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Hedrick NG, Wright WJ, Komiyama T. Local and global predictors of synapse elimination during motor learning. SCIENCE ADVANCES 2024; 10:eadk0540. [PMID: 38489360 PMCID: PMC10942101 DOI: 10.1126/sciadv.adk0540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 02/12/2024] [Indexed: 03/17/2024]
Abstract
During learning, synaptic connections between excitatory neurons in the brain display considerable dynamism, with new connections being added and old connections eliminated. Synapse elimination offers an opportunity to understand the features of synapses that the brain deems dispensable. However, with limited observations of synaptic activity and plasticity in vivo, the features of synapses subjected to elimination remain poorly understood. Here, we examined the functional basis of synapse elimination in the apical dendrites of L2/3 neurons in the primary motor cortex throughout motor learning. We found no evidence that synapse elimination is facilitated by a lack of activity or other local forms of plasticity. Instead, eliminated synapses display asynchronous activity with nearby synapses, suggesting that functional synaptic clustering is a critical component of synapse survival. In addition, eliminated synapses show delayed activity timing with respect to postsynaptic output. Thus, synaptic inputs that fail to be co-active with their neighboring synapses or are mistimed with neuronal output are targeted for elimination.
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Affiliation(s)
- Nathan G. Hedrick
- Department of Neurobiology, University of California San Diego, La Jolla, CA, USA
- Center for Neural Circuits and Behavior, University of California San Diego, La Jolla, CA, USA
- Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
- Halıcıoğlu Data Science Institute, University of California San Diego, La Jolla, CA, USA
| | - William J. Wright
- Department of Neurobiology, University of California San Diego, La Jolla, CA, USA
- Center for Neural Circuits and Behavior, University of California San Diego, La Jolla, CA, USA
- Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
- Halıcıoğlu Data Science Institute, University of California San Diego, La Jolla, CA, USA
| | - Takaki Komiyama
- Department of Neurobiology, University of California San Diego, La Jolla, CA, USA
- Center for Neural Circuits and Behavior, University of California San Diego, La Jolla, CA, USA
- Department of Neurosciences, University of California San Diego, La Jolla, CA, USA
- Halıcıoğlu Data Science Institute, University of California San Diego, La Jolla, CA, USA
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Yang L, Zhang J, Liu S, Zhang Y, Wang L, Wang X, Wang S, Li K, Wei M, Zhang C. Establishment of transgenic fluorescent mice for labeling synapses and screening synaptogenic adhesion molecules. eLife 2024; 13:e81884. [PMID: 38450720 PMCID: PMC10948142 DOI: 10.7554/elife.81884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 03/05/2024] [Indexed: 03/08/2024] Open
Abstract
Synapse is the fundamental structure for neurons to transmit information between cells. The proper synapse formation is crucial for developing neural circuits and cognitive functions of the brain. The aberrant synapse formation has been proved to cause many neurological disorders, including autism spectrum disorders and intellectual disability. Synaptic cell adhesion molecules (CAMs) are thought to play a major role in achieving mechanistic cell-cell recognition and initiating synapse formation via trans-synaptic interactions. Due to the diversity of synapses in different brain areas, circuits and neurons, although many synaptic CAMs, such as Neurexins (NRXNs), Neuroligins (NLGNs), Synaptic cell adhesion molecules (SynCAMs), Leucine-rich-repeat transmembrane neuronal proteins (LRRTMs), and SLIT and NTRK-like protein (SLITRKs) have been identified as synaptogenic molecules, how these molecules determine specific synapse formation and whether other molecules driving synapse formation remain undiscovered are unclear. Here, to provide a tool for synapse labeling and synaptic CAMs screening by artificial synapse formation (ASF) assay, we generated synaptotagmin-1-tdTomato (Syt1-tdTomato) transgenic mice by inserting the tdTomato-fused synaptotagmin-1 coding sequence into the genome of C57BL/6J mice. In the brain of Syt1-tdTomato transgenic mice, the tdTomato-fused synaptotagmin-1 (SYT1-tdTomato) signals were widely observed in different areas and overlapped with synapsin-1, a widely-used synaptic marker. In the olfactory bulb, the SYT1-tdTomato signals are highly enriched in the glomerulus. In the cultured hippocampal neurons, the SYT1-tdTomato signals showed colocalization with several synaptic markers. Compared to the wild-type (WT) mouse neurons, cultured hippocampal neurons from Syt1-tdTomato transgenic mice presented normal synaptic neurotransmission. In ASF assays, neurons from Syt1-tdTomato transgenic mice could form synaptic connections with HEK293T cells expressing NLGN2, LRRTM2, and SLITRK2 without immunostaining. Therefore, our work suggested that the Syt1-tdTomato transgenic mice with the ability to label synapses by tdTomato, and it will be a convenient tool for screening synaptogenic molecules.
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Affiliation(s)
- Lei Yang
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical UniversityBeijingChina
| | - Jingtao Zhang
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical UniversityBeijingChina
| | - Sen Liu
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical UniversityBeijingChina
| | - Yanning Zhang
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical UniversityBeijingChina
| | - Li Wang
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical UniversityBeijingChina
| | - Xiaotong Wang
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical UniversityBeijingChina
| | - Shanshan Wang
- Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking UniversityBeijingChina
| | - Ke Li
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical UniversityBeijingChina
| | - Mengping Wei
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical UniversityBeijingChina
| | - Chen Zhang
- School of Basic Medical Sciences, Beijing Key Laboratory of Neural Regeneration and Repair, Advanced Innovation Center for Human Brain Protection, Capital Medical UniversityBeijingChina
- Chinese Institute for Brain ResearchBeijingChina
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Wang M, Fan J, Shao Z. Cellular and Molecular Mechanisms Underlying Synaptic Subcellular Specificity. Brain Sci 2024; 14:155. [PMID: 38391729 PMCID: PMC10886843 DOI: 10.3390/brainsci14020155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Revised: 01/03/2024] [Accepted: 01/09/2024] [Indexed: 02/24/2024] Open
Abstract
Chemical synapses are essential for neuronal information storage and relay. The synaptic signal received or sent from spatially distinct subcellular compartments often generates different outcomes due to the distance or physical property difference. Therefore, the final output of postsynaptic neurons is determined not only by the type and intensity of synaptic inputs but also by the synaptic subcellular location. How synaptic subcellular specificity is determined has long been the focus of study in the neurodevelopment field. Genetic studies from invertebrates such as Caenorhabditis elegans (C. elegans) have uncovered important molecular and cellular mechanisms required for subcellular specificity. Interestingly, similar molecular mechanisms were found in the mammalian cerebellum, hippocampus, and cerebral cortex. This review summarizes the comprehensive advances in the cellular and molecular mechanisms underlying synaptic subcellular specificity, focusing on studies from C. elegans and rodents.
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Affiliation(s)
- Mengqing Wang
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Neurosurgery, Zhongshan Hospital, Fudan University, 131 Dong An Rd, Research Building B4017, Shanghai 200032, China
| | - Jiale Fan
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Neurosurgery, Zhongshan Hospital, Fudan University, 131 Dong An Rd, Research Building B4017, Shanghai 200032, China
| | - Zhiyong Shao
- State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Department of Neurosurgery, Zhongshan Hospital, Fudan University, 131 Dong An Rd, Research Building B4017, Shanghai 200032, China
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Rabinowitch I, Colón-Ramos DA, Krieg M. Understanding neural circuit function through synaptic engineering. Nat Rev Neurosci 2024; 25:131-139. [PMID: 38172626 DOI: 10.1038/s41583-023-00777-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/29/2023] [Indexed: 01/05/2024]
Abstract
Synapses are a key component of neural circuits, facilitating rapid and specific signalling between neurons. Synaptic engineering - the synthetic insertion of new synaptic connections into in vivo neural circuits - is an emerging approach for neural circuit interrogation. This approach is especially powerful for establishing causality in neural circuit structure-function relationships, for emulating synaptic plasticity and for exploring novel patterns of circuit connectivity. Contrary to other approaches for neural circuit manipulation, synaptic engineering targets specific connections between neurons and functions autonomously with no user-controlled external activation. Synaptic engineering has been successfully implemented in several systems and in different forms, including electrical synapses constructed from ectopically expressed connexin gap junction proteins, synthetic optical synapses composed of presynaptic photon-emitting luciferase coupled with postsynaptic light-gated channels, and artificial neuropeptide signalling pathways. This Perspective describes these different methods and how they have been applied, and examines how the field may advance.
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Affiliation(s)
- Ithai Rabinowitch
- Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel.
| | - Daniel A Colón-Ramos
- Wu Tsai Institute, Department of Neuroscience and Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Michael Krieg
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, Spain
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Matcham AC, Toma K, Tsai NY, Sze CJ, Lin PY, Stewart IF, Duan X. Cadherin-13 Maintains Retinotectal Synapses via Transneuronal Interactions. J Neurosci 2024; 44:e1310232023. [PMID: 38123991 PMCID: PMC10860569 DOI: 10.1523/jneurosci.1310-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Revised: 12/03/2023] [Accepted: 12/05/2023] [Indexed: 12/23/2023] Open
Abstract
Maintaining precise synaptic contacts between neuronal partners is critical to ensure the proper functioning of the mammalian central nervous system (CNS). Diverse cell recognition molecules, such as classic cadherins (Cdhs), are part of the molecular machinery mediating synaptic choices during development and synaptic maintenance. Yet, the principles governing neuron-neuron wiring across diverse CNS neuron types remain largely unknown. The retinotectal synapses, connections from the retinal ganglion cells (RGCs) to the superior collicular (SC) neurons, offer an ideal experimental system to reveal molecular logic underlying synaptic choices and formation. This is due to the retina's unidirectional and laminar-restricted projections to the SC and the large databases of presynaptic RGC subtypes and postsynaptic SC neuronal types. Here, we focused on determining the role of Type II Cdhs in wiring the retinotectal synapses. We surveyed Cdhs expression patterns at neuronal resolution and revealed that Cdh13 is enriched in the wide-field neurons in the superficial SC (sSC). In either the Cdh13 null mutant or selective adult deletion within the wide-field neurons, there is a significant reduction of spine densities in the distal dendrites of these neurons in both sexes. Additionally, Cdh13 removal from presynaptic RGCs reduced dendritic spines in the postsynaptic wide-field neurons. Cdh13-expressing RGCs use differential mechanisms than αRGCs and On-Off Direction-Selective Ganglion Cells (ooDSGCs) to form specific retinotectal synapses. The results revealed a selective transneuronal interaction mediated by Cdh13 to maintain proper retinotectal synapses in vivo.
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Affiliation(s)
- Angela C Matcham
- Neuroscience Graduate Program, Department of Ophthalmology, Kavli Institute for Fundamental Neuroscience, University of California SanFrancisco, San Francisco 94143-2811, California
| | - Kenichi Toma
- Neuroscience Graduate Program, Department of Ophthalmology, Kavli Institute for Fundamental Neuroscience, University of California SanFrancisco, San Francisco 94143-2811, California
| | - Nicole Y Tsai
- Neuroscience Graduate Program, Department of Ophthalmology, Kavli Institute for Fundamental Neuroscience, University of California SanFrancisco, San Francisco 94143-2811, California
| | - Christina J Sze
- Neuroscience Graduate Program, Department of Ophthalmology, Kavli Institute for Fundamental Neuroscience, University of California SanFrancisco, San Francisco 94143-2811, California
| | - Pin-Yeh Lin
- Neuroscience Graduate Program, Department of Ophthalmology, Kavli Institute for Fundamental Neuroscience, University of California SanFrancisco, San Francisco 94143-2811, California
| | - Ilaria F Stewart
- Neuroscience Graduate Program, Department of Ophthalmology, Kavli Institute for Fundamental Neuroscience, University of California SanFrancisco, San Francisco 94143-2811, California
| | - Xin Duan
- Neuroscience Graduate Program, Department of Ophthalmology, Kavli Institute for Fundamental Neuroscience, University of California SanFrancisco, San Francisco 94143-2811, California
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Bergamo D, Handjaras G, Petruso F, Talami F, Ricciardi E, Benuzzi F, Vaudano AE, Meletti S, Bernardi G, Betta M. Maturation-dependent changes in cortical and thalamic activity during sleep slow waves: Insights from a combined EEG-fMRI study. Sleep Med 2024; 113:357-369. [PMID: 38113618 DOI: 10.1016/j.sleep.2023.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2023] [Revised: 11/24/2023] [Accepted: 12/02/2023] [Indexed: 12/21/2023]
Abstract
INTRODUCTION Studies using scalp EEG have shown that slow waves (0.5-4 Hz), the most prominent hallmark of NREM sleep, undergo relevant changes from childhood to adulthood, mirroring brain structural modifications and the acquisition of cognitive skills. Here we used simultaneous EEG-fMRI to investigate the cortical and subcortical correlates of slow waves in school-age children and determine their relative developmental changes. METHODS We analyzed data from 14 school-age children with self-limited focal epilepsy of childhood who fell asleep during EEG-fMRI recordings. Brain regions associated with slow-wave occurrence were identified using a voxel-wise regression that also modelled interictal epileptic discharges and sleep spindles. At the group level, a mixed-effects linear model was used. The results were qualitatively compared with those obtained from 2 adolescents with epilepsy and 17 healthy adults. RESULTS Slow waves were associated with hemodynamic-signal decreases in bilateral somatomotor areas. Such changes extended more posteriorly relative to those in adults. Moreover, the involvement of areas belonging to the default mode network changes as a function of age. No significant hemodynamic responses were observed in subcortical structures. However, we identified a significant correlation between age and thalamic hemodynamic changes. CONCLUSIONS Present findings indicate that the somatomotor cortex may have a key role in slow-wave expression throughout the lifespan. At the same time, they are consistent with a posterior-to-anterior shift in slow-wave distribution mirroring brain maturational changes. Finally, our results suggest that slow-wave changes may not reflect only neocortical modifications but also the maturation of subcortical structures, including the thalamus.
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Affiliation(s)
- Damiana Bergamo
- MoMiLab, IMT School for Advanced Studies Lucca, Lucca, Italy
| | | | - Flavia Petruso
- MoMiLab, IMT School for Advanced Studies Lucca, Lucca, Italy; Sant'Anna School of Advanced Studies, Pisa, Italy
| | - Francesca Talami
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy; Neurology Dept., Azienda Ospedaliera Universitaria di Modena, Italy
| | | | - Francesca Benuzzi
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy
| | - Anna Elisabetta Vaudano
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy; Neurology Dept., Azienda Ospedaliera Universitaria di Modena, Italy
| | - Stefano Meletti
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, Italy; Neurology Dept., Azienda Ospedaliera Universitaria di Modena, Italy
| | - Giulio Bernardi
- MoMiLab, IMT School for Advanced Studies Lucca, Lucca, Italy
| | - Monica Betta
- MoMiLab, IMT School for Advanced Studies Lucca, Lucca, Italy.
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Dorskind JM, Sudarsanam S, Hand RA, Ziak J, Amoah-Dankwah M, Guzman-Clavel L, Soto-Vargas JL, Kolodkin AL. Drebrin Regulates Collateral Axon Branching in Cortical Layer II/III Somatosensory Neurons. J Neurosci 2023; 43:7745-7765. [PMID: 37798130 PMCID: PMC10648559 DOI: 10.1523/jneurosci.0553-23.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 09/19/2023] [Accepted: 10/02/2023] [Indexed: 10/07/2023] Open
Abstract
Proper cortical lamination is essential for cognition, learning, and memory. Within the somatosensory cortex, pyramidal excitatory neurons elaborate axon collateral branches in a laminar-specific manner that dictates synaptic partners and overall circuit organization. Here, we leverage both male and female mouse models, single-cell labeling and imaging approaches to identify intrinsic regulators of laminar-specific collateral, also termed interstitial, axon branching. We developed new approaches for the robust, sparse, labeling of Layer II/III pyramidal neurons to obtain single-cell quantitative assessment of axon branch morphologies. We combined these approaches with cell-autonomous loss-of-function (LOF) and overexpression (OE) manipulations in an in vivo candidate screen to identify regulators of cortical neuron axon branch lamination. We identify a role for the cytoskeletal binding protein drebrin (Dbn1) in regulating Layer II/III cortical projection neuron (CPN) collateral axon branching in vitro LOF experiments show that Dbn1 is necessary to suppress the elongation of Layer II/III CPN collateral axon branches within Layer IV, where axon branching by Layer II/III CPNs is normally absent. Conversely, Dbn1 OE produces excess short axonal protrusions reminiscent of nascent axon collaterals that fail to elongate. Structure-function analyses implicate Dbn1S142 phosphorylation and Dbn1 protein domains known to mediate F-actin bundling and microtubule (MT) coupling as necessary for collateral branch initiation upon Dbn1 OE. Taken together, these results contribute to our understanding of the molecular mechanisms that regulate collateral axon branching in excitatory CPNs, a key process in the elaboration of neocortical circuit formation.SIGNIFICANCE STATEMENT Laminar-specific axon targeting is essential for cortical circuit formation. Here, we show that the cytoskeletal protein drebrin (Dbn1) regulates excitatory Layer II/III cortical projection neuron (CPN) collateral axon branching, lending insight into the molecular mechanisms that underlie neocortical laminar-specific innervation. To identify branching patterns of single cortical neurons in vivo, we have developed tools that allow us to obtain detailed images of individual CPN morphologies throughout postnatal development and to manipulate gene expression in these same neurons. Our results showing that Dbn1 regulates CPN interstitial axon branching both in vivo and in vitro may aid in our understanding of how aberrant cortical neuron morphology contributes to dysfunctions observed in autism spectrum disorder and epilepsy.
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Affiliation(s)
- Joelle M Dorskind
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins Kavli Neuroscience Discovery Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Sriram Sudarsanam
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins Kavli Neuroscience Discovery Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Randal A Hand
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins Kavli Neuroscience Discovery Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Jakub Ziak
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins Kavli Neuroscience Discovery Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Maame Amoah-Dankwah
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins Kavli Neuroscience Discovery Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Luis Guzman-Clavel
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins Kavli Neuroscience Discovery Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Summer Internship Program (NeuroSIP), Solomon H. Snyder Department of Neuroscience, Johns Hopkins Kavli Neuroscience Discovery Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - John Lee Soto-Vargas
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins Kavli Neuroscience Discovery Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
- Basic Science Institute-Summer Internship Program (BSI-SIP), Johns Hopkins Kavli Neuroscience Discovery Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Alex L Kolodkin
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins Kavli Neuroscience Discovery Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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Galindo SE, Wood AJ, Cooney PC, Hammond LA, Grueber WB. Axon-axon interactions determine modality-specific wiring and subcellular synaptic specificity in a somatosensory circuit. Development 2023; 150:dev199832. [PMID: 36920224 PMCID: PMC10112896 DOI: 10.1242/dev.199832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 02/09/2023] [Indexed: 03/16/2023]
Abstract
Synaptic connections between neurons are often formed in precise subcellular regions of dendritic arbors with implications for information processing within neurons. Cell-cell interactions are widely important for circuit wiring; however, their role in subcellular specificity is not well understood. We studied the role of axon-axon interactions in precise targeting and subcellular wiring of Drosophila somatosensory circuitry. Axons of nociceptive and gentle touch neurons terminate in adjacent, non-overlapping layers in the central nervous system (CNS). Nociceptor and touch receptor axons synapse onto distinct dendritic regions of a second-order interneuron, the dendrites of which span these layers, forming touch-specific and nociceptive-specific connectivity. We found that nociceptor ablation elicited extension of touch receptor axons and presynapses into the nociceptor recipient region, supporting a role for axon-axon interactions in somatosensory wiring. Conversely, touch receptor ablation did not lead to expansion of nociceptor axons, consistent with unidirectional axon-axon interactions. Live imaging provided evidence for sequential arborization of nociceptive and touch neuron axons in the CNS. We propose that axon-axon interactions and modality-specific timing of axon targeting play key roles in subcellular connection specificity of somatosensory circuitry.
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Affiliation(s)
- Samantha E. Galindo
- Department of Genetics and Development, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Abby J. Wood
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
- Department of Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10027, USA
| | - Patricia C. Cooney
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
- Department of Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10027, USA
| | - Luke A. Hammond
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Wesley B. Grueber
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
- Department of Neuroscience, Mortimer B. Zuckerman Mind Brain Behavior Institute, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10027, USA
- Department of Physiology and Cellular Biophysics, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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Palmateer CM, Artikis C, Brovero SG, Friedman B, Gresham A, Arbeitman MN. Single-cell transcriptome profiles of Drosophila fruitless-expressing neurons from both sexes. eLife 2023; 12:e78511. [PMID: 36724009 PMCID: PMC9891730 DOI: 10.7554/elife.78511] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 01/08/2023] [Indexed: 02/02/2023] Open
Abstract
Drosophila melanogaster reproductive behaviors are orchestrated by fruitless neurons. We performed single-cell RNA-sequencing on pupal neurons that produce sex-specifically spliced fru transcripts, the fru P1-expressing neurons. Uniform Manifold Approximation and Projection (UMAP) with clustering generates an atlas containing 113 clusters. While the male and female neurons overlap in UMAP space, more than half the clusters have sex differences in neuron number, and nearly all clusters display sex-differential expression. Based on an examination of enriched marker genes, we annotate clusters as circadian clock neurons, mushroom body Kenyon cell neurons, neurotransmitter- and/or neuropeptide-producing, and those that express doublesex. Marker gene analyses also show that genes that encode members of the immunoglobulin superfamily of cell adhesion molecules, transcription factors, neuropeptides, neuropeptide receptors, and Wnts have unique patterns of enriched expression across the clusters. In vivo spatial gene expression links to the clusters are examined. A functional analysis of fru P1 circadian neurons shows they have dimorphic roles in activity and period length. Given that most clusters are comprised of male and female neurons indicates that the sexes have fru P1 neurons with common gene expression programs. Sex-specific expression is overlaid on this program, to build the potential for vastly different sex-specific behaviors.
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Affiliation(s)
- Colleen M Palmateer
- Department of Biomedical Sciences, Florida State University, College of MedicineTallahasseeUnited States
| | - Catherina Artikis
- Department of Biomedical Sciences, Florida State University, College of MedicineTallahasseeUnited States
| | - Savannah G Brovero
- Department of Biomedical Sciences, Florida State University, College of MedicineTallahasseeUnited States
| | - Benjamin Friedman
- Department of Biomedical Sciences, Florida State University, College of MedicineTallahasseeUnited States
| | - Alexis Gresham
- Department of Biomedical Sciences, Florida State University, College of MedicineTallahasseeUnited States
| | - Michelle N Arbeitman
- Department of Biomedical Sciences, Florida State University, College of MedicineTallahasseeUnited States
- Program of Neuroscience, Florida State UniversityTallahasseeUnited States
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Hong N, Kim HJ, Kang K, Park JO, Mun S, Kim HG, Kang BH, Chung PS, Lee MY, Ahn JC. Photobiomodulation improves the synapses and cognitive function and ameliorates epileptic seizure by inhibiting downregulation of Nlgn3. Cell Biosci 2023; 13:8. [PMID: 36635704 PMCID: PMC9837965 DOI: 10.1186/s13578-022-00949-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 12/21/2022] [Indexed: 01/13/2023] Open
Abstract
BACKGROUND Temporal lobe epilepsy (TLE) remains one of the most drug-resistant focal epilepsies. Glutamate excitotoxicity and neuroinflammation which leads to loss of synaptic proteins and neuronal death appear to represent a pathogen that characterizes the neurobiology of TLE. Photobiomodulation (PBM) is a rapidly growing therapy for the attenuation of neuronal degeneration harboring non-invasiveness benefits. However, the detailed effects of PBM on excitotoxicity or neuroinflammation remain unclear. We investigated whether tPBM exerts neuroprotective effects on hippocampal neurons in epilepsy mouse model by regulating synapse and synapse-related genes. METHODS In an in vitro study, we performed imaging analysis and western blot in primary hippocampal neurons from embryonic (E17) rat pups. In an in vivo study, RNA sequencing was performed to identify the gene regulatory by PBM. Histological stain and immunohistochemistry analyses were used to assess synaptic connections, neuroinflammation and neuronal survival. Behavioral tests were used to evaluate the effects of PBM on cognitive functions. RESULTS PBM was upregulated synaptic connections in an in vitro. In addition, it was confirmed that transcranial PBM reduced synaptic degeneration, neuronal apoptosis, and neuroinflammation in an in vivo. These effects of PBM were supported by RNA sequencing results showing the relation of PBM with gene regulatory networks of neuronal functions. Specifically, Nlgn3 showed increase after PBM and silencing the Nlgn3 reversed the positive effect of PBM in in vitro. Lastly, behavioral alterations including hypoactivity, anxiety and impaired memory were recovered along with the reduction of seizure score in PBM-treated mice. CONCLUSIONS Our findings demonstrate that PBM attenuates epileptic excitotoxicity, neurodegeneration and cognitive decline induced by TLE through inhibition of the Nlgn3 gene decrease induced by excitotoxicity.
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Affiliation(s)
- Namgue Hong
- grid.411982.70000 0001 0705 4288Medical Laser Research Center, Dankook University, Cheonan, Republic of Korea ,grid.411982.70000 0001 0705 4288Department of Biomedical Science, College of Medicine, Dankook University, Cheonan, Republic of Korea
| | - Hee Jung Kim
- grid.411982.70000 0001 0705 4288Department of Physiology, College of Medicine, Dankook University, Cheonan, Republic of Korea
| | - Keunsoo Kang
- grid.411982.70000 0001 0705 4288Department of Microbiology, College of Science & Technology, Dankook University, Cheonan, Republic of Korea
| | - Ji On Park
- grid.411982.70000 0001 0705 4288Department of Medicine, Graduate School of Dankook University, Dankook University, Cheonan, Republic of Korea
| | - Seyoung Mun
- grid.411982.70000 0001 0705 4288Department of Microbiology, College of Science & Technology, Dankook University, Cheonan, Republic of Korea ,grid.411982.70000 0001 0705 4288Center for Bio-Medical Engineering Core Facility, Dankook University, Cheonan, Republic of Korea
| | - Hyung-Gun Kim
- grid.411982.70000 0001 0705 4288Department of Pharmacology, College of Medicine, Dankook University, Cheonan, Republic of Korea
| | - Bong Hui Kang
- grid.411982.70000 0001 0705 4288Department of Neurology, Dankook University Hospital, Dankook University, Cheonan, Republic of Korea
| | - Phil-Sang Chung
- grid.411982.70000 0001 0705 4288Beckman Laser Institute Korea, Dankook University Hospital, Dankook University, Cheonan, Republic of Korea ,grid.411982.70000 0001 0705 4288Department of Otolaryngology-Head & Neck Surgery, College of Medicine, Dankook University Hospital, Dankook University, Cheonan, Republic of Korea
| | - Min Young Lee
- grid.411982.70000 0001 0705 4288Medical Laser Research Center, Dankook University, Cheonan, Republic of Korea ,grid.411982.70000 0001 0705 4288Department of Biomedical Science, College of Medicine, Dankook University, Cheonan, Republic of Korea ,grid.411982.70000 0001 0705 4288Beckman Laser Institute Korea, Dankook University Hospital, Dankook University, Cheonan, Republic of Korea ,grid.411982.70000 0001 0705 4288Department of Otolaryngology-Head & Neck Surgery, College of Medicine, Dankook University Hospital, Dankook University, Cheonan, Republic of Korea
| | - Jin-Chul Ahn
- grid.411982.70000 0001 0705 4288Medical Laser Research Center, Dankook University, Cheonan, Republic of Korea ,grid.411982.70000 0001 0705 4288Department of Biomedical Science, College of Medicine, Dankook University, Cheonan, Republic of Korea ,grid.411982.70000 0001 0705 4288Beckman Laser Institute Korea, Dankook University Hospital, Dankook University, Cheonan, Republic of Korea
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11
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Washburn HR, Chander P, Srikanth KD, Dalva MB. Transsynaptic Signaling of Ephs in Synaptic Development, Plasticity, and Disease. Neuroscience 2023; 508:137-152. [PMID: 36460219 DOI: 10.1016/j.neuroscience.2022.11.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 11/22/2022] [Accepted: 11/23/2022] [Indexed: 12/03/2022]
Abstract
Synapse formation between neurons is critical for proper circuit and brain function. Prior to activity-dependent refinement of connections between neurons, activity-independent cues regulate the contact and recognition of potential synaptic partners. Formation of a synapse results in molecular recognition events that initiate the process of synaptogenesis. Synaptogenesis requires contact between axon and dendrite, selection of correct and rejection of incorrect partners, and recruitment of appropriate pre- and postsynaptic proteins needed for the establishment of functional synaptic contact. Key regulators of these events are families of transsynaptic proteins, where one protein is found on the presynaptic neuron and the other is found on the postsynaptic neuron. Of these families, the EphBs and ephrin-Bs are required during each phase of synaptic development from target selection, recruitment of synaptic proteins, and formation of spines to regulation of synaptic plasticity at glutamatergic spine synapses in the mature brain. These roles also place EphBs and ephrin-Bs as important regulators of human neurological diseases. This review will focus on the role of EphBs and ephrin-Bs at synapses.
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Affiliation(s)
- Halley R Washburn
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA; Department of Neuroscience, Jefferson Synaptic Biology Center, Sidney Kimmel Medical College at Thomas Jefferson University, 233 South 10th Street, Bluemle Life Sciences Building, Room 324, Philadelphia, PA 19107, USA
| | - Praveen Chander
- Department of Neuroscience, Jefferson Synaptic Biology Center, Sidney Kimmel Medical College at Thomas Jefferson University, 233 South 10th Street, Bluemle Life Sciences Building, Room 324, Philadelphia, PA 19107, USA
| | - Kolluru D Srikanth
- Department of Neuroscience, Jefferson Synaptic Biology Center, Sidney Kimmel Medical College at Thomas Jefferson University, 233 South 10th Street, Bluemle Life Sciences Building, Room 324, Philadelphia, PA 19107, USA
| | - Matthew B Dalva
- Department of Neuroscience, Jefferson Synaptic Biology Center, Sidney Kimmel Medical College at Thomas Jefferson University, 233 South 10th Street, Bluemle Life Sciences Building, Room 324, Philadelphia, PA 19107, USA.
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12
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Saadatmehr B, Edalati M, Routier L, Mahmoudzadeh M, Safaie J, Kongolo G, Ghostine G, Wallois F, Moghimi S. Evolution of cross-frequency coupling between endogenous oscillations over the temporal cortex in very premature neonates. Cereb Cortex 2022; 33:278-289. [PMID: 35235654 PMCID: PMC10103643 DOI: 10.1093/cercor/bhac067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 01/28/2022] [Accepted: 01/29/2022] [Indexed: 01/17/2023] Open
Abstract
Temporal theta activity in coalescence with slow-wave (TTA-SW) is one of the first neurobiomarkers of the neurodevelopment of perisylvian networks in the electroencephalography (EEG). Dynamic changes in the microstructure and activity within neural networks are reflected in the EEG. Slow oscillation slope can reflect synaptic strength, and cross-frequency coupling (CFC), associated with several putative functions in adults, can reflect neural communication. Here, we investigated the evolution of CFC, in terms of SW theta phase-amplitude coupling (PAC), during the course of very early development between 25 and 32 weeks of gestational age in 23 premature neonates. We used high-resolution EEG and dipole models as spatial filters to extract the source waveforms corresponding to TTA-SW. We also carried out nonlinear phase-dependent correlation measurements to examine whether the characteristics of the SW slopes are associated with TTA-SW coupling. We show that neurodevelopment leads to temporal accumulation of the SW theta PAC toward the trough of SW. Steepness of the negative going slope of SW determined the degree of this coupling. Systematic modulation of SW-TTA CFC during development is a signature of the complex development of local cortico-cortical perisylvian networks and distant thalamo-cortical neural circuits driving this nested activity over the perisylvian networks.
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Affiliation(s)
- Bahar Saadatmehr
- Inserm UMR1105, Groupe de Recherches sur l'Analyse Multimodale de la Fonction Cérébrale, CURS, Avenue Laennec, 80036 Amiens Cedex, France
| | - Mohammadreza Edalati
- Inserm UMR1105, Groupe de Recherches sur l'Analyse Multimodale de la Fonction Cérébrale, CURS, Avenue Laennec, 80036 Amiens Cedex, France
| | - Laura Routier
- Inserm UMR1105, Groupe de Recherches sur l'Analyse Multimodale de la Fonction Cérébrale, CURS, Avenue Laennec, 80036 Amiens Cedex, France.,Inserm UMR1105, EFSN Pédiatriques, CHU Amiens sud, Avenue Laennec, 80054 Amiens Cedex, France
| | - Mahdi Mahmoudzadeh
- Inserm UMR1105, Groupe de Recherches sur l'Analyse Multimodale de la Fonction Cérébrale, CURS, Avenue Laennec, 80036 Amiens Cedex, France.,Inserm UMR1105, EFSN Pédiatriques, CHU Amiens sud, Avenue Laennec, 80054 Amiens Cedex, France
| | - Javad Safaie
- Electrical Engineering Department, Ferdowsi University of Mashhad, 9177948974 Mashhad, Iran
| | - Guy Kongolo
- Inserm UMR1105, Groupe de Recherches sur l'Analyse Multimodale de la Fonction Cérébrale, CURS, Avenue Laennec, 80036 Amiens Cedex, France.,Inserm UMR1105, NICU, CHU Amiens sud, Avenue Laennec, 80054 Amiens Cedex, France
| | - Ghida Ghostine
- Inserm UMR1105, Groupe de Recherches sur l'Analyse Multimodale de la Fonction Cérébrale, CURS, Avenue Laennec, 80036 Amiens Cedex, France.,Inserm UMR1105, NICU, CHU Amiens sud, Avenue Laennec, 80054 Amiens Cedex, France
| | - Fabrice Wallois
- Inserm UMR1105, Groupe de Recherches sur l'Analyse Multimodale de la Fonction Cérébrale, CURS, Avenue Laennec, 80036 Amiens Cedex, France.,Inserm UMR1105, EFSN Pédiatriques, CHU Amiens sud, Avenue Laennec, 80054 Amiens Cedex, France
| | - Sahar Moghimi
- Inserm UMR1105, Groupe de Recherches sur l'Analyse Multimodale de la Fonction Cérébrale, CURS, Avenue Laennec, 80036 Amiens Cedex, France.,Inserm UMR1105, EFSN Pédiatriques, CHU Amiens sud, Avenue Laennec, 80054 Amiens Cedex, France
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13
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Hendi A, Niu LG, Snow AW, Ikegami R, Wang ZW, Mizumoto K. Channel-independent function of UNC-9/Innexin in spatial arrangement of GABAergic synapses in C. elegans. eLife 2022; 11:80555. [PMID: 36378164 PMCID: PMC9665852 DOI: 10.7554/elife.80555] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 11/03/2022] [Indexed: 11/16/2022] Open
Abstract
Precise synaptic connection of neurons with their targets is essential for the proper functioning of the nervous system. A plethora of signaling pathways act in concert to mediate the precise spatial arrangement of synaptic connections. Here we show a novel role for a gap junction protein in controlling tiled synaptic arrangement in the GABAergic motor neurons in Caenorhabditis elegans, in which their axons and synapses overlap minimally with their neighboring neurons within the same class. We found that while EGL-20/Wnt controls axonal tiling, their presynaptic tiling is mediated by a gap junction protein UNC-9/Innexin, that is localized at the presynaptic tiling border between neighboring dorsal D-type GABAergic motor neurons. Strikingly, the gap junction channel activity of UNC-9 is dispensable for its function in controlling tiled presynaptic patterning. While gap junctions are crucial for the proper functioning of the nervous system as channels, our finding uncovered the novel channel-independent role of UNC-9 in synapse patterning.
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Affiliation(s)
- Ardalan Hendi
- Department of Zoology, University of British Columbia
- Life Sciences Institute, University of British Columbia
| | - Long-Gang Niu
- Department of Neuroscience, University of Connecticut Health Center
| | - Andrew William Snow
- Graduate Program in Cell and Developmental Biology, University of British Columbia
| | | | - Zhao-Wen Wang
- Department of Neuroscience, University of Connecticut Health Center
| | - Kota Mizumoto
- Department of Zoology, University of British Columbia
- Life Sciences Institute, University of British Columbia
- Graduate Program in Cell and Developmental Biology, University of British Columbia
- Djavad Mowafaghian Centre for Brain Health, University of British Columbia
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14
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Palumbos SD, Holzbaur ELF. VAB-8 stops dynein in its tracks to regulate synaptic delivery. Dev Cell 2022; 57:1789-1791. [PMID: 35944475 DOI: 10.1016/j.devcel.2022.07.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
How synaptogenic signals trigger the targeted delivery of synaptic material is a fundamental question in neuroscience. In this issue of Developmental Cell, Balseiro-Gomez et al. identify a mechanism through which local synatogenic pathways control synaptic cargo delivery.
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Affiliation(s)
- Sierra D Palumbos
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Erika L F Holzbaur
- Department of Physiology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
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15
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Hauser D, Behr K, Konno K, Schreiner D, Schmidt A, Watanabe M, Bischofberger J, Scheiffele P. Targeted proteoform mapping uncovers specific Neurexin-3 variants required for dendritic inhibition. Neuron 2022; 110:2094-2109.e10. [PMID: 35550065 PMCID: PMC9275415 DOI: 10.1016/j.neuron.2022.04.017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2021] [Revised: 02/05/2022] [Accepted: 04/15/2022] [Indexed: 12/21/2022]
Abstract
The diversification of cell adhesion molecules by alternative splicing is proposed to underlie molecular codes for neuronal wiring. Transcriptomic approaches mapped detailed cell-type-specific mRNA splicing programs. However, it has been hard to probe the synapse-specific localization and function of the resulting protein splice isoforms, or “proteoforms,” in vivo. We here apply a proteoform-centric workflow in mice to test the synapse-specific functions of the splice isoforms of the synaptic adhesion molecule Neurexin-3 (NRXN3). We uncover a major proteoform, NRXN3 AS5, that is highly expressed in GABAergic interneurons and at dendrite-targeting GABAergic terminals. NRXN3 AS5 abundance significantly diverges from Nrxn3 mRNA distribution and is gated by translation-repressive elements. Nrxn3 AS5 isoform deletion results in a selective impairment of dendrite-targeting interneuron synapses in the dentate gyrus without affecting somatic inhibition or glutamatergic perforant-path synapses. This work establishes cell- and synapse-specific functions of a specific neurexin proteoform and highlights the importance of alternative splicing regulation for synapse specification. Translational regulation guides alternative Neurexin proteoform expression NRXN3 AS5 proteoforms are concentrated at dendrite-targeting interneuron synapses A proteome-centric workflow uncovers NRXN3 AS5 interactors in vivo Loss of NRXN3 AS5 leads to selective impairments in dendritic inhibition
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Affiliation(s)
- David Hauser
- Biozentrum of the University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
| | - Katharina Behr
- Department of Biomedicine, University of Basel, Pestalozzistrasse 20, 4056 Basel, Switzerland
| | - Kohtarou Konno
- Department of Anatomy, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Dietmar Schreiner
- Biozentrum of the University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
| | - Alexander Schmidt
- Biozentrum of the University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
| | - Masahiko Watanabe
- Department of Anatomy, Faculty of Medicine, Hokkaido University, Sapporo, Japan
| | - Josef Bischofberger
- Department of Biomedicine, University of Basel, Pestalozzistrasse 20, 4056 Basel, Switzerland
| | - Peter Scheiffele
- Biozentrum of the University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland.
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16
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Udvary D, Harth P, Macke JH, Hege HC, de Kock CPJ, Sakmann B, Oberlaender M. The impact of neuron morphology on cortical network architecture. Cell Rep 2022; 39:110677. [PMID: 35417720 PMCID: PMC9035680 DOI: 10.1016/j.celrep.2022.110677] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 09/22/2021] [Accepted: 03/22/2022] [Indexed: 11/17/2022] Open
Abstract
The neurons in the cerebral cortex are not randomly interconnected. This specificity in wiring can result from synapse formation mechanisms that connect neurons, depending on their electrical activity and genetically defined identity. Here, we report that the morphological properties of the neurons provide an additional prominent source by which wiring specificity emerges in cortical networks. This morphologically determined wiring specificity reflects similarities between the neurons’ axo-dendritic projections patterns, the packing density, and the cellular diversity of the neuropil. The higher these three factors are, the more recurrent is the topology of the network. Conversely, the lower these factors are, the more feedforward is the network’s topology. These principles predict the empirically observed occurrences of clusters of synapses, cell type-specific connectivity patterns, and nonrandom network motifs. Thus, we demonstrate that wiring specificity emerges in the cerebral cortex at subcellular, cellular, and network scales from the specific morphological properties of its neuronal constituents. Neuronal network architectures reflect the morphologies of their constituents Morphology predicts nonrandom connectivity from subcellular to network scales Morphology predicts connectivity patterns consistent with those observed empirically Neuron morphology is a major source for wiring specificity in the cerebral cortex
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Affiliation(s)
- Daniel Udvary
- In Silico Brain Sciences Group, Max Planck Institute for Neurobiology of Behavior - caesar, Ludwig Erhard Allee 2, 53175 Bonn, Germany
| | - Philipp Harth
- Department of Visual and Data-Centric Computing, Zuse Institute Berlin, Takustraße 7, 14195 Berlin, Germany
| | - Jakob H Macke
- Machine Learning in Science, Tübingen University, Maria von Linden Straße 6, 72076 Tübingen, Germany
| | - Hans-Christian Hege
- Department of Visual and Data-Centric Computing, Zuse Institute Berlin, Takustraße 7, 14195 Berlin, Germany
| | - Christiaan P J de Kock
- Department of Integrative Neurophysiology, Center for Neurogenomics and Cognitive Research, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 Amsterdam, the Netherlands
| | - Bert Sakmann
- Max Planck Institute of Neurobiology, Am Klopferspitz 18, 82152 Martinsried, Germany
| | - Marcel Oberlaender
- In Silico Brain Sciences Group, Max Planck Institute for Neurobiology of Behavior - caesar, Ludwig Erhard Allee 2, 53175 Bonn, Germany.
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17
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Semaphorin 1a-mediated dendritic wiring of the Drosophila mushroom body extrinsic neurons. Proc Natl Acad Sci U S A 2022; 119:e2111283119. [PMID: 35286204 PMCID: PMC8944846 DOI: 10.1073/pnas.2111283119] [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] [Indexed: 11/18/2022] Open
Abstract
The adult Drosophila mushroom body (MB) is one of the most extensively studied neural circuits. However, how its circuit organization is established during development is unclear. In this study, we provide an initial characterization of the assembly process of the extrinsic neurons (dopaminergic neurons and MB output neurons) that target the vertical MB lobes. We probe the cellular mechanisms guiding the neurite targeting of these extrinsic neurons and demonstrate that Semaphorin 1a is required in several MB output neurons for their dendritic innervations to three specific MB lobe zones. Our study reveals several intriguing molecular and cellular principles governing assembly of the MB circuit. The Drosophila mushroom body (MB) is composed of parallel axonal fibers from intrinsic Kenyon cells (KCs). The parallel fibers are bundled into five MB lobes innervated by extrinsic neurons, including dopaminergic neurons (DANs) and MB output neurons (MBONs) that project axons or dendrites to the MB lobes, respectively. Each DAN and MBON innervates specific regions in the lobes and collectively subdivides them into 15 zones. How such modular circuit architecture is established remains unknown. Here, we followed the development of the DANs and MBONs targeting the vertical lobes of the adult MB. We found that these extrinsic neurons innervate the lobes sequentially and their neurite arborizations in the MB lobe zones are independent of each other. Ablation of DAN axons or MBON dendrites in a zone had a minimal effect on other extrinsic neurites in the same or neighboring zones, suggesting that these neurons do not use tiling mechanisms to establish zonal borders. In contrast, KC axons are necessary for the development of extrinsic neurites. Dendrites of some vertical lobe-innervating MBONs were redirected to specific zones in the horizontal lobes when their normal target lobes were missing, indicating a hierarchical organization of guidance signals for the MBON dendrites. We show that Semaphorin 1a is required in MBONs to innervate three specific MB zones, and overexpression of semaphorin 1a is sufficient to redirect DAN dendrites to these zones. Our study provides an initial characterization of the cellular and molecular mechanisms underlying the assembly process of MB extrinsic neurons.
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18
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Molecular mechanisms regulating the spatial configuration of neurites. Semin Cell Dev Biol 2022; 129:103-114. [PMID: 35248463 DOI: 10.1016/j.semcdb.2022.02.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 02/13/2022] [Accepted: 02/17/2022] [Indexed: 02/08/2023]
Abstract
Precise neural networks, composed of axons and dendrites, are the structural basis for information processing in the brain. Therefore, the correct formation of neurites is critical for accurate neural function. In particular, the three-dimensional structures of dendrites vary greatly among neuron types, and the unique shape of each dendrite is tightly linked to specific synaptic connections with innervating axons and is correlated with its information processing. Although many systems are involved in neurite formation, the developmental mechanisms that control the orientation, size, and arborization pattern of neurites definitively defines their three-dimensional structure in tissues. In this review, we summarize these regulatory mechanisms that establish proper spatial configurations of neurites, especially dendrites, in invertebrates and vertebrates.
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19
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Sando R, Ho ML, Liu X, Südhof TC. Engineered synaptic tools reveal localized cAMP signaling in synapse assembly. J Cell Biol 2022; 221:e202109111. [PMID: 34913963 PMCID: PMC8685283 DOI: 10.1083/jcb.202109111] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 11/15/2021] [Accepted: 11/30/2021] [Indexed: 12/18/2022] Open
Abstract
The physiological mechanisms driving synapse formation are elusive. Although numerous signals are known to regulate synapses, it remains unclear which signaling mechanisms organize initial synapse assembly. Here, we describe new tools, referred to as "SynTAMs" for synaptic targeting molecules, that enable localized perturbations of cAMP signaling in developing postsynaptic specializations. We show that locally restricted suppression of postsynaptic cAMP levels or of cAMP-dependent protein-kinase activity severely impairs excitatory synapse formation without affecting neuronal maturation, dendritic arborization, or inhibitory synapse formation. In vivo, suppression of postsynaptic cAMP signaling in CA1 neurons prevented formation of both Schaffer-collateral and entorhinal-CA1/temporoammonic-path synapses, suggesting a general principle. Retrograde trans-synaptic rabies virus tracing revealed that postsynaptic cAMP signaling is required for continuous replacement of synapses throughout life. Given that postsynaptic latrophilin adhesion-GPCRs drive synapse formation and produce cAMP, we suggest that spatially restricted postsynaptic cAMP signals organize assembly of postsynaptic specializations during synapse formation.
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Affiliation(s)
- Richard Sando
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA
- Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA
- Department of Pharmacology, Vanderbilt University, Nashville, TN
| | - Milan Lyndie Ho
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA
- Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA
| | - Xinran Liu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT
| | - Thomas C. Südhof
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA
- Howard Hughes Medical Institute, Stanford University School of Medicine, Stanford, CA
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20
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Fischer S, Mathias S, Stadermann A, Yang S, Schmieder V, Zeh N, Schmidt N, Richter P, Wright S, Zimmermann E, Ley Y, van der Meer J, Hartsch T, Bernloehr C, Otte K, Bradl H, Gamer M, Schulz P. Loss of a Newly Discovered microRNA in Chinese Hamster Ovary Cells Leads to Upregulation of NGNA Sialylation on Monoclonal Antibodies. Biotechnol Bioeng 2021; 119:832-844. [PMID: 34935124 PMCID: PMC9306616 DOI: 10.1002/bit.28015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 12/10/2021] [Accepted: 12/11/2021] [Indexed: 11/30/2022]
Abstract
Chinese hamster ovary (CHO) cells are known not to express appreciable levels of the sialic acid residue N‐glycolylneuraminic acid (NGNA) on monoclonal antibodies. However, we actually have identified a recombinant CHO cell line expressing an IgG with unusually high levels of NGNA sialylation (>30%). Comprehensive multi‐OMICs based experimental analyses unraveled the root cause of this atypical sialylation: (1) expression of the cytidine monophosphate‐N‐acetylneuraminic acid hydroxylase (CMAH) gene was spontaneously switched on, (2) CMAH mRNA showed an anti‐correlated expression to the newly discovered Cricetulus griseus (cgr) specific microRNA cgr‐miR‐111 and exhibits two putative miR‐111 binding sites, (3) miR‐111 expression depends on the transcription of its host gene SDK1, and (4) a single point mutation within the promoter region of the sidekick cell adhesion molecule 1 (SDK1) gene generated a binding site for the transcriptional repressor histone H4 transcription factor HINF‐P. The resulting transcriptional repression of SDK1 led to a downregulation of its co‐expressed miR‐111 and hence to a spontaneous upregulation of CMAH expression finally increasing NGNA protein sialylation.
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Affiliation(s)
- Simon Fischer
- Cell Line Development, Bioprocess Development Biologicals, Boehringer Ingelheim GmbH & Co. KG, Birkendorfer Strasse 65, 88397, Biberach, Germany
| | - Sven Mathias
- Early Stage Bioprocess Development, Bioprocess Development Biologicals, Boehringer Ingelheim GmbH & Co. KG, Birkendorfer Strasse 65, 88397, Biberach, Germany.,Institute of Applied Biotechnology, University of Applied Sciences, Hubertus-Liebrecht Strasse 35, 88400, Biberach, Germany
| | - Anna Stadermann
- Cell Line Development, Bioprocess Development Biologicals, Boehringer Ingelheim GmbH & Co. KG, Birkendorfer Strasse 65, 88397, Biberach, Germany
| | - Shumin Yang
- Process Science, Boehringer Ingelheim Fremont Inc., Fremont, CA, USA
| | - Valerie Schmieder
- Cell Line Development, Bioprocess Development Biologicals, Boehringer Ingelheim GmbH & Co. KG, Birkendorfer Strasse 65, 88397, Biberach, Germany
| | - Nikolas Zeh
- Cell Line Development, Bioprocess Development Biologicals, Boehringer Ingelheim GmbH & Co. KG, Birkendorfer Strasse 65, 88397, Biberach, Germany
| | - Nicoletta Schmidt
- Cell Line Development, Bioprocess Development Biologicals, Boehringer Ingelheim GmbH & Co. KG, Birkendorfer Strasse 65, 88397, Biberach, Germany
| | - Patrick Richter
- Cell Line Development, Bioprocess Development Biologicals, Boehringer Ingelheim GmbH & Co. KG, Birkendorfer Strasse 65, 88397, Biberach, Germany
| | - Sara Wright
- Analytical Science, Boehringer Ingelheim Fremont Inc., Fremont, CA, USA
| | - Eike Zimmermann
- Analytical Science, Boehringer Ingelheim Fremont Inc., Fremont, CA, USA
| | - Yan Ley
- Analytical Science, Boehringer Ingelheim Fremont Inc., Fremont, CA, USA
| | | | | | - Christian Bernloehr
- Early Stage Bioprocess Development, Bioprocess Development Biologicals, Boehringer Ingelheim GmbH & Co. KG, Birkendorfer Strasse 65, 88397, Biberach, Germany
| | - Kerstin Otte
- Institute of Applied Biotechnology, University of Applied Sciences, Hubertus-Liebrecht Strasse 35, 88400, Biberach, Germany
| | - Harald Bradl
- Protein Science, Bioprocess & Analytical Development, Boehringer Ingelheim GmbH & Co. KG, Birkendorfer Strasse 65, 88397, Biberach, Germany
| | - Martin Gamer
- Cell Line Development, Bioprocess Development Biologicals, Boehringer Ingelheim GmbH & Co. KG, Birkendorfer Strasse 65, 88397, Biberach, Germany
| | - Patrick Schulz
- Cell Line Development, Bioprocess Development Biologicals, Boehringer Ingelheim GmbH & Co. KG, Birkendorfer Strasse 65, 88397, Biberach, Germany
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21
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Palumbos SD, Skelton R, McWhirter R, Mitchell A, Swann I, Heifner S, Von Stetina S, Miller DM. cAMP controls a trafficking mechanism that maintains the neuron specificity and subcellular placement of electrical synapses. Dev Cell 2021; 56:3235-3249.e4. [PMID: 34741804 DOI: 10.1016/j.devcel.2021.10.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Revised: 08/30/2021] [Accepted: 10/08/2021] [Indexed: 11/28/2022]
Abstract
Electrical synapses are established between specific neurons and within distinct subcellular compartments, but the mechanisms that direct gap junction assembly in the nervous system are largely unknown. Here, we show that a developmental program tunes cAMP signaling to direct the neuron-specific assembly and placement of electrical synapses in the C. elegans motor circuit. We use live-cell imaging to visualize electrical synapses in vivo and an optogenetic assay to confirm that they are functional. In ventral A class (VA) motor neurons, the UNC-4 transcription factor blocks expression of cAMP antagonists that promote gap junction miswiring. In unc-4 mutants, VA electrical synapses are established with an alternative synaptic partner and are repositioned from the VA axon to soma. cAMP counters these effects by driving gap junction trafficking into the VA axon for electrical synapse assembly. Thus, our experiments establish that cAMP regulates gap junction trafficking for the biogenesis of functional electrical synapses.
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Affiliation(s)
- Sierra D Palumbos
- Neuroscience Program, Vanderbilt University, Nashville, TN 37212, USA
| | - Rachel Skelton
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37212, USA
| | - Rebecca McWhirter
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37212, USA
| | - Amanda Mitchell
- Vanderbilt Summer Science Academy, Vanderbilt University, Nashville, TN 37212, USA
| | - Isaiah Swann
- Vanderbilt Summer Science Academy, Vanderbilt University, Nashville, TN 37212, USA
| | | | - Stephen Von Stetina
- Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37212, USA
| | - David M Miller
- Neuroscience Program, Vanderbilt University, Nashville, TN 37212, USA; Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37212, USA.
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22
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Gutman-Wei AY, Brown SP. Mechanisms Underlying Target Selectivity for Cell Types and Subcellular Domains in Developing Neocortical Circuits. Front Neural Circuits 2021; 15:728832. [PMID: 34630048 PMCID: PMC8497978 DOI: 10.3389/fncir.2021.728832] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 08/25/2021] [Indexed: 11/25/2022] Open
Abstract
The cerebral cortex contains numerous neuronal cell types, distinguished by their molecular identity as well as their electrophysiological and morphological properties. Cortical function is reliant on stereotyped patterns of synaptic connectivity and synaptic function among these neuron types, but how these patterns are established during development remains poorly understood. Selective targeting not only of different cell types but also of distinct postsynaptic neuronal domains occurs in many brain circuits and is directed by multiple mechanisms. These mechanisms include the regulation of axonal and dendritic guidance and fine-scale morphogenesis of pre- and postsynaptic processes, lineage relationships, activity dependent mechanisms and intercellular molecular determinants such as transmembrane and secreted molecules, many of which have also been implicated in neurodevelopmental disorders. However, many studies of synaptic targeting have focused on circuits in which neuronal processes target different lamina, such that cell-type-biased connectivity may be confounded with mechanisms of laminar specificity. In the cerebral cortex, each cortical layer contains cell bodies and processes from intermingled neuronal cell types, an arrangement that presents a challenge for the development of target-selective synapse formation. Here, we address progress and future directions in the study of cell-type-biased synaptic targeting in the cerebral cortex. We highlight challenges to identifying developmental mechanisms generating stereotyped patterns of intracortical connectivity, recent developments in uncovering the determinants of synaptic target selection during cortical synapse formation, and current gaps in the understanding of cortical synapse specificity.
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Affiliation(s)
- Alan Y. Gutman-Wei
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Solange P. Brown
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
- Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD, United States
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23
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Rochon PL, Theriault C, Rangel Olguin AG, Krishnaswamy A. The cell adhesion molecule Sdk1 shapes assembly of a retinal circuit that detects localized edges. eLife 2021; 10:e70870. [PMID: 34545809 PMCID: PMC8514235 DOI: 10.7554/elife.70870] [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: 06/01/2021] [Accepted: 09/11/2021] [Indexed: 01/10/2023] Open
Abstract
Nearly 50 different mouse retinal ganglion cell (RGC) types sample the visual scene for distinct features. RGC feature selectivity arises from their synapses with a specific subset of amacrine (AC) and bipolar cell (BC) types, but how RGC dendrites arborize and collect input from these specific subsets remains poorly understood. Here we examine the hypothesis that RGCs employ molecular recognition systems to meet this challenge. By combining calcium imaging and type-specific histological stains, we define a family of circuits that express the recognition molecule Sidekick-1 (Sdk1), which include a novel RGC type (S1-RGC) that responds to local edges. Genetic and physiological studies revealed that Sdk1 loss selectively disrupts S1-RGC visual responses, which result from a loss of excitatory and inhibitory inputs and selective dendritic deficits on this neuron. We conclude that Sdk1 shapes dendrite growth and wiring to help S1-RGCs become feature selective.
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24
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Silva CA, Yalnizyan-Carson A, Fernández Busch MV, van Zwieten M, Verhage M, Lohmann C. Activity-dependent regulation of mitochondrial motility in developing cortical dendrites. eLife 2021; 10:62091. [PMID: 34491202 PMCID: PMC8423438 DOI: 10.7554/elife.62091] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 08/24/2021] [Indexed: 11/13/2022] Open
Abstract
Developing neurons form synapses at a high rate. Synaptic transmission is very energy-demanding and likely requires ATP production by mitochondria nearby. Mitochondria might be targeted to active synapses in young dendrites, but whether such motility regulation mechanisms exist is unclear. We investigated the relationship between mitochondrial motility and neuronal activity in the primary visual cortex of young mice in vivo and in slice cultures. During the first 2 postnatal weeks, mitochondrial motility decreases while the frequency of neuronal activity increases. Global calcium transients do not affect mitochondrial motility. However, individual synaptic transmission events precede local mitochondrial arrest. Pharmacological stimulation of synaptic vesicle release, but not focal glutamate application alone, stops mitochondria, suggesting that an unidentified factor co-released with glutamate is required for mitochondrial arrest. A computational model of synaptic transmission-mediated mitochondrial arrest shows that the developmental increase in synapse number and transmission frequency can contribute substantially to the age-dependent decrease of mitochondrial motility.
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Affiliation(s)
- Catia Ap Silva
- Department of Synapse and Network Development, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
| | | | - M Victoria Fernández Busch
- Department of Synapse and Network Development, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
| | - Mike van Zwieten
- Department of Synapse and Network Development, Netherlands Institute for Neuroscience, Amsterdam, Netherlands
| | - Matthijs Verhage
- Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, University Amsterdam, Amsterdam, Netherlands
| | - Christian Lohmann
- Department of Synapse and Network Development, Netherlands Institute for Neuroscience, Amsterdam, Netherlands.,Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, University Amsterdam, Amsterdam, Netherlands
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25
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Jeong S. Molecular Mechanisms Underlying Motor Axon Guidance in Drosophila. Mol Cells 2021; 44:549-556. [PMID: 34385406 PMCID: PMC8424136 DOI: 10.14348/molcells.2021.0129] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/29/2021] [Accepted: 07/02/2021] [Indexed: 11/30/2022] Open
Abstract
Decoding the molecular mechanisms underlying axon guidance is key to precise understanding of how complex neural circuits form during neural development. Although substantial progress has been made over the last three decades in identifying numerous axon guidance molecules and their functional roles, little is known about how these guidance molecules collaborate to steer growth cones to their correct targets. Recent studies in Drosophila point to the importance of the combinatorial action of guidance molecules, and further show that selective fasciculation and defasciculation at specific choice points serve as a fundamental strategy for motor axon guidance. Here, I discuss how attractive and repulsive guidance cues cooperate to ensure the recognition of specific choice points that are inextricably linked to selective fasciculation and defasciculation, and correct pathfinding decision-making.
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Affiliation(s)
- Sangyun Jeong
- Division of Life Sciences (Molecular Biology Major), Department of Bioactive Material Sciences, and Research Center of Bioactive Materials, Jeonbuk National University, Jeonju 54896, Korea
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26
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Simon F, Konstantinides N. Single-cell transcriptomics in the Drosophila visual system: Advances and perspectives on cell identity regulation, connectivity, and neuronal diversity evolution. Dev Biol 2021; 479:107-122. [PMID: 34375653 DOI: 10.1016/j.ydbio.2021.08.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 07/10/2021] [Accepted: 08/03/2021] [Indexed: 11/17/2022]
Abstract
The Drosophila visual system supports complex behaviors and shares many of its anatomical and molecular features with the vertebrate brain. Yet, it contains a much more manageable number of neurons and neuronal types. In addition to the extensive Drosophila genetic toolbox, this relative simplicity has allowed decades of work to yield a detailed account of its neuronal type diversity, morphology, connectivity and specification mechanisms. In the past three years, numerous studies have applied large scale single-cell transcriptomic approaches to the Drosophila visual system and have provided access to the complete gene expression profile of most neuronal types throughout development. This makes the fly visual system particularly well suited to perform detailed studies of the genetic mechanisms underlying the evolution and development of neuronal systems. Here, we highlight how these transcriptomic resources allow exploring long-standing biological questions under a new light. We first present the efforts made to characterize neuronal diversity in the Drosophila visual system and suggest ways to further improve this description. We then discuss current advances allowed by the single-cell datasets, and envisage how these datasets can be further leveraged to address fundamental questions regarding the regulation of neuronal identity, neuronal circuit development and the evolution of neuronal diversity.
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Affiliation(s)
- Félix Simon
- Department of Biology, New York University, New York, NY, 10003, USA.
| | - Nikolaos Konstantinides
- Department of Biology, New York University, New York, NY, 10003, USA; Institut Jacques Monod, Centre National de la Recherche Scientifique-UMR 7592, Université Paris Diderot, Paris, France.
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27
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Multiple signaling pathways are essential for synapse formation induced by synaptic adhesion molecules. Proc Natl Acad Sci U S A 2021; 118:2000173118. [PMID: 33431662 DOI: 10.1073/pnas.2000173118] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Little is known about the cellular signals that organize synapse formation. To explore what signaling pathways may be involved, we employed heterologous synapse formation assays in which a synaptic adhesion molecule expressed in a nonneuronal cell induces pre- or postsynaptic specializations in cocultured neurons. We found that interfering pharmacologically with microtubules or actin filaments impaired heterologous synapse formation, whereas blocking protein synthesis had no effect. Unexpectedly, pharmacological inhibition of c-jun N-terminal kinases (JNKs), protein kinase-A (PKA), or AKT kinases also suppressed heterologous synapse formation, while inhibition of other tested signaling pathways-such as MAP kinases or protein kinase C-did not alter heterologous synapse formation. JNK and PKA inhibitors suppressed formation of both pre- and postsynaptic specializations, whereas AKT inhibitors impaired formation of post- but not presynaptic specializations. To independently test whether heterologous synapse formation depends on AKT signaling, we targeted PTEN, an enzyme that hydrolyzes phosphatidylinositol 3-phosphate and thereby prevents AKT kinase activation, to postsynaptic sites by fusing PTEN to Homer1. Targeting PTEN to postsynaptic specializations impaired heterologous postsynaptic synapse formation induced by presynaptic adhesion molecules, such as neurexins and additionally decreased excitatory synapse function in cultured neurons. Taken together, our results suggest that heterologous synapse formation is driven via a multifaceted and multistage kinase network, with diverse signals organizing pre- and postsynaptic specializations.
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28
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Cucchiara F, Frumento P, Banfi T, Sesso G, Di Galante M, D'Ascanio P, Valvo G, Sicca F, Faraguna U. Electrophysiological features of sleep in children with Kir4.1 channel mutations and Autism-Epilepsy phenotype: a preliminary study. Sleep 2021; 43:5625283. [PMID: 31722434 PMCID: PMC7157183 DOI: 10.1093/sleep/zsz255] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2019] [Revised: 09/17/2019] [Indexed: 12/24/2022] Open
Abstract
Study Objectives Recently, a role for gain-of-function (GoF) mutations of the astrocytic potassium channel Kir4.1 (KCNJ10 gene) has been proposed in subjects with Autism–Epilepsy phenotype (AEP). Epilepsy and autism spectrum disorder (ASD) are common and complexly related to sleep disorders. We tested whether well characterized mutations in KCNJ10 could result in specific sleep electrophysiological features, paving the way to the discovery of a potentially relevant biomarker for Kir4.1-related disorders. Methods For this case–control study, we recruited seven children with ASD either comorbid or not with epilepsy and/or EEG paroxysmal abnormalities (AEP) carrying GoF mutations of KCNJ10 and seven children with similar phenotypes but wild-type for the same gene, comparing period-amplitude features of slow waves detected by fronto-central bipolar EEG derivations (F3-C3, F4-C4, and Fz-Cz) during daytime naps. Results Children with Kir4.1 mutations displayed longer slow waves periods than controls, in Fz-Cz (mean period = 112,617 ms ± SE = 0.465 in mutated versus mean period = 105,249 ms ± SE = 0.375 in controls, p < 0.001). An analog result was found in F3-C3 (mean period = 125,706 ms ± SE = 0.397 in mutated versus mean period = 120,872 ms ± SE = 0.472 in controls, p < 0.001) and F4-C4 (mean period = 127,914 ms ± SE = 0.557 in mutated versus mean period = 118,174 ms ± SE = 0.442 in controls, p < 0.001). Conclusion This preliminary finding suggests that period-amplitude slow wave features are modified in subjects carrying Kir4.1 GoF mutations. Potential clinical applications of this finding are discussed.
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Affiliation(s)
- Federico Cucchiara
- SONNOLab, Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Pisa, Italy.,Clinical Pharmacology and Pharmacogenetic Unit, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Paolo Frumento
- Unit of Biostatistics, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Tommaso Banfi
- The BioRobotics Institute, Scuola Superiore Sant'Anna, Pontedera, Italy
| | - Gianluca Sesso
- Neuropsychiatry Complex Unit, Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy
| | - Marco Di Galante
- Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, Pisa, Italy
| | - Paola D'Ascanio
- SONNOLab, Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Pisa, Italy
| | - Giulia Valvo
- Child and Adolescent Neuropsychiatric Unit, Azienda USL Toscana Sudest, Grosseto, Italy
| | - Federico Sicca
- Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, Pisa, Italy
| | - Ugo Faraguna
- SONNOLab, Department of Translational Research and of New Surgical and Medical Technologies, University of Pisa, Pisa, Italy.,Department of Developmental Neuroscience, IRCCS Stella Maris Foundation, Pisa, Italy
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29
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Jankowska M, Klimek A, Valsecchi C, Stankiewicz M, Wyszkowska J, Rogalska J. Electromagnetic field and TGF-β enhance the compensatory plasticity after sensory nerve injury in cockroach Periplaneta americana. Sci Rep 2021; 11:6582. [PMID: 33753758 PMCID: PMC7985317 DOI: 10.1038/s41598-021-85341-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2020] [Accepted: 03/01/2021] [Indexed: 11/17/2022] Open
Abstract
Recovery of function after sensory nerves injury involves compensatory plasticity, which can be observed in invertebrates. The aim of the study was the evaluation of compensatory plasticity in the cockroach (Periplaneta americana) nervous system after the sensory nerve injury and assessment of the effect of electromagnetic field exposure (EMF, 50 Hz, 7 mT) and TGF-β on this process. The bioelectrical activities of nerves (pre-and post-synaptic parts of the sensory path) were recorded under wind stimulation of the cerci before and after right cercus ablation and in insects exposed to EMF and treated with TGF-β. Ablation of the right cercus caused an increase of activity of the left presynaptic part of the sensory path. Exposure to EMF and TGF-β induced an increase of activity in both parts of the sensory path. This suggests strengthening effects of EMF and TGF-β on the insect ability to recognize stimuli after one cercus ablation. Data from locomotor tests proved electrophysiological results. The takeover of the function of one cercus by the second one proves the existence of compensatory plasticity in the cockroach escape system, which makes it a good model for studying compensatory plasticity. We recommend further research on EMF as a useful factor in neurorehabilitation.
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Affiliation(s)
- Milena Jankowska
- Department of Animal Physiology and Neurobiology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, Lwowska 1, 87-100, Toruń, Poland
| | - Angelika Klimek
- Department of Animal Physiology and Neurobiology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, Lwowska 1, 87-100, Toruń, Poland
| | - Chiara Valsecchi
- Federal University of Pampa, Campus Alegrete, Alegrete, RS, Brazil
| | - Maria Stankiewicz
- Department of Animal Physiology and Neurobiology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, Lwowska 1, 87-100, Toruń, Poland
| | - Joanna Wyszkowska
- Department of Animal Physiology and Neurobiology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, Lwowska 1, 87-100, Toruń, Poland.
| | - Justyna Rogalska
- Department of Animal Physiology and Neurobiology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, Lwowska 1, 87-100, Toruń, Poland
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30
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Takechi H, Hakeda-Suzuki S, Nitta Y, Ishiwata Y, Iwanaga R, Sato M, Sugie A, Suzuki T. Glial insulin regulates cooperative or antagonistic Golden goal/Flamingo interactions during photoreceptor axon guidance. eLife 2021; 10:66718. [PMID: 33666170 PMCID: PMC7987344 DOI: 10.7554/elife.66718] [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: 01/20/2021] [Accepted: 03/02/2021] [Indexed: 11/29/2022] Open
Abstract
Transmembrane protein Golden goal (Gogo) interacts with atypical cadherin Flamingo (Fmi) to direct R8 photoreceptor axons in the Drosophila visual system. However, the precise mechanisms underlying Gogo regulation during columnar- and layer-specific R8 axon targeting are unknown. Our studies demonstrated that the insulin secreted from surface and cortex glia switches the phosphorylation status of Gogo, thereby regulating its two distinct functions. Non-phosphorylated Gogo mediates the initial recognition of the glial protrusion in the center of the medulla column, whereas phosphorylated Gogo suppresses radial filopodia extension by counteracting Flamingo to maintain a one axon-to-one column ratio. Later, Gogo expression ceases during the midpupal stage, thus allowing R8 filopodia to extend vertically into the M3 layer. These results demonstrate that the long- and short-range signaling between the glia and R8 axon growth cones regulates growth cone dynamics in a stepwise manner, and thus shapes the entire organization of the visual system.
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Affiliation(s)
- Hiroki Takechi
- Graduate School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Satoko Hakeda-Suzuki
- Graduate School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Yohei Nitta
- Center for Transdisciplinary Research, Niigata University, Niigata, Japan.,Brain Research Institute, Niigata University, Niigata, Japan
| | - Yuichi Ishiwata
- Graduate School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Riku Iwanaga
- Graduate School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
| | - Makoto Sato
- Mathematical Neuroscience Unit, Institute for Frontier Science Initiative, Kanazawa University, Kanazawa, Japan.,Laboratory of Developmental Neurobiology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Japan
| | - Atsushi Sugie
- Center for Transdisciplinary Research, Niigata University, Niigata, Japan.,Brain Research Institute, Niigata University, Niigata, Japan
| | - Takashi Suzuki
- Graduate School of Life Science and Technology, Tokyo Institute of Technology, Yokohama, Japan
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31
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Sando R, Südhof TC. Latrophilin GPCR signaling mediates synapse formation. eLife 2021; 10:e65717. [PMID: 33646123 PMCID: PMC7954527 DOI: 10.7554/elife.65717] [Citation(s) in RCA: 37] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Accepted: 02/26/2021] [Indexed: 12/17/2022] Open
Abstract
Neural circuit assembly in the brain requires precise establishment of synaptic connections, but the mechanisms of synapse assembly remain incompletely understood. Latrophilins are postsynaptic adhesion-GPCRs that engage in trans-synaptic complexes with presynaptic teneurins and FLRTs. In mouse CA1-region neurons, Latrophilin-2 and Latrophilin-3 are essential for formation of entorhinal-cortex-derived and Schaffer-collateral-derived synapses, respectively. However, it is unknown whether latrophilins function as GPCRs in synapse formation. Here, we show that Latrophilin-2 and Latrophilin-3 exhibit constitutive GPCR activity that increases cAMP levels, which was blocked by a mutation interfering with G-protein and arrestin interactions of GPCRs. The same mutation impaired the ability of Latrophilin-2 and Latrophilin-3 to rescue the synapse-loss phenotype in Latrophilin-2 and Latrophilin-3 knockout neurons in vivo. Our results suggest that Latrophilin-2 and Latrophilin-3 require GPCR signaling in synapse formation, indicating that latrophilins promote synapse formation in the hippocampus by activating a classical GPCR-signaling pathway.
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Affiliation(s)
- Richard Sando
- Department of Molecular & Cellular Physiology and Howard Hughes Medical Institute, Stanford University School of MedicineStanfordUnited States
| | - Thomas C Südhof
- Department of Molecular & Cellular Physiology and Howard Hughes Medical Institute, Stanford University School of MedicineStanfordUnited States
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32
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Heckman EL, Doe CQ. Establishment and Maintenance of Neural Circuit Architecture. J Neurosci 2021; 41:1119-1129. [PMID: 33568445 PMCID: PMC7888231 DOI: 10.1523/jneurosci.1143-20.2020] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 11/29/2020] [Accepted: 12/09/2020] [Indexed: 02/03/2023] Open
Abstract
The ability to sense the world, process information, and navigate the environment depends on the assembly and continuous function of neural circuits in the brain. Within the past two decades, new technologies have rapidly advanced our understanding of how neural circuits are wired during development and how they are stably maintained, often for years. Electron microscopy reconstructions of model organism connectomes have provided a map of the stereotyped (and variable) connections in the brain; advanced light microscopy techniques have enabled direct observation of the cellular dynamics that underlie circuit construction and maintenance; transcriptomic and proteomic surveys of both developing and mature neurons have provided insights into the molecular and genetic programs governing circuit establishment and maintenance; and advanced genetic techniques have allowed for high-throughput discovery of wiring regulators. These tools have empowered scientists to rapidly generate and test hypotheses about how circuits establish and maintain connectivity. Thus, the set of principles governing circuit formation and maintenance have been expanded. These principles are discussed in this review.
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Affiliation(s)
- Emily L Heckman
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, Oregon 97403
| | - Chris Q Doe
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, Oregon 97403
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33
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Dorskind JM, Kolodkin AL. Revisiting and refining roles of neural guidance cues in circuit assembly. Curr Opin Neurobiol 2021; 66:10-21. [PMID: 32823181 PMCID: PMC10725571 DOI: 10.1016/j.conb.2020.07.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/16/2020] [Accepted: 07/27/2020] [Indexed: 12/14/2022]
Abstract
Neural guidance mechanisms ensure the precise targeting and synaptogenesis events essential for normal circuit function. Neuronal growth cones encounter numerous attractive and repulsive cues as they navigate toward their intermediate and final targets; temporal and spatial regulation of these responses are critical for circuit assembly. Recent work highlights the complexity of these events throughout neural development and the multifaceted functions of a wide range of guidance cues. Here, we discuss recent studies that leverage advances in genetics, single cell tracing, transcriptomics and proteomics to further our understanding of the molecular mechanisms underlying neural guidance and overall circuit organization.
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Affiliation(s)
- Joelle M Dorskind
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| | - Alex L Kolodkin
- The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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34
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Maldonado PP, Nuno-Perez A, Kirchner JH, Hammock E, Gjorgjieva J, Lohmann C. Oxytocin Shapes Spontaneous Activity Patterns in the Developing Visual Cortex by Activating Somatostatin Interneurons. Curr Biol 2021; 31:322-333.e5. [PMID: 33157028 PMCID: PMC7846278 DOI: 10.1016/j.cub.2020.10.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 08/28/2020] [Accepted: 10/09/2020] [Indexed: 01/15/2023]
Abstract
Spontaneous network activity shapes emerging neuronal circuits during early brain development prior to sensory perception. However, how neuromodulation influences this activity is not fully understood. Here, we report that the neuromodulator oxytocin differentially shapes spontaneous activity patterns across sensory cortices. In vivo, oxytocin strongly decreased the frequency and pairwise correlations of spontaneous activity events in the primary visual cortex (V1), but it did not affect the frequency of spontaneous network events in the somatosensory cortex (S1). Patch-clamp recordings in slices and RNAscope showed that oxytocin affects S1 excitatory and inhibitory neurons similarly, whereas in V1, oxytocin targets only inhibitory neurons. Somatostatin-positive (SST+) interneurons expressed the oxytocin receptor and were activated by oxytocin in V1. Accordingly, pharmacogenetic silencing of V1 SST+ interneurons fully blocked oxytocin's effect on inhibition in vitro as well its effect on spontaneous activity patterns in vivo. Thus, oxytocin decreases the excitatory/inhibitory (E/I) ratio by recruiting SST+ interneurons and modulates specific features of V1 spontaneous activity patterns that are crucial for the wiring and refining of developing sensory circuits.
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Affiliation(s)
- Paloma P Maldonado
- Department of Synapse and Network Development, Netherlands Institute for Neuroscience, 1105 BA Amsterdam, the Netherlands.
| | - Alvaro Nuno-Perez
- Department of Synapse and Network Development, Netherlands Institute for Neuroscience, 1105 BA Amsterdam, the Netherlands.
| | - Jan H Kirchner
- Max Planck Institute for Brain Research, Computation in Neural Circuits, 60438 Frankfurt am Main, Germany; TUM School of Life Sciences, Technical University of Munich, 85354 Freising, Germany.
| | - Elizabeth Hammock
- Program in Neuroscience, The Florida State University, Tallahassee, FL 32306, USA; Department of Psychology, The Florida State University, Tallahassee, FL 32306, USA.
| | - Julijana Gjorgjieva
- Max Planck Institute for Brain Research, Computation in Neural Circuits, 60438 Frankfurt am Main, Germany; TUM School of Life Sciences, Technical University of Munich, 85354 Freising, Germany.
| | - Christian Lohmann
- Department of Synapse and Network Development, Netherlands Institute for Neuroscience, 1105 BA Amsterdam, the Netherlands; Department of Functional Genomics, Center for Neurogenomics and Cognitive Research, VU University Amsterdam, 1081 HV Amsterdam, the Netherlands.
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35
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Xie Q, Brbic M, Horns F, Kolluru SS, Jones RC, Li J, Reddy AR, Xie A, Kohani S, Li Z, McLaughlin CN, Li T, Xu C, Vacek D, Luginbuhl DJ, Leskovec J, Quake SR, Luo L, Li H. Temporal evolution of single-cell transcriptomes of Drosophila olfactory projection neurons. eLife 2021; 10:e63450. [PMID: 33427646 PMCID: PMC7870145 DOI: 10.7554/elife.63450] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 01/05/2021] [Indexed: 12/18/2022] Open
Abstract
Neurons undergo substantial morphological and functional changes during development to form precise synaptic connections and acquire specific physiological properties. What are the underlying transcriptomic bases? Here, we obtained the single-cell transcriptomes of Drosophila olfactory projection neurons (PNs) at four developmental stages. We decoded the identity of 21 transcriptomic clusters corresponding to 20 PN types and developed methods to match transcriptomic clusters representing the same PN type across development. We discovered that PN transcriptomes reflect unique biological processes unfolding at each stage-neurite growth and pruning during metamorphosis at an early pupal stage; peaked transcriptomic diversity during olfactory circuit assembly at mid-pupal stages; and neuronal signaling in adults. At early developmental stages, PN types with adjacent birth order share similar transcriptomes. Together, our work reveals principles of cellular diversity during brain development and provides a resource for future studies of neural development in PNs and other neuronal types.
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Affiliation(s)
- Qijing Xie
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
- Neurosciences Graduate Program, Stanford UniversityStanfordUnited States
| | - Maria Brbic
- Department of Computer Science, Stanford UniversityStanfordUnited States
| | - Felix Horns
- Department of Bioengineering, Stanford UniversityStanfordUnited States
- Biophysics Graduate Program, Stanford UniversityStanfordUnited States
| | | | - Robert C Jones
- Department of Bioengineering, Stanford UniversityStanfordUnited States
| | - Jiefu Li
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - Anay R Reddy
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - Anthony Xie
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - Sayeh Kohani
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - Zhuoran Li
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - Colleen N McLaughlin
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - Tongchao Li
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - Chuanyun Xu
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - David Vacek
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - David J Luginbuhl
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - Jure Leskovec
- Department of Computer Science, Stanford UniversityStanfordUnited States
| | - Stephen R Quake
- Department of Bioengineering, Stanford UniversityStanfordUnited States
- Department of Applied Physics, Stanford UniversityStanfordUnited States
- Chan Zuckerberg BiohubStanfordUnited States
| | - Liqun Luo
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
| | - Hongjie Li
- Department of Biology, Howard Hughes Medical Institute, Stanford UniversityStanfordUnited States
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36
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Wang M, Witvliet D, Wu M, Kang L, Shao Z. Temperature regulates synaptic subcellular specificity mediated by inhibitory glutamate signaling. PLoS Genet 2021; 17:e1009295. [PMID: 33428618 PMCID: PMC7822552 DOI: 10.1371/journal.pgen.1009295] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 01/22/2021] [Accepted: 12/05/2020] [Indexed: 01/13/2023] Open
Abstract
Environmental factors such as temperature affect neuronal activity and development. However, it remains unknown whether and how they affect synaptic subcellular specificity. Here, using the nematode Caenorhabditis elegans AIY interneurons as a model, we found that high cultivation temperature robustly induces defects in synaptic subcellular specificity through glutamatergic neurotransmission. Furthermore, we determined that the functional glutamate is mainly released by the ASH sensory neurons and sensed by two conserved inhibitory glutamate-gated chloride channels GLC-3 and GLC-4 in AIY. Our work not only presents a novel neurotransmission-dependent mechanism underlying the synaptic subcellular specificity, but also provides a potential mechanistic insight into high-temperature-induced neurological defects.
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Affiliation(s)
- Mengqing Wang
- Department of Neurosurgery, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Daniel Witvliet
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Mengting Wu
- Department of Neurosurgery, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Lijun Kang
- Department of Neurobiology and Department of Neurosurgery of the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Zhiyong Shao
- Department of Neurosurgery, State Key Laboratory of Medical Neurobiology and MOE Frontiers Center for Brain Science, Institutes of Brain Science, Zhongshan Hospital, Fudan University, Shanghai, China
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Ohta S, Ji YR, Martin D, Wu DK. Emx2 regulates hair cell rearrangement but not positional identity within neuromasts. eLife 2020; 9:e60432. [PMID: 33377867 PMCID: PMC7806267 DOI: 10.7554/elife.60432] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 12/29/2020] [Indexed: 11/13/2022] Open
Abstract
Each hair cell (HC) precursor of zebrafish neuromasts divides to form two daughter HCs of opposite hair bundle orientations. Previously, we showed that transcription factor Emx2, expressed in only one of the daughter HCs, generates this bidirectional HC pattern (Jiang et al., 2017). Here, we asked whether Emx2 mediates this effect by changing location of hair bundle establishment or positions of HCs since daughter HCs are known to switch positions with each other. We showed this HC rearrangement, redefined as two processes named Rock and Roll, is required for positional acquisition of HCs. Apical protrusion formation of nascent HCs and planar polarity signaling are both important for the Rock and Roll. Emx2 facilitates Rock and Roll by delaying apical protrusion of its nascent HCs but it does not determine HCs' ultimate positions, indicating that Emx2 mediates bidirectional HC pattern by changing the location where hair bundle is established in HCs.
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Affiliation(s)
- Sho Ohta
- National Institute on Deafness and Other Communication Disorders, National Institutes of HealthBethesdaUnited States
| | - Young Rae Ji
- National Institute on Deafness and Other Communication Disorders, National Institutes of HealthBethesdaUnited States
| | - Daniel Martin
- Genomics and Computational Biology Core, National Institute on Deafness and Other Communication Disorders, National Institutes of HealthBethesdaUnited States
| | - Doris K Wu
- National Institute on Deafness and Other Communication Disorders, National Institutes of HealthBethesdaUnited States
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38
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Tsuboi A. LRR-Containing Oncofetal Trophoblast Glycoprotein 5T4 Shapes Neural Circuits in Olfactory and Visual Systems. Front Mol Neurosci 2020; 13:581018. [PMID: 33192298 PMCID: PMC7655536 DOI: 10.3389/fnmol.2020.581018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 09/22/2020] [Indexed: 01/19/2023] Open
Abstract
In mammals, the sensory experience can regulate the development of various brain structures, including the cortex, hippocampus, retina, and olfactory bulb (OB). Odor experience-evoked neural activity drives the development of dendrites on excitatory projection neurons in the OB, such as mitral and tufted cells, as well as inhibitory interneurons. OB interneurons are generated continuously in the subventricular zone and differentiate into granule cells (GCs) and periglomerular cells (PGCs). However, it remains unknown what role each type of OB interneuron plays in controlling olfactory behaviors. Recent studies showed that among the various types of OB interneurons, a subtype of GCs expressing oncofetal trophoblast glycoprotein 5T4 is required for simple odor detection and discrimination behaviors. Mouse 5T4 (also known as Tpbg) is a type I membrane glycoprotein whose extracellular domain contains seven leucine-rich repeats (LRRs) sandwiched between characteristic LRR-N and LRR-C regions. Recently, it was found that the developmental expression of 5T4 increases dramatically in the retina just before eye-opening. Single-cell transcriptomics further suggests that 5T4 is involved in the development and maintenance of functional synapses in a subset of retinal interneurons, including rod bipolar cells (RBCs) and amacrine cells (ACs). Collectively, 5T4, expressed in interneurons of the OB and retina, plays a key role in sensory processing in the olfactory and visual systems.
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Affiliation(s)
- Akio Tsuboi
- Graduate School of Frontier Biosciences, Osaka University, Suita, Japan
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39
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Winnubst J, Spruston N, Harris JA. Linking axon morphology to gene expression: a strategy for neuronal cell-type classification. Curr Opin Neurobiol 2020; 65:70-76. [PMID: 33181399 DOI: 10.1016/j.conb.2020.10.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 10/04/2020] [Accepted: 10/05/2020] [Indexed: 12/28/2022]
Abstract
To study how the brain drives cognition and behavior we need to understand its cellular composition. Advances in single-cell transcriptomics have revolutionized our ability to characterize neuronal diversity. To arrive at meaningful descriptions of cell types, however, gene expression must be linked to structural and functional properties. Axonal projection patterns are an appropriate measure, as they are diverse, change only gradually over time, and they influence and constrain circuit function. Here, we consider how efforts to map transcriptional and morphological diversity in the mouse brain could be linked to generate a modern taxonomy of the mouse brain.
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Affiliation(s)
- Johan Winnubst
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Nelson Spruston
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Julie A Harris
- Allen Institute for Brain Science, Seattle, WA, 98109, USA
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40
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Hiesinger PR. Brain wiring with composite instructions. Bioessays 2020; 43:e2000166. [PMID: 33145823 DOI: 10.1002/bies.202000166] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 09/27/2020] [Accepted: 09/29/2020] [Indexed: 11/12/2022]
Abstract
The quest for molecular mechanisms that guide axons or specify synaptic contacts has largely focused on molecules that intuitively relate to the idea of an "instruction." By contrast, "permissive" factors are traditionally considered background machinery without contribution to the information content of a molecularly executed instruction. In this essay, I recast this dichotomy as a continuum from permissive to instructive actions of single factors that provide relative contributions to a necessarily collaborative effort. Individual molecules or other factors do not constitute absolute instructions by themselves; they provide necessary context for each other, thereby creating a composite that defines the overall instruction. The idea of composite instructions leads to two main conclusions: first, a composite of many seemingly permissive factors can define a specific instruction even in the absence of a single dominant contributor; second, individual factors are not necessarily related intuitively to the overall instruction or phenotypic outcome.
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Affiliation(s)
- P Robin Hiesinger
- Division of Neurobiology, Institute for Biology, Freie Universität Berlin, Berlin, Germany
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41
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Valdes-Aleman J, Fetter RD, Sales EC, Heckman EL, Venkatasubramanian L, Doe CQ, Landgraf M, Cardona A, Zlatic M. Comparative Connectomics Reveals How Partner Identity, Location, and Activity Specify Synaptic Connectivity in Drosophila. Neuron 2020; 109:105-122.e7. [PMID: 33120017 PMCID: PMC7837116 DOI: 10.1016/j.neuron.2020.10.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 08/12/2020] [Accepted: 10/05/2020] [Indexed: 01/30/2023]
Abstract
The mechanisms by which synaptic partners recognize each other and establish appropriate numbers of connections during embryonic development to form functional neural circuits are poorly understood. We combined electron microscopy reconstruction, functional imaging of neural activity, and behavioral experiments to elucidate the roles of (1) partner identity, (2) location, and (3) activity in circuit assembly in the embryonic nerve cord of Drosophila. We found that postsynaptic partners are able to find and connect to their presynaptic partners even when these have been shifted to ectopic locations or silenced. However, orderly positioning of axon terminals by positional cues and synaptic activity is required for appropriate numbers of connections between specific partners, for appropriate balance between excitatory and inhibitory connections, and for appropriate functional connectivity and behavior. Our study reveals with unprecedented resolution the fine connectivity effects of multiple factors that work together to control the assembly of neural circuits.
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Affiliation(s)
- Javier Valdes-Aleman
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA; Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Richard D Fetter
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Emily C Sales
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
| | - Emily L Heckman
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
| | | | - Chris Q Doe
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
| | - Matthias Landgraf
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Albert Cardona
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA; Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK; MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Marta Zlatic
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA 20147, USA; Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK; MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Francis Crick Avenue, Cambridge CB2 0QH, UK.
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42
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Synapse type-specific proteomic dissection identifies IgSF8 as a hippocampal CA3 microcircuit organizer. Nat Commun 2020; 11:5171. [PMID: 33057002 PMCID: PMC7560607 DOI: 10.1038/s41467-020-18956-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 09/23/2020] [Indexed: 12/20/2022] Open
Abstract
Excitatory and inhibitory neurons are connected into microcircuits that generate circuit output. Central in the hippocampal CA3 microcircuit is the mossy fiber (MF) synapse, which provides powerful direct excitatory input and indirect feedforward inhibition to CA3 pyramidal neurons. Here, we dissect its cell-surface protein (CSP) composition to discover novel regulators of MF synaptic connectivity. Proteomic profiling of isolated MF synaptosomes uncovers a rich CSP composition, including many CSPs without synaptic function and several that are uncharacterized. Cell-surface interactome screening identifies IgSF8 as a neuronal receptor enriched in the MF pathway. Presynaptic Igsf8 deletion impairs MF synaptic architecture and robustly decreases the density of bouton filopodia that provide feedforward inhibition. Consequently, IgSF8 loss impairs excitation/inhibition balance and increases excitability of CA3 pyramidal neurons. Our results provide insight into the CSP landscape and interactome of a specific excitatory synapse and reveal IgSF8 as a critical regulator of CA3 microcircuit connectivity and function. Mossy fiber synapses are key in CA3 microcircuit function. Here, the authors profile the mossy fiber synapse proteome and cell-surface interactome. They uncover a diverse repertoire of cell-surface proteins and identify the receptor IgSF8 as a regulator of CA3 microcircuit connectivity and function.
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43
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Ng SY, Ljubicic V. Recent insights into neuromuscular junction biology in Duchenne muscular dystrophy: Impacts, challenges, and opportunities. EBioMedicine 2020; 61:103032. [PMID: 33039707 PMCID: PMC7648118 DOI: 10.1016/j.ebiom.2020.103032] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/28/2020] [Accepted: 09/11/2020] [Indexed: 12/13/2022] Open
Abstract
Duchenne muscular dystrophy (DMD) is the most common and relentless form of muscular dystrophy. The pleiotropic effects of dystrophin deficiency include remarkable impacts on neuromuscular junction (NMJ) structure and function. Some of these alterations contribute to the severe muscle wasting and weakness that distinguish DMD, while others attempt to compensate for them. Experimental approaches that correct NMJ biology in pre-clinical models of DMD attenuate disease progression and improve functional outcomes, which suggests that targeting the NMJ may be an effective therapeutic strategy for DMD patients. The objectives of this review are to 1) survey the distinctions in NMJ structure, function, and gene expression in the dystrophic context as compared to the healthy condition, and 2) summarize the efforts, opportunities and challenges to correct NMJ biology in DMD. This information will expand our basic understanding of neuromuscular biology and may be useful for designing novel NMJ-targeted drug or behavioural strategies to mitigate the dystrophic pathology and other disorders of the neuromuscular system.
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Affiliation(s)
- Sean Y Ng
- Department of Kinesiology, McMaster University, Hamilton L8S 4L8, Ontario, Canada
| | - Vladimir Ljubicic
- Department of Kinesiology, McMaster University, Hamilton L8S 4L8, Ontario, Canada.
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Abstract
Many of the immunoglobulin superfamily (IgSF) molecules play pivotal roles in cell communication. The Sidekick (Sdk) gene, first described in Drosophila, encodes the single-pass transmembrane protein, Sdk, which is one of the largest among IgSF membrane proteins. Sdk first appeared in multicellular animals during the Precambrian age and later evolved to Sdk1 and Sdk2 in vertebrates by gene duplication. In flies, a single Sdk is involved in positioning photoreceptor neurons and their axons in the visual system and is responsible for dynamically rearranging cell shapes by strictly populating tricellular adherens junctions in epithelia. In vertebrates, Sdk1 and Sdk2 are expressed by unique sets of cell types and distinctively participate in the formation and/or maintenance of neural circuits in the retina, indicating that they are determinants of synaptic specificity. These functions are mediated by specific homophilic binding of their ectodomains and by intracellular association with PDZ scaffold proteins. Recent human genetic studies as well as animal experiments implicate that Sdk genes may influence various neurodevelopmental and psychiatric disorders, such as autism spectrum disorders, attention-deficit hyperactivity disorder, addiction, and depression. The gigantic Sdk1 gene is susceptible to erratic gene rearrangements or mutations in both somatic and germ-line cells, potentially contributing to neurological disorders and some types of cancers. This review summarizes what is known about the structure and roles of Sdks.
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Affiliation(s)
- Masahito Yamagata
- Department of Molecular and Cellular Biology, Center for Brain Science, Harvard University, Cambridge, MA, United States
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45
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Interplay between cell-adhesion molecules governs synaptic wiring of cone photoreceptors. Proc Natl Acad Sci U S A 2020; 117:23914-23924. [PMID: 32879010 DOI: 10.1073/pnas.2009940117] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Establishment of functional synaptic connections in a selective manner is essential for nervous system operation. In mammalian retinas, rod and cone photoreceptors form selective synaptic connections with different classes of bipolar cells (BCs) to propagate light signals. While there has been progress in elucidating rod wiring, molecular mechanisms used by cones to establish functional synapses with BCs have remained unknown. Using an unbiased proteomic strategy in cone-dominant species, we identified the cell-adhesion molecule ELFN2 to be pivotal for the functional wiring of cones with the ON type of BC. It is selectively expressed in cones and transsynaptically recruits the key neurotransmitter receptor mGluR6 in ON-BCs to enable synaptic transmission. Remarkably, ELFN2 in cone terminals functions in synergy with a related adhesion molecule, ELFN1, and their concerted interplay during development specifies selective wiring and transmission of cone signals. These findings identify a synaptic connectivity mechanism of cones and illustrate how interplay between adhesion molecules and postsynaptic transmitter receptors orchestrates functional synaptic specification in a neural circuit.
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46
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Rangel Olguin AG, Rochon PL, Krishnaswamy A. New Optical Tools to Study Neural Circuit Assembly in the Retina. Front Neural Circuits 2020; 14:44. [PMID: 32848633 PMCID: PMC7424070 DOI: 10.3389/fncir.2020.00044] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2020] [Accepted: 06/23/2020] [Indexed: 12/17/2022] Open
Abstract
During development, neurons navigate a tangled thicket of thousands of axons and dendrites to synapse with just a few specific targets. This phenomenon termed wiring specificity, is critical to the assembly of neural circuits and the way neurons manage this feat is only now becoming clear. Recent studies in the mouse retina are shedding new insight into this process. They show that specific wiring arises through a series of stages that include: directed axonal and dendritic growth, the formation of neuropil layers, positioning of such layers, and matching of co-laminar synaptic partners. Each stage appears to be directed by a distinct family of recognition molecules, suggesting that the combinatorial expression of such family members might act as a blueprint for retinal connectivity. By reviewing the evidence in support of each stage, and by considering their underlying molecular mechanisms, we attempt to synthesize these results into a wiring model which generates testable predictions for future studies. Finally, we conclude by highlighting new optical methods that could be used to address such predictions and gain further insight into this fundamental process.
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47
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Oentaryo MJ, Tse ACK, Lee CW. Neuronal MT1-MMP mediates ECM clearance and Lrp4 cleavage for agrin deposition and signaling in presynaptic development. J Cell Sci 2020; 133:jcs246710. [PMID: 32591486 DOI: 10.1242/jcs.246710] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Accepted: 06/16/2020] [Indexed: 08/31/2023] Open
Abstract
Agrin is a crucial factor that induces postsynaptic differentiation at neuromuscular junctions (NMJs), but how secreted agrin is locally deposited in the context of extracellular matrix (ECM) environment and its function in presynaptic differentiation remain largely unclear. Here, we report that the proteolytic activity of neuronal membrane-type 1 matrix metalloproteinase (MT1-MMP; also known as MMP14) facilitates agrin deposition and signaling during presynaptic development at NMJs. Firstly, agrin deposition along axons exhibits a time-dependent increase in cultured neurons that requires MMP-mediated focal ECM degradation. Next, local agrin stimulation induces the clustering of mitochondria and synaptic vesicles, two well-known presynaptic markers, and regulates vesicular trafficking and surface insertion of MT1-MMP. MMP inhibitor or MT1-MMP knockdown suppresses agrin-induced presynaptic differentiation, which can be rescued by treatment with the ectodomain of low-density lipoprotein receptor-related protein 4 (Lrp4). Finally, neuronal MT1-MMP knockdown inhibits agrin deposition and nerve-induced acetylcholine receptor clustering in nerve-muscle co-cultures and affects synaptic structures at Xenopus NMJs in vivo Collectively, our results demonstrate a previously unappreciated role of agrin, as well as dual functions of neuronal MT1-MMP proteolytic activity in orchestrating agrin deposition and signaling, in presynaptic development.
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Affiliation(s)
- Marilyn Janice Oentaryo
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
| | - Anna Chung-Kwan Tse
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
| | - Chi Wai Lee
- School of Biomedical Sciences, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
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48
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Kirrel3-Mediated Synapse Formation Is Attenuated by Disease-Associated Missense Variants. J Neurosci 2020; 40:5376-5388. [PMID: 32503885 DOI: 10.1523/jneurosci.3058-19.2020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Revised: 05/24/2020] [Accepted: 05/26/2020] [Indexed: 12/12/2022] Open
Abstract
Missense variants in Kirrel3 are repeatedly identified as risk factors for autism spectrum disorder and intellectual disability, but it has not been reported if or how these variants disrupt Kirrel3 function. Previously, we studied Kirrel3 loss of function using KO mice and showed that Kirrel3 is a synaptic adhesion molecule necessary to form one specific type of hippocampal synapse in vivo Here, we developed an in vitro, gain-of-function assay for Kirrel3 using neuron cultures prepared from male and female mice and rats. We find that WT Kirrel3 induces synapse formation selectively between Kirrel3-expressing neurons via homophilic, transcellular binding. We tested six disease-associated Kirrel3 missense variants and found that five attenuate this synaptogenic function. All variants tested traffic to the cell surface and localize to synapses similar to WT Kirrel3. Two tested variants lack homophilic transcellular binding, which likely accounts for their reduced synaptogenic function. Interestingly, we also identified variants that bind in trans but cannot induce synapses, indicating that Kirrel3 transcellular binding is necessary but not sufficient for its synaptogenic function. Collectively, these results suggest Kirrel3 functions as a synaptogenic, cell-recognition molecule, and this function is attenuated by missense variants associated with autism spectrum disorder and intellectual disability. Thus, we provide critical insight to the mechanism of Kirrel3 function and the consequences of missense variants associated with autism and intellectual disability.SIGNIFICANCE STATEMENT Here, we advance our understanding of mechanisms mediating target-specific synapse formation by providing evidence that Kirrel3 transcellular interactions mediate target recognition and signaling to promote synapse development. Moreover, this study tests the effects of disease-associated Kirrel3 missense variants on synapse formation, and thereby, increases understanding of the complex etiology of neurodevelopmental disorders arising from rare missense variants in synaptic genes.
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49
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Semaphorin-Mediated Corticospinal Axon Elimination Depends on the Activity-Induced Bax/Bak-Caspase Pathway. J Neurosci 2020; 40:5402-5412. [PMID: 32471877 DOI: 10.1523/jneurosci.3190-18.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 05/03/2020] [Accepted: 05/04/2020] [Indexed: 12/11/2022] Open
Abstract
Axon guidance molecules and neuronal activity have been implicated in the establishment and refinement of neural circuits during development. It is unclear, however, whether these guidance molecule- and activity-dependent mechanisms interact with one another to shape neural circuit formation. The formation of corticospinal (CS) circuits, which are essential for voluntary movements, involves both guidance molecule- and activity-dependent components during development. We previously showed that semaphorin6D (Sema6D)-plexinA1 (PlexA1) signaling eliminates ipsilateral projections of CS neurons in the spinal cord, while other studies demonstrate that CS projections to the spinal cord are eliminated in an activity-dependent manner. Here we show that inhibition of cortical neurons during postnatal development causes defects in elimination of ipsilateral CS projections in mice. We further show that mice that lack the activity-dependent Bax/Bak pathway or caspase-9 similarly exhibit defects in elimination of ipsilateral CS projections, suggesting that the activity-dependent Bax/Bak-caspase-9 pathway is essential for the removal of ipsilateral CS projections. Interestingly, either inhibition of neuronal activity in the cortex or deletion of Bax/Bak in mice causes a reduction in PlexA1 protein expression in corticospinal neurons. Finally, intracortical microstimulation induces activation of only contralateral forelimb muscles in control mice, whereas it induces activation of both contralateral and ipsilateral muscles in mice with cortical inhibition, suggesting that the ipsilaterally projecting CS axons that have been maintained in mice with cortical inhibition form functional connections. Together, these results provide evidence of a potential link between the repellent signaling of Sema6D-PlexA1 and neuronal activity to regulate axon elimination.SIGNIFICANCE STATEMENT Both axon guidance molecules and neuronal activity regulate axon elimination to refine neuronal circuits during development. However, the degree to which these mechanisms operate independently or cooperatively to guide network generation is unclear. Here, we show that neuronal activity-driven Bax/Bak-caspase signaling induces expression of the PlexA1 receptor for the repellent Sema6D molecule in corticospinal neurons (CSNs). This cascade eliminates ipsilateral projections of CSNs in the spinal cord during early postnatal development. The absence of PlexA1, neuronal activity, Bax and Bak, or caspase-9 leads to the maintenance of ipsilateral projections of CSNs, which can form functional connections with spinal neurons. Together, these studies reveal how the Sema6D-PlexA1 signaling and neuronal activity may play a cooperative role in refining CS axonal projections.
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de Vivo L, Nagai H, De Wispelaere N, Spano GM, Marshall W, Bellesi M, Nemec KM, Schiereck SS, Nagai M, Tononi G, Cirelli C. Evidence for sleep-dependent synaptic renormalization in mouse pups. Sleep 2020; 42:5543176. [PMID: 31374117 PMCID: PMC6802737 DOI: 10.1093/sleep/zsz184] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 06/13/2019] [Indexed: 12/14/2022] Open
Abstract
In adolescent and adult brains several molecular, electrophysiological, and ultrastructural measures of synaptic strength are higher after wake than after sleep [1, 2]. These results support the proposal that a core function of sleep is to renormalize the increase in synaptic strength associated with ongoing learning during wake, to reestablish cellular homeostasis and avoid runaway potentiation, synaptic saturation, and memory interference [2, 3]. Before adolescence however, when the brain is still growing and many new synapses are forming, sleep is widely believed to promote synapse formation and growth. To assess the role of sleep on synapses early in life, we studied 2-week-old mouse pups (both sexes) whose brain is still undergoing significant developmental changes, but in which sleep and wake are easy to recognize. In two strains (CD-1, YFP-H) we found that pups spend ~50% of the day asleep and show an immediate increase in total sleep duration after a few hours of enforced wake, indicative of sleep homeostasis. In YFP-H pups we then used serial block-face electron microscopy to examine whether the axon-spine interface (ASI), an ultrastructural marker of synaptic strength, changes between wake and sleep. We found that the ASI of cortical synapses (layer 2, motor cortex) was on average 33.9% smaller after sleep relative to after extended wake and the differences between conditions were consistent with multiplicative scaling. Thus, the need for sleep-dependent synaptic renormalization may apply also to the young, pre-weaned cerebral cortex, at least in the superficial layers of the primary motor area.
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Affiliation(s)
- Luisa de Vivo
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI
| | - Hirotaka Nagai
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI
| | | | | | - William Marshall
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI
| | - Michele Bellesi
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI
| | | | | | - Midori Nagai
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI
| | - Giulio Tononi
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI
| | - Chiara Cirelli
- Department of Psychiatry, University of Wisconsin-Madison, Madison, WI
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