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Transcriptome Analysis in a Mouse Model of Premature Aging of Dentate Gyrus: Rescue of Alpha-Synuclein Deficit by Virus-Driven Expression or by Running Restores the Defective Neurogenesis

ABSTRACT: To identify genes responsible for stem and progenitor cells maintenance, we sought here to find genes underlying premature neural aging, and whose deregulated expression could be rescued by running. Through RNA sequencing we analyzed the transcriptomic profiles of the dentate gyrus isolated from Btg1 wild-type or Btg1 knockout adult (two-month-old) mice submitted to physical exercise or sedentary. In Btg1 knockout mice, 545 genes were deregulated, relative to wild-type, while 2081 genes were deregulated by running. We identified 42 genes whose expression was not only down-regulated in the dentate gyrus of Btg1 knockout, but was also counter-regulated to control levels by running in Btg1 knockout mice, vs. sedentary.

ORGANISM(S): Mus musculus

PROVIDER: GSE179081 | GEO | 2021/08/06

REPOSITORIES: GEO

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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.

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Transcriptome Analysis in a Mouse Model of Premature Aging of Dentate Gyrus: Rescue of Alpha-Synuclein Deficit by Virus-Driven Expression or by Running Restores the Defective Neurogenesis

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