RESUMO
STXBP1 and SCN2A gene mutations are observed in patients with epilepsies, although the circuit basis remains elusive. Here, we show that mice with haplodeficiency for these genes exhibit absence seizures with spike-and-wave discharges (SWDs) initiated by reduced cortical excitatory transmission into the striatum. Mice deficient for Stxbp1 or Scn2a in cortico-striatal but not cortico-thalamic neurons reproduce SWDs. In Stxbp1 haplodeficient mice, there is a reduction in excitatory transmission from the neocortex to striatal fast-spiking interneurons (FSIs). FSI activity transiently decreases at SWD onset, and pharmacological potentiation of AMPA receptors in the striatum but not in the thalamus suppresses SWDs. Furthermore, in wild-type mice, pharmacological inhibition of cortico-striatal FSI excitatory transmission triggers absence and convulsive seizures in a dose-dependent manner. These findings suggest that impaired cortico-striatal excitatory transmission is a plausible mechanism that triggers epilepsy in Stxbp1 and Scn2a haplodeficient mice.
Assuntos
Corpo Estriado/metabolismo , Proteínas Munc18/genética , Canal de Sódio Disparado por Voltagem NAV1.2/genética , Neocórtex/metabolismo , Convulsões/genética , Transmissão Sináptica , Potenciais de Ação/efeitos dos fármacos , Animais , Anticonvulsivantes/farmacologia , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/patologia , Dioxóis/farmacologia , Eletroencefalografia , Epilepsia Tipo Ausência/tratamento farmacológico , Epilepsia Tipo Ausência/genética , Epilepsia Tipo Ausência/metabolismo , Epilepsia Tipo Ausência/fisiopatologia , Etossuximida/farmacologia , Regulação da Expressão Gênica , Haploinsuficiência , Interneurônios/efeitos dos fármacos , Interneurônios/metabolismo , Interneurônios/patologia , Camundongos , Camundongos Knockout , Proteínas Munc18/deficiência , Canal de Sódio Disparado por Voltagem NAV1.2/deficiência , Neocórtex/efeitos dos fármacos , Neocórtex/patologia , Vias Neurais/efeitos dos fármacos , Vias Neurais/metabolismo , Piperidinas/farmacologia , Receptores de AMPA/genética , Receptores de AMPA/metabolismo , Convulsões/metabolismo , Convulsões/fisiopatologia , Convulsões/prevenção & controle , Transdução de Sinais , Tálamo/efeitos dos fármacos , Tálamo/metabolismoRESUMO
The PAX6 gene is involved in ocular morphogenesis and is expressed in the developing central nervous system and numerous ocular tissues during development. PAX6 mutations have been detected in various ocular anomalies, including aniridia, Peters anomaly, corneal dystrophy, congenital cataracts, and foveal hypoplasia. However, it has not been identified in patients with optic-nerve malformations. Here, we identified novel mutations in eight pedigrees with optic-nerve malformations, including coloboma, morning glory disc anomaly, optic-nerve hypoplasia/aplasia, and persistent hyperplastic primary vitreous. A functional assay demonstrated that each mutation decreased the transcriptional activation potential of PAX6 through the paired DNA-binding domain. PAX6 and PAX2 are each thought to downregulate the expression of the other. Four of the detected mutations affected PAX6-mediated transcriptional repression of the PAX2 promoter in a reporter assay. Because PAX2 gene mutations were detected in papillorenal syndrome, alternation of PAX2 function by PAX6 mutations may affect phenotypic manifestations of optic-nerve malformations.
Assuntos
Proteínas de Homeodomínio/genética , Mutação , Nervo Óptico/anormalidades , Adulto , Animais , Sequência de Bases , Linhagem Celular , Pré-Escolar , Proteínas do Olho , Feminino , Genes Supressores , Humanos , Lactente , Masculino , Camundongos , Dados de Sequência Molecular , Fator de Transcrição PAX6 , Fatores de Transcrição Box Pareados , Linhagem , Regiões Promotoras Genéticas , Proteínas Repressoras , Ativação TranscricionalRESUMO
Remodeling of the extracellular matrix (ECM) is pivotal for various biological processes, including organ morphology and development. The Caenorhabditis elegans male tail has male-specific copulatory organs, the rays and the fan. Ray morphogenesis, which involves a rapid remodeling of the ECM, is an important model of morphogenesis, although its mechanism is poorly understood. ADAMTS (a disintegrin-like and metalloproteinase with thrombospondin type I motifs) is a novel metalloproteinase family that is thought to be an important regulator for ECM remodeling during development and pathological states. We report here that a new C. elegans ADAMTS family gene, adt-1, plays an important regulatory role in ray morphogenesis. Inactivation of the adt-1 gene resulted in morphological changes in the rays as well as the appearance of abnormal protuberances around the rays. In addition, mating ability was remarkably impaired in adt-1 deletion mutant males. Furthermore, we found that the green fluorescent protein reporter driven by the adt-1 promoter was specifically expressed throughout the rays in the male tail. We hypothesize that ADT-1 controls the ray extension process via remodeling of the ECM in the cuticle.
