2011 — 2012 |
Arrant, Andrew Emmett |
F31Activity Code Description: To provide predoctoral individuals with supervised research training in specified health and health-related areas leading toward the research degree (e.g., Ph.D.). |
Serotonergic Contribution to Adolescent Risk Taking
DESCRIPTION (provided by applicant): Risk taking behavior peaks during adolescence and can lead to undesired behaviors such as drug use and unsafe sexual activity. Immaturity of the neural circuitry that controls motivated behavior may contribute to adolescent risk taking. Serotonin modulates this neural circuit and may be important for adolescent risk taking because it has been shown to facilitate behavioral inhibition in response to aversive outcomes. However, few studies have investigated the role of serotonin in adolescent risk taking. In preliminary studies we tested the behavioral effects of serotonergic drugs in adult male 67-73 day old (PN67-73) and early adolescent male (PN28-34) rats. We used rodent anxiety tests because behavior in these tests may reflect behavioral inhibition and risk taking as well as anxiety. Depletion of serotonin with the tryptophan hydroxylase inhibitor p- chlorophenylalanine (PCPA) was anxiolytic in adult rats in the novelty induced hypophagia (NIH) test, but had no effect on anxiety in adolescent rats. Adolescent rats were also less sensitive than adults to the anxiogenic effects of the serotonin releaser fenfluramine (2 mg/kg) and the serotonin reuptake inhibitor fluoxetine (10 mg/kg) in the light/dark (LD) test. Preliminary microdialysis in the prefrontal cortex showed that adolescent rats have a lower serotonergic response to fenfluramine (1, 2.5, and 10 mg/kg) than adults. We hypothesize that adolescents have immature serotonergic innervation to the forebrain that results in disinhibited behavior. We will investigate this hypothesis with three specific aims using PN28-32 and PN67-73 male rats. In aim one we will test the impact of serotonin tone and stores by evaluating the effects of fenfluramine (1, 2.5, and 10 mg/kg), fluoxetine (5, 10, and 20 mg/kg), and PCPA (2 doses of 150 mg/kg) in the elevated plus maze (EPM). Aim two will use microdialysis to investigate age differences in serotonergic function in the medial prefrontal cortex, a region in which serotonin modulates anxiety-like behavior and impulsivity. We will use the zero net flux method to compare baseline serotonin levels in adult and adolescent rats. We will complete our preliminary fenfluramine study and use potassium depolarization to assess the capacity to release serotonin. We will then measure the response to a range of doses of fluoxetine (5, 10, and 20 mg/kg) and pretreat animals used in this experiment with saline or 0.3 mg/kg WAY-100635 to compare 5-HT1A regulation of the fluoxetine response. Aim three will determine where in the brain serotonin exerts age-specific effects during performance of an anxiety test. We will compare neuronal activation after performance of the NIH test using expression of the immediate early gene c-Fos in adult and adolescent rats treated with PCPA or vehicle. This proposal is relevant to NIMH strategic objective 1.1 because its goal is to investigate how development of the serotonin system across adolescence changes serotonergic modulation of behavior. This proposal also addresses NIMH strategic objective 2.1 as developmental changes in the serotonergic system could affect the emergence of mood disorders and modulate the effects of drugs used to treat these disorders in adolescents. PUBLIC HEALTH RELEVANCE: This proposal investigates how serotonergic modulation of risk taking behavior may change between adolescence and adulthood. Findings of developmental differences in how serotonin modulates behavior in rodents will increase our understanding of why adolescents engage in negative risk taking behaviors and may also have implications for the emergence and treatment of mood disorders during adolescence.
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0.97 |
2015 |
Arrant, Andrew Emmett |
F32Activity Code Description: To provide postdoctoral research training to individuals to broaden their scientific background and extend their potential for research in specified health-related areas. |
Mechanisms of Frontotemporal Dementia Like Behavior in Progranulin Deficient Mice @ University of Alabama At Birmingham
? DESCRIPTION (provided by applicant): Frontotemporal dementia (FTD) is a progressive, fatal neurodegenerative disorder in which patients suffer personality changes, social withdrawal, and disinhibition. There is currently no treatment for this disease. Loss-of-function mutations in progranulin (GRN) that cause progranulin deficiency are a major genetic cause of FTD (5-10% of all cases). Grn+/- and Grn-/- mice are an animal model of progranulin deficiency, and may model some of the behavioral and neuronal dysfunction seen in FTD. Both Grn+/- and Grn-/- mice develop abnormal social behavior, conditioned fear deficits, and amygdala dysfunction around 6 months of age. Grn-/- mice also develop lipofuscinosis that may model neuronal ceroid lipofuscinosis, which occurs in patients homozygous for loss-of-function GRN mutations. The mechanism by which progranulin deficiency causes neuronal dysfunction is unknown, and is a key gap in our understanding of FTD. Grn+/- mice may be a useful model to address this question. In preliminary studies, we observed elevated phosphorylation of ribosomal protein S6 (Ser235/236) and Akt (Ser473) in the amygdala of Grn+/- mice. These data suggest increased signaling in the mTOR pathway, which causes abnormal social behavior in other mouse models. The goal of this proposal is to investigate the hypothesis that progranulin deficiency causes abnormal social behavior, conditioned fear, and amygdala dysfunction through elevated mTOR signaling. We will investigate this hypothesis using Grn+/+ and Grn+/- mice. In aim 1 we will determine if increased mTOR signaling causes abnormal behavior and amygdala dysfunction in progranulin-deficient mice. First, we will measure phosphorylated and total levels of mTOR pathway signaling molecules (p-Akt, p-mTOR, p-S6 kinase, and p-S6) in FTD-associated brain regions (amygdala and prefrontal cortex) and a region not expected to be affected (cerebellum) in Grn+/+ and Grn+/- mice at ages before (3 months), during (5 and 7 months) and after (9 months) the transition to abnormal behavior. We will then determine if inhibiting mTOR signaling will prevent or reverse the phenotype of Grn+/- mice. Mice will be fed either a control or a rapamycin-supplemented diet for four weeks before (age 5-6 months) or after (age 9-12 months) the emergence of abnormal behavior. Immediately after this four week period, the mice will be tested for abnormal behavior and amygdala dysfunction. Amygdala function will be tested by measuring c-Fos expression after exposure to a novel, social environment. Inhibition of mTOR signaling will be confirmed by western blotting of cortex and amygdala samples. In aim 2 we will investigate whether increasing progranulin levels with an AAV-Grn vector will normalize behavior, amygdala function, and mTOR signaling in Grn+/- mice. We will infuse AAV-Grn or AAV- Gfp into the prefrontal cortex and amygdala of Grn+/+ and Grn+/- before (age 5-6 months) or after (age 9-12 months) the emergence of abnormal behavior. Behavior, amygdala function, and mTOR signaling will be tested four weeks after AAV injection, using the assays described in aim one.
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1 |
2017 — 2018 |
Arrant, Andrew Emmett |
K99Activity Code Description: To support the initial phase of a Career/Research Transition award program that provides 1-2 years of mentored support for highly motivated, advanced postdoctoral research scientists. |
Abnormal Late Endosomal Trafficking in Frontotemporal Dementia Due to Progranulin Mutations @ University of Alabama At Birmingham
Project Summary/Abstract. Candidate: My goal is to become an independent scientist investigating endolysosomal dysfunction in neurodegenerative disease, with a focus on endosomal maturation and trafficking. My background is in neuropharmacology and mechanisms of rodent behavior, but I have recently shifted to investigating abnormal endosomal trafficking in progranulin-insufficient mice. Having received my PhD in 2012, this is my final cycle of eligibility for a K99/R00 award. My goal is to establish a laboratory to investigate endolysosomal dysfunction in multiple genetic models of frontotemporal dementia (FTD). After establishing expertise in this field, I hope to investigate models of Alzheimer?s disease and eventually begin to explore how environmental factors (ex. exercise, environmental enrichment, etc.) interact with neuronal endolysosomal function to influence behavior. Training: In addition to my primary mentor, Dr. Erik Roberson, I have assembled an advisory committee that includes experts on endolysosomal function (Dr. James Collawn) and exosome analysis (Dr. Andrew West), as well as Dr. David Standaert, the chair of our Department of Neurology with extensive postdoctoral training experience. I will present at international meetings and take courses (both external and internal to UAB) for technical training (cell biology, endosomal trafficking, and exosome analysis), professional development (lab management, budgeting, scientific writing, and the tenure process), and ethical conduct of research. Research: Loss-of-function mutations in progranulin (GRN) are a major cause of FTD, and are thought to cause FTD through progranulin haploinsufficiency. This proposal will test the hypothesis that FTD due to progranulin (GRN) mutations (FTD-GRN) is caused by endolysosomal dysfunction. We hypothesize that progranulin insufficiency impairs lysosomal activity, which disrupts late endosomal trafficking and ultimately causes FTD in humans and disrupts behavior in mice. Progranulin is critical for normal lysosomal function as complete progranulin deficiency causes a lysosomal storage disorder. In preliminary studies, we have observed elevated levels of exosome in plasma from FTD-GRN patients, as well as progranulin-insufficient (Grn+/?) mouse plasma and primary neuron culture media. In aim 1, we will test whether this enhanced exosome production reflects a shift in trafficking of multivesicular bodies (MVBs) away from lysosomal degradation and toward exosome secretion. In aim 2A we will determine if lysosomal dysfunction causes this enhanced exosome secretion and in aim 2B we will determine if this endolysosomal dysfunction causes behavior deficits in Grn+/? mice. In aim 3 we will compare levels of late endosomal/lysosomal proteins and MVB morphology in brains of FTD-GRN patients with healthy controls and Alzheimer?s disease patients to control for nonspecific effects of neurodegeneration. These studies will give me experience with primary neuronal culture, endosomal tracking analysis, shRNA gene knockdown, and exosome isolation and analysis.
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1 |
2019 — 2021 |
Arrant, Andrew Emmett |
R00Activity Code Description: To support the second phase of a Career/Research Transition award program that provides 1 -3 years of independent research support (R00) contingent on securing an independent research position. Award recipients will be expected to compete successfully for independent R01 support from the NIH during the R00 research transition award period. |
Abnormal Late Endosomal Trafficking in Frontotemporal Dementia Due to Progranulin Mutation @ University of Alabama At Birmingham
Project Summary/Abstract. Candidate: My goal is to become an independent scientist investigating endolysosomal dysfunction in neurodegenerative disease, with a focus on endosomal maturation and trafficking. My background is in neuropharmacology and mechanisms of rodent behavior, but I have recently shifted to investigating abnormal endosomal trafficking in progranulin-insufficient mice. Having received my PhD in 2012, this is my final cycle of eligibility for a K99/R00 award. My goal is to establish a laboratory to investigate endolysosomal dysfunction in multiple genetic models of frontotemporal dementia (FTD). After establishing expertise in this field, I hope to investigate models of Alzheimer?s disease and eventually begin to explore how environmental factors (ex. exercise, environmental enrichment, etc.) interact with neuronal endolysosomal function to influence behavior. Training: In addition to my primary mentor, Dr. Erik Roberson, I have assembled an advisory committee that includes experts on endolysosomal function (Dr. James Collawn) and exosome analysis (Dr. Andrew West), as well as Dr. David Standaert, the chair of our Department of Neurology with extensive postdoctoral training experience. I will present at international meetings and take courses (both external and internal to UAB) for technical training (cell biology, endosomal trafficking, and exosome analysis), professional development (lab management, budgeting, scientific writing, and the tenure process), and ethical conduct of research. Research: Loss-of-function mutations in progranulin (GRN) are a major cause of FTD, and are thought to cause FTD through progranulin haploinsufficiency. This proposal will test the hypothesis that FTD due to progranulin (GRN) mutations (FTD-GRN) is caused by endolysosomal dysfunction. We hypothesize that progranulin insufficiency impairs lysosomal activity, which disrupts late endosomal trafficking and ultimately causes FTD in humans and disrupts behavior in mice. Progranulin is critical for normal lysosomal function as complete progranulin deficiency causes a lysosomal storage disorder. In preliminary studies, we have observed elevated levels of exosome in plasma from FTD-GRN patients, as well as progranulin-insufficient (Grn+/?) mouse plasma and primary neuron culture media. In aim 1, we will test whether this enhanced exosome production reflects a shift in trafficking of multivesicular bodies (MVBs) away from lysosomal degradation and toward exosome secretion. In aim 2A we will determine if lysosomal dysfunction causes this enhanced exosome secretion and in aim 2B we will determine if this endolysosomal dysfunction causes behavior deficits in Grn+/? mice. In aim 3 we will compare levels of late endosomal/lysosomal proteins and MVB morphology in brains of FTD-GRN patients with healthy controls and Alzheimer?s disease patients to control for nonspecific effects of neurodegeneration. These studies will give me experience with primary neuronal culture, endosomal tracking analysis, shRNA gene knockdown, and exosome isolation and analysis.
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1 |
2020 — 2021 |
Arrant, Andrew Emmett |
R21Activity Code Description: To encourage the development of new research activities in categorical program areas. (Support generally is restricted in level of support and in time.) |
Regulation of Extracellular Progranulin in the Brain @ University of Alabama At Birmingham
Project Summary/Abstract Genetic studies indicate a link between low progranulin levels and neurodegenerative disease. Loss-of- function progranulin (GRN) mutations are one of the most common dominant genetic causes of frontotemporal dementia (FTD), accounting for around 5% of FTD cases. GRN polymorphisms are associated with increased risk for Alzheimer's disease (AD), FTD, and Parkinson's disease. Most pathogenic GRN mutations cause progranulin haploinsufficiency, and the best-known GRN polymorphism that increases risk of AD and FTD is associated with around 20% reduction of progranulin. Progranulin is secreted by multiple cell types throughout the body and is present in both blood and cerebrospinal fluid (CSF). Extracellular progranulin may interact with cell-surface signaling receptors to exert neurotrophic and anti-inflammatory effects. Extracellular progranulin is also taken up by cells and trafficked to lysosomes, where it enhances lysosomal enzyme activity. Progranulin haploinsufficiency is thought to drive FTD pathogenesis in GRN mutation carriers through loss of these beneficial effects. Progranulin-boosting therapies are under development to correct progranulin haploinsufficiency in GRN mutation carriers, either by increasing progranulin expression or reducing progranulin uptake. Both strategies should increase levels of extracellular progranulin, which could produce widespread correction of progranulin haploinsufficiency. However, very little is known about the regulation of extracellular progranulin in the brain. This is a major gap in the field that limits our ability to test progranulin- boosting therapies and investigate the physiologic functions of progranulin. Studies of progranulin in blood and CSF indicate differential regulation of extracellular progranulin levels in the periphery versus the central nervous system, highlighting the importance of studying extracellular progranulin in the brain. To address this need, we have adapted in vivo microdialysis to measure extracellular progranulin in the brain of mouse models. We propose to use this technique to investigate the mechanisms regulating brain extracellular progranulin levels. We hypothesize that brain extracellular progranulin levels are regulated by the balance between secretion and cellular uptake, and that these processes are dynamic, producing short-term fluctuations in extracellular progranulin levels. Progranulin is constitutively secreted, so in aim 1 we will test the hypothesis that progranulin expression is a major driver of secretion and thus extracellular progranulin levels. In aim 2 we will test the hypothesis that sortilin-mediated uptake is a major regulator of brain extracellular progranulin levels. We will conduct these experiments using a mouse-reactive analog of the sortilin-blocking antibody AL001, which is entering phase 2 clinical trials for FTD due to GRN mutations. In aim 3 we will test the hypothesis that neuronal activity increases brain extracellular progranulin levels. We anticipate that this work will lay the foundation for future studies of progranulin-boosting therapies and progranulin physiology.
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