Research
Ongoing Research Support
R21 NS058375-01A2 Eells (PI) 09/26/08-07/31/11
Sponsor: National Institutes of Health
Title: Regulation and function of Nurr1 in nigrostriatal dopamine neurons.
Goals: This project uses microdialysis, in vivo gene knockdown, and laser capture microdissection to investigate the regulation of Nurr1 expression and putative target genes of Nurr1 specifically in nigrostriatal dopamine neurons.
Responsibilities: Performing and training students on stereotaxic and surgical procedures, laser capture microdissection and tissue dissections and overall organization and administration of the project.
Role: PI
Abstract: Parkinson's disease is a common neurological disorder, the symptoms of which are caused primarily by a loss of dopamine neurons in the substantia nigra and reduced dopamine in the striatum. The transcription factor Nurr1 is necessary for normal dopamine neuron development as demonstrated by a failure of dopamine neurons to develop properly in Nurr1-null homozygous mice. Nurr1 also appears to function in maintaining normal dopamine synthesis and dopamine neuron survival as mice with a single deletion of the Nurr1 gene are impaired in both parameters. Additionally, the expression of Nurr1 has been shown to fluctuate as a result of changes in electrical activity and after treatments that can affect the activation of dopamine autoreceptors. The relative contribution of these factors on Nurr1 expression have not been determined. Based on this data, we hypothesize that increasing neuronal activity and inhibition of dopamine autoreceptors will increase Nurr1 expression in dopamine neurons. Furthermore, we hypothesize that attenuating Nurr1 expression will attenuate target genes of Nurr1, dopamine synthesis and dopamine neuron survival. Currently, little is known about the mechanism(s) that regulate Nurr1 expression in adult dopamine neurons, how changes in Nurr1 affect dopamine synthesis or how Nurr1 functions in dopamine neuron survival. The specific aims of the current proposal are 1) to establish the conditions that control Nurr1 expression in dopamine neurons in vivo by comparing the contributions of changes in neuronal activity and dopamine autoreceptor activation by stimulating or inhibiting activity alone or in combination with a dopamine receptor agonist or antagonist introduced via reverse microdialysis, and 2) to identify the extent by which Nurr1 controls dopamine neuron function by measuring changes in dopamine neuron gene expression and parameters of dopamine synthesis and changes in dopamine neuron survival in conditions of attenuated Nurr1 expression (antisense oligonucleotides and aging in Nurr1-null heterozygous mice). By using a combination of laser capture microdissection with gene expression technology of quantitative real-time PCR and eXpress profiling multiplex capillary electrophoresis based quantitative PCR, these experiments will demonstrate the utility of these techniques for investigating the role of transcription factors in the regulation of neurotransmission genes and specifically, the regulation of dopamine neurotransmission genes by Nurr1. The long term goal is to better understand the role of transcription factors in the function and survival of dopamine neurons as they relate to the pathogenesis of Parkinson’s disease. The current proposal will ascertain how Nurr1 expression in dopamine neurons is regulated in vivo and how Nurr1 functions to regulate dopamine synthesis and survival of dopamine neurons. This data will aid in determining the potential for targeting Nurr1 expression as a means to elevate dopamine synthesis and dopamine neuron survival as a treatment of Parkinson's disease.
R15 MH084209-01A1 Eells (PI) 04/16/09-04/15/12
Sponsor: National Institutes of Health
Title: Molecular biology of mesocortical and mesoaccumbens dopamine neurons.
Goals: This project uses the combination of retrograde tracers and laser capture microdissection to investigate the molecular differences between mesocortical and mesoaccumbens dopamine neurons under basal conditions and after inactivation of the prefrontal cortex.
Responsibilities: Performing and training on stereotaxic surgical procedures on rats, using the laser capture microdissection (LCM) microscope, RNA amplification and the overall organization and administration of the project.
Role: PI
Abstract: Aberrant dopamine neurotransmission has been implicated in schizophrenia with elevated mesoaccumbens (or subcortical) dopamine neurotransmission contributing to positive symptoms of schizophrenia (paranoia, hallucinations, delusions, and bizarre behavior) and attenuated mesocortical dopamine neurotransmission affecting negative symptoms (social withdrawal, blunted emotions, and cognitive deficits). Targeting the dopamine system has proven effective at treating positive symptoms of schizophrenia as all currently approved antipsychotics block the dopamine D2 receptor but the efficacy of antipsychotic at alleviating negative symptoms is limited. The mesocortical and mesoaccumbens dopamine neurons have distinct afferent innervation, pharmacology, neurochemistry and electrophysiology properties; however, there is an important gap in information about the genes expressed by these two dopamine neuron populations and how they are regulated. The first part of our hypothesis is that mesocortical and mesoaccumbens dopamine neurons will have distinct expression profiles of neurotransmitter receptor, transcription factor and dopamine neurotransmission genes that underlie their differences in function. Additionally, we hypothesize that the prefrontal cortex will have opposing effects on gene expression between these two populations. Specifically, that inactivation of the prefrontal cortex will attenuate expression of transcription factors and dopamine neurotransmission genes in mesocortical dopamine neurons and elevate these parameters in mesoaccumbens dopamine neurons. This is based on the observation that pyramidal neurons from the prefrontal cortex make excitatory synapses on mesocortical dopamine neurons but inhibit mesoaccumbens dopamine neurons via an intermediate GABAergic neuron. The specific aims of the current proposal are: 1) Elucidate differential gene expression between mesocortical and mesoaccumbens dopamine neurons and 2) Determine prefrontal cortex regulation of mesocortical and mesoaccumbens dopamine neuron gene expression. To achieve these aims, the combination of rapid tyrosine hydroxylase fluorescent immunocytochemistry and the fluorescently labeled retrograde tracer cholera toxin subunit B will be used to visualize mesocortical and mesoaccumbens dopamine neurons and laser capture microdissection will be used to isolate RNA specifically from these dopamine neurons under basal conditions or after inactivation of the prefrontal cortex. Gene eXpress profiling (GeXP) multiplex capillary electrophoresis based quantitative PCR will be used to determine the expression profiles of mesocortical and mesoaccumbens dopamine neurons. These experiments are expected to elucidate unique gene expression profiles and differential regulation of gene expression. Once we understand the features that distinguish these dopamine neuronal populations and how they are regulated, we can begin to investigate strategies to specifically target either of these systems to control abnormal dopamine neurotransmission in pathological conditions such as schizophrenia.
Completed Research Support
5-P20-RR017661-03 Chambers (PI) 09/01/02-08/31/08
Sponsor: National Institutes of Health/NCRR
Title: Pesticide Toxicity to the Nervous and Endocrine Systems.
Goals: This is a Center of Biomedical Research Excellence (COBRE) grant to promote junior faculty competitiveness and to create a competitive research center.
Project Title: The role of Nurr1 in the regulation of dopamine neuron damage induced by neurotoxins.
Goal of Project: This is a competitive project within the COBRE that investigated the susceptibility of the dopamine neurons in the Nurr1-null heterozygous mice to neurotoxin exposure.
Role on Project: PI
297001-182070-022000-383050 Eells (PI) 01/01/04-12/31/04
Sponsor: Mississippi State University Research Initiation Program
Title: “Examination of Dopamine Neurotransmission in Nurr1-null Heterozygous Mice”
Goal: This project compared gene expression and parameters of dopamine synthesis between the Nurr1-null heterozygous and wild-type mice
Role: PI
04-010083 Eells (PI) 07/01/04-06/30/07
Sponsor: Young Investigator Award -National Alliance for Research on Schizophrenia and Depression (NARSAD)
Title: “Dopamine function in the Nurr1(NR4A2)-null heterozygous mouse - a potential animal model of schizophrenia”
Goal: This project investigates the regional neurochemical differences between isolation and group raised Nurr1-null heterozygous mice and wild-type mice as measured by microdialysis