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Luo Y, Good CH, Diaz-Ruiz O, Zhang Y, Hoffman AF, Shan L, Kuang SY, Malik N, Chefer VI, Tomac AC, Lupica CR, Bäckman CM. NMDA receptors on non-dopaminergic neurons in the VTA support cocaine sensitization. PLoS One 2010; 5:e12141. [PMID: 20808436 PMCID: PMC2922329 DOI: 10.1371/journal.pone.0012141] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 07/19/2010] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND The initiation of behavioral sensitization to cocaine and other psychomotor stimulants is thought to reflect N-methyl-D-aspartate receptor (NMDAR)-mediated synaptic plasticity in the mesolimbic dopamine (DA) circuitry. The importance of drug induced NMDAR mediated adaptations in ventral tegmental area (VTA) DA neurons, and its association with drug seeking behaviors, has recently been evaluated in Cre-loxp mice lacking functional NMDARs in DA neurons expressing Cre recombinase under the control of the endogenous dopamine transporter gene (NR1(DATCre) mice). METHODOLOGY AND PRINCIPAL FINDINGS Using an additional NR1(DATCre) mouse transgenic model, we demonstrate that while the selective inactivation of NMDARs in DA neurons eliminates the induction of molecular changes leading to synaptic strengthening, behavioral measures such as cocaine induced locomotor sensitization and conditioned place preference remain intact in NR1(DATCre) mice. Since VTA DA neurons projecting to the prefrontal cortex and amygdala express little or no detectable levels of the dopamine transporter, it has been speculated that NMDA receptors in DA neurons projecting to these brain areas may have been spared in NR1(DATCre) mice. Here we demonstrate that the NMDA receptor gene is ablated in the majority of VTA DA neurons, including those exhibiting undetectable DAT expression levels in our NR1(DATCre) transgenic model, and that application of an NMDAR antagonist within the VTA of NR1(DATCre) animals still blocks sensitization to cocaine. CONCLUSIONS/SIGNIFICANCE These results eliminate the possibility of NMDAR mediated neuroplasticity in the different DA neuronal subpopulations in our NR1(DATCre) mouse model and therefore suggest that NMDARs on non-DA neurons within the VTA must play a major role in cocaine-related addictive behavior.
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Affiliation(s)
- Yu Luo
- Cellular Neurobiology Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Cameron H. Good
- Cellular Neurobiology Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Oscar Diaz-Ruiz
- Cellular Neurobiology Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - YaJun Zhang
- Cellular Neurobiology Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Alexander F. Hoffman
- Cellular Neurobiology Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Lufei Shan
- Cellular Neurobiology Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Serena Y. Kuang
- Cellular Neurobiology Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Nasir Malik
- Cellular Neurobiology Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Vladimir I. Chefer
- Behavioral Neuroscience Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Andreas C. Tomac
- Cellular Neurobiology Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Carl R. Lupica
- Cellular Neurobiology Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Cristina M. Bäckman
- Cellular Neurobiology Research Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
- * E-mail:
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302
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Bai Q, Burton EA. Cis-acting elements responsible for dopaminergic neuron-specific expression of zebrafish slc6a3 (dopamine transporter) in vivo are located remote from the transcriptional start site. Neuroscience 2009; 164:1138-51. [PMID: 19755139 DOI: 10.1016/j.neuroscience.2009.09.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Revised: 08/13/2009] [Accepted: 09/05/2009] [Indexed: 11/19/2022]
Abstract
The purpose of this study was to analyze the transcriptional regulation of the zebrafish solute carrier family 6 member 3 gene (slc6a3, dopamine transporter, dat), as a first step towards isolating regulatory sequences useful for driving transgene expression within dopaminergic neurons of the zebrafish CNS in vivo. We found that the 3.0 kb slc6a3 mRNA is expressed in each of the major groups of dopaminergic neurons previously identified in the zebrafish CNS. The slc6a3 gene spans >20 kb of genomic DNA and contains 15 exons. The genomic organization of slc6a3 is highly conserved with respect to its human orthologue, including the presence of an untranslated first exon. The promoter lacks a canonical TATA box and there are multiple transcriptional start sites. Functional analysis of cis-acting elements responsible for the expression pattern of slc6a3 was carried out by generating stable transgenic zebrafish lines expressing fluorescent reporters under transcriptional control of fragments of slc6a3 genomic sequence. The region between -2 kb and +5 kb with respect to the transcriptional start site contains the core slc6a3 promoter, in addition to neuronal enhancers and/or non-neuronal repressors that restrict expression to the CNS, but this region lacks cis-acting elements responsible for slc6a3 expression in dopaminergic neurons. The upstream sequence between -6 kb and -2 kb contains an enhancer element that drives slc6a3 expression in dopaminergic neurons of the pretectal region, and additional sequences that partially repress expression in non-dopaminergic neurons. However, expression of slc6a3 in dopaminergic neurons of the ventral diencephalon and telencephalon is dependent on elements that lie outside the region -6 kb to +5 kb. These data provide a detailed analysis of the slc6a3 gene and show that its expression in different populations of dopamine neurons is driven by discrete enhancers, rather than a single target sequence for a terminal factor involved in specifying neurochemical phenotype.
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Affiliation(s)
- Q Bai
- Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh School of Medicine, Pittsburgh, PA 15217, USA
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303
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Diaz-Ruiz O, Zapata A, Shan L, Zhang Y, Tomac AC, Malik N, de la Cruz F, Bäckman CM. Selective deletion of PTEN in dopamine neurons leads to trophic effects and adaptation of striatal medium spiny projecting neurons. PLoS One 2009; 4:e7027. [PMID: 19750226 PMCID: PMC2736587 DOI: 10.1371/journal.pone.0007027] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2009] [Accepted: 07/14/2009] [Indexed: 11/18/2022] Open
Abstract
The widespread distribution of the tumor suppressor PTEN in the nervous system suggests a role in a broad range of brain functions. PTEN negatively regulates the signaling pathways initiated by protein kinase B (Akt) thereby regulating signals for growth, proliferation and cell survival. Pten deletion in the mouse brain has revealed its role in controlling cell size and number. In this study, we used Cre-loxP technology to specifically inactivate Pten in dopamine (DA) neurons (Pten KO mice). The resulting mutant mice showed neuronal hypertrophy, and an increased number of dopaminergic neurons and fibers in the ventral mesencephalon. Interestingly, quantitative microdialysis studies in Pten KO mice revealed no alterations in basal DA extracellular levels or evoked DA release in the dorsal striatum, despite a significant increase in total DA tissue levels. Striatal dopamine receptor D1 (DRD1) and prodynorphin (PDyn) mRNA levels were significantly elevated in KO animals, suggesting an enhancement in neuronal activity associated with the striatonigral projection pathway, while dopamine receptor D2 (DRD2) and preproenkephalin (PPE) mRNA levels remained unchanged. In addition, PTEN inactivation protected DA neurons and significantly enhanced DA-dependent behavioral functions in KO mice after a progressive 6OHDA lesion. These results provide further evidence about the role of PTEN in the brain and suggest that manipulation of the PTEN/Akt signaling pathway during development may alter the basal state of dopaminergic neurotransmission and could provide a therapeutic strategy for the treatment of Parkinson's disease, and other neurodegenerative disorders.
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Affiliation(s)
- Oscar Diaz-Ruiz
- Cellular Neurobiology Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Agustin Zapata
- Behavioral Neuroscience Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Lufei Shan
- Cellular Neurobiology Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - YaJun Zhang
- Cellular Neurobiology Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Andreas C. Tomac
- Cellular Neurobiology Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Nasir Malik
- Cellular Neurobiology Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Fidel de la Cruz
- Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City, Mexico
| | - Cristina M. Bäckman
- Cellular Neurobiology Branch, National Institute on Drug Abuse, National Institutes of Health, Baltimore, Maryland, United States of America
- * E-mail:
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304
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Abstract
Parkinson's disease (PD), a common progressive neurodegenerative disorder, is characterized by degeneration of dopamine neurons in the substantia nigra and neuronal proteinaceous aggregates called Lewy bodies (LBs). The etiology of PD is probably a combination of environmental and genetic factors. Recent progress in molecular genetics has identified several genes causing PD, including alpha-synuclein, leucine-rich repeat kinase 2 (LRRK2), Parkin, DJ-1 and PTEN-induced kinase 1 (PINK1), many of them coding for proteins found in LBs and/or implicated in mitochondrial function. However, the mechanism(s) leading to the development of the disease have not been identified, despite intensive research. Animal models help us to obtain insights into the mechanisms of several symptoms of PD, allowing us to investigate new therapeutic strategies and, in addition, provide an indispensable tool for basic research. As PD does not arise spontaneously in animals, characteristic and specific functional changes have to be induced by administration of toxins or by genetic manipulations. This review will focus on the comparison of three types of rodent animal models used to study different aspects of PD: (a) animal models using neurotoxins; (b) genetically modified mouse models reproducing findings from PD linkage studies or based on ablation of genes necessary for the development and survival of dopamine neurons; and (c) tissue-specific knockouts in mice targeting dopamine neurons. The advantages and disadvantages of these models are discussed.
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Affiliation(s)
- Mügen Terzioglu
- Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Dagmar Galter
- Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
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305
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Postnatally Derived Ventral Midbrain Dopamine Neuron Cultures as a Model System for Studying Neurotoxicity and Parkinson's Disease. PARKINSONS DISEASE 2008. [DOI: 10.1016/b978-0-12-374028-1.00037-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register]
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306
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Specific expression of lacZ and cre recombinase in fetal thymic epithelial cells by multiplex gene targeting at the Foxn1 locus. BMC DEVELOPMENTAL BIOLOGY 2007; 7:69. [PMID: 17577402 PMCID: PMC1906761 DOI: 10.1186/1471-213x-7-69] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/16/2006] [Accepted: 06/18/2007] [Indexed: 02/03/2023]
Abstract
Background Thymic epithelial cells (TECs) promote thymocyte maturation and are required for the early stages of thymocyte development and for positive selection. However, investigation of the mechanisms by which TECs perform these functions has been inhibited by the lack of genetic tools. Since the Foxn1 gene is expressed in all presumptive TECs from the early stages of thymus organogenesis and broadly in the adult thymus, it is an ideal locus for driving gene expression in differentiating and mature TECs. Results We generated two knock-in alleles of Foxn1 by inserting IRES-Cre or IRES-lacZ cassettes into the 3' UTR of the Foxn1 locus. We simultaneously electroporated the two targeting vectors to generate the two independent alleles in the same experiment, demonstrating the feasibility of multiplex gene targeting at this locus. Our analysis shows that the knockin alleles drive expression of Cre or lacZ in all TECs in the fetal thymus. Furthermore, the knockin alleles express Cre or lacZ in a Foxn1-like pattern without disrupting Foxn1 function as determined by phenotype analysis of Foxn1 knockin/Foxn1 null compound heterozygotes. Conclusion These data show that multiplex gene targeting into the 3' UTR of the Foxn1 locus is an efficient method to express any gene of interest in TECs from the earliest stage of thymus organogenesis. The resulting alleles will make possible new molecular and genetic studies of TEC differentiation and function. We also discuss evidence indicating that gene targeting into the 3' UTR is a technique that may be broadly applicable for the generation of genetically neutral driver strains.
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307
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Turiault M, Parnaudeau S, Milet A, Parlato R, Rouzeau JD, Lazar M, Tronche F. Analysis of dopamine transporter gene expression pattern -- generation of DAT-iCre transgenic mice. FEBS J 2007; 274:3568-3577. [PMID: 17565601 DOI: 10.1111/j.1742-4658.2007.05886.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The dopamine transporter is an essential component of the dopaminergic synapse. It is located in the presynaptic neurons and regulates extracellular dopamine levels. We generated a transgenic mouse line expressing the Cre recombinase under the control of the regulatory elements of the dopamine transporter gene, for investigations of gene function in dopaminergic neurons. The codon-improved Cre recombinase (iCre) gene was inserted into the dopamine transporter gene on a bacterial artificial chromosome. The pattern of expression of the bacterial artificial chromosome-dopamine transporter-iCre transgene was similar to that of the endogenous dopamine transporter gene, as shown by immunohistochemistry. Recombinase activity was further studied in mice carrying both the bacterial artificial chromosome-dopamine transporter-iCre transgene and a construct expressing the beta-galactosidase gene after Cre-mediated recombination. In situ studies showed that beta-galactosidase (5-bromo-4-chloroindol-3-yl beta-D-galactoside staining) and the dopamine transporter (immunofluorescence) had identical distributions in the ventral midbrain. We used this animal model to study the distribution of dopamine transporter gene expression in hypothalamic nuclei in detail. The expression profile of tyrosine hydroxylase (an enzyme required for dopamine synthesis) was broader than that of beta-galactosidase in A12 to A15. Thus, only a fraction of neurons synthesizing dopamine expressed the dopamine transporter gene. The bacterial artificial chromosome-dopamine transporter-iCre transgenic line is a unique tool for targeting Cre/loxP-mediated DNA recombination to dopamine neurons for studies of gene function or for labeling living cells, following the crossing of these mice with transgenic Cre reporter lines producing fluorescent proteins.
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Affiliation(s)
- Marc Turiault
- CNRS UMR7148, Molecular Genetics, Neurophysiology and Behavior, Collège de France, Institut de Biologie, Paris, France Molecular Biology of the Cell I, German Cancer Research Center, Heidelberg, Germany
| | - Sébastien Parnaudeau
- CNRS UMR7148, Molecular Genetics, Neurophysiology and Behavior, Collège de France, Institut de Biologie, Paris, France Molecular Biology of the Cell I, German Cancer Research Center, Heidelberg, Germany
| | - Aude Milet
- CNRS UMR7148, Molecular Genetics, Neurophysiology and Behavior, Collège de France, Institut de Biologie, Paris, France Molecular Biology of the Cell I, German Cancer Research Center, Heidelberg, Germany
| | - Rosanna Parlato
- CNRS UMR7148, Molecular Genetics, Neurophysiology and Behavior, Collège de France, Institut de Biologie, Paris, France Molecular Biology of the Cell I, German Cancer Research Center, Heidelberg, Germany
| | - Jean-Denis Rouzeau
- CNRS UMR7148, Molecular Genetics, Neurophysiology and Behavior, Collège de France, Institut de Biologie, Paris, France Molecular Biology of the Cell I, German Cancer Research Center, Heidelberg, Germany
| | - Monique Lazar
- CNRS UMR7148, Molecular Genetics, Neurophysiology and Behavior, Collège de France, Institut de Biologie, Paris, France Molecular Biology of the Cell I, German Cancer Research Center, Heidelberg, Germany
| | - François Tronche
- CNRS UMR7148, Molecular Genetics, Neurophysiology and Behavior, Collège de France, Institut de Biologie, Paris, France Molecular Biology of the Cell I, German Cancer Research Center, Heidelberg, Germany
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