Cognitive aspects of Fragile X syndrome

Using Organoids to Model Sex Differences in the Human Brain

Sex differences are widespread during neurodevelopment and play a role in neuropsychiatric conditions such as autism, which is more prevalent in males than females. In humans, males have been shown to have larger brain volumes than females with development of the hippocampus and amygdala showing prominent sex differences. Mechanistically, sex steroids and sex chromosomes drive these differences in brain development, which seem to peak during prenatal and pubertal stages. Animal models have played a crucial role in understanding sex differences, but the study of human sex differences requires an experimental model that can recapitulate complex genetic traits. To fill this gap, human induced pluripotent stem cell-derived brain organoids are now being used to study how complex genetic traits influence prenatal brain development. For example, brain organoids from individuals with autism and individuals with X chromosome-linked Rett syndrome and fragile X syndrome have revealed prenatal differences in cell proliferation, a measure of brain volume differences, and excitatory-inhibitory imbalances. Brain organoids have also revealed increased neurogenesis of excitatory neurons due to androgens. However, despite growing interest in using brain organoids, several key challenges remain that affect its validity as a model system. In this review, we discuss how sex steroids and the sex chromosomes each contribute to sex differences in brain development. Then, we examine the role of X chromosome inactivation as a factor that drives sex differences. Finally, we discuss the combined challenges of modeling X chromosome inactivation and limitations of brain organoids that need to be taken into consideration when studying sex differences.

Enhancing task performance in adults with intellectual disability through modified goal management training and assistive technology with errorless learning: A randomized controlled trial

Individuals with intellectual disabilities often fail to learn complex tasks. Modified Goal Management Training (mGMT) or Errorless Learning combined with assistive technology (App + EL) can help. The goal is to demonstrate the effectiveness of mGMT and/or App + EL in learning complex tasks. We employed a randomized controlled crossover design. One group started with mGMT (N = 16), and the other with App + EL (N = 15). We compared their performance with that of a passive control group (N = 15). The training consisted of six sessions of 30 minutes each. Success was analyzed using the Goal Attainment Scale (GAS). Three different tasks were assessed before and after each intervention period: "Practiced", "Non-Practiced", or "Previously Practiced". Generalization was evaluated through neuropsychological tests. Results indicated that both interventions significantly improved "Practiced" tasks compared with "Non-Practiced" tasks and the control group. Crossing the intervention did not interfere with the stable performance on the "Previously Practiced" task. However, starting with mGMT reduced, but did not eliminate, the efficacy of App + EL after crossing, but this pattern was not observed for the reverse sequence. Only the Tower of London task documented improvements related to interventions. In conclusion, the mGMT and App + EL were effective in learning complex tasks and retaining performance after learning a second task.Trial registration: German Clinical Trials Register identifier: DRKS00021674.

Circadian Rhythm and Sleep Analyses in a Fruit Fly Model of Fragile X Syndrome Using a Video-Based Automated Behavioral Research System

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.

Longitudinal follow-up of metformin treatment in Fragile X Syndrome

Introduction

Metformin 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.

Method

Individuals 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).

Result

There were no significant changes in non-verbal IQ or in the adaptive behavior measurements at FDR < 0.05. The findings thus far indicate that both IQ and adaptive behavior are stable over time, and we did not see a significant decline in either measure.

Conclusion

Overall, the small sample size and short follow-up duration limit the interpretation of the effects of metformin on cognitive development and adaptive functioning. There is individual variability but overall for the group there was no significant decline in IQ or adaptive behavior.

A holistic approach to fragile X syndrome integrated guidance for person-centred care

BACKGROUND

The Fragile X community has expressed a desire for centralised, national guidelines in the form of integrated guidance for Fragile X Syndrome (FXS).

METHODS

This article draws on existing literature reviews, primary research and clinical trials on FXS, a Fragile X Society conference workshop and first-hand experience of clinicians who have worked with those living with FXS over many years.

RESULTS

The article scopes proposed integrated guidance over the life course, including appendices of symptoms, comorbidities and referral options for FXS and Fragile X Premutation Associated Conditions.

CONCLUSION

Integrated guidance would provide an authoritative source for doctors, health professionals, therapists, care workers, social workers, educators, employers, families and those living with FXS, so that a holistic, person-centred approach can be taken across the United Kingdom to garner the best outcomes for those with FXS.

Behavioral and Psychiatric Disorders in Syndromic Autism

Syndromic autism refers to autism spectrum disorder diagnosed in the context of a known genetic syndrome. The specific manifestations of any one of these syndromic autisms are related to a clinically defined genetic syndrome that can be traced to certain genes and variants, genetic deletions, or duplications at the chromosome level. The genetic mutations or defects in single genes associated with these genetic disorders result in a significant elevation of risk for developing autism relative to the general population and are related to recurrence with inheritance patterns. Additionally, these syndromes are associated with typical behavioral characteristics or phenotypes as well as an increased risk for specific behavioral or psychiatric disorders and clinical findings. Knowledge of these associations helps guide clinicians in identifying potentially treatable conditions that can help to improve the lives of affected patients and their families.

Pressure overload-induced systolic heart failure is associated with characteristic myocardial microRNA expression signature and post-transcriptional gene regulation in male rats

Although systolic function characteristically shows gradual impairment in pressure overload (PO)-evoked left ventricular (LV) hypertrophy (LVH), rapid progression to congestive heart failure (HF) occurs in distinct cases. The molecular mechanisms for the differences in maladaptation are unknown. Here, we examined microRNA (miRNA) expression and miRNA-driven posttranscriptional gene regulation in the two forms of PO-induced LVH (with/without systolic HF). PO was induced by aortic banding (AB) in male Sprague-Dawley rats. Sham-operated animals were controls. The majority of AB animals demonstrated concentric LVH and slightly decreased systolic function (termed as ABLVH). In contrast, in some AB rats severely reduced ejection fraction, LV dilatation and increased lung weight-to-tibial length ratio was noted (referred to as ABHF). Global LV miRNA sequencing revealed fifty differentially regulated miRNAs in ABHF compared to ABLVH. Network theoretical miRNA-target analysis predicted more than three thousand genes with miRNA-driven dysregulation between the two groups. Seventeen genes with high node strength value were selected for target validation, of which five (Fmr1, Zfpm2, Wasl, Ets1, Atg16l1) showed decreased mRNA expression in ABHF by PCR. PO-evoked systolic HF is associated with unique miRNA alterations, which negatively regulate the mRNA expression of Fmr1, Zfmp2, Wasl, Ets1 and Atg16l1.

Distinct neuroanatomical and neuropsychological features of Down syndrome compared to related neurodevelopmental disorders: a systematic review

Objectives

We critically review research findings on the unique changes in brain structure and cognitive function characteristic of Down syndrome (DS) and summarize the similarities and differences with other neurodevelopmental disorders such as Williams syndrome, 22q11.2 deletion syndrome, and fragile X syndrome.

Methods

We conducted a meta-analysis and systematic literature review of 84 studies identified by searching PubMed, Google Scholar, and Web of Science from 1977 to October 2022. This review focuses on the following issues: (1) specific neuroanatomic and histopathological features of DS as revealed by autopsy and modern neuroimaging modalities, (2) language and memory deficits in DS, (3) the relationships between these neuroanatomical and neuropsychological features, and (4) neuroanatomic and neuropsychological differences between DS and related neurodevelopmental syndromes.

Results

Numerous post-mortem and morphometric neuroimaging investigations of individuals with DS have reported complex changes in regional brain volumes, most notably in the hippocampal formation, temporal lobe, frontal lobe, parietal lobe, and cerebellum. Moreover, neuropsychological assessments have revealed deficits in language development, emotional regulation, and memory that reflect these structural changes and are more severe than expected from general cognitive dysfunction. Individuals with DS also show relative preservation of multiple cognitive, linguistic, and social domains compared to normally developed controls and individuals with other neurodevelopmental disorders. However, all these neurodevelopment disorders exhibit substantial heterogeneity among individuals.

Conclusion

People with Down syndrome demonstrate unique neurodevelopmental abnormalities but cannot be regarded as a homogenous group. A comprehensive evaluation of individual intellectual skills is essential for all individuals with neurodevelopment disorders to develop personalized care programs.

Executive Function and Working Memory Deficits in Females with Fragile X Premutation

The Fragile X premutation is a genetic instability of the FMR1 gene caused by 55–199 recurrences of the CGG sequence, whereas there are only 7–54 repeats of the CGG sequence in the normal condition. While males with the premutation of Fragile X were found to have difficulties in executive functions and working memory, little data have been collected on females. This study is among the first to address executive functions and phonological memory in females with the Fragile X premutation. Twenty-three female carriers aged 20–55 years and twelve non carrier females matched in age and levels of education (in years) participated in this study. Executive functions and phonological memory were assessed using the self-report questionnaire The Behavior Rating Inventory of Executive Function (BRIEF) and behavioral measures (nonword repetitions, forward and backward digit span). Females who were carriers of the premutation of the FMR1 gene reported less efficient executive functions in the BRIEF questionnaire compared to the control group. In addition, a relationship was found between the number of repetitions on the CGG sequence of nucleotides, nonword repetitions, and forward digit span. The findings suggest that the premutation of Fragile X in females affects their performance of executive functions and may have impact on everyday functioning.

The Role of Aberrant Neural Oscillations in the Hippocampal-Medial Prefrontal Cortex Circuit in Neurodevelopmental and Neurological Disorders

The hippocampus (HPC) and medial prefrontal cortex (mPFC) have well-established roles in cognition, emotion, and sensory processing. In recent years, interests have shifted towards developing a deeper understanding of the mechanisms underlying interactions between the HPC and mPFC in achieving these functions. Considerable research supports the idea that synchronized activity between the HPC and the mPFC is a general mechanism by which brain functions are regulated. In this review, we summarize current knowledge on the hippocampal-medial prefrontal cortex (HPC-mPFC) circuit in normal brain function with a focus on oscillations and highlight several neurodevelopmental and neurological disorders associated with aberrant HPC-mPFC circuitry. We further discuss oscillatory dynamics across the HPC-mPFC circuit as potentially useful biomarkers to assess interventions for neurodevelopmental and neurological disorders. Finally, advancements in brain stimulation, gene therapy and pharmacotherapy are explored as promising therapies for disorders with aberrant HPC-mPFC circuit dynamics.

Autism Symptoms in Children and Young Adults With Fragile X Syndrome, Angelman Syndrome, Tuberous Sclerosis Complex, and Neurofibromatosis Type 1: A Cross-Syndrome Comparison

OBJECTIVE

The etiology of autism spectrum disorder (ASD) remains unclear, due to genetic heterogeneity and heterogeneity in symptoms across individuals. This study compares ASD symptomatology between monogenetic syndromes with a high ASD prevalence, in order to reveal syndrome specific vulnerabilities and to clarify how genetic variations affect ASD symptom presentation.

METHODS

We assessed ASD symptom severity in children and young adults (aged 0-28 years) with Fragile X Syndrome (FXS, n = 60), Angelman Syndrome (AS, n = 91), Neurofibromatosis Type 1 (NF1, n = 279) and Tuberous Sclerosis Complex (TSC, n = 110), using the Autism Diagnostic Observation Schedule and Social Responsiveness Scale. Assessments were part of routine clinical care at the ENCORE expertise center in Rotterdam, the Netherlands. First, we compared the syndrome groups on the ASD classification prevalence and ASD severity scores. Then, we compared individuals in our syndrome groups with an ASD classification to a non-syndromic ASD group (nsASD, n = 335), on both ASD severity scores and ASD symptom profiles. Severity scores were compared using MANCOVAs with IQ and gender as covariates.

RESULTS

Overall, ASD severity scores were highest for the FXS group and lowest for the NF1 group. Compared to nsASD, individuals with an ASD classification in our syndrome groups showed less problems on the instruments' social domains. We found a relative strength in the AS group on the social cognition, communication and motivation domains and a relative challenge in creativity; a relative strength of the NF1 group on the restricted interests and repetitive behavior scale; and a relative challenge in the FXS and TSC groups on the restricted interests and repetitive behavior domain.

CONCLUSION

The syndrome-specific strengths and challenges we found provide a frame of reference to evaluate an individual's symptoms relative to the larger syndromic population and to guide treatment decisions. Our findings support the need for personalized care and a dimensional, symptom-based diagnostic approach, in contrast to a dichotomous ASD diagnosis used as a prerequisite for access to healthcare services. Similarities in ASD symptom profiles between AS and FXS, and between NF1 and TSC may reflect similarities in their neurobiology. Deep phenotyping studies are required to link neurobiological markers to ASD symptomatology.

Neuropsychological and ASD phenotypes in rare genetic syndromes: A critical review of the literature

OBJECTIVE

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition characterized by core deficits in social communication and restricted and repetitive behaviors and interests. Recent advances in clinical genetics have improved our understanding of genetic syndromes associated with ASD, which has helped clarify distinct etiologies of ASD and document syndrome-specific profiles of neurocognitive strengths and weaknesses. Pediatric neuropsychologists have the potential to be impactful members of the care team for children with genetic syndromes and their families.

METHOD

We provide a critical review of the current literature related to the neuropsychological profiles of children with four genetic syndromes associated with ASD, including Tuberous Sclerosis Complex (TSC), fragile X syndrome (FXS), 22q11.2 deletion syndrome, and Angelman syndrome. Recommendations for assessment, intervention, and future directions are provided.

RESULTS

There is vast heterogeneity in terms of the cognitive, language, and developmental abilities of these populations. The within- and across-syndrome variability characteristic of genetic syndromes should be carefully considered during clinical evaluations, including possible measurement limitations, presence of intellectual disability, and important qualitative differences in the ASD-phenotypes across groups.

CONCLUSIONS

Individuals with genetic disorders pose challenging diagnostic and assessment questions. Pediatric neuropsychologists with expertise in neurodevelopmental processes are well suited to address these questions and identify profiles of neurocognitive strengths and weaknesses, tailor individualized recommendations, and provide diagnostic clarification.

Functional Neurophysiological Biomarkers of Early-Stage Alzheimer's Disease: A Perspective of Network Hyperexcitability in Disease Progression

Network hyperexcitability (NH) has recently been suggested as a potential neurophysiological indicator of Alzheimer’s disease (AD), as new, more accurate biomarkers of AD are sought. NH has generated interest as a potential indicator of certain stages in the disease trajectory and even as a disease mechanism by which network dysfunction could be modulated. NH has been demonstrated in several animal models of AD pathology and multiple lines of evidence point to the existence of NH in patients with AD, strongly supporting the physiological and clinical relevance of this readout. Several hypotheses have been put forward to explain the prevalence of NH in animal models through neurophysiological, biochemical, and imaging techniques. However, some of these hypotheses have been built on animal models with limitations and caveats that may have derived NH through other mechanisms or mechanisms without translational validity to sporadic AD patients, potentially leading to an erroneous conclusion of the underlying cause of NH occurring in patients with AD. In this review, we discuss the substantiation for NH in animal models of AD pathology and in human patients, as well as some of the hypotheses considering recently developed animal models that challenge existing hypotheses and mechanisms of NH. In addition, we provide a preclinical perspective on how the development of animal models incorporating AD-specific NH could provide physiologically relevant translational experimental data that may potentially aid the discovery and development of novel therapies for AD.

Local Translation Across Neural Development: A Focus on Radial Glial Cells, Axons, and Synaptogenesis

In the past two decades, significant progress has been made in our understanding of mRNA localization and translation at distal sites in axons and dendrites. The existing literature shows that local translation is regulated in a temporally and spatially restricted manner and is critical throughout embryonic and post-embryonic life. Here, recent key findings about mRNA localization and local translation across the various stages of neural development, including neurogenesis, axon development, and synaptogenesis, are reviewed. In the early stages of development, mRNAs are localized and locally translated in the endfeet of radial glial cells, but much is still unexplored about their functional significance. Recent in vitro and in vivo studies have provided new information about the specific mechanisms regulating local translation during axon development, including growth cone guidance and axon branching. Later in development, localization and translation of mRNAs help mediate the major structural and functional changes that occur in the axon during synaptogenesis. Clinically, changes in local translation across all stages of neural development have important implications for understanding the etiology of several neurological disorders. Herein, local translation and mechanisms regulating this process across developmental stages are compared and discussed in the context of function and dysfunction.

Decreased FMR1 mRNA levels found in men with substance use disorders

FMR1 gene (fragile X mental retardation 1) represents a genetic and epigenetic factor in a number of human diseases. Though the role of FMR1 gene in substance use disorders (SUDs) is not well studied, a number of investigations indicate that SUDs and FMR1-accociated disorders may share common underlying mechanisms. We examined the relative FMR1 mRNA levels and their sex-distribution in leukocytes from patients with alcohol and drug dependence compared to healthy controls. The study included 44 participants, 16 with alcohol dependence (mean age 43, 10 males and 6 females), 17 with drug dependence (mean age 41, 12 males and 5 females) and 11 healthy controls (mean age 47, 5 males and 6 females). Participants donated 5–6 ml of blood and completed a specialized questionnaire. Total RNA was isolated and cDNA was synthesized and used as a template for qRT-PCR analysis. The studied persons with alcohol and drug dependence share common socio-demographic and substance-use related characteristics. Significant FMR1 down-regulation was observed in the alcohol dependent group (25 % decrease; p = 0.005). Sex-associated analysis revealed that FMR1 down-regulation was primarily in alcohol-dependent men (40% decrease; p = 0.001) and did not reach significance in women. A similar sex-dependent pattern was observed among drug-dependent individuals. Drug-dependent men had significantly lower FMR1 mRNA levels (24% decrease; p = 0.015) compared with controls, while no significant difference was observed in drug-dependent females. These data indicate FMR1 mRNA down-regulation in persons with alcohol- and drug-dependence, relative to controls, is sex-dependent. This implies a role for FMR1 in substance use disorders. These findings require confirmation by including protein measures and the recruitment of larger cohorts.

Parent Perspectives on Augmentative and Alternative Communication Integration for Children With Fragile X Syndrome: It Starts in the Home

Many children with fragile X syndrome (FXS) have complex communication needs and may benefit from augmentative and alternative communication (AAC). This qualitative study explored how four mother-child dyads used AAC in the home. Data were collected using participant observations, open-ended interviews, and record reviews, and analyzed using grounded theory methods. Findings revealed that mothers found AAC to be a useful tool for addressing their children's complex communication needs, but practical and personal factors impacted its use in the home. This study sheds light on how mothers of children with FXS view and utilize AAC as a way to promote communication at home. Understanding parental perspectives can help to guide professionals in planning appropriate AAC interventions specific to FXS.

Understanding attention, memory and social biases in fragile X syndrome: Going below the surface with a multi-method approach

Fragile X syndrome (FXS) is characterised by atypical social behaviours, such as gaze aversion. However, it remains unclear whether, or if so how, these behaviours affect cognitive processing and influence memory. We asked children with FXS (N = 16) and typically developing children (TD; N = 46) to explore naturalistic scenes containing social and non-social salient items unrelated to their task at hand (searching for a simple target object). We also assessed children's memory for target locations. We complemented behavioural responses with eye-tracking data for the subset of participants who managed to comply with calibration and the demands of the experimental testing session (6 children with FXS and 43 TD children). Children with FXS performed well at the experimental task, and showed similar accuracy and speed in locating targets in natural scenes to children of equivalent verbal abilities. They also learned target locations over blocks, but their memory of target locations was not as precise as that of comparison children. In addition, children with FXS initially directed few first looks to salient social items within the scenes, but these looks increased over blocks. Like TD children, children with FXS also dwelled gaze upon social items while recalling target locations from memory. Individual differences in everyday social characteristics also related to gaze and behavioural measures. In conclusion, experimental approaches can highlight cognitive underpinnings of atypical social behaviour in FXS, pinpointing both similarities and differences to TD individuals.

Infant EEG theta modulation predicts childhood intelligence

Intellectual functioning is a critical determinant of economic and personal productivity. Identifying early neural predictors of cognitive function in infancy will allow us to map the neurodevelopmental pathways that underpin individual differences in intellect. Here, in three different cohorts we investigate the association between a putative neurophysiological indicator of information encoding (change in frontal theta during a novel video) in infancy and later general cognitive outcome. In a discovery cohort of 12-month-old typically developing infants, we recorded EEG during presentation of dynamic movies of people and objects. Frontal theta power (3-6 Hz) significantly increased during the course of viewing each video. Critically, increase in frontal theta during viewing of a video was associated with a differential response to repetition of that specific video, confirming relation to learning. Further, individual differences in the magnitude of change in frontal theta power were related to concurrent nonverbal cognitive level. We then sought to extend this association in two independent samples enriched for variation in cognitive outcome due to the inclusion of infants at familial risk for autism. We observed similar patterns of theta EEG change at 12 months, and found a predictive relation to verbal and nonverbal cognitive skills measured at 2, 3 and 7 years of age. For the subset of high-risk infants later diagnosed with autism, infant theta EEG explained over 80% of the variance in nonverbal skills at age 3 years. We suggest that EEG theta change in infancy is an excellent candidate predictive biomarker that could yield substantial insight into the mechanisms that underlie individual differences in childhood intelligence, particularly in high risk populations.

Blood-Based Biomarkers Predictive of Metformin Target Engagement in Fragile X Syndrome

Recent advances in neurobiology have provided several molecular entrees for targeted treatments for Fragile X syndrome (FXS). However, the efficacy of these treatments has been demonstrated mainly in animal models and has not been consistently predictive of targeted drugs' response in the preponderance of human clinical trials. Because of the heterogeneity of FXS at various levels, including the molecular level, phenotypic manifestation, and drug response, it is critically important to identify biomarkers that can help in patient stratification and prediction of therapeutic efficacy. The primary objective of this study was to assess the ability of molecular biomarkers to predict phenotypic subgroups, symptom severity, and treatment response to metformin in clinically treated patients with FXS. We specifically tested a triplex protein array comprising of hexokinase 1 (HK1), RAS (all isoforms), and Matrix Metalloproteinase 9 (MMP9) that we previously demonstrated were dysregulated in the FXS mouse model and in blood samples from patient with FXS. Seventeen participants with FXS, 12 males and 5 females, treated clinically with metformin were included in this study. The disruption in expression abundance of these proteins was normalized and associated with significant self-reported improvement in clinical phenotypes (CGI-I in addition to BMI) in a subset of participants with FXS. Our preliminary findings suggest that these proteins are of strong molecular relevance to the FXS pathology that could make them useful molecular biomarkers for this syndrome.

Repeat expansion and methylation-sensitive triplet-primed polymerase chain reaction for fragile X mental retardation 1 gene screening in institutionalised intellectually disabled individuals

INTRODUCTION

Fragile X syndrome (FXS) is the most prevalent X-linked intellectual disability (ID) and a leading genetic cause of autism, characterised by cognitive and behavioural impairments. The hyperexpansion of a CGG repeat in the fragile X mental retardation 1 (FMR1) gene leads to abnormal hypermethylation, resulting in the lack or absence of its protein. Tools for establishing the diagnosis of FXS have been extensively developed, including assays based on triplet-primed polymerase chain reaction (TP-PCR) for detection and quantification of the CGG trinucleotide repeat expansion, as well as determination of the methylation status of the alleles. This study aimed to utilise a simple, quick and affordable method for high sensitivity and specificity screening and diagnosis of FXS in institutionalised individuals with ID.

METHODS

A total of 109 institutionalised individuals at the Center for Social Rehabilitation of Intellectual Disability Kartini, Temanggung, Central Java, Indonesia, were screened in a three-step process using FastFrax™ Identification, Sizing and Methylation Status Kits.

RESULTS

Two samples that were classified as indeterminate with respect to the 41-repeat control at the identification step were subsequently determined to be non-expanded by both sizing and methylation status analyses. Two samples classified as expanded at the identification step were determined to carry full mutation expansions > 200 repeats that were fully methylated using sizing and methylation status analyses, respectively, yielding a disease prevalence of 1.83%.

CONCLUSION

Repeat expansion and methylation-specific TP-PCR is practical, effective and inexpensive for the diagnosis of FXS, especially in high-risk populations of individuals with ID of undetermined aetiology.

Impaired Attention Orienting in Young Children With Fragile X Syndrome

Fragile X syndrome (FXS) is a genetic disorder caused by a trinucleotide CGG expansion within the FMR1 gene located on the X chromosome. Children with FXS have been shown to be impaired in dynamic visual attention processing. A key component of dynamic processing is orienting—a perceptual ability that requires disengagement and engagement of attention from one stimulus to fixate on a second. Orienting, specifically the disengagement and engagement of attention, has previously not been studied in young children with FXS. Using an eye tracking gap-overlap task, the present study investigated visual disengagement and engagement in young children with FXS, compared to mental age (MA)- and chronological age (CA)-matched typically developing children. On gap trials, the central stimulus elicited fixation, but then disappeared before the peripheral target appeared, imposing a visual gap between stimuli. On overlap trials, the central stimulus elicited fixation, and remained present when the peripheral target appeared, creating visual competition. A gap effect emerges when latencies to shift to the peripheral target are longer in overlap versus gap conditions, reflecting the recruitment of cortical and subcortical disengagement and engagement mechanisms. The gap effect was measured as the latency to orient attention to the peripheral target during gap versus overlap conditions. Both MA and CA groups showed the expected gap effect, where children were slower to orient to peripheral targets on overlap trials than on gap trials. In contrast, in the FXS group, saccadic latencies between gap and overlap trials were not significantly different, indicating no significant gap effect. These findings suggest disrupted attentional engagement patterns in FXS that may be underlying impairments in attention orienting, and suggest potential targets for attention training in this population.

Preventive care services and health behaviors in children with fragile X syndrome

BACKGROUND

This is the first description of preventive care services specifically received by children and young adults with fragile X syndrome (FXS). We compare these rates to those of other pediatric populations and identify care disparities within our cohort.

OBJECTIVE

Describe the frequency of preventive care services and health behaviors by young people with FXS, and identify disparities in care.

METHODS

We assessed four preventive care outcomes and the total number of preventive care guidelines met among individuals under 21 years from the ongoing Fragile X Online Registry with Accessible Research Database (N = 406) using data from 2012 to 2015. We used adjusted odds ratios (AORs) from multiple logistic regression models to describe associations between demographic factors and preventive care outcomes.

RESULTS

Seventy-five percent of our sample met dental care guidelines, 55.4% met influenza vaccination guidelines, 92.1% met immunization guidelines, and 24.4% met physical activity (PA) guidelines. Compared to children six to 10 years, younger children were less likely to have seen a dentist as recommended (AOR: 0.26) and young adults aged 16-20 were less likely to have received immunizations (AOR: 0.14) or to have engaged in recommended PA (AOR: 0.29). Black participants (AOR: 0.25) were less likely to have received an influenza vaccination than white participants. Individuals with autism (AOR: 0.25) were less likely to have sufficient PA, while individuals with hypersensitivity were more likely to have sufficient PA (AOR: 2.37) than unaffected individuals.

CONCLUSIONS

The proportion of young people with FXS that meet basic recommendations in preventive care guidelines varies according to health condition and demographic characteristics. This proportion could be increased for some groups, particularly in the cases of influenza vaccination and physical activity.

Executive Function in Fragile X Syndrome: A Systematic Review

Executive function (EF) supports goal-directed behavior and includes key aspects such as working memory, inhibitory control, cognitive flexibility, attention, processing speed, and planning. Fragile X syndrome (FXS) is the leading inherited monogenic cause of intellectual disability and is phenotypically characterized by EF deficits beyond what is expected given general cognitive impairments. Yet, a systematic review of behavioral studies using performance-based measures is needed to provide a summary of EF deficits across domains in males and females with FXS, discuss clinical and biological correlates of these EF deficits, identify critical limitations in available research, and offer suggestions for future studies in this area. Ultimately, this review aims to advance our understanding of the underlying pathophysiological mechanisms contributing to EF in FXS and to inform the development of outcome measures of EF and identification of new treatment targets in FXS.

A Description of the Educational Setting Among Individuals With Fragile X Syndrome

Children with fragile X syndrome (FXS) display wide-ranging intellectual and behavioral abilities that affect daily life. We describe the educational setting of students with FXS and assess the relationships between school setting, co-occurring conditions, and functional ability using a national survey sample ( n = 982). The majority of students with FXS in this sample have formal individualized education plans, spend part of the day outside regular classrooms, and receive modifications when in a regular classroom. Males with FXS and certain co-occurring conditions (autism, aggression, and self-injurious behavior) are more likely to spend the entire day outside regular classrooms, compared to males without these co-occurring conditions. Students who spend more time in regular classrooms are more likely to perform functional tasks without help.

Differential Adulthood Onset mGlu5 Signaling Saves Prefrontal Function in the Fragile X Mouse

The final maturation of the prefrontal cortex (PFC) continues into early adulthood and is delayed compared with other forebrain structures. However, how these late onset changes in the PFC relate to neurodevelopment disorders is poorly understood. Fragile X syndrome (FXS) is a prevalent neurogenetic disorder linked to deficits in PFC function. mGlu5 is an important molecular hub in the etiology of FXS. Thus we have examined changes in mGlu5 function in the PFC in a mouse model of FXS (Fmr1 knockout) during early adulthood and subsequent maturity. An unusual endophenotype was identified; during early adulthood (2-month-old) Fmr1 knockout mice show a severe deficit in mGlu5 dependent eCB synaptic plasticity; however, in 1-year-old this deficit self rectifies. This adulthood onset correction in mGlu5 function is linked to an engagement of TRPV1 receptors in 1-year-old mice. In 2-month-old Fmr1 knockout mice, mGlu5 mediated synaptic plasticity could be recovered with eCB system targeted drugs, but also by direct enhancement of mGlu5 function with a positive allosteric modulator. These results point to further refinements to the role of mGlu5 in FXS. Furthermore our findings suggest when studying neurodevelopmental disorders with a significant PFC phenotype consideration of late onset changes may be important.

Genetic and maternal predictors of cognitive and behavioral trajectories in females with fragile X syndrome

Background

Fragile X syndrome (FXS) is caused by a mutation in the FMR1 gene on the X chromosome, leading to decreased levels of FMR1 protein (FMRP), which causes the array of neuropsychological impairments that define FXS. Because FXS is an X-linked condition, fewer females display FXS and females with FXS are more mildly affected than males, on average. However, there is a considerable variability in terms of severity of affectedness among females with FXS. The current study was designed to investigate potential genetic (FMRP level and ratio of affected to total chromosomes) and environmental factors (maternal psychological distress and closeness in the mother–child relationship) influencing the cognitive (fluid and crystallized intelligence) and behavioral (anxiety and withdrawal) phenotype of females with FXS.

Methods

We conducted a prospective 3-year longitudinal study of 16 females with FXS (with up to four assessments, each separated by a year) using an accelerated longitudinal design so that we had coverage of the age range of 10–15 years at study start and 13–18 at study end. We focused on both the level of functioning related to chronological age expectations (standard scores) and absolute change in skill (raw scores) over the 3-year period.

Results

At a cross-sectional level, fluid intelligence and crystallized intelligence were both predicted by a closer mother–child relationship and lower maternal psychological distress. However, only fluid intelligence was predicted by a lower ratio of affected to total chromosomes. Anxiety and withdrawal were predicted by a higher ratio of affected to total chromosomes. Withdrawal was also predicted by lower closeness in the mother–child relationship and higher maternal distress. In terms of longitudinal change, gains were observed in fluid and crystallized intelligence, whereas anxious and withdrawn behaviors remained stable over visits. Gains in fluid intelligence were solely predicted by FXS biomarkers (higher FMRP level and lower ratio of affected to total chromosomes), while gains in crystallized intelligence were not predicted by any of the biological and environmental variables.

Conclusions

Our results show that FXS biomarkers and maternal variables contribute differentially to the cognitive and behavioral features of the adolescent female with FXS. These findings can help in the design of treatment studies aimed at enhancing cognitive and behavioral abilities in the FXS population.

Of Men and Mice: Modeling the Fragile X Syndrome

The Fragile X Syndrome (FXS) is one of the most common forms of inherited intellectual disability in all human societies. Caused by the transcriptional silencing of a single gene, the fragile x mental retardation gene FMR1, FXS is characterized by a variety of symptoms, which range from mental disabilities to autism and epilepsy. More than 20 years ago, a first animal model was described, the Fmr1 knock-out mouse. Several other models have been developed since then, including conditional knock-out mice, knock-out rats, a zebrafish and a drosophila model. Using these model systems, various targets for potential pharmaceutical treatments have been identified and many treatments have been shown to be efficient in preclinical studies. However, all attempts to turn these findings into a therapy for patients have failed thus far. In this review, I will discuss underlying difficulties and address potential alternatives for our future research.

Common Clinical Characteristics and Rare Medical Problems of Fragile X Syndrome in Thai Patients and Review of the Literature

Background. Clinical characteristics of fragile X syndrome (FXS) have been well documented in Caucasians, whereas in Asians they have rarely been described. Those that have been conducted used small cohorts that utilized DNA for diagnosis and larger cohorts that utilized cytogenetics for diagnosis. This study is to describe clinical characteristics of FXS in a large cohort of Thai patients diagnosed by standard molecular methods. Methods. Seventy-seven index cases and 46 affected relatives diagnosed with FXS were recruited into the study. To determine frequencies of common characteristics of FXS in prepubertal boys, we reviewed 56 unrelated cases aged between 18 and 146 months. To list rare medical problems, we reviewed 75 cases aged between 8 months to 71 years old, including 53 index cases and 22 affected relatives. In addition, we selected 16 clinical studies from various ethnicities for comparison with our findings. Results. In prepubertal boys with FXS, attention deficit and/or hyperactivity, prominent ears, macroorchidism, and elongated face were observed in 96%, 80%, 53%, and 48% of patients, respectively, whereas recognizable X-linked inheritance presented in 11% of patients. IQ scores ranged between 30 and 64 (mean ± SD = 43 ± 9, n = 25). We observed clinical findings that rarely or have never been reported, for example, medulloblastoma and tetralogy of Fallot. Conclusion. Attention deficit and/or hyperactivity and prominent ear are the most common behavioral and physical features in prepubertal boys with FXS, respectively. There are differences in frequencies of clinical characteristics observed between ethnicities; however, it is difficult to draw a solid conclusion due to different recruitment criteria and sample sizes within each study.

Noncomprehension Signaling in Males and Females With Fragile X Syndrome

Purpose

This study used a prospective longitudinal design to evaluate the trajectory and predictors of noncomprehension signaling in male and female youth with fragile X syndrome (FXS).

Method

A direction-following task in which some of the directions were inadequate was administered. Participants were 52 youth (36 boys, 16 girls) with FXS. Upon study entry, participants ranged from 10 to 16 years. The average number of annual assessments per participant was 3.65 (range = 1-4), providing 198 data points for analysis.

Results

Participants with FXS were less likely to signal noncomprehension than younger, typically developing, cognitively matched children. The average rate of change in noncomprehension signaling was not significantly different from 0 for either boys or girls, suggesting a plateau. Both FMRP and nonverbal IQ were significant independent predictors of noncomprehension signaling for boys. Variability in noncomprehension signaling among girls was not explained by any of the predictors, but trends similar to those observed for boys were observed.

Conclusions

Noncomprehension signaling appears to be an area of weakness for individuals with FXS. Because the failure to signal noncomprehension can have negative, cumulative effects on comprehension, the results suggest a need for interventions targeting the requisite cognitive skills.

Public Health Literature Review of Fragile X Syndrome

OBJECTIVES

The purpose of this systematic literature review is to describe what is known about fragile X syndrome (FXS) and to identify research gaps. The results can be used to help inform future public health research and provide pediatricians with up-to-date information about the implications of the condition for individuals and their families.

METHODS

An electronic literature search was conducted, guided by a variety of key words. The search focused on 4 areas of both clinical and public health importance: (1) the full mutation phenotype, (2) developmental trajectories across the life span, (3) available interventions and treatments, and (4) impact on the family. A total of 661 articles were examined and 203 were included in the review.

RESULTS

The information is presented in the following categories: developmental profile (cognition, language, functional skills, and transition to adulthood), social-emotional profile (cooccurring psychiatric conditions and behavior problems), medical profile (physical features, seizures, sleep, health problems, and physiologic features), treatment and interventions (educational/behavioral, allied health services, and pharmacologic), and impact on the family (family environment and financial impact). Research gaps also are presented.

CONCLUSIONS

The identification and treatment of FXS remains an important public health and clinical concern. The information presented in this article provides a more robust understanding of FXS and the impact of this complex condition for pediatricians. Despite a wealth of information about the condition, much work remains to fully support affected individuals and their families.

[Triplet expansion cytosine-guanine-guanine: Three cases of OMIM syndrome in the same family]

INTRODUCTION

The dynamic increase in the number of triplet repeats of cytosine-guanine-guanine (CGG) in the FMR1 gene mutation is responsible for three OMIM syndromes with a distinct clinical phenotype: Fragile X syndrome (FXS) and two pathologies in adult carriers of the premutation (55-200 CGG repeats): Primary ovarian insufficiency (FXPOI) and tremor-ataxia syndrome (FXTAS) associated with FXS.

CLINICAL OBSERVATION AND METHODS

CGG mutation dynamics of the FMR1 gene were studied in DNA samples from peripheral blood from the index case and other relatives of first, second and third degree by TP-PCR, and the percentage methylation.

RESULTS

Diagnosis of FXS was confirmed in three patients (21.4%), eight patients (57.1%) were confirmed in the premutation range transmitters, one male patient with full mutation/permutation mosaicism (7.1%) and two patients (14.3%) with normal study. Of the eight permutated patients, three had FXPOI and one male patient had FXTAS.

DISCUSSION

Our study suggests the importance of making an early diagnosis of SXF in order to carry out a family study and genetic counselling, which allow the identification of new cases or premutated patients with FMR1 gene- associated syndromes (FXTAS, FXPOI).