scholarly journals Imbalance of Neocortical Excitation and Inhibition and Altered UP States Reflect Network Hyperexcitability in the Mouse Model of Fragile X Syndrome

2008 ◽  
Vol 100 (5) ◽  
pp. 2615-2626 ◽  
Author(s):  
Jay R. Gibson ◽  
Aundrea F. Bartley ◽  
Seth A. Hays ◽  
Kimberly M. Huber
Keyword(s):  
Mouse Model ◽  
Fragile X Syndrome ◽  
Barrel Cortex ◽  
Feedback Inhibition ◽  
Fragile X ◽  
Inhibitory Neurons ◽  
Neurological Deficits ◽  
Membrane Excitability ◽  
Up States ◽  
Layer 4

Despite the pronounced neurological deficits associated with mental retardation and autism, it is unknown if altered neocortical circuit function occurs in these prevalent disorders. Here we demonstrate specific alterations in local synaptic connections, membrane excitability, and circuit activity of defined neuron types in sensory neocortex of the mouse model of Fragile X Syndrome—the Fmr1 knockout (KO). Overall, these alterations result in hyperexcitability of neocortical circuits in the Fmr1 KO. Specifically, we observe a substantial deficit in local excitatory drive (∼50%) targeting fast-spiking (FS) inhibitory neurons in layer 4 of somatosensory, barrel cortex. This persists until at least 4 wk of age suggesting it may be permanent. In contrast, monosynaptic GABAergic synaptic transmission was unaffected. Overall, these changes indicate that local feedback inhibition in neocortical layer 4 is severely impaired in the Fmr1 KO mouse. An increase in the intrinsic membrane excitability of excitatory neurons may further contribute to hyperexcitability of cortical networks. In support of this idea, persistent neocortical circuit activity, or UP states, elicited by thalamic stimulation was longer in duration in the Fmr1 KO mouse. In addition, network inhibition during the UP state was less synchronous, including a 14% decrease in synchrony in the gamma frequency range (30–80 Hz). These circuit changes may be involved in sensory stimulus hypersensitivity, epilepsy, and cognitive impairment associated with Fragile X and autism.

scholarly journals Multifaceted Changes in Synaptic Composition and Astrocytic Involvement in a Mouse Model of Fragile X Syndrome

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Anish K. Simhal ◽  
Yi Zuo ◽  
Marc M. Perez ◽  
Daniel V. Madison ◽  
Guillermo Sapiro ◽  
...  
Keyword(s):  
Mouse Model ◽  
Fragile X Syndrome ◽  
Knockout Mouse ◽  
Fragile X ◽  
Inhibitory Synapses ◽  
Excitatory Synapses ◽  
Array Tomography ◽  
Layer 4 ◽  
Fmr1 Knockout Mouse ◽  
Circuit Function

Abstract Fragile X Syndrome (FXS), a common inheritable form of intellectual disability, is known to alter neocortical circuits. However, its impact on the diverse synapse types comprising these circuits, or on the involvement of astrocytes, is not well known. We used immunofluorescent array tomography to quantify different synaptic populations and their association with astrocytes in layers 1 through 4 of the adult somatosensory cortex of a FXS mouse model, the FMR1 knockout mouse. The collected multi-channel data contained approximately 1.6 million synapses which were analyzed using a probabilistic synapse detector. Our study reveals complex, synapse-type and layer specific changes in the neocortical circuitry of FMR1 knockout mice. We report an increase of small glutamatergic VGluT1 synapses in layer 4 accompanied by a decrease in large VGluT1 synapses in layers 1 and 4. VGluT2 synapses show a rather consistent decrease in density in layers 1 and 2/3. In all layers, we observe the loss of large inhibitory synapses. Lastly, astrocytic association of excitatory synapses decreases. The ability to dissect the circuit deficits by synapse type and astrocytic involvement will be crucial for understanding how these changes affect circuit function, and ultimately defining targets for therapeutic intervention.

scholarly journals Restoration of FMRP expression in adult V1 neurons rescues visual deficits in a mouse model of fragile X syndrome

2021 ◽  
Author(s):  
Chaojuan Yang ◽  
Yonglu Tian ◽  
Feng Su ◽  
Yangzhen Wang ◽  
Mengna Liu ◽  
...  
Keyword(s):  
Mouse Model ◽  
Fragile X Syndrome ◽  
Visual Processing ◽  
Fragile X ◽  
Autism Spectrum ◽  
Inhibitory Neurons ◽  
Local Network ◽  
V1 Neurons ◽  
Processing Deficits

AbstractMany people affected by fragile X syndrome (FXS) and autism spectrum disorders have sensory processing deficits, such as hypersensitivity to auditory, tactile, and visual stimuli. Like FXS in humans, loss of Fmr1 in rodents also cause sensory, behavioral, and cognitive deficits. However, the neural mechanisms underlying sensory impairment, especially vision impairment, remain unclear. It remains elusive whether the visual processing deficits originate from corrupted inputs, impaired perception in the primary sensory cortex, or altered integration in the higher cortex, and there is no effective treatment. In this study, we used a genetic knockout mouse model (Fmr1KO), in vivo imaging, and behavioral measurements to show that the loss of Fmr1 impaired signal processing in the primary visual cortex (V1). Specifically, Fmr1KO mice showed enhanced responses to low-intensity stimuli but normal responses to high-intensity stimuli. This abnormality was accompanied by enhancements in local network connectivity in V1 microcircuits and increased dendritic complexity of V1 neurons. These effects were ameliorated by the acute application of GABAA receptor activators, which enhanced the activity of inhibitory neurons, or by reintroducing Fmr1 gene expression in knockout V1 neurons in both juvenile and young-adult mice. Overall, V1 plays an important role in the visual abnormalities of Fmr1KO mice and it could be possible to rescue the sensory disturbances in developed FXS and autism patients.

scholarly journals Multifaceted Changes in Synaptic Composition and Astrocytic Involvement in a Mouse Model of Fragile X Syndrome

2019 ◽  
Author(s):  
Anish K. Simhal ◽  
Yi Zuo ◽  
Marc M. Perez ◽  
Daniel V. Madison ◽  
Guillermo Sapiro ◽  
...  
Keyword(s):  
Mouse Model ◽  
Fragile X Syndrome ◽  
Knockout Mouse ◽  
Fragile X ◽  
Glutamatergic Synapses ◽  
Array Tomography ◽  
Layer 4 ◽  
Gabaergic Synapses ◽  
Fmr1 Knockout Mouse ◽  
Circuit Function

ABSTRACTFragile X Syndrome (FXS), a common inheritable form of intellectual disability, is known to alter neocortical circuits. However, its impact on the diverse synapse types comprising these circuits, or on the involvement of astrocytes, is not well known. We used immunofluorescent array tomography to quantify different synaptic populations and their association with astrocytes in layers 1 through 4 of the adult somatosensory cortex of a FXS mouse model, the FMR1 knockout mouse. The collected multi-channel data contained approximately 1.6 million synapses which were analyzed using a probabilistic synapse detector. Our study reveals complex, synapse-type and layer specific changes in the neocortical circuitry of FMR1 knockout mice. In layers 1 and 2/3, there is a significant decrease in the density of excitatory glutamatergic synapses, both VGluT1 and VGluT2 type, and their association with astrocytes, while the changes in inhibitory GABAergic synapses are less pronounced. Meanwhile in layer 4, there is a significant increase in the density of small VGluT1 synapses, with no changes in the astrocytic association of synapses. The ability to dissect the circuit deficits by synapse type and astrocytic involvement, will be crucial for understanding how these changes affect circuit function, and ultimately define targets for therapeutic intervention.

scholarly journals Loss of Calretinin in L5a impairs the formation of the barrel cortex leading to abnormal whisker-mediated behaviors

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Mingzhao Su ◽  
Junhua Liu ◽  
Baocong Yu ◽  
Kaixing Zhou ◽  
Congli Sun ◽  
...  
Keyword(s):  
Information Integration ◽  
Pyramidal Neurons ◽  
Barrel Cortex ◽  
Sensory Information ◽  
Membrane Excitability ◽  
Novelty Preference ◽  
Layer 4 ◽  
Dendritic Complexity ◽  
Cortex System

AbstractThe rodent whisker-barrel cortex system has been established as an ideal model for studying sensory information integration. The barrel cortex consists of barrel and septa columns that receive information input from the lemniscal and paralemniscal pathways, respectively. Layer 5a is involved in both barrel and septa circuits and play a key role in information integration. However, the role of layer 5a in the development of the barrel cortex remains unclear. Previously, we found that calretinin is dynamically expressed in layer 5a. In this study, we analyzed calretinin KO mice and found that the dendritic complexity and length of layer 5a pyramidal neurons were significantly decreased after calretinin ablation. The membrane excitability and excitatory synaptic transmission of layer 5a neurons were increased. Consequently, the organization of the barrels was impaired. Moreover, layer 4 spiny stellate cells were not able to properly gather, leading to abnormal formation of barrel walls as the ratio of barrel/septum size obviously decreased. Calretinin KO mice exhibited deficits in exploratory and whisker-associated tactile behaviors as well as social novelty preference. Our study expands our knowledge of layer 5a pyramidal neurons in the formation of barrel walls and deepens the understanding of the development of the whisker-barrel cortex system.

scholarly journals Impaired Dendritic Expression and Plasticity of h-Channels in the fmr1−/y Mouse Model of Fragile X Syndrome

Cell Reports ◽  
2012 ◽  
Vol 1 (3) ◽  
pp. 225-233 ◽  
Author(s):  
Darrin H. Brager ◽  
Arvin R. Akhavan ◽  
Daniel Johnston
Keyword(s):  
Mouse Model ◽  
Fragile X Syndrome ◽  
Fragile X ◽  
H Channels

Mouse model of fragile X syndrome: Behavioral and hormonal response to stressors.

2009 ◽  
Vol 123 (3) ◽  
pp. 677-686 ◽  
Author(s):  
Darci M. Nielsen ◽  
Jeffrey J. Evans ◽  
William J. Derber ◽  
Kenzie A. Johnston ◽  
Mark L. Laudenslager ◽  
...  
Keyword(s):  
Mouse Model ◽  
Fragile X Syndrome ◽  
Fragile X ◽  
Hormonal Response

scholarly journals The PDE10A Inhibitor TAK-063 Reverses Sound-Evoked EEG Abnormalities in a Mouse Model of Fragile X Syndrome

2021 ◽  
Author(s):  
Carrie R. Jonak ◽  
Manbir S. Sandhu ◽  
Samantha A. Assad ◽  
Jacqueline A. Barbosa ◽  
Mahindra Makhija ◽  
...  
Keyword(s):  
Mouse Model ◽  
Fragile X Syndrome ◽  
Fragile X ◽  
Eeg Abnormalities
Sign in / Sign up

Export Citation Format

Share Document