Unknown,Transcriptomics,Genomics,Proteomics

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Dynamics and Function of Distal Regulatory Elements during Neurogenesis and Neuroplasticity

ABSTRACT: Gene regulation in mammals involves a complex interplay between promoter and distal regulatory elements that function in concert to drive precise spatio-temporal gene expression programs. However, the dynamics of distal gene regulatory elements and its function in transcriptional reprogramming that underlies neurogenesis and neuronal activity remain largely unknown. Here we use a combinatorial analysis of genomewide datasets for chromatin accessibility (FAIRE-Seq) and enhancer mark H3K27ac to reveal a highly dynamic nature of chromatin accessibility during neurogenesis that gets restricted to certain genomic regions as neurons acquire a post-mitotic, terminally differentiated state. We further reveal that the distal open regions serve as target sites of distinct transcription factors that function in a stage-specific manner to contribute to the transcriptional program underlying neuronal commitment and maturation. A prolonged NMDA-driven neural activity results in epigenetic reprogramming at a large number of distal regulatory elements as well as dramatic reorganization of super-enhancers that in turn mediate critical transcriptional responses. Taken together, these findings reveal dynamics of distal regulatory landscape during neurogenesis and uncover novel regulatory elements that function in concert with epigenetic mechanisms and transcription factors to generate transcriptome underlying neuronal development and function. FAIRE-Seq and H3K27ac profiles for three stages on neuronal differentation viz. neuronal progenitors, day 1 neurons and day 10 neurons, were generated to understand the dynamics of accessible and ehancer chromatin landscape. Along with this we also generated RNASeq and H3K27ac profiles for day 10 neurons upon control and NMDA treatment.

ORGANISM(S): Mus musculus

SUBMITTER: Sudhir Thakurela

PROVIDER: E-GEOD-65713 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Primary cortical neurons were isolated from E15 mice and after 5 days in vitro were untreated or treated for 24 h with mesenchymal stem cell conditioned medium and then untreated or treated for a further 24 h with NMDA. Neuron gene expression was profiled and compared between the four different conditions (neurons, neurons+MSC cm, neurons+NMDA, neurons+MSC cm+NMDA) to investigate the molecular mechanisms of MSC neuroprotection. Mesenchymal stem cells (MSC) promote functional recovery in experimental models of central nervous system (CNS) pathology and are currently being tested in clinical trials for stroke, multiple sclerosis and CNS injury. Their beneficial effects are attributed to activation of endogenous CNS repair processes and immune regulation but their mechanisms of action are poorly understood. Here we investigated the neuroprotective effects of MSC in simplified MSC-neuron co-culture systems and in mice using models of glutamate excitotoxicity. MSC protected primary cortical neurons against glutamate (NMDA) receptor-induced death and conditioned medium from MSC (MSC cm), but not control NIH3T3 cells, was sufficient for this effect. MSC cm neuroprotection in mouse cortical neurons was reduced by neutralizing antibodies to bFGF and associated with altered gene expression in neurons towards an immature phenotype as well as reduced neuronal Grin1, Grin2a and Grin2b mRNA levels in response to NMDA stimulation. Further, MSC cm neuroprotection in rat retinal ganglion cells was associated with absence of glutamate-induced calcium influx. Adoptive transfer of EGFP+MSC in a mouse kainic acid seizure model reduced CA3 neuron damage and hippocampal astrocytosis and resulted in the increased expression of neuronal genes that are upregulated by MSC cm, Bmi1, Ddx4, Ezh1, in the hippocampus. These results show that MSC mediate direct neuroprotection against glutamate excitotoxicity by secreting bFGF, reducing glutamate receptor expression and function and altering neuron gene expression towards an immature pattern, and provide evidence for a link between the therapeutic effects of MSC and the activation of endogenous repair processes following CNS injury. In vitro cultures primary cortical neurons from mice were protected from glutamate excitotoxicity when pre-treated with MSC cm. Global gene expression changes induced in neurons before and after treatment with MSC cm and/or NMDA were investigated using a cDNA spotted macroarray filter. Four samples were analysed in duplicate: neurons alone (untreated), neurons+MSC cm, neurons+NMDA, neurons+MSC cm+NMDA.

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Dynamics and Function of Distal Regulatory Elements during Neurogenesis and Neuroplasticity

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