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Neuropeptide Release is Impaired in a Mouse Model of Fragile X Mental Retardation Syndrome.

ABSTRACT: Fragile X syndrome (FXS), an inherited disorder characterized by mental retardation and autismlike behaviors, is caused by the failure to transcribe the gene for fragile X mental retardation protein (FMRP), a translational regulator and transporter of select mRNAs. FXS model mice (Fmr1 KO mice) exhibit impaired neuropeptide release. Release of biogenic amines does not differ between wild-type (WT) and Fmr1 KO mice. Rab3A, an mRNA cargo of FMRP involved in the recruitment of vesicles, is decreased by ∼50% in synaptoneurosomes of Fmr1 KO mice; however, the number of dense-core vesicles (DCVs) does not differ between WT and Fmr1 KO mice. Therefore, deficits associated with FXS may reflect this aberrant vesicle release, specifically involving docking and fusion of peptidergic DCVs, and may lead to defective maturation/maintenance of synaptic connections.

SUBMITTER: Annangudi SP

PROVIDER: S-EPMC2873207 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Dopamine Release and Uptake Impairments and Behavioral Alterations Observed in Mice that Model Fragile X Mental Retardation Syndrome.

Project description:In this study we evaluated the relationship between amphetamine-induced behavioral alterations and dopamine release and uptake characteristics in Fmr1 knockout (Fmr1 KO) mice, which model fragile X syndrome. The behavioral analyses, obtained at millisecond temporal resolution and 2 mm spatial resolution using a force-plate actometer, revealed that Fmr1 KO mice express a lower degree of focused stereotypy compared to wild type (WT) control mice after injection with 10 mg/kg (ip) amphetamine. To identify potentially related neurochemical mechanisms underlying this phenomenon, we measured electrically-evoked dopamine release and uptake using fast-scan cyclic voltammetry at carbon-fiber microelectrodes in striatal brain slices. At 10 weeks of age, dopamine release per pulse, which is dopamine release corrected for differences in uptake, was unchanged. However, at 15 (the age of behavioral testing) and 20 weeks of age, dopamine per pulse and the maximum rate of dopamine uptake was diminished in Fmr1 KO mice compared to WT mice. Dopamine uptake measurements, obtained at different amphetamine concentrations, indicated that dopamine transporters in both genotypes have equal affinities for amphetamine. Moreover, dopamine release measurements from slices treated with quinpirole, a D2-family receptor agonist, rule out enhanced D2 autoreceptor sensitivity as a mechanism of release inhibition. However, dopamine release, uncorrected for uptake and normalized against the corresponding pre-drug release peaks, increased in Fmr1 KO mice, but not in WT mice. Collectively, these data are consistent with a scenario in which a decrease in extracellular dopamine levels in the striatum result in diminished expression of focused stereotypy in Fmr1 KO mice.

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Project description:The fragile X mental retardation protein (FMRP) plays an important role in normal brain development. Absence of FMRP results in abnormal neuronal morphologies in a selected manner throughout the brain, leading to intellectual deficits and sensory dysfunction in the fragile X syndrome (FXS). Despite FMRP importance for proper brain function, its overall expression pattern in the mammalian brain at the resolution of individual neuronal cell groups is not known. In this study we used FMR1 knockout and isogenic wildtype mice to systematically map the distribution of FMRP expression in the entire mouse brain. Using immunocytochemistry and cellular quantification analyses, we identified a large number of prominent cell groups expressing high levels of FMRP at the subcortical levels, in particular sensory and motor neurons in the brainstem and thalamus. In contrast, many cell groups in the midbrain and hypothalamus exhibit low FMRP levels. More important, we describe differential patterns of FMRP distribution in both cortical and subcortical brain regions. Almost all major brain areas contain high and low levels of FMRP cell groups adjacent to each other or between layers of the same cortical areas. These differential patterns indicate that FMRP expression appears to be specific to individual neuronal cell groups instead of being associated with all neurons in distinct brain regions, as previously considered. Taken together, these findings support the notion of FMRP differential neuronal regulation and strongly implicate the contribution of fundamental sensory and motor processing at subcortical levels to FXS pathology. J. Comp. Neurol. 525:818-849, 2017. © 2016 Wiley Periodicals, Inc.

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Neuroanatomy of fragile X syndrome is associated with aberrant behavior and the fragile X mental retardation protein (FMRP).

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The Fragile X Mental Retardation Protein (FMRP) controls diacylglycerol kinase in neurons

2016-06-01 | GSE51649 | GEO

The Fragile X Mental Retardation Protein (FMRP) controls diacylglycerol kinase in neurons

Project description:In this study, we sought to identify the mRNAs associated to FMRP protein in mouse cortical neuron using a cross linking immunoprecipitation and microarray (CLIP-microarray). The mRNAs crosslinked at 254 nm to FMRP in mouse cortical neurons cultured 8 days in vitro (8 DIV) were immunoprecipitated with H120 anti-FMRP (Santa Cruz) and reverse transcribed to labeled cDNAs with Ovation Pico WTA system V2 (Nugen) and hybridized on Mouse Gene 1.0ST (Affymetrix) We analyzed total RNA (Input) and FMRP-CLIPed RNA (Clip) from 10 primary cortical neuron mouse cultures (5 Wt Input, 5 FMR1-KO Input, 5 Wt Clip, 5 FMR1-KO Clip). Array data was processed by Affymetrix Exon Array Computational Tool. No technical replicates were performed.

2016-06-01 | E-GEOD-51649 | biostudies-arrayexpress

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