Ketema N. Paul, Ph.D. - US grants

The primary objective of this research proposal is to characterize the role of NMDA, substance P, and the NK1 tachykinin receptor subtype in the generation and entrainment of circadian rhythms. The specific aims are to determine: 1) the extent that the tachykinin substance P induces or modulates phase shifts of SCN generated circadian rhythms, 2) the extent that the expression of the NK1 tachykinin receptor is necessary for the generation or entrainment of SCN generated circadian rhythms, and 3) the extent that the EAA receptor agonist NMDA can mimic the light induced suppression of nocturnal levels of pineal melatonin The studies will be performed using the Syrian hamster (Mesocricetus auratus). This animal model provides an advantage because it has a highly reproducible wheel-running rhythm and relatively high nocturnal levels of pineal melatonin. The results of the above studies will increase our understanding of the pharmacology of circadian entrainment, and may lead to the development of drugs to combat disorders of the circadian system.

2-Naphthacenecarboxamide, 4-(dimethylamino)-1,4,4a,5,5a,6,11,12a-octahydro-3,5,10,12,12a-pentahydroxy-6-methyl-1,11-dioxo-, (4S-(4alpha,4aalpha,5alpha,5aalpha,6alpha,12aalpha))-; Architecture; Attenuated; BACs (Chromosomes); Bacterial Artificial Chromosomes; Body Tissues; Brain; Cell Nucleus; Circadian Rhythms; Condition; DNA Alteration; DNA mutation; Daily; Development; Disease; Disorder; Diurnal Rhythm; Doxycycline; Dysfunction; Elements; Encephalon; Encephalons; Engineering / Architecture; Environmental Sleep Disorder; Functional disorder; Gene Alteration; Gene Expression; Gene Mutation; Genes; Genetic; Genetic Alteration; Genetic Change; Genetic defect; Genetic mutation; Goals; Knockout Mice; Link; Location; Mammals, Mice; Measures; Mediating; Messenger RNA; Mice; Mice, Knock-out; Mice, Knockout; Mice, Transgenic; Molecular; Murine; Mus; Mutate; Mutation; Nervous; Nervous System, Brain; Nucleus; Null Mouse; Nyctohemeral Rhythm; Output; Peripheral; Physiologic; Physiological; Physiology; Physiopathology; Process; RNA, Messenger; Sequence Alteration; Sleep; Sleep Disorder, Environmental; Sleep Disorders; Sleep Wake Cycle; System; System, LOINC Axis 4; Technology; Testing; Time; Tissues; Transcript; Transgenic Mice; Transgenic Organisms; Twenty-Four Hour Rhythm; Vibramycin; Wakefulness; Wakefulnesses; alpha-6-Deoxyoxytetracycline; brain tissue; circadian; circadian process; daily biorhythm; disease/disorder; diurnal variation; experiment; experimental research; experimental study; genome mutation; mRNA; neural; new therapeutics; next generation therapeutics; novel therapeutics; pathophysiology; relating to nervous system; research study; response; sleep problem; therapeutic target; transgenic

DESCRIPTION (provided by applicant): Sleep-deprived women have higher rates of cardiovascular disease, obesity, and metabolic dysregulation than do sleep-deprived men. The influences of sex on the ability to recover from sleep loss may underlie these increased risks for morbidity in women. Identification of the factors that are responsible for sex differences in the ability to recover from sleep loss is therefore critical to reducing, and someday eliminating, this gender disparity in sleep health. We have shown that sex differences in the daily sleep amount of mice are dependent on circulating reproductive hormones and that the ability to recover from sleep loss by increasing sleep amount and altering SWA is relatively insensitive to these hormones. This finding led us to hypothesize that sex chromosomes directly influence the ability to recover from sleep loss. Human studies are limited in their ability to examine: 1) the contributions of genetic and phenotypic sex to gender differences in sleep traits and 2) polysomnographic sleep responses to extended chronic sleep loss in men and women. These limitations underscore the need for effective animal models to determine whether sex-specific genetic and hormonal interactions influence sleep opportunities during and after chronic sleep loss. An exciting mouse model of genetic sex now provides an opportunity to examine the discrete contributions of sex chromosomes to sleep regulatory mechanisms. In this four core genotype mouse model of genetic sex, the sex chromosome complement is the opposite of gonadal and phenotypic sex. In addition, refinements in the ability to obtain intracortical recording of slow wave activity (SWA) in active rodents now provide a unique opportunity to determine the regulatory influences of sex on homeostatic sleep responses. By employing a more rigid electrophysiological measurement of SWA and by examining whether sex chromosome complement has influences on the ability of chronic sleep loss to disrupt sleep regulatory mechanisms, these studies will determine the nature of sex differences in sleep alterations caused by chronic sleep loss and increase understanding of the mechanisms underlying those differences.

Paul- Project 1 Program Director/Principal Investigator (Last, First, Middle): MacLeish, Peter R. PROJECT SUMMARY (See instructions): In today's demanding 24-hour society the prevalence of sleep disorders continues to increase; however, the development of effective treatments for those disorders has not kept pace. One of the primary reasons is that many of the genetic and molecular pathways that underlie basic sleep processes are still undefined. Forward genetics approaches have yielded novel therapeutic targets and more effective treatments for a variety of diseases; however, similar milestones in the study of sleep disorders have been elusive. It has become apparent in the last several years that the genetics of sleep are complex, involving multiple genes and gene interactions with potentially small effect sizes. Larger-scale genomic approaches are likely to provide the necessary power uncover the genes that underlie sleep processes. In this application we propose a forward genetics approach that takes advantage of natural variation occurring in inbred mice. We have characterized 53 sleep-wake phenotypes in 14 inbred mouse strains in sleep-replete and sleep-deprived conditions. We propose to expand this dataset to add a minimum of 11 additional strains to provide sufficient statistical power for quantitative trait loci (QTL) analysis and positional cloning in subsequent recombinant hybrid crosses to transition from QTL to gene. This endeavor will combine a well-established paradigm of comparative phenotyping of a genetically tractable animal model with powerful genetic mapping tools to identify novel sleep regulatory genes. Consequently, these experiments will not only identify new sleep genes, they will also help verify and clarify previously mapped genes whose roles are not yet clearly defined. Ancillary benefits of this proposal include the potential identification of practical biomarkers of sleepiness, which is often cited as one of the most pressing needs in contemporary sleep research.

DESCRIPTION (provided by applicant): Sleep-deprived women have higher rates of cardiovascular disease, obesity, and metabolic dysregulation than do sleep-deprived men. The influences of sex on the ability to recover from sleep loss may underlie these increased risks for morbidity in women. Identification of the factors that are responsible for sex differences in the ability to recover from sleep loss is therefore critical to reducing, and someday eliminating, this gender disparity in sleep health. We have shown that sex differences in the daily sleep amount of mice are dependent on circulating reproductive hormones and that the ability to recover from sleep loss by increasing sleep amount and altering SWA is relatively insensitive to these hormones. This finding led us to hypothesize that sex chromosomes directly influence the ability to recover from sleep loss. Human studies are limited in their ability to examine: 1) the contributions of genetic and phenotypic sex to gender differences in sleep traits and 2) polysomnographic sleep responses to extended chronic sleep loss in men and women. These limitations underscore the need for effective animal models to determine whether sex-specific genetic and hormonal interactions influence sleep opportunities during and after chronic sleep loss. An exciting mouse model of genetic sex now provides an opportunity to examine the discrete contributions of sex chromosomes to sleep regulatory mechanisms. In this four core genotype mouse model of genetic sex, the sex chromosome complement is the opposite of gonadal and phenotypic sex. In addition, refinements in the ability to obtain intracortical recording of slow wave activity (SWA) in active rodents now provide a unique opportunity to determine the regulatory influences of sex on homeostatic sleep responses. By employing a more rigid electrophysiological measurement of SWA and by examining whether sex chromosome complement has influences on the ability of chronic sleep loss to disrupt sleep regulatory mechanisms, these studies will determine the nature of sex differences in sleep alterations caused by chronic sleep loss and increase understanding of the mechanisms underlying those differences.

Disturbances in the daily sleep-wake cycle are a common feature experienced by individuals with neurodegenerative disorders. They have difficulty sleeping at night and staying awake during the day. These disturbances have a major impact on their quality of life as well as on the family members who care for them. Huntington's disease (HD) is the most common genetically determined neurodegenerative disease and we have documented that circadian rhythms are disrupted early in the disease progression in three distinct mouse models of HD. Using a mouse model of HD which expresses the human mutation (BACHD), we have successfully improved the behavioral and some of the autonomic deficits using a protocol that limits the daily food intake into a 6-hr window during the animal's active phase, and is thus named: time restricted feeding (TRF). This feeding/fasting cycle improved behaviorally defined sleep in the BACHD model when applied early in disease progression. To our knowledge, this is the first demonstration that TRF can improve sleep parameters in mice although earlier work has shown that a similar schedule can improve behavioral sleep patterns in Drosophila. A critical gap in our knowledge is whether TRF specifically alters the temporal pattern of sleep stages, sleep homeostasis or cortical up/down states reflecting slow wave activity. This proposal will employ electrophysiological and optical approaches to close this gap and determine if such treatments can be usefully employed in HD. Given the shared pathology including the formation of protein aggregates and cell death, treatment strategies that prove to be effective in HD are likely to be broadly beneficial in the management of neurodegenerative diseases.

Project Summary/Abstract Sex differences in daily sleep amount, sleep fragmentation, and basal slow wave activity (SWA) are largely driven by gonadal hormones. However, sex differences in the mid-active phase sleep amount and the ability to recover from sleep loss are largely insensitive to gonadal hormones, and are regulated in part by sex chromosomes. Preliminary data in this application show that a key determinant of sex differences in active phase sleep amount is the presence or absence of the Sry gene of the Y chromosome, which encodes the testis-determining factor. This study will use two mouse lines with altered sex chromosomes to elucidate the origin of sex differences in sleep and in order to determine the respective roles of Sry gene and chromosome complement on sleep regulatory mechanisms. The first specific aim will test the hypothesis that Sry gene establishes sex differences in sleep homeostasis during development by observing sleep-wake patterns in the EMG of neonatal, prepubertal mice, and EEG/EMG of adult mice with altered sex chromosomes and hormones. The second specific aim will test the hypothesis that X chromosome dosage drives sex differences in the ability to recover from sleep loss. During each of these studies, active-phase sleep amount in mice will be used as a biomarker for sleep homeostasis. These experiments are important and required to understand the role of the sleep homeostat in regulating sleep and how it is established. They are the first comprehensive analysis of sex differences in a juvenile mammalian species and the first to examine the specific effects of either X or Y chromosome dosage on sleep. The overarching goal of these experiments is to identify the specific mechanisms through which sex chromosomes and sex-linked genes are able to regulate sleep. These studies will uncover the origins of sex differences in the homeostatic ability to recover from sleep loss. These findings will likely lead to improved therapies for sleep disorders that exhibit sex differences in incidence and severity, particularly those more prevalent in women.

Disturbances in the daily sleep-wake cycle are a common feature experienced by individuals with neurodegenerative disorders. They have difficulty sleeping at night and staying awake during the day. These disturbances have a major impact on their quality of life as well as on the family members who care for them. Huntington's disease (HD) is the most common genetically determined neurodegenerative disease and we have documented that circadian rhythms are disrupted early in the disease progression in three distinct mouse models of HD. Using a mouse model of HD which expresses the human mutation (BACHD), we have successfully improved the behavioral and some of the autonomic deficits using a protocol that limits the daily food intake into a 6-hr window during the animal's active phase, and is thus named: time restricted feeding (TRF). This feeding/fasting cycle improved behaviorally defined sleep in the BACHD model when applied early in disease progression. To our knowledge, this is the first demonstration that TRF can improve sleep parameters in mice although earlier work has shown that a similar schedule can improve behavioral sleep patterns in Drosophila. A critical gap in our knowledge is whether TRF specifically alters the temporal pattern of sleep stages, sleep homeostasis or cortical up/down states reflecting slow wave activity. This proposal will employ electrophysiological and optical approaches to close this gap and determine if such treatments can be usefully employed in HD. Given the shared pathology including the formation of protein aggregates and cell death, treatment strategies that prove to be effective in HD are likely to be broadly beneficial in the management of neurodegenerative diseases.