David Weinshenker, Ph.D. - US grants

DESCRIPTION (provided by applicant): Epilepsy and depression are 2 of the most common neurological diseases. Although the manifestations of these diseases are distinct, there is compelling evidence that they share common underlying mechanisms. (1) Epidemiological studies demonstrate that depression is the most common comorbid psychiatric disorder in patients with epilepsy, and patients with major depression also have a higher frequency of epilepsy. (2) Some anticonvulsant therapies, such as valproic acid and vagus nerve stimulation, are also effective in treating affective disorders. The interaction between epilepsy and depression has not been empirically studied in animal models, and the common molecular mechanism(s) underlying these 2 diseases have not been identified. The goal of this proposal is to use rodent behavioral models to further investigate the link between epilepsy and depression. Our preliminary data indicate that rats selectively bred for susceptibility or resistance to depression-like phenotypes also have alterations in seizure susceptibility, suggesting that these rats are a good model to study genes that influence both phenotypes. In Aim 1 of this proposal, we will further characterize and validate the seizure susceptibility phenotype of our selectively bred rats. In Aim 2, we will genetically characterize our 6 selectively bred rat strains using genome-wide microsatellite markers. Completion of these aims will develop animal models with which to study epilepsy and depression comorbidity and lay the groundwork for identification of genes that contribute to both diseases.

[unreadable] DESCRIPTION (provided by applicant): Dopamine beta-hydroxylase (DBH) converts dopamine (DA) to norepinephrine (NE) in noradrenergic neurons, adrenergic neurons, and adrenal chromaffin cells. Therefore, DBH controls both NE synthesis and the DA/NE ratio in noradrenergic cells. DBH enzymatic activity in humans varies between individuals. A common polymorphism (a C to T change at position -1021) has been identified in the human Dbh gene that accounts for most of the genetic variability and about half of the total variability observed in DBH enzymatic activity. DBH has recently become of interest in the field of drug addiction for two reasons. First, the rewarding and aversive effects of cocaine appear to be influenced by Dbh genotype in humans. Second, the DBH inhibitor disulfiram has shown promise as a pharmacotherapy for cocaine dependence. Because of technical and ethical issues in human research, very little is known about the neurochemical consequences of the Dbh C-1021T polymorphism. Therefore, it is of interest to create a rodent model of the C-1021T polymorphism and assess both neurochemical and behavioral differences between the C and the T alleles of Dbh. We propose to create transgenic mice bearing a bacterial artificial chromosome (BAG) that contains either the C allele or the T allele of the human Dbh gene. Completion of this aim will provide us with the tools necessary to ascertain how the C-1021T polymorphism controls DBH enzymatic activity, its effect on catecholamine neurochemistry, and the behavioral consequences of these changes, especially as they relate to drug addiction. [unreadable] [unreadable]

The mesolimbic dopamine (DA) system has been primarily implicated in the effects of psychostimulants. While this pathway and DA signaling are the focus of most research in this area, it is also clear that norepinephrine (NE) plays an important role in modulating the neurochemical and behavioral responses to in animal models. The enzyme dopamine beta-hydroxylase (DBH) converts DA to NE in noradrenegic cells, thus controlling the abundance of both NE and DA in the brain. Genetic and pharmacological data in humans support an important role for DBH in modulating psychostimulant-related behaviors. First, a common polymorphism in the human Dbh gene is a critical determinant of DBH enzymatic activity and appears to influence behavioral and cognitive responses to cocaine. Second, the DBH inhibitor disulfiram (Antabuse) has shown striking promise as a treatment for cocaine dependence. The objective of this proposal is to determine the influence of DBH activity on catecholamine neurochemistry and cocaine-related behaviors, including sensitization, reward, aversion, and relapse, which will be accomplished by using a combination of genetics (Dbh knockout mice), and pharmacology (DBH inhibitors). Completion of the aims in this proposal will contribute to our understanding of how the interaction between noradrenergic and dopaminergic systems influences drug addiction and the mechanism of disulfiram-induced cocaine abstinence, and will suggest novel treatments for psychostimulant dependence.

[unreadable] DESCRIPTION (provided by applicant): The mesolimbic dopamine (DA) system has been primarily implicated in the reinforcing effects of drugs of abuse. While this pathway and DA signaling are the focus of most research in this area, it is also clear that norepinephrine (NE), via interactions with the dopaminergic system, plays an important role in modulating the neurochemical and behavioral responses to drugs of abuse in animal models. The enzyme dopamine (Beta-hydroxylase (DBH) converts DA to NE in noradrenegic cells, thus controlling the abundance of both NE and DA in the brain. Genetic and pharmacological data in humans support an important role for DBH in modulating psychostimulant-related behaviors. First, a common polymorphism in the human Dbh gene is a critical determinant of DBH enzymatic activity and appears to influence behavioral and cognitive responses to cocaine. Second, the DBH inhibitor disulfiram (Antabuse) has shown striking promise as a treatment for cocaine dependence, yet its mechanism of action is unknown. [unreadable] The objective of this proposal is to determine the influence of DBH activity on catecholamine neurochemistry and cocaine-related behaviors, including sensitization, reward, aversion, and relapse, and to understand why disulfiram administration results in cocaine abstinence in dependent humans. This will be accomplished by using a combination of genetics (Dbh knockout mice), and pharmacology (disulfiram). Completion of the aims in this proposal will contribute to our understanding of how the interaction between noradrenergic and dopaminergic systems influences drug addiction and the mechanism of disulfiram- induced cocaine abstinence, and will suggest novel treatments for psychostimulant dependence [unreadable] [unreadable]

Alzheimer's disease (AD) is the most common cause of cognitive impairment in older patients and is expected to increase greatly in prevalence. Neuropathologically, AD is characterized by beta-amyloid containing plaques, tau-containing neurofibrillary tangles, and neuronal loss. A well described yet underappreciated eariy feature of AD pathogenesis is the degeneration ofthe locus coeruleus (LC), which is the sole source of forebrain norepinephrine (NE). Previous studies have shown that LC lesions exacerbate AD-like neuropathology and cognitive deficits in mouse models of AD, while increasing NE is neuroprotective. However, the mechanism underiying the protective effect of LC neurons in AD is not understood. We have recently discovered that NE and other endogenous catecholamines function as direct agonists forthe TrkB neurotrophin receptor. TrkB signaling is neuroprotective, retards A(3 toxicity, and is critical for neuronal plasticity and learning and memory. The goal of this proposal is to test whether this novel NE-TrkB interaction contributes to the role ofthe LC in AD pathogenesis. In Aim 1, we will test the ability of NE and novel synthetic catecholamine-derived TrkB agonists to decrease AB production and toxicity in primary neuronal cultures. In Aim 2, we will test the ability of the most promising TrkB agonists identified in Aim 1 to ameliorate AD-like neuropathology and cognitive deficits in a transgenic mouse model of AD. In Aim 3, we will test the hypothesis that LC loss in mild cognitive impairment (MCI) and AD impairs TrkB activation and correlates with amyloid pathology and cognitive impairment using human postmortem cases.

DESCRIPTION (provided by applicant): One of the most challenging aspects of treating drug addiction is preventing relapse due to daily challenges such as stress or exposure to drugs or drug-associated cues. Despite many years of research, no generally accepted pharmacotherapy exists. Aerobic exercise has beneficial effects on both physical and mental health, suggesting that it may also be an effective therapy for the treatment of drug dependence. We and others have shown that activation of the central noradrenergic system is essential for stress-induced and drug-primed reinstatement in the rat model of drug self- administration. We have also discovered that chronic exercise increases expression of the neuropeptide galanin in noradrenergic neurons and impairs stress-induced norepinephrine release. The purpose of this proposal is to test the hypothesis that voluntary exercise can attenuate stress-induced and drug-primed reinstatement of cocaine seeking. In Aim 1 of this proposal, we will determine whether chronic voluntary exercise (wheel running) blunts stress-induced or drug-primed reinstatement of cocaine seeking in rats. In Aim 2, we will determine whether a negative correlation exists between the magnitude of wheel running-induced galanin expression in the noradrenergic locus coeruleus and reinstatement, and whether blockade of galanin signaling reverses the beneficial effects of exercise. In Aim 3, we will further investigate the interaction between exercise-induced galanin expression and norepinephrine release. PUBLIC HEALTH RELEVANCE: Drug addiction is a chronic, relapsing disease that is very difficult to treat and places enormous social and economic stress on society. Aerobic exercise is beneficial for many aspects of physical and mental health, and may be beneficial for the treatment of drug dependence. The purpose of this proposal is to assess the effects of aerobic exercise in a rat model of drug relapse, and to investigate potential underlying mechanisms. Completion of these experiments may indicate a new therapy for the treatment of drug addiction.

DESCRIPTION (provided by applicant): Project Summary/Abstract Recent exciting progress in schizophrenia genetics has revealed genomic copy number changes with large susceptibility for disease. Large (~1Mb), heterozygous, typically de novo copy number changes on chromosomes 1q21, 15q11, 15q13, 16p11, 22q11, and most recently a deletion on chromosome 3q29 are all enriched in SZ patients relative to controls. Interestingly, these copy number changes are also enriched in autism and intellectual disability cohorts. However, these discoveries have been unaccompanied by identification of the specific gene responsible for the phenotype(s). At Emory we have established an interdisciplinary team that consists of the labs of Stephen Warren, Tamara Caspary and David Weinshenker, and our initial goal is to recapitulate the human 3q29 interval by creating mouse models of the deletion and reciprocal duplication, and ascertaining the behavioral consequences on multiple mouse strain backgrounds using a comprehensive battery of tests. Ascertaining the full behavioral spectrum in alternate genomic contexts will allow us to elicit differences that are predicated on mouse strain background, recapitulating the variable phenotypes observed in humans. For the microdeletion, we further propose to create a series of smaller overlapping deletions in the two strains with the most robust phenotypes. In this way we will establish the minimal deletion (and therefore minimal genes) required for a behavioral phenotype. This approach will enable us to 1) create models of the 3q29 deletion and duplication syndromes, 2) discern whether disruption of an individual gene or combination of genes are responsible for the SZ, ID and autism-like features exhibited by deletion patients or if distinct genes are responsible for the different phenotypes and 3) identify the causative gene(s) which will, in turn, provide a molecular handle through which these neuropsychiatric conditions can be better understood and treated. Using these mouse models combined with behavioral testing, we expect to identify the gene responsible for the 3q29 deletion phenotype, a major candidate gene for schizophrenia, intellectual disability, and autism. Thus this grant will develop a valuable mouse model and provide a molecular handle of the genetic pathways that the community requires to advance psychiatric genetic research.

DESCRIPTION (provided by applicant): Cocaine abuse is a major public health concern in the United States, yet no FDA-approved pharmacotherapies exist. A prominent feature of cocaine abuse and dependence disorders is the frequent occurrence of relapse episodes. Because psychological distress and negative emotional affect are known to induce drug craving and promote relapse in addicted individuals, an understanding of the relationship between stress and addictive processes may help identify effective medications and/or behavioral strategies for relapse prevention. Relapse to drug use is frequently modeled in experimental animals using the reinstatement procedure. In this paradigm, animals are trained to self-administer drugs of abuse via operant responding (e.g. lever-press). Once self-administration behavior is stable, responding can be extinguished by withholding drug availability and/or drug-associated environmental stimuli. Once extinguished, responding can be reinstated by exposing the animal to various stimuli, including stress. However, the most commonly-used stressors to reinstate cocaine- seeking behavior in animals are physical and pharmacological stressors which lack face validity as compared to psychological stressors that induce craving and promote relapse in humans. Social defeat stress occurs in both wild and laboratory rats and can be engendered by placing an intruder rat into the home cage of a resident territorial rat. The resident will quickly threaten and ultimately defeat the intruder. Importantly, the psychologicl stress experienced by the intruder has been described as a valid model of the types of psychosocial stress that drug abusers experience prior to a relapse episode. However, whether social defeat stress reinstates cocaine-seeking behavior in animals has not been investigated. This research proposal therefore aims to develop and characterize a novel model of stress-induced reinstatement in rats following exposure to the ethologically-valid psychosocial stressor, social defeat. Rats will be trained to self-administer cocaine and responding will subsequently be extinguished. The first set of experiments will determine whether exposure to acute or repeated social defeat stress reinstates cocaine- seeking behavior, and if so, whether the underlying mechanisms are different from those described previously for physical and pharmacological stressors. Furthermore, as it is known that social defeat stress enhances many of the abuse-related effects of cocaine, a separate set of experiments will examine whether cocaine-primed reinstatement is potentiated in rats with a recent history of social defeat exposure. Overall, the results of these studies would be the first to describe a preclinical model of drug relapse using a rodent psychosocial stressor that closely models the types of stressors that have been found to induce craving and promote relapse in human substance abusers. With such a model available, it may be possible to subsequently identify novel pharmacotherapeutic and/or behavioral strategies to mitigate the effects of psychosocial stress and facilitate relapse prevention in individuals with substance abuse disorders.

DESCRIPTION (provided by applicant): Alzheimer's disease (AD), a neurodegenerative disease that is the most common cause of dementia in the elderly and poses immense burdens on society, is characterized neuropathologically by ¿-amyloid plaques and tau neurofibrillary tangles. A recent series of papers has revealed that AD-like neuropathology can first be detected in the locus coeruleus (LC), a brainstem noradrenergic nucleus implicated in learning and memory that degenerates early in AD. Furthermore, LC lesions exacerbate, while pro-noradrenergic treatments ameliorate, AD-like neuropathology and cognitive deficits in transgenic mouse models of the disease. However, these studies have been limited by reliance on mouse AD models that do not recapitulate critical aspects of the disease such as bona fide tau tangles and neuronal loss. In addition, current noradrenergic manipulations cannot distinguish between the two distinct modes of LC firing, tonic and phasic, which have very different effects on cognition and neurotransmitter release. To overcome these limitations, we will use optogenetics to drive tonic or phasic LC activity in the TgF344-AD transgenic rat that manifests all critical neuropathological and cognitive hallmarks of AD. Completion of these studies will identify the most beneficial firing modes and neuromodulators responsible for the pro-cognitive and neuroprotective properties of the LC, thus laying the groundwork for the design of LC-based therapies for the treatment of AD.

SUMMARY The mission of the Rodent Behavioral core (RBC) is to provide planning, execution, and analysis of behavioral experiments relevant to neurological diseases and stroke using mice and rats. The RBC strives to provide the Emory research community ready access to high quality rodent behavioral methodologies and associated resources. Like other ENNCF cores, the RBC was seeded with institutional support (the Center for Neurodegenerative Disease, Department of Human Genetics, the Emory University Neuroscience Initiative, and the School of Medicine), to meet the growing needs of neuroscience investigators with services that had not been available otherwise. With NINDS funded investigators comprising a very high percentage of RBC users (14 out of 25 PIs), and well-matched goals with those of the ENNCF, it was decided to add the RBC to this P30 application. Addition of the RBC to the ENNCF will provide Emory NINDS investigators with preferred and subsidized access to the multiple rodent behavioral assays and surgical services offered by the RBC. Because no individual NINDS-funded laboratory has the array of behavioral tasks, expertise, and equipment offered by the RBC, this access will be vital to the success of their research programs. The inclusion of the RBC will put a full range of behavioral services at the fingertips of these investigators at a fraction of the cost it would take to acquire the equipment and trained personnel to conduct rodent behavioral research. The primary objectives of the RBC are to provide: (1) access to state-of-the-art rodent behavioral testing equipment and emerging technologies, (2) expertise and guidance in the planning, execution, and analysis of rodent behavioral research experiments, and (3) an outstanding research environment that provides infrastructure, education and resources to foster collaborations between investigators and cores. These objectives implemented by the RBC have proven to stimulate multidisciplinary research and innovation in basic and translational neuroscience.

DESCRIPTION (provided by applicant): Norepinephrine (NE) provides excitatory drive onto midbrain dopamine (DA) neurons and modulates responses to dopaminergic drugs, including psychostimulants. Chronic loss of noradrenergic tone impairs DA neuron firing and DA release, leading to compensatory alterations in postsynaptic DA receptor signaling and a paradoxical hypersensitivity to dopaminergic drugs. The goal of this proposal is to identify the molecular and cellular mechanisms underlying the behavioral hypersensitivity to cocaine following chronic inhibition of the NE biosynthetic enzyme, dopamine ?ydroxylase (DBH). Based on our preliminary data, we propose that a chronic loss of NE produces a decrease in ?rrestin2 (?r2) in the nucleus accumbens (NAc), which promotes a reversal in the valence of D2 responses from inhibitory to excitatory, potentially via a G?to-G?switch in D2 receptor coupling. In Aim 1, we will determine the consequences of increasing or reducing the amount of ?r2 selectively in D1 or D2 NAc neurons on behavioral responses to D2 agonist and cocaine. We will also test whether decreasing NAc neuron excitability normalizes cocaine responses following chronic DBH inhibition. In Aim 2, we will use slice electrophysiology to determine whether decreasing ?r2 specifically in D1 or D2 NAc neurons is necessary and sufficient to trigger the switch from D2-mediated inhibition to excitation and further investigate alterations in D2 G protein coupling. In Aim 3, we will assess the effects of chronic DBH inhibition and reduction of ?r2 on the aversive properties of cocaine using the runway model of cocaine self-administration in rats. Completion of these Specific Aims will contribute to our understanding of noradrenergic modulation of mesolimbic DA transmission, the plasticity of DA receptor signaling pathways, and NE-DA interactions underlying aversive responses to drugs of abuse.

Project Summary/Abstract Cocaine abuse has persisted as a major public health concern within the United States for several decades despite substantial efforts to develop therapeutic strategies for its treatment. In particular, medications development efforts have failed to yield a single FDA-approved or generally accepted pharmacotherapy for cocaine dependence. Prominent and problematic consequences of prolonged drug abuse include the persistent devaluation of natural nondrug rewards that previously functioned as effective reinforcers prior to drug exposure, and an increase in the ?incentive salience? of drug-associated stimuli, leading to the model that drugs ?hijack? the brain's natural reward system. The purpose of this proposal is to determine whether a behavioral modification strategy encompassing occasional, unexpected presentation of a high-value, alternate reinforcer will increase the hedonic value and/or motivational salience of a natural reward such that it will reduce cocaine seeking in rats. In Aim 1, we will use an operant cocaine vs. food choice procedure to determine whether a rare, unexpected reward will shift preferred responding from cocaine to food and alter associated dopamine transmission in the nucleus accumbens. Aim 2 will examine the consequences of this behavioral manipulation in a model of relapse-like behavior.

DESCRIPTION (provided by applicant): Norepinephrine (NE) provides excitatory drive onto midbrain dopamine (DA) neurons and modulates responses to dopaminergic drugs, including psychostimulants. Chronic loss of noradrenergic tone impairs DA neuron firing and DA release, leading to compensatory alterations in postsynaptic DA receptor signaling and a paradoxical hypersensitivity to dopaminergic drugs. The goal of this proposal is to identify the molecular and cellular mechanisms underlying the behavioral hypersensitivity to cocaine following chronic inhibition of the NE biosynthetic enzyme, dopamine ?ydroxylase (DBH). Based on our preliminary data, we propose that a chronic loss of NE produces a decrease in ?rrestin2 (?r2) in the nucleus accumbens (NAc), which promotes a reversal in the valence of D2 responses from inhibitory to excitatory, potentially via a G?to-G?switch in D2 receptor coupling. In Aim 1, we will determine the consequences of increasing or reducing the amount of ?r2 selectively in D1 or D2 NAc neurons on behavioral responses to D2 agonist and cocaine. We will also test whether decreasing NAc neuron excitability normalizes cocaine responses following chronic DBH inhibition. In Aim 2, we will use slice electrophysiology to determine whether decreasing ?r2 specifically in D1 or D2 NAc neurons is necessary and sufficient to trigger the switch from D2-mediated inhibition to excitation and further investigate alterations in D2 G protein coupling. In Aim 3, we will assess the effects of chronic DBH inhibition and reduction of ?r2 on the aversive properties of cocaine using the runway model of cocaine self-administration in rats. Completion of these Specific Aims will contribute to our understanding of noradrenergic modulation of mesolimbic DA transmission, the plasticity of DA receptor signaling pathways, and NE-DA interactions underlying aversive responses to drugs of abuse.

Project Summary/Abstract Sleep disorders constitute a major public health problem in the United States, and abnormalities in arousal often occur in concert with other neurological or neuropsychiatric diseases. The locus coeruleus (NE), the major source of norepinephrine (NE) in the brain, promotes arousal, attention, and wakefulness, but the neural substrates that transduce these actions of the LC have not been fully identified. One intriguing candidate is an understudied population of wake-promoting dopamine (DA) neurons in the ventral periaqueductal gray (vPAG). The LC projects to the vPAG, and our preliminary data indicate that NE provides excitatory drive onto DA neurons in this brain region via ?1-adrenergic receptors (?1ARs), suggesting that NE-DA interactions in the vPAG may promote arousal. The goal of this proposal is to delineate this LC-vPAG circuit. In Aim 1, we will use tract tracing and immunohistochemistry at the electron microscopic level to map the connections between the LC and vPAG as well as specific localization of ?1ARs. In Aim 2, we will use ex vivo slice electrophysiology to determine the cellular mechanisms underlying the ability of NE to enhance excitatory drive onto vPAG DA neurons. In Aim 3, we will use DREADD chemogenetics to assess the behavioral consequences of inhibiting or stimulating various nodes of the LC-vPAG arousal circuit. These studies will define a novel arousal circuit and identify candidate neuroanatomical and molecular targets for the treatment of both primary and disease- associated deficits.

3q29 deletion syndrome is caused by a recurrent, typically de novo 1.6 Mb heterozygous deletion that is associated with a range of neuropsychiatric phenotypes, including mild to moderate intellectual disability, autism, anxiety, and a 40-fold increased risk for schizophrenia. The high risk conferred by this deletion for neuropsychiatric phenotypes, coupled with its relatively low complexity (22 genes in the deletion interval), make it ideal for molecular dissection. Our team at Emory University has created the first mouse model of 3q29 deletion syndrome, and we show behavioral deficits consistent with compromised neurodevelopment. This model is therefore an excellent tool for interrogating the precise genetic and molecular mechanisms underlying 3q29 deletion syndrome. We propose using this model to a) identify the range of behaviors and other phenotypic manifestations with the largest departure from wild type; b) systematically pare the interval down to the minimal genes responsible for behavioral phenotypes by creating sub-deletion mice and assessing behavior; and c) identify the genes and pathways that are the molecular drivers of 3q29 deletion syndrome by evaluating transcriptional and proteomic changes in 3 distinct brain regions in full deletion and sub-deletion mice. Data from this project will be compared to our companion NIH-funded project where we are investigating molecular signatures in cells from human patients (?Modeling the Human Neuronal Phenotype of the Schizophrenia-Associated 3q29 Deletion,? 1 R01 MH110701). Understanding the specific biological processes disrupted in 3q29 deletion syndrome may provide a molecular window into key neurodevelopmental processes relevant to neuropsychiatric phenotypes, and can serve as a scaffold for integrating other targets identified in genetic studies of schizophrenia, autism, and intellectual disability. All molecular data and mouse lines will be readily and rapidly shared through NIH-approved databases and repositories.

? DESCRIPTION (provided by applicant): Huntington's disease (HD) represents an age-dependent neurodegenerative disease family including Alzheimer's (AD) and Parkinson's (PD) diseases. These diseases are characterized by selective neurodegeneration that is caused by misfolded proteins in an age-dependent manner. In HD, the disease protein huntingtin (htt) carries an expanded polyglutamine repeat, accumulates in the brain, forms aggregates as patients become old, and causes progressive neurological symptoms. Given the known genetic mutation in HD and its well-characterized neuropathology, HD makes an ideal model for investigating how selective neuropathology occurs in an age-dependent manner. Most previous studies focused on the effect of mutant htt on neuronal cells and revealed that N-terminal fragments of mutant htt are misfolded and cause cell-autonomous and non-cell-autonomous pathological events in a variety of animal models. In the brain, the majority of cells are non-neuronal cells that provide essential support to the survival and function of neuronal cells. These non-neuronal cells mainly consist of three types of glial cells: astrocytes, microglial cells and oligodendrocytes. It is known that oligodendrocytes produce myelin proteins for myelination of axons, and astrocytes can release neurotrophins to support neuronal survival and function. However, whether mutant htt in glial cells affects these important functions remains to be investigated. We have established transgenic mouse models that express mutant htt specifically in astrocytes (GFAP-160Q) or oligodendrocytes (PLP-150Q). Both HD mouse models develop age-dependent neurological phenotypes, suggesting that mutant htt in glial cells affects glial function during aging and critically contribute to the age-dependent clinical phenotypes. We also found that in our GFAP-160Q HD transgenic mice, mutant htt can reduce BDNF release from astrocytes and cause demyelination or neuronal death reminiscent the pathological events in previous HD mouse models and human HD patient's brains. In this application, we propose three aims to investigate how expression of mutant htt in glial cells causes neuronal dysfunction and neurological phenotypes in HD transgenic mice. Aim 1 is to examine the effect of mutant htt on secretion of neurotrophic factors from glial cells. Aim 2 is to explore how mutant htt in glial cells causes age-dependent neurological phenotypes and neuropathology. Aim 3 is to investigate the protective effects of reducing htt in glial cells or improving glial function in HD mouse brains. These studies will help understand the mechanisms for age-dependent neuropathology in HD and the contribution of glial htt to HD pathology. Because glial cells are a desirable transplant population for therapy, the findings from our study may also provide a new therapeutic target for treating HD.

Project Summary Amyloid-? (A?) plaques and tau neurofibrillary tangles, as well as neuronal death, are the pathologic hallmarks of Alzheimer?s disease (AD). Therapeutic efforts focused on A? have thus far failed, underscoring the urgent need for alternate approaches, particularly those that can target early AD. Aberrant tau in the locus coeruleus (LC), the major noradrenergic nucleus in the brain that regulates attention, arousal, stress responses, and cognition, is the earliest detectable AD-like neuropathology in the human brain, and thus represents a potential therapeutic target. However, we do not know why LC neurons are selectively vulnerable to developing early tau pathology and degenerating later in disease, nor whether the LC might seed the stereotypical spread of tau pathology to the rest of the brain. Based on a wealth of cell culture and in vivo preliminary data, we propose to test the hypothesis that the toxic norepinephrine (NE) metabolite DOPEGAL activates asparagine endopeptidase (AEP), which cleaves tau at residue N368 into aggregation- and propagation-prone forms, thus leading to LC degeneration and the spread of tau pathology to the forebrain. In Aim 1, we will examine the impact of DOPEGAL on tau pathology and toxicity in primary mouse LC neurons using various knockout, viral vector, and pharmacological tools to manipulate NE metabolism and AEP. In Aim 2, we will determine whether DOPEGAL-induced AEP cleavage of tau is necessary for toxicity in vivo by exploring the effects of P301S tau overexpression in the LC on DOPEGAL levels, pathogenic tau accrual, and noradrenergic function following genetic or pharmacological inhibition of the NE-DOPEGAL-AEP-Tau pathway. In Aim 3, we will test the contribution of the NE-DOPEGAL-AEP-Tau pathway and neuronal activity on the spread of pathogenic tau from the LC to the forebrain. Completion of these experiments will reveal the role of DOPEGAL and AEP in the selective vulnerability of LC neurons in AD and lay the foundation for the development of LC/AEP-based therapies that retard progression of the disease.

Amyloid-? (A?) plaques and tau neurofibrillary tangles, as well as neuronal death, are the pathologic hallmarks of Alzheimer's disease (AD). Therapeutic efforts focused on A? have thus far failed, underscoring the urgent need for alternate approaches, particularly those that can target early AD. Aberrant tau in the locus coeruleus (LC), the major noradrenergic nucleus in the brain that regulates attention, arousal, stress responses, and cognition, is the earliest detectable AD-like neuropathology in the human brain, and LC degeneration is ubiquitious in later AD. Recent research indicates that early LC dysfunction may contribute to prodromal AD symptoms such as depression, anxiety, and sleep disorders, while later LC degeneration exacerbates cognitive impairment. Although these data suggest that the LC is a promising therapeutic target in AD, almost nothing known about how pathogenic tau impacts LC function and survival. We have developed a viral vector that drives the expression of wild-type human tau exclusively in LC neurons, which over time becomes hyperphosphorylated and misfolded, thus recapitulating the earliest forms of human AD. We will use this novel tool to study the consequences tau pathology in the LC. In Aim 1, we will determine the impact of different forms of aberrant tau on LC neuron morphology, survival, and local inflammation, and assess the potential of LC-derived tau pathology to spread to interconnected forebrain regions. In Aim 2, we will use in vivo electrophysiology and behavioral paradigms to evaluate how tau pathology affects LC activity and performance in neuropsychiatric and cognitive domains. In Aim 3, we will combine optogenetics and fMRI to determine how aberrant tau influences LC-forebrain functional connectivity. Completion of these aims will lay the groundwork for LC/tau-based therapies for early AD.

SUMMARY/ABSTRACT: RESEARCH EDUCATION COMPONENT Alzheimer?s disease (AD) is the most common cause of dementia, affecting more than 5 million Americans. At the same time that the prevalence of AD is increasing, the number of new investigators in the US is decreasing, which may severely hamper our efforts to develop better diagnostic and treatment tools for AD and related dementias (ADRD). The goal of the Research Education Component (REC) of the Goizueta Alzheimer?s Disease Research Center (ADRC) at Emory is to support research educational activities that complement and enhance the training of the future workforce to meet the nation?s biomedical, behavioral and clinical needs in ADRD. We will achieve this goal by identifying and supporting the research education of junior investigators and trainees from diverse backgrounds and disciplines. In Aim 1, REC leadership and mentors will work with these trainees to develop and execute tailored educational plans for new and early stage investigators to advance towards independence in conducting AD-related research. In Aim 2, we will leverage Emory?s wealth of basic and clinical scientists as well as partner Atlanta-area institutions to identify, recruit and support the research training of new/early stage investigators and trainees from diverse backgrounds and disciplines, with special emphasis on URMs, to engage in AD-related research. In Aim 3, the REC leadership and external advisory committee will rigorously monitor and evaluate the trainees, mentors, and the overall program, and implement improvements when necessary. Success of the REC will result in rolling cohorts of new investigators with a focus on diversity to lead the next generation of ADRD research.

Project Summary The opioid epidemic has been declared a national public health emergency. Current treatments have abuse liability, target acute overdose only, and/or are ineffective for many people suffering from opioid addiction, and new therapies are desperately needed. One promising target is the brain galanin system; reducing galanin levels exacerbates morphine reward and withdrawal, while increasing galanin opposes opioid addiction-like behaviors. However, the neuroanatomical source and target of this protective galanin have not been identified, and the effects of galanin on voluntary opioid intake have not been investigated. The locus coeruleus (LC) modulates the activity of the mesolimbic reward pathway and has been implicated in opioid addiction, and 80% of noradrenergic neurons in this nucleus co-express galanin. We have assembled a set of genetically altered mice that either lack or overexpress galanin specifically in noradrenergic neurons to test the hypothesis that LC-derived galanin suppresses the ability of opioids to disinhibit dopamine (DA) neurons in the ventral tegmental area (VTA) and attenuates opioid reward/reinforcement, as well as acts in an autocrine manner to prevent LC hyperactivity and reduces withdrawal symptoms. In Aim 1, we will use in situ hybridization to determine the neurochemical identity of galanin receptor-expressing cells in the VTA, and slice and in vivo electrophysiology to investigate the circuitry and cellular mechanisms underlying the ability of galanin to oppose opioid-induced VTA DA neuron activity. In Aim 2, we will use the transgenic mice described above to test the hypothesis that LC-derived galanin inhibits opioid reinforcement using an operant i.v. opioid self- administration paradigm. In Aim 3, we will assess the ability of galanin to suppress LC hyperactivity, cellular plasticity, and aversive symptoms during opioid withdrawal. Completion of these aims will lay the groundwork for LC/galanin-based therapies for opioid addiction.