RESUMEN
During development, neural stem cells in the cerebral cortex, also known as radial glial cells (RGCs), generate excitatory neurons, followed by production of cortical macroglia and inhibitory neurons that migrate to the olfactory bulb (OB). Understanding the mechanisms for this lineage switch is fundamental for unraveling how proper numbers of diverse neuronal and glial cell types are controlled. We and others recently showed that Sonic Hedgehog (Shh) signaling promotes the cortical RGC lineage switch to generate cortical oligodendrocytes and OB interneurons. During this process, cortical RGCs generate intermediate progenitor cells that express critical gliogenesis genes Ascl1, Egfr, and Olig2. The increased Ascl1 expression and appearance of Egfr+ and Olig2+ cortical progenitors are concurrent with the switch from excitatory neurogenesis to gliogenesis and OB interneuron neurogenesis in the cortex. While Shh signaling promotes Olig2 expression in the developing spinal cord, the exact mechanism for this transcriptional regulation is not known. Furthermore, the transcriptional regulation of Olig2 and Egfr has not been explored. Here, we show that in cortical progenitor cells, multiple regulatory programs, including Pax6 and Gli3, prevent precocious expression of Olig2, a gene essential for production of cortical oligodendrocytes and astrocytes. We identify multiple enhancers that control Olig2 expression in cortical progenitors and show that the mechanisms for regulating Olig2 expression are conserved between the mouse and human. Our study reveals evolutionarily conserved regulatory logic controlling the lineage switch of cortical neural stem cells.
Asunto(s)
Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico , Corteza Cerebral , Receptores ErbB , Proteínas Hedgehog , Proteínas del Tejido Nervioso , Células-Madre Neurales , Neurogénesis , Factor de Transcripción 2 de los Oligodendrocitos , Factor de Transcripción PAX6 , Animales , Neurogénesis/fisiología , Corteza Cerebral/metabolismo , Corteza Cerebral/citología , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/metabolismo , Factores de Transcripción con Motivo Hélice-Asa-Hélice Básico/genética , Receptores ErbB/metabolismo , Receptores ErbB/genética , Ratones , Factor de Transcripción 2 de los Oligodendrocitos/metabolismo , Factor de Transcripción 2 de los Oligodendrocitos/genética , Proteínas del Tejido Nervioso/metabolismo , Proteínas del Tejido Nervioso/genética , Proteínas Hedgehog/metabolismo , Proteínas Hedgehog/genética , Factor de Transcripción PAX6/metabolismo , Factor de Transcripción PAX6/genética , Células-Madre Neurales/metabolismo , Células-Madre Neurales/citología , Proteínas de Homeodominio/metabolismo , Proteínas de Homeodominio/genética , Proteína Gli3 con Dedos de Zinc/metabolismo , Proteína Gli3 con Dedos de Zinc/genética , Proteínas del Ojo/metabolismo , Proteínas del Ojo/genética , Proteínas Represoras/metabolismo , Proteínas Represoras/genética , Factores de Transcripción Paired Box/metabolismo , Factores de Transcripción Paired Box/genética , Neuroglía/metabolismo , Neuroglía/citología , Regulación del Desarrollo de la Expresión Génica , Transducción de Señal , Bulbo Olfatorio/metabolismo , Bulbo Olfatorio/citología , Linaje de la Célula , HumanosRESUMEN
In situ transgenesis methods such as viruses and electroporation can rapidly create somatic transgenic mice but lack control over copy number, zygosity, and locus specificity. Here we establish mosaic analysis by dual recombinase-mediated cassette exchange (MADR), which permits stable labeling of mutant cells expressing transgenic elements from precisely defined chromosomal loci. We provide a toolkit of MADR elements for combination labeling, inducible and reversible transgene manipulation, VCre recombinase expression, and transgenesis of human cells. Further, we demonstrate the versatility of MADR by creating glioma models with mixed reporter-identified zygosity or with "personalized" driver mutations from pediatric glioma. MADR is extensible to thousands of existing mouse lines, providing a flexible platform to democratize the generation of somatic mosaic mice. VIDEO ABSTRACT.
Asunto(s)
Neoplasias Encefálicas/genética , Modelos Animales de Enfermedad , Marcación de Gen/métodos , Sitios Genéticos/genética , Glioma/genética , Mutagénesis Insercional/métodos , Transgenes/genética , Animales , Línea Celular Tumoral , Femenino , Células HEK293 , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Células-Madre Neurales/metabolismo , Recombinasas/metabolismo , TransfecciónRESUMEN
Generation of distinct cortical projection neuron subtypes during development relies in part on repression of alternative neuron identities. It was reported that the special AT-rich sequence-binding protein 2 (Satb2) is required for proper development of callosal neuron identity and represses expression of genes that are essential for subcerebral axon development. Surprisingly, Satb2 has recently been shown to be necessary for subcerebral axon development. Here, we unravel a previously unidentified mechanism underlying this paradox. We show that SATB2 directly activates transcription of forebrain embryonic zinc finger 2 (Fezf2) and SRY-box 5 (Sox5), genes essential for subcerebral neuron development. We find that the mutual regulation between Satb2 and Fezf2 enables Satb2 to promote subcerebral neuron identity in layer 5 neurons, and to repress subcerebral characters in callosal neurons. Thus, Satb2 promotes the development of callosal and subcerebral neurons in a cell context-dependent manner.