RESUMO
Periventricular nodular heterotopia (PH) is a human brain malformation caused by defective neuronal migration that results in ectopic neuronal nodules lining the lateral ventricles beneath a normal appearing cortex. Most affected patients have seizures and their cognitive level varies from normal to severely impaired. Mutations in the Filamin-A (or FLNA) gene are the main cause of PH, but the underlying pathological mechanism remains unknown. Although two FlnA knockout mouse strains have been generated, none of them showed the presence of ectopic nodules. To recapitulate the loss of FlnA function in the developing rat brain, we used an in utero RNA interference-mediated knockdown approach and successfully reproduced a PH phenotype in rats comparable with that observed in human patients. In FlnA-knockdown rats, we report that PH results from a disruption of the polarized radial glial scaffold in the ventricular zone altering progression of neural progenitors through the cell cycle and impairing migration of neurons into the cortical plate. Similar alterations of radial glia are observed in human PH brains of a 35-week fetus and a 3-month-old child, harboring distinct FLNA mutations not previously reported. Finally, juvenile FlnA-knockdown rats are highly susceptible to seizures, confirming the reliability of this novel animal model of PH. Our findings suggest that the disorganization of radial glia is the leading cause of PH pathogenesis associated with FLNA mutations. Rattus norvegicus FlnA mRNA (GenBank accession number FJ416060).
Assuntos
Córtex Cerebral/metabolismo , Proteínas Contráteis/metabolismo , Proteínas dos Microfilamentos/metabolismo , Neuroglia/fisiologia , Heterotopia Nodular Periventricular/metabolismo , Heterotopia Nodular Periventricular/patologia , Animais , Movimento Celular , Proliferação de Células , Córtex Cerebral/embriologia , Córtex Cerebral/patologia , Ventrículos Cerebrais/patologia , Proteínas Contráteis/genética , Modelos Animais de Doenças , Feminino , Filaminas , Humanos , Lactente , Proteínas dos Microfilamentos/genética , Dados de Sequência Molecular , Neocórtex/embriologia , Neocórtex/metabolismo , Neocórtex/patologia , Células-Tronco Neurais/metabolismo , Células-Tronco Neurais/fisiologia , Neuroglia/metabolismo , Neuroglia/ultraestrutura , Neurônios/fisiologia , Interferência de RNA , Ratos , Convulsões/etiologiaRESUMO
Nogo-A is a protein associated with central nervous system (CNS) myelin thought to impair regenerative responses and to suppress sprouting and plastic changes of synaptic terminals. In this study, we report that serum IgM autoantibodies to the recombinant large N-terminal inhibitory domain of Nogo-A are a frequent finding in multiple sclerosis (MS) and acute inflammatory (IND) and non-inflammatory neurological diseases (OND), but not in neurodegenerative diseases (ND), systemic inflammatory disease and healthy controls. Furthermore, we demonstrate intrathecal production of anti-Nogo-A antibodies measured by increased IgG indices. Intrathecal anti-Nogo antibodies were significantly more frequent in patients with relapsing-remitting as compared to chronic progressive (CP) MS. We also found a highly significant negative correlation of these antibody responses with age indicating that they are more frequent in younger patients. We finally demonstrate that human anti-Nogo-A antibodies recognize native Nogo-A in brain extracts, oligodendrocytes and cells expressing human Nogo-A.
Assuntos
Autoanticorpos/sangue , Autoanticorpos/líquido cefalorraquidiano , Autoantígenos/imunologia , Esclerose Múltipla/imunologia , Proteínas da Mielina/imunologia , Doença Aguda , Adulto , Idoso , Animais , Autoanticorpos/biossíntese , Autoanticorpos/metabolismo , Encéfalo/imunologia , Encéfalo/metabolismo , Células CHO , Células Cultivadas , Doenças do Sistema Nervoso Central/sangue , Doenças do Sistema Nervoso Central/líquido cefalorraquidiano , Doenças do Sistema Nervoso Central/imunologia , Cricetinae , Humanos , Imunoglobulina G/biossíntese , Imunoglobulina G/líquido cefalorraquidiano , Imunoglobulina M/biossíntese , Imunoglobulina M/sangue , Pessoa de Meia-Idade , Esclerose Múltipla/sangue , Esclerose Múltipla/líquido cefalorraquidiano , Proteínas Nogo , Oligodendroglia/imunologia , Oligodendroglia/metabolismo , Ratos , TransfecçãoRESUMO
Protocadherins gamma (Pcdhgamma) are a family of transmembrane proteins in which variable extracellular domains are associated with an invariant cytoplasmic domain, potentially allowing these proteins to trigger common cellular responses through diverse extracellular signals. We studied the expression of the family by in situ hybridisation and immunohistochemistry for the conserved portion of the mRNA or protein. During mouse development, Pcdhgamma expression is highest in neural tissues, but is also present in some nonneural tissues. In the adult, Pcdhgamma expression is maintained at high levels in brain, in particular in hippocampus and in the Purkinje cells of the cerebellum, whereas it is downregulated in spinal cord. Using antibodies against the conserved cytoplasmic domain, we show that in cultured embryonic spinal cord neurons, Pcdhgamma protein is present initially in both axonal and dendritic growth cones. At later stages of differentiation in vitro, Pcdhgamma distribution becomes polarised to the somatodendritic compartment. We propose that members of the Pcdhgamma family may play roles in neuronal growth and maturation.