Project description:The histone deacetylase HDAC2, which negatively regulates neuronal plasticity and synaptic gene expression, is upregulated both in Alzheimer’s disease (AD) patients and mouse models (Graff et al., 2012). Therapeutics targeting HDAC2 are speculated to be a promising avenue for ameliorating AD related cognitive impairment. However, attempts to generate HDAC2-specific inhibitors have not been successful. Here, we take a novel approach utilizing integrative genomics to identify proteins that mediate HDAC2 recruitment to synaptic plasticity genes. Functional screening revealed that knockdown of the transcription factor Sp3 phenocopied HDAC2 knockdown, and that Sp3 facilitated the recruitment of HDAC2 to synaptic genes. Importantly, like HDAC2, Sp3 expression was elevated in AD patients and mouse models, where Sp3 knockdown ameliorated synaptic dysfunction. Furthermore, exogenous expression of an HDAC2 fragment containing the Sp3 binding domain fully restored synaptic plasticity and memory in a mouse model with severe neurodegeneration. Our findings indicate that targeting the HDAC2-Sp3 complex could enhance synaptic and cognitive function, without affecting HDAC2 function in other processes.
Project description:Brain-Derived Neurotrophic Factor (BDNF) is crucial for neuronal survival, differentiation, synaptic plasticity, memory formation, and neurocognitive health. Molecular mechanisms of BDNF promoting cellular survival and synaptic plasticity have been intensely studied, yet its role in genome regulation is obscure. Using human induced pluripotent stem cell (hiPSC)-derived neurons via lentiviral delivery of the neuronal transcription factor Ngn2, we performed a temporal profiling (1h, 6h and 10h) of chromatin accessibility upon BDNF treatment or depolarization (KCl) to identify BDNF-specific chromatin-to-gene expression programs.
Project description:Brain-Derived Neurotrophic Factor (BDNF) is crucial for neuronal survival, differentiation, synaptic plasticity, memory formation, and neurocognitive health. Molecular mechanisms of BDNF promoting cellular survival and synaptic plasticity have been intensely studied, yet its role in genome regulation is obscure. Using human induced pluripotent stem cell (hiPSC)-derived neurons via lentiviral delivery of the neuronal transcription factor Ngn2, we performed a temporal profiling (1h, 6h and 10h) of chromatin accessibility upon BDNF treatment or depolarization (KCl) to identify BDNF-specific chromatin-to-gene expression programs.
Project description:Regulation of neurons by circadian clock genes is thought to contribute to the maintenance of neuronal functions that ultimately underlie animal behavior. However, the impact of circadian genes on cellular and molecular mechanisms that influnce synaptic plasticity and cognitive function remain to be identified. Here, we show that conditional deletion of the circadian gene Timeless in the adult forebrain leads to an impairment in working and fear memory in mice. These cognitive phenotypes were accompanied with LTP attenuation of hippocampal Schaffer-collateral synapses. We discovered TIMELESS protein acts as a transcriptional factor regulating phosphodiesterase 4B (PDE4B) expression. Through Pde4b transcription, TIMELESS negatively regulates cAMP signaling to modulate AMPA receptor GluA1 function and fine-tune synaptic plasticity. Our data provide insights into the neuron-specific function of mammalian TIMELESS by defining a mechanism that regulates synaptic plasticity and cognitive function.
Project description:Multiple sclerosis (MS) is an inflammatory disease of the central nervous system and is generally considered to be autoimmune in nature. We previously demonstrated that the transcription factor Sp3 is significantly down-regulated in immune cells from MS patients. The potential role of Sp3 down-regulation in MS pathogenesis is not well understood. The function of endogenous Sp3 was assessed in vitro after siRNA-mediated knockdown of its transcript in Jurkat cells. Sp3 protein levels were reduced an average of 70%. ELISA studies demonstrated decreased endogenous production of IL-10 and TGFβ1 and increased endogenous production of TNFα (p<0.05 in all assays). Subsequent microarray analysis demonstrated significantly altered expression of 36 genes (p<0.001 for each gene) compared with control samples. Analysis showed differential expression (p<0.005) of 8 gene pathways. Many of the genes and pathways that were regulated by Sp3 are involved in immune function, specifically with regard to apoptosis, cell-to-cell adhesion, integrin signaling, T-cell differentiation, and cytokine production. This study identifies mechanisms by which Sp3 may regulate immune function and suggests a basis for its potential contribution to MS disease pathogenesis. Experiment Overall Design: Two Sp3 siRNA knockdown groups (siRNA Sp3 #2: n=3, and #6: n=3) were clustered together into the Treated condition, and the two control groups (siRNA for GAPDH: n=3, and Non-transfected cells: n=3)were assembled to constitute the Control condition. Thus a total of 12 arrays (6 Controls and 6 treated) were used in this experiment.
Project description:Multiple sclerosis (MS) is an inflammatory disease of the central nervous system and is generally considered to be autoimmune in nature. We previously demonstrated that the transcription factor Sp3 is significantly down-regulated in immune cells from MS patients. The potential role of Sp3 down-regulation in MS pathogenesis is not well understood. The function of endogenous Sp3 was assessed in vitro after siRNA-mediated knockdown of its transcript in Jurkat cells. Sp3 protein levels were reduced an average of 70%. ELISA studies demonstrated decreased endogenous production of IL-10 and TGFβ1 and increased endogenous production of TNFα (p<0.05 in all assays). Subsequent microarray analysis demonstrated significantly altered expression of 36 genes (p<0.001 for each gene) compared with control samples. Analysis showed differential expression (p<0.005) of 8 gene pathways. Many of the genes and pathways that were regulated by Sp3 are involved in immune function, specifically with regard to apoptosis, cell-to-cell adhesion, integrin signaling, T-cell differentiation, and cytokine production. This study identifies mechanisms by which Sp3 may regulate immune function and suggests a basis for its potential contribution to MS disease pathogenesis. Keywords: siRNA knockdown; Jurkat T-cells; Multiple Sclerosis
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.
Project description:The functional output of the hippocampus, a brain region subserving memory processes, depends on highly orchestrated cellular and molecular processes that regulate synaptic plasticity throughout life. The structural requirements of such plasticity and molecular processes involved in this regulation are poorly understood. Specific molecules, including tissue inhibitor of metalloproteinases-2 (TIMP2) have been implicated in serving a pro-plasticity role in the hippocampus, a role that decreases with brain aging. Here, we report that TIMP2 is highly expressed by neurons within the hippocampus and its loss drives changes in cellular programs related to adult neurogenesis and dendritic spine turnover with corresponding impairments in hippocampus-dependent memory. We find that TIMP2 regulates accumulation of extracellular matrix (ECM) around synapses in the hippocampus with concomitant hindrance in migration of newborn neurons through a denser ECM network. A conditional TIMP2 KO mouse reveals that neuronal TIMP2 regulates adult neurogenesis, accumulation of ECM, and ultimately hippocampus-dependent memory. Our results define a mechanism whereby hippocampus-dependent function is regulated by TIMP2 and its interactions with the ECM to regulate diverse processes associated with synaptic plasticity.
Project description:Ongoing neuronal activity during development and plasticity acts to refine synaptic connections and contributes to the induction of plasticity and ultimately long term memory storage. Activity-dependent post-transcriptional control of mRNAs occurs through transport to axonal and dendritic compartments, local translation, and mRNA stability. We have identified a mechanism that contributes to activity-dependent regulation of mRNA stability during synaptic plasticity. In this study we demonstrate rapid, post-transtriptional control over process-enriched mRNAs by neuronal activity. Systematic analysis of the 3'-UTRs of destablized transcripts, identifies enrichment in sequence motifs corresponding to miRNA binding sites. The miRNAs that were identified, miR-326-3p/miR-330-5p, miR-485-5p, miR-666-3p, and miR-761 are predicted to regulate networks of genes important in plasticity and development. We find that these miRNAs are developmentally regulated in the hippocampus, many increasing by postnatal day 14. We further show that miR-485-5p controls NGF-induced neurite outgrowth in PC12 cells, tau expression, and axonal development in hippocampal neurons. miRNAs can function at the synapse to rapidly control and affect short- and long-term changes at the synapse. These processes likely occur during refinement of synaptic connections and contribute to the induction of plasticity and learning and memory. 12 hippocampal cell culture samples analysed, 3 coverslips pooled per sample. Treatments are as follows: Block: an inhibitor cocktail containing 50 µM D-APV, 40 µM CNQX, and 100 nM TTX for 3 hrs Activity: 50 µM bicuculline (BiC)/500 µM 4-Aminopyridine ActD: 25 µM actinomycin D
Project description:Ongoing neuronal activity during development and plasticity acts to refine synaptic connections and contributes to the induction of plasticity and ultimately long term memory storage. Activity-dependent post-transcriptional control of mRNAs occurs through transport to axonal and dendritic compartments, local translation, and mRNA stability. We have identified a mechanism that contributes to activity-dependent regulation of mRNA stability during synaptic plasticity. In this study we demonstrate rapid, post-transtriptional control over process-enriched mRNAs by neuronal activity. Systematic analysis of the 3'-UTRs of destablized transcripts, identifies enrichment in sequence motifs corresponding to miRNA binding sites. The miRNAs that were identified, miR-326-3p/miR-330-5p, miR-485-5p, miR-666-3p, and miR-761 are predicted to regulate networks of genes important in plasticity and development. We find that these miRNAs are developmentally regulated in the hippocampus, many increasing by postnatal day 14. We further show that miR-485-5p controls NGF-induced neurite outgrowth in PC12 cells, tau expression, and axonal development in hippocampal neurons. miRNAs can function at the synapse to rapidly control and affect short- and long-term changes at the synapse. These processes likely occur during refinement of synaptic connections and contribute to the induction of plasticity and learning and memory. 4 samples analysed, 3 coverslips pooled per sample. Mouse DRG neuron cell bodies and axons were separated in multicompartment cell cultures allowing electrical stimulation of axons, growing under a high-resistance partition between compartments, through platinum electrodes in the lid of the culture dish (Reference: http://www.ncbi.nlm.nih.gov/pubmed/9295372)