RESUMO
Cortical dysplasias are alterations in the organization of the layers of the brain cortex due to problems in neuronal migration during development. The neuronal component has been widely studied in experimental models of cortical dysplasias. In contrast, little is known about how glia are affected. In the cerebellum, Bergmann glia (BG) are essential for neuronal migration during development, and in adult they mediate the control of fine movements through glutamatergic transmission. The aim of this study was to characterize the morphology and intracellular calcium dynamics of BG and astrocytes from mouse cerebellum and their modifications in a model of cortical dysplasia induced by carmustine (BCNU). Carmustine-treated mice were affected in their motor coordination and balance. Cerebellar dysplasias and heterotopias were more frequently found in lobule X. Morphology of BG cells and astrocytes was affected, as were their spontaneous [Ca2+]i transients in slice preparation and in vitro.
Assuntos
Sinalização do Cálcio , Cerebelo/patologia , Malformações do Desenvolvimento Cortical/metabolismo , Malformações do Desenvolvimento Cortical/patologia , Neuroglia/metabolismo , Neuroglia/patologia , Animais , Astrócitos/patologia , Carmustina , Células Cultivadas , Malformações do Desenvolvimento Cortical/induzido quimicamente , Camundongos Transgênicos , Atividade MotoraRESUMO
OBJECTIVE: Focal cortical dysplasias (FCDs) are an important cause of drug-resistant epilepsy. In this work, we aimed to investigate whether abnormal gene regulation, mediated by microRNA, could be involved in FCD type II. METHODS: We used total RNA from the brain tissue of 16 patients with FCD type II and 28 controls. MicroRNA expression was initially assessed by microarray. Quantitative polymerase chain reaction, in situ hybridization, luciferase reporter assays, and deep sequencing for genes in the mTOR pathway were performed to validate and further explore our initial study. RESULTS: hsa-let-7f (p = 0.039), hsa-miR-31 (p = 0.0078), and hsa-miR34a (p = 0.021) were downregulated in FCD type II, whereas a transcription factor involved in neuronal and glial fate specification, NEUROG2 (p < 0.05), was upregulated. We also found that the RND2 gene, a NEUROG2-target, is upregulated (p < 0.001). In vitro experiments showed that hsa-miR-34a downregulates NEUROG2 by binding to its 5'-untranslated region. Moreover, we observed strong nuclear expression of NEUROG2 in balloon cells and dysmorphic neurons and found that 28.5% of our patients presented brain somatic mutations in genes of the mTOR pathway. INTERPRETATION: Our findings suggest a new molecular mechanism, in which NEUROG2 has a pivotal and central role in the pathogenesis of FCD type II. In this way, we found that the downregulation of hsa-miR-34a leads to upregulation of NEUROG2, and consequently to overexpression of the RND2 gene. These findings indicate that a faulty coupling in neuronal differentiation and migration mechanisms may explain the presence of aberrant cells and complete dyslamination in FCD type II. Ann Neurol 2018;83:623-635.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Epilepsia/metabolismo , Hipoplasia Dérmica Focal/metabolismo , Malformações do Desenvolvimento Cortical/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Adolescente , Adulto , Criança , Pré-Escolar , Epilepsia Resistente a Medicamentos/genética , Epilepsia/tratamento farmacológico , Epilepsia/genética , Feminino , Hipoplasia Dérmica Focal/genética , Humanos , Lactente , Masculino , Neurônios/metabolismo , Serina-Treonina Quinases TOR/metabolismo , Fatores de Transcrição/genética , Adulto Jovem , Proteínas rho de Ligação ao GTP/metabolismoRESUMO
ABC-transporters prevent the access of antiepileptic drugs into brain parenchyma, which partly explains why seizures are frequently refractory to AEDs treatment. Overexpression of ABC-transporters and stem-cell markers including CD34, have been detected in malformations of cortical development (MCD) and brain tumors. ABC-transporters are constitutively expressed during maturation of normal progenitor stem-cells and cancer stem-cells. These abnormal/immature cells of MCD or brain tumors play an active role in the epileptogenesis but the precise nature of this phenomenon is unclear. Irrespective of their property in the pharmacoresistance, ABCB1-transporter P-glycoprotein also plays a role in the membrane depolarization, suggesting that constitutive P-glycprotein overexpression in MCD and brain tumors could explain their epileptogeneic properties. MCD as wells as brain tumors arise from abnormal progenitor cells, where ABC-t together with others stem cell markers, could help to better identification of these abnormal progenitor cells and serve as biomarker of risk for seizure relapse after epilepsy surgery.
Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Biomarcadores/metabolismo , Neoplasias Encefálicas/metabolismo , Encéfalo/metabolismo , Epilepsia/metabolismo , Células-Tronco/metabolismo , Anticonvulsivantes/uso terapêutico , Encéfalo/patologia , Neoplasias Encefálicas/complicações , Neoplasias Encefálicas/patologia , Resistência a Medicamentos , Epilepsia/complicações , Epilepsia/tratamento farmacológico , Humanos , Malformações do Desenvolvimento Cortical/metabolismoRESUMO
PURPOSE: The aim of this study was to evaluate phospholipid metabolism in patients with malformations of cortical development (MCDs). METHODS: Thirty-seven patients with MCDs and 31 control subjects were studied using three-dimensional phosphorus magnetic resonance spectroscopy ((31)P-MRS) at 3.0 T. The voxels in the lesions and in the frontoparietal cortex of the control subjects were compared (the effective volumes were 12.5 cm(3)). Robust quantification methods were applied to fit the time-domain data to the following resonances: phosphoethanolamine (PE); phosphocholine (PC); inorganic phosphate (Pi); glycerophosphoethanolamine (GPE); glycerophosphocholine (GPC); phosphocreatine (PCr); and α-, ß-, and γ-adenosine triphosphate (ATP). We also estimated the total ATP (ATP(t) = α-+ß-+γ-ATP), phosphodiesters (PDE = GPC+GPE), phosphomonoesters (PME = PE+PC), and the PME/PDE, PCr/ATP(t) and PCr/Pi ratios. The magnesium (Mg(2+)) levels and pH values were calculated based on PCr, Pi, and ß-ATP chemical shifts. KEY FINDINGS: Compared to controls and assuming that a p-value < 0.05 indicates statistical significance, the patients with MCDs exhibited significantly lower pH values and higher Mg(2+) levels. In addition, the patients with MCDs had lower GPC and PDE and an increased PME/PDE ratio. SIGNIFICANCE: Mg(2+) and pH are important in the regulation of bioenergetics and are involved in many electrical activity pathways in the brain. Our data support the idea that neurometabolic impairments occur during seizure onset and propagation. The GPC, PDE, and PME/PDE abnormalities also demonstrate that there are membrane turnover disturbances in patients with MCDs.