Excitatory/Inhibitory Balance and Circuit Homeostasis in Autism Spectrum Disorders

Nelson, Sacha B.; Valakh, Vera

doi:10.1016/j.neuron.2015.07.033

Cited by 899 publications

(855 citation statements)

References 205 publications

(206 reference statements)

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“…Our results demonstrate that rhIGF1 treatment in MeCP2 mutant mice improves not only PV + responses but also cell-specific and circuit-dependent responses of pyramidal neurons, likely via multiple mechanisms that jointly target inhibition and excitation. More broadly, such approaches may be crucial for addressing neurodevelopmental disorders where homeostatic and compensatory regulation accompanies constitutive loss or mutant protein expression (106).…”

Section: Discussionmentioning

confidence: 99%

Jointly reduced inhibition and excitation underlies circuit-wide changes in cortical processing in Rett syndrome

Banerjee

Rikhye

Breton-Provencher

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

159

202

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Rett syndrome (RTT) arises from loss-of-function mutations in methyl-CpG binding protein 2 gene (Mecp2), but fundamental aspects of its physiological mechanisms are unresolved. Here, by whole-cell recording of synaptic responses in MeCP2 mutant mice in vivo, we show that visually driven excitatory and inhibitory conductances are both reduced in cortical pyramidal neurons. The excitation-to-inhibition (E/I) ratio is increased in amplitude and prolonged in time course. These changes predict circuit-wide reductions in response reliability and selectivity of pyramidal neurons to visual stimuli, as confirmed by two-photon imaging. and increases KCC2 expression to normalize the KCC2/NKCC1 ratio. Thus, loss of MeCP2 in the brain alters both excitation and inhibition in brain circuits via multiple mechanisms. Loss of MeCP2 from a specific interneuron subtype contributes crucially to the cell-specific and circuit-wide deficits of RTT. The joint restoration of inhibition and excitation in cortical circuits is pivotal for functionally correcting the disorder.MeCP2 | E/I balance | parvalbumin neurons | IGF1 | chloride transporters S ynaptic excitation (E) and inhibition (I), along with the neuronal balance of excitation and inhibition (E/I), is key to the function of brain circuits, and is often disrupted in neurodevelopmental disorders, including autism spectrum disorders (ASDs) (1-3). Rett syndrome (RTT) is a severe neurodevelopmental and adult disorder that arises from sporadic loss-of-function mutations in the X-linked (Xq28) methyl-CpG binding protein 2 gene (Mecp2) encoding the protein MeCP2 (4-7). MeCP2 is a critical regulator of brain development and adult neural function (8), and arrested brain maturation due to synaptic dysfunction is one of the hallmarks of RTT (3). However, the effects of MeCP2 on excitatory and inhibitory synaptic mechanisms in vivo, and on neuronal and circuit function underlying RTT pathophysiology, are unknown.MeCP2 is ubiquitously expressed in multiple cell types and subregions of the brain (4, 6, 9), including inhibitory interneurons, and has cell-autonomous as well as non-cell-autonomous effects (10); thus, it has been particularly challenging to identify its role in cell-specific brain circuits. Anatomically diverse inhibitory interneuron subtypes with distinct physiological signatures influence different aspects of neocortical function and behavior (11,12). Soma-targeting parvalbumin-expressing (PV + ) and dendritetargeting somatostatin-expressing (SOM + ) interneurons are the two major nonoverlapping populations of interneurons in mice that target cortical pyramidal neurons (13). Inhibition by PV + and SOM + neurons powerfully influences neuronal responses and circuit computations in visual cortex (14-17). Deletion of MeCP2 from all forebrain GABAergic interneurons recapitulates key aspects of RTT (18), demonstrating that altered inhibitory function is an important facet of RTT pathophysiology. Indeed, a major phenotype of MeCP2 reduction in individuals with RTT and in mouse models is ...

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Section: Discussionmentioning

confidence: 99%

Jointly reduced inhibition and excitation underlies circuit-wide changes in cortical processing in Rett syndrome

Banerjee

Rikhye

Breton-Provencher

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

159

202

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“…Most likely this is due to the fact that in patients with RTT, as in other disorders related to autism (ASD), the presence of the mutation may affect different brain regions or different neuronal types, while in other neurons the genotype is normal; even in the same area of the brain, different mixtures of excitation and inhibition can coexist, leading to an imbalance in the relationship between neuronal excitation and inhibition that would affect the expression of many genes, including Brain-Derived Nerve Factor (BDNF), that depend on neuronal activity. In this situation, the functional homeostasis of the brain would be affected (see [44] for a detailed review). Therefore, in RTT, as in other ASD, any phenotype could be secondary to the development of other compensatory adaptive mechanisms, which in fact are rather maladaptive, in terms of brain plasticity, because they would contribute to the appearance of the symptoms in each case.…”

Section: Discussionmentioning

confidence: 99%

Rett Syndrome: Treatment with IGF-I, Melatonin, Blackcurrant Extracts, and Rehabilitation

Devesa¹,

Devesa²,

Carrillo³

et al. 2018

Reports

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Abstract:(1) This study describes the good evolution of a 6-year-old girl genetically diagnosed (R106X) with Rett syndrome (RTT), after having been treated with IGF-I, melatonin (MT), blackcurrant extracts (BC) and rehabilitated for 6 months. (2) The patient stopped normal development in the first year of age. The patient showed short stature and weight and fulfilled the main criteria for typical RTT. Despite her young age, there was pubic hair (Tanner II), very high plasma testosterone, and low levels of plasma gonadotrophins. There were no adrenal enzymatic deficits, and abdominal ultrasound studies were normal. The treatment consisted of IGF-I (0.04 mg/kg/day, 5 days/week, subcutaneous (sc)) for 3 months and then 15 days of rest, MT (50 mg/day, orally, without interruption) and neurorehabilitation. A new blood test, after 3 months of treatment, was absolutely normal and the pubic hair disappeared (Tanner I). Then, a new treatment was started with IGF-I, MT, and BC for another 3 months. In this period, the degree of pubertal development increased to Tanner III (pubic level), without a known cause. (3) The treatment followed led to clear improvements in most of the initial abnormalities, perhaps due to the neurotrophic effect of IGF-I, the antioxidant effects of MT and BC, and the cerebral increase in the cyclic glycine-proline (cGP) achieved with administration of BC. (4) A continuous treatment with IGF-I, MT, and BC appears to be useful in RTT.

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“…E/I is thought to be critical for neural circuit stability and normal brain function 2 . Disrupted E/I is associated with several neurological diseases, including epilepsy, schizophrenia and autism spectrum disorders [35][36][37] . Here we showed All rights reserved.…”

Section: Discussionmentioning

confidence: 99%

Cell-autonomous regulation of structural and functional plasticity in inhibitory neurons by excitatory synaptic inputs

Shen

Zheng

et al. 2017

Preprint

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Functional circuit assembly is thought to require coordinated development of excitation and inhibition, but whether they are co-regulated cell-autonomously remains unclear. We investigated effects of decreased glutamatergic synaptic input on inhibitory synapses by expressing AMPAR subunit, GluA1 and GluA2, C-terminal peptides (GluA1CTP and GluA2CTP) in developing Xenopus tectal neurons. GluACTP decreased excitatory synaptic inputs and cell-autonomously decreased inhibitory synaptic inputs in excitatory and inhibitory neurons. Visually-evoked excitatory and inhibitory currents decreased proportionately, maintaining excitation/inhibition. GluACTP affected dendrite structure and visual experience-dependent structural plasticity differently in excitatory and inhibitory neurons. Deficits in excitatory and inhibitory synaptic transmission and experience-dependent plasticity manifested in altered visual receptive field properties. Both visual avoidance behavior and learning-induced behavioral plasticity were impaired, suggesting that maintaining excitation/inhibition alone is insufficient to preserve circuit function. We demonstrate that excitatory synaptic dysfunction in individual neurons cell-autonomously decreases inhibitory inputs and disrupts neuronal and circuit plasticity, information processing and learning.

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Excitatory/Inhibitory Balance and Circuit Homeostasis in Autism Spectrum Disorders

Cited by 899 publications

References 205 publications

Jointly reduced inhibition and excitation underlies circuit-wide changes in cortical processing in Rett syndrome

Jointly reduced inhibition and excitation underlies circuit-wide changes in cortical processing in Rett syndrome

Rett Syndrome: Treatment with IGF-I, Melatonin, Blackcurrant Extracts, and Rehabilitation

Cell-autonomous regulation of structural and functional plasticity in inhibitory neurons by excitatory synaptic inputs

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