1. Alvarez-Mora MI, Rodriguez-Revenga L, Madrigal I, Garcia-Garcia F, Duran M, Dopazo J, Estivill X, Mila M. {{Deregulation of key signaling pathways involved in oocyte maturation in FMR1 premutation carriers with Fragile X-associated primary ovarian insufficiency}}. {Gene};2015 (Oct 15);571(1):52-57.
FMR1 premutation female carriers are at risk for Fragile X-associated primary ovarian insufficiency (FXPOI). Insights from knock-in mouse model have recently demonstrated that FXPOI is due to an increased rate of follicle depletion or an impaired development of the growing follicles. Molecular mechanisms responsible for this reduced viability are still unknown. In an attempt to provide new data on the mechanisms that lead to FXPOI, we report the first investigation involving transcription profiling of total blood from FMR1 premutation female carriers with and without FXPOI. A total of 16 unrelated female individuals (6 FMR1 premutated females with FXPOI; 6 FMR1 premutated females without FXPOI; and 4 no-FXPOI females) were studied by whole human genome oligonucleotide microarray (Agilent Technologies). Fold change analysis did not show any genes with significant differential gene expression. However, functional profiling by gene set analysis showed large number of statistically significant deregulated GO annotations as well as numerous KEGG pathways in FXPOI females. These results suggest that the impairment of fertility in these females might be due to a generalized deregulation of key signaling pathways involved in oocyte maturation. In particular, the vasoendotelial growth factor signaling, the inositol phosphate metabolism, the cell cycle, and the MAPK signaling pathways were found to be down-regulated in FXPOI females. Furthermore, a high statistical enrichment of biological processes involved in cell death and survival were found deregulated among FXPOI females. Our results provide new strategic approaches to further investigate the molecular mechanisms and potential therapeutic targets for FXPOI not focused in a single gene but rather in the set of genes involved in these pathways.
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2. De Rubeis S, Buxbaum JD. {{Genetics and genomics of autism spectrum disorder: embracing complexity}}. {Hum Mol Genet};2015 (Oct 15);24(R1):R24-31.
Autism spectrum disorder (ASD) is a neurodevelopmental disorder (NDD) characterized by impairments in social communication and social interaction and the presence of repetitive behaviors and/or restricted interests. ASD has profound etiological and clinical heterogeneity, which has impeded the identification of risk factors and pathophysiological processes underlying the disorder. A constellation of (i) types of genetic variation, (ii) modes of inheritance and (iii) specific genomic loci and genes have all recently been implicated in ASD risk, and these findings are currently being extended with functional analyses in model organisms and genotype-phenotype correlation studies. The overlap of risk loci between ASD and other NDDs raises intriguing questions around the mechanisms of risk. In this review, we will touch upon these aspects of ASD and how they might be addressed.
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3. Deutsch SI, Burket JA, Urbano MR, Benson AD. {{The alpha7 nicotinic acetylcholine receptor: A mediator of pathogenesis and therapeutic target in autism spectrum disorders and Down syndrome}}. {Biochem Pharmacol};2015 (Oct 15);97(4):363-377.
Currently, there are no medications that target core deficits of social communication and restrictive, repetitive patterns of behavior in persons with autism spectrum disorders (ASDs). Adults with Down syndrome (DS) display a progressive worsening of adaptive functioning, which is associated with Alzheimer’s disease (AD)-like histopathological changes in brain. Similar to persons with ASDs, there are no effective medication strategies to prevent or retard the progressive worsening of adaptive functions in adults with DS. Data suggest that the alpha7-subunit containing nicotinic acetylcholine receptor (alpha7nAChR) is implicated in the pathophysiology and serves as a promising therapeutic target of these disorders. In DS, production of the amyloidogenic Abeta1-42 peptide is increased and binds to the alpha7nAChR or the lipid milieu associated with this receptor, causing a cascade that results in cytotoxicity and deposition of amyloid plaques. Independently of their ability to inhibit the complexing of Abeta1-42 with the alpha7nAChR, alpha7nAChR agonists and positive allosteric modulators (PAMs) also possess procognitive and neuroprotective effects in relevant in vivo and in vitro models. The procognitive and neuroprotective effects of alpha7nAChR agonist interventions may be due, at least in part, to stimulation of the PI3K/Akt signaling cascade, cross-talk with the Wnt/beta-catenin signaling cascade and both transcriptional and non-transcriptional effects of beta-catenin, and effects of transiently increased intraneuronal concentrations of Ca(2+) on metabolism and the membrane potential. Importantly, alpha7nAChR PAMs are particularly attractive medication candidates because they lack intrinsic efficacy and act only when and where endogenous acetylcholine is released or choline is generated.
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4. Gonzalez-Gronow M, Cuchacovich M, Francos R, Cuchacovich S, Blanco A, Sandoval R, Gomez CF, Valenzuela JA, Ray R, Pizzo SV. {{Catalytic autoantibodies against myelin basic protein (MBP) isolated from serum of autistic children impair in vitro models of synaptic plasticity in rat hippocampus}}. {J Neuroimmunol};2015 (Oct 15);287:1-8.
Autoantibodies from autistic spectrum disorder (ASD) patients react with multiple proteins expressed in the brain. One such autoantibody targets myelin basic protein (MBP). ASD patients have autoantibodies to MBP of both the IgG and IgA classes in high titers, but no autoantibodies of the IgM class. IgA autoantibodies act as serine proteinases and degrade MBP in vitro. They also induce a decrease in long-term potentiation in the hippocampi of rats either perfused with or previously inoculated with this IgA. Because this class of autoantibody causes myelin sheath destruction in multiple sclerosis (MS), we hypothesized a similar pathological role for them in ASD.
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5. McGrane IR, Loveland JG, Zaluski HJ, Foster KD. {{Serum Quetiapine Concentration Changes with Concomitant Oxcarbazepine Therapy in a Boy with Autism Spectrum Disorder}}. {J Child Adolesc Psychopharmacol};2015 (Oct 15)
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6. Pintaudi M, Veneselli E, Voci A, Vignoli A, Castiglione D, Calevo MG, Grasselli E, Ragazzoni M, Cogliati F, Calzari L, Scornavacca GF, Russo S, Vergani L. {{Blood oxidative stress and metallothionein expression in Rett syndrome: Probing for markers}}. {World J Biol Psychiatry};2015 (Oct 15):1-12.
OBJECTIVES: Oxidative stress seems to be involved in Rett syndrome (RTT). The aim of this study was to assess the antioxidant status in RTT children with MECP2 gene mutations with respect to healthy controls, and to explore novel blood antioxidant markers for RTT severity. METHODS: In erythrocytes from RTT females aged 2-14 years (n = 27) and age-matched controls (n = 27), we measured the levels of malonaldehyde and the activity of two antioxidant enzymes, Cu/Zn-superoxide dismutase and catalase, by spectrophotometric assays. In leukocytes, the expression of metallothioneins, the main non-enzymatic antioxidants, was assessed by real-time RT-PCR. In nine selected RTT children, methylome analysis was also performed. RESULTS: Blood of RTT patients showed increased lipid peroxidation and a dysregulated pattern of MT expression, while enzymatic activities did not change significantly with respect to controls. Moreover, we observed no epigenetic dysregulation in CpG-enriched promoter regions of the analysed genes but significant hypomethylation in the random loci. CONCLUSIONS: As the haematic level of MT-1A directly correlates with the phenotype severity, this metallothionein can represent a marker for RTT severity. Moreover, the attempt to link the level of blood oxidative stress with MECP2 mutation and specific clinical features led us to draw some interesting conclusions.
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7. Pohodich AE, Zoghbi HY. {{Rett syndrome: disruption of epigenetic control of postnatal neurological functions}}. {Hum Mol Genet};2015 (Oct 15);24(R1):R10-16.
Loss-of-function mutations in the X-linked gene Methyl-CpG-binding protein 2 (MECP2) cause a devastating pediatric neurological disorder called Rett syndrome. In males, these mutations typically result in severe neonatal encephalopathy and early lethality. On the other hand, owing to expression of the normal allele in approximately 50% of cells, females do not suffer encephalopathy but instead develop Rett syndrome. Typically females with Rett syndrome exhibit a delayed onset of neurologic dysfunction that manifests around the child’s first birthday and progresses over the next few years. Features of this disorder include loss of acquired language and motor skills, intellectual impairment and hand stereotypies. The developmental regression observed in patients with Rett syndrome arises from altered neuronal function and is not the result of neurodegeneration. Maintenance of an appropriate level of MeCP2 appears integral to the function of healthy neurons as patients with increased levels of MeCP2, owing to duplication of the Xq28 region encompassing the MECP2 locus, also present with intellectual disability and progressive neurologic symptoms. Despite major efforts over the past two decades to elucidate the molecular functions of MeCP2, the mechanisms underlying the delayed appearance of symptoms remain unclear. In this review, we will highlight recent findings that have expanded our knowledge of MeCP2’s functions, and we will discuss how epigenetic regulation, chromatin organization and circuit dynamics may contribute to the postnatal onset of Rett syndrome.
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8. Speed HE, Masiulis I, Gibson JR, Powell CM. {{Increased Cortical Inhibition in Autism-Linked Neuroligin-3R451C Mice Is Due in Part to Loss of Endocannabinoid Signaling}}. {PLoS One};2015;10(10):e0140638.
A single, maternally inherited, X-linked point mutation leading to an arginine to cysteine substitution at amino acid 451 (R451C) of Neuroligin 3 (NLGN3R451C) is a likely cause of autism in two brothers. Knockin mice expressing the Nlgn3R451C mutation in place of wild-type Nlgn3 demonstrate increased inhibitory synaptic strength in somatosensory cortex, resulting in an excitatory/inhibitory (E/I) imbalance that is potentially relevant for autism-associated behavioral deficits characteristic of these mice. We have replicated the increase in evoked inhibitory postsynaptic currents (eIPSCs) onto layer II/III cortical pyramidal neurons. We also find that increased frequency of spontaneous mIPSCs in Nlgn3R451C mice occurs in the absence of action potential-driven transmission. This suggests the E/I imbalance is due to changes at the synapse level, as opposed to the network level. Next, we use paired whole-cell recordings in an attempt to identify specific interneuron subtypes affected by the Nlgn3R451C mutation. Curiously, we observe no change in the amplitude of cell-to-cell, unitary IPSCs (uIPSCs) from parvalbumin-positive (PV) or somatostatin-positive (SOM) interneurons onto pyramidal neurons. We also observe no change in the number or density of PV and SOM interneurons in LII/III of somatosensory cortex. This effectively rules out a role for these particular interneurons in the increased inhibitory synaptic transmission, pointing to perhaps alternative interneuron subtypes. Lastly, impaired endocannabinoid signaling has been implicated in hippocampal synaptic dysfunction in Nlgn3R451C mice, but has not been investigated at cortical synapses. We find that bath application of the CB1 antagonist, AM 251 in WT mice eliminates the Nlgn3R451C increase in eIPSC amplitude and mIPSC frequency, indicating that increased inhibitory transmission in mutant mice is due, at least in part, to a loss of endocannabinoid signaling through CB1 receptors likely acting at interneurons other than PV or SOM.
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9. Telias M, Mayshar Y, Amit A, Ben-Yosef D. {{Molecular Mechanisms Regulating Impaired Neurogenesis of Fragile X Syndrome Human Embryonic Stem Cells}}. {Stem Cells Dev};2015 (Oct 15);24(20):2353-2365.
Fragile X syndrome (FXS) is the most common form of inherited cognitive impairment. It is caused by developmental inactivation of the FMR1 gene and the absence of its encoded protein FMRP, which plays pivotal roles in brain development and function. In FXS embryos with full FMR1 mutation, FMRP is expressed during early embryogenesis and is gradually downregulated at the third trimester of pregnancy. FX-human embryonic stem cells (FX-hESCs), derived from FX human blastocysts, demonstrate the same pattern of developmentally regulated FMR1 inactivation when subjected to in vitro neural differentiation (IVND). In this study, we used this in vitro human platform to explore the molecular mechanisms downstream to FMRP in the context of early human embryonic neurogenesis. Our results show a novel role for the SOX superfamily of transcription factors, specifically for SOX2 and SOX9, which could explain the reduced and delayed neurogenesis observed in FX cells. In addition, we assess in this study the « GSK3beta theory of FXS » for the first time in a human-based model. We found no evidence for a pathological increase in GSK3beta protein levels upon cellular loss of FMRP, in contrast to what was found in the brain of Fmr1 knockout mice. Our study adds novel data on potential downstream targets of FMRP and highlights the importance of the FX-hESC IVND system.
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10. Uzunova G, Pallanti S, Hollander E. {{Excitatory/inhibitory imbalance in autism spectrum disorders: Implications for interventions and therapeutics}}. {World J Biol Psychiatry};2015 (Oct 15):1-13.
OBJECTIVES: Imbalance between excitation and inhibition and increased excitatory-inhibitory (E-I) ratio is a common mechanism in autism spectrum disorders (ASD) that is responsible for the learning and memory, cognitive, sensory, motor deficits, and seizures occurring in these disorders. ASD are very heterogeneous and better understanding of E-I imbalance in brain will lead to better diagnosis and treatments. METHODS: We perform a critical literature review of the causes and presentations of E-I imbalance in ASD. RESULTS: E-I imbalance in ASD is due primarily to abnormal glutamatergic and GABAergic neurotransmission in key brain regions such as neocortex, hippocampus, amygdala, and cerebellum. Other causes are due to dysfunction of neuropeptides (oxytocin), synaptic proteins (neuroligins), and immune system molecules (cytokines). At the neuropathological level E-I imbalance in ASD is presented as a « minicolumnopathy ». E-I imbalance alters the manner by which the brain processes information and regulates behaviour. New developments for investigating E-I imbalance such as optogenetics and transcranial magnetic stimulation (TMS) are presented. Non-invasive brain stimulation methods such as TMS for treatment of the core symptoms of ASD are discussed. CONCLUSIONS: Understanding E-I imbalance has important implications for developing better pharmacological and behavioural treatments for ASD, including TMS, new drugs, biomarkers and patient stratification.
