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Riley VA, Shankar V, Holmberg JC, Sokolov AM, Neckles VN, Williams K, Lyman R, Mackay TF, Feliciano DM. Tsc2 coordinates neuroprogenitor differentiation. iScience 2023; 26:108442. [PMID: 38107199 PMCID: PMC10724693 DOI: 10.1016/j.isci.2023.108442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 09/22/2023] [Accepted: 11/09/2023] [Indexed: 12/19/2023] Open
Abstract
Neural stem cells (NSCs) of the ventricular-subventricular zone (V-SVZ) generate numerous cell types. The uncoupling of mRNA transcript availability and translation occurs during the progression from stem to differentiated states. The mTORC1 kinase pathway acutely controls proteins that regulate mRNA translation. Inhibiting mTORC1 during differentiation is hypothesized to be critical for brain development since somatic mutations of mTORC1 regulators perturb brain architecture. Inactivating mutations of TSC1 or TSC2 genes cause tuberous sclerosis complex (TSC). TSC patients have growths near the striatum and ventricles. Here, it is demonstrated that V-SVZ NSC Tsc2 inactivation causes striatal hamartomas. Tsc2 removal altered translation factors, translatomes, and translational efficiency. Single nuclei RNA sequencing following in vivo loss of Tsc2 revealed changes in NSC activation states. The inability to decouple mRNA transcript availability and translation delayed differentiation leading to the retention of immature phenotypes in hamartomas. Taken together, Tsc2 is required for translational repression and differentiation.
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Affiliation(s)
- Victoria A. Riley
- Department of Biological Sciences, Clemson University, Clemson, SC, USA
| | - Vijay Shankar
- Department of Biochemistry and Genetics, Clemson University, Clemson, SC, USA
- Center for Human Genetics, Clemson University, Greenwood, SC, USA
| | | | - Aidan M. Sokolov
- Department of Biological Sciences, Clemson University, Clemson, SC, USA
| | | | - Kaitlyn Williams
- Clemson University Genomics and Bioinformatics Facility (CUGBF), Clemson University, Clemson, SC, USA
| | - Rachel Lyman
- Department of Biochemistry and Genetics, Clemson University, Clemson, SC, USA
- Center for Human Genetics, Clemson University, Greenwood, SC, USA
| | - Trudy F.C. Mackay
- Department of Biochemistry and Genetics, Clemson University, Clemson, SC, USA
- Center for Human Genetics, Clemson University, Greenwood, SC, USA
| | - David M. Feliciano
- Department of Biological Sciences, Clemson University, Clemson, SC, USA
- Center for Human Genetics, Clemson University, Greenwood, SC, USA
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Bychkova E, Dorofeeva M, Levov A, Kislyakov A, Karandasheva K, Strelnikov V, Anoshkin K. Specific Features of Focal Cortical Dysplasia in Tuberous Sclerosis Complex. Curr Issues Mol Biol 2023; 45:3977-3996. [PMID: 37232723 DOI: 10.3390/cimb45050254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 04/23/2023] [Accepted: 04/26/2023] [Indexed: 05/27/2023] Open
Abstract
Patients with tuberous sclerosis complex present with cognitive, behavioral, and psychiatric impairments, such as intellectual disabilities, autism spectrum disorders, and drug-resistant epilepsy. It has been shown that these disorders are associated with the presence of cortical tubers. Tuberous sclerosis complex results from inactivating mutations in the TSC1 or TSC2 genes, resulting in hyperactivation of the mTOR signaling pathway, which regulates cell growth, proliferation, survival, and autophagy. TSC1 and TSC2 are classified as tumor suppressor genes and function according to Knudson's two-hit hypothesis, which requires both alleles to be damaged for tumor formation. However, a second-hit mutation is a rare event in cortical tubers. This suggests that the molecular mechanism of cortical tuber formation may be more complicated and requires further research. This review highlights the issues of molecular genetics and genotype-phenotype correlations, considers histopathological characteristics and the mechanism of morphogenesis of cortical tubers, and also presents data on the relationship between these formations and the development of neurological manifestations, as well as treatment options.
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Affiliation(s)
- Ekaterina Bychkova
- Research Centre for Medical Genetics, Moskvorechye Street 1, 115522 Moscow, Russia
- Faculty of Biomedicine, Pirogov Russian National Research Medical University, Ostrovityanova Street 1, 117997 Moscow, Russia
| | - Marina Dorofeeva
- Veltischev Research and Clinical Institute for Pediatrics and Pediatric Surgery, Pirogov Russian National Research Medical University, Taldomskaya 2, 125412 Moscow, Russia
| | - Aleksandr Levov
- Morozov Children's City Clinical Hospital, 4th Dobryninsky Lane, 1/9, 119049 Moscow, Russia
| | - Alexey Kislyakov
- Morozov Children's City Clinical Hospital, 4th Dobryninsky Lane, 1/9, 119049 Moscow, Russia
| | | | - Vladimir Strelnikov
- Research Centre for Medical Genetics, Moskvorechye Street 1, 115522 Moscow, Russia
| | - Kirill Anoshkin
- Research Centre for Medical Genetics, Moskvorechye Street 1, 115522 Moscow, Russia
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Kashii H, Kasai S, Sato A, Hagino Y, Nishito Y, Kobayashi T, Hino O, Mizuguchi M, Ikeda K. Tsc2 mutation rather than Tsc1 mutation dominantly causes a social deficit in a mouse model of tuberous sclerosis complex. Hum Genomics 2023; 17:4. [PMID: 36732866 PMCID: PMC9893559 DOI: 10.1186/s40246-023-00450-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Accepted: 01/18/2023] [Indexed: 02/04/2023] Open
Abstract
BACKGROUND Tuberous sclerosis complex (TSC) is an autosomal dominant disorder that is associated with neurological symptoms, including autism spectrum disorder. Tuberous sclerosis complex is caused by pathogenic germline mutations of either the TSC1 or TSC2 gene, but somatic mutations were identified in both genes, and the combined effects of TSC1 and TSC2 mutations have been unknown. METHODS The present study investigated social behaviors by the social interaction test and three-chambered sociability tests, effects of rapamycin treatment, and gene expression profiles with a gene expression microarray in Tsc1 and Tsc2 double heterozygous mutant (TscD+/-) mice. RESULTS TscD+/- mice exhibited impairments in social behaviors, and the severity of impairments was similar to Tsc2+/- mice rather than Tsc1+/- mice. Impairments in social behaviors were rescued by rapamycin treatment in all mutant mice. Gene expression profiles in the brain were greatly altered in TscD+/- mice more than in Tsc1+/- and Tsc2+/- mice. The gene expression changes compared with wild type (WT) mice were similar between TscD+/- and Tsc2+/- mice, and the overlapping genes whose expression was altered in mutant mice compared with WT mice were enriched in the neoplasm- and inflammation-related canonical pathways. The "signal transducer and activator of transcription 3, interferon regulatory factor 1, interferon regulatory factor 4, interleukin-2R α chain, and interferon-γ" signaling pathway, which is initiated from signal transducer and activator of transcription 4 and PDZ and LIM domain protein 2, was associated with impairments in social behaviors in all mutant mice. LIMITATIONS It is unclear whether the signaling pathway also plays a critical role in autism spectrum disorders not caused by Tsc1 and Tsc2 mutations. CONCLUSIONS These findings suggest that TSC1 and TSC2 double mutations cause autistic behaviors similarly to TSC2 mutations, although significant changes in gene expression were attributable to the double mutations. These findings contribute to the knowledge of genotype-phenotype correlations in TSC and suggest that mutations in both the TSC1 and TSC2 genes act in concert to cause neurological symptoms, including autism spectrum disorder.
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Affiliation(s)
- Hirofumi Kashii
- grid.272456.00000 0000 9343 3630Addictive Substance Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-Ku, Tokyo, 156-8506 Japan ,grid.417106.5Department of Neuropediatrics, Tokyo Metropolitan Neurological Hospital, 2-6-1 Musashidai, Fuchu, Tokyo, 183-0042 Japan
| | - Shinya Kasai
- grid.272456.00000 0000 9343 3630Addictive Substance Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-Ku, Tokyo, 156-8506 Japan
| | - Atsushi Sato
- grid.272456.00000 0000 9343 3630Addictive Substance Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-Ku, Tokyo, 156-8506 Japan ,grid.412708.80000 0004 1764 7572Department of Pediatrics, The University of Tokyo Hospital, 7-3-1 Hongo, Bunkyo-Ku, Tokyo, 113-8655 Japan
| | - Yoko Hagino
- grid.272456.00000 0000 9343 3630Addictive Substance Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-Ku, Tokyo, 156-8506 Japan
| | - Yasumasa Nishito
- grid.272456.00000 0000 9343 3630Center for Basic Technology Research, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-Ku, Tokyo, 156-8506 Japan
| | - Toshiyuki Kobayashi
- grid.258269.20000 0004 1762 2738Department of Pathology and Oncology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-Ku, Tokyo, 113-8421 Japan
| | - Okio Hino
- grid.258269.20000 0004 1762 2738Department of Pathology and Oncology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-Ku, Tokyo, 113-8421 Japan
| | - Masashi Mizuguchi
- Department of Pediatrics, National Rehabilitation Center for Children with Disabilities, 1-1-10 Komone, Itabashi-Ku, Tokyo, 173-0037 Japan
| | - Kazutaka Ikeda
- Addictive Substance Project, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-Ku, Tokyo, 156-8506, Japan.
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De Meulemeester AS, Heylen L, Siekierska A, Mills JD, Romagnolo A, Van Der Wel NN, Aronica E, de Witte PAM. Hyperactivation of mTORC1 in a double hit mutant zebrafish model of tuberous sclerosis complex causes increased seizure susceptibility and neurodevelopmental abnormalities. Front Cell Dev Biol 2022; 10:952832. [PMID: 36238691 PMCID: PMC9552079 DOI: 10.3389/fcell.2022.952832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 09/05/2022] [Indexed: 11/16/2022] Open
Abstract
Tuberous sclerosis complex (TSC) is a multisystem genetic disorder caused by pathogenic variants in TSC1 and TSC2 genes. TSC patients present with seizures and brain abnormalities such as tubers and subependymal giant cells astrocytoma (SEGA). Despite common molecular and clinical features, the severity of the disease varies greatly, even intrafamilially. The second hit hypothesis suggests that an additional, inactivating mutation in the remaining functional allele causes a more severe phenotype and therefore explains the phenotypic variability. Recently, second hit mutations have been detected frequently in mTORopathies. To investigate the pathophysiological effects of second hit mutations, several mouse models have been developed. Here, we opted for a double mutant zebrafish model that carries a LOF mutation both in the tsc2 and the depdc5 gene. To the best of our knowledge, this is the first time a second-hit model has been studied in zebrafish. Significantly, the DEP domain-containing protein 5 (DEPDC5) gene has an important role in the regulation of mTORC1, and the combination of a germline TSC2 and somatic DEPDC5 mutation has been described in a TSC patient with intractable epilepsy. Our depdc5−/−x tsc2−/− double mutant zebrafish line displayed greatly increased levels of mammalian target of rapamycin (mTORC1) activity, augmented seizure susceptibility, and early lethality which could be rescued by rapamycin. Histological analysis of the brain revealed ventricular dilatation in the tsc2 and double homozygotes. RNA-sequencing showed a linear relation between the number of differentially expressed genes (DEGs) and the degree of mTORC1 hyperactivity. Enrichment analysis of their transcriptomes revealed that many genes associated with neurological developmental processes were downregulated and mitochondrial genes were upregulated. In particular, the transcriptome of human SEGA lesions overlapped strongly with the double homozygous zebrafish larvae. The data highlight the clinical relevance of the depdc5−/− x tsc2−/− double mutant zebrafish larvae that showed a more severe phenotype compared to the single mutants. Finally, analysis of gene-drug interactions identified interesting pharmacological targets for SEGA, underscoring the value of our small zebrafish vertebrate model for future drug discovery efforts.
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Affiliation(s)
| | - Lise Heylen
- Laboratory for Molecular Biodiscovery, KU Leuven, Leuven, Belgium
| | | | - James D. Mills
- Department of (Neuro)Pathology Amsterdam Neuroscience, Amsterdam UMC Location University of Amsterdam, Amsterdam, Netherlands
- Department of Clinical and Experimental Epilepsy, UCL Queen Square Institute of Neurology, London, United Kingdom
- Chalfont Centre for Epilepsy, Chalfont St Peter, United Kingdom
| | - Alessia Romagnolo
- Department of (Neuro)Pathology Amsterdam Neuroscience, Amsterdam UMC Location University of Amsterdam, Amsterdam, Netherlands
| | - Nicole N. Van Der Wel
- Department of Medical Biology, Electron Microscopy Center Amsterdam, Amsterdam UMC Location University of Amsterdam, Amsterdam, Netherlands
| | - Eleonora Aronica
- Department of (Neuro)Pathology Amsterdam Neuroscience, Amsterdam UMC Location University of Amsterdam, Amsterdam, Netherlands
- Stichting Epilepsie Instelling Nederland (SEIN), Heemstede, Netherlands
| | - Peter A. M. de Witte
- Laboratory for Molecular Biodiscovery, KU Leuven, Leuven, Belgium
- *Correspondence: Peter A. M. de Witte,
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Wu X, Sosunov AA, Lado W, Teoh JJ, Ham A, Li H, Al-Dalahmah O, Gill BJA, Arancio O, Schevon CA, Frankel WN, McKhann GM, Sulzer D, Goldman JE, Tang G. Synaptic hyperexcitability of cytomegalic pyramidal neurons contributes to epileptogenesis in tuberous sclerosis complex. Cell Rep 2022; 40:111085. [PMID: 35858542 PMCID: PMC9376014 DOI: 10.1016/j.celrep.2022.111085] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 02/15/2022] [Accepted: 06/22/2022] [Indexed: 11/27/2022] Open
Abstract
Tuberous sclerosis complex (TSC) is a developmental disorder associated with epilepsy, autism, and cognitive impairment. Despite inactivating mutations in the TSC1 or TSC2 genes and hyperactive mechanistic target of rapamycin (mTOR) signaling, the mechanisms underlying TSC-associated neurological symptoms remain incompletely understood. Here we generate a Tsc1 conditional knockout (CKO) mouse model in which Tsc1 inactivation in late embryonic radial glia causes social and cognitive impairment and spontaneous seizures. Tsc1 depletion occurs in a subset of layer 2/3 cortical pyramidal neurons, leading to development of cytomegalic pyramidal neurons (CPNs) that mimic dysplastic neurons in human TSC, featuring abnormal dendritic and axonal overgrowth, enhanced glutamatergic synaptic transmission, and increased susceptibility to seizure-like activities. We provide evidence that enhanced synaptic excitation in CPNs contributes to cortical hyperexcitability and epileptogenesis. In contrast, astrocytic regulation of synapse formation and synaptic transmission remains unchanged after late embryonic radial glial Tsc1 inactivation, and astrogliosis evolves secondary to seizures. Wu et al. demonstrate that Tsc1 inactivation in late embryonic radial glial cells (RGCs) produces cytomegalic pyramidal neurons that mimic TSC-like dysplastic neurons. They find that enhanced excitatory synaptic transmission in Tsc1-null cytomegalic pyramidal neurons contributes to cortical hyperexcitability and epileptogenesis.
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Affiliation(s)
- Xiaoping Wu
- Department of Neurological Surgery, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Alexander A Sosunov
- Department of Neurological Surgery, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Wudu Lado
- Department of Neurology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Jia Jie Teoh
- Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Ahrom Ham
- Department of Neurology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Hongyu Li
- Department of Neurology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Osama Al-Dalahmah
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Brian J A Gill
- Department of Neurological Surgery, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Ottavio Arancio
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Medicine, Columbia University Irving Medical Center, New York, NY 10032, USA; The Taub Institute, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Catherine A Schevon
- Department of Neurology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Wayne N Frankel
- Institute for Genomic Medicine, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Guy M McKhann
- Department of Neurological Surgery, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - David Sulzer
- Department of Psychiatry, Columbia University Irving Medical Center, New York, NY 10032, USA; Department of Pharmacology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - James E Goldman
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY 10032, USA; The Taub Institute, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Guomei Tang
- Department of Neurology, Columbia University Irving Medical Center, New York, NY 10032, USA.
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Schrötter S, Yuskaitis CJ, MacArthur MR, Mitchell SJ, Hosios AM, Osipovich M, Torrence ME, Mitchell JR, Hoxhaj G, Sahin M, Manning BD. The non-essential TSC complex component TBC1D7 restricts tissue mTORC1 signaling and brain and neuron growth. Cell Rep 2022; 39:110824. [PMID: 35584673 PMCID: PMC9175135 DOI: 10.1016/j.celrep.2022.110824] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 03/21/2022] [Accepted: 04/23/2022] [Indexed: 11/16/2022] Open
Abstract
The tuberous sclerosis complex (TSC) 1 and 2 proteins associate with TBC1D7 to form the TSC complex, which is an essential suppressor of mTOR complex 1 (mTORC1), a ubiquitous driver of cell and tissue growth. Loss-of-function mutations in TSC1 or TSC2, but not TBC1D7, give rise to TSC, a pleiotropic disorder with aberrant activation of mTORC1 in various tissues. Here, we characterize mice with genetic deletion of Tbc1d7, which are viable with normal growth and development. Consistent with partial loss of function of the TSC complex, Tbc1d7 knockout (KO) mice display variable increases in tissue mTORC1 signaling with increased muscle fiber size but with strength and motor defects. Their most pronounced phenotype is brain overgrowth due to thickening of the cerebral cortex, with enhanced neuron-intrinsic mTORC1 signaling and growth. Thus, TBC1D7 is required for full TSC complex function in tissues, and the brain is particularly sensitive to its growth-suppressing activities.
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Affiliation(s)
- Sandra Schrötter
- Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, MA, USA; Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Christopher J Yuskaitis
- Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Michael R MacArthur
- Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Sarah J Mitchell
- Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Aaron M Hosios
- Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, MA, USA; Department of Cell Biology, Harvard Medical School, Boston, MA, USA
| | - Maria Osipovich
- Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Margaret E Torrence
- Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - James R Mitchell
- Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Gerta Hoxhaj
- Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Mustafa Sahin
- Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Brendan D Manning
- Department of Molecular Metabolism, Harvard T.H. Chan School of Public Health, Boston, MA, USA; Department of Cell Biology, Harvard Medical School, Boston, MA, USA.
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7
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Terry BK, Park R, Cho SH, Crino PB, Kim S. Abnormal activation of Yap/Taz contributes to the pathogenesis of tuberous sclerosis complex. Hum Mol Genet 2022; 31:1979-1996. [PMID: 34999833 PMCID: PMC9239747 DOI: 10.1093/hmg/ddab374] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 10/31/2021] [Accepted: 12/27/2021] [Indexed: 01/09/2023] Open
Abstract
The multi-systemic genetic disorder tuberous sclerosis complex (TSC) impacts multiple neurodevelopmental processes including neuronal morphogenesis, neuronal migration, myelination and gliogenesis. These alterations contribute to the development of cerebral cortex abnormalities and malformations. Although TSC is caused by mTORC1 hyperactivation, cognitive and behavioral impairments are not improved through mTORC1 targeting, making the study of the downstream effectors of this complex important for understanding the mechanisms underlying TSC. As mTORC1 has been shown to promote the activity of the transcriptional co-activator Yap, we hypothesized that altered Yap/Taz signaling contributes to the pathogenesis of TSC. We first observed that the levels of Yap/Taz are increased in human cortical tuber samples and in embryonic cortices of Tsc2 conditional knockout (cKO) mice. Next, to determine how abnormal upregulation of Yap/Taz impacts the neuropathology of TSC, we deleted Yap/Taz in Tsc2 cKO mice. Importantly, Yap/Taz/Tsc2 triple conditional knockout (tcKO) animals show reduced cortical thickness and cortical neuron cell size, despite the persistence of high mTORC1 activity, suggesting that Yap/Taz play a downstream role in cytomegaly. Furthermore, Yap/Taz/Tsc2 tcKO significantly restored cortical and hippocampal lamination defects and reduced hippocampal heterotopia formation. Finally, the loss of Yap/Taz increased the distribution of myelin basic protein in Tsc2 cKO animals, consistent with an improvement in myelination. Overall, our results indicate that targeting Yap/Taz lessens the severity of neuropathology in a TSC animal model. This study is the first to implicate Yap/Taz as contributors to cortical pathogenesis in TSC and therefore as potential novel targets in the treatment of this disorder.
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Affiliation(s)
- Bethany K Terry
- Department of Neural Sciences, Lewis Katz School of Medicine, Shriners Hospitals Pediatrics Research Center, Temple University, Philadelphia, PA 19140, USA,Biomedical Sciences Graduate Program, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Raehee Park
- Department of Neural Sciences, Lewis Katz School of Medicine, Shriners Hospitals Pediatrics Research Center, Temple University, Philadelphia, PA 19140, USA
| | - Seo-Hee Cho
- Department of Medicine, Sidney Kimmel Medical College, Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Peter B Crino
- Department of Neurology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Seonhee Kim
- To whom correspondence should be addressed. Tel: 215-926-9360; Fax: 215-926-9325;
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8
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Synaptic Alterations in a Transgenic Model of Tuberous Sclerosis Complex: Relevance to Autism Spectrum Disorders. Int J Mol Sci 2021; 22:ijms221810058. [PMID: 34576223 PMCID: PMC8466868 DOI: 10.3390/ijms221810058] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 09/08/2021] [Accepted: 09/14/2021] [Indexed: 01/02/2023] Open
Abstract
Tuberous sclerosis complex (TSC) is a rare, multi-system genetic disease with serious neurological and mental symptoms, including autism. Mutations in the TSC1/TSC2 genes lead to the overactivation of mTOR signalling, which is also linked to nonsyndromic autism. Our aim was to analyse synaptic pathology in a transgenic model of TSC: two-month-old male B6;129S4-Tsc2tm1Djk/J mice with Tsc2 haploinsufficiency. Significant brain-region-dependent alterations in the expression of several synaptic proteins were identified. The most prominent changes were observed in the immunoreactivity of presynaptic VAMP1/2 (ca. 50% increase) and phospho-synapsin-1 (Ser62/67) (ca. 80% increase). Transmission electron microscopy demonstrated serious ultrastructural abnormalities in synapses such as a blurred structure of synaptic density and a significantly increased number of synaptic vesicles. The impairment of synaptic mitochondrial ultrastructure was represented by excessive elongation, swelling, and blurred crista contours. Polyribosomes in the cytoplasm and swollen Golgi apparatus suggest possible impairment of protein metabolism. Moreover, the delamination of myelin and the presence of vacuolar structures in the cell nucleus were observed. We also report that Tsc2+/- mice displayed increased brain weights and sizes. The behavioural analysis demonstrated the impairment of memory function, as established in the novel object recognition test. To summarise, our data indicate serious synaptic impairment in the brains of male Tsc2+/- mice.
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Bassetti D, Luhmann HJ, Kirischuk S. Effects of Mutations in TSC Genes on Neurodevelopment and Synaptic Transmission. Int J Mol Sci 2021; 22:ijms22147273. [PMID: 34298906 PMCID: PMC8305053 DOI: 10.3390/ijms22147273] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 07/02/2021] [Accepted: 07/04/2021] [Indexed: 12/11/2022] Open
Abstract
Mutations in TSC1 or TSC2 genes are linked to alterations in neuronal function which ultimately lead to the development of a complex neurological phenotype. Here we review current research on the effects that reduction in TSC1 or TSC2 can produce on the developing neural network. A crucial feature of the disease pathophysiology appears to be an early deviation from typical neurodevelopment, in the form of structural abnormalities. Epileptic seizures are one of the primary early manifestation of the disease in the CNS, followed by intellectual deficits and autism spectrum disorders (ASD). Research using mouse models suggests that morphological brain alterations might arise from the interaction of different cellular types, and hyperexcitability in the early postnatal period might be transient. Moreover, the increased excitation-to-inhibition ratio might represent a transient compensatory adjustment to stabilize the developing network rather than a primary factor for the development of ASD symptoms. The inhomogeneous results suggest region-specificity as well as an evolving picture of functional alterations along development. Furthermore, ASD symptoms and epilepsy might originate from different but potentially overlapping mechanisms, which can explain recent observations obtained in patients. Potential treatment is determined not only by the type of medicament, but also by the time point of treatment.
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HK2 Mediated Glycolytic Metabolism in Mouse Photoreceptors Is Not Required to Cause Late Stage Age-Related Macular Degeneration-Like Pathologies. Biomolecules 2021; 11:biom11060871. [PMID: 34208233 PMCID: PMC8230848 DOI: 10.3390/biom11060871] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 06/01/2021] [Accepted: 06/09/2021] [Indexed: 12/12/2022] Open
Abstract
Age-related macular degeneration (AMD) is a multifactorial disease of unclear etiology. We previously proposed that metabolic adaptations in photoreceptors (PRs) play a role in disease progression. We mimicked these metabolic adaptations in mouse PRs through deletion of the tuberous sclerosis complex (TSC) protein TSC1. Here, we confirm our previous findings by deletion of the other complex protein, namely TSC2, in rod photoreceptors. Similar to deletion of Tsc1, mice with deletion of Tsc2 in rods develop AMD-like pathologies, including accumulation of apolipoproteins, migration of microglia, geographic atrophy, and neovascular pathologies. Subtle differences between the two mouse models, such as a significant increase in microglia activation with loss of Tsc2, were seen as well. To investigate the role of altered glucose metabolism in disease pathogenesis, we generated mice with simulation deletions of Tsc2 and hexokinase-2 (Hk2) in rods. Although retinal lactate levels returned to normal in mice with Tsc2-Hk2 deletion, AMD-like pathologies still developed. The data suggest that the metabolic adaptations in PRs that cause AMD-like pathologies are independent of HK2-mediated aerobic glycolysis.
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Zimmer TS, Broekaart DWM, Gruber VE, van Vliet EA, Mühlebner A, Aronica E. Tuberous Sclerosis Complex as Disease Model for Investigating mTOR-Related Gliopathy During Epileptogenesis. Front Neurol 2020; 11:1028. [PMID: 33041976 PMCID: PMC7527496 DOI: 10.3389/fneur.2020.01028] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Accepted: 08/06/2020] [Indexed: 12/13/2022] Open
Abstract
Tuberous sclerosis complex (TSC) represents the prototypic monogenic disorder of the mammalian target of rapamycin (mTOR) pathway dysregulation. It provides the rational mechanistic basis of a direct link between gene mutation and brain pathology (structural and functional abnormalities) associated with a complex clinical phenotype including epilepsy, autism, and intellectual disability. So far, research conducted in TSC has been largely neuron-oriented. However, the neuropathological hallmarks of TSC and other malformations of cortical development also include major morphological and functional changes in glial cells involving astrocytes, oligodendrocytes, NG2 glia, and microglia. These cells and their interglial crosstalk may offer new insights into the common neurobiological mechanisms underlying epilepsy and the complex cognitive and behavioral comorbidities that are characteristic of the spectrum of mTOR-associated neurodevelopmental disorders. This review will focus on the role of glial dysfunction, the interaction between glia related to mTOR hyperactivity, and its contribution to epileptogenesis in TSC. Moreover, we will discuss how understanding glial abnormalities in TSC might give valuable insight into the pathophysiological mechanisms that could help to develop novel therapeutic approaches for TSC or other pathologies characterized by glial dysfunction and acquired mTOR hyperactivation.
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Affiliation(s)
- Till S Zimmer
- Department of (Neuro)Pathology, Amsterdam Neuroscience, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, Netherlands
| | - Diede W M Broekaart
- Department of (Neuro)Pathology, Amsterdam Neuroscience, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, Netherlands
| | | | - Erwin A van Vliet
- Department of (Neuro)Pathology, Amsterdam Neuroscience, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, Netherlands.,Swammerdam Institute for Life Sciences, Center for Neuroscience, University of Amsterdam, Amsterdam, Netherlands
| | - Angelika Mühlebner
- Department of (Neuro)Pathology, Amsterdam Neuroscience, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, Netherlands
| | - Eleonora Aronica
- Department of (Neuro)Pathology, Amsterdam Neuroscience, Amsterdam University Medical Centers, University of Amsterdam, Amsterdam, Netherlands.,Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, Netherlands
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12
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Kapfhamer D, McKenna J, Yoon CJ, Murray-Stewart T, Casero RA, Gambello MJ. Ornithine decarboxylase, the rate-limiting enzyme of polyamine synthesis, modifies brain pathology in a mouse model of tuberous sclerosis complex. Hum Mol Genet 2020; 29:2395-2407. [PMID: 32588887 PMCID: PMC7424721 DOI: 10.1093/hmg/ddaa121] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2020] [Revised: 05/18/2020] [Accepted: 06/11/2020] [Indexed: 12/11/2022] Open
Abstract
Tuberous sclerosis complex (TSC) is a rare autosomal dominant neurodevelopmental disorder characterized by variable expressivity. TSC results from inactivating variants within the TSC1 or TSC2 genes, leading to constitutive activation of mechanistic target of rapamycin complex 1 signaling. Using a mouse model of TSC (Tsc2-RG) in which the Tsc2 gene is deleted in radial glial precursors and their neuronal and glial descendants, we observed increased ornithine decarboxylase (ODC) enzymatic activity and concentration of its product, putrescine. To test if increased ODC activity and dysregulated polyamine metabolism contribute to the neurodevelopmental defects of Tsc2-RG mice, we used pharmacologic and genetic approaches to reduce ODC activity in Tsc2-RG mice, followed by histologic assessment of brain development. We observed that decreasing ODC activity and putrescine levels in Tsc2-RG mice worsened many of the neurodevelopmental phenotypes, including brain growth and neuronal migration defects, astrogliosis and oxidative stress. These data suggest a protective effect of increased ODC activity and elevated putrescine that modify the phenotype in this developmental Tsc2-RG model.
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Affiliation(s)
- David Kapfhamer
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia
| | - James McKenna
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia
| | - Caroline J Yoon
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia
| | - Tracy Murray-Stewart
- The Sidney Kimmel Comprehensive Cancer Center, The Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Robert A Casero
- The Sidney Kimmel Comprehensive Cancer Center, The Johns Hopkins School of Medicine, Baltimore, MD, USA
| | - Michael J Gambello
- Department of Human Genetics, Emory University School of Medicine, Atlanta, Georgia
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13
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Feliciano DM. The Neurodevelopmental Pathogenesis of Tuberous Sclerosis Complex (TSC). Front Neuroanat 2020; 14:39. [PMID: 32765227 PMCID: PMC7381175 DOI: 10.3389/fnana.2020.00039] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 06/10/2020] [Indexed: 12/22/2022] Open
Abstract
Tuberous sclerosis complex (TSC) is a model disorder for understanding brain development because the genes that cause TSC are known, many downstream molecular pathways have been identified, and the resulting perturbations of cellular events are established. TSC, therefore, provides an intellectual framework to understand the molecular and biochemical pathways that orchestrate normal brain development. The TSC1 and TSC2 genes encode Hamartin and Tuberin which form a GTPase activating protein (GAP) complex. Inactivating mutations in TSC genes (TSC1/TSC2) cause sustained Ras homologue enriched in brain (RHEB) activation of the mammalian isoform of the target of rapamycin complex 1 (mTORC1). TOR is a protein kinase that regulates cell size in many organisms throughout nature. mTORC1 inhibits catabolic processes including autophagy and activates anabolic processes including mRNA translation. mTORC1 regulation is achieved through two main upstream mechanisms. The first mechanism is regulation by growth factor signaling. The second mechanism is regulation by amino acids. Gene mutations that cause too much or too little mTORC1 activity lead to a spectrum of neuroanatomical changes ranging from altered brain size (micro and macrocephaly) to cortical malformations to Type I neoplasias. Because somatic mutations often underlie these changes, the timing, and location of mutation results in focal brain malformations. These mutations, therefore, provide gain-of-function and loss-of-function changes that are a powerful tool to assess the events that have gone awry during development and to determine their functional physiological consequences. Knowledge about the TSC-mTORC1 pathway has allowed scientists to predict which upstream and downstream mutations should cause commensurate neuroanatomical changes. Indeed, many of these predictions have now been clinically validated. A description of clinical imaging and histochemical findings is provided in relation to laboratory models of TSC that will allow the reader to appreciate how human pathology can provide an understanding of the fundamental mechanisms of development.
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Affiliation(s)
- David M Feliciano
- Department of Biological Sciences, Clemson University, Clemson, SC, United States
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14
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Sundberg M, Tochitsky I, Buchholz DE, Winden K, Kujala V, Kapur K, Cataltepe D, Turner D, Han MJ, Woolf CJ, Hatten ME, Sahin M. Purkinje cells derived from TSC patients display hypoexcitability and synaptic deficits associated with reduced FMRP levels and reversed by rapamycin. Mol Psychiatry 2018; 23:2167-2183. [PMID: 29449635 PMCID: PMC6093816 DOI: 10.1038/s41380-018-0018-4] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Revised: 12/06/2017] [Accepted: 12/11/2017] [Indexed: 12/11/2022]
Abstract
Accumulating evidence suggests that cerebellar dysfunction early in life is associated with autism spectrum disorder (ASD), but the molecular mechanisms underlying the cerebellar deficits at the cellular level are unclear. Tuberous sclerosis complex (TSC) is a neurocutaneous disorder that often presents with ASD. Here, we developed a cerebellar Purkinje cell (PC) model of TSC with patient-derived human induced pluripotent stem cells (hiPSCs) to characterize the molecular mechanisms underlying cerebellar abnormalities in ASD and TSC. Our results show that hiPSC-derived PCs from patients with pathogenic TSC2 mutations displayed mTORC1 pathway hyperactivation, defects in neuronal differentiation and RNA regulation, hypoexcitability and reduced synaptic activity when compared with those derived from controls. Our gene expression analyses revealed downregulation of several components of fragile X mental retardation protein (FMRP) targets in TSC2-deficient hiPSC-PCs. We detected decreased expression of FMRP, glutamate receptor δ2 (GRID2), and pre- and post-synaptic markers such as synaptophysin and PSD95 in the TSC2-deficient hiPSC-PCs. The mTOR inhibitor rapamycin rescued the deficits in differentiation, synaptic dysfunction, and hypoexcitability of TSC2 mutant hiPSC-PCs in vitro. Our findings suggest that these gene expression changes and cellular abnormalities contribute to aberrant PC function during development in TSC affected individuals.
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Affiliation(s)
- Maria Sundberg
- Department of Neurology, F.M. Kirby Center for Neurobiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA
| | - Ivan Tochitsky
- Department of Neurology, F.M. Kirby Center for Neurobiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - David E Buchholz
- Laboratory of Developmental Neurobiology, The Rockefeller University, New York, NY, USA
| | - Kellen Winden
- Department of Neurology, F.M. Kirby Center for Neurobiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Ville Kujala
- Harvard John A. Paulson School of Engineering and Applied Sciences, Boston, MA, USA
| | - Kush Kapur
- Department of Neurology, F.M. Kirby Center for Neurobiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Deniz Cataltepe
- Department of Neurology, F.M. Kirby Center for Neurobiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Daria Turner
- Department of Neurology, F.M. Kirby Center for Neurobiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Min-Joon Han
- Department of Neurology, F.M. Kirby Center for Neurobiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
| | - Clifford J Woolf
- Department of Neurology, F.M. Kirby Center for Neurobiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA
| | - Mary E Hatten
- Laboratory of Developmental Neurobiology, The Rockefeller University, New York, NY, USA
| | - Mustafa Sahin
- Department of Neurology, F.M. Kirby Center for Neurobiology, Boston Children's Hospital, Harvard Medical School, Boston, MA, USA.
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA.
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15
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Grabole N, Zhang JD, Aigner S, Ruderisch N, Costa V, Weber FC, Theron M, Berntenis N, Spleiss O, Ebeling M, Yeo GW, Jagasia R, Kiialainen A. Genomic analysis of the molecular neuropathology of tuberous sclerosis using a human stem cell model. Genome Med 2016; 8:94. [PMID: 27655340 PMCID: PMC5031259 DOI: 10.1186/s13073-016-0347-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Accepted: 08/18/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Tuberous sclerosis complex (TSC) is a genetic disease characterized by benign tumor growths in multiple organs and neurological symptoms induced by mTOR hyperfunction. Because the molecular pathology is highly complex and the etiology poorly understood, we employed a defined human neuronal model with a single mTOR activating mutation to dissect the disease-relevant molecular responses driving the neuropathology and suggest new targets for treatment. METHODS We investigate the disease phenotype of TSC by neural differentiation of a human stem cell model that had been deleted for TSC2 by genome editing. Comprehensive genomic analysis was performed by RNA sequencing and ribosome profiling to obtain a detailed genome-wide description of alterations on both the transcriptional and translational level. The molecular effect of mTOR inhibitors used in the clinic was monitored and comparison to published data from patient biopsies and mouse models highlights key pathogenic processes. RESULTS TSC2-deficient neural stem cells showed severely reduced neuronal maturation and characteristics of astrogliosis instead. Transcriptome analysis indicated an active inflammatory response and increased metabolic activity, whereas at the level of translation ribosomal transcripts showed a 5'UTR motif-mediated increase in ribosome occupancy. Further, we observed enhanced protein synthesis rates of angiogenic growth factors. Treatment with mTOR inhibitors corrected translational alterations but transcriptional dysfunction persisted. CONCLUSIONS Our results extend the understanding of the molecular pathophysiology of TSC brain lesions, and suggest phenotype-tailored pharmacological treatment strategies.
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Affiliation(s)
- Nils Grabole
- Roche Pharma Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, 4070, Switzerland.
| | - Jitao David Zhang
- Roche Pharma Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, 4070, Switzerland
| | - Stefan Aigner
- Department of Cellular and Molecular Medicine, Institute for Genomic Medicine, UCSD Stem Cell Program, Sanford Consortium for Regenerative Medicine, University of California at San Diego, La Jolla, CA, 92037, USA
| | - Nadine Ruderisch
- Roche Pharma Research and Early Development, Neuroscience, Ophthalmology and Rare Diseases, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, 4070, Switzerland
| | - Veronica Costa
- Roche Pharma Research and Early Development, Neuroscience, Ophthalmology and Rare Diseases, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, 4070, Switzerland
| | - Felix C Weber
- Roche Pharma Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, 4070, Switzerland
| | - Michel Theron
- Roche Pharma Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, 4070, Switzerland
| | - Nikolaos Berntenis
- Roche Pharma Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, 4070, Switzerland
| | - Olivia Spleiss
- Roche Pharma Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, 4070, Switzerland
| | - Martin Ebeling
- Roche Pharma Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, 4070, Switzerland
| | - Gene W Yeo
- Department of Cellular and Molecular Medicine, Institute for Genomic Medicine, UCSD Stem Cell Program, Sanford Consortium for Regenerative Medicine, University of California at San Diego, La Jolla, CA, 92037, USA
| | - Ravi Jagasia
- Roche Pharma Research and Early Development, Neuroscience, Ophthalmology and Rare Diseases, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, 4070, Switzerland
| | - Anna Kiialainen
- Roche Pharma Research and Early Development, Pharmaceutical Sciences, Roche Innovation Center Basel, F. Hoffmann-La Roche Ltd, Grenzacherstrasse 124, Basel, 4070, Switzerland
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16
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Davis PE, Peters JM, Krueger DA, Sahin M. Tuberous Sclerosis: A New Frontier in Targeted Treatment of Autism. Neurotherapeutics 2015; 12:572-83. [PMID: 25986747 PMCID: PMC4489948 DOI: 10.1007/s13311-015-0359-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Tuberous sclerosis complex (TSC) is a genetic disorder with a high prevalence of autism spectrum disorder (ASD). Tremendous progress in understanding the pathogenesis of TSC has been made in recent years, along with initial trials of medical treatment aimed specifically at the underlying mechanism of the disorder. At the cellular level, loss of TSC1 or TSC2 results in upregulation of the mechanistic target of rapamycin (mTOR) pathway. At the circuitry level, TSC and mTOR play crucial roles in axonal, dendritic, and synaptic development and function. In this review, we discuss the molecular mechanism underlying TSC, and how this disease results in aberrant neural connectivity at multiple levels in the central nervous system, leading to ASD symptoms. We then review recent advances in mechanism-based treatments of TSC, and the promise that these treatments provide for future mechanism-based treatment of ASD. Because of these recent advances, TSC represents an ideal model for how to make progress in understanding and treating the mechanisms that underlie ASD in general.
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Affiliation(s)
- Peter E. Davis
- />Department of Neurology, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, 02115 MA USA
| | - Jurriaan M. Peters
- />Department of Neurology, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, 02115 MA USA
| | - Darcy A. Krueger
- />Division of Neurology, Department of Pediatrics, Cincinnati Children’s Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH USA
| | - Mustafa Sahin
- />Department of Neurology, Boston Children’s Hospital, Harvard Medical School, 300 Longwood Avenue, Boston, 02115 MA USA
- />F.M. Kirby Neurobiology Center, Boston Children’s Hospital, Harvard Medical School, Boston, MA USA
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Abstract
The mammalian target of rapamycin (mTOR) pathway integrates multiple signals and regulates crucial cell functions via the molecular complexes mTORC1 and mTORC2. These complexes are functionally dependent on their raptor (mTORC1) or rictor (mTORC2) subunits. mTOR has been associated with oligodendrocyte differentiation and myelination downstream of the PI3K/Akt pathway, but the functional contributions of individual complexes are largely unknown. We show, by oligodendrocyte-specific genetic deletion of Rptor and/or Rictor in the mouse, that CNS myelination is mainly dependent on mTORC1 function, with minor mTORC2 contributions. Myelin-associated lipogenesis and protein gene regulation are strongly reliant on mTORC1. We found that also oligodendrocyte-specific overactivation of mTORC1, via ablation of tuberous sclerosis complex 1 (TSC1), causes hypomyelination characterized by downregulation of Akt signaling and lipogenic pathways. Our data demonstrate that a delicately balanced regulation of mTORC1 activation and action in oligodendrocytes is essential for CNS myelination, which has practical overtones for understanding CNS myelin disorders.
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