Cited by 53Genetics and Neurodevelopmental DisordersNeuroscience and Neuropharmacology ResearchAutism Spectrum Disorder Research

Hyperexcitability and homeostasis in fragile X Syndrome.

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Liu, Xiaopeng, Kumar, Vipendra, Tsai, Nien-Pei, Auerbach, Benjamin D.·2022·Frontiers in Molecular Neuroscience

Abstract

Fragile X Syndrome (FXS) is a leading inherited cause of autism and intellectual disability, resulting from a mutation in the FMR1 gene and subsequent loss of its protein product FMRP. Despite this simple genetic origin, FXS is a phenotypically complex disorder with a range of physical and neurocognitive disruptions. While numerous molecular and cellular pathways are affected by FMRP loss, there is growing evidence that circuit hyperexcitability may be a common convergence point that can account for many of the wide-ranging phenotypes seen in FXS. The mechanisms for hyperexcitability in FXS include alterations to excitatory synaptic function and connectivity, reduced inhibitory neuron activity, as well as changes to ion channel expression and conductance. However, understanding the impact of FMR1 mutation on circuit function is complicated by the inherent plasticity in neural circuits, which display an array of homeostatic mechanisms to maintain activity near set levels. FMRP is also an important regulator of activity-dependent plasticity in the brain, meaning that dysregulated plasticity can be both a cause and consequence of hyperexcitable networks in FXS. This makes it difficult to separate the direct effects of FMR1 mutation from the myriad and pleiotropic compensatory changes associated with it, both of which are likely to contribute to FXS pathophysiology. Here we will: (1) review evidence for hyperexcitability and homeostatic plasticity phenotypes in FXS models, focusing on similarities/differences across brain regions, cell-types, and developmental time points; (2) examine how excitability and plasticity disruptions interact with each other to ultimately contribute to circuit dysfunction in FXS; and (3) discuss how these synaptic and circuit deficits contribute to disease-relevant behavioral phenotypes like epilepsy and sensory hypersensitivity. Through this discussion of where the current field stands, we aim to introduce perspectives moving forward in FXS research.

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Crossref · 10.3389/fnmol.2021.805929

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  • Increased glutamatergic signaling and altered excitatory/inhibitory balance is recognized as a hallmark of FXS.

    “Increased glutamatergic signaling and altered excitatory/inhibitory balance is recognized as a hallmark of FXS (Liu et al., 2022).”

    From Astrocytes in fragile X syndrome (2024) · cites this paper as Liu et al., 2022

    The Introduction’s “Hyperexcitable Neurons and Networks in Fragile X Syndrome” section describes altered excitatory/inhibitory balance as a contributor to FXS hyperexcitability. The “Altered Excitatory Synaptic Function and Plasticity in FXS” section reports enhanced mGluR-mediated effects in FMR1 knockout mice, but does not establish a general increase in glutamatergic signaling across FXS; it notes that some excitatory-synapse changes could decrease excitatory drive. (LLM, conf=0.83)

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Research works printed but not linked: 2

  1. Hammond L. S. Macias M. M. Tarleton J. C. Shashidhar Pai G. (1997). Fragile X syndrome and deletions in FMR1: new case and review of the literature. Am. J. Med. Genet. 72, 430– 434. 9375726
  2. Zhang Z. Rumschlag J. Jonak C. R. Binder D. K. Razak K. A. Gibson J. R.. (2021). FMRP regulates experience-dependent maturation of callosal synaptic connections and bilateral cortical synchrony. BioRxiv [Preprint]. 10.1101/2021.06.25.449490 · DOI

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Authors
Liu, X., Kumar, V., Tsai, N.-P., & Auerbach, B. D.
Affiliations
University of Illinois Urbana-Champaign (US)
Corresponding author
Auerbach, Benjamin D.
Venue
Frontiers in Molecular Neuroscience
Published
2022-01-06
Volume
14
Pages
805929-805929
ISSN
1662-5099 (ISSN-L)
OpenAlex
W4205495648
Cited by
53
References
291
Citations by year
2026: 9 · 2025: 13 · 2024: 10 · 2023: 11 · 2022: 8 · 2021: 2
FWCI
6.33
Type
journal article
Language
en
Open access
Locations
  • Frontiers in Molecular Neuroscience (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
Funders
  • National Institute of Mental Health (R01MH124827)
  • National Institute on Deafness and Other Communication Disorders (K01DC018310)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Genetics and Neurodevelopmental Disorders
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuroscience and Neuropharmacology Research
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Autism Spectrum Disorder Research
Keywords
fragile X syndrome, FMRP, neuronal hyperexcitability, neuronal homeostasis, homeostatic plasticity, inhibitory neurons, ion channels, activity-dependent plasticity, autism spectrum disorder, intellectual disability, epilepsy, sensory hypersensitivity, circuit dysfunction

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