ABSTRACT
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.
Subject(s)
Basic Helix-Loop-Helix Transcription Factors , Cerebral Cortex , ErbB Receptors , Hedgehog Proteins , Nerve Tissue Proteins , Neural Stem Cells , Neurogenesis , Oligodendrocyte Transcription Factor 2 , PAX6 Transcription Factor , Animals , Neurogenesis/physiology , Cerebral Cortex/metabolism , Cerebral Cortex/cytology , Basic Helix-Loop-Helix Transcription Factors/metabolism , Basic Helix-Loop-Helix Transcription Factors/genetics , ErbB Receptors/metabolism , ErbB Receptors/genetics , Mice , Oligodendrocyte Transcription Factor 2/metabolism , Oligodendrocyte Transcription Factor 2/genetics , Nerve Tissue Proteins/metabolism , Nerve Tissue Proteins/genetics , Hedgehog Proteins/metabolism , Hedgehog Proteins/genetics , PAX6 Transcription Factor/metabolism , PAX6 Transcription Factor/genetics , Neural Stem Cells/metabolism , Neural Stem Cells/cytology , Homeodomain Proteins/metabolism , Homeodomain Proteins/genetics , Zinc Finger Protein Gli3/metabolism , Zinc Finger Protein Gli3/genetics , Eye Proteins/metabolism , Eye Proteins/genetics , Repressor Proteins/metabolism , Repressor Proteins/genetics , Paired Box Transcription Factors/metabolism , Paired Box Transcription Factors/genetics , Neuroglia/metabolism , Neuroglia/cytology , Gene Expression Regulation, Developmental , Signal Transduction , Olfactory Bulb/metabolism , Olfactory Bulb/cytology , Cell Lineage , HumansABSTRACT
Neural stem cells (NSCs) in the prenatal neocortex progressively generate different subtypes of glutamatergic projection neurons. Following that, NSCs have a major switch in their progenitor properties and produce γ-aminobutyric acid (GABAergic) interneurons for the olfactory bulb (OB), cortical oligodendrocytes, and astrocytes. Herein, we provide evidence for the molecular mechanism that underlies this switch in the state of neocortical NSCs. We show that, at around E16.5, mouse neocortical NSCs start to generate GSX2-expressing (GSX2+) intermediate progenitor cells (IPCs). In vivo lineage-tracing study revealed that GSX2+ IPC population gives rise not only to OB interneurons but also to cortical oligodendrocytes and astrocytes, suggesting that they are a tri-potential population. We demonstrated that Sonic hedgehog signaling is both necessary and sufficient for the generation of GSX2+ IPCs by reducing GLI3R protein levels. Using single-cell RNA sequencing, we identify the transcriptional profile of GSX2+ IPCs and the process of the lineage switch of cortical NSCs.