1
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Malin JA, Chen YC, Simon F, Keefer E, Desplan C. Spatial patterning controls neuron numbers in the Drosophila visual system. Dev Cell 2024; 59:1132-1145.e6. [PMID: 38531357 PMCID: PMC11078608 DOI: 10.1016/j.devcel.2024.03.004] [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: 08/10/2023] [Revised: 12/18/2023] [Accepted: 03/01/2024] [Indexed: 03/28/2024]
Abstract
Neurons must be made in the correct proportions to communicate with the appropriate synaptic partners and form functional circuits. In the Drosophila visual system, multiple subtypes of distal medulla (Dm) inhibitory interneurons are made in distinct, reproducible numbers-from 5 to 800 per optic lobe. These neurons are born from a crescent-shaped neuroepithelium called the outer proliferation center (OPC), which can be subdivided into specific domains based on transcription factor and growth factor expression. We fate mapped Dm neurons and found that more abundant neural types are born from larger neuroepithelial subdomains, while less abundant subtypes are born from smaller ones. Additionally, morphogenetic Dpp/BMP signaling provides a second layer of patterning that subdivides the neuroepithelium into smaller domains to provide more granular control of cell proportions. Apoptosis appears to play a minor role in regulating Dm neuron abundance. This work describes an underappreciated mechanism for the regulation of neuronal stoichiometry.
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Affiliation(s)
- Jennifer A Malin
- Department of Biology, New York University, New York, NY 10003, USA.
| | - Yen-Chung Chen
- Department of Biology, New York University, New York, NY 10003, USA
| | - Félix Simon
- Department of Biology, New York University, New York, NY 10003, USA
| | - Evelyn Keefer
- Department of Biology, New York University, New York, NY 10003, USA
| | - Claude Desplan
- Department of Biology, New York University, New York, NY 10003, USA.
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2
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Sagner A. Temporal patterning of the vertebrate developing neural tube. Curr Opin Genet Dev 2024; 86:102179. [PMID: 38490162 DOI: 10.1016/j.gde.2024.102179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2023] [Revised: 12/29/2023] [Accepted: 02/20/2024] [Indexed: 03/17/2024]
Abstract
The chronologically ordered generation of distinct cell types is essential for the establishment of neuronal diversity and the formation of neuronal circuits. Recently, single-cell transcriptomic analyses of various areas of the developing vertebrate nervous system have provided evidence for the existence of a shared temporal patterning program that partitions neurons based on the timing of neurogenesis. In this review, I summarize the findings that lead to the proposal of this shared temporal program before focusing on the developing spinal cord to discuss how temporal patterning in general and this program specifically contributes to the ordered formation of neuronal circuits.
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Affiliation(s)
- Andreas Sagner
- Institut für Biochemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstraße 17, 91054 Erlangen, Germany.
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3
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Zhang Y, Li X. Development of the Drosophila Optic Lobe. Cold Spring Harb Protoc 2024; 2024:108156. [PMID: 37758285 DOI: 10.1101/pdb.top108156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/03/2023]
Abstract
The Drosophila visual system has been a great model to study fundamental questions in neurobiology, such as neural fate specification, axon guidance, circuit formation, and information processing. The Drosophila visual system is composed of the compound eye and the optic lobe. The optic lobe is divided into four neuropils-namely, the lamina, medulla, lobula, and lobula plate. There are around 200 types of optic lobe neurons, which wire together to form a complex neural structure to processes visual information. These neurons are derived from two neuroepithelial structures-namely, the outer proliferation center (OPC) and the inner proliferation center (IPC), in the larval brain. Recent work on the Drosophila optic lobe has revealed basic principles underlying the development of this complex neural structure, and immunostaining has been a key tool in these studies. Here, we provide a brief overview of the Drosophila optic lobe structure and development, as revealed by immunostaining. First, we introduce the structure of the adult optic lobe. Then, we summarize recent advances in the study of neural fate specification during development of different parts of the optic lobe. Last, we briefly summarize general aspects of axon guidance and neuropil assembly in the optic lobe. With this review, we aim to familiarize readers with this complex neural structure and highlight the power of this great model to study neural development to facilitate further developmental and functional studies using this system.
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Affiliation(s)
- Yu Zhang
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - Xin Li
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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4
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Simon F, Holguera I, Chen YC, Malin J, Valentino P, Erclik T, Desplan C. High-throughput identification of the spatial origins of Drosophila optic lobe neurons using single-cell mRNA-sequencing. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.05.578975. [PMID: 38370610 PMCID: PMC10871188 DOI: 10.1101/2024.02.05.578975] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
The medulla is the largest neuropil of the Drosophila optic lobe. It contains about 100 neuronal types that have been comprehensively characterized morphologically and molecularly. These neuronal types are specified from a larval neuroepithelium called the Outer Proliferation Center (OPC) via the integration of temporal, spatial, and Notch-driven mechanisms. Although we recently characterized the temporal windows of origin of all medulla neurons, as well as their Notch status, their spatial origins remained unknown. Here, we isolated cells from different OPC spatial domains and performed single-cell mRNA-sequencing to identify the neuronal types produced in these domains. This allowed us to characterize in a high-throughput manner the spatial origins of all medulla neurons and to identify two new spatial subdivisions of the OPC. Moreover, our work shows that the most abundant neuronal types are produced from epithelial domains of different sizes despite being present in a similar number of copies. Combined with our previously published scRNA-seq developmental atlas of the optic lobe, our work opens the door for further studies on how specification factor expression in progenitors impacts gene expression in developing and adult neurons.
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Affiliation(s)
- Félix Simon
- Department of Biology, New York University, New York, NY 10003, USA
| | - Isabel Holguera
- Department of Biology, New York University, New York, NY 10003, USA
| | - Yen-Chung Chen
- Department of Biology, New York University, New York, NY 10003, USA
| | - Jennifer Malin
- Department of Biology, New York University, New York, NY 10003, USA
| | - Priscilla Valentino
- Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 1A1, Canada
| | - Ted Erclik
- Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 1A1, Canada
| | - Claude Desplan
- Department of Biology, New York University, New York, NY 10003, USA
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5
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Dillon NR, Manning L, Hirono K, Doe CQ. Seven-up acts in neuroblasts to specify adult central complex neuron identity and initiate neuroblast decommissioning. Development 2024; 151:dev202504. [PMID: 38230563 PMCID: PMC10906098 DOI: 10.1242/dev.202504] [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: 11/03/2023] [Accepted: 12/22/2023] [Indexed: 01/18/2024]
Abstract
An unanswered question in neurobiology is how are diverse neuron cell types generated from a small number of neural stem cells? In the Drosophila larval central brain, there are eight bilateral Type 2 neuroblast (T2NB) lineages that express a suite of early temporal factors followed by a different set of late temporal factors and generate the majority of the central complex (CX) neurons. The early-to-late switch is triggered by the orphan nuclear hormone receptor Seven-up (Svp), yet little is known about how this Svp-dependent switch is involved in specifying CX neuron identities. Here, we: (1) birth date the CX neurons P-EN and P-FN (early and late, respectively); (2) show that Svp is transiently expressed in all early T2NBs; and (3) show that loss of Svp expands the population of early born P-EN neurons at the expense of late born P-FN neurons. Furthermore, in the absence of Svp, T2NBs fail decommissioning and abnormally extend their lineage into week-old adults. We conclude that Svp is required to specify CX neuron identity, as well as to initiate T2NB decommissioning.
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Affiliation(s)
- Noah R. Dillon
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
| | - Laurina Manning
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
| | - Keiko Hirono
- 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
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6
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Xu C, Ramos TB, Marshall OJ, Doe CQ. Notch signaling and Bsh homeodomain activity are integrated to diversify Drosophila lamina neuron types. eLife 2024; 12:RP90136. [PMID: 38193901 PMCID: PMC10945509 DOI: 10.7554/elife.90136] [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] [Indexed: 01/10/2024] Open
Abstract
Notch signaling is an evolutionarily conserved pathway for specifying binary neuronal fates, yet how it specifies different fates in different contexts remains elusive. In our accompanying paper, using the Drosophila lamina neuron types (L1-L5) as a model, we show that the primary homeodomain transcription factor (HDTF) Bsh activates secondary HDTFs Ap (L4) and Pdm3 (L5) and specifies L4/L5 neuronal fates. Here we test the hypothesis that Notch signaling enables Bsh to differentially specify L4 and L5 fates. We show asymmetric Notch signaling between newborn L4 and L5 neurons, but they are not siblings; rather, Notch signaling in L4 is due to Delta expression in adjacent L1 neurons. While Notch signaling and Bsh expression are mutually independent, Notch is necessary and sufficient for Bsh to specify L4 fate over L5. The NotchON L4, compared to NotchOFF L5, has a distinct open chromatin landscape which allows Bsh to bind distinct genomic loci, leading to L4-specific identity gene transcription. We propose a novel model in which Notch signaling is integrated with the primary HDTF activity to diversify neuron types by directly or indirectly generating a distinct open chromatin landscape that constrains the pool of genes that a primary HDTF can activate.
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Affiliation(s)
- Chundi Xu
- Institute of Neuroscience, Howard Hughes Medical Institute, University of OregonEugeneUnited States
| | - Tyler B Ramos
- Institute of Neuroscience, Howard Hughes Medical Institute, University of OregonEugeneUnited States
| | - Owen J Marshall
- Menzies Institute for Medical Research, University of TasmaniaHobartAustralia
| | - Chris Q Doe
- Institute of Neuroscience, Howard Hughes Medical Institute, University of OregonEugeneUnited States
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7
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Xu C, Ramos TB, Rogers EM, Reiser MB, Doe CQ. Homeodomain proteins hierarchically specify neuronal diversity and synaptic connectivity. eLife 2024; 12:RP90133. [PMID: 38180023 PMCID: PMC10942767 DOI: 10.7554/elife.90133] [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] [Indexed: 01/06/2024] Open
Abstract
How our brain generates diverse neuron types that assemble into precise neural circuits remains unclear. Using Drosophila lamina neuron types (L1-L5), we show that the primary homeodomain transcription factor (HDTF) brain-specific homeobox (Bsh) is initiated in progenitors and maintained in L4/L5 neurons to adulthood. Bsh activates secondary HDTFs Ap (L4) and Pdm3 (L5) and specifies L4/L5 neuronal fates while repressing the HDTF Zfh1 to prevent ectopic L1/L3 fates (control: L1-L5; Bsh-knockdown: L1-L3), thereby generating lamina neuronal diversity for normal visual sensitivity. Subsequently, in L4 neurons, Bsh and Ap function in a feed-forward loop to activate the synapse recognition molecule DIP-β, thereby bridging neuronal fate decision to synaptic connectivity. Expression of a Bsh:Dam, specifically in L4, reveals Bsh binding to the DIP-β locus and additional candidate L4 functional identity genes. We propose that HDTFs function hierarchically to coordinate neuronal molecular identity, circuit formation, and function. Hierarchical HDTFs may represent a conserved mechanism for linking neuronal diversity to circuit assembly and function.
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Affiliation(s)
- Chundi Xu
- Institute of Neuroscience, Howard Hughes Medical Institute, University of OregonEugeneUnited States
| | - Tyler B Ramos
- Institute of Neuroscience, Howard Hughes Medical Institute, University of OregonEugeneUnited States
| | - Edward M Rogers
- Janelia Research Campus, Howard Hughes Medical Institute, Helix DriveAshburnUnited States
| | - Michael B Reiser
- Janelia Research Campus, Howard Hughes Medical Institute, Helix DriveAshburnUnited States
| | - Chris Q Doe
- Institute of Neuroscience, Howard Hughes Medical Institute, University of OregonEugeneUnited States
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8
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Dillon NR, Manning L, Hirono K, Doe CQ. Seven-up acts in neuroblasts to specify adult central complex neuron identity and initiate neuroblast decommissioning. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.02.565340. [PMID: 37961302 PMCID: PMC10635090 DOI: 10.1101/2023.11.02.565340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
An open question in neurobiology is how diverse neuron cell types are generated from a small number of neural stem cells. In the Drosophila larval central brain, there are eight bilateral Type 2 neuroblast (T2NB) lineages that express a suite of early temporal factors followed by a different set of late temporal factors and generate the majority of the central complex (CX) neurons. The early-to-late switch is triggered by the orphan nuclear hormone receptor Seven-up (Svp), yet little is known about this Svp-dependent switch in specifying CX neuron identities. Here, we (i) birthdate the CX neurons P-EN and P-FN (early and late, respectively); (ii) show that Svp is transiently expressed in all early T2NBs; and (iii) show that loss of Svp expands the population of early born P-EN neurons at the expense of late born P-FN neurons. Furthermore, in the absence of Svp, T2NBs fail decommissioning and abnormally extend their lineage into week-old adults. We conclude that Svp is required to specify CX neuron identity, as well as to initiate T2NB decommissioning.
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Affiliation(s)
- Noah R. Dillon
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Laurina Manning
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Keiko Hirono
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
| | - Chris Q. Doe
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403
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9
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Wani AR, Chowdhury B, Luong J, Chaya GM, Patel K, Isaacman-Beck J, Shafer O, Kayser MS, Syed MH. Stem cell-specific ecdysone signaling regulates the development and function of a Drosophila sleep homeostat. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.29.560022. [PMID: 37873323 PMCID: PMC10592846 DOI: 10.1101/2023.09.29.560022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Complex behaviors arise from neural circuits that are assembled from diverse cell types. Sleep is a conserved and essential behavior, yet little is known regarding how the nervous system generates neuron types of the sleep-wake circuit. Here, we focus on the specification of Drosophila sleep-promoting neurons-long-field tangential input neurons that project to the dorsal layers of the fan-shaped body neuropil in the central complex (CX). We use lineage analysis and genetic birth dating to identify two bilateral Type II neural stem cells that generate these dorsal fan-shaped body (dFB) neurons. We show that adult dFB neurons express Ecdysone-induced protein E93, and loss of Ecdysone signaling or E93 in Type II NSCs results in the misspecification of the adult dFB neurons. Finally, we show that E93 knockdown in Type II NSCs affects adult sleep behavior. Our results provide insight into how extrinsic hormonal signaling acts on NSCs to generate neuronal diversity required for adult sleep behavior. These findings suggest that some adult sleep disorders might derive from defects in stem cell-specific temporal neurodevelopmental programs.
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Affiliation(s)
- Adil R Wani
- Neural Diversity Lab, Department of Biology, University of New Mexico, 219 Yale Blvd Ne, 87131 Albuquerque, NM, USA
| | - Budhaditya Chowdhury
- The Advanced Science Research Center, City University of New York, New York, NY 10031, USA
| | - Jenny Luong
- Department of Psychiatry, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Gonzalo Morales Chaya
- Neural Diversity Lab, Department of Biology, University of New Mexico, 219 Yale Blvd Ne, 87131 Albuquerque, NM, USA
| | - Krishna Patel
- Neural Diversity Lab, Department of Biology, University of New Mexico, 219 Yale Blvd Ne, 87131 Albuquerque, NM, USA
| | | | - Orie Shafer
- The Advanced Science Research Center, City University of New York, New York, NY 10031, USA
| | - Matthew S. Kayser
- Department of Psychiatry, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
- Chronobiology Sleep Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Mubarak Hussain Syed
- Neural Diversity Lab, Department of Biology, University of New Mexico, 219 Yale Blvd Ne, 87131 Albuquerque, NM, USA
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10
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Lago-Baldaia I, Cooper M, Seroka A, Trivedi C, Powell GT, Wilson SW, Ackerman SD, Fernandes VM. A Drosophila glial cell atlas reveals a mismatch between transcriptional and morphological diversity. PLoS Biol 2023; 21:e3002328. [PMID: 37862379 PMCID: PMC10619882 DOI: 10.1371/journal.pbio.3002328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Revised: 11/01/2023] [Accepted: 09/08/2023] [Indexed: 10/22/2023] Open
Abstract
Morphology is a defining feature of neuronal identity. Like neurons, glia display diverse morphologies, both across and within glial classes, but are also known to be morphologically plastic. Here, we explored the relationship between glial morphology and transcriptional signature using the Drosophila central nervous system (CNS), where glia are categorised into 5 main classes (outer and inner surface glia, cortex glia, ensheathing glia, and astrocytes), which show within-class morphological diversity. We analysed and validated single-cell RNA sequencing data of Drosophila glia in 2 well-characterised tissues from distinct developmental stages, containing distinct circuit types: the embryonic ventral nerve cord (VNC) (motor) and the adult optic lobes (sensory). Our analysis identified a new morphologically and transcriptionally distinct surface glial population in the VNC. However, many glial morphological categories could not be distinguished transcriptionally, and indeed, embryonic and adult astrocytes were transcriptionally analogous despite differences in developmental stage and circuit type. While we did detect extensive within-class transcriptomic diversity for optic lobe glia, this could be explained entirely by glial residence in the most superficial neuropil (lamina) and an associated enrichment for immune-related gene expression. In summary, we generated a single-cell transcriptomic atlas of glia in Drosophila, and our extensive in vivo validation revealed that glia exhibit more diversity at the morphological level than was detectable at the transcriptional level. This atlas will serve as a resource for the community to probe glial diversity and function.
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Affiliation(s)
- Inês Lago-Baldaia
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Maia Cooper
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Austin Seroka
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, Oregon, United States of America
| | - Chintan Trivedi
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Gareth T. Powell
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Stephen W. Wilson
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Sarah D. Ackerman
- Department of Pathology and Immunology, Brain Immunology and Glia Center, Washington University School of Medicine, Saint Louis, Missouri, United States of America
- Department of Developmental Biology, Washington University School of Medicine, Saint Louis, Missouri, United States of America
| | - Vilaiwan M. Fernandes
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
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11
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Temporal control of neuronal wiring. Semin Cell Dev Biol 2023; 142:81-90. [PMID: 35644877 DOI: 10.1016/j.semcdb.2022.05.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 05/13/2022] [Accepted: 05/16/2022] [Indexed: 12/22/2022]
Abstract
Wiring an animal brain is a complex process involving a staggering number of cell-types born at different times and locations in the developing brain. Incorporation of these cells into precise circuits with high fidelity is critical for animal survival and behavior. Assembly of neuronal circuits is heavily dependent upon proper timing of wiring programs, requiring neurons to express specific sets of genes (sometimes transiently) at the right time in development. While cell-type specificity of genetic programs regulating wiring has been studied in detail, mechanisms regulating proper timing and coordination of these programs across cell-types are only just beginning to emerge. In this review, we discuss some temporal regulators of wiring programs and how their activity is controlled over time and space. A common feature emerges from these temporal regulators - they are induced by cell-extrinsic cues and control transcription factors capable of regulating a highly cell-type specific set of target genes. Target specificity in these contexts comes from cell-type specific transcription factors. We propose that the spatiotemporal specificity of wiring programs is controlled by the combinatorial activity of temporal programs and cell-type specific transcription factors. Going forward, a better understanding of temporal regulators will be key to understanding the mechanisms underlying brain wiring, and will be critical for the development of in vitro models like brain organoids.
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12
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Sen SQ. Generating neural diversity through spatial and temporal patterning. Semin Cell Dev Biol 2023; 142:54-66. [PMID: 35738966 DOI: 10.1016/j.semcdb.2022.06.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Revised: 06/08/2022] [Accepted: 06/08/2022] [Indexed: 11/19/2022]
Abstract
The nervous system consists of a vast diversity of neurons and glia that are accurately assembled into functional circuits. What are the mechanisms that generate these diverse cell types? During development, an epithelial sheet with neurogenic potential is initially regionalised into spatially restricted domains of gene expression. From this, pools of neural stem cells (NSCs) with distinct molecular profiles and the potential to generate different neuron types, are specified. These NSCs then divide asymmetrically to self-renew and generate post-mitotic neurons or glia. As NSCs age, they experience transitions in gene expression, which further allows them to generate different neurons or glia over time. Versions of this general template of spatial and temporal patterning operate during the development of different parts of different nervous systems. Here, I cover our current knowledge of Drosophila brain and optic lobe development as well as the development of the vertebrate cortex and spinal cord within the framework of this above template. I highlight where our knowledge is lacking, where mechanisms beyond these might operate, and how the emergence of new technologies might help address unanswered questions.
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Affiliation(s)
- Sonia Q Sen
- Tata Institute for Genetics and Society, UAS-GKVK Campus, Bellary Road, Bangalore, India.
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13
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Zhang Y, Lowe S, Ding AZ, Li X. Axon targeting of Drosophila medulla projection neurons requires diffusible Netrin and is coordinated with neuroblast temporal patterning. Cell Rep 2023; 42:112144. [PMID: 36821439 PMCID: PMC10155933 DOI: 10.1016/j.celrep.2023.112144] [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: 01/13/2022] [Revised: 10/19/2022] [Accepted: 02/07/2023] [Indexed: 02/24/2023] Open
Abstract
How axon guidance pathways are utilized in coordination with temporal and spatial patterning of neural progenitors to regulate neuropil assembly is not well understood. We study this question in the Drosophila medulla using the transmedullary (Tm) projection neurons that target lobula through the inner optic chiasm (IOC). We demonstrate that the Netrin pathway plays multiple roles in guidance of Tm axons and that temporal patterning of medulla neuroblasts determines pioneer versus follower Tm neurons during this process. Loss of Frazzled (Fra) in early-born pioneer Tm neurons leads to IOC defects, while loss of Fra from follower neurons does not affect the IOC. In the follower projection neurons, Fra is required in other targeting steps including lobula branch extension and layer-specific targeting. Furthermore, different from other identified scenarios of Netrin/Fra involved axon guidance in Drosophila, we demonstrate that diffusible Netrin is required for the correct axon targeting and optic lobe organization.
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Affiliation(s)
- Yu Zhang
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Scott Lowe
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Andrew Z Ding
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Xin Li
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
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14
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Zhang Y, Lowe S, Ding AZ, Li X. Notch-dependent binary fate choice regulates the Netrin pathway to control axon guidance of Drosophila visual projection neurons. Cell Rep 2023; 42:112143. [PMID: 36821442 PMCID: PMC10124989 DOI: 10.1016/j.celrep.2023.112143] [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: 01/13/2022] [Revised: 10/22/2022] [Accepted: 02/07/2023] [Indexed: 02/24/2023] Open
Abstract
Notch-dependent binary fate choice between sister neurons is one of the mechanisms to generate neural diversity. How these upstream neural fate specification programs regulate downstream effector genes to control axon targeting and neuropil assembly remains less well understood. Here, we report that Notch-dependent binary fate choice in Drosophila medulla neurons is required to regulate the Netrin axon guidance pathway, which controls targeting of transmedullary (Tm) neurons to lobula. In medulla neurons of Notch-on hemilineage composed of mostly lobula-targeting neurons, Notch signaling is required to activate the expression of Netrin-B and repress the expression of its repulsive receptor Unc-5. Turning off Unc-5 is necessary for Tm neurons to target lobula. Furthermore, Netrin-B provided by Notch-on medulla neurons is required for correct targeting of Tm axons from later-generated medulla columns. Thus, the coordinate regulation of Netrin pathway components by Notch signaling ensures correct targeting of Tm axons and contributes to the neuropil assembly.
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Affiliation(s)
- Yu Zhang
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Scott Lowe
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Andrew Z Ding
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
| | - Xin Li
- Department of Cell and Developmental Biology, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
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15
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Javed A, Santos-França PL, Mattar P, Cui A, Kassem F, Cayouette M. Ikaros family proteins redundantly regulate temporal patterning in the developing mouse retina. Development 2023; 150:286611. [PMID: 36537580 DOI: 10.1242/dev.200436] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Accepted: 12/06/2022] [Indexed: 12/24/2022]
Abstract
Temporal identity factors regulate competence of neural progenitors to generate specific cell types in a time-dependent manner, but how they operate remains poorly defined. In the developing mouse retina, the Ikaros zinc-finger transcription factor Ikzf1 regulates production of early-born cell types, except cone photoreceptors. In this study we show that, during early stages of retinal development, another Ikaros family protein, Ikzf4, functions redundantly with Ikzf1 to regulate cone photoreceptor production. Using CUT&RUN and functional assays, we show that Ikzf4 binds and represses genes involved in late-born rod photoreceptor specification, hence favoring cone production. At late stages, when Ikzf1 is no longer expressed in progenitors, we show that Ikzf4 re-localizes to target genes involved in gliogenesis and is required for Müller glia production. We report that Ikzf4 regulates Notch signaling genes and is sufficient to activate the Hes1 promoter through two Ikzf GGAA-binding motifs, suggesting a mechanism by which Ikzf4 may influence gliogenesis. These results uncover a combinatorial role for Ikaros family members during nervous system development and provide mechanistic insights on how they temporally regulate cell fate output.
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Affiliation(s)
- Awais Javed
- Cellular Neurobiology Research Unit, Institut de recherches cliniques de Montréal (IRCM), Montreal H2W 1R7, Canada
- Molecular Biology Program, Université de Montréal, Montreal H3T 1J4, Canada
| | - Pedro L Santos-França
- Cellular Neurobiology Research Unit, Institut de recherches cliniques de Montréal (IRCM), Montreal H2W 1R7, Canada
- Molecular Biology Program, Université de Montréal, Montreal H3T 1J4, Canada
| | - Pierre Mattar
- Cellular Neurobiology Research Unit, Institut de recherches cliniques de Montréal (IRCM), Montreal H2W 1R7, Canada
| | - Allie Cui
- Cellular Neurobiology Research Unit, Institut de recherches cliniques de Montréal (IRCM), Montreal H2W 1R7, Canada
| | - Fatima Kassem
- Cellular Neurobiology Research Unit, Institut de recherches cliniques de Montréal (IRCM), Montreal H2W 1R7, Canada
- Integrated Program in Neuroscience, McGill University, Montreal H3A 0G4, Canada
| | - Michel Cayouette
- Cellular Neurobiology Research Unit, Institut de recherches cliniques de Montréal (IRCM), Montreal H2W 1R7, Canada
- Molecular Biology Program, Université de Montréal, Montreal H3T 1J4, Canada
- Integrated Program in Neuroscience, McGill University, Montreal H3A 0G4, Canada
- Department of Medicine, Université de Montréal, Montreal H3T 1J4, Canada
- Department of Anatomy and Cell Biology, Division of Experimental Medicine, McGill University, Montreal H3A 0G4, Canada
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16
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Özel MN, Gibbs CS, Holguera I, Soliman M, Bonneau R, Desplan C. Coordinated control of neuronal differentiation and wiring by sustained transcription factors. Science 2022; 378:eadd1884. [PMID: 36480601 DOI: 10.1126/science.add1884] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The large diversity of cell types in nervous systems presents a challenge in identifying the genetic mechanisms that encode it. Here, we report that nearly 200 distinct neurons in the Drosophila visual system can each be defined by unique combinations of on average 10 continuously expressed transcription factors. We show that targeted modifications of this terminal selector code induce predictable conversions of neuronal fates that appear morphologically and transcriptionally complete. Cis-regulatory analysis of open chromatin links one of these genes to an upstream patterning factor that specifies neuronal fates in stem cells. Experimentally validated network models describe the synergistic regulation of downstream effectors by terminal selectors and ecdysone signaling during brain wiring. Our results provide a generalizable framework of how specific fates are implemented in postmitotic neurons.
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Affiliation(s)
| | - Claudia Skok Gibbs
- Flatiron Institute, Center for Computational Biology, Simons Foundation, New York, NY 10010, USA.,Center for Data Science, New York University, New York, NY 10003, USA
| | - Isabel Holguera
- Department of Biology, New York University, New York, NY 10003, USA
| | - Mennah Soliman
- Department of Biology, New York University, New York, NY 10003, USA
| | - Richard Bonneau
- Department of Biology, New York University, New York, NY 10003, USA.,Flatiron Institute, Center for Computational Biology, Simons Foundation, New York, NY 10010, USA.,Center for Data Science, New York University, New York, NY 10003, USA
| | - Claude Desplan
- Department of Biology, New York University, New York, NY 10003, USA.,New York University Abu Dhabi, Saadiyat Island, Abu Dhabi, United Arab Emirates
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17
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Ma W, Li X, Yang L, Pan J, Chen Y, Lu Y, Dong X, Li D, Gan W. High VSX1 expression promotes the aggressiveness of clear cell renal cell carcinoma by transcriptionally regulating FKBP10. J Transl Med 2022; 20:554. [PMID: 36463181 PMCID: PMC9719260 DOI: 10.1186/s12967-022-03772-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 11/12/2022] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND Clear cell renal cell carcinoma (ccRCC), the most common urological malignancy, has an unfavorable prognosis and an unknown mechanism of progression. Through survival analyses screening of The Cancer Genome Atlas (TCGA) dataset, we identified Visual system homeobox1 (VSX1) as a novel potential prognostic biomarker in ccRCC and subsequently investigated the oncogenic role of VSX1 in ccRCC. METHODS The differential expression of VSX1 in human tumors and the clinical prognoses were analyzed in the TCGA dataset and Gene Expression Omnibus. Spearman's correlation coefficient was determined for the correlation analysis of VSX1 expression and other genes of interest. The roles of VSX1 in cell proliferation, invasion, and migration of ccRCC cells were evaluated via the CCK-8 assay, colony formation assay, and Transwell assay, respectively. Further results were demonstrated by western blotting, immunohistochemistry, qRT-PCR, tumor sphere formation, flow cytometry, and the dual‑luciferase reporter assay. RESULTS VSX1 mRNA upregulation was generally observed in multiple human malignancies from the TCGA database and was confirmed in ccRCC clinical specimens from our department. High VSX1 expression usually indicated that overall and disease-free survival were unfavorable for patients with ccRCC. In terms of mechanism, knockdown or overexpression of VSX1 affected ccRCC aggressiveness in vitro. The dual-luciferase reporter gene assay implied that VSX1 overexpression significantly increased the luciferase activity of TMEM44, FKBP10, and TRIB3, which indicated that VSX1 promoted ccRCC invasiveness via transcriptional regulation of these genes. The significantly enhanced growth in vitro that was induced by stable VSX1 overexpression was almost restored to normal by the knockdown of FKBP10. CONCLUSIONS This study demonstrated that VSX1 was a novel prognostic biomarker in ccRCC and that high VSX1 expression promoted cell proliferation, invasion, and migration in ccRCC via transcriptional activation of downstream target genes.
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Affiliation(s)
- Wenliang Ma
- grid.41156.370000 0001 2314 964XDepartment of Urology, Affiliated Drum Tower Hospital, Medical School of Nanjing University, No. 321 Zhongshan Road, Nanjing, 210008 Jiangsu People’s Republic of China
| | - Xin Li
- grid.41156.370000 0001 2314 964XImmunology and Reproduction Biology Laboratory & State Key Laboratory of Analytical Chemistry for Life Science, Medical School, Nanjing University, Nanjing, 210093 Jiangsu People’s Republic of China
| | - Lei Yang
- grid.41156.370000 0001 2314 964XImmunology and Reproduction Biology Laboratory & State Key Laboratory of Analytical Chemistry for Life Science, Medical School, Nanjing University, Nanjing, 210093 Jiangsu People’s Republic of China
| | - Jun Pan
- grid.41156.370000 0001 2314 964XDepartment of Urology, Affiliated Drum Tower Hospital, Medical School of Nanjing University, No. 321 Zhongshan Road, Nanjing, 210008 Jiangsu People’s Republic of China
| | - Yi Chen
- grid.41156.370000 0001 2314 964XImmunology and Reproduction Biology Laboratory & State Key Laboratory of Analytical Chemistry for Life Science, Medical School, Nanjing University, Nanjing, 210093 Jiangsu People’s Republic of China
| | - Yanwen Lu
- grid.41156.370000 0001 2314 964XDepartment of Urology, Affiliated Drum Tower Hospital, Medical School of Nanjing University, No. 321 Zhongshan Road, Nanjing, 210008 Jiangsu People’s Republic of China
| | - Xiang Dong
- grid.41156.370000 0001 2314 964XDepartment of Urology, Affiliated Drum Tower Hospital, Medical School of Nanjing University, No. 321 Zhongshan Road, Nanjing, 210008 Jiangsu People’s Republic of China
| | - Dongmei Li
- grid.41156.370000 0001 2314 964XImmunology and Reproduction Biology Laboratory & State Key Laboratory of Analytical Chemistry for Life Science, Medical School, Nanjing University, Nanjing, 210093 Jiangsu People’s Republic of China ,grid.41156.370000 0001 2314 964XJiangsu Key Laboratory of Molecular Medicine, Nanjing University, Nanjing, 210093 Jiangsu China
| | - Weidong Gan
- grid.41156.370000 0001 2314 964XDepartment of Urology, Affiliated Drum Tower Hospital, Medical School of Nanjing University, No. 321 Zhongshan Road, Nanjing, 210008 Jiangsu People’s Republic of China
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18
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Valentino P, Erclik T. Spalt and disco define the dorsal-ventral neuroepithelial compartments of the developing Drosophila medulla. Genetics 2022; 222:iyac145. [PMID: 36135799 PMCID: PMC9630984 DOI: 10.1093/genetics/iyac145] [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: 06/14/2022] [Accepted: 09/14/2022] [Indexed: 11/14/2022] Open
Abstract
Spatial patterning of neural stem cell populations is a powerful mechanism by which to generate neuronal diversity. In the developing Drosophila medulla, the symmetrically dividing neuroepithelial cells of the outer proliferation center crescent are spatially patterned by the nonoverlapping expression of 3 transcription factors: Vsx1 in the center, Optix in the adjacent arms, and Rx in the tips. These spatial genes compartmentalize the outer proliferation center and, together with the temporal patterning of neuroblasts, act to diversify medulla neuronal fates. The observation that the dorsal and ventral halves of the outer proliferation center also grow as distinct compartments, together with the fact that a subset of neuronal types is generated from only one half of the crescent, suggests that additional transcription factors spatially pattern the outer proliferation center along the dorsal-ventral axis. Here, we identify the spalt (salm and salr) and disco (disco and disco-r) genes as the dorsal-ventral patterning transcription factors of the outer proliferation center. Spalt and Disco are differentially expressed in the dorsal and ventral outer proliferation center from the embryo through to the third instar larva, where they cross-repress each other to form a sharp dorsal-ventral boundary. We show that hedgehog is necessary for Disco expression in the embryonic optic placode and that disco is subsequently required for the development of the ventral outer proliferation center and its neuronal progeny. We further demonstrate that this dorsal-ventral patterning axis acts independently of Vsx1-Optix-Rx and thus propose that Spalt and Disco represent a third outer proliferation center patterning axis that may act to further diversify medulla fates.
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Affiliation(s)
- Priscilla Valentino
- Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 1A1, Canada
| | - Ted Erclik
- Department of Biology, University of Toronto Mississauga, Mississauga, ON L5L 1C6, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON M5S 1A1, Canada
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19
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Ray A, Li X. A Notch-dependent transcriptional mechanism controls expression of temporal patterning factors in Drosophila medulla. eLife 2022; 11:e75879. [PMID: 36040415 PMCID: PMC9427115 DOI: 10.7554/elife.75879] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 07/19/2022] [Indexed: 11/24/2022] Open
Abstract
Temporal patterning is an important mechanism for generating a great diversity of neuron subtypes from a seemingly homogenous progenitor pool in both vertebrates and invertebrates. Drosophila neuroblasts are temporally patterned by sequentially expressed Temporal Transcription Factors (TTFs). These TTFs are proposed to form a transcriptional cascade based on mutant phenotypes, although direct transcriptional regulation between TTFs has not been verified in most cases. Furthermore, it is not known how the temporal transitions are coupled with the generation of the appropriate number of neurons at each stage. We use neuroblasts of the Drosophila optic lobe medulla to address these questions and show that the expression of TTFs Sloppy-paired 1/2 (Slp1/2) is directly regulated at the transcriptional level by two other TTFs and the cell-cycle dependent Notch signaling through two cis-regulatory elements. We also show that supplying constitutively active Notch can rescue the delayed transition into the Slp stage in cell cycle arrested neuroblasts. Our findings reveal a novel Notch-pathway dependent mechanism through which the cell cycle progression regulates the timing of a temporal transition within a TTF transcriptional cascade.
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Affiliation(s)
- Alokananda Ray
- Department of Cell and Developmental Biology, University of Illinois at Urbana-ChampaignUrbanaUnited States
| | - Xin Li
- Department of Cell and Developmental Biology, University of Illinois at Urbana-ChampaignUrbanaUnited States
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20
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Bostock MP, Prasad AR, Donoghue A, Fernandes VM. Photoreceptors generate neuronal diversity in their target field through a Hedgehog morphogen gradient in Drosophila. eLife 2022; 11:78093. [PMID: 36004721 PMCID: PMC9507128 DOI: 10.7554/elife.78093] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 08/23/2022] [Indexed: 11/13/2022] Open
Abstract
Defining the origin of neuronal diversity is a major challenge in developmental neurobiology. The Drosophila visual system is an excellent paradigm to study how cellular diversity is generated. Photoreceptors from the eye disc grow their axons into the optic lobe and secrete Hedgehog (Hh) to induce the lamina, such that for every unit eye there is a corresponding lamina unit made up of post-mitotic precursors stacked into columns. Each differentiated column contains five lamina neuron types (L1-L5), making it the simplest neuropil in the optic lobe, yet how this diversity is generated was unknown. Here, we found that Hh pathway activity is graded along the distal-proximal axis of lamina columns and further determined that this gradient in pathway activity arises from a gradient of Hh ligand. We manipulated Hh pathway activity cell-autonomously in lamina precursors and non-cell autonomously by inactivating the Hh ligand, and by knocking it down in photoreceptors. These manipulations showed that different thresholds of activity specify unique cell identities, with more proximal cell types specified in response to progressively lower Hh levels. Thus, our data establish that Hh acts as a morphogen to pattern the lamina. Although, this is the first such report during Drosophila nervous system development, our work uncovers a remarkable similarity with the vertebrate neural tube, which is patterned by Sonic Hedgehog. Altogether, we show that differentiating neurons can regulate the neuronal diversity of their distant target fields through morphogen gradients.
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Affiliation(s)
- Matthew P Bostock
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Anadika R Prasad
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Alicia Donoghue
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
| | - Vilaiwan M Fernandes
- Department of Cell and Developmental Biology, University College London, London, United Kingdom
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21
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Islam IM, Erclik T. Imp and Syp mediated temporal patterning of neural stem cells in the developing Drosophila CNS. Genetics 2022; 222:6650182. [PMID: 35881070 PMCID: PMC9434295 DOI: 10.1093/genetics/iyac103] [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: 04/21/2022] [Accepted: 06/21/2022] [Indexed: 11/12/2022] Open
Abstract
The assembly of complex neural circuits requires that stem cells generate diverse types of neurons in the correct temporal order. Pioneering work in the Drosophila embryonic ventral nerve cord has shown that neural stem cells are temporally patterned by the sequential expression of rapidly changing transcription factors to generate diversity in their progeny. In recent years, a second temporal patterning mechanism, driven by the opposing gradients of the Imp and Syp RNA-binding proteins, has emerged as a powerful way to generate neural diversity. This long-range temporal patterning mechanism is utilized in the extended neural stem cell lineages of the postembryonic fly brain. Here, we review the role played by Imp and Syp gradients in several neural stem cell lineages, focusing on how they specify sequential neural fates through the post-transcriptional regulation of target genes, including the Chinmo and Mamo transcription factors. We further discuss how upstream inputs, including hormonal signals, modify the output of these gradients to couple neurogenesis with the development of the organism. Finally, we review the roles that the Imp and Syp gradients play beyond the generation of diversity, including the regulation of stem cell proliferation, the timing of neural stem cell lineage termination, and the coupling of neuronal birth order to circuit assembly.
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Affiliation(s)
- Ishrat Maliha Islam
- Departments of Biology and Cell & Systems Biology, University of Toronto-Mississauga, Mississauga, ON L5L 1C6, Canada
| | - Ted Erclik
- Departments of Biology and Cell & Systems Biology, University of Toronto-Mississauga, Mississauga, ON L5L 1C6, Canada
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22
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Damage-responsive neuro-glial clusters coordinate the recruitment of dormant neural stem cells in Drosophila. Dev Cell 2022; 57:1661-1675.e7. [PMID: 35716661 DOI: 10.1016/j.devcel.2022.05.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 03/31/2022] [Accepted: 05/18/2022] [Indexed: 11/23/2022]
Abstract
Recruitment of stem cells is crucial for tissue repair. Although stem cell niches can provide important signals, little is known about mechanisms that coordinate the engagement of disseminated stem cells across an injured tissue. In Drosophila, adult brain lesions trigger local recruitment of scattered dormant neural stem cells suggesting a mechanism for creating a transient stem cell activation zone. Here, we find that injury triggers a coordinated response in neuro-glial clusters that promotes the spread of a neuron-derived stem cell factor via glial secretion of the lipocalin-like transporter Swim. Strikingly, swim is induced in a Hif1-α-dependent manner in response to brain hypoxia. Mammalian Swim (Lcn7) is also upregulated in glia of the mouse hippocampus upon brain injury. Our results identify a central role of neuro-glial clusters in promoting neural stem cell activation at a distance, suggesting a conserved function of the HIF1-α/Swim/Wnt module in connecting injury-sensing and regenerative outcomes.
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23
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Konstantinides N, Holguera I, Rossi AM, Escobar A, Dudragne L, Chen YC, Tran TN, Martínez Jaimes AM, Özel MN, Simon F, Shao Z, Tsankova NM, Fullard JF, Walldorf U, Roussos P, Desplan C. A complete temporal transcription factor series in the fly visual system. Nature 2022; 604:316-322. [PMID: 35388222 DOI: 10.1038/s41586-022-04564-w] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 02/18/2022] [Indexed: 01/17/2023]
Abstract
The brain consists of thousands of neuronal types that are generated by stem cells producing different neuronal types as they age. In Drosophila, this temporal patterning is driven by the successive expression of temporal transcription factors (tTFs)1-6. Here we used single-cell mRNA sequencing to identify the complete series of tTFs that specify most Drosophila optic lobe neurons. We verify that tTFs regulate the progression of the series by activating the next tTF(s) and repressing the previous one(s), and also identify more complex mechanisms of regulation. Moreover, we establish the temporal window of origin and birth order of each neuronal type in the medulla and provide evidence that these tTFs are sufficient to explain the generation of all of the neuronal diversity in this brain region. Finally, we describe the first steps of neuronal differentiation and show that these steps are conserved in humans. We find that terminal differentiation genes, such as neurotransmitter-related genes, are present as transcripts, but not as proteins, in immature larval neurons. This comprehensive analysis of a temporal series of tTFs in the optic lobe offers mechanistic insights into how tTF series are regulated, and how they can lead to the generation of a complete set of neurons.
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Affiliation(s)
- Nikolaos Konstantinides
- Department of Biology, New York University, New York, NY, USA. .,Université de Paris, CNRS, Institut Jacques Monod, Paris, France.
| | - Isabel Holguera
- Department of Biology, New York University, New York, NY, USA
| | - Anthony M Rossi
- Department of Biology, New York University, New York, NY, USA.,Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, MA, USA
| | | | | | - Yen-Chung Chen
- Department of Biology, New York University, New York, NY, USA
| | - Thinh N Tran
- Department of Biology, New York University, New York, NY, USA.,Center for Genomics and Systems Biology, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | | | | | - Félix Simon
- Department of Biology, New York University, New York, NY, USA
| | - Zhiping Shao
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, Institute for Genomics and Multiscale Biology, New York, NY, USA
| | - Nadejda M Tsankova
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - John F Fullard
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, Institute for Genomics and Multiscale Biology, New York, NY, USA.,Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Uwe Walldorf
- Developmental Biology, Saarland University, Homburg, Germany
| | - Panos Roussos
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, Institute for Genomics and Multiscale Biology, New York, NY, USA.,Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA.,Mental Illness Research, Education and Clinical Center (VISN 2 South), James J. Peters VA Medical Center, New York, NY, USA
| | - Claude Desplan
- Department of Biology, New York University, New York, NY, USA. .,Center for Genomics and Systems Biology, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
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24
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Chen YC, Konstantinides N. Integration of Spatial and Temporal Patterning in the Invertebrate and Vertebrate Nervous System. Front Neurosci 2022; 16:854422. [PMID: 35392413 PMCID: PMC8981590 DOI: 10.3389/fnins.2022.854422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 02/15/2022] [Indexed: 11/25/2022] Open
Abstract
The nervous system is one of the most sophisticated animal tissues, consisting of thousands of interconnected cell types. How the nervous system develops its diversity from a few neural stem cells remains a challenging question. Spatial and temporal patterning mechanisms provide an efficient model through which diversity can be generated. The molecular mechanism of spatiotemporal patterning has been studied extensively in Drosophila melanogaster, where distinct sets of transcription factors define the spatial domains and temporal windows that give rise to different cell types. Similarly, in vertebrates, spatial domains defined by transcription factors produce different types of neurons in the brain and neural tube. At the same time, different cortical neuronal types are generated within the same cell lineage with a specific birth order. However, we still do not understand how the orthogonal information of spatial and temporal patterning is integrated into the progenitor and post-mitotic cells to combinatorially give rise to different neurons. In this review, after introducing spatial and temporal patterning in Drosophila and mice, we discuss possible mechanisms that neural progenitors may use to integrate spatial and temporal information. We finally review the functional implications of spatial and temporal patterning and conclude envisaging how small alterations of these mechanisms can lead to the evolution of new neuronal cell types.
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Affiliation(s)
- Yen-Chung Chen
- Department of Biology, New York University, New York, NY, United States
- *Correspondence: Yen-Chung Chen,
| | - Nikolaos Konstantinides
- Université de Paris, Centre National de la Recherche Scientifique, Institut Jacques Monod, Paris, France
- Nikolaos Konstantinides,
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25
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Zhu H, Zhao SD, Ray A, Zhang Y, Li X. A comprehensive temporal patterning gene network in Drosophila medulla neuroblasts revealed by single-cell RNA sequencing. Nat Commun 2022; 13:1247. [PMID: 35273186 PMCID: PMC8913700 DOI: 10.1038/s41467-022-28915-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 02/12/2022] [Indexed: 12/24/2022] Open
Abstract
During development, neural progenitors are temporally patterned to sequentially generate a variety of neural types. In Drosophila neural progenitors called neuroblasts, temporal patterning is regulated by cascades of Temporal Transcription Factors (TTFs). However, known TTFs were mostly identified through candidate approaches and may not be complete. In addition, many fundamental questions remain concerning the TTF cascade initiation, progression, and termination. In this work, we use single-cell RNA sequencing of Drosophila medulla neuroblasts of all ages to identify a list of previously unknown TTFs, and experimentally characterize their roles in temporal patterning and neuronal specification. Our study reveals a comprehensive temporal gene network that patterns medulla neuroblasts from start to end. Furthermore, the speed of the cascade progression is regulated by Lola transcription factors expressed in all medulla neuroblasts. Our comprehensive study of the medulla neuroblast temporal cascade illustrates mechanisms that may be conserved in the temporal patterning of neural progenitors. During development, neural progenitors generate a variety of neural types sequentially. Here the authors examine gene expression patterns in Drosophila neural progenitors at single-cell level, and identify a gene regulatory network controlling the sequential generation of different neural types.
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Affiliation(s)
- Hailun Zhu
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Sihai Dave Zhao
- Department of Statistics, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Alokananda Ray
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Yu Zhang
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Xin Li
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
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26
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Lyu P, Hoang T, Santiago CP, Thomas ED, Timms AE, Appel H, Gimmen M, Le N, Jiang L, Kim DW, Chen S, Espinoza DF, Telger AE, Weir K, Clark BS, Cherry TJ, Qian J, Blackshaw S. Gene regulatory networks controlling temporal patterning, neurogenesis, and cell-fate specification in mammalian retina. Cell Rep 2021; 37:109994. [PMID: 34788628 PMCID: PMC8642835 DOI: 10.1016/j.celrep.2021.109994] [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: 09/08/2021] [Revised: 09/30/2021] [Accepted: 10/21/2021] [Indexed: 12/30/2022] Open
Abstract
Gene regulatory networks (GRNs), consisting of transcription factors and their target sites, control neurogenesis and cell-fate specification in the developing central nervous system. In this study, we use integrated single-cell RNA and single-cell ATAC sequencing (scATAC-seq) analysis in developing mouse and human retina to identify multiple interconnected, evolutionarily conserved GRNs composed of cell-type-specific transcription factors that both activate genes within their own network and inhibit genes in other networks. These GRNs control temporal patterning in primary progenitors, regulate transition from primary to neurogenic progenitors, and drive specification of each major retinal cell type. We confirm that NFI transcription factors selectively activate expression of genes promoting late-stage temporal identity in primary retinal progenitors and identify other transcription factors that regulate rod photoreceptor specification in postnatal retina. This study inventories cis- and trans-acting factors that control retinal development and can guide cell-based therapies aimed at replacing retinal neurons lost to disease.
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Affiliation(s)
- Pin Lyu
- Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Thanh Hoang
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Clayton P Santiago
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Eric D Thomas
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Andrew E Timms
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA 98101, USA
| | - Haley Appel
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Megan Gimmen
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Nguyet Le
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Lizhi Jiang
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Dong Won Kim
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Siqi Chen
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - David F Espinoza
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Ariel E Telger
- Department of Ophthalmology and Visual Sciences, Brotman Baty Institute, Seattle, WA 98195, USA
| | - Kurt Weir
- Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Brian S Clark
- Department of Ophthalmology and Visual Sciences, Brotman Baty Institute, Seattle, WA 98195, USA; Brotman Baty Institute, Seattle, WA 98195, USA; Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Timothy J Cherry
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, Seattle, WA 98101, USA; Brotman Baty Institute, Seattle, WA 98195, USA; Department of Pediatrics, University of Washington School of Medicine, Seattle, WA 98195, USA
| | - Jiang Qian
- Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
| | - Seth Blackshaw
- Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Ophthalmology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Kavli Neuroscience Discovery Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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Klöppel C, Hildebrandt K, Kolb D, Fürst N, Bley I, Karlowatz RJ, Walldorf U. Functional analysis of enhancer elements regulating the expression of the Drosophila homeodomain transcription factor DRx by gene targeting. Hereditas 2021; 158:42. [PMID: 34736520 PMCID: PMC8569992 DOI: 10.1186/s41065-021-00210-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 10/18/2021] [Indexed: 11/17/2022] Open
Abstract
Background The Drosophila brain is an ideal model system to study stem cells, here called neuroblasts, and the generation of neural lineages. Many transcriptional activators are involved in formation of the brain during the development of Drosophila melanogaster. The transcription factor Drosophila Retinal homeobox (DRx), a member of the 57B homeobox gene cluster, is also one of these factors for brain development. Results In this study a detailed expression analysis of DRx in different developmental stages was conducted. We show that DRx is expressed in the embryonic brain in the protocerebrum, in the larval brain in the DM and DL lineages, the medulla and the lobula complex and in the central complex of the adult brain. We generated a DRx enhancer trap strain by gene targeting and reintegration of Gal4, which mimics the endogenous expression of DRx. With the help of eight existing enhancer-Gal4 strains and one made by our group, we mapped various enhancers necessary for the expression of DRx during all stages of brain development from the embryo to the adult. We made an analysis of some larger enhancer regions by gene targeting. Deletion of three of these enhancers showing the most prominent expression patterns in the brain resulted in specific temporal and spatial loss of DRx expression in defined brain structures. Conclusion Our data show that DRx is expressed in specific neuroblasts and defined neural lineages and suggest that DRx is another important factor for Drosophila brain development. Supplementary Information The online version contains supplementary material available at 10.1186/s41065-021-00210-z.
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Affiliation(s)
- Christine Klöppel
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany
| | - Kirsten Hildebrandt
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany
| | - Dieter Kolb
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany
| | - Nora Fürst
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany.,Present address: Genetics/Epigenetics, Saarland University, Building A2.4, 66123, Saarbrücken, Germany
| | - Isabelle Bley
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany.,Present address: Research Institute Children's Cancer Center Hamburg, Building N63, Martinistr. 52, 20251, Hamburg, Germany
| | | | - Uwe Walldorf
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany.
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28
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Hildebrandt K, Kübel S, Minet M, Fürst N, Klöppel C, Steinmetz E, Walldorf U. Enhancer analysis of the Drosophila zinc finger transcription factor Earmuff by gene targeting. Hereditas 2021; 158:41. [PMID: 34732265 PMCID: PMC8567707 DOI: 10.1186/s41065-021-00209-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 10/08/2021] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Many transcription factors are involved in the formation of the brain during the development of Drosophila melanogaster. The transcription factor Earmuff (Erm), a member of the forebrain embryonic zinc finger family (Fezf), is one of these important factors for brain development. One major function of Earmuff is the regulation of proliferation within type II neuroblast lineages in the brain; here, Earmuff is expressed in intermediate neural progenitor cells (INPs) and balances neuronal differentiation versus stem cell maintenance. Erm expression during development is regulated by several enhancers. RESULTS In this work we show a functional analysis of erm and some of its enhancers. We generated a new erm mutant allele by gene targeting and reintegrated Gal4 to make an erm enhancer trap strain that could also be used on an erm mutant background. The deletion of three of the previously analysed enhancers showing the most prominent expression patterns of erm by gene targeting resulted in specific temporal and spatial defects in defined brain structures. These defects were already known but here could be assigned to specific enhancer regions. CONCLUSION This analysis is to our knowledge the first systematic analysis of several large enhancer deletions of a Drosophila gene by gene targeting and will enable deeper analysis of erm enhancer functions in the future.
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Affiliation(s)
- Kirsten Hildebrandt
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany
| | - Sabrina Kübel
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany
- Present address: Clinical and Molecular Virology, Friedrich-Alexander University, 91054, Erlangen, Germany
| | - Marie Minet
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany
- Present address: Human Genetics, Saarland University, Building 60, 66421, Homburg/Saar, Germany
| | - Nora Fürst
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany
- Present address: Genetics/Epigenetics, Saarland University, Building A2.4, 66123, Saarbrücken, Germany
| | - Christine Klöppel
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany
| | - Eva Steinmetz
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany
- Present address: Zoology and Physiology, Saarland University, Building B2.1, 66123, Saarbrücken, Germany
| | - Uwe Walldorf
- Developmental Biology, Saarland University, Building 61, 66421, Homburg/Saar, Germany.
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Sagner A, Zhang I, Watson T, Lazaro J, Melchionda M, Briscoe J. A shared transcriptional code orchestrates temporal patterning of the central nervous system. PLoS Biol 2021; 19:e3001450. [PMID: 34767545 PMCID: PMC8612522 DOI: 10.1371/journal.pbio.3001450] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 11/24/2021] [Accepted: 10/20/2021] [Indexed: 01/13/2023] Open
Abstract
The molecular mechanisms that produce the full array of neuronal subtypes in the vertebrate nervous system are incompletely understood. Here, we provide evidence of a global temporal patterning program comprising sets of transcription factors that stratifies neurons based on the developmental time at which they are generated. This transcriptional code acts throughout the central nervous system, in parallel to spatial patterning, thereby increasing the diversity of neurons generated along the neuraxis. We further demonstrate that this temporal program operates in stem cell-derived neurons and is under the control of the TGFβ signaling pathway. Targeted perturbation of components of the temporal program, Nfia and Nfib, reveals their functional requirement for the generation of late-born neuronal subtypes. Together, our results provide evidence for the existence of a previously unappreciated global temporal transcriptional program of neuronal subtype identity and suggest that the integration of spatial and temporal patterning mechanisms diversifies and organizes neuronal subtypes in the vertebrate nervous system.
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Affiliation(s)
- Andreas Sagner
- The Francis Crick Institute, London, United Kingdom
- Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom
- Institut für Biochemie, Emil-Fischer-Zentrum, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Isabel Zhang
- The Francis Crick Institute, London, United Kingdom
| | | | - Jorge Lazaro
- The Francis Crick Institute, London, United Kingdom
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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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31
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Profile of Claude Desplan. Proc Natl Acad Sci U S A 2021; 118:2110547118. [PMID: 34244438 DOI: 10.1073/pnas.2110547118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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32
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Microenvironmental innate immune signaling and cell mechanical responses promote tumor growth. Dev Cell 2021; 56:1884-1899.e5. [PMID: 34197724 DOI: 10.1016/j.devcel.2021.06.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 05/01/2021] [Accepted: 06/09/2021] [Indexed: 01/08/2023]
Abstract
Tissue homeostasis is achieved by balancing stem cell maintenance, cell proliferation and differentiation, as well as the purging of damaged cells. Elimination of unfit cells maintains tissue health; however, the underlying mechanisms driving competitive growth when homeostasis fails, for example, during tumorigenesis, remain largely unresolved. Here, using a Drosophila intestinal model, we find that tumor cells outcompete nearby enterocytes (ECs) by influencing cell adhesion and contractility. This process relies on activating the immune-responsive Relish/NF-κB pathway to induce EC delamination and requires a JNK-dependent transcriptional upregulation of the peptidoglycan recognition protein PGRP-LA. Consequently, in organisms with impaired PGRP-LA function, tumor growth is delayed and lifespan extended. Our study identifies a non-cell-autonomous role for a JNK/PGRP-LA/Relish signaling axis in mediating death of neighboring normal cells to facilitate tumor growth. We propose that intestinal tumors "hijack" innate immune signaling to eliminate enterocytes in order to support their own growth.
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33
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Neural specification, targeting, and circuit formation during visual system assembly. Proc Natl Acad Sci U S A 2021; 118:2101823118. [PMID: 34183440 DOI: 10.1073/pnas.2101823118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Like other sensory systems, the visual system is topographically organized: Its sensory neurons, the photoreceptors, and their targets maintain point-to-point correspondence in physical space, forming a retinotopic map. The iterative wiring of circuits in the visual system conveniently facilitates the study of its development. Over the past few decades, experiments in Drosophila have shed light on the principles that guide the specification and connectivity of visual system neurons. In this review, we describe the main findings unearthed by the study of the Drosophila visual system and compare them with similar events in mammals. We focus on how temporal and spatial patterning generates diverse cell types, how guidance molecules distribute the axons and dendrites of neurons within the correct target regions, how vertebrates and invertebrates generate their retinotopic map, and the molecules and mechanisms required for neuronal migration. We suggest that basic principles used to wire the fly visual system are broadly applicable to other systems and highlight its importance as a model to study nervous system development.
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Zhang T, Liu T, Mora N, Guegan J, Bertrand M, Contreras X, Hansen AH, Streicher C, Anderle M, Danda N, Tiberi L, Hippenmeyer S, Hassan BA. Generation of excitatory and inhibitory neurons from common progenitors via Notch signaling in the cerebellum. Cell Rep 2021; 35:109208. [PMID: 34107249 DOI: 10.1016/j.celrep.2021.109208] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 03/29/2021] [Accepted: 05/11/2021] [Indexed: 12/17/2022] Open
Abstract
Brain neurons arise from relatively few progenitors generating an enormous diversity of neuronal types. Nonetheless, a cardinal feature of mammalian brain neurogenesis is thought to be that excitatory and inhibitory neurons derive from separate, spatially segregated progenitors. Whether bi-potential progenitors with an intrinsic capacity to generate both lineages exist and how such a fate decision may be regulated are unknown. Using cerebellar development as a model, we discover that individual progenitors can give rise to both inhibitory and excitatory lineages. Gradations of Notch activity determine the fates of the progenitors and their daughters. Daughters with the highest levels of Notch activity retain the progenitor fate, while intermediate levels of Notch activity generate inhibitory neurons, and daughters with very low levels of Notch signaling adopt the excitatory fate. Therefore, Notch-mediated binary cell fate choice is a mechanism for regulating the ratio of excitatory to inhibitory neurons from common progenitors.
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Affiliation(s)
- Tingting Zhang
- Institut du Cerveau (ICM), Sorbonne Université, INSERM, CNRS, Hôpital Pitié-Salpêtrière, Paris, France; Doctoral School of Biomedical Sciences, KU Leuven, 3000 Leuven, Belgium
| | - Tengyuan Liu
- Institut du Cerveau (ICM), Sorbonne Université, INSERM, CNRS, Hôpital Pitié-Salpêtrière, Paris, France; Doctoral School of Biomedical Sciences, KU Leuven, 3000 Leuven, Belgium
| | - Natalia Mora
- Institut du Cerveau (ICM), Sorbonne Université, INSERM, CNRS, Hôpital Pitié-Salpêtrière, Paris, France
| | - Justine Guegan
- Institut du Cerveau (ICM), Sorbonne Université, INSERM, CNRS, Hôpital Pitié-Salpêtrière, Paris, France
| | - Mathilde Bertrand
- Institut du Cerveau (ICM), Sorbonne Université, INSERM, CNRS, Hôpital Pitié-Salpêtrière, Paris, France
| | - Ximena Contreras
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
| | - Andi H Hansen
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
| | - Carmen Streicher
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
| | - Marica Anderle
- Armenise-Harvard Laboratory of Brain Disorders and Cancer, CIBIO, University of Trento, Via Sommarive 9, 38123 Trento, Italy
| | - Natasha Danda
- Institut du Cerveau (ICM), Sorbonne Université, INSERM, CNRS, Hôpital Pitié-Salpêtrière, Paris, France
| | - Luca Tiberi
- Armenise-Harvard Laboratory of Brain Disorders and Cancer, CIBIO, University of Trento, Via Sommarive 9, 38123 Trento, Italy
| | - Simon Hippenmeyer
- Institute of Science and Technology Austria, Am Campus 1, 3400 Klosterneuburg, Austria
| | - Bassem A Hassan
- Institut du Cerveau (ICM), Sorbonne Université, INSERM, CNRS, Hôpital Pitié-Salpêtrière, Paris, France.
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35
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Douthit J, Hairston A, Lee G, Morrison CA, Holguera I, Treisman JE. R7 photoreceptor axon targeting depends on the relative levels of lost and found expression in R7 and its synaptic partners. eLife 2021; 10:65895. [PMID: 34003117 PMCID: PMC8205486 DOI: 10.7554/elife.65895] [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: 12/18/2020] [Accepted: 05/17/2021] [Indexed: 01/17/2023] Open
Abstract
As neural circuits form, growing processes select the correct synaptic partners through interactions between cell surface proteins. The presence of such proteins on two neuronal processes may lead to either adhesion or repulsion; however, the consequences of mismatched expression have rarely been explored. Here, we show that the Drosophila CUB-LDL protein Lost and found (Loaf) is required in the UV-sensitive R7 photoreceptor for normal axon targeting only when Loaf is also present in its synaptic partners. Although targeting occurs normally in loaf mutant animals, removing loaf from photoreceptors or expressing it in their postsynaptic neurons Tm5a/b or Dm9 in a loaf mutant causes mistargeting of R7 axons. Loaf localizes primarily to intracellular vesicles including endosomes. We propose that Loaf regulates the trafficking or function of one or more cell surface proteins, and an excess of these proteins on the synaptic partners of R7 prevents the formation of stable connections.
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Affiliation(s)
- Jessica Douthit
- Kimmel Center for Biology and Medicine at the Skirball Institute and Department of Cell Biology, NYU School of Medicine, New York, United States
| | - Ariel Hairston
- Kimmel Center for Biology and Medicine at the Skirball Institute and Department of Cell Biology, NYU School of Medicine, New York, United States
| | - Gina Lee
- Kimmel Center for Biology and Medicine at the Skirball Institute and Department of Cell Biology, NYU School of Medicine, New York, United States
| | - Carolyn A Morrison
- Kimmel Center for Biology and Medicine at the Skirball Institute and Department of Cell Biology, NYU School of Medicine, New York, United States
| | - Isabel Holguera
- Department of Biology, New York University, New York, United States
| | - Jessica E Treisman
- Kimmel Center for Biology and Medicine at the Skirball Institute and Department of Cell Biology, NYU School of Medicine, New York, United States
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36
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Choi BJ, Chen YCD, Desplan C. Building a circuit through correlated spontaneous neuronal activity in the developing vertebrate and invertebrate visual systems. Genes Dev 2021; 35:677-691. [PMID: 33888564 PMCID: PMC8091978 DOI: 10.1101/gad.348241.121] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
During the development of the vertebrate nervous systems, genetic programs assemble an immature circuit that is subsequently refined by neuronal activity evoked by external stimuli. However, prior to sensory experience, the intrinsic property of the developing nervous system also triggers correlated network-level neuronal activity, with retinal waves in the developing vertebrate retina being the best documented example. Spontaneous activity has also been found in the visual system of Drosophila Here, we compare the spontaneous activity of the developing visual system between mammalian and Drosophila and suggest that Drosophila is an emerging model for mechanistic and functional studies of correlated spontaneous activity.
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Affiliation(s)
- Ben Jiwon Choi
- Department of Biology, New York University, New York, New York 10003, USA
| | | | - Claude Desplan
- Department of Biology, New York University, New York, New York 10003, USA
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37
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Sancer G, Wernet MF. The development and function of neuronal subtypes processing color and skylight polarization in the optic lobes of Drosophila melanogaster. ARTHROPOD STRUCTURE & DEVELOPMENT 2021; 61:101012. [PMID: 33618155 DOI: 10.1016/j.asd.2020.101012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 11/01/2020] [Accepted: 11/19/2020] [Indexed: 06/12/2023]
Abstract
The retinal mosaics of many insects contain different ommatidial subtypes harboring photoreceptors that are both molecularly and morphologically specialized for comparing between different wavelengths versus detecting the orientation of skylight polarization. The neural circuits underlying these different inputs and the characterization of their specific cellular elements are the subject of intense research. Here we review recent progress on the description of both assembly and function of color and skylight polarization circuitry, by focusing on two cell types located in the distal portion of the medulla neuropil of the fruit fly Drosophila melanogaster's optic lobes, called Dm8 and Dm9. In the main part of the retina, Dm8 cells fall into two molecularly distinct subtypes whose center becomes specifically connected to either one of randomly distributed 'pale' or 'yellow' R7 photoreceptor fates during development. Only in the 'dorsal rim area' (DRA), both polarization-sensitive R7 and R8 photoreceptors are connected to different Dm8-like cell types, called Dm-DRA1 and Dm-DRA2, respectively. An additional layer of interommatidial integration is introduced by Dm9 cells, which receive input from multiple neighboring R7 and R8 cells, as well as providing feedback synapses back into these photoreceptors. As a result, the response properties of color-sensitive photoreceptor terminals are sculpted towards being both maximally decorrelated, as well as harboring several levels of opponency (both columnar as well as intercolumnar). In the DRA, individual Dm9 cells appear to mix both polarization and color signals, thereby potentially serving as the first level of integration of different celestial stimuli. The molecular mechanisms underlying the establishment of these synaptic connections are beginning to be revealed, by using a combination of live imaging, developmental genetic studies, and cell type-specific transcriptomics.
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Affiliation(s)
- Gizem Sancer
- Freie Universität Berlin, Fachbereich Biologie, Chemie und Pharmazie, Institut für Biologie - Neurobiologie, Königin-Luise Strasse 1-3, 14195 Berlin, Germany
| | - Mathias F Wernet
- Freie Universität Berlin, Fachbereich Biologie, Chemie und Pharmazie, Institut für Biologie - Neurobiologie, Königin-Luise Strasse 1-3, 14195 Berlin, Germany.
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Rossi AM, Jafari S, Desplan C. Integrated Patterning Programs During Drosophila Development Generate the Diversity of Neurons and Control Their Mature Properties. Annu Rev Neurosci 2021; 44:153-172. [PMID: 33556251 DOI: 10.1146/annurev-neuro-102120-014813] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
During the approximately 5 days of Drosophila neurogenesis (late embryogenesis to the beginning of pupation), a limited number of neural stem cells produce approximately 200,000 neurons comprising hundreds of cell types. To build a functional nervous system, neuronal types need to be produced in the proper places, appropriate numbers, and correct times. We discuss how neural stem cells (neuroblasts) obtain so-called area codes for their positions in the nervous system (spatial patterning) and how they keep time to sequentially produce neurons with unique fates (temporal patterning). We focus on specific examples that demonstrate how a relatively simple patterning system (Notch) can be used reiteratively to generate different neuronal types. We also speculate on how different modes of temporal patterning that operate over short versus long time periods might be linked. We end by discussing how specification programs are integrated and lead to the terminal features of different neuronal types.
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Affiliation(s)
- Anthony M Rossi
- Department of Biology, New York University, New York, NY 10003, USA; .,Department of Neurobiology, Blavatnik Institute, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Shadi Jafari
- Department of Biology, New York University, New York, NY 10003, USA;
| | - Claude Desplan
- Department of Biology, New York University, New York, NY 10003, USA;
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Niederhuber MJ, McKay DJ. Mechanisms underlying the control of dynamic regulatory element activity and chromatin accessibility during metamorphosis. CURRENT OPINION IN INSECT SCIENCE 2021; 43:21-28. [PMID: 32979530 PMCID: PMC7985040 DOI: 10.1016/j.cois.2020.08.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 08/25/2020] [Indexed: 05/10/2023]
Abstract
Cis-regulatory modules of metazoan genomes determine the when and where of gene expression during development. Here we discuss insights into the genetic and molecular mechanisms behind cis-regulatory module usage that have come from recent application of genomics assays to insect metamorphosis. Assays including FAIRE-seq, ATAC-seq, and CUT&RUN indicate that sequential changes in chromatin accessibility play a key role in mediating stage-specific cis-regulatory module activity and gene expression. We review the current understanding of what controls precisely coordinated changes in chromatin accessibility during metamorphosis and describe evidence that points to systemic hormone signaling as a primary signal to trigger genome-wide shifts in accessibility patterns and cis-regulatory module usage.
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Affiliation(s)
- Matthew J Niederhuber
- Curriculum in Genetics and Molecular Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, United States; Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, United States; Department of Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, United States; Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, United States
| | - Daniel J McKay
- Department of Biology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, United States; Department of Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, United States; Integrative Program for Biological and Genome Sciences, The University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, United States.
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40
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Neuronal diversity and convergence in a visual system developmental atlas. Nature 2020; 589:88-95. [PMID: 33149298 PMCID: PMC7790857 DOI: 10.1038/s41586-020-2879-3] [Citation(s) in RCA: 109] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Accepted: 08/27/2020] [Indexed: 01/01/2023]
Abstract
Deciphering how neuronal diversity is established and maintained requires a detailed knowledge of neuronal gene expression throughout development. In contrast to mammalian brains1,2, the large neuronal diversity of the Drosophila optic lobes3 and its connectome4–6 are almost completely characterized. However, a molecular characterization of this diversity, particularly during development, has been lacking. We present novel insights into brain development through a nearly exhaustive description of the transcriptomic diversity of the optic lobes. We acquired the transcriptome of 275,000 single-cells at adult and five pupal stages, and developed a machine learning framework to assign them to almost 200 cell-types at all timepoints. We discovered two large neuronal populations that wrap neuropils during development but die just before adulthood, as well as neuronal subtypes that partition dorsal and ventral visual circuits by differential Wnt signaling throughout development. Moreover, we showed that neurons of the same type but produced days apart synchronize their transcriptomes shortly after being produced. We also resolved during synaptogenesis neuronal subtypes that converge to indistinguishable transcriptomic profiles in adults while greatly differing in morphology and connectivity. Our datasets almost completely account for the known neuronal diversity of the optic lobes and serve as a paradigm to understand brain development across species.
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41
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Islam IM, Ng J, Valentino P, Erclik T. Identification of enhancers that drive the spatially restricted expression of Vsx1 and Rx in the outer proliferation center of the developing Drosophila optic lobe. Genome 2020; 64:109-117. [PMID: 33054400 DOI: 10.1139/gen-2020-0034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Combinatorial spatial and temporal patterning of stem cells is a powerful mechanism for the generation of neural diversity in insect and vertebrate nervous systems. In the developing Drosophila medulla, the neural stem cells of the outer proliferation center (OPC) are spatially patterned by the mutually exclusive expression of three homeobox transcription factors: Vsx1 in the center of the OPC crescent (cOPC), Optix in the main arms (mOPC), and Rx in the posterior tips (pOPC). These spatial factors act together with a temporal cascade of transcription factors in OPC neuroblasts to specify the greater than 80 medulla cell types. Here, we identify the enhancers that are sufficient to drive the spatially restricted expression of the Vsx1 and Rx genes in the OPC. We show that removal of the cOPC enhancer in the Muddled inversion mutant leads to the loss of Vsx1 expression in the cOPC. Analysis of the evolutionarily conserved sequences within these enhancers suggests that direct repression by Optix may restrict the expression of Vsx1 and Rx to the cOPC and pOPC, respectively.
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Affiliation(s)
- Ishrat Maliha Islam
- Departments of Biology and Cell & Systems Biology, University of Toronto - Mississauga, Mississauga, ON., Canada
| | - June Ng
- Department of Biology, New York University, New York, USA
| | - Priscilla Valentino
- Departments of Biology and Cell & Systems Biology, University of Toronto - Mississauga, Mississauga, ON., Canada
| | - Ted Erclik
- Departments of Biology and Cell & Systems Biology, University of Toronto - Mississauga, Mississauga, ON., Canada
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42
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Das P, Bhadra MP. Histone deacetylase (Rpd3) regulates Drosophila early brain development via regulation of Tailless. Open Biol 2020; 10:200029. [PMID: 32873153 PMCID: PMC7536075 DOI: 10.1098/rsob.200029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Accepted: 07/29/2020] [Indexed: 11/29/2022] Open
Abstract
Tailless is a committed transcriptional repressor and principal regulator of the brain and eye development in Drosophila. Rpd3, the histone deacetylase, is an established repressor that interacts with co-repressors like Sin3a, Prospero, Brakeless and Atrophin. This study aims at deciphering the role of Rpd3 in embryonic segmentation and larval brain development in Drosophila. It delineates the mechanism of Tailless regulation by Rpd3, along with its interacting partners. There was a significant reduction in Tailless in Rpd3 heteroallelic mutant embryos, substantiating that Rpd3 is indispensable for the normal Tailless expression. The expression of the primary readout, Tailless was correlative to the expression of the neural cell adhesion molecule homologue, Fascilin2 (Fas2). Rpd3 also aids in the proper development of the mushroom body. Both Tailless and Fas2 expression are reported to be antagonistic to the epidermal growth factor receptor (EGFR) expression. The decrease in Tailless and Fas2 expression highlights that EGFR is upregulated in the larval mutants, hindering brain development. This study outlines the axis comprising Rpd3, dEGFR, Tailless and Fas2, which interact to fine-tune the early segmentation and larval brain development. Therefore, Rpd3 along with Tailless has immense significance in early embryogenesis and development of the larval brain.
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Affiliation(s)
- Paromita Das
- Applied Biology Division, CSIR-Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007, India
- Academy of Scientific and Innovative Research (AcSIR) Training and Development Complex, CSIR Campus, CSIR Road, Taramani, Chennai 600 113, India
| | - Manika Pal Bhadra
- Applied Biology Division, CSIR-Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500 007, India
- Academy of Scientific and Innovative Research (AcSIR) Training and Development Complex, CSIR Campus, CSIR Road, Taramani, Chennai 600 113, India
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43
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Liu C, Trush O, Han X, Wang M, Takayama R, Yasugi T, Hayashi T, Sato M. Dscam1 establishes the columnar units through lineage-dependent repulsion between sister neurons in the fly brain. Nat Commun 2020; 11:4067. [PMID: 32792493 PMCID: PMC7426427 DOI: 10.1038/s41467-020-17931-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2019] [Accepted: 07/24/2020] [Indexed: 11/15/2022] Open
Abstract
The brain is organized morphologically and functionally into a columnar structure. According to the radial unit hypothesis, neurons from the same lineage form a radial unit that contributes to column formation. However, the molecular mechanisms that link neuronal lineage and column formation remain elusive. Here, we show that neurons from the same lineage project to different columns under control of Down syndrome cell adhesion molecule (Dscam) in the fly brain. Dscam1 is temporally expressed in newly born neuroblasts and is inherited by their daughter neurons. The transient transcription of Dscam1 in neuroblasts enables the expression of the same Dscam1 splice isoform within cells of the same lineage, causing lineage-dependent repulsion. In the absence of Dscam1 function, neurons from the same lineage project to the same column. When the splice diversity of Dscam1 is reduced, column formation is significantly compromised. Thus, Dscam1 controls column formation through lineage-dependent repulsion. Columns are the functional and morphological unit of the brain, but how neurons assemble into this structure was unclear. Here, the authors show that Dscam gene rewires neurons that derive from the same stem cell to establish columns through the process of lineage-dependent repulsion.
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Affiliation(s)
- Chuyan Liu
- Laboratory of Developmental Neurobiology, Graduate School of Medical Sciences, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan
| | - Olena Trush
- Laboratory of Developmental Neurobiology, Graduate School of Medical Sciences, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan
| | - Xujun Han
- Mathematical Neuroscience Unit, Institute for Frontier Science Initiative, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan
| | - Miaoxing Wang
- Mathematical Neuroscience Unit, Institute for Frontier Science Initiative, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan
| | - Rie Takayama
- Mathematical Neuroscience Unit, Institute for Frontier Science Initiative, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan
| | - Tetsuo Yasugi
- Mathematical Neuroscience Unit, Institute for Frontier Science Initiative, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan
| | - Takashi Hayashi
- Mathematical Neuroscience Unit, Institute for Frontier Science Initiative, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan
| | - Makoto Sato
- Laboratory of Developmental Neurobiology, Graduate School of Medical Sciences, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan. .,Mathematical Neuroscience Unit, Institute for Frontier Science Initiative, Kanazawa University, 13-1 Takaramachi, Kanazawa, Ishikawa, 920-8640, Japan.
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44
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Naidu VG, Zhang Y, Lowe S, Ray A, Zhu H, Li X. Temporal progression of Drosophila medulla neuroblasts generates the transcription factor combination to control T1 neuron morphogenesis. Dev Biol 2020; 464:35-44. [PMID: 32442418 PMCID: PMC7377279 DOI: 10.1016/j.ydbio.2020.05.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Revised: 05/06/2020] [Accepted: 05/11/2020] [Indexed: 12/19/2022]
Abstract
Proper neural function depends on the correct specification of individual neural fates, controlled by combinations of neuronal transcription factors. Different neural types are sequentially generated by neural progenitors in a defined order, and this temporal patterning process can be controlled by Temporal Transcription Factors (TTFs) that form temporal cascades in neural progenitors. The Drosophila medulla, part of the visual processing center of the brain, contains more than 70 neural types generated by medulla neuroblasts which sequentially express several TTFs, including Homothorax (Hth), eyeless (Ey), Sloppy paired 1 and 2 (Slp), Dichaete (D) and Tailless (Tll). However, it is not clear how such a small number of TTFs could give rise to diverse combinations of neuronal transcription factors that specify a large number of medulla neuron types. Here we report how temporal patterning specifies one neural type, the T1 neuron. We show that the T1 neuron is the only medulla neuron type that expresses the combination of three transcription factors Ocelliless (Oc or Otd), Sox102F and Ets65A. Using CRISPR-Cas9 system, we show that each transcription factor is required for the correct morphogenesis of T1 neurons. Interestingly, Oc, Sox102F and Ets65A initiate expression in neurons beginning at different temporal stages and last in a few subsequent temporal stages. Oc expressing neurons are generated in the Ey, Slp and D stages; Sox102F expressing neurons are produced in the Slp and D stages; while Ets65A is expressed in subsets of medulla neurons born in the D and later stages. The TTF Ey, Slp or D is required to initiate the expression of Oc, Sox102F or Ets65A in neurons, respectively. Thus, the neurons expressing all three transcription factors are born in the D stage and become T1 neurons. In neurons where the three transcription factors do not overlap, each of the three transcription factors can act in combination with other neuronal transcription factors to specify different neural fates. We show that this way of expression regulation of neuronal transcription factors by temporal patterning can generate more possible combinations of transcription factors in neural progeny to diversify neural fates.
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Affiliation(s)
- Vamsikrishna G Naidu
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, Urbana, IL, USA
| | - Yu Zhang
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, Urbana, IL, USA
| | - Scott Lowe
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, Urbana, IL, USA
| | - Alokananda Ray
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, Urbana, IL, USA
| | - Hailun Zhu
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, Urbana, IL, USA
| | - Xin Li
- Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, Urbana, IL, USA.
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45
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Maurange C. Temporal patterning in neural progenitors: from Drosophila development to childhood cancers. Dis Model Mech 2020; 13:dmm044883. [PMID: 32816915 PMCID: PMC7390627 DOI: 10.1242/dmm.044883] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The developing central nervous system (CNS) is particularly prone to malignant transformation, but the underlying mechanisms remain unresolved. However, periods of tumor susceptibility appear to correlate with windows of increased proliferation, which are often observed during embryonic and fetal stages and reflect stereotypical changes in the proliferative properties of neural progenitors. The temporal mechanisms underlying these proliferation patterns are still unclear in mammals. In Drosophila, two decades of work have revealed a network of sequentially expressed transcription factors and RNA-binding proteins that compose a neural progenitor-intrinsic temporal patterning system. Temporal patterning controls both the identity of the post-mitotic progeny of neural progenitors, according to the order in which they arose, and the proliferative properties of neural progenitors along development. In addition, in Drosophila, temporal patterning delineates early windows of cancer susceptibility and is aberrantly regulated in developmental tumors to govern cellular hierarchy as well as the metabolic and proliferative heterogeneity of tumor cells. Whereas recent studies have shown that similar genetic programs unfold during both fetal development and pediatric brain tumors, I discuss, in this Review, how the concept of temporal patterning that was pioneered in Drosophila could help to understand the mechanisms of initiation and progression of CNS tumors in children.
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Affiliation(s)
- Cédric Maurange
- Aix Marseille University, CNRS, IBDM, Equipe Labellisée LIGUE Contre le Cancer, Marseille 13009, France
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46
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Zechner C, Nerli E, Norden C. Stochasticity and determinism in cell fate decisions. Development 2020; 147:147/14/dev181495. [PMID: 32669276 DOI: 10.1242/dev.181495] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
During development, cells need to make decisions about their fate in order to ensure that the correct numbers and types of cells are established at the correct time and place in the embryo. Such cell fate decisions are often classified as deterministic or stochastic. However, although these terms are clearly defined in a mathematical sense, they are sometimes used ambiguously in biological contexts. Here, we provide some suggestions on how to clarify the definitions and usage of the terms stochastic and deterministic in biological experiments. We discuss the frameworks within which such clear definitions make sense and highlight when certain ambiguity prevails. As an example, we examine how these terms are used in studies of neuronal cell fate decisions and point out areas in which definitions and interpretations have changed and matured over time. We hope that this Review will provide some clarification and inspire discussion on the use of terminology in relation to fate decisions.
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Affiliation(s)
- Christoph Zechner
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany .,Max Planck Center for Systems Biology, Pfotenhauerstraße 108, 01307 Dresden, Germany.,Cluster of Excellence Physics of Life, TU Dresden, 01062 Dresden, Germany
| | - Elisa Nerli
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany
| | - Caren Norden
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstraße 108, 01307 Dresden, Germany .,Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
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47
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Mira H, Morante J. Neurogenesis From Embryo to Adult - Lessons From Flies and Mice. Front Cell Dev Biol 2020; 8:533. [PMID: 32695783 PMCID: PMC7339912 DOI: 10.3389/fcell.2020.00533] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 06/08/2020] [Indexed: 12/30/2022] Open
Abstract
The human brain is composed of billions of cells, including neurons and glia, with an undetermined number of subtypes. During the embryonic and early postnatal stages, the vast majority of these cells are generated from neural progenitors and stem cells located in all regions of the neural tube. A smaller number of neurons will continue to be generated throughout our lives, in localized neurogenic zones, mainly confined at least in rodents to the subependymal zone of the lateral ventricles and the subgranular zone of the hippocampal dentate gyrus. During neurogenesis, a combination of extrinsic cues interacting with temporal and regional intrinsic programs are thought to be critical for increasing neuronal diversity, but their underlying mechanisms need further elucidation. In this review, we discuss the recent findings in Drosophila and mammals on the types of cell division and cell interactions used by neural progenitors and stem cells to sustain neurogenesis, and how they are influenced by glia.
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Affiliation(s)
- Helena Mira
- Instituto de Biomedicina de Valencia, Consejo Superior de Investigaciones Científicas, Valencia, Spain
| | - Javier Morante
- Instituto de Neurociencias, Consejo Superior de Investigaciones Científicas y Universidad Miguel Hernandez, Alicante, Spain
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48
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Lee YJ, Yang CP, Miyares RL, Huang YF, He Y, Ren Q, Chen HM, Kawase T, Ito M, Otsuna H, Sugino K, Aso Y, Ito K, Lee T. Conservation and divergence of related neuronal lineages in the Drosophila central brain. eLife 2020; 9:53518. [PMID: 32255422 PMCID: PMC7173964 DOI: 10.7554/elife.53518] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 04/06/2020] [Indexed: 12/31/2022] Open
Abstract
Wiring a complex brain requires many neurons with intricate cell specificity, generated by a limited number of neural stem cells. Drosophila central brain lineages are a predetermined series of neurons, born in a specific order. To understand how lineage identity translates to neuron morphology, we mapped 18 Drosophila central brain lineages. While we found large aggregate differences between lineages, we also discovered shared patterns of morphological diversification. Lineage identity plus Notch-mediated sister fate govern primary neuron trajectories, whereas temporal fate diversifies terminal elaborations. Further, morphological neuron types may arise repeatedly, interspersed with other types. Despite the complexity, related lineages produce similar neuron types in comparable temporal patterns. Different stem cells even yield two identical series of dopaminergic neuron types, but with unrelated sister neurons. Together, these phenomena suggest that straightforward rules drive incredible neuronal complexity, and that large changes in morphology can result from relatively simple fating mechanisms.
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Affiliation(s)
- Ying-Jou Lee
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Ching-Po Yang
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Rosa L Miyares
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Yu-Fen Huang
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Yisheng He
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Qingzhong Ren
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Hui-Min Chen
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Takashi Kawase
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Masayoshi Ito
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Hideo Otsuna
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Ken Sugino
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Yoshi Aso
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Kei Ito
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
| | - Tzumin Lee
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, United States
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49
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Chen YC, Desplan C. Gene regulatory networks during the development of the Drosophila visual system. Curr Top Dev Biol 2020; 139:89-125. [PMID: 32450970 DOI: 10.1016/bs.ctdb.2020.02.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The Drosophila visual system integrates input from 800 ommatidia and extracts different features in stereotypically connected optic ganglia. The development of the Drosophila visual system is controlled by gene regulatory networks that control the number of precursor cells, generate neuronal diversity by integrating spatial and temporal information, coordinate the timing of retinal and optic lobe cell differentiation, and determine distinct synaptic targets of each cell type. In this chapter, we describe the known gene regulatory networks involved in the development of the different parts of the visual system and explore general components in these gene networks. Finally, we discuss the advantages of the fly visual system as a model for gene regulatory network discovery in the era of single-cell transcriptomics.
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Affiliation(s)
- Yen-Chung Chen
- Department of Biology, New York University, New York, NY, United States
| | - Claude Desplan
- Department of Biology, New York University, New York, NY, United States.
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50
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A network approach to analyze neuronal lineage and layer innervation in the Drosophila optic lobes. PLoS One 2020; 15:e0227897. [PMID: 32023281 PMCID: PMC7001925 DOI: 10.1371/journal.pone.0227897] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 01/02/2020] [Indexed: 12/05/2022] Open
Abstract
The optic lobes of the fruit fly Drosophila melanogaster form a highly wired neural network composed of roughly 130.000 neurons of more than 80 different types. How neuronal diversity arises from very few cell progenitors is a central question in developmental neurobiology. We use the optic lobe of the fruit fly as a paradigm to understand how neuroblasts, the neural stem cells, generate multiple neuron types. Although the development of the fly brain has been the subject of extensive research, very little is known about the lineage relationships of the cell types forming the adult optic lobes. Here we perform a large-scale lineage bioinformatics analysis using the graph theory. We generated a large collection of cell clones that genetically label the progeny of neuroblasts and built a database to draw graphs showing the lineage relationships between cell types. By establishing biological criteria that measures the strength of the neuronal relationships and applying community detection tools we have identified eight clusters of neurons. Each cluster contains different cell types that we pose are the product of eight distinct classes of neuroblasts. Three of these clusters match the available lineage data, supporting the predictive value of the analysis. Finally, we show that the neuronal progeny of a neuroblast do not have preferential innervation patterns, but instead become part of different layers and neuropils. Here we establish a new methodology that helps understanding the logic of Drosophila brain development and can be applied to the more complex vertebrate brains.
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