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BACKGROUND: The differential diagnosis of patients presenting for the first time with a depressive episode into unipolar disorder versus bipolar disorder is crucial to establish the correct pharmacological therapy (antidepressants vs mood stabilizers), but no biological markers are currently available. Several lines of evidence indicate an involvement of Glycogen Synthase Kinase-3 (GSK3) in the pathophysiology of depression. However, previous reports about GSK3 in peripheral blood were incomplete or inconsistent, so a specific marker is not yet available. The aim was to search for consistent differences in GSK3α and GSK3ß or of their phosphorylated forms in samples of peripheral blood from patients with unipolar and bipolar depression. METHODS: Mononucleate peripheral blood cells (PBMCs) of samples from patients presenting with a depressive episode were analyzed with the western blot technique. RESULTS: The total amount of GSK3ß in PBMCs was significantly lower in patients with bipolar disorder than in patients with unipolar depression. The sensitivity based on GSK3ß was 85%. GSK3α was not significantly different but allowed a correct detection of 57% of BD patients. The combination in series of GSK3ß and GSK3α yields a sensitivity of about 100%, but with 26.7% false negatives. CONCLUSIONS: Our results suggest that PBMC GSK3ß could be a candidate biomarker for the differential diagnosis of bipolar disorder versus unipolar depression. This finding may help in implementing the still limited panel of peripheral biomarkers for differential diagnosis between unipolar and bipolar disorder in patients presenting with a depressive episode.
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Fatty acid elongase ELOVL5 is part of a protein family of multipass transmembrane proteins that reside in the endoplasmic reticulum where they regulate long-chain fatty acid elongation. A missense variant (c.689G>T p.Gly230Val) in ELOVL5 causes Spinocerebellar Ataxia subtype 38 (SCA38), a neurodegenerative disorder characterized by autosomal dominant inheritance, cerebellar Purkinje cell demise and adult-onset ataxia. Having previously showed aberrant accumulation of p.G230V in the Golgi complex, here we further investigated the pathogenic mechanisms triggered by p.G230V, integrating functional studies with bioinformatic analyses of protein sequence and structure. Biochemical analysis showed that p.G230V enzymatic activity was normal. In contrast, SCA38-derived fibroblasts showed reduced expression of ELOVL5, Golgi complex enlargement and increased proteasomal degradation with respect to controls. By heterologous overexpression, p.G230V was significantly more active than wild-type ELOVL5 in triggering the unfolded protein response and in decreasing viability in mouse cortical neurons. By homology modelling, we generated native and p.G230V protein structures whose superposition revealed a shift in Loop 6 in p.G230V that altered a highly conserved intramolecular disulphide bond. The conformation of this bond, connecting Loop 2 and Loop 6, appears to be elongase-specific. Alteration of this intramolecular interaction was also observed when comparing wild-type ELOVL4 and the p.W246G variant which causes SCA34. We demonstrate by sequence and structure analyses that ELOVL5 p.G230V and ELOVL4 p.W246G are position-equivalent missense variants. We conclude that SCA38 is a conformational disease and propose combined loss of function by mislocalization and gain of toxic function by ER/Golgi stress as early events in SCA38 pathogenesis.
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Ataxias Espinocerebelares , Animais , Camundongos , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/patologia , Ataxia , Elongases de Ácidos Graxos/genética , Sequência de Aminoácidos , MutaçãoRESUMO
Several studies indicate a relationship between maternal gut microbiota alteration and increased risk of autism spectrum disorders (ASD) in offspring. The possibility of compensating for such metabolic dysfunction at a very early stage of disease via maternal treatment has not been enough explored. Here, we examined in BTBR mouse model of ASD the effect of maternal treatment with the gut microbial metabolite butyrate (BUT) on the behavioral and synaptic plasticity deficits in juvenile and adult offspring. We show that BUT treatment of BTBR dams rescues the social and partially the repetitive behavior deficits in the offspring. In addition, maternal BUT implementation prevents the cerebellar cortex hypertrophy as well as the Purkinje cells firing and long-term synaptic plasticity deficits in BTBR mice. Our results demonstrate, for the first time, that maternal BUT treatment can improve ASD-like symptoms in offspring thus providing new directions for the early treatment of neurodevelopmental disorders.
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Transtorno do Espectro Autista , Transtorno Autístico , Camundongos , Animais , Transtorno Autístico/tratamento farmacológico , Ácido Butírico/farmacologia , Comportamento Social , Transtorno do Espectro Autista/tratamento farmacológico , Transtorno do Espectro Autista/prevenção & controle , Transtorno do Espectro Autista/metabolismo , Camundongos Endogâmicos , Modelos Animais de Doenças , Camundongos Endogâmicos C57BL , Comportamento AnimalRESUMO
BACKGROUND: Spinocerebellar ataxia 38 (SCA38) is a rare autosomal neurological disorder characterized by ataxia and cerebellar atrophy. SCA38 is caused by mutations of ELOVL5 gene. ELOVL5 gene encodes a protein, which elongates long chain polyunsaturated fatty acids (PUFAs). Knockout mice lacking Elovl5 recapitulate SCA38 symptoms, including motor coordination impairment and disruption of cerebellar architecture. We asked whether, in Elovl5 knockout mice (Elovl5-/-), a diet with both ω3 and ω6 PUFAs downstream Elovl5 can prevent the development of SCA38 symptoms, and at which age such treatment is more effective. Elovl5-/- mice were fed either with a diet without or containing PUFAs downstream the Elovl5 enzyme, starting at different ages. Motor behavior was assessed by the balance beam test and cerebellar structure by morphometric analysis. RESULTS: The administration from birth of the diet containing PUFAs downstream Elovl5 led to a significant amelioration of the motor performance in the beam test of Elovl5-/- mice, with a reduction of foot slip errors at 6 months from 2.2 ± 0.3 to 1.3 ± 0.2 and at 8 months from 3.1 ± 0.5 to 1.9 ± 0.3. On the contrary, administration at 1 month of age or later had no effect on the motor impairment. The cerebellar Purkinje cell layer and the white matter area of Elovl5-/ -mice were not rescued even by the administration of diet from birth, suggesting that the improvement of motor performance in the beam test was due to a functional recovery of the cerebellar circuitry. CONCLUSIONS: These results suggest that the dietary intervention in SCA38, whenever possible, should be started from birth or as early as possible.
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Ácidos Graxos , Ataxias Espinocerebelares , Animais , Cerebelo , Modelos Animais de Doenças , Elongases de Ácidos Graxos/metabolismo , Ácidos Graxos/administração & dosagem , Ácidos Graxos Insaturados , Camundongos , Camundongos Knockout , Ataxias Espinocerebelares/dietoterapiaRESUMO
The transcription factor NURR1 is essential to the generation and maintenance of midbrain dopaminergic (mDA) neurons and its deregulation is involved in the development of dopamine (DA)-associated brain disorders, such as Parkinson's disease (PD). The old male NURR1 heterozygous knockout (NURR1-KO) mouse has been proposed as a model of PD due to its altered motor performance that was, however, not confirmed in a subsequent study. Based on these controversial results, we explored the effects of the NURR1 deficiency on locomotor activity, motor coordination, brain and plasma DA levels, blood pressure and heart rate of old mice, also focusing on the potential effect of sex. As a probable consequence of the role of NURR1 in DA pathway, we observed that the old NURR1-KO mouse is characterized by motor impairment, and increased brain DA level and heart rate, independently from sex. However, we also observed an alteration in spontaneous locomotor activity that only affects males. In conclusion, NURR1 deficiency triggers sex- and age-specific alterations of behavioral responses, of DA levels and cardiovascular abnormalities. Further studies in simplified systems will be necessary to dissect the mechanism underlying these observations.
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Membro 2 do Grupo A da Subfamília 4 de Receptores Nucleares , Doença de Parkinson , Animais , Dopamina/metabolismo , Neurônios Dopaminérgicos/metabolismo , Feminino , Masculino , Camundongos , Camundongos Knockout , Membro 2 do Grupo A da Subfamília 4 de Receptores Nucleares/genética , Doença de Parkinson/metabolismo , Fenótipo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Elovl5 elongates fatty acids with 18 carbon atoms and in cooperation with other enzymes guarantees the normal levels of very long-chain fatty acids, which are necessary for a proper membrane structure. Action potential conduction along myelinated axons depends on structural integrity of myelin, which is maintained by a correct amount of fatty acids and a proper interaction between fatty acids and myelin proteins. We hypothesized that in Elovl5-/- mice, the lack of elongation of Elovl5 substrates might cause alterations of myelin structure. The analysis of myelin ultrastructure showed an enlarged periodicity with reduced G-ratio across all axonal diameters. We hypothesized that the structural alteration of myelin might affect the conduction of action potentials. The sciatic nerve conduction velocity was significantly reduced without change in the amplitude of the nerve compound potential, suggesting a myelin defect without a concomitant axonal degeneration. Since Elovl5 is important in attaining normal amounts of polyunsaturated fatty acids, which are the principal component of myelin, we performed a lipidomic analysis of peripheral nerves of Elovl5-deficient mice. The results revealed an unbalance, with reduction of fatty acids longer than 18 carbon atoms relative to shorter ones. In addition, the ratio of saturated to unsaturated fatty acids was strongly increased. These findings point out the essential role of Elovl5 in the peripheral nervous system in supporting the normal structure of myelin, which is the key element for a proper conduction of electrical signals along myelinated nerves.
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Axônios , Bainha de Mielina , Potenciais de Ação/genética , Animais , Axônios/fisiologia , Elongases de Ácidos Graxos/genética , Ácidos Graxos/metabolismo , Camundongos , Bainha de Mielina/metabolismo , Condução Nervosa/genética , Nervos PeriféricosRESUMO
ELOVL5 (Elongase of Very-Long Fatty Acid 5) gene encodes for an enzyme that elongates long chain fatty acids, with a marked preference for polyunsaturated molecules. In particular, it plays an essential role in the elongation of omega-3 and omega-6 fatty acids, precursors for long-chain polyunsaturated fatty acids (PUFAs). Mutations of ELOVL5 cause the spino-cerebellar ataxia type 38 (SCA38), a rare autosomal neurological disease characterized by gait abnormality, dysarthria, dysphagia, hyposmia and peripheral neuropathy, conditions well represented by a mouse model with a targeted deletion of this gene (Elovl5-/- mice). However, the expression pattern of this enzyme in neuronal and glial cells of the central nervous system (CNS) is still uninvestigated. This work is aimed at filling this gap of knowledge by taking advantage of an Elovl5-reporter mouse line and immunofluorescence analyses on adult mouse CNS sections and glial cell primary cultures. Notably, Elovl5 appears expressed in a region- and cell type-specific manner. Abundant Elovl5-positive cells were found in the cerebellum, brainstem, and primary and accessory olfactory regions, where mitral cells show the most prominent expression. Hippocampal pyramidal cells of CA2/CA3 where also moderately labeled, while in the rest of the telencephalon Elovl5 expression was high in regions related to motor control. Analysis of primary glial cell cultures revealed Elovl5 expression in oligodendroglial cells at various maturation steps and in microglia, while astrocytes showed a heterogeneous in vivo expression of Elovl5. The elucidation of Elovl5 CNS distribution provides relevant information to understand the physiological functions of this enzyme and its PUFA products, whose unbalance is known to be involved in many pathological conditions.
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Convergent lines of evidence have recently highlighted ß3-adrenoreceptors (ARs) as a potentially critical target in the regulation of nervous and behavioral functions, including memory consolidation, anxiety, and depression. Nevertheless, the role of ß3-ARs in the cerebellum has been never investigated. To address this issue, we first examined the effects of pharmacological manipulation of ß3-ARs on motor learning in mice. We found that blockade of ß3-ARs by SR 59230A impaired the acquisition of the rotarod task with no effect on general locomotion. Since the parallel fiber-Purkinje cell (PF-PC) synapse is considered to be the main cerebellar locus of motor learning, we assessed ß3-AR modulatory action on this synapse as well as its expression in cerebellar slices. We demonstrate, for the first time, a strong expression of ß3-ARs on Purkinje cell soma and dendrites. In addition, whole-cell patch-clamp recordings revealed that bath application of ß3-AR agonist CL316,243 depressed the PF-PC excitatory postsynaptic currents via a postsynaptic mechanism mediated by the PI3K signaling pathway. Application of CL316,243 also interfered with the expression of PF long-term potentiation, whereas SR 59230A prevented the induction of LTD at PF-PC synapse. These results underline the critical role of ß3-AR on cerebellar synaptic transmission and plasticity and provide a new mechanism for adrenergic modulation of motor learning.
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Córtex Cerebelar/fisiologia , Receptores Adrenérgicos beta 3/fisiologia , Transmissão Sináptica/fisiologia , Animais , Córtex Cerebelar/metabolismo , Potenciais Pós-Sinápticos Excitadores , Feminino , Potenciação de Longa Duração , Depressão Sináptica de Longo Prazo , Masculino , Camundongos , Plasticidade Neuronal/fisiologia , Técnicas de Patch-Clamp , Fosfatidilinositol 3-Quinases/metabolismo , Células de Purkinje/metabolismo , Receptores Adrenérgicos beta 3/metabolismo , Teste de Desempenho do Rota-Rod , Sinapses/fisiologiaRESUMO
G-protein-coupled inwardly rectifying potassium (GIRK) channels contribute to the resting membrane potential of many neurons and play an important role in controlling neuronal excitability. Although previous studies have revealed a high expression of GIRK subunits in the cerebellum, their functional role has never been clearly described. Using patch-clamp recordings in mice cerebellar slices, we examined the properties of the GIRK currents in Purkinje cells (PCs) and investigated the effects of a selective agonist of GIRK1-containing channels, ML297 (ML), on PC firing and synaptic plasticity. We demonstrated that GIRK channel activation decreases the PC excitability by inhibiting both sodium and calcium spikes and, in addition, modulates the complex spike response evoked by climbing fiber stimulation. Our results indicate that GIRK channels have also a marked effect on synaptic plasticity of the parallel fiber-PC synapse, as the application of ML297 increased the expression of LTP while preventing LTD. We, therefore, propose that the recruitment of GIRK channels represents a crucial mechanism by which neuromodulators can control synaptic strength and membrane conductance for proper refinement of the neural network involved in memory storage and higher cognitive functions.
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Potenciais Pós-Sinápticos Excitadores/fisiologia , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/fisiologia , Plasticidade Neuronal/fisiologia , Neurotransmissores/farmacologia , Células de Purkinje/fisiologia , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Animais , Animais Recém-Nascidos , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Feminino , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/agonistas , Masculino , Camundongos , Plasticidade Neuronal/efeitos dos fármacos , Compostos de Fenilureia/farmacologia , Células de Purkinje/efeitos dos fármacos , Pirazóis/farmacologiaRESUMO
INTRODUCTION: Spinocerebellar Ataxia 38 (SCA38) is caused by ELOVL5 gene mutation, with significant reduction of serum docosahexaenoic acid (DHA) levels. DHA supplementation has been proven effective at short-term follow-up. In the present paper, we evaluated long-term safety and efficacy of 600â¯mg/day oral DHA in SCA38 by a 2-year open label extension study. METHODS: Nine SCA38 patients underwent standardised clinical assessment at 62 (T1), 82 (T2) and 104 (T3) weeks, and compared to pre-treatment scores (T0). Brain 18-Fluorodeoxyglucose Positron Emission Tomography and electroneurography were performed at T0 and T3. RESULTS: We found a significant maintenance of clinical symptom improvement at each follow-up time-point (pâ¯<â¯0.001) as compared to T0, a sustained increase of cerebellar metabolism at T3 as compared to T0 (pâ¯=â¯0.013), and no worsening of neurophysiological parameters. No side effect was recorded. CONCLUSIONS: Long-term DHA supplementation is an eligible treatment for SCA38.
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Ácidos Docosa-Hexaenoicos/farmacologia , Ataxias Espinocerebelares/tratamento farmacológico , Ataxias Espinocerebelares/fisiopatologia , Adulto , Ácidos Docosa-Hexaenoicos/administração & dosagem , Ácidos Docosa-Hexaenoicos/efeitos adversos , Estimulação Elétrica , Eletromiografia , Elongases de Ácidos Graxos/genética , Feminino , Fluordesoxiglucose F18 , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Tomografia por Emissão de Pósitrons , Compostos Radiofarmacêuticos , Ataxias Espinocerebelares/diagnóstico por imagem , Ataxias Espinocerebelares/genéticaRESUMO
Sexual disturbances, and aggressivity are a major social problem. However, the molecular mechanisms involved in the control of these behaviors are largely unknown. FGF14, which is an intracellular protein controlling neuronal excitability and synaptic transmission, has been implied in neurologic and psychiatric disorders. Mice with Fgf14 deletion show blunted responses to drugs of abuse. By behavioral tests we show that male Fgf14 knockout mice have a marked reduction of several behaviors including aggressivity and sexual behavior. Other behaviors driven by spontaneous initiative like burying novel objects and spontaneous digging and climbing are also reduced in Fgf14 knockout mice. These deficits cannot be attributed to a generalized decrease of activity levels, because in the open field test Fgf14 knockout mice have the same spontaneous locomotion as wild types and increased rearing. Our results show that Fgf14 is important to preserve a set of behaviors and suggest that fine tuning of neuronal function by Fgf14 is an important mechanism of control for such behaviors.
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Axônios/fisiologia , Fatores de Crescimento de Fibroblastos/genética , Hipocampo/fisiologia , Neurônios/fisiologia , Animais , Comportamento Animal/fisiologia , Locomoção/fisiologia , Masculino , Camundongos KnockoutRESUMO
Spinocerebellar ataxia 28 is an autosomal dominant neurodegenerative disorder caused by missense mutations affecting the proteolytic domain of AFG3L2, a major component of the mitochondrial m-AAA protease. However, little is known of the underlying pathogenetic mechanisms or how to treat patients with SCA28. Currently available Afg3l2 mutant mice harbour deletions that lead to severe, early-onset neurological phenotypes that do not faithfully reproduce the late-onset and slowly progressing SCA28 phenotype. Here we describe production and detailed analysis of a new knock-in murine model harbouring an Afg3l2 allele carrying the p.Met665Arg patient-derived mutation. Heterozygous mutant mice developed normally but adult mice showed signs of cerebellar ataxia detectable by beam test. Although cerebellar pathology was negative, electrophysiological analysis showed a trend towards increased spontaneous firing in Purkinje cells from heterozygous mutants with respect to wild-type controls. As homozygous mutants died perinatally with evidence of cardiac atrophy, for each genotype we generated mouse embryonic fibroblasts (MEFs) to investigate mitochondrial function. MEFs from mutant mice showed altered mitochondrial bioenergetics, with decreased basal oxygen consumption rate, ATP synthesis and mitochondrial membrane potential. Mitochondrial network formation and morphology was altered, with greatly reduced expression of fusogenic Opa1 isoforms. Mitochondrial alterations were also detected in cerebella of 18-month-old heterozygous mutants and may be a hallmark of disease. Pharmacological inhibition of de novo mitochondrial protein translation with chloramphenicol caused reversal of mitochondrial morphology in homozygous mutant MEFs, supporting the relevance of mitochondrial proteotoxicity for SCA28 pathogenesis and therapy development.
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Proteases Dependentes de ATP/genética , ATPases Associadas a Diversas Atividades Celulares/genética , Modelos Animais de Doenças , Mitocôndrias/metabolismo , Ataxias Espinocerebelares/congênito , Animais , Feminino , Técnicas de Introdução de Genes , Potencial da Membrana Mitocondrial , Camundongos Endogâmicos C57BL , Proteínas Mitocondriais/metabolismo , Mutação de Sentido Incorreto , Células de Purkinje/fisiologia , Células de Purkinje/ultraestrutura , Ataxias Espinocerebelares/genética , Ataxias Espinocerebelares/metabolismo , Ataxias Espinocerebelares/patologiaRESUMO
The role of the cerebellum in Alzheimer's disease (AD) has been neglected for a long time. Recent studies carried out using transgenic mouse models have demonstrated that amyloid-ß (Aß) is deposited in the cerebellum and affects synaptic transmission and plasticity, sometimes before plaque formation. A wide variability of motor phenotype has been observed in the different murine models of AD, without a consistent correlation with the extent of cerebellar histopathological changes or with cognitive deficits. The loss of noradrenergic drive may contribute to the impairment of cerebellar synaptic function and motor learning observed in these mice. Furthermore, cerebellar neurons, particularly granule cells, have been used as in vitro model of Aß-induced neuronal damage. An unexpected conclusion is that the cerebellum, for a long time thought to be somehow protected from AD pathology, is actually considered as a region vulnerable to Aß toxic damage, even at the early stage of the disease, with consequences on motor performance.
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Sox2 is a transcription factor active in the nervous system, within different cell types, ranging from radial glia neural stem cells to a few specific types of differentiated glia and neurons. Mutations in the human SOX2 transcription factor gene cause various central nervous system (CNS) abnormalities, involving hippocampus and eye defects, as well as ataxia. Conditional Sox2 mutation in mouse, with different Cre transgenes, previously recapitulated different essential features of the disease, such as hippocampus and eye defects. In the cerebellum, Sox2 is active from early embryogenesis in the neural progenitors of the cerebellar primordium; Sox2 expression is maintained, postnatally, within Bergmann glia (BG), a differentiated cell type essential for Purkinje neurons functionality and correct motor control. By performing Sox2 Cre-mediated ablation in the developing and postnatal mouse cerebellum, we reproduced ataxia features. Embryonic Sox2 deletion (with Wnt1Cre) leads to reduction of the cerebellar vermis, known to be commonly related to ataxia, preceded by deregulation of Otx2 and Gbx2, critical regulators of vermis development. Postnatally, BG is progressively disorganized, mislocalized, and reduced in mutants. Sox2 postnatal deletion, specifically induced in glia (with GLAST-CreERT2), reproduces the BG defect, and causes (milder) ataxic features. Our results define a role for Sox2 in cerebellar function and development, and identify a functional requirement for Sox2 within postnatal BG, of potential relevance for ataxia in mouse mutants, and in human patients.
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Ataxia/metabolismo , Vermis Cerebelar/crescimento & desenvolvimento , Vermis Cerebelar/metabolismo , Neuroglia/metabolismo , Fatores de Transcrição SOXB1/metabolismo , Animais , Animais Recém-Nascidos , Ataxia/patologia , Células Cultivadas , Vermis Cerebelar/patologia , Regulação da Expressão Gênica/fisiologia , Ácido Glutâmico/metabolismo , Proteínas de Homeodomínio/metabolismo , Camundongos Transgênicos , Mutação , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/patologia , Neuroglia/patologia , Fatores de Transcrição Otx/metabolismo , Fatores de Transcrição SOXB1/genética , Transmissão Sináptica/fisiologiaRESUMO
Purkinje cell (PC) dysfunction or degeneration is the most frequent finding in animal models with ataxic symptoms. Mutations affecting intrinsic membrane properties can lead to ataxia by altering the firing rate of PCs or their firing pattern. However, the relationship between specific firing alterations and motor symptoms is not yet clear, and in some cases PC dysfunction precedes the onset of ataxic signs. Moreover, a great variety of ionic and synaptic mechanisms can affect PC signaling, resulting in different features of motor dysfunction. Mutations affecting Na+ channels (NaV1.1, NaV1.6, NaVß4, Fgf14 or Rer1) reduce the firing rate of PCs, mainly via an impairment of the Na+ resurgent current. Mutations that reduce Kv3 currents limit the firing rate frequency range. Mutations of Kv1 channels act mainly on inhibitory interneurons, generating excessive GABAergic signaling onto PCs, resulting in episodic ataxia. Kv4.3 mutations are responsible for a complex syndrome with several neurologic dysfunctions including ataxia. Mutations of either Cav or BK channels have similar consequences, consisting in a disruption of the firing pattern of PCs, with loss of precision, leading to ataxia. Another category of pathogenic mechanisms of ataxia regards alterations of synaptic signals arriving at the PC. At the parallel fiber (PF)-PC synapse, mutations of glutamate delta-2 (GluD2) or its ligand Crbl1 are responsible for the loss of synaptic contacts, abolishment of long-term depression (LTD) and motor deficits. At the same synapse, a correct function of metabotropic glutamate receptor 1 (mGlu1) receptors is necessary to avoid ataxia. Failure of climbing fiber (CF) maturation and establishment of PC mono-innervation occurs in a great number of mutant mice, including mGlu1 and its transduction pathway, GluD2, semaphorins and their receptors. All these models have in common the alteration of PC output signals, due to a variety of mechanisms affecting incoming synaptic signals or the way they are processed by the repertoire of ionic channels responsible for intrinsic membrane properties. Although the PC is a final common pathway of ataxia, the link between specific firing alterations and neurologic symptoms has not yet been systematically studied and the alterations of the cerebellar contribution to motor signals are still unknown.
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Spino-Cerebellar-Ataxia type 38 (SCA38) is caused by missense mutations in the very long chain fatty acid elongase 5 gene, ELOVL5. The main clinical findings in this disease are ataxia, hyposmia and cerebellar atrophy. Mice in which Elovl5 has been knocked out represent a model of the loss of function hypothesis of SCA38. In agreement with this hypothesis, Elovl5 knock out mice reproduced the main symptoms of patients, motor deficits at the beam balance test and hyposmia. The cerebellar cortex of Elovl5 knock out mice showed a reduction of thickness of the molecular layer, already detectable at 6 months of age, confirmed at 12 and 18 months. The total perimeter length of the Purkinje cell (PC) layer was also reduced in Elovl5 knock out mice. Since Elovl5 transcripts are expressed by PCs, whose dendrites are a major component of the molecular layer, we hypothesized that an alteration of their dendrites might be responsible for the reduced thickness of this layer. Reconstruction of the dendritic tree of biocytin-filled PCs, followed by Sholl analysis, showed that the distribution of distal dendrites was significantly reduced in Elovl5 knock out mice. Dendritic spine density was conserved. These results suggest that Elovl5 knock out mice recapitulate SCA38 symptoms and that their cerebellar atrophy is due, at least in part, to a reduced extension of PC dendritic arborization.
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OBJECTIVE: Spinocerebellar ataxia 38 (SCA38) is caused by mutations in the ELOVL5 gene, which encodes an elongase involved in the synthesis of polyunsaturated fatty acids, including docosahexaenoic acid (DHA). As a consequence, DHA is significantly reduced in the serum of SCA38 subjects. In the present study, we evaluated the safety of DHA supplementation, its efficacy for clinical symptoms, and changes of brain functional imaging in SCA38 patients. METHODS: We enrolled 10 SCA38 patients, and carried out a double-blind randomized placebo-controlled study for 16 weeks, followed by an open-label study with overall 40-week DHA treatment. At baseline and at follow-up visit, patients underwent standardized clinical assessment, brain 18-fluorodeoxyglucose positron emission tomography, electroneurography, and ELOVL5 expression analysis. RESULTS: After 16 weeks, we showed a significant pre-post clinical improvement in the DHA group versus placebo, using the Scale for the Assessment and Rating of Ataxia (SARA; mean difference [MD] = +2.70, 95% confidence interval [CI] = +0.13 to + 5.27, p = 0.042). At 40-week treatment, clinical improvement was found significant by both SARA (MD = +2.2, 95% CI = +0.93 to + 3.46, p = 0.008) and International Cooperative Ataxia Rating Scale (MD = +3.8, 95% CI = +1.39 to + 6.41, p = 0.02) scores; clinical data were corroborated by significant improvement of cerebellar hypometabolism (statistical parametric mapping analyses, false discovery rate corrected). We also showed a decreased expression of ELOVL5 in patients' blood at 40 weeks as compared to baseline. No side effect was recorded. INTERPRETATION: DHA supplementation is a safe and effective treatment for SCA38, showing an improvement of clinical symptoms and cerebellar hypometabolism. Ann Neurol 2017;82:615-621.
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Suplementos Nutricionais , Ácidos Docosa-Hexaenoicos/uso terapêutico , Ataxias Espinocerebelares/tratamento farmacológico , Adulto , Ataxinas/genética , Encéfalo/diagnóstico por imagem , Método Duplo-Cego , Eletromiografia , Feminino , Fluordesoxiglucose F18/farmacocinética , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Mutação/genética , Avaliação de Resultados em Cuidados de Saúde , Tomografia por Emissão de Pósitrons , Ataxias Espinocerebelares/diagnóstico por imagem , Ataxias Espinocerebelares/genética , Resultado do TratamentoRESUMO
The formation of the complex cerebellar cortical circuits follows different phases, with initial synaptogenesis and subsequent processes of refinement guided by a variety of mechanisms. The regularity of the cellular and synaptic organization of the cerebellar cortex allowed detailed studies of the structural plasticity mechanisms underlying the formation of new synapses and retraction of redundant ones. For the attainment of the monoinnervation of the Purkinje cell by a single climbing fiber, several signals are involved, including electrical activity, contact signals, homosynaptic and heterosynaptic interaction, calcium transients, postsynaptic receptors, and transduction pathways. An important role in this developmental program is played by serotonergic projections that, acting on temporally and spatially regulated postsynaptic receptors, induce and modulate the phases of synaptic formation and maturation. In the adult cerebellar cortex, many developmental mechanisms persist but play different roles, such as supporting synaptic plasticity during learning and formation of cerebellar memory traces. A dysfunction at any stage of this process can lead to disorders of cerebellar origin, which include autism spectrum disorders but are not limited to motor deficits. Recent evidence in animal models links impairment of Purkinje cell function with autism-like symptoms including sociability deficits, stereotyped movements, and interspecific communication by vocalization.
Assuntos
Transtorno Autístico/patologia , Córtex Cerebelar/crescimento & desenvolvimento , Rede Nervosa/crescimento & desenvolvimento , Serotonina/metabolismo , Animais , Transtorno Autístico/metabolismo , Córtex Cerebelar/metabolismo , Córtex Cerebelar/patologia , Modelos Animais de Doenças , Humanos , Camundongos , Rede Nervosa/metabolismo , Rede Nervosa/patologia , Plasticidade Neuronal/fisiologia , Neurônios/metabolismo , Neurônios/patologia , Sinapses/fisiologiaRESUMO
The parallel fiber-Purkinje cell (PF-PC) synapse represents the point of maximal signal divergence in the cerebellar cortex with an estimated number of about 60 billion synaptic contacts in the rat and 100,000 billions in humans. At the same time, the Purkinje cell dendritic tree is a site of remarkable convergence of more than 100,000 parallel fiber synapses. Parallel fiber activity generates fast postsynaptic currents via α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, and slower signals, mediated by mGlu1 receptors, resulting in Purkinje cell depolarization accompanied by sharp calcium elevation within dendritic regions. Long-term depression (LTD) and long-term potentiation (LTP) have been widely described for the PF-PC synapse and have been proposed as mechanisms for motor learning. The mechanisms of induction for LTP and LTD involve different signaling mechanisms within the presynaptic terminal and/or at the postsynaptic site, promoting enduring modification in the neurotransmitter release and change in responsiveness to the neurotransmitter. The PF-PC synapse is finely modulated by several neurotransmitters, including serotonin, noradrenaline and acetylcholine. The ability of these neuromodulators to gate LTP and LTD at the PF-PC synapse could, at least in part, explain their effect on cerebellar-dependent learning and memory paradigms. Overall, these findings have important implications for understanding the cerebellar involvement in a series of pathological conditions, ranging from ataxia to autism. For example, PF-PC synapse dysfunctions have been identified in several murine models of spino-cerebellar ataxia (SCA) types 1, 3, 5 and 27. In some cases, the defect is specific for the AMPA receptor signaling (SCA27), while in others the mGlu1 pathway is affected (SCA1, 3, 5). Interestingly, the PF-PC synapse has been shown to be hyper-functional in a mutant mouse model of autism spectrum disorder, with a selective deletion of Pten in Purkinje cells. However, the full range of methodological approaches, that allowed the discovery of the physiological principles of PF-PC synapse function, has not yet been completely exploited to investigate the pathophysiological mechanisms of diseases involving the cerebellum. We, therefore, propose to extend the spectrum of experimental investigations to tackle this problem.
RESUMO
INTRODUCTION: SCA38 (MIM 611805) caused by mutations within the ELOVL5 gene, which encodes an enzyme involved in the synthesis of long-chain fatty acids with a high and specific expression in Purkinje cells, has recently been identified. OBJECTIVE: The present study was aimed at describing the clinical and neuroimaging features, and the natural history of SCA38. METHODS: We extended our clinical and brain neuroimaging data on SCA38 including 21 cases from three Italian families. All had the ELOVL5 c.689G > T (p.Gly230Val) missense mutation. RESULTS: Age at disease onset was in the fourth decade of life. The presenting features were nystagmus (100% of cases) and slowly progressive gait ataxia (95%). Frequent signs and symptoms included pes cavus (82%) and hyposmia (76%); rarer symptoms were hearing loss (33%) and anxiety disorder (33%). The disease progressed with cerebellar symptoms such as limb ataxia, dysarthria, dysphagia, and ophtalmoparesis followed in the later stages by ophtalmoplegia. Peripheral nervous system involvement was present in the last phase of disease with sensory loss. Dementia or extrapyramidal signs were not detected. Significant loss of abilities of daily living was reported only after 20 years of the disease. Brain imaging documented cerebellar atrophy with sparing of cerebral cortex and no white matter disease. CONCLUSIONS: SCA38 is a rare form of inherited ataxia with characteristic clinical features, including pes cavus and hyposmia, that may guide genetic screening and prompt diagnosis in light of possible future therapeutic interventions.