RESUMO
Short seizure episodes are associated with remodeling of neuronal connections. One region where such reorganization occurs is the hippocampus, and in particular, the mossy fiber pathway. Using genetic and pharmacological approaches, we show here a critical role in vivo for tissue plasminogen activator (tPA), an extracellular protease that converts plasminogen to plasmin, to induce mossy fiber sprouting. We identify DSD-1-PG/phosphacan, an extracellular matrix component associated with neurite reorganization, as a physiological target of plasmin. Mice lacking tPA displayed decreased mossy fiber outgrowth and an aberrant band at the border of the supragranular region of the dentate gyrus that coincides with the deposition of unprocessed DSD-1-PG/phosphacan and excessive Timm-positive, mossy fiber termini. Plasminogen-deficient mice also exhibit the laminar band and DSD- 1-PG/phosphacan deposition, but mossy fiber outgrowth through the supragranular region is normal. These results demonstrate that tPA functions acutely, both through and independently of plasmin, to mediate mossy fiber reorganization.
Assuntos
Proteoglicanas de Sulfatos de Condroitina/fisiologia , Fibrinolisina/metabolismo , Hipocampo/fisiologia , Fibras Nervosas/fisiologia , Neuritos/fisiologia , Plasminogênio/metabolismo , Convulsões/fisiopatologia , Ativador de Plasminogênio Tecidual/metabolismo , Tonsila do Cerebelo/efeitos dos fármacos , Tonsila do Cerebelo/fisiologia , Tonsila do Cerebelo/fisiopatologia , Animais , Hipocampo/fisiopatologia , Hipocampo/ultraestrutura , Ácido Caínico/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fibras Nervosas/efeitos dos fármacos , Fibras Nervosas/ultraestrutura , Neuritos/efeitos dos fármacos , Neuritos/ultraestrutura , Plasminogênio/deficiência , Plasminogênio/genética , Proteínas Tirosina Fosfatases Classe 5 Semelhantes a Receptores , Convulsões/induzido quimicamente , Ativador de Plasminogênio Tecidual/deficiência , Ativador de Plasminogênio Tecidual/genéticaRESUMO
Single-nucleotide polymorphisms (SNPs) are the most frequent type of variation in the human genome, and they provide powerful tools for a variety of medical genetic studies. In a large-scale survey for SNPs, 2.3 megabases of human genomic DNA was examined by a combination of gel-based sequencing and high-density variation-detection DNA chips. A total of 3241 candidate SNPs were identified. A genetic map was constructed showing the location of 2227 of these SNPs. Prototype genotyping chips were developed that allow simultaneous genotyping of 500 SNPs. The results provide a characterization of human diversity at the nucleotide level and demonstrate the feasibility of large-scale identification of human SNPs.
Assuntos
Mapeamento Cromossômico/métodos , Desoxirribonucleotídeos/genética , Técnicas Genéticas , Genoma Humano , Genótipo , Polimorfismo Genético , Algoritmos , Alelos , DNA Complementar , Bases de Dados Factuais , Fosfatos de Dinucleosídeos , Expressão Gênica , Marcadores Genéticos , Variação Genética , Heterozigoto , Homozigoto , Humanos , Dados de Sequência Molecular , Hibridização de Ácido Nucleico , Reação em Cadeia da Polimerase , Reprodutibilidade dos Testes , Análise de Sequência de DNA , Sitios de Sequências RotuladasRESUMO
Tissue plasminogen activator (tPA) may play a deleterious role after brain injury. Here, we compared the response to traumatic brain injury in tPA knockout (KO) and wildtype (WT) mice after controlled cortical impact. At 6 h after trauma, blood-brain barrier permeability was equally increased in all mice. However, by 24 h specific gravity measurements of brain edema were significantly worse in WT mice than in KO mice. At 1 and 2 days post-trauma, mice showed deficits in rotarod performance, but by day 7 all mice recovered motor function and there were no differences between WT and KO mice. At 7 days, cortical lesion volumes were significantly reduced in KO mice compared with WT mice. However, there were no significant differences in CA3 hippocampal neuron survival. These data suggest that tPA amplifies cortical brain damage and edema in this mouse model of traumatic brain injury.
Assuntos
Edema Encefálico/fisiopatologia , Lesões Encefálicas/fisiopatologia , Córtex Cerebral/lesões , Ativador de Plasminogênio Tecidual/genética , Animais , Barreira Hematoencefálica/fisiologia , Edema Encefálico/patologia , Lesões Encefálicas/patologia , Sobrevivência Celular/fisiologia , Córtex Cerebral/irrigação sanguínea , Córtex Cerebral/patologia , Corantes/farmacocinética , Azul Evans/farmacocinética , Matriz Extracelular/fisiologia , Hipocampo/irrigação sanguínea , Hipocampo/lesões , Hipocampo/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Atividade Motora , Neurônios/patologia , Recuperação de Função FisiológicaRESUMO
Prion propagation involves conversion of host PrP(C) to a disease-related isoform, PrP(Sc), which accumulates during disease and is the principal component of the transmissible agent. Proteolysis seems to play an important role in PrP metabolism. Plasminogen, a serine protease precursor, has been shown to interact with PrP(Sc). Plasminogen can be proteolytically activated by tissue plasminogen activator (tPA). Recent reports imply a crosstalk between tPA-mediated plasmin activation and PrP. In our study, both tPA activity and tPA gene expression were found elevated in TSE-infected brains as compared to their normal counterparts. Furthermore, it was proved that PrP(Sc), in contrast to PrP(C), could not be degraded by plasmin. In addition, it was observed that TSE symptoms and subsequent death of plasminogen-deficient and tPA-deficient scrapie challenged mice preceded that of wild-type controls. Our data imply that enhanced tPA activity observed in prion infected brains may reflect a neuro-protective response.