Latent Class Analysis Identifies Distinctive Behavioral Subtypes in Children with Fragile X Syndrome

Scheduled feeding improves behavioral outcomes and reduces inflammation in a mouse model of Fragile X syndrome

Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by the abnormal expansion of CGG repeats in the fragile X mental retardation 1 (FMR1) gene. Many FXS patients experience sleep disruptions, and we sought to explore these symptoms along with the possible benefits of a scheduled feeding intervention using the Fmr1 knockout (KO) mouse model. These mutants displayed clear evidence for sleep and circadian disturbances including delay in the onset of sleep and fragmented activity rhythms with increases in cycle-to-cycle variability. Importantly, the Fmr1 KO mice exhibited deficits in their circadian behavioral response to light with reduced masking, longer time to resetting to shifts in the Light-Dark cycle, altered synchronization to a skeleton photoperiod and lower magnitude light-induced phase shifts of activity rhythms. Investigation of the retinal input to the surprachiasmatic nucleus (SCN) with the neurotracer cholera toxin (β subunit) and quantification of the light-evoked cFos expression in the SCN revealed an abnormal retinal innervation of the SCN in the Fmr1 KO, providing a possible mechanistic explanation for the observed behavioral deficits. Interestingly, disruptions in social and repetitive behaviors correlated with sleep duration and fragmentation. Understanding the nature of the deficits, we decided to apply a scheduled feeding regimen (6-hr/18-hr feed/fast cycle) as a circadian-based strategy to boast circadian rhythms independently of light. This intervention significantly improved the activity rhythms and sleep in the mutants. Strikingly, the scheduled feeding ameliorated social interactions and reduced repetitive behaviors as well as the levels of Interferon-gamma and Interleukin-12 in the Fmr1 KO mutants, suggesting that timed eating may be an effective way to lessen inflammation. Collectively, this work adds support to efforts to develop circadian based interventions to help with symptoms of neurodevelopmental disorders.

The Aberrant Behavior Checklist for Fragile X Syndrome: A Qualitative Clinician Evaluation of Content Validity

Objective: The current intense period of drug development for fragile X syndrome (FXS) and other neurodevelopmental disorders (NDDs) indications has highlighted the importance of behavioral outcome measures with strong psychometric properties and specifically content validity. The Aberrant Behavior Checklist-Community Edition (ABC-C), which has successfully been applied to autism spectrum disorder drug trials, has been revised for FXS (ABCFX) and is widely used for both clinical and research purposes. Despite its strong psychometric validation, the ABCFX and its parent measure have not been subjected to qualitative content validity evaluations. The present study intended to fill this gap. Methods: Using two surveys administered sequentially and developed with guidance and review from the Food and Drug Administration (FDA), we asked 10 clinicians experienced in FXS and related NDDs to determine the adequacy of the ABCFX for assessing its behavioral constructs, its relevance to FXS, and its potential for detecting response to interventions. Various descriptive statistic parameters and ad hoc metrics were used to analyze categorical and Likert-like scale responses. Results: Experts considered that most items and all six ABCFX subscales indeed evaluated their explicit or implicit behavioral constructs. However, item and subscale specificity were relatively low (∼25%-30%). Relevance of items of the Hyperactivity subscale was relatively high while low for many items of the Socially Unresponsive/Lethargic subscale. These items were also considered of low responsiveness potential. Irritability, Hyperactivity, Stereotypy, and Social Avoidance were the subscales with the strongest profiles, although the experts estimated that Stereotypy items may not be that responsive to treatment. A novel Anxiety construct, representing mainly recently reported observable behaviors, contributed mainly by Irritability items, emerged as a potential measure. Conclusions: The present study demonstrated the overall adequacy of the ABCFX for its behavioral constructs, its relevance to FXS, and its potential for detecting response to treatment. It also showed that anxiety, a distinctive feature of FXS and other genetic NDDs, can also be measured by the ABCFX. These findings can help with the implementation and interpretation of the ABCFX, as well as with potential improvements to the measure in FXS and other NDDs.

Sensory Symptoms and Signs of Hyperarousal in Individuals with Fragile X Syndrome: Findings from the FORWARD Registry and Database Multisite Study

This study was designed to increase our understanding about characteristics and the impact of sensory symptoms (SS) and signs of hyperarousal (HA) in individuals with fragile X syndrome (FXS) from childhood through early adulthood and by gender. Data derived from the Fragile X Online Registry With Accessible Research Database (FORWARD), a natural history study of FXS, were analyzed using descriptive statistics and multivariate linear and logistic regression models to examine SS and signs of HA, their impact on behavioral regulation and limitations on the subject/family. The sample (N = 933) consisted of 720 males and 213 females. More males were affected with SS (87% vs. 68%) and signs of HA (92% vs. 79%). Subjects who were endorsed as having a strong sensory response had more comorbidities, including behavioral problems. The predominant SS was difficulty with eye gaze that increased with age in both genders. As individuals age, there was less use of non-medication therapies, such as occupational therapy (OT)/physical therapy (PT), but there was more use of psychopharmacological medications and investigational drugs for behaviors. Multiple regression models suggested that endorsing SS and signs of HA was associated with statistically significantly increased ABC-C-I subscale scores and limited participation in everyday activities. This study improves our understanding of SS and signs of HA as well as their impact in FXS. It supports the need for more research regarding these clinical symptoms, especially to understand how they contribute to well-known behavioral concerns.

Variation of FMRP Expression in Peripheral Blood Mononuclear Cells from Individuals with Fragile X Syndrome

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