Project description:Adult neurogenesis, found in two neurogenic regions of the brain, has profound roles in neural plasticity and brain function. A hallmark feature of neurodegeneration is neuroinflammation, which can either enhance or inhibit neurogenesis depending on the context of the brain microenvironment. The consequences of deficient DNA repair in adult neurogenesis and neuroinflammation are poorly understood despite their potential relevance for homeostasis. We previously reported that loss of NEIL1, an important DNA glycosylase involved in DNA base excision repair, is associated with deficiencies in spatial memory, olfaction, and protection against ischemic stroke in mice. Here, we show that Neil1-/- mice display an anxiety-mediated behavior in the open field test, a deficient recognitive memory in novel object recognition and increased neuroinflammatory response under basal conditions. Further, mice lacking NEIL1 have decreased neurogenesis and deficient resolution of neuroinflammation following gamma irradiation (IR)-induced stress compared to WT mice. Neil1-/- IR-exposed mice also exhibit increased DNA damage and apoptosis in the hippocampus. Interestingly, behavioral tests two weeks after IR showed impaired stress response in the Neil1-/- mice. Our data indicate that NEIL1 plays an important role in adult neurogenesis and in the resolution of neuroinflammation.
Project description:Cellular exposure to ionizing radiation leads to oxidatively generated DNA damage, which has been implicated in neurodegenerative diseases. DNA damage is repaired by the evolutionarily conserved base excision repair (BER) system. Exposure of mice to ionizing radiation affects neurogenesis and neuroinflammation. However, the consequences of deficient DNA repair on adult neurogenesis and neuroinflammation are poorly understood despite their potential relevance for homeostasis. We previously reported that loss of NEIL1, an important DNA glycosylase involved in BER, is associated with deficiencies in spatial memory, olfaction, and protection against ischemic stroke in mice. Here, we show that Neil1-/- mice display an anxiety-mediated behavior in the open field test, a deficient recognitive memory in novel object recognition and increased neuroinflammatory response under basal conditions. Further, mice lacking NEIL1 have decreased neurogenesis and deficient resolution of neuroinflammation following gamma irradiation (IR)-induced stress compared to WT mice. Neil1-/- IR-exposed mice also exhibit increased DNA damage and apoptosis in the hippocampus. Interestingly, behavioral tests two weeks after IR showed impaired stress response in the Neil1-/- mice. Our data indicate that NEIL1 plays an important role in adult neurogenesis and in the resolution of neuroinflammation.
Project description:We report the bisulfite sequencing and RNA-seq in hippocampus of Neil deficient adult mice. By genome-wide bisulphite sequencing (GWBS) analysis, NEIL depletion mice (including Neil1-/-, Neil2-/- and Neil1-/- Neil2-/-) consistently displayed global hypo-methylation of 5mC in base resolution in CG context, as well as in gene feature regions including transcription start sites (TSS) in CHG and CHH context by compared to wild type. RNA-seq reveals differentially expressed genes are mainly overlapped with differential methylation. A subset of overlap genes is enriched in synaptic function. Together, NEIL1 and NEIL2 functionally promote DNA methylation and impact gene expression.
Project description:The bifunctional DNA glycosylases / AP lyases NEIL1 and NEIL2 excise oxidative base damages, but can also enhance the steady-state turnover of thymine DNA glycosylase (TDG) during oxidative DNA demethylation (Schomacher et al. 2016; doi:10.1038/nsmb.3151). The dual role of NEILs in antagonizing base damages and promoting epigenetic gene reactivation prompted us to investigate the consequences of NEIL deficiency during embryonic stem cell differentiation. To account for any possible functional redundancy in the NEIL family, all three paralogs NEIL1, NEIL2 and NEIL3 were inactivated using CRISPR/Cas9 in mouse embryonic stem cells.
Project description:Neuroinflammation plays a role in the progression of several neurodegenerative disorders. We used a lipolysaccharide (LPS) model of neuroinflammation to characterize the gene expression changes underlying the inflammatory and behavioral effects of neuroinflammation. A single intracerebroventricular injection of LPS (5 ug) was administered into the lateral ventricle of mice and, 24 hours later, we examined gene expression in the cerebral cortex and hippocampus using microarray technology. Gene Ontology (GO) terms for inflammation and the ribosome were significantly enriched by LPS, whereas GO terms associated with learning and memory had decreased expression. We detected 224 changed transcripts in the cerebral cortex and 170 in the hippocampus. Expression of Egr1 (also known as Zif268) and Arc, two genes associated with learning and memory, was significantly lower in the cortex, but not hippocampus, of LPS-treated animals. Overall, altered expression of these genes may underlie some of the inflammatory and behavioral effects of neuroinflammation. Mice were given intracerebroventricular injections of saline vehicle (n = 4) or lipopolysaccharide (n = 4). Twenty-four hours later, we dissected the hippocampus and cerebral cortex and processed the tissue for microarray analysis. Gene expression changes observed in the microaray data were validated with quantitative real-time PCR.
Project description:Physical exercise stimulates adult hippocampal neurogenesis in mammals, and is considered a relevant strategy for preventing age-related cognitive decline in aging humans. However, its mechanism is controversial. Here, by investigating microRNAs (miRNAs) and their downstream pathways, we uncover that downregulation of miR-135a-5p mediates exercise-induced proliferation of adult NPCs in adult neurogenesis in the mouse hippocampus, likely by activation of phosphatidylinositol (IP3) signaling. Specifically, while overexpression of miR-135 prevents exercise-induced proliferation in the adult mouse hippocampus in vivo and in NPCs in vitro, its inhibition activates NPCs proliferation in resting and aged mice. Label free proteomics and bioinformatics analysis identifies 11 potential targets of miR-135 in NPCs, several of them involved in phosphatidylinositol signaling. Thus, miR-135a is key in mediating exercise-induced adult neurogenesis and opens intriguing perspectives toward the therapeutic exploitation of miR-135 to delay or prevent pathological brain ageing.Physical exercise stimulates adult hippocampal neurogenesis in mammals, and is considered a relevant strategy for preventing age-related cognitive decline in aging humans. However, its mechanism is controversial. Here, by investigating microRNAs (miRNAs) and their downstream pathways, we uncover that downregulation of miR-135a-5p mediates exercise-induced proliferation of adult NPCs in adult neurogenesis in the mouse hippocampus, likely by activation of phosphatidylinositol (IP3) signaling. Specifically, while overexpression of miR-135 prevents exercise-induced proliferation in the adult mouse hippocampus in vivo and in NPCs in vitro, its inhibition activates NPCs proliferation in resting and aged mice. Label free proteomics and bioinformatics analysis identifies 11 potential targets of miR-135 in NPCs, several of them involved in phosphatidylinositol signaling. Thus, miR-135a is key in mediating exercise-induced adult neurogenesis and opens intriguing perspectives toward the therapeutic exploitation of miR-135 to delay or prevent pathological brain ageing.
Project description:NEIL 1-3 DNA glycosylases initiate the base excision repair pathway by removing oxidized bases from the DNA. NEIL1 and NEIL3 have been shown to protect the brain from ischemic stroke-induced injury in adult and perinatal mice, respectively. To assess the role of NEIL1 and NEIL2 in newborn mice, we used the Levine model of hypoxic-ischemic encephalopathy (HIE), modified for use in perinatal mice. We found that NEIL1 deficiency increased sensitivity to cerebral ischemia in newborn mice. In contrast, NEIL2 deficiency rendered the mice more resistant to hypoxia-ischemia. Importantly, no effect was seen in mice expressing base excision activity-deficient NEIL proteins and the global levels of the oxidative DNA lesion 5-hydroxycytosine, which is a substrate for the NEIL enzymes, did not differ significantly between the genotypes. Transcriptome analysis of NEIL1- and NEIL2-deficient hippocampus revealed changes in Neil2-deficient hippocampus that favour cell survival and limit brain injury after HI. Our data suggest a role of NEIL2 in regulating the early transcriptional stress response, critical for neuronal cell death, after brain injury. This function seems to be independent of the base excision activity of the proteins. The protective effect of NEIL2 deficiency makes NEIL2 a potential therapeutic target in treatment of perinatal HIE.