Project description:Neurons utilize glucose to generate adenosine triphosphate (ATP) essential for their survival, excitability and synaptic signaling, as well as initiating changes in neuronal structure and function. Defects in oxidative metabolism and mitochondria functions are also associated with aging and diverse human neurological diseases1-4. While neurons are known to adapt their metabolism to meet the increased energy demands of complex behaviors such as learning and memory, the molecular underpinnings regulating this process remain poorly understood4-6. Here we show that the orphan nuclear receptor estrogen related receptor gamma (ERRγ) becomes highly expressed during retinoic-acid induced neurogenesis and is widely expressed in neuronal nuclei throughout the brain. Mechanistically, we show that ERRγ directly orchestrates the expression of networks of genes involved in mitochondrial oxidative phosphorylation and energy generation in neurons. The importance of this regulation is evidenced by decreased adaptive metabolic capacity in cultured neurons lacking ERRγ, and reduced long-term potentiation (LTP) in ERRγ-/- hippocampal slices. Notably, the defect in LTP was rescued by the metabolic intermediate pyruvate, functionally linking the ERRγ knockout metabolic phenotype and memory formation. Consistent with this notion, mice lacking neuronal ERRγ exhibit defects in spatial learning and memory. These findings implicate ERRγ in the metabolic adaptations required for long-term memory formation. We used ChIP-Seq analysis to determine the genome-wide binding of ERRγ in neurons derived from ES cells.
Project description:Neurons utilize glucose to generate adenosine triphosphate (ATP) essential for their survival, excitability and synaptic signaling, as well as initiating changes in neuronal structure and function. Defects in oxidative metabolism and mitochondria functions are also associated with aging and diverse human neurological diseases1-4. While neurons are known to adapt their metabolism to meet the increased energy demands of complex behaviors such as learning and memory, the molecular underpinnings regulating this process remain poorly understood4-6. Here we show that the orphan nuclear receptor estrogen related receptor gamma (ERRγ) becomes highly expressed during retinoic-acid induced neurogenesis and is widely expressed in neuronal nuclei throughout the brain. Mechanistically, we show that ERRγ directly orchestrates the expression of networks of genes involved in mitochondrial oxidative phosphorylation and energy generation in neurons. The importance of this regulation is evidenced by decreased adaptive metabolic capacity in cultured neurons lacking ERRγ, and reduced long-term potentiation (LTP) in ERRγ-/- hippocampal slices. Notably, the defect in LTP was rescued by the metabolic intermediate pyruvate, functionally linking the ERRγ knockout metabolic phenotype and memory formation. Consistent with this notion, mice lacking neuronal ERRγ exhibit defects in spatial learning and memory. These findings implicate ERRγ in the metabolic adaptations required for long-term memory formation. We used microarray analysis to compare the genome-wide gene expression changes between wild type (WT) and ERRγ-/- P0 cerebral cortex as it contains mainly neuronal lineage at this stage compared to adult cortex.
Project description:Neurons utilize glucose to generate adenosine triphosphate (ATP) essential for their survival, excitability and synaptic signaling, as well as initiating changes in neuronal structure and function. Defects in oxidative metabolism and mitochondria functions are also associated with aging and diverse human neurological diseases1-4. While neurons are known to adapt their metabolism to meet the increased energy demands of complex behaviors such as learning and memory, the molecular underpinnings regulating this process remain poorly understood4-6. Here we show that the orphan nuclear receptor estrogen related receptor gamma (ERRγ) becomes highly expressed during retinoic-acid induced neurogenesis and is widely expressed in neuronal nuclei throughout the brain. Mechanistically, we show that ERRγ directly orchestrates the expression of networks of genes involved in mitochondrial oxidative phosphorylation and energy generation in neurons. The importance of this regulation is evidenced by decreased adaptive metabolic capacity in cultured neurons lacking ERRγ, and reduced long-term potentiation (LTP) in ERRγ-/- hippocampal slices. Notably, the defect in LTP was rescued by the metabolic intermediate pyruvate, functionally linking the ERRγ knockout metabolic phenotype and memory formation. Consistent with this notion, mice lacking neuronal ERRγ exhibit defects in spatial learning and memory. These findings implicate ERRγ in the metabolic adaptations required for long-term memory formation.
Project description:Neurons utilize glucose to generate adenosine triphosphate (ATP) essential for their survival, excitability and synaptic signaling, as well as initiating changes in neuronal structure and function. Defects in oxidative metabolism and mitochondria functions are also associated with aging and diverse human neurological diseases1-4. While neurons are known to adapt their metabolism to meet the increased energy demands of complex behaviors such as learning and memory, the molecular underpinnings regulating this process remain poorly understood4-6. Here we show that the orphan nuclear receptor estrogen related receptor gamma (ERRγ) becomes highly expressed during retinoic-acid induced neurogenesis and is widely expressed in neuronal nuclei throughout the brain. Mechanistically, we show that ERRγ directly orchestrates the expression of networks of genes involved in mitochondrial oxidative phosphorylation and energy generation in neurons. The importance of this regulation is evidenced by decreased adaptive metabolic capacity in cultured neurons lacking ERRγ, and reduced long-term potentiation (LTP) in ERRγ-/- hippocampal slices. Notably, the defect in LTP was rescued by the metabolic intermediate pyruvate, functionally linking the ERRγ knockout metabolic phenotype and memory formation. Consistent with this notion, mice lacking neuronal ERRγ exhibit defects in spatial learning and memory. These findings implicate ERRγ in the metabolic adaptations required for long-term memory formation.
Project description:MicroRNAs (miRNA) are small, non-coding RNAs mediating post-transcriptional regulation of gene expression. miRNAs have recently been implicated in hippocampus-dependent functions such as learning and memory, although the roles of individual miRNAs in these processes remain largely unknown. Here, we achieved stable inhibition using AAV-delivered miRNA sponges of individual, highly expressed and brain-enriched miRNAs; miR-124, miR-9 and miR-34, in hippocampal neurons. Molecular and cognitive studies revealed a role for miR-124 in learning and memory. Inhibition of miR-124 resulted in an enhanced spatial learning and working memory capacity, potentially through altered levels of genes linked to synaptic plasticity and neuronal transmission. In contrast, inhibition of miR-9 or miR-34 led to a decreased capacity of spatial learning and of reference memory, respectively. On a molecular level, miR-9 inhibition resulted in altered expression of genes related to cell adhesion, endocytosis and cell death, while miR-34 inhibition caused transcriptome changes linked to neuroactive ligand-receptor transduction and cell communication. In summary, this study establishes distinct roles for individual miRNAs in hippocampal function. Three RNA samples containing bilateral entire hippocampi from three different mice, per group. Group 1 were injected with vector containing GFP and a miR34sp/miR9sp and the other group were subjected to a vector expressing GFP only.
Project description:Aging is often associated with cognitive decline, but many elderly individuals maintain a high level of function throughout life. Here we studied outbred rats, which also exhibit individual differences across a spectrum of outcomes that includes both preserved and impaired spatial memory. Previous work in this model identified the CA3 subfield of the hippocampus as a region critically affected by age and integral to differing cognitive outcomes. Earlier microarray profiling revealed distinct gene expression profiles in the CA3 region, under basal conditions, for aged rats with intact memory and those with impairment. Because prominent age-related deficits within the CA3 occur during neural encoding of new information, here we used microarray analysis to gain a broad perspective of the aged CA3 transcriptome under activated conditions. Behaviorally induced CA3 expression profiles differentiated aged rats with intact memory from those with impaired memory. In the activated profile, we observed substantial numbers of genes (greater than 1000) exhibiting increased expression in aged unimpaired rats relative to aged impaired, including many involved in synaptic plasticity and memory mechanisms. This unimpaired aged profile also overlapped significantly with a learning induced gene profile previously acquired in young adults. Alongside the increased transcripts common to both young learning and aged rats with preserved memory, many transcripts behaviorally-activated in the current study had previously been identified as repressed in the aged unimpaired phenotype in basal expression. A further distinct feature of the activated profile of aged rats with intact memory is the increased expression of an ensemble of genes involved in inhibitory synapse function, which could control the phenotype of neural hyperexcitability found in the CA3 region of aged impaired rats. These data support the conclusion that aged subjects with preserved memory recruit adaptive mechanisms to retain tight control over excitability under both basal and activated conditions. RNA profiles from cognitively unimpaired and impaired aged rats were compared under 2 conditions: spatial learning task and a non-spatial learning task.
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:A theoretical framework for the function of the medial temporal lobe system in memory defines differential contributions of the hippocampal subregions with regard to pattern recognition retrieval processes and encoding of new information. To investigate molecular programs of relevance, we designed a spatial learning protocol to engage a pattern separation function to encode new information. After background training, two groups of animals experienced the same new training in a novel environment, however only one group was provided spatial information and demonstrated spatial memory in a retention test. Global transcriptional analysis of the microdissected subregions of the hippocampus exposed a CA3 pattern that was sufficient to clearly segregate spatial learning animals from control. Individual gene and functional group analysis anchored these results to previous work in neural plasticity. From a multitude of expression changes, increases in camk2a, rasgrp1 and nlgn1 were confirmed by in situ hybridization. Furthermore, siRNA inhibition of nlgn1 within the CA3 subregion impaired spatial memory performance, pointing to mechanisms of synaptic remodeling as a basis for rapid encoding of new information in long-term memory. Experiment Overall Design: RNA samples from animals subjected to a spatial learning paradigm were compared to controls using Affymetirx RAE230a chips. An N of 7 was used in each of the two experimental conditions.