ABSTRACT
The enhancement of associative synaptic plasticity often results in impaired rather than enhanced learning. Previously, we proposed that such learning impairments can result from saturation of the plasticity mechanism (Nguyen-Vu et al., 2017), or, more generally, from a history-dependent change in the threshold for plasticity. This hypothesis was based on experimental results from mice lacking two class I major histocompatibility molecules, MHCI H2-Kb and H2-Db (MHCI KbDb-/-), which have enhanced associative long-term depression at the parallel fiber-Purkinje cell synapses in the cerebellum (PF-Purkinje cell LTD). Here, we extend this work by testing predictions of the threshold metaplasticity hypothesis in a second mouse line with enhanced PF-Purkinje cell LTD, the Fmr1 knockout mouse model of Fragile X syndrome (FXS). Mice lacking Fmr1 gene expression in cerebellar Purkinje cells (L7-Fmr1 KO) were selectively impaired on two oculomotor learning tasks in which PF-Purkinje cell LTD has been implicated, with no impairment on LTD-independent oculomotor learning tasks. Consistent with the threshold metaplasticity hypothesis, behavioral pre-training designed to reverse LTD at the PF-Purkinje cell synapses eliminated the oculomotor learning deficit in the L7-Fmr1 KO mice, as previously reported in MHCI KbDb-/-mice. In addition, diazepam treatment to suppress neural activity and thereby limit the induction of associative LTD during the pre-training period also eliminated the learning deficits in L7-Fmr1 KO mice. These results support the hypothesis that cerebellar LTD-dependent learning is governed by an experience-dependent sliding threshold for plasticity. An increased threshold for LTD in response to elevated neural activity would tend to oppose firing rate stability, but could serve to stabilize synaptic weights and recently acquired memories. The metaplasticity perspective could inform the development of new clinical approaches for addressing learning impairments in autism and other disorders of the nervous system.
Subject(s)
Disease Models, Animal , Fragile X Mental Retardation Protein , Fragile X Syndrome , Mice, Knockout , Purkinje Cells , Animals , Fragile X Syndrome/physiopathology , Fragile X Syndrome/genetics , Mice , Fragile X Mental Retardation Protein/genetics , Fragile X Mental Retardation Protein/metabolism , Purkinje Cells/metabolism , Neuronal Plasticity , Male , LearningABSTRACT
Prostate adenocarcinoma (PRAD) is the second most common tumor associated with death. The role and mechanisms of the fragile X mental retardation 1 (FMR1) gene in PRAD remain unknown. We conducted an analysis of FMR1 expression in PRAD to determine its prognostic importance and connection to carcinogenic pathways such as PI3K_AKT_mTOR. Survival analyses were utilized to establish a correlation between FMR1 expression and patient outcomes. We used the integration of genomic data with bioinformatic predictions to predict the regulatory factors of the FMR1 gene in PRAD. Our data revealed that individuals with higher levels of FMR1 expression experience worse survival outcomes compared to those with lower expression (hazard ratio [HR] = 5.08, 95% confidence interval [CI] = 1.07 - 24, p = 0.0412). FMR1 expression was significantly higher in patients with advanced pathological tumor stages, particularly in the pT3 and pT4 combined stages and the pN1 nodal stage. Furthermore, patients with high Gleason scores (GSs) (combined GSs 8 and 9) exhibited increased levels of FMR1 expression. Our results further identify a possible regulatory link between FMR1 and key oncogenic pathways, including PI3K_AKT_mTOR, and predict the possible mechanism by which FMR1 is regulated in PRAD. Our data suggest that the FMR1 gene could serve as a biomarker for PRAD progression. However, in-depth investigations, including those with large patient samples and in vitro studies, are needed to validate this finding and understand the mechanisms involved.
Subject(s)
Adenocarcinoma , Fragile X Mental Retardation Protein , Gene Expression Regulation, Neoplastic , Prostatic Neoplasms , Humans , Fragile X Mental Retardation Protein/genetics , Fragile X Mental Retardation Protein/metabolism , Male , Prostatic Neoplasms/genetics , Prostatic Neoplasms/metabolism , Prostatic Neoplasms/pathology , Prostatic Neoplasms/mortality , Prognosis , Adenocarcinoma/genetics , Adenocarcinoma/metabolism , Adenocarcinoma/pathology , Adenocarcinoma/mortality , Aged , Middle Aged , Biomarkers, Tumor/genetics , Biomarkers, Tumor/metabolism , TOR Serine-Threonine Kinases/metabolism , TOR Serine-Threonine Kinases/genetics , Signal Transduction/genetics , Phosphatidylinositol 3-Kinases/metabolism , Phosphatidylinositol 3-Kinases/genetics , Proto-Oncogene Proteins c-akt/metabolism , Proto-Oncogene Proteins c-akt/geneticsABSTRACT
Fragile X syndrome (FXS) is caused by the full mutation in the FMR1 gene on the Xq27.3 chromosome region. It is the most common monogenic cause of autism spectrum disorder (ASD) and inherited intellectual disability (ID). Besides ASD and ID and other symptoms, individuals with FXS may exhibit sleep problems and impairment of circadian rhythm (CR). The Drosophila melanogaster models of FXS, such as dFMR1B55, represent excellent models for research in the FXS field. During this study, sleep patterns and CR in dFMR1B55 mutants were analyzed, using a new platform based on continuous high-resolution videography integrated with a highly-customized version of an open-source software. This methodology provides more sensitive results, which could be crucial for all further research in this model of fruit flies. The study revealed that dFMR1B55 male mutants sleep more and can be considered weak rhythmic flies rather than totally arrhythmic and present a good alternative animal model of genetic disorder, which includes impairment of CR and sleep behavior. The combination of affordable videography and software used in the current study is a significant improvement over previous methods and will enable broader adaptation of such high-resolution behavior monitoring methods.
Subject(s)
Circadian Rhythm , Disease Models, Animal , Drosophila melanogaster , Fragile X Mental Retardation Protein , Fragile X Syndrome , Sleep , Animals , Fragile X Syndrome/genetics , Circadian Rhythm/genetics , Drosophila melanogaster/genetics , Sleep/physiology , Fragile X Mental Retardation Protein/genetics , Male , Drosophila Proteins/genetics , Drosophila Proteins/metabolism , Behavior, Animal , Mutation , Video Recording , FemaleABSTRACT
Fragile X syndrome (FXS), the most frequent monogenic form of intellectual disability, is caused by transcriptional silencing of the FMR1 gene that could render neuronal hyperexcitability. Here we show that pyramidal cells (PCs) in the dorsal CA1 region of the hippocampus elicited a larger action potential (AP) number in response to suprathreshold stimulation in juvenile Fmr1 knockout (KO) than wild-type (WT) mice. Because Kv7/M channels modulate CA1 PC excitability in rats, we investigated if their dysfunction produces neuronal hyperexcitability in Fmr1 KO mice. Immunohistochemical and western blot analyses showed no differences in the expression of Kv7.2 and Kv7.3 channel subunits between genotypes; however, the current mediated by Kv7/M channels was reduced in Fmr1 KO mice. In both genotypes, bath application of XE991 (10 µM), a blocker of Kv7/M channels: produced an increased AP number, produced an increased input resistance, produced a decreased AP voltage threshold and shaped AP medium afterhyperpolarization by increasing mean velocities. Retigabine (10 µM), an opener of Kv7/M channels, produced opposite effects to XE991. Both XE991 and retigabine abolished differences in all these parameters found in control conditions between genotypes. Furthermore, a low concentration of retigabine (2.5 µM) normalized CA1 PC excitability of Fmr1 KO mice. Finally, ex vivo seizure-like events evoked by 4-aminopyiridine (200 µM) in the dorsal CA1 region were more frequent in Fmr1 KO mice, and were abolished by retigabine (5-10 µM). We conclude that CA1 PCs of Fmr1 KO mice exhibit hyperexcitability, caused by Kv7/M channel dysfunction, and increased epileptiform activity, which were abolished by retigabine. KEY POINTS: Dorsal pyramidal cells of the hippocampal CA1 region of Fmr1 knockout mice exhibit hyperexcitability. Kv7/M channel activity, but not expression, is reduced in pyramidal cells of the hippocampal CA1 region of Fmr1 knockout mice. Kv7/M channel dysfunction causes hyperexcitability in pyramidal cells of the hippocampal CA1 region of Fmr1 knockout mice by increasing input resistance, decreasing AP voltage threshold and shaping medium afterhyperpolarization. A Kv7/M channel opener normalizes neuronal excitability in pyramidal cells of the hippocampal CA1 region of Fmr1 knockout mice. Ex vivo seizure-like events evoked in the dorsal CA1 region were more frequent in Fmr1 KO mice, and such an epileptiform activity was abolished by a Kv7/M channel opener depending on drug concentration. Kv7/M channels may represent a therapeutic target for treating symptoms associated with hippocampal alterations in fragile X syndrome.
Subject(s)
Action Potentials , CA1 Region, Hippocampal , Fragile X Mental Retardation Protein , Mice, Knockout , Phenylenediamines , Pyramidal Cells , Animals , Fragile X Mental Retardation Protein/genetics , Pyramidal Cells/physiology , Pyramidal Cells/metabolism , Pyramidal Cells/drug effects , Phenylenediamines/pharmacology , CA1 Region, Hippocampal/physiopathology , CA1 Region, Hippocampal/metabolism , Mice , Carbamates/pharmacology , KCNQ2 Potassium Channel/genetics , KCNQ2 Potassium Channel/metabolism , Anthracenes/pharmacology , KCNQ3 Potassium Channel/genetics , KCNQ3 Potassium Channel/metabolism , Male , Mice, Inbred C57BL , Fragile X Syndrome/physiopathology , Fragile X Syndrome/genetics , Nerve Tissue ProteinsABSTRACT
Behavioral and pharmaceutical interventions reverse defects associated with increased cerebellar long-term depression in a mouse model of Fragile X syndrome.
Subject(s)
Cerebellum , Disease Models, Animal , Fragile X Syndrome , Learning , Animals , Fragile X Syndrome/physiopathology , Cerebellum/physiology , Mice , Fragile X Mental Retardation Protein/genetics , Fragile X Mental Retardation Protein/metabolismABSTRACT
BACKGROUND AND OBJECTIVES: Fragile X Syndrome (FXS) is the most common cause of inherited intellectual disability, caused by CGG-repeat expansions (> 200) in the FMR1 gene leading to lack of expression. Espansion between 55 and 200 triplets fall within the premutation range (PM) and can lead to different clinical conditions, including fragile X- primary ovarian insufficiency (FXPOI), fragile X-associated neuropsychiatric disorders (FXAND) and fragile X-associated tremor/ataxia syndrome (FXTAS). Although there is not a current cure for FXS and for the Fragile X-PM associated conditions (FXPAC), timely diagnosis as well as the implementation of treatment strategies, psychoeducation and behavioral intervention may improve the quality of life (QoL) of people with FXS or FXPAC. With the aim to investigate the main areas of concerns and the priorities of treatment in these populations, the Italian National Fragile X Association in collaboration with Bambino Gesù Children's Hospital, conducted a survey among Italian participants. METHOD: Here, we present a survey based on the previous study that Weber and colleagues conducted in 2019 and that aimed to investigate the main symptoms and challenges in American individuals with FXS. The survey has been translated into Italian language to explore FXS needs of treatment also among Italian individuals affected by FXS, family members, caretakers, and professionals. Furthermore, we added a section designated only to people with PM, to investigate the main symptoms, daily living challenges and treatment priorities. RESULTS: Anxiety, challenging behaviors, language difficulties and learning disabilities were considered the major areas of concern in FXS, while PM was reported as strongly associated to cognitive problems, social anxiety, and overthinking. Anxiety was reported as a treatment priority in both FXS and PM. CONCLUSION: FXS and PM can be associated with a range of cognitive, affective, and physical health complications. Taking a patient-first perspective may help clinicians to better characterize the cognitive-behavioral phenotype associated to these conditions, and eventually to implement tailored therapeutic approaches.
Subject(s)
Fragile X Mental Retardation Protein , Fragile X Syndrome , Fragile X Syndrome/genetics , Fragile X Syndrome/therapy , Humans , Fragile X Mental Retardation Protein/genetics , Female , Italy , Male , Surveys and Questionnaires , Adult , Quality of Life , Middle Aged , Ataxia/genetics , Ataxia/therapy , Young Adult , Adolescent , Tremor/genetics , Tremor/therapy , ChildABSTRACT
Fragile X syndrome (FXS) is the most common genetic cause of autism spectrum disorder engendered by transcriptional silencing of the fragile X messenger ribonucleoprotein 1 (FMR1) gene. Given the early onset of behavioral and molecular changes, it is imperative to know the optimal timing for therapeutic intervention. Case reports documented benefits of metformin treatment in FXS children between 2 and 14 y old. In this study, we administered metformin from birth to Fmr1-/y mice which corrected up-regulated mitogen-2 activated protein kinase/extracellular signal-regulated kinase and mammalian/mechanistic target of rapamycin complex 1 signaling pathways and specific synaptic mRNA-binding targets of FMRP. Metformin rescued increased number of calls in ultrasonic vocalization and repetitive behavior in Fmr1-/y mice. Our findings demonstrate that in mice, early-in-life metformin intervention is effective in treating FXS pathophysiology.
Subject(s)
Fragile X Mental Retardation Protein , Fragile X Syndrome , Metformin , Metformin/pharmacology , Metformin/therapeutic use , Fragile X Syndrome/drug therapy , Fragile X Syndrome/genetics , Fragile X Syndrome/physiopathology , Fragile X Syndrome/metabolism , Animals , Fragile X Mental Retardation Protein/genetics , Fragile X Mental Retardation Protein/metabolism , Mice , Male , Mice, Knockout , Mechanistic Target of Rapamycin Complex 1/metabolism , Disease Models, Animal , Signal Transduction/drug effectsABSTRACT
Fragile X syndrome (FXS) is an intellectual developmental disorder characterized, inter alia, by deficits in the short-term processing of neural information, such as sensory processing and working memory. The primary cause of FXS is the loss of fragile X messenger ribonucleoprotein (FMRP), which is profoundly involved in synaptic function and plasticity. Short-term synaptic plasticity (STSP) may play important roles in functions that are affected by FXS. Recent evidence points to the crucial involvement of the presynaptic calcium sensor synaptotagmin-7 (Syt-7) in STSP. However, how the loss of FMRP affects STSP and Syt-7 have been insufficiently studied. Furthermore, males and females are affected differently by FXS, but the underlying mechanisms remain elusive. The aim of the present study was to investigate possible changes in STSP and the expression of Syt-7 in the dorsal (DH) and ventral (VH) hippocampus of adult males and females in a Fmr1-knockout (KO) rat model of FXS. We found that the paired-pulse ratio (PPR) and frequency facilitation/depression (FF/D), two forms of STSP, as well as the expression of Syt-7, are normal in adult KO males, but the PPR is increased in the ventral hippocampus of KO females (6.4 ± 3.7 vs. 18.3 ± 4.2 at 25 ms in wild type (WT) and KO, respectively). Furthermore, we found no gender-related differences, but did find robust region-dependent difference in the STSP (e.g., the PPR at 50 ms: 50.0 ± 5.5 vs. 17.6 ± 2.9 in DH and VH of WT male rats; 53.1 ± 3.6 vs. 19.3 ± 4.6 in DH and VH of WT female rats; 48.1 ± 2.3 vs. 19.1 ± 3.3 in DH and VH of KO male rats; and 51.2 ± 3.3 vs. 24.7 ± 4.3 in DH and VH of KO female rats). AMPA receptors are similarly expressed in the two hippocampal segments of the two genotypes and in both genders. Also, basal excitatory synaptic transmission is higher in males compared to females. Interestingly, we found more than a twofold higher level of Syt-7, not synaptotagmin-1, in the dorsal compared to the ventral hippocampus in the males of both genotypes (0.43 ± 0.1 vs. 0.16 ± 0.02 in DH and VH of WT male rats, and 0.6 ± 0.13 vs. 0.23 ± 0.04 in DH and VH of KO male rats) and in the WT females (0.97 ± 0.23 vs. 0.31 ± 0.09 in DH and VH). These results point to the susceptibility of the female ventral hippocampus to FMRP loss. Importantly, the different levels of Syt-7, which parallel the higher score of the dorsal vs. ventral hippocampus on synaptic facilitation, suggest that Syt-7 may play a pivotal role in defining the striking differences in STSP along the long axis of the hippocampus.
Subject(s)
Disease Models, Animal , Fragile X Mental Retardation Protein , Fragile X Syndrome , Hippocampus , Neuronal Plasticity , Synaptotagmins , Animals , Female , Male , Rats , Fragile X Mental Retardation Protein/metabolism , Fragile X Mental Retardation Protein/genetics , Fragile X Syndrome/metabolism , Fragile X Syndrome/genetics , Fragile X Syndrome/physiopathology , Hippocampus/metabolism , Synaptotagmins/metabolism , Synaptotagmins/geneticsABSTRACT
Although hyperactivity is associated with a wide variety of neurodevelopmental disorders, the early embryonic origins of locomotion have hindered investigation of pathogenesis of these debilitating behaviors. The earliest motor output in vertebrate animals is generated by clusters of early-born motor neurons (MNs) that occupy distinct regions of the spinal cord, innervating stereotyped muscle groups. Gap junction electrical synapses drive early spontaneous behavior in zebrafish, prior to the emergence of chemical neurotransmitter networks. We use a genetic model of hyperactivity to gain critical insight into the consequences of errors in motor circuit formation and function, finding that Fragile X syndrome model mutant zebrafish are hyperexcitable from the earliest phases of spontaneous behavior, show altered sensitivity to blockade of electrical gap junctions, and have increased expression of the gap junction protein Connexin 34/35. We further show that this hyperexcitable behavior can be rescued by pharmacological inhibition of electrical synapses. We also use functional imaging to examine MN and interneuron (IN) activity in early embryogenesis, finding genetic disruption of electrical gap junctions uncouples activity between mnx1 + MNs and INs. Taken together, our work highlights the importance of electrical synapses in motor development and suggests that the origins of hyperactivity in neurodevelopmental disorders may be established during the initial formation of locomotive circuits.
Subject(s)
Electrical Synapses , Fragile X Syndrome , Motor Neurons , Zebrafish Proteins , Zebrafish , Animals , Fragile X Syndrome/physiopathology , Fragile X Syndrome/genetics , Electrical Synapses/physiology , Zebrafish Proteins/genetics , Zebrafish Proteins/metabolism , Motor Neurons/physiology , Disease Models, Animal , Connexins/genetics , Connexins/metabolism , Animals, Genetically Modified , Hyperkinesis/physiopathology , Interneurons/physiology , Interneurons/metabolism , Gap Junctions/drug effects , Gap Junctions/metabolism , Fragile X Mental Retardation Protein/genetics , Fragile X Mental Retardation Protein/metabolismABSTRACT
Sleep problems are a significant phenotype in children with fragile X syndrome. Our prior work assessed sleep-wake cycles in Fmr1KO male mice and wild type (WT) littermate controls in response to ketogenic diet therapy where mice were treated from weaning (postnatal day 18) through study completion (5-6 months of age). A potentially confounding issue with commencing treatment during an active period of growth is the significant reduction in weight gain in response to the ketogenic diet. The aim here was to employ sleep electroencephalography (EEG) to assess sleep-wake cycles in mice in response to the Fmr1 genotype and a ketogenic diet, with treatment starting at postnatal day 95. EEG results were compared with prior sleep outcomes to determine if the later intervention was efficacious, as well as with published rest-activity patterns to determine if actigraphy is a viable surrogate for sleep EEG. The data replicated findings that Fmr1KO mice exhibit sleep-wake patterns similar to wild type littermates during the dark cycle when maintained on a control purified-ingredient diet but revealed a genotype-specific difference during hours 4-6 of the light cycle of the increased wake (decreased sleep and NREM) state in Fmr1KO mice. Treatment with a high-fat, low-carbohydrate ketogenic diet increased the percentage of NREM sleep in both wild type and Fmr1KO mice during the dark cycle. Differences in sleep microstructure (length of wake bouts) supported the altered sleep states in response to ketogenic diet. Commencing ketogenic diet treatment in adulthood resulted in a 15% (WT) and 8.6% (Fmr1KO) decrease in body weight after 28 days of treatment, but not the severe reduction in body weight associated with starting treatment at weaning. We conclude that the lack of evidence for improved sleep during the light cycle (mouse sleep time) in Fmr1KO mice in response to ketogenic diet therapy in two studies suggests that ketogenic diet may not be beneficial in treating sleep problems associated with fragile X and that actigraphy is not a reliable surrogate for sleep EEG in mice.
Subject(s)
Diet, Ketogenic , Fragile X Mental Retardation Protein , Fragile X Syndrome , Mice, Inbred C57BL , Mice, Knockout , Sleep , Animals , Mice , Fragile X Syndrome/diet therapy , Male , Sleep/physiology , Fragile X Mental Retardation Protein/genetics , Electroencephalography , Disease Models, AnimalABSTRACT
Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability and is the leading known single-gene cause of autism spectrum disorder. Patients with FXS display varied behavioural deficits that include mild to severe cognitive impairments in addition to mood disorders. Currently, there is no cure for this condition; however, there is an emerging focus on therapies that inhibit mechanistic target of rapamycin (mTOR)-dependent protein synthesis owing to the clinical effectiveness of metformin for alleviating some behavioural symptoms in FXS. Adiponectin (APN) is a neurohormone that is released by adipocytes and provides an alternative means to inhibit mTOR activation in the brain. In these studies, we show that Fmr1 knockout mice, like patients with FXS, show reduced levels of circulating APN and that both long-term potentiation (LTP) and long-term depression (LTD) in the dentate gyrus (DG) are impaired. Brief (20 min) incubation of hippocampal slices in APN (50 nM) was able to rescue both LTP and LTD in the DG and increased both the surface expression and phosphorylation of GluA1 receptors. These results provide evidence for reduced APN levels in FXS playing a role in decreasing bidirectional synaptic plasticity and show that therapies which enhance APN levels may have therapeutic potential for this and related conditions.This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.
Subject(s)
Adiponectin , Dentate Gyrus , Disease Models, Animal , Fragile X Mental Retardation Protein , Fragile X Syndrome , Mice, Knockout , Neuronal Plasticity , Animals , Fragile X Syndrome/physiopathology , Fragile X Syndrome/drug therapy , Fragile X Syndrome/metabolism , Dentate Gyrus/metabolism , Dentate Gyrus/drug effects , Mice , Neuronal Plasticity/drug effects , Fragile X Mental Retardation Protein/metabolism , Fragile X Mental Retardation Protein/genetics , Adiponectin/metabolism , Long-Term Potentiation/drug effects , Male , Receptors, AMPA/metabolismABSTRACT
Fragile X syndrome (FXS) is characterized by impairments in executive function including different types of learning and memory. Long-term potentiation (LTP), thought to underlie the formation of memories, has been studied in the Fmr1 mouse model of FXS. However, there have been many discrepancies in the literature with inconsistent use of littermate and non-littermate Fmr1 knockout (KO) and wild-type (WT) control mice. Here, the influence of the breeding strategy (cage effect) on short-term potentiation (STP), LTP, contextual fear conditioning (CFC), expression of N-methyl-d-aspartate receptor (NMDAR) subunits and the modulation of NMDARs, were examined. The largest deficits in STP, LTP and CFC were found in KO mice compared with non-littermate WT. However, the expression of NMDAR subunits was unchanged in this comparison. Rather, NMDAR subunit (GluN1, 2A, 2B) expression was sensitive to the cage effect, with decreased expression in both WT and KO littermates compared with non-littermates. Interestingly, an NMDAR-positive allosteric modulator, UBP714, was only effective in potentiating the induction of LTP in non-littermate KO mice and not the littermate KO mice. These results suggest that commonly studied phenotypes in Fmr1 KOs are sensitive to the cage effect and therefore the breeding strategy may contribute to discrepancies in the literature.This article is part of a discussion meeting issue 'Long-term potentiation: 50 years on'.
Subject(s)
Disease Models, Animal , Fragile X Mental Retardation Protein , Fragile X Syndrome , Mice, Knockout , Neuronal Plasticity , Receptors, N-Methyl-D-Aspartate , Animals , Fragile X Syndrome/physiopathology , Fragile X Syndrome/genetics , Mice , Fragile X Mental Retardation Protein/genetics , Fragile X Mental Retardation Protein/metabolism , Receptors, N-Methyl-D-Aspartate/metabolism , Receptors, N-Methyl-D-Aspartate/genetics , Long-Term Potentiation , Male , Mice, Inbred C57BL , Housing, Animal , FearABSTRACT
Fragile X syndrome (FXS) is a genetic disorder caused by a mutation in the fragile X messenger ribonucleoprotein 1 (FMR1) gene and known to be a leading cause of inherited intellectual disability globally. It results in a range of intellectual, developmental, and behavioral problems. Fragile X premutation-associated conditions (FXPAC), caused by a smaller CGG expansion (55 to 200 CGG repeats) in the FMR1 gene, are linked to other conditions that increase morbidity and mortality for affected persons. Limited research has been conducted on the burden, characteristics, diagnosis, and management of these conditions in Africa. This comprehensive review provides an overview of the current literature on FXS and FXPAC in Africa. The issues addressed include epidemiology, clinical features, discrimination against affected persons, limited awareness and research, and poor access to resources, including genetic services and treatment programs. This paper provides an in-depth analysis of the existing worldwide data for the diagnosis and treatment of fragile X disorders. This review will improve the understanding of FXS and FXPAC in Africa by incorporating existing knowledge, identifying research gaps, and potential topics for future research to enhance the well-being of individuals and families affected by FXS and FXPAC.
Subject(s)
Fragile X Mental Retardation Protein , Fragile X Syndrome , Fragile X Syndrome/genetics , Fragile X Syndrome/epidemiology , Humans , Fragile X Mental Retardation Protein/genetics , Africa/epidemiology , Mutation , Trinucleotide Repeat Expansion/geneticsABSTRACT
The human genome has many short tandem repeats, yet the normal functions of these repeats are unclear. The 5' untranslated region (UTR) of the fragile X messenger ribonucleoprotein 1 (FMR1) gene contains polymorphic CGG repeats, the length of which has differing effects on FMR1 expression and human health, including the neurodevelopmental disorder fragile X syndrome. We deleted the CGG repeats in the FMR1 gene (0CGG) in human stem cells and examined the effects on differentiated neurons. 0CGG neurons have altered subcellular localization of FMR1 mRNA and protein, and differential expression of cellular stress proteins compared with neurons with normal repeats (31CGG). In addition, 0CGG neurons have altered responses to glucocorticoid receptor (GR) activation, including FMR1 mRNA localization, GR chaperone HSP90α expression, GR localization, and cellular stress protein levels. Therefore, the CGG repeats in the FMR1 gene are important for the homeostatic responses of neurons to stress signals.
Subject(s)
Fragile X Mental Retardation Protein , Neurons , RNA, Messenger , Humans , Fragile X Mental Retardation Protein/metabolism , Fragile X Mental Retardation Protein/genetics , Neurons/metabolism , RNA, Messenger/metabolism , RNA, Messenger/genetics , Receptors, Glucocorticoid/metabolism , Receptors, Glucocorticoid/genetics , Stress, Physiological/genetics , 5' Untranslated Regions/genetics , HSP90 Heat-Shock Proteins/metabolism , HSP90 Heat-Shock Proteins/genetics , Trinucleotide Repeats/genetics , Trinucleotide Repeat Expansion/geneticsABSTRACT
Fmr1 (fragile X messenger ribonucleoprotein 1)-knockout (KO) rats, modeling the human Fragile X Syndrome (FXS), are of particular interest for exploring the ASD-like phenotype in preclinical studies. Gestational exposure to chlorpyrifos (CPF) has been associated with ASD diagnosis in humans and ASD-like behaviors in rodents and linked to the microbiota-gut-brain axis. In this study, we have used both Fmr1-KO and wild-type male rats (F2 generation) at postnatal days (PND) 7 and 40 obtained after F1 pregnant females were randomly exposed to 1â¯mg/kg/mL/day of CPF or vehicle. A nuclear magnetic resonance (NMR) metabolomics approach together with gene expression profiles of these F2 generation rats were employed to analyze different brain regions (such as prefrontal cortex, hippocampus, and cerebellum), whole large intestine (at PND7) and gut content (PND40). The statistical comparison of each matrix spectral profile unveiled tissue-specific metabolic fingerprints. Significant variations in some biomarker levels were detected among brain tissues of different genotypes, including taurine, myo-inositol, and 3-hydroxybutyric acid, and exposure to CPF induced distinct metabolic alterations, particularly in serine and myo-inositol. Additionally, this study provides a set of metabolites associated with gastrointestinal dysfunction in ASD, encompassing several amino acids, choline-derived compounds, bile acids, and sterol molecules. In terms of gene expression, genotype and gestational exposure to CPF had only minimal effects on decarboxylase 2 (gad2) and cholinergic receptor muscarinic 2 (chrm2) genes.
Subject(s)
Autism Spectrum Disorder , Biomarkers , Brain-Gut Axis , Chlorpyrifos , Fragile X Mental Retardation Protein , Gastrointestinal Microbiome , Prenatal Exposure Delayed Effects , Animals , Chlorpyrifos/toxicity , Pregnancy , Female , Male , Fragile X Mental Retardation Protein/genetics , Gastrointestinal Microbiome/drug effects , Biomarkers/metabolism , Autism Spectrum Disorder/chemically induced , Autism Spectrum Disorder/metabolism , Brain-Gut Axis/drug effects , Rats , Brain/metabolism , Brain/drug effectsABSTRACT
Fragile X syndrome (FXS) is caused by epigenetic silencing of the Fmr1 gene, leading to the deletion of the coding protein FMRP. FXS induces abnormal hippocampal autophagy and mTOR overactivation. However, it remains unclear whether FMRP regulates hippocampal autophagy through the AKT/mTOR pathway, which influences the neural behavior of FXS. Our study revealed that FMRP deficiency increased the protein levels of p-ULK-1 and p62 and decreased LC3II/LC3I level in Fmr1 knockout (KO) mice. The mouse hippocampal neuronal cell line HT22 with knockdown of Fmr1 by lentivirus showed that the protein levels of p-ULK-1 and p62 were increased, whereas LC3II/LC3I was unchanged. Further observations revealed that FMRP deficiency obstructed autophagic flow in HT22 cells. Therefore, FMRP deficiency inhibited autophagy in the mouse hippocampus and HT22 cells. Moreover, FMRP deficiency increased reactive oxygen species (ROS) level, decreased the co-localization between the mitochondrial outer membrane proteins TOM20 and LC3 in HT22 cells, and caused a decrease in the mitochondrial autophagy protein PINK1 in HT22 cells and Fmr1 KO mice, indicating that FMRP deficiency caused mitochondrial autophagy disorder in HT22 cells and Fmr1 KO mice. To explore the mechanism by which FMRP deficiency inhibits autophagy, we examined the AKT/mTOR signaling pathway in the hippocampus of Fmr1 KO mice, found that FMRP deficiency caused overactivation of the AKT/mTOR pathway. Rapamycin-mediated mTOR inhibition activated and enhanced mitochondrial autophagy. Finally, we examined whether rapamycin affected the neurobehavior of Fmr1 KO mice. The Fmr1 KO mice exhibited stereotypical behavior, impaired social ability, and learning and memory impairment, while rapamycin treatment improved behavioral disorders in Fmr1 KO mice. Thus, our study revealed the molecular mechanism by which FMRP regulates autophagy function, clarifying the role of hippocampal neuron mitochondrial autophagy in the pathogenesis of FXS, and providing novel insights into potential therapeutic targets of FXS.
Subject(s)
Autophagy , Fragile X Mental Retardation Protein , Fragile X Syndrome , Hippocampus , Mice, Knockout , Proto-Oncogene Proteins c-akt , Signal Transduction , TOR Serine-Threonine Kinases , Animals , Fragile X Mental Retardation Protein/genetics , Fragile X Mental Retardation Protein/metabolism , Hippocampus/metabolism , Hippocampus/pathology , Autophagy/physiology , TOR Serine-Threonine Kinases/metabolism , Fragile X Syndrome/metabolism , Fragile X Syndrome/pathology , Proto-Oncogene Proteins c-akt/metabolism , Signal Transduction/physiology , Mice , Male , Mice, Inbred C57BL , Cell LineABSTRACT
Fragile X syndrome (FXS) is a genetic cause of intellectual disability and autism spectrum disorder. The mesocorticolimbic system, which includes the prefrontal cortex (PFC), basolateral amygdala (BLA), and nucleus accumbens core (NAcC), is essential for regulating socioemotional behaviors. We employed optogenetics to compare the functional properties of the BLAâNAcC, PFCâNAcC, and reciprocal PFCâBLA pathways in Fmr1-/y::Drd1a-tdTomato male mice. In FXS mice, the PFCâBLA reciprocal pathway was unaffected, while significant synaptic modifications occurred in the BLA/PFCâNAcC pathways. We observed distinct changes in D1 striatal projection neurons (SPNs) and separate modifications in D2 SPNs. In FXS mice, the BLA/PFCâNAcC-D2 SPN pathways demonstrated heightened synaptic strength. Focusing on the BLAâNAcC pathway, linked to autistic symptoms, we found increased AMPAR and NMDAR currents and elevated spine density in D2 SPNs. Conversely, the amplified firing probability of BLAâNAcC-D1 SPNs was not accompanied by increased synaptic strength, AMPAR and NMDAR currents, or spine density. These pathway-specific alterations resulted in an overall enhancement of excitatory-to-spike coupling, a physiologically relevant index of how efficiently excitatory inputs drive neuronal firing, in both BLAâNAcC-D1 and BLAâNAcC-D2 pathways. Finally, the absence of fragile X messenger ribonucleoprotein 1 (FMRP) led to impaired long-term depression specifically in BLAâD1 SPNs. These distinct alterations in synaptic transmission and plasticity within circuits targeting the NAcC highlight the potential role of postsynaptic mechanisms in selected SPNs in the observed circuit-level changes. This research underscores the heightened vulnerability of the NAcC in the context of FMRP deficiency, emphasizing its pivotal role in the pathophysiology of FXS.
Subject(s)
Fragile X Mental Retardation Protein , Fragile X Syndrome , Nucleus Accumbens , Animals , Fragile X Syndrome/physiopathology , Fragile X Syndrome/metabolism , Fragile X Syndrome/genetics , Mice , Male , Nucleus Accumbens/metabolism , Fragile X Mental Retardation Protein/genetics , Fragile X Mental Retardation Protein/metabolism , Neural Pathways/physiopathology , Optogenetics , Prefrontal Cortex/metabolism , Prefrontal Cortex/physiopathology , Mice, Inbred C57BL , Basolateral Nuclear Complex/metabolism , Basolateral Nuclear Complex/physiopathology , Mice, Knockout , Neurons/metabolism , Neurons/physiology , Neuronal Plasticity/physiologyABSTRACT
OBJECTIVE: To investigate the mechanism by which fragile X mental retardation protein (FMRP) regulates ferroptosis evasion in colorectal cancer (CRC) cells. METHODS: We examined FMRP expression levels in CRC cell lines using RT-qPCR and Western blotting and analyzed the biological functions and signaling pathways involved in FMRP-mediated regulation of CRC progression using the TCGA database. A lentiviral FMRP overexpression vector (Lv-FMRP) and 3 knockdown vectors (siFMRP-1, siFMRP-2, and siFMRP-3) were constructed, and their effects on proliferation of HCT116 cells were examined using CCK8 assay and plate clone formation assay; the changes in cell ferroptosis level was determined using MDA/ROS/GSH/Fe2+ kits, mitochondrial membrane potential changes were detected using JC-1 fluorescence staining, and the expressions of proteins associated with ferroptosis and the RAS/MAPK signaling pathway were detected using Western blotting. The subcutaneous tumorigenic potential of the transfected cells was evaluated in nude mice. RESULTS: Compared with normal colonic mucosal epithelial NCM460 cells, the CRC cell lines had significantly higher FMRP expression level. Bioinformatics analysis suggested the involvement of FMRP in regulation of reactive oxygen, oxidative stress-induced cell death, mitochondrial respiration, and glutathione metabolism pathways. In the cell experiments, FMRP knockdown significantly inhibited proliferation of HCT116 cells, lowered cellular GSH content, increased MDA and ROS levels, Fe2+ fluorescence intensity, and mitochondrial membrane potential, and decreased SLC7A11/GPX4 protein expressions and the phosphorylation levels of ERK, MEK, MAPK, and RAS proteins; FMRP overexpression resulted in the opposite changes in the cells. In the tumor-bearing nude mice, HCT116 cells with FMRP knockdown showed attenuated tumorigenic potential with lowered xenograft growth rate and reduced SLC7A11 expression in the xenograft. CONCLUSION: The high expression of FMRP inhibits ferroptosis in CRC cells and promotes progression of CRC by activating the RAS/MAPK signaling pathway.
Subject(s)
Cell Proliferation , Colorectal Neoplasms , Ferroptosis , Fragile X Mental Retardation Protein , MAP Kinase Signaling System , Mice, Nude , Humans , Colorectal Neoplasms/metabolism , Colorectal Neoplasms/pathology , Colorectal Neoplasms/genetics , Animals , Mice , Fragile X Mental Retardation Protein/metabolism , Fragile X Mental Retardation Protein/genetics , Cell Line, Tumor , HCT116 Cells , Signal Transduction , Membrane Potential, Mitochondrial , ras Proteins/metabolismABSTRACT
PURPOSE: The Fragile X Messenger Ribonucleoprotein-1 (FMR1) premutation (FXpm) is a genetic variant that is common in the general population and is associated with health symptoms and disease in adulthood. However, poor understanding of the clinical phenotype during childhood has hindered the development of clinical practice guidelines for screening and intervention. Given that social communication difficulties have been widely documented in adults with the FXpm and are linked with reduced psychosocial functioning, the present study aimed to characterize the communication profile of the FXpm during early childhood. METHOD: Eighteen children with the FXpm who were identified through cascade testing (89%) or screening at birth (11%) were compared to 21 matched typically developing children, aged 2-4 years. Participants completed standardized assessments of language (Mullen Scales of Early Learning) and adaptive communication (Vineland Adaptive Behavior Scales-II). Social communication was rated from seminaturalistic interaction samples using the Brief Observation of Social Communication Change. RESULTS: Children with the FXpm showed delayed social communication development, with the magnitude of group differences highlighting social communication as a feature that distinguishes children with the FXpm from their peers (p = .046, ηp2 = .12). The groups did not differ on the standardized language and adaptive communication measures (ps > .297, ηp2s < .03). CONCLUSIONS: Early screening and treatment of social communication delays may be key to optimizing outcomes for children with the FXpm. Further research is needed to replicate findings in a larger sample, delineate the trajectory and consequences of social communication difficulties across the life span in the FXpm, and determine the potential epidemiological significance of FMR1 as a mediator of developmental communication differences within the general population.
Subject(s)
Fragile X Mental Retardation Protein , Humans , Male , Female , Fragile X Mental Retardation Protein/genetics , Child, Preschool , Fragile X Syndrome/genetics , Fragile X Syndrome/psychology , Mutation , Language Development Disorders/genetics , Language Development Disorders/psychology , Social Communication Disorder/genetics , Social Communication Disorder/psychologyABSTRACT
BACKGROUND: Premutations in the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene, defined as between 55 and 200 CGGs, have been implicated in fragile X-associated primary ovarian insufficiency (FXPOI). Only 20% of female premutation carriers develop early ovulatory dysfunction, the reason for this incomplete penetrance is unknown. This study validated the mathematical model in premutation alleles, after assigning each allele a score representing allelic complexity. Subsequently, allelic scores were used to investigate the impact of allele complexity on age at amenorrhea for 58 premutation cases (116 alleles) previously published. METHODS: The allelic score was determined using a formula previously described by our group. The impact of each allelic score on age at amenorrhea was analyzed using Pearson's test and a contour plot generated to visualize the effect. RESULTS: Correlation of allelic score revealed two distinct complexity behaviors in premutation alleles. No significant correlation was observed between the allelic score of premutation alleles and age at amenorrhea. The same lack of significant correlation was observed regarding normal-sized alleles, despite a nearly significant trend. CONCLUSIONS: Our results suggest that the use of allelic scores combination have the potential to explain female infertility, namely the development of FXPOI, or ovarian dysfunction, despite the lack of correlation with age at amenorrhea. Such a finding is of great clinical significance for early identification of females at risk of ovulatory dysfunction, enhancement of fertility preservation techniques, and increasing the probability for a successful pregnancy in females with premutations. Additional investigation is necessary to validate this hypothesis.