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Kenworthy AK. What's past is prologue: FRAP keeps delivering 50 years later. Biophys J 2023; 122:3577-3586. [PMID: 37218127 PMCID: PMC10541474 DOI: 10.1016/j.bpj.2023.05.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2023] [Revised: 03/03/2023] [Accepted: 05/11/2023] [Indexed: 05/24/2023] Open
Abstract
Fluorescence recovery after photobleaching (FRAP) has emerged as one of the most widely utilized techniques to quantify binding and diffusion kinetics of biomolecules in biophysics. Since its inception in the mid-1970s, FRAP has been used to address an enormous array of questions including the characteristic features of lipid rafts, how cells regulate the viscosity of their cytoplasm, and the dynamics of biomolecules inside condensates formed by liquid-liquid phase separation. In this perspective, I briefly summarize the history of the field and discuss why FRAP has proven to be so incredibly versatile and popular. Next, I provide an overview of the extensive body of knowledge that has emerged on best practices for quantitative FRAP data analysis, followed by some recent examples of biological lessons learned using this powerful approach. Finally, I touch on new directions and opportunities for biophysicists to contribute to the continued development of this still-relevant research tool.
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Affiliation(s)
- Anne K Kenworthy
- Center for Membrane and Cell Physiology, University of Virginia, Charlottesville, Virginia; Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville, Virginia.
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Wang J, Chen HS, Li HH, Wang HJ, Zou RS, Lu XJ, Wang J, Nie BB, Wu JF, Li S, Shan BC, Wu PF, Long LH, Hu ZL, Chen JG, Wang F. Microglia-dependent excessive synaptic pruning leads to cortical underconnectivity and behavioral abnormality following chronic social defeat stress in mice. Brain Behav Immun 2023; 109:23-36. [PMID: 36581303 DOI: 10.1016/j.bbi.2022.12.019] [Citation(s) in RCA: 27] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Revised: 12/17/2022] [Accepted: 12/24/2022] [Indexed: 12/28/2022] Open
Abstract
Synapse loss in medial prefrontal cortex (mPFC) has been implicated in stress-related mood disorders, such as depression. However, the exact effect of synapse elimination in the depression and how it is triggered are largely unknown. Through repeated longitudinal imaging of mPFC in the living brain, we found both presynaptic and postsynaptic components were declined, together with the impairment of synapse remodeling and cross-synaptic signal transmission in the mPFC during chronic stress. Meanwhile, chronic stress also induced excessive microglia phagocytosis, leading to engulfment of excitatory synapses. Further investigation revealed that the elevated complement C3 during the stress acted as the tag of synapses to be eliminated by microglia. Besides, chronic stress induced a reduction of the connectivity between the mPFC and neighbor regions. C3 knockout mice displayed significant reduction of synaptic pruning and alleviation of disrupted functional connectivity in mPFC, resulting in more resilience to chronic stress. These results indicate that complement-mediated excessive microglia phagocytosis in adulthood induces synaptic dysfunction and cortical hypo-connectivity, leading to stress-related behavioral abnormality.
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Affiliation(s)
- Ji Wang
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan City, Hubei 430030, China
| | - Hong-Sheng Chen
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan City, Hubei 430030, China
| | - Hou-Hong Li
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan City, Hubei 430030, China
| | - Hua-Jie Wang
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan City, Hubei 430030, China
| | - Ruo-Si Zou
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan City, Hubei 430030, China
| | - Xiao-Jia Lu
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan City, Hubei 430030, China
| | - Jie Wang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, Hubei 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Bin-Bin Nie
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, Hubei 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Jin-Feng Wu
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, Hubei 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Shuang Li
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, Hubei 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Bao-Ci Shan
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, Hubei 430071, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Peng-Fei Wu
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan City, Hubei 430030, China; The Research Center for Depression, Tongji Medical College, Huazhong University of Science and Technology, 430030 Wuhan, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, 430030 Wuhan, China; Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, Wuhan City, Hubei 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, 430030 Wuhan, China
| | - Li-Hong Long
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan City, Hubei 430030, China; The Research Center for Depression, Tongji Medical College, Huazhong University of Science and Technology, 430030 Wuhan, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, 430030 Wuhan, China; Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, Wuhan City, Hubei 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, 430030 Wuhan, China
| | - Zhuang-Li Hu
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan City, Hubei 430030, China; The Research Center for Depression, Tongji Medical College, Huazhong University of Science and Technology, 430030 Wuhan, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, 430030 Wuhan, China; Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, Wuhan City, Hubei 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, 430030 Wuhan, China.
| | - Jian-Guo Chen
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan City, Hubei 430030, China; The Research Center for Depression, Tongji Medical College, Huazhong University of Science and Technology, 430030 Wuhan, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, 430030 Wuhan, China; Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, Wuhan City, Hubei 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, 430030 Wuhan, China.
| | - Fang Wang
- Department of Pharmacology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan City, Hubei 430030, China; The Research Center for Depression, Tongji Medical College, Huazhong University of Science and Technology, 430030 Wuhan, China; The Key Laboratory for Drug Target Researches and Pharmacodynamic Evaluation of Hubei Province, 430030 Wuhan, China; Key Laboratory of Neurological Diseases (HUST), Ministry of Education of China, Wuhan, Wuhan City, Hubei 430030, China; Laboratory of Neuropsychiatric Diseases, The Institute of Brain Research, Huazhong University of Science and Technology, 430030 Wuhan, China.
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3
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Knodel MM, Dutta Roy R, Wittum G. Influence of T-Bar on Calcium Concentration Impacting Release Probability. Front Comput Neurosci 2022; 16:855746. [PMID: 35586479 PMCID: PMC9108211 DOI: 10.3389/fncom.2022.855746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Accepted: 03/09/2022] [Indexed: 11/25/2022] Open
Abstract
The relation of form and function, namely the impact of the synaptic anatomy on calcium dynamics in the presynaptic bouton, is a major challenge of present (computational) neuroscience at a cellular level. The Drosophila larval neuromuscular junction (NMJ) is a simple model system, which allows studying basic effects in a rather simple way. This synapse harbors several special structures. In particular, in opposite to standard vertebrate synapses, the presynaptic boutons are rather large, and they have several presynaptic zones. In these zones, different types of anatomical structures are present. Some of the zones bear a so-called T-bar, a particular anatomical structure. The geometric form of the T-bar resembles the shape of the letter “T” or a table with one leg. When an action potential arises, calcium influx is triggered. The probability of vesicle docking and neurotransmitter release is superlinearly proportional to the concentration of calcium close to the vesicular release site. It is tempting to assume that the T-bar causes some sort of calcium accumulation and hence triggers a higher release probability and thus enhances neurotransmitter exocytosis. In order to study this influence in a quantitative manner, we constructed a typical T-bar geometry and compared the calcium concentration close to the active zones (AZs). We compared the case of synapses with and without T-bars. Indeed, we found a substantial influence of the T-bar structure on the presynaptic calcium concentrations close to the AZs, indicating that this anatomical structure increases vesicle release probability. Therefore, our study reveals how the T-bar zone implies a strong relation between form and function. Our study answers the question of experimental studies (namely “Wichmann and Sigrist, Journal of neurogenetics 2010”) concerning the sense of the anatomical structure of the T-bar.
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Affiliation(s)
- Markus M. Knodel
- Goethe Center for Scientific Computing (GCSC), Goethe Universität Frankfurt, Frankfurt, Germany
- *Correspondence: Markus M. Knodel ; orcid.org/0000-0001-8739-0803
| | | | - Gabriel Wittum
- Goethe Center for Scientific Computing (GCSC), Goethe Universität Frankfurt, Frankfurt, Germany
- Applied Mathematics and Computational Science, Computer, Electrical and Mathematical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
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Saxton WM, Lim A, Djagaeva I. Dissection and Direct Imaging of Axonal Transport in Drosophila Segmental Nerves. Methods Mol Biol 2022; 2431:367-384. [PMID: 35412287 DOI: 10.1007/978-1-0716-1990-2_19] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
For neurons, especially those with long axons, the forceful transport of mitochondria, vesicles, and other cytoplasmic components by cytoskeletal motors is vital. Defects in cytoplasmic transport machinery cause a degradation of signaling capacity that is most severe for neurons with the longest axons. In humans, with motor axons up to a meter long, even a mild mutation in one copy of the gene that codes for kinesin-1, the primary anterograde axonal transport motor, can cause spastic paraplegia and other distal neuropathies.To address questions about the molecular mechanisms of organelle movement, we turned to Drosophila as a model system, because it offered rigorous genetic and molecular approaches to the identification and inhibition of specific elements of transport machinery. However, methods for direct observation of organelle transport were largely lacking. We describe here an approach that we developed for imaging the transport behaviors of specific organelles in the long motor axons of larvae. It is straightforward, the equipment is commonly available, and it provides a powerful tool for studying the contributions of specific proteins to organelle transport mechanisms.
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Affiliation(s)
- William M Saxton
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA, USA.
| | - Angeline Lim
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Inna Djagaeva
- Department of Molecular, Cell and Developmental Biology, University of California Santa Cruz, Santa Cruz, CA, USA
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5
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Ji H, Han C. LarvaSPA, A Method for Mounting Drosophila Larva for Long-Term Time-Lapse Imaging. J Vis Exp 2020. [PMID: 32176208 DOI: 10.3791/60792] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Live imaging is a valuable approach for investigating cell biology questions. The Drosophila larva is particularly suited for in vivo live imaging because the larval body wall and most internal organs are transparent. However, continuous live imaging of intact Drosophila larvae for longer than 30 min has been challenging because it is difficult to noninvasively immobilizeimmobilizing larvae for a long time. Here we present a larval mounting method called LarvaSPA that allows for continuous imaging of live Drosophila larvae with high temporal and spatial resolution for longer than 10 hours. This method involves partially attaching larvae to the coverslip using a UV-reactive glue and additionally restraining larval movement using a polydimethylsiloxane (PDMS) block. This method is compatible with larvae at developmental stages from second instar to wandering third instar. We demonstrate applications of this method in studying dynamic processes of Drosophila somatosensory neurons, including dendrite growth and injury-induced dendrite degeneration. This method can also be applied to study many other cellular processes that happen near the larval body wall.
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Affiliation(s)
- Hui Ji
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University
| | - Chun Han
- Weill Institute for Cell and Molecular Biology and Department of Molecular Biology and Genetics, Cornell University;
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6
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Kakanj P, Eming SA, Partridge L, Leptin M. Long-term in vivo imaging of Drosophila larvae. Nat Protoc 2020; 15:1158-1187. [DOI: 10.1038/s41596-019-0282-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Accepted: 12/09/2019] [Indexed: 02/07/2023]
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7
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Zabihihesari A, Hilliker AJ, Rezai P. Localized microinjection of intact Drosophila melanogaster larva to investigate the effect of serotonin on heart rate. LAB ON A CHIP 2020; 20:343-355. [PMID: 31828261 DOI: 10.1039/c9lc00963a] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In this paper, we present a novel hybrid microfluidic device for localized microinjection and heart monitoring of intact Drosophila melanogaster larvae at different developmental stages. Drosophila heart at the larval stage has been used as a model for cardiac disorder studies. However, previous pharmacological and toxicological cardiac studies are limited to dissected (semi-intact) Drosophila larvae which cannot be used for post-treatment studies. Challenges associated with microinjection of intact larvae include delicate handling of individual larvae, proper orientation for microneedle penetration, localized microinjection with controlled amount of chemicals into the hemolymph and reversible immobilization for post-injection phenotypic studies, all addressed by our microfluidic device. Larva loading and orientation were achieved by glass capillaries integrated into the PDMS microfluidic device. Side suction channels were used for immobilization prior to heart activity recording. Localized microinjection was achieved with a one degree-of-freedom microneedle and a custom-made pressure driven reagent delivery system, without any adverse effect on heart rate and animal viability. Precision in localized injection into the body cavity close to the heart chamber or the fat body was demonstrated with our microfluidic device. A MATLAB-based heartbeat quantification technique was used to investigate the dose-dependent effect of serotonin (5-hydroxytryptamine), a neurotransmitter, on the heart rate of intact Drosophila larvae, for the first time. Injection of 40 nL serotonin with ≥0.01 mM concentration significantly increased the heart rate of 3rd instar larvae by 21 ± 7% (SEM). Injection of 5 nL serotonin with a concentration of 0.01 mM significantly increased the heart rate of 2nd instar larvae by 12 ± 3% (SEM). The proposed microfluidic injection and heartbeat monitoring technique can be used for dye angiography and hemolymph circulation studies as well as screening intravenous drugs in vivo using the whole-animal Drosophila melanogaster.
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Affiliation(s)
- Alireza Zabihihesari
- Department of Mechanical Engineering, York University, BRG 433B, 4700 Keele St, Toronto, ON M3J 1P3, Canada.
| | | | - Pouya Rezai
- Department of Mechanical Engineering, York University, BRG 433B, 4700 Keele St, Toronto, ON M3J 1P3, Canada.
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8
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Zabihihesari A, Hilliker AJ, Rezai P. Fly-on-a-Chip: Microfluidics for Drosophila melanogaster Studies. Integr Biol (Camb) 2020; 11:425-443. [DOI: 10.1093/intbio/zyz037] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 10/21/2019] [Accepted: 10/26/2019] [Indexed: 12/16/2022]
Abstract
Abstract
The fruit fly or Drosophila melanogaster has been used as a promising model organism in genetics, developmental and behavioral studies as well as in the fields of neuroscience, pharmacology, and toxicology. Not only all the developmental stages of Drosophila, including embryonic, larval, and adulthood stages, have been used in experimental in vivo biology, but also the organs, tissues, and cells extracted from this model have found applications in in vitro assays. However, the manual manipulation, cellular investigation and behavioral phenotyping techniques utilized in conventional Drosophila-based in vivo and in vitro assays are mostly time-consuming, labor-intensive, and low in throughput. Moreover, stimulation of the organism with external biological, chemical, or physical signals requires precision in signal delivery, while quantification of neural and behavioral phenotypes necessitates optical and physical accessibility to Drosophila. Recently, microfluidic and lab-on-a-chip devices have emerged as powerful tools to overcome these challenges. This review paper demonstrates the role of microfluidic technology in Drosophila studies with a focus on both in vivo and in vitro investigations. The reviewed microfluidic devices are categorized based on their applications to various stages of Drosophila development. We have emphasized technologies that were utilized for tissue- and behavior-based investigations. Furthermore, the challenges and future directions in Drosophila-on-a-chip research, and its integration with other advanced technologies, will be discussed.
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Affiliation(s)
| | | | - Pouya Rezai
- Department of Mechanical Engineering, York University, Toronto, ON, Canada
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Cevik D, Acker M, Arefi P, Ghaemi R, Zhang J, Selvaganapathy PR, Dworkin I, Jacobs JR. Chloroform and desflurane immobilization with recovery of viable Drosophila larvae for confocal imaging. JOURNAL OF INSECT PHYSIOLOGY 2019; 117:103900. [PMID: 31202852 DOI: 10.1016/j.jinsphys.2019.103900] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 06/03/2019] [Accepted: 06/12/2019] [Indexed: 06/09/2023]
Abstract
Imaging of living, intact Drosophila larvae is challenged if normal bodily function must be observed or when healthy larvae must be recovered for subsequent studies. Here, we describe a simple and short protocol that employs transient airborne chloroform or desflurane (1,2,2,2-tetrafluoroethyl difluoromethyl ether) to efficiently immobilize larvae without the use of manipulation devices, vaporizers or imaging chambers. This non-lethal method allows the use of anesthetics while allowing tracking of individual Drosophila into adulthood for follow-up experiments. At dosages sufficient to immobilize larvae, Desflurane, but not chloroform reduced the central nervous system response to auditory stimulus. Desflurane doses were sufficient to arrest the heart, however significant rapid recovery was observed. With our method, chloroform provided more rapid anesthesia but slower recovery than Desflurane. Without specialized hardware, this technique allows for repeated imaging of living Drosophila larvae.
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Affiliation(s)
- Duygu Cevik
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Meryl Acker
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Pouya Arefi
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Reza Ghaemi
- Department of Mechanical Engineering, McMaster University, Hamilton L8S 4L7, Canada
| | - Jimmy Zhang
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada
| | | | - Ian Dworkin
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada; Department of Mechanical Engineering, McMaster University, Hamilton L8S 4L7, Canada
| | - J Roger Jacobs
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada.
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10
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Böhme MA, McCarthy AW, Grasskamp AT, Beuschel CB, Goel P, Jusyte M, Laber D, Huang S, Rey U, Petzoldt AG, Lehmann M, Göttfert F, Haghighi P, Hell SW, Owald D, Dickman D, Sigrist SJ, Walter AM. Rapid active zone remodeling consolidates presynaptic potentiation. Nat Commun 2019; 10:1085. [PMID: 30842428 PMCID: PMC6403334 DOI: 10.1038/s41467-019-08977-6] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 02/07/2019] [Indexed: 01/22/2023] Open
Abstract
Neuronal communication across synapses relies on neurotransmitter release from presynaptic active zones (AZs) followed by postsynaptic transmitter detection. Synaptic plasticity homeostatically maintains functionality during perturbations and enables memory formation. Postsynaptic plasticity targets neurotransmitter receptors, but presynaptic mechanisms regulating the neurotransmitter release apparatus remain largely enigmatic. By studying Drosophila neuromuscular junctions (NMJs) we show that AZs consist of nano-modular release sites and identify a molecular sequence that adds modules within minutes of inducing homeostatic plasticity. This requires cognate transport machinery and specific AZ-scaffolding proteins. Structural remodeling is not required for immediate potentiation of neurotransmitter release, but necessary to sustain potentiation over longer timescales. Finally, mutations in Unc13 disrupting homeostatic plasticity at the NMJ also impair short-term memory when central neurons are targeted, suggesting that both plasticity mechanisms utilize Unc13. Together, while immediate synaptic potentiation capitalizes on available material, it triggers the coincident incorporation of modular release sites to consolidate synaptic potentiation.
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Affiliation(s)
- Mathias A Böhme
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany.,Institute for Biology/Genetics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Anthony W McCarthy
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany
| | - Andreas T Grasskamp
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany.,NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany
| | - Christine B Beuschel
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany.,Institute for Biology/Genetics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Pragya Goel
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Meida Jusyte
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany
| | - Desiree Laber
- Institut für Neurophysiologie, Charité Universitätsmedizin, 10117, Berlin, Germany
| | - Sheng Huang
- Institute for Biology/Genetics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Ulises Rey
- Institute for Biology/Genetics, Freie Universität Berlin, 14195, Berlin, Germany.,Department of Theory and Bio-systems, Max Planck Institute of Colloids and Interfaces, Science Park Golm, 14424, Potsdam, Germany
| | - Astrid G Petzoldt
- Institute for Biology/Genetics, Freie Universität Berlin, 14195, Berlin, Germany
| | - Martin Lehmann
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany
| | - Fabian Göttfert
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany
| | | | - Stefan W Hell
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, 37077, Göttingen, Germany
| | - David Owald
- Institut für Neurophysiologie, Charité Universitätsmedizin, 10117, Berlin, Germany
| | - Dion Dickman
- Department of Neurobiology, University of Southern California, Los Angeles, CA, 90089, USA
| | - Stephan J Sigrist
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin, 10117, Berlin, Germany. .,Institute for Biology/Genetics, Freie Universität Berlin, 14195, Berlin, Germany.
| | - Alexander M Walter
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125, Berlin, Germany.
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11
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Presynaptic Biogenesis Requires Axonal Transport of Lysosome-Related Vesicles. Neuron 2018; 99:1216-1232.e7. [DOI: 10.1016/j.neuron.2018.08.004] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 05/18/2018] [Accepted: 08/02/2018] [Indexed: 01/05/2023]
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12
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Akbergenova Y, Cunningham KL, Zhang YV, Weiss S, Littleton JT. Characterization of developmental and molecular factors underlying release heterogeneity at Drosophila synapses. eLife 2018; 7:38268. [PMID: 29989549 PMCID: PMC6075867 DOI: 10.7554/elife.38268] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 06/30/2018] [Indexed: 12/14/2022] Open
Abstract
Neurons communicate through neurotransmitter release at specialized synaptic regions known as active zones (AZs). Using biosensors to visualize single synaptic vesicle fusion events at Drosophila neuromuscular junctions, we analyzed the developmental and molecular determinants of release probability (Pr) for a defined connection with ~300 AZs. Pr was heterogeneous but represented a stable feature of each AZ. Pr remained stable during high frequency stimulation and retained heterogeneity in mutants lacking the Ca2+ sensor Synaptotagmin 1. Pr correlated with both presynaptic Ca2+ channel abundance and Ca2+ influx at individual release sites. Pr heterogeneity also correlated with glutamate receptor abundance, with high Pr connections developing receptor subtype segregation. Intravital imaging throughout development revealed that AZs acquire high Pr during a multi-day maturation period, with Pr heterogeneity largely reflecting AZ age. The rate of synapse maturation was activity-dependent, as both increases and decreases in neuronal activity modulated glutamate receptor field size and segregation. To send a message to its neighbor, a neuron releases chemicals called neurotransmitters into the gap – or synapse – between them. The neurotransmitter molecules bind to proteins on the receiver neuron called receptors. But what causes the sender neuron to release neurotransmitter in the first place? The process starts when an electrical impulse called an action potential arrives at the sender cell. Its arrival causes channels in the membrane of the sender neuron to open, so that calcium ions flood into the cell. The calcium ions interact with packages of neurotransmitter molecules, known as synaptic vesicles. This causes some of the vesicles to empty their contents into the synapse. But this process is not particularly reliable. Only a small fraction of action potentials cause vesicles to fuse with the synaptic membrane. How likely this is to occur varies greatly between neurons, and even between synapses formed by the same neuron. Synapses that are likely to release neurotransmitter are said to be strong. They are good at passing messages from the sender neuron to the receiver. Synapses with a low probability of release are said to be weak. But what exactly differs between strong and weak synapses? Akbergenova et al. studied synapses between motor neurons and muscle cells in the fruit fly Drosophila. Each motor neuron forms several hundred synapses. Some of these synapses are 50 times more likely to release neurotransmitter than others. Using calcium imaging and genetics, Akbergenova et al. showed that sender cells at strong synapses have more calcium channels than sender cells at weak synapses. The subtypes and arrangement of receptor proteins also differ between the receiver neurons of strong versus weak synapses. Finally, studies in larvae revealed that newly formed synapses all start out weak and then gradually become stronger. How fast this strengthening occurs depends on how active the neuron at the synapse is. This study has shown, in unprecedented detail, key molecular factors that make some fruit fly synapses more likely to release neurotransmitter than others. Many proteins at synapses of mammals resemble those at fruit fly synapses. This means that similar factors may also explain differences in synaptic strength in the mammalian brain. Changes in the strength of synapses underlie the ability to learn. Furthermore, many neurological and psychiatric disorders result from disruption of synapses. Understanding the molecular basis of synapses will thus provide clues to the origins of certain brain diseases.
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Affiliation(s)
- Yulia Akbergenova
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Karen L Cunningham
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
| | - Yao V Zhang
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - Shirley Weiss
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, United States
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13
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Lim A, Rechtsteiner A, Saxton WM. Two kinesins drive anterograde neuropeptide transport. Mol Biol Cell 2017; 28:3542-3553. [PMID: 28904207 PMCID: PMC5683764 DOI: 10.1091/mbc.e16-12-0820] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Revised: 08/16/2017] [Accepted: 09/08/2017] [Indexed: 11/11/2022] Open
Abstract
Motor-dependent anterograde transport, a process that moves cytoplasmic components from sites of biosynthesis to sites of use within cells, is crucial in neurons with long axons. Evidence has emerged that multiple anterograde kinesins can contribute to some transport processes. To test the multi-kinesin possibility for a single vesicle type, we studied the functional relationships of axonal kinesins to dense core vesicles (DCVs) that were filled with a GFP-tagged neuropeptide in the Drosophila nervous system. Past work showed that Unc-104 (a kinesin-3) is a key anterograde DCV motor. Here we show that anterograde DCV transport requires the well-known mitochondrial motor Khc (kinesin-1). Our results indicate that this influence is direct. Khc mutations had specific effects on anterograde run parameters, neuron-specific inhibition of mitochondrial transport by Milton RNA interference had no influence on anterograde DCV runs, and detailed colocalization analysis by superresolution microscopy revealed that Unc-104 and Khc coassociate with individual DCVs. DCV distribution analysis in peptidergic neurons suggest the two kinesins have compartment specific influences. We suggest a mechanism in which Unc-104 is particularly important for moving DCVs from cell bodies into axons, and then Unc-104 and kinesin-1 function together to support fast, highly processive runs toward axon terminals.
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Affiliation(s)
- Angeline Lim
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - Andreas Rechtsteiner
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
| | - William M Saxton
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, Santa Cruz, CA 95064
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14
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Reddy-Alla S, Böhme MA, Reynolds E, Beis C, Grasskamp AT, Mampell MM, Maglione M, Jusyte M, Rey U, Babikir H, McCarthy AW, Quentin C, Matkovic T, Bergeron DD, Mushtaq Z, Göttfert F, Owald D, Mielke T, Hell SW, Sigrist SJ, Walter AM. Stable Positioning of Unc13 Restricts Synaptic Vesicle Fusion to Defined Release Sites to Promote Synchronous Neurotransmission. Neuron 2017; 95:1350-1364.e12. [DOI: 10.1016/j.neuron.2017.08.016] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 05/10/2017] [Accepted: 08/09/2017] [Indexed: 12/24/2022]
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15
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Spencer AK, Schaumberg AJ, Zallen JA. Scaling of cytoskeletal organization with cell size in Drosophila. Mol Biol Cell 2017; 28:1519-1529. [PMID: 28404752 PMCID: PMC5449150 DOI: 10.1091/mbc.e16-10-0691] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 03/31/2017] [Accepted: 04/05/2017] [Indexed: 11/11/2022] Open
Abstract
Actin-rich denticle precursors are regularly distributed in the Drosophila embryo. Cytoskeletal scaling occurs through changes in denticle number and spacing. Denticle spacing scales with cell length over a 10-fold range. Accurate denticle positioning requires the microtubule cytoskeleton. Spatially organized macromolecular complexes are essential for cell and tissue function, but the mechanisms that organize micron-scale structures within cells are not well understood. Microtubule-based structures such as mitotic spindles scale with cell size, but less is known about the scaling of actin structures within cells. Actin-rich denticle precursors cover the ventral surface of the Drosophila embryo and larva and provide templates for cuticular structures involved in larval locomotion. Using quantitative imaging and statistical modeling, we demonstrate that denticle number and spacing scale with cell length over a wide range of cell sizes in embryos and larvae. Denticle number and spacing are reduced under space-limited conditions, and both features robustly scale over a 10-fold increase in cell length during larval growth. We show that the relationship between cell length and denticle spacing can be recapitulated by specific mathematical equations in embryos and larvae and that accurate denticle spacing requires an intact microtubule network and the microtubule minus end–binding protein, Patronin. These results identify a novel mechanism of microtubule-dependent actin scaling that maintains precise patterns of actin organization during tissue growth.
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Affiliation(s)
- Alison K Spencer
- Gerstner Sloan Kettering Graduate School of Biomedical Sciences.,Howard Hughes Medical Institute and Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Andrew J Schaumberg
- Weill Cornell Graduate School of Medical Sciences and the Tri-Institutional PhD Program in Computational Biology and Medicine, Memorial Sloan Kettering Cancer Center, New York, NY 10065
| | - Jennifer A Zallen
- Howard Hughes Medical Institute and Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065
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16
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Böhme MA, Beis C, Reddy-Alla S, Reynolds E, Mampell MM, Grasskamp AT, Lützkendorf J, Bergeron DD, Driller JH, Babikir H, Göttfert F, Robinson IM, O'Kane CJ, Hell SW, Wahl MC, Stelzl U, Loll B, Walter AM, Sigrist SJ. Active zone scaffolds differentially accumulate Unc13 isoforms to tune Ca2+ channel–vesicle coupling. Nat Neurosci 2016; 19:1311-20. [DOI: 10.1038/nn.4364] [Citation(s) in RCA: 136] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 07/20/2016] [Indexed: 01/05/2023]
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17
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Abstract
Polyglutamine (polyQ) expansion within Huntingtin (Htt) causes the fatal neurodegenerative disorder Huntington’s Disease (HD). Although Htt is ubiquitously expressed and conserved from Drosophila to humans, its normal biological function is still being elucidated. Here we characterize a role for the Drosophila Htt homolog (dHtt) in fast axonal transport (FAT). Generation and expression of transgenic dHtt-mRFP and human Htt-mRFP fusion proteins in Drosophila revealed co-localization with mitochondria and synaptic vesicles undergoing FAT. However, Htt was not ubiquitously associated with the transport machinery, as it was excluded from dense-core vesicles and APLIP1 containing vesicles. Quantification of cargo movement in dHtt deficient axons revealed that mitochondria and synaptic vesicles show a decrease in the distance and duration of transport, and an increase in the number of pauses. In addition, the ratio of retrograde to anterograde flux was increased in mutant animals. Densecore vesicles did not display similar defects in processivity, but did show altered retrograde to anterograde flux along axons. Given the co-localization with mitochondria and synaptic vesicles, but not dense-core vesicles, the data suggest dHtt likely acts locally at cargo interaction sites to regulate processivity. An increase in dynein heavy chain expression was also observed in dHtt mutants, suggesting that the altered flux observed for all cargo may represent secondary transport changes occurring independent of dHtt’s primary function. Expression of dHtt in a milton (HAP1) mutant background revealed that the protein does not require mitochondria or HAP1 to localize along axons, suggesting Htt has an independent mechanism for coupling with motors to regulate their processivity during axonal transport.
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Affiliation(s)
- Kurt R Weiss
- a Department of Biology , The Picower Institute for Learning and Memory, Massachusetts Institute of Technology , Cambridge , MA , USA.,b Department of Brain and Cognitive Sciences , The Picower Institute for Learning and Memory, Massachusetts Institute of Technology , Cambridge , MA , USA
| | - J Troy Littleton
- a Department of Biology , The Picower Institute for Learning and Memory, Massachusetts Institute of Technology , Cambridge , MA , USA.,b Department of Brain and Cognitive Sciences , The Picower Institute for Learning and Memory, Massachusetts Institute of Technology , Cambridge , MA , USA
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18
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Deshpande M, Rodal AA. The Crossroads of Synaptic Growth Signaling, Membrane Traffic and Neurological Disease: Insights from Drosophila. Traffic 2015; 17:87-101. [PMID: 26538429 DOI: 10.1111/tra.12345] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 10/29/2015] [Accepted: 10/29/2015] [Indexed: 12/13/2022]
Abstract
Neurons require target-derived autocrine and paracrine growth factors to maintain proper identity, innervation, homeostasis and survival. Neuronal growth factor signaling is highly dependent on membrane traffic, both for the packaging and release of the growth factors themselves, and for regulation of intracellular signaling by their transmembrane receptors. Here, we review recent findings from the Drosophila larval neuromuscular junction (NMJ) that illustrate how specific steps of intracellular traffic and inter-organelle interactions impinge on signaling, particularly in the bone morphogenic protein, Wingless and c-Jun-activated kinase pathways, regulating elaboration and stability of NMJ arbors, construction of synapses and synaptic transmission and homeostasis. These membrane trafficking and signaling pathways have been implicated in human motor neuron diseases including amyotrophic lateral sclerosis and hereditary spastic paraplegia, highlighting their importance for neuronal health and survival.
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Affiliation(s)
| | - Avital A Rodal
- Department of Biology, Brandeis University, Waltham, MA, USA
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19
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Siebert M, Böhme MA, Driller JH, Babikir H, Mampell MM, Rey U, Ramesh N, Matkovic T, Holton N, Reddy-Alla S, Göttfert F, Kamin D, Quentin C, Klinedinst S, Andlauer TF, Hell SW, Collins CA, Wahl MC, Loll B, Sigrist SJ. A high affinity RIM-binding protein/Aplip1 interaction prevents the formation of ectopic axonal active zones. eLife 2015; 4. [PMID: 26274777 PMCID: PMC4536467 DOI: 10.7554/elife.06935] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 07/24/2015] [Indexed: 12/17/2022] Open
Abstract
Synaptic vesicles (SVs) fuse at active zones (AZs) covered by a protein scaffold, at Drosophila synapses comprised of ELKS family member Bruchpilot (BRP) and RIM-binding protein (RBP). We here demonstrate axonal co-transport of BRP and RBP using intravital live imaging, with both proteins co-accumulating in axonal aggregates of several transport mutants. RBP, via its C-terminal Src-homology 3 (SH3) domains, binds Aplip1/JIP1, a transport adaptor involved in kinesin-dependent SV transport. We show in atomic detail that RBP C-terminal SH3 domains bind a proline-rich (PxxP) motif of Aplip1/JIP1 with submicromolar affinity. Pointmutating this PxxP motif provoked formation of ectopic AZ-like structures at axonal membranes. Direct interactions between AZ proteins and transport adaptors seem to provide complex avidity and shield synaptic interaction surfaces of pre-assembled scaffold protein transport complexes, thus, favouring physiological synaptic AZ assembly over premature assembly at axonal membranes. DOI:http://dx.doi.org/10.7554/eLife.06935.001 To pass on information, the neurons that make up the nervous system connect at structures known as synapses. Chemical messengers called neurotransmitters are released from one neuron, and travel across the synapse to trigger a response in the neighbouring cell. The formation of new synapses plays an important role in learning and memory, but many aspects of this process are not well understood. In a specific region of the synapse called the active zone, a scaffold of proteins helps to release the neurotransmitters. These proteins are made in the cell body of the neuron, and are then transported to the end of the long, thin axons that protrude from the cell body. This presents a challenge for the cell, because the components of the active zone scaffold must be correctly targeted to the synapse at the end of the axon, ensuring the active zone scaffold assembles only at its proper location. Siebert, Böhme et al. studied how some of the proteins that are found in the active zone scaffold of the fruit fly Drosophila are transported along axons. Labelling the proteins with fluorescent markers allowed their movement to be examined under a microscope in living Drosophila larvae. The results showed that two of the proteins—known as BRP and RBP—are transported along the axons together. Further investigation revealed that a transport adaptor protein called Aplip1, which binds to RBP, is required for this movement. Siebert, Böhme et al. established the structure of the part of RBP where this interaction occurs, and found that mutating this region causes premature active zone scaffold assembly in the axonal part of the neuron. The interaction between RBP and Aplip1 is very strong, and this helps to prevent the scaffold assembling before it has reached the correct part of the neuron. Exactly how the transport adaptor and active zone protein are separated once they reach their final destination (the synapse) remains to be discovered. DOI:http://dx.doi.org/10.7554/eLife.06935.002
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Affiliation(s)
- Matthias Siebert
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Mathias A Böhme
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Jan H Driller
- Institute of Chemistry and Biochemisty/Structural Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Husam Babikir
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Malou M Mampell
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Ulises Rey
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Niraja Ramesh
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Tanja Matkovic
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Nicole Holton
- Institute of Chemistry and Biochemisty/Structural Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Suneel Reddy-Alla
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Fabian Göttfert
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Dirk Kamin
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Christine Quentin
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Susan Klinedinst
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Till Fm Andlauer
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
| | - Stefan W Hell
- Department of Nanobiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Catherine A Collins
- Department of Molecular Cellular and Developmental Biology, University of Michigan, Ann Arbor, United States
| | - Markus C Wahl
- Institute of Chemistry and Biochemisty/Structural Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Bernhard Loll
- Institute of Chemistry and Biochemisty/Structural Biochemistry, Freie Universität Berlin, Berlin, Germany
| | - Stephan J Sigrist
- Institute for Biology/Genetics, Freie Universität Berlin, Berlin, Germany
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20
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Lin CH, Li H, Lee YN, Cheng YJ, Wu RM, Chien CT. Lrrk regulates the dynamic profile of dendritic Golgi outposts through the golgin Lava lamp. J Cell Biol 2015. [PMID: 26216903 PMCID: PMC4523617 DOI: 10.1083/jcb.201411033] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Lrrk regulates Golgi outpost (GOP) dynamics in dendrites by antagonizing the interaction between the golgin Lva and dynein heavy chain at GOPs, thereby disrupting minus end–directed transport along dendritic microtubules by dynein. Constructing the dendritic arbor of neurons requires dynamic movements of Golgi outposts (GOPs), the prominent component in the dendritic secretory pathway. GOPs move toward dendritic ends (anterograde) or cell bodies (retrograde), whereas most of them remain stationary. Here, we show that Leucine-rich repeat kinase (Lrrk), the Drosophila melanogaster homologue of Parkinson’s disease–associated Lrrk2, regulates GOP dynamics in dendrites. Lrrk localized at stationary GOPs in dendrites and suppressed GOP movement. In Lrrk loss-of-function mutants, anterograde movement of GOPs was enhanced, whereas Lrrk overexpression increased the pool size of stationary GOPs. Lrrk interacted with the golgin Lava lamp and inhibited the interaction between Lva and dynein heavy chain, thus disrupting the recruitment of dynein to Golgi membranes. Whereas overexpression of kinase-dead Lrrk caused dominant-negative effects on GOP dynamics, overexpression of the human LRRK2 mutant G2019S with augmented kinase activity promoted retrograde movement. Our study reveals a pathogenic pathway for LRRK2 mutations causing dendrite degeneration.
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Affiliation(s)
- Chin-Hsien Lin
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei 100, Taiwan
| | - Hsun Li
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan Taiwan International Graduate Program in Interdisciplinary Neuroscience, National Yang-Ming University and Academia Sinica, Taipei 115, Taiwan
| | - Yi-Nan Lee
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan
| | - Ying-Ju Cheng
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan
| | - Ruey-Meei Wu
- Department of Neurology, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei 100, Taiwan
| | - Cheng-Ting Chien
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan
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21
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Butzlaff M, Hannan SB, Karsten P, Lenz S, Ng J, Voßfeldt H, Prüßing K, Pflanz R, Schulz JB, Rasse T, Voigt A. Impaired retrograde transport by the Dynein/Dynactin complex contributes to Tau-induced toxicity. Hum Mol Genet 2015; 24:3623-37. [DOI: 10.1093/hmg/ddv107] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Accepted: 03/17/2015] [Indexed: 11/12/2022] Open
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22
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Heemskerk I, Lecuit T, LeGoff L. Dynamic clonal analysis based on chronic in vivo imaging allows multiscale quantification of growth in the Drosophila wing disc. Development 2014; 141:2339-48. [PMID: 24866118 DOI: 10.1242/dev.109264] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In the course of morphogenesis, tissues change shape and grow. How this is orchestrated is largely unknown, partly owing to the lack of experimental methods to visualize and quantify growth. Here, we describe a novel experimental approach to investigate the growth of tissues in vivo on a time-scale of days, as employed to study the Drosophila larval imaginal wing disc, the precursor of the adult wing. We developed a protocol to image wing discs at regular intervals in living anesthetized larvae so as to follow the growth of the tissue over extended periods of time. This approach can be used to image cells at high resolution in vivo. At intermediate scale, we tracked the increase in cell number within clones as well as the changes in clone area and shape. At scales extending to the tissue level, clones can be used as landmarks for measuring strain, as a proxy for growth. We developed general computational tools to extract strain maps from clonal shapes and landmark displacements in individual tissues, and to combine multiple datasets into a mean strain. In the disc, we use these to compare properties of growth at the scale of clones (a few cells) and at larger regional scales.
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Affiliation(s)
- Idse Heemskerk
- Kavli Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA
| | - Thomas Lecuit
- Aix Marseille Université, CNRS, IBDML UMR7288, case 907, Marseille 13009, France
| | - Loïc LeGoff
- Aix Marseille Université, CNRS, IBDML UMR7288, case 907, Marseille 13009, France
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23
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Csordás G, Varga GIB, Honti V, Jankovics F, Kurucz É, Andó I. In vivo immunostaining of hemocyte compartments in Drosophila for live imaging. PLoS One 2014; 9:e98191. [PMID: 24892745 PMCID: PMC4043501 DOI: 10.1371/journal.pone.0098191] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 04/29/2014] [Indexed: 11/18/2022] Open
Abstract
In recent years, Drosophila melanogaster has become an attractive model organism in which to study the structure and development of the cellular immune components. The emergence of immunological markers greatly accelerated the identification of the immune cells (hemocytes), while the creation of genetic reporter constructs allowed unique insight into the structural organization of hematopoietic tissues. However, investigation of the hemocyte compartments by the means of immunological markers requires dissection and fixation, which regularly disrupt the delicate structure and hamper the microanatomical characterization. Moreover, the investigation of transgenic reporters alone can be misleading as their expression often differs from the native expression pattern of their respective genes. We describe here a method that combines the reporter constructs and the immunological tools in live imaging, thereby allowing use of the array of available immunological markers while retaining the structural integrity of the hematopoietic compartments. The procedure allows the reversible immobilization of Drosophila larvae for high-resolution confocal imaging and the time-lapse video analysis of in vivo reporters. When combined with our antibody injection-based in situ immunostaining assay, the resulting double labeling of the hemocyte compartments can provide new information on the microanatomy and functional properties of the hematopoietic tissues in an intact state. Although this method was developed to study the immune system of Drosophila melanogaster, we anticipate that such a combination of genetic and immunological markers could become a versatile technique for in vivo studies in other biological systems too.
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Affiliation(s)
- Gábor Csordás
- Immunology Unit, Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Gergely I. B. Varga
- Immunology Unit, Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Viktor Honti
- Immunology Unit, Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Ferenc Jankovics
- Developmental Genetics Unit, Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Éva Kurucz
- Immunology Unit, Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - István Andó
- Immunology Unit, Institute of Genetics, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
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24
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Iacobucci GJ, Rahman NA, Valtueña AA, Nayak TK, Gunawardena S. Spatial and temporal characteristics of normal and perturbed vesicle transport. PLoS One 2014; 9:e97237. [PMID: 24878565 PMCID: PMC4039462 DOI: 10.1371/journal.pone.0097237] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2013] [Accepted: 04/16/2014] [Indexed: 11/19/2022] Open
Abstract
Efficient intracellular transport is essential for healthy cellular function and structural integrity, and problems in this pathway can lead to neuronal cell death and disease. To spatially and temporally evaluate how transport defects are initiated, we adapted a primary neuronal culture system from Drosophila larval brains to visualize the movement dynamics of several cargos/organelles along a 90 micron axonal neurite over time. All six vesicles/organelles imaged showed robust bi-directional motility at both day 1 and day 2. Reduction of motor proteins decreased the movement of vesicles/organelles with increased numbers of neurite blocks. Neuronal growth was also perturbed with reduction of motor proteins. Strikingly, we found that all blockages were not fixed, permanent blocks that impeded transport of vesicles as previously thought, but that some blocks were dynamic clusters of vesicles that resolved over time. Taken together, our findings suggest that non-resolving blocks may likely initiate deleterious pathways leading to death and degeneration, while resolving blocks may be benign. Therefore evaluating the spatial and temporal characteristics of vesicle transport has important implications for our understanding of how transport defects can affect other pathways to initiate death and degeneration.
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Affiliation(s)
- Gary J. Iacobucci
- Department of Biological Sciences, The State University of New York at Buffalo, Buffalo, New York, United States of America
| | - Noura Abdel Rahman
- Department of Biological Sciences, The State University of New York at Buffalo, Buffalo, New York, United States of America
| | - Aida Andrades Valtueña
- Department of Biological Sciences, The State University of New York at Buffalo, Buffalo, New York, United States of America
| | - Tapan Kumar Nayak
- Department of Physiology and Biophysics, The State University of New York at Buffalo, Buffalo, New York, United States of America
| | - Shermali Gunawardena
- Department of Biological Sciences, The State University of New York at Buffalo, Buffalo, New York, United States of America
- * E-mail:
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25
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Mishra B, Ghannad-Rezaie M, Li J, Wang X, Hao Y, Ye B, Chronis N, Collins CA. Using microfluidics chips for live imaging and study of injury responses in Drosophila larvae. J Vis Exp 2014:e50998. [PMID: 24562098 PMCID: PMC4117361 DOI: 10.3791/50998] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Live imaging is an important technique for studying cell biological processes, however this can be challenging in live animals. The translucent cuticle of the Drosophila larva makes it an attractive model organism for live imaging studies. However, an important challenge for live imaging techniques is to noninvasively immobilize and position an animal on the microscope. This protocol presents a simple and easy to use method for immobilizing and imaging Drosophila larvae on a polydimethylsiloxane (PDMS) microfluidic device, which we call the 'larva chip'. The larva chip is comprised of a snug-fitting PDMS microchamber that is attached to a thin glass coverslip, which, upon application of a vacuum via a syringe, immobilizes the animal and brings ventral structures such as the nerve cord, segmental nerves, and body wall muscles, within close proximity to the coverslip. This allows for high-resolution imaging, and importantly, avoids the use of anesthetics and chemicals, which facilitates the study of a broad range of physiological processes. Since larvae recover easily from the immobilization, they can be readily subjected to multiple imaging sessions. This allows for longitudinal studies over time courses ranging from hours to days. This protocol describes step-by-step how to prepare the chip and how to utilize the chip for live imaging of neuronal events in 3rd instar larvae. These events include the rapid transport of organelles in axons, calcium responses to injury, and time-lapse studies of the trafficking of photo-convertible proteins over long distances and time scales. Another application of the chip is to study regenerative and degenerative responses to axonal injury, so the second part of this protocol describes a new and simple procedure for injuring axons within peripheral nerves by a segmental nerve crush.
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Affiliation(s)
- Bibhudatta Mishra
- Department of Molecular, Cellular and Developmental Biology, University of Michigan
| | | | - Jiaxing Li
- Department of Molecular, Cellular and Developmental Biology, University of Michigan
| | - Xin Wang
- Department of Molecular, Cellular and Developmental Biology, University of Michigan
| | - Yan Hao
- Department of Molecular, Cellular and Developmental Biology, University of Michigan
| | - Bing Ye
- Life Sciences Institute, University of Michigan; Department of Cell and Developmental Biology, University of Michigan
| | - Nikos Chronis
- Department of Biomedical Engineering, University of Michigan; Department of Mechanical Engineering, University of Michigan
| | - Catherine A Collins
- Department of Molecular, Cellular and Developmental Biology, University of Michigan;
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Keroles MB, Dusseault SK, Liu C, Mohammed MR, Vadakkan CM, Amiel JH, Abel SN, Bensoussan ER, Russell BL, Baker J. Imaging through the pupal case of Drosophila melanogaster. J Vis Exp 2014:e51239. [PMID: 24513575 DOI: 10.3791/51239] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The longstanding use of Drosophila as a model for cell and developmental biology has yielded an array of tools. Together, these techniques have enabled analysis of cell and developmental biology from a variety of methodological angles. Live imaging is an emerging method for observing dynamic cell processes, such as cell division or cell motility. Having isolated mutations in uncharacterized putative cell cycle proteins it became essential to observe mitosis in situ using live imaging. Most live imaging studies in Drosophila have focused on the embryonic stages that are accessible to manipulation and observation because of their small size and optical clarity. However, in these stages the cell cycle is unusual in that it lacks one or both of the gap phases. By contrast, cells of the pupal wing of Drosophila have a typical cell cycle and undergo a period of rapid mitosis spanning about 20 hr of pupal development. It is easy to identify and isolate pupae of the appropriate stage to catch mitosis in situ. Mounting intact pupae provided the best combination of tractability and durability during imaging, allowing experiments to run for several hours with minimal impact on cell and animal viability. The method allows observation of features as small as, or smaller than, fly chromosomes. Adjustment of microscope settings and the details of mounting, allowed extension of the preparation to visualize membrane dynamics of adjacent cells and fluorescently labeled proteins such as tubulin. This method works for all tested fluorescent proteins and can capture submicron scale features over a variety of time scales. While limited to the outer 20 µm of the pupa with a conventional confocal microscope, this approach to observing protein and cellular dynamics in pupal tissues in vivo may be generally useful in the study of cell and developmental biology in these tissues.
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Zhu JY, Vereshchagina N, Sreekumar V, Burbulla LF, Costa AC, Daub KJ, Woitalla D, Martins LM, Krüger R, Rasse TM. Knockdown of Hsc70-5/mortalin induces loss of synaptic mitochondria in a Drosophila Parkinson's disease model. PLoS One 2013; 8:e83714. [PMID: 24386261 PMCID: PMC3875477 DOI: 10.1371/journal.pone.0083714] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 11/07/2013] [Indexed: 02/02/2023] Open
Abstract
Mortalin is an essential component of the molecular machinery that imports nuclear-encoded proteins into mitochondria, assists in their folding, and protects against damage upon accumulation of dysfunctional, unfolded proteins in aging mitochondria. Mortalin dysfunction associated with Parkinson’s disease (PD) increases the vulnerability of cultured cells to proteolytic stress and leads to changes in mitochondrial function and morphology. To date, Drosophila melanogaster has been successfully used to investigate pathogenesis following the loss of several other PD-associated genes. We generated the first loss-of-Hsc70-5/mortalin-function Drosophila model. The reduction of Mortalin expression recapitulates some of the defects observed in the existing Drosophila PD-models, which include reduced ATP levels, abnormal wing posture, shortened life span, and reduced spontaneous locomotor and climbing ability. Dopaminergic neurons seem to be more sensitive to the loss of mortalin than other neuronal sub-types and non-neuronal tissues. The loss of synaptic mitochondria is an early pathological change that might cause later degenerative events. It precedes both behavioral abnormalities and structural changes at the neuromuscular junction (NMJ) of mortalin-knockdown larvae that exhibit increased mitochondrial fragmentation. Autophagy is concomitantly up-regulated, suggesting that mitochondria are degraded via mitophagy. Ex vivo data from human fibroblasts identifies increased mitophagy as an early pathological change that precedes apoptosis. Given the specificity of the observed defects, we are confident that the loss-of-mortalin model presented in this study will be useful for further dissection of the complex network of pathways that underlie the development of mitochondrial parkinsonism.
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Affiliation(s)
- Jun-yi Zhu
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Graduate School of Cellular & Molecular Neuroscience, University of Tübingen, Tübingen, Germany
| | - Natalia Vereshchagina
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Vrinda Sreekumar
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Graduate School of Cellular & Molecular Neuroscience, University of Tübingen, Tübingen, Germany
- German Center for Neurodegenerative Diseases, Tübingen, Germany
| | - Lena F. Burbulla
- German Center for Neurodegenerative Diseases, Tübingen, Germany
- Department of Neurodegenerative Diseases and Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Ana C. Costa
- Cell Death Regulation Laboratory, MRC Toxicology Unit, Leicester, United Kingdom
| | - Katharina J. Daub
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Dirk Woitalla
- Department of Neurology, St. Josef-Hospital, Ruhr-University Bochum, Bochum, Germany
| | - L. Miguel Martins
- Cell Death Regulation Laboratory, MRC Toxicology Unit, Leicester, United Kingdom
| | - Rejko Krüger
- German Center for Neurodegenerative Diseases, Tübingen, Germany
- Department of Neurodegenerative Diseases and Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Werner Reichardt Centre for Integrative Neuroscience, University of Tübingen, Tübingen, Germany
- * E-mail: (TMR); (RK)
| | - Tobias M. Rasse
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- * E-mail: (TMR); (RK)
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New approaches for studying synaptic development, function, and plasticity using Drosophila as a model system. J Neurosci 2013; 33:17560-8. [PMID: 24198346 DOI: 10.1523/jneurosci.3261-13.2013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The fruit fly Drosophila melanogaster has been established as a premier experimental model system for neuroscience research. These organisms are genetically tractable, yet their nervous systems are sufficiently complex to study diverse processes that are conserved across metazoans, including neural cell fate determination and migration, axon guidance, synaptogenesis and function, behavioral neurogenetics, and responses to neuronal injury. For several decades, Drosophila neuroscientists have taken advantage of a vast toolkit of genetic and molecular techniques to reveal fundamental principles of neuroscience illuminating to all systems, including the first behavioral mutants from Seymour Benzer's pioneering work in the 1960s and 1970s, the cloning of the first potassium channel in the 1980s, and the identification of the core genes that orchestrate axon guidance and circadian rhythms in the 1990s. Over the past decade, new tools and innovations in genetic, imaging, and electrophysiological technologies have enabled the visualization, in vivo, of dynamic processes in synapses with unprecedented resolution. We will review some of the fresh insights into synaptic development, function, and plasticity that have recently emerged in Drosophila with an emphasis on the unique advantages of this model system.
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Hamon M, Hong JW. New tools and new biology: recent miniaturized systems for molecular and cellular biology. Mol Cells 2013; 36:485-506. [PMID: 24305843 PMCID: PMC3887968 DOI: 10.1007/s10059-013-0333-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 11/14/2013] [Indexed: 01/09/2023] Open
Abstract
Recent advances in applied physics and chemistry have led to the development of novel microfluidic systems. Microfluidic systems allow minute amounts of reagents to be processed using μm-scale channels and offer several advantages over conventional analytical devices for use in biological sciences: faster, more accurate and more reproducible analytical performance, reduced cell and reagent consumption, portability, and integration of functional components in a single chip. In this review, we introduce how microfluidics has been applied to biological sciences. We first present an overview of the fabrication of microfluidic systems and describe the distinct technologies available for biological research. We then present examples of microsystems used in biological sciences, focusing on applications in molecular and cellular biology.
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Affiliation(s)
- Morgan Hamon
- Materials Research and Education Center, Department of Mechanical Engineering, Auburn University, Auburn, AL 36849,
USA
| | - Jong Wook Hong
- Materials Research and Education Center, Department of Mechanical Engineering, Auburn University, Auburn, AL 36849,
USA
- College of Pharmacy, Seoul National University, Seoul 151-741,
Korea
- Department of Bionano Engineering, Hanyang University, Ansan 426-791,
Korea
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Lloyd TE. Axonal transport disruption in peripheral nerve disease: From Jack's discoveries as a resident to recent contributions. J Peripher Nerv Syst 2013; 17 Suppl 3:46-51. [PMID: 23279432 DOI: 10.1111/j.1529-8027.2012.00431.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Many neurodegenerative diseases and neuropathies have been proposed to be caused by a disruption of axonal transport. However, the mechanisms whereby impaired transport causes disease remain unclear. Proposed mechanisms include impairment in delivery of organelles such as mitochondria, defective retrograde neurotrophic signaling, and disruption of the synaptic vesicle cycle within the synaptic terminal. Simple model organisms such as the fruitfly, Drosophila melanogaster, allow live imaging of axonal transport to be combined with high-throughput genetic screens and are providing insights into the pathophysiology of peripheral nerve diseases.
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Affiliation(s)
- Thomas E Lloyd
- Department of Neurology and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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31
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Abstract
Kinesin-based transport is important for synaptogenesis, neuroplasticity, and maintaining synaptic function. In an anatomical screen of neurodevelopmental mutants, we identified the exchange of a conserved residue (R561H) in the forkhead-associated domain of the kinesin-3 family member Unc-104/KIF1A as the genetic cause for defects in synaptic terminal- and dendrite morphogenesis. Previous structure-based analysis suggested that the corresponding residue in KIF1A might be involved in stabilizing the activated state of kinesin-3 dimers. Herein we provide the first in vivo evidence for the functional importance of R561. The R561H allele (unc-104bris) is not embryonic lethal, which allowed us to investigate consequences of disturbed Unc-104 function on postembryonic synapse development and larval behavior. We demonstrate that Unc-104 regulates the reliable apposition of active zones and postsynaptic densities, possibly by controlling site-specific delivery of its cargo. Next, we identified a role for Unc-104 in restraining neuromuscular junction growth and coordinating dendrite branch morphogenesis, suggesting that Unc-104 is also involved in dendritic transport. Mutations in KIF1A/unc-104 have been associated with hereditary spastic paraplegia and hereditary sensory and autonomic neuropathy type 2. However, we did not observe synapse retraction or dystonic posterior paralysis. Overall, our study demonstrates the specificity of defects caused by selective impairments of distinct molecular motors and highlights the critical importance of Unc-104 for the maturation of neuronal structures during embryonic development, larval synaptic terminal outgrowth, and dendrite morphogenesis.
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Füger P, Sreekumar V, Schüle R, Kern JV, Stanchev DT, Schneider CD, Karle KN, Daub KJ, Siegert VK, Flötenmeyer M, Schwarz H, Schöls L, Rasse TM. Spastic paraplegia mutation N256S in the neuronal microtubule motor KIF5A disrupts axonal transport in a Drosophila HSP model. PLoS Genet 2012; 8:e1003066. [PMID: 23209432 PMCID: PMC3510046 DOI: 10.1371/journal.pgen.1003066] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 09/20/2012] [Indexed: 01/21/2023] Open
Abstract
Hereditary spastic paraplegias (HSPs) comprise a group of genetically heterogeneous neurodegenerative disorders characterized by spastic weakness of the lower extremities. We have generated a Drosophila model for HSP type 10 (SPG10), caused by mutations in KIF5A. KIF5A encodes the heavy chain of kinesin-1, a neuronal microtubule motor. Our results imply that SPG10 is not caused by haploinsufficiency but by the loss of endogenous kinesin-1 function due to a selective dominant-negative action of mutant KIF5A on kinesin-1 complexes. We have not found any evidence for an additional, more generalized toxicity of mutant Kinesin heavy chain (Khc) or the affected kinesin-1 complexes. Ectopic expression of Drosophila Khc carrying a human SPG10-associated mutation (N256S) is sufficient to disturb axonal transport and to induce motoneuron disease in Drosophila. Neurofilaments, which have been recently implicated in SPG10 disease manifestation, are absent in arthropods. Impairments in the transport of kinesin-1 cargos different from neurofilaments are thus sufficient to cause HSP–like pathological changes such as axonal swellings, altered structure and function of synapses, behavioral deficits, and increased mortality. Hereditary spastic paraplegias (HSPs) comprise a group of inherited neurological diseases. The main feature of HSP is progressive stiffness of the lower limbs due to a dysfunction of nerve cells. We study HSP type 10, which is caused by mutations in the neuronal motor protein KIF5A. HSP type 10 is inherited in an autosomal-dominant manner, which means that patients have a normal and a mutated copy of the KIF5A gene. KIF5A plays an important role in neuronal function: it transports cargos to the synapse that can be up to 1 m from the cell body. We use the fruit fly as a model to investigate the role of mutations in KIF5A. Our fly model replicates a central feature of HSP: muscles that are activated by nerve cells that have long cellular processes are more severely impaired. We now address why one mutated copy of KIF5A is sufficient to cause HSP. To date, it has been thought that patients might have HSP because they have insufficient functional KIF5A or because mutated KIF5A disturbs the function of normal KIF5A. We provide evidence for the latter possibility.
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Affiliation(s)
- Petra Füger
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Graduate School of Cellular and Molecular Neuroscience, University of Tübingen, Tübingen, Germany
| | - Vrinda Sreekumar
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Graduate School of Cellular and Molecular Neuroscience, University of Tübingen, Tübingen, Germany
- German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany
| | - Rebecca Schüle
- Hertie-Institute for Clinical Brain Research and Center for Neurology, Department of Neurodegenerative Disease, University of Tübingen, Tübingen, Germany
| | - Jeannine V. Kern
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Doychin T. Stanchev
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Carola D. Schneider
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Graduate School of Cellular and Molecular Neuroscience, University of Tübingen, Tübingen, Germany
| | - Kathrin N. Karle
- Hertie-Institute for Clinical Brain Research and Center for Neurology, Department of Neurodegenerative Disease, University of Tübingen, Tübingen, Germany
| | - Katharina J. Daub
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
| | - Vera K. Siegert
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- Hertie-Institute for Clinical Brain Research and Center for Neurology, Department of Neurodegenerative Disease, University of Tübingen, Tübingen, Germany
| | | | - Heinz Schwarz
- Max Planck Institute for Developmental Biology, Tübingen, Germany
| | - Ludger Schöls
- German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany
- Hertie-Institute for Clinical Brain Research and Center for Neurology, Department of Neurodegenerative Disease, University of Tübingen, Tübingen, Germany
| | - Tobias M. Rasse
- Junior Research Group Synaptic Plasticity, Hertie-Institute for Clinical Brain Research, University of Tübingen, Tübingen, Germany
- * E-mail:
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33
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Abstracts of Neurofly 2012. September 3-7, 2012. Padua, Italy. J Neurogenet 2012; 26 Suppl 1:1-88. [PMID: 23163745 DOI: 10.3109/01677063.2012.741306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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34
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Nienhaus U, Aegerter-Wilmsen T, Aegerter CM. In-vivo imaging of the Drosophila wing imaginal disc over time: novel insights on growth and boundary formation. PLoS One 2012; 7:e47594. [PMID: 23091633 PMCID: PMC3473014 DOI: 10.1371/journal.pone.0047594] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 09/12/2012] [Indexed: 01/12/2023] Open
Abstract
In developmental biology, the sequence of gene induction and pattern formation is best studied over time as an organism develops. However, in the model system of Drosophila larvae this oftentimes proves difficult due to limitations in imaging capabilities. Using the larval wing imaginal disc, we show that both overall growth, as well as the creation of patterns such as the distinction between the anterior(A) and posterior(P) compartments and the dorsal(D) and ventral(V) compartments can be studied directly by imaging the wing disc as it develops inside a larva. Imaged larvae develop normally, as can be seen by the overall growth curve of the wing disc. Yet, the fact that we can follow the development of individual discs through time provides the opportunity to simultaneously assess individual variability. We for instance find that growth rates can vary greatly over time. In addition, we observe that mechanical forces act on the wing disc within the larva at times when there is an increase in growth rates. Moreover, we observe that A/P boundary formation follows the established sequence and a smooth boundary is present from the first larval instar on. The division of the wing disc into a dorsal and a ventral compartment, on the other hand, develops quite differently. Contrary to expectation, the specification of the dorsal compartment starts with only one or two cells in the second larval instar and a smooth boundary is not formed until the third larval instar.
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Cell wall amidase AmiC1 is required for cellular communication and heterocyst development in the cyanobacterium Anabaena PCC 7120 but not for filament integrity. J Bacteriol 2012; 194:5218-27. [PMID: 22821973 DOI: 10.1128/jb.00912-12] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Filamentous cyanobacteria of the order Nostocales display typical properties of multicellular organisms. In response to nitrogen starvation, some vegetative cells differentiate into heterocysts, where fixation of N(2) takes place. Heterocysts provide a micro-oxic compartment to protect nitrogenase from the oxygen produced by the vegetative cells. Differentiation involves fundamental remodeling of the gram-negative cell wall by deposition of a thick envelope and by formation of a neck-like structure at the contact site to the vegetative cells. Cell wall-hydrolyzing enzymes, like cell wall amidases, are involved in peptidoglycan maturation and turnover in unicellular bacteria. Recently, we showed that mutation of the amidase homologue amiC2 gene in Nostoc punctiforme ATCC 29133 distorts filament morphology and function. Here, we present the functional characterization of two amiC paralogues from Anabaena sp. strain PCC 7120. The amiC1 (alr0092) mutant was not able to differentiate heterocysts or to grow diazotrophically, whereas the amiC2 (alr0093) mutant did not show an altered phenotype under standard growth conditions. In agreement, fluorescence recovery after photobleaching (FRAP) studies showed a lack of cell-cell communication only in the AmiC1 mutant. Green fluorescent protein (GFP)-tagged AmiC1 was able to complement the mutant phenotype to wild-type properties. The protein localized in the septal regions of newly dividing cells and at the neck region of differentiating heterocysts. Upon nitrogen step-down, no mature heterocysts were developed in spite of ongoing heterocyst-specific gene expression. These results show the dependence of heterocyst development on amidase function and highlight a pivotal but so far underestimated cellular process, the remodeling of peptidoglycan, for the biology of filamentous cyanobacteria.
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36
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Three routes to suppression of the neurodegenerative phenotypes caused by kinesin heavy chain mutations. Genetics 2012; 192:173-83. [PMID: 22714410 DOI: 10.1534/genetics.112.140798] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Kinesin-1 is a motor protein that moves stepwise along microtubules by employing dimerized kinesin heavy chain (Khc) subunits that alternate cycles of microtubule binding, conformational change, and ATP hydrolysis. Mutations in the Drosophila Khc gene are known to cause distal paralysis and lethality preceded by the occurrence of dystrophic axon terminals, reduced axonal transport, organelle-filled axonal swellings, and impaired action potential propagation. Mutations in the equivalent human gene, Kif5A, result in similar problems that cause hereditary spastic paraplegia (HSP) and Charcot-Marie-Tooth type 2 (CMT2) distal neuropathies. By comparing the phenotypes and the complementation behaviors of a large set of Khc missense alleles, including one that is identical to a human Kif5A HSP allele, we identified three routes to suppression of Khc phenotypes: nutrient restriction, genetic background manipulation, and a remarkable intramolecular complementation between mutations known or likely to cause reciprocal changes in the rate of microtubule-stimulated ADP release by kinesin-1. Our results reveal the value of large-scale complementation analysis for gaining insight into protein structure-function relationships in vivo and point to possible paths for suppressing symptoms of HSP and related distal neuropathies.
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37
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Jordán-Álvarez S, Fouquet W, Sigrist SJ, Acebes A. Presynaptic PI3K activity triggers the formation of glutamate receptors at neuromuscular terminals of Drosophila. J Cell Sci 2012; 125:3621-9. [PMID: 22505608 DOI: 10.1242/jcs.102806] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Synapse transmission depends on the precise structural and functional assembly between pre- and postsynaptic elements. This tightly regulated interaction has been thoroughly characterised in vivo in the Drosophila glutamatergic larval neuromuscular junction (NMJ) synapse, a suitable model to explore synapse formation, dynamics and plasticity. Previous findings have demonstrated that presynaptic upregulation of phosphoinositide 3-kinase (PI3K) increases synapse number, generating new functional contacts and eliciting changes in behaviour. Here, we show that genetically driven overexpression of PI3K in the presynaptic element also leads to a correlated increase in the levels of glutamate receptor (GluRII) subunits and the number of postsynaptic densities (PSDs), without altering GluRII formation and assembly dynamics. In addition to GluRIIs, presynaptic PI3K activity also modifies the expression of the postsynaptic protein Discs large (Dlg). Remarkably, PI3K specifically overexpressed in the final larval stages is sufficient for the formation of NMJ synapses. No differences in the number of synapses and PSDs were detected when PI3K was selectively expressed in the postsynaptic compartment. Taken together, these results demonstrate that PI3K-dependent synaptogenesis plays an instructive role in PSD formation and growth from the presynaptic side.
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Affiliation(s)
- Sheila Jordán-Álvarez
- Cajal Institute, Consejo Superior de Investigaciones Científicas, Ave Dr Arce 37, Madrid 28002, Spain
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Andlauer TFM, Sigrist SJ. In vivo imaging of the Drosophila larval neuromuscular junction. Cold Spring Harb Protoc 2012; 2012:481-9. [PMID: 22474664 DOI: 10.1101/pdb.prot068593] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In the past decade, a significant number of proteins involved in the developmental assembly and maturation of synapses have been identified. However, detailed knowledge of the molecular processes underlying developmental synapse assembly is still sparse. We have developed an approach that makes extended in vivo imaging of selected proteins in live Drosophila larvae feasible at a single-synapse resolution. This protocol describes the repetitive, noninvasive imaging of the neuromuscular junction (NMJ) of a live, intact, anesthetized Drosophila larva over extended periods of time with confocal microscopy. Proteins of interest must be tagged with a fluorescent label and have to be expressed in transgenic fly strains. The method has proven highly useful for the study of synaptic assembly and the trafficking of proteins. These data contribute to our understanding of synaptic assembly under in vivo conditions.
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Andlauer TFM, Sigrist SJ. Building an imaging chamber for in vivo imaging of Drosophila larvae. Cold Spring Harb Protoc 2012; 2012:476-80. [PMID: 22474663 DOI: 10.1101/pdb.prot068585] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In the past decade, a significant number of proteins involved in the developmental assembly and maturation of synapses have been identified. However, detailed knowledge of the molecular processes underlying developmental synapse assembly is still sparse. We have developed an approach that makes extended in vivo imaging of selected proteins in live Drosophila larvae feasible at a single-synapse resolution. The intact larvae are anesthetized and noninvasively imaged with confocal microscopy. This method allows for both protein trafficking and protein turnover kinetics to be studied at various points in time during the development of an animal. These data contribute to our understanding of synaptic assembly under in vivo conditions. This protocol describes the assembly of the imaging chamber needed for in vivo imaging of Drosophila larvae. It also covers the construction of an appropriate anesthetization device.
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40
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Andlauer TFM, Sigrist SJ. In vivo imaging of Drosophila larval neuromuscular junctions to study synapse assembly. Cold Spring Harb Protoc 2012; 2012:407-13. [PMID: 22474662 DOI: 10.1101/pdb.top068577] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In the past decade, a significant number of proteins involved in the developmental assembly and maturation of synapses have been identified. However, detailed knowledge of the molecular processes underlying developmental synapse assembly is still sparse. Here, we discuss an approach that makes extended in vivo imaging of selected proteins in live Drosophila larvae feasible at a single-synapse resolution. The intact larvae are anesthetized and neuromuscular junctions (NMJs) are noninvasively imaged with confocal microscopy. This method allows for both protein trafficking and protein turnover kinetics to be studied at various points in time during the development of an animal. These data contribute to our understanding of synaptic assembly under in vivo conditions.
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Ghannad-Rezaie M, Wang X, Mishra B, Collins C, Chronis N. Microfluidic chips for in vivo imaging of cellular responses to neural injury in Drosophila larvae. PLoS One 2012; 7:e29869. [PMID: 22291895 PMCID: PMC3264548 DOI: 10.1371/journal.pone.0029869] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2011] [Accepted: 12/05/2011] [Indexed: 12/17/2022] Open
Abstract
With powerful genetics and a translucent cuticle, the Drosophila larva is an ideal model system for live imaging studies of neuronal cell biology and function. Here, we present an easy-to-use approach for high resolution live imaging in Drosophila using microfluidic chips. Two different designs allow for non-invasive and chemical-free immobilization of 3rd instar larvae over short (up to 1 hour) and long (up to 10 hours) time periods. We utilized these ‘larva chips’ to characterize several sub-cellular responses to axotomy which occur over a range of time scales in intact, unanaesthetized animals. These include waves of calcium which are induced within seconds of axotomy, and the intracellular transport of vesicles whose rate and flux within axons changes dramatically within 3 hours of axotomy. Axonal transport halts throughout the entire distal stump, but increases in the proximal stump. These responses precede the degeneration of the distal stump and regenerative sprouting of the proximal stump, which is initiated after a 7 hour period of dormancy and is associated with a dramatic increase in F-actin dynamics. In addition to allowing for the study of axonal regeneration in vivo, the larva chips can be utilized for a wide variety of in vivo imaging applications in Drosophila.
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Affiliation(s)
- Mostafa Ghannad-Rezaie
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Xing Wang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Bibhudatta Mishra
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Catherine Collins
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail: (NC); (CC)
| | - Nikos Chronis
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America
- * E-mail: (NC); (CC)
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Gopalakrishnan G, Yam PT, Madwar C, Bostina M, Rouiller I, Colman DR, Lennox RB. Label-free visualization of ultrastructural features of artificial synapses via cryo-EM. ACS Chem Neurosci 2011; 2:700-4. [PMID: 22860164 PMCID: PMC3369721 DOI: 10.1021/cn200094j] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2011] [Accepted: 10/04/2011] [Indexed: 01/26/2023] Open
Abstract
The ultrastructural details of presynapses formed between artificial substrates of submicrometer silica beads and hippocampal neurons are visualized via cryo-electron microscopy (cryo-EM). The silica beads are derivatized by poly-d-lysine or lipid bilayers. Molecular features known to exist at presynapses are clearly present at these artificial synapses, as visualized by cryo-EM. Key synaptic features such as the membrane contact area at synaptic junctions, the presynaptic bouton containing presynaptic vesicles, as well as microtubular structures can be identified. This is the first report of the direct, label-free observation of ultrastructural details of artificial synapses.
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Affiliation(s)
- Gopakumar Gopalakrishnan
- Department of Chemistry, McGill
University, 801 Sherbrooke Street West, H3A
2K6 Montreal, Canada
- Montreal
Neurological Institute, McGill University, 3801 University Street, H3A 2B4
Montreal, Canada
| | - Patricia T. Yam
- Montreal
Neurological Institute, McGill University, 3801 University Street, H3A 2B4
Montreal, Canada
| | - Carolin Madwar
- Department of Chemistry, McGill
University, 801 Sherbrooke Street West, H3A
2K6 Montreal, Canada
| | - Mihnea Bostina
- Facility
for Electron Microscopy Research (FEMR), Department of Anatomy & Cell
Biology, McGill University, 3640 University Street, H3A
2B2 Montreal, Canada
| | - Isabelle Rouiller
- Facility
for Electron Microscopy Research (FEMR), Department of Anatomy & Cell
Biology, McGill University, 3640 University Street, H3A
2B2 Montreal, Canada
| | - David R. Colman
- Montreal
Neurological Institute, McGill University, 3801 University Street, H3A 2B4
Montreal, Canada
| | - R. Bruce Lennox
- Department of Chemistry, McGill
University, 801 Sherbrooke Street West, H3A
2K6 Montreal, Canada
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Huntingtin aggregation kinetics and their pathological role in a Drosophila Huntington's disease model. Genetics 2011; 190:581-600. [PMID: 22095086 DOI: 10.1534/genetics.111.133710] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Huntington's disease is a neurodegenerative disorder resulting from expansion of a polyglutamine tract in the Huntingtin protein. Mutant Huntingtin forms intracellular aggregates within neurons, although it is unclear whether aggregates or more soluble forms of the protein represent the pathogenic species. To examine the link between aggregation and neurodegeneration, we generated Drosophila melanogaster transgenic strains expressing fluorescently tagged human huntingtin encoding pathogenic (Q138) or nonpathogenic (Q15) proteins, allowing in vivo imaging of Huntingtin expression and aggregation in live animals. Neuronal expression of pathogenic Huntingtin leads to pharate adult lethality, accompanied by formation of large aggregates within the cytoplasm of neuronal cell bodies and neurites. Live imaging and Fluorescence Recovery After Photobleaching (FRAP) analysis of pathogenic Huntingtin demonstrated that new aggregates can form in neurons within 12 hr, while preexisting aggregates rapidly accumulate new Huntingtin protein within minutes. To examine the role of aggregates in pathology, we conducted haplo-insufficiency suppressor screens for Huntingtin-Q138 aggregation or Huntingtin-Q138-induced lethality, using deficiencies covering ~80% of the Drosophila genome. We identified two classes of interacting suppressors in our screen: those that rescue viability while decreasing Huntingtin expression and aggregation and those that rescue viability without disrupting Huntingtin aggregation. The most robust suppressors reduced both soluble and aggregated Huntingtin levels, suggesting toxicity is likely to be associated with both forms of the mutant protein in Huntington's disease.
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Lehner J, Zhang Y, Berendt S, Rasse TM, Forchhammer K, Maldener I. The morphogene AmiC2 is pivotal for multicellular development in the cyanobacterium Nostoc punctiforme. Mol Microbiol 2011; 79:1655-69. [DOI: 10.1111/j.1365-2958.2011.07554.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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Moua P, Fullerton D, Serbus LR, Warrior R, Saxton WM. Kinesin-1 tail autoregulation and microtubule-binding regions function in saltatory transport but not ooplasmic streaming. Development 2011; 138:1087-92. [PMID: 21307100 DOI: 10.1242/dev.048645] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The N-terminal head domain of kinesin heavy chain (Khc) is well known for generating force for transport along microtubules in cytoplasmic organization processes during metazoan development, but the functions of the C-terminal tail are not clear. To address this, we studied the effects of tail mutations on mitochondria transport, determinant mRNA localization and cytoplasmic streaming in Drosophila. Our results show that two biochemically defined elements of the tail - the ATP-independent microtubule-binding sequence and the IAK autoinhibitory motif - are essential for development and viability. Both elements have positive functions in the axonal transport of mitochondria and determinant mRNA localization in oocytes, processes that are accomplished by biased saltatory movement of individual cargoes. Surprisingly, there were no indications that the IAK autoinhibitory motif acts as a general downregulator of Kinesin-1 in those processes. Time-lapse imaging indicated that neither tail region is needed for fast cytoplasmic streaming in oocytes, which is a non-saltatory bulk transport process driven solely by Kinesin-1. Thus, the Khc tail is not constitutively required for Kinesin-1 activation, force transduction or linkage to cargo. It might instead be crucial for more subtle elements of motor control and coordination in the stop-and-go movements of biased saltatory transport.
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Affiliation(s)
- Pangkong Moua
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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Zhang Y, Füger P, Hannan SB, Kern JV, Lasky B, Rasse TM. In vivo imaging of intact Drosophila larvae at sub-cellular resolution. J Vis Exp 2010:2249. [PMID: 20864927 PMCID: PMC3157860 DOI: 10.3791/2249] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Recent improvements in optical imaging, genetically encoded fluorophores and genetic tools allowing efficient establishment of desired transgenic animal lines have enabled biological processes to be studied in the context of a living, and in some instances even behaving, organism. In this protocol we will describe how to anesthetize intact Drosophila larvae, using the volatile anesthetic desflurane, to follow the development and plasticity of synaptic populations at sub-cellular resolution1-3. While other useful methods to anesthetize Drosophila melanogaster larvae have been previously described4,5,6,7,8, the protocol presented herein demonstrates significant improvements due to the following combined key features: (1) A very high degree of anesthetization; even the heart beat is arrested allowing for lateral resolution of up to 150 nm1, (2) a high survival rate of > 90% per anesthetization cycle, permitting the recording of more than five time-points over a period of hours to days2 and (3) a high sensitivity enabling us in 2 instances to study the dynamics of proteins expressed at physiological levels. In detail, we were able to visualize the postsynaptic glutamate receptor subunit GluR-IIA expressed via the endogenous promoter1 in stable transgenic lines and the exon trap line FasII-GFP1. (4) In contrast to other methods4,7 the larvae can be imaged not only alive, but also intact (i.e. non-dissected) allowing observation to occur over a number of days1. The accompanying video details the function of individual parts of the in vivo imaging chamber2,3, the correct mounting of the larvae, the anesthetization procedure, how to re-identify specific positions within a larva and the safe removal of the larvae from the imaging chamber.
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Affiliation(s)
- Yao Zhang
- Junior Research Group Synaptic Plasticity, Hertie Institute for Clinical Brain Research, University of Tübingen
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Abstract
The synapse is composed of an active zone apposed to a postsynaptic cluster of neurotransmitter receptors. Each Drosophila neuromuscular junction comprises hundreds of such individual release sites apposed to clusters of glutamate receptors. Here, we show that protein phosphatase 2A (PP2A) is required for the development of structurally normal active zones opposite glutamate receptors. When PP2A is inhibited presynaptically, many glutamate receptor clusters are unapposed to Bruchpilot (Brp), an active zone protein required for normal transmitter release. These unapposed receptors are not due to presynaptic retraction of synaptic boutons, since other presynaptic components are still apposed to the entire postsynaptic specialization. Instead, these data suggest that Brp localization is regulated at the level of individual release sites. Live imaging of glutamate receptors demonstrates that this disruption to active zone development is accompanied by abnormal postsynaptic development, with decreased formation of glutamate receptor clusters. Remarkably, inhibition of the serine-threonine kinase GSK-3beta completely suppresses the active zone defect, as well as other synaptic morphology phenotypes associated with inhibition of PP2A. These data suggest that PP2A and GSK-3beta function antagonistically to control active zone development, providing a potential mechanism for regulating synaptic efficacy at a single release site.
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Fouquet W, Owald D, Wichmann C, Mertel S, Depner H, Dyba M, Hallermann S, Kittel RJ, Eimer S, Sigrist SJ. Maturation of active zone assembly by Drosophila Bruchpilot. ACTA ACUST UNITED AC 2009; 186:129-45. [PMID: 19596851 PMCID: PMC2712991 DOI: 10.1083/jcb.200812150] [Citation(s) in RCA: 287] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Synaptic vesicles fuse at active zone (AZ) membranes where Ca2+ channels are clustered and that are typically decorated by electron-dense projections. Recently, mutants of the Drosophilamelanogaster ERC/CAST family protein Bruchpilot (BRP) were shown to lack dense projections (T-bars) and to suffer from Ca2+ channel–clustering defects. In this study, we used high resolution light microscopy, electron microscopy, and intravital imaging to analyze the function of BRP in AZ assembly. Consistent with truncated BRP variants forming shortened T-bars, we identify BRP as a direct T-bar component at the AZ center with its N terminus closer to the AZ membrane than its C terminus. In contrast, Drosophila Liprin-α, another AZ-organizing protein, precedes BRP during the assembly of newly forming AZs by several hours and surrounds the AZ center in few discrete punctae. BRP seems responsible for effectively clustering Ca2+ channels beneath the T-bar density late in a protracted AZ formation process, potentially through a direct molecular interaction with intracellular Ca2+ channel domains.
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Affiliation(s)
- Wernher Fouquet
- Institute for Biology/Genetics, Free University Berlin, Berlin, Germany
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Abstract
Positional cloning of chemically induced mutations is the rate-limiting step in forward genetic screens in Drosophila. Single-nucleotide polymorphisms (SNPs) are useful markers to locate a mutated region in the genome. Here, we provide a protocol for high-throughput, high-resolution SNP mapping that enables rapid and cost-effective positional cloning in Drosophila. In stage 1 of the protocol, we use highly multiplexed tag-array mini-sequencing assays to map mutations to an interval of 1-2 Mb. In these assays, SNPs are genotyped by primer extension using fluorescently labeled dideoxy-nucleotides. Fluorescent primers are captured and detected on a microarray. In stage 2, we selectively isolate recombinants within the identified 1-2 Mb interval for fine mapping of mutations to about 50 kb. We have previously demonstrated the applicability of this protocol by mapping 14 muscle morphogenesis mutants within 4 months, which represents a significant acceleration compared with other commonly used mapping strategies that may take years.
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