The aging of neurons causes dysfunction and cognitive decline, but exactly how neurons age is not yet understood. In particular, the key genes that are responsible for these changes have not been identified, but would be ideal therapeutic targets if found. Our hypothesis is that a subset of the genes that change with age in specific neurons is responsible for changes in declines in cognitive ability with age. Our work identifying gene expression changes in aging adults and in longevity mutants that maintain cognitive functions longer will allow us to identify these key genes. These regulators, if evolutionarily conserved, may be good targets for intervention if they also decline with age in human neurons. In our previous studies, we developed assays to measure C. elegans positive olfactory learning, short-term memory, and long-term memory. We found that the molecular components of these processes are shared between worms and mammals, demonstrating that C. elegans is a good model system to more fully understand the molecular and cellular requirements of memory. Further, we assessed the changes in learning, short-term memory, and long-term memory with age, in longevity mutants, and in models of Alzheimer's Disease. We found that levels of the transcription factor CREB limit long-term memory and fall with age, explaining the loss of memory ability with age. We went on to identify CREB's downstream targets required for memory, as well as the neuronal site of CREB activity, extending the knowledge of CREB's activity beyond what is known in other systems. However, how other behaviors are limited with age is not yet understood at the molecular level, and we aim to identify key factors that regulate the maintenance of cognitive function with age. In order to refine our analyses, we have developed a novel method to isolate cells from adult C. elegans, allowing transcriptional analysis of single cell types in aging worms for the first time. We are leveraging that new technique to identify genes that change with age and in longevity mutants in different neuron types. In addition to obtaining the basal transcriptome for individual cell types n order to characterize their identities, we can now assess their individual transcriptional changes with age. We have also utilized longevity mutants with extended functions, allowing us to identify key genes that maintain function with age. This is a key tool that is uniquely available i C. elegans. The effect of these changes can then be assessed through tests of motility, chemotaxis, learning, memory, regeneration, and morphology with age. The proposed experiments will use our newly developed methodology to determine how neurons lose the ability to carry out specific functions with age. Further, we will combine neuron-specific rescue o these key genes with behavioral assays to determine their roles and test whether their activity is sufficient to prevent specific behavioral declines with age. This information will give us unprecedented resolution in identifying causative changes in neurons with age.
The loss of memory is one of the most devastating effects of aging. New approaches to prevent these losses with age and with age-related neurodegenerative diseases will become more important as the population ages. We have developed assays to test the ability of C. elegans to learn and to remember. Surprisingly, the molecules C. elegans uses to carry out these tasks are very well conserved evolutionarily, allowing us to use worms as a model system for mammalian cognitive decline. We will take advantage of the speed of C. elegans genetics, the power of new genomic techniques, and our behavioral assays to study behavioral decline. Because C. elegans has also been used as a model in aging and longevity studies, and the pathways that extend longevity in worms are shared with higher organisms, we can combine these attributes to learn how memory changes with age, and how it is maintained in longevity mutants. Additionally, we recently developed a novel method to isolate cells from adult worms, which allows us to study changes with age in a cell-specific manner. Here we propose to determine the rate-limiting components of neuronal health with age, utilizing our new transcriptional tools and assays to test the functions of specifc cell types.
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