1
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Torii T, Miyamoto Y, Yamauchi J. Myelination by signaling through Arf guanine nucleotide exchange factor. J Neurochem 2024. [PMID: 38894552 DOI: 10.1111/jnc.16141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 05/19/2024] [Accepted: 05/23/2024] [Indexed: 06/21/2024]
Abstract
During myelination, large quantities of proteins are synthesized and transported from the endoplasmic reticulum (ER)-trans-Golgi network (TGN) to their appropriate locations within the intracellular region and/or plasma membrane. It is widely believed that oligodendrocytes uptake neuronal signals from neurons to regulate the endocytosis- and exocytosis-mediated intracellular trafficking of major myelin proteins such as myelin-associated glycoprotein (MAG) and proteolipid protein 1 (PLP1). The small GTPases of the adenosine diphosphate (ADP) ribosylation factor (Arf) family constitute a large group of signal transduction molecules that act as regulators for intracellular signaling, vesicle sorting, or membrane trafficking in cells. Studies on mice deficient in Schwann cell-specific Arfs-related genes have revealed abnormal myelination formation in peripheral nerves, indicating that Arfs-mediated signaling transduction is required for myelination in Schwann cells. However, the complex roles in these events remain poorly understood. This review aims to provide an update on signal transduction, focusing on Arf and its activator ArfGEF (guanine nucleotide exchange factor for Arf) in oligodendrocytes and Schwann cells. Future studies are expected to provide important information regarding the cellular and physiological processes underlying the myelination of oligodendrocytes and Schwann cells and their function in modulating neural activity.
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Affiliation(s)
- Tomohiro Torii
- Department of Biochemistry, Kitasato University School of Medicine, Sagamihara-shi, Kanagawa, Japan
| | - Yuki Miyamoto
- Department of Pharmacology, National Research Institute for Child Health and Development, Tokyo, Japan
| | - Junji Yamauchi
- Laboratory of Molecular Neuroscience and Neurology, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo, Japan
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2
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Ren Y, Luo X, Tong H, Wang S, Yan J, Lin L, Chen Y. Preliminary Study on Clinical Characteristics and Pathogenesis of IQSEC2 Mutations Patients. Pharmgenomics Pers Med 2024; 17:289-318. [PMID: 38827181 PMCID: PMC11144418 DOI: 10.2147/pgpm.s455840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 05/18/2024] [Indexed: 06/04/2024] Open
Abstract
Background The IQ motif and Sec7 domain ArfGEF 2 (IQSEC2), an X-linked gene that encodes the BRAG1 protein, is a guanine nucleotide exchange factor for the ADP ribosylation factor (ARF) protein family in the small guanosine triphosphate (GTP) binding protein. Mutations in this gene result in disorders such as intellectual disability (ID) and epilepsy. In this study, we analyze the clinical features of two patients with IQSEC2-mutation-related disease and discuss their possible pathogenesis. Methods The two patients were diagnosed with ID and epilepsy. Genetic testing was performed using whole-exome sequencing, and the three-dimensional protein structure was analyzed. UCSC Genome Browser was used to analyze the conservation of IQSEC2 in different species. We compared IQSEC2 expression in the proband families with that in a control group, as well as the expression of the postsynaptic identity protein 95 (PSD-95), synapse-associated protein 97 (SAP97), ADP ribosylation factor 6 (ARF-6), and insulin receptor substrate 53kDa (IRSP53) genes interacting with IQSEC2. Results We identified two semi-zygote mutations located in conserved positions in different species: an unreported de novo mutation, C.3576C>A (p. Tyr1192*), and a known mutation, c.2983C>T (p. Arg995Trp). IQSEC2 mutations resulted in significant changes in the predicted three-dimensional protein structure, while its expression in the two probands was significantly lower than that in the age-matched control group, and IQSEC2 expression in proband 1 was lower than that in his family members. The expression levels of PSD-95, ARF-6, and SAP97, IRSP 53, which interact with IQSEC2, were also significantly different from those in the family members and age-matched healthy children. Conclusion The clinical phenotype resulting from IQSEC2 mutations can be explained by the significant decrease in its expression, loss of function of the mutant protein, and change in the expression of related genes. Our results provide novel insights into the molecular phenotype conferred by the IQSEC2 variants.
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Affiliation(s)
- Yun Ren
- Department of Neurology, Shanghai Children’s Hospital, School of Medicine, Shanghai JiaoTong University, Shanghai, People’s Republic of China
| | - Xiaona Luo
- Department of Neurology, Shanghai Children’s Hospital, School of Medicine, Shanghai JiaoTong University, Shanghai, People’s Republic of China
| | - Haiyan Tong
- Department of Neurology, Shanghai Children’s Hospital, School of Medicine, Shanghai JiaoTong University, Shanghai, People’s Republic of China
| | - Simei Wang
- Department of Neurology, Shanghai Children’s Hospital, School of Medicine, Shanghai JiaoTong University, Shanghai, People’s Republic of China
| | - Jinbin Yan
- Department of Neurology, Shanghai Children’s Hospital, School of Medicine, Shanghai JiaoTong University, Shanghai, People’s Republic of China
| | - Longlong Lin
- Department of Neurology, Shanghai Children’s Hospital, School of Medicine, Shanghai JiaoTong University, Shanghai, People’s Republic of China
| | - Yucai Chen
- Department of Neurology, Shanghai Children’s Hospital, School of Medicine, Shanghai JiaoTong University, Shanghai, People’s Republic of China
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3
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Nakashima M, Shiroshima T, Fukaya M, Sugawara T, Sakagami H, Yamazawa K. C-terminal truncations in IQSEC2: implications for synaptic localization, guanine nucleotide exchange factor activity, and neurological manifestations. J Hum Genet 2024; 69:119-123. [PMID: 38200111 DOI: 10.1038/s10038-023-01210-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 11/29/2023] [Accepted: 11/30/2023] [Indexed: 01/12/2024]
Abstract
IQSEC2 gene on chromosome Xq11.22 encodes a member of guanine nucleotide exchange factor (GEF) protein that is implicated in the activation of ADP-ribosylation factors (Arfs) at the postsynaptic density (PSD), and plays a crucial role in synaptic transmission and dendritic spine formation. Alterations in IQSEC2 have been linked to X-linked intellectual developmental disorders including epilepsy and behavioral abnormalities. Of interest, truncating variants at the C-terminus of IQSEC2 can cause severe phenotypes, akin to truncating variants located in other regions. Here, we present a 5-year-old boy with severe intellectual disability and progressive epilepsy. The individual carried a nonsense variant p.Q1227* in the last exon of the IQSEC2 gene that was supposed to escape nonsense-mediated mRNA decay, thereby leading to a translation of C-terminus truncated IQSEC2 protein with residual activity. The functional analyses showed that the GEF activity of IQSEC2 Q1227* was compromised, and that the IQSEC2 Q1227* lacked preferential synaptic localization due to the absence of functional domains for binding to scaffolding proteins in the PSD. The impaired GEF activity and disrupted synaptic localization of the mutant IQSEC2 protein could impact dendritic and spine development in neurons, potentially explaining the patient's severe neurological manifestations. Our findings indicate that C-terminal truncations in IQSEC2, previously not well-characterized, may have significant pathogenic implications.
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Affiliation(s)
- Moeko Nakashima
- Department of Medical Genetics, NHO Tokyo Medical Center, Tokyo, 152-8902, Japan
| | - Tomoko Shiroshima
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, 252-0374, Japan
| | - Masahiro Fukaya
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, 252-0374, Japan
| | - Takeyuki Sugawara
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, 252-0374, Japan
| | - Hiroyuki Sakagami
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, 252-0374, Japan.
| | - Kazuki Yamazawa
- Department of Medical Genetics, NHO Tokyo Medical Center, Tokyo, 152-8902, Japan.
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4
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Shokhen M, Walikonis R, Uversky VN, Allbeck A, Zezelic C, Feldman D, Levy NS, Levy AP. Molecular modeling of ARF6 dysregulation caused by mutations in IQSEC2. J Biomol Struct Dyn 2024; 42:1268-1279. [PMID: 37078745 DOI: 10.1080/07391102.2023.2199085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Accepted: 03/29/2023] [Indexed: 04/21/2023]
Abstract
IQSEC2 gene mutations are associated with epilepsy, autism, and intellectual disability. The primary function IQSEC2, mediated via its Sec 7 domain, is to act as a guanine nucleotide exchange factor for ARF6. We sought to develop a molecular model, which may explain the aberrant Sec 7 activity on ARF6 of different human IQSEC2 mutations. We integrated experimental data of IQSEC2 mutants with protein structure prediction by the RaptorX server combined with molecular modeling and molecular dynamics simulations. Normally, apocalmodulin (apoCM) binds to IQSEC2 resulting in its N-terminal fragment inhibiting access of its Sec 7 domain to ARF6. An increase in Ca2+ concentration destabilizes the interaction of IQSEC2 with apoCM and removes steric hindrance of Sec 7 binding with ARF6. Mutations at amino acid residue 350 of IQSEC2 result in loss of steric hindrance of Sec 7 binding with ARF6 leading to constitutive activation of ARF6 by Sec 7. On the other hand, a mutation at amino acid residue 359 of IQSEC2 results in constitutive hindrance of Sec 7 binding to ARF6 leading to the loss of the ability of IQSEC2 to activate ARF6. These studies provide a model for dysregulation of IQSEC2 Sec 7 activity by mutant IQSEC2 proteins.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- Michael Shokhen
- Department of Chemistry, Bar Ilan University, Ramat Gan, Israel
| | - Randall Walikonis
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, Connecticut, USA
| | - Vladimir N Uversky
- Department of Molecular Medicine and Byrd Alzheimer's Center and Research Institute, University of South Florida, Tampa, Florida, USA
| | - Amnon Allbeck
- Department of Chemistry, Bar Ilan University, Ramat Gan, Israel
| | - Camryn Zezelic
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Danielle Feldman
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Nina S Levy
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Andrew P Levy
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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5
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Bai G, Li H, Qin P, Guo Y, Yang W, Lian Y, Ye F, Chen J, Wu M, Huang R, Li J, Lu Y, Zhang M. Ca2+-induced release of IQSEC2/BRAG1 autoinhibition under physiological and pathological conditions. J Cell Biol 2023; 222:e202307117. [PMID: 37787765 PMCID: PMC10548395 DOI: 10.1083/jcb.202307117] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 08/31/2023] [Accepted: 09/14/2023] [Indexed: 10/04/2023] Open
Abstract
IQSEC2 (aka BRAG1) is a guanine nucleotide exchange factor (GEF) highly enriched in synapses. As a top neurodevelopmental disorder risk gene, numerous mutations are identified in Iqsec2 in patients with intellectual disabilities accompanied by other developmental, neurological, and psychiatric symptoms, though with poorly understood underlying molecular mechanisms. The atomic structures of IQSECs, together with biochemical analysis, presented in this study reveal an autoinhibition and Ca2+-dependent allosteric activation mechanism for all IQSECs and rationalize how each identified Iqsec2 mutation can alter the structure and function of the enzyme. Transgenic mice modeling two pathogenic variants of Iqsec2 (R359C and Q801P), with one activating and the other inhibiting the GEF activity of the enzyme, recapitulate distinct clinical phenotypes in patients. Our study demonstrates that different mutations on one gene such as Iqsec2 can have distinct neurological phenotypes and accordingly will require different therapeutic strategies.
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Affiliation(s)
- Guanhua Bai
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Hao Li
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Pengwei Qin
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Yiqing Guo
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Wanfa Yang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Yinmiao Lian
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Fei Ye
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
| | - Jianxin Chen
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
- School of Life Science and Technology, Shanghai Tech University, Shanghai, China
| | - Meiling Wu
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
| | - Ruifeng Huang
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
| | - Jinsong Li
- State Key Laboratory of Cell Biology, Shanghai Key Laboratory of Molecular Andrology, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai, China
- School of Life Science and Technology, Shanghai Tech University, Shanghai, China
| | - Youming Lu
- Department of Pathophysiology, School of Basic Medicine and Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
- The Institute for Brain Research, Collaborative Innovation Center for Brain Science, Huazhong University of Science and Technology, Wuhan, China
| | - Mingjie Zhang
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, China
- Greater Bay Biomedical Innocenter, Shenzhen Bay Laboratory, Shenzhen, China
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6
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Brown JC, Hell JW, Gerges NZ. BRAG about (s)lots. J Cell Biol 2023; 222:e202310023. [PMID: 37938213 PMCID: PMC10631466 DOI: 10.1083/jcb.202310023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2023] Open
Abstract
Mutations in IQSEC2/BRAG1 cause intellectual dysfunction by impairing ARF-GEF activity and long-term depression. In this issue, Bai et al. (https://doi.org/10.1083/jcb.202307117) discover how constitutive ARF-GEF activity is regulated by a closed conformation which opens in the presence of Ca2+. Two known pathogenic mutations cause "leaky" autoinhibition with reduced synaptic dynamic range and impaired cognitive performance.
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Affiliation(s)
- Joshua C. Brown
- Division of Depression and Anxiety Disorders, Brain Stimulation Mechanisms Laboratory, McLean Hospital, Belmont, MA, USA
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Johannes W. Hell
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, USA
| | - Nashaat Z. Gerges
- Biopharmaceutical Sciences Department, School of Pharmacy, Medical College of Wisconsin, Milwaukee, WI, USA
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7
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Belloso-Iguerategui A, Zamarbide M, Merino-Galan L, Rodríguez-Chinchilla T, Gago B, Santamaria E, Fernández-Irigoyen J, Cotman CW, Prieto GA, Quiroga-Varela A, Rodríguez-Oroz MC. Hippocampal synaptic failure is an early event in experimental parkinsonism with subtle cognitive deficit. Brain 2023; 146:4949-4963. [PMID: 37403195 PMCID: PMC10690043 DOI: 10.1093/brain/awad227] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 05/25/2023] [Accepted: 06/20/2023] [Indexed: 07/06/2023] Open
Abstract
Learning and memory mainly rely on correct synaptic function in the hippocampus and other brain regions. In Parkinson's disease, subtle cognitive deficits may even precede motor signs early in the disease. Hence, we set out to unravel the earliest hippocampal synaptic alterations associated with human α-synuclein overexpression prior to and soon after the appearance of cognitive deficits in a parkinsonism model. We bilaterally injected adeno-associated viral vectors encoding A53T-mutated human α-synuclein into the substantia nigra of rats, and evaluated them 1, 2, 4 and 16 weeks post-inoculation by immunohistochemistry and immunofluorescence to study degeneration and distribution of α-synuclein in the midbrain and hippocampus. The object location test was used to evaluate hippocampal-dependent memory. Sequential window acquisition of all theoretical mass spectrometry-based proteomics and fluorescence analysis of single-synapse long-term potentiation were used to study alterations to protein composition and plasticity in isolated hippocampal synapses. The effect of L-DOPA and pramipexole on long-term potentiation was also tested. Human α-synuclein was found within dopaminergic and glutamatergic neurons of the ventral tegmental area, and in dopaminergic, glutamatergic and GABAergic axon terminals in the hippocampus from 1 week post-inoculation, concomitant with mild dopaminergic degeneration in the ventral tegmental area. In the hippocampus, differential expression of proteins involved in synaptic vesicle cycling, neurotransmitter release and receptor trafficking, together with impaired long-term potentiation were the first events observed (1 week post-inoculation), preceding cognitive deficits (4 weeks post-inoculation). Later on, at 16 weeks post-inoculation, there was a deregulation of proteins involved in synaptic function, particularly those involved in the regulation of membrane potential, ion balance and receptor signalling. Hippocampal long-term potentiation was impaired before and soon after the onset of cognitive deficits, at 1 and 4 weeks post-inoculation, respectively. L-DOPA recovered hippocampal long-term potentiation more efficiently at 4 weeks post-inoculation than pramipexole, which partially rescued it at both time points. Overall, we found impaired synaptic plasticity and proteome dysregulation at hippocampal terminals to be the first events that contribute to the development of cognitive deficits in experimental parkinsonism. Our results not only point to dopaminergic but also to glutamatergic and GABAergic dysfunction, highlighting the relevance of the three neurotransmitter systems in the ventral tegmental area-hippocampus interaction from the earliest stages of parkinsonism. The proteins identified in the current work may constitute potential biomarkers of early synaptic damage in the hippocampus and hence, therapies targeting these could potentially restore early synaptic malfunction and consequently, cognitive deficits in Parkinson's disease.
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Affiliation(s)
| | - Marta Zamarbide
- Neuroscience Program, Center for Applied Medical Research (CIMA), Universidad de Navarra, 31008 Pamplona, Spain
| | - Leyre Merino-Galan
- Neuroscience Program, Center for Applied Medical Research (CIMA), Universidad de Navarra, 31008 Pamplona, Spain
- Neuroscience Department, University of the Basque Country (UPV/EHU), 48940 Leioa, Spain
| | | | - Belén Gago
- Faculty of Medicine, IBIMA Plataforma BIONAND, Universidad de Málaga, 29016 Málaga, Spain
| | - Enrique Santamaria
- Clinical Neuroproteomics Unit, Proteomics Platform, Proteored-ISCIII, Navarrabiomed, Complejo Hospitalario de Navarra (CHN), Universidad Pública de Navarra (UPNA), 31008 Pamplona, Spain
- Neurosciences and Mental Health Area, Navarra Institute for Health Research (IdiSNA), 31008 Pamplona, Spain
| | - Joaquín Fernández-Irigoyen
- Clinical Neuroproteomics Unit, Proteomics Platform, Proteored-ISCIII, Navarrabiomed, Complejo Hospitalario de Navarra (CHN), Universidad Pública de Navarra (UPNA), 31008 Pamplona, Spain
- Neurosciences and Mental Health Area, Navarra Institute for Health Research (IdiSNA), 31008 Pamplona, Spain
| | - Carl W Cotman
- Institute for Memory Impairments and Neurological Disorders, University of California-Irvine, Irvine, CA 92697, USA
| | - G Aleph Prieto
- Institute for Memory Impairments and Neurological Disorders, University of California-Irvine, Irvine, CA 92697, USA
- Instituto de Neurobiología, Universidad Nacional Autónoma de México, 76010 Querétaro, México
| | - Ana Quiroga-Varela
- Neuroscience Program, Center for Applied Medical Research (CIMA), Universidad de Navarra, 31008 Pamplona, Spain
- Neurosciences and Mental Health Area, Navarra Institute for Health Research (IdiSNA), 31008 Pamplona, Spain
| | - María Cruz Rodríguez-Oroz
- Neuroscience Program, Center for Applied Medical Research (CIMA), Universidad de Navarra, 31008 Pamplona, Spain
- Neurosciences and Mental Health Area, Navarra Institute for Health Research (IdiSNA), 31008 Pamplona, Spain
- Neurology Department, Clínica Universidad de Navarra (CUN), 31008 Pamplona, Spain
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8
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Leoncini S, Boasiako L, Lopergolo D, Altamura M, Fazzi C, Canitano R, Grosso S, Meloni I, Baldassarri M, Croci S, Renieri A, Mastrangelo M, De Felice C. Natural Course of IQSEC2-Related Encephalopathy: An Italian National Structured Survey. CHILDREN (BASEL, SWITZERLAND) 2023; 10:1442. [PMID: 37761403 PMCID: PMC10528631 DOI: 10.3390/children10091442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 08/16/2023] [Accepted: 08/22/2023] [Indexed: 09/29/2023]
Abstract
Pathogenic loss-of-function variants in the IQ motif and SEC7 domain containing protein 2 (IQSEC2) gene cause intellectual disability with Rett syndrome (RTT)-like features. The aim of this study was to obtain systematic information on the natural history and extra-central nervous system (CNS) manifestations for the Italian IQSEC2 population (>90%) by using structured family interviews and semi-quantitative questionnaires. IQSEC2 encephalopathy prevalence estimate was 7.0 to 7.9 × 10-7. Criteria for typical RTT were met in 42.1% of the cases, although psychomotor regression was occasionally evidenced. Genetic diagnosis was occasionally achieved in infancy despite a clinical onset before the first 24 months of life. High severity in both the CNS and extra-CNS manifestations for the IQSEC2 patients was documented and related to a consistently adverse quality of life. Neurodevelopmental delay was diagnosed before the onset of epilepsy by 1.8 to 2.4 years. An earlier age at menarche in IQSEC2 female patients was reported. Sleep disturbance was highly prevalent (60 to 77.8%), with mandatory co-sleeping behavior (50% of the female patients) being related to de novo variant origin, younger age, taller height with underweight, better social interaction, and lower life quality impact for the family and friends area. In conclusion, the IQSEC2 encephalopathy is a rare and likely underdiagnosed developmental encephalopathy leading to an adverse life quality impact.
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Affiliation(s)
- Silvia Leoncini
- Neonatal Intensive Care Unit, Department of Women’s and Children’s Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy; (S.L.); (L.B.); (M.A.); (C.F.)
- Rett Syndrome Trial Center, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Lidia Boasiako
- Neonatal Intensive Care Unit, Department of Women’s and Children’s Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy; (S.L.); (L.B.); (M.A.); (C.F.)
- Rett Syndrome Trial Center, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Diego Lopergolo
- Department of Medicine, Surgery and Neurosciences, University of Siena, 53100 Siena, Italy;
- UOC Neurologia e Malattie Neurometaboliche, Azienda Ospedaliero Universitaria Senese, Policlinico Le Scotte, 53100 Siena, Italy
- IRCCS Stella Maris Foundation, Molecular Medicine for Neurodegenerative and Neuromuscular Diseases Unit, 56018 Pisa, Italy
| | - Maria Altamura
- Neonatal Intensive Care Unit, Department of Women’s and Children’s Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy; (S.L.); (L.B.); (M.A.); (C.F.)
- Rett Syndrome Trial Center, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Caterina Fazzi
- Neonatal Intensive Care Unit, Department of Women’s and Children’s Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy; (S.L.); (L.B.); (M.A.); (C.F.)
- Rett Syndrome Trial Center, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Roberto Canitano
- Child Neuropsychiatry Unit, Department of Mental Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy;
| | - Salvatore Grosso
- Department of Molecular and Developmental Medicine, University of Siena, 53100 Siena, Italy;
- Pediatric Unit, Department of Women’s and Children’s Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Ilaria Meloni
- Medical Genetics, University of Siena, 53100 Siena, Italy; (I.M.); (M.B.); (S.C.); (A.R.)
- Med Biotech Hub and Competence Center, Department of Medical Biotechnologies, University of Siena, 53100 Siena, Italy
| | - Margherita Baldassarri
- Medical Genetics, University of Siena, 53100 Siena, Italy; (I.M.); (M.B.); (S.C.); (A.R.)
- Med Biotech Hub and Competence Center, Department of Medical Biotechnologies, University of Siena, 53100 Siena, Italy
- Genetica Medica, Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Susanna Croci
- Medical Genetics, University of Siena, 53100 Siena, Italy; (I.M.); (M.B.); (S.C.); (A.R.)
- Med Biotech Hub and Competence Center, Department of Medical Biotechnologies, University of Siena, 53100 Siena, Italy
| | - Alessandra Renieri
- Medical Genetics, University of Siena, 53100 Siena, Italy; (I.M.); (M.B.); (S.C.); (A.R.)
- Med Biotech Hub and Competence Center, Department of Medical Biotechnologies, University of Siena, 53100 Siena, Italy
- Genetica Medica, Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
| | - Mario Mastrangelo
- Maternal Infantile and Urological Sciences Department, Sapienza University of Rome, 00185 Rome, Italy;
- Child Neurology and Psychiatry Unit, Department of Neurosciences and Mental Health, Azienda Ospedaliero-Universitaria Policlinico Umberto I, 00161 Rome, Italy
| | - Claudio De Felice
- Neonatal Intensive Care Unit, Department of Women’s and Children’s Health, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy; (S.L.); (L.B.); (M.A.); (C.F.)
- Rett Syndrome Trial Center, University Hospital Azienda Ospedaliera Universitaria Senese, 53100 Siena, Italy
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9
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Molecular Insights into IQSEC2 Disease. Int J Mol Sci 2023; 24:ijms24054984. [PMID: 36902414 PMCID: PMC10003148 DOI: 10.3390/ijms24054984] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 03/02/2023] [Accepted: 03/02/2023] [Indexed: 03/08/2023] Open
Abstract
Recent insights into IQSEC2 disease are summarized in this review as follows: (1) Exome sequencing of IQSEC2 patient DNA has led to the identification of numerous missense mutations that delineate at least six and possibly seven essential functional domains present in the IQSEC2 gene. (2) Experiments using IQSEC2 transgenic and knockout (KO) mouse models have recapitulated the presence of autistic-like behavior and epileptic seizures in affected animals; however, seizure severity and etiology appear to vary considerably between models. (3) Studies in IQSEC2 KO mice reveal that IQSEC2 is involved in inhibitory as well as stimulatory neurotransmission. The overall picture appears to be that mutated or absent IQSEC2 arrests neuronal development, resulting in immature neuronal networks. Subsequent maturation is aberrant, leading to increased inhibition and reduced neuronal transmission. (4) The levels of Arf6-GTP remain constitutively high in IQSEC2 knockout mice despite the absence of IQSEC2 protein, indicating impaired regulation of the Arf6 guanine nucleotide exchange cycle. (5) A new therapy that has been shown to reduce the seizure burden for the IQSEC2 A350V mutation is heat treatment. Induction of the heat shock response may be responsible for this therapeutic effect.
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Daily Brief Heat Therapy Reduces Seizures in A350V IQSEC2 Mice and Is Associated with Correction of AMPA Receptor-Mediated Synaptic Dysfunction. Int J Mol Sci 2023; 24:ijms24043924. [PMID: 36835332 PMCID: PMC9965438 DOI: 10.3390/ijms24043924] [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: 02/02/2023] [Revised: 02/12/2023] [Accepted: 02/13/2023] [Indexed: 02/17/2023] Open
Abstract
Purposeful induction of fever for healing, including the treatment of epilepsy, was used over 2000 years ago by Hippocrates. More recently, fever has been demonstrated to rescue behavioral abnormalities in children with autism. However, the mechanism of fever benefit has remained elusive due in large part to the lack of appropriate human disease models recapitulating the fever effect. Pathological mutations in the IQSEC2 gene are frequently seen in children presenting with intellectual disability, autism and epilepsy. We recently described a murine A350V IQSEC2 disease model, which recapitulates important aspects of the human A350V IQSEC2 disease phenotype and the favorable response to a prolonged and sustained rise in body core temperature in a child with the mutation. Our goal has been to use this system to understand the mechanism of fever benefit and then develop drugs that can mimic this effect and reduce IQSEC2-associated morbidity. In this study, we first demonstrate a reduction in seizures in the mouse model following brief periods of heat therapy, similar to what was observed in a child with the mutation. We then show that brief heat therapy is associated with the correction of synaptic dysfunction in neuronal cultures of A350V mice, likely mediated by Arf6-GTP.
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Vigne M, Kweon J, Sharma P, Greenberg BD, Carpenter LL, Brown JC. Chronic caffeine consumption curbs rTMS-induced plasticity. Front Psychiatry 2023; 14:1137681. [PMID: 36911138 PMCID: PMC9993245 DOI: 10.3389/fpsyt.2023.1137681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 02/07/2023] [Indexed: 02/24/2023] Open
Abstract
BACKGROUND Caffeine is a widely used psychostimulant. In the brain, caffeine acts as a competitive, non-selective adenosine receptor antagonist of A1 and A2A, both known to modulate long-term potentiation (LTP), the cellular basis of learning and memory. Repetitive transcranial magnetic stimulation (rTMS) is theorized to work through LTP induction and can modulate cortical excitability as measured by motor evoked potentials (MEPs). The acute effects of single caffeine doses diminish rTMS-induced corticomotor plasticity. However, plasticity in chronic daily caffeine users has not been examined. METHOD We conducted a post hoc secondary covariate analysis from two previously published plasticity-inducing pharmaco-rTMS studies combining 10 Hz rTMS and D-cycloserine (DCS) in twenty healthy subjects. RESULTS In this hypothesis-generating pilot study, we observed enhanced MEP facilitation in non-caffeine users compared to caffeine users and placebo. CONCLUSION These preliminary data highlight a need to directly test the effects of caffeine in prospective well-powered studies, because in theory, they suggest that chronic caffeine use could limit learning or plasticity, including rTMS effectiveness.
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Affiliation(s)
- Megan Vigne
- Neuromodulation Research Facility, TMS Clinic, Butler Hospital, Providence, RI, United States
| | - Jamie Kweon
- Neuromodulation Research Facility, TMS Clinic, Butler Hospital, Providence, RI, United States
| | - Prayushi Sharma
- Neuromodulation Research Facility, TMS Clinic, Butler Hospital, Providence, RI, United States
| | - Benjamin D Greenberg
- Neuromodulation Research Facility, TMS Clinic, Butler Hospital, Providence, RI, United States.,Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University, Providence, RI, United States
| | - Linda L Carpenter
- Neuromodulation Research Facility, TMS Clinic, Butler Hospital, Providence, RI, United States.,Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University, Providence, RI, United States
| | - Joshua C Brown
- Neuromodulation Research Facility, TMS Clinic, Butler Hospital, Providence, RI, United States.,Department of Psychiatry and Human Behavior, Warren Alpert Medical School of Brown University, Providence, RI, United States.,Department of Neurology, Warren Alpert Medical School of Brown University, Providence, RI, United States
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Brown JC, Higgins ES, George MS. Synaptic Plasticity 101: The Story of the AMPA Receptor for the Brain Stimulation Practitioner. Neuromodulation 2022; 25:1289-1298. [PMID: 35088731 PMCID: PMC10479373 DOI: 10.1016/j.neurom.2021.09.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 08/10/2021] [Accepted: 09/08/2021] [Indexed: 02/04/2023]
Abstract
The fields of Neurobiology and Neuromodulation have never been closer. Consequently, the phrase "synaptic plasticity" has become very familiar to non-basic scientists, without actually being very familiar. We present the "Story of the AMPA receptor," an easy-to-understand "10,000 ft" narrative overview of synaptic plasticity, oriented toward the brain stimulation clinician or scientist without basic science training. Neuromodulation is unparalleled in its capacity to both modulate and probe plasticity, yet many are not comfortable with their grasp of the topic. Here, we describe the seminal discoveries that defined the canonical mechanisms of long-term potentiation (LTP), long-term depression (LTD), and homeostatic plasticity. We then provide a conceptual framework for how plasticity at the synapse is accomplished, describing the functional roles of N-methyl-d-aspartate (NMDA) receptors and calcium, their effect on calmodulin, phosphatases (ie, calcineurin), kinases (ie, calcium/calmodulin-dependent protein kinase [CaMKII]), and structural "scaffolding" proteins (ie, post-synaptic density protein [PSD-95]). Ultimately, we describe how these affect the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor. More specifically, AMPA receptor delivery to (LTP induction), removal from (LTD), or recycling within (LTP maintenance) the synapse is determined by the status of phosphorylation and protein binding at specific sites on the tails of AMPA receptor subunits: GluA1 and GluA2. Finally, we relate these to transcranial magnetic stimulation (TMS) treatment, highlighting evidences for LTP as the basis of high-frequency TMS therapy, and briefly touch on the role of plasticity for other brain stimulation modalities. In summary, we present Synaptic Plasticity 101 as a singular introductory reference for those less familiar with the mechanisms of synaptic plasticity.
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Affiliation(s)
- Joshua C Brown
- Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC, USA; Department of Neurology, Medical University of South Carolina, Charleston, SC, USA; Department of Psychiatry and Human Behavior, Alpert Medical School of Brown University, Providence, RI, USA.
| | - Edmund S Higgins
- Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC, USA
| | - Mark S George
- Department of Psychiatry and Behavioral Sciences, Medical University of South Carolina, Charleston, SC, USA; Ralph Johnson VA Medical Center, Charleston, SC, USA
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Ito A, Fukaya M, Okamoto H, Sakagami H. Physiological and Pathological Roles of the Cytohesin Family in Neurons. Int J Mol Sci 2022; 23:5087. [PMID: 35563476 PMCID: PMC9104363 DOI: 10.3390/ijms23095087] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Revised: 05/01/2022] [Accepted: 05/02/2022] [Indexed: 02/05/2023] Open
Abstract
The cytohesin proteins, consisting of four closely related members (cytohesins-1, -2, -3, and -4), are a subfamily of the Sec7 domain-containing guanine nucleotide exchange factors for ADP ribosylation factors (Arfs), which are critical regulators of membrane trafficking and actin cytoskeleton remodeling. Recent advances in molecular biological techniques and the development of a specific pharmacological inhibitor for cytohesins, SecinH3, have revealed the functional involvement of the cytohesin-Arf pathway in diverse neuronal functions from the formation of axons and dendrites, axonal pathfinding, and synaptic vesicle recycling, to pathophysiological processes including chronic pain and neurotoxicity induced by proteins related to neurodegenerative disorders, such as amyotrophic lateral sclerosis and Alzheimer's disease. Here, we review the physiological and pathological roles of the cytohesin-Arf pathway in neurons and discuss the future directions of this research field.
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Affiliation(s)
- Akiko Ito
- Department of Anesthesiology, Kitasato University School of Medicine, Sagamihara 252-0374, Kanagawa, Japan; (A.I.); (H.O.)
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara 252-0374, Kanagawa, Japan;
| | - Masahiro Fukaya
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara 252-0374, Kanagawa, Japan;
| | - Hirotsugu Okamoto
- Department of Anesthesiology, Kitasato University School of Medicine, Sagamihara 252-0374, Kanagawa, Japan; (A.I.); (H.O.)
| | - Hiroyuki Sakagami
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara 252-0374, Kanagawa, Japan;
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Kane O, McCoy A, Jada R, Borisov V, Zag L, Zag A, Schragenheim-Rozales K, Shalgi R, Levy NS, Levy AP, Marsh ED. Characterization of spontaneous seizures and EEG abnormalities in a mouse model of the human A350V IQSEC2 mutation and identification of a possible target for precision medicine based therapy. Epilepsy Res 2022; 182:106907. [DOI: 10.1016/j.eplepsyres.2022.106907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 02/01/2022] [Accepted: 03/11/2022] [Indexed: 11/16/2022]
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15
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Jada R, Zag L, Borisov V, Levy NS, Netser S, Jabarin R, Wagner S, Schragenheim-Rozales K, Shalgi R, Levy AP. Housing of A350V IQSEC2 pups at 37 °C ambient temperature prevents seizures and permits the development of social vocalizations in adulthood. Int J Hyperthermia 2021; 38:1495-1501. [PMID: 34666607 DOI: 10.1080/02656736.2021.1988730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
OBJECTIVES Mutations in the human IQSEC2 gene are associated with drug-resistant epilepsy and severe behavioral dysfunction. We have focused on understanding one human IQSEC2 missense mutation (A350V) for which we have created a corresponding A350V IQSEC2 mouse model by CRISPR which demonstrates seizures when the mice are 15-20 days old and impaired social vocalizations in adulthood. We observed that a child with the A350V mutation stops having seizures when experiencing a fever of greater than 38 °C. In this study, we first sought to determine if we could recapitulate this phenomenon in A350V 15-20 day old mice using a previously established protocol to raise body temperature to 39 °C achieved by housing the mice at 37 °C. We then sought to determine if mice in whom seizure activity had been prevented as pups would develop social vocalization activity in adulthood. METHODS 15-20 day old A350V male mice were housed either at 37 °C or 22 °C. Ultrasonic vocalizations of these mice were assessed at 8-10 weeks in response to a female stimulus. RESULTS Housing of 15-20 day old A350V mice at 37 °C resulted in a reduction in lethal seizures to 2% (1/41) compared to 45% (48/108) in mice housed at 22 °C, p = 0.0001. Adult A350V mice who had been housed at 37 °C as pups displayed a significant improvement in the production of social vocalizations. CONCLUSION Raising the body temperature by raising the ambient temperature might provide a means to reduce seizures associated with the A350V IQSEC2 mutation and thereby allow for an improved neurodevelopmental trajectory.
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Affiliation(s)
- Reem Jada
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Liron Zag
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Veronika Borisov
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Nina S Levy
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Shai Netser
- Faculty of Natural Sciences, Sagol Department of Neurobiology, University of Haifa, Haifa, Israel
| | - Renad Jabarin
- Faculty of Natural Sciences, Sagol Department of Neurobiology, University of Haifa, Haifa, Israel
| | - Shlomo Wagner
- Faculty of Natural Sciences, Sagol Department of Neurobiology, University of Haifa, Haifa, Israel
| | | | - Reut Shalgi
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Andrew P Levy
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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Mehta A, Shirai Y, Kouyama-Suzuki E, Zhou M, Yoshizawa T, Yanagawa T, Mori T, Tabuchi K. IQSEC2 Deficiency Results in Abnormal Social Behaviors Relevant to Autism by Affecting Functions of Neural Circuits in the Medial Prefrontal Cortex. Cells 2021; 10:2724. [PMID: 34685703 PMCID: PMC8534507 DOI: 10.3390/cells10102724] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 10/08/2021] [Accepted: 10/09/2021] [Indexed: 12/28/2022] Open
Abstract
IQSEC2 is a guanine nucleotide exchange factor (GEF) for ADP-ribosylation factor 6 (Arf6), of which protein is exclusively localized to the postsynaptic density of the excitatory synapse. Human genome studies have revealed that the IQSEC2 gene is associated with X-linked neurodevelopmental disorders, such as intellectual disability (ID), epilepsy, and autism. In this study, we examined the behavior and synapse function in IQSEC2 knockout (KO) mice that we generated using CRIPSR/Cas9-mediated genome editing to solve the relevance between IQSEC2 deficiency and the pathophysiology of neurodevelopmental disorders. IQSEC2 KO mice exhibited autistic behaviors, such as overgrooming and social deficits. We identified that up-regulation of c-Fos expression in the medial prefrontal cortex (mPFC) induced by social stimulation was significantly attenuated in IQSEC2 KO mice. Whole cell electrophysiological recording identified that synaptic transmissions mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), N-methyl-D-aspartate receptor (NMDAR), and γ-aminobutyric acid receptor (GABAR) were significantly decreased in pyramidal neurons in layer 5 of the mPFC in IQSEC2 KO mice. Reexpression of IQSEC2 isoform 1 in the mPFC of IQSEC2 KO mice using adeno-associated virus (AAV) rescued both synaptic and social deficits, suggesting that impaired synaptic function in the mPFC is responsible for social deficits in IQSEC2 KO mice.
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Affiliation(s)
- Anuradha Mehta
- Department of Molecular and Cellular Physiology, Shinshu University School of Medicine, Matsumoto 390-8621, Japan; (A.M.); (Y.S.); (E.K.-S.); (M.Z.); (T.M.)
| | - Yoshinori Shirai
- Department of Molecular and Cellular Physiology, Shinshu University School of Medicine, Matsumoto 390-8621, Japan; (A.M.); (Y.S.); (E.K.-S.); (M.Z.); (T.M.)
| | - Emi Kouyama-Suzuki
- Department of Molecular and Cellular Physiology, Shinshu University School of Medicine, Matsumoto 390-8621, Japan; (A.M.); (Y.S.); (E.K.-S.); (M.Z.); (T.M.)
| | - Mengyun Zhou
- Department of Molecular and Cellular Physiology, Shinshu University School of Medicine, Matsumoto 390-8621, Japan; (A.M.); (Y.S.); (E.K.-S.); (M.Z.); (T.M.)
| | - Takahiro Yoshizawa
- Research Center for Advanced Science and Technology, Shinshu University, Matsumoto 390-8621, Japan;
| | - Toru Yanagawa
- Department of Oral and Maxillofacial Surgery, Faculty of Medicine, University of Tsukuba, Tsukuba 305-8575, Japan;
| | - Takuma Mori
- Department of Molecular and Cellular Physiology, Shinshu University School of Medicine, Matsumoto 390-8621, Japan; (A.M.); (Y.S.); (E.K.-S.); (M.Z.); (T.M.)
- Department of NeuroHealth Innovation, Institute for Biomedical Sciences, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, Matsumoto 390-8621, Japan
| | - Katsuhiko Tabuchi
- Department of Molecular and Cellular Physiology, Shinshu University School of Medicine, Matsumoto 390-8621, Japan; (A.M.); (Y.S.); (E.K.-S.); (M.Z.); (T.M.)
- Department of NeuroHealth Innovation, Institute for Biomedical Sciences, Interdisciplinary Cluster for Cutting Edge Research, Shinshu University, Matsumoto 390-8621, Japan
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Izumi T, Aihara Y, Kikuchi A, Kure S. Electroencephalographic findings and genetic characterization of two brothers with IQSEC2 pathogenic variant. Brain Dev 2021; 43:652-656. [PMID: 33494955 DOI: 10.1016/j.braindev.2020.12.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 12/19/2020] [Accepted: 12/27/2020] [Indexed: 10/22/2022]
Abstract
Two brothers with an IQSEC2 pathogenic variant presented with early onset intellectual disability, intractable epileptic seizures, autism spectrum disorders, postnatal microcephalus and slowly progressive rigid-spasticity. Their epileptic seizures were characterized by intractability, early onset epileptic spasms, and then clusters of tonic/tonic-clonic seizures, exacerbated by valproate. Electroencephalography showed periodic discharges, including periodic high voltage slow complexes and burst-suppression activity. Whole exome sequencing, using DNA from peripheral blood of both brothers, identified a pathogenic variant, c.2776 C > T, p.(Arg 926*) in exon 9 of IQSEC2 (NM 001111125.3). Their parents and another brother did not have this variant, which may suggest that maternal gonadal mosaicism is the most likely mechanism.
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Affiliation(s)
- Tatsuro Izumi
- Department of Pediatrics and Child Neurology, Nanao National Hospital, Nanao, Ishikawa 9268531, Japan.
| | - Yu Aihara
- Department of Pediatrics, Tohoku University Graduate School of Medicine, Sendai, Miyagi 9808575, Japan
| | - Atsuo Kikuchi
- Department of Pediatrics, Tohoku University Graduate School of Medicine, Sendai, Miyagi 9808575, Japan
| | - Shigeo Kure
- Department of Pediatrics, Tohoku University Graduate School of Medicine, Sendai, Miyagi 9808575, Japan
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Jabarin R, Levy N, Abergel Y, Berman JH, Zag A, Netser S, Levy AP, Wagner S. Pharmacological modulation of AMPA receptors rescues specific impairments in social behavior associated with the A350V Iqsec2 mutation. Transl Psychiatry 2021; 11:234. [PMID: 33888678 PMCID: PMC8062516 DOI: 10.1038/s41398-021-01347-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 03/19/2021] [Accepted: 03/30/2021] [Indexed: 12/18/2022] Open
Abstract
In this study we tested the hypothesis that pharmacological modulation of glutamatergic neurotransmission could rescue behavioral deficits exhibited by mice carrying a specific mutation in the Iqsec2 gene. The IQSEC2 protein plays a key role in glutamatergic synapses and mutations in the IQSEC2 gene are a frequent cause of neurodevelopmental disorders. We have recently reported on the molecular pathophysiology of one such mutation A350V and demonstrated that this mutation downregulates AMPA type glutamatergic receptors (AMPAR) in A350V mice. Here we sought to identify behavioral deficits in A350V mice and hypothesized that we could rescue these deficits by PF-4778574, a positive AMPAR modulator. Using a battery of social behavioral tasks, we found that A350V Iqsec2 mice exhibit specific deficits in sex preference and emotional state preference behaviors as well as in vocalizations when encountering a female mouse. The social discrimination deficits, but not the impaired vocalization, were rescued with a single dose of PF-4778574. We conclude that social behavior deficits associated with the A350V Iqsec2 mutation may be rescued by enhancing AMPAR mediated synaptic transmission.
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Affiliation(s)
- Renad Jabarin
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Nina Levy
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Yasmin Abergel
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Joshua H Berman
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Amir Zag
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - Shai Netser
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel
| | - Andrew P Levy
- Technion Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
| | - Shlomo Wagner
- Sagol Department of Neurobiology, Faculty of Natural Sciences, University of Haifa, Haifa, Israel.
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Lichtman D, Bergmann E, Kavushansky A, Cohen N, Levy NS, Levy AP, Kahn I. Structural and functional brain-wide alterations in A350V Iqsec2 mutant mice displaying autistic-like behavior. Transl Psychiatry 2021; 11:181. [PMID: 33753721 PMCID: PMC7985214 DOI: 10.1038/s41398-021-01289-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 02/15/2021] [Accepted: 02/24/2021] [Indexed: 12/21/2022] Open
Abstract
IQSEC2 is an X-linked gene that is associated with autism spectrum disorder (ASD), intellectual disability, and epilepsy. IQSEC2 is a postsynaptic density protein, localized on excitatory synapses as part of the NMDA receptor complex and is suggested to play a role in AMPA receptor trafficking and mediation of long-term depression. Here, we present brain-wide structural volumetric and functional connectivity characterization in a novel mouse model with a missense mutation in the IQ domain of IQSEC2 (A350V). Using high-resolution structural and functional MRI, we show that animals with the A350V mutation display increased whole-brain volume which was further found to be specific to the cerebral cortex and hippocampus. Moreover, using a data-driven approach we identify putative alterations in structure-function relations of the frontal, auditory, and visual networks in A350V mice. Examination of these alterations revealed an increase in functional connectivity between the anterior cingulate cortex and the dorsomedial striatum. We also show that corticostriatal functional connectivity is correlated with individual variability in social behavior only in A350V mice, as assessed using the three-chamber social preference test. Our results at the systems-level bridge the impact of previously reported changes in AMPA receptor trafficking to network-level disruption and impaired social behavior. Further, the A350V mouse model recapitulates similarly reported brain-wide changes in other ASD mouse models, with substantially different cellular-level pathologies that nonetheless result in similar brain-wide alterations, suggesting that novel therapeutic approaches in ASD that result in systems-level rescue will be relevant to IQSEC2 mutations.
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Affiliation(s)
- Daniela Lichtman
- Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, 31096, Israel
| | - Eyal Bergmann
- Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, 31096, Israel
| | - Alexandra Kavushansky
- Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, 31096, Israel
| | - Nadav Cohen
- Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, 31096, Israel
| | - Nina S Levy
- Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, 31096, Israel
| | - Andrew P Levy
- Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, 31096, Israel.
| | - Itamar Kahn
- Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, 31096, Israel.
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IQSEC2 mutation associated with epilepsy, intellectual disability, and autism results in hyperexcitability of patient-derived neurons and deficient synaptic transmission. Mol Psychiatry 2021; 26:7498-7508. [PMID: 34535765 PMCID: PMC8873005 DOI: 10.1038/s41380-021-01281-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Revised: 07/09/2021] [Accepted: 08/24/2021] [Indexed: 12/03/2022]
Abstract
Mutations in the IQSEC2 gene are associated with drug-resistant, multifocal infantile and childhood epilepsy; autism; and severe intellectual disability (ID). We used induced pluripotent stem cell (iPSC) technology to obtain hippocampal neurons to investigate the neuropathology of IQSEC2-mediated disease. The neurons were characterized at three-time points during differentiation to assess developmental progression. We showed that immature IQSEC2 mutant dentate gyrus (DG) granule neurons were extremely hyperexcitable, exhibiting increased sodium and potassium currents compared to those of CRISPR-Cas9-corrected isogenic controls, and displayed dysregulation of genes involved in differentiation and development. Immature IQSEC2 mutant cultured neurons exhibited a marked reduction in the number of inhibitory neurons, which contributed further to hyperexcitability. As the mutant neurons aged, they became hypoexcitable, exhibiting reduced sodium and potassium currents and a reduction in the rate of synaptic and network activity, and showed dysregulation of genes involved in synaptic transmission and neuronal differentiation. Mature IQSEC2 mutant neurons were less viable than wild-type mature neurons and had reduced expression of surface AMPA receptors. Our studies provide mechanistic insights into severe infantile epilepsy and neurodevelopmental delay associated with this mutation and present a human model for studying IQSEC2 mutations in vitro.
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Briševac D, Scholz R, Du D, Elagabani MN, Köhr G, Kornau HC. The small GTPase Arf6 is dysregulated in a mouse model for fragile X syndrome. J Neurochem 2020; 157:666-683. [PMID: 33125726 DOI: 10.1111/jnc.15230] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Revised: 10/09/2020] [Accepted: 10/27/2020] [Indexed: 11/29/2022]
Abstract
Fragile X syndrome (FXS), the most common inherited cause of intellectual disability, results from silencing of the fragile X mental retardation gene 1 (FMR1). The analyses of FXS patients' brain autopsies revealed an increased density of immature dendritic spines in cortical areas. We hypothesize that the small GTPase Arf6, an actin regulator critical for the development of glutamatergic synapses and dendritic spines, is implicated in FXS. Here, we determined the fraction of active, GTP-bound Arf6 in cortical neuron cultures and synaptoneurosomes from Fmr1 knockout mice, measured actin polymerization in neurons expressing Arf6 mutants with variant GTP- or GDP-binding properties, and recorded hippocampal long-term depression induced by metabotropic glutamate receptors (mGluR-LTD) in acute brain slices. We detected a persistently elevated Arf6 activity, a loss of Arf6 sensitivity to synaptic stimulation and an increased Arf6-dependent dendritic actin polymerization in mature Fmr1 knockout neurons. Similar imbalances in Arf6-GTP levels and actin filament assembly were caused in wild-type neurons by RNAi-mediated depletion of the postsynaptic Arf6 guanylate exchange factors IQSEC1 (BRAG2) or IQSEC2 (BRAG1). Targeted deletion of Iqsec1 in hippocampal neurons of 3-week-old mice interfered with mGluR-LTD in wild-type, but not in Fmr1 knockout mice. Collectively, these data suggest an aberrant Arf6 regulation in Fmr1 knockout neurons with consequences for the actin cytoskeleton, spine morphology, and synaptic plasticity. Moreover, FXS and syndromes caused by genetic variants in IQSEC1 and IQSEC2 share intellectual disabilities and developmental delay as main symptoms. Therefore, dysregulation of Arf6 may contribute to the cognitive impairment in FXS.
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Affiliation(s)
- Dušica Briševac
- Neuroscience Research Center (NWFZ), Charité - Universitätsmedizin Berlin, Berlin, Germany.,Department of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, Berlin, Germany
| | - Ralf Scholz
- Center for Molecular Neurobiology (ZMNH), University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany
| | - Dan Du
- Central Institute of Mental Health, Mannheim Center for Translational Neuroscience, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | | | - Georg Köhr
- Central Institute of Mental Health, Mannheim Center for Translational Neuroscience, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany.,Department of Neurophysiology, Mannheim Center for Translational Neuroscience, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Hans-Christian Kornau
- Neuroscience Research Center (NWFZ), Charité - Universitätsmedizin Berlin, Berlin, Germany.,Center for Molecular Neurobiology (ZMNH), University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany.,German Center for Neurodegenerative Diseases (DZNE) Berlin, Berlin, Germany
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22
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Nagabushana D, Chatterjee A, Kenchaiah R, Asranna A, Arunachal G, Mundlamuri RC. Response to Steroids in IQSEC2-Related Encephalopathy Presenting with Rett-Like Phenotype and Infantile Spasms. J Pediatr Genet 2020; 12:76-80. [PMID: 36684544 PMCID: PMC9848762 DOI: 10.1055/s-0040-1721371] [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: 08/29/2020] [Accepted: 10/14/2020] [Indexed: 01/25/2023]
Abstract
Introduction IQSEC2-related encephalopathy is an X-linked childhood neurodevelopmental disorder with intellectual disability, epilepsy, and autism. This disorder is caused by a mutation in the IQSEC2 gene, the product of which plays an important role in the development of the central nervous system. Case Report We describe the symptomatology, clinical course, and management of a 17-month-old male child with a novel IQSEC2 mutation. He presented with an atypical Rett syndrome phenotype with developmental delay, autistic features, midline stereotypies, microcephaly, hypotonia and epilepsy with multiple seizure types including late-onset infantile spasms. Spasms were followed by worsening of behavior and cognition, and regression of acquired milestones. Treatment with steroids led to control of spasms and improved attention, behavior and recovery of lost motor milestone. In the past 10 months following steroid therapy, child lags in development, remains autistic with no further seizure recurrence. Conclusion IQSEC2-related encephalopathy may present with Rett atypical phenotypes and childhood spasms. In resource-limited settings, steroids may be considered for spasm remission in IQSEC2-related epileptic encephalopathy.
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Affiliation(s)
- Divya Nagabushana
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, India
| | - Aparajita Chatterjee
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, India
| | - Raghavendra Kenchaiah
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, India
| | - Ajay Asranna
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, India
| | - Gautham Arunachal
- Department of Human Genetics, National Institute of Mental Health and Neurosciences, Bengaluru, India
| | - Ravindranadh Chowdary Mundlamuri
- Department of Neurology, National Institute of Mental Health and Neurosciences, Bengaluru, India,Address for correspondence Ravindranadh Chowdary Mundlamuri, DM Department of Neurology, National Institute of Mental Health and NeurosciencesBengaluru 560029India
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23
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Psychiatric features and variable neurodevelopment outcome in four females with IQSEC2 spectrum disorder. J Genet 2020. [DOI: 10.1007/s12041-020-01204-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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24
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Altered excitatory transmission onto hippocampal interneurons in the IQSEC2 mouse model of X-linked neurodevelopmental disease. Neurobiol Dis 2020; 137:104758. [PMID: 31978606 DOI: 10.1016/j.nbd.2020.104758] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Revised: 12/16/2019] [Accepted: 01/20/2020] [Indexed: 02/01/2023] Open
Abstract
Mutations in the X-linked gene IQSEC2 are associated with multiple cases of epilepsy, epileptic encephalopathy, intellectual disability and autism spectrum disorder, the mechanistic understanding and successful treatment of which remain a significant challenge in IQSEC2 and related neurodevelopmental genetic diseases. To investigate disease etiology, we studied behaviors and synaptic function in IQSEC2 deficient mice. Hemizygous Iqsec2 null males exhibit growth deficits, hyperambulation and hyperanxiety phenotypes. Adult hemizygotes experience lethal spontaneous seizures, but paradoxically have a significantly increased threshold to electrically induced limbic seizures and relative resistance to chemically induced seizures. Although there are no gross defects in brain morphology, hemizygotes exhibit stark hippocampal reactive astrogliosis. Electrophysiological recordings of hippocampal neurons reveal increased excitatory drive specifically onto interneurons, and significant alterations in intrinsic electrical properties specific to the interneuron population. As they age, hemizygotes also develop an increased abundance of parvalbumin-positive interneurons in the hippocampus, neurons in which IQSEC2 is expressed in addition to the excitatory neurons. These findings point to a novel role of IQSEC2 in hippocampal interneuron synaptic function and development with implications for a class of intractable neurodevelopmental diseases.
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25
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Kim H, Jung H, Jung H, Kwon SK, Ko J, Um JW. The small GTPase ARF6 regulates GABAergic synapse development. Mol Brain 2020; 13:2. [PMID: 31907062 PMCID: PMC6945580 DOI: 10.1186/s13041-019-0543-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 12/23/2019] [Indexed: 01/05/2023] Open
Abstract
ADP ribosylation factors (ARFs) are a family of small GTPases composed of six members (ARF1-6) that control various cellular functions, including membrane trafficking and actin cytoskeletal rearrangement, in eukaryotic cells. Among them, ARF1 and ARF6 are the most studied in neurons, particularly at glutamatergic synapses, but their roles at GABAergic synapses have not been investigated. Here, we show that a subset of ARF6 protein is localized at GABAergic synapses in cultured hippocampal neurons. In addition, we found that knockdown (KD) of ARF6, but not ARF1, triggered a reduction in the number of GABAergic synaptic puncta in mature cultured neurons in an ARF activity-dependent manner. ARF6 KD also reduced GABAergic synaptic density in the mouse hippocampal dentate gyrus (DG) region. Furthermore, ARF6 KD in the DG increased seizure susceptibility in an induced epilepsy model. Viewed together, our results suggest that modulating ARF6 and its regulators could be a therapeutic strategy against brain pathologies involving hippocampal network dysfunction, such as epilepsy.
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Affiliation(s)
- Hyeonho Kim
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), 333 Techno Jungangdae-Ro, Hyeonpoong-eup, Dalseong-gun, Daegu, 42988, South Korea
| | - Hyeji Jung
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), 333 Techno Jungangdae-Ro, Hyeonpoong-eup, Dalseong-gun, Daegu, 42988, South Korea
| | - Hyunsu Jung
- Division of Life Sciences, Korea University, Seoul, 02841, South Korea.,Center for Functional Connectomics, Brain Science Institute, Korea Institute of Science and Technology, Seoul, 02792, South Korea
| | - Seok-Kyu Kwon
- Center for Functional Connectomics, Brain Science Institute, Korea Institute of Science and Technology, Seoul, 02792, South Korea
| | - Jaewon Ko
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), 333 Techno Jungangdae-Ro, Hyeonpoong-eup, Dalseong-gun, Daegu, 42988, South Korea
| | - Ji Won Um
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), 333 Techno Jungangdae-Ro, Hyeonpoong-eup, Dalseong-gun, Daegu, 42988, South Korea.
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26
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Ansar M, Chung HL, Al-Otaibi A, Elagabani MN, Ravenscroft TA, Paracha SA, Scholz R, Abdel Magid T, Sarwar MT, Shah SF, Qaisar AA, Makrythanasis P, Marcogliese PC, Kamsteeg EJ, Falconnet E, Ranza E, Santoni FA, Aldhalaan H, Al-Asmari A, Faqeih EA, Ahmed J, Kornau HC, Bellen HJ, Antonarakis SE. Bi-allelic Variants in IQSEC1 Cause Intellectual Disability, Developmental Delay, and Short Stature. Am J Hum Genet 2019; 105:907-920. [PMID: 31607425 DOI: 10.1016/j.ajhg.2019.09.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Accepted: 09/11/2019] [Indexed: 12/30/2022] Open
Abstract
We report two consanguineous families with probands that exhibit intellectual disability, developmental delay, short stature, aphasia, and hypotonia in which homozygous non-synonymous variants were identified in IQSEC1 (GenBank: NM_001134382.3). In a Pakistani family, the IQSEC1 segregating variant is c.1028C>T (p.Thr343Met), while in a Saudi Arabian family the variant is c.962G>A (p.Arg321Gln). IQSEC1-3 encode guanine nucleotide exchange factors for the small GTPase ARF6 and their loss affects a variety of actin-dependent cellular processes, including AMPA receptor trafficking at synapses. The ortholog of IQSECs in the fly is schizo and its loss affects growth cone guidance at the midline in the CNS, also an actin-dependent process. Overexpression of the reference IQSEC1 cDNA in wild-type flies is lethal, but overexpression of the two variant IQSEC1 cDNAs did not affect viability. Loss of schizo caused embryonic lethality that could be rescued to 2nd instar larvae by moderate expression of the human reference cDNA. However, the p.Arg321Gln and p.Thr343Met variants failed to rescue embryonic lethality. These data indicate that the variants behave as loss-of-function mutations. We also show that schizo in photoreceptors is required for phototransduction. Finally, mice with a conditional Iqsec1 deletion in cortical neurons exhibited an increased density of dendritic spines with an immature morphology. The phenotypic similarity of the affecteds and the functional experiments in flies and mice indicate that IQSEC1 variants are the cause of a recessive disease with intellectual disability, developmental delay, and short stature, and that axonal guidance and dendritic projection defects as well as dendritic spine dysgenesis may underlie disease pathogenesis.
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27
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Jackson MR, Loring KE, Homan CC, Thai MH, Määttänen L, Arvio M, Jarvela I, Shaw M, Gardner A, Gecz J, Shoubridge C. Heterozygous loss of function of IQSEC2/ Iqsec2 leads to increased activated Arf6 and severe neurocognitive seizure phenotype in females. Life Sci Alliance 2019; 2:2/4/e201900386. [PMID: 31439632 PMCID: PMC6706959 DOI: 10.26508/lsa.201900386] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 07/25/2019] [Accepted: 08/15/2019] [Indexed: 12/30/2022] Open
Abstract
Clinical presentations of mutations in the IQSEC2 gene on the X-chromosome initially implicated to cause non-syndromic intellectual disability (ID) in males have expanded to include early onset seizures in males as well as in females. The molecular pathogenesis is not well understood, nor the mechanisms driving disease expression in heterozygous females. Using a CRISPR/Cas9-edited Iqsec2 KO mouse model, we confirm the loss of Iqsec2 mRNA expression and lack of Iqsec2 protein within the brain of both founder and progeny mice. Both male (52%) and female (46%) Iqsec2 KO mice present with frequent and recurrent seizures. Focusing on Iqsec2 KO heterozygous female mice, we demonstrate increased hyperactivity, altered anxiety and fear responses, decreased social interactions, delayed learning capacity and decreased memory retention/novel recognition, recapitulating psychiatric issues, autistic-like features, and cognitive deficits present in female patients with loss-of-function IQSEC2 variants. Despite Iqsec2 normally acting to activate Arf6 substrate, we demonstrate that mice modelling the loss of Iqsec2 function present with increased levels of activated Arf6. We contend that loss of Iqsec2 function leads to altered regulation of activated Arf6-mediated responses to synaptic signalling and immature synaptic networks. We highlight the importance of IQSEC2 function for females by reporting a novel nonsense variant c.566C > A, p.(S189*) in an elderly female patient with profound intellectual disability, generalised seizures, and behavioural disturbances. Our human and mouse data reaffirm IQSEC2 as another disease gene with an unexpected X-chromosome heterozygous female phenotype. Our Iqsec2 mouse model recapitulates the phenotypes observed in human patients despite the differences in the IQSEC2/Iqsec2 gene X-chromosome inactivation between the species.
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Affiliation(s)
- Matilda R Jackson
- Intellectual Disability Research, Adelaide Medical School, The University of Adelaide, Adelaide, Australia.,Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia
| | - Karagh E Loring
- Intellectual Disability Research, Adelaide Medical School, The University of Adelaide, Adelaide, Australia.,Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia
| | - Claire C Homan
- Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia
| | - Monica Hn Thai
- Intellectual Disability Research, Adelaide Medical School, The University of Adelaide, Adelaide, Australia
| | - Laura Määttänen
- Department of Child Neurology, Turku University Hospital, Turku, Finland
| | - Maria Arvio
- Department of Child Neurology, Turku University Hospital, Turku, Finland.,Joint Authority for Päijät-Häme Social and Health Care, Lahti, Finland.,PEDEGO, Oulu University Hospital, Oulu, Finland
| | - Irma Jarvela
- Department of Medical Genetics, University of Helsinki, Helsinki, Finland
| | - Marie Shaw
- Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia
| | - Alison Gardner
- Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia
| | - Jozef Gecz
- Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia.,South Australian Health and Medical Research Institute, Adelaide, Australia
| | - Cheryl Shoubridge
- Intellectual Disability Research, Adelaide Medical School, The University of Adelaide, Adelaide, Australia .,Department of Paediatrics, Robinson Research Institute, University of Adelaide, Adelaide, Australia
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28
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Levy NS, Umanah GKE, Rogers EJ, Jada R, Lache O, Levy AP. IQSEC2-Associated Intellectual Disability and Autism. Int J Mol Sci 2019; 20:ijms20123038. [PMID: 31234416 PMCID: PMC6628259 DOI: 10.3390/ijms20123038] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 06/19/2019] [Indexed: 01/02/2023] Open
Abstract
Mutations in IQSEC2 cause intellectual disability (ID), which is often accompanied by seizures and autism. A number of studies have shown that IQSEC2 is an abundant protein in excitatory synapses and plays an important role in neuronal development as well as synaptic plasticity. Here, we review neuronal IQSEC2 signaling with emphasis on those aspects likely to be involved in autism. IQSEC2 is normally bound to N-methyl-D-aspartate (NMDA)-type glutamate receptors via post synaptic density protein 95 (PSD-95). Activation of NMDA receptors results in calcium ion influx and binding to calmodulin present on the IQSEC2 IQ domain. Calcium/calmodulin induces a conformational change in IQSEC2 leading to activation of the SEC7 catalytic domain. GTP is exchanged for GDP on ADP ribosylation factor 6 (ARF6). Activated ARF6 promotes downregulation of surface α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors through a c-jun N terminal kinase (JNK)-mediated pathway. NMDA receptors, AMPA receptors, and PSD-95 are all known to be adversely affected in autism. An IQSEC2 transgenic mouse carrying a constitutively active mutation (A350V) shows autistic features and reduced levels of surface AMPA receptor subunit GluA2. Sec7 activity and AMPA receptor recycling are presented as two targets, which may respond to drug treatment in IQSEC2-associated ID and autism.
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Affiliation(s)
- Nina S Levy
- Technion Israel Institute of Technology, 1 Efron St., Haifa, 3525422, Israel.
| | - George K E Umanah
- Department of Neurology, Johns Hopkins University, Baltimore, MD 21205, USA.
| | - Eli J Rogers
- Technion Israel Institute of Technology, 1 Efron St., Haifa, 3525422, Israel.
| | - Reem Jada
- Technion Israel Institute of Technology, 1 Efron St., Haifa, 3525422, Israel.
| | - Orit Lache
- Technion Israel Institute of Technology, 1 Efron St., Haifa, 3525422, Israel.
| | - Andrew P Levy
- Technion Israel Institute of Technology, 1 Efron St., Haifa, 3525422, Israel.
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29
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Radley JA, O'Sullivan RB, Turton SE, Cox H, Vogt J, Morton J, Jones E, Smithson S, Lachlan K, Rankin J, Clayton-Smith J, Willoughby J, Elmslie FF, Sansbury FH, Cooper N, Balasubramanian M. Deep phenotyping of 14 new patients with IQSEC2
variants, including monozygotic twins of discordant phenotype. Clin Genet 2019; 95:496-506. [PMID: 30666632 DOI: 10.1111/cge.13507] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 01/09/2019] [Accepted: 01/11/2019] [Indexed: 01/22/2023]
Affiliation(s)
- Jessica A. Radley
- West Midlands Regional Clinical Genetics Service and Birmingham Health Partners; Birmingham Women's and Children's Hospitals NHS Foundation Trust; Birmingham UK
| | | | - Sarah E. Turton
- West Midlands Regional Genetics Laboratory Birmingham Women's and Children's Hospitals NHS Foundation Trust; Birmingham UK
| | - Helen Cox
- West Midlands Regional Clinical Genetics Service and Birmingham Health Partners; Birmingham Women's and Children's Hospitals NHS Foundation Trust; Birmingham UK
| | - Julie Vogt
- West Midlands Regional Clinical Genetics Service and Birmingham Health Partners; Birmingham Women's and Children's Hospitals NHS Foundation Trust; Birmingham UK
| | - Jenny Morton
- West Midlands Regional Clinical Genetics Service and Birmingham Health Partners; Birmingham Women's and Children's Hospitals NHS Foundation Trust; Birmingham UK
| | - Elizabeth Jones
- Manchester Centre for Genomic Medicine, Manchester University Hospitals NHS Foundation Trust; Manchester UK
- Division of Evolution and Genomic Sciences, School of Biological Sciences; University of Manchester; Manchester UK
| | - Sarah Smithson
- University Hospitals Bristol NHS Foundation Trust; Clinical Genetics, St. Michael's Hospital; Bristol UK
| | - Katherine Lachlan
- Wessex Clinical Genetics Service; University Hospitals of Southampton NHS Trust; Southampton UK
| | - Julia Rankin
- Peninsula Clinical Genetics; Royal Devon and Exeter NHS Trust; Exeter UK
| | - Jill Clayton-Smith
- Manchester Centre for Genomic Medicine, Manchester University Hospitals NHS Foundation Trust; Manchester UK
- Division of Evolution and Genomic Sciences, School of Biological Sciences; University of Manchester; Manchester UK
| | - Josh Willoughby
- Sheffield Diagnostic Genetics Service; Sheffield Children's NHS Foundation Trust; Sheffield UK
| | - Frances F. Elmslie
- South West Thames Regional Genetics Service; St George's University Hospitals NHS Foundation Trust; London UK
| | - Francis H. Sansbury
- University Hospitals Bristol NHS Foundation Trust; Clinical Genetics, St. Michael's Hospital; Bristol UK
- All Wales Medical Genetics Service, Cardiff and Vale University Health Board, Institute of Medical Genetics; University Hospital of Wales; Cardiff UK
| | - Nicola Cooper
- West Midlands Regional Clinical Genetics Service and Birmingham Health Partners; Birmingham Women's and Children's Hospitals NHS Foundation Trust; Birmingham UK
| | - Meena Balasubramanian
- Sheffield Clinical Genetics Service; Sheffield Children's NHS Foundation Trust; Sheffield UK
- Academic Unit of Child Health, Department of Oncology and Metabolism; University of Sheffield; Sheffield UK
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30
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Rogers EJ, Jada R, Schragenheim-Rozales K, Sah M, Cortes M, Florence M, Levy NS, Moss R, Walikonis RS, Palty R, Shalgi R, Lichtman D, Kavushansky A, Gerges NZ, Kahn I, Umanah GKE, Levy AP. An IQSEC2 Mutation Associated With Intellectual Disability and Autism Results in Decreased Surface AMPA Receptors. Front Mol Neurosci 2019; 12:43. [PMID: 30842726 PMCID: PMC6391579 DOI: 10.3389/fnmol.2019.00043] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2018] [Accepted: 02/01/2019] [Indexed: 12/30/2022] Open
Abstract
We have recently described an A350V mutation in IQSEC2 associated with intellectual disability, autism and epilepsy. We sought to understand the molecular pathophysiology of this mutation with the goal of developing targets for drug intervention. We demonstrate here that the A350V mutation results in interference with the binding of apocalmodulin to the IQ domain of IQSEC2. We further demonstrate that this mutation results in constitutive activation of the guanine nucleotide exchange factor (GEF) activity of IQSEC2 resulting in increased production of the active form of Arf6. In a CRISPR generated mouse model of the A350V IQSEC2 mutation, we demonstrate that the surface expression of GluA2 AMPA receptors in mouse hippocampal tissue was significantly reduced in A350V IQSEC2 mutant mice compared to wild type IQSEC2 mice and that there is a significant reduction in basal synaptic transmission in the hippocampus of A350V IQSEC2 mice compared to wild type IQSEC2 mice. Finally, the A350V IQSEC2 mice demonstrated increased activity, abnormal social behavior and learning as compared to wild type IQSEC2 mice. These findings suggest a model of how the A350V mutation in IQSEC2 may mediate disease with implications for targets for drug therapy. These studies provide a paradigm for a personalized approach to precision therapy for a disease that heretofore has no therapy.
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Affiliation(s)
- Eli J Rogers
- Technion Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
| | - Reem Jada
- Technion Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
| | | | - Megha Sah
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, United States
| | - Marisol Cortes
- Department of Neurology, Johns Hopkins University, Baltimore, MD, United States
| | - Matthew Florence
- Department of Biopharmaceutical Sciences and Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Nina S Levy
- Technion Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
| | - Rachel Moss
- Technion Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
| | - Randall S Walikonis
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT, United States
| | - Raz Palty
- Technion Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
| | - Reut Shalgi
- Technion Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
| | - Daniela Lichtman
- Technion Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
| | - Alexandra Kavushansky
- Technion Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
| | - Nashaat Z Gerges
- Department of Biopharmaceutical Sciences and Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Itamar Kahn
- Technion Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
| | - George K E Umanah
- Department of Neurology, Johns Hopkins University, Baltimore, MD, United States
| | - Andrew P Levy
- Technion Faculty of Medicine, Technion Israel Institute of Technology, Haifa, Israel
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31
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Shoubridge C, Harvey RJ, Dudding-Byth T. IQSEC2mutation update and review of the female-specific phenotype spectrum including intellectual disability and epilepsy. Hum Mutat 2018; 40:5-24. [DOI: 10.1002/humu.23670] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 10/11/2018] [Accepted: 10/15/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Cheryl Shoubridge
- Department of Paediatrics; University of Adelaide; Adelaide South Australia 5005 Australia
- Robinson Research Institute; University of Adelaide; Adelaide South Australia 5005 Australia
| | - Robert J. Harvey
- School of Health and Sport Sciences; University of the Sunshine Coast; Maroochydore DC Queensland 4558 Australia
- Sunshine Coast Health Institute; Birtinya Queensland 4575 Australia
| | - Tracy Dudding-Byth
- NSW Genetics of Learning Disability Service; Hunter New England Health Service; New South Wales 2298 Australia
- Grow-Up-Well Priority Research Centre; University of Newcastle; Newcastle New South Wales 2308 Australia
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32
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Mignot C, McMahon AC, Bar C, Campeau PM, Davidson C, Buratti J, Nava C, Jacquemont ML, Tallot M, Milh M, Edery P, Marzin P, Barcia G, Barnerias C, Besmond C, Bienvenu T, Bruel AL, Brunga L, Ceulemans B, Coubes C, Cristancho AG, Cunningham F, Dehouck MB, Donner EJ, Duban-Bedu B, Dubourg C, Gardella E, Gauthier J, Geneviève D, Gobin-Limballe S, Goldberg EM, Hagebeuk E, Hamdan FF, Hančárová M, Hubert L, Ioos C, Ichikawa S, Janssens S, Journel H, Kaminska A, Keren B, Koopmans M, Lacoste C, Laššuthová P, Lederer D, Lehalle D, Marjanovic D, Métreau J, Michaud JL, Miller K, Minassian BA, Morales J, Moutard ML, Munnich A, Ortiz-Gonzalez XR, Pinard JM, Prchalová D, Putoux A, Quelin C, Rosen AR, Roume J, Rossignol E, Simon MEH, Smol T, Shur N, Shelihan I, Štěrbová K, Vyhnálková E, Vilain C, Soblet J, Smits G, Yang SP, van der Smagt JJ, van Hasselt PM, van Kempen M, Weckhuysen S, Helbig I, Villard L, Héron D, Koeleman B, Møller RS, Lesca G, Helbig KL, Nabbout R, Verbeek NE, Depienne C. IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients. Genet Med 2018; 21:837-849. [PMID: 30206421 PMCID: PMC6752297 DOI: 10.1038/s41436-018-0268-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 07/31/2018] [Indexed: 12/19/2022] Open
Abstract
Purpose Variants in IQSEC2, escaping X inactivation, cause X-linked intellectual disability with frequent epilepsy in males and females. We aimed to investigate sex-specific differences. Methods We collected the data of 37 unpublished patients (18 males and 19 females) with IQSEC2 pathogenic variants and 5 individuals with variants of unknown significance and reviewed published variants. We compared variant types and phenotypes in males and females and performed an analysis of IQSEC2 isoforms. Results IQSEC2 pathogenic variants mainly led to premature truncation and were scattered throughout the longest brain-specific isoform, encoding the synaptic IQSEC2/BRAG1 protein. Variants occurred de novo in females but were either de novo (2/3) or inherited (1/3) in males, with missense variants being predominantly inherited. Developmental delay and intellectual disability were overall more severe in males than in females. Likewise, seizures were more frequently observed and intractable, and started earlier in males than in females. No correlation was observed between the age at seizure onset and severity of intellectual disability or resistance to antiepileptic treatments. Conclusion This study provides a comprehensive overview of IQSEC2-related encephalopathy in males and females, and suggests that an accurate dosage of IQSEC2 at the synapse is crucial during normal brain development.
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Affiliation(s)
- Cyril Mignot
- INSERM, U 1127, CNRS UMR 7225, Sorbonne Universites, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle epiniere, ICM, Paris, France. .,APHP, Hôpital Pitie-Salpetriere, Departement de Genetique et de Cytogenetique; Centre de Reference Deficience Intellectuelle de Causes Rares; GRC UPMC «Deficience Intellectuelle et Autisme», Paris, France.
| | - Aoife C McMahon
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK
| | - Claire Bar
- APHP, Reference Centre for Rare Epilepsies, Necker-Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France.,INSERM U1163, Imagine Institute, Paris, France.,Paris Descartes University, Paris, France
| | - Philippe M Campeau
- Division of Medical Genetics, Department of Pediatrics, CHU Sainte-Justine and University of Montreal, Montreal, QC, Canada
| | - Claire Davidson
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK
| | - Julien Buratti
- APHP, Hôpital Pitie-Salpetriere, Departement de Genetique et de Cytogenetique; Centre de Reference Deficience Intellectuelle de Causes Rares; GRC UPMC «Deficience Intellectuelle et Autisme», Paris, France
| | - Caroline Nava
- INSERM, U 1127, CNRS UMR 7225, Sorbonne Universites, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle epiniere, ICM, Paris, France.,APHP, Hôpital Pitie-Salpetriere, Departement de Genetique et de Cytogenetique; Centre de Reference Deficience Intellectuelle de Causes Rares; GRC UPMC «Deficience Intellectuelle et Autisme», Paris, France
| | | | - Marilyn Tallot
- CHU La Reunion-Groupe Hospitalier Sud Reunion, La Reunion, France
| | - Mathieu Milh
- APHM, Hôpital d'Enfants de La Timone, Service de Neurologie Pediatrique, centre de reference deficiences intellectuelles de cause rare, Marseille, France.,Aix Marseille University, INSERM, MMG, UMR-S 1251, Faculte de medecine, Marseille, France
| | - Patrick Edery
- Service de Genetique, Centre de Reference Anomalies du Developpement, Hospices Civils de Lyon, Bron, France.,INSERM U1028, CNRS UMR5292, Centre de Recherche en Neurosciences de Lyon, GENDEV Team, Universite Claude Bernard Lyon 1, Bron, France.,Claude Bernard Lyon I University, Lyon, France
| | - Pauline Marzin
- APHP, Hôpital Pitie-Salpetriere, Departement de Genetique et de Cytogenetique; Centre de Reference Deficience Intellectuelle de Causes Rares; GRC UPMC «Deficience Intellectuelle et Autisme», Paris, France
| | - Giulia Barcia
- INSERM U1163, Imagine Institute, Paris, France.,Paris Descartes University, Paris, France.,APHP, Service de genetique medicale, Necker-Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France
| | - Christine Barnerias
- APHP, Unite fonctionnelle de Neurologie, Necker-Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France
| | - Claude Besmond
- INSERM U1163, Imagine Institute, Paris, France.,Paris Descartes University, Paris, France
| | - Thierry Bienvenu
- APHP, Laboratoire de Genetique et Biologie Moleculaires, Hôpital Cochin, HUPC, Paris, France.,Universite Paris Descartes Paris, Institut de Psychiatrie et de Neurosciences de Paris, Inserm U894, Paris, France
| | - Ange-Line Bruel
- FHU-TRANSLAD, Universite de Bourgogne/CHU Dijon, Dijon, France.,INSERM UMR 1231 GAD team, Genetics of Developmental disorders, Universite de Bourgogne-Franche Comte, Dijon, France
| | - Ledia Brunga
- Division of Neurology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada
| | - Berten Ceulemans
- Department of Pediatric Neurology, University Hospital and University of Antwerp, Antwerp, Belgium
| | - Christine Coubes
- Departement de Genetique Medicale, Maladies rares et Medecine Personnalisee, CHU de Montpellier, Montpellier, France
| | - Ana G Cristancho
- Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Fiona Cunningham
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK
| | | | - Elizabeth J Donner
- Division of Neurology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada
| | - Bénédicte Duban-Bedu
- Centre de Genetique Chromosomique, Hôpital St-Vincent-de-Paul, GHICL, Lille, France
| | - Christèle Dubourg
- CHU Rennes, Service de Genetique Moleculaire et Genomique, Rennes, France
| | - Elena Gardella
- Danish Epilepsy Centre Filadelfia, Dianalund, Denmark.,Institute for Regional Health Services, University of Southern Denmark, Odense, Denmark
| | - Julie Gauthier
- Division of Medical Genetics, Department of Pediatrics, CHU Sainte-Justine and University of Montreal, Montreal, QC, Canada
| | - David Geneviève
- Departement de Genetique Medicale, Maladies rares et Medecine Personnalisee, CHU de Montpellier, Montpellier, France.,INSERM U1183, Montpellier, France
| | - Stéphanie Gobin-Limballe
- APHP, Service de genetique medicale, Necker-Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France
| | - Ethan M Goldberg
- Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Eveline Hagebeuk
- Stichting Epilepsie Instellingen Nederland, SEIN, Zwolle, The Netherlands
| | - Fadi F Hamdan
- Division of Medical Genetics, Department of Pediatrics, CHU Sainte-Justine and University of Montreal, Montreal, QC, Canada
| | - Miroslava Hančárová
- Department of Biology and Medical Genetics, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Laurence Hubert
- INSERM U1163, Imagine Institute, Paris, France.,Paris Descartes University, Paris, France
| | - Christine Ioos
- APHP, University Hospital of Paris ïle-de-France ouest, Raymond Poincare Hospital, Garches, France
| | - Shoji Ichikawa
- Department of Clinical Diagnostics, Ambry Genetics, Aliso Viejo, CA, USA
| | - Sandra Janssens
- Centre for Medical Genetics Ghent, Ghent University Hospital, C. Heymanslaan 10, Ghent, Belgium
| | - Hubert Journel
- Service de Genetique Medicale, Hôpital Chubert, Vannes, France
| | - Anna Kaminska
- APHP, Department of Clinical Neurophysiology, Necker-Enfants Malades Hospital, Paris, France
| | - Boris Keren
- APHP, Hôpital Pitie-Salpetriere, Departement de Genetique et de Cytogenetique; Centre de Reference Deficience Intellectuelle de Causes Rares; GRC UPMC «Deficience Intellectuelle et Autisme», Paris, France
| | - Marije Koopmans
- Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Caroline Lacoste
- Departement de Genetique Medicale, APHM, Hopital d'Enfants de La Timone, Marseille, France
| | - Petra Laššuthová
- Child Neurology Department, 2nd Faculty of Medicine, Charles University and Motol Hospital, Prague, Czech Republic
| | - Damien Lederer
- Centre de Genetique Humaine, Institut de Pathologie et de Genetique, Gosselies, Belgium
| | - Daphné Lehalle
- FHU-TRANSLAD, Universite de Bourgogne/CHU Dijon, Dijon, France.,Unite fonctionnelle de genetique clinique, Centre Hospitalier Intercommunal de Creteil, Creteil, France
| | | | - Julia Métreau
- APHP, Service de neurologie pediatrique, Hôpital Universitaire Bicetre, Le Kremlin-Bicetre, France
| | - Jacques L Michaud
- Division of Medical Genetics, Department of Pediatrics, CHU Sainte-Justine and University of Montreal, Montreal, QC, Canada
| | - Kathryn Miller
- Department of Pediatrics, Albany Medical Center, Albany, NY, USA
| | - Berge A Minassian
- Division of Neurology, Department of Paediatrics, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada
| | - Joannella Morales
- European Molecular Biology Laboratory, European Bioinformatics Institute, Wellcome Genome Campus, Hinxton, Cambridge, UK
| | - Marie-Laure Moutard
- APHP, Hôpital Trousseau, service de neuropediatrie, Paris, France.,Sorbonne Universite, GRC n°19, pathologies Congenitales du Cervelet-LeucoDystrophies, APHP, Hôpital Armand Trousseau, Paris, France
| | - Arnold Munnich
- INSERM U1163, Imagine Institute, Paris, France.,Paris Descartes University, Paris, France.,APHP, Service de genetique medicale, Necker-Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France
| | | | - Jean-Marc Pinard
- Division of Neuropediatrics, CHU Raymond Poincare (APHP), Garches, France
| | - Darina Prchalová
- Department of Biology and Medical Genetics, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Audrey Putoux
- Service de Genetique, Centre de Reference Anomalies du Developpement, Hospices Civils de Lyon, Bron, France.,INSERM U1028, CNRS UMR5292, Centre de Recherche en Neurosciences de Lyon, GENDEV Team, Universite Claude Bernard Lyon 1, Bron, France.,Claude Bernard Lyon I University, Lyon, France
| | - Chloé Quelin
- Service de Genetique Medicale, CLAD Ouest CHU Hôpital Sud, Rennes, France
| | - Alyssa R Rosen
- Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Joelle Roume
- Unite de Genetique Medicale, Centre de Reference des Maladies rares du Developpement (AnD DI Rares), CHI Poissy-St Germain en Laye, Poissy, France
| | - Elsa Rossignol
- Departments of Pediatrics and Neurosciences, CHU Sainte-Justine and University of Montreal, Montreal, Canada
| | - Marleen E H Simon
- Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Thomas Smol
- Institut de Genetique Medicale, CHRU Lille, Universite de Lille, Lille, France
| | - Natasha Shur
- Department of Pediatrics, Albany Medical Center, Albany, NY, USA
| | - Ivan Shelihan
- Division of Medical Genetics, Department of Pediatrics, CHU Sainte-Justine and University of Montreal, Montreal, QC, Canada
| | - Katalin Štěrbová
- Child Neurology Department, 2nd Faculty of Medicine, Charles University and Motol Hospital, Prague, Czech Republic
| | - Emílie Vyhnálková
- Department of Biology and Medical Genetics, Charles University 2nd Faculty of Medicine and University Hospital Motol, Prague, Czech Republic
| | - Catheline Vilain
- Department of Genetics, Hôpital Universitaire des Enfants Reine Fabiola, ULB Center of Human Genetics, Universite Libre de Bruxelles, Brussels, Belgium.,Department of Genetics, Hôpital Erasme, ULB Center of Human Genetics, Universite Libre de Bruxelles, Brussels, Belgium.,Interuniversity Institute of Bioinformatics in Brussels, Universite Libre de Bruxelles, Brussels, Belgium
| | - Julie Soblet
- Department of Genetics, Hôpital Universitaire des Enfants Reine Fabiola, ULB Center of Human Genetics, Universite Libre de Bruxelles, Brussels, Belgium.,Department of Genetics, Hôpital Erasme, ULB Center of Human Genetics, Universite Libre de Bruxelles, Brussels, Belgium.,Interuniversity Institute of Bioinformatics in Brussels, Universite Libre de Bruxelles, Brussels, Belgium
| | - Guillaume Smits
- Department of Genetics, Hôpital Universitaire des Enfants Reine Fabiola, ULB Center of Human Genetics, Universite Libre de Bruxelles, Brussels, Belgium.,Department of Genetics, Hôpital Erasme, ULB Center of Human Genetics, Universite Libre de Bruxelles, Brussels, Belgium.,Interuniversity Institute of Bioinformatics in Brussels, Universite Libre de Bruxelles, Brussels, Belgium
| | - Samuel P Yang
- Clinical Genomics & Predictive Medicine, Providence Medical Group, Dayton, WA, USA
| | | | - Peter M van Hasselt
- Department of Metabolic Diseases, Wilhelmina Children's Hospital, University Medical Center, Utrecht, The Netherlands
| | - Marjan van Kempen
- Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Sarah Weckhuysen
- Neurogenetics Group, Center of Molecular Neurology, VIB, Antwerp, Belgium.,Neurology Department, University Hospital Antwerp, Antwerp, Belgium
| | - Ingo Helbig
- Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Laurent Villard
- Aix Marseille University, INSERM, MMG, UMR-S 1251, Faculte de medecine, Marseille, France.,Departement de Genetique Medicale, APHM, Hopital d'Enfants de La Timone, Marseille, France
| | - Delphine Héron
- APHP, Hôpital Pitie-Salpetriere, Departement de Genetique et de Cytogenetique; Centre de Reference Deficience Intellectuelle de Causes Rares; GRC UPMC «Deficience Intellectuelle et Autisme», Paris, France
| | - Bobby Koeleman
- Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Rikke S Møller
- CHU Rennes, Service de Genetique Moleculaire et Genomique, Rennes, France.,Danish Epilepsy Centre Filadelfia, Dianalund, Denmark
| | - Gaetan Lesca
- Service de Genetique, Centre de Reference Anomalies du Developpement, Hospices Civils de Lyon, Bron, France.,INSERM U1028, CNRS UMR5292, Centre de Recherche en Neurosciences de Lyon, GENDEV Team, Universite Claude Bernard Lyon 1, Bron, France.,Claude Bernard Lyon I University, Lyon, France
| | - Katherine L Helbig
- Division of Neurology, Children's Hospital of Philadelphia, Philadelphia, PA, USA
| | - Rima Nabbout
- APHP, Reference Centre for Rare Epilepsies, Necker-Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France.,INSERM U1163, Imagine Institute, Paris, France.,Paris Descartes University, Paris, France
| | - Nienke E Verbeek
- Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Christel Depienne
- INSERM, U 1127, CNRS UMR 7225, Sorbonne Universites, UPMC Univ Paris 06 UMR S 1127, Institut du Cerveau et de la Moelle epiniere, ICM, Paris, France. .,IGBMC, CNRS UMR 7104/INSERM U964/Universite de Strasbourg, Illkirch, France. .,Institute of Human Genetics, University Hospital Essen, University of Duisburg-Essen, Essen, Germany.
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Petersen A, Brown JC, Gerges NZ. BRAG1/IQSEC2 as a regulator of small GTPase-dependent trafficking. Small GTPases 2018; 11:1-7. [PMID: 29363391 DOI: 10.1080/21541248.2017.1361898] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
Abstract
Precise trafficking events, such as those that underlie synaptic transmission and plasticity, require complex regulation. G-protein signaling plays an essential role in the regulation of membrane and protein trafficking. However, it is not well understood how small GTPases and their regulatory proteins coordinate such specific events. Our recent publication focused on a highly abundant synaptic GEF, BRAG1, whose physiologic relevance was unknown. We find that BRAG1s GEF activity is required for activity-dependent trafficking of AMPARs. Moreover, BRAG1 bidirectionally regulates synaptic transmission in a manner independent of this activity. In addition to the GEF domain, BRAG1 contains several functional domains whose roles are not yet understood but may mediate protein-protein interactions and regulatory effects necessary for its role in regulation of AMPAR trafficking. In this commentary, we explore the potential for BRAG1 to provide specificity of small GTPase signaling, coordinating activity-dependent activation of small GTPase activity with signaling and scaffolding molecules involved in trafficking through its GEF activity and other functional domains.
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Affiliation(s)
- Amber Petersen
- Department of Cell Biology, Neurobiology and Anatomy, The Medical College of Wisconsin, Milwaukee, Wisconsin, USA
| | - Joshua C Brown
- Department of Psychiatry and Behavioral Science, Medical University of South Carolina, Charleston, SC, USA
| | - Nashaat Z Gerges
- Department of Cell Biology, Neurobiology and Anatomy, The Medical College of Wisconsin, Milwaukee, Wisconsin, USA.,Department of Biopharmaceutical Sciences, School of Pharmacy, The Medical College of Wisconsin, Milwaukee, Wisconsin, USA
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Multiple interactions between an Arf/GEF complex and charged lipids determine activation kinetics on the membrane. Proc Natl Acad Sci U S A 2017; 114:11416-11421. [PMID: 28923919 DOI: 10.1073/pnas.1707970114] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Lipidated small GTPases and their regulators need to bind to membranes to propagate actions in the cell, but an integrated understanding of how the lipid bilayer exerts its effect has remained elusive. Here we focused on ADP ribosylation factor (Arf) GTPases, which orchestrate a variety of regulatory functions in lipid and membrane trafficking, and their activation by the guanine-nucleotide exchange factor (GEF) Brag2, which controls integrin endocytosis and cell adhesion and is impaired in cancer and developmental diseases. Biochemical and structural data are available that showed the exceptional efficiency of Arf activation by Brag2 on membranes. We determined the high-resolution crystal structure of unbound Brag2 containing the GEF (Sec7) and membrane-binding (pleckstrin homology) domains, revealing that it has a constitutively active conformation. We used this structure to analyze the interaction of uncomplexed Brag2 and of the myristoylated Arf1/Brag2 complex with a phosphatidylinositol bisphosphate (PIP2) -containing lipid bilayer, using coarse-grained molecular dynamics. These simulations revealed that the system forms a close-packed, oriented interaction with the membrane, in which multiple PIP2 lipids bind the canonical lipid-binding site and unique peripheral sites of the PH domain, the Arf GTPase and, unexpectedly, the Sec7 domain. We cross-validated these predictions by reconstituting the binding and kinetics of Arf and Brag2 in artificial membranes. Our coarse-grained structural model thus suggests that the high efficiency of Brag2 requires interaction with multiple lipids and a well-defined orientation on the membrane, resulting in a local PIP2 enrichment, which has the potential to signal toward the Arf pathway.
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Helm BM, Powis Z, Prada CE, Casasbuenas-Alarcon OL, Balmakund T, Schaefer GB, Kahler SG, Kaylor J, Winter S, Zarate YA, Schrier Vergano SA. The role of IQSEC2 in syndromic intellectual disability: Narrowing the diagnostic odyssey. Am J Med Genet A 2017; 173:2814-2820. [PMID: 28815955 DOI: 10.1002/ajmg.a.38404] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 07/03/2017] [Accepted: 07/20/2017] [Indexed: 01/16/2023]
Abstract
While X-linked intellectual disability (XLID) syndromes pose a diagnostic challenge for clinicians, an increasing number of recognized disorders and their genetic etiologies are providing answers for patients and their families. The availability of clinical exome sequencing is broadening the ability to identify mutations in genes previously unrecognized as causing XLID. In recent years, the IQSEC2 gene, located at Xp11.22, has emerged as the cause of multiple cases of both nonsyndromic and syndromic XLID. Herein we present a case series of six individuals (five males, one female) with intellectual disability and seizures found to have alterations in IQSEC2. In all cases, the diagnostic odyssey was extensive and expensive, often including invasive testing such as muscle biopsies, before ultimately reaching the diagnosis. We report these cases to demonstrate the exhaustive work-up prior to finding the changes in IQSEC2 gene, recommend that this gene be considered earlier in the diagnostic evaluation of individuals with global developmental delay, microcephaly, and severe, intractable epilepsy, and support the use of intellectual disability panels including IQSEC2 in the first-line evaluation of these patients.
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Affiliation(s)
- Benjamin M Helm
- Department of Medical and Molecular Genetics, Indiana University School of Medicine and Riley Hospital for Children at IU Health, Indianapolis, Indiana
| | - Zoe Powis
- Ambry Genetics, Department of Clinical Genomics, Aliso Viejo, California
| | - Carlos E Prada
- Division of Human Genetics, Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, Ohio.,Centro de Medicina Genomica y Metabolismo, Fundación Cardiovascular de Colombia, Floridablanca, Colombia
| | | | - Tonya Balmakund
- Division of Neurology, Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - G B Schaefer
- Section of Genetics and Metabolism, Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Stephen G Kahler
- Section of Genetics and Metabolism, Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Julie Kaylor
- Arkansas Children's Hospital, Little Rock, Arkansas
| | - Susan Winter
- Valley Children's Hospital, Department of Genetic Medicine and Metabolism, Madera, California
| | - Yuri A Zarate
- Section of Genetics and Metabolism, Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Samantha A Schrier Vergano
- Division of Medical Genetics and Metabolism, Children's Hospital of The King's Daughters, Norfolk, Virginia.,Department of Pediatrics, Eastern Virginia Medical School, Norfolk, Virginia
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36
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Incorrect dosage of IQSEC2, a known intellectual disability and epilepsy gene, disrupts dendritic spine morphogenesis. Transl Psychiatry 2017; 7:e1110. [PMID: 28463240 PMCID: PMC5534949 DOI: 10.1038/tp.2017.81] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 02/23/2017] [Indexed: 12/18/2022] Open
Abstract
There is considerable genetic and phenotypic heterogeneity associated with intellectual disability (ID), specific learning disabilities, attention-deficit hyperactivity disorder, autism and epilepsy. The intelligence quotient (IQ) motif and SEC7 domain containing protein 2 gene (IQSEC2) is located on the X-chromosome and harbors mutations that contribute to non-syndromic ID with and without early-onset seizure phenotypes in both sexes. Although IQ and Sec7 domain mutations lead to partial loss of IQSEC2 enzymatic activity, the in vivo pathogenesis resulting from these mutations is not known. Here we reveal that IQSEC2 has a key role in dendritic spine morphology. Partial loss-of-function mutations were modeled using a lentiviral short hairpin RNA (shRNA) approach, which achieved a 57% knockdown of Iqsec2 expression in primary hippocampal cell cultures from mice. Investigating gross morphological parameters after 8 days of in vitro culture (8DIV) identified a 32% reduction in primary axon length, in contrast to a 27% and 31% increase in the number and complexity of dendrites protruding from the cell body, respectively. This increase in dendritic complexity and spread was carried through dendritic spine development, with a 34% increase in the number of protrusions per dendritic segment compared with controls at 15DIV. Although the number of dendritic spines had normalized by 21DIV, a reduction was noted in the number of immature spines. In contrast, when modeling increased dosage, overexpression of wild-type IQSEC2 led to neurons with shorter axons that were more compact and displayed simpler dendritic branching. Disturbances to dendritic morphology due to knockdown of Iqsec2 were recapitulated in neurons from Iqsec2 knockout mice generated in our laboratory using CRISPR/Cas9 technology. These observations provide evidence of dosage sensitivity for IQSEC2, which normally escapes X-inactivation in females, and links these disturbances in expression to alterations in the morphology of developing neurons.
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37
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Um JW. Synaptic functions of the IQSEC family of ADP-ribosylation factor guanine nucleotide exchange factors. Neurosci Res 2017; 116:54-59. [DOI: 10.1016/j.neures.2016.06.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 06/15/2016] [Accepted: 06/15/2016] [Indexed: 01/08/2023]
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