Project description:Tomosyn (STXBP5) is a non-canonical SNARE protein enriched in many secretory cells and implicated in regulation of exocytosis. In neurons, loss of tomosyn affects fusion of synaptic vesicles. Here, we examined the impact of the loss of tomosyn (STXBP5) and its close paralog, tomosyn-2 (STXBP5L), on the proteome of primary mouse hippocampal neurons. To do this, we used a mouse model carrying floxed alleles of Stxbp5 and Stxbp5l genes. Primary hippocampal neurons isolated from these mice were transduced with Cre-recombinase, which expression resulted in a nearly complete loss of the two genes expression. As control, we used neurons from the same culture preparation but expressing Cre-recombinase lacking DNA-binding domain (ΔCre). This dataset provides the comparison of proteome of control ('WT') and Stxbp5/5l double knockout ('DKO') neurons.
Project description:Synaptic activity drives changes in gene expression to promote long-lasting adaptations of neuronal structure and function. One example of such an adaptive response is the buildup of acquired neuroprotection, a synaptic activity- and gene transcription-mediated increase in the resistance of neurons against harmful conditions. A hallmark of acquired neuroprotection is the stabilization of mitochondrial structure and function. We therefore re-examined previously identified sets of synaptic activity-regulated genes to identify genes that are directly linked to mitochondrial function. In mouse and rat primary hippocampal cultures synaptic activity caused an upregulation of glycolytic genes and a concomitant downregulation of genes required for oxidative phosphorylation, mitochondrial biogenesis and maintenance. Changes in metabolic gene expression were induced by action potential bursting, but not by glutamate bath application activating extrasynaptic NMDA receptors. The specific pattern of gene expression changes suggested that synaptic activity promotes a shift of neuronal energy metabolism from oxidative phosphorylation toward aerobic glycolysis, also known as Warburg effect. The ability of neurons to upregulate glycolysis has, however, been debated. We therefore used FACS sorting to show that, in mixed neuron glia co-cultures, activity-dependent regulation of metabolic gene expression occurred in neurons. Changes in gene expression were accompanied by changes in the phosphorylation-dependent regulation of the key metabolic enzyme, pyruvate dehydrogenase. Finally, increased synaptic activity caused an increase in the ratio of L-lactate production to oxygen consumption in primary hippocampal cultures. Based on these data we suggest the existence of a synaptic activity-mediated neuronal Warburg effect that may promote mitochondrial homeostasis and neuroprotection.
2017-02-28 | GSE92275 | GEO
Project description:Study of activity-regulated genes in mouse primary cultured neurons
Project description:Gene expression profiles of Ngn3-overexpressing cultured hippocampal neurons was compared to the profile of the corresponding control populations. (neurons expressing GFP). Neurogenin3, a proneural transcription factor controlled by Notch receptor, is involved in hippocampal neuron differentiation and synapses, but little is known about the molecular bases of Ngn3 activity in neurons. Microarray analysis indicated that overexpression of Ngn3 upregulated a number of genes related with cytoskeleton dynamics. One of then was Fmn1 whose protein is associated with actin and microtubule cytoskeleton. Overexpression of the isoform Fmn1-Ib in cultured hippocampal neurons induced an increase in the number of primary dendrites and in the number of glutamatergic synaptic inputs without affecting GABAergic synapses resulting in a modification in the balance between excitation and inhibition. The same changes were provoked by overexpression of Ngn3. In addition downregulation of Fmn1 by the use of Fmn1-siRNAs impaired such morphological and synaptic changes induced by Ngn3 overexpression in neurons. These results reveal a previously unknown involvement of Formin1 in dendritic and synaptic plasticity as a key protein in the Nng3 signaling pathway that contributes to understanding of molecular mechanisms of the neuronal differentiation. Cultured hippocampal neurons were transduced using Sindbis virus bearing myc-tagged Ngn3 or GFP as control. Cells were lysed and total RNA was extracted.Gene expression profiles were obtained for each sample and compared
Project description:We studied the synaptic activity-regulated gene expression response in the human genetic background using cultured human iPSC-derived (hiPSCd) neuronal networks and networks of hiPSCd neurons mixed with mouse primary neurons. Our results confirm that genetic changes affect the synaptic activity-regulated gene program, proposing a functional mechanism how they have driven evolution of human cognitive abilities.
Project description:N-methyl-D-aspartate type glutamate receptors (NMDARs) are key mediators of synaptic activity-regulated gene transcription in neurons, both during development and in the adult brain. Developmental differences in the GluN2 subunit composition of NMDARs determines whether NMDARs activate the transcription factor CREB. However, whether the developmentally-regulated GluN3A subunit also modulates NMDAR-induced transcription was unknown. Here we show that knocking down GluN3A in rat hippocampal neurons promotes the inducible transcription of a subset of NMDAR-sensitive genes. This enhancement is mediated by the accumulation of phosphorylated p38 MAP kinase in the nucleus, which drives the activation of the transcription factor MEF2C and promotes the transcription of a subset of synaptic activity-induced genes including Bdnf and Arc. Our evidence that GluN3A negatively regulates MEF2C-dependent transcription reveals a novel mechanism by which NMDAR subunit composition confers specificity on the program of synaptic activity-regulated gene transcription in developing neurons.
Project description:Hippocampal synaptic plasticity is important for learning and memory formation. Homeostatic synaptic plasticity is a specific form of synaptic plasticity that is induced upon prolonged changes in neuronal activity to maintain network homeostasis. While astrocytes are important regulators of synaptic transmission and plasticity, it is largely unclear how they interact with neurons to regulate synaptic plasticity at the circuit level. Here, we show that neuronal activity blockade selectively increases the expression and secretion of IL-33 (interleukin-33) by astrocytes in the hippocampal cornu ammonis 1 (CA1) subregion. This IL-33 stimulates an increase in excitatory synapses and neurotransmission through the activation of neuronal IL-33 receptor complex and synaptic recruitment of the scaffold protein PSD-95. We found that acute administration of tetrodotoxin in hippocampal slices or inhibition of hippocampal CA1 excitatory neurons by optogenetic manipulation increases IL-33 expression in CA1 astrocytes. Furthermore, IL-33 administration in vivo promotes the formation of functional excitatory synapses in hippocampal CA1 neurons, whereas conditional knockout of IL-33 in CA1 astrocytes decreases the number of excitatory synapses therein. Importantly, blockade of IL-33 and its receptor signaling in vivo by intracerebroventricular administration of its decoy receptor inhibits homeostatic synaptic plasticity in CA1 pyramidal neurons and impairs spatial memory formation in mice. These results collectively reveal an important role of astrocytic IL-33 in mediating the negative-feedback signaling mechanism in homeostatic synaptic plasticity, providing insights into how astrocytes maintain hippocampal network homeostasis.