Altered Expression of GABAergic Markers in the Forebrain of Young and Adult Engrailed-2 Knockout Mice

Impaired function of GABAergic interneurons, and the subsequent alteration of excitation/inhibition balance, is thought to contribute to autism spectrum disorders (ASD). Altered numbers of GABAergic interneurons and reduced expression of GABA receptors has been detected in the brain of ASD subjects and mouse models of ASD. We previously showed a reduced expression of GABAergic interneuron markers parvalbumin (PV) and somatostatin (SST) in the forebrain of adult mice lacking the Engrailed2 gene (En2-/- mice). Here, we extended this analysis to postnatal day (P) 30 by using in situ hybridization, immunohistochemistry, and quantitative RT-PCR to study the expression of GABAergic interneuron markers in the hippocampus and somatosensory cortex of En2-/- and wild type (WT) mice. In addition, GABA receptor subunit mRNA expression was investigated by quantitative RT-PCR in the same brain regions of P30 and adult En2-/- and WT mice. As observed in adult animals, PV and SST expression was decreased in En2-/- forebrain of P30 mice. The expression of GABA receptor subunits (including the ASD-relevant Gabrb3) was also altered in young and adult En2-/- forebrain. Our results suggest that GABAergic neurotransmission deficits are already evident at P30, confirming that neurodevelopmental defects of GABAergic interneurons occur in the En2 mouse model of ASD.

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GABAergic interneuron to astrocyte signalling: a neglected form of cell communication in the brain

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2013.0609 ◽

2014 ◽

Vol 369 (1654) ◽

pp. 20130609 ◽

Cited By ~ 30

Author(s):

Gabriele Losi ◽

Letizia Mariotti ◽

Giorgio Carmignoto

Keyword(s):

Gaba Receptors ◽

Cortical Neurons ◽

Cell Communication ◽

Brain Network ◽

Gabaergic Interneuron ◽

Gabaergic Interneurons ◽

Gabaergic Neurotransmission ◽

Glutamatergic Neurons ◽

Excitatory Transmission ◽

Novel Therapeutic Strategies

GABAergic interneurons represent a minority of all cortical neurons and yet they efficiently control neural network activities in all brain areas. In parallel, glial cell astrocytes exert a broad control of brain tissue homeostasis and metabolism, modulate synaptic transmission and contribute to brain information processing in a dynamic interaction with neurons that is finely regulated in time and space. As most studies have focused on glutamatergic neurons and excitatory transmission, our knowledge of functional interactions between GABAergic interneurons and astrocytes is largely defective. Here, we critically discuss the currently available literature that hints at a potential relevance of this specific signalling in brain function. Astrocytes can respond to GABA through different mechanisms that include GABA receptors and transporters. GABA-activated astrocytes can, in turn, modulate local neuronal activity by releasing gliotransmitters including glutamate and ATP. In addition, astrocyte activation by different signals can modulate GABAergic neurotransmission. Full clarification of the reciprocal signalling between different GABAergic interneurons and astrocytes will improve our understanding of brain network complexity and has the potential to unveil novel therapeutic strategies for brain disorders.

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Heterogeneity in expression of functional ionotropic glutamate and GABA receptors in astrocytes across brain regions: insights from the thalamus

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2013.0602 ◽

2014 ◽

Vol 369 (1654) ◽

pp. 20130602 ◽

Cited By ~ 33

Author(s):

Simon Höft ◽

Stephanie Griemsmann ◽

Gerald Seifert ◽

Christian Steinhäuser

Keyword(s):

Ampa Receptors ◽

Indirect Effects ◽

Gaba Receptors ◽

Brain Regions ◽

Aminobutyric Acid ◽

Gamma Aminobutyric Acid ◽

Functional Heterogeneity ◽

Rt Pcr ◽

Ventrobasal Thalamus ◽

The Impact

Astrocytes may express ionotropic glutamate and gamma-aminobutyric acid (GABA) receptors, which allow them to sense and to respond to neuronal activity. However, so far the properties of astrocytes have been studied only in a few brain regions. Here, we provide the first detailed receptor analysis of astrocytes in the murine ventrobasal thalamus and compare the properties with those in other regions. To improve voltage-clamp control and avoid indirect effects during drug applications, freshly isolated astrocytes were employed. Two sub-populations of astrocytes were found, expressing or lacking α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. AMPA receptor-bearing astrocytes displayed a lower Kir current density than cells lacking the receptors. In contrast, all cells expressed GABA A receptors. Single-cell RT-PCR was employed to identify the receptor subunits in thalamic astrocytes. Our findings add to the emerging evidence of functional heterogeneity of astrocytes, the impact of which still remains to be defined.

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Function of Oncogene Mycn in Adult Neurogenesis and Oligodendrogenesis

Molecular Neurobiology ◽

10.1007/s12035-021-02584-7 ◽

2021 ◽

Author(s):

Jiao Chen ◽

Zhonghui Guan

Keyword(s):

Subventricular Zone ◽

Brain Regions ◽

Embryonic Brain ◽

Subgranular Zone ◽

Wild Type ◽

Rt Pcr ◽

Proliferating Cells ◽

Adult Mice ◽

Nerve System ◽

Embryonic Brain Development

AbstractHuman MYCN is an oncogene amplified in neuroblastoma and many other tumors. Both human MYCN and mouse Mycn genes are important in embryonic brain development, but their functions in adult healthy nerve system are completely unknown. Here, with Mycn-eGFP mice and quantitative RT-PCR, we found that Mycn was expressed in specific brain regions of young adult mice, including subventricular zone (SVZ), subgranular zone (SGZ), olfactory bulb (OB), subcallosal zone (SCZ), and corpus callosum (CC). With immunohistochemistry (IHC), we found that many Mycn-expressing cells expressed neuroblast marker doublecortin (DCX) and proliferation marker Ki67. With Dcx-creER and Mki67-creER mouse lines, we fate mapped Dcx-expressing neuroblasts and Mki67-expressing proliferation cells, along with deleting Mycn from these cells in adult mice. We found that knocking out Mycn from adult neuroblasts or proliferating cells significantly reduced cells in proliferation in SVZ, SGZ, OB, SCZ, and CC. We also demonstrated that the Mycn-deficient neuroblasts in SGZ matured quicker than wild-type neuroblasts, and that Mycn-deficient proliferating cells were more likely to survive in SVZ, SGZ, OB, SCZ, and CC compared to wild type. Thus, our results demonstrate that, in addition to causing tumors in the nervous system, oncogene Mycn has a crucial function in neurogenesis and oligodendrogenesis in adult healthy brain.

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Electroencephalography in Assessment of Autism Spectrum Disorders: A Review

Frontiers in Psychiatry ◽

10.3389/fpsyt.2021.686021 ◽

2021 ◽

Vol 12 ◽

Author(s):

Maja Milovanovic ◽

Roberto Grujicic

Keyword(s):

Pyramidal Cells ◽

Quantitative Eeg ◽

Brain Regions ◽

Autism Spectrum ◽

Gabaergic Interneuron ◽

Behavioral Impairment ◽

Epileptiform Discharges ◽

Co Morbidity ◽

Spectrum Disorders ◽

Neurochemical Changes

Electroencephalography (EEG) can further out our understanding of autistic spectrum disorders (ASD) neurophysiology. Epilepsy and ASD comorbidity range between 5 and 46%, but its temporal relationship, causal mechanisms and interplay with intellectual disability are still unknown. Epileptiform discharges with or without seizures go as high as 60%, and associate with epileptic encephalopathies, conceptual term suggesting that epileptic activity can lead to cognitive and behavioral impairment beyond the underlying pathology. Seizures and ASD may be the result of similar mechanisms, such as abnormalities in GABAergic fibers or GABA receptor function. Epilepsy and ASD are caused by a number of genetic disorders and variations that induce such dysregulation. Similarly, initial epilepsy may influence synaptic plasticity and cortical connection, predisposing a growing brain to cognitive delays and behavioral abnormalities. The quantitative EEG techniques could be a useful tool in detecting and possibly measuring dysfunctions in specific brain regions and neuronal regulation in ASD. Power spectra analysis reveals a U-shaped pattern of power abnormalities, with excess power in the low and high frequency bands. These might be the consequence of a complicated network of neurochemical changes affecting the inhibitory GABAergic interneurons and their regulation of excitatory activity in pyramidal cells. EEG coherence studies of functional connectivity found general local over-connectivity and long-range under-connectivity between different brain areas. GABAergic interneuron growth and connections are presumably impaired in the prefrontal and temporal cortices in ASD, which is important for excitatory/inhibitory balance. Recent advances in quantitative EEG data analysis and well-known epilepsy ASD co-morbidity consistently indicate a role of aberrant GABAergic transmission that has consequences on neuronal organization and connectivity especially in the frontal cortex.

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Local GABA Receptor Blockade Reveals Hindlimb Responses in the SI Forelimb-Stump Representation of Neonatally Amputated Rats

Journal of Neurophysiology ◽

10.1152/jn.01169.2003 ◽

2004 ◽

Vol 92 (1) ◽

pp. 372-379 ◽

Cited By ~ 5

Author(s):

Charles P. Pluto ◽

Richard D. Lane ◽

Robert W. Rhoades

Keyword(s):

Gaba Receptors ◽

Gaba Receptor ◽

Receptor Blockade ◽

Gabaergic Interneurons ◽

Adult Rats ◽

Unit Recording ◽

Gaba A ◽

Cortical Regions ◽

Stimulation Of

In adult rats that sustained forelimb amputation on the day of birth, there are numerous multi-unit recording sites in the forelimb-stump representation of primary somatosensory cortex (SI) that also respond to cutaneous stimulation of the hindlimb when cortical receptors for GABA are blocked. These normally suppressed hindlimb inputs originate in the SI hindlimb representation and synapse in the dysgranular cortex before exciting SI forelimb-stump neurons. In our previous studies, GABA (A + B) receptor blockade was achieved by topically applying a bicuculline methiodide/saclofen solution (BMI/SAC) to the cortical surface. This treatment blocks receptors throughout SI and does not allow determination of where along the above circuit the GABA-mediated suppression of hindlimb information occurs. In this study, focal injections of BMI/SAC were delivered to three distinct cortical regions that are involved in the hindlimb-to-forelimb-stump pathway. Blocking GABA receptors in the SI hindlimb representation and in the dysgranular cortex was largely ineffective in revealing hindlimb inputs (∼10% of hindlimb inputs were revealed in both cases). In contrast, when the blockade was targeted at forelimb-stump recording sites, >80% of hindlimb inputs were revealed. Thus GABAergic interneurons within the forelimb-stump representation suppress the expression of reorganized hindlimb inputs to the region. A circuit model incorporating these and previous observations is presented and discussed.

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Increased locomotor activity via regulation of GABAergic signalling in foxp2 mutant zebrafish—implications for neurodevelopmental disorders

Translational Psychiatry ◽

10.1038/s41398-021-01651-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Teresa M. Lüffe ◽

Andrea D’Orazio ◽

Moritz Bauer ◽

Zoi Gioga ◽

Victoria Schoeffler ◽

...

Keyword(s):

Locomotor Activity ◽

Neurodevelopmental Disorders ◽

Gaba Receptors ◽

Model Organism ◽

Brain Regions ◽

Autism Spectrum ◽

Loss Of Function ◽

Gaba A ◽

Reverse Translation ◽

Hyperactive Behaviour

AbstractRecent advances in the genetics of neurodevelopmental disorders (NDDs) have identified the transcription factor FOXP2 as one of numerous risk genes, e.g. in autism spectrum disorders (ASD) and attention-deficit/hyperactivity disorder (ADHD). FOXP2 function is suggested to be involved in GABAergic signalling and numerous studies demonstrate that GABAergic function is altered in NDDs, thus disrupting the excitation/inhibition balance. Interestingly, GABAergic signalling components, including glutamate-decarboxylase 1 (Gad1) and GABA receptors, are putative transcriptional targets of FOXP2. However, the specific role of FOXP2 in the pathomechanism of NDDs remains elusive. Here we test the hypothesis that Foxp2 affects behavioural dimensions via GABAergic signalling using zebrafish as model organism. We demonstrate that foxp2 is expressed by a subset of GABAergic neurons located in brain regions involved in motor functions, including the subpallium, posterior tuberculum, thalamus and medulla oblongata. Using CRISPR/Cas9 gene-editing we generated a novel foxp2 zebrafish loss-of-function mutant that exhibits increased locomotor activity. Further, genetic and/or pharmacological disruption of Gad1 or GABA-A receptors causes increased locomotor activity, resembling the phenotype of foxp2 mutants. Application of muscimol, a GABA-A receptor agonist, rescues the hyperactive phenotype induced by the foxp2 loss-of-function. By reverse translation of the therapeutic effect on hyperactive behaviour exerted by methylphenidate, we note that application of methylphenidate evokes different responses in wildtype compared to foxp2 or gad1b loss-of-function animals. Together, our findings support the hypothesis that foxp2 regulates locomotor activity via GABAergic signalling. This provides one targetable mechanism, which may contribute to behavioural phenotypes commonly observed in NDDs.

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Absence of TRIM32 Leads to Reduced GABAergic Interneuron Generation and Autism-like Behaviors in Mice via Suppressing mTOR Signaling

Cerebral Cortex ◽

10.1093/cercor/bhz306 ◽

2019 ◽

Vol 30 (5) ◽

pp. 3240-3258 ◽

Cited By ~ 6

Author(s):

Jian-Wei Zhu ◽

Ming-Ming Zou ◽

Yi-Fei Li ◽

Wen-Jin Chen ◽

Ji-Chuan Liu ◽

...

Keyword(s):

Mammalian Target Of Rapamycin ◽

Autism Spectrum ◽

Mtor Signaling ◽

Gabaergic Interneuron ◽

Gabaergic Interneurons ◽

Protein Signaling ◽

Pathological Mechanism ◽

Lateral Ganglionic Eminence ◽

Model Mouse ◽

Mtor Activity

Abstract Mammalian target of rapamycin (mTOR) signaling plays essential roles in brain development. Hyperactive mTOR is an essential pathological mechanism in autism spectrum disorder (ASD). Here, we show that tripartite motif protein 32 (TRIM32), as a maintainer of mTOR activity through promoting the proteasomal degradation of G protein signaling protein 10 (RGS10), regulates the proliferation of medial/lateral ganglionic eminence (M/LGE) progenitors. Deficiency of TRIM32 results in an impaired generation of GABAergic interneurons and autism-like behaviors in mice, concomitant with an elevated autophagy, which can be rescued by treatment embryonically with 3BDO, an mTOR activator. Transplantation of M/LGE progenitors or treatment postnatally with clonazepam, an agonist of the GABAA receptor, rescues the hyperexcitability and the autistic behaviors of TRIM32−/− mice, indicating a causal contribution of GABAergic disinhibition. Thus, the present study suggests a novel mechanism for ASD etiology in that TRIM32 deficiency-caused hypoactive mTOR, which is linked to an elevated autophagy, leads to autism-like behaviors via impairing generation of GABAergic interneurons. TRIM32−/− mouse is a novel autism model mouse.

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GABAergic cell loss in mice lacking autism-associated geneSema6A

10.1101/663419 ◽

2019 ◽

Author(s):

Karlie Menzel ◽

Gábor Szabó ◽

Yuchio Yanagawa ◽

Turhan Cocksaygan ◽

Céline Plachez

Keyword(s):

Brain Development ◽

Neuronal Networks ◽

Cell Loss ◽

Cell Number ◽

Autism Spectrum ◽

Mutant Mice ◽

Gabaergic Interneuron ◽

Gabaergic Interneurons ◽

Neuronal Connectivity ◽

Histological Techniques

AbstractBackgroundDuring brain development, a multitude of neuronal networks form as neurons find their correct position within the brain and send out axons to synapse onto specific targets. Altered neuronal connectivity within these complex networks has been reported in Autism Spectrum Disorder (ASD), leading to alterations in brain function and multisensory integration. Semaphorins (also referred to as Semas), a large protein family of about 30 members, have been shown to play an important role in neuronal circuit formation and have been implicated in the etiology of ASD. The purpose of the current study is to investigate howSema6Amutation affects neuronal connectivity in ASD. SinceSema6Ais involved in cell migration, we hypothesized that during brain development the migration of GABAergic interneurons is affected by the loss ofSema6Agene, leading to alterations in Excitatory/Inhibitory (E/I) balance.MethodsSema6Atransgenic mice were crossed with either GAD65-GFP mice or GAD67-GFP mice to allow for both a reliable and robust staining of the GABAergic interneuron population within theSema6Amouse line. Using histological techniques we studies the expression of interneurons subtypes in the Sema6A mutant mice.ResultsAnalysis ofSema6Amutant mice crossed with either GAD65-GFP or GAD67-GFP knock-in mice revealed a reduced number of GABAergic interneurons in the primary somatosensory cortex, hippocampus, and reticular thalamic nucleus (RTN) in adultSema6Amutant mice. This reduction in cell number appeared to be targeted to the Parvalbumin (PV) interneuron cell population since neither the Calretinin nor the Calbindin expressing interneurons were affected by theSema6Amutation.LimitationsAlthough the use of animal models has been crucial for understanding the biological basis of autism, the complexity of the human brain can never truly be replicated by these models.ConclusionsTaken together, these findings suggest thatSema6Agene loss affects only the fast spiking-PV population and reveal the importance of an axon guidance molecule in the formation of GABAergic neuronal networks and provide insight into the molecular pathways that may lead to altered neuronal connectivity and E/I imbalance in ASD.

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The gamma-Protocadherins regulate the survival of GABAergic interneurons during developmentally-regulated cell death

10.1101/2020.01.15.908087 ◽

2020 ◽

Cited By ~ 2

Author(s):

Candace H. Carriere ◽

Anson D. Sing ◽

Wendy Xueyi Wang ◽

Brian E. Jones ◽

Yohan Yee ◽

...

Keyword(s):

Cell Death ◽

Molecular Mechanisms ◽

Brain Regions ◽

Inhibitory Neurons ◽

Motor Deficits ◽

Gabaergic Interneuron ◽

Gabaergic Interneurons ◽

Developmentally Regulated ◽

Regulated Cell Death ◽

Inhibitory Networks

SUMMARYInhibitory interneurons integrate into developing circuits in specific ratios and distributions. In the cortex, the formation of inhibitory networks occurs concurrently with the apoptotic elimination of a third of GABAergic interneurons. The molecular mechanisms that select GABAergic interneurons to survive or die are unknown. Here we report that the clustered Protocadherins regulate GABAergic cell survival in the developing brain. Deletion of the Pcdh-gamma genes (Pcdhgs) from GABAergic neurons in mice causes a severe loss of inhibitory neurons in multiple brain regions and results in motor deficits and seizure activities. By focusing on the neocortex and cerebellar cortex, we demonstrate that GABAergic interneuron loss results from elevated apoptosis during the postnatal wave of Bax-dependent programmed cell death. Pro-survival AKT signals are reduced in Pcdhg-deficient interneurons, diminishing the intrinsic capacity of interneurons to compete and incorporate into developing networks. We propose that the Pcdhgs mediate selective GABAergic interneuron survival to contribute to the formation of balanced inhibitory networks.

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