scholarly journals Interneuron Dysfunction and Inhibitory Deficits in Autism and Fragile X Syndrome

Cells ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 2610
Author(s):  
Toshihiro Nomura
Keyword(s):  
Fragile X Syndrome ◽  
Therapeutic Potential ◽  
Fragile X ◽  
Single Gene ◽  
Autism Spectrum ◽  
Gamma Aminobutyric Acid ◽  
Inhibitory Neurotransmitter ◽  
Inhibitory Circuits ◽  
Inhibitory Deficits ◽  
Inhibitory Circuit

The alteration of excitatory–inhibitory (E–I) balance has been implicated in various neurological and psychiatric diseases, including autism spectrum disorder (ASD). Fragile X syndrome (FXS) is a single-gene disorder that is the most common known cause of ASD. Understanding the molecular and physiological features of FXS is thought to enhance our knowledge of the pathophysiology of ASD. Accumulated evidence implicates deficits in the inhibitory circuits in FXS that tips E–I balance toward excitation. Deficits in interneurons, the main source of an inhibitory neurotransmitter, gamma-aminobutyric acid (GABA), have been reported in FXS, including a reduced number of cells, reduction in intrinsic cellular excitability, or weaker synaptic connectivity. Manipulating the interneuron activity ameliorated the symptoms in the FXS mouse model, which makes it reasonable to conceptualize FXS as an interneuronopathy. While it is still poorly understood how the developmental profiles of the inhibitory circuit go awry in FXS, recent works have uncovered several developmental alterations in the functional properties of interneurons. Correcting disrupted E–I balance by potentiating the inhibitory circuit by targeting interneurons may have a therapeutic potential in FXS. I will review the recent evidence about the inhibitory alterations and interneuron dysfunction in ASD and FXS and will discuss the future directions of this field.

scholarly journals Cerebral Expression of Metabotropic Glutamate Receptor Subtype 5 in Idiopathic Autism Spectrum Disorder and Fragile X Syndrome: A Pilot Study

2021 ◽  
Vol 22 (6) ◽  
pp. 2863
Author(s):  
James Robert Brašić ◽  
Ayon Nandi ◽  
David S. Russell ◽  
Danna Jennings ◽  
Olivier Barret ◽  
...  
Keyword(s):  
Autism Spectrum Disorder ◽  
Fragile X Syndrome ◽  
Glutamate Receptor ◽  
Metabotropic Glutamate Receptor ◽  
Fragile X ◽  
Single Gene ◽  
Autism Spectrum ◽  
Spectrum Disorder ◽  
Receptor Subtype ◽  
Metabotropic Glutamate

Multiple lines of evidence suggest that dysfunction of the metabotropic glutamate receptor subtype 5 (mGluR5) plays a role in the pathogenesis of autism spectrum disorder (ASD). Yet animal and human investigations of mGluR5 expression provide conflicting findings about the nature of dysregulation of cerebral mGluR5 pathways in subtypes of ASD. The demonstration of reduced mGluR5 expression throughout the living brains of men with fragile X syndrome (FXS), the most common known single-gene cause of ASD, provides a clue to examine mGluR5 expression in ASD. We aimed to (A) compare and contrast mGluR5 expression in idiopathic autism spectrum disorder (IASD), FXS, and typical development (TD) and (B) show the value of positron emission tomography (PET) for the application of precision medicine for the diagnosis and treatment of individuals with IASD, FXS, and related conditions. Two teams of investigators independently administered 3-[18F]fluoro-5-(2-pyridinylethynyl)benzonitrile ([18F]FPEB), a novel, specific mGluR5 PET ligand to quantitatively measure the density and the distribution of mGluR5s in the brain regions, to participants of both sexes with IASD and TD and men with FXS. In contrast to participants with TD, mGluR5 expression was significantly increased in the cortical regions of participants with IASD and significantly reduced in all regions of men with FXS. These results suggest the feasibility of this protocol as a valuable tool to measure mGluR5 expression in clinical trials of individuals with IASD and FXS and related conditions.

scholarly journals Phenotypic Trade-Offs: Deciphering the Impact of Neurodiversity on Drug Development in Fragile X Syndrome

2021 ◽  
Vol 12 ◽  
Author(s):  
Truong An Bui ◽  
Julie Shatto ◽  
Tania Cuppens ◽  
Arnaud Droit ◽  
François V. Bolduc
Keyword(s):  
Clinical Trials ◽  
Fragile X Syndrome ◽  
Fragile X ◽  
Single Gene ◽  
Specific Treatment ◽  
Autism Spectrum ◽  
New Paradigm ◽  
Trade Offs ◽  
Wide Range ◽  
The Impact

Fragile X syndrome (FXS) is the most common single-gene cause of intellectual disability and autism spectrum disorder. Individuals with FXS present with a wide range of severity in multiple phenotypes including cognitive delay, behavioral challenges, sleep issues, epilepsy, and anxiety. These symptoms are also shared by many individuals with other neurodevelopmental disorders (NDDs). Since the discovery of the FXS gene, FMR1, FXS has been the focus of intense preclinical investigation and is placed at the forefront of clinical trials in the field of NDDs. So far, most studies have aimed to translate the rescue of specific phenotypes in animal models, for example, learning, or improving general cognitive or behavioral functioning in individuals with FXS. Trial design, selection of outcome measures, and interpretation of results of recent trials have shown limitations in this type of approach. We propose a new paradigm in which all phenotypes involved in individuals with FXS would be considered and, more importantly, the possible interactions between these phenotypes. This approach would be implemented both at the baseline, meaning when entering a trial or when studying a patient population, and also after the intervention when the study subjects have been exposed to the investigational product. This approach would allow us to further understand potential trade-offs underlying the varying effects of the treatment on different individuals in clinical trials, and to connect the results to individual genetic differences. To better understand the interplay between different phenotypes, we emphasize the need for preclinical studies to investigate various interrelated biological and behavioral outcomes when assessing a specific treatment. In this paper, we present how such a conceptual shift in preclinical design could shed new light on clinical trial results. Future clinical studies should take into account the rich neurodiversity of individuals with FXS specifically and NDDs in general, and incorporate the idea of trade-offs in their designs.

Abnormal neurogensis in the hippocampus of a mouse model of fragile X syndromes

2007 ◽  
Vol 30 (4) ◽  
pp. 80
Author(s):  
B Eadie ◽  
B Christie
Keyword(s):  
Mouse Model ◽  
Learning And Memory ◽  
Fragile X Syndrome ◽  
Knockout Mice ◽  
Fragile X ◽  
Single Gene ◽  
Neurodevelopmental Disorder ◽  
Autism Spectrum ◽  
Fmr1 Gene ◽  
Learning Impairment

Fragile X syndrome is the most common inherited form of mental retardation. It is a neurodevelopmental disorder that is similar in clinical presentation to autism spectrum disorder. However, unlike autism, Fragile X syndrome is caused by the silencing of a single gene, and in recent years, a mouse model of Fragile X syndrome has been generated by deletion of the Fmr1 gene. Surprisingly, a clear neurobiological basis for the learning impairment observed in both these knockout mice and patients has been difficult to elucidate. We hypothesized that neurogenesis, a process that continues into adulthood in the hippocampus, may be abnormal in this syndrome. Support for such a hypothesis comes from the findings that these new neurons may disproportionately contribute to synaptic plasticity in networks engaged during learning and memory. We have shown that the survival of new cells in the hippocampus of young Fmr1 knockout mice is significantly decreased in the ventral hippocampus, a sub-region which may be more involved with emotional, rather than, spatial memory. Further experiments are being conducted to assess the differentiation of these new cells into neurons and glia. We are also characterizing the normal expression of the Fmr1 gene product, FMRP, across the phases of neurogenesis in control mice. In conclusion, we have discovered a clear impairment in a process that may be critical to emotionally-significant learning and memory in a mouse model of Fragile X syndrome.

scholarly journals Fragile X syndrome – a common disease rarely diagnosed

2017 ◽  
Vol 30 (1) ◽  
pp. 27-30
Author(s):  
Malgorzata Zofia Lisik
Keyword(s):  
Mental Retardation ◽  
Fragile X Syndrome ◽  
Fragile X ◽  
Single Gene ◽  
Strong Association ◽  
Autism Spectrum ◽  
Common Disease ◽  
Medical Evaluation ◽  
The Family ◽  
Physical Features

Abstract Fragile X syndrome (FXS) is a single-gene disorder with a broad spectrum of involvement, including cognitive and behavioural impairments of varying degrees with specific physical features and with strong association with autism. The study was conducted on 23 males (10-32 years old) who had full mutation in the FMR1 gene. A complete medical evaluation, including medical history, family history, psychological testing and physical examination was conducted on each subject. Three of the FXS patients (13%) were isolated cases of mental retardation in the family. The remaining 20 FXS patients belonged to 15 families, where there were other mentally retarded family members present. The degree of mental retardation (MR) varied. Mild MR was diagnosed in 1/23 (4.35%), moderate MR in 12/23 (52.17%), severe MR in 10/23 (43.48 %). Moreover, autism spectrum disorder was diagnosed in 5/23 (21.74%) FXS patients. Analysis of the BMI showed that in FXS patients, 14 of 23 (60.68%) had too high body weight - 9/23 (39.13%) were overweight and 5/23 (21.74%) were obese. The diagnosis of FXS is difficult because of nonspecific symptoms, yet early diagnosis is crucial for early intervention and genetic counseling. The risk of recurrence is 50%.

Fragile X Syndrome: Lessons Learned and What New Treatment Avenues Are on the Horizon

2021 ◽  
Vol 62 (1) ◽  
Author(s):  
Randi J. Hagerman ◽  
Paul J. Hagerman
Keyword(s):  
Fragile X Syndrome ◽  
Fragile X ◽  
Single Gene ◽  
Neurodevelopmental Disorder ◽  
Autism Spectrum ◽  
Lessons Learned ◽  
Annual Review ◽  
Publication Date ◽  
Cgg Repeat ◽  
New Treatment

Fragile X syndrome (FXS) is the most common form of inherited intellectual disability and the leading single-gene form of autism spectrum disorder, encompassing cognitive, behavioral, and physical forms of clinical involvement. FXS is caused by large expansions of a noncoding CGG repeat (>200 repeats) in the FMR1 gene, at which point the gene is generally silenced. Absence of FMR1 protein (FMRP), important for synaptic development and maintenance, gives rise to the neurodevelopmental disorder. There is, at present, no therapeutic approach that directly reverses the loss of FMRP; however, there is an increasing number of potential treatments that target the pathways dysregulated in FXS, including those that address the enhanced activity of the mGluR5 pathway and deficits in GABA pathways. Based on studies of targeted therapeutics to date, the prospects are good for one or more effective therapies for FXS in the near future. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

scholarly journals How Knowledge Mapping Can Bridge the Communication Gap Between Caregivers and Health Professionals Supporting Individuals With Complex Medical Needs: A Study in Fragile X Syndrome

2021 ◽  
Vol 12 ◽  
Author(s):  
Karen Kelm ◽  
Francois V. Bolduc
Keyword(s):  
Fragile X Syndrome ◽  
Health Professionals ◽  
Concept Maps ◽  
Healthcare Professionals ◽  
Fragile X ◽  
Single Gene ◽  
Autism Spectrum ◽  
Knowledge Mapping ◽  
Medical Needs ◽  
Care Maps

The challenges of caring for children with complex health needs, such as intellectual disability (ID) and autism spectrum disorder (ASD), are multiple and experienced by both caregivers and health professionals. Fragile X syndrome (FXS) is the most common single gene cause of ID and ASD, and provides a pertinent model to understand these complexities of care, as well as the communication challenges experienced between caregivers and healthcare professionals. In recent years both caregivers and healthcare professionals have recognized the need for enhancing communication both in clinical and research settings. Knowledge mapping has emerged as a tool to support quality communication between team participants. Here we review how differences in mental models, as well as challenges related to health literacy and knowledge transfer can have an impact on communication. Next, we present different knowledge mapping approaches used in complex situations, with a focus on concept maps and care maps. Finally, we highlight the potential benefits and limitations of mapping to improve communication issues related to caring for individuals with FXS and potentially other neurodevelopmental disorders (NDDs).

scholarly journals Local Protein Translation and RNA Processing of Synaptic Proteins in Autism Spectrum Disorder

2021 ◽  
Vol 22 (6) ◽  
pp. 2811
Author(s):  
Yuyoung Joo ◽  
David R. Benavides
Keyword(s):  
Autism Spectrum Disorder ◽  
Fragile X ◽  
Single Gene ◽  
Protein Translation ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Spectrum Disorder ◽  
Synaptic Proteins ◽  
Local Translation ◽  
Translation Control

Autism spectrum disorder (ASD) is a heritable neurodevelopmental condition associated with impairments in social interaction, communication and repetitive behaviors. While the underlying disease mechanisms remain to be fully elucidated, dysfunction of neuronal plasticity and local translation control have emerged as key points of interest. Translation of mRNAs for critical synaptic proteins are negatively regulated by Fragile X mental retardation protein (FMRP), which is lost in the most common single-gene disorder associated with ASD. Numerous studies have shown that mRNA transport, RNA metabolism, and translation of synaptic proteins are important for neuronal health, synaptic plasticity, and learning and memory. Accordingly, dysfunction of these mechanisms may contribute to the abnormal brain function observed in individuals with autism spectrum disorder (ASD). In this review, we summarize recent studies about local translation and mRNA processing of synaptic proteins and discuss how perturbations of these processes may be related to the pathophysiology of ASD.

scholarly journals Impaired perceptual learning in Fragile X syndrome is mediated by parvalbumin neuron dysfunction in V1 and is reversible

2017 ◽  
Author(s):  
Anubhuti Goel ◽  
Daniel A. Cantu ◽  
Janna Guilfoyle ◽  
Gunvant R. Chaudhari ◽  
Aditi Newadkar ◽  
...  
Keyword(s):  
Perceptual Learning ◽  
Fragile X Syndrome ◽  
Visual Discrimination ◽  
Fragile X ◽  
Human Subjects ◽  
Autistic Traits ◽  
Autism Spectrum ◽  
Orientation Tuning ◽  
Mechanistic Basis

Atypical sensory processing is a core characteristic in autism spectrum disorders1 that negatively impacts virtually all activities of daily living. Sensory symptoms are predictive of the subsequent appearance of impaired social behavior and other autistic traits2, 3. Thus, a better understanding of the changes in neural circuitry that disrupt perceptual learning in autism could shed light into the mechanistic basis and potential therapeutic avenues for a range of autistic symptoms2. Likewise, the lack of directly comparable behavioral paradigms in both humans and animal models currently limits the translational potential of discoveries in the latter. We adopted a symptom-to-circuit approach to uncover the circuit-level alterations in the Fmr1-/- mouse model of Fragile X syndrome (FXS) that underlie atypical visual discrimination in this disorder4, 5. Using a go/no-go task and in vivo 2-photon calcium imaging in primary visual cortex (V1), we find that impaired discrimination in Fmr1-/- mice correlates with marked deficits in orientation tuning of principal neurons, and a decrease in the activity of parvalbumin (PV) interneurons in V1. Restoring visually evoked activity in PV cells in Fmr1-/- mice with a chemogenetic (DREADD) strategy was sufficient to rescue their behavioral performance. Finally, we found that human subjects with FXS exhibit strikingly similar impairments in visual discrimination as Fmr1-/- mice. We conclude that manipulating orientation tuning in autism could improve visually guided behaviors that are critical for playing sports, driving or judging emotions.

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