Lisa C. Lyons, Ph.D. - US grants

DESCRIPTION (provided by applicant): To fully understand learning and the formation of memory, it is necessary to understand both the basic mechanisms responsible for the induction and consolidation of memory, as well as the processes responsible for the modulation of those basic processes. Many factors modulate the processes of memory formation including general health, stress, motivation, age and the time of day. The long-term objectives of our research are to understand the modulation of long-term associative memory formation by the circadian clock including the underlying molecular mechanisms, the physiological function and the behavioral consequences. The circadian clock regulates long-term memory formation in Aplysia californica, such that animals form robust long-term memory when trained during the day, but no long-term memory when trained at night. We will investigate the signaling pathways involved in an operant, associative form of learning in Aplysia, learning that food is inedible (LFI), and modulation by the circadian clock using behavioral, pharmacological and biochemical assays. In Specific Aim 1, we will identify the kinase signaling pathways necessary for LFI and determine whether the activation of these kinases is modulated by the circadian clock. Specifically, we will determine whether PKG, MARK and PKA signaling are necessary for LFI. The goal of Aim 2 is to determine whether the circadian clock modulates learning-induced transcription for LFI memory and whether the transcription factor ApC/EBP is involved in LFI. Specific Aim 3 examines the effect, at the molecular level, of training animals at night when they only form short-term memories and investigates methods of converting the partial memory into long-term memory. In Aim 4, we examine negative regulatory elements in long-term memory formation. We will investigate whether the circadian clock regulates p38 kinase activity or phosphatase activity. This research will significantly contribute to our understanding of the molecular mechanisms underlying associative operant learning in Aplysia as well as greatly furthering our understanding of the regulation of output behaviors by the circadian clock. One objective of the proposed experiments is to determine how circadian suppression of long-term memory formation at night may be relieved to improve memory formation at night. Thus, this research will provide a basis of research for future therapeutic treatments to improve memory and performance.

DESCRIPTION (provided by applicant): Project Summary Acute alcohol abuse and alcohol dependence create an enormous burden on individuals, families and society through health and socioeconomic impacts. Binge drinking episodes and long-term alcohol consumption result in the increased incidence of multiple diseases, accompanied by cellular damage and tissue injury. Differential sensitivity to alcohol can result in differences in drinking behavior and variation in alcohol toxicity at the cellular and tissue levels. Understanding and treating the physical consequences of alcohol abuse requires identification of those factors affecting differential alcohol sensitivity and alcohol toxicity and the cellular and molecular mechanisms through which these factors modulate responses to alcohol. Endogenous circadian clocks allow organisms to optimize behavioral and physiological processes relative to the time of day. Recent research in several model systems has shown clear interactions between the endogenous circadian clock and differential sensitivity and toxicity to alcohol, however, the mechanisms through which this occurs remain unclear. There exists a critical need for studies examining the interactions of the circadian clock with physiological and metabolic responses to alcohol to be performed in a system that allows for the molecular mechanisms underlying this interaction to be identified. Drosophila has long been recognized as a superior model system for studies of the core functioning of the circadian clock and the circadian regulation of metabolic, physiological and behavioral outputs. Drosophila also has been established as a model system for the study of alcohol response behaviors and their underlying mechanisms as the response to alcohol appears remarkably conserved between flies and humans. Our preliminary research indicates that the circadian system is tightly intertwined with acute sensitivity to alcohol in Drosophila. Te objectives of this application focus on identifying the molecular mechanisms through which the circadian clock modulates alcohol sensitivity and identifying the impact of circadian modulation on alcohol-induced cellular damage. The tremendous number of available mutants and transgenic techniques for specific gene expression combined with fast generation time and the practicality of animal maintenance have made Drosophila a superb system for the identification of genes involved in complex behaviors. Given the evolutionarily conserved mechanisms underlying circadian oscillators as well as the high degree of conservation in signaling pathways affected by alcohol, the experimental results from this research in Drosophila will be broadly applicable across species. Thus, these experiments will provide a foundation for the future development of therapeutic drugs and treatments for prevention of the adverse health effects associated with alcohol abuse.

DESCRIPTION (provided by applicant): Memory formation represents a dynamic process modulated by multiple factors including the circadian clock and sleep. In the past few decades, sleep loss and sleep deprivation have developed into major societal problems with individuals working longer hours, fragmented sleep patterns due to shift work, technological interferences and social jet lag. Sleep loss and sleep deprivation exact a heavy toll on society and individuals through increased traffic accidents, increased industrial and occupational accidents, and decreased productivity and performance. Sleep deprivation causes significant decrements in short and long-term memory. In order to ameliorate the consequences of sleep deprivation, it is necessary to understand how systems level problems and changes in behavior affect molecular and cellular processes at the level of individual neuronal circuits and neuron groups. Defining the mechanisms through which sleep and sleep loss impact memory formation is crucial to identifying methods to optimize performance and health in modern society. Given the high molecular conservation underlying memory formation across species, the marine mollusk Aplysia californica with its simple neural circuitry provides an ideal model for detailing in vivo interactions between sleep, the circadian clock and memory. Previously, we described short, intermediate and long-term memory for an operant learning paradigm, learning that food is inedible (LFI). We have characterized sleep in Aplysia and found that Aplysia sleep patterns resemble human sleep patterns with sleep occurring only at night in long consolidated bouts. Our long-term objective is to define the mechanisms through which the sleep deprivation affects the formation of associative memories and identify mechanisms through which the circadian clock and sleep interact to regulate memory. The goal of this proposal is to identify cellular changes and changes in gene expression caused by sleep deprivation specifically in the neurons involved in feeding behaviors and LFI memory and to identify genes and pathways necessary for long-term memory formation that are inhibited by sleep deprivation. These studies will further our understanding of the functions of sleep and importantly, provide a research base for future therapeutic treatments to improve memory and performance.

Project Summary Sleep deprivation presents an increasing threat to individual health and public safety as well as an economic burden due to lost productivity, traffic accidents, occupational accidents, and skyrocketing healthcare costs. There has been an astonishing rise in the number of individuals affected by sleep deprivation with approximately 35% of U.S. adults and a staggering 70% of teenagers reporting insufficient sleep. Sleep deprivation induces significant impairments in memory and performance, aggravates psychiatric and neurological disorders and increases disease risk, especially neurodegenerative disorders such as Alzheimer?s disease. Given the significant number of people affected by sleep deprivation, and the potentially devastating consequences of sleep loss in terms of disease and dementia, it is essential to identify the cellular consequences of sleep deprivation and to define the specific molecular targets and processes impacted. Recent research suggests that the influence of acute sleep deprivation on memory occurs at the cellular and synaptic level, although the specific mechanisms through which sleep deprivation exerts these effects remain poorly understood. The hippocampus, a critical brain region for memory, is particularly susceptible to the effects of acute sleep deprivation. Previously, we found that sleep deprivation decreases protein synthesis in the hippocampus leading to impairments and deficits in synaptic plasticity. We hypothesize that sleep deprivation targets multiple processes that affect the regulation of gene expression, which is comprised of changes in transcription, RNA processing and localization, and protein synthesis. The objectives of this proposal are to define the molecular and cellular mechanisms through which sleep deprivation impacts gene regulation and to define the affected subregions and cell types within the hippocampus. In Specific Aim 1, we focus on the signaling pathways through which sleep deprivation affects protein synthesis to adversely impact long-term memory and synaptic plasticity with a focus on identifying mechanisms of resilience to sleep loss. In Specific Aim 2, we investigate the effects of sleep deprivation on RNA fate at the subcellular level and explicitly detail the effects of sleep deprivation on the pool of mRNA available for translation. In Specific Aim 3, we employ state of the art techniques to define the impact of sleep deprivation across subregions within the hippocampus and within individual cell types providing a detailed spatial map and cellular signature of the effects of sleep deprivation. The results from our comprehensive proposal integrating in vivo behavioral manipulations to mitigate the effects of sleep deprivation on memory, the subcellular analysis of the effects of sleep deprivation on RNA fate and protein synthesis, and the identification of cell specific signatures of sleep deprivation, will provide significant insights into the negative impacts of sleep deprivation on memory, potentially leading to the development of therapeutics to counteract the consequences of sleep loss on cognition and neurodegenerative disorders.