ABSTRACT
During corticogenesis, distinct classes of neurons are born from progenitor cells located in the ventricular and subventricular zones, from where they migrate towards the pial surface to assemble into highly organized layer-specific circuits. However, the precise and coordinated transcriptional network activity defining neuronal identity is still not understood. Here, we show that genetic depletion of the basic helix-loop-helix (bHLH) transcription factor E2A splice variant E47 increased the number of Tbr1-positive deep layer and Satb2-positive upper layer neurons at E14.5, while depletion of the alternatively spliced E12 variant did not affect layer-specific neurogenesis. While ChIP-Seq identified a big overlap for E12- and E47-specific binding sites in embryonic NSCs, including sites at the cyclin-dependent kinase inhibitor (CDKI) Cdkn1c gene locus, RNA-Seq revealed a unique transcriptional regulation by each splice variant. E47 activated the expression of the CDKI Cdkn1c through binding to a distal enhancer. Finally, overexpression of E47 in embryonic NSCs in vitro impaired neurite outgrowth, and overexpression of E47 in vivo by in utero electroporation disturbed proper layer-specific neurogenesis and upregulated p57(KIP2) expression. Overall, this study identifies E2A target genes in embryonic NSCs and demonstrates that E47 regulates neuronal differentiation via p57(KIP2).
Subject(s)
Alternative Splicing/genetics , Basic Helix-Loop-Helix Transcription Factors/metabolism , Cell Differentiation/genetics , Cerebral Cortex/embryology , Cyclin-Dependent Kinase Inhibitor p57/genetics , Neurons/cytology , Transcription Factor 3/metabolism , Animals , Base Sequence , Binding Sites/genetics , Cell Cycle/genetics , Cerebral Cortex/cytology , Chromatin/metabolism , Cyclin-Dependent Kinase Inhibitor p57/metabolism , Enhancer Elements, Genetic/genetics , Gene Expression Regulation, Developmental , Mice, Inbred C57BL , Neural Stem Cells/cytology , Neural Stem Cells/metabolism , Neurogenesis/genetics , Neurons/metabolism , Protein Binding , Transcription Factor 3/deficiency , Transcription, GeneticABSTRACT
Adult neural stem/precursor cells (NSPCs) of the subventricular zone (SVZ) are an endogenous source for neuronal replacement in CNS disease. However, adult neurogenesis is compromised after brain injury in favor of a glial cell fate, which is mainly attributed to changes in the NSPC environment. Yet, it is unknown how this unfavorable extracellular environment translates into a transcriptional program altering NSPC differentiation. Here, we show that genetic depletion of the transcriptional regulator Id3 decreased the number of astrocytes generated from SVZ-derived adult NSPCs in the cortical lesion area after traumatic brain injury. Cortical brain injury resulted in rapid BMP-2 and Id3 up-regulation in the SVZ stem cell niche. Id3(-/-) adult NSPCs failed to differentiate into BMP-2-induced astrocytes, while NSPCs deficient for the Id3-controlled transcription factor E47 readily differentiated into astrocytes in the absence of BMP-2. Mechanistically, E47 repressed the expression of several astrocyte-specific genes in adult NSPCs. These results identify Id3 as the BMP-2-induced transcriptional regulator, promoting adult NSPC differentiation into astrocytes upon CNS injury and reveal a molecular link between environmental changes and NSPC differentiation in the CNS after injury.
Subject(s)
Adult Stem Cells/metabolism , Astrocytes/metabolism , Cell Differentiation , Inhibitor of Differentiation Proteins/metabolism , Neural Stem Cells/metabolism , Transcription Factor 3/metabolism , Adult Stem Cells/pathology , Animals , Astrocytes/pathology , Bone Morphogenetic Protein 2/biosynthesis , Bone Morphogenetic Protein 2/genetics , Brain Injuries/genetics , Brain Injuries/metabolism , Brain Injuries/pathology , Cerebral Cortex/injuries , Cerebral Cortex/metabolism , Cerebral Cortex/pathology , Inhibitor of Differentiation Proteins/genetics , Mice , Mice, Knockout , Neural Stem Cells/pathology , Transcription Factor 3/genetics , Up-RegulationABSTRACT
Astrocytes modulate neuronal activity and inhibit regeneration. We show that cleaved p75 neurotrophin receptor (p75(NTR)) is a component of the nuclear pore complex (NPC) required for glial scar formation and reduced gamma oscillations in mice via regulation of transforming growth factor (TGF)-ß signaling. Cleaved p75(NTR) interacts with nucleoporins to promote Smad2 nucleocytoplasmic shuttling. Thus, NPC remodeling by regulated intramembrane cleavage of p75(NTR) controls astrocyte-neuronal communication in response to profibrotic factors.
