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Booker SA, Simões de Oliveira L, Anstey NJ, Kozic Z, Dando OR, Jackson AD, Baxter PS, Isom LL, Sherman DL, Hardingham GE, Brophy PJ, Wyllie DJ, Kind PC. Input-Output Relationship of CA1 Pyramidal Neurons Reveals Intact Homeostatic Mechanisms in a Mouse Model of Fragile X Syndrome. Cell Rep 2020; 32:107988. [PMID: 32783927 PMCID: PMC7435362 DOI: 10.1016/j.celrep.2020.107988] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 04/01/2020] [Accepted: 07/14/2020] [Indexed: 12/13/2022] Open
Abstract
Cellular hyperexcitability is a salient feature of fragile X syndrome animal models. The cellular basis of hyperexcitability and how it responds to changing activity states is not fully understood. Here, we show increased axon initial segment length in CA1 of the Fmr1-/y mouse hippocampus, with increased cellular excitability. This change in length does not result from reduced AIS plasticity, as prolonged depolarization induces changes in AIS length independent of genotype. However, depolarization does reduce cellular excitability, the magnitude of which is greater in Fmr1-/y neurons. Finally, we observe reduced functional inputs from the entorhinal cortex, with no genotypic difference in the firing rates of CA1 pyramidal neurons. This suggests that AIS-dependent hyperexcitability in Fmr1-/y mice may result from adaptive or homeostatic regulation induced by reduced functional synaptic connectivity. Thus, while AIS length and intrinsic excitability contribute to cellular hyperexcitability, they may reflect a homeostatic mechanism for reduced synaptic input onto CA1 neurons.
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Affiliation(s)
- Sam A. Booker
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK,Corresponding author
| | - Laura Simões de Oliveira
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK
| | - Natasha J. Anstey
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK,Centre for Brain Development and Repair, InStem, GKVK Campus, Bangalore 560065, India
| | - Zrinko Kozic
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK
| | - Owen R. Dando
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK,Dementia Research Institute, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK,Centre for Brain Development and Repair, InStem, GKVK Campus, Bangalore 560065, India
| | - Adam D. Jackson
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK,Centre for Brain Development and Repair, InStem, GKVK Campus, Bangalore 560065, India
| | - Paul S. Baxter
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Dementia Research Institute, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK
| | - Lori L. Isom
- Department of Pharmacology, University of Michigan Medical School, Ann Arbor, MI 48109-5632, USA
| | - Diane L. Sherman
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - Giles E. Hardingham
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Dementia Research Institute, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK
| | - Peter J. Brophy
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
| | - David J.A. Wyllie
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK,Centre for Brain Development and Repair, InStem, GKVK Campus, Bangalore 560065, India
| | - Peter C. Kind
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK,Simons Initiative for the Developing Brain, University of Edinburgh, Edinburgh, UK,Patrick Wild Centre for Autism Research, University of Edinburgh, Edinburgh, UK,Centre for Brain Development and Repair, InStem, GKVK Campus, Bangalore 560065, India,Corresponding author
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