Changes in gene expression have been observed in the aging human brain, but our understanding of the underlying regulatory mechanisms remains limited. To unravel these complexities, we analyzed single-nucleus gene expression, chromatin accessibility, DNA methylation, and three-dimensional (3D) chromatin architecture from human hippocampal tissues spanning the adult lifespan. We identified both linear and nonlinear dynamic gene regulatory programs during aging. Between the ages of 50 to 75, embryonic yolk sac-derived microglia were depleted and replaced by cells resembling peripheral blood monocyte-derived microglia. Hippocampal astrocytes decreased substantially with age, including those regulating synaptic transmission. Across cell types, 3D genome architecture underwent global erosion. Our analysis provides insights for how altered gene regulatory programs promote cell type-specific aging phenotypes in the human brain.

INTRODUCTION:EXERT was a multisite randomized controlled trial (RCT) examining the effects of moderate-high intensity aerobic training (AX) versus lower-intensity stretching/balance/range of motion (SBR) on cognitive trajectories in older adults with amnestic mild cognitive impairment (aMCI). METHODS:Preplanned post-hoc analyses were conducted to compare each arm to a propensity-matched usual care (no intervention) group from Alzheimer's Disease Neuroimaging Initiative 1 (ADNI-1) selected for similarity across key characteristics. Differences in 12-month trajectories in the primary endpoint (ADAS-Cog-Exec) and magnetic resonance imaging (MRI) volumes in prespecified brain regions were compared. RESULTS:AX and SBR showed significantly less 12-month cognitive decline than ADNI-1 (AX:n = 109, β = 0.169, 95% confidence interval [CI] 0.011-0.328; SBR:n = 105, β = 0.181, 95% CI 0.007-0.354). There were trends of less prefrontal cortex volume loss for both EXERT groups and less AD signature region volume loss for SBR relative to ADNI-1 over 12 months. DISCUSSION:Moderate-high intensity aerobic or low-intensity flexibility exercise for 12 months in participants with aMCI may provide protection against decline relative to usual care. CLINICAL TRIAL REGISTRATION:The EXERT clinical trial is registered at clinicaltrials.gov (NCT02814526). HIGHLIGHTS:EXERT was a randomized controlled trial in sedentary older adults with aMCI. EXERT arms were propensity-matched to a usual care (no intervention) group (Alzheimer's Disease Neuroimaging Initiative 1 [ADNI-1]). High and low-intensity exercise arms had less 12-mo cognitive decline than ADNI-1. There were trends of less prefrontal cortex volume loss for each arm versus ADNI-1.

INTRODUCTION:The EXERT study (Exercise in Adults with Mild Memory Problems) was a Phase 3, multicenter, randomized controlled trial that examined effects of exercise on cognition and other measures of brain health in sedentary older adults with amnestic mild cognitive impairment (MCI). METHODS:Participants were randomized to moderate-high intensity aerobic training (AX) or low-intensity stretching/balance/range of motion (SBR) for 18 months. Exercise was supervised for the first 12 months. Assessments were administered at baseline and every 6 months. The primary outcome was a global cognitive composite. RESULTS:A total of 296 participants were enrolled, and intervention adherence was high (supervised session attendance: AX = 81%, SBR = 87%). Intervention effects on cognition did not differ for AX and SBR (regression = -0.078, standard error [SE] = 0.074; p = 0.3). Notably, there was no 12 month  cognition decline for either group, and mean 12 month  hippocampal volume loss for both groups was low at 0.51%. DISCUSSION:Exercise intensity did not differentially affect cognitive trajectory. Intervention delivery was successful (high adherence) and cognition remained stable over 12 months  for both MCI groups, an association that warrants further study. HIGHLIGHTS:Exercise in Adults with Mild Memory Problems (EXERT) was a large multisite randomized controlled trial of moderate-high intensity aerobic training versus lower-intensity flexibility and balance exercise in sedentary older adults with amnestic mild cognitive impairment (MCI). A sensitive and validated measure of global cognitive function, the Alzheimer's Disease Assessment Scale-Cognition supplemented with tests of executive function (ADAS-Cog-Exec), was used to assess intervention efficacy with 12 months of supervised exercise. There was no intervention group difference on the 12-month cognitive trajectory of the ADAS-Cog-Exec. Intervention delivery was successful (high adherence), and cognition remained stable over 12 months for both exercise groups. Regular supported moderate-high or lower-intensity exercise may stall decline in adults with amnestic MCI, but further investigation is needed.

Exercise has beneficial effects on cognition throughout the lifespan. Here, we demonstrate that specific exercise patterns transform insufficient, subthreshold training into long-term memory in mice. Our findings reveal a potential molecular memory window such that subthreshold training within this window enables long-term memory formation. We performed RNA-seq on dorsal hippocampus and identify genes whose expression correlate with conditions in which exercise enables long-term memory formation. Among these genes we found Acvr1c, a member of the TGF ß family. We find that exercise, in any amount, alleviates epigenetic repression at the Acvr1c promoter during consolidation. Additionally, we find that ACVR1C can bidirectionally regulate synaptic plasticity and long-term memory in mice. Furthermore, Acvr1c expression is impaired in the aging human and mouse brain, as well as in the 5xFAD mouse model, and over-expression of Acvr1c enables learning and facilitates plasticity in mice. These data suggest that promoting ACVR1C may protect against cognitive impairment.

Background: Basic research and clinical trials universally demonstrate the benefits of exercise for cognitive function.In recent studies, we determined that a period of initial exercise also creates and maintains a molecular memory window for exercise benefits on cognitive function in male and female mice where a brief, 2-day exercise session following a break can also re-engage cognitive benefits, re-facilitate long-term potentiation, and allow for learning under insufficient, subthreshold training conditions.Here, we build on these exercise parameters to begin to define a mechanism responsible for maintaining cognitive benefits underlying this molecular memory window by initial exercise and driving long-term memory formation.Methods: We utilized RNA-sequencing to uncover genes in the dorsal hippocampus that are differentially expressed under conditions where exercise benefits are maintained throughout sedentary delay periods and enable the formation of long-term memory and synaptic plasticity.Specifically, adult male mice underwent 14 days of initial exercise, received a sedentary delay period (0-2 weeks), and a brief 2-day period of reactivating exercise, followed by 3 min inadequate, subthreshold training in an object location memory (OLM) task and hippocampus was dissected during the consolidation window, 1 hour after training.Those parameters were then used to examine hippocampal longterm potentiation (LTP) using theta burst stimulation in the schaffer collateral pathway.To assess how exercise modulates epigenetic regulation of genes up-regulated only under conditions where exercise enabled the formation of long-term memory and synaptic plasticity, histone modifications were examined at Acvr1c and Bdnf IV promoters using chromatin immunoprecipitation (ChIP-qPCR).To examine the role of Acvr1c, a gene coding for a type 1 activin A membrane receptor kinase of the TGF-β family of signaling molecules, in hippocampus-dependent long term memory formation and synaptic plasticity, we used intrahippocampal delivery of AAV1-ACVR1C point mutant constructs that either enhance or disrupt function.Next, sedentary mice were trained using either a subthreshold (3 min) or standard (10 min) OLM task and memory was tested the following day.The same mice from behavioral studies were used to assess the impact of Acvr1c manipulation on hippocampal LTP.Given misregulation of the TGF-β pathway that occurs with age and in AD patients, we examine whether Acvr1c declines with age in mouse and human hippocampus (Genotype-Tissue Expression Project).Dorsal hippocampus was obtained from 3 and 20 mo.female and male C57BL/6J mice and processed for RT-qPCR.Additionally, Acvr1c transcripts per million (TPM) values from RNA-Seq data set obtained through the MODEL-AD consortium were analyzed from 4, 8 and 12 mo.C57BL/6J and 5xFAD female and male mice.We next aimed to determine whether enhancing ACVR1C through virus-mediated overexpression of wildtype ACVR1C would regulate long-term memory formation and synaptic plasticity in aging 18 mo.and 12 and 18 mo.Alzheimer's Disease (AD) mouse hippocampus and ameliorate impairments.Results: We demonstrate that specific exercise patterns transform insufficient, subthreshold training into long-term memory (Group: (F(6,64) = 8.13, P < 0.0001; Tukey test: P < 0.001, 14D vs. Sed) and synaptic plasticity (Group: (F(6,89) = 22.22,P < 0.0001; Tukey test: P < 0.0001) in adult mice compared to sedentary, effects which can be maintained and re-engaged with brief 2-day re-introduction to exercise following a sedentary delay (Behavior: Tukey test: P < 0.05, LTP: P < 0.0001, 2-day re-introduction vs sedentary).We identify a small number of genes whose expression correlate with conditions in which exercise facilitates long-term memory formation.Among these genes we found Acvr1c and Bdnf.We find that exercise, in any amount, alleviates epigenetic repression at the Acvr1c (Group (F(5,49) = 9.377, P < 0.0001) and Bdnf IV (Group (F(5,53) = 13.90,P < 0.0001) promoters during consolidation in a persistent manner, providing initial insight for maintenance of exercise benefits on long term memory.Disrupted ACVR1C function under adequate learning conditions in adults impairs memory (t(17) = 4.65, P = 0.0002) and synaptic plasticity (t(18) = 3.512, P = 0.0025).Conversely, overexpression of ACVR1C enables learning under inadequate training conditions in adults (t(18) = 3.303, P = 0.004) and enhances LTP (t(14) = 3.953, P = 0.0014).Furthermore, Acvr1c expression is impaired in the aging human (t(91) = 6.64,P = 0.0001), mouse (t(26) = 2.72, P = 0.01) and AD mouse brain (5xFAD) (Age: (F(2,48) = 54.95,P < 0.0001), and over-expression of Acvr1c ameliorates plasticity www.nature.com/npp1234567890();,:and cognitive impairment in aging (18 mo.C57: Behavior: (t(12) = 2.350, P = 0.036), LTP: (t(14) = 3.953, P = 0.001), 12 mo.5xFAD: Behavior: (t(21) = 2.287, P = 0.032), LTP: (t(16) = 5.617, P < 0.0001), 18 mo.5xFAD: LTP: (t(10) = 9.653, P = 0.001)).Conclusions: Together, these findings provide a new paradigm for uncovering mechanistic drivers of exercise-facilitated learning and provide opportunity to explore how specific exercise parameters allow for periods of maintained epigenetic and molecular changes through sedentary periods that facilitate cognitive function.As we have demonstrated here, identification of such mechanisms may extend beyond the context of exercise and aid in ameliorating age and AD-associated cognitive impairment.

Learning and memory mainly rely on correct synaptic function in the hippocampus and other brain regions. In Parkinson's disease, subtle cognitive deficits may even precede motor signs early in the disease. Hence, we set out to unravel the earliest hippocampal synaptic alterations associated with human α-synuclein overexpression prior to and soon after the appearance of cognitive deficits in a parkinsonism model. We bilaterally injected adeno-associated viral vectors encoding A53T-mutated human α-synuclein into the substantia nigra of rats, and evaluated them 1, 2, 4 and 16 weeks post-inoculation by immunohistochemistry and immunofluorescence to study degeneration and distribution of α-synuclein in the midbrain and hippocampus. The object location test was used to evaluate hippocampal-dependent memory. Sequential window acquisition of all theoretical mass spectrometry-based proteomics and fluorescence analysis of single-synapse long-term potentiation were used to study alterations to protein composition and plasticity in isolated hippocampal synapses. The effect of L-DOPA and pramipexole on long-term potentiation was also tested. Human α-synuclein was found within dopaminergic and glutamatergic neurons of the ventral tegmental area, and in dopaminergic, glutamatergic and GABAergic axon terminals in the hippocampus from 1 week post-inoculation, concomitant with mild dopaminergic degeneration in the ventral tegmental area. In the hippocampus, differential expression of proteins involved in synaptic vesicle cycling, neurotransmitter release and receptor trafficking, together with impaired long-term potentiation were the first events observed (1 week post-inoculation), preceding cognitive deficits (4 weeks post-inoculation). Later on, at 16 weeks post-inoculation, there was a deregulation of proteins involved in synaptic function, particularly those involved in the regulation of membrane potential, ion balance and receptor signalling. Hippocampal long-term potentiation was impaired before and soon after the onset of cognitive deficits, at 1 and 4 weeks post-inoculation, respectively. L-DOPA recovered hippocampal long-term potentiation more efficiently at 4 weeks post-inoculation than pramipexole, which partially rescued it at both time points. Overall, we found impaired synaptic plasticity and proteome dysregulation at hippocampal terminals to be the first events that contribute to the development of cognitive deficits in experimental parkinsonism. Our results not only point to dopaminergic but also to glutamatergic and GABAergic dysfunction, highlighting the relevance of the three neurotransmitter systems in the ventral tegmental area-hippocampus interaction from the earliest stages of parkinsonism. The proteins identified in the current work may constitute potential biomarkers of early synaptic damage in the hippocampus and hence, therapies targeting these could potentially restore early synaptic malfunction and consequently, cognitive deficits in Parkinson's disease.

DNA damage is a central contributor to the aging process. In the brain, a major threat to the DNA is the considerable amount of reactive oxygen species produced, which can inflict oxidative DNA damage. This type of damage is removed by the base excision repair (BER) pathway, an essential DNA repair mechanism, which contributes to genome stability in the brain. Despite the crucial role of the BER pathway, insights into how this pathway is affected by aging in the human brain and the underlying regulatory mechanisms are very limited. By microarray analysis of four cortical brain regions from humans aged 20-99 years (n = 57), we show that the expression of core BER genes is largely downregulated during aging across brain regions. Moreover, we find that expression of many BER genes correlates positively with the expression of the neurotrophin brain-derived neurotrophic factor (BDNF) in the human brain. In line with this, we identify binding sites for the BDNF-activated transcription factor, cyclic-AMP response element-binding protein (CREB), in the promoter of most BER genes and confirm the ability of BDNF to regulate several BER genes by BDNF treatment of mouse primary hippocampal neurons. Together, these findings uncover the transcriptional landscape of BER genes during aging of the brain and suggest BDNF as an important regulator of BER in the human brain.

Radiation therapy (XRT) has a well-established role in cancer treatment. Given the encouraging results on immunostimulatory effects, radiation has been increasingly used with immune-check-point inhibitors in metastatic disease, especially when immunotherapy fails due to tumor immune evasion. We hypothesized that using high-dose stereotactic radiation in cycles (pulses) would increase T-cell priming and repertoire with each pulse and build immune memory in an incremental manner. To prove this hypothesis, we studied the combination of anti-CTLA-4 and Pulsed radiation therapy in our 344SQ non-small cell lung adenocarcinoma murine model. Primary and secondary tumors were bilaterally implanted in 129Sv/Ev mice. In the Pulsed XRT group, both primary and secondary tumors received 12Gyx2 radiation one week apart, and blood was collected seven days afterwards for TCR repertoire analysis. As for the delayed-Pulse group, primary tumors received 12Gyx2, and after a window of two weeks, the secondary tumors received 12Gyx2. Blood was collected seven days after the second cycle of radiation. The immunotherapy backbone for both groups was anti-CTLA-4 antibody to help with priming. Treatment with Pulsed XRT + anti-CTLA-4 led to significantly improved survival and resulted in a delayed tumor growth, where we observed enhanced antitumor efficacy at primary tumor sites beyond XRT + anti-CTLA-4 treatment group. More importantly, Pulsed XRT treatment led to increased CD4+ effector memory compared to single-cycle XRT. Pulsed XRT demonstrated superior efficacy to XRT in driving antitumor effects that were largely dependent on CD4+ T cells and partially dependent on CD8+ T cells. These results suggest that combinatorial strategies targeting multiple points of tumor immune evasion may lead to a robust and sustained antitumor response.

Decades of experimental work support the idea that synapses are the anatomical substrate for experience-dependent plasticity in the brain. Changes in the synaptic strength underlie learning and memory via the accumulation of glutamate AMPA receptors (AMPAR) at the surface of excitatory synapses. AMPAR are tetrameric receptors constituted by multiple combination of four subunits: GluA1 GluA2, GluA3, and GluA4. However, the relative contribution of each AMPAR subunit on learning and memory is relatively unexplored. Here, we introduce Fluorescence Analysis of Single-Synapse Potentiation induced by Learning (FASS-PiL), a flow cytometry-based method to quantify surface levels of all four GluA-AMPAR subunits, in parallel, in isolated synaptosomes after a learning episode in rodents. We evaluated surface levels of all four AMPAR subunits in synaptosomes of mice trained in a learning protocol commonly used for studying episodic memory in the hippocampus (e.g., Object Location Memory (OLM) and Object Recognition Memory (ORM) tasks). Briefly, after exploring novel objects in a novel environment for 10 min, mice were returned to their home cage for 60 min. After hippocampus dissection, synaptosome isolation, and immunostaining, samples were analyzed via flow cytometry. We first demonstrated that FASS-PiL is a simple and sensitive method to track all four GluAs at the synaptosome surface (each GluA subunit was paired with the presynaptic marker Neurexin-1beta to focus on synaptosome particles containing both pre- and postsynaptic compartments). Notably, by profiling hundreds of events, our data showed that the OLM training increases the number of hippocampal synaptosomes expressing high levels of GluA1 and GluA2, but not GluA3 and GluA4 (vs control animals). Our results indicate that plasticity-related mechanisms underlying learning are AMPA-subunit-specific in hippocampal synapses. Our approach could provide the basis for protocols to study behavioral-relevant mechanisms of plasticity directly at the synapse, with single-event resolution.

Background: Chronic inflammation and neurodegeneration are well-characterized pathogenic factors in depression and dementia, especially late-life depression and Alzheimer's Dementia (AD), and a potential therapeutic target for treatment.One important mechanism linking inflammatory and neurodegenerative biomarkers with specific cellular activation and communication is the release of extracellular vesicles (EVs).EVs are nano-sized vesicles, have specific membrane proteins, and contain nucleic acid (microRNA) and protein cargo.EVs can be released from cells under various conditions, including chronic inflammation and stress, demonstrating significant age-dependent differences in their pro-inflammatory profile.In addition, brain cells, such as neurons and astrocytes, release EVs that can be extracted from plasma samples.The EVs can be divided into three groups based on size.The most studied vesicle is the exosome, ranging from 30 to 150 nm.The exosomes are considered cell-specific vesicles, and the evaluation of their content can provide detailed information about the biological changes of specific cell types than the evaluation of whole plasma content.Exosomes from brain cells, such as neuron-(NDEs) and astrocytes-derived exosomes (ADEs), can easily cross the bloodbrain barrier and be identified in the periphery.The NDEs and ADEs role is a new research field and an intricate pathway involving the crosstalk between the CNS, the neuroendocrine, and the immune systems.While studies have advanced in AD, the role of exosomes in LLD is poorly investigated.In addition, LLD is multifactorial and could be a prodromal state associated with neurodegenerative diseases, including AD, frontal, temporal dementia (FTD), and vascular dementia (VD).Therefore, the signature of the exosomes could share common pathways and molecules between LLD and AD.There are no studies in the literature comparing NDEs and ADEs in those two neuropsychiatric illnesses until the present moment.The aim of this project is to characterize biosignatures in NDEs and ADEs (cell-specific) and plasma (non-cell-specific), creating a molecular profile for LLD and AD.Methods: Therefore, 46 LLD subjects, 25 AD patients, and 34 healthy elderly controls were recruited, matched by age and gender.After the psychiatric evaluation, the blood was collected and centrifuged to obtain the plasma-free platelet.The sample was collected and stored at -80°C.We used the kit vFC™ vesicle flow cytometry for counting and sizing vesicles.Results: Individuals with LLD presented lower levels of NDE and ADE compared to controls.For ADE, the opposite was demonstrated in AD Patients, with 2 times more ADE than CT and LLD.Next, we evaluate 49 pro-inflammatory cytokines and neurodegenerative protein levels in total exosomes and plasma samples.There was an overlap in the production of 32 proteins when comparing plasma and exosome evaluation.Twelve proteins were identified only in the plasma sample, and 5 only in the exosomes.CXCL2, GDNF, NF-light, GFAP, DR3, and IL-4 receptor levels in the exosomes increased compared to plasma, showing a cell-specific driving response via exosomes.Overlapping the protein evaluation in the exosomes from LLD and AD individuals, 14 proteins were common for both disorders, 15 were exclusive in LLD exosomes, and none of the proteins evaluated were exclusive in the exosomes of AD participants.Conclusions: These preliminary conclusions reinforce the importance of the exosomes in cellular communication, and the common biomarkers shared in LLD and AD.This mechanism can contribute to the crosstalk between brain cells and the periphery as a window to directly evaluate the molecular pathology of LLD and AD.

The EXERT trial (NCT02814526) was a Phase 3, multicenter, randomized single-blind study that examined the effects of regular exercise on cognition and other measures of brain function in a planned sample of 300 older adults with amnestic mild cognitive impairment (MCI). The Alzheimer’s Disease Cooperative Study (ADCS) coordinated the trial, in partnership with Wake Forest and the YMCA of the USA. Participants were randomized to moderate intensity aerobic training (AX), or to stretching, balance and range of motion (SBR) for 18 months. In the first 12 months, exercise was supervised 2x/week and completed independently 2x/week. All exercise was unsupervised in Months 13-18. Outcomes assessments were completed at baseline and every 6 months. The primary endpoint was 12-month change from baseline on the ADAS-Cog-Exec, a validated measure of global cognitive function. In addition, 12-month changes in the ADAS-Cog-Exec and CDR-SB were compared for EXERT intervention groups relative to other cohorts to estimate effects of intervention versus no intervention (i.e., “Usual Care”). 296 participants were enrolled, and over 31,000 exercise sessions were completed during the first 12 months. Attendance remained high (AX: 81%; SBR: 87%), and >60% of participants reported continued exercise through the pandemic. Neither the AX group nor the SBR group showed 12-month declines on the ADAS-Cog-Exec and CDR-SB. There were no significant treatment differences between AX and SBR on these outcomes. In the Usual Care analysis comparing ADNI-1 and EXERT participants matched on key variables (demographics, baseline cognitive function, APOE4), ADNI-1 MCI participants showed the expected 12-month decline on the ADAS-Cog-Exec, but the EXERT AX and SBR groups did not (ADNI-1 vs. AX: p = 0.012; vs. SBR: p = 0.00049). Global cognitive function did not change over 12 months of follow-up for MCI participants in EXERT, suggesting that both the AX and SBR interventions may have stalled cognitive decline. EXERT is the longest exercise trial conducted in MCI to date, and greater ‘volume’ of exercise may have provided more protection, regardless of exercise intensity. Both groups received equal amounts of weekly socialization, which may have contributed to this protection. Our results are noteworthy given that trial was conducted during the COVID-19 pandemic.

Histone modifications are key contributors to the cognitive decline that occurs in aging and Alzheimer’s disease. Our lab has previously shown that elevated H3K9me3 in aged mice is correlated with synaptic loss, cognitive impairment and a reduction in brain derived neurotrophic factor (BDNF). However, the mechanism of H3K9me3 regulation remains poorly understood. In this study, we investigated the role of age-associated stressors on H3K9me3 regulation and examined if changes in H3K9me3 were age dependent. We used cultured hippocampal neurons at 6, 12, and 21 days in vitro (DIV) to examine the effect of different stressors on H3K9me3 across neuron ages. We found that the oxidative stressor hydrogen peroxide (H2O2) does not induce H3K9me3 in 12 DIV neurons. Inhibiting BDNF signaling via TrkB-Fc elevated H3K9me3 in 12 and 21 DIV neurons compared to 6 DIV neurons. Antioxidant treatment prevented H3K9me3 elevation in 12 DIV neurons treated with TrkB-Fc and H2O2. H2O2 elevated the epigenetic regulator SIRT1 in 6 DIV neurons but did not increase H3K9me3 levels. Our findings demonstrate that inhibiting BDNF signaling elevates hippocampal H3K9me3 in a manner dependent on in vitro age and oxidative stress.

This scientific commentary refers to ‘Striatal synaptic bioenergetic and autophagic decline in premotor experimental parkinsonism’ by Merino-Galán et al. (https://doi.org/10.1093/brain/awac087).

Exercise improves cognition in the aging brain and is a key regulator of neuronal plasticity genes such as BDNF. However, the mechanism by which exercise modifies gene expression continues to be explored. The repressive histone modification H3K9me3 has been shown to impair cognition, reduce synaptic density and decrease BDNF in aged but not young mice. Treatment with ETP69, a selective inhibitor of H3K9me3’s catalyzing enzyme (SUV39H1), restores synapses, BDNF and cognitive performance. GABA receptor expression, which modulates BDNF secretion, is also modulated by exercise and H3K9me3. In this study, we examined if exercise and ETP69 regulated neuronal plasticity genes by reducing H3K9me3 at their promoter regions. We further determined the effect of age on H3K9me3 promoter binding and neuronal plasticity gene expression. Exercise and ETP69 decreased H3K9me3 at BDNF promoter VI in aged mice, corresponding with an increase in BDNF VI expression with ETP69. Exercise increased GABRA2 in aged mice while increasing BDNF 1 in young mice, and both exercise and ETP69 reduced GABRA2 in young mice. Overall, H3K9me3 repression at BDNF and GABA receptor promoters decreased with age. Our findings suggest that exercise and SUV39H1 inhibition differentially modulate BDNF and GABRA2 expression in an age dependent manner.