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Guangming G, Mei C, Qinfeng Y, Xiang G, Chenchen Z, Qingyuan S, Wei X, Junhua G. Neurexin and neuroligins jointly regulate synaptic degeneration at the Drosophila neuromuscular junction based on TEM studies. Front Cell Neurosci 2023; 17:1257347. [PMID: 38026694 PMCID: PMC10646337 DOI: 10.3389/fncel.2023.1257347] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 09/12/2023] [Indexed: 12/01/2023] Open
Abstract
The Drosophila larval neuromuscular junction (NMJ) is a well-known model system and is often used to study synapse development. Here, we show synaptic degeneration at NMJ boutons, primarily based on transmission electron microscopy (TEM) studies. When degeneration starts, the subsynaptic reticulum (SSR) swells, retracts and folds inward, and the residual SSR then degenerates into a disordered, thin or linear membrane. The axon terminal begins to degenerate from the central region, and the T-bar detaches from the presynaptic membrane with clustered synaptic vesicles to accelerate large-scale degeneration. There are two degeneration modes for clear synaptic vesicles. In the first mode, synaptic vesicles without actin filaments degenerate on the membrane with ultrafine spots and collapse and disperse to form an irregular profile with dark ultrafine particles. In the second mode, clear synaptic vesicles with actin filaments degenerate into dense synaptic vesicles, form irregular dark clumps without a membrane, and collapse and disperse to form an irregular profile with dark ultrafine particles. Last, all residual membranes in NMJ boutons degenerate into a linear shape, and all the residual elements in axon terminals degenerate and eventually form a cluster of dark ultrafine particles. Swelling and retraction of the SSR occurs prior to degradation of the axon terminal, which degenerates faster and with more intensity than the SSR. NMJ bouton degeneration occurs under normal physiological conditions but is accelerated in Drosophila neurexin (dnrx) dnrx273, Drosophila neuroligin (dnlg) dnlg1 and dnlg4 mutants and dnrx83;dnlg3 and dnlg2;dnlg3 double mutants, which suggests that both neurexin and neuroligins play a vital role in preventing synaptic degeneration.
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Affiliation(s)
- Gan Guangming
- School of Medicine, Southeast University, Nanjing, Jiangsu, China
- School of Life Science and Technology, The Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu, China
| | - Chen Mei
- School of Life Science and Technology, The Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu, China
| | - Yu Qinfeng
- School of Medicine, Southeast University, Nanjing, Jiangsu, China
| | - Gao Xiang
- School of Medicine, Southeast University, Nanjing, Jiangsu, China
| | - Zhang Chenchen
- School of Medicine, Southeast University, Nanjing, Jiangsu, China
| | - Sheng Qingyuan
- School of Life Science and Technology, The Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu, China
| | - Xie Wei
- School of Life Science and Technology, The Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu, China
- The Collaborative Innovation Center for Brain Science, Southeast University, Nanjing, Jiangsu, China
| | - Geng Junhua
- School of Life Science and Technology, The Key Laboratory of Developmental Genes and Human Disease, Southeast University, Nanjing, Jiangsu, China
- Shenzhen Research Institute of Southeast University, Shenzhen, Guangdong, China
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Improved analysis method of neuromuscular junction in Drosophila larvae by transmission electron microscopy. Anat Sci Int 2021; 97:147-154. [PMID: 34661863 PMCID: PMC8732911 DOI: 10.1007/s12565-021-00635-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 10/04/2021] [Indexed: 11/04/2022]
Abstract
The Drosophila neuromuscular junction is an excellent model for neuroscience research. However, the distribution of neuromuscular junctions is very diffuse, and it is not easy to accurately locate during ultrathin sectioning, which seriously interferes with the ultrastructural analysis under electron microscopy that only has a small field of view. Here, we reported an efficient method for acquiring the ultrastructural picture of neuromuscular junctions in Drosophila larva under electron microscopy. The procedure was as follows: first, the larval sample of body wall muscle was placed between the metal mesh and was dehydrated with alcohol and infiltrated with epoxy resin to prevent the sample from curling or bending, after it was dissected and fixed into thin slices. Second, the sample was embedded in resin into a flat sheet to facilitate the positioning of the muscles. Third, carefully and gradually remove the excess resin and the cuticle of the larvae, cut off both ends of the special body segment, and trim the excess specific muscles according to the recommended ratio of trimming muscles, which would reduce the workload exponentially. At last, the trimmed sample were prepared into serial about 1000 ultrathin sections that was about total 80 microns thickness, and 30–40 sections were gathered into a grid to stain with lead citrate and uranyl acetate. This method could also be applied to the other small and thin samples such as the Drosophila embryo, ventral nerve cord and brain.
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Lehmkuhl EM, Loganathan S, Alsop E, Blythe AD, Kovalik T, Mortimore NP, Barrameda D, Kueth C, Eck RJ, Siddegowda BB, Joardar A, Ball H, Macias ME, Bowser R, Van Keuren-Jensen K, Zarnescu DC. TDP-43 proteinopathy alters the ribosome association of multiple mRNAs including the glypican Dally-like protein (Dlp)/GPC6. Acta Neuropathol Commun 2021; 9:52. [PMID: 33762006 PMCID: PMC7992842 DOI: 10.1186/s40478-021-01148-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 03/06/2021] [Indexed: 12/12/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) is a genetically heterogeneous neurodegenerative disease in which 97% of patients exhibit cytoplasmic aggregates containing the RNA binding protein TDP-43. Using tagged ribosome affinity purifications in Drosophila models of TDP-43 proteinopathy, we identified TDP-43 dependent translational alterations in motor neurons impacting the spliceosome, pentose phosphate and oxidative phosphorylation pathways. A subset of the mRNAs with altered ribosome association are also enriched in TDP-43 complexes suggesting that they may be direct targets. Among these, dlp mRNA, which encodes the glypican Dally like protein (Dlp)/GPC6, a wingless (Wg/Wnt) signaling regulator is insolubilized both in flies and patient tissues with TDP-43 pathology. While Dlp/GPC6 forms puncta in the Drosophila neuropil and ALS spinal cords, it is reduced at the neuromuscular synapse in flies suggesting compartment specific effects of TDP-43 proteinopathy. These findings together with genetic interaction data show that Dlp/GPC6 is a novel, physiologically relevant target of TDP-43 proteinopathy.
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Affiliation(s)
- Erik M. Lehmkuhl
- Department of Cellular and Molecular Biology, University of Arizona, 1007 E. Lowell St, LSS RM 548A, Tucson, AZ 85721 USA
| | - Suvithanandhini Loganathan
- Department of Cellular and Molecular Biology, University of Arizona, 1007 E. Lowell St, LSS RM 548A, Tucson, AZ 85721 USA
| | - Eric Alsop
- Translational Genomics Research Institute, 445 N 5th St, Phoenix, AZ 85004 USA
| | - Alexander D. Blythe
- Department of Cellular and Molecular Biology, University of Arizona, 1007 E. Lowell St, LSS RM 548A, Tucson, AZ 85721 USA
| | - Tina Kovalik
- Department of Neurobiology, Barrow Neurological Institute, 350 W Thomas Rd, Phoenix, AZ 85013 USA
| | - Nicholas P. Mortimore
- Department of Cellular and Molecular Biology, University of Arizona, 1007 E. Lowell St, LSS RM 548A, Tucson, AZ 85721 USA
| | - Dianne Barrameda
- Department of Cellular and Molecular Biology, University of Arizona, 1007 E. Lowell St, LSS RM 548A, Tucson, AZ 85721 USA
| | - Chuol Kueth
- Department of Cellular and Molecular Biology, University of Arizona, 1007 E. Lowell St, LSS RM 548A, Tucson, AZ 85721 USA
| | - Randall J. Eck
- Department of Cellular and Molecular Biology, University of Arizona, 1007 E. Lowell St, LSS RM 548A, Tucson, AZ 85721 USA
| | - Bhavani B. Siddegowda
- Department of Cellular and Molecular Biology, University of Arizona, 1007 E. Lowell St, LSS RM 548A, Tucson, AZ 85721 USA
| | - Archi Joardar
- Department of Cellular and Molecular Biology, University of Arizona, 1007 E. Lowell St, LSS RM 548A, Tucson, AZ 85721 USA
| | - Hannah Ball
- Department of Cellular and Molecular Biology, University of Arizona, 1007 E. Lowell St, LSS RM 548A, Tucson, AZ 85721 USA
| | - Maria E. Macias
- Department of Cellular and Molecular Biology, University of Arizona, 1007 E. Lowell St, LSS RM 548A, Tucson, AZ 85721 USA
| | - Robert Bowser
- Department of Neurobiology, Barrow Neurological Institute, 350 W Thomas Rd, Phoenix, AZ 85013 USA
| | | | - Daniela C. Zarnescu
- Department of Cellular and Molecular Biology, University of Arizona, 1007 E. Lowell St, LSS RM 548A, Tucson, AZ 85721 USA
- Department of Neuroscience, University of Arizona, 1040 4th St, Tucson, AZ 85721 USA
- Department of Neurology, University of Arizona, 1501 N Campbell Ave, Tucson, AZ 85724 USA
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Guangming G, Junhua G, Chenchen Z, Yang M, Wei X. Neurexin and Neuroligins Maintain the Balance of Ghost and Satellite Boutons at the Drosophila Neuromuscular Junction. Front Neuroanat 2020; 14:19. [PMID: 32581727 PMCID: PMC7296126 DOI: 10.3389/fnana.2020.00019] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 03/26/2020] [Indexed: 11/22/2022] Open
Abstract
Neurexins and neuroligins are common synaptic adhesion molecules that are associated with autism and interact with each other in the synaptic cleft. The Drosophila neuromuscular junction (NMJ) bouton is a well-known model system in neuroscience, and ghost and satellite boutons, respectively, indicate the poor development and overgrowth of the NMJ boutons. However, the Drosophila neurexin (DNrx) and Drosophila neuroligins (DNlgs) are mainly observed in type Ib boutons, indicating the ultrastructural and developmental phenotypes of the Drosophila NMJ. Here, we identified the ultrastructural and developmental features of ghost and satellite boutons by utilizing dneurexin (dnrx) and dneuroligins (dnlgs) fly mutants and other associated fly strains. Ghost boutons contain synaptic vesicles with multiple diameters but very rarely contain T-bar structures and swollen or thin subsynaptic reticulum (SSR) membranes. The muscle cell membrane is invaginated at different sites, stretches to the ghost bouton from different directions, forms several layers that enwrap the ghost bouton, and then branches into the complex SSR. Satellite boutons share a common SSR membrane and present either a typical profile in which a main bouton is encircled by small boutons or two atypical profiles in which the small boutons are grouped together or distributed in beads without a main bouton. Electron and confocal microscopy data showed that dnrx, dnlg1, dnlg2, dnlg3, and dnlg4 mutations led to ghost boutons; the overexpression of dnrx, dnlg1, dnlg2, dnlg3, and dnlg4 led to satellite boutons; and the dnlg2;dnlg3 double mutation also led to satellite boutons. These results suggested that DNrx and DNlgs jointly maintain the development and function of NMJ boutons by regulating the balance of ghost and satellite boutons in Drosophila.
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Affiliation(s)
- Gan Guangming
- School of Medicine, Southeast University, Nanjing, China.,The Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing, China
| | - Geng Junhua
- The Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing, China
| | - Zhang Chenchen
- School of Medicine, Southeast University, Nanjing, China.,The Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing, China
| | - Mou Yang
- School of Medicine, Southeast University, Nanjing, China
| | - Xie Wei
- The Key Laboratory of Developmental Genes and Human Disease, Institute of Life Sciences, Southeast University, Nanjing, China.,Institute of Life Sciences, The Collaborative Innovation Center for Brain Science, Southeast University, Nanjing, China
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Rai D, Dey S, Ray K. A method for estimating relative changes in the synaptic density in Drosophila central nervous system. BMC Neurosci 2018; 19:30. [PMID: 29769037 PMCID: PMC5956817 DOI: 10.1186/s12868-018-0430-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 05/02/2018] [Indexed: 12/16/2022] Open
Abstract
Background Synapse density is an essential indicator of development and functioning of the central nervous system. It is estimated indirectly through the accumulation of pre and postsynaptic proteins in tissue sections. 3D reconstruction of the electron microscopic images in serial sections is one of the most definitive means of estimating the formation of active synapses in the brain. It is tedious and highly skill-dependent. Confocal imaging of whole mounts or thick sections of the brain provides a natural alternative for rapid gross estimation of the synapse density in large areas. The optical resolution and other deep-tissue imaging aberrations limit the quantitative scope of this technique. Results Here we demonstrate a simple sample preparation method that could enhance the clarity of the confocal images of the neuropil regions of the ventral nerve cord of Drosophila larvae, providing a clear view of synapse distributions. We estimated the gross volume occupied by the synaptic junctions using 3D object counter plug-in of Fiji/ImageJ®. It gave us a proportional estimate of the number of synaptic junctions in the neuropil region. The method is corroborated by correlated super-resolution imaging analysis and through genetic perturbation of synaptogenesis in the larval brain. Conclusions The method provides a significant improvement in the relative estimate of region-specific synapse density in the central nervous system. Also, it reduced artifacts in the super-resolution images obtained using the stimulated emission depletion microscopy technique. Electronic supplementary material The online version of this article (10.1186/s12868-018-0430-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Dipti Rai
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, 400005, India
| | - Swagata Dey
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, 400005, India
| | - Krishanu Ray
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai, 400005, India.
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Gan G, Zhang C. The precise subcellular localization of Dlg in the Drosophila larva body wall using improved pre-embedding immuno-EM. J Neurosci Res 2017; 96:467-480. [PMID: 29231975 DOI: 10.1002/jnr.24139] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2017] [Revised: 07/12/2017] [Accepted: 07/21/2017] [Indexed: 12/21/2022]
Abstract
Discs-large (Dlg) plays important roles in nerve tissue and epithelial tissue in Drosophila. However, the precise positioning of Dlg in the neuromuscular junction remains to be confirmed using an optimized labeling method. In this study, we improved the method of pre-embedding immunogold electron microscopy without the osmic tetroxide procedure, and we found that Lowicryl K4 M resin and low temperature helped to preserve the authenticity of the labeling signal with relatively good contrast. Dlg was strongly expressed in the entire subsynaptic reticulum (SSR) membrane of type Ib boutons, expressed in parts of the SSR membrane of type Is boutons, weakly expressed in axon terminals and axons, and not expressed in pre- or postsynaptic membranes of type Is boutons. In muscle cells and stratum corneum cells, Dlg was expressed both in the cytoplasm and in organelles with biomembranes. The precise location of Dlg in SSR membranes, rather than in postsynaptic membranes, shows that Dlg, with its multiple domains, acts as a remote or indirect regulator in postsynaptic signal transduction.
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Affiliation(s)
- Guangming Gan
- Medical School Southeast University, Nanjing, China.,Key Laboratory for Developmental Genes and Human Disease, Ministry of Education, Southeast University, Nanjing, China
| | - Chenchen Zhang
- Medical School Southeast University, Nanjing, China.,Key Laboratory for Developmental Genes and Human Disease, Ministry of Education, Southeast University, Nanjing, China
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Anger Emotional Stress Influences VEGF/VEGFR2 and Its Induced PI3K/AKT/mTOR Signaling Pathway. Neural Plast 2016; 2016:4129015. [PMID: 27057362 PMCID: PMC4769761 DOI: 10.1155/2016/4129015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 01/06/2016] [Accepted: 01/11/2016] [Indexed: 12/18/2022] Open
Abstract
Objective. We discuss the influence of anger emotional stress upon VEGF/VEGFR2 and its induced PI3K/AKT/mTOR signal pathway. Methods. We created a rat model of induced anger (anger-out and anger-in) emotional response using social isolation and resident-intruder paradigms and assessed changes in hippocampus' VEGF content, neuroplasticity, and the PI3K/AKT/mTOR signaling pathway. Results. The resident-intruder method successfully generated anger-out and anger-in models that differed significantly in composite aggression score, aggression incubation, open field behavior, sucrose preference, and weight gain. Anger emotional stress decreased synaptic connections and VEGFR2 expression. Anger emotional stress led to abnormal expression of VEGF/VEGFR2 mRNA and protein and disorderly expression of key factors in the PI3K/AKT/mTOR signal pathway. Fluoxetine administration ameliorated behavioral abnormalities and damage to hippocampal neurons caused by anger emotional stress, as well as abnormal expression of some proteins in VEGF/VEGFR2 and its induced PI3K/AKT/mTOR signal pathway. Conclusion. This research provides a detailed classification of anger emotion and verifies its influence upon VEGF and the VEGF-induced signaling pathway, thus providing circumstantial evidence of mechanisms by which anger emotion damages neurogenesis. As VEGFR2 can promote neurogenesis and vasculogenesis in the hippocampus and frontal lobe, these results suggest that anger emotional stress can result in decreased neurogenesis.
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