onset in pediatric epilepsy. Aberrant brain growth trajectories are also common in both disorders, as evidenced by blunted gray matter maturation and white matter maturation. Although the etiological factors that explain these abnormalities are unclear, high heritability estimates for gray matter volume and white matter microstructure demonstrate that genetic factors assert a strong influence on brain structure. In addition, histopathological studies of ASD and epilepsy brain tissue reveal elevated rates of malformations of cortical development (MCDs), such as focal cortical dysplasia and heterotopias, which supports disruption of neuronal migration as a contributing factor. Although MCDs are not always visible on MRI with conventional radiological analysis, quantitative MRI detection methods show high sensitivity to subtle malformations in epilepsy and can be potentially applied to MCD detection in ASD. Such an approach is critical for establishing quantitative neuroanatomic endophenotypes that can be used in genetic research. In the context of emerging drug treatments for seizures and autism symptoms, such as rapamycin and rapalogs, in vivo neuroimaging markers of subtle structural brain abnormalities could improve sample stratification in human clinical trials and potentially extend the range of patients that might benefit from treatment. This article is part of a Special Issue entitled "Autism and Epilepsy".
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Affiliation(s)
- Karen Blackmon
- Comprehensive Epilepsy Center, Department of Neurology, New York University School of Medicine, New York, NY 10016, USA; Center for Mind/Brain Sciences, University of Trento, Rovereto, Trento 38068, Italy.
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58
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Lin YX, Lin K, Kang DZ, Liu XX, Wang XF, Zheng SF, Yu LH, Lin ZY. Similar PDK1–AKT–mTOR pathway activation in balloon cells and dysmorphic neurons of type II focal cortical dysplasia with refractory epilepsy. Epilepsy Res 2015; 112:137-49. [DOI: 10.1016/j.eplepsyres.2015.02.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 01/25/2015] [Accepted: 02/06/2015] [Indexed: 11/30/2022]
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59
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Crino PB. mTOR signaling in epilepsy: insights from malformations of cortical development. Cold Spring Harb Perspect Med 2015; 5:5/4/a022442. [PMID: 25833943 DOI: 10.1101/cshperspect.a022442] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Over the past decade enhanced activation of the mammalian target of rapamycin (mTOR)-signaling cascade has been identified in focal malformations of cortical development (MCD) subtypes, which have been collectively referred to as "mTORopathies." Mutations in mTOR regulatory genes (e.g., TSC1, TSC2, AKT3, DEPDC5) have been associated with several focal MCD highly associated with epilepsy such as tuberous sclerosis complex (TSC), hemimegalencephaly (HME; brain malformation associated with dramatic enlargement of one brain hemisphere), and cortical dysplasia. mTOR plays important roles in the regulation of cell division, growth, and survival, and, thus, aberrant activation of the cascade during cortical development can cause dramatic alterations in cell size, cortical lamination, and axon and dendrite outgrowth often observed in focal MCD. Although it is widely believed that structural alterations induced by hyperactivated mTOR signaling are critical for epileptogenesis, newer evidence suggests that mTOR activation on its own may enhance neuronal excitability. Clinical trials with mTOR inhibitors have shown efficacy in the treatment of seizures associated with focal MCD.
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Affiliation(s)
- Peter B Crino
- Shriners Hospital Pediatric Research Center and Department of Neurology, Temple University, Philadelphia, Pennsylvania 19140
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60
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Li CY, Li X, Liu SF, Qu WS, Wang W, Tian DS. Inhibition of mTOR pathway restrains astrocyte proliferation, migration and production of inflammatory mediators after oxygen–glucose deprivation and reoxygenation. Neurochem Int 2015; 83-84:9-18. [DOI: 10.1016/j.neuint.2015.03.001] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Revised: 03/02/2015] [Accepted: 03/05/2015] [Indexed: 12/01/2022]
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61
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Nguyen LH, Brewster AL, Clark ME, Regnier-Golanov A, Sunnen CN, Patil VV, D'Arcangelo G, Anderson AE. mTOR inhibition suppresses established epilepsy in a mouse model of cortical dysplasia. Epilepsia 2015; 56:636-46. [PMID: 25752454 DOI: 10.1111/epi.12946] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/21/2015] [Indexed: 12/21/2022]
Abstract
OBJECTIVE Hyperactivation of the mechanistic target of rapamycin (mTOR; also known as mammalian target of rapamycin) pathway has been demonstrated in human cortical dysplasia (CD) as well as in animal models of epilepsy. Although inhibition of mTOR signaling early in epileptogenesis suppressed epileptiform activity in the neuron subset-specific Pten knockout (NS-Pten KO) mouse model of CD, the effects of mTOR inhibition after epilepsy is fully established were not previously examined in this model. Here, we investigated whether mTOR inhibition suppresses epileptiform activity and other neuropathological correlates in adult NS-Pten KO mice with severe and well-established epilepsy. METHODS The progression of epileptiform activity, mTOR pathway dysregulation, and associated neuropathology with age in NS-Pten KO mice were evaluated using video-electroencephalography (EEG) recordings, Western blotting, and immunohistochemistry. A cohort of NS-Pten KO mice was treated with the mTOR inhibitor rapamycin (10 mg/kg i.p., 5 days/week) starting at postnatal week 9 and video-EEG monitored for epileptiform activity. Western blotting and immunohistochemistry were performed to evaluate the effects of rapamycin on the associated pathology. RESULTS Epileptiform activity worsened with age in NS-Pten KO mice, with parallel increases in the extent of hippocampal mTOR complex 1 and 2 (mTORC1 and mTORC2, respectively) dysregulation and progressive astrogliosis and microgliosis. Rapamycin treatment suppressed epileptiform activity, improved baseline EEG activity, and increased survival in severely epileptic NS-Pten KO mice. At the molecular level, rapamycin treatment was associated with a reduction in both mTORC1 and mTORC2 signaling and decreased astrogliosis and microgliosis. SIGNIFICANCE These findings reveal a wide temporal window for successful therapeutic intervention with rapamycin in the NS-Pten KO mouse model, and they support mTOR inhibition as a candidate therapy for established, late-stage epilepsy associated with CD and genetic dysregulation of the mTOR pathway.
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Affiliation(s)
- Lena H Nguyen
- Department of Neuroscience, Baylor College of Medicine, Houston, Texas, U.S.A; The Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas, U.S.A; The Gordon and Mary Cain Pediatric Neurology Research Foundation Laboratories, Texas Children's Hospital, Houston, Texas, U.S.A
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62
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Jansen LA, Mirzaa GM, Ishak GE, O'Roak BJ, Hiatt JB, Roden WH, Gunter SA, Christian SL, Collins S, Adams C, Rivière JB, St-Onge J, Ojemann JG, Shendure J, Hevner RF, Dobyns WB. PI3K/AKT pathway mutations cause a spectrum of brain malformations from megalencephaly to focal cortical dysplasia. Brain 2015; 138:1613-28. [PMID: 25722288 DOI: 10.1093/brain/awv045] [Citation(s) in RCA: 241] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 12/22/2014] [Indexed: 11/15/2022] Open
Abstract
Malformations of cortical development containing dysplastic neuronal and glial elements, including hemimegalencephaly and focal cortical dysplasia, are common causes of intractable paediatric epilepsy. In this study we performed multiplex targeted sequencing of 10 genes in the PI3K/AKT pathway on brain tissue from 33 children who underwent surgical resection of dysplastic cortex for the treatment of intractable epilepsy. Sequencing results were correlated with clinical, imaging, pathological and immunohistological phenotypes. We identified mosaic activating mutations in PIK3CA and AKT3 in this cohort, including cancer-associated hotspot PIK3CA mutations in dysplastic megalencephaly, hemimegalencephaly, and focal cortical dysplasia type IIa. In addition, a germline PTEN mutation was identified in a male with hemimegalencephaly but no peripheral manifestations of the PTEN hamartoma tumour syndrome. A spectrum of clinical, imaging and pathological abnormalities was found in this cohort. While patients with more severe brain imaging abnormalities and systemic manifestations were more likely to have detected mutations, routine histopathological studies did not predict mutation status. In addition, elevated levels of phosphorylated S6 ribosomal protein were identified in both neurons and astrocytes of all hemimegalencephaly and focal cortical dysplasia type II specimens, regardless of the presence or absence of detected PI3K/AKT pathway mutations. In contrast, expression patterns of the T308 and S473 phosphorylated forms of AKT and in vitro AKT kinase activities discriminated between mutation-positive dysplasia cortex, mutation-negative dysplasia cortex, and non-dysplasia epilepsy cortex. Our findings identify PI3K/AKT pathway mutations as an important cause of epileptogenic brain malformations and establish megalencephaly, hemimegalencephaly, and focal cortical dysplasia as part of a single pathogenic spectrum.
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Affiliation(s)
- Laura A Jansen
- 1 University of Virginia, Neurology, Charlottesville, VA, USA 2 Seattle Children's Research Institute, Centre for Integrative Brain Research, Seattle, WA, USA
| | - Ghayda M Mirzaa
- 2 Seattle Children's Research Institute, Centre for Integrative Brain Research, Seattle, WA, USA 3 University of Washington, Paediatrics, Seattle, WA, USA
| | - Gisele E Ishak
- 4 Seattle Children's Hospital, Radiology, Seattle, WA, USA
| | - Brian J O'Roak
- 5 University of Washington, Genome Sciences, Seattle, WA, USA 6 Oregon Health and Science University, Molecular and Medical Genetics, Portland, OR, USA
| | - Joseph B Hiatt
- 5 University of Washington, Genome Sciences, Seattle, WA, USA
| | - William H Roden
- 2 Seattle Children's Research Institute, Centre for Integrative Brain Research, Seattle, WA, USA
| | - Sonya A Gunter
- 1 University of Virginia, Neurology, Charlottesville, VA, USA
| | - Susan L Christian
- 2 Seattle Children's Research Institute, Centre for Integrative Brain Research, Seattle, WA, USA
| | - Sarah Collins
- 2 Seattle Children's Research Institute, Centre for Integrative Brain Research, Seattle, WA, USA
| | - Carissa Adams
- 2 Seattle Children's Research Institute, Centre for Integrative Brain Research, Seattle, WA, USA
| | - Jean-Baptiste Rivière
- 2 Seattle Children's Research Institute, Centre for Integrative Brain Research, Seattle, WA, USA 7 Université de Bourgogne, Equipe Génétique des Anomalies du Développement, Dijon, France
| | - Judith St-Onge
- 2 Seattle Children's Research Institute, Centre for Integrative Brain Research, Seattle, WA, USA 7 Université de Bourgogne, Equipe Génétique des Anomalies du Développement, Dijon, France
| | | | - Jay Shendure
- 5 University of Washington, Genome Sciences, Seattle, WA, USA
| | - Robert F Hevner
- 2 Seattle Children's Research Institute, Centre for Integrative Brain Research, Seattle, WA, USA 8 University of Washington, Neurosurgery, Seattle, WA, USA
| | - William B Dobyns
- 2 Seattle Children's Research Institute, Centre for Integrative Brain Research, Seattle, WA, USA 3 University of Washington, Paediatrics, Seattle, WA, USA
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63
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van Vliet E, Aronica E, Gorter J. Blood–brain barrier dysfunction, seizures and epilepsy. Semin Cell Dev Biol 2015; 38:26-34. [DOI: 10.1016/j.semcdb.2014.10.003] [Citation(s) in RCA: 134] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 10/21/2014] [Accepted: 10/23/2014] [Indexed: 02/06/2023]
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64
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Abdijadid S, Mathern GW, Levine MS, Cepeda C. Basic mechanisms of epileptogenesis in pediatric cortical dysplasia. CNS Neurosci Ther 2014; 21:92-103. [PMID: 25404064 DOI: 10.1111/cns.12345] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2014] [Revised: 09/29/2014] [Accepted: 10/03/2014] [Indexed: 12/25/2022] Open
Abstract
Cortical dysplasia (CD) is a neurodevelopmental disorder due to aberrant cell proliferation and differentiation. Advances in neuroimaging have proven effective in early identification of the more severe lesions and timely surgical removal to treat epilepsy. However, the exact mechanisms of epileptogenesis are not well understood. This review examines possible mechanisms based on anatomical and electrophysiological studies. CD can be classified as CD type I consisting of architectural abnormalities, CD type II with the presence of dysmorphic cytomegalic neurons and balloon cells, and CD type III which occurs in association with other pathologies. Use of freshly resected brain tissue has allowed a better understanding of basic mechanisms of epileptogenesis and has delineated the role of abnormal cells and synaptic activity. In CD type II, it was demonstrated that balloon cells do not initiate epileptic activity, whereas dysmorphic cytomegalic and immature neurons play an important role in generation and propagation of epileptic discharges. An unexpected finding in pediatric CD was that GABA synaptic activity is not reduced, and in fact, it may facilitate the occurrence of epileptic activity. This could be because neuronal circuits display morphological and functional signs of dysmaturity. In consequence, drugs that increase GABA function may prove ineffective in pediatric CD. In contrast, drugs that counteract depolarizing actions of GABA or drugs that inhibit the mammalian target of rapamycin (mTOR) pathway could be more effective.
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Affiliation(s)
- Sara Abdijadid
- Intellectual and Developmental Disabilities Research Center, Semel Institute for Neuroscience and Human Behavior, University of California Los Angeles, Los Angeles, CA, USA
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65
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Gürol G, Demiralp DÖ, Yılmaz AK, Akman Ö, Ateş N, Karson A. Comparative proteomic approach in rat model of absence epilepsy. J Mol Neurosci 2014; 55:632-43. [PMID: 25323782 DOI: 10.1007/s12031-014-0402-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Accepted: 08/11/2014] [Indexed: 12/21/2022]
Abstract
The aim of this study was to investigate cellular proteins in the pathogenesis of the genetic rat model of absence epilepsy. Protein spots were identified with peptide mass fingerprinting analysis using matrix-assisted laser desorption ionization time of flight mass spectrometry. Data were gathered from the frontoparietal cortex and thalamus of Wistar Albino Glaxo/Rij (WAG/Rij) and Wistar by using two-dimensional gel electrophoresis (2D-PAGE). Six proteins (Clathrin light chain-A protein, Transmembrane EMP24 Domain-Containing Protein, Stathmin-4, Myosin Light Chain4, Rheb, phosphoserine phosphatase) were found to be differentially expressed in the frontoparietal cortex of WAG/Rij and Wistar rats in both age groups. Another set of six proteins (Protein FAM89A and Oasl1, Gemin2, NuDEL1, Pur-beta, 3-alpha HSD) were found to be differentially expressed in the thalamus of WAG/Rij and Wistar rats. Findings from the frontoparietal cortex suggest the presence of altered serine metabolism and increased vesicular trafficking in the frontoparietal cortex of WAG/Rij rats compared with Wistar rats. These differences in the protein levels might reflect the crucial role of these proteins and related pathways in the generation of absence seizures. In the thalamic specimens, age-dependent changes in protein expression were remarkable, suggesting that this phenomenon may be a precursor or a consequence of absence seizures. Our findings further highlight the potential role of the mTOR signaling pathway in absence epilepsy.
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Affiliation(s)
- Gönül Gürol
- Department of Physiology, Faculty of Medicine, Sakarya University, Sakarya, Turkey
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Avet-Rochex A, Carvajal N, Christoforou CP, Yeung K, Maierbrugger KT, Hobbs C, Lalli G, Cagin U, Plachot C, McNeill H, Bateman JM. Unkempt is negatively regulated by mTOR and uncouples neuronal differentiation from growth control. PLoS Genet 2014; 10:e1004624. [PMID: 25210733 PMCID: PMC4161320 DOI: 10.1371/journal.pgen.1004624] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 07/23/2014] [Indexed: 01/21/2023] Open
Abstract
Neuronal differentiation is exquisitely controlled both spatially and temporally during nervous system development. Defects in the spatiotemporal control of neurogenesis cause incorrect formation of neural networks and lead to neurological disorders such as epilepsy and autism. The mTOR kinase integrates signals from mitogens, nutrients and energy levels to regulate growth, autophagy and metabolism. We previously identified the insulin receptor (InR)/mTOR pathway as a critical regulator of the timing of neuronal differentiation in the Drosophila melanogaster eye. Subsequently, this pathway has been shown to play a conserved role in regulating neurogenesis in vertebrates. However, the factors that mediate the neurogenic role of this pathway are completely unknown. To identify downstream effectors of the InR/mTOR pathway we screened transcriptional targets of mTOR for neuronal differentiation phenotypes in photoreceptor neurons. We identified the conserved gene unkempt (unk), which encodes a zinc finger/RING domain containing protein, as a negative regulator of the timing of photoreceptor differentiation. Loss of unk phenocopies InR/mTOR pathway activation and unk acts downstream of this pathway to regulate neurogenesis. In contrast to InR/mTOR signalling, unk does not regulate growth. unk therefore uncouples the role of the InR/mTOR pathway in neurogenesis from its role in growth control. We also identified the gene headcase (hdc) as a second downstream regulator of the InR/mTOR pathway controlling the timing of neurogenesis. Unk forms a complex with Hdc, and Hdc expression is regulated by unk and InR/mTOR signalling. Co-overexpression of unk and hdc completely suppresses the precocious neuronal differentiation phenotype caused by loss of Tsc1. Thus, Unk and Hdc are the first neurogenic components of the InR/mTOR pathway to be identified. Finally, we show that Unkempt-like is expressed in the developing mouse retina and in neural stem/progenitor cells, suggesting that the role of Unk in neurogenesis may be conserved in mammals. The development of a functional nervous system requires that nerve cells are generated at exactly the right time and place to be correctly integrated. Defects in the timing at which nerve cells are generated, or ‘differentiate’, lead to neurological disorders such as epilepsy and autism. However, very little is known about the identity of the genes that control the timing of nerve cell differentiation. Using developing photoreceptor nerves in the eye of the fruit fly, Drosophila, as a model, we showed previously that a molecular pathway known as ‘mTOR signalling’ is a key regulator of the timing of differentiation. In this study we have identified two new genes, unkempt and headcase, which control the timing of photoreceptor differentiation in Drosophila. The activity of unkempt and headcase is controlled by mTOR signalling and it is through these genes that mTOR is able to control nerve cell differentiation. The proteins encoded by unkempt and headcase form a complex and act synergistically to control the development of Drosophila photoreceptors. mTOR signalling controls a number of important cellular processes, but unkempt and headcase are the first components of this pathway to be identified that control nerve cell differentiation.
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Affiliation(s)
- Amélie Avet-Rochex
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Nancy Carvajal
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | | | - Kelvin Yeung
- The Lunenfeld-Tanenbaum Research Centre, Toronto, Ontario, Canada
| | - Katja T. Maierbrugger
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Carl Hobbs
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Giovanna Lalli
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Umut Cagin
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Cedric Plachot
- The Lunenfeld-Tanenbaum Research Centre, Toronto, Ontario, Canada
| | - Helen McNeill
- The Lunenfeld-Tanenbaum Research Centre, Toronto, Ontario, Canada
| | - Joseph M. Bateman
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
- * E-mail:
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van Vliet E, Aronica E, Gorter J. Role of blood–brain barrier in temporal lobe epilepsy and pharmacoresistance. Neuroscience 2014; 277:455-73. [DOI: 10.1016/j.neuroscience.2014.07.030] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Revised: 07/17/2014] [Accepted: 07/21/2014] [Indexed: 12/14/2022]
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Lozovaya N, Gataullina S, Tsintsadze T, Tsintsadze V, Pallesi-Pocachard E, Minlebaev M, Goriounova NA, Buhler E, Watrin F, Shityakov S, Becker AJ, Bordey A, Milh M, Scavarda D, Bulteau C, Dorfmuller G, Delalande O, Represa A, Cardoso C, Dulac O, Ben-Ari Y, Burnashev N. Selective suppression of excessive GluN2C expression rescues early epilepsy in a tuberous sclerosis murine model. Nat Commun 2014; 5:4563. [PMID: 25081057 PMCID: PMC4143949 DOI: 10.1038/ncomms5563] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Accepted: 06/30/2014] [Indexed: 01/06/2023] Open
Abstract
Tuberous sclerosis complex (TSC), caused by dominant mutations in either
TSC1 or
TSC2 tumour
suppressor genes is characterized by the presence of brain malformations, the
cortical tubers that are thought to contribute to the generation of
pharmacoresistant epilepsy. Here we report that tuberless heterozygote
Tsc1+/− mice show
functional upregulation of cortical GluN2C-containing N-methyl-D-aspartate receptors (NMDARs) in an
mTOR-dependent manner and exhibit recurrent, unprovoked seizures during early
postnatal life (<P19). Seizures are generated intracortically in the granular
layer of the neocortex. Slow kinetics of aberrant GluN2C-mediated currents in spiny stellate cells promotes
excessive temporal integration of persistent NMDAR-mediated recurrent excitation and
seizure generation. Accordingly, specific GluN2C/D antagonists block seizures in Tsc1+/− mice in vivo
and in vitro. Likewise, GluN2C expression is upregulated in TSC human surgical
resections, and a GluN2C/D
antagonist reduces paroxysmal hyperexcitability. Thus, GluN2C receptor constitutes a promising
molecular target to treat epilepsy in TSC patients. Tuberous sclerosis complex (TSC) is a rare genetic condition
characterized by epileptic seizures that start in infancy. Here, the authors show that
these seizures are modulated by GluN2C-containing NMDA receptors in the cortex of a
mouse model of TSC, and that suppressing their activity attenuates seizures.
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Affiliation(s)
- N Lozovaya
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France [3] INSERM U1129; University Paris Descartes, CEA, Gif sur Yvette, 149 Rue de Sèvres, 75015 Paris, France [4]
| | - S Gataullina
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France [3] INSERM U1129; University Paris Descartes, CEA, Gif sur Yvette, 149 Rue de Sèvres, 75015 Paris, France [4]
| | - T Tsintsadze
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France [3]
| | - V Tsintsadze
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France
| | - E Pallesi-Pocachard
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France
| | - M Minlebaev
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France [3] Laboratory of Neurobiology, Kazan Federal University, Kremlevskaya street 18, 420000 Kazan, Russia
| | - N A Goriounova
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France
| | - E Buhler
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France
| | - F Watrin
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France
| | - S Shityakov
- Department of Anaesthesia and Critical Care, University of Würzburg, Josef-Schneider-Street 2, 97080 Würzburg, Germany
| | - A J Becker
- Department of Neuropathology, University of Bonn Medical Center, Sigmund Freud Street 25, D-53105 Bonn, Germany
| | - A Bordey
- Neurosurgery, and Cellular and Molecular Physiology Departments, Yale University School of Medicine, PO Box 208082, New Haven, Connecticut 06520-8082, USA
| | - M Milh
- APHM, Department of Pediatric Neurosurgery and Neurology, CHU Timone, 264 Rue Saint-Pierre, 13385 Marseille Cedex 5, France
| | - D Scavarda
- APHM, Department of Pediatric Neurosurgery and Neurology, CHU Timone, 264 Rue Saint-Pierre, 13385 Marseille Cedex 5, France
| | - C Bulteau
- 1] INSERM U1129; University Paris Descartes, CEA, Gif sur Yvette, 149 Rue de Sèvres, 75015 Paris, France [2] Department of Pediatric Neurosurgery, Foundation Rothschild, 29 Rue Manin, 75019 Paris, France
| | - G Dorfmuller
- 1] INSERM U1129; University Paris Descartes, CEA, Gif sur Yvette, 149 Rue de Sèvres, 75015 Paris, France [2] Department of Pediatric Neurosurgery, Foundation Rothschild, 29 Rue Manin, 75019 Paris, France
| | - O Delalande
- Department of Pediatric Neurosurgery, Foundation Rothschild, 29 Rue Manin, 75019 Paris, France
| | - A Represa
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France
| | - C Cardoso
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France
| | - O Dulac
- 1] INSERM U1129; University Paris Descartes, CEA, Gif sur Yvette, 149 Rue de Sèvres, 75015 Paris, France [2] Department of Pediatric Neurosurgery, Foundation Rothschild, 29 Rue Manin, 75019 Paris, France [3] APHP, Necker Hospital, 149 Rue de Sèvres, 75015 Paris, France
| | - Y Ben-Ari
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France
| | - N Burnashev
- 1] INSERM U901, INMED, Parc Scientifique et Technologique de Luminy 163, route de Luminy-BP 13, 13273 Marseille Cedex 09, France [2] UMR901, Aix-Marseille University, 58 Boulevard Charles Livon, 13284 Marseille, France
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Evidence for mTOR pathway activation in a spectrum of epilepsy-associated pathologies. Acta Neuropathol Commun 2014; 2:71. [PMID: 25005575 PMCID: PMC4230418 DOI: 10.1186/2051-5960-2-71] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 06/06/2014] [Indexed: 02/07/2023] Open
Abstract
INTRODUCTION Activation of the mTOR pathway has been linked to the cytopathology and epileptogenicity of malformations, specifically Focal Cortical Dysplasia (FCD) and Tuberous Sclerosis (TSC). Experimental and clinical trials have shown than mTOR inhibitors have anti-epileptogenic effects in TS. Dysmorphic neurones and balloon cells are hallmarks of FCDIIb and TSC, but similar cells are also occasionally observed in other acquired epileptogenic pathologies, including hippocampal sclerosis (HS) and Rasmussen's encephalitis (RE). Our aim was to explore mTOR pathway activation in a range of epilepsy-associated pathologies and in lesion-negative cases. RESULTS 50 epilepsy surgical pathologies were selected including HS ILAE type 1 with (5) and without dysmorphic neurones (4), FCDIIa (1), FCDIIb (5), FCDIIIa (5), FCDIIIb (3), FCDIIId (3), RE (5) and cortex adjacent to cavernoma (1). We also included pathology-negative epilepsy cases; temporal cortex (7), frontal cortex (2), paired frontal cortical samples with different ictal activity according to intracranial EEG recordings (4), cortex with acute injuries from electrode tracks (5) and additionally non-epilepsy surgical controls (3). Immunohistochemistry for phospho-S6 (pS6) ser240/244 and ser235/236 and double-labelling for Iba1, neurofilament, GFAP, GFAPdelta, doublecortin, and nestin were performed. Predominant neuronal labelling was observed with pS6 ser240/244 and glial labelling with pS6 ser235/236 in all pathology types but with evidence for co-expression in a proportion of cells in all pathologies. Intense labelling of dysmorphic neurones and balloon cells was observed in FCDIIb, but dysmorphic neurones were also labelled in RE and HS. There was no difference in pS6 labelling in paired samples according to ictal activity. Double-labelling immunofluorescent studies further demonstrated the co-localisation of pS6 with nestin, doublecortin, GFAPdelta in populations of small, immature neuroglial cells in a range of epilepsy pathologies. CONCLUSIONS Although mTOR activation has been more studied in the FCDIIb and TSC, our observations suggest this pathway is activated in a variety of epilepsy-associated pathologies, and in varied cell types including dysmorphic neurones, microglia and immature cell types. There was no definite evidence from our studies to suggest that pS6 expression is directly related to disease activity.
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70
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Pitkänen A, Huusko N, Ndode-Ekane XE, Kyyriäinen J, Lipponen A, Lipsanen A, Sierra A, Bolkvadze T. Gender issues in antiepileptogenic treatments. Neurobiol Dis 2014; 72 Pt B:224-32. [PMID: 24912075 DOI: 10.1016/j.nbd.2014.05.037] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2014] [Revised: 05/23/2014] [Accepted: 05/29/2014] [Indexed: 12/12/2022] Open
Abstract
Disease modification of epilepsy refers to the alleviation of epileptogenesis or comorbidities after genetic or acquired epileptogenic brain insults. There are currently 30 proof-of-concept experimental pharmacologic studies that have demonstrated some beneficial disease-modifying effects. None of these studies, however, has yet passed from the laboratory to the clinic. The International League Against Epilepsy and American Epilepsy Society working groups on antiepileptogenic (AEG) therapies recently released recommendations for conducting preclinical AEG studies, taking into account many of the critiques raised by previous study designs. One of the issues relates to the lack of analysis of AEG efficacy in both sexes. A review of the literature reveals that most of the preclinical studies have been performed using male rodents, whereas clinical study cohorts include both males and females. Therefore, it is important to determine whether sex differences should be taken into account to a greater extent than they have been historically at different phases of experimental studies. Here we address the following questions based on analysis of available experimental AEG studies: (a) whether sex differences should be considered when searching for novel AEG targets, (b) how sex differences can affect the preclinical AEG study designs and analysis of outcome measures, and (c) what factors should be considered when examining the effect of sex on outcome of clinical AEG trials or the clinical use of AEGs.
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Affiliation(s)
- Asla Pitkänen
- Epilepsy Research Laboratory, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, PO Box 1627, FIN-70211 Kuopio, Finland; Department of Neurology, Kuopio University Hospital, PO Box 1777, FIN-70211 Kuopio, Finland.
| | - Noora Huusko
- Epilepsy Research Laboratory, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, PO Box 1627, FIN-70211 Kuopio, Finland
| | - Xavier Ekolle Ndode-Ekane
- Epilepsy Research Laboratory, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, PO Box 1627, FIN-70211 Kuopio, Finland
| | - Jenni Kyyriäinen
- Epilepsy Research Laboratory, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, PO Box 1627, FIN-70211 Kuopio, Finland
| | - Anssi Lipponen
- Epilepsy Research Laboratory, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, PO Box 1627, FIN-70211 Kuopio, Finland
| | - Anu Lipsanen
- Epilepsy Research Laboratory, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, PO Box 1627, FIN-70211 Kuopio, Finland
| | - Alejandra Sierra
- Biomedical Imaging Unit, A. I. Virtanen Institute for Molecular Sciences, University of Eastern, Finland, PO Box 1627, FIN-70211 Kuopio, Finland
| | - Tamuna Bolkvadze
- Epilepsy Research Laboratory, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, PO Box 1627, FIN-70211 Kuopio, Finland
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Kassai H, Sugaya Y, Noda S, Nakao K, Maeda T, Kano M, Aiba A. Selective activation of mTORC1 signaling recapitulates microcephaly, tuberous sclerosis, and neurodegenerative diseases. Cell Rep 2014; 7:1626-1639. [PMID: 24857653 DOI: 10.1016/j.celrep.2014.04.048] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Revised: 03/18/2014] [Accepted: 04/22/2014] [Indexed: 02/06/2023] Open
Abstract
Mammalian target of rapamycin (mTOR) has been implicated in human neurological diseases such as tuberous sclerosis complex (TSC), neurodegeneration, and autism. However, little is known about when and how mTOR is involved in the pathogenesis of these diseases, due to a lack of animal models that directly increase mTOR activity. Here, we generated transgenic mice expressing a gain-of-function mutant of mTOR in the forebrain in a temporally controlled manner. Selective activation of mTORC1 in embryonic stages induced cortical atrophy caused by prominent apoptosis of neuronal progenitors, associated with upregulation of HIF-1α. In striking contrast, activation of the mTORC1 pathway in adulthood resulted in cortical hypertrophy with fatal epileptic seizures, recapitulating human TSC. Activated mTORC1 in the adult cortex also promoted rapid accumulation of cytoplasmic inclusions and activation of microglial cells, indicative of progressive neurodegeneration. Our findings demonstrate that mTORC1 plays different roles in developmental and adult stages and contributes to human neurological diseases.
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Affiliation(s)
- Hidetoshi Kassai
- Laboratory of Animal Resources, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Yuki Sugaya
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Shoko Noda
- Laboratory of Animal Resources, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Kazuki Nakao
- Laboratory of Animal Resources, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan; Laboratory for Animal Resources and Genetic Engineering, RIKEN Center for Developmental Biology, Kobe 650-0047, Japan
| | - Tatsuya Maeda
- Institute of Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113-0032, Japan
| | - Masanobu Kano
- Department of Neurophysiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Atsu Aiba
- Laboratory of Animal Resources, Center for Disease Biology and Integrative Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan.
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Rossini L, Medici V, Tassi L, Cardinale F, Tringali G, Bramerio M, Villani F, Spreafico R, Garbelli R. Layer-specific gene expression in epileptogenic type II focal cortical dysplasia: normal-looking neurons reveal the presence of a hidden laminar organization. Acta Neuropathol Commun 2014; 2:45. [PMID: 24735483 PMCID: PMC4023625 DOI: 10.1186/2051-5960-2-45] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Accepted: 04/04/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Type II focal cortical dysplasias (FCDs) are malformations of cortical development characterised by the disorganisation of the normal neocortical structure and the presence of dysmorphic neurons (DNs) and balloon cells (BCs). The pathogenesis of FCDs has not yet been clearly established, although a number of histopathological patterns and molecular findings suggest that they may be due to abnormal neuronal and glial proliferation and migration processes.In order to gain further insights into cortical layering disruption and investigate the origin of DNs and BCs, we used in situ RNA hybridisation of human surgical specimens with a neuropathologically definite diagnosis of Type IIa/b FCD and a panel of layer-specific genes (LSGs) whose expression covers all cortical layers. We also used anti-phospho-S6 ribosomal protein antibody to investigate mTOR pathway hyperactivation. RESULTS LSGs were expressed in both normal and abnormal cells (BCs and DNs) but their distribution was different. Normal-looking neurons, which were visibly reduced in the core of the lesion, were apparently located in the appropriate cortical laminae thus indicating a partial laminar organisation. On the contrary, DNs and BCs, labelled with anti-phospho-S6 ribosomal protein antibody, were spread throughout the cortex without any apparent rule and showed a highly variable LSG expression pattern. Moreover, LSGs did not reveal any differences between Type IIa and IIb FCD. CONCLUSION These findings suggest the existence of hidden cortical lamination involving normal-looking neurons, which retain their ability to migrate correctly in the cortex, unlike DNs which, in addition to their morphological abnormalities and mTOR hyperactivation, show an altered migratory pattern.Taken together these data suggest that an external or environmental hit affecting selected precursor cells during the very early stages of cortical development may disrupt normal cortical development.
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Affiliation(s)
- Laura Rossini
- Clinical Epileptology and Experimental Neurophysiology Unit, Istituto Neurologico “C. Besta”, Via Amadeo 42, 20133 Milano, Italy
| | - Valentina Medici
- Clinical Epileptology and Experimental Neurophysiology Unit, Istituto Neurologico “C. Besta”, Via Amadeo 42, 20133 Milano, Italy
| | - Laura Tassi
- C. Munari Epilepsy Surgery Centre, Niguarda Hospital, Milan, Italy
| | | | - Giovanni Tringali
- Department of Neurosurgery, Fondazione IRCCS, Istituto Neurologico “C. Besta”, Milan, Italy
| | | | - Flavio Villani
- Clinical Epileptology and Experimental Neurophysiology Unit, Istituto Neurologico “C. Besta”, Via Amadeo 42, 20133 Milano, Italy
| | - Roberto Spreafico
- Clinical Epileptology and Experimental Neurophysiology Unit, Istituto Neurologico “C. Besta”, Via Amadeo 42, 20133 Milano, Italy
| | - Rita Garbelli
- Clinical Epileptology and Experimental Neurophysiology Unit, Istituto Neurologico “C. Besta”, Via Amadeo 42, 20133 Milano, Italy
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Abstract
Descriptions of epileptic seizures and epilepsy date back to antiquity, and research into fundamental mechanisms of epilepsy in animal models, as well as patients, has been carried out for over a century. Studies of epileptogenesis, however, as distinct from ictogenesis, have been pursued for only a few decades, and antiepileptogenesis, the prevention of epilepsy or its progression, and the reversal of the epileptogenic process or cure, are relatively recent interests of the basic research community. The goal to develop antiepileptogenic interventions would be greatly facilitated by the identification of reliable biomarkers of epileptogenesis that could be used to create cost-effective, high-throughput screening models for potential antiepileptogenic compounds, as well as enrich patient populations and serve as surrogate endpoints for clinical trials. Without such biomarkers, the cost for clinical validation of antiepileptogenic interventions would be prohibitive. Epileptogenic mechanisms, antiepileptogenic interventions, and biomarkers are likely to be specific for the many different causes of epilepsy, which include genetic influences, cell loss and synaptic plasticity, malformations of cortical development, and autoimmune disorders, to name but a few. A high priority is currently being placed on investigations to elucidate fundamental mechanisms of epileptogenesis and identify biomarkers for specific models of human epilepsy, such as mesial temporal lobe epilepsy with hippocampal sclerosis, traumatic brain injury, and a variety of pediatric diseases, including tuberous sclerosis and West syndrome.
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Affiliation(s)
- Asla Pitkänen
- />Department of Neurobiology, A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
- />Department of Neurology, Kuopio University Hospital, Kuopio, Finland
| | - Jerome Engel
- />Department of Neurology, Neurobiology, and Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine at UCLA, 710 Westwood Plaza, Los Angeles, CA 90095-1769 USA
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74
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Lee JY, Park AK, Lee ES, Park WY, Park SH, Choi JW, Phi JH, Wang KC, Kim SK. miRNA expression analysis in cortical dysplasia: Regulation of mTOR and LIS1 pathway. Epilepsy Res 2014; 108:433-41. [DOI: 10.1016/j.eplepsyres.2014.01.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Revised: 12/11/2013] [Accepted: 01/14/2014] [Indexed: 01/08/2023]
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Leventer RJ, Jansen FE, Mandelstam SA, Ho A, Mohamed I, Sarnat HB, Kato M, Fukasawa T, Saitsu H, Matsumoto N, Itoh M, Kalnins RM, Chow CW, Harvey AS, Jackson GD, Crino PB, Berkovic SF, Scheffer IE. Is focal cortical dysplasia sporadic? Family evidence for genetic susceptibility. Epilepsia 2014; 55:e22-6. [DOI: 10.1111/epi.12533] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/02/2013] [Indexed: 02/01/2023]
Affiliation(s)
- Richard J. Leventer
- Department of Neurology; Royal Children's Hospital; Melbourne Victoria Australia
- Murdoch Childrens Research Institute; Melbourne Victoria Australia
- Department of Pediatrics; University of Melbourne; Melbourne Victoria Australia
| | - Floor E. Jansen
- Department of Pediatric Neurology; Rudolf Magnus Institute of Neurosciences; University Medical Center Utrecht; Utrecht The Netherlands
- Epilepsy Research Centre; University of Melbourne; Austin Health; Melbourne Victoria Australia
| | - Simone A. Mandelstam
- The Florey Institute of Neuroscience and Mental Health; Melbourne Victoria Australia
- Department of Radiology; University of Melbourne; Melbourne Victoria Australia
| | - Alice Ho
- Departments of Pediatrics and Clinical Neurosciences; Alberta Children's Hospital; University of Calgary; Calgary Alberta Canada
| | - Ismail Mohamed
- Department of Pediatrics; IWK Health Center; Dalhousie University; Halifax Nova Scotia Canada
| | - Harvey B. Sarnat
- Department of Pediatrics, Pathology, (Neuropathology) and Clinical Neurosciences; University of Calgary Faculty of Medicine; Alberta Children's Hospital; Calgary Alberta Canada
| | - Mitsuhiro Kato
- Department of Pediatrics; Yamagata University Faculty of Medicine; Yamagata Japan
| | | | - Hirotomo Saitsu
- Department of Human Genetics; Yokohama City University Graduate School of Medicine; Yokohama Japan
| | - Naomichi Matsumoto
- Department of Human Genetics; Yokohama City University Graduate School of Medicine; Yokohama Japan
| | - Masayuki Itoh
- Department of Mental Retardation and Birth Defect Research; National Institute of Neuroscience; National Center of Neurology and Psychiatry; Tokyo Japan
| | - Renate M. Kalnins
- Department of Anatomical Pathology; Austin Hospital; Melbourne Victoria Australia
- Department of Pathology; University of Melbourne; Melbourne Victoria Australia
| | - Chung W. Chow
- Department of Pediatrics; University of Melbourne; Melbourne Victoria Australia
- Department of Anatomical Pathology; Royal Children's Hospital; Melbourne Victoria Australia
| | - A. Simon Harvey
- Department of Neurology; Royal Children's Hospital; Melbourne Victoria Australia
- Murdoch Childrens Research Institute; Melbourne Victoria Australia
- Department of Pediatrics; University of Melbourne; Melbourne Victoria Australia
| | - Graeme D. Jackson
- Epilepsy Research Centre; University of Melbourne; Austin Health; Melbourne Victoria Australia
- Department of Radiology; University of Melbourne; Melbourne Victoria Australia
| | - Peter B. Crino
- Shriners Hospitals Pediatric Research Center; Temple University; Philadelphia Pennsylvania U.S.A
| | - Samuel F. Berkovic
- Epilepsy Research Centre; University of Melbourne; Austin Health; Melbourne Victoria Australia
| | - Ingrid E. Scheffer
- Department of Neurology; Royal Children's Hospital; Melbourne Victoria Australia
- Department of Pediatrics; University of Melbourne; Melbourne Victoria Australia
- Epilepsy Research Centre; University of Melbourne; Austin Health; Melbourne Victoria Australia
- Department of Radiology; University of Melbourne; Melbourne Victoria Australia
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Wong M. A critical review of mTOR inhibitors and epilepsy: from basic science to clinical trials. Expert Rev Neurother 2014; 13:657-69. [PMID: 23739003 DOI: 10.1586/ern.13.48] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Present medications for epilepsy have substantial limitations, such as medical intractability in many patients and lack of antiepileptogenic properties to prevent epilepsy. Drugs with novel mechanisms of action are needed to overcome these limitations. The mTOR signaling pathway has emerged as a possible therapeutic target for epilepsy. Preliminary clinical trials suggest that mTOR inhibitors reduce seizures in tuberous sclerosis complex (TSC) patients with intractable epilepsy. Furthermore, mTOR inhibitors have antiepileptogenic properties in preventing epilepsy in animal models of TSC. Besides TSC, accumulating preclinical data suggest that mTOR inhibitors may have antiseizure or antiepileptogenic actions in other types of epilepsy, including infantile spasms, neonatal hypoxic seizures, absence epilepsy and acquired temporal lobe epilepsy following brain injury, but these effects depend on a number of conditions. Future clinical and basic research is needed to establish whether mTOR inhibitors are an effective treatment for epilepsy.
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Affiliation(s)
- Michael Wong
- Department of Neurology and the Hope Center for Neurological Disorders, Washington University School of Medicine, St Louis, MO 63110, USA.
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77
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Abstract
The mammalian target of rapamycin (mTOR) pathway is an essential cellular signaling pathway involved in a number of important physiological functions, including cell growth, proliferation, metabolism, protein synthesis, and autophagy. Dysregulation of the mTOR pathway has been implicated in the pathophysiology of a number of neurological diseases. Hyperactivation of the mTOR pathway, leading to increased cell growth and proliferation, has been most convincingly shown to stimulate tumor growth in the brain and other organs in the genetic disorder, tuberous sclerosis complex (TSC). In addition, mTOR may also play a role in promoting epileptogenesis or maintaining seizures in TSC, as well as in acquired epilepsies following brain injury. Finally, the mTOR pathway may also be involved in the pathogenesis of cognitive dysfunction and other neurological deficits in developmental disorders and neurodegenerative diseases. mTOR inhibitors, such as rapamycin and its analogs, may represent novel, rational therapies for a variety of neurological disorders.
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Affiliation(s)
- Michael Wong
- Department of Neurology and the Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO 63110, USA.
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78
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mTOR complexes in neurodevelopmental and neuropsychiatric disorders. Nat Neurosci 2013; 16:1537-43. [PMID: 24165680 DOI: 10.1038/nn.3546] [Citation(s) in RCA: 264] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Accepted: 09/11/2013] [Indexed: 02/07/2023]
Abstract
The mechanistic target of rapamycin (mTOR) acts as a highly conserved signaling "hub" that integrates neuronal activity and a variety of synaptic inputs. mTOR is found in two functionally distinct complexes, mTORC1 and mTORC2, that crucially control long-term synaptic efficacy and memory storage. Dysregulation of mTOR signaling is associated with neurodevelopmental and neuropsychiatric disorders. In this Review, we describe the most recent advances in studies of mTOR signaling in the brain and the possible mechanisms underlying the many different functions of the mTOR complexes in neurological diseases. In addition, we discuss the medical relevance of these findings.
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79
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Kim H, Mansi T, Bernasconi N. Disentangling hippocampal shape anomalies in epilepsy. Front Neurol 2013; 4:131. [PMID: 24062718 PMCID: PMC3769634 DOI: 10.3389/fneur.2013.00131] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Accepted: 08/26/2013] [Indexed: 11/13/2022] Open
Abstract
Drug-resistant temporal lobe epilepsy (TLE) and epileptic syndromes related to malformations of cortical development (MCD) are associated with complex hippocampal morphology. The contribution of volume and position to the overall hippocampal shape in these conditions has not been studied. We propose a surface-based framework to localize volume changes through measurement of Jacobian determinants, and quantify fine-scale position and curvature through a medial axis model. We applied our methodology to T1-weighted 3D volumetric MRI of 88 patients with TLE and 78 patients with MCD, including focal cortical dysplasia (FCD, n = 29), heterotopia (HET, n = 40), and polymicrogyria (PMG, n = 19). Patients were compared to 46 age- and sex-matched healthy controls. Surface-based analysis of volume in TLE revealed severe ipsilateral atrophy mainly along the rostro-caudal extent of the hippocampal CA1 subfield. In MCD, patterns of volume changes included bilateral CA1 atrophy in HET and FCD, and left dentate hypertrophy in all three groups. The analysis of curvature revealed medial bending of the posterior hippocampus in TLE, whereas in MCD there was a supero-medial shift of the hippocampal body. Albeit hippocampal shape anomalies in TLE and MCD result from a combination of volume and positional changes, their nature and distribution suggest different pathogenic mechanisms.
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Affiliation(s)
- Hosung Kim
- Neuroimaging of Epilepsy Laboratory, McConnell Brain Imaging Center, Montreal Neurological Institute and Hospital, McGill University , Montreal, QC , Canada
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80
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Krueger DA, Wilfong AA, Holland-Bouley K, Anderson AE, Agricola K, Tudor C, Mays M, Lopez CM, Kim MO, Franz DN. Everolimus treatment of refractory epilepsy in tuberous sclerosis complex. Ann Neurol 2013; 74:679-87. [PMID: 23798472 DOI: 10.1002/ana.23960] [Citation(s) in RCA: 303] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Revised: 05/28/2013] [Accepted: 06/07/2013] [Indexed: 01/14/2023]
Abstract
OBJECTIVE Epilepsy is a major manifestation of tuberous sclerosis complex (TSC). Everolimus is an mammalian target of rapamycin complex 1 inhibitor with demonstrated benefit in several aspects of TSC. We report the first prospective human clinical trial to directly assess whether everolimus will also benefit epilepsy in TSC patients. METHODS The effect of everolimus on seizure control was assessed using a prospective, multicenter, open-label, phase I/II clinical trial. Patients≥2 years of age with confirmed diagnosis of TSC and medically refractory epilepsy were treated for a total of 12 weeks. The primary endpoint was percentage of patients with a ≥50% reduction in seizure frequency over a 4-week period before and after treatment. Secondary endpoints assessed impact on electroencephalography (EEG), behavior, and quality of life. RESULTS Twenty-three patients were enrolled, and 20 patients were treated with everolimus. Seizure frequency was reduced by ≥50% in 12 of 20 subjects. Overall, seizures were reduced in 17 of the 20 by a median reduction of 73% (p<0.001). Seizure frequency was also reduced during 23-hour EEG monitoring (p=0.007). Significant reductions in seizure duration and improvement in parent-reported behavior and quality of life were also observed. There were 83 reported adverse events that were thought to be treatment-related, all of which were mild or moderate in severity. INTERPRETATION Seizure control improved in the majority of TSC patients with medically refractory epilepsy following treatment with everolimus. Everolimus demonstrated additional benefits on behavior and quality of life. Treatment was safe and well tolerated. Everolimus may be a therapeutic option for refractory epilepsy in this population.
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Affiliation(s)
- Darcy A Krueger
- Departments of Pediatrics and Neurology, University of Cincinnati College of Medicine and Division of Child Neurology Cincinnati Children's Hospital Medical Center, Cincinnati, OH
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Interaction Between Akt1-Positive Neurons and Age at Surgery Is Associated With Surgical Outcome in Children With Isolated Focal Cortical Dysplasia. J Neuropathol Exp Neurol 2013; 72:884-91. [DOI: 10.1097/nen.0b013e3182a38d88] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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Baek ST, Gibbs EM, Gleeson JG, Mathern GW. Hemimegalencephaly, a paradigm for somatic postzygotic neurodevelopmental disorders. Curr Opin Neurol 2013; 26:122-7. [PMID: 23449172 DOI: 10.1097/wco.0b013e32835ef373] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
PURPOSE OF REVIEW Combining human genomics and molecular biology, recent studies have made pivotal progress toward understanding the cause of hemimegalencephaly (HME) and other cerebral megalencephaly syndromes. The present article highlights recent advances of the genetic cause of these conditions, and considers the role of somatic postzygotic genetic lesions in brain maldevelopment. RECENT FINDINGS Studies over the past 12 months have identified de-novo somatic mutations as one possible cause in HME. The gene mutations involve components of the phosphatidylinositol 3-kinase (PI3K)-AKT (also known as protein kinase B)-mammalian target of rapamycin (mTOR) pathway and include PIK3CA, PIK3R2, AKT3, and MTOR. These mutations were identified by comparing genomic data obtained from surgically resected brain tissue with nondiseased tissue, and by single-neuron sequencing in combination with molecular biology techniques. The association between the somatic mutations and downstream activation of the PI3K-mTOR pathway suggests that HME is a neurodevelopmental disease caused by gain-of-function activation of the PI3K-AKT-mTOR pathway. SUMMARY The studies reviewed suggest that somatic mutations of the PI3K-AKT-mTOR pathway limited to the brain may represent one cause of HME. Dysregulation of this pathway has possible therapeutic potential in the identification of HME. Somatic mutations may be an important yet underappreciated disease mechanism in developmental neurological diseases.
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Affiliation(s)
- Seung Tae Baek
- Department of Neurosciences, Howard Hughes Medical Institute, University of California San Diego, La Jolla, California, USA
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83
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Yasin SA, Ali AM, Tata M, Picker SR, Anderson GW, Latimer-Bowman E, Nicholson SL, Harkness W, Cross JH, Paine SML, Jacques TS. mTOR-dependent abnormalities in autophagy characterize human malformations of cortical development: evidence from focal cortical dysplasia and tuberous sclerosis. Acta Neuropathol 2013; 126:207-18. [PMID: 23728790 DOI: 10.1007/s00401-013-1135-4] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 05/23/2013] [Accepted: 05/24/2013] [Indexed: 12/18/2022]
Abstract
Focal cortical dysplasia (FCD) is a localized malformation of cortical development and is the commonest cause of severe childhood epilepsy in surgical practice. Children with FCD are severely disabled by their epilepsy, presenting with frequent seizures early in life. The commonest form of FCD in children is characterized by the presence of an abnormal population of cells, known as balloon cells. Similar pathological changes are seen in the cortical malformations that characterize patients with tuberous sclerosis complex (TSC). However, the cellular and molecular mechanisms that underlie the malformations of FCD and TSC are not well understood. We provide evidence for a defect in autophagy in FCD and TSC. We have found that balloon cells contain vacuoles that include components of the autophagy pathway. Specifically, we show that balloon cells contain prominent lysosomes by electron microscopy, immunohistochemistry for LAMP1 and LAMP2, LysoTracker labelling and enzyme histochemistry for acid phosphatase. Furthermore, we found that balloon cells contain components of the ATG pathway and that there is cytoplasmic accumulation of the regulator of autophagy, DOR. Most importantly we found that there is abnormal accumulation of the autophagy cargo protein, p62. We show that this defect in autophagy can be, in part, reversed in vitro by inhibition of the mammalian target of rapamycin (mTOR) suggesting that abnormal activation of mTOR may contribute directly to a defect in autophagy in FCD and TSC.
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Affiliation(s)
- Shireena A Yasin
- Neural Development Unit, Birth Defects Research Centre, UCL Institute of Child Health, 30 Guilford Street, London, WC1N 1EH, UK
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84
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Lim KC, Crino PB. Focal malformations of cortical development: new vistas for molecular pathogenesis. Neuroscience 2013; 252:262-76. [PMID: 23892008 DOI: 10.1016/j.neuroscience.2013.07.037] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Revised: 07/10/2013] [Accepted: 07/10/2013] [Indexed: 12/16/2022]
Abstract
Focal malformations of cortical development (FMCD) are highly associated with several neurological disorders including intractable epilepsy and neurocognitive disabilities. Over the past decade, several FMCD subtypes have been linked to hyperactivation of the mammalian target of rapamycin (mTOR) signaling cascade. In view of the roles that mTOR plays in cell proliferation, size, motility, and stem cell phenotype, many of the features of FMCD such as cytomegaly, disorganized lamination, and expression of stem cell markers can be explained by enhanced mTOR signaling. FMCD result from several distinct and fascinating molecular mechanisms including biallelic gene inactivation, somatic mutation, and potentially, viral infection. These mechanisms have been directly linked to mTOR activation. Perhaps most compelling, pharmacological inhibition of mTOR has been implemented successfully in clinical trials for select FMCD and provides a new vista for treatment.
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Affiliation(s)
- K-C Lim
- Department of Neurology, University of Pennsylvania Medical Center, Philadelphia, PA, United States
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85
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Meng XF, Yu JT, Song JH, Chi S, Tan L. Role of the mTOR signaling pathway in epilepsy. J Neurol Sci 2013; 332:4-15. [PMID: 23773767 DOI: 10.1016/j.jns.2013.05.029] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Revised: 05/19/2013] [Accepted: 05/23/2013] [Indexed: 11/19/2022]
Abstract
Epilepsy, a common neurological disorder and cause of significant morbidity and mortality, places an enormous burden on the individual and society. Presently, most drugs for epilepsy primarily suppress seizures as symptomatic therapies but do not possess actual antiepileptogenic or disease-modifying properties. The mTOR (mammalian target of rapamycin) signaling pathway is involved in major multiple cellular functions, including protein synthesis, cell growth and proliferation and synaptic plasticity, which may influence neuronal excitability and be responsible for epileptogenesis. Intriguing findings of the frequent hyperactivation of mTOR signaling in epilepsy make it a potential mechanism in the pathogenesis as well as an attractive target for the therapeutic intervention, and have driven the significant ongoing efforts to pharmacologically target this pathway. This review explores the relevance of the mTOR pathway to epileptogenesis and its potential as a therapeutic target in epilepsy treatment by presenting the current results on mTOR inhibitors, in particular, rapamycin, in animal models of diverse types of epilepsy. Limited clinical studies in human epilepsy, some paradoxical experimental data and outstanding questions have also been discussed.
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Affiliation(s)
- Xiang-Fei Meng
- Department of Neurology, School of Medicine, Qingdao Municipal Hospital, Qingdao University, China
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86
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Macias M, Blazejczyk M, Kazmierska P, Caban B, Skalecka A, Tarkowski B, Rodo A, Konopacki J, Jaworski J. Spatiotemporal characterization of mTOR kinase activity following kainic acid induced status epilepticus and analysis of rat brain response to chronic rapamycin treatment. PLoS One 2013; 8:e64455. [PMID: 23724051 PMCID: PMC3665782 DOI: 10.1371/journal.pone.0064455] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 04/15/2013] [Indexed: 01/09/2023] Open
Abstract
Mammalian target of rapamycin (mTOR) is a protein kinase that senses nutrient availability, trophic factors support, cellular energy level, cellular stress, and neurotransmitters and adjusts cellular metabolism accordingly. Adequate mTOR activity is needed for development as well as proper physiology of mature neurons. Consequently, changes in mTOR activity are often observed in neuropathology. Recently, several groups reported that seizures increase mammalian target of rapamycin (mTOR) kinase activity, and such increased activity in genetic models can contribute to spontaneous seizures. However, the current knowledge about the spatiotemporal pattern of mTOR activation induced by proconvulsive agents is rather rudimentary. Also consequences of insufficient mTOR activity on a status epilepticus are poorly understood. Here, we systematically investigated these two issues. We showed that mTOR signaling was activated by kainic acid (KA)-induced status epilepticus through several brain areas, including the hippocampus and cortex as well as revealed two waves of mTOR activation: an early wave (2 h) that occurs in neurons and a late wave that predominantly occurs in astrocytes. Unexpectedly, we found that pretreatment with rapamycin, a potent mTOR inhibitor, gradually (i) sensitized animals to KA treatment and (ii) induced gross anatomical changes in the brain.
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Affiliation(s)
- Matylda Macias
- Laboratory of Molecular and Cell Neurobiology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Magdalena Blazejczyk
- Laboratory of Molecular and Cell Neurobiology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | | | - Bartosz Caban
- Department of Neurobiology, University of Lodz, Lodz, Poland
| | - Agnieszka Skalecka
- Laboratory of Molecular and Cell Neurobiology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Bartosz Tarkowski
- Laboratory of Molecular and Cell Neurobiology, International Institute of Molecular and Cell Biology, Warsaw, Poland
| | - Anna Rodo
- Department of Pathology and Veterinary Diagnostics, Warsaw University of Life Sciences-SGGW, Warsaw, Poland
| | - Jan Konopacki
- Department of Neurobiology, University of Lodz, Lodz, Poland
| | - Jacek Jaworski
- Laboratory of Molecular and Cell Neurobiology, International Institute of Molecular and Cell Biology, Warsaw, Poland
- * E-mail:
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88
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Iyer A, Prabowo A, Anink J, Spliet WGM, van Rijen PC, Aronica E. Cell injury and premature neurodegeneration in focal malformations of cortical development. Brain Pathol 2013; 24:1-17. [PMID: 23586324 DOI: 10.1111/bpa.12060] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Accepted: 03/26/2013] [Indexed: 12/17/2022] Open
Abstract
Several lines of evidence suggest that cell injury may occur in malformations of cortical development associated with epilepsy. Moreover, recent studies support the link between neurodevelopmental and neurodegenerative mechanisms. We evaluated a series of focal cortical dysplasia (FCD, n=26; type I and II) and tuberous sclerosis complex (TSC, n=6) cases. Sections were processed for terminal deoxynucleotidyl transferase-mediated 2'-deoxyuridine 5'-triphosphate nick-end labeling (TUNEL) labeling and immunohistochemistry using markers for the evaluation of apoptosis signaling pathways and neurodegeneration-related proteins/pathways. In both FCD II and TSC specimens, we observed significant increases in both TUNEL-positive and caspase-3-positive cells compared with controls and FCD I. Expression of β-amyloid precursor protein was observed in neuronal soma and processes in FCD II and TSC. In these specimens, we also observed an abnormal expression of death receptor-6. Immunoreactivity for phosphorylated tau was only found in older patients with FCD II and TSC. In these cases, prominent nuclear/cytoplasmic p62 immunoreactivity was detected in both dysmorphic neurons and balloon/giant cells. Our data provide evidence of complex, but similar, mechanisms of cell injury in focal malformations of cortical development associated with mammalian target of rapamycin pathway hyperactivation, with prominent induction of apoptosis-signaling pathways and premature activation of mechanisms of neurodegeneration.
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Affiliation(s)
- Anand Iyer
- Department of (Neuro)Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
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89
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mTORC2 controls actin polymerization required for consolidation of long-term memory. Nat Neurosci 2013; 16:441-8. [PMID: 23455608 PMCID: PMC3615448 DOI: 10.1038/nn.3351] [Citation(s) in RCA: 222] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Accepted: 01/29/2013] [Indexed: 02/07/2023]
Abstract
A major goal of biomedical research has been the identification of molecular mechanisms that can enhance memory. Here we report a novel signaling pathway that regulates the conversion from short- to long-term memory. The mTOR complex 2 (mTORC2), which contains the key regulatory protein Rictor (Rapamycin-Insensitive Companion of mTOR), was discovered only recently, and little is known about its physiological role. We show that conditional deletion of rictor in the postnatal murine forebrain greatly reduces mTORC2 activity and selectively impairs both long-term memory (LTM) and the late (but not the early) phase of hippocampal long-term potentiation (LTP). Actin polymerization is reduced in the hippocampus of mTORC2-deficient mice and its restoration rescues both L-LTP and LTM. More importantly, a compound that selectively promotes mTORC2 activity converts early-LTP into late-LTP and enhances LTM. These findings indicate that mTORC2 could be a novel therapeutic target for the treatment of cognitive dysfunction.
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90
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Ryther RCC, Wong M. Mammalian target of rapamycin (mTOR) inhibition: potential for antiseizure, antiepileptogenic, and epileptostatic therapy. Curr Neurol Neurosci Rep 2012; 12:410-8. [PMID: 22544534 DOI: 10.1007/s11910-012-0276-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
New epilepsy treatments are needed that not only inhibit seizures symptomatically (antiseizure) but also prevent the development of epilepsy (antiepileptogenic). The mammalian target of rapamycin (mTOR) pathway may mediate mechanisms of epileptogenesis and serve as a rational therapeutic target. mTOR inhibitors have antiepileptogenic and antiseizure effects in animal models of the genetic disease, tuberous sclerosis complex. The mTOR pathway is also implicated in epileptogenesis in animal models of acquired epilepsy and infantile spasms, although the effects of mTOR inhibitors are variable depending on the specific conditions and model. Furthermore, beneficial effects on seizures are lost when treatment is withdrawn, suggesting that mTOR inhibitors are "epileptostatic" in only stalling epilepsy progression during treatment. Clinical studies of rapamycin in human epilepsy are limited, but suggest that mTOR inhibitors at least have antiseizure effects in tuberous sclerosis patients. Further studies are needed to assess the full potential of mTOR inhibitors for epilepsy treatment.
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Affiliation(s)
- Robin C C Ryther
- Department of Neurology and the Hope Center for Neurological Disorders, Washington University School of Medicine, Box 8111, 660 South Euclid Avenue, St. Louis, MO 63110, USA.
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Russo E, Citraro R, Constanti A, De Sarro G. The mTOR Signaling Pathway in the Brain: Focus on Epilepsy and Epileptogenesis. Mol Neurobiol 2012; 46:662-81. [DOI: 10.1007/s12035-012-8314-5] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 07/13/2012] [Indexed: 01/09/2023]
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92
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Sosunov AA, Wu X, McGovern RA, Coughlin DG, Mikell CB, Goodman RR, McKhann GM. The mTOR pathway is activated in glial cells in mesial temporal sclerosis. Epilepsia 2012; 53 Suppl 1:78-86. [PMID: 22612812 DOI: 10.1111/j.1528-1167.2012.03478.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Mammalian target of rapamycin (mTOR) is a key protein kinase that regulates basic cellular processes, including development and growth. Mutations in mTOR cause tuberous sclerosis complex (TSC), a condition that is characterized by developmental brain malformations (cortical tubers) and epilepsy. Although considerable insight has been gained recently into the pathologic dysfunction of mTOR in tubers in TSC-related epilepsy, data on the mTOR cascade in mesial temporal lobe epilepsy (MTLE) are lacking. Immunohistochemical investigation with confocal microscopy was performed to evaluate mTOR cascade and to correlate its activity with cellular alterations observed in surgically resected samples of human neocortex and hippocampus in MTLE. We compared results in human tissue to findings in the rat pilocarpine model of sclerotic MTLE. In nonsclerotic and control hippocampus, many neurons in the CA1 subfield expressed high levels of phospho-S6 (p-S6), a reliable marker of mTOR activation. In nonsclerotic and control hippocampus, as well as in magnetic resonance imaging (MRI) normal human neocortex, protoplasmic astrocytes did not express p-S6. In contrast, in sclerotic hippocampus, prominent p-S6 immunostaining was observed mainly in astrocytes and microglia located in the areas of neuronal loss and astrogliosis, whereas neurons in preserved areas of CA1 expressed significantly lower levels of p-S6 immunopositivity than neurons in nonsclerotic or control CA1 subfields. In surgically resected neocortex with chronic astroglial scar tissue, only microglia revealed moderate p-S6 immunoreactivity. Different from human sclerotic epileptic hippocampus, astrogliosis in the chronic rat pilocarpine model of epilepsy was not characterized by glial cells with mTOR activation. The mTOR cascade is activated in astroglial cells in sclerotic MTLE, but not in astrocytes in chronic neocortical scarring or in the pilocarpine model of MTLE. These findings suggest that the astroglial "scar" in sclerotic MTLE has active, ongoing cellular changes. Targeting mTOR in MTLE may provide new pathways for the medical therapy of epilepsy.
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Affiliation(s)
- Alexander A Sosunov
- Department of Neurosurgery, The Neurological Institute, Columbia University, 710 W. 168th Street, New York, NY 10032, U.S.A
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van Vliet EA, Forte G, Holtman L, den Burger JCG, Sinjewel A, de Vries HE, Aronica E, Gorter JA. Inhibition of mammalian target of rapamycin reduces epileptogenesis and blood-brain barrier leakage but not microglia activation. Epilepsia 2012; 53:1254-63. [DOI: 10.1111/j.1528-1167.2012.03513.x] [Citation(s) in RCA: 128] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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94
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Galanopoulou AS, Gorter JA, Cepeda C. Finding a better drug for epilepsy: the mTOR pathway as an antiepileptogenic target. Epilepsia 2012; 53:1119-30. [PMID: 22578218 DOI: 10.1111/j.1528-1167.2012.03506.x] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The mammalian target of rapamycin (mTOR) signaling pathway regulates cell growth, differentiation, proliferation, and metabolism. Loss-of-function mutations in upstream regulators of mTOR have been highly associated with dysplasias, epilepsy, and neurodevelopmental disorders. These include tuberous sclerosis, which is due to mutations in TSC1 or TSC2 genes; mutations in phosphatase and tensin homolog (PTEN) as in Cowden syndrome, polyhydramnios, megalencephaly, symptomatic epilepsy syndrome (PMSE) due to mutations in the STE20-related kinase adaptor alpha (STRADalpha); and neurofibromatosis type 1 attributed to neurofibromin 1 mutations. Inhibition of the mTOR pathway with rapamycin may prevent epilepsy and improve the underlying pathology in mouse models with disrupted mTOR signaling, due to PTEN or TSC mutations. However the timing and duration of its administration appear critical in defining the seizure and pathology-related outcomes. Rapamycin application in human cortical slices from patients with cortical dysplasias reduces the 4-aminopyridine-induced oscillations. In the multiple-hit model of infantile spasms, pulse high-dose rapamycin administration can reduce the cortical overactivation of the mTOR pathway, suppresses spasms, and has disease-modifying effects by partially improving cognitive deficits. In post-status epilepticus models of temporal lobe epilepsy, rapamycin may ameliorate the development of epilepsy-related pathology and reduce the expression of spontaneous seizures, but its effects depend on the timing and duration of administration, and possibly the model used. The observed recurrence of seizures and epilepsy-related pathology after rapamycin discontinuation suggests the need for continuous administration to maintain the benefit. However, the use of pulse administration protocols may be useful in certain age-specific epilepsy syndromes, like infantile spasms, whereas repetitive-pulse rapamycin protocols may suffice to sustain a long-term benefit in genetic disorders of the mTOR pathway. In summary, mTOR dysregulation has been implicated in several genetic and acquired forms of epileptogenesis. The use of mTOR inhibitors can reverse some of these epileptogenic processes, although their effects depend upon the timing and dose of administration as well as the model used.
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Affiliation(s)
- Aristea S Galanopoulou
- Saul R. Korey Department of Neurology, Dominick P. Purpura Department of Neuroscience, Laboratory of Developmental Epilepsy, Montefiore/Einstein Epilepsy Management Center, Albert Einstein College of Medicine, Bronx, New York, USA.
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95
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Crino PB. mTOR: A pathogenic signaling pathway in developmental brain malformations. Trends Mol Med 2011; 17:734-42. [DOI: 10.1016/j.molmed.2011.07.008] [Citation(s) in RCA: 193] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 07/19/2011] [Accepted: 07/21/2011] [Indexed: 11/16/2022]
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Wong M. Mammalian target of rapamycin (mTOR) activation in focal cortical dysplasia and related focal cortical malformations. Exp Neurol 2011; 244:22-6. [PMID: 22015915 DOI: 10.1016/j.expneurol.2011.10.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Accepted: 10/03/2011] [Indexed: 01/20/2023]
Abstract
Focal cortical dysplasia (FCD) and other localized malformations of cortical development represent common causes of intractable pediatric epilepsy. Insights into the cellular and molecular pathogenesis of focal cortical malformations may reveal information about associated mechanisms of epileptogenesis and suggest new therapies for seizures caused by these developmental lesions. In animal models and human studies of FCD and the related disease of Tuberous Sclerosis Complex (TSC), the mammalian target of rapamycin (mTOR) pathway has been implicated in mediating cellular and molecular changes leading to the formation of the cortical malformations and the expression of epilepsy. The use of mTOR inhibitors may represent a rational therapeutic strategy for treating or even preventing epilepsy due to FCD and TSC.
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Affiliation(s)
- Michael Wong
- Department of Neurology and the Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, MO 63110, USA.
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97
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Sunnen CN, Brewster AL, Lugo JN, Vanegas F, Turcios E, Mukhi S, Parghi D, D'Arcangelo G, Anderson AE. Inhibition of the mammalian target of rapamycin blocks epilepsy progression in NS-Pten conditional knockout mice. Epilepsia 2011; 52:2065-75. [PMID: 21973019 DOI: 10.1111/j.1528-1167.2011.03280.x] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE Increased activity of mTOR Complex 1 (mTORC1) has been demonstrated in cortical dysplasia and tuberous sclerosis complex, as well as in animal models of epilepsy. Recent studies in such models revealed that inhibiting mTORC1 with rapamycin effectively suppressed seizure activity. However, seizures can recur after treatment cessation, and continuous rapamycin exposure can adversely affect animal growth and health. Here, we evaluated the efficacy of an intermittent rapamycin treatment protocol on epilepsy progression using neuron subset-specific-Pten (NS-Pten) conditional knockout mice. METHODS NS-Pten knockouts were treated with a single course of rapamycin during postnatal weeks 4 and 5, or intermittently over a period of 5 months. Epileptiform activity was monitored using video-electroencephalography (EEG) recordings, and mossy fiber sprouting was evaluated using Timm staining. Survival and body weight were assessed in parallel. KEY FINDINGS NS-Pten knockouts treated with a single course of rapamycin had recurrence of epilepsy 4-7 weeks after treatment ended. In contrast, epileptiform activity remained suppressed, and survival increased if knockout mice received additional rapamycin during weeks 10-11 and 16-17. Aberrant mossy fiber sprouting, present by 4 weeks of age and progressing in parallel with epileptiform activity, was also blocked by rapamycin. SIGNIFICANCE These findings demonstrate that a single course of rapamycin treatment suppresses epileptiform activity and mossy fiber sprouting for several weeks before epilepsy recurs. However, additional intermittent treatments with rapamycin prevented this recurrence and enhanced survival without compromising growth. Therefore, these studies add to the growing body of evidence implicating an important role for mTORC1 signaling in epilepsy.
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Affiliation(s)
- C Nicole Sunnen
- The Cain Foundation Laboratories and The Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, Texas 77030, USA
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Abstract
Prevention of epileptogenesis after brain trauma is an unmet medical challenge. Recent molecular profiling studies have provided an insight into molecular changes that contribute to formation of ictogenic neuronal networks, including genes regulating synaptic or neuronal plasticity, cell death, proliferation, and inflammatory or immune responses. These mechanisms have been targeted to prevent epileptogenesis in animal models. Favourable effects have been obtained using immunosuppressants, antibodies blocking adhesion of leucocytes to endothelial cells, gene therapy driving expression of neurotrophic factors, pharmacological neurostimulation, or even with conventional antiepileptic drugs by administering them before the appearance of genetic epilepsy. Further studies are needed to clarify the optimum time window and aetiological specificity of treatments. Questions related to adverse events also need further consideration. Encouragingly, the recent experimental studies emphasise that the complicated process of epileptogenesis can be favourably modified, and that antiepileptogenesis as a treatment indication might not be an impossible mission.
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Affiliation(s)
- Asla Pitkänen
- Department of Neurobiology, A I Virtanen Institute for Molecular Sciences, University of Eastern Finland, and Department of Neurology, Kuopio University Hospital, Kuopio, Finland.
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99
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Therapeutic role of mammalian target of rapamycin (mTOR) inhibition in preventing epileptogenesis. Neurosci Lett 2011; 497:231-9. [PMID: 21354266 DOI: 10.1016/j.neulet.2011.02.037] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Revised: 01/25/2011] [Accepted: 02/15/2011] [Indexed: 12/19/2022]
Abstract
Traditionally, medical therapy for epilepsy has aimed to suppress seizure activity, but has been unable to alter the progression of the underlying disease. Recent advances in our understanding of mechanisms of epileptogenesis open the door for the development of new therapies which prevent the pathogenic changes in the brain that predispose to spontaneous seizures. In particular, the mammalian target of rapamycin (mTOR) signaling pathway has recently garnered interest as an important regulator of cellular changes involved in epileptogenesis, and mTOR inhibitors have generated excitement as potential antiepileptogenic agents. mTOR hyperactivation occurs in tuberous sclerosis complex (TSC), a common genetic cause of epilepsy, as a result of genetic mutations in upstream regulatory molecules. mTOR inhibition prevents epilepsy and brain pathology in animal models of TSC. mTOR dysregulation has also been demonstrated in a variety of other genetic and acquired epilepsies, including brain tumors, focal cortical dysplasias, and animal models of brain injury due to status epilepticus or trauma. Indeed, mTOR inhibitors appear to possess antiepileptogenic properties in animal models of acquired epilepsy as well. Thus, mTOR dysregulation may represent a final common pathway in epilepsies of various causes. Therefore, mTOR inhibition is an exciting potential antiepileptogenic strategy with broad applications for epilepsy and could be involved in a number of treatment modalities, including the ketogenic diet. Further research is necessary to determine the clinical utility of rapamycin and other mTOR inhibitors for antiepileptogenesis, and to devise new therapeutic targets by further elucidating the signaling molecules involved in epileptogenesis.
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TSC1/TSC2 signaling in the CNS. FEBS Lett 2011; 585:973-80. [PMID: 21329690 DOI: 10.1016/j.febslet.2011.02.001] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Revised: 02/01/2011] [Accepted: 02/01/2011] [Indexed: 12/17/2022]
Abstract
Over the past several years, the study of a hereditary tumor syndrome, tuberous sclerosis complex (TSC), has shed light on the regulation of cellular proliferation and growth. TSC is an autosomal dominant disorder that is due to inactivating mutations in TSC1 or TSC2 and characterized by benign tumors (hamartomas) involving multiple organ systems. The TSC1/2 complex has been found to play a crucial role in an evolutionarily-conserved signaling pathway that regulates cell growth: the mTORC1 pathway. This pathway promotes anabolic processes and inhibits catabolic processes in response to extracellular and intracellular factors. Findings in cancer biology have reinforced the critical role for TSC1/2 in cell growth and proliferation. In contrast to cancer cells, in the CNS, the TSC1/2 complex not only regulates cell growth/proliferation, but also orchestrates an intricate and finely tuned system that has distinctive roles under different conditions, depending on cell type, stage of development, and subcellular localization. Overall, TSC1/2 signaling in the CNS, via its multi-faceted roles, contributes to proper neural connectivity. Here, we will review the TSC signaling in the CNS.
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