Aurore Curie

Epigenetic Modification of the FMR1 Gene in Fragile X Syndrome Is Associated with Differential Response to the mGluR5 Antagonist AFQ056

An antagonist for the metabotropic glutamate receptor may improve symptoms in patients with fragile X syndrome whose FMR1 promoters are fully methylated. A Methylation Marker for Fragile X Syndrome Through the practice of meditation, students of Eastern philosophies are taught to turn down the noise to find the silence within. But for patients suffering from fragile X syndrome, it is the silence within that turns up the noise. In this disorder, a defect in the fragile X mental retardation 1 gene (FMR1) silences its expression, which gives rise to myriad molecular changes, most notably a turning up of signaling through the metabotropic glutamate receptor mGluR5. This noisy signaling pathway contributes to the cognitive deficits and differences that first become apparent in patients during childhood, and currently these symptoms are treatable only with supportive behavioral measures. But in mice and fruit flies that carry the same genetic defects as patients and also show enhanced glutamate receptor signaling and behavioral problems, administration of an mGluR5 antagonist improves the symptoms. Jacquemont et al. have now treated a group of 30 fragile X patients with such an antagonist. Not all subjects showed improvement, but an analysis of those who did revealed that the promoter of the FMR1 gene in drug-responsive patients is fully methylated, a sign that gene expression is completely silenced. This molecular aberration might serve as a signature that defines fragile X patients who could benefit from treatment with mGluR5 antagonists. In individuals with fragile X syndrome, the FMR1 gene can contain as many as several thousand extra repeats of the triplet base pairs CGG, a distortion that is accompanied by extra methylation at the gene’s promoter and thus impaired transcription. Because the number of triplet repeats differs widely from person to person—and even from generation to generation—there is a broad variation among patients in the structure of the gene and its methylation pattern. So when the authors tested the effects of a newly described mGluR5 inhibitor on fragile X patients, they assayed the methylation status of the FMR1 promoter, as well as running a large battery of behavioral tests designed to detect stereotypic behavior, hyperactivity, and inappropriate speech. In this clinical trial, the mGluR5 antagonist had no effect on the behaviors measured by these primary tests, but administration of the drug did correlate with differences observed in a secondary collection of tests, when the drug-treated patient group was compared with subjects who were given a placebo treatment. In a subsequent exploratory analysis, the authors found that each member of the subgroup of patients who harbored fully methylated FMR1 promoters showed improvement by the primary behavioral measures, exhibiting a boost in performance 19 or 20 days after treatment was started. The patient group with partially methylated promoters showed no such changes. This correlation between response to treatment and methylation status of the FMR1 promoter provides the basis for a larger study, appropriately designed to test whether methylation can serve as a predictor of a positive antagonist response in a population of patients with fragile X syndrome. It also offers hope that inhibition of the metabotropic glutamate system—believed to underlie many of the characteristic behaviors associated with fragile X—may be accomplished routinely, at least in patients in which the silence within lies in the FMR1 promoter. Fragile X syndrome (FXS) is an X-linked condition associated with intellectual disability and behavioral problems. It is caused by expansion of a CGG repeat in the 5′ untranslated region of the fragile X mental retardation 1 (FMR1) gene. This mutation is associated with hypermethylation at the FMR1 promoter and resultant transcriptional silencing. FMR1 silencing has many consequences, including up-regulation of metabotropic glutamate receptor 5 (mGluR5)–mediated signaling. mGluR5 receptor antagonists have shown promise in preclinical FXS models and in one small open-label study of FXS. We examined whether a receptor subtype–selective inhibitor of mGluR5, AFQ056, improves the behavioral symptoms of FXS in a randomized, double-blind, two-treatment, two-period, crossover study of 30 male FXS patients aged 18 to 35 years. We detected no significant effects of treatment on the primary outcome measure, the Aberrant Behavior Checklist–Community Edition (ABC-C) score, at day 19 or 20 of treatment. In an exploratory analysis, however, seven patients with full FMR1 promoter methylation and no detectable FMR1 messenger RNA improved, as measured with the ABC-C, significantly more after AFQ056 treatment than with placebo (P < 0.001). We detected no response in 18 patients with partial promoter methylation. Twenty-four patients experienced an adverse event, which was mostly mild to moderately severe fatigue or headache. If confirmed in larger and longer-term studies, these results suggest that blockade of the mGluR5 receptor in patients with full methylation at the FMR1 promoter may show improvement in the behavioral attributes of FXS.

The Renpenning syndrome spectrum: new clinical insights supported by 13 new PQBP1-mutated males.

D Germanaud, M Rossi, G Bussy, D Gérard, L Hertz‐Pannier, P Blanchet, H Dollfus, F Giuliano, V Bennouna‐Greene, P Sarda, S Sigaudy, A Curie, MC Vincent, R Touraine, V des Portes. The Renpenning syndrome spectrum: new clinical insights supported by 13 new PQBP1‐mutated males.

Implicit procedural learning in fragile X and Down syndrome.

BACKGROUND Procedural learning refers to rule-based motor skill learning and storage. It involves the cerebellum, striatum and motor areas of the frontal lobe network. Fragile X syndrome, which has been linked with anatomical abnormalities within the striatum, may result in implicit procedural learning deficit. METHODS To address this issue, a serial reaction time (RT) task including six blocks of trials was performed by 14 individuals with fragile X syndrome, 12 individuals with Down syndrome and 12 mental age-matched control subjects. The first (B1) and fifth (B5) blocks were random whereas the others (B2, B3, B4 and B6) consisted of a repeated 10-step sequence. Results were analysed by Kruskal-Wallis one-way analysis of variance and Wilcoxon signed-rank test. RESULTS For patients with fragile X syndrome, the RT was highly suggestive of preserved implicit learning as a significant difference was observed between blocks B5 and B6 (P = 0.009). However, the difference of RT between B4 and B5 did not reach significance, possibly due to a subgroup of individuals who did not learn. In contrast, in the Down syndrome group, RT decreased significantly between B4 and B5 (W = 2; P = 0.003) but not between the last ordered block (B6) and the last random block (B5), suggesting a weakness in procedural learning which was sensitive to the interfering random block. CONCLUSION implicit learning is variable in genetic syndromes and therefore relatively independent of general intellectual capacities. The results are discussed together with previous reports.

Placebo Responses in Genetically Determined Intellectual Disability: A Meta-Analysis

Background Genetically determined Intellectual Disability (ID) is an intractable condition that involves severe impairment of mental abilities such as learning, reasoning and predicting the future. As of today, little is known about the placebo response in patients with ID. Objective To determine if placebo response exists in patients with genetically determined ID. Data sources and Study selection We searched Medline/PubMed, EMBASE, CENTRAL and PsycINFO to find all placebo-controlled double-blind randomized clinical trials (RCTs) in patients with genetically determined ID, published up to April 2013, focusing on core ID symptoms. Data extraction and synthesis Two investigators extracted outcome data independently. Main outcomes and measures Bias-corrected standardized mean difference (Hedge’s g) was computed for each outcome measure, using the Comprehensive Meta-Analysis software. A priori defined patient sub-groups were analyzed using a mixed-effect model. The relationship between pre-defined continuous variable moderators (age, IQ, year of publication and trial duration) and effect size was analyzed using meta-regression Results Twenty-two placebo-controlled double-blind RCTs met the inclusion criteria (n = 721, mean age = 17.1 years, 62% men, mean trial duration = 35 weeks). There was a significant overall placebo response from pre- to post-treatment in patients with ID (g = 0.468, p = 0.002), both for “subjective outcomes” (a third-person’s evaluation of the patient) (g = 0.563, p = 0.022) and “objective outcomes” (direct evaluation of the patient’s abilities) (g = 0.434, p = 0.036). Individuals with higher IQ had higher response to placebo (p = 0.02) and no placebo response was observed in ID patients with comorbid dementia. A significant effect of age (p = 0.02) was found, indicating higher placebo responses in treatment of younger patients. Conclusions and relevance Results suggest that patients with genetically determined ID improve in the placebo arm of RCTs. Several mechanisms may contribute to placebo effects in ID, including expectancy, implicit learning and “placebo-by-proxy” induced by clinicians/family members. As the condition is refractory, there is little risk that improvements are explained by spontaneous remission. While new avenues for treatment of genetically determined ID are emerging, our results demonstrate how contextual factors can affect clinical outcomes and emphasize the importance of being vigilant on the role of placebos when testing novel treatments in ID.

Drug development for neurodevelopmental disorders: lessons learned from fragile X syndrome

Neurodevelopmental disorders such as fragile X syndrome (FXS) result in lifelong cognitive and behavioural deficits and represent a major public health burden. FXS is the most frequent monogenic form of intellectual disability and autism, and the underlying pathophysiology linked to its causal gene, FMR1, has been the focus of intense research. Key alterations in synaptic function thought to underlie this neurodevelopmental disorder have been characterized and rescued in animal models of FXS using genetic and pharmacological approaches. These robust preclinical findings have led to the implementation of the most comprehensive drug development programme undertaken thus far for a genetically defined neurodevelopmental disorder, including phase IIb trials of metabotropic glutamate receptor 5 (mGluR5) antagonists and a phase III trial of a GABAB receptor agonist. However, none of the trials has been able to unambiguously demonstrate efficacy, and they have also highlighted the extent of the knowledge gaps in drug development for FXS and other neurodevelopmental disorders. In this Review, we examine potential issues in the previous studies and future directions for preclinical and clinical trials. FXS is at the forefront of efforts to develop drugs for neurodevelopmental disorders, and lessons learned in the process will also be important for such disorders.

Stroke by Carotid Artery Complete Occlusion in Kawasaki Disease: Case Report and Review of Literature

BACKGROUND Kawasaki disease is an acute and time-limited systemic vasculitis primarily affecting young children. PATIENT We describe an 18-month-old girl with Kawasaki disease who developed cerebral infarction following complete occlusion of her right internal carotid artery. RESULTS The occlusion occurred 10 days after the onset of fever, while she was on high-dose aspirin, and the day after she received intravenous immunoglobulin treatment. We present the first literature review on this very rare complication. CONCLUSION Stroke is a rare neurological complication in Kawasaki disease. Optimal treatment should be begun as soon as possible after diagnosis. Intravenous immunoglobulins seem to reduce the cerebrovascular complications, but evaluation of hydration status is strongly recommended before performing such treatment.

A Novel Analog Reasoning Paradigm: New Insights in Intellectually Disabled Patients

Background Intellectual Disability (ID) is characterized by deficits in intellectual functions such as reasoning, problem-solving, planning, abstract thinking, judgment, and learning. As new avenues are emerging for treatment of genetically determined ID (such as Down’s syndrome or Fragile X syndrome), it is necessary to identify objective reliable and sensitive outcome measures for use in clinical trials. Objective We developed a novel visual analogical reasoning paradigm, inspired by the Progressive Raven’s Matrices, but appropriate for Intellectually Disabled patients. This new paradigm assesses reasoning and inhibition abilities in ID patients. Methods We performed behavioural analyses for this task (with a reaction time and error rate analysis, Study 1) in 96 healthy controls (adults and typically developed children older than 4) and 41 genetically determined ID patients (Fragile X syndrome, Down syndrome and ARX mutated patients). In order to establish and quantify the cognitive strategies used to solve the task, we also performed an eye-tracking analysis (Study 2). Results Down syndrome, ARX and Fragile X patients were significantly slower and made significantly more errors than chronological age-matched healthy controls. The effect of inhibition on error rate was greater than the matrix complexity effect in ID patients, opposite to findings in adult healthy controls. Interestingly, ID patients were more impaired by inhibition than mental age-matched healthy controls, but not by the matrix complexity. Eye-tracking analysis made it possible to identify the strategy used by the participants to solve the task. Adult healthy controls used a matrix-based strategy, whereas ID patients used a response-based strategy. Furthermore, etiologic-specific reasoning differences were evidenced between ID patients groups. Conclusion We suggest that this paradigm, appropriate for ID patients and developmental populations as well as adult healthy controls, provides an objective and quantitative assessment of visual analogical reasoning and cognitive inhibition, enabling testing for the effect of pharmacological or behavioural intervention in these specific populations.

The c.429_452 duplication of the ARX gene: a unique developmental-model of limb kinetic apraxia

BackgroundThe c.429_452dup24 of the ARX gene is a rare genetic anomaly, leading to X-Linked Intellectual Disability without brain malformation. While in certain cases c.429_452dup24 has been associated with specific clinical patterns such as Partington syndrome, the consequence of this mutation has been also often classified as “non-specific Intellectual Disability”. The present work aims at a more precise description of the clinical features linked to the c.429_452dup24 mutation.MethodsWe clinically reviewed all affected patients identified in France over a five-year period, i.e. 27 patients from 12 different families. Detailed cognitive, behavioural, and motor evaluation, as well as standardized videotaped assessments of oro-lingual and gestural praxis, were performed. In a sub-group of 13 ARX patients, kinematic and MRI studies were further accomplished to better characterize the motor impairment prevalent in the ARX patients group. To ensure that data were specific to the ARX gene mutation and did not result from low-cognitive functioning per se, a group of 27 age- and IQ-matched Down syndrome patients served as control.ResultsNeuropsychological and motor assessment indicated that the c.429_452dup24 mutation constitutes a recognizable clinical syndrome: ARX patients exhibiting Intellectual Disability, without primary motor impairment, but with a very specific upper limb distal motor apraxia associated with a pathognomonic hand-grip. Patients affected with the so-called Partington syndrome, which involves major hand dystonia and orolingual apraxia, exhibit the most severe symptoms of the disorder. The particular “reach and grip” impairment which was observed in all ARX patients, but not in Down syndrome patients, was further characterized by the kinematic data: (i) loss of preference for the index finger when gripping an object, (ii) major impairment of fourth finger deftness, and (iii) a lack of pronation movements. This lack of distal movement coordination exhibited by ARX patients is associated with the loss of independent digital dexterity and is similar to the distortion of individual finger movements and posture observed in Limb Kinetic Apraxia.ConclusionThese findings suggest that the ARX c.429_452dup24 mutation may be a developmental model for Limb Kinetic Apraxia.

Certainty of genuine treatment increases drug responses among intellectually disabled patients

Objective: To determine the placebo component of treatment responses in patients with intellectual disability (ID). Methods: A statistical meta-analysis comparing bias-corrected effect sizes (Hedges g) of drug responses in open-label vs placebo-controlled clinical trials was performed, as these trial types represent different certainty of receiving genuine treatment (100% vs 50%). Studies in fragile X, Down, Prader-Willi, and Williams syndrome published before June 2015 were considered. Results: Seventeen open-label trials (n = 261, 65% male; mean age 23.6 years; mean trial duration 38 weeks) and 22 placebo-controlled trials (n = 721, 62% male; mean age 17.1 years; mean trial duration 35 weeks) were included. The overall effect size from pre to post treatment in open-label studies was g = 0.602 (p = 0.001). The effect of trial type was statistically significant (p = 0.001), and revealed higher effect sizes in studies with 100% likelihood of getting active drug, compared to both the drug and placebo arm of placebo-controlled trials. We thus provide evidence for genuine placebo effects, not explainable by natural history or regression toward the mean, among patients with ID. Conclusions: Our data suggest that clinical trials in patients with severe cognitive deficits are influenced by the certainty of receiving genuine medication, and open-label design should thus not be used to evaluate the effect of pharmacologic treatments in ID, as the results will be biased by an enhanced placebo component.

Syntax at hand: common syntactic structures for actions and language.

Evidence that the motor and the linguistic systems share common syntactic representations would open new perspectives on language evolution. Here, crossing disciplinary boundaries, we explore potential parallels between the structure of simple actions and that of sentences. First, examining Typically Developing (TD) children displacing a bottle with or without knowledge of its weight prior to movement onset, we provide kinematic evidence that the sub-phases of this displacing action (reaching + moving the bottle) manifest a structure akin to linguistic embedded dependencies. Then, using the same motor task, we reveal that children suffering from specific language impairment (SLI), whose core deficit affects syntactic embedding and dependencies, manifest specific structural motor anomalies parallel to their linguistic deficits. In contrast to TD children, SLI children performed the displacing-action as if its sub-phases were juxtaposed rather than embedded. The specificity of SLI’s structural motor deficit was confirmed by testing an additional control group: Fragile-X Syndrome patients, whose language capacity, though delayed, comparatively spares embedded dependencies, displayed slower but structurally normal motor performances. By identifying the presence of structural representations and dependency computations in the motor system and by showing their selective deficit in SLI patients, these findings point to a potential motor origin for language syntax.