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Ramakers GJA, Wolfer D, Rosenberger G, Kuchenbecker K, Kreienkamp HJ, Prange-Kiel J, Rune G, Richter K, Langnaese K, Masneuf S, Bösl MR, Fischer KD, Krugers HJ, Lipp HP, van Galen E, Kutsche K. Dysregulation of Rho GTPases in the αPix/Arhgef6 mouse model of X-linked intellectual disability is paralleled by impaired structural and synaptic plasticity and cognitive deficits. Hum Mol Genet 2011; 21:268-86. [PMID: 21989057 DOI: 10.1093/hmg/ddr457] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Mutations in the ARHGEF6 gene, encoding the guanine nucleotide exchange factor αPIX/Cool-2 for the Rho GTPases Rac1 and Cdc42, cause X-linked intellectual disability (ID) in humans. We show here that αPix/Arhgef6 is primarily expressed in neuropil regions of the hippocampus. To study the role of αPix/Arhgef6 in neuronal development and plasticity and gain insight into the pathogenic mechanisms underlying ID, we generated αPix/Arhgef6-deficient mice. Gross brain structure in these mice appeared to be normal; however, analysis of Golgi-Cox-stained pyramidal neurons revealed an increase in both dendritic length and spine density in the hippocampus, accompanied by an overall loss in spine synapses. Early-phase long-term potentiation was reduced and long-term depression was increased in the CA1 hippocampal area of αPix/Arhgef6-deficient animals. Knockout animals exhibited impaired spatial and complex learning and less behavioral control in mildly stressful situations, suggesting that this model mimics the human ID phenotype. The structural and electrophysiological alterations in the hippocampus were accompanied by a significant reduction in active Rac1 and Cdc42, but not RhoA. In conclusion, we suggest that imbalance in activity of different Rho GTPases may underlie altered neuronal connectivity and impaired synaptic function and cognition in αPix/Arhgef6 knockout mice.
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Affiliation(s)
- Ger J A Ramakers
- Department of Neurons and Networks, Netherlands Institute for Neuroscience, an Institute of the Royal Netherlands Academy of Arts and Sciences, Amsterdam, The Netherlands
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Khelfaoui M, Denis C, van Galen E, de Bock F, Schmitt A, Houbron C, Morice E, Giros B, Ramakers G, Fagni L, Chelly J, Nosten-Bertrand M, Billuart P. Loss of X-linked mental retardation gene oligophrenin1 in mice impairs spatial memory and leads to ventricular enlargement and dendritic spine immaturity. J Neurosci 2007; 27:9439-50. [PMID: 17728457 PMCID: PMC6673114 DOI: 10.1523/jneurosci.2029-07.2007] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Loss of oligophrenin1 (OPHN1) function in human causes X-linked mental retardation associated with cerebellar hypoplasia and, in some cases, with lateral ventricle enlargement. In vitro studies showed that ophn1 regulates dendritic spine through the control of Rho GTPases, but its in vivo function remains unknown. We generated a mouse model of ophn1 deficiency and showed that it mimics the ventricles enlargement without affecting the cerebellum morphoanatomy. The ophn1 knock-out mice exhibit behavioral defects in spatial memory together with impairment in social behavior, lateralization, and hyperactivity. Long-term potentiation and mGluR-dependent long-term depression are normal in the CA1 hippocampal area of ophn1 mutant, whereas paired-pulse facilitation is reduced. This altered short-term plasticity that reflects changes in the release of neurotransmitters from the presynaptic processes is associated with normal synaptic density together with a reduction in mature dendritic spines. In culture, inactivation of ophn1 function increases the density and proportion of immature spines. Using a conditional model of loss of ophn1 function, we confirmed this immaturity defect and showed that ophn1 is required at all the stages of the development. These studies show that, depending of the context, ophn1 controls the maturation of dendritic spines either by maintaining the density of mature spines or by limiting the extension of new filopodia. Altogether, these observations indicate that cognitive impairment related to OPHN1 loss of function is associated with both presynaptic and postsynaptic alterations.
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Affiliation(s)
- Malik Khelfaoui
- Department of Genetic and Development, Institut Cochin, Université Paris Descartes, Centre National de la Recherche Scientifique (CNRS) [Unité Mixte de Recherche (UMR) 8104], F-75014 Paris, France
- Inserm, U567, F-75014 Paris, France
| | - Cécile Denis
- Inserm, U513, Neurobiology and Psychiatry, F-94010 Créteil, France
| | - Elly van Galen
- Netherlands Institute for Neurosciences, Neurons, and Networks, 1105 AZ Amsterdam, The Netherlands
| | - Frédéric de Bock
- Department of Neurobiology, Institut de Genomique Fonctionnelle, Université Montpellier 1 et 2, CNRS (UMR 5203), F-34094 Montpellier, France, and
- Inserm, U661, F-34094 Montpellier, France
| | - Alain Schmitt
- Department of Genetic and Development, Institut Cochin, Université Paris Descartes, Centre National de la Recherche Scientifique (CNRS) [Unité Mixte de Recherche (UMR) 8104], F-75014 Paris, France
- Inserm, U567, F-75014 Paris, France
| | - Christophe Houbron
- Department of Genetic and Development, Institut Cochin, Université Paris Descartes, Centre National de la Recherche Scientifique (CNRS) [Unité Mixte de Recherche (UMR) 8104], F-75014 Paris, France
- Inserm, U567, F-75014 Paris, France
| | - Elise Morice
- Inserm, U513, Neurobiology and Psychiatry, F-94010 Créteil, France
| | - Bruno Giros
- Inserm, U513, Neurobiology and Psychiatry, F-94010 Créteil, France
| | - Ger Ramakers
- Netherlands Institute for Neurosciences, Neurons, and Networks, 1105 AZ Amsterdam, The Netherlands
| | - Laurent Fagni
- Department of Neurobiology, Institut de Genomique Fonctionnelle, Université Montpellier 1 et 2, CNRS (UMR 5203), F-34094 Montpellier, France, and
- Inserm, U661, F-34094 Montpellier, France
| | - Jamel Chelly
- Department of Genetic and Development, Institut Cochin, Université Paris Descartes, Centre National de la Recherche Scientifique (CNRS) [Unité Mixte de Recherche (UMR) 8104], F-75014 Paris, France
- Inserm, U567, F-75014 Paris, France
| | | | - Pierre Billuart
- Department of Genetic and Development, Institut Cochin, Université Paris Descartes, Centre National de la Recherche Scientifique (CNRS) [Unité Mixte de Recherche (UMR) 8104], F-75014 Paris, France
- Inserm, U567, F-75014 Paris, France
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