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BACKGROUND: Fragile X syndrome (FXS) and autism spectrum disorder (ASD) are neurodevelopmental conditions that often have a substantial impact on daily functioning and quality of life. FXS is the most common cause of inherited intellectual disability (ID) and the most common monogenetic cause of ASD. Previous literature has shown that electrophysiological activity measured by electroencephalogram (EEG) during resting state is perturbated in FXS and ASD. However, whether electrophysiological profiles of participants with FXS and ASD are similar remains unclear. The aim of this study was to compare EEG alterations found in these two clinical populations presenting varying degrees of cognitive and behavioral impairments. METHODS: Resting state EEG signal complexity, alpha peak frequency (APF) and power spectral density (PSD) were compared between 47 participants with FXS (aged between 5-20), 49 participants with ASD (aged between 6-17), and 52 neurotypical (NT) controls with a similar age distribution using MANCOVAs with age as covariate when appropriate. MANCOVAs controlling for age, when appropriate, and nonverbal intelligence quotient (NVIQ) score were subsequently performed to determine the impact of cognitive functioning on EEG alterations. RESULTS: Our results showed that FXS participants manifested decreased signal complexity and APF compared to ASD participants and NT controls, as well as altered power in the theta, alpha and low gamma frequency bands. ASD participants showed exaggerated beta power compared to FXS participants and NT controls, as well as enhanced low and high gamma power compared to NT controls. However, ASD participants did not manifest altered signal complexity or APF. Furthermore, when controlling for NVIQ, results of decreased complexity in higher scales and lower APF in FXS participants compared to NT controls and ASD participants were not replicated. CONCLUSIONS: These findings suggest that signal complexity and APF might reflect cognitive functioning, while altered power in the low gamma frequency band might be associated with neurodevelopmental conditions, particularly FXS and ASD.

A study was performed on a family from Cali, Colombia in which nine patients were evaluated, three of which presented with intellectual disability with no previous etiological diagnosis. The proband was diagnosed with Fragile X syndrome by DNA molecular testing and, cascade testing, performed on all available family members, identifying two additional individuals with the full mutation and four carriers of a premutation allele. With this report we seek to contribute to Colombian epidemiology of the syndrome and emphasize the importance of diagnosis to provide a comprehensive and specific treatment to those affected. Further we seek to identify premutation carriers in their families or women with a full mutation without the classic phenotype for genetic counseling and education about potential associated pathologies.

OBJECTIVE: Mitochondrial impairments have been implicated in the pathogenesis of Fragile X-associated tremor/ataxia syndrome (FXTAS) based on analysis of mitochondria in peripheral tissues and cultured cells. We sought to assess whether mitochondrial abnormalities present in postmortem brain tissues of patients with FXTAS are also present in plasma neuron-derived extracellular vesicles (NDEVs) from living carriers of fragile X messenger ribonucleoprotein1 (FMR1) gene premutations at an early asymptomatic stage of the disease continuum. METHODS: We utilized postmortem frozen cerebellar and frontal cortex samples from a cohort of eight patients with FXTAS and nine controls and measured the quantity and activity of the mitochondrial proteins complex IV and complex V. In addition, we evaluated the same measures in isolated plasma NDEVs by selective immunoaffinity capture targeting L1CAM from a separate cohort of eight FMR1 premutation carriers and four age-matched controls. RESULTS: Lower complex IV and V quantity and activity were observed in the cerebellum of FXTAS patients compared to controls, without any differences in total mitochondrial content. No patient-control differences were observed in the frontal cortex. In NDEVs, FMR1 premutation carriers compared to controls had lower activity of Complex IV and Complex V, but higher Complex V quantity. INTERPRETATION: Quantitative and functional abnormalities in mitochondrial electron transport chain complexes IV and V seen in the cerebellum of patients with FXTAS are also manifest in plasma NDEVs of FMR1 premutation carriers. Plasma NDEVs may provide further insights into mitochondrial pathologies in this syndrome and could potentially lead to the development of biomarkers for predicting symptomatic FXTAS among premutation carriers and disease monitoring.

This case series plus review seeks to describe the clinical characteristics and pathophysiology of VM among individuals with the fragile X premutation. We also seek to discuss treatment and future steps in addressing VM in this population.

BACKGROUNDFXLEARN, the first-ever large multisite trial of effects of disease-targeted pharmacotherapy on learning, was designed to explore a paradigm for measuring effects of mechanism-targeted treatment in fragile X syndrome (FXS). In FXLEARN, the effects of metabotropic glutamate receptor type 5 (mGluR5) negative allosteric modulator (NAM) AFQ056 on language learning were evaluated in 3- to 6-year-old children with FXS, expected to have more learning plasticity than adults, for whom prior trials of mGluR5 NAMs have failed.METHODSAfter a 4-month single-blind placebo lead-in, participants were randomized 1:1 to AFQ056 or placebo, with 2 months of dose optimization to the maximum tolerated dose, then 6 months of treatment during which a language-learning intervention was implemented for both groups. The primary outcome was a centrally scored videotaped communication measure, the Weighted Communication Scale (WCS). Secondary outcomes were objective performance-based and parent-reported cognitive and language measures.RESULTSFXLEARN enrolled 110 participants, randomized 99, and had 91 who completed the placebo-controlled period. Although both groups made language progress and there were no safety issues, the change in WCS score during the placebo-controlled period was not significantly different between the AFQ056 and placebo-treated groups, nor were there any significant between-group differences in change in any secondary measures.CONCLUSIONDespite the large body of evidence supporting use of mGluR5 NAMs in animal models of FXS, this study suggests that this mechanism of action does not translate into benefit for the human FXS population and that better strategies are needed to determine which mechanisms will translate from preclinical models to humans in genetic neurodevelopmental disorders.TRIAL REGISTRATIONClincalTrials.gov NCT02920892.FUNDING SOURCESNeuroNEXT network NIH grants U01NS096767, U24NS107200, U24NS107209, U01NS077323, U24NS107183, U24NS107168, U24NS107128, U24NS107199, U24NS107198, U24NS107166, U10NS077368, U01NS077366, U24NS107205, U01NS077179, and U01NS077352; NIH grant P50HD103526; and Novartis IIT grant AFQ056X2201T for provision of AFQ056.

BackgroundFragile X syndrome, with an approximate incidence rate of 1 in 4000 males to 1 in 8000 females, is the most prevalent genetic cause of heritable intellectual disability and the most common monogenic cause of autism spectrum disorder. The full mutation of the Fragile X Messenger Ribonucleoprotein-1 gene, characterized by an expansion of CGG trinucleotide repeats (>200 CGG repeats), leads to fragile X syndrome. Currently, there are no targeted treatments available for fragile X syndrome. In a recent large multi-site trial, FXLEARN, the effects of the mGluR5 negative allosteric modulator, AFQ056 (mavoglurant), were investigated, but did not show a significant impact of AFQ056 on language development in children with fragile X syndrome aged 3-6 years.ObjectivesThe current analyses from biospecimens collected in the FXLEARN study aimed to determine whether AFQ056 affects the level of potential biomarkers associated with Akt/mTOR and matrix metalloproteinase 9 signaling in young individuals with fragile X syndrome. Previous research has indicated that these biomarkers play crucial roles in the pathophysiology of fragile X syndrome.DesignA double-blind placebo-controlled parallel-group flexible-dose forced titration design.MethodsBlood samples for biomarkers were collected during the FXLEARN at baseline and subsequent visits (1- and 8-month visits). Biomarker analyses included fragile X messenger ribonucleoprotein-1 genotyping by Southern blot and PCR approaches, fragile X messenger ribonucleoprotein-1 mRNA levels determined by PCR, matrix metalloproteinase 9 levels' detection using a magnetic bead panel, and targets of the Akt/mTOR signaling pathway with their phosphorylation levels detected.ResultsThis research revealed that administering AFQ056 does not affect the expression levels of the investigated blood biomarkers in young children with fragile X syndrome.ConclusionOur findings of the lack of association between clinical improvement and biomarkers' levels in the treatment group are in line with the lack of benefit observed in the FXLEARN study. These findings indicate that AFQ056 does not provide benefits as assessed by primary or secondary endpoints.RegistrationClincalTrials.gov NCT02920892.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is an age-related neurodegenerative disorder caused by a premutation of the FMR1 gene on the X chromosome. Despite the pervasive physical and cognitive effects of FXTAS, no studies have examined language in symptomatic males and females, limiting utility as an outcome measure in clinical trials of FXTAS. The goal of this work is to determine (a) the extent to which male and female FMR1 premutation carriers with FXTAS symptoms differ in their language use and (b) whether language production predicts FXTAS symptoms. Thirty-one individuals with the FMR1 premutation (21M, 10F), ages 58-85 years with some symptoms of FXTAS, were recruited from a larger cross-sectional study. Participants completed a five-minute monologic language sample. Language transcripts were assessed for rate of dysfluencies, lexical-semantics, syntax, and speech rate. Multivariable linear and ordinal regressions were used to predict FXTAS-associated symptoms, cognitive functioning, and executive functioning. Males and females did not differ in their language use. Language production predicted FXTAS symptom severity, cognitive functioning, and executive functioning. Language production difficulties may co-occur with FXTAS-associated symptoms and may be a viable outcome measure in future clinical trials, with future research needed.

In this study, the potential role and interaction of the APOε and KLOTHO genes on the penetrance of fragile X-associated tremor/ataxia syndrome (FXTAS) and on the IQ trajectory were investigated. FXTAS was diagnosed based on molecular, clinical and radiological criteria. Males with the premutation (PM) over 50 years, 165 with and 34 without an FXTAS diagnosis, were included in this study and were compared based on their APO (ε2-ε3-ε4) and KLOTHO variant (KL-VS) genotypes. The effect of APOε4 on FXTAS stage and on diagnosis did not differ significantly by KL-VS genotype with interaction effect p = 0.662 and p = 0.91, respectively. In the FXTAS individuals with an APOε2 allele, a marginal significance was observed towards a larger decline in verbal IQ (VIQ) in individuals with an APOε4 allele compared to those without an APOε4 allele (p = 0.071). In conclusion, our findings suggest that the APOε4 and KL-VS genotypes alone or through their interaction effect do not appear to predispose to either FXTAS diagnosis or stage in male carriers of the PM allele. A further study is needed to establish the trend of IQ decline in the FXTAS individuals who carry APOε4 with APOε2 compared to those without APOε4.

IntroductionMetformin has been used as a targeted treatment to potentially improve cognition and slow the typical IQ decline that occurs during development among individuals with fragile X syndrome (FXS). In this follow-up study, we are following the trajectory of IQ and adaptive behavior changes over 1 to 3 years in individuals with FXS who are clinically treated with metformin in an open label trial.MethodIndividuals with FXS ages 6 to 25 years (mean 13.15 ± 5.50) and nonverbal IQ mean 57.69 (±15.46) were treated for 1-3 years (1.88 ± 0.63). They all had a baseline IQ test using the Leiter-III non-verbal cognitive assessment and the Vineland-III adaptive behavior assessment before the start of metformin. Repeat Leiter-III and Vineland-III were completed after at least 1 year of metformin (500-1,000 mg/dose given twice a day).ResultThere were no significant changes in non-verbal IQ or in the adaptive behavior measurements at FDR

Fragile X syndrome (FXS) is the leading inherited cause of intellectual disability (ID) and single gene cause of autism. Although most patients with FXS and the full mutation (FM) have complete methylation of the fragile X messenger ribonucleoprotein 1 (FMR1) gene, some have mosaicism in methylation and/or CGG repeat size, and few have completely unmethylated FM alleles. Those with a complete lack of methylation are rare, with little literature about the cognitive and behavioral phenotypes of these individuals. A review of past literature was conducted regarding individuals with unmethylated and mosaic FMR1 FM. We report three patients with an unmethylated FM FMR1 alleles without any behavioral or cognitive deficits. This is an unusual presentation for men with FM as most patients with an unmethylated FM and no behavioral phenotypes do not receive fragile X DNA testing or a diagnosis of FXS. Our cases showed that mosaic males with unmethylated FMR1 FM alleles may lack behavioral phenotypes due to the presence of smaller alleles producing the FMR1 protein (FMRP). However, these individuals could be at a higher risk of developing fragile X-associated tremor/ataxia syndrome (FXTAS) due to the increased expression of mRNA, similar to those who only have a premutation.

Fragile X syndrome (FXS) is the most common heritable cause of intellectual disability and autism spectrum disorder. The syndrome is often caused by greatly reduced or absent protein expression from the fragile X messenger ribonucleoprotein 1 (FMR1) gene due to expansion of a 5'-non-coding trinucleotide (CGG) element beyond 200 repeats (full mutation). To better understand the complex relationships among FMR1 allelotype, methylation status, mRNA expression, and FMR1 protein (FMRP) levels, FMRP was quantified in peripheral blood mononuclear cells for a large cohort of FXS (n = 154) and control (n = 139) individuals using time-resolved fluorescence resonance energy transfer. Considerable size and methylation mosaicism were observed among individuals with FXS, with FMRP detected only in the presence of such mosaicism. No sample with a minimum allele size greater than 273 CGG repeats had significant levels of FMRP. Additionally, an association was observed between FMR1 mRNA and FMRP levels in FXS samples, predominantly driven by those with the lowest FMRP values. This study underscores the complexity of FMR1 allelotypes and FMRP expression and prompts a reevaluation of FXS therapies aimed at reactivating large full mutation alleles that are likely not capable of producing sufficient FMRP to improve cognitive function.

BackgroundVestibular migraine (VM) is one of the most common causes of recurrent vertigo and presents with a history of spontaneous or positional vertigo with a history of migraine headaches. While research has identified a high prevalence of migraine headaches and vestibular deficits among fragile X premutation carriers, there has been no discussion about VM within this population.ObjectiveThis case series and review seeks to describe the clinical characteristics and pathophysiology of VM among individuals with the fragile X premutation. We also seek to discuss treatment and future steps in addressing VM in this population.MethodsA review of the literature regarding vestibular migraine and presentation of migraine headaches and vestibular deficits among premutation carriers was performed. A detailed clinical history of migraine headaches and vertigo was obtained from three patients with the fragile X premutation seen by the senior author (RJH).ResultsAll three cases first developed symptoms of migraine headaches earlier in life, with the development of VM near menopause. Two of the three cases developed progressive balance issues following the development of VM. All three cases found that their VM episodes were improved or resolved with pharmacological and/or lifestyle interventions.ConclusionsIt is important to recognize VM among premutation carriers because beneficial treatments are available. Future studies are needed regarding the prevalence of VM and the relationship to subsequent FXTAS. The pathophysiology of VM remains uncertain but possibilities include mitochondrial abnormalities, cranial nerve VIII toxicity secondary to neurotoxic protein accumulation, and calcitonin gene-related peptide (CGRP) signaling dysfunction due to altered levels of fragile X messenger ribonucleoprotein (FMRP).

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder that affects older premutation carriers (55-200 CGG repeats) of the fragile X gene. Despite the high prevalence of the FXTAS disorder, neuropathology studies of individuals affected by FXTAS are limited. We performed hematoxylin and eosin (H&E) staining in the hippocampus of 26 FXTAS cases and analyzed the tissue microscopically. The major neuropathological characteristics were white matter disease, intranuclear inclusions in neurons and astrocytes, and neuron loss. Astrocytes contained more and larger inclusions than neurons. There was a negative correlation between age of death and CGG repeat length in cases over the age of 60. The number of astroglial inclusions (CA3 and dentate gyrus) and the number of CA3 neuronal inclusions increased with elevated CGG repeat length. In the two cases with a CGG repeat size less than 65, FXTAS intranuclear inclusions were not present in the hippocampus, while in the two cases with less than 70 (65-70) CGG repeat expansion, neurons and astrocytes with inclusions were occasionally identified in the CA1 sub-region. These findings add hippocampus neuropathology to the previously reported changes in other areas of the brain in FXTAS patients, with implications for understanding FXTAS pathogenesis.

This study aimed to determine the association between severity of autism spectrum disorder (ASD) and cognitive, behavioral, and molecular measures in individuals with fragile X syndrome (FXS). Study inclusion criteria included individuals with FXS and (1) age 6-40 years, (2) full-scale IQ

Dysregulation of protein synthesis is one of the key mechanisms underlying autism spectrum disorder (ASD). However, the role of a major pathway controlling protein synthesis, the integrated stress response (ISR), in ASD remains poorly understood. Here, we demonstrate that the main arm of the ISR, eIF2α phosphorylation (p-eIF2α), is suppressed in excitatory, but not inhibitory, neurons in a mouse model of fragile X syndrome (FXS; Fmr1-/y). We further show that the decrease in p-eIF2α is mediated via activation of mTORC1. Genetic reduction of p-eIF2α only in excitatory neurons is sufficient to increase general protein synthesis and cause autism-like behavior. In Fmr1-/y mice, restoration of p-eIF2α solely in excitatory neurons reverses elevated protein synthesis and rescues autism-related phenotypes. Thus, we reveal a previously unknown causal relationship between excitatory neuron-specific translational control via the ISR pathway, general protein synthesis, and core phenotypes reminiscent of autism in a mouse model of FXS.

Individuals with autism spectrum disorder present with difficulties in social communication, restricted interests or behaviors and other co-morbidities. About 2 to 10% of cases of autism have a genetic cause, and Fragile X Syndrome (FXS) is reported in 0 to 6.5% of individuals with autism. However, the FXS and premutation prevalence among Filipino children has never been reported. The aim of the study was to establish the presence of FXS or premutation carriers among Filipino children with autism and to describe the phenotypic characteristic of cases identified. Blood was collected from 235 children aged 2-6 years old and diagnosed with autism. Samples were analyzed using PCR methods to amplify CGG repeats in the FMRI gene. The diagnosis of autism was confirmed through the Autism Diagnostic Observation Schedule-2. Additional characteristics were documented from a physical examination, Griffiths Scales of Child Development assessment and a parent-answered questionnaire using the Vineland Adaptive Behavior Scale. Fragile X testing through PCR methods in 235 children with diagnosed autism showed 220 (93.6%) were negative, no full mutations, 1 (0.436%) premutation carrier and 14 (5.95%) cases contained intermediate alleles. The FXS testing was limited to confirmed cases of autism, which is considered a high-risk group and does not provide prevalence for the general Filipino population. Subjects were self-referred or referred by clinicians, which may not represent the Filipino autism population with a bias towards those with means for clinical consultations and ability to travel to the place of testing. Samples were not measured for mosaicism, DNA methylation or AGG interspersion patterns. These may have effects on the CGG repeat expansion and overall presentation of FXS. Findings from a single premutation carrier cannot characterize features distinctly present in Filipinos with the mutation. Nevertheless, these results support the data that the prevalence of FXS in Asian populations may be lower than non-Asian populations. This can contribute to a better understanding of FXS and genetic causes of autism in the Philippines and other Asian populations.

The premutation of the fragile X messenger ribonucleoprotein 1 (FMR1) gene is characterized by an expansion of the CGG trinucleotide repeats (55 to 200 CGGs) in the 5 untranslated region and increased levels of FMR1 mRNA. Molecular mechanisms leading to fragile X-premutation-associated conditions (FXPAC) include cotranscriptional R-loop formations, FMR1 mRNA toxicity through both RNA gelation into nuclear foci and sequestration of various CGG-repeat-binding proteins, and the repeat-associated non-AUG (RAN)-initiated translation of potentially toxic proteins. Such molecular mechanisms contribute to subsequent consequences, including mitochondrial dysfunction and neuronal death. Clinically, premutation carriers may exhibit a wide range of symptoms and phenotypes. Any of the problems associated with the premutation can appropriately be called FXPAC. Fragile X-associated tremor/ataxia syndrome (FXTAS), fragile X-associated primary ovarian insufficiency (FXPOI), and fragile X-associated neuropsychiatric disorders (FXAND) can fall under FXPAC. Understanding the molecular and clinical aspects of the premutation of the FMR1 gene is crucial for the accurate diagnosis, genetic counseling, and appropriate management of affected individuals and families. This paper summarizes all the known problems associated with the premutation and documents the presentations and discussions that occurred at the International Premutation Conference, which took place in New Zealand in 2023.

Fragile X-associated Tremor/Ataxia Syndrome (FXTAS) is a neurodegenerative disorder associated with the FMR1 premutation. Currently, it is not possible to determine when and if individual premutation carriers will develop FXTAS. Thus, with the aim to identify biomarkers for early diagnosis, development, and progression of FXTAS, along with associated dysregulated pathways, we performed blood proteomic profiling of premutation carriers (PM) who, as part of an ongoing longitudinal study, emerged into two distinct groups: those who developed symptoms of FXTAS (converters, CON) over time (at subsequent visits) and those who did not (non-converters, NCON). We compared these groups to age-matched healthy controls (HC). We assessed CGG repeat allele size by Southern blot and PCR analysis. The proteomic profile was obtained by liquid chromatography mass spectrometry (LC-MS/MS). We identified several significantly differentiated proteins between HC and the PM groups at Visit 1 (V1), Visit 2 (V2), and between the visits. We further reported the dysregulated protein pathways, including sphingolipid and amino acid metabolism. Our findings are in agreement with previous studies showing that pathways involved in mitochondrial bioenergetics, as observed in other neurodegenerative disorders, are significantly altered and appear to contribute to the development of FXTAS. Lastly, we compared the blood proteome of the PM who developed FXTAS over time with the CSF proteome of the FXTAS patients recently reported and found eight significantly differentially expressed proteins in common. To our knowledge, this is the first report of longitudinal proteomic profiling and the identification of unique biomarkers and dysregulated protein pathways in FXTAS.

BackgroundFragile X syndrome (FXS) and fetal alcohol syndrome disorders are both common causes of intellectual disability in children. When both conditions are present in the same individual, the resultant phenotype may make identification of clinical issues and management challenging.Case presentationIn this case report, we present a case of triplets who had significant in utero alcohol exposure; 2 of whom also have FXS and the other not having the fragile X mutation. The siblings with FXS have subtle differences in the physical phenotype compared with the other one, who has prominent features of partial fetal alcohol syndrome instead. However, all 3 siblings have intellectual impairment (although this is more severe in the 2 with FXS), meet diagnostic criteria for autism spectrum disorder, and present with severe behavioral challenges. The clinical presentation of the 2 siblings with FXS is much more severe as compared to a child with FXS alone, and this is likely due to the additive effect of in utero alcohol exposure and environmental factors. We discuss the combination of these 2 pathologies and how this can affect the overall clinical presentation.ConclusionIn the management of children with FXS, evaluation for other risk factors that can have neurobehavioral sequelae is important, and these can affect clinical presentation and prognosis.

Brain changes at the end-stage of fragile X-associated tremor/ataxia syndrome (FXTAS) are largely unknown due to mobility impairment. We conducted a postmortem MRI study of FXTAS to quantify cerebrovascular disease, brain atrophy and iron content, and examined their relationships using principal component analysis (PCA). Intracranial hemorrhage (ICH) was observed in 4/17 FXTAS cases, among which one was confirmed by histologic staining. Compared with seven control brains, FXTAS cases showed higher ratings of T2-hyperintensities (indicating cerebral small vessel disease) in the cerebellum, globus pallidus and frontoparietal white matter, and significant atrophy in the cerebellar white matter, red nucleus and dentate nucleus. PCA of FXTAS cases revealed negative associations of T2-hyperintensity ratings with anatomic volumes and iron content in the white matter, hippocampus and amygdala, that were independent from a highly correlated number of regions with ICH and iron content in subcortical nuclei. Post-hoc analysis confirmed PCA findings and further revealed increased iron content in the white matter, hippocampus and amygdala in FXTAS cases compared to controls, after adjusting for T2-hyperintensity ratings. These findings indicate that both ischemic and hemorrhagic brain damage may occur in FXTAS, with the former being marked by demyelination/iron depletion and atrophy, and the latter by ICH and iron accumulation in basal ganglia.

ContextThe Modified Checklist for Autism in Toddlers, Revised with Follow-up (M-CHAT-R/F) is used worldwide to screen for autism spectrum disorder (ASD).ObjectiveTo calculate psychometric properties of the M-CHAT-R/F for subsequent diagnosis of ASD.Data sourcesSystematic searches of Medline, Embase, SCOPUS, and Trip Pro databases from January 2014 to November 2021.Study selectionStudies were included if they (1) used the M-CHAT-R/F (2) applied standard scoring protocol, (3) used a diagnostic assessment for ASD, and (4) reported at least 1 psychometric property of the M-CHAT-R/F.Data extractionTwo independent reviewers completed screening, full-text review, data extraction, and quality assessment, following Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. A random-effects model was used to derive pooled estimates and assess for between-study heterogeneity.ResultsOf 667 studies identified, 15 with 18 distinct samples from 10 countries (49 841 children) were used in the meta-analysis. Pooled positive predictive value (PPV), was 57.7% (95% confidence interval [CI] 48.6-66.8, τ2 = 0.031). PPV was higher among high-risk (75.6% [95% CI 66.0-85.2]) than low-risk samples (51.2% [95% CI 43.0-59.5]). Pooled negative predictive value was 72.5% (95% CI 62.5-82.4 τ2 = 0.031), sensitivity was 82.6% (95% CI 76.2-88.9) and specificity 45.7% (95% CI 25.0-66.4).LimitationsNegative predictive value, sensitivity, and specificity were calculated based on small sample sizes because of limited or no evaluation of screen-negative children.ConclusionsThese results support use of the M-CHAT-R/F as a screening tool for ASD. Caregiver counseling regarding likelihood of an ASD diagnosis after positive screen should acknowledge the moderate PPV.

Fragile X Syndrome (FXS) is one of the most common causes of intellectual disability. It is the result of the expansion of the trinucleotide CGG repeat (>200) in the fragile x messenger ribonucleoprotein 1 (FMR1) gene, leading to a deficiency or absence of the fragile X messenger ribonucleoprotein (FMRP). Many studies have found that there is a trend of IQdecline among FXS individuals around adolescent years. Recent studies also found that metformin rescues some of the cognitive deficits in FXS mouse models, and case reports show similar benefits in FXS individuals.This suggests that metformin may have clinical value as a targeted treatment to slow IQ decline in FXS individuals. In this follow-up study, we are assessing pre- and post-metformin IQ scores among individuals with FXS after 1 year of treatment.

Fragile X (FMR1) premutation is a common mutation that affects about 1 in 200 females and 1 in 450 males and can lead to the development of fragile-X-associated tremor/ataxia syndrome (FXTAS). Although there is no targeted, proven treatment for FXTAS, research suggests that sulforaphane, an antioxidant present in cruciferous vegetables, can enhance mitochondrial function and maintain redox balance in the dermal fibroblasts of individuals with FXTAS, potentially leading to improved cognitive function. In a 24-week open-label trial involving 15 adults aged 60-88 with FXTAS, 11 participants successfully completed the study, demonstrating the safety and tolerability of sulforaphane. Clinical outcomes and biomarkers were measured to elucidate the effects of sulforaphane. While there were nominal improvements in multiple clinical measures, they were not significantly different after correction for multiple comparisons. PBMC energetic measures showed that the level of citrate synthase was higher after sulforaphane treatment, resulting in lower ATP production. The ratio of complex I to complex II showed positive correlations with the MoCA and BDS scores. Several mitochondrial biomarkers showed increased activity and quantity and were correlated with clinical improvements.

[This corrects the article DOI: 10.3389/fped.2023.1064104.].

The course of pathophysiological mechanisms involved in fragile X-associated tremor/ataxia syndrome (FXTAS) remains largely unknown. Previous proteomics and metabolomics studies conducted in blood samples collected from FMR1 premutation carriers with FXTAS reported abnormalities in energy metabolism, and precursors of gluconeogenesis showed significant changes in plasma expression levels in FMR1 premutation carriers who developed FXTAS. We conducted an analysis of postmortem human brain tissues from 44 donors, 25 brains with FXTAS, and 19 matched controls. We quantified the metabolite relative abundance in the inferior temporal gyrus and the cerebellum using untargeted mass spectrometry (MS)-based metabolomics. We investigated how the metabolite type and abundance relate to the number of cytosine-guanine-guanine (CGG) repeats, to markers of neurodegeneration, and to the symptoms of FXTAS. A metabolomic analysis identified 191 primary metabolites, the data were log-transformed and normalized prior to the analysis, and the relative abundance was compared between the groups. The changes in the relative abundance of a set of metabolites were region-specific with some overlapping results; 22 metabolites showed alterations in the inferior temporal gyrus, while 21 showed differences in the cerebellum. The relative abundance of cytidine was decreased in the inferior temporal gyrus, and a lower abundance was found in the cases with larger CGG expansions; oleamide was significantly decreased in the cerebellum. The abundance of 11 metabolites was influenced by changes in the CGG repeat number. A histological evaluation found an association between the presence of microhemorrhages in the inferior temporal gyrus and a lower abundance of 2,5-dihydroxypyrazine. Our study identified alterations in the metabolites involved in the oxidative-stress response and bioenergetics in the brains of individuals with FXTAS. Significant changes in the abundance of cytidine and oleamide suggest their potential as biomarkers and therapeutic targets for FXTAS.

Fragile X syndrome is caused by the expansion of CGG triplets in the FMR1 gene, which generates epigenetic changes that silence its expression. The absence of the protein coded by this gene, FMRP, causes cellular dysfunction, leading to impaired brain development and functional abnormalities. The physical and neurologic manifestations of the disease appear early in life and may suggest the diagnosis. However, it must be confirmed by molecular tests. It affects multiple areas of daily living and greatly burdens the affected individuals and their families. Fragile X syndrome is the most common monogenic cause of intellectual disability and autism spectrum disorder; the diagnosis should be suspected in every patient with neurodevelopmental delay. Early interventions could improve the functional prognosis of patients with Fragile X syndrome, significantly impacting their quality of life and daily functioning. Therefore, healthcare for children with Fragile X syndrome should include a multidisciplinary approach.

This study contributes to a greater understanding of the utility of molecular biomarkers to identify clinical phenotypes of fragile X syndrome (FXS). Correlations of baseline clinical trial data (molecular measures-FMR1 mRNA, CYFIP1 mRNA, MMP9 and FMRP protein expression levels, nonverbal IQ, body mass index and weight, language level, NIH Toolbox, adaptive behavior rating, autism, and other mental health correlates) of 59 participants with FXS ages of 6-32 years are reported. FMR1 mRNA expression levels correlated positively with adaptive functioning levels, expressive language, and specific NIH Toolbox measures. The findings of a positive correlation of MMP-9 levels with obesity, CYFIP1 mRNA with mood and autistic symptoms, and FMR1 mRNA expression level with better cognitive, language, and adaptive functions indicate potential biomarkers for specific FXS phenotypes. These may be potential markers for future clinical trials for targeted treatments of FXS.

Carriers of the FMR1 premutation (PM) allele are at risk of one or more clinical conditions referred to as FX premutation-associated conditions (FXPAC). Since the FMR1 gene is on the X chromosome, the activation ratio (AR) may impact the risk, age of onset, progression, and severity of these conditions. The aim of this study was to evaluate the reliability of AR measured using different approaches and to investigate potential correlations with clinical outcomes. Molecular and clinical assessments were obtained for 30 PM female participants, and AR was assessed using both Southern blot analysis (AR-Sb) and methylation PCR (AR-mPCR). Higher ARs were associated with lower FMR1 transcript levels for any given repeat length. The higher AR-Sb was significantly associated with performance, verbal, and full-scale IQ scores, confirming previous reports. However, the AR-mPCR was not significantly associated (p > 0.05) with these measures. Similarly, the odds of depression and the number of medical conditions were correlated with higher AR-Sb but not correlated with a higher AR-mPCR. This study suggests that AR-Sb may be a more reliable measure of the AR in female carriers of PM alleles. However, further studies are warranted in a larger sample size to fully evaluate the methylation status in these participants and how it may affect the clinical phenotype.

Carriers of a premutation allele (PM) in the FMR1 gene are at risk of developing a number of Fragile X premutation asssociated disorders (FXPAC), including Fragile X-associated Tremor/Ataxia Syndrome (FXTAS), Fragile X-associated Primary Ovarian Insufficiency (FXPOI), and Fragile X-associated neuropsychiatric disorders (FXAND). We have recently reported somatic CGG allele expansion in female PM; however, its clinical significance remains unclear. The aim of this study was to examine the potential clinical association between somatic FMR1 allele instability and PM associated disorders. Participants comprised of 424 female PM carriers age 0.3- 90 years. FMR1 molecular measures and clinical information on the presence of medical conditions, were determined for all subjects for primary analysis. Two sub-groups of participants (age ≥ 25, N = 377 and age ≥ 50, N = 134) were used in the analysis related to presence of FXPOI and FXTAS, respectively. Among all participants (N = 424), the degree of instability (expansion) was significantly higher (median 2.5 vs 2.0, P = 0.026) in participants with a diagnosis of attention deficit hyperactivity disorder (ADHD) compared to those without. FMR1 mRNA expression was significantly higher in subjects with any psychiatric disorder diagnosis (P = 0.0017); specifically, in those with ADHD (P = 0.009), and with depression (P = 0.025). Somatic FMR1 expansion was associated with the presence of ADHD in female PM and FMR1 mRNA levels were associated with the presence of mental health disorders. The findings of our research are innovative as they suggest a potential role of the CGG expansion in the clinical phenotype of PM and may potentially guide clinical prognosis and management.

Fragile X syndrome (FXS) is a global neurodevelopmental disorder caused by the expansion of CGG trinucleotide repeats (≥200) in the Fragile X Messenger Ribonucleoprotein 1 (FMR1) gene. FXS is the hallmark of Fragile X-associated disorders (FXD) and the most common monogenic cause of inherited intellectual disability and autism spectrum disorder. There are several animal models used to study FXS. In the FXS model of Drosophila, the only ortholog of FMR1, dfmr1, is mutated so that its protein is missing. This model has several relevant phenotypes, including defects in the circadian output pathway, sleep problems, memory deficits in the conditioned courtship and olfactory conditioning paradigms, deficits in social interaction, and deficits in neuronal development. In addition to FXS, a model of another FXD, Fragile X-associated tremor/ataxia syndrome (FXTAS), has also been established in Drosophila. This review summarizes many years of research on FXD in Drosophila models.

Multiple lines of evidence suggest a central role for the endocannabinoid system (ECS) in the neuronal development and cognitive function and in the pathogenesis of fragile X syndrome (FXS). This review describes the ECS, its role in the central nervous system, how it is dysregulated in FXS, and the potential role of cannabidiol as a treatment for FXS. FXS is caused by deficiency or absence of the fragile X messenger ribonucleoprotein 1 (FMR1) protein, FMRP, typically due to the presence of >200 cytosine, guanine, guanine sequence repeats leading to methylation of the FMR1 gene promoter. The absence of FMRP, following FMR1 gene-silencing, disrupts ECS signaling, which has been implicated in FXS pathogenesis. The ECS facilitates synaptic homeostasis and plasticity through the cannabinoid receptor 1, CB1, on presynaptic terminals, resulting in feedback inhibition of neuronal signaling. ECS-mediated feedback inhibition and synaptic plasticity are thought to be disrupted in FXS, leading to overstimulation, desensitization, and internalization of presynaptic CB1 receptors. Cannabidiol may help restore synaptic homeostasis by acting as a negative allosteric modulator of CB1, thereby attenuating the receptor overstimulation, desensitization, and internalization. Moreover, cannabidiol affects DNA methylation, serotonin 5HT1A signal transduction, gamma-aminobutyric acid receptor signaling, and dopamine D2 and D3 receptor signaling, which may contribute to beneficial effects in patients with FXS. Consistent with these proposed mechanisms of action of cannabidiol in FXS, in the CONNECT-FX trial the transdermal cannabidiol gel, ZYN002, was associated with improvements in measures of social avoidance, irritability, and social interaction, particularly in patients who are most affected, showing ≥90% methylation of the FMR1 gene.

IntroductionFragile X syndrome (FXS) is a X-linked neurodevelopmental disorder (NDD). This study aims to investigate the incidence of FXS in Chinese children and analyze the comprehensive clinical characteristics of these FXS children.MethodsChildren diagnosed with idiopathic NDD were recruited between 2016 and 2021 from the department of Child Health Care, Children's Hospital of Fudan University. We combined tetraplet-primed PCR-capillary electrophoresis and whole exome sequencing (WES)/panel or array-based comparative genomic hybridization (array-CGH) to identify the size of the CGG repeats and the mutations or copy number variations (CNVs) in the genome and in FMR1. The clinical features of FXS children were analyzed according to pediatricians' recording, parental questionnaires, the results of examinations and follow-up.ResultsThe incidence of FXS in Chinese children with idiopathic NDD was 2.4% (42/1753) and in those with FXS, 2.38% had a deletion (1/42). Here, we present the clinical characteristics of 36 children with FXS. Overweight was observed in two boys. The average intelligence quotient (IQ)/development quotient (DQ) of all FXS patients was 48. The average ages of meaningful words and walking alone were 2 years and 10 months and 1 year and 7 months, respectively. The most frequent repetitive behavior was stimulated by hyperarousal to sensory stimulation. On social aspects, social withdrawal, social anxiety, and shyness accounted for 75%, 58%, and 56% of the total number of children, respectively. Approximately 60% of FXS children in this cohort were emotionally labile and prone to temper tantrums. Self-injury and aggression toward others could also be observed, at 19% and 28%, respectively. The most frequent behavioral problem was attention-deficit hyperactivity disorder (ADHD) seen in 64% and the most common facial features were a narrow and elongated face and large or prominent ears in 92% of patients.DiscussionScreening of FMR1 full mutation provides the possibility for patients' further medical supports and the clinical features of FXS children obtained in this study will increase the understanding and diagnosis of FXS.

PurposeThis study examined relationships among family characteristics, caregiver change in use of strategies, and child growth in spoken language over the course of a parent-implemented language intervention (PILI) that was developed to address some of the challenges associated with the fragile X syndrome (FXS) phenotype.MethodParticipants were 43 parent-child dyads from two different PILI studies, both of which taught parents various language facilitation strategies to support child language. Before starting the intervention, parents reported on their mental health, parenting stress, and parenting competence. This study focused on potential barriers to treatment gains by examining correlations between the measures of parent well-being and (a) parent change in use of intervention strategies taught in the PILI and (b) changes in child language outcomes from preto post-intervention.ResultsParents in this study had elevated mental health symptoms across several domains and increased rates of parenting stress. Furthermore, although PILI resulted in treatment gains for both parents and children, a variety of parent mental health symptoms were found to be significantly and negatively associated with change in use of strategies and growth in child language over the course of the intervention. Some inconsistent findings also emerged regarding the relationships between parenting stress and competence and change in parent strategy use and growth in child language.ConclusionsThis study provides preliminary evidence that parents who are experiencing significant mental health challenges may have a more difficult time participating fully in PILIs and that there may be subsequent effects on child outcomes. Future PILIs could benefit from addressing parent well-being as a substantial part of the intervention program.

BackgroundCarriers of the FMR1 premutation are at increased risk of developing a late-onset progressive neurodegenerative disease, fragile X-associated tremor/ataxia syndrome (FXTAS), characterized by intention tremor, gait ataxia, and cognitive decline. Cross-sectional studies to date have provided evidence that neuropsychological changes, such as executive function alterations, or subtle motor changes, may precede the onset of formal FXTAS, perhaps characterizing a prodromal state. However, the lack of longitudinal data has prevented the field from forming a clear picture of progression over time within individuals, and we lack consensus regarding early markers of risk and measures that may be used to track response to intervention.MethodsThis was a longitudinal study of 64 male FMR1 premutation carriers (Pm) without FXTAS at study entry and 30 normal controls (Nc), aged 40 to 80 years (Pm M = 60.0 years; Nc M = 57.4 years). Fifty of the Pm and 22 of the Nc were re-assessed after an average of 2.33 years, and 37 Pm and 20 Nc were re-assessed a third time after an average of another 2.15 years. Eighteen of 64 carriers (28%) converted to FXTAS during the study to date. Neuropsychological assessments at each time point, including components of the Cambridge Neuropsychological Test Automated Battery (CANTAB), tapped domains of episodic and working memory, inhibitory control, visual attention, planning, executive control of movement, and manual speed and dexterity. Age-based mixed models were used to examine group differences in change over time on the outcomes in the full sample, and differences were further evaluated in 15 trios (n = 45; 15 Pm "converters," 15 Pm "nonconverters," 15 Nc) that were one-one matched on age, education, and socioeconomic status.ResultsCompared to Nc, Pm showed significantly greater rates of change over time in visual working memory, motor dexterity, inhibitory control, and manual movement speed. After multiple comparison correction, significant effects remained for motor dexterity. Worsening inhibitory control and slower manual movements were related to progression in FXTAS stage, but these effects became statistically non-significant after correcting for multiple comparisons. Higher FMR1 mRNA correlated with worsening manual reaction time but did not survive multiple comparisons and no other molecular measures correlated with neuropsychological changes. Finally, trio comparisons revealed greater rate of decline in planning and manual movement speed in Pm converters compared to Pm nonconverters.ConclusionsAccelerated decline in executive function and subtle motor changes, likely mediated by frontocerebellar circuits, may precede, and then track with the emergence of formal FXTAS symptoms. Further research to develop and harmonize clinical assessment of FMR1 carriers across centers is needed to prepare for future prophylactic and treatment trials for this disorder.

Fragile X syndrome (FXS) is caused by the full mutation in the fragile x messenger ribonucleoprotein 1 (FMR1) gene leading to the absence of the fragile X protein (FXP). Previous studies show that individuals with FXS exhibit changing behavior over time; therefore, this study aimed to elucidate the aberrant behavior profile of FXS individuals. The Aberrant Behavior Checklist-Community (ABC-C) was used to measure the aberrant behavior profile of individuals with FXS, which was rated by the parent/caregiver combined with clinical impression. A total of 58 items were used to assess aberrant behaviors across five subscales. Forty-nine individuals with FXS were included (32 males, 17 females) with a mean age of 32.9 ± 14.62 years in males and 33.4 ± 13.98 years in females. The average score of irritability and hyperactivity was significantly higher in male FXS individuals (5.37 ± 6.231 and 10.28 ± 8.524) than in female individuals (3.24 ± 7.093 and 3.76 ± 3.327) with p = 0.046 and p = 0.001, respectively. Overall irritability in FXS individuals significantly decreased over time (ß = -0.141; p = 0.032). A modest worsening in lethargy/social withdrawal in males across age and a gentle improvement in hyperactivity/noncompliance in male of FXS individuals were observed. FXS males had higher hyperactivity problems than FXS female individuals across age.

BackgroundFragile X syndrome (FXS) is associated with dysregulated endocannabinoid signaling and may therefore respond to cannabidiol therapy.DesignCONNECT-FX was a double-blind, randomized phase 3 trial assessing efficacy and safety of ZYN002, transdermal cannabidiol gel, for the treatment of behavioral symptoms in children and adolescents with FXS.MethodsPatients were randomized to 12 weeks of ZYN002 (250 mg or 500 mg daily [weight-based]) or placebo, as add-on to standard of care. The primary endpoint assessed change in social avoidance (SA) measured by the Aberrant Behavior Checklist-Community Edition FXS (ABC-CFXS) SA subscale in a full cohort of patients with a FXS full mutation, regardless of the FMR1 methylation status. Ad hoc analyses assessed efficacy in patients with ≥ 90% and 100% methylation of the promoter region of the FMR1 gene, in whom FMR1 gene silencing is most likely.ResultsA total of 212 patients, mean age 9.7 years, 75% males, were enrolled. A total of 169 (79.7%) patients presented with ≥ 90% methylation of the FMR1 promoter and full mutation of FMR1. Although statistical significance for the primary endpoint was not achieved in the full cohort, significant improvement was demonstrated in patients with ≥ 90% methylation of FMR1 (nominal P = 0.020). This group also achieved statistically significant improvements in Caregiver Global Impression-Change in SA and isolation, irritable and disruptive behaviors, and social interactions (nominal P-values: P = 0.038, P = 0.028, and P = 0.002). Similar results were seen in patients with 100% methylation of FMR1. ZYN002 was safe and well tolerated. All treatment-emergent adverse events (TEAEs) were mild or moderate. The most common treatment-related TEAE was application site pain (ZYN002: 6.4%; placebo: 1.0%).ConclusionsIn CONNECT-FX, ZYN002 was well tolerated in patients with FXS and demonstrated evidence of efficacy with a favorable benefit risk relationship in patients with ≥ 90% methylation of the FMR1 gene, in whom gene silencing is most likely, and the impact of FXS is typically most severe.Trial registrationThe CONNECT-FX trial is registered on Clinicaltrials.gov (NCT03614663).

Premutation alleles with 55-200 CGG repeats in FMR1 can lead to fragile X-associated tremor/ataxia syndrome (FXTAS). In this case study, we report uncontrolled gout in a 68-year-old male with FXTAS with multiple sites of involvement including a rare gouty tophus in the nasal region.

BackgroundFragile X syndrome is characterized by a myriad of physical features, behavioral features, and medical problems. Commonly found behavioral features are hyperactivity, anxiety, socialization difficulties, and ASD. There is also a higher incidence than in the general population of strabismus, otitis media, and mitral valve prolapse. In addition, one of the most common medical problems associated with FXS is an increased risk of seizures. A subset of individuals carrying the full mutation of the FMR1 gene and diagnosed with fragile X syndrome (FXS) are reported to experience seizures, mostly during the first 10 years of their life span.MethodsAs part of a larger project to identify genetic variants that modify the risk of seizures, we collected clinical information from 49 carriers with FXS who experienced seizures and 46 without seizures. We compared seizure type and comorbid conditions based on the source of data as well as family history of seizures.ResultsWe found that the concordance of seizure types observed by parents and medical specialists varied by type of seizure. The most common comorbid condition among those with seizures was autism spectrum disorder (47% per medical records vs. 33% per parent report compared with 19% among those without seizures per parent report); the frequency of other comorbid conditions did not differ among groups. We found a slightly higher frequency of family members who experienced seizures among the seizure group compared with the nonseizure group.ConclusionThis study confirms previously reported features of seizures in FXS, supports additional genetic factors, and highlights the importance of information sources, altogether contributing to a better understanding of seizures in FXS.

Fragile X (FXS) and Turner (TS) syndromes are X-chromosome-associated disorders. Herein, we report the case of a girl in middle childhood with bicuspid aortic valve in infancy, growth failure, global developmental delay (GDD), visual problems, and coexisting attention-deficit/hyperactivity and anxiety disorders. A high-resolution karyotype in 20 cells revealed 46,X,Idic(X)(p11.21)[19]/45,X[1], suggestive of variant TS. Given her atypical phenotype, subsequent DNA testing was performed. Four FMR1 cytosine-guanine-guanine repeats (30, 410, 580 and 800) were identified, confirming the additional FXS diagnosis. This case study highlights the importance of additional genetic testing in individuals with atypical variant TS, such as unexplained GDD and distinct facial characteristics. The additional FXS diagnosis prompted new therapeutic development for the patient to advance precision healthcare.

BackgroundWhile an association between full mutation CGG-repeat expansions of the Fragile X Mental Retardation 1 (FMR1) gene and connective tissue problems are clearly described, problems in fragile X premutation carriers (fXPCs) CGG-repeat range (55-200 repeats) of the FMR1 gene may be overlooked.ObjectiveTo report five FMR1 fXPCs cases with the hypermobile Ehlers-Danlos syndrome (hEDS) phenotype.MethodsWe collected medical histories and FMR1 molecular measures from five cases who presented with joint hypermobility and loose connective tissue and met inclusion criteria for hEDS.ResultsFive cases were female and ranged between 16 and 49 years. The range of CGG-repeat allele sizes ranged from 66 to 150 repeats. All had symptoms of hEDS since early childhood. Commonalities in molecular pathogenesis and coexisting conditions between the fXPCs and hEDS are also presented. The premutation can lead to a reduction of fragile X mental retardation protein, which is crucial in maintaining functions of the extracellular matrix-related proteins, particularly matrix metallopeptidase 9 and elastin. Moreover, elevated FMR1 messenger RNA causes sequestration of proteins, which results in RNA toxicity.ConclusionBoth hEDS phenotype and premutation involvement may co-occur because of related commonalities in pathogenesis.

Fragile X Syndrome (FXS), the leading monogenic cause of intellectual disability and autism spectrum disorder, is caused by expansion of a CGG trinucleotide repeat in the 5'-UTR of the Fragile X Mental Retardation-1 (FMR1) gene. Epigenetic silencing of FMR1 results in loss of the Fragile X Mental Retardation Protein (FMRP). Although most studies to date have focused on excitatory neurons, recent evidence suggests that GABAergic inhibitory networks are also affected. To investigate human GABAergic neurogenesis, we established a method to reproducibly derive inhibitory neurons from multiple FXS and control human pluripotent stem cell (hPSC) lines. Electrophysiological analyses suggested that the developing FXS neurons had a delay in the GABA functional switch, a transition in fetal development that converts the GABAA channel's function from depolarization to hyperpolarization, with profound effects on the developing brain. To investigate the cause of this delay, we analyzed 14 400 single-cell transcriptomes from FXS and control cells at 2 stages of GABAergic neurogenesis. While control and FXS cells were similar at the earlier time point, the later-stage FXS cells retained expression of neuroblast proliferation-associated genes and had lower levels of genes associated with action potential regulation, synapses, and mitochondria compared with controls. Our analysis suggests that loss of FMRP prolongs the proliferative stage of progenitors, which may result in more neurons remaining immature during the later stages of neurogenesis. This could have profound implications for homeostatic excitatory-inhibitory circuit development in FXS, and suggests a novel direction for understanding disease mechanisms that may help to guide therapeutic interventions.

BackgroundQuantitative measurement of eye movements can reveal subtle progression in neurodegenerative diseases.ObjectiveTo determine if quantitative measurements of eye movements may reveal subtle progression of fragile X-associated tremor and ataxia (FXTAS).MethodsProsaccade (PS) and antisaccade (AS) behavior was analyzed in 25 controls, 57 non-FXTAS carriers, and 46 carriers with FXTAS.ResultsSymptomatic individuals with FXTAS had longer AS latencies, increased rates of AS errors, and increased AS dysmetria relative to non-FXTAS carriers and controls. These deficits, along with PS latency and velocity, were greater in advanced FXTAS stages.ConclusionAS deficits differentiated FXTAS from non-FXTAS premutation carriers implicating top-down control and frontostriatal deterioration. However, the absence of group differences between non-FXTAS carriers and controls in AS and PS markers suggests saccade performance may not be a sensitive enough measure for detecting conversion to FXTAS, but instead more helpful as translational biomarkers of FXTAS progression.

Neurodevelopmental disorders (NDDs) are conditions that present with brain dysfunction due to alterations in the processes of brain development. They present with neuropsychiatric, cognitive, and motor symptoms. Autism spectrum disorder (ASD) and Fragile X syndrome (FXS) are two of the most common NDDs. Human brain tissue is a scarce resource that is obtained from postmortem donations. In the case of NDDs, specifically autism, the reduced donation rate of brains prevents researchers to investigate its pathology and fine anatomy. The Hispano-American Brain Bank of Neurodevelopmental Disorders (Banco Hispanoamericano de CErebros de trastornos del NEurodesarrollo) or CENE is a large-scale brain bank for neurodevelopmental disorders in Hispano-America and the US. CENE's objectives are to collect and distribute brains of patients with NDDS, with a focus on ASD and FXS, to perform research, promote education of future scientists, and enhance public awareness about the importance of human tissue availability for scientific research on brain function and disease. CENE has thus far established a bilingual system of nodes and teams in several American countries including California-US, Pennsylvania-US, México, Puerto Rico, Colombia, and Dominican Republic. CENE ensures that postmortem NDD samples used in research better match the world's genetic and ethnic diversity. CENE enables and expands NDD brain research worldwide, particularly with respect to ASD and FXS.