Project description:Neural stem cells divide throughout adulthood in neurogenic niches - the dentate gyrus of the hippocampus and the subventricular zone (SVZ) - producing progenitor cells and new neurons. Moreover, stem cells self-renew, thus preserving their pool. The number of stem/progenitor cells in the neurogenic niches declines with age. We have previously demonstrated that the cyclin-dependent kinase inhibitor p16Ink4a maintains, in aged mice, the pool of dentate gyrus stem cells by preventing their activation after a neurogenic stimulus such as exercise (running). We showed that, although p16Ink4a ablation by itself does not activate stem/progenitor cells, exercise strongly induced stem cell proliferation in p16Ink4a knockout dentate gyrus, but not in wild-type. As p16Ink4a regulates stem cell self-renewal during aging, we sought to profile the dentate gyrus transcriptome from p16Ink4a wild-type and knockout aged mice, either sedentary or running for 12 days. By pairwise comparisons of differentially expressed genes and by correlative analyses through the DESeq2 software, we identified genes regulated by p16Ink4a deletion, either without stimulus (running) added, or following running. The p16Ink4a knockout basic gene signature, i.e. in sedentary mice, involves up-regulation of apoptotic, neuroinflammation- and synaptic activity-associated genes, suggesting a reactive cellular state. Conversely, another set of 106 genes we identified, whose differential expression specifically reflects the pattern of proliferative response of p16 knockout stem cells to running, are involved in processes regulating stem cells activation, i.e., synaptic function, neurotransmitter metabolism, stem cell proliferation control, and regulation of ROS levels. Moreover, we analyzed the regulation of these stem cell-specific genes after a second running stimulus. Surprisingly, the second running neither activated stem cell proliferation in the p16Ink4a knockout dentate gyrus nor changed the expression of these genes, confirming that they are correlated to the stem cell reactivity to stimulus.

Project description:We sought to find molecular signatures of the SGZ cell types, and to characterize the molecular pathways and transcription factor cascades that define the neurogenic niche. We used laser capture microdissection and DNA microarrays to profile gene expression in the inner (SGZ) and outer portions of the dentate gyrus (DG). Since the vast majority of the cells in the DG are mature granule cells, we compared the expression of the inner and outer portions to reveal molecular markers for the less numerous populations of the SGZ. This data set is part of a larger study assessing conserved molecular signatures of neurogenesis in the hippocampal subgranular zone of rodents and primates. Using a combination of selective SGZ transcriptional profiling with laser microdissection and DNA microarrays as well as in situ hybridization (ISH), we developed an extensive molecular characterization of the mouse SGZ, identifying 367 genes enriched in the SGZ compared to mature granule neurons. These genes displayed a wide range of cellular expression patterns reflecting the cellular milieu of the SGZ, including progenitor and dividing cells, immature granule cells, astrocytes, oligodendrocytes, and GABAergic interneurons. We next used a comparable microarray data set in rhesus monkey that profiled the SGZ across postnatal development to identify genes related to developmentally regulated granule cell neurogenesis. The rhesus monkey SGZ showed highly significant similarity to mouse, whereas network analysis of these data identified SGZ-enriched gene sets with different temporal profiles reflecting differential time-courses for maturation of glia and granule neurons. One neurogenesis-related gene network showed a steady decrease in expression across postnatal rhesus development from birth to adulthood. This temporal pattern is highly correlated with the number of proliferating cells in the dentate gyrus, and the neurogenic transcription factors Sox4 and Sox11 are central hub genes for this gene network. A number of the genes in this network showed a similar postnatal downregulation in mouse, suggesting a general conservation of molecular mechanisms underlying developmental and adult neurogenesis in rodents and primates. Primate data available at: http://www.blueprintnhpatlas.org/ Brains from 10- to 11-week-old C57BL/6 male mice housed in three conditions (no running, 4 days of running, 30 days of running) were sectioned and the dentate gyrus was isolated. For each brain, the inner granule cell layer (containing the subgranular zone) and outer GCL were separated using laser capture microdissection, and RNA from each region was collected and processed as described in the protocols.

Project description:Exercise improves brain function enhancing neuronal plasticity and cognitive enhancement. For voluntary resistance wheel running (RWR) exercise, with a load of 30% of body weight, we reported enhancement of neurogenesis and spatial memory associated with hippocampal brain-derived neurotrophic factor (BDNF) signaling compared to wheel running (WR) without a load (Lee et al., 2012; Lee et al., 2013). Despite these new evidences, mechanisms for RWR-induced improvement of hippocampal function remained to be clarified. In the present study, we have utilized the high-throughput DNA microarray approach to gain deep insight into molecular mechanisms underlying these changes that could be novel targets of RWR-induced hippocampal plasticity. To do so, whole genome (4x44K) high-density oligonucleotide microarrays were used to monitor the expression level of gene transcripts in the hippocampus of rats voluntary running for 4 weeks in comparison with sedentary animals. These rats showed a significant decrease in average running distance although average work levels immensely increased 12-fold in the RWR group, resulting in muscular adaptation for the fast-twitch plantaris muscle. DNA microarray analysis revealed that 122 (sedentary x WR) and 157 (sedentary x RWR) genes were up-regulated (> 1.5-fold change) as compared with 97 (sedentary x WR) and 467 (sedentary x RWR) down-regulated genes (< 0.75-fold change). Functional categorization using the Ingenuity Pathway Analysis (IPA) revealed expression pattern changes in the major categories of disease and disorders, molecular functions and physiological system development and function. Among these, RWR up-regulated genes such as NFATc1, AVPR1A and FGFR4, which are crucial role for neuronal development and its functions. The down-regulated inflammatory cytokines (IL1B, IL10, IL2RA, TNF) and chemokines (CXCL1, CXCL9, CXCL10, CCL2, CCL13, CCR4) might be important to neuronal dysfunction and vulnerability. Taken together, these gene candidates are suggested to play a critical role in hippocampal plasticity. This is a first study presenting not only new information into the voluntary RWR influenced transcriptome in the rat hippocampus, but also provides a hypothesis for the RWR influenced enhancement in brain function. 10-week-old male Wistar rats were randomly allocated to three groups: (1) housed in standard cages and used as non-active controls (sedentary, n = 10), (2) wheel running with no resistance (WR, n = 8), and (3) housed in cages with resistance running wheels with an adjustable resistance (RWR, n = 8). Rats of both running wheel groups (WR and RWR) were housed individually and had free access to a specially designed running wheel apparatus for 24 h/day. Between 08:00 and 12:00 on the day after the final day of exercise, the animals were immediately decapitated using a guillotine. The hippocampi were rapidly dissected, snap frozen in liquid nitrogen and stored at —80°C prior to further analysis. The deep-frozen hippocampi were transferred to a precooled (in liquid nitrogen) mortar and ground with a pestle to a very fine powder with liquid nitrogen. Total RNA was extracted and validated followed by checking subsequently synthesized cDNA by RT-PCR. A rat 4x44K whole genome oligo DNA microarray chip was used for global gene expression analysis using the hippocampi. Fluorescently labeled targets of Sed, WR and RWR samples were hybridized to the same microarray slide with 60-mer probes. A flip labeling (dye swap or reverse labeling with Cy3 and Cy5 dyes) procedure was followed to nullify the dye bias associated with unequal incorporation of the two Cy dyes into cDNA. Briefly, to select differentially expressed genes, we identified genes that were up regulated in chip 1 (Cy3/Cy5 label for sedentary and WR, respectively) but down regulated in chip 2 (Cy3/Cy5 label for WR and sedentary, respectively) for the hippocampus. The same selection criteria were applied for chips 3-4 (sedentary and RWR). Hybridization and wash processes were performed according to the manufacturer’s instructions, and hybridized microarrays were scanned using an agilent microarray scanner. The functional and network analysis were generated through the use of IPA (Ingenuity® Systems, www.ingenuity.com). To validate gene changes in array data and test the BDNF signaling-related molecules and expression of select transcripts were determined by quantitative real-time RT-PCR.

Project description:Exercise improves brain function enhancing neuronal plasticity and cognitive enhancement. For voluntary resistance wheel running (RWR) exercise, with a load of 30% of body weight, we reported enhancement of neurogenesis and spatial memory associated with hippocampal brain-derived neurotrophic factor (BDNF) signaling compared to wheel running (WR) without a load (Lee et al., 2012; Lee et al., 2013). Despite these new evidences, mechanisms for RWR-induced improvement of hippocampal function remained to be clarified. In the present study, we have utilized the high-throughput DNA microarray approach to gain deep insight into molecular mechanisms underlying these changes that could be novel targets of RWR-induced hippocampal plasticity. To do so, whole genome (4x44K) high-density oligonucleotide microarrays were used to monitor the expression level of gene transcripts in the hippocampus of rats voluntary running for 4 weeks in comparison with sedentary animals. These rats showed a significant decrease in average running distance although average work levels immensely increased 12-fold in the RWR group, resulting in muscular adaptation for the fast-twitch plantaris muscle. DNA microarray analysis revealed that 122 (sedentary x WR) and 157 (sedentary x RWR) genes were up-regulated (> 1.5-fold change) as compared with 97 (sedentary x WR) and 467 (sedentary x RWR) down-regulated genes (< 0.75-fold change). Functional categorization using the Ingenuity Pathway Analysis (IPA) revealed expression pattern changes in the major categories of disease and disorders, molecular functions and physiological system development and function. Among these, RWR up-regulated genes such as NFATc1, AVPR1A and FGFR4, which are crucial role for neuronal development and its functions. The down-regulated inflammatory cytokines (IL1B, IL10, IL2RA, TNF) and chemokines (CXCL1, CXCL9, CXCL10, CCL2, CCL13, CCR4) might be important to neuronal dysfunction and vulnerability. Taken together, these gene candidates are suggested to play a critical role in hippocampal plasticity. This is a first study presenting not only new information into the voluntary RWR influenced transcriptome in the rat hippocampus, but also provides a hypothesis for the RWR influenced enhancement in brain function.

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Adult Born Hippocampal Neurons Mount Unique Translational Changes in Response to Voluntary Running

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