RESUMO
Brief visual experience causes rapid physiological changes in the visual cortex during early postnatal development. A possible mediator of these effects is the immediate early genes whose protein products are involved in the rapid response of neurons to transsynaptic stimulation. Here we report evidence that the levels of immediate early gene mRNAs in the visual cortex can be altered by manipulating the visual environment. Specifically, we find that brief (1 h) visual experience in dark-reared cats causes dramatic transient inductions of egr1, c-fos, and junB mRNAs in the visual cortex but not in the frontal cortex. Levels of c-jun and c-myc mRNAs are unaffected. These results suggest that select combinatorial interactions of immediate early gene proteins are an important step in the cascade of events through which visually elicited activity controls visual cortical development.
Assuntos
Lobo Frontal/fisiologia , Genes Reguladores , Visão Ocular/fisiologia , Córtex Visual/fisiologia , Percepção Visual/fisiologia , Animais , Northern Blotting , Gatos , Proteínas de Ligação a DNA/genética , Escuridão , Expressão Gênica , Genes jun , Genes myc , Luz , RNA/genética , RNA/isolamento & purificação , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Mapeamento por Restrição , Fatores de Transcrição/genética , Dedos de Zinco/genéticaRESUMO
Postnatal brain development involves interactions between extracellular signals and preprogrammed genetic events. Immediate early genes (IEGs) are a group of genes that are induced by extracellular signals and their protein products alter transcription by binding regulatory elements in other genes. Using Northern and slot blot analysis of total RNA isolated from visual cortex, frontal cortex, and cerebellum of cats, we have determined the postnatal development patterns of mRNA expression for 5 of these genes, c-fos, erg-1, c-jun, jun-B, and c-myc. Each gene had a distinct developmental pattern of mRNA expression, and for a given gene, these patterns were often different in different brain structures. These results suggest that temporal changes in the combinatorial interaction of different IEGs during early postnatal life are important for normal brain development.
Assuntos
Cerebelo/crescimento & desenvolvimento , Córtex Cerebral/crescimento & desenvolvimento , Regulação da Expressão Gênica , Genes Reguladores , Proto-Oncogenes , Envelhecimento , Animais , Northern Blotting , Gatos , Proteínas de Ligação a DNA/genética , Lobo Frontal/crescimento & desenvolvimento , Genes fos , Genes jun , Genes myc , Gliceraldeído-3-Fosfato Desidrogenases/genética , RNA/isolamento & purificação , RNA Mensageiro/genética , RNA Mensageiro/isolamento & purificação , Fatores de Transcrição/genética , Córtex Visual/crescimento & desenvolvimento , Dedos de Zinco/genéticaRESUMO
We have used RNA from human hypothalamus as template for the production of cDNAs encoding insulin-like growth factor II (IGF-II). The prohormone coding sequence of brain IGF-II RNA is identical to that found in liver; however, the 5' untranslated sequence of the brain cDNA has no homology to the 5' untranslated sequence of the previously reported liver cDNAs. By using hybridization to specific probes as well as a method based on the properties of RNase H, we found that the human IGF-II gene has at least three exons that encode alternative 5' untranslated regions and that are expressed in a tissue-specific manner. A probe specific to the brain cDNA 5' untranslated region hybridizes to a 6.0-kilobase transcript present in placenta, hypothalamus, adrenal gland, kidney, Wilms tumor, and a pheochromocytoma. The 5' untranslated sequence of the brain cDNA does not hybridize to a 5.3-kilobase transcript found in liver or to a 5.0-kb transcript found in pheochromocytoma. By using RNase H to specifically fragment the IGF-II transcripts into 3' and 5' fragments, we found that the RNAs vary in size due to differences in the 5' end but not the 3' end.