ABSTRACT
Fragile X messenger ribonucleoprotein 1 (FMRP) is a widely expressed RNA binding protein involved in several steps of mRNA metabolism. Mutations in the FMR1 gene encoding FMRP are responsible for fragile X syndrome (FXS), a leading genetic cause of intellectual disability and autism spectrum disorder, and fragile X-associated tremor-ataxia syndrome (FXTAS), a neurodegenerative disorder in aging men. Although FMRP is mainly expressed in neurons, it is also present in glial cells and its deficiency or altered expression can affect functions of glial cells with implications for the pathophysiology of brain disorders. The present review focuses on recent advances on the role of glial subtypes, astrocytes, oligodendrocytes and microglia, in the pathophysiology of FXS and FXTAS, and describes how the absence or reduced expression of FMRP in these cells can impact on glial and neuronal functions. We will also briefly address the role of FMRP in radial glial cells and its effects on neural development, and gliomas and will speculate on the role of glial FMRP in other brain disorders.
Subject(s)
Fragile X Mental Retardation Protein , Fragile X Syndrome , Neuroglia , Humans , Fragile X Mental Retardation Protein/metabolism , Fragile X Mental Retardation Protein/genetics , Neuroglia/metabolism , Animals , Fragile X Syndrome/metabolism , Fragile X Syndrome/physiopathology , Fragile X Syndrome/pathology , Brain Diseases/metabolism , Brain Diseases/physiopathology , Brain Diseases/genetics , Ataxia/metabolism , Ataxia/physiopathology , Ataxia/genetics , Tremor/metabolism , Tremor/physiopathology , Tremor/geneticsABSTRACT
OBJECTIVE: Mitochondrial impairments have been implicated in the pathogenesis of Fragile X-associated tremor/ataxia syndrome (FXTAS) based on analysis of mitochondria in peripheral tissues and cultured cells. We sought to assess whether mitochondrial abnormalities present in postmortem brain tissues of patients with FXTAS are also present in plasma neuron-derived extracellular vesicles (NDEVs) from living carriers of fragile X messenger ribonucleoprotein1 (FMR1) gene premutations at an early asymptomatic stage of the disease continuum. METHODS: We utilized postmortem frozen cerebellar and frontal cortex samples from a cohort of eight patients with FXTAS and nine controls and measured the quantity and activity of the mitochondrial proteins complex IV and complex V. In addition, we evaluated the same measures in isolated plasma NDEVs by selective immunoaffinity capture targeting L1CAM from a separate cohort of eight FMR1 premutation carriers and four age-matched controls. RESULTS: Lower complex IV and V quantity and activity were observed in the cerebellum of FXTAS patients compared to controls, without any differences in total mitochondrial content. No patient-control differences were observed in the frontal cortex. In NDEVs, FMR1 premutation carriers compared to controls had lower activity of Complex IV and Complex V, but higher Complex V quantity. INTERPRETATION: Quantitative and functional abnormalities in mitochondrial electron transport chain complexes IV and V seen in the cerebellum of patients with FXTAS are also manifest in plasma NDEVs of FMR1 premutation carriers. Plasma NDEVs may provide further insights into mitochondrial pathologies in this syndrome and could potentially lead to the development of biomarkers for predicting symptomatic FXTAS among premutation carriers and disease monitoring.
Subject(s)
Ataxia , Extracellular Vesicles , Fragile X Mental Retardation Protein , Fragile X Syndrome , Mitochondria , Tremor , Humans , Fragile X Syndrome/genetics , Fragile X Syndrome/metabolism , Fragile X Syndrome/pathology , Fragile X Syndrome/physiopathology , Tremor/genetics , Tremor/metabolism , Tremor/physiopathology , Tremor/pathology , Extracellular Vesicles/metabolism , Ataxia/genetics , Ataxia/metabolism , Ataxia/pathology , Ataxia/physiopathology , Male , Aged , Female , Fragile X Mental Retardation Protein/genetics , Fragile X Mental Retardation Protein/metabolism , Middle Aged , Mitochondria/metabolism , Mitochondria/pathology , Cerebellum/metabolism , Cerebellum/pathology , Aged, 80 and over , Brain/metabolism , Brain/pathology , Frontal Lobe/metabolism , Frontal Lobe/pathologyABSTRACT
Dichlorodiphenyltrichloroethane (DDT) is a broad-spectrum insecticide, widely detected in environments due to its high stability characteristic and long natural half-life period. The adverse impact of DDT exposure on organisms and humans has attracted great concern worldwide. The current study explored the developmental and neurobehavioral toxicity response of DDT in embryonic zebrafish. The embryos were treated with DDT (0, 0.1, 1, 2.5 and 5 µM) during 6 h post fertilization (hpf) to 144 hpf. Our result indicated that DDT exposures increased the embryo hatching rate at 48 and 60 hpf, the larval malformation rate at 120 hpf and mortality rate at 144 hpf. The manifested malformations included uninflated swim bladder, bent spine and tail, deformed liver, and pericardial edema. The 120 hpf larval organs size of the gut and swim bladder was decreased in higher exposed concentration groups. Besides, DDT exposure resulted in hyperactivity for the embryo spontaneous movement at 24 hpf and tremor like movement measured by the free larval activity at 72 hpf, as well as the larval activity at 96 hpf under light-dark transition stimulus. Mechanistic examinations at 120 hpf revealed DDT exposure elevated oxidative stress through MDA formation increase, ATP level decrease as well as antioxidant enzyme genes (sod1 and gpx1a) expression decrease. DDT exposure induced abnormal neurotransmitters expression with DA level increase, 5-HT and NOS level decrease. DDT exposure suppressed the gene expressions involved in axon development (rab33a and nrxn2a) and potassium channel (kcnq2 and kcnq3). Our results suggest that the hyperactivity and tremor like movement in DDT-exposed embryos/larvae may result from oxidative stress involved with neuronal damage.
Subject(s)
DDT , Zebrafish , Animals , Humans , Zebrafish/metabolism , DDT/metabolism , Embryo, Nonmammalian/metabolism , Tremor/metabolism , Dose-Response Relationship, Drug , Larva/physiology , Embryonic DevelopmentABSTRACT
Harmaline is one of the ß-carboline derivative compounds that is widely distributed in the food chain and human tissues. Harmine, a dehydrogenated form of harmaline, appeared to have a higher concentration in the brain, and appeared to be elevated in essential tremor (ET) and Parkinson's disease. Exogenous harmaline exposure in high concentration has myriad consequences, including inducing tremor, and causing neurodegeneration of Purkinje cells in the cerebellum. Harmaline-induced tremor is an established animal model for human ET, but its underlying mechanism is still controversial. One hypothesis posits that the inferior olive-cerebellum pathway is involved, and CaV3.1 T-type Ca2+ channel is a critical target of action. However, accumulating evidence indicates that tremor can be generated without disturbing T-type channels. This implies that additional neural circuits or molecular targets are involved. Using in vitro slice Ca2+-imaging and patch clamping, we demonstrated that harmaline reduced intracellular Ca2+ and suppressed depolarization-induced spiking activity of medium spiny striatal neurons (MSN), and this effect of harmaline can be partially attenuated by sulpiride (5 µM). In addition, the frequencies of spontaneous excitatory post-synaptic currents (sEPSCs) on MSNs were also significantly attenuated. Furthermore, the induced tremor in C57BL/6 J mice by harmaline injections (i.p. 12.5-18 mg/kg) was also shown to be attenuated by sulpiride (20 mg/kg). This series of experiments suggests that the dorsal striatum is a site of harmaline toxic action and might contribute to tremor generation. The findings also provide evidence that D2 signaling might be a part of the mechanism underlying essential tremor.
Subject(s)
Essential Tremor , Tremor , Mice , Humans , Animals , Tremor/chemically induced , Tremor/metabolism , Harmaline/toxicity , Harmaline/metabolism , Essential Tremor/chemically induced , Essential Tremor/metabolism , Sulpiride/adverse effects , Sulpiride/metabolism , Mice, Inbred C57BL , NeuronsABSTRACT
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder that appears in adult FMR1 premutation carriers. The neuropathological hallmark of FXTAS is an intranuclear inclusion in neurons and astrocytes. Nearly 200 different proteins have been identified in FXTAS inclusions, being the small ubiquitin-related modifier 2 (SUMO2), ubiquitin and p62 the most highly abundant. These proteins are components of the protein degradation machinery. This study aimed to characterize SUMO2/3 expression levels and autophagy process in human postmortem brain samples and skin fibroblast cultures from FXTAS patients. Results revealed that FXTAS postmortem brain samples are positive for SUMO2/3 conjugates and supported the idea that SUMO2/3 accumulation is involved in inclusion formation. Insights from RNA-sequencing data indicated that SUMOylation processes are significantly upregulated in FXTAS samples. In addition, the analysis of the autophagy flux showed the accumulation of p62 protein levels and autophagosomes in skin fibroblasts from FXTAS patients. Similarly, gene set analysis evidenced a significant downregulation in gene ontology terms related to autophagy in FXTAS samples. Overall, this study provides new evidence supporting the role of SUMOylation and autophagic processes in the pathogenic mechanisms underlying FXTAS.
Subject(s)
Fragile X Syndrome , Tremor , Adult , Humans , Tremor/genetics , Tremor/metabolism , Tremor/pathology , Ubiquitin/metabolism , Fragile X Mental Retardation Protein/genetics , Fragile X Syndrome/pathology , Ataxia/pathology , Autophagy , Small Ubiquitin-Related Modifier Proteins/metabolismABSTRACT
Essential Tremor (ET) is a prevalent neurological disease characterized by an 8-10 Hz action tremor. Molecular mechanisms of ET remain poorly understood. Clinical data suggest the importance of the cerebellum in disease pathophysiology, and pathological studies indicate Purkinje Cells (PCs) incur damage. Our recent cerebellar cortex and PC-specific transcriptome studies identified alterations in calcium (Ca2+) signaling pathways that included ryanodine receptor type 1 (RyR1) in ET. RyR1 is an intracellular Ca2+ release channel located on the Endoplasmic Reticulum (ER), and in cerebellum is predominantly expressed in PCs. Under stress conditions, RyR1 undergoes several post-translational modifications (protein kinase A [PKA] phosphorylation, oxidation, nitrosylation), coupled with depletion of the channel-stabilizing binding partner calstabin1, which collectively characterize a "leaky channel" biochemical signature. In this study, we found markedly increased PKA phosphorylation at the RyR1-S2844 site, increased RyR1 oxidation and nitrosylation, and calstabin1 depletion from the RyR1 complex in postmortem ET cerebellum. Decreased calstabin1-RyR1-binding affinity correlated with loss of PCs and climbing fiber-PC synapses in ET. This 'leaky' RyR1 signature was not seen in control or Parkinson's disease cerebellum. Microsomes from postmortem cerebellum demonstrated excessive ER Ca2+ leak in ET vs. controls, attenuated by channel stabilization. We further studied the role of RyR1 in tremor using a mouse model harboring a RyR1 point mutation that mimics constitutive site-specific PKA phosphorylation (RyR1-S2844D). RyR1-S2844D homozygous mice develop a 10 Hz action tremor and robust abnormal oscillatory activity in cerebellar physiological recordings. Intra-cerebellar microinfusion of RyR1 agonist or antagonist, respectively, increased or decreased tremor amplitude in RyR1-S2844D mice, supporting a direct role of cerebellar RyR1 leakiness for tremor generation. Treating RyR1-S2844D mice with a novel RyR1 channel-stabilizing compound, Rycal, effectively dampened cerebellar oscillatory activity, suppressed tremor, and normalized cerebellar RyR1-calstabin1 binding. These data collectively support that stress-associated ER Ca2+ leak via RyR1 may contribute to tremor pathophysiology.
Subject(s)
Calcium , Ryanodine Receptor Calcium Release Channel , Humans , Ryanodine Receptor Calcium Release Channel/metabolism , Calcium/metabolism , Tremor/metabolism , Cerebellum/metabolism , Endoplasmic Reticulum/metabolism , Muscle, Skeletal/metabolismABSTRACT
Repeat-associated non-AUG (RAN) translation is a pathogenic mechanism in which repetitive sequences are translated into aggregation-prone proteins from multiple reading frames, even without a canonical AUG start codon. Since its discovery in spinocerebellar ataxia type 8 (SCA8) and myotonic dystrophy type 1 (DM1), RAN translation is now known to occur in the context of 12 disease-linked repeat expansions. This review discusses recent advances in understanding the regulatory mechanisms controlling RAN translation and its contribution to the pathophysiology of repeat expansion diseases. We discuss the key findings in the context of Fragile X Tremor Ataxia Syndrome (FXTAS), a neurodegenerative disorder caused by a CGG repeat expansion in the 5' untranslated region of FMR1.
Subject(s)
Fragile X Syndrome , Neurodegenerative Diseases , Humans , Fragile X Mental Retardation Protein/metabolism , Fragile X Syndrome/genetics , Fragile X Syndrome/metabolism , Fragile X Syndrome/pathology , Ataxia/metabolism , Ataxia/pathology , Tremor/genetics , Tremor/metabolism , Tremor/pathologyABSTRACT
BACKGROUND: The tremor mutant mice present motor impairments comprised of whole-body tremors, ataxia, decreased exploratory behavior, and audiogenic seizures. OBJECTIVES: This study aims to investigate the development of motor dysfunction in this mutant mouse and the relationships with cortical, striatal, and cerebellar levels of GABA, glutamate, glycine, dopamine (DA), serotonin (5-HT), noradrenaline (NOR), and its metabolites. The serum cytokines levels, myelin content, and the astrocytic expression of the glial fibrillary acidic protein (GFAP) investigated the possible influence of inflammation in motor dysfunction. RESULTS: Relative to wild-type (WT) mice, the tremor mice presented: increased tremors and bradykinesia associated with postural instability, decreased range of motion, and difficulty in initiating voluntary movements directly proportional to age; reduced step length for right and left hindlimbs; reduced cortical GABA, glutamate and, aspartate levels, the DOPAC/DA and ratio and increased the NOR levels; in the striatum, the levels of glycine and aspartate were reduced while the HVA levels, the HVA/DA and 5HIAA/5-HT ratios increased; in the cerebellum the glycine, NOR and 5-HIAA levels increased. CONCLUSIONS: We suggest that the motor disturbances resulted mainly from the activation of the indirect striatal inhibitory pathway to the frontal cortex mediated by GABA, glutamate, and aspartate, reducing the dopaminergic activity at the prefrontal cortex, which was associated with the progressive tremor. The reduced striatal and increased cerebellar glycine levels could be partially responsible for the mutant tremor motor disturbances.
Subject(s)
Motor Disorders , Tremor , Mice , Animals , Tremor/metabolism , Serotonin/metabolism , Aspartic Acid/metabolism , Seizures/metabolism , Dopamine/metabolism , Glutamic Acid/metabolism , Corpus Striatum/metabolism , Norepinephrine/metabolism , Neurotransmitter Agents/metabolism , gamma-Aminobutyric Acid/metabolism , Glycine/metabolismABSTRACT
PURPOSE: Sleep benefit (SB) is a well-known phenomenon in patients with Parkinson's disease (PD); however, the mechanisms underlying this phenomenon remain unclear. This study aimed to evaluate whether the SB phenomenon in PD patients is associated with dopamine transporter (DAT) expression levels in the striatum. METHODS: The data of 125 PD patients were collected and divided into SB (n = 61) and non-SB (nSB) groups (n = 54) depending on whether they had SB or not. DAT expression on both sides of the striatum in PD patients was measured using 2b-carbomethoxy-3b-(4-trimethylstannylphenyl) tropane (11C-CFT) positron emission tomography imaging. The clinical variables, sleep scores, and striatum 11C-CFT uptake index of PD patients between the SB and nSB groups were compared. The associations of clinical variables, sleep scores, and striatum 11C-CFT uptake index with the SB variable were analyzed using logistic regression analysis. A receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of the striatum 11C-CFT uptake index in distinguishing SB patients from nSB patients. RESULTS: The tremor subtype ratio (P = 0.011), levodopa equivalent daily dose (LEDD) (P < 0.001), sleep efficiency score (P = 0.025), habitual sleep efficiency (P = 0.012), and night sleep duration (P = 0.005) in the SB group were significantly different from those in the nSB group. The 11C-CFT uptake index in both the contralateral and ipsilateral striata in the SB group was significantly higher than that in the nSB group (P < 0.05). The binary logistic regression showed that SB variables were significantly and independently associated with tremor subtype (P = 0.048), LEDD (P = 0.021), sleep duration at night (P = 0.035), 11C-CFT uptake index in the contralateral (P = 0.013) and ipsilateral (P = 0.019) putamen in PD patients after correction for important clinical confounders. ROC analysis showed that the 11C-CFT uptake index on the onset side of the putamen had a high capacity (AUC: 0.916) to distinguish SB patients from nSB patients with high sensitivity (83.33 %) and specificity (88.89 %). CONCLUSION: DAT expression in the putamen was associated with the SB phenomenon in PD patients, and the putamen DAT expression level could predict the SB phenomenon in PD patients.
Subject(s)
Cocaine , Parkinson Disease , Humans , Dopamine Plasma Membrane Transport Proteins/metabolism , Parkinson Disease/metabolism , Putamen/metabolism , Tremor/metabolism , Cocaine/metabolism , Corpus Striatum/metabolism , Levodopa/metabolism , SleepABSTRACT
Neuroinflammation plays a protective role in the brain; however, in neurological diseases such as epilepsy, overactivated neuroinflammation, along with overexpression of inflammatory mediators, can cause neuronal tissue damage, which can trigger seizures due to loss of ionic or neurotransmitter homeostasis. Therefore, we aimed to evaluate mRNA expression levels of proinflammatory cytokines, early growth response factor 3 (Egr3), and GABA A receptors in the hippocampus of naive audiogenic mutant tremor mice, and stimulated tremor mice after a seizure. Gene expression of Il-1ß, Il-6, Tnf-α, Ccl2, Ccl3, Egr3, Gabra1, and Gabra4 from hippocampal samples of naive and stimulated tremor mice were measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Relative to resistant mice, Ccl3 gene expression was increased and Il6 was decreased in the hippocampus of naïve tremor mice. Thirty minutes after a seizure, Ccl3 and Il-1ß mRNA expression were decreased (p < 0.0001; p = 0.0034, respectively) while Il6 was increased (p = 0.0052) in stimulated tremor mice, relative to naïve animals. In addition, Egr3, Gabra1, and Gabra4 mRNA expression was decreased in the hippocampus of naive tremor mice, relative to resistant mice, which increased 30 minutes after a seizure (p = 0.0496; p = 0.0447, and p = 0.0011, respectively), relative to naïve animals. In conclusion, overexpression of Ccl3 in the hippocampus of naive tremor mice, followed by downregulation soon after seizure in stimulated tremor mice, could be involved in changes in the blood-brain barrier (BBB) permeability in epilepsy. Il-1ß may be involved in hippocampal downregulation of GABA A receptors of naive tremor mice, characterizing an important mechanism in audiogenic seizures triggering. Hippocampal alterations of proinflammatory cytokines, Egr3, and GABA A receptors in tremor mice reinforce them as an alternative tool to modeling temporal lobe epilepsy.
Subject(s)
Epilepsy, Reflex , Receptors, GABA-A , Mice , Animals , Receptors, GABA-A/metabolism , Tremor/metabolism , Seizures/genetics , Hippocampus/metabolism , Epilepsy, Reflex/genetics , RNA, Messenger , Chemokine CCL3/genetics , Chemokine CCL3/metabolismABSTRACT
Fragile X-associated primary ovarian insufficiency (FXPOI) is characterized by oligo/amenorrhea and hypergonadotropic hypogonadism and is caused by the expansion of the CGG repeat in the 5'UTR of Fragile X Mental Retardation 1 (FMR1). Approximately 20% of women carrying an FMR1 premutation (PM) allele (55-200 CGG repeat) develop FXPOI. Repeat Associated Non-AUG (RAN)-translation dependent on the variable CGG-repeat length is thought to cause FXPOI, due to the production of a polyglycine-containing FMR1 protein, FMRpolyG. Peripheral blood monocyte cells (PBMCs) and granulosa cells (GCs) were collected to detect FMRpolyG and its cell type-specific expression in FMR1 PM carriers by immunofluorescence staining (IF), Western blotting (WB), and flow cytometric analysis (FACS). For the first time, FMRpolyG aggregates were detected as ubiquitin-positive inclusions in PBMCs from PM carriers, whereas only a weak signal without inclusions was detected in the controls. The expression pattern of FMRpolyG in GCs was comparable to that in the lymphocytes. We detected FMRpolyG as a 15- to 25-kDa protein in the PBMCs from two FMR1 PM carriers, with 124 and 81 CGG repeats. Flow cytometric analysis revealed that FMRpolyG was significantly higher in the T cells from PM carriers than in those from non-PM carriers. The detection of FMRpolyG aggregates in the peripheral blood and granulosa cells of PM carriers suggests that it may have a toxic potential and an immunological role in ovarian damage in the development of FXPOI.
Subject(s)
Fragile X Syndrome , Intellectual Disability , Ataxia/genetics , Ataxia/metabolism , Case-Control Studies , Female , Fragile X Mental Retardation Protein/genetics , Fragile X Syndrome/genetics , Humans , Intellectual Disability/genetics , Leukocytes, Mononuclear/metabolism , Tremor/genetics , Tremor/metabolismABSTRACT
Expansion of CGG trinucleotide repeats in 5' untranslated region of the FMR1 gene is the causative mutation of neurological diseases such as fragile X syndrome (FXS), fragile X-associated tremor/ataxia syndrome (FXTAS), and ovarian disorder such as fragile X-associated primary ovarian insufficiency (FXPOI). CGG repeats containing FMR1 transcripts form the toxic ribonuclear aggregates, abrupt pre-mRNA splicing, and cause repeat-associated non-AUG translation, leading to the disease symptoms. Here, we utilized a small molecule library of ~ 250,000 members obtained from the National Cancer Institute (NCI) and implemented a shape-based screening approach to identify the candidate small molecules that mitigate toxic CGG RNA-mediated pathogenesis. The compounds obtained from screening were further assessed for their affinity and selectivity towards toxic CGG repeat RNA by employing fluorescence-binding experiment and isothermal calorimetry titration assay. Three candidate molecules B1, B4, and B11 showed high affinity and selectivity for expanded CGG repeats RNA. Further, NMR spectroscopy, gel mobility shift assay, CD spectroscopy, UV-thermal denaturation assay, and molecular docking affirmed their high affinity and selectivity for toxic CGG RNAs. Next, these lead compounds selectively improved the pre-mRNA alternative splicing defects with no perturbation in global splicing efficacy and simultaneously reduced the FMR1polyG protein aggregate formation without affecting the downstream expression of the gene. Taken together these findings, we addressed compound B1, B4, and B11 as potential lead molecules for developing promising therapeutics against FXTAS. Herein, this study, we have utilized shape similarity approach to screen the NCI library and found out the potential candidate which improves the pre-mRNA splicing defects and reduces FMR1polyG aggregations.
Subject(s)
Fragile X Syndrome , Ataxia/metabolism , Fragile X Mental Retardation Protein/genetics , Fragile X Mental Retardation Protein/metabolism , Fragile X Syndrome/drug therapy , Fragile X Syndrome/genetics , Fragile X Syndrome/metabolism , Humans , Molecular Docking Simulation , Protein Aggregates , Tremor/metabolism , Trinucleotide Repeat Expansion/geneticsABSTRACT
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder affecting subjects (premutation carriers) with a 55-200 CGG-trinucleotide expansion in the 5'UTR of the fragile X mental retardation 1 gene (FMR1) typically after age 50. As both the presence of white matter hyperintensities (WMHs) and atrophied gray matter on magnetic resonance imaging (MRI) are linked to age-dependent decline in cognition, here we tested whether MRI outcomes (WMH volume (WMHV) and brain volume) were correlated with mitochondrial bioenergetics from peripheral blood monocytic cells in 87 carriers with and without FXTAS. As a parameter assessing cumulative damage, WMHV was correlated to both FXTAS stages and age, and brain volume discriminated between carriers and non-carriers. Similarly, mitochondrial mass and ATP production showed an age-dependent decline across all participants, but in contrast to WMHV, only FADH2-linked ATP production was significantly reduced in carriers vs. non-carriers. In carriers, WMHV negatively correlated with ATP production sustained by glucose-glutamine and FADH2-linked substrates, whereas brain volume was positively associated with the latter and mitochondrial mass. The observed correlations between peripheral mitochondrial bioenergetics and MRI findings-and the lack of correlations with FXTAS diagnosis/stages-may stem from early brain bioenergetic deficits even before overt FXTAS symptoms and/or imaging findings.
Subject(s)
Adenosine Triphosphate/metabolism , Aging/metabolism , Ataxia/metabolism , Brain/diagnostic imaging , Fragile X Syndrome/metabolism , Monocytes/metabolism , Tremor/metabolism , White Matter/diagnostic imaging , Adult , Aged , Ataxia/diagnostic imaging , Brain/growth & development , Cells, Cultured , Energy Metabolism , Female , Flavin-Adenine Dinucleotide/analogs & derivatives , Flavin-Adenine Dinucleotide/metabolism , Fragile X Mental Retardation Protein/genetics , Fragile X Mental Retardation Protein/metabolism , Fragile X Syndrome/diagnostic imaging , Humans , Male , Middle Aged , Mitochondria/metabolism , Tremor/diagnostic imaging , White Matter/growth & developmentABSTRACT
CGG expansions between 55 and 200 in the 5'-untranslated region of the fragile-X mental retardation gene (FMR1) increase the risk of developing the late-onset debilitating neuromuscular disease Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS). While the science behind this mutation, as a paradigm for RNA-mediated nucleotide triplet repeat expansion diseases, has progressed rapidly, no treatment has proven effective at delaying the onset or decreasing morbidity, especially at later stages of the disease. Here, we demonstrated the beneficial effect of the phytochemical sulforaphane (SFN), exerted through NRF2-dependent and independent manner, on pathways relevant to brain function, bioenergetics, unfolded protein response, proteosome, antioxidant defenses, and iron metabolism in fibroblasts from FXTAS-affected subjects at all disease stages. This study paves the way for future clinical studies with SFN in the treatment of FXTAS, substantiated by the established use of this agent in clinical trials of diseases with NRF2 dysregulation and in which age is the leading risk factor.
Subject(s)
Ataxia/metabolism , Fibroblasts/drug effects , Fragile X Syndrome/metabolism , Isothiocyanates/pharmacology , Mitochondria/drug effects , Oxidative Stress/drug effects , Sulfoxides/pharmacology , Tremor/metabolism , Aged , Aged, 80 and over , Energy Metabolism/drug effects , Female , Fibroblasts/metabolism , Humans , In Vitro Techniques , Iron/metabolism , Male , Middle Aged , Mitochondria/metabolism , NF-E2-Related Factor 2/drug effects , NF-E2-Related Factor 2/metabolism , Proteasome Endopeptidase Complex/drug effects , Proteasome Endopeptidase Complex/metabolism , Unfolded Protein ResponseABSTRACT
Parkinson's disease is characterized by both hypokinetic and hyperkinetic symptoms. While increased subthalamic burst discharges have a direct causal relationship with the hypokinetic manifestations (e.g., rigidity and bradykinesia), the origin of the hyperkinetic symptoms (e.g., resting tremor and propulsive gait) has remained obscure. Neuronal burst discharges are presumed to be autonomous or less responsive to synaptic input, thereby interrupting the information flow. We, however, demonstrate that subthalamic burst discharges are dependent on cortical glutamatergic synaptic input, which is enhanced by A-type K+ channel inhibition. Excessive top-down-triggered subthalamic burst discharges then drive highly correlative activities bottom-up in the motor cortices and skeletal muscles. This leads to hyperkinetic behaviors such as tremors, which are effectively ameliorated by inhibition of cortico-subthalamic AMPAergic synaptic transmission. We conclude that subthalamic burst discharges play an imperative role in cortico-subcortical information relay, and they critically contribute to the pathogenesis of both hypokinetic and hyperkinetic parkinsonian symptoms.
Subject(s)
Globus Pallidus/physiopathology , Hyperkinesis/physiopathology , Motor Cortex/physiopathology , Parkinson Disease, Secondary/physiopathology , Subthalamic Nucleus/physiopathology , Tremor/physiopathology , 4-Aminopyridine/pharmacology , 6-Cyano-7-nitroquinoxaline-2,3-dione/pharmacology , Animals , Excitatory Amino Acid Agonists/pharmacology , Excitatory Amino Acid Antagonists/pharmacology , Female , Globus Pallidus/drug effects , Globus Pallidus/metabolism , Glutamic Acid/metabolism , Glutamic Acid/pharmacology , Humans , Hyperkinesis/metabolism , Male , Membrane Potentials/drug effects , Mice, Inbred C57BL , Motor Cortex/drug effects , Motor Cortex/metabolism , Muscle, Skeletal/drug effects , Muscle, Skeletal/metabolism , Muscle, Skeletal/physiopathology , Optogenetics/methods , Parkinson Disease, Secondary/metabolism , Rats , Rats, Wistar , Subthalamic Nucleus/drug effects , Subthalamic Nucleus/metabolism , Synapses/drug effects , Synapses/metabolism , Synapses/pathology , Synaptic Transmission , Tremor/metabolism , alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid/pharmacologyABSTRACT
INTRODUCTION: In vivo dopamine transporter imaging is a useful tool for distinguishing nigrostriatal pathologies (e.g. Parkinson's disease) from other causes of tremor. However, while many of the motoric features of Parkinson's disease (e.g. bradykinesia, rigidity, hypomimia) correlate well with reduced striatal dopamine transporter binding, the same relationship has not been demonstrated for tremor. We investigated the relationship between striatal dopamine transporter binding and quantitative measures of tremor. METHODS: 23 participants with Parkinson's disease underwent standardised clinical assessment including structured, videotaped clinical examination, tremor neurophysiology study of both upper limbs using accelerometry and surface EMG, and Technitium-99 m TRODAT-1 brain SPECT imaging. Normalised striatal uptake values were calculated. Tremor EMG and accelerometry time series were processed with Fourier transformation to identify peak tremor power within a window of 3-10Hz and to calculate the tremor stability index (TSI). RESULTS: Spearman correlation analyses revealed an association between tremor power and contralaterally reduced striatal uptake in a number of recording conditions. This association was strongest for rest tremor, followed by postural tremor, with the weakest association observed for kinetic tremor. Lower TSI was also associated with lower contralateral striatal uptake in a number of rest and postural conditions. CONCLUSION: These data suggest a relationship between Parkinsonian rest tremor and contralateral reduction in striatal dopamine binding. Use of quantitative neurophysiology techniques may allow the demonstration of clinico-pathophysiological relationships in tremor that have remained occult to previous studies.
Subject(s)
Dopamine Plasma Membrane Transport Proteins/pharmacokinetics , Neostriatum , Parkinson Disease , Tremor , Aged , Female , Humans , Male , Middle Aged , Neostriatum/diagnostic imaging , Neostriatum/metabolism , Neostriatum/pathology , Parkinson Disease/complications , Parkinson Disease/metabolism , Parkinson Disease/pathology , Parkinson Disease/physiopathology , Rest , Tomography, Emission-Computed, Single-Photon , Tremor/etiology , Tremor/metabolism , Tremor/pathology , Tremor/physiopathologyABSTRACT
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disease that develops in some premutation (PM) carriers of the FMR1 gene with alleles bearing 55-200 CGG repeats. The discovery of a broad spectrum of clinical and cell-developmental abnormalities among PM carriers with or without FXTAS and in model systems suggests that neurodegeneration seen in FXTAS could be the inevitable end-result of pathophysiological processes set during early development. Hence, it is imperative to trace early PM-induced pathological abnormalities. Previous studies have shown that transgenic Drosophila carrying PM-length CGG repeats are sufficient to cause neurodegeneration. Here, we used the same transgenic model to understand the effect of CGG repeats on the structure and function of the developing nervous system. We show that presynaptic expression of CGG repeats restricts synaptic growth, reduces the number of synaptic boutons, leads to aberrant presynaptic varicosities, and impairs synaptic transmission at the larval neuromuscular junctions. The postsynaptic analysis shows that both glutamate receptors and subsynaptic reticulum proteins were normal. However, a high percentage of boutons show a reduced density of Bruchpilot protein, a key component of presynaptic active zones required for vesicle release. The electrophysiological analysis shows a significant reduction in quantal content, a measure of total synaptic vesicles released per excitation potential. Together, these findings suggest that synapse perturbation caused by riboCGG (rCGG) repeats mediates presynaptically during larval neuromuscular junction development. We also suggest that the stress-activated c-Jun N-terminal kinase protein Basket and CIDE-N protein Drep-2 positively mediate Bruchpilot active zone defects caused by rCGG repeats.
Subject(s)
Ataxia , Drosophila Proteins , Fragile X Mental Retardation Protein , Fragile X Syndrome , Mutation , Synapses , Synaptic Transmission/genetics , Tremor , Trinucleotide Repeats , Animals , Animals, Genetically Modified , Ataxia/genetics , Ataxia/metabolism , Drosophila Proteins/genetics , Drosophila Proteins/metabolism , Drosophila melanogaster , Fragile X Mental Retardation Protein/genetics , Fragile X Mental Retardation Protein/metabolism , Fragile X Syndrome/genetics , Fragile X Syndrome/metabolism , Humans , Larva , Synapses/genetics , Synapses/metabolism , Tremor/genetics , Tremor/metabolismABSTRACT
Fragile X-related tremor/ataxia syndrome (FXTAS) is a neurodegenerative disease caused by CGG triplet repeat expansions in FMR1, which elicit repeat-associated non-AUG (RAN) translation and produce the toxic protein FMRpolyG. We show that FMRpolyG interacts with pathogenic CGG repeat-derived RNA G-quadruplexes (CGG-G4RNA), propagates cell to cell, and induces neuronal dysfunction. The FMRpolyG polyglycine domain has a prion-like property, preferentially binding to CGG-G4RNA. Treatment with 5-aminolevulinic acid, which is metabolized to protoporphyrin IX, inhibited RAN translation of FMRpolyG and CGG-G4RNA-induced FMRpolyG aggregation, ameliorating aberrant synaptic plasticity and behavior in FXTAS model mice. Thus, we present a novel therapeutic strategy to target G4RNA prionoids.
Subject(s)
Fragile X Syndrome , G-Quadruplexes , Neurodegenerative Diseases , Animals , Ataxia/genetics , Ataxia/metabolism , Ataxia/pathology , Fragile X Mental Retardation Protein/genetics , Fragile X Syndrome/genetics , Mice , Tremor/genetics , Tremor/metabolismABSTRACT
Fragile X-associated tremor/ataxia syndrome (FXTAS) is an incurable neurodegenerative disorder caused by expansion of CGG repeats in the FMR1 5'UTR. The RNA containing expanded CGG repeats (rCGGexp) causes cell damage by interaction with complementary DNA, forming R-loop structures, sequestration of nuclear proteins involved in RNA metabolism and initiation of translation of polyglycine-containing protein (FMRpolyG), which forms nuclear insoluble inclusions. Here we show the therapeutic potential of short antisense oligonucleotide steric blockers (ASOs) targeting directly the rCGGexp. In nuclei of FXTAS cells ASOs affect R-loop formation and correct miRNA biogenesis and alternative splicing, indicating that nuclear proteins are released from toxic sequestration. In cytoplasm, ASOs significantly decrease the biosynthesis and accumulation of FMRpolyG. Delivery of ASO into a brain of FXTAS mouse model reduces formation of inclusions, improves motor behavior and corrects gene expression profile with marginal signs of toxicity after a few weeks from a treatment.
Subject(s)
Ataxia/metabolism , Fragile X Mental Retardation Protein/metabolism , Fragile X Syndrome/metabolism , Oligonucleotides, Antisense/metabolism , Tremor/metabolism , Trinucleotide Repeat Expansion/genetics , Trinucleotide Repeat Expansion/physiology , Alternative Splicing/genetics , Alternative Splicing/physiology , Animals , Ataxia/genetics , Exons/genetics , Female , Fragile X Mental Retardation Protein/genetics , Fragile X Syndrome/genetics , Male , Mice , Mice, Transgenic , MicroRNAs/genetics , MicroRNAs/metabolism , Nuclear Proteins/genetics , Nuclear Proteins/metabolism , Oligonucleotides, Antisense/genetics , Tremor/geneticsABSTRACT
Parkinson's disease (PD) is often classified into tremor dominant (TD) and postural instability gait disorder (PIGD) subtypes. Degeneration of subcortical/cortical pathways is different between PD subtypes, which leads to differences in motor behavior. However, the influence of PD subtype on cortical activity during walking remains poorly understood. Therefore, we aimed to investigate the influence of PD motor subtypes on cortical activity during unobstructed walking and obstacle avoidance. Seventeen PIGD and 19 TD patients performed unobstructed walking and obstacle avoidance conditions. Brain activity was measured using a mobile functional near-infrared spectroscopy-electroencephalography (EEG) systems, and gait parameters were analyzed using an electronic carpet. Concentrations of oxygenated hemoglobin (HbO2) of the prefrontal cortex (PFC) and EEG absolute power from alpha, beta, and gamma bands in FCz, Cz, CPz, and Oz channels were calculated. These EEG channels correspond to supplementary motor area, primary motor cortex, posterior parietal cortex, and visual cortex, respectively. Postural instability gait disorder patients presented higher PFC activity than TD patients, regardless of the walking condition. Tremor dominant patients presented reduced beta power in the Cz channel during obstacle avoidance compared to unobstructed walking. Both TD and PIGD patients decreased alpha and beta power in the FCz and CPz channels. In conclusion, PIGD patients need to recruit additional cognitive resources from the PFC for walking. Both TD and PIGD patients presented changes in the activation of brain areas related to motor/sensorimotor areas in order to maintain balance control during obstacle avoidance, being that TD patients presented further changes in the motor area (Cz channel) to avoid obstacles.