Project description:Understanding cellular and molecular drivers of age-related cognitive decline is necessary to identify targets to restore cognition at old age. Here we report that ferritin light chain 1 (FTL1) is a pro-aging neuronal factor that impairs cognition. Targeting neuronal FTL1 in the hippocampi of aged mice elicits synaptic and metabolic-related molecular changes and rescues cognitive impairments. Our data identify neuronal FTL1 as a key molecular mediator of cognitive rejuvenation.
Project description:A central hallmark of brain aging is the alteration of neuronal functions in the hippocampus, leading to a progressive decline in learning and memory. Multiple reports have shown the importance of blood-borne factors in inter-tissue communication for the maintenance of cognitive fitness and proper regulation of neuronal homeostasis throughout life. Among these blood-borne factors, we identified Osteocalcin (OCN), a bone-derived hormone. OCN induces autophagy machinery in hippocampal neurons which is essential for activity-dependent synaptic plasticity. However, the way in which blood-borne factors like OCN communicate with neurons, including their regulatory mechanisms, remains largely elusive. Here, we show the importance of a core primary cilium (PC)-proteins/autophagy machinery axis in hippocampal neurons that mediate the effects of the pro-youthful blood factor OCN on neuronal homeostasis and cognitive fitness. We found that OCN’s receptor, GPR158, is present at the PC of hippocampal neurons and mediates the regulation of autophagy machinery by OCN. During aging, PC-core proteins are reduced in hippocampal neurons and associated with neuronal PC morphological abnormalities. Restoring their levels is sufficient to improve neuronal autophagy and cognitive impairments in aged mice. Mechanistically, we found that OCN promotes neuronal autophagy in the hippocampus by the induction of PC-dependent cAMP response element-binding protein (CREB) signaling pathway. Altogether, this study proposes a novel paradigm for blood factor-neuron communication dependent on a neuronal PC/autophagy axis by identifying a novel regulatory pathway fostering cognitive fitness and providing the foundation for autophagy-based therapeutic strategies to treat age-related cognitive dysfunction.
Project description:Aging is the predominant risk factor for neurodegenerative diseases. One key phenotype as brain ages is the aberrant innate immune response characterized by proinflammation. However, the molecular mechanisms underlying aging-associated proinflammation are poorly defined. Whether chronic inflammation plays a causal role in cognitive decline in aging and neurodegeneration has not been established. Here we established a mechanistic link between chronic inflammation and aging microglia, and demonstrated a causal role of aging microglia in neurodegenerative cognitive deficits. Expression of microglial SIRT1 reduces with the aging of microglia. Genetic reduction of microglial SIRT1 elevates IL-1β selectively, and exacerbates cognitive deficits in aging and in transgenic mouse models of frontotemporal dementia (FTD). Interestingly, the selective activation of IL-1β transcription by SIRT1 deficiency is likely mediated through hypomethylating the proximal promoter of IL-1β. Consistent with our findings in mice, selective hypomethylation of IL-1β at two CpG sites are found in normal aging humans and demented patients with tauopathy. Our findings reveal a novel epigenetic mechanism in aging microglia that contributes to cognitive deficits in neurodegenerative diseases. Study of changes related to alterations of SIRT1 levels in microglia of young and aged animals and in models of neurodegenerative dementia
Project description:Components of the proteostasis network malfunction in the aging brain and this reduced neuronal protein quality control has been proposed to increase risk for neurodegeneration. Here, we have focused on chaperone-mediated autophagy (CMA), a selective type of autophagy that contributes to turnover of neurodegeneration-related proteins. We generated mouse models with CMA blockage in dopaminergic or glutamatergic neurons to investigate the physiological role of CMA in neurons in vivo and the consequences of neuronal CMA loss in aging, We found that loss of neuronal CMA leads to behavioral impairments, altered neuronal function, selective changes in the neuronal proteome and proteotoxicity, all reminiscent of brain aging. Furthermore, imposing CMA loss on an experimental mouse model of Alzheimer’s disease, increased neuronal disease vulnerability and accelerated disease progression. We conclude that functional CMA is essential for neuronal proteostasis and that CMA activation could be an efficient disease-modifying therapy in neurodegenerative disorders.
Project description:The aim of this study was to identify alterations in hippocampal synaptic mRNA expression with aging and cognitive decline. Transcriptional profiling and subsequent bioinformatic analysis was performed to identify the most highly regulated pathways of genes. Interestingly, the antigen processing and presentation pathway was identified as the most highly regulated pathway with aging. Adult (12 month) and aged (28 month) Fischer 344 x Brown Norway (F1) hybrid rats were assessed for cognitive performance using the Morris water maze task and were divided into Adult (n=5), Aged Cognitively Intact (n=8), and Aged Cognitively Impaired (n=7) groups. One week following testing, all animals were sacrificed, the hippocampi were dissected, and synaptosomes were isolated for subsequent transcriptomic profiling. Only 5 cognitively intact animals were processed on the arrays.
Project description:Molecular mechanisms underlying aging associated impairments in learning and long-term memory storage are poorly understood. Here we leveraged an identified motor neuron L7, mediating long-term sensitization of siphon-withdrawal reflex, a form of non-associative learning in sea slug Aplysia, to assess the impact of aging on transcriptional changes during learning. RNAseq analysis of single L7 motor neuron isolated following short-term or long-term sensitization training from 8,10 and 12 months old Aplysia corresponding to mature, late mature and senescent stages have identified progressive impairments in transcriptional plasticity during aging. Specifically, we uncover modulation of the expression of multiple lncRNAs, and mRNAs encoding transcription factors, regulators of translation, RNA methylation, and cytoskeletal rearrangements during learning and their deficits during aging. Our comparative gene expression analysis also revealed the recruitment of specific transcriptional changes in two other neurons, a motor neuron L11 and giant cholinergic neuron R2 whose roles in long-term sensitization were previously not known. Taken together, our analyses establish cell type specific escalating impairments in the expression of learning and LTM relevant components of transcriptomes during aging.
Project description:The excitatory amino acid transporter 2 (EAAT2) is the major glutamate transporter in the brain expressed predominantly in astrocytes and at low levels in neurons and axonal terminals. EAAT2 expression is reduced in aging and sporadic Alzheimer’s disease (AD) patients’ brains. The role EAAT2 plays in cognitive aging and its associated mechanisms remains largely unknown. Here, we show that conditional deletion of astrocytic and neuronal EAAT2 results in age-related cognitive deficits. Astrocytic, but not neuronal EAAT2, deletion leads to early deficits in short-term memory and in spatial reference learning and long-term memory. Neuronal EAAT2 loss results in late-onset spatial reference long-term memory deficit. Neuronal EAAT2 deletion leads to dysregulation of the kynurenine pathway, and astrocytic EAAT2 deficiency results in dysfunction of innate and adaptive immune pathways, which correlate with cognitive decline. Astrocytic EAAT2 deficiency also shows transcriptomic overlaps with human aging and AD. Overall, the present study shows that in addition to the widely recognized astrocytic EAAT2, neuronal EAAT2 plays a role in hippocampus-dependent memory. Furthermore, the gene expression profiles associated with astrocytic and neuronal EAAT2 deletion are substantially different, with the former associated with inflammation and synaptic function similar to changes observed in human AD and gene expression changes associated with inflammation similar to the aging human brain.
Project description:DNA methylation has emerged as a critical modulator of neuronal plasticity and cognitive function. Notwithstanding, the role of enzymes that demethylate DNA remain to be fully explored. Here, we report that loss of ten-eleven translocation methylcytosine dioxygenase 2 (Tet2), which catalyzes oxidation of 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), in adult neurons enhances cognitive function. In the adult mouse hippocampus, we detected an enrichment of Tet2 in neurons. Viral-mediated neuronal overexpression and RNA interference of Tet2 altered dendritic complexity and synaptic-plasticity-related gene expression in vitro. Overexpression of neuronal Tet2 in adult hippocampus, and loss of Tet2 in adult glutamatergic neurons, resulted in differential hydroxymethylation associated with genes involved in synaptic transmission. Functionally, overexpression of neuronal Tet2 impaired hippocampal-dependent memory, while loss of neuronal Tet2 enhanced memory. Ultimately, these data identify neuronal Tet2 as a molecular target to boost cognitive function.
Project description:Age-related cognitive decline is a serious health concern in our aging society. Decreased cognitive function observed during healthy brain aging is most likely caused by changes in brain connectivity and synaptic dysfunction in particular brain regions. Here we show that aged C57BL/6J wildtype mice have hippocampus-dependent spatial memory impairments. To identify the molecular mechanisms that are relevant to these memory deficits we investigated the temporal profile of mouse hippocampal synaptic proteome changes at 20, 40, 50, 60, 70, 80, 90 and 100 weeks of age. Extracellular matrix proteins were the only group of proteins that showed a robust and progressive upregulation over time. This was confirmed by immunoblotting and histochemical analysis, indicating that the increased levels of hippocampal extracellular matrix may limit synaptic plasticity as a potential cause of age-related cognitive decline. In addition, we observed that stochasticity in synaptic protein expression increased with age, in particular for proteins that were previously linked with various neurodegenerative diseases, whereas low variance in expression was observed for proteins that play a basal role in neuronal function and synaptic neurotransmission. Together, our findings show that both specific changes and increased variance in synaptic protein expression are associated with aging and may underlie reduced synaptic plasticity and impaired cognitive performance at old age.