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Foxp2 loss of function increases striatal direct pathway inhibition via increased GABA release. Brain Struct Funct 2018; 223:4211-4226. [PMID: 30187194 PMCID: PMC6267273 DOI: 10.1007/s00429-018-1746-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 08/31/2018] [Indexed: 12/19/2022]
Abstract
Heterozygous mutations of the Forkhead-box protein 2 (FOXP2) gene in humans cause childhood apraxia of speech. Loss of Foxp2 in mice is known to affect striatal development and impair motor skills. However, it is unknown if striatal excitatory/inhibitory balance is affected during development and if the imbalance persists into adulthood. We investigated the effect of reduced Foxp2 expression, via a loss-of-function mutation, on striatal medium spiny neurons (MSNs). Our data show that heterozygous loss of Foxp2 decreases excitatory (AMPA receptor-mediated) and increases inhibitory (GABA receptor-mediated) currents in D1 dopamine receptor positive MSNs of juvenile and adult mice. Furthermore, reduced Foxp2 expression increases GAD67 expression, leading to both increased presynaptic content and release of GABA. Finally, pharmacological blockade of inhibitory activity in vivo partially rescues motor skill learning deficits in heterozygous Foxp2 mice. Our results suggest a novel role for Foxp2 in the regulation of striatal direct pathway activity through managing inhibitory drive.
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Buren C, Tu G, Parsons MP, Sepers MD, Raymond LA. Influence of cortical synaptic input on striatal neuronal dendritic arborization and sensitivity to excitotoxicity in corticostriatal coculture. J Neurophysiol 2016; 116:380-90. [PMID: 27121581 DOI: 10.1152/jn.00933.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 04/25/2016] [Indexed: 11/22/2022] Open
Abstract
Corticostriatal cocultures are utilized to recapitulate the cortex-striatum connection in vitro as a convenient model to investigate the development, function, and regulation of synapses formed between cortical and striatal neurons. However, optimization of this dissociated neuronal system to more closely reproduce in vivo circuits has not yet been explored. We studied the effect of varying the plating ratio of cortical to striatal neurons on striatal spiny projection neuron (SPN) characteristics in primary neuronal cocultures. Despite the large difference in cortical-striatal neuron ratio (1:1 vs. 1:3) at day of plating, by 18 days in vitro the difference became modest (∼25% lower cortical-striatal neuron ratio in 1:3 cocultures) and the neuronal density was lower in the 1:3 cocultures, indicating enhanced loss of striatal SPNs. Comparing SPNs in cocultures plated at a 1:1 vs. 1:3 ratio, we found that resting membrane potential, input resistance, current injection-induced action potential firing rates, and input-output curves were similar in the two conditions. However, SPNs in the cocultures plated at the lower cortical ratio exhibited reduced membrane capacitance along with significantly shorter total dendritic length, decreased dendritic complexity, and fewer excitatory synapses, consistent with their trend toward reduced miniature excitatory postsynaptic current frequency. Strikingly, the proportion of NMDA receptors found extrasynaptically in recordings from SPNs was significantly higher in the less cortical coculture. Consistently, SPNs in cocultures with reduced cortical input showed decreased basal pro-survival signaling through cAMP response element binding protein and enhanced sensitivity to NMDA-induced apoptosis. Altogether, our study indicates that abundance of cortical input regulates SPN dendritic arborization and survival/death signaling.
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Affiliation(s)
- Caodu Buren
- Graduate Program in Neuroscience, University of British Columbia, Vancouver, Canada; Department of Psychiatry and Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, Canada; and
| | - Gaqi Tu
- School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China
| | - Matthew P Parsons
- Department of Psychiatry and Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, Canada; and
| | - Marja D Sepers
- Department of Psychiatry and Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, Canada; and
| | - Lynn A Raymond
- Department of Psychiatry and Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, Canada; and
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Differential changes in thalamic and cortical excitatory synapses onto striatal spiny projection neurons in a Huntington disease mouse model. Neurobiol Dis 2015; 86:62-74. [PMID: 26621114 DOI: 10.1016/j.nbd.2015.11.020] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Revised: 11/09/2015] [Accepted: 11/23/2015] [Indexed: 01/18/2023] Open
Abstract
Huntington disease (HD), a neurodegenerative disorder caused by CAG repeat expansion in the gene encoding huntingtin, predominantly affects the striatum, especially the spiny projection neurons (SPN). The striatum receives excitatory input from cortex and thalamus, and the role of the former has been well-studied in HD. Here, we report that mutated huntingtin alters function of thalamostriatal connections. We used a novel thalamostriatal (T-S) coculture and an established corticostriatal (C-S) coculture, generated from YAC128 HD and WT (FVB/NJ background strain) mice, to investigate excitatory neurotransmission onto striatal SPN. SPN in T-S coculture from WT mice showed similar mini-excitatory postsynaptic current (mEPSC) frequency and amplitude as in C-S coculture; however, both the frequency and amplitude were significantly reduced in YAC128 T-S coculture. Further investigation in T-S coculture showed similar excitatory synapse density in WT and YAC128 SPN dendrites by immunostaining, suggesting changes in total dendritic length or probability of release as possible explanations for mEPSC frequency changes. Synaptic N-methyl-D-aspartate receptor (NMDAR) current was similar, but extrasynaptic current, associated with cell death signaling, was enhanced in YAC128 SPN in T-S coculture. Employing optical stimulation of cortical versus thalamic afferents and recording from striatal SPN in brain slice, we found increased glutamate release probability and reduced AMPAR/NMDAR current ratios in thalamostriatal synapses, most prominently in YAC128. Enhanced extrasynaptic NMDAR current in YAC128 SPN was apparent with both cortical and thalamic stimulation. We conclude that thalamic afferents to the striatum are affected early, prior to an overt HD phenotype; however, changes in NMDAR localization in SPN are independent of the source of glutamatergic input.
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Arama J, Abitbol K, Goffin D, Fuchs C, Sihra TS, Thomson AM, Jovanovic JN. GABAA receptor activity shapes the formation of inhibitory synapses between developing medium spiny neurons. Front Cell Neurosci 2015; 9:290. [PMID: 26300728 PMCID: PMC4526800 DOI: 10.3389/fncel.2015.00290] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Accepted: 07/15/2015] [Indexed: 11/30/2022] Open
Abstract
Basal ganglia play an essential role in motor coordination and cognitive functions. The GABAergic medium spiny neurons (MSNs) account for ~95% of all the neurons in this brain region. Central to the normal functioning of MSNs is integration of synaptic activity arriving from the glutamatergic corticostriatal and thalamostriatal afferents, with synaptic inhibition mediated by local interneurons and MSN axon collaterals. In this study we have investigated how the specific types of GABAergic synapses between the MSNs develop over time, and how the activity of GABAA receptors (GABAARs) influences this development. Isolated embryonic (E17) MSNs form a homogenous population in vitro and display spontaneous synaptic activity and functional properties similar to their in vivo counterparts. In dual whole-cell recordings of synaptically connected pairs of MSNs, action potential (AP)-activated synaptic events were detected between 7 and 14 days in vitro (DIV), which coincided with the shift in GABAAR operation from depolarization to hyperpolarization, as detected indirectly by intracellular calcium imaging. In parallel, the predominant subtypes of inhibitory synapses, which innervate dendrites of MSNs and contain GABAAR α1 or α2 subunits, underwent distinct changes in the size of postsynaptic clusters, with α1 becoming smaller and α2 larger over time, while both the percentage and the size of mixed α1/α2-postsynaptic clusters were increased. When activity of GABAARs was under chronic blockade between 4–7 DIV, the structural properties of these synapses remained unchanged. In contrast, chronic inhibition of GABAARs between 7–14 DIV led to reduction in size of α1- and α1/α2-postsynaptic clusters and a concomitant increase in number and size of α2-postsynaptic clusters. Thus, the main subtypes of GABAergic synapses formed by MSNs are regulated by GABAAR activity, but in opposite directions, and thus appear to be driven by different molecular mechanisms.
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Affiliation(s)
- Jessica Arama
- UCL School of Pharmacy, University College London London, UK
| | - Karine Abitbol
- UCL School of Pharmacy, University College London London, UK
| | - Darren Goffin
- UCL School of Pharmacy, University College London London, UK
| | - Celine Fuchs
- UCL School of Pharmacy, University College London London, UK
| | - Talvinder S Sihra
- Neuroscience, Physiology and Pharmacology, UCL Division of Biosciences, University College London London, UK
| | - Alex M Thomson
- UCL School of Pharmacy, University College London London, UK
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Brown LE, Fuchs C, Nicholson MW, Stephenson FA, Thomson AM, Jovanovic JN. Inhibitory synapse formation in a co-culture model incorporating GABAergic medium spiny neurons and HEK293 cells stably expressing GABAA receptors. J Vis Exp 2014:e52115. [PMID: 25489750 PMCID: PMC4354098 DOI: 10.3791/52115] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Inhibitory neurons act in the central nervous system to regulate the dynamics and spatio-temporal co-ordination of neuronal networks. GABA (γ-aminobutyric acid) is the predominant inhibitory neurotransmitter in the brain. It is released from the presynaptic terminals of inhibitory neurons within highly specialized intercellular junctions known as synapses, where it binds to GABAA receptors (GABAARs) present at the plasma membrane of the synapse-receiving, postsynaptic neurons. Activation of these GABA-gated ion channels leads to influx of chloride resulting in postsynaptic potential changes that decrease the probability that these neurons will generate action potentials. During development, diverse types of inhibitory neurons with distinct morphological, electrophysiological and neurochemical characteristics have the ability to recognize their target neurons and form synapses which incorporate specific GABAARs subtypes. This principle of selective innervation of neuronal targets raises the question as to how the appropriate synaptic partners identify each other. To elucidate the underlying molecular mechanisms, a novel in vitro co-culture model system was established, in which medium spiny GABAergic neurons, a highly homogenous population of neurons isolated from the embryonic striatum, were cultured with stably transfected HEK293 cell lines that express different GABAAR subtypes. Synapses form rapidly, efficiently and selectively in this system, and are easily accessible for quantification. Our results indicate that various GABAAR subtypes differ in their ability to promote synapse formation, suggesting that this reduced in vitro model system can be used to reproduce, at least in part, the in vivo conditions required for the recognition of the appropriate synaptic partners and formation of specific synapses. Here the protocols for culturing the medium spiny neurons and generating HEK293 cells lines expressing GABAARs are first described, followed by detailed instructions on how to combine these two cell types in co-culture and analyze the formation of synaptic contacts.
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Affiliation(s)
| | - Celine Fuchs
- UCL School of Pharmacy, University College London
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Victor MB, Richner M, Hermanstyne TO, Ransdell JL, Sobieski C, Deng PY, Klyachko VA, Nerbonne JM, Yoo AS. Generation of human striatal neurons by microRNA-dependent direct conversion of fibroblasts. Neuron 2014; 84:311-23. [PMID: 25374357 DOI: 10.1016/j.neuron.2014.10.016] [Citation(s) in RCA: 217] [Impact Index Per Article: 21.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/06/2014] [Indexed: 12/11/2022]
Abstract
The promise of using reprogrammed human neurons for disease modeling and regenerative medicine relies on the ability to induce patient-derived neurons with high efficiency and subtype specificity. We have previously shown that ectopic expression of brain-enriched microRNAs (miRNAs), miR-9/9* and miR-124 (miR-9/9*-124), promoted direct conversion of human fibroblasts into neurons. Here we show that coexpression of miR-9/9*-124 with transcription factors enriched in the developing striatum, BCL11B (also known as CTIP2), DLX1, DLX2, and MYT1L, can guide the conversion of human postnatal and adult fibroblasts into an enriched population of neurons analogous to striatal medium spiny neurons (MSNs). When transplanted in the mouse brain, the reprogrammed human cells persisted in situ for over 6 months, exhibited membrane properties equivalent to native MSNs, and extended projections to the anatomical targets of MSNs. These findings highlight the potential of exploiting the synergism between miR-9/9*-124 and transcription factors to generate specific neuronal subtypes.
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Affiliation(s)
- Matheus B Victor
- Department of Developmental Biology, Washington University School of Medicine, Saint Louis, MO 63110, USA; Program in Neuroscience, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Michelle Richner
- Department of Developmental Biology, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Tracey O Hermanstyne
- Department of Developmental Biology, Washington University School of Medicine, Saint Louis, MO 63110, USA; Center for Cardiovascular Research, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Joseph L Ransdell
- Department of Developmental Biology, Washington University School of Medicine, Saint Louis, MO 63110, USA; Center for Cardiovascular Research, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Courtney Sobieski
- Program in Neuroscience, Washington University School of Medicine, Saint Louis, MO 63110, USA; Department of Psychiatry, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Pan-Yue Deng
- Departments of Biomedical Engineering and Cell Biology and Physiology, CIMED, Washington University, Saint Louis, MO 63110, USA
| | - Vitaly A Klyachko
- Departments of Biomedical Engineering and Cell Biology and Physiology, CIMED, Washington University, Saint Louis, MO 63110, USA
| | - Jeanne M Nerbonne
- Department of Developmental Biology, Washington University School of Medicine, Saint Louis, MO 63110, USA; Center for Cardiovascular Research, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Andrew S Yoo
- Department of Developmental Biology, Washington University School of Medicine, Saint Louis, MO 63110, USA.
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