Pubmed du 03/07/17

lundi 3 juillet 2017

1. Brigida AL, Schultz S, Cascone M, Antonucci N, Siniscalco D. Endocannabinod Signal Dysregulation in Autism Spectrum Disorders : A Correlation Link between Inflammatory State and Neuro-Immune Alterations. Int J Mol Sci. 2017 ; 18(7).

Several studies highlight a key involvement of endocannabinoid (EC) system in autism pathophysiology. The EC system is a complex network of lipid signaling pathways comprised of arachidonic acid-derived compounds (anandamide, AEA) and 2-arachidonoyl glycerol (2-AG), their G-protein-coupled receptors (cannabinoid receptors CB1 and CB2) and the associated enzymes. In addition to autism, the EC system is also involved in several other psychiatric disorders (i.e., anxiety, major depression, bipolar disorder and schizophrenia). This system is a key regulator of metabolic and cellular pathways involved in autism, such as food intake, energy metabolism and immune system control. Early studies in autism animal models have demonstrated alterations in the brain’s EC system. Autism is also characterized by immune system dysregulation. This alteration includes differential monocyte and macrophage responses, and abnormal cytokine and T cell levels. EC system dysfunction in a monocyte and macrophagic cellular model of autism has been demonstrated by showing that the mRNA and protein for CB2 receptor and EC enzymes were significantly dysregulated, further indicating the involvement of the EC system in autism-associated immunological disruptions. Taken together, these new findings offer a novel perspective in autism research and indicate that the EC system could represent a novel target option for autism pharmacotherapy.

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2. Delaney KR. Restoring EEAqualibrium : rebalancing excitation and inhibition in Rett mouse model neurons with early endosome antigen-1. J Physiol. 2017.

Rett syndrome is a neurological disorder resulting from loss of function of MECP2, an X-linked transcription factor, which controls expression of hundreds of genes involved in synapse formation and development by binding primarily to methylated DNA. This article is protected by copyright. All rights reserved.

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3. Garcia-Pino E, Gessele N, Koch U. Enhanced Excitatory Connectivity and Disturbed Sound Processing in the Auditory Brainstem of Fragile X Mice. J Neurosci. 2017.

Hypersensitivity to sounds is one of the prevalent symptoms in individuals with Fragile X syndrome (FXS). It manifests behaviorally early during development and is often used as a landmark for treatment efficacy. However, the physiological mechanisms and circuit-level alterations underlying this aberrant behavior remain poorly understood. Using the mouse model of FXS (Fmr1 KO) we demonstrate that functional maturation of auditory brainstem synapses is impaired in FXS. Fmr1 KO mice showed a greatly enhanced excitatory synaptic input strength in neurons of the lateral superior olive (LSO), a prominent auditory brainstem nucleus, which integrates ipsilateral excitation and contralateral inhibition to compute interaural level differences (ILDs). Conversely, the glycinergic, inhibitory input properties remained unaffected. The enhanced excitation was the result of an increased number of cochlear nucleus fibers converging onto one LSO neuron, without changing individual synapse properties. Concomitantly, immunolabeling of excitatory ending markers revealed an increase in the immunolabeled area, supporting abnormally elevated excitatory input numbers. Intrinsic firing properties were only slightly enhanced. In line with the disturbed development of LSO circuitry auditory processing was also affected in adult Fmr1 KO mice as shown with single-unit recordings of LSO neurons. These processing deficits manifested as an increase in firing rate, a broadening of the frequency response area and a shift in the ILD function of LSO neurons. Our results suggest that this aberrant synaptic development of auditory brainstem circuits might be a major underlying cause of the auditory processing deficits in FXS.SIGNIFICANCE STATEMENTFragile X Syndrome (FXS) is the most common inheritable form of intellectual impairment, including autism. A core symptom of FXS is extreme sensitivity to loud sounds. This is one reason why individuals with FXS tend to avoid social interactions, contributing to their isolation. Here, a mouse model of FXS was used to investigate the auditory brainstem where basic sound information is first processed. Loss of the Fragile X mental retardation protein leads to excessive excitatory compared to inhibitory inputs in neurons extracting information about sound levels. Functionally, this elevated excitation results in increased firing rates, and abnormal coding of frequency and binaural sound localization cues. Imbalanced early stage sound level processing could partially explain the auditory processing deficits in FXS.

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4. Muskens JB, Velders FP, Staal WG. Medical comorbidities in children and adolescents with autism spectrum disorders and attention deficit hyperactivity disorders : a systematic review. Eur Child Adolesc Psychiatry. 2017.

Somatic disorders occur more often in adult psychiatric patients than in the general adult population. However, in child and adolescent psychiatry this association is unclear, mainly due to a lack of integration of existing data. To address this issue, we here present a systematic review on medical comorbidity in the two major developmental disorders autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) and formulate clinical recommendations. The literature was searched using the PubMed and PsycINFO databases (2000-1 May 2016) with the keywords "[((child and adolescent) AND (Autism OR Attention Deficit Hyperactivity Disorder* OR ADHD)) AND ("Cardiovascular Diseases" [Mesh] OR "Endocrine System Diseases" [Mesh] OR "Immune System Diseases" [Mesh] OR "Neurobehavioral Manifestations" [Mesh] OR "Gastrointestinal Disorders" [Mesh] OR Somatic OR Autoimmune disease OR Nervous system disease OR Infection OR Infectious disease)]. Two raters independently assessed the quality of the eligible studies. The initial search identified 5278 articles. Based on inclusion and exclusion criteria 104 papers were selected and subsequently subjected to a quality control. This quality was assessed according to a standardized and validated set of criteria and yielded 29 studies for inclusion. This thorough literature search provides an overview of relevant articles on medical comorbidity in ADHD and/or ASD, and shows that medical disorders in these children and adolescents appear to be widespread. Those who work with children with ASD and/or ADHD should be well aware of this and actively promote routine medical assessment. Additionally, case-control studies and population-based studies are needed to provide reliable prevalence estimates. Future studies should furthermore focus on a broader evaluation of medical disorders in children and adolescents with ADHD and/or ASD to improve treatment algorithm in this vulnerable group.

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5. Olde Loohuis NFM, Martens GJM, van Bokhoven H, Kaplan BB, Homberg JR, Aschrafi A. Altered expression of circadian rhythm and extracellular matrix genes in the medial prefrontal cortex of a valproic acid rat model of autism. Prog Neuropsychopharmacol Biol Psychiatry. 2017 ; 77 : 128-32.

Autism spectrum disorders (ASD) are a highly heterogeneous group of neurodevelopmental disorders caused by complex interplay between various genes and environmental factors during embryonic development. Changes at the molecular, cellular and neuroanatomical levels are especially evident in the medial prefrontal cortex (mPFC) of ASD patients and are particularly contributing to social impairments. In the present study we tested the hypothesis that altered neuronal development and plasticity, as seen in the mPFC of ASD individuals, may result from aberrant expression of functionally connected genes. Towards this end, we combined transcriptome sequencing and computational gene ontology analysis to identify the molecular networks impaired in the mPFC of a valproic acid (VPA) rat model of autism. This investigation identified two subsets of genes differentially expressed in the mPFC of VPA rats : one group of genes being functionally involved in the regulation of the circadian rhythm, while the second group encompasses a set of differentially expressed collagen genes acting within the extracellular matrix. Ultimately, our integrated transcriptome analysis identified a distinct subset of altered gene networks in the mPFC of VPA rats, contributing to our understanding of autism at the molecular level, thus providing novel insight into the genetic alterations associated with this neurodevelopmental disorder.

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6. Ye K, Iossifov I, Levy D, Yamrom B, Buja A, Krieger AM, Wigler M. Measuring shared variants in cohorts of discordant siblings with applications to autism. Proc Natl Acad Sci U S A. 2017 ; 114(27) : 7073-6.

We develop a method of analysis [affected to discordant sibling pairs (A2DS)] that tests if shared variants contribute to a disorder. Using a standard measure of genetic relation, test individuals are compared with a cohort of discordant sibling pairs (CDS) to derive a comparative similarity score. We ask if a test individual is more similar to an unrelated affected than to the unrelated unaffected sibling from the CDS and then, sum over such individuals and pairs. Statistical significance is judged by randomly permuting the affected status in the CDS. In the analysis of published genotype data from the Simons Simplex Collection (SSC) and the Autism Genetic Resource Exchange (AGRE) cohorts of children with autism spectrum disorder (ASD), we find strong statistical significance that the affected are more similar to the affected than to the unaffected of the CDS (P value approximately 0.00001). Fathers in multiplex families have marginally greater similarity (P value = 0.02) to unrelated affected individuals. These results do not depend on ethnic matching or gender.

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