RESUMO
We found the voltage-gated K+ channel Kv12.2 to be a potent regulator of excitability in hippocampal pyramidal neurons. Genetic deletion and pharmacologic block of Kv12.2 substantially reduced the firing threshold of these neurons. Kv12.2-/- (also known as Kcnh3-/-) mice showed signs of persistent neuronal hyperexcitability including frequent interictal spiking, spontaneous seizures and increased sensitivity to the chemoconvulsant pentylenetetrazol.
Assuntos
Epilepsia/fisiopatologia , Canais de Potássio Éter-A-Go-Go/metabolismo , Hipocampo/fisiopatologia , Neurônios/fisiologia , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Animais , Linhagem Celular , Células Cultivadas , Convulsivantes/toxicidade , Epilepsia/induzido quimicamente , Epilepsia/genética , Canais de Potássio Éter-A-Go-Go/antagonistas & inibidores , Canais de Potássio Éter-A-Go-Go/genética , Feminino , Hipocampo/efeitos dos fármacos , Humanos , Técnicas In Vitro , Masculino , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neurônios/efeitos dos fármacos , Pentilenotetrazol/toxicidade , Células Piramidais/efeitos dos fármacos , Células Piramidais/fisiopatologia , Convulsões/induzido quimicamente , Convulsões/genética , Convulsões/fisiopatologia , Gravação em Vídeo , XenopusRESUMO
The intermediate filament protein keratin 8 (K8) is critical for the development of most mouse embryos beyond midgestation. We find that 68% of K8-/- embryos, in a sensitive genetic background, are rescued from placental bleeding and subsequent death by cellular complementation with wild-type tetraploid extraembryonic cells. This indicates that the primary defect responsible for K8-/- lethality is trophoblast giant cell layer failure. Furthermore, the genetic absence of maternal but not paternal TNF doubles the number of viable K8-/- embryos. Finally, we show that K8-/- concepti are more sensitive to a TNF-dependent epithelial apoptosis induced by the administration of concanavalin A (ConA) to pregnant mothers. The ConA-induced failure of the trophoblast giant cell barrier results in hematoma formation between the trophoblast giant cell layer and the embryonic yolk sac in a phenocopy of dying K8-deficient concepti in a sensitive genetic background. We conclude the lethality of K8-/- embryos is due to a TNF-sensitive failure of trophoblast giant cell barrier function. The keratin-dependent protection of trophoblast giant cells from a maternal TNF-dependent apoptotic challenge may be a key function of simple epithelial keratins.