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Wang YW, Wreden CC, Levy M, Meng JL, Marshall ZD, MacLean J, Heckscher E. Sequential addition of neuronal stem cell temporal cohorts generates a feed-forward circuit in the Drosophila larval nerve cord. eLife 2022; 11:79276. [PMID: 35723253 PMCID: PMC9333992 DOI: 10.7554/elife.79276] [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: 04/06/2022] [Accepted: 06/17/2022] [Indexed: 02/06/2023] Open
Abstract
How circuits self-assemble starting from neuronal stem cells is a fundamental question in developmental neurobiology. Here, we addressed how neurons from different stem cell lineages wire with each other to form a specific circuit motif. In Drosophila larvae, we combined developmental genetics (twin-spot mosaic analysis with a repressible cell marker, multi-color flip out, permanent labeling) with circuit analysis (calcium imaging, connectomics, network science). For many lineages, neuronal progeny are organized into subunits called temporal cohorts. Temporal cohorts are subsets of neurons born within a tight time window that have shared circuit-level function. We find sharp transitions in patterns of input connectivity at temporal cohort boundaries. In addition, we identify a feed-forward circuit that encodes the onset of vibration stimuli. This feed-forward circuit is assembled by preferential connectivity between temporal cohorts from different lineages. Connectivity does not follow the often-cited early-to-early, late-to-late model. Instead, the circuit is formed by sequential addition of temporal cohorts from different lineages, with circuit output neurons born before circuit input neurons. Further, we generate new tools for the fly community. Our data raise the possibility that sequential addition of neurons (with outputs oldest and inputs youngest) could be one fundamental strategy for assembling feed-forward circuits.
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Affiliation(s)
- Yi-wen Wang
- Department of Molecular Genetics and Cell Biology, University of ChicagoChicagoUnited States
| | - Chris C Wreden
- Department of Molecular Genetics and Cell Biology, University of ChicagoChicagoUnited States
| | - Maayan Levy
- Committee on Computational Neuroscience, University of ChicagoChicagoUnited States
| | - Julia L Meng
- Program in Cell and Molecular Biology, University of ChicagoChicagoUnited States
| | - Zarion D Marshall
- Committee on Neurobiology, University of ChicagoChicagoUnited States
| | - Jason MacLean
- Committee on Computational Neuroscience, University of ChicagoChicagoUnited States,Committee on Neurobiology, University of ChicagoChicagoUnited States,Department of Neurobiology, University of ChicagoChicagoUnited States,University of Chicago Neuroscience InstituteChicagoUnited States
| | - Ellie Heckscher
- Department of Molecular Genetics and Cell Biology, University of ChicagoChicagoUnited States,Committee on Computational Neuroscience, University of ChicagoChicagoUnited States,Program in Cell and Molecular Biology, University of ChicagoChicagoUnited States,Department of Neurobiology, University of ChicagoChicagoUnited States,University of Chicago Neuroscience InstituteChicagoUnited States
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2
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The Five Faces of Notch Signalling During Drosophila melanogaster Embryonic CNS Development. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1218:39-58. [PMID: 32060870 DOI: 10.1007/978-3-030-34436-8_3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
During central nervous system (CNS) development, a complex series of events play out, starting with the establishment of neural progenitor cells, followed by their asymmetric division and formation of lineages and the differentiation of neurons and glia. Studies in the Drosophila melanogaster embryonic CNS have revealed that the Notch signal transduction pathway plays at least five different and distinct roles during these events. Herein, we review these many faces of Notch signalling and discuss the mechanisms that ensure context-dependent and compartment-dependent signalling. We conclude by discussing some outstanding issues regarding Notch signalling in this system, which likely have bearing on Notch signalling in many species.
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Crews ST. Drosophila Embryonic CNS Development: Neurogenesis, Gliogenesis, Cell Fate, and Differentiation. Genetics 2019; 213:1111-1144. [PMID: 31796551 PMCID: PMC6893389 DOI: 10.1534/genetics.119.300974] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Accepted: 09/26/2019] [Indexed: 01/04/2023] Open
Abstract
The Drosophila embryonic central nervous system (CNS) is a complex organ consisting of ∼15,000 neurons and glia that is generated in ∼1 day of development. For the past 40 years, Drosophila developmental neuroscientists have described each step of CNS development in precise molecular genetic detail. This has led to an understanding of how an intricate nervous system emerges from a single cell. These studies have also provided important, new concepts in developmental biology, and provided an essential model for understanding similar processes in other organisms. In this article, the key genes that guide Drosophila CNS development and how they function is reviewed. Features of CNS development covered in this review are neurogenesis, gliogenesis, cell fate specification, and differentiation.
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Affiliation(s)
- Stephen T Crews
- Department of Biochemistry and Biophysics, Integrative Program for Biological and Genome Sciences, School of Medicine, The University of North Carolina at Chapel Hill, North Carolina 27599
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Otsuki L, Brand AH. Dorsal-Ventral Differences in Neural Stem Cell Quiescence Are Induced by p57 KIP2/Dacapo. Dev Cell 2019; 49:293-300.e3. [PMID: 30905769 PMCID: PMC6486397 DOI: 10.1016/j.devcel.2019.02.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 01/28/2019] [Accepted: 02/15/2019] [Indexed: 12/27/2022]
Abstract
Quiescent neural stem cells (NSCs) in the adult brain are regenerative cells that could be activated therapeutically to repair damage. It is becoming apparent that quiescent NSCs exhibit heterogeneity in their propensity for activation and in the progeny that they generate. We discovered recently that NSCs undergo quiescence in either G0 or G2 in the Drosophila brain, challenging the notion that all quiescent stem cells are G0 arrested. We found that G2-quiescent NSCs become activated prior to G0 NSCs. Here, we show that the cyclin-dependent kinase inhibitor Dacapo (Dap; ortholog of p57KIP2) determines whether NSCs enter G0 or G2 quiescence during embryogenesis. We demonstrate that the dorsal patterning factor, Muscle segment homeobox (Msh; ortholog of MSX1/2/3) binds directly to the Dap locus and induces Dap expression in dorsal NSCs, resulting in G0 arrest, while more ventral NSCs undergo G2 quiescence. Our results reveal region-specific regulation of stem cell quiescence. p57/Dap determines whether neural stem cells enter G0 quiescence or G2 quiescence The dorsal patterning factor MSX/Msh promotes p57/Dap expression and G0 quiescence Ventral stem cells instead express NKX/Vnd and undergo G2 quiescence Stem cells undergo distinct types of quiescence depending on axial identity
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Affiliation(s)
- Leo Otsuki
- The Gurdon Institute and Department of Physiology, Development and Neuroscience, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Andrea H Brand
- The Gurdon Institute and Department of Physiology, Development and Neuroscience, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK.
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Miyares RL, Lee T. Temporal control of Drosophila central nervous system development. Curr Opin Neurobiol 2018; 56:24-32. [PMID: 30500514 DOI: 10.1016/j.conb.2018.10.016] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 10/30/2018] [Indexed: 12/19/2022]
Abstract
A complex nervous system requires precise numbers of various neuronal types produced with exquisite spatiotemporal control. This striking diversity is generated by a limited number of neural stem cells (NSC), where spatial and temporal patterning intersect. Drosophila is a genetically tractable model system that has significant advantages for studying stem cell biology and neuronal fate specification. Here we review the latest findings in the rich literature of temporal patterning of neuronal identity in the Drosophila central nervous system. Rapidly changing consecutive transcription factors expressed in NSCs specify short series of neurons with considerable differences. More slowly progressing changes are orchestrated by NSC intrinsic temporal factor gradients which integrate extrinsic signals to coordinate nervous system and organismal development.
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Affiliation(s)
- Rosa Linda Miyares
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Tzumin Lee
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA.
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Rickert C, Lüer K, Vef O, Technau GM. Progressive derivation of serially homologous neuroblast lineages in the gnathal CNS of Drosophila. PLoS One 2018; 13:e0191453. [PMID: 29415052 PMCID: PMC5802887 DOI: 10.1371/journal.pone.0191453] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 01/04/2018] [Indexed: 11/18/2022] Open
Abstract
Along the anterior-posterior axis the central nervous system is subdivided into segmental units (neuromeres) the composition of which is adapted to their region-specific functional requirements. In Drosophila melanogaster each neuromere is formed by a specific set of identified neural stem cells (neuroblasts, NBs). In the thoracic and anterior abdominal region of the embryonic ventral nerve cord segmental sets of NBs resemble the ground state (2nd thoracic segment, which does not require input of homeotic genes), and serial (segmental) homologs generate similar types of lineages. The three gnathal head segments form a transitional zone between the brain and the ventral nerve cord. It has been shown recently that although all NBs of this zone are serial homologs of NBs in more posterior segments, they progressively differ from the ground state in anterior direction (labial > maxillary > mandibular segment) with regard to numbers and expression profiles. To study the consequences of their derived characters we traced the embryonic lineages of gnathal NBs using the Flybow and DiI-labelling techniques. For a number of clonal types serial homology is rather clearly reflected by their morphology (location and projection patterns) and cell specific markers, despite of reproducible segment-specific differences. However, many lineages, particularly in the mandibular segment, show a degree of derivation that impedes their assignment to ground state serial homologs. These findings demonstrate that differences in gene expression profiles of gnathal NBs go along with anteriorly directed progressive derivation in the composition of their lineages. Furthermore, lineage sizes decrease from labial to mandibular segments, which in concert with decreasing NB-numbers lead to reduced volumes of gnathal neuromeres, most significantly in the mandibular segment.
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Affiliation(s)
- Christof Rickert
- Institute of Developmental Biology and Neurobiology, University of Mainz, J.-J.-Becherweg 32,Mainz, Germany
- * E-mail: (CR); (GMT)
| | - Karin Lüer
- Institute of Developmental Biology and Neurobiology, University of Mainz, J.-J.-Becherweg 32,Mainz, Germany
| | - Olaf Vef
- Institute of Developmental Biology and Neurobiology, University of Mainz, J.-J.-Becherweg 32,Mainz, Germany
| | - Gerhard M. Technau
- Institute of Developmental Biology and Neurobiology, University of Mainz, J.-J.-Becherweg 32,Mainz, Germany
- * E-mail: (CR); (GMT)
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Syed MH, Mark B, Doe CQ. Steroid hormone induction of temporal gene expression in Drosophila brain neuroblasts generates neuronal and glial diversity. eLife 2017; 6:26287. [PMID: 28394252 PMCID: PMC5403213 DOI: 10.7554/elife.26287] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 04/09/2017] [Indexed: 12/14/2022] Open
Abstract
An important question in neuroscience is how stem cells generate neuronal diversity. During Drosophila embryonic development, neural stem cells (neuroblasts) sequentially express transcription factors that generate neuronal diversity; regulation of the embryonic temporal transcription factor cascade is lineage-intrinsic. In contrast, larval neuroblasts generate longer ~50 division lineages, and currently only one mid-larval molecular transition is known: Chinmo/Imp/Lin-28+ neuroblasts transition to Syncrip+ neuroblasts. Here we show that the hormone ecdysone is required to down-regulate Chinmo/Imp and activate Syncrip, plus two late neuroblast factors, Broad and E93. We show that Seven-up triggers Chinmo/Imp to Syncrip/Broad/E93 transition by inducing expression of the Ecdysone receptor in mid-larval neuroblasts, rendering them competent to respond to the systemic hormone ecdysone. Importantly, late temporal gene expression is essential for proper neuronal and glial cell type specification. This is the first example of hormonal regulation of temporal factor expression in Drosophila embryonic or larval neural progenitors.
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Affiliation(s)
- Mubarak Hussain Syed
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Brandon Mark
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Chris Q Doe
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
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Monedero Cobeta I, Salmani BY, Thor S. Anterior-Posterior Gradient in Neural Stem and Daughter Cell Proliferation Governed by Spatial and Temporal Hox Control. Curr Biol 2017; 27:1161-1172. [PMID: 28392108 DOI: 10.1016/j.cub.2017.03.023] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 02/09/2017] [Accepted: 03/10/2017] [Indexed: 01/16/2023]
Abstract
A readily evident feature of animal central nervous systems (CNSs), apparent in all vertebrates and many invertebrates alike, is its "wedge-like" appearance, with more cells generated in anterior than posterior regions. This wedge could conceivably be established by an antero-posterior (A-P) gradient in the number of neural progenitor cells, their proliferation behaviors, and/or programmed cell death (PCD). However, the contribution of each of these mechanisms, and the underlying genetic programs, are not well understood. Building upon recent progress in the Drosophila melanogaster (Drosophila) ventral nerve cord (VNC), we address these issues in a comprehensive manner. We find that, although PCD plays a role in controlling cell numbers along the A-P axis, the main driver of the wedge is a gradient of daughter proliferation, with divisions directly generating neurons (type 0) being more prevalent posteriorly and dividing daughters (type I) more prevalent anteriorly. In addition, neural progenitor (NB) cell-cycle exit occurs earlier posteriorly. The gradient of type I > 0 daughter proliferation switch and NB exit combine to generate radically different average lineage sizes along the A-P axis, differing by more than 3-fold in cell number. We find that the Hox homeotic genes, expressed in overlapping A-P gradients and with a late temporal onset in NBs, trigger the type I > 0 daughter proliferation switch and NB exit. Given the highly evolutionarily conserved expression of overlapping Hox homeotic genes in the CNS, our results point to a common mechanism for generating the CNS wedge.
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Affiliation(s)
- Ignacio Monedero Cobeta
- Department of Clinical and Experimental Medicine, Linkoping University, 58185 Linkoping, Sweden
| | | | - Stefan Thor
- Department of Clinical and Experimental Medicine, Linkoping University, 58185 Linkoping, Sweden.
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Gunnar E, Bivik C, Starkenberg A, Thor S. sequoia Controls the type I>0 daughter proliferation switch in the developing Drosophila nervous system. J Cell Sci 2016. [DOI: 10.1242/jcs.198549] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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