1
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Das A, Smith MA, O'Dowd DK. A Behavioral Screen for Heat-Induced Seizures in Mouse Models of Epilepsy. J Vis Exp 2021. [PMID: 34309607 DOI: 10.3791/62846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Transgenic mouse models have proved to be powerful tools in studying various aspects of human neurological disorders, including epilepsy. The SCN1A-associated genetic epilepsies comprise a wide spectrum of seizure disorders with incomplete penetrance and clinical variability. SCN1A mutations can result in a large variety of seizure phenotype ranging from simple, self-limited fever-associated febrile seizures (FS), moderate-level genetic epilepsy with febrile seizures plus (GEFS+) to more severe Dravet Syndrome (DS). Although FS are commonly seen in children below 6-7 years of age who do not have genetic epilepsy, FS in GEFS+ patients continue to occur into adulthood. Traditionally, experimental FS have been induced in mice by exposing the animal to a stream of dry air or heating lamps, and the rate of change in body temperature is often not well controlled. Here, we describe a custom-built heating chamber, with a plexiglass front, that is fitted with a digital temperature controller and a heater-equipped electric fan, which can send heated forced air into the test arena in a temperature-controlled manner. The body temperature of a mouse placed in the chamber, monitored through a rectal probe, can be increased to 40-42 °C in a reproducible manner by increasing the temperature inside the chamber. Continual visual monitoring of the animals during the heating period demonstrates induction of heat-induced seizures in mice carrying an FS mutation at a body temperature that does not elicit behavioral seizures in wild-type litter mates. Animals can be easily removed from the chamber and placed on a cooling pad to rapidly return body temperature to normal. This method provides for a simple, rapid, and reproducible screening protocol for the occurrence of heat-induced seizures in epilepsy mouse models.
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Affiliation(s)
- Antara Das
- Department of Developmental and Cell Biology, University of California;
| | - Martin A Smith
- Department of Anatomy and Neurobiology, University of California
| | - Diane K O'Dowd
- Department of Developmental and Cell Biology, University of California;
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2
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Williams AE, O'Dowd DK. Seven practical strategies to add active learning to a science lecture. Neurosci Lett 2020; 743:135317. [PMID: 33310061 DOI: 10.1016/j.neulet.2020.135317] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 08/03/2020] [Accepted: 08/18/2020] [Indexed: 10/22/2022]
Abstract
Multiple research studies have shown active learning can increase student performance, reduce fail rates, and increase the success of marginalized students in STEM. In this mini-review we discuss a simple framework for planning and implementing active learning in the classroom. We provide seven strategies to support faculty members who want to implement this framework, with five suggested teaching activities and two mechanisms of creating space in the lecture to use the activities. Each strategy is given with a foundational research paper describing the evidence that it improves learning, engagement and inclusion in the classroom. We include our own experiences using these strategies in large biology lectures that had segments devoted to neuroscience topics, but they are effective in smaller classes as well.
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Affiliation(s)
- Adrienne E Williams
- Department of Developmental and Cell Biology, 2014 Biological Sciences 3 University of California Irvine Irvine, CA 92697-2300, USA.
| | - Diane K O'Dowd
- Department of Developmental and Cell Biology, 2014 Biological Sciences 3 University of California Irvine Irvine, CA 92697-2300, USA.
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3
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Xie Y, Ng NN, Safrina OS, Ramos CM, Ess KC, Schwartz PH, Smith MA, O'Dowd DK. Comparisons of dual isogenic human iPSC pairs identify functional alterations directly caused by an epilepsy associated SCN1A mutation. Neurobiol Dis 2019; 134:104627. [PMID: 31786370 DOI: 10.1016/j.nbd.2019.104627] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 09/05/2019] [Accepted: 09/26/2019] [Indexed: 02/06/2023] Open
Abstract
Over 1250 mutations in SCN1A, the Nav1.1 voltage-gated sodium channel gene, are associated with seizure disorders including GEFS+. To evaluate how a specific mutation, independent of genetic background, causes seizure activity we generated two pairs of isogenic human iPSC lines by CRISPR/Cas9 gene editing. One pair is a control line from an unaffected sibling, and the mutated control carrying the GEFS+ K1270T SCN1A mutation. The second pair is a GEFS+ patient line with the K1270T mutation, and the corrected patient line. By comparing the electrophysiological properties in inhibitory and excitatory iPSC-derived neurons from these pairs, we found the K1270T mutation causes cell type-specific alterations in sodium current density and evoked firing, resulting in hyperactive neural networks. We also identified differences associated with genetic background and interaction between the mutation and genetic background. Comparisons within and between dual pairs of isogenic iPSC-derived neuronal cultures provide a novel platform for evaluating cellular mechanisms underlying a disease phenotype and for developing patient-specific anti-seizure therapies.
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Affiliation(s)
- Yunyao Xie
- Department of Developmental and Cell Biology, University of California, Irvine, CA, United States of America
| | - Nathan N Ng
- Department of Developmental and Cell Biology, University of California, Irvine, CA, United States of America
| | - Olga S Safrina
- Department of Developmental and Cell Biology, University of California, Irvine, CA, United States of America
| | - Carmen M Ramos
- Department of Developmental and Cell Biology, University of California, Irvine, CA, United States of America
| | - Kevin C Ess
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - Philip H Schwartz
- Children's Hospital of Orange County Research Institute, Orange, CA, United States of America
| | - Martin A Smith
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, United States of America
| | - Diane K O'Dowd
- Department of Developmental and Cell Biology, University of California, Irvine, CA, United States of America.
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4
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Abstract
Institutions should value teaching and service, and not just research, when considering faculty for promotion and tenure.
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Affiliation(s)
- Andrew W Murray
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, United States
| | - Diane K O'Dowd
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, United States
| | - Chris D Impey
- Department of Astronomy, University of Arizona, Tucson, United States
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5
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Abstract
Cost-effective and efficient, the fruit fly (Drosophila melanogaster) has been used to make many key discoveries in the field of neuroscience and to model a number of neurological disorders. Great strides in understanding have been made using sophisticated molecular genetic tools and behavioral assays. Functional analysis of neural activity was initially limited to the neuromuscular junction (NMJ) and in the central nervous system (CNS) of embryos and larvae. Elucidating the cellular mechanisms underlying neurological processes and disorders in the mature nervous system have been more challenging due to difficulty in recording from neurons in adult brains. To this aim we developed an ex vivo preparation in which a whole brain is isolated from the head capsule of an adult fly and placed in a recording chamber. With this preparation, whole cell recording of identified neurons in the adult brain can be combined with genetic, pharmacological and environmental manipulations to explore cellular mechanisms of neuronal function and dysfunction. It also serves as an important platform for evaluating the mechanism of action of new therapies identified through behavioral assays for treating neurological diseases. Here we present our protocol for ex vivo preparations and whole-cell recordings in the adult Drosophila brain.
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Affiliation(s)
- Alexa J Roemmich
- Department of Developmental and Cell Biology, University of California, Irvine, California, USA
| | - Soleil S Schutte
- Department of Anesthesiology, University of Florida, Gainesville, Florida, USA
| | - Diane K O'Dowd
- Department of Developmental and Cell Biology, University of California, Irvine, California, USA
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6
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Xie Y, Schutte RJ, Ng NN, Ess KC, Schwartz PH, O'Dowd DK. Reproducible and efficient generation of functionally active neurons from human hiPSCs for preclinical disease modeling. Stem Cell Res 2017; 26:84-94. [PMID: 29272856 PMCID: PMC5899925 DOI: 10.1016/j.scr.2017.12.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 10/22/2017] [Accepted: 12/07/2017] [Indexed: 02/08/2023] Open
Abstract
The use of human induced pluripotent stem cell (hiPSC)-derived neuronal cultures to study the mechanisms of neurological disorders is often limited by low efficiency and high variability in differentiation of functional neurons. Here we compare the functional properties of neurons in cultures prepared with two hiPSC differentiation protocols, both plated on astroglial feeder layers. Using a protocol with an expandable intermediate stage, only a small percentage of cells with neuronal morphology were excitable by 21-23days in culture. In contrast, a direct differentiation strategy of the same hiPSC line produced cultures in which the majority of neurons fired action potentials as early as 4-5days. By 35-38days over 80% of the neurons fired repetitively and many fired spontaneously. Spontaneous post-synaptic currents were observed in ~40% of the neurons at 4-5days and in ~80% by 21-23days. The majority (75%) received both glutamatergic and GABAergic spontaneous postsynaptic currents. The rate and degree of maturation of excitability and synaptic activity was similar between multiple independent platings from a single hiPSC line, and between two different control hiPSC lines. Cultures of rapidly functional neurons will facilitate identification of cellular mechanisms underlying genetically defined neurological disorders and development of novel therapeutics.
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Affiliation(s)
- Yunyao Xie
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA, United States
| | - Ryan J Schutte
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA, United States
| | - Nathan N Ng
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA, United States
| | - Kevin C Ess
- Department of Pediatrics, Vanderbilt University Medical Center, Nashville, TN, United States
| | - Philip H Schwartz
- Children's Hospital of Orange County Research Institute, Orange, CA, United States
| | - Diane K O'Dowd
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA, United States.
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7
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Schutte RJ, Xie Y, Ng NN, Figueroa P, Pham AT, O'Dowd DK. Astrocyte-enriched feeder layers from cryopreserved cells support differentiation of spontaneously active networks of human iPSC-derived neurons. J Neurosci Methods 2017; 294:91-101. [PMID: 28746822 DOI: 10.1016/j.jneumeth.2017.07.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2016] [Revised: 07/19/2017] [Accepted: 07/19/2017] [Indexed: 01/08/2023]
Abstract
BACKGROUND Human induced pluripotent stem cell (hiPSC)-derived neuronal cultures are a useful tool for studying the mechanisms of neurological disorders and developing novel therapeutics. While plating hiPSC-derived neuronal progenitors onto glial feeder layers prepared from rodent cortex has been reported to promote functional differentiation of neuronal networks, this has not been examined in detail. NEW METHOD Here we describe a method of using cryopreserved cells from primary cultures for generation of mouse astrocyte-enriched, neuron-free feeder layers that grow from 10% to 100% confluence in 1 week. RESULTS Electrophysiological analysis demonstrated that compared to biochemical substrates alone, astrocyte-enriched feeder layers support more rapid differentiation of hiPSC-derived progenitors into excitable neurons that form spontaneously active networks in culture. There was a positive correlation between the degree of astroglial confluence at the time of progenitor plating and the average frequency of postsynaptic currents 3 weeks after plating. One disadvantage to plating on 100% confluent feeder layers was a high incidence of the astroglial layer with the overlying neurons detaching from the coverslips during transfer to the recording chamber. COMPARISON WITH EXISTING METHOD(S) Prevailing methods using primary glial feeder layers can result in possible contamination with rodent neurons and an unpredictable rate of growth. We provide a reliable method of generating mouse astroglial feeder layers from cryopreserved primary cultures to support differentiation of hiPSC-derived neurons. CONCLUSIONS The ability to make astrocyte-enriched feeder layers of defined confluence from cryopreserved primary cultures will facilitate the use of human stem cell derived neuronal cultures for disease modeling.
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Affiliation(s)
- Ryan J Schutte
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA 92697, United States
| | - Yunyao Xie
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA 92697, United States
| | - Nathan N Ng
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA 92697, United States
| | - Priscilla Figueroa
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA 92697, United States
| | - An T Pham
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA 92697, United States
| | - Diane K O'Dowd
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA 92697, United States.
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8
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Dennin M, Schultz ZD, Feig A, Finkelstein N, Greenhoot AF, Hildreth M, Leibovich AK, Martin JD, Moldwin MB, O'Dowd DK, Posey LA, Smith TL, Miller ER. Aligning Practice to Policies: Changing the Culture to Recognize and Reward Teaching at Research Universities. CBE Life Sci Educ 2017; 16:16/4/es5. [PMID: 29196430 PMCID: PMC5749974 DOI: 10.1187/cbe.17-02-0032] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Revised: 08/24/2017] [Accepted: 08/25/2017] [Indexed: 05/14/2023]
Abstract
Recent calls for improvement in undergraduate education within STEM (science, technology, engineering, and mathematics) disciplines are hampered by the methods used to evaluate teaching effectiveness. Faculty members at research universities are commonly assessed and promoted mainly on the basis of research success. To improve the quality of undergraduate teaching across all disciplines, not only STEM fields, requires creating an environment wherein continuous improvement of teaching is valued, assessed, and rewarded at various stages of a faculty member's career. This requires consistent application of policies that reflect well-established best practices for evaluating teaching at the department, college, and university levels. Evidence shows most teaching evaluation practices do not reflect stated policies, even when the policies specifically espouse teaching as a value. Thus, alignment of practice to policy is a major barrier to establishing a culture in which teaching is valued. Situated in the context of current national efforts to improve undergraduate STEM education, including the Association of American Universities Undergraduate STEM Education Initiative, this essay discusses four guiding principles for aligning practice with stated priorities in formal policies: 1) enhancing the role of deans and chairs; 2) effectively using the hiring process; 3) improving communication; and 4) improving the understanding of teaching as a scholarly activity. In addition, three specific examples of efforts to improve the practice of evaluating teaching are presented as examples: 1) Three Bucket Model of merit review at the University of California, Irvine; (2) Evaluation of Teaching Rubric, University of Kansas; and (3) Teaching Quality Framework, University of Colorado, Boulder. These examples provide flexible criteria to holistically evaluate and improve the quality of teaching across the diverse institutions comprising modern higher education.
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Affiliation(s)
- Michael Dennin
- Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697
| | - Zachary D Schultz
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA 92697
| | - Andrew Feig
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556
| | - Noah Finkelstein
- Department of Chemistry, Graduate School, Wayne State University, Detroit, MI 48202
| | | | - Michael Hildreth
- Department of Psychology and Center for Teaching Excellence, University of Kansas, Lawrence, KS 66045
| | - Adam K Leibovich
- Research and Graduate Studies, College of Science, and Department of Physics, University of Notre Dame, Notre Dame, IN 46556
| | - James D Martin
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260
| | - Mark B Moldwin
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695
| | - Diane K O'Dowd
- Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109
| | - Lynmarie A Posey
- Department of Chemistry, Michigan State University, East Lansing, MI 48824
| | - Tobin L Smith
- Association of American Universities, Washington, DC 20005
| | - Emily R Miller
- Association of American Universities, Washington, DC 20005
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9
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Guven-Ozkan T, Busto GU, Schutte SS, Cervantes-Sandoval I, O'Dowd DK, Davis RL. MiR-980 Is a Memory Suppressor MicroRNA that Regulates the Autism-Susceptibility Gene A2bp1. Cell Rep 2016; 14:1698-1709. [PMID: 26876166 DOI: 10.1016/j.celrep.2016.01.040] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 10/26/2015] [Accepted: 01/09/2016] [Indexed: 01/07/2023] Open
Abstract
MicroRNAs have been associated with many different biological functions, but little is known about their roles in conditioned behavior. We demonstrate that Drosophila miR-980 is a memory suppressor gene functioning in multiple regions of the adult brain. Memory acquisition and stability were both increased by miR-980 inhibition. Whole cell recordings and functional imaging experiments indicated that miR-980 regulates neuronal excitability. We identified the autism susceptibility gene, A2bp1, as an mRNA target for miR-980. A2bp1 levels varied inversely with miR-980 expression; memory performance was directly related to A2bp1 levels. In addition, A2bp1 knockdown reversed the memory gains produced by miR-980 inhibition, consistent with A2bp1 being a downstream target of miR-980 responsible for the memory phenotypes. Our results indicate that miR-980 represses A2bp1 expression to tune the excitable state of neurons, and the overall state of excitability translates to memory impairment or improvement.
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Affiliation(s)
- Tugba Guven-Ozkan
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL 33458, USA
| | - Germain U Busto
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL 33458, USA
| | - Soleil S Schutte
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA 92697, USA; Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, CA 92697, USA
| | | | - Diane K O'Dowd
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA 92697, USA; Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, CA 92697, USA
| | - Ronald L Davis
- Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL 33458, USA.
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10
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Schutte SS, Schutte RJ, Barragan EV, O'Dowd DK. Model systems for studying cellular mechanisms of SCN1A-related epilepsy. J Neurophysiol 2016; 115:1755-66. [PMID: 26843603 DOI: 10.1152/jn.00824.2015] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 01/22/2016] [Indexed: 11/22/2022] Open
Abstract
Mutations in SCN1A, the gene encoding voltage-gated sodium channel NaV1.1, cause a spectrum of epilepsy disorders that range from genetic epilepsy with febrile seizures plus to catastrophic disorders such as Dravet syndrome. To date, more than 1,250 mutations in SCN1A have been linked to epilepsy. Distinct effects of individual SCN1A mutations on neuronal function are likely to contribute to variation in disease severity and response to treatment in patients. Several model systems have been used to explore seizure genesis in SCN1A epilepsies. In this article we review what has been learned about cellular mechanisms and potential new therapies from these model systems, with a particular emphasis on the novel model system of knock in Drosophila and a look toward the future with expanded use of patient-specific induced pluripotent stem cell-derived neurons.
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Affiliation(s)
- Soleil S Schutte
- Department of Developmental and Cell Biology and Department of Anatomy and Neurobiology, University of California, Irvine, California
| | - Ryan J Schutte
- Department of Developmental and Cell Biology and Department of Anatomy and Neurobiology, University of California, Irvine, California
| | - Eden V Barragan
- Department of Developmental and Cell Biology and Department of Anatomy and Neurobiology, University of California, Irvine, California
| | - Diane K O'Dowd
- Department of Developmental and Cell Biology and Department of Anatomy and Neurobiology, University of California, Irvine, California
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11
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Brick DJ, Nethercott HE, Montesano S, Banuelos MG, Stover AE, Schutte SS, O'Dowd DK, Hagerman RJ, Ono M, Hessl DR, Tassone F, Schwartz PH. The Autism Spectrum Disorders Stem Cell Resource at Children's Hospital of Orange County: Implications for Disease Modeling and Drug Discovery. Stem Cells Transl Med 2015; 4:1369. [PMID: 26508786 DOI: 10.5966/sctm.2014-0073erratum] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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12
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Brick DJ, Nethercott HE, Montesano S, Banuelos MG, Stover AE, Schutte SS, O'Dowd DK, Hagerman RJ, Ono M, Hessl DR, Tassone F, Schwartz PH. The Autism Spectrum Disorders Stem Cell Resource at Children's Hospital of Orange County: Implications for Disease Modeling and Drug Discovery. Stem Cells Transl Med 2014; 3:1275-86. [PMID: 25273538 PMCID: PMC4214842 DOI: 10.5966/sctm.2014-0073] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Accepted: 08/15/2014] [Indexed: 12/28/2022] Open
Abstract
The autism spectrum disorders (ASDs) comprise a set of neurodevelopmental disorders that are, at best, poorly understood but are the fastest growing developmental disorders in the United States. Because animal models of polygenic disorders such as the ASDs are difficult to validate, the derivation of induced pluripotent stem cells (iPSCs) by somatic cell reprogramming offers an alternative strategy for identifying the cellular mechanisms contributing to ASDs and the development of new treatment options. Access to statistically relevant numbers of ASD patient cell lines, however, is still a limiting factor for the field. We describe a new resource with more than 200 cell lines (fibroblasts, iPSC clones, neural stem cells, glia) from unaffected volunteers and patients with a wide range of clinical ASD diagnoses, including fragile X syndrome. We have shown that both normal and ASD-specific iPSCs can be differentiated toward a neural stem cell phenotype and terminally differentiated into action-potential firing neurons and glia. The ability to evaluate and compare data from a number of different cell lines will facilitate greater insight into the cause or causes and biology of the ASDs and will be extremely useful for uncovering new therapeutic and diagnostic targets. Some drug treatments have already shown promise in reversing the neurobiological abnormalities in iPSC-based models of ASD-associated diseases. The ASD Stem Cell Resource at the Children's Hospital of Orange County will continue expanding its collection and make all lines available on request with the goal of advancing the use of ASD patient cells as disease models by the scientific community.
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Affiliation(s)
- David J Brick
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California, USA; Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California, USA; Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Department of Pediatrics, and Department of Biochemistry and Molecular Medicine, University of California, Davis, Sacramento, California, USA
| | - Hubert E Nethercott
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California, USA; Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California, USA; Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Department of Pediatrics, and Department of Biochemistry and Molecular Medicine, University of California, Davis, Sacramento, California, USA
| | - Samantha Montesano
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California, USA; Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California, USA; Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Department of Pediatrics, and Department of Biochemistry and Molecular Medicine, University of California, Davis, Sacramento, California, USA
| | - Maria G Banuelos
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California, USA; Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California, USA; Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Department of Pediatrics, and Department of Biochemistry and Molecular Medicine, University of California, Davis, Sacramento, California, USA
| | - Alexander E Stover
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California, USA; Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California, USA; Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Department of Pediatrics, and Department of Biochemistry and Molecular Medicine, University of California, Davis, Sacramento, California, USA
| | - Soleil Sun Schutte
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California, USA; Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California, USA; Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Department of Pediatrics, and Department of Biochemistry and Molecular Medicine, University of California, Davis, Sacramento, California, USA
| | - Diane K O'Dowd
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California, USA; Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California, USA; Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Department of Pediatrics, and Department of Biochemistry and Molecular Medicine, University of California, Davis, Sacramento, California, USA
| | - Randi J Hagerman
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California, USA; Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California, USA; Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Department of Pediatrics, and Department of Biochemistry and Molecular Medicine, University of California, Davis, Sacramento, California, USA
| | - Michele Ono
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California, USA; Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California, USA; Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Department of Pediatrics, and Department of Biochemistry and Molecular Medicine, University of California, Davis, Sacramento, California, USA
| | - David R Hessl
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California, USA; Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California, USA; Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Department of Pediatrics, and Department of Biochemistry and Molecular Medicine, University of California, Davis, Sacramento, California, USA
| | - Flora Tassone
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California, USA; Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California, USA; Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Department of Pediatrics, and Department of Biochemistry and Molecular Medicine, University of California, Davis, Sacramento, California, USA
| | - Philip H Schwartz
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California, USA; Department of Developmental and Cell Biology, University of California, Irvine, Irvine, California, USA; Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, Department of Pediatrics, and Department of Biochemistry and Molecular Medicine, University of California, Davis, Sacramento, California, USA
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13
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Schutte RJ, Schutte SS, Algara J, Barragan EV, Gilligan J, Staber C, Savva YA, Smith MA, Reenan R, O'Dowd DK. Knock-in model of Dravet syndrome reveals a constitutive and conditional reduction in sodium current. J Neurophysiol 2014; 112:903-12. [PMID: 24805083 DOI: 10.1152/jn.00135.2014] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hundreds of mutations in the SCN1A sodium channel gene confer a wide spectrum of epileptic disorders, requiring efficient model systems to study cellular mechanisms and identify potential therapeutic targets. We recently demonstrated that Drosophila knock-in flies carrying the K1270T SCN1A mutation known to cause a form of genetic epilepsy with febrile seizures plus (GEFS+) exhibit a heat-induced increase in sodium current activity and seizure phenotype. To determine whether different SCN1A mutations cause distinct phenotypes in Drosophila as they do in humans, this study focuses on a knock-in line carrying a mutation that causes a more severe seizure disorder termed Dravet syndrome (DS). Introduction of the DS SCN1A mutation (S1231R) into the Drosophila sodium channel gene para results in flies that exhibit spontaneous and heat-induced seizures with distinct characteristics and lower onset temperature than the GEFS+ flies. Electrophysiological studies of GABAergic interneurons in the brains of adult DS flies reveal, for the first time in an in vivo model system, that a missense DS mutation causes a constitutive and conditional reduction in sodium current activity and repetitive firing. In addition, feeding with the serotonin precursor 5-HTP suppresses heat-induced seizures in DS but not GEFS+ flies. The distinct alterations of sodium currents in DS and GEFS+ GABAergic interneurons demonstrate that both loss- and gain-of-function alterations in sodium currents are capable of causing reduced repetitive firing and seizure phenotypes. The mutation-specific effects of 5-HTP on heat-induced seizures suggest the serotonin pathway as a potential therapeutic target for DS.
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Affiliation(s)
- Ryan J Schutte
- Department of Developmental and Cell Biology, University of California, Irvine, California; Department of Anatomy and Neurobiology, University of California, Irvine, California
| | - Soleil S Schutte
- Department of Developmental and Cell Biology, University of California, Irvine, California; Department of Anatomy and Neurobiology, University of California, Irvine, California
| | - Jacqueline Algara
- Department of Developmental and Cell Biology, University of California, Irvine, California
| | - Eden V Barragan
- Department of Developmental and Cell Biology, University of California, Irvine, California
| | - Jeff Gilligan
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Cynthia Staber
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Yiannis A Savva
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Martin A Smith
- Department of Anatomy and Neurobiology, University of California, Irvine, California
| | - Robert Reenan
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island
| | - Diane K O'Dowd
- Department of Developmental and Cell Biology, University of California, Irvine, California; Department of Anatomy and Neurobiology, University of California, Irvine, California;
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14
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Narayanareddy BRJ, Vartiainen S, Hariri N, O'Dowd DK, Gross SP. A biophysical analysis of mitochondrial movement: differences between transport in neuronal cell bodies versus processes. Traffic 2014; 15:762-71. [PMID: 24673933 DOI: 10.1111/tra.12171] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 03/11/2014] [Accepted: 03/11/2014] [Indexed: 11/28/2022]
Abstract
There is an increasing interest in factors that can impede cargo transport by molecular motors inside the cell. Although potentially relevant (Yi JY, Ori-McKenney KM, McKenney RJ, Vershinin M, Gross SP, Vallee RB. High-resolution imaging reveals indirect coordination of opposite motors and a role for LIS1 in high-load axonal transport. J Cell Biol 2011;195:193-201), the importance of cargo size and subcellular location has received relatively little attention. Here we address these questions taking advantage of the fact that mitochondria - a common cargo - in Drosophila neurons exhibit a wide distribution of sizes. In addition, the mitochondria can be genetically marked with green fluorescent protein (GFP) making it possible to visualize and compare their movement in the cell bodies and in the processes of living cells. Using total internal reflection microscopy coupled with particle tracking and analysis, we quantified the transport properties of GFP-positive mitochondria as a function of their size and location. In neuronal cell bodies, we find little evidence for significant opposition to motion, consistent with a previous study on lipid droplets (Shubeita GT, Tran SL, Xu J, Vershinin M, Cermelli S, Cotton SL, Welte MA, Gross SP. Consequences of motor copy number on the intracellular transport of kinesin-1-driven lipid droplets. Cell 2008;135:1098-1107). However, in the processes, we observe an inverse relationship between the mitochondrial size and velocity and the run distances. This can be ameliorated via hypotonic treatment to increase process size, suggesting that motor-mediated movement is impeded in this more-confined environment. Interestingly, we also observe local mitochondrial accumulations in processes but not in cell bodies. Such accumulations do not completely block the transport but do increase the probability of mitochondria-mitochondria interactions. They are thus particularly interesting in relation to mitochondrial exchange of elements.
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15
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Stover AE, Brick DJ, Nethercott HE, Banuelos MG, Sun L, O'Dowd DK, Schwartz PH. Process-based expansion and neural differentiation of human pluripotent stem cells for transplantation and disease modeling. J Neurosci Res 2013; 91:1247-62. [PMID: 23893392 DOI: 10.1002/jnr.23245] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Revised: 03/20/2013] [Accepted: 03/20/2013] [Indexed: 02/07/2023]
Abstract
Robust strategies for developing patient-specific, human, induced pluripotent stem cell (iPSC)-based therapies of the brain require an ability to derive large numbers of highly defined neural cells. Recent progress in iPSC culture techniques includes partial-to-complete elimination of feeder layers, use of defined media, and single-cell passaging. However, these techniques still require embryoid body formation or coculture for differentiation into neural stem cells (NSCs). In addition, none of the published methodologies has employed all of the advances in a single culture system. Here we describe a reliable method for long-term, single-cell passaging of PSCs using a feeder-free, defined culture system that produces confluent, adherent PSCs that can be differentiated into NSCs. To provide a basis for robust quality control, we have devised a system of cellular nomenclature that describes an accurate genotype and phenotype of the cells at specific stages in the process. We demonstrate that this protocol allows for the efficient, large-scale, cGMP-compliant production of transplantable NSCs from all lines tested. We also show that NSCs generated from iPSCs produced with the process described are capable of forming both glia defined by their expression of S100β and neurons that fire repetitive action potentials.
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Affiliation(s)
- Alexander E Stover
- National Human Neural Stem Cell Resource, Centers for Neuroscience and Translational Research, Children's Hospital of Orange County Research Institute, Orange, California
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16
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Iniguez J, Schutte SS, O'Dowd DK. Cav3-type α1T calcium channels mediate transient calcium currents that regulate repetitive firing in Drosophila antennal lobe PNs. J Neurophysiol 2013; 110:1490-6. [PMID: 23864373 DOI: 10.1152/jn.00368.2013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Projection neurons (PNs), located in the antennal lobe region of the insect brain, play a key role in processing olfactory information. To explore how activity is regulated at the level of single PNs within this central circuit we have recorded from these neurons in adult Drosophila melanogaster brains. Our previous study demonstrated that PNs express voltage-gated calcium currents with a transient and sustained component. We found that the sustained component is mediated by cac gene-encoded Cav2-type channels involved in regulating action potential-independent release of neurotransmitter at excitatory cholinergic synapses. The function of the transient calcium current and the gene encoding the underlying channels, however, were unknown. Here we report that the transient current blocked by prepulse inactivation is sensitive to amiloride, a vertebrate Cav3-type channel blocker. In addition PN-specific RNAi knockdown of α1T, the Drosophila Cav3-type gene, caused a dramatic reduction in the transient current without altering the sustained component. These data demonstrate that the α1T gene encodes voltage-gated calcium channels underlying the amiloride-sensitive transient current. Alterations in evoked firing and spontaneous burst firing in the α1T knockdowns demonstrate that the Cav3-type calcium channels are important in regulating excitability in adult PNs.
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Affiliation(s)
- Jorge Iniguez
- Department of Developmental and Cell Biology and Department of Anatomy and Neurobiology, University of California, Irvine, California
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17
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Anderson WA, Amasino RM, Ares M, Banerjee U, Bartel B, Corces VG, Drennan CL, Elgin SCR, Epstein IR, Fanning E, Guillette LJ, Handelsman J, Hatfull GF, Hoy RR, Kelley D, Leinwand LA, Losick R, Lu Y, Lynn DG, Neuhauser C, O'Dowd DK, Olivera T, Pevzner P, Richards-Kortum RR, Rine J, Sah RL, Strobel SA, Walker GC, Walt DR, Warner IM, Wessler S, Willard HF, Zare RN. Competencies: a cure for pre-med curriculum. Science 2011; 334:760-1. [PMID: 22076362 DOI: 10.1126/science.334.6057.760-b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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18
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Ren P, Zhang H, Qiu F, Liu YQ, Gu H, O'Dowd DK, Zhou QY, Hu WP. Prokineticin 2 regulates the electrical activity of rat suprachiasmatic nuclei neurons. PLoS One 2011; 6:e20263. [PMID: 21687716 PMCID: PMC3110640 DOI: 10.1371/journal.pone.0020263] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Accepted: 04/21/2011] [Indexed: 12/11/2022] Open
Abstract
Neuropeptide signaling plays roles in coordinating cellular activities and maintaining robust oscillations within the mammalian suprachiasmatic nucleus (SCN). Prokineticin2 (PK2) is a signaling molecule from the SCN and involves in the generation of circadian locomotor activity. Prokineticin receptor 2 (PKR2), a receptor for PK2, has been shown to be expressed in the SCN. However, very little is known about the cellular action of PK2 within the SCN. In the present study, we investigated the effect of PK2 on spontaneous firing and miniature inhibitory postsynaptic currents (mIPSCs) using whole cell patch-clamp recording in the SCN slices. PK2 dose-dependently increased spontaneous firing rates in most neurons from the dorsal SCN. PK2 acted postsynaptically to reduce γ-aminobutyric acid (GABA)-ergic function within the SCN, and PK2 reduced the amplitude but not frequency of mIPSCs. Furthermore, PK2 also suppressed exogenous GABA-induced currents. And the inhibitory effect of PK2 required PKC activation in the postsynaptic cells. Our data suggest that PK2 could alter cellular activities within the SCN and may influence behavioral and physiological rhythms.
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Affiliation(s)
- Ping Ren
- Department of Pharmacology, Xianning College, Xianning, Hubei, People's Republic of China
| | - Huiping Zhang
- Family Planning Research Institute, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Fang Qiu
- Department of Pharmacology, Xianning College, Xianning, Hubei, People's Republic of China
| | - Yu-Qiang Liu
- Department of Pharmacology, Xianning College, Xianning, Hubei, People's Republic of China
| | - Huaiyu Gu
- Departments of Anatomy and Neurobiology, Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America
| | - Diane K. O'Dowd
- Departments of Anatomy and Neurobiology, Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America
| | - Qun-Yong Zhou
- Department of Pharmacology, University of California Irvine, Irvine, California, United States of America
| | - Wang-Ping Hu
- Department of Pharmacology, Xianning College, Xianning, Hubei, People's Republic of China
- * E-mail:
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19
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Anderson WA, Banerjee U, Drennan CL, Elgin SCR, Epstein IR, Handelsman J, Hatfull GF, Losick R, O'Dowd DK, Olivera BM, Strobel SA, Walker GC, Warner IM. Science education. Changing the culture of science education at research universities. Science 2011; 331:152-3. [PMID: 21233371 DOI: 10.1126/science.1198280] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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20
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Moravec M, Williams A, Aguilar-Roca N, O'Dowd DK. Learn before lecture: A strategy that improves learning outcomes in a large introductory biology class. CBE Life Sci Educ 2010; 9:473-81. [PMID: 21123694 PMCID: PMC2995765 DOI: 10.1187/cbe.10-04-0063] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
Actively engaging students in lecture has been shown to increase learning gains. To create time for active learning without displacing content we used two strategies for introducing material before class in a large introductory biology course. Four to five slides from 2007/8 were removed from each of three lectures in 2009 and the information introduced in preclass worksheets or narrated PowerPoint videos. In class, time created by shifting lecture material to learn before lecture (LBL) assignments was used to engage students in application of their new knowledge. Learning was evaluated by comparing student performance in 2009 versus 2007/8 on LBL-related question pairs, matched by level and format. The percentage of students who correctly answered five of six LBL-related exam questions was significantly higher (p < 0.001) in 2009 versus 2007/8. The mean increase in performance was 21% across the six LBL-related questions compared with <3% on all non-LBL exam questions. The worksheet and video LBL formats were equally effective based on a cross-over experimental design. These results demonstrate that LBLs combined with interactive exercises can be implemented incrementally and result in significant increases in learning gains in large introductory biology classes.
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Affiliation(s)
- Marin Moravec
- Department of Developmental and Cell Biology, University of California, Irvine, 92697-1280, USA
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21
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Hilgenberg LGW, Pham B, Ortega M, Walid S, Kemmerly T, O'Dowd DK, Smith MA. Agrin regulation of alpha3 sodium-potassium ATPase activity modulates cardiac myocyte contraction. J Biol Chem 2009; 284:16956-16965. [PMID: 19376779 DOI: 10.1074/jbc.m806855200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Drugs that inhibit Na,K-ATPases, such as digoxin and ouabain, alter cardiac myocyte contractility. We recently demonstrated that agrin, a protein first identified at the vertebrate neuromuscular junction, binds to and regulates the activity of alpha3 subunit-containing isoforms of the Na,K-ATPase in the mammalian brain. Both agrin and the alpha3 Na,K-ATPase are expressed in heart, but their potential for interaction and effect on cardiac myocyte function was unknown. Here we show that agrin binds to the alpha3 subunit of the Na,K-ATPase in cardiac myocyte membranes, inducing tyrosine phosphorylation and inhibiting activity of the pump. Agrin also triggers a rapid increase in cytoplasmic Na(+) in cardiac myocytes, suggesting a role in cardiac myocyte function. Consistent with this hypothesis, spontaneous contraction frequencies of cultured cardiac myocytes prepared from mice in which agrin expression is blocked by mutation of the Agrn gene are significantly higher than in the wild type. The Agrn mutant phenotype is rescued by acute treatment with recombinant agrin. Furthermore, exposure of wild type myocytes to an agrin antagonist phenocopies the Agrn mutation. These data demonstrate that the basal frequency of myocyte contraction depends on endogenous agrin-alpha3 Na,K-ATPase interaction and suggest that agrin modulation of the alpha3 Na,K-ATPase is important in regulating heart function.
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Affiliation(s)
| | - Bryan Pham
- From the Departments of Anatomy and Neurobiology, Irvine, California 92697
| | - Maria Ortega
- From the Departments of Anatomy and Neurobiology, Irvine, California 92697; Developmental and Cell Biology, University of California, Irvine, California 92697
| | - Saif Walid
- From the Departments of Anatomy and Neurobiology, Irvine, California 92697
| | - Thomas Kemmerly
- From the Departments of Anatomy and Neurobiology, Irvine, California 92697; Developmental and Cell Biology, University of California, Irvine, California 92697
| | - Diane K O'Dowd
- From the Departments of Anatomy and Neurobiology, Irvine, California 92697; Developmental and Cell Biology, University of California, Irvine, California 92697
| | - Martin A Smith
- From the Departments of Anatomy and Neurobiology, Irvine, California 92697.
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Abstract
Colorful PowerPoint presentations with detailed drawings, micrographs, and short animations have become the standard format for illustrating the fundamental features of cell biology in large introductory classes. In this essay, we describe a low-tech tool that can be included in a standard lecture to help students visualize, understand, and remember the dynamic aspects of microscopic cell biological processes. This approach involves use of common objects, including pipe insulation and a garden hose, to illustrate basic processes such as protein folding and cloning, hence the appellation "garage demos." The demonstrations are short, minimizing displacement of course content, easy to make, and provide an avenue for increasing student-faculty interaction in a large lecture hall. Student feedback over the past 4 years has been overwhelmingly positive. In an anonymous postclass survey in 2007, 90% of the respondents rated garage demos as having been very or somewhat helpful for understanding course concepts. Direct measurements of learning gains on specific concepts illustrated by garage demos are the focus of an ongoing study.
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Affiliation(s)
- Diane K O'Dowd
- Departments of Developmental and Cell Biology and Anatomy and Neurobiology, University of California, Irvine, Irvine, CA 92697-1280, USA.
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23
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Gu H, Jiang SA, Campusano JM, Iniguez J, Su H, Hoang AA, Lavian M, Sun X, O'Dowd DK. Cav2-type calcium channels encoded by cac regulate AP-independent neurotransmitter release at cholinergic synapses in adult Drosophila brain. J Neurophysiol 2008; 101:42-53. [PMID: 19004991 DOI: 10.1152/jn.91103.2008] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated calcium channels containing alpha1 subunits encoded by Ca(v)2 family genes are critical in regulating release of neurotransmitter at chemical synapses. In Drosophila, cac is the only Ca(v)2-type gene. Cacophony (CAC) channels are localized in motor neuron terminals where they have been shown to mediate evoked, but not AP-independent, release of glutamate at the larval neuromuscular junction (NMJ). Cultured embryonic neurons also express CAC channels, but there is no information about the properties of CAC-mediated currents in adult brain nor how these channels regulate transmission in central neural circuits where fast excitatory synaptic transmission is predominantly cholinergic. Here we report that wild-type neurons cultured from late stage pupal brains and antennal lobe projection neurons (PNs) examined in adult brains, express calcium currents with two components: a slow-inactivating current sensitive to the spider toxin Plectreurys toxin II (PLTXII) and a fast-inactivating PLTXII-resistant component. CAC channels are the major contributors to the slow-inactivating PLTXII-sensitive current based on selective reduction of this component in hypomorphic cac mutants (NT27 and TS3). Another characteristic of cac mutant neurons both in culture and in whole brain recordings is a reduced cholinergic miniature excitatory postsynaptic current frequency that is mimicked in wild-type neurons by acute application of PLTXII. These data demonstrate that cac encoded Ca(v)2-type calcium channels regulate action potential (AP)-independent release of neurotransmitter at excitatory cholinergic synapses in the adult brain, a function not predicted from studies at the larval NMJ.
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Affiliation(s)
- Huaiyu Gu
- Department of Anatomy and Neurobiology, University of California, Irvine, CA, USA
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24
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Oh HW, Campusano JM, Hilgenberg LGW, Sun X, Smith MA, O'Dowd DK. Ultrastructural analysis of chemical synapses and gap junctions between Drosophila brain neurons in culture. Dev Neurobiol 2008; 68:281-94. [PMID: 18044733 DOI: 10.1002/dneu.20575] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Dissociated cultures from many species have been important tools for exploring factors that regulate structure and function of central neuronal synapses. We have previously shown that cells harvested from brains of late stage Drosophila pupae can regenerate their processes in vitro. Electrophysiological recordings demonstrate the formation of functional synaptic connections as early as 3 days in vitro (DIV), but no information about synapse structure is available. Here, we report that antibodies against pre-synaptic proteins Synapsin and Bruchpilot result in punctate staining of regenerating neurites. Puncta density increases as neuritic plexuses develop over the first 4 DIV. Electron microscopy reveals that closely apposed neurites can form chemical synapses with both pre- and postsynaptic specializations characteristic of many inter-neuronal synapses in the adult brain. Chemical synapses in culture are restricted to neuritic processes and some neurite pairs form reciprocal synapses. GABAergic synapses have a significantly higher percentage of clear core versus granular vesicles than non-GABA synapses. Gap junction profiles, some adjacent to chemical synapses, suggest that neurons in culture can form purely electrical as well as mixed synapses, as they do in the brain. However, unlike adult brain, gap junctions in culture form between neuronal somata as well as neurites, suggesting soma ensheathing glia, largely absent in culture, regulate gap junction location in vivo. Thus pupal brain cultures, which support formation of interneuronal synapses with structural features similar to synapses in adult brain, are a useful model system for identifying intrinsic and extrinsic regulators of central synapse structure as well as function.
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Affiliation(s)
- Hyun-Woo Oh
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697-1280, USA
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25
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Sheeba V, Gu H, Sharma VK, O'Dowd DK, Holmes TC. Circadian- and light-dependent regulation of resting membrane potential and spontaneous action potential firing of Drosophila circadian pacemaker neurons. J Neurophysiol 2007; 99:976-88. [PMID: 18077664 DOI: 10.1152/jn.00930.2007] [Citation(s) in RCA: 161] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The ventral lateral neurons (LNvs) of adult Drosophila brain express oscillating clock proteins and regulate circadian behavior. Whole cell current-clamp recordings of large LNvs in freshly dissected Drosophila whole brain preparations reveal two spontaneous activity patterns that correlate with two underlying patterns of oscillating membrane potential: tonic and burst firing of sodium-dependent action potentials. Resting membrane potential and spontaneous action potential firing are rapidly and reversibly regulated by acute changes in light intensity. The LNv electrophysiological light response is attenuated, but not abolished, in cry(b) mutant flies hypomorphic for the cell-autonomous light-sensing protein CRYPTOCHROME. The electrical activity of the large LNv is circadian regulated, as shown by significantly higher resting membrane potential and frequency of spontaneous action potential firing rate and burst firing pattern during circadian subjective day relative to subjective night. The circadian regulation of membrane potential, spontaneous action potential firing frequency, and pattern of Drosophila large LNvs closely resemble mammalian circadian neuron electrical characteristics, suggesting a general evolutionary conservation of both physiological and molecular oscillator mechanisms in pacemaker neurons.
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Affiliation(s)
- Vasu Sheeba
- Department of Physiology and Biophysics, University of California, Irvine, Irvine, CA 92697, USA
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26
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Abstract
In this video, we demonstrate the procedure for isolating whole brains from adult Drosophila in preparation for recording from single neurons. We begin by describing the dissecting solution and capture of the adult females used in our studies. The procedure for removing the whole brain intact, including both optic lobes, is illustrated. Dissection of the overlying trachea is also shown. The isolated brain is not only small but needs special care in handling at this stage to prevent damage to the neurons, many of which are close to the outer surface of the tissue. We show how a special holder we developed is used to stabilize the brain in the recording chamber. A standard electrophysiology set up is used for recording from single neurons or pairs of neurons. A fluorescent image, viewed through the recording microscope, from a GAL4 line driving GFP expression (GH146) illustrates how projection neurons (PNs) are identified in the live brain. A high power Nomarski image shows a view of a single neuron that is being targeted for whole cell recording. When the brain is successfully removed without damage, the majority of the neurons are spontaneously active, firing action potentials and/or exhibiting spontaneous synaptic input. This in situ preparation, in which whole cell recording of identified neurons in the whole brain can be combined with genetic and pharmacological manipulations, is a useful model for exploring cellular physiology and plasticity in the adult CNS.
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Affiliation(s)
- Huaiyu Gu
- Department of Development and Cell Biology, University of California, Irvine, USA
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27
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Abstract
This video illustrates the procedure for making primary neuronal cultures from midgastrula stage Drosophila embryos. The methods for collecting embryos and their dechorionation using bleach are demonstrated. Using a glass pipet attached to a mouth suction tube, we illustrate the removal of all cells from single embryos. The method for dispersing cells from each embryo into a small (5 l) drop of medium on an uncoated glass coverslip is demonstrated. A view through the microscope at 1 hour after plating illustrates the preferred cell density. Most of the cells that survive when grown in defined medium are neuroblasts that divide one or more times in culture before extending neuritic processes by 12-24 hours. A view through the microscope illustrates the level of neurite outgrowth and branching expected in a healthy culture at 2 days in vitro. The cultures are grown in a simple bicarbonate based defined medium, in a 5% CO(2) incubator at 22-24 degrees C. Neuritic processes continue to elaborate over the first week in culture and when they make contact with neurites from neighboring cells they often form functional synaptic connections. Neurons in these cultures express voltage-gated sodium, calcium, and potassium channels and are electrically excitable. This culture system is useful for studying molecular genetic and environmental factors that regulate neuronal differentiation, excitability, and synapse formation/function.
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Affiliation(s)
- Beatriz Sicaeros
- Department of Development and Cell Biology, University of California, Irvine, USA
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Tan Z, Sun X, Hou FS, Oh HW, Hilgenberg LGW, Hol EM, van Leeuwen FW, Smith MA, O'Dowd DK, Schreiber SS. Mutant ubiquitin found in Alzheimer's disease causes neuritic beading of mitochondria in association with neuronal degeneration. Cell Death Differ 2007; 14:1721-32. [PMID: 17571083 PMCID: PMC3258508 DOI: 10.1038/sj.cdd.4402180] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
A dinucleotide deletion in human ubiquitin (Ub) B messenger RNA leads to formation of polyubiquitin (UbB)+1, which has been implicated in neuronal cell death in Alzheimer's and other neurodegenerative diseases. Previous studies demonstrate that UbB+1 protein causes proteasome dysfunction. However, the molecular mechanism of UbB+1-mediated neuronal degeneration remains unknown. We now report that UbB+1 causes neuritic beading, impairment of mitochondrial movements, mitochondrial stress and neuronal degeneration in primary neurons. Transfection of UbB+1 induced a buildup of mitochondria in neurites and dysregulation of mitochondrial motor proteins, in particular, through detachment of P74, the dynein intermediate chain, from mitochondria and decreased mitochondria-microtubule interactions. Altered distribution of mitochondria was associated with activation of both the mitochondrial stress and p53 cell death pathways. These results support the hypothesis that neuritic clogging of mitochondria by UbB+1 triggers a cascade of events characterized by local activation of mitochondrial stress followed by global cell death. Furthermore, UbB+1 small interfering RNA efficiently blocked expression of UbB+1 protein, attenuated neuritic beading and preserved cellular morphology, suggesting a potential neuroprotective strategy for certain neurodegenerative disorders.
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Affiliation(s)
- Z Tan
- Department of Neurology, University of California, Irvine, CA 92697, USA.
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29
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Abstract
In this video, we demonstrate the preparation of primary neuronal cultures from the brains of late stage Drosophila pupae. The procedure begins with the removal of brains from animals at 70-78 hrs after puparium formation. The isolated brains are shown after brief incubation in papain followed by several washes in serum-free growth medium. The process of mechanical dissociation of each brain in a 5 ul drop of media on a coverslip is illustrated. The axons and dendrites of the post-mitotic neurons are sheered off near the soma during dissociation but the neurons begin to regenerate processes within a few hours of plating. Images show live cultures at 2 days. Neurons continue to elaborate processes during the first week in culture. Specific neuronal populations can be identified in culture using GAL4 lines to drive tissue specific expression of fluorescent markers such as GFP or RFP. Whole cell recordings have demonstrated the cultured neurons form functional, spontaneously active cholinergic and GABAergic synapses. A short video segment illustrates calcium dynamics in the cultured neurons using Fura-2 as a calcium indicator dye to monitor spontaneous calcium transients and nicotine evoked calcium responses in a dish of cultured neurons. These pupal brain cultures are a useful model system in which genetic and pharmacological tools can be used to identify intrinsic and extrinsic factors that influence formation and function of central synapses.
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Affiliation(s)
- Beatriz Sicaeros
- Department of Development and Cell Biology, Department of Anatomy and Neurobiology, University of California, Irvine, USA
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30
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Abstract
In Drosophila, nicotinic acetylcholine receptors (nAChRs) mediate fast excitatory synaptic transmission in mushroom body Kenyon cells, a neuronal population involved in generation of complex behaviors, including responses to drugs of abuse. To determine whether activation of nAChRs can induce cellular changes that contribute to functional plasticity in these neurons, we examined nicotine-evoked responses in cells cultured from brains of late stage OK107-GAL4 pupae. Kenyon cells can be identified by expression of green fluorescent protein (GFP+). Nicotine activates alpha-bungarotoxin-sensitive nAChRs, causing a rapid increase in intracellular calcium levels in over 95% of the Kenyon cells. The nicotine-evoked calcium increase has a voltage-gated calcium channel (VGCC) dependent component and a VGCC-independent component that involves calcium influx directly through nAChRs. Thapsigargin treatment reduces the nicotine response consistent with amplification by calcium release from intracellular stores. The response to nicotine is experience-dependent: a short conditioning pulse of nicotine causes a transient 50% reduction in the magnitude of the response to a test pulse of nicotine when the interpulse interval is 4 h. This cellular plasticity is dependent on activation of the VGCC-component of the nicotine response and on cAMP-signaling, but not on protein synthesis. These data demonstrate that activation of nAChRs induces a calcium-dependent plasticity in Kenyon cells that could contribute to adult behaviors involving information processing in the mushroom bodies including responses to nicotine.
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Affiliation(s)
- Jorge M Campusano
- Department of Anatomy and Neurobiology, University of California-Irvine, Irvine, CA 92697-1280, USA
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31
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Hilgenberg LGW, Su H, Gu H, O'Dowd DK, Smith MA. Alpha3Na+/K+-ATPase is a neuronal receptor for agrin. Cell 2006; 125:359-69. [PMID: 16630822 DOI: 10.1016/j.cell.2006.01.052] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2005] [Revised: 12/12/2005] [Accepted: 01/18/2006] [Indexed: 11/25/2022]
Abstract
Agrin, through its interaction with the receptor tyrosine kinase MuSK, mediates accumulation of acetylcholine receptors (AChR) at the developing neuromuscular junction. Agrin has also been implicated in several functions in brain. However, the mechanism by which agrin exerts its effects in neural tissue is unknown. Here we present biochemical evidence that agrin binds to the alpha3 subunit of the Na+/K+-ATPase (NKA) in CNS neurons. Colocalization with agrin binding sites at synapses supports the hypothesis that the alpha3NKA is a neuronal agrin receptor. Agrin inhibition of alpha3NKA activity results in membrane depolarization and increased action potential frequency in cortical neurons in culture and acute slice. An agrin fragment that acts as a competitive antagonist depresses action potential frequency, showing that endogenous agrin regulates native alpha3NKA function. These data demonstrate that, through its interaction with the alpha3NKA, agrin regulates activity-dependent processes in neurons, providing a molecular framework for agrin action in the CNS.
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Affiliation(s)
- Lutz G W Hilgenberg
- Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, CA 92697, USA
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32
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Abstract
Behavioral and genetic studies in Drosophila have contributed to our understanding of molecular mechanisms that underlie the complex processes of learning and memory. Use of this model organism for exploration of the cellular mechanisms of memory formation requires the ability to monitor synaptic activity in the underlying neural networks, a challenging task in the tiny adult fly. Here, we describe an isolated whole-brain preparation in which it is possible to obtain in situ whole-cell recordings from adult Kenyon cells, key members of a neural circuit essential for olfactory associative learning in Drosophila. The presence of sodium action potential (AP)-dependent synaptic potentials and synaptic currents in >50% of the Kenyon cells shows that these neurons are members of a spontaneously active neural circuit in the isolated brain. The majority of sodium AP-dependent synaptic transmission is blocked by curare and by alpha-bungarotoxin (alpha-BTX). This demonstrates that nicotinic acetylcholine receptors (nAChRs) are responsible for most of the spontaneous excitatory drive in this circuit in the absence of normal sensory input. Furthermore, analysis of sodium AP-independent synaptic currents provides the first direct demonstration that alpha-BTX-sensitive nAChRs mediate fast excitatory synaptic transmission in Kenyon cells in the adult Drosophila brain. This new preparation, in which whole-cell recordings and pharmacology can be combined with genetic approaches, will be critical in understanding the contribution of nAChR-mediated fast synaptic transmission to cellular plasticity in the neural circuits underlying olfactory associative learning.
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Affiliation(s)
- Huaiyu Gu
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697-1280, USA
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Jiang SA, Campusano JM, Su H, O'Dowd DK. DrosophilaMushroom Body Kenyon Cells Generate Spontaneous Calcium Transients Mediated by PLTX-Sensitive Calcium Channels. J Neurophysiol 2005; 94:491-500. [PMID: 15772240 DOI: 10.1152/jn.00096.2005] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Spontaneous calcium oscillations in mushroom bodies of late stage pupal and adult Drosophila brains have been implicated in memory consolidation during olfactory associative learning. This study explores the cellular mechanisms regulating calcium dynamics in Kenyon cells, principal neurons in mushroom bodies. Fura-2 imaging shows that Kenyon cells cultured from late stage Drosophila pupae generate spontaneous calcium transients in a cell autonomous fashion, at a frequency similar to calcium oscillations in vivo (10–20/h). The expression of calcium transients is up regulated during pupal development. Although the ability to generate transients is a property intrinsic to Kenyon cells, transients can be modulated by bath application of nicotine and GABA. Calcium transients are blocked, and baseline calcium levels reduced, by removal of external calcium, addition of cobalt, or addition of Plectreurys toxin (PLTX), an insect-specific calcium channel antagonist. Transients do not require calcium release from intracellular stores. Whole cell recordings reveal that the majority of voltage-gated calcium channels in Kenyon cells are PLTX-sensitive. Together these data show that influx of calcium through PLTX-sensitive voltage-gated calcium channels mediates spontaneous calcium transients and regulates basal calcium levels in cultured Kenyon cells. The data also suggest that these calcium transients represent cellular events underlying calcium oscillations in the intact mushroom bodies. However, spontaneous calcium transients are not unique to Kenyon cells as they are present in approximately 60% of all cultured central brain neurons. This suggests the calcium transients play a more general role in maturation or function of adult brain neurons.
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Affiliation(s)
- Shaojuan Amy Jiang
- Department of Anatomy and Neurobiology, 112 Irvine Hall, University of California, Irvine, California 92697-1280, USA
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Schwartz PH, Bryant PJ, Fuja TJ, Su H, O'Dowd DK, Klassen H. Isolation and characterization of neural progenitor cells from post-mortem human cortex. J Neurosci Res 2004; 74:838-51. [PMID: 14648588 DOI: 10.1002/jnr.10854] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Post-mortem human brain tissue represents a vast potential source of neural progenitor cells for use in basic research as well as therapeutic applications. Here we describe five human neural progenitor cell cultures derived from cortical tissue harvested from premature infants. Time-lapse videomicrography of the passaged cultures revealed them to be highly dynamic, with high motility and extensive, evanescent intercellular contacts. Karyotyping revealed normal chromosomal complements. Prior to differentiation, most of the cells were nestin, Sox2, vimentin, and/or GFAP positive, and a subpopulation was doublecortin positive. Multilineage potential of these cells was demonstrated after differentiation, with some subpopulations of cells expressing the neuronal markers beta-tubulin, MAP2ab, NeuN, FMRP, and Tau and others expressing the oligodendroglial marker O1. Still other cells expressed the classic glial marker glial fibrillary acidic protein (GFAP). RT-PCR confirmed nestin, SOX2, GFAP, and doublecortin expression and also showed epidermal growth factor receptor and nucleostemin expression during the expansion phase. Flow cytometry showed high levels of the neural stem cell markers CD133, CD44, CD81, CD184, CD90, and CD29. CD133 markedly decreased in high-passage, lineage-restricted cultures. Electrophysiological analysis after differentiation demonstrated that the majority of cells with neuronal morphology expressed voltage-gated sodium and potassium currents. These data suggest that post-mortem human brain tissue is an important source of neural progenitor cells that will be useful for analysis of neural differentiation and for transplantation studies.
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Affiliation(s)
- Philip H Schwartz
- National Human Neural Stem Cell Resource, Children's Hospital of Orange County Research Institute, Orange, California 92868-3874, USA.
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35
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Su H, O'Dowd DK. Fast synaptic currents in Drosophila mushroom body Kenyon cells are mediated by alpha-bungarotoxin-sensitive nicotinic acetylcholine receptors and picrotoxin-sensitive GABA receptors. J Neurosci 2003; 23:9246-53. [PMID: 14534259 PMCID: PMC6740836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023] Open
Abstract
The mushroom bodies, bilaterally symmetric regions in the insect brain, play a critical role in olfactory associative learning. Genetic studies in Drosophila suggest that plasticity underlying acquisition and storage of memory occurs at synapses on the dendrites of mushroom body Kenyon cells (Dubnau et al., 2001). Additional exploration of the mechanisms governing synaptic plasticity contributing to these aspects of olfactory associative learning requires identification of the receptors that mediate fast synaptic transmission in Kenyon cells. To this end, we developed a culture system that supports the formation of excitatory and inhibitory synaptic connections between neurons harvested from the central brain region of late-stage Drosophila pupae. Mushroom body Kenyon cells are identified as small-diameter, green fluorescent protein-positive (GFP+) neurons in cultures from OK107-GAL4;UAS-GFP pupae. In GFP+ Kenyon cells, fast EPSCs are mediated by alpha-bungarotoxin-sensitive nicotinic acetylcholine receptors (nAChRs). The miniature EPSCs have rapid rise and decay kinetics and a broad, positively skewed amplitude distribution. Fast IPSCs are mediated by picrotoxin-sensitive chloride conducting GABA receptors. The miniature IPSCs also have a rapid rate of rise and decay and a broad amplitude distribution. The vast majority of spontaneous synaptic currents in the cultured Kenyon cells are mediated byalpha-bungarotoxin-sensitive nAChRs or picrotoxin-sensitive GABA receptors. Therefore, these receptors are also likely to mediate synaptic transmission in Kenyon cells in vivo and to contribute to plasticity during olfactory associative learning.
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Affiliation(s)
- Hailing Su
- Department of Anatomy and Neurobiology, University of California Irvine, Irvine, California 92697-1280, USA
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36
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Lee D, Su H, O'Dowd DK. GABA receptors containing Rdl subunits mediate fast inhibitory synaptic transmission in Drosophila neurons. J Neurosci 2003; 23:4625-34. [PMID: 12805302 PMCID: PMC6740792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/03/2023] Open
Abstract
GABAergic inhibition in Drosophila, as in other insects and mammals, is important for regulation of activity in the CNS. However, the functional properties of synaptic GABA receptors in Drosophila have not been described. Here, we report that spontaneous GABAergic postsynaptic currents (sPSCs) in cultured embryonic Drosophila neurons are mediated by picrotoxin-sensitive chloride-conducting receptors. A rapid increase in spontaneous firing in response to bath application of picrotoxin demonstrates that these GABA receptors mediate inhibition in the neuronal networks formed in culture. Many of the spontaneous GABAergic synaptic currents are sodium action potential independent [miniature IPSCs (mIPSCs)] but are regulated by external calcium levels. The large variation in mIPSC frequency, amplitude, and kinetics properties between neurons suggests heterogeneity in GABA receptor number, location, and/or subtype. A decrease in the mean mIPSC decay time constant between 2 and 5 d, in the absence of a correlated change in rise time, demonstrates that the functional properties of the synaptic GABA receptors are regulated during maturation in vitro. Finally, neurons from the GABA receptor subunit mutant Rdl exhibit reduced sensitivity to picrotoxin blockade of the mIPSCs and resistance to picrotoxin-induced increases in spontaneous firing frequency. This demonstrates that Rdl containing GABA receptors play a direct role in mediating synaptic inhibition in Drosophila neural circuits formed in culture.
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Affiliation(s)
- Daewoo Lee
- Departments of Anatomy and Neurobiology, Developmental and Cell Biology, University of California, Irvine, California 92697-1280
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37
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Rohrbough J, O'Dowd DK, Baines RA, Broadie K. Cellular bases of behavioral plasticity: establishing and modifying synaptic circuits in the Drosophila genetic system. J Neurobiol 2003; 54:254-71. [PMID: 12486708 DOI: 10.1002/neu.10171] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Genetic malleability and amenability to behavioral assays make Drosophila an attractive model for dissecting the molecular mechanisms of complex behaviors, such as learning and memory. At a cellular level, Drosophila has contributed a wealth of information on the mechanisms regulating membrane excitability and synapse formation, function, and plasticity. Until recently, however, these studies have relied almost exclusively on analyses of the peripheral neuromuscular junction, with a smaller body of work on neurons grown in primary culture. These experimental systems are, by themselves, clearly inadequate for assessing neuronal function at the many levels necessary for an understanding of behavioral regulation. The pressing need is for access to physiologically relevant neuronal circuits as they develop and are modified throughout life. In the past few years, progress has been made in developing experimental approaches to examine functional properties of identified populations of Drosophila central neurons, both in cell culture and in vivo. This review focuses on these exciting developments, which promise to rapidly expand the frontiers of functional cellular neurobiology studies in Drosophila. We discuss here the technical advances that have begun to reveal the excitability and synaptic transmission properties of central neurons in flies, and discuss how these studies promise to substantially increase our understanding of neuronal mechanisms underlying behavioral plasticity.
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Affiliation(s)
- Jeffrey Rohrbough
- Department of Biological Sciences, Vanderbilt University, VU Station B, Box 35-1634, Nashville, Tennessee 37235-1634, USA.
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38
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Abstract
The tipE gene, originally identified by a temperature-sensitive paralytic mutation in Drosophila, encodes a transmembrane protein that dramatically influences sodium channel expression in Xenopus oocytes. There is evidence that tipE also modulates sodium channel expression in the fly; however, its role in regulating neuronal excitability remains unclear. Here we report that the majority of neurons in both wild-type and tipE mutant (tipE-) embryo cultures fire sodium-dependent action potentials in response to depolarizing current injection. However, the percentage of tipE- neurons capable of firing repetitively during a sustained depolarization is significantly reduced. Expression of a tipE+ transgene, in tipE- neurons, restores repetitive firing to wild-type levels. Analysis of underlying currents reveals a slower rate of repolarization-dependent recovery of voltage-gated sodium currents during repeated activation in tipE- neurons. This phenotype is also rescued by expression of the tipE+ transgene. These data demonstrate that tipE regulates sodium-dependent repetitive firing and recovery of sodium currents during repeated activation. Furthermore, the duration of the interstimulus interval necessary to fire a second full-sized action potential is significantly longer in single- versus multiple-spiking transgenic neurons, suggesting that a slow rate of recovery of sodium currents contributes to the decrease in repetitive firing in tipE- neurons.
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Affiliation(s)
- Dianne D Hodges
- Department of Anatomy and Neurobiology, University of California at Irvine, Irvine, California 92697-1280, USA
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39
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Hilgenberg LGW, Ho KD, Lee D, O'Dowd DK, Smith MA. Agrin regulates neuronal responses to excitatory neurotransmitters in vitro and in vivo. Mol Cell Neurosci 2002; 19:97-110. [PMID: 11817901 DOI: 10.1006/mcne.2001.1056] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Agrin mediates motor neuron-induced differentiation of the postsynaptic apparatus of the neuromuscular junction but its function in brain remains unknown. Here we report that expression of c-fos, induced by activation of nicotinic or glutamatergic receptors, was significantly lower in cortical neurons cultured from agrin-deficient mutant mouse embryos compared to wildtype. Agrin-deficient neurons also exhibited increased resistance to excitotoxic injury. Treatment with recombinant agrin restored glutamate-induced c-fos expression and excitotoxicity of the agrin-deficient neurons to near wild-type levels, confirming the agrin dependence of the phenotype. The observation that c-fos induction by activation of voltage-gated Ca2+ channels is also reduced in agrin-deficient neurons raises the possibility that agrin may play a wider role by regulating responses to Ca(2+)-mediated signals. Consistent with the decline in response of cultured mutant neurons to glutamate, decreases in kainic acid-induced seizure and mortality were observed in adult agrin heterozygous mice. Together, these data demonstrate that agrin plays an important role in defining neuronal responses to excitatory neurotransmitters both in vitro and in vivo.
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Affiliation(s)
- Lutz G W Hilgenberg
- Department of Anatomy and Neurobiology, University of California at Irvine, Irvine, California 92697, USA
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40
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Lee D, O'Dowd DK. cAMP-dependent plasticity at excitatory cholinergic synapses in Drosophila neurons: alterations in the memory mutant dunce. J Neurosci 2000; 20:2104-11. [PMID: 10704484 PMCID: PMC6772507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/1999] [Revised: 12/27/1999] [Accepted: 01/04/2000] [Indexed: 02/15/2023] Open
Abstract
It is well known that cAMP signaling plays a role in regulating functional plasticity at central glutamatergic synapses. However, in the Drosophila CNS, where acetylcholine is thought to be a primary excitatory neurotransmitter, cellular changes in neuronal communication mediated by cAMP remain unexplored. In this study we examined the effects of elevated cAMP levels on fast excitatory cholinergic synaptic transmission in cultured embryonic Drosophila neurons. We report that chronic elevation in neuronal cAMP (in dunce neurons or wild-type neurons grown in db-cAMP) results in an increase in the frequency of cholinergic miniature EPSCs (mEPSCs). The absence of alterations in mEPSC amplitude or kinetics suggests that the locus of action is presynaptic. Furthermore, a brief exposure to db-cAMP induces two distinct changes in transmission at established cholinergic synapses in wild-type neurons: a short-term increase in the frequency of spontaneous action potential-dependent synaptic currents and a long-lasting, protein synthesis-dependent increase in the mEPSC frequency. A more persistent increase in cholinergic mEPSC frequency induced by repetitive, spaced db-cAMP exposure in wild-type neurons is absent in neurons from the memory mutant dunce. These data demonstrate that interneuronal excitatory cholinergic synapses in Drosophila, like central excitatory glutamatergic synapses in other species, are sites of cAMP-dependent plasticity. In addition, the alterations in dunce neurons suggest that cAMP-dependent plasticity at cholinergic synapses could mediate changes in neuronal communication that contribute to memory formation.
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Affiliation(s)
- D Lee
- Department of Developmental Biology, University of California at Irvine, Irvine, California 92697-1280, USA
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41
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Dunning DD, Hoover CL, Soltesz I, Smith MA, O'Dowd DK. GABA(A) receptor-mediated miniature postsynaptic currents and alpha-subunit expression in developing cortical neurons. J Neurophysiol 1999; 82:3286-97. [PMID: 10601460 DOI: 10.1152/jn.1999.82.6.3286] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Previous studies have described maturational changes in GABAergic inhibitory synaptic transmission in the rodent somatosensory cortex during the early postnatal period. To determine whether alterations in the functional properties of synaptically localized GABA(A) receptors (GABA(A)Rs) contribute to development of inhibitory transmission, we used the whole cell recording technique to examine GABAergic miniature postsynaptic currents (mPSCs) in developing cortical neurons. Neurons harvested from somatosensory cortices of newborn mice showed a progressive, eightfold increase in GABAergic mPSC frequency during the first 4 wk of development in dissociated cell culture. A twofold decrease in the decay time of the GABAergic mPSCs, between 1 and 4 wk, demonstrates a functional change in the properties of GABA(A)Rs mediating synaptic transmission in cortical neurons during development in culture. A similar maturational profile observed in GABAergic mPSC frequency and decay time in cortical neurons developing in vivo (assessed in slices), suggests that these changes in synaptically localized GABA(A)Rs contribute to development of inhibition in the rodent neocortex. Pharmacological and reverse transcription-polymerase chain reaction (RT-PCR) studies were conducted to determine whether changes in subunit expression might contribute to the observed developmental alterations in synaptic GABA(A)Rs. Zolpidem (300 nM), a subunit-selective benzodiazepine agonist with high affinity for alpha1-subunits, caused a reversible slowing of the mPSC decay kinetics in cultured cortical neurons. Development was characterized by an increase in the potency of zolpidem in modulating the mPSC decay, suggesting a maturational increase in percentage of functionally active GABA(A)Rs containing alpha1 subunits. The relative expression of alpha1 versus alpha5 GABA(A)R subunit mRNA in cortical tissue, both in vivo and in vitro, also increased during this same period. Furthermore, single-cell RT-multiplex PCR analysis revealed more rapidly decaying mPSCs in individual neurons in which alpha1 versus alpha5 mRNA was amplified. Together these data suggest that changes in alpha-subunit composition of GABA(A)Rs contribute to the maturation of GABAergic mPSCs mediating inhibition in developing cortical neurons.
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Affiliation(s)
- D D Dunning
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697-1280, USA
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42
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Lee D, O'Dowd DK. Fast excitatory synaptic transmission mediated by nicotinic acetylcholine receptors in Drosophila neurons. J Neurosci 1999; 19:5311-21. [PMID: 10377342 PMCID: PMC6782340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/1999] [Revised: 04/14/1999] [Accepted: 04/22/1999] [Indexed: 02/12/2023] Open
Abstract
Difficulty in recording from single neurons in vivo has precluded functional analyses of transmission at central synapses in Drosophila, where the neurotransmitters and receptors mediating fast synaptic transmission have yet to be identified. Here we demonstrate that spontaneously active synaptic connections form between cultured neurons prepared from wild-type embryos and provide the first direct evidence that both acetylcholine and GABA mediate fast interneuronal synaptic transmission in Drosophila. The predominant type of fast excitatory transmission between cultured neurons is mediated by nicotinic acetylcholine receptors (nAChRs). Detailed analysis of cholinergic transmission reveals that spontaneous EPSCs (sEPSCs) are composed of both evoked and action potential-independent [miniature EPSC (mEPSC)] components. The mEPSCs are characterized by a broad, positively skewed amplitude histogram in which the variance is likely to reflect differences in the currents induced by single quanta. Biophysical characteristics of the cholinergic mEPSCs include a rapid rise time (0.6 msec) and decay (tau = 2 msec). Regulation of mEPSC frequency by external calcium and cobalt suggests that calcium influx through voltage-gated channels influences the probability of ACh release. In addition, brief depolarization of the cultures with KCl can induce a calcium-dependent increase in sEPSC frequency that persists for up to 3 hr after termination of the stimulus, illustrating one form of plasticity at these cholinergic synapses. These data demonstrate that cultured embryonic neurons, amenable to both genetic and biochemical manipulations, present a unique opportunity to define genes/signal transduction cascades involved in functional regulation of fast excitatory transmission at interneuronal cholinergic synapses in Drosophila.
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Affiliation(s)
- D Lee
- Departments of Developmental and Cell Biology, Anatomy and Neurobiology, University of California Irvine, Irvine, California 92697-1280, USA
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43
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Abstract
Numerous studies suggest that the extracellular matrix protein agrin directs the formation of the postsynaptic apparatus at the neuromuscular junction (NMJ). Strong support for this hypothesis comes from the observation that the high density of acetylcholine receptors (AChR) normally present at the neuromuscular junction fails to form in muscle of embryonic agrin mutant mice. Agrin is expressed by many populations of neurons in the central nervous system (CNS), suggesting that this molecule may also play a role in neuron-neuron synapse formation. To test this hypothesis, we examined synapse formation between cultured cortical neurons isolated from agrin-deficient mouse embryos. Our data show that glutamate receptors accumulate at synaptic sites on agrin-deficient neurons. Moreover, electrophysiological analysis demonstrates that functional glutamatergic and gamma-aminobutyric acid (GABA)ergic synapses form between mutant neurons. The frequency and amplitude of miniature postsynaptic glutamatergic and GABAergic currents are similar in mutant and age-matched wild-type neurons during the first 3 weeks in culture. These results demonstrate that neuron-specific agrin is not required for formation and early development of functional synaptic contacts between CNS neurons, and suggest that mechanisms of interneuronal synaptogenesis are distinct from those regulating synapse formation at the neuromuscular junction.
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Affiliation(s)
- Z Li
- Department of Anatomy and Neurobiology, University of California at Irvine, 92697, USA
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44
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45
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Bina KG, Park M, O'Dowd DK. Regulation of alpha7 nicotinic acetylcholine receptors in mouse somatosensory cortex following whisker removal at birth. J Comp Neurol 1998; 397:1-9. [PMID: 9671275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Previous studies in postnatal mouse demonstrating high levels of alpha7 nicotinic acetylcholine receptors on layer IV somatosensory cortical neurons coincident with the onset of functional synaptic transmission led us to investigate whether the number and/or the localization of these receptors could be regulated by activity. Accordingly, we examined alpha-bungarotoxin binding in mouse somatosensory cortex following removal of all of the vibrissae on one side of the face, either by vibrissal follicle cauterization or daily plucking beginning on the day of birth. Following vibrissa plucking, the levels of [125I]alpha-bungarotoxin binding on postnatal day 6 were significantly higher (23 +/- 7%) in the denervated cortex (contralateral to the peripheral manipulation) than the intact cortex. Cauterization also resulted in significantly higher (14 +/- 3%) [125I]alpha-bungarotoxin binding in the contralateral vs. the ipsilateral cortex. In contrast, there was no difference in [125I]alpha-bungarotoxin binding in the left and right cortices of unoperated control animals. At postnatal day 14, levels of [125I]alpha-bungarotoxin binding in layer IV were very low in control animals as well as in animals subjected to whisker plucking or cautery. These findings suggest that reducing activity in the somatosensory pathway regulates the density of alpha7 nicotinic acetylcholine receptors during the first postnatal week. However, the normal decrease in receptor density that is seen during the second postnatal week of development proceeds despite altered sensory activity.
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Affiliation(s)
- K G Bina
- Department of Developmental and Cell Biology, University of California at Irvine, 92697-1280, USA
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46
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Abstract
The metameric organization of the vertebrate hindbrain into rhombomeres appears to result from the patterned expression of several transcription factors and putative signaling molecules. We have applied a refined single-cell reverse transcription-polymerase chain reaction strategy to examine the molecular logic proposed to pattern the hindbrain at the single-cell level. This technique allows analysis of the concurrent expression of several genes within an individual cell at higher sensitivity than by in situ hybridization. Our results demonstrate that cells in rhombomere (r) 4 and r5 are heterogeneous in their expression of Hoxa-3, Hoxb-2, Sek-1, and Krox-20, suggesting that single cells are dynamically regulating their rhombomere-specific gene-expression profiles. Furthermore, the strong correlation between Sek-1 and Krox-20 expression at stage 12 was greatly diminished by stage 16, suggesting that the proposed interdependence of these two genes is present only at early stages of hindbrain development.
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Affiliation(s)
- K Kato
- Division of Biology, California Institute of Technology, Pasadena 91125, USA
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Abstract
Agrin is an extracellular matrix protein involved in the formation of the postsynaptic apparatus of the neuromuscular junction. In addition to spinal motor neurons, agrin is expressed by many other neuronal populations throughout the nervous system. Agrin's role outside of the neuromuscular junction, however, is poorly understood. Here we use the polymerase chain reaction to examine expression and alternative splicing of agrin in mouse somatosensory cortex during early postnatal development in vivo and in dissociated cell culture. Peak levels of agrin gene expression in developing cortex coincide with ingrowth of thalamic afferent fibres and formation of thalamocortical and intracortical synapses. Analysis of alternatively spliced agrin messenger RNA variants shows that greater than 95% of all agrin in developing and adult somatosensory cortex originates in neurons, including isoforms that have little or no activity in acetylcholine receptor aggregation assays. The levels of expression of "active" and "inactive" isoforms, however, are regulated during development. A similar pattern of agrin gene expression is also observed during a period when new synapses are being formed between somatosensory neurons growing in dissociated cell culture. Changes in agrin gene expression, observed both in vivo and in vitro, are consistent with a role for agrin in synapse formation in the central nervous system.
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Affiliation(s)
- Z Li
- Department of Anatomy and Neurobiology, University of California at Irvine, 92697, U.S.A
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48
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Massengill JL, Smith MA, Son DI, O'Dowd DK. Differential expression of K4-AP currents and Kv3.1 potassium channel transcripts in cortical neurons that develop distinct firing phenotypes. J Neurosci 1997; 17:3136-47. [PMID: 9096148 PMCID: PMC6573663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Maturation of electrical excitability during early postnatal development is critical to formation of functional neural circuitry in the mammalian neocortex. Little is known, however, about the changes in gene expression underlying the development of firing properties that characterize different classes of cortical neurons. Here we describe the development of cortical neurons with two distinct firing phenotypes, regular-spiking (RS) and fast-spiking (FS), that appear to emerge from a population of immature multiple-spiking (IMS) neurons during the first two postnatal weeks, both in vivo (within layer IV) and in vitro. We report the expression of a slowly inactivating, 4-AP-sensitive potassium current (K4-AP) at significantly higher density in FS compared with RS neurons. The same current is expressed at intermediate levels in IMS neurons. The kinetic, voltage-dependent, and pharmacological properties of the K4-AP current are similar to those observed by heterologous expression of Kv3.1 potassium channel mRNA. Single-cell RT-PCR analysis demonstrates that PCR products representing Kv3.1 transcripts are amplified more frequently from FS than RS neurons, with an intermediate frequency of Kv3.1 detection in neurons with immature firing properties. Taken together, these data suggest that the Kv3.1 gene encodes the K4-AP current and that expression of this gene is regulated in a cell-specific manner during development. Analysis of the effects of 4-AP on firing properties suggests that the K4-AP current is important for rapid action potential repolarization, fast after-hyperpolarization, brief refractory period, and high firing frequency characteristic of FS GABAergic interneurons.
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Affiliation(s)
- J L Massengill
- Department of Anatomy, University of California, Irvine, California 92697-1280, USA
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49
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Abstract
The characteristic functions of tissues and organs result from the integrated activity of individual cells. Nowhere is this more evident than in the nervous system, where the activities of single neurons communicating via electrical and chemical signals mediate complex functions, such as learning and memory. The past decade has seen an explosion in the identification of genes encoding proteins, such as voltage-gated channels and neurotransmitter receptors, responsible for neuronal excitability. These studies have highlighted the fact that even within a neuroanatomically defined region, the coexistence of multiple cell types makes it difficult, if not impossible, to correlate patterns of gene expression with function. The recent development of techniques sensitive enough to study gene expression at the single-cell level promises to break this bottleneck to our further understanding. Using examples taken from our own laboratories and the work of others, we review these techniques, their application, and discuss some of the difficulties associated with the interpretation of the data.
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Affiliation(s)
- D K O'Dowd
- Department of Anatomy and Neurobiology, U.C. Irvine, CA 92697-1280, USA
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50
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Agmon A, Hollrigel G, O'Dowd DK. Functional GABAergic synaptic connection in neonatal mouse barrel cortex. J Neurosci 1996; 16:4684-95. [PMID: 8764656 PMCID: PMC6579032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Intracortical inhibition is crucial to proper functioning of the mature neocortex, yet, paradoxically, is reported to be rare or absent in the neonatal animal. We reexamined this issue by recording whole-cell postsynaptic currents (PSCs) of barrel cortex neurons in thalamocortical brain slices from neonatal mice. Monosynaptic, excitatory thalamocortical responses were elicited in layers V/VI neurons as early as postnatal day 0 (P0, the first 24 hr after birth) and in presumptive layer IV as early as P2. At very low stimulation frequencies, the monosynaptic response was invariably followed by a prolonged (up to 1 sec) synaptic barrage, which fatigued at stimulus repetition rates of 2/min or higher. This barrage consisted of postsynaptic responses to spiking activity in neighboring cortical cells, because (1) it could also be evoked by intracortical stimulation in coronal slices and (2) it was abolished by antagonists to NMDA receptors (NMDARs), even when NMDARs on the recorded cell were under a voltage-dependent block. Some of the larger polysynaptic events changed polarity at a negative reversal potential and were blocked by GABAA receptor (GABAAR) antagonists, with a concurrent enhancement of the extracellular field potential, indicating that they were GABAAR- mediated, CI-dependent inhibitory PSCs (IPSCs). We conclude that a network of functional intracortical GABAAR-mediated synaptic connections exists from the earliest postnatal ages, although it gives rise to responses that differ from mature IPSCs in reversal potential and latency.
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Affiliation(s)
- A Agmon
- Department of Anatomy, University of California, Irvine 92717, USA
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