Prevalence, nature, and correlates of sleep problems among children with fragile X syndrome based on a large scale parent survey

Adaptive group behavior of Fragile X mice in unfamiliar environments

Fragile X Syndrome (FXS) stands out as a prominent cause of inherited intellectual disability and a prevalent disorder closely linked to autism. FXS is characterized by substantial alterations in social behavior, encompassing social withdrawal, avoidance of eye contact, heightened social anxiety, increased arousal levels, language deficits, and challenges in regulating emotions. Conventional behavioral assessments primarily focus on short-term interactions within controlled settings. In this study, we conducted a comprehensive examination of the adaptive group behavior of Fmr1 KO male mice over a three-day period, without introducing experimental interventions or task-based evaluations. The data unveiled intricate behavioral anomalies, with the most significant changes manifesting during the initial adaptation to unfamiliar environments. Notably, certain behaviors exhibited a gradual return to typical patterns over time. This dynamic Fmr1 KO phenotype exhibited heightened activity, featuring increased exploration, amplified social interest, and an unconventional approach to social interactions characterized by a higher frequency of shorter engagements. These findings contribute to the growing understanding of social behavior in individuals with FXS and underscore the significance of comprehending their adaptive responses in various environmental contexts.

Do metabolic deficits contribute to sleep disruption in monogenic intellectual disability syndromes?

Intellectual disability is defined as limitations in cognitive and adaptive behavior that often arise during development. Disordered sleep is common in intellectual disability and, given the importance of sleep for cognitive function, it may contribute to other behavioral phenotypes. Animal models of intellectual disability, in particular of monogenic intellectual disability syndromes (MIDS), recapitulate many disease phenotypes and have been invaluable for linking some of these phenotypes to specific molecular pathways. An emerging feature of MIDS, in both animal models and humans, is the prevalence of metabolic abnormalities, which could be relevant for behavior. Focusing on specific MIDS that have been molecularly characterized, we review sleep, circadian, and metabolic phenotypes in animal models and humans and propose that altered metabolic state contributes to the abnormal sleep/circadian phenotypes in MIDS.

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.

Hypnotic treatment improves sleep architecture and EEG disruptions and rescues memory deficits in a mouse model of fragile X syndrome

Fragile X syndrome (FXS) is associated with disrupted cognition and sleep abnormalities. Sleep loss negatively impacts cognitive function, and one untested possibility is that disrupted cognition in FXS is exacerbated by abnormal sleep. We tested whether ML297, a hypnotic acting on G-protein-activated inward-rectifying potassium (GIRK) channels, could reverse sleep phenotypes and disrupted memory in Fmr1-/y mice. Fmr1-/y mice exhibit reduced non-rapid eye movement (NREM) sleep and fragmented NREM architecture, altered sleep electroencephalogram (EEG) oscillations, and reduced EEG coherence between cortical areas; these are partially reversed following ML297 administration. Treatment following contextual fear or spatial learning restores disrupted memory consolidation in Fmr1-/y mice. During memory recall, Fmr1-/y mice show an altered balance of activity among hippocampal principal neurons vs. parvalbumin-expressing interneurons; this is partially reversed by ML297. Because sleep disruption could impact neurophysiological phenotypes in FXS, augmenting sleep may improve disrupted cognition in this disorder.

Adult Inception of Ketogenic Diet Therapy Increases Sleep during the Dark Cycle in C57BL/6J Wild Type and Fragile X Mice

Sleep problems are a significant phenotype in children with fragile X syndrome. Our prior work assessed sleep-wake cycles in Fmr1KO male mice and wild type (WT) littermate controls in response to ketogenic diet therapy where mice were treated from weaning (postnatal day 18) through study completion (5-6 months of age). A potentially confounding issue with commencing treatment during an active period of growth is the significant reduction in weight gain in response to the ketogenic diet. The aim here was to employ sleep electroencephalography (EEG) to assess sleep-wake cycles in mice in response to the Fmr1 genotype and a ketogenic diet, with treatment starting at postnatal day 95. EEG results were compared with prior sleep outcomes to determine if the later intervention was efficacious, as well as with published rest-activity patterns to determine if actigraphy is a viable surrogate for sleep EEG. The data replicated findings that Fmr1KO mice exhibit sleep-wake patterns similar to wild type littermates during the dark cycle when maintained on a control purified-ingredient diet but revealed a genotype-specific difference during hours 4-6 of the light cycle of the increased wake (decreased sleep and NREM) state in Fmr1KO mice. Treatment with a high-fat, low-carbohydrate ketogenic diet increased the percentage of NREM sleep in both wild type and Fmr1KO mice during the dark cycle. Differences in sleep microstructure (length of wake bouts) supported the altered sleep states in response to ketogenic diet. Commencing ketogenic diet treatment in adulthood resulted in a 15% (WT) and 8.6% (Fmr1KO) decrease in body weight after 28 days of treatment, but not the severe reduction in body weight associated with starting treatment at weaning. We conclude that the lack of evidence for improved sleep during the light cycle (mouse sleep time) in Fmr1KO mice in response to ketogenic diet therapy in two studies suggests that ketogenic diet may not be beneficial in treating sleep problems associated with fragile X and that actigraphy is not a reliable surrogate for sleep EEG in mice.

The intersection of sleep and synaptic translation in synaptic plasticity deficits in neurodevelopmental disorders

Individuals with neurodevelopmental disorders experience persistent sleep deficits, and there is increasing evidence that sleep dysregulation is an underlying cause, rather than merely an effect, of the synaptic and behavioral defects observed in these disorders. At the molecular level, dysregulation of the synaptic proteome is a common feature of neurodevelopmental disorders, though the mechanism connecting these molecular and behavioral phenotypes is an ongoing area of investigation. A role for eIF2α in shifting the local proteome in response to changes in the conditions at the synapse has emerged. Here, we discuss recent progress in characterizing the intersection of local synaptic translation and sleep and propose a reciprocal mechanism of dysregulation in the development of synaptic plasticity defects in neurodevelopmental disorders.

Analyzing the Quality of Life in Individuals with Fragile X Syndrome in Relation to Sleep and Mental Health

The purpose of this paper was to examine the physical, emotional, social and school functioning domains of quality of life of individuals with Fragile X Syndrome, in relation to mental health and sleep patterns to gain a better understanding of how these aspects are affected by the disorder. This study included 119 individuals with Fragile X Syndrome who were given different cognitive examinations by a neuropsychologist or by parent-proxy questionnaires. This study focused on the Pediatric Quality of Life Inventory (PedsQoL), the Anxiety, Depression and Mood Scale (ADAMS), the Children's Sleep Habits Questionnaire (CSHQ), but did include other cognitive tests (Vineland Adaptive Behaviour Scales, Nonverbal IQ, Autism Diagnostic Observation Schedule). We identified significant associations between decreases in emotional, social and school domains of PedsQoL and the ADAMS subtests of Generalized Anxiety, Manic/Hyperactivity and Obsessive/Compulsivity, with the subtest of Depressed Mood having associations with lower physical and emotional domains. We also identified a significant impact between CSHQ subtests of Sleep Anxiety, Night Wakings, Daytime Sleepiness, and Parasomnia with the emotional and school domains of PedsQoL. There were associations connecting school functioning with Bedtime Resistance, and additional associations connecting emotional functioning with Sleep Duration and Sleep Onset Delay. Physical functioning was also associated with Sleep Anxiety. Our study shows how mental health and sleep defects impact improper sleep patterns and mental health which leads to decreases in the quality of life for individuals with FXS, and how it is important to screen for these symptoms in order to alleviate issues.

The Lighter Touch: Less-Restriction in Sequentially Implemented Behavioral Sleep Interventions for Children with Rare Genetic Neurodevelopmental Conditions

PURPOSE

The prevalence of sleep difficulties among children with rare genetic neurodevelopmental conditions (RGNC) is high. Behavioral interventions are commonly used in the treatment of sleep difficulties in children with neurodevelopmental conditions such as autism, however, research is scarce in children with RGNC. The range of co-occurring complexities within this population, means there is a need for research to not only determine the effectiveness of behavioral sleep interventions, but also which components might be the least restrictive (i.e., intensive/aversive) and minimally sufficient.

METHODS

This study used a single-case multiple baseline design to investigate the effectiveness and acceptability of behavioral sleep interventions, indicated within a Functional Behavior formulation in eight children with RGNC (M = 7.3 years). Intervention components were sequentially administered across up to three phases, based on the principle of less restriction (from least to relatively more intensive) to determine what might be minimally sufficient.

RESULTS

Results showed an improvement in sleep onset latency, night wakings, early morning waking and unwanted bed-sharing for 7/7, 6/7, 3/3 and 3/3 children respectively. Improvement was observed for most participants following the less restrictive phases of intervention (circadian modifications, antecedent modifications and positive reinforcement), however, more restrictive, albeit modified, extinction procedures were still implemented for five participants. Improvements were maintained at follow-up and interventions were deemed acceptable to parents.

CONCLUSIONS

Less restrictive function-based behavioral strategies are an effective, and in some cases sufficient, contribution to a sequence of interventions for a range of sleep difficulties. They should be implemented first, before more restrictive strategies.

Sleep and Circadian Disturbances in Children With Neurodevelopmental Disorders

Sleep problems are highly prevalent in those with neurodevelopmental disorders (NDDs). We propose this is secondary to multiple factors that directly and indirectly negatively impact sleep and circadian processes in those with NDDs, which in turn, further perturbs development, resulting in a "developmental and sleep/circadian-related encephalopathy." In this review, we discuss select NDDs with known or suspected sleep and circadian phenotypes. We also highlight important considerations when evaluating and treating sleep and circadian disorders in these populations.

Ketogenic Diet Affects Sleep Architecture in C57BL/6J Wild Type and Fragile X Mice

Nearly half of children with fragile X syndrome experience sleep problems including trouble falling asleep and frequent nighttime awakenings. The goals here were to assess sleep-wake cycles in mice in response to Fmr1 genotype and a dietary intervention that reduces hyperactivity. Electroencephalography (EEG) results were compared with published rest-activity patterns to determine if actigraphy is a viable surrogate for sleep EEG. Specifically, sleep-wake patterns in adult wild type and Fmr1KO littermate mice were recorded after EEG electrode implantation and the recordings manually scored for vigilance states. The data indicated that Fmr1KO mice exhibited sleep-wake patterns similar to wild type littermates when maintained on a control purified ingredient diet. Treatment with a high-fat, low-carbohydrate ketogenic diet increased the percentage of non-rapid eye movement (NREM) sleep in both wild type and Fmr1KO mice during the dark cycle, which corresponded to decreased activity levels. Treatment with a ketogenic diet flattened diurnal sleep periodicity in both wild type and Fmr1KO mice. Differences in several sleep microstructure outcomes (number and length of sleep and wake bouts) supported the altered sleep states in response to a ketogenic diet and were correlated with altered rest-activity cycles. While actigraphy may be a less expensive, reduced labor surrogate for sleep EEG during the dark cycle, daytime resting in mice did not correlate with EEG sleep states.

Hypnotic treatment reverses NREM sleep disruption and EEG desynchronization in a mouse model of Fragile X syndrome to rescue memory consolidation deficits

Fragile X syndrome (FXS) is a highly-prevalent genetic cause of intellectual disability, associated with disrupted cognition and sleep abnormalities. Sleep loss itself negatively impacts cognitive function, yet the contribution of sleep loss to impaired cognition in FXS is vastly understudied. One untested possibility is that disrupted cognition in FXS is exacerbated by abnormal sleep. We hypothesized that restoration of sleep-dependent mechanisms could improve functions such as memory consolidation in FXS. We examined whether administration of ML297, a hypnotic drug acting on G-protein-activated inward-rectifying potassium channels, could restore sleep phenotypes and improve disrupted memory consolidation in Fmr1 -/y mice. Using 24-h polysomnographic recordings, we found that Fmr1 -/y mice exhibit reduced non-rapid eye movement (NREM) sleep and fragmented NREM sleep architecture, alterations in NREM EEG spectral power (including reductions in sleep spindles), and reduced EEG coherence between cortical areas. These alterations were reversed in the hours following ML297 administration. Hypnotic treatment following contextual fear or spatial learning also ameliorated disrupted memory consolidation in Fmr1 -/y mice. Hippocampal activation patterns during memory recall was altered in Fmr1 -/y mice, reflecting an altered balance of activity among principal neurons vs. parvalbumin-expressing (PV+) interneurons. This phenotype was partially reversed by post-learning ML297 administration. These studies suggest that sleep disruption could have a major impact on neurophysiological and behavioral phenotypes in FXS, and that hypnotic therapy may significantly improve disrupted cognition in this disorder.

The effect of intensive rehabilitation treatment on sleep disorder in children with motor delays

BACKGROUND

Although the importance of sleep problems has been increasingly emphasized due to the effects on children's development and children's and families' daytime behaviors, physical health, and quality of life, they have been overlooked in clinical practice. However, there have been few studies on the effects of rehabilitation on sleep problems. Therefore, in this study, we investigated the effects of an intensive rehabilitation program on sleep problems in children with developmental delays (DD).

METHODS

We included 36 children with DD (30 outpatients, 6 inpatients) and their caregivers who completed all items on the Sleep Disturbance Scale for Children. Of the children with DD, 19 (59.3%) had cerebral palsy (CP) and 13 (40.7%) had DD of non-CP origins, of which 6 (18.8%) had prematurity, 4 (12.5%) had genetic causes, and 3 (9.4%) had an unknown origin. Changes in sleep problems after the intensive rehabilitation program were evaluated using a paired or unpaired t-test, depending on the distribution of the continuous variables.

RESULTS

After the intensive rehabilitation program, in 36 children with DD, there was a significant improvement in the difficulty in initiating and maintaining sleep (DIMS) sub-score (p < 0.05). However, there was no significant improvement in the total score or other sub-scores, such as those for sleep breathing disorders (SBD), disorders of arousal (DA), sleep-wake transition disorders (SWTD), disorders of excessive somnolence (DOES), and sleep hyperhidrosis (SH). In the subgroup analysis according to the cause of DD, children with CP had a significant improvement in DIMS and DOES sub-scores (p < 0.05).

CONCLUSION

The intensive rehabilitation program, consisting of more than two sessions per day, effectively alleviated sleep problems in children with DD, especially in those with CP. Among the sleep problems, the intensive rehabilitative program was most effective at improving the DIMS. However, further prospective studies with a larger number of patients with DD and a more standardized protocol are necessary to generalize this effect.

CNS-dominant human FMRP isoform rescues seizures, fear, and sleep abnormalities in Fmr1-KO mice

Fragile X syndrome is a neurodevelopmental disorder caused by the absence of the mRNA-binding protein fragile X messenger ribonucleoprotein (FMRP). Because FMRP is a highly pleiotropic protein controlling the expression of hundreds of genes, viral vector-mediated gene replacement therapy is viewed as a potential viable treatment to correct the fundamental underlying molecular pathology inherent in the disorder. Here, we studied the safety profile and therapeutic effects of a clinically relevant dose of a self-complementary adeno-associated viral (AAV) vector containing a major human brain isoform of FMRP after intrathecal injection into wild-type and fragile X-KO mice. Analysis of the cellular transduction in the brain indicated primarily neuronal transduction with relatively sparse glial expression, similar to endogenous FMRP expression in untreated wild-type mice. AAV vector-treated KO mice showed recovery from epileptic seizures, normalization of fear conditioning, reversal of slow-wave deficits as measured via electroencephalographic recordings, and restoration of abnormal circadian motor activity and sleep. Further assessment of vector efficacy by tracking and analyzing individual responses demonstrated correlations between the level and distribution of brain transduction and drug response. These preclinical findings further demonstrate the validity of AAV vector-mediated gene therapy for treating the most common genetic cause of cognitive impairment and autism in children.

Sleep disturbances in autism spectrum disorder: Animal models, neural mechanisms, and therapeutics

Sleep is crucial for brain development. Sleep disturbances are prevalent in children with autism spectrum disorder (ASD). Strikingly, these sleep problems are positively correlated with the severity of ASD core symptoms such as deficits in social skills and stereotypic behavior, indicating that sleep problems and the behavioral characteristics of ASD may be related. In this review, we will discuss sleep disturbances in children with ASD and highlight mouse models to study sleep disturbances and behavioral phenotypes in ASD. In addition, we will review neuromodulators controlling sleep and wakefulness and how these neuromodulatory systems are disrupted in animal models and patients with ASD. Lastly, we will address how the therapeutic interventions for patients with ASD improve various aspects of sleep. Together, gaining mechanistic insights into the neural mechanisms underlying sleep disturbances in children with ASD will help us to develop better therapeutic interventions.

Neurological, Psychiatric, and Multisystemic Involvement of Fragile X Syndrome Along With Its Pathophysiology, Methods of Screening, and Current Treatment Modalities

Fragile X syndrome (FXS) is a hereditary disease that predominantly leads to intellectual disability (ID) in boys. It is the second prominent cause of ID, which manifests as a result of the atypical development of the cytosine-guanine-guanine (CGG) region. This irregular extension of the CGG region gives rise to methylation and silencing of the fragile X mental retardation 1 (FMR1) gene, causing a loss of the fragile X mental retardation 1 protein (FMRP). This reduction or loss of FMRP is the main cause of ID. It has a multisystemic involvement showing neuropsychiatric features such as ID, speech and language delay, autism spectrum disorder, sensory hyperarousal, social anxiety, abnormal eye contact, shyness, and aggressive behaviour. It is also known to cause musculoskeletal symptoms, ocular symptoms, cardiac abnormalities, and gastrointestinal symptoms. The management is challenging, and there is no known cure for the disease; hence an early diagnosis of the condition is needed through prenatal screening offered to couples with familial history of ID before conception. The management rests on non-pharmacological modalities, including applied behaviour analysis, physical therapy, occupational therapy, speech-language therapy, and pharmacologic management through symptomatic treatment of comorbid behaviours and psychiatric problems and some forms of targeted therapy.

The incidence and clinical characteristics of fragile X syndrome in China

Introduction

Fragile 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.

Methods

Children 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.

Results

The 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.

Discussion

Screening 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.

Behavioral and Molecular Consequences of Chronic Sleep Restriction During Development in Fragile X Mice

Sleep is critical for brain development and synaptic plasticity. In male wild-type mice, chronic sleep restriction during development results in long-lasting impairments in behavior including hypoactivity, decreased sociability, and increased repetitive behavior. Disordered sleep is characteristic of many neurodevelopmental disorders. Moreover, the severity of behavioral symptoms is correlated with the degree of disordered sleep. We hypothesized that chronic developmental sleep restriction in a mouse model of fragile X syndrome (FXS) would exacerbate behavioral phenotypes. To test our hypothesis, we sleep-restricted Fmr1 knockout (KO) mice for 3 h per day from P5 to P52 and subjected mice to behavioral tests beginning on P42. Contrary to our expectations, sleep restriction improved the hyperactivity and lack of preference for social novelty phenotypes in Fmr1 KO mice but had no measurable effect on repetitive activity. Sleep restriction also resulted in changes in regional distribution of myelin basic protein, suggesting effects on myelination. These findings have implications for the role of disrupted sleep in the severity of symptoms in FXS.

Advancing artificial intelligence-assisted pre-screening for fragile X syndrome

BACKGROUND

Fragile X syndrome (FXS), the most common inherited cause of intellectual disability and autism, is significantly underdiagnosed in the general population. Diagnosing FXS is challenging due to the heterogeneity of the condition, subtle physical characteristics at the time of birth and similarity of phenotypes to other conditions. The medical complexity of FXS underscores an urgent need to develop more efficient and effective screening methods to identify individuals with FXS. In this study, we evaluate the effectiveness of using artificial intelligence (AI) and electronic health records (EHRs) to accelerate FXS diagnosis.

METHODS

The EHRs of 2.1 million patients served by the University of Wisconsin Health System (UW Health) were the main data source for this retrospective study. UW Health includes patients from south central Wisconsin, with approximately 33 years (1988-2021) of digitized health data. We identified all participants who received a code for FXS in the form of International Classification of Diseases (ICD), Ninth or Tenth Revision (ICD9 = 759.83, ICD10 = Q99.2). Only individuals who received the FXS code on at least two occasions ("Rule of 2") were classified as clinically diagnosed cases. To ensure the availability of sufficient data prior to clinical diagnosis to test the model, only individuals who were diagnosed after age 10 were included in the analysis. A supervised random forest classifier was used to create an AI-assisted pre-screening tool to identify cases with FXS, 5 years earlier than the time of clinical diagnosis based on their medical records. The area under receiver operating characteristic curve (AUROC) was reported. The AUROC shows the level of success in identification of cases and controls (AUROC = 1 represents perfect classification).

RESULTS

52 individuals were identified as target cases and matched with 5200 controls. AI-assisted pre-screening tool successfully identified cases with FXS, 5 years earlier than the time of clinical diagnosis with an AUROC of 0.717. A separate model trained and tested on UW Health cases achieved the AUROC of 0.798.

CONCLUSIONS

This result shows the potential utility of our tool in accelerating FXS diagnosis in real clinical settings. Earlier diagnosis can lead to more timely intervention and access to services with the goal of improving patients' health outcomes.

Effects of Treatment With Hypnotics on Reduced Sleep Duration and Behavior Abnormalities in a Mouse Model of Fragile X Syndrome

Many patients with fragile X syndrome (FXS) have sleep disturbances, and Fmr1 knockout (KO) mice (a model of FXS) have reduced sleep duration compared to wild type (WT). Sleep is important for brain development, and chronic sleep restriction during development has long-lasting behavioral effects in WT mice. We hypothesized that the sleep abnormalities in FXS may contribute to behavioral impairments and that increasing sleep duration might improve behavior. We treated adult male Fmr1 KO and WT mice subacutely with three different classes of hypnotics (DORA-22, ramelteon, and zolpidem) and caffeine, a methylxanthine stimulant, and we tested the effects of treatments on sleep duration and behavior. Behavior tests included activity response to a novel environment, anxiety-like behavior, and social behavior. As expected, all hypnotics increased, and caffeine decreased sleep duration in the circadian phase in which drugs were administered. Caffeine and DORA-22 treatment significantly reduced activity in the open field regardless of genotype. Other effects were not as apparent.

Synaptic dysfunction connects autism spectrum disorder and sleep disturbances: A perspective from studies in model organisms

Sleep disturbances (SD) accompany many neurodevelopmental disorders, suggesting SD is a transdiagnostic process that can account for behavioral deficits and influence underlying neuropathogenesis. Autism Spectrum Disorder (ASD) comprises a complex set of neurodevelopmental conditions characterized by challenges in social interaction, communication, and restricted, repetitive behaviors. Diagnosis of ASD is based primarily on behavioral criteria, and there are no drugs that target core symptoms. Among the co-occurring conditions associated with ASD, SD are one of the most prevalent. SD often arises before the onset of other ASD symptoms. Sleep interventions improve not only sleep but also daytime behaviors in children with ASD. Here, we examine sleep phenotypes in multiple model systems relevant to ASD, e.g., mice, zebrafish, fruit flies and worms. Given the functions of sleep in promoting brain connectivity, neural plasticity, emotional regulation and social behavior, all of which are of critical importance in ASD pathogenesis, we propose that synaptic dysfunction is a major mechanism that connects ASD and SD. Common molecular targets in this interplay that are involved in synaptic function might be a novel avenue for therapy of individuals with ASD experiencing SD. Such therapy would be expected to improve not only sleep but also other ASD symptoms.

Sleep problems in fragile X syndrome: Cross-sectional analysis of a large clinic-based cohort

Fragile X syndrome (FXS), the leading cause of inherited intellectual disability and autism spectrum disorder, is associated with multiple neurobehavioral abnormalities including sleep difficulties. Nonetheless, frequency, severity, and consequences of sleep problems are still unclear. The Fragile X Online Registry with Accessible Research Database (FORWARD-version-3), including Clinician Report and Parent Report forms, was analyzed for frequency, severity, relationship with behavioral problems, and impact of sleep difficulties in a mainly pediatric cohort. A focused evaluation of sleep apnea was also conducted. Six surveyed sleep difficulties were moderately frequent (~23%-46%), relatively mild, affected predominantly younger males, and considered a problem for 7%-20% of families. Snoring was more prevalent in older individuals. All sleep difficulties were associated with irritability/aggression and most also to hyperactivity. Only severe snoring was correlated with sleep apnea (loud snoring: 30%; sleep apnea: 2%-3%). Sleep difficulties are prevalent in children with FXS and, although they tend to be mild, they are associated with behavioral problems and negative impact to families. Because of its cross-sectional nature, clinic-origin, use of ad hoc data collection forms, and lack of treatment data, the present study should be considered foundational for future research aiming at better recognition and management of sleep problems in FXS.

Sleep deficiency as a driver of cellular stress and damage in neurological disorders

Neurological disorders encompass an extremely broad range of conditions, including those that present early in development and those that progress slowly or manifest with advanced age. Although these disorders have distinct underlying etiologies, the activation of shared pathways, e.g., integrated stress response (ISR) and the development of shared phenotypes (sleep deficits) may offer clues toward understanding some of the mechanistic underpinnings of neurologic dysfunction. While it is incontrovertibly complex, the relationship between sleep and persistent stress in the brain has broad implications in understanding neurological disorders from development to degeneration. The convergent nature of the ISR could be a common thread linking genetically distinct neurological disorders through the dysregulation of a core cellular homeostasis pathway.

EEG as a translational biomarker and outcome measure in fragile X syndrome

Targeted treatments for fragile X syndrome (FXS) have frequently failed to show efficacy in clinical testing, despite success at the preclinical stages. This has highlighted the need for more effective translational outcome measures. EEG differences observed in FXS, including exaggerated N1 ERP amplitudes, increased resting gamma power and reduced gamma phase-locking in the sensory cortices, have been suggested as potential biomarkers of the syndrome. These abnormalities are thought to reflect cortical hyper excitability resulting from an excitatory (glutamate) and inhibitory (GABAergic) imbalance in FXS, which has been the target of several pharmaceutical remediation studies. EEG differences observed in humans also show similarities to those seen in laboratory models of FXS, which may allow for greater translational equivalence and better predict clinical success of putative therapeutics. There is some evidence from clinical trials showing that treatment related changes in EEG may be associated with clinical improvements, but these require replication and extension to other medications. Although the use of EEG characteristics as biomarkers is still in the early phases, and further research is needed to establish its utility in clinical trials, the current research is promising and signals the emergence of an effective translational biomarker.

Gene therapy using an ortholog of human fragile X mental retardation protein partially rescues behavioral abnormalities and EEG activity

Fragile X syndrome (FXS), a neurodevelopmental disorder with no known cure, is caused by a lack of expression of the fragile X mental retardation protein (FMRP). As a single-gene disorder, FXS is an excellent candidate for viral-vector-based gene therapy, although that is complicated by the existence of multiple isoforms of FMRP, whose individual cellular functions are unknown. We studied the effects of rat and mouse orthologs of human isoform 17, a major expressed isoform of FMRP. Injection of neonatal Fmr1 knockout rats and mice with adeno-associated viral vectors (AAV9 serotype) under the control of an MeCP2 mini-promoter resulted in widespread distribution of the FMRP transgenes throughout the telencephalon and diencephalon. Transgene expression occurred mainly in non-GABAergic neurons, with little expression in glia. Early postnatal treatment resulted in partial rescue of the Fmr1 KO rat phenotype, including improved social dominance in treated Fmr1 KO females and partial rescue of locomotor activity in males. Electro-encephalogram (EEG) recordings showed correction of abnormal slow-wave activity during the sleep-like state in male Fmr1 KO rats. These findings support the use of AAV-based gene therapy as a treatment for FXS and specifically demonstrate the potential therapeutic benefit of human FMRP isoform 17 orthologs.

Artificial intelligence-assisted phenotype discovery of fragile X syndrome in a population-based sample

PURPOSE

Fragile X syndrome (FXS), the most prevalent inherited cause of intellectual disability, remains underdiagnosed in the general population. Clinical studies have shown that individuals with FXS have a complex health profile leading to unique clinical needs. However, the full impact of this X-linked disorder on the health of affected individuals is unclear and the prevalence of co-occurring conditions is unknown.

METHODS

We mined the longitudinal electronic health records from more than one million individuals to investigate the health characteristics of patients who have been clinically diagnosed with FXS. Additionally, using machine-learning approaches, we created predictive models to identify individuals with FXS in the general population.

RESULTS

Our discovery-oriented approach identified the associations of FXS with a wide range of medical conditions including circulatory, endocrine, digestive, and genitourinary, in addition to mental and neurological disorders. We successfully created predictive models to identify cases five years prior to clinical diagnosis of FXS without relying on any genetic or familial data.

CONCLUSION

Although FXS is often thought of primarily as a neurological disorder, it is in fact a multisystem syndrome involving many co-occurring conditions, some primary and some secondary, and they are associated with a considerable burden on patients and their families.

Impact of the COVID-19 Italian Lockdown on the Physiological and Psychological Well-Being of Children with Fragile X Syndrome and Their Families

On 10 March 2020, in Italy, a total lockdown was put in place to limit viral transmission of COVID-19 infection as much as possible. Research on the psychological impact of the COVID-19 pandemic highlighted detrimental effects in children and their parents. However, little is known about such effects in children with neurodevelopment disorders and their caregivers. The present study investigated how the lockdown has impacted the physiological and psychological well-being of children with Fragile X-Syndrome (FXS), aged from 2 to 16 years, and their mothers. In an online survey, 48 mothers of FXS children reported their perception of self-efficacy as caregivers and, at the same time, their children’s sleep habits, behavioral and emotional difficulties during, and retrospectively, before the lockdown. Results showed a general worsening of sleep quality, and increasing behavioral problems. Although mothers reported a reduction in external support, their perception of self-efficacy as caregivers did not change during the home confinement compared to the period before. Overall, the present study suggested that specific interventions to manage sleep problems, as well as specific therapeutic and social support for increasing children and mother psychological well-being, need to be in place to mitigate the long-term effects of a lockdown.

Channelopathies in fragile X syndrome

Fragile X syndrome (FXS) is the most common inherited form of intellectual disability and the leading monogenic cause of autism. The condition stems from loss of fragile X mental retardation protein (FMRP), which regulates a wide range of ion channels via translational control, protein-protein interactions and second messenger pathways. Rapidly increasing evidence demonstrates that loss of FMRP leads to numerous ion channel dysfunctions (that is, channelopathies), which in turn contribute significantly to FXS pathophysiology. Consistent with this, pharmacological or genetic interventions that target dysregulated ion channels effectively restore neuronal excitability, synaptic function and behavioural phenotypes in FXS animal models. Recent studies further support a role for direct and rapid FMRP-channel interactions in regulating ion channel function. This Review lays out the current state of knowledge in the field regarding channelopathies and the pathogenesis of FXS, including promising therapeutic implications.

Dysregulated CRMP Mediates Circadian Deficits in a Drosophila Model of Fragile X Syndrome

Fragile X syndrome (FXS) is the leading inherited cause of intellectual disability, resulting from the lack of functional fragile X mental retardation protein (FMRP), an mRNA binding protein mainly serving as a translational regulator. Loss of FMRP leads to dysregulation of target mRNAs. The Drosophila model of FXS show an abnormal circadian rhythm with disruption of the output pathway downstream of the clock network. Yet the FMRP targets involved in circadian regulation have not been identified. Here, we identified collapsing response mediator protein (CRMP) mRNA as a target of FMRP. Knockdown of pan-neuronal CRMP expression ameliorated the circadian defects and abnormal axonal structures of clock neurons (ventral lateral neurons) in dfmr1 mutant flies. Furthermore, specific reduction of CRMP in the downstream output insulin-producing cells attenuated the aberrant circadian behaviors. Molecular analyses revealed that FMRP binds with CRMP mRNA and negatively regulates its translation. Our results indicate that CRMP is an FMRP target and establish an essential role for CRMP in the circadian output in FXS Drosophila.

Endogenous melatonin and sleep in individuals with Rare Genetic Neurodevelopmental Disorders (RGND): A systematic review

Individuals with Rare Genetic Neurodevelopmental Disorders (RGND) present with significant sleep problems and circadian rhythm abnormalities of uncertain aetiology. Abnormal melatonin secretion may play a role in sleep disturbance in individuals with higher incidence developmental disabilities, however, RGND research is limited. This review compared the melatonin profiles in a range of RGND with that of the general population and considered the impact of any differences on sleep. A systematic search identified 19 studies that met inclusion criteria. Each study was examined to extract data relating to the study design, participant characteristics, objectives, sleep measures and results, and melatonin measures and findings. Studies were evaluated using the BIOCROSS quality appraisal tool. Nine studies focussed on Smith-Magenis syndrome (SMS), the rest included individuals with Angelman (AS), Fragile-X (FXS), Prader-Willi (PWS), septo-optic dysplasia, PAX6/WAGR and Williams (WS) syndromes (N = 349). Individuals with RGND present with a range of sleep problems, particularly dyssomnias. The melatonin profile varied within and between RGND, with low nocturnal melatonin levels commonly reported. Understanding the relationship between specific sleep and melatonin parameters within RGND may help inform sleep intervention.

Neurodevelopmental Disorders Commonly Presenting with Sleep Disturbances

There are multiple disorders of neurodevelopment that present with co-occurring sleep disturbances. Many of these neurodevelopmental disorders (NDD) include sleep disturbances in their diagnostic criteria. Neurobiological, genetic, and environmental factors overlap to cause different sleep disorders in individuals with NDD. Caregivers often present reporting either insomnia or hypersomnia, and based on the clinical history and findings from diagnostic tests, an appropriate diagnosis can be made. It is crucial that clinicians understand the different presentations of sleep disturbances in individuals with NDD.

Sexually dimorphic patterns in electroencephalography power spectrum and autism-related behaviors in a rat model of fragile X syndrome

Fragile X syndrome (FXS), a neurodevelopmental disorder with autistic features, is caused by the loss of the fragile X mental retardation protein. Sex-specific differences in the clinical profile have been observed in FXS patients, but few studies have directly compared males and females in rodent models of FXS. To address this, we performed electroencephalography (EEG) recordings and a battery of autism-related behavioral tasks on juvenile and young adult Fmr1 knockout (KO) rats. EEG analysis demonstrated that compared to wild-type, male Fmr1 KO rats showed an increase in gamma frequency band power in the frontal cortex during the sleep-like immobile state, and both male and female KO rats failed to show an increase in delta frequency power in the sleep-like state, as observed in wild-type rats. Previous studies of EEG profiles in FXS subjects also reported abnormally increased gamma frequency band power, highlighting this parameter as a potential translatable biomarker. Both male and female Fmr1 KO rats displayed reduced exploratory behaviors in the center zone of the open field test, and increased distance travelled in an analysis of 24-h home cage activity, an effect that was more prominent during the nocturnal phase. Reduced wins against wild-type opponents in the tube test of social dominance was seen in both sexes. In contrast, increased repetitive behaviors in the wood chew test was observed in male but not female KO rats, while increased freezing in a fear conditioning test was observed only in the female KO rats. Our findings highlight sex differences between male and female Fmr1 KO rats, and indicate that the rat model of FXS could be a useful tool for the development of new therapeutics for treating this debilitating neurodevelopmental disorder.

Preclinical testing of the ketogenic diet in fragile X mice

The ketogenic diet is highly effective at attenuating seizures in refractory epilepsy, and accumulating evidence in the literature suggests that it may be beneficial in autism. To our knowledge, no one has studied the ketogenic diet in any fragile X syndrome (FXS) model. FXS is the leading known genetic cause of autism. Herein, we tested the effects of chronic ketogenic diet treatment on seizures, body weight, ketone and glucose levels, diurnal activity levels, learning and memory, and anxiety behaviors in Fmr1^KO and littermate control mice as a function of age. The ketogenic diet selectively attenuates seizures in male but not female Fmr1^KO mice and differentially affects weight gain and diurnal activity levels dependent on Fmr1 genotype, sex and age.

Sleep as a translationally-relevant endpoint in studies of autism spectrum disorder (ASD)

Sleep has numerous advantages for aligning clinical and preclinical (basic neuroscience) studies of neuropsychiatric illness. Sleep has high translational relevance, because the same endpoints can be studied in humans and laboratory animals. In addition, sleep experiments are conducive to continuous data collection over long periods (hours/days/weeks) and can be based on highly objective neurophysiological measures. Here, we provide a translationally-oriented review on what is currently known about sleep in the context of autism spectrum disorder (ASD), including ASD-related conditions, thought to have genetic, environmental, or mixed etiologies. In humans, ASD is frequently associated with comorbid medical conditions including sleep disorders. Animal models used in the study of ASD frequently recapitulate dysregulation of sleep and biological (diurnal, circadian) rhythms, suggesting common pathophysiologies across species. As our understanding of the neurobiology of ASD and sleep each become more refined, it is conceivable that sleep-derived metrics may offer more powerful biomarkers of altered neurophysiology in ASD than the behavioral tests currently used in humans or lab animals. As such, the study of sleep in animal models for ASD may enable fundamentally new insights on the condition and represent a basis for strategies that enable the development of more effective therapeutics.

Feasibility of a Complex Setting for Assessing Sleep and Circadian Rhythmicity in a Fragile X Cohort

INTRODUCTION

Sleep, circadian rhythms, (mental) health, and development are assumed to be intertwined. However, differentiated and reliable parameters of sleep and circadian rhythms are particularly difficult to assess for Fragile X (FXS) individuals. As those parameters need to be observed in complex settings, the feasibility of measurements for people with FXS was to be proven. Findings from this pilot study can inform further research and help to estimate sample sizes for future studies on FXS patients.

METHODS AND SAMPLE

Nine individuals (male and female) with full mutation of the FMR1 gene were integrated in the study and underwent a complex measurement including actigraphy, sleep log, and 24-h saliva sampling in order to examine profiles of melatonin and cortisol, and a polysomnography.

RESULTS

Seven actigraphy profiles, eight sleep logs, eight saliva profiles and seven polysomnographic data sets were collected. Complete data were analyzed for six individuals [mean age 14.87 years (SD 4.12), mean BMI 25.90 (SD 4.44)] were collected. No drop outs due to the constraints of the assessment were registered.

DISCUSSION

All assessments and the setting in total were tolerated well by participants and caregivers. Procedures were adapted to individual needs of the participants.

CONCLUSION

All its components and the setting in total are absolutely feasible in the specific population of FXS individuals. Losses during consenting and recruiting have to be planned as well as high amounts of interindividual variances have to be taken into account.

FMRP has a cell-type-specific role in CA1 pyramidal neurons to regulate autism-related transcripts and circadian memory

Loss of the RNA binding protein FMRP causes Fragile X Syndrome (FXS), the most common cause of inherited intellectual disability, yet it is unknown how FMRP function varies across brain regions and cell types and how this contributes to disease pathophysiology. Here we use conditional tagging of FMRP and CLIP (FMRP cTag CLIP) to examine FMRP mRNA targets in hippocampal CA1 pyramidal neurons, a critical cell type for learning and memory relevant to FXS phenotypes. Integrating these data with analysis of ribosome-bound transcripts in these neurons revealed CA1-enriched binding of autism-relevant mRNAs, and CA1-specific regulation of transcripts encoding circadian proteins. This contrasted with different targets in cerebellar granule neurons, and was consistent with circadian defects in hippocampus-dependent memory in Fmr1 knockout mice. These findings demonstrate differential FMRP-dependent regulation of mRNAs across neuronal cell types that may contribute to phenotypes such as memory defects and sleep disturbance associated with FXS.

Polysomnographic Findings in Fragile X Syndrome Children with EEG Abnormalities

Fragile X syndrome (FXS) is a genetic syndrome with intellectual disability due to the loss of expression of the FMR1 gene located on chromosome X (Xq27.3). This mutation can suppress the fragile X mental retardation protein (FMRP) with an impact on synaptic functioning and neuronal plasticity. Among associated sign and symptoms of this genetic condition, sleep disturbances have been already described, but few polysomnographic reports in pediatric age have been reported. This multicenter case-control study is aimed at assessing the sleep macrostructure and at analyzing the presence of EEG abnormalities in a cohort of FXS children. We enrolled children with FXS and, as controls, children with typical development. All subjects underwent at least 1 overnight polysomnographic recording (PSG). All recorded data obtained from patients and controls were compared. In children with FXS, all PSG-recorded parameters resulted pathological values compared to those obtained from controls, and in FXS children only, we recorded interictal epileptiform discharges (IEDs), as diffuse or focal spikes and sharp waves, usually singles or in brief runs with intermittent or occasional incidence. A possible link between IEDs and alterations in the circadian sleep-wake cycle may suggest a common dysregulation of the balance between inhibitory and excitatory pathways in these patients. The alteration in sleep pattern in children with FXS may negatively impact the neuropsychological and behavioral functioning, adding increasing burn of the disease on the overall management of these patients. In this regard, treating physicians have to early detect sleep disturbances in their patients for tailored management, in order to prevent adjunctive comorbidities.

Clinical Development of Targeted Fragile X Syndrome Treatments: An Industry Perspective

Fragile X syndrome (FXS) is the leading known cause of inherited intellectual disability and autism spectrum disorder. It is caused by a mutation of the fragile X mental retardation 1 (FMR1) gene, resulting in a deficit of fragile X mental retardation protein (FMRP). The clinical presentation of FXS is variable, and is typically associated with developmental delays, intellectual disability, a wide range of behavioral issues, and certain identifying physical features. Over the past 25 years, researchers have worked to understand the complex relationship between FMRP deficiency and the symptoms of FXS and, in the process, have identified several potential targeted therapeutics, some of which have been tested in clinical trials. Whereas most of the basic research to date has been led by experts at academic institutions, the pharmaceutical industry is becoming increasingly involved with not only the scientific community, but also with patient advocacy organizations, as more promising pharmacological agents are moving into the clinical stages of development. The objective of this review is to provide an industry perspective on the ongoing development of mechanism-based treatments for FXS, including identification of challenges and recommendations for future clinical trials.

Sleep in children with neurodevelopmental difficulties

Sleep disorders in children with neurodevelopmental disorders are complex and reflect underlying genetic/biological and behavioural components. The sleep disorders are the same as in the typically developing child, although there may be some modifications to the presentation or the frequency depending on the phenotype. Consideration of the known phenotypes and environmental issues are important in defining management strategies. Despite this complexity, defined behavioural strategies with good sleep hygiene can have a significant effect on the sleep problem and on parental management of the behaviours.

Abnormal Sleep Architecture and Hippocampal Circuit Dysfunction in a Mouse Model of Fragile X Syndrome

Fragile X syndrome (FXS) is the most common heritable cause of intellectual disability and single-gene cause of autism spectrum disorder. The Fmr1 null mouse models much of the human disease including hyperarousal, sensory hypersensitivity, seizure activity, and hippocampus-dependent cognitive impairment. Sleep architecture is disorganized in FXS patients, but has not been examined in Fmr1 knockout (Fmr1-KO) mice. Hippocampal neural activity during sleep, which is implicated in memory processing, also remains uninvestigated in Fmr1-KO mice. We performed in vivo electrophysiological studies of freely behaving Fmr1-KO mice to assess neural activity, in the form of single-unit spiking and local field potential (LFP), within the hippocampal CA1 region during multiple differentiated sleep and wake states. Here, we demonstrate that Fmr1-KO mice exhibited a deficit in rapid eye movement sleep (REM) due to a reduction in the frequency of bouts of REM, consistent with sleep architecture abnormalities of FXS patients. Fmr1-KO CA1 pyramidal cells (CA1-PCs) were hyperactive in all sleep and wake states. Increased low gamma power in CA1 suggests that this hyperactivity was related to increased input to CA1 from CA3. By contrast, slower sharp-wave ripple events (SWRs) in Fmr1-KO mice exhibited longer event duration, slower oscillation frequency, with reduced CA1-PC firing rates during SWRs, yet the incidence rate of SWRs remained intact. These results suggest abnormal neuronal activity in the Fmr1-KO mouse during SWRs, and hyperactivity during other wake and sleep states, with likely adverse consequences for memory processes.

Negative Effects of Chronic Rapamycin Treatment on Behavior in a Mouse Model of Fragile X Syndrome

Fragile X syndrome (FXS), the most common form of inherited intellectual disability, is also highly associated with autism spectrum disorders (ASD). It is caused by expansion of a CGG repeat sequence on the X chromosome resulting in silencing of the FMR1 gene. This is modeled in the mouse by deletion of Fmr1 (Fmr1 KO). Fmr1 KO mice recapitulate many of the behavioral features of the disorder including seizure susceptibility, hyperactivity, impaired social behavior, sleep problems, and learning and memory deficits. The mammalian target of rapamycin pathway (mTORC1) is upregulated in Fmr1 KO mice and is thought to be important for the pathogenesis of this disorder. We treated Fmr1 KO mice chronically with an mTORC1 inhibitor, rapamycin, to determine if rapamycin treatment could reverse behavioral phenotypes. We performed open field, zero maze, social behavior, sleep, passive avoidance, and audiogenic seizure testing. We found that pS6 was upregulated in Fmr1 KO mice and normalized by rapamycin treatment, but, except for an anxiogenic effect, it did not reverse any of the behavioral phenotypes examined. In fact, rapamycin treatment had an adverse effect on sleep and social behavior in both control and Fmr1 KO mice. These results suggest that targeting the mTOR pathway in FXS is not a good treatment strategy and that other pathways should be considered.

Fragile X syndrome

Fragile X syndrome (FXS) is the leading inherited form of intellectual disability and autism spectrum disorder, and patients can present with severe behavioural alterations, including hyperactivity, impulsivity and anxiety, in addition to poor language development and seizures. FXS is a trinucleotide repeat disorder, in which >200 repeats of the CGG motif in FMR1 leads to silencing of the gene and the consequent loss of its product, fragile X mental retardation 1 protein (FMRP). FMRP has a central role in gene expression and regulates the translation of potentially hundreds of mRNAs, many of which are involved in the development and maintenance of neuronal synaptic connections. Indeed, disturbances in neuroplasticity is a key finding in FXS animal models, and an imbalance in inhibitory and excitatory neuronal circuits is believed to underlie many of the clinical manifestations of this disorder. Our knowledge of the proteins that are regulated by FMRP is rapidly growing, and this has led to the identification of multiple targets for therapeutic intervention, some of which have already moved into clinical trials or clinical practice.

Deficient Sleep in Mouse Models of Fragile X Syndrome

In patients with fragile X syndrome (FXS), sleep problems are commonly observed but are not well characterized. In animal models of FXS (dfmr1 and Fmr1 knockout (KO)/Fxr2 heterozygote) circadian rhythmicity is affected, but sleep per se has not been examined. We used a home-cage monitoring system to assess total sleep time in both light and dark phases in Fmr1 KO mice at different developmental stages. Fmr1 KOs at P21 do not differ from controls, but genotype × phase interactions in both adult (P70 and P180) groups are statistically significant indicating that sleep in Fmr1 KOs is reduced selectively in the light phase compared to controls. Our results show the emergence of abnormal sleep in Fmr1 KOs during the later stages of brain maturation. Treatment of adult Fmr1 KO mice with a GABA_B agonist, R-baclofen, did not restore sleep duration in the light phase. In adult (P70) Fmr1 KO/Fxr2 heterozygote animals, total sleep time was further reduced, once again in the light phase. Our data highlight the importance of the fragile X genes (Fmr1 and Fxr2) in sleep physiology and confirm the utility of these mouse models in enhancing our understanding of sleep disorders in FXS.

Altered Developmental Expression of the Astrocyte-Secreted Factors Hevin and SPARC in the Fragile X Mouse Model

Astrocyte dysfunction has been indicated in many neurodevelopmental disorders, including Fragile X Syndrome (FXS). FXS is caused by a deficiency in fragile X mental retardation protein (FMRP). FMRP regulates the translation of numerous mRNAs and its loss disturbs the composition of proteins important for dendritic spine and synapse development. Here, we investigated whether the astrocyte-derived factors hevin and SPARC, known to regulate excitatory synapse development, have altered expression in FXS. Specifically, we analyzed the expression of these factors in wild-type (WT) mice and in fragile X mental retardation 1 (Fmr1) knock-out (KO) mice that lack FMRP expression. Samples were collected from the developing cortex and hippocampus (regions of dendritic spine abnormalities in FXS) of Fmr1 KO and WT pups. Hevin and SPARC showed altered expression patterns in Fmr1 KO mice compared to WT, in a brain-region specific manner. In cortical tissue, we found a transient increase in the level of hevin in postnatal day (P)14 Fmr1 KO mice, compared to WT. Additionally, there were modest decreases in Fmr1 KO cortical levels of SPARC at P7 and P14. In the hippocampus, hevin expression was much lower in P7 Fmr1 KO mice than in WT. At P14, hippocampal hevin levels were similar between genotypes, and by P21 Fmr1 KO hevin expression surpassed WT levels. These findings imply aberrant astrocyte signaling in FXS and suggest that the altered expression of hevin and SPARC contributes to abnormal synaptic development in FXS.

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.

FORWARD: A Registry and Longitudinal Clinical Database to Study Fragile X Syndrome

BACKGROUND AND OBJECTIVE

Advances in the care of patients with fragile X syndrome (FXS) have been hampered by lack of data. This deficiency has produced fragmentary knowledge regarding the natural history of this condition, healthcare needs, and the effects of the disease on caregivers. To remedy this deficiency, the Fragile X Clinic and Research Consortium was established to facilitate research. Through a collective effort, the Fragile X Clinic and Research Consortium developed the Fragile X Online Registry With Accessible Research Database (FORWARD) to facilitate multisite data collection. This report describes FORWARD and the way it can be used to improve health and quality of life of FXS patients and their relatives and caregivers.

METHODS

FORWARD collects demographic information on individuals with FXS and their family members (affected and unaffected) through a 1-time registry form. The longitudinal database collects clinician- and parent-reported data on individuals diagnosed with FXS, focused on those who are 0 to 24 years of age, although individuals of any age can participate.

RESULTS

The registry includes >2300 registrants (data collected September 7, 2009 to August 31, 2014). The longitudinal database includes data on 713 individuals diagnosed with FXS (data collected September 7, 2012 to August 31, 2014). Longitudinal data continue to be collected on enrolled patients along with baseline data on new patients.

CONCLUSIONS

FORWARD represents the largest resource of clinical and demographic data for the FXS population in the United States. These data can be used to advance our understanding of FXS: the impact of cooccurring conditions, the impact on the day-to-day lives of individuals living with FXS and their families, and short-term and long-term outcomes.

Autism Spectrum Disorder in Fragile X Syndrome: Cooccurring Conditions and Current Treatment

BACKGROUND AND OBJECTIVE

Individuals with fragile X syndrome (FXS) are frequently codiagnosed with autism spectrum disorder (ASD). Most of our current knowledge about ASD in FXS comes from family surveys and small studies. The objective of this study was to examine the impact of the ASD diagnosis in a large clinic-based FXS population to better inform the care of people with FXS.

METHODS

The study employed a data set populated by data from individuals with FXS seen at specialty clinics across the country. The data were collected by clinicians at the patient visit and by parent report for nonclinical and behavioral outcomes from September 7, 2012 through August 31, 2014. Data analyses were performed by using χ² tests for association, t tests, and multiple logistic regression to examine the association between clinical and other factors with ASD status.

RESULTS

Half of the males and nearly 20% of females met Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria for current ASD. Relative to the FXS-only group, the FXS with ASD (FXS+ASD) group had a higher prevalence of seizures (20.7% vs 7.6%, P < .001), persistence of sleep problems later in childhood, increased behavior problems, especially aggressive/disruptive behavior, and higher use of α-agonists and antipsychotics. Behavioral services, including applied behavior analysis, appeared to be underused in children with FXS+ASD (only 26% and 16% in prekindergarten and school-age periods, respectively) relative to other populations with idiopathic ASD.

CONCLUSIONS

These findings confirm among individuals with FXS an association of an ASD diagnosis with important cooccurring conditions and identify gaps between expected and observed treatments among individuals with FXS+ASD.

Deficits in the activity of presynaptic γ-aminobutyric acid type B receptors contribute to altered neuronal excitability in fragile X syndrome

The behavioral and anatomical deficits seen in fragile X syndrome (FXS) are widely believed to result from imbalances in the relative strengths of excitatory and inhibitory neurotransmission. Although modified neuronal excitability is thought to be of significance, the contribution that alterations in GABAergic inhibition play in the pathophysiology of FXS are ill defined. Slow sustained neuronal inhibition is mediated by γ-aminobutyric acid type B (GABAB) receptors, which are heterodimeric G-protein-coupled receptors constructed from R1a and R2 or R1b and R2 subunits. Via the activation of Gi/o, they limit cAMP accumulation, diminish neurotransmitter release, and induce neuronal hyperpolarization. Here we reveal that selective deficits in R1a subunit expression are seen in Fmr1 knock-out mice (KO) mice, a widely used animal model of FXS, but the levels of the respective mRNAs were unaffected. Similar trends of R1a expression were seen in a subset of FXS patients. GABAB receptors (GABABRs) exert powerful pre- and postsynaptic inhibitory effects on neurotransmission. R1a-containing GABABRs are believed to mediate presynaptic inhibition in principal neurons. In accordance with this result, deficits in the ability of GABABRs to suppress glutamate release were seen in Fmr1-KO mice. In contrast, the ability of GABABRs to suppress GABA release and induce postsynaptic hyperpolarization was unaffected. Significantly, this deficit contributes to the pathophysiology of FXS as the GABABR agonist (R)-baclofen rescued the imbalances between excitatory and inhibitory neurotransmission evident in Fmr1-KO mice. Collectively, our results provided evidence that selective deficits in the activity of presynaptic GABABRs contribute to the pathophysiology of FXS.

Fragile X syndrome: a review of clinical and molecular diagnoses

Background

Fragile X Syndrome (FXS) is the second cause of intellectual disability after Down syndrome and the most prevalent cause of intellectual disability in males, affecting 1:5000–7000 men and 1:4000–6000 women. It is caused by an alteration of the FMR1 gene, which maps at the Xq27.3 band: more than 99% of individuals have a CGG expansion (>200 triplets) in the 5′ UTR of the gene, and FMR1 mutations and duplication/deletion are responsible for the remaining (<1%) molecular diagnoses of FXS. The aim of this review was to gather the current clinical and molecular knowledge about FXS to provide clinicians with a tool to guide the initial assessment and follow-up of FXS and to offer to laboratory workers and researchers an update about the current diagnostic procedures.

Discussion

FXS is a well-known condition; however, most of the studies thus far have focused on neuropsychiatric features. Unfortunately, some of the available studies have limitations, such as the paucity of patients enrolled or bias due to the collection of the data in a single-country population, which may be not representative of the average global FXS population. In recent years, insight into the adult presentation of the disease has progressively increased. Pharmacological treatment of FXS is essentially symptom based, but the growing understanding of the molecular and biological mechanisms of the disease are paving the way to targeted therapy, which may reverse the effects of FMRP deficiency and be a real cure for the disease itself, not just its symptoms.

Conclusions

The clinical spectrum of FXS is wide, presenting not only as an isolated intellectual disability but as a multi-systemic condition, involving predominantly the central nervous system but potentially affecting any apparatus. Given the relative high frequency of the condition and its complex clinical management, FXS appears to have an important economic and social burden.

Fragile X and Obstructive Sleep Apnea Syndrome: Case Presentation and Management Challenges

ABSTRACT

A high prevalence of obstructive sleep apnea (OSA) has been reported in individuals with fragile X syndrome (FXS). Untreated OSA can further complicate both medical and cognitive sequelae. Thus, identifying the diagnostic and treatment challenges that arise in these individuals is essential. We describe an adolescent with FXS who presented with significant OSA symptoms, and the challenges associated with management in this case.