1
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Grmai L, Jimenez E, Baxter E, Doren MV. Steroid signaling controls sex-specific development in an invertebrate. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.12.22.573099. [PMID: 38187640 PMCID: PMC10769319 DOI: 10.1101/2023.12.22.573099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
In vertebrate sexual development, two important steroid hormones, testosterone and estrogen, regulate the sex-specific development of many tissues. In contrast, invertebrates utilize a single steroid hormone, ecdysone, to regulate developmental timing in both sexes. However, here we show that in Drosophila melanogaster, sex-specific ecdysone (E) signaling controls important aspects of gonad sexual dimorphism. Rather than being regulated at the level of hormone production, hormone activity is regulated cell-autonomously through sex-specific hormone reception. Ecdysone receptor (EcR) expression is restricted to the developing ovary and is repressed in the testis at a time when ecdysone initiates ovary morphogenesis. Interestingly, EcR expression is regulated downstream of the sex determination factor Doublesex (Dsx), the founding member of the Dsx/Mab3 Related Transcription Factor (DMRT) family that regulates gonad development in all animals. E signaling is required for normal ovary development1,2, and ectopic activation of E signaling in the testis antagonized stem cell niche identity and feminized somatic support cells, which were transformed into follicle-like cells. This work demonstrates that invertebrates can also use steroid hormone signaling to control sex-specific development. Further, it may help explain recent work showing that vertebrate sexual development is surprisingly cell-autonomous. For example, chickens utilize testosterone and estrogen to control sex-specific development, but when they have a mixture of cells with male and female genotypes, the male cells develop as male and the female cells develop as female despite exposure to the same circulating hormones3. Sex-specific regulation of steroid hormone signaling may well underly such cell-autonomous sexual fate choices in vertebrates as it does in Drosophila.
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Affiliation(s)
- Lydia Grmai
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Erin Jimenez
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Ellen Baxter
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
| | - Mark Van Doren
- Department of Biology, Johns Hopkins University, Baltimore, Maryland, USA
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2
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Lee GG, Peterson AJ, Kim MJ, O’Connor MB, Park JH. Multiple isoforms of the Activin-like receptor baboon differentially regulate proliferation and conversion behaviors of neuroblasts and neuroepithelial cells in the Drosophila larval brain. PLoS One 2024; 19:e0305696. [PMID: 38913612 PMCID: PMC11195991 DOI: 10.1371/journal.pone.0305696] [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: 03/22/2024] [Accepted: 06/04/2024] [Indexed: 06/26/2024] Open
Abstract
In Drosophila coordinated proliferation of two neural stem cells, neuroblasts (NB) and neuroepithelial (NE) cells, is pivotal for proper larval brain growth that ultimately determines the final size and performance of an adult brain. The larval brain growth displays two phases based on behaviors of NB and NEs: the first one in early larval stages, influenced by nutritional status and the second one in the last larval stage, promoted by ecdysone signaling after critical weight checkpoint. Mutations of the baboon (babo) gene that produces three isoforms (BaboA-C), all acting as type-I receptors of Activin-type transforming growth factor β (TGF-β) signaling, cause a small brain phenotype due to severely reduced proliferation of the neural stem cells. In this study we show that loss of babo function severely affects proliferation of NBs and NEs as well as conversion of NEs from both phases. By analyzing babo-null and newly generated isoform-specific mutants by CRISPR mutagenesis as well as isoform-specific RNAi knockdowns in a cell- and stage-specific manner, our data support differential contributions of the isoforms for these cellular events with BaboA playing the major role. Stage-specific expression of EcR-B1 in the brain is also regulated primarily by BaboA along with function of the other isoforms. Blocking EcR function in both neural stem cells results in a small brain phenotype that is more severe than baboA-knockdown alone. In summary, our study proposes that the Babo-mediated signaling promotes proper behaviors of the neural stem cells in both phases and achieves this by acting upstream of EcR-B1 expression in the second phase.
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Affiliation(s)
- Gyunghee G. Lee
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee, United States of America
| | - Aidan J. Peterson
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Myung-Jun Kim
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Michael B. O’Connor
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Jae H. Park
- Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee, United States of America
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3
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Nguyen PK, Cheng LY. Drosophila medulla neuroblast termination via apoptosis, differentiation, and gliogenic switch is scheduled by the depletion of the neuroepithelial stem cell pool. eLife 2024; 13:e96876. [PMID: 38905123 PMCID: PMC11262793 DOI: 10.7554/elife.96876] [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: 02/22/2024] [Accepted: 06/20/2024] [Indexed: 06/23/2024] Open
Abstract
The brain is consisted of diverse neurons arising from a limited number of neural stem cells. Drosophila neural stem cells called neuroblasts (NBs) produces specific neural lineages of various lineage sizes depending on their location in the brain. In the Drosophila visual processing centre - the optic lobes (OLs), medulla NBs derived from the neuroepithelium (NE) give rise to neurons and glia cells of the medulla cortex. The timing and the mechanisms responsible for the cessation of medulla NBs are so far not known. In this study, we show that the termination of medulla NBs during early pupal development is determined by the exhaustion of the NE stem cell pool. Hence, altering NE-NB transition during larval neurogenesis disrupts the timely termination of medulla NBs. Medulla NBs terminate neurogenesis via a combination of apoptosis, terminal symmetric division via Prospero, and a switch to gliogenesis via Glial Cell Missing (Gcm); however, these processes occur independently of each other. We also show that temporal progression of the medulla NBs is mostly not required for their termination. As the Drosophila OL shares a similar mode of division with mammalian neurogenesis, understanding when and how these progenitors cease proliferation during development can have important implications for mammalian brain size determination and regulation of its overall function.
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Affiliation(s)
- Phuong-Khanh Nguyen
- Peter MacCallum Cancer CentreMelbourneAustralia
- Department of Anatomy and Physiology, The University of MelbourneMelbourneAustralia
| | - Louise Y Cheng
- Peter MacCallum Cancer CentreMelbourneAustralia
- Department of Anatomy and Physiology, The University of MelbourneMelbourneAustralia
- Sir Peter MacCallum Department of Oncology, The University of MelbourneMelbourneAustralia
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4
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Nguyen TH, Vicidomini R, Choudhury SD, Han TH, Maric D, Brody T, Serpe M. scRNA-seq data from the larval Drosophila ventral cord provides a resource for studying motor systems function and development. Dev Cell 2024; 59:1210-1230.e9. [PMID: 38569548 PMCID: PMC11078614 DOI: 10.1016/j.devcel.2024.03.016] [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: 06/27/2023] [Revised: 12/05/2023] [Accepted: 03/06/2024] [Indexed: 04/05/2024]
Abstract
The Drosophila larval ventral nerve cord (VNC) shares many similarities with the spinal cord of vertebrates and has emerged as a major model for understanding the development and function of motor systems. Here, we use high-quality scRNA-seq, validated by anatomical identification, to create a comprehensive census of larval VNC cell types. We show that the neural lineages that comprise the adult VNC are already defined, but quiescent, at the larval stage. Using fluorescence-activated cell sorting (FACS)-enriched populations, we separate all motor neuron bundles and link individual neuron clusters to morphologically characterized known subtypes. We discovered a glutamate receptor subunit required for basal neurotransmission and homeostasis at the larval neuromuscular junction. We describe larval glia and endorse the general view that glia perform consistent activities throughout development. This census represents an extensive resource and a powerful platform for future discoveries of cellular and molecular mechanisms in repair, regeneration, plasticity, homeostasis, and behavioral coordination.
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Affiliation(s)
| | | | | | | | - Dragan Maric
- Flow and Imaging Cytometry Core, NINDS, NIH, Bethesda, MD 20892, USA
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5
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Sood C, Nahid MA, Branham KR, Pahl M, Doyle SE, Siegrist SE. Delta-dependent Notch activation closes the early neuroblast temporal program to promote lineage progression and neurogenesis termination in Drosophila. eLife 2024; 12:RP88565. [PMID: 38391176 PMCID: PMC10942576 DOI: 10.7554/elife.88565] [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: 02/24/2024] Open
Abstract
Neuroblasts in Drosophila divide asymmetrically, sequentially expressing a series of intrinsic factors to generate a diversity of neuron types. These intrinsic factors known as temporal factors dictate timing of neuroblast transitions in response to steroid hormone signaling and specify early versus late temporal fates in neuroblast neuron progeny. After completing their temporal programs, neuroblasts differentiate or die, finalizing both neuron number and type within each neuroblast lineage. From a screen aimed at identifying genes required to terminate neuroblast divisions, we identified Notch and Notch pathway components. When Notch is knocked down, neuroblasts maintain early temporal factor expression longer, delay late temporal factor expression, and continue dividing into adulthood. We find that Delta, expressed in cortex glia, neuroblasts, and after division, their GMC progeny, regulates neuroblast Notch activity. We also find that Delta in neuroblasts is expressed high early, low late, and is controlled by the intrinsic temporal program: early factor Imp promotes Delta, late factors Syp/E93 reduce Delta. Thus, in addition to systemic steroid hormone cues, forward lineage progression is controlled by local cell-cell signaling between neuroblasts and their cortex glia/GMC neighbors: Delta transactivates Notch in neuroblasts bringing the early temporal program and early temporal factor expression to a close.
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Affiliation(s)
- Chhavi Sood
- Department of Biology, University of VirginiaCharlottesvilleUnited States
| | | | - Kendall R Branham
- Department of Biology, University of VirginiaCharlottesvilleUnited States
| | - Matt Pahl
- Department of Biology, University of VirginiaCharlottesvilleUnited States
| | - Susan E Doyle
- Department of Biology, University of VirginiaCharlottesvilleUnited States
| | - Sarah E Siegrist
- Department of Biology, University of VirginiaCharlottesvilleUnited States
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6
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Hamid A, Gattuso H, Caglar AN, Pillai M, Steele T, Gonzalez A, Nagel K, Syed MH. The conserved RNA-binding protein Imp is required for the specification and function of olfactory navigation circuitry in Drosophila. Curr Biol 2024; 34:473-488.e6. [PMID: 38181792 PMCID: PMC10872534 DOI: 10.1016/j.cub.2023.12.020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 11/14/2023] [Accepted: 12/07/2023] [Indexed: 01/07/2024]
Abstract
Complex behaviors depend on the precise developmental specification of neuronal circuits, but the relationship between genetic programs for neural development, circuit structure, and behavioral output is often unclear. The central complex (CX) is a conserved sensory-motor integration center in insects, which governs many higher-order behaviors and largely derives from a small number of type II neural stem cells (NSCs). Here, we show that Imp, a conserved IGF-II mRNA-binding protein expressed in type II NSCs, plays a role in specifying essential components of CX olfactory navigation circuitry. We show the following: (1) that multiple components of olfactory navigation circuitry arise from type II NSCs. (2) Manipulating Imp expression in type II NSCs alters the number and morphology of many of these circuit elements, with the most potent effects on neurons targeting the ventral layers of the fan-shaped body (FB). (3) Imp regulates the specification of Tachykinin-expressing ventral FB input neurons. (4) Imp is required in type II NSCs for establishing proper morphology of the CX neuropil structures. (5) Loss of Imp in type II NSCs abolishes upwind orientation to attractive odor while leaving locomotion and odor-evoked regulation of movement intact. Taken together, our findings establish that a temporally expressed gene can regulate the expression of a complex behavior by developmentally regulating the specification of multiple circuit components and provides a first step toward a developmental dissection of the CX and its roles in behavior.
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Affiliation(s)
- Aisha Hamid
- Department of Biology, University of New Mexico, 219 Yale Blvd NE, Albuquerque, NM 87131, USA
| | - Hannah Gattuso
- Neuroscience Institute, NYU Medical Center, 435 E 30th St., New York, NY 10016, USA
| | - Aysu Nora Caglar
- Department of Biology, University of New Mexico, 219 Yale Blvd NE, Albuquerque, NM 87131, USA
| | - Midhula Pillai
- Neuroscience Institute, NYU Medical Center, 435 E 30th St., New York, NY 10016, USA
| | - Theresa Steele
- Neuroscience Institute, NYU Medical Center, 435 E 30th St., New York, NY 10016, USA
| | - Alexa Gonzalez
- Department of Biology, University of New Mexico, 219 Yale Blvd NE, Albuquerque, NM 87131, USA
| | - Katherine Nagel
- Neuroscience Institute, NYU Medical Center, 435 E 30th St., New York, NY 10016, USA.
| | - Mubarak Hussain Syed
- Department of Biology, University of New Mexico, 219 Yale Blvd NE, Albuquerque, NM 87131, USA.
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7
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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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8
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Munroe JA, Doe CQ. Imp is expressed in INPs and newborn neurons where it regulates neuropil targeting in the central complex. Neural Dev 2023; 18:9. [PMID: 38031099 PMCID: PMC10685609 DOI: 10.1186/s13064-023-00177-9] [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: 09/05/2023] [Accepted: 11/06/2023] [Indexed: 12/01/2023] Open
Abstract
The generation of neuronal diversity remains incompletely understood. In Drosophila, the central brain is populated by neural stem cells derived from progenitors called neuroblasts (NBs). There are two types of NBs, type 1 and 2. T1NBs have a relatively simple lineage, whereas T2NBs expand and diversify the neural population with the generation of intermediate neural progenitors (INPs), contributing many neurons to the adult central complex, a brain region essential for navigation. However, it is not fully understood how neural diversity is created in T2NB and INP lineages. Imp, an RNA-binding protein, is expressed in T2NBs in a high-to-low temporal gradient, while the RNA-binding protein Syncrip forms an opposing gradient. It remains unknown if Imp expression is carried into INPs; whether it forms a gradient similar to NBs; and whether INP expression of Imp is required for generating neuronal identity or morphology. Here, we show that Imp/Syp are both present in INPs, but not always in opposing gradients. We find that newborn INPs adopt their Imp/Syp levels from their parental T2NBs; that Imp and Syp are expressed in stage-specific high-to-low gradients in INPs. In addition, there is a late INP pulse of Imp. We find that neurons born from old INPs (E-PG and PF-R neurons) have altered morphology following both Imp knock-down and Imp overexpression. We conclude that Imp functions in INPs and newborn neurons to determine proper neuronal morphology and central complex neuropil organization.
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Affiliation(s)
- Jordan A Munroe
- Institute of Neuroscience, Howard Hughes Medical Institute, Univ. of Oregon, Eugene, OR, 97403, USA
| | - Chris Q Doe
- Institute of Neuroscience, Howard Hughes Medical Institute, Univ. of Oregon, Eugene, OR, 97403, USA.
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9
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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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10
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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: 1] [Impact Index Per Article: 1.0] [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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11
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Sood C, Nahid MA, Branham KR, Pahl MC, Doyle SE, Siegrist SE. Delta-dependent Notch activation closes the early neuroblast temporal program to promote lineage progression and neurogenesis termination in Drosophila. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.28.534626. [PMID: 37034719 PMCID: PMC10081207 DOI: 10.1101/2023.03.28.534626] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Neuroblasts in Drosophila divide asymmetrically, sequentially expressing a series of intrinsic factors to generate a diversity of neuron types. These intrinsic factors known as temporal factors dictate timing of neuroblast transitions in response to steroid hormone signaling and specify early versus late temporal fates in neuroblast neuron progeny. After completing their temporal programs, neuroblasts differentiate or die, finalizing both neuron number and type within each neuroblast lineage. From a screen aimed at identifying genes required to terminate neuroblast divisions, we identified Notch and Notch pathway components. When Notch is knocked down, neuroblasts maintain early temporal factor expression longer, delay late temporal factor expression, and continue dividing into adulthood. We find that Delta, expressed in cortex glia, neuroblasts, and after division, their GMC progeny, regulates neuroblast Notch activity. We also find that Delta in neuroblasts is expressed high early, low late, and is controlled by the intrinsic temporal program: early factor Imp promotes Delta, late factors Syp/E93 reduce Delta. Thus, in addition to systemic steroid hormone cues, forward lineage progression is controlled by local cell-cell signaling between neuroblasts and their cortex glia/GMC neighbors: Delta transactivates Notch in neuroblasts bringing the early temporal program and early temporal factor expression to a close.
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12
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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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13
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Hamid A, Gutierrez A, Munroe J, Syed MH. The Drivers of Diversity: Integrated genetic and hormonal cues regulate neural diversity. Semin Cell Dev Biol 2023; 142:23-35. [PMID: 35915026 DOI: 10.1016/j.semcdb.2022.07.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 07/06/2022] [Accepted: 07/17/2022] [Indexed: 11/17/2022]
Abstract
Proper functioning of the nervous system relies not only on the generation of a vast repertoire of distinct neural cell types but also on the precise neural circuitry within them. How the generation of highly diverse neural populations is regulated during development remains a topic of interest. Landmark studies in Drosophila have identified the genetic and temporal cues regulating neural diversity and thus have provided valuable insights into our understanding of temporal patterning of the central nervous system. The development of the Drosophila central complex, which is mostly derived from type II neural stem cell (NSC) lineages, showcases how a small pool of NSCs can give rise to vast and distinct progeny. Similar to the human outer subventricular zone (OSVZ) neural progenitors, type II NSCs generate intermediate neural progenitors (INPs) to expand and diversify lineages that populate higher brain centers. Each type II NSC has a distinct spatial identity and timely regulated expression of many transcription factors and mRNA binding proteins. Additionally, INPs derived from them show differential expression of genes depending on their birth order. Together type II NSCs and INPs display a combinatorial temporal patterning that expands neural diversity of the central brain lineages. We cover advances in current understanding of type II NSC temporal patterning and discuss similarities and differences in temporal patterning mechanisms of various NSCs with a focus on how cell-intrinsic and extrinsic hormonal cues regulate temporal transitions in NSCs during larval development. Cell extrinsic ligands activate conserved signaling pathways and extrinsic hormonal cues act as a temporal switch that regulate temporal progression of the NSCs. We conclude by elaborating on how a progenitor's temporal code regulates the fate specification and identity of distinct neural types. At the end, we also discuss open questions in linking developmental cues to neural identity, circuits, and underlying behaviors in the adult fly.
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Affiliation(s)
- Aisha Hamid
- Department of Biology, University of New Mexico, Albuquerque, NM 87113, USA
| | - Andrew Gutierrez
- Department of Biology, University of New Mexico, Albuquerque, NM 87113, USA
| | - Jordan Munroe
- Institute of Neuroscience, University of Oregon, Eugene, OR 97403, USA
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14
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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: 6] [Impact Index Per Article: 6.0] [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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15
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Hamid A, Gattuso H, Caglar AN, Pillai M, Steele T, Gonzalez A, Nagel K, Syed MH. The RNA-binding protein, Imp specifies olfactory navigation circuitry and behavior in Drosophila. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.26.542522. [PMID: 37398350 PMCID: PMC10312496 DOI: 10.1101/2023.05.26.542522] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Complex behaviors depend on the precise developmental specification of neuronal circuits, but the relationship between genetic prograssms for neural development, circuit structure, and behavioral output is often unclear. The central complex (CX) is a conserved sensory-motor integration center in insects that governs many higher order behaviors and largely derives from a small number of Type II neural stem cells. Here, we show that Imp, a conserved IGF-II mRNA-binding protein expressed in Type II neural stem cells, specifies components of CX olfactory navigation circuitry. We show: (1) that multiple components of olfactory navigation circuitry arise from Type II neural stem cells and manipulating Imp expression in Type II neural stem cells alters the number and morphology of many of these circuit elements, with the most potent effects on neurons targeting the ventral layers of the fan-shaped body. (2) Imp regulates the specification of Tachykinin expressing ventral fan-shaped body input neurons. (3) Imp in Type II neural stem cells alters the morphology of the CX neuropil structures. (4) Loss of Imp in Type II neural stem cells abolishes upwind orientation to attractive odor while leaving locomotion and odor-evoked regulation of movement intact. Taken together, our work establishes that a single temporally expressed gene can regulate the expression of a complex behavior through the developmental specification of multiple circuit components and provides a first step towards a developmental dissection of the CX and its roles in behavior.
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Affiliation(s)
- Aisha Hamid
- Department of Biology, 219 Yale Blvd NE, University of New Mexico, Albuquerque, NM 87131, USA
| | - Hannah Gattuso
- Neuroscience Institute, NYU Medical Center, 435 E 30th St., New York, NY 10016, USA
| | - Aysu Nora Caglar
- Current address: Biochemistry & Molecular Biology, 915 Camino De Salud NE, Albuquerque, NM 87132, USA
| | - Midhula Pillai
- Neuroscience Institute, NYU Medical Center, 435 E 30th St., New York, NY 10016, USA
| | - Theresa Steele
- Neuroscience Institute, NYU Medical Center, 435 E 30th St., New York, NY 10016, USA
| | - Alexa Gonzalez
- Department of Biology, 219 Yale Blvd NE, University of New Mexico, Albuquerque, NM 87131, USA
| | - Katherine Nagel
- Neuroscience Institute, NYU Medical Center, 435 E 30th St., New York, NY 10016, USA
| | - Mubarak Hussain Syed
- Department of Biology, 219 Yale Blvd NE, University of New Mexico, Albuquerque, NM 87131, USA
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16
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Goldblatt D, Huang S, Greaney MR, Hamling KR, Voleti V, Perez-Campos C, Patel KB, Li W, Hillman EMC, Bagnall MW, Schoppik D. Neuronal birthdate reveals topography in a vestibular brainstem circuit for gaze stabilization. Curr Biol 2023; 33:1265-1281.e7. [PMID: 36924768 PMCID: PMC10089979 DOI: 10.1016/j.cub.2023.02.048] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 01/03/2023] [Accepted: 02/15/2023] [Indexed: 03/17/2023]
Abstract
Across the nervous system, neurons with similar attributes are topographically organized. This topography reflects developmental pressures. Oddly, vestibular (balance) nuclei are thought to be disorganized. By measuring activity in birthdated neurons, we revealed a functional map within the central vestibular projection nucleus that stabilizes gaze in the larval zebrafish. We first discovered that both somatic position and stimulus selectivity follow projection neuron birthdate. Next, with electron microscopy and loss-of-function assays, we found that patterns of peripheral innervation to projection neurons were similarly organized by birthdate. Finally, birthdate revealed spatial patterns of axonal arborization and synapse formation to projection neuron outputs. Collectively, we find that development reveals previously hidden organization to the input, processing, and output layers of a highly conserved vertebrate sensorimotor circuit. The spatial and temporal attributes we uncover constrain the developmental mechanisms that may specify the fate, function, and organization of vestibulo-ocular reflex neurons. More broadly, our data suggest that, like invertebrates, temporal mechanisms may assemble vertebrate sensorimotor architecture.
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Affiliation(s)
- Dena Goldblatt
- Departments of Otolaryngology, Neuroscience & Physiology, and the Neuroscience Institute, New York University Grossman School of Medicine, New York, NY 10016, USA; Center for Neural Science, New York University, New York, NY 10004, USA
| | - Stephanie Huang
- Departments of Otolaryngology, Neuroscience & Physiology, and the Neuroscience Institute, New York University Grossman School of Medicine, New York, NY 10016, USA; Center for Neural Science, New York University, New York, NY 10004, USA
| | - Marie R Greaney
- Departments of Otolaryngology, Neuroscience & Physiology, and the Neuroscience Institute, New York University Grossman School of Medicine, New York, NY 10016, USA; University of Chicago, Chicago, IL 60637, USA
| | - Kyla R Hamling
- Departments of Otolaryngology, Neuroscience & Physiology, and the Neuroscience Institute, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Venkatakaushik Voleti
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Citlali Perez-Campos
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Kripa B Patel
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Wenze Li
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Elizabeth M C Hillman
- Mortimer B. Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10027, USA
| | - Martha W Bagnall
- Department of Neuroscience, Washington University, St. Louis, MO 63130, USA
| | - David Schoppik
- Departments of Otolaryngology, Neuroscience & Physiology, and the Neuroscience Institute, New York University Grossman School of Medicine, New York, NY 10016, USA.
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17
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Truman JW, Riddiford LM. Drosophila postembryonic nervous system development: a model for the endocrine control of development. Genetics 2023; 223:iyac184. [PMID: 36645270 PMCID: PMC9991519 DOI: 10.1093/genetics/iyac184] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 12/13/2022] [Indexed: 01/17/2023] Open
Abstract
During postembryonic life, hormones, including ecdysteroids, juvenile hormones, insulin-like peptides, and activin/TGFβ ligands act to transform the larval nervous system into an adult version, which is a fine-grained mosaic of recycled larval neurons and adult-specific neurons. Hormones provide both instructional signals that make cells competent to undergo developmental change and timing cues to evoke these changes across the nervous system. While touching on all the above hormones, our emphasis is on the ecdysteroids, ecdysone and 20-hydroxyecdysone (20E). These are the prime movers of insect molting and metamorphosis and are involved in all phases of nervous system development, including neurogenesis, pruning, arbor outgrowth, and cell death. Ecdysteroids appear as a series of steroid peaks that coordinate the larval molts and the different phases of metamorphosis. Each peak directs a stereotyped cascade of transcription factor expression. The cascade components then direct temporal programs of effector gene expression, but the latter vary markedly according to tissue and life stage. The neurons read the ecdysteroid titer through various isoforms of the ecdysone receptor, a nuclear hormone receptor. For example, at metamorphosis the pruning of larval neurons is mediated through the B isoforms, which have strong activation functions, whereas subsequent outgrowth is mediated through the A isoform through which ecdysteroids play a permissive role to allow local tissue interactions to direct outgrowth. The major circulating ecdysteroid can also change through development. During adult development ecdysone promotes early adult patterning and differentiation while its metabolite, 20E, later evokes terminal adult differentiation.
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Affiliation(s)
- James W Truman
- Friday Harbor Laboratories, University of Washington, Friday Harbor, WA 98250, USA
- Department of Biology, University of Washington, Box 351800, Seattle, WA 98195, USA
| | - Lynn M Riddiford
- Friday Harbor Laboratories, University of Washington, Friday Harbor, WA 98250, USA
- Department of Biology, University of Washington, Box 351800, Seattle, WA 98195, USA
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18
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Noncoding RNA Regulation of Hormonal and Metabolic Systems in the Fruit Fly Drosophila. Metabolites 2023; 13:metabo13020152. [PMID: 36837772 PMCID: PMC9967906 DOI: 10.3390/metabo13020152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/12/2023] [Accepted: 01/16/2023] [Indexed: 01/22/2023] Open
Abstract
The importance of RNAs is commonly recognised thanks to protein-coding RNAs, whereas non-coding RNAs (ncRNAs) were conventionally regarded as 'junk'. In the last decade, ncRNAs' significance and roles are becoming noticeable in various biological activities, including those in hormonal and metabolic regulation. Among the ncRNAs: microRNA (miRNA) is a small RNA transcript with ~20 nucleotides in length; long non-coding RNA (lncRNA) is an RNA transcript with >200 nucleotides; and circular RNA (circRNA) is derived from back-splicing of pre-mRNA. These ncRNAs can regulate gene expression levels at epigenetic, transcriptional, and post-transcriptional levels through various mechanisms in insects. A better understanding of these crucial regulators is essential to both basic and applied entomology. In this review, we intend to summarise and discuss the current understanding and knowledge of miRNA, lncRNA, and circRNA in the best-studied insect model, the fruit fly Drosophila.
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19
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Imp is required for timely exit from quiescence in Drosophila type II neuroblasts. PLoS One 2022; 17:e0272177. [PMID: 36520944 PMCID: PMC9754222 DOI: 10.1371/journal.pone.0272177] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Accepted: 09/06/2022] [Indexed: 12/23/2022] Open
Abstract
Stem cells must balance proliferation and quiescence, with excess proliferation favoring tumor formation, and premature quiescence preventing proper organogenesis. Drosophila brain neuroblasts are a model for investigating neural stem cell entry and exit from quiescence. Neuroblasts begin proliferating during embryogenesis, enter quiescence prior to larval hatching, and resume proliferation 12-30h after larval hatching. Here we focus on the mechanism used to exit quiescence, focusing on "type II" neuroblasts. There are 16 type II neuroblasts in the brain, and they undergo the same cycle of embryonic proliferation, quiescence, and proliferation as do most other brain neuroblasts. We focus on type II neuroblasts due to their similar lineage as outer radial glia in primates (both have extended lineages with intermediate neural progenitors), and because of the availability of specific markers for type II neuroblasts and their progeny. Here we characterize the role of Insulin-like growth factor II mRNA-binding protein (Imp) in type II neuroblast proliferation and quiescence. Imp has previously been shown to promote proliferation in type II neuroblasts, in part by acting antagonistically to another RNA-binding protein called Syncrip (Syp). Here we show that reducing Imp levels delays exit from quiescence in type II neuroblasts, acting independently of Syp, with Syp levels remaining low in both quiescent and newly proliferating type II neuroblasts. We conclude that Imp promotes exit from quiescence, a function closely related to its known role in promoting neuroblast proliferation.
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20
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Dillon N, Cocanougher B, Sood C, Yuan X, Kohn AB, Moroz LL, Siegrist SE, Zlatic M, Doe CQ. Single cell RNA-seq analysis reveals temporally-regulated and quiescence-regulated gene expression in Drosophila larval neuroblasts. Neural Dev 2022; 17:7. [PMID: 36002894 PMCID: PMC9404614 DOI: 10.1186/s13064-022-00163-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 05/19/2022] [Indexed: 12/12/2022] Open
Abstract
The mechanisms that generate neural diversity during development remains largely unknown. Here, we use scRNA-seq methodology to discover new features of the Drosophila larval CNS across several key developmental timepoints. We identify multiple progenitor subtypes - both stem cell-like neuroblasts and intermediate progenitors - that change gene expression across larval development, and report on new candidate markers for each class of progenitors. We identify a pool of quiescent neuroblasts in newly hatched larvae and show that they are transcriptionally primed to respond to the insulin signaling pathway to exit from quiescence, including relevant pathway components in the adjacent glial signaling cell type. We identify candidate "temporal transcription factors" (TTFs) that are expressed at different times in progenitor lineages. Our work identifies many cell type specific genes that are candidates for functional roles, and generates new insight into the differentiation trajectory of larval neurons.
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Affiliation(s)
- Noah Dillon
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, OR, 97403, Eugene, USA
| | - Ben Cocanougher
- Department of Zoology, University of Cambridge, Cambridge, UK
| | - Chhavi Sood
- Department of Biology, University of Virginia, VA, 22904, Charlottesville, USA
| | - Xin Yuan
- Department of Biology, University of Virginia, VA, 22904, Charlottesville, USA
| | - Andrea B Kohn
- Whitney Laboratory for Marine Biosciences, University of Florida, FL, 32080, St. Augustine, USA
| | - Leonid L Moroz
- Whitney Laboratory for Marine Biosciences, University of Florida, FL, 32080, St. Augustine, USA
| | - Sarah E Siegrist
- Department of Biology, University of Virginia, VA, 22904, Charlottesville, USA
| | - Marta Zlatic
- MRC Laboratory of Molecular Biology, Dept of Zoology, University of Cambridge, Cambridge, UK.,Janelia Research Campus, VA, Ashburn, USA
| | - Chris Q Doe
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, OR, 97403, Eugene, USA.
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21
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Pfeifer K, Wolfstetter G, Anthonydhason V, Masudi T, Arefin B, Bemark M, Mendoza-Garcia P, Palmer RH. Patient-associated mutations in Drosophila Alk perturb neuronal differentiation and promote survival. Dis Model Mech 2022; 15:dmm049591. [PMID: 35972154 PMCID: PMC9403751 DOI: 10.1242/dmm.049591] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Accepted: 06/27/2022] [Indexed: 12/13/2022] Open
Abstract
Activating anaplastic lymphoma kinase (ALK) receptor tyrosine kinase (RTK) mutations occur in pediatric neuroblastoma and are associated with poor prognosis. To study ALK-activating mutations in a genetically controllable system, we employed CRIPSR/Cas9, incorporating orthologs of the human oncogenic mutations ALKF1174L and ALKY1278S in the Drosophila Alk locus. AlkF1251L and AlkY1355S mutant Drosophila exhibited enhanced Alk signaling phenotypes, but unexpectedly depended on the Jelly belly (Jeb) ligand for activation. Both AlkF1251L and AlkY1355S mutant larval brains displayed hyperplasia, represented by increased numbers of Alk-positive neurons. Despite this hyperplasic phenotype, no brain tumors were observed in mutant animals. We showed that hyperplasia in Alk mutants was not caused by significantly increased rates of proliferation, but rather by decreased levels of apoptosis in the larval brain. Using single-cell RNA sequencing, we identified perturbations during temporal fate specification in AlkY1355S mutant mushroom body lineages. These findings shed light on the role of Alk in neurodevelopmental processes and highlight the potential of Alk-activating mutations to perturb specification and promote survival in neuronal lineages. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Kathrin Pfeifer
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Georg Wolfstetter
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Vimala Anthonydhason
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Tafheem Masudi
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Badrul Arefin
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Mats Bemark
- Department of Microbiology and Immunology, Mucosal Immunobiology and Vaccine Center, Institute of Biomedicine, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Patricia Mendoza-Garcia
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, SE-405 30 Gothenburg, Sweden
| | - Ruth H. Palmer
- Department of Medical Biochemistry and Cell Biology, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, SE-405 30 Gothenburg, Sweden
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22
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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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23
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Post-transcriptional regulation of transcription factor codes in immature neurons drives neuronal diversity. Cell Rep 2022; 39:110992. [PMID: 35767953 PMCID: PMC9479746 DOI: 10.1016/j.celrep.2022.110992] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 04/15/2022] [Accepted: 06/01/2022] [Indexed: 12/31/2022] Open
Abstract
How the vast array of neuronal diversity is generated remains an unsolved problem. Here, we investigate how 29 morphologically distinct leg motoneurons are generated from a single stem cell in Drosophila. We identify 19 transcription factor (TF) codes expressed in immature motoneurons just before their morphological differentiation. Using genetic manipulations and a computational tool, we demonstrate that the TF codes are progressively established in immature motoneurons according to their birth order. Comparing RNA and protein expression patterns of multiple TFs reveals that post-transcriptional regulation plays an essential role in shaping these TF codes. Two RNA-binding proteins, Imp and Syp, expressed in opposing gradients in immature motoneurons, control the translation of multiple TFs. The varying sensitivity of TF mRNAs to the opposing gradients of Imp and Syp in immature motoneurons decrypts these gradients into distinct TF codes, establishing the connectome between motoneuron axons and their target muscles.
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24
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Emerging Roles of RNA-Binding Proteins in Neurodevelopment. J Dev Biol 2022; 10:jdb10020023. [PMID: 35735914 PMCID: PMC9224834 DOI: 10.3390/jdb10020023] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Revised: 06/02/2022] [Accepted: 06/08/2022] [Indexed: 02/06/2023] Open
Abstract
Diverse cell types in the central nervous system (CNS) are generated by a relatively small pool of neural stem cells during early development. Spatial and temporal regulation of stem cell behavior relies on precise coordination of gene expression. Well-studied mechanisms include hormone signaling, transcription factor activity, and chromatin remodeling processes. Much less is known about downstream RNA-dependent mechanisms including posttranscriptional regulation, nuclear export, alternative splicing, and transcript stability. These important functions are carried out by RNA-binding proteins (RBPs). Recent work has begun to explore how RBPs contribute to stem cell function and homeostasis, including their role in metabolism, transport, epigenetic regulation, and turnover of target transcripts. Additional layers of complexity are provided by the different target recognition mechanisms of each RBP as well as the posttranslational modifications of the RBPs themselves that alter function. Altogether, these functions allow RBPs to influence various aspects of RNA metabolism to regulate numerous cellular processes. Here we compile advances in RNA biology that have added to our still limited understanding of the role of RBPs in neurodevelopment.
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25
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Gaultier C, Foppolo S, Maurange C. Regulation of developmental hierarchy in Drosophila neural stem cell tumors by COMPASS and Polycomb complexes. SCIENCE ADVANCES 2022; 8:eabi4529. [PMID: 35544555 PMCID: PMC9094666 DOI: 10.1126/sciadv.abi4529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Accepted: 03/23/2022] [Indexed: 06/15/2023]
Abstract
COMPASS and Polycomb complexes are antagonistic chromatin complexes that are frequently inactivated in cancers, but how these events affect the cellular hierarchy, composition, and growth of tumors is unclear. These characteristics can be systematically investigated in Drosophila neuroblast tumors in which cooption of temporal patterning induces a developmental hierarchy that confers cancer stem cell (CSC) properties to a subset of neuroblasts retaining an early larval temporal identity. Here, using single-cell transcriptomics, we reveal that the trithorax/MLL1/2-COMPASS-like complex guides the developmental trajectory at the top of the tumor hierarchy. Consequently, trithorax knockdown drives larval-to-embryonic temporal reversion and the marked expansion of CSCs that remain locked in a spectrum of early temporal states. Unexpectedly, this phenotype is amplified by concomitant inactivation of Polycomb repressive complex 2 genes, unleashing tumor growth. This study illustrates how inactivation of specific COMPASS and Polycomb complexes cooperates to impair tumor hierarchies, inducing CSC plasticity, heterogeneity, and expansion.
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Affiliation(s)
| | - Sophie Foppolo
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living systems, Equipe Labellisée Ligue Contre le Cancer, Campus de Luminy Case 907, 13288 Cedex 09 Marseille, France
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26
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Nguyen PK, Cheng LY. Non-autonomous regulation of neurogenesis by extrinsic cues: a Drosophila perspective. OXFORD OPEN NEUROSCIENCE 2022; 1:kvac004. [PMID: 38596708 PMCID: PMC10913833 DOI: 10.1093/oons/kvac004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 03/20/2022] [Accepted: 03/23/2022] [Indexed: 04/11/2024]
Abstract
The formation of a functional circuitry in the central nervous system (CNS) requires the correct number and subtypes of neural cells. In the developing brain, neural stem cells (NSCs) self-renew while giving rise to progenitors that in turn generate differentiated progeny. As such, the size and the diversity of cells that make up the functional CNS depend on the proliferative properties of NSCs. In the fruit fly Drosophila, where the process of neurogenesis has been extensively investigated, extrinsic factors such as the microenvironment of NSCs, nutrients, oxygen levels and systemic signals have been identified as regulators of NSC proliferation. Here, we review decades of work that explores how extrinsic signals non-autonomously regulate key NSC characteristics such as quiescence, proliferation and termination in the fly.
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Affiliation(s)
- Phuong-Khanh Nguyen
- Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Department of Anatomy and Physiology, The University of Melbourne, Victoria 3010, Australia
| | - Louise Y Cheng
- Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia
- Sir Peter MacCallum Department of Oncology, The University of Melbourne, Victoria 3010, Australia
- Department of Anatomy and Physiology, The University of Melbourne, Victoria 3010, Australia
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27
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Chinmo is the larval member of the molecular trinity that directs Drosophila metamorphosis. Proc Natl Acad Sci U S A 2022; 119:e2201071119. [PMID: 35377802 PMCID: PMC9169713 DOI: 10.1073/pnas.2201071119] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The genome of insects with complete metamorphosis contains the instructions for making three distinct body forms, that of the larva, of the pupa, and of the adult. However, the molecular mechanisms by which each gene set is called forth and stably expressed are poorly understood. A half century ago, it was proposed that there was a set of three master genes that inhibited each other’s expression and enabled the expression of genes for each respective stage. We show that the transcription factor chinmo is essential for maintaining the larval stage in Drosophila, and with two other regulatory genes, broad and E93, makes up the trinity of mutually repressive master genes that underlie insect metamorphosis. The molecular control of insect metamorphosis from larva to pupa to adult has long been a mystery. The Broad and E93 transcription factors, which can modify chromatin domains, are known to direct the production of the pupa and the adult, respectively. We now show that chinmo, a gene related to broad, is essential for the repression of these metamorphic genes. Chinmo is strongly expressed during the formation and growth of the larva and its removal results in the precocious expression of broad and E93 in the first stage larva, causing a shift from larval to premetamorphic functions. This trinity of Chinmo, Broad, and E93 regulatory factors is mutually inhibitory. The interaction of this network with regulatory hormones likely ensures the orderly progression through insect metamorphosis.
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28
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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: 20] [Impact Index Per Article: 10.0] [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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29
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A global timing mechanism regulates cell-type-specific wiring programmes. Nature 2022; 603:112-118. [PMID: 35197627 DOI: 10.1038/s41586-022-04418-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Accepted: 01/10/2022] [Indexed: 01/04/2023]
Abstract
The assembly of neural circuits is dependent on precise spatiotemporal expression of cell recognition molecules1-5. Factors controlling cell type specificity have been identified6-8, but how timing is determined remains unknown. Here we describe induction of a cascade of transcription factors by a steroid hormone (ecdysone) in all fly visual system neurons spanning target recognition and synaptogenesis. We demonstrate through single-cell sequencing that the ecdysone pathway regulates the expression of a common set of targets required for synaptic maturation and cell-type-specific targets enriched for cell-surface proteins regulating wiring specificity. Transcription factors in the cascade regulate the expression of the same wiring genes in complex ways, including activation in one cell type and repression in another. We show that disruption of the ecdysone pathway generates specific defects in dendritic and axonal processes and synaptic connectivity, with the order of transcription factor expression correlating with sequential steps in wiring. We also identify shared targets of a cell-type-specific transcription factor and the ecdysone pathway that regulate specificity. We propose that neurons integrate a global temporal transcriptional module with cell-type-specific transcription factors to generate different cell-type-specific patterns of cell recognition molecules regulating wiring.
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30
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Lam G, Nam HJ, Velentzas PD, Baehrecke EH, Thummel CS. Drosophila E93 promotes adult development and suppresses larval responses to ecdysone during metamorphosis. Dev Biol 2022; 481:104-115. [PMID: 34648816 PMCID: PMC8665130 DOI: 10.1016/j.ydbio.2021.10.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 09/30/2021] [Accepted: 10/05/2021] [Indexed: 01/03/2023]
Abstract
Pulses of the steroid hormone ecdysone act through transcriptional cascades to direct the major developmental transitions during the Drosophila life cycle. These include the prepupal ecdysone pulse, which occurs 10 hours after pupariation and triggers the onset of adult morphogenesis and larval tissue destruction. E93 encodes a transcription factor that is specifically induced by the prepupal pulse of ecdysone, supporting a model proposed by earlier work that it specifies the onset of adult development. Although a number of studies have addressed these functions for E93, little is known about its roles in the salivary gland where the E93 locus was originally identified. Here we show that E93 is required for development through late pupal stages, with mutants displaying defects in adult differentiation and no detectable effect on the destruction of larval salivary glands. RNA-seq analysis demonstrates that E93 regulates genes involved in development and morphogenesis in the salivary glands, but has little effect on cell death gene expression. We also show that E93 is required to direct the proper timing of ecdysone-regulated gene expression in salivary glands, and that it suppresses earlier transcriptional programs that occur during larval and prepupal stages. These studies support the model that the stage-specific induction of E93 in late prepupae provides a critical signal that defines the end of larval development and the onset of adult differentiation.
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Affiliation(s)
- Geanette Lam
- Department of Human Genetics, University of Utah School of Medicine, 15 N 2030 E Rm 5100, Salt Lake City, UT 84112 USA
| | - Hyuck-Jin Nam
- Department of Human Genetics, University of Utah School of Medicine, 15 N 2030 E Rm 5100, Salt Lake City, UT 84112 USA
| | - Panagiotis D. Velentzas
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605 USA
| | - Eric H. Baehrecke
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Medical School, Worcester, MA 01605 USA
| | - Carl S. Thummel
- Department of Human Genetics, University of Utah School of Medicine, 15 N 2030 E Rm 5100, Salt Lake City, UT 84112 USA,Corresponding author. (C.S. Thummel)
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31
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Gospocic J, Glastad KM, Sheng L, Shields EJ, Berger SL, Bonasio R. Kr-h1 maintains distinct caste-specific neurotranscriptomes in response to socially regulated hormones. Cell 2021; 184:5807-5823.e14. [PMID: 34739833 DOI: 10.1016/j.cell.2021.10.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 07/13/2021] [Accepted: 10/07/2021] [Indexed: 10/19/2022]
Abstract
Behavioral plasticity is key to animal survival. Harpegnathos saltator ants can switch between worker and queen-like status (gamergate) depending on the outcome of social conflicts, providing an opportunity to study how distinct behavioral states are achieved in adult brains. Using social and molecular manipulations in live ants and ant neuronal cultures, we show that ecdysone and juvenile hormone drive molecular and functional differences in the brains of workers and gamergates and direct the transcriptional repressor Kr-h1 to different target genes. Depletion of Kr-h1 in the brain caused de-repression of "socially inappropriate" genes: gamergate genes were upregulated in workers, whereas worker genes were upregulated in gamergates. At the phenotypic level, loss of Kr-h1 resulted in the emergence of worker-specific behaviors in gamergates and gamergate-specific traits in workers. We conclude that Kr-h1 is a transcription factor that maintains distinct brain states established in response to socially regulated hormones.
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Affiliation(s)
- Janko Gospocic
- Epigenetics Institute and Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA; Department of Urology and Institute of Neuropathology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Karl M Glastad
- Epigenetics Institute and Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Lihong Sheng
- Epigenetics Institute and Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Emily J Shields
- Epigenetics Institute and Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA; Department of Urology and Institute of Neuropathology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Shelley L Berger
- Epigenetics Institute and Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA; Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA; Department of Biology, University of Pennsylvania School of Arts and Sciences, Philadelphia, PA 19104, USA.
| | - Roberto Bonasio
- Epigenetics Institute and Department of Cell and Developmental Biology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
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32
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Glia-derived temporal signals orchestrate neurogenesis in the Drosophila mushroom body. Proc Natl Acad Sci U S A 2021; 118:2020098118. [PMID: 34078666 DOI: 10.1073/pnas.2020098118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Intrinsic mechanisms such as temporal series of transcription factors orchestrate neurogenesis from a limited number of neural progenitors in the brain. Extrinsic regulations, however, remain largely unexplored. Here we describe a two-step glia-derived signal that regulates neurogenesis in the Drosophila mushroom body (MB). In a temporal manner, glial-specific ubiquitin ligase dSmurf activates non-cell-autonomous Hedgehog signaling propagation by targeting the receptor Patched to suppress and promote the exit of MB neuroblast (NB) proliferation, thereby specifying the correct α/β cell number without affecting differentiation. Independent of NB proliferation, dSmurf also stabilizes the expression of the cell-adhesion molecule Fasciclin II (FasII) via its WW domains and regulates FasII homophilic interaction between glia and MB axons to refine α/β-lobe integrity. Our findings provide insights into how extrinsic glia-to-neuron communication coordinates with NB proliferation capacity to regulate MB neurogenesis; glial proteostasis is likely a generalized mechanism in orchestrating neurogenesis.
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33
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Mark B, Lai SL, Zarin AA, Manning L, Pollington HQ, Litwin-Kumar A, Cardona A, Truman JW, Doe CQ. A developmental framework linking neurogenesis and circuit formation in the Drosophila CNS. eLife 2021; 10:67510. [PMID: 33973523 PMCID: PMC8139831 DOI: 10.7554/elife.67510] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Accepted: 05/10/2021] [Indexed: 01/02/2023] Open
Abstract
The mechanisms specifying neuronal diversity are well characterized, yet it remains unclear how or if these mechanisms regulate neural circuit assembly. To address this, we mapped the developmental origin of 160 interneurons from seven bilateral neural progenitors (neuroblasts) and identify them in a synapse-scale TEM reconstruction of the Drosophila larval central nervous system. We find that lineages concurrently build the sensory and motor neuropils by generating sensory and motor hemilineages in a Notch-dependent manner. Neurons in a hemilineage share common synaptic targeting within the neuropil, which is further refined based on neuronal temporal identity. Connectome analysis shows that hemilineage-temporal cohorts share common connectivity. Finally, we show that proximity alone cannot explain the observed connectivity structure, suggesting hemilineage/temporal identity confers an added layer of specificity. Thus, we demonstrate that the mechanisms specifying neuronal diversity also govern circuit formation and function, and that these principles are broadly applicable throughout the nervous system.
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Affiliation(s)
- Brandon Mark
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Sen-Lin Lai
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Aref Arzan Zarin
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Laurina Manning
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Heather Q Pollington
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Ashok Litwin-Kumar
- Mortimer B Zuckerman Mind Brain Behavior Institute, Department of Neuroscience, Columbia University, New York, United States
| | - Albert Cardona
- Janelia Research Campus, Howard Hughes Medical Institute, MRC Laboratory of Molecular Biology, Department of Physiology, Development & Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - James W Truman
- Janelia Research Campus, Howard Hughes Medical Institute, Friday Harbor Laboratories, University of Washington, Friday Harbor, United States
| | - Chris Q Doe
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
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34
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Michki NS, Li Y, Sanjasaz K, Zhao Y, Shen FY, Walker LA, Cao W, Lee CY, Cai D. The molecular landscape of neural differentiation in the developing Drosophila brain revealed by targeted scRNA-seq and multi-informatic analysis. Cell Rep 2021; 35:109039. [PMID: 33909998 PMCID: PMC8139287 DOI: 10.1016/j.celrep.2021.109039] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 01/19/2021] [Accepted: 04/06/2021] [Indexed: 01/16/2023] Open
Abstract
The Drosophila type II neuroblast lineages present an attractive model to investigate the neurogenesis and differentiation process as they adapt to a process similar to that in the human outer subventricular zone. We perform targeted single-cell mRNA sequencing in third instar larval brains to study this process of the type II NB lineage. Combining prior knowledge, in silico analyses, and in situ validation, our multi-informatic investigation describes the molecular landscape from a single developmental snapshot. 17 markers are identified to differentiate distinct maturation stages. 30 markers are identified to specify the stem cell origin and/or cell division numbers of INPs, and at least 12 neuronal subtypes are identified. To foster future discoveries, we provide annotated tables of pairwise gene-gene correlation in single cells and MiCV, a web tool for interactively analyzing scRNA-seq datasets. Taken together, these resources advance our understanding of the neural differentiation process at the molecular level.
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Affiliation(s)
- Nigel S Michki
- Biophysics LS&A, University of Michigan, Ann Arbor, MI, USA
| | - Ye Li
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Kayvon Sanjasaz
- Molecular, Cellular, and Developmental Biology LS&A, University of Michigan, Ann Arbor, MI, USA
| | - Yimeng Zhao
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Fred Y Shen
- Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Logan A Walker
- Biophysics LS&A, University of Michigan, Ann Arbor, MI, USA
| | - Wenjia Cao
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, USA
| | - Cheng-Yu Lee
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA; Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA; Division of Genetic Medicine, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI, USA; Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI, USA
| | - Dawen Cai
- Biophysics LS&A, University of Michigan, Ann Arbor, MI, USA; Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI, USA; Neuroscience Graduate Program, University of Michigan Medical School, Ann Arbor, MI, USA.
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35
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Grmai L, Harsh S, Lu S, Korman A, Deb IB, Bach EA. Transcriptomic analysis of feminizing somatic stem cells in the Drosophila testis reveals putative downstream effectors of the transcription factor Chinmo. G3 (BETHESDA, MD.) 2021; 11:jkab067. [PMID: 33751104 PMCID: PMC8759813 DOI: 10.1093/g3journal/jkab067] [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] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 02/24/2021] [Indexed: 11/12/2022]
Abstract
One of the best examples of sexual dimorphism is the development and function of the gonads, ovaries and testes, which produce sex-specific gametes, oocytes, and spermatids, respectively. The development of these specialized germ cells requires sex-matched somatic support cells. The sexual identity of somatic gonadal cells is specified during development and must be actively maintained during adulthood. We previously showed that the transcription factor Chinmo is required to ensure the male sexual identity of somatic support cells in the Drosophila melanogaster testis. Loss of chinmo from male somatic gonadal cells results in feminization: they transform from squamous to epithelial-like cells that resemble somatic cells in the female gonad but fail to properly ensheath the male germline, causing infertility. To identify potential target genes of Chinmo, we purified somatic cells deficient for chinmo from the adult Drosophila testis and performed next-generation sequencing to compare their transcriptome to that of control somatic cells. Bioinformatics revealed 304 and 1549 differentially upregulated and downregulated genes, respectively, upon loss of chinmo in early somatic cells. Using a combination of methods, we validated several differentially expressed genes. These data sets will be useful resources to the community.
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Affiliation(s)
- Lydia Grmai
- Department of Biochemistry & Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY
| | - Sneh Harsh
- Department of Biochemistry & Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY
| | - Sean Lu
- Department of Biochemistry & Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY
| | - Aryeh Korman
- Department of Biochemistry & Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY
| | - Ishan B Deb
- Department of Biochemistry & Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY
| | - Erika A Bach
- Department of Biochemistry & Molecular Pharmacology, NYU Grossman School of Medicine, New York, NY
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36
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Hatch HAM, Belalcazar HM, Marshall OJ, Secombe J. A KDM5-Prospero transcriptional axis functions during early neurodevelopment to regulate mushroom body formation. eLife 2021; 10:63886. [PMID: 33729157 PMCID: PMC7997662 DOI: 10.7554/elife.63886] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 03/16/2021] [Indexed: 02/06/2023] Open
Abstract
Mutations in the lysine demethylase 5 (KDM5) family of transcriptional regulators are associated with intellectual disability, yet little is known regarding their spatiotemporal requirements or neurodevelopmental contributions. Utilizing the mushroom body (MB), a major learning and memory center within the Drosophila brain, we demonstrate that KDM5 is required within ganglion mother cells and immature neurons for proper axogenesis. Moreover, the mechanism by which KDM5 functions in this context is independent of its canonical histone demethylase activity. Using in vivo transcriptional and binding analyses, we identify a network of genes directly regulated by KDM5 that are critical modulators of neurodevelopment. We find that KDM5 directly regulates the expression of prospero, a transcription factor that we demonstrate is essential for MB morphogenesis. Prospero functions downstream of KDM5 and binds to approximately half of KDM5-regulated genes. Together, our data provide evidence for a KDM5-Prospero transcriptional axis that is essential for proper MB development.
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Affiliation(s)
- Hayden AM Hatch
- Dominick P. Purpura Department of Neuroscience Albert Einstein College of Medicine, Bronx, United States
| | - Helen M Belalcazar
- Department of Genetics Albert Einstein College of Medicine, Bronx, United States
| | - Owen J Marshall
- Menzies Institute for Medical Research University of Tasmania, Hobart, Australia
| | - Julie Secombe
- Dominick P. Purpura Department of Neuroscience Albert Einstein College of Medicine, Bronx, United States.,Department of Genetics Albert Einstein College of Medicine, Bronx, United States
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37
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RNA-binding protein syncrip regulates starvation-induced hyperactivity in adult Drosophila. PLoS Genet 2021; 17:e1009396. [PMID: 33617535 PMCID: PMC7932510 DOI: 10.1371/journal.pgen.1009396] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/04/2021] [Accepted: 02/03/2021] [Indexed: 11/28/2022] Open
Abstract
How to respond to starvation determines fitness. One prominent behavioral response is increased locomotor activities upon starvation, also known as Starvation-Induced Hyperactivity (SIH). SIH is paradoxical as it promotes food seeking but also increases energy expenditure. Despite its importance in fitness, the genetic contributions to SIH as a behavioral trait remains unexplored. Here, we examined SIH in the Drosophila melanogaster Genetic Reference Panel (DGRP) and performed genome-wide association studies. We identified 23 significant loci, corresponding to 14 genes, significantly associated with SIH in adult Drosophila. Gene enrichment analyses indicated that genes encoding ion channels and mRNA binding proteins (RBPs) were most enriched in SIH. We are especially interested in RBPs because they provide a potential mechanism to quickly change protein expression in response to environmental challenges. Using RNA interference, we validated the role of syp in regulating SIH. syp encodes Syncrip (Syp), an RBP. While ubiquitous knockdown of syp led to semi-lethality in adult flies, adult flies with neuron-specific syp knockdown were viable and exhibited decreased SIH. Using the Temporal and Regional Gene Expression Targeting (TARGET) system, we further confirmed the role of Syp in adult neurons in regulating SIH. To determine how syp is regulated by starvation, we performed RNA-seq using the heads of flies maintained under either food or starvation conditions. RNA-seq analyses revealed that syp was alternatively spliced under starvation while its expression level was unchanged. We further generated an alternatively-spliced-exon-specific knockout (KO) line and found that KO flies showed reduced SIH. Together, this study demonstrates a significant genetic contribution to SIH as a behavioral trait, identifies syp as a SIH gene, and highlights the significance of RBPs and post-transcriptional processes in the brain in regulating behavioral responses to starvation. Animals living in the wild often face periods of starvation. How to physiologically and behaviorally respond to starvation is essential for survival. One behavioral response is Starvation-Induced Hyperactivity (SIH). We used the Drosophila melanogaster Genetic Reference Panel, derived from a wild population, to study the genetic basis of SIH. Our results show that there is a significant genetic contribution to SIH in this population, and that genes encoding RNA binding proteins (RBPs) are especially important. Using RNA interference and the TARGET system, we confirmed the role of an RBP Syp in adult neurons in SIH. Using RNA-seq and Western blotting, we found that syp was alternatively spliced under starvation while its expression level was unchanged. Further studies from syp exon-specific knockout flies showed that alternative splicing involving two exons in syp was important for SIH. Together, this study identifies syp as a SIH gene and highlights an essential role of post-transcriptional modification in regulating this behavior.
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38
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Oliveira AC, Rebelo AR, Homem CCF. Integrating animal development: How hormones and metabolism regulate developmental transitions and brain formation. Dev Biol 2021; 475:256-264. [PMID: 33549549 DOI: 10.1016/j.ydbio.2021.01.016] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2020] [Revised: 01/15/2021] [Accepted: 01/29/2021] [Indexed: 10/22/2022]
Abstract
Our current knowledge on how individual tissues or organs are formed during animal development is considerable. However, the development of each organ does not occur in isolation and thus their formation needs to be done in a coordinated manner. This coordination is regulated by hormones, systemic signals that instruct the simultaneous development of all organs and direct tissue specific developmental programs. In addition, multi- and individual-organ development requires the integration of the nutritional state of the animal, since this affects nutrient availability necessary for the progression of development and growth. Variations in the nutritional state of the animal are normal during development, as the sources and access to nutrients greatly differ depending on the animal stage. Furthermore, adversities of the external environment also exert major alterations in extrinsic nutritional conditions. Thus, both in normal and malnutrition circumstances, the animal needs to trigger metabolic changes to maintain energy homeostasis and sustain growth and development. This metabolic flexibility is mediated by hormones, that drive both developmental encoded metabolic transitions throughout development and adaptation responses according to the nutritional state of the animal. This review aims to provide a comprehensive summary of the current knowledge of how endocrine regulation coordinates multi-organ development by orchestrating metabolic transitions and how it integrates metabolic adaptation responses to starvation. We also focus on the particular case of brain development, as it is extremely sensitive to hormonally induced metabolic changes. Finally, we discuss how brain development is prioritized over the development of other organs, as its growth can be spared from nutrient deprivation.
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Affiliation(s)
- Andreia C Oliveira
- iNOVA4Health, CEDOC, NOVA Medical School, NMS, Universidade Nova de Lisboa, 1169-056, Lisboa, Portugal
| | - Ana R Rebelo
- iNOVA4Health, CEDOC, NOVA Medical School, NMS, Universidade Nova de Lisboa, 1169-056, Lisboa, Portugal
| | - Catarina C F Homem
- iNOVA4Health, CEDOC, NOVA Medical School, NMS, Universidade Nova de Lisboa, 1169-056, Lisboa, Portugal.
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39
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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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40
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Sood C, Doyle SE, Siegrist SE. Steroid hormones, dietary nutrients, and temporal progression of neurogenesis. CURRENT OPINION IN INSECT SCIENCE 2021; 43:70-77. [PMID: 33127508 PMCID: PMC8058227 DOI: 10.1016/j.cois.2020.10.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 10/10/2020] [Accepted: 10/16/2020] [Indexed: 05/13/2023]
Abstract
Temporal patterning of neural progenitors, in which different factors are sequentially expressed, is an evolutionarily conserved strategy for generating neuronal diversity during development. In the Drosophila embryo, mechanisms that mediate temporal patterning of neural stem cells (neuroblasts) are largely cell-intrinsic. However, after embryogenesis, neuroblast temporal patterning relies on extrinsic cues as well, as freshly hatched larvae seek out nutrients and other key resources in varying natural environments. We recap current understanding of neuroblast-intrinsic temporal programs and discuss how neuroblast extrinsic cues integrate and coordinate with neuroblast intrinsic programs to control numbers and types of neurons produced. One key emerging extrinsic factor that impacts temporal patterning of neuroblasts and their daughters as well as termination of neurogenesis is the steroid hormone, ecdysone, a known regulator of large-scale developmental transitions in insects and arthropods. Lastly, we consider evolutionary conservation and discuss recent work on thyroid hormone signaling in early vertebrate brain development.
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Affiliation(s)
- Chhavi Sood
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Susan E Doyle
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA
| | - Sarah E Siegrist
- Department of Biology, University of Virginia, Charlottesville, VA 22904, USA.
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Lopes A, Magrinelli E, Telley L. Emerging Roles of Single-Cell Multi-Omics in Studying Developmental Temporal Patterning. Int J Mol Sci 2020; 21:E7491. [PMID: 33050604 PMCID: PMC7589732 DOI: 10.3390/ijms21207491] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 10/06/2020] [Accepted: 10/08/2020] [Indexed: 01/16/2023] Open
Abstract
The complexity of brain structure and function is rooted in the precise spatial and temporal regulation of selective developmental events. During neurogenesis, both vertebrates and invertebrates generate a wide variety of specialized cell types through the expansion and specification of a restricted set of neuronal progenitors. Temporal patterning of neural progenitors rests on fine regulation between cell-intrinsic and cell-extrinsic mechanisms. The rapid emergence of high-throughput single-cell technologies combined with elaborate computational analysis has started to provide us with unprecedented biological insights related to temporal patterning in the developing central nervous system (CNS). Here, we present an overview of recent advances in Drosophila and vertebrates, focusing both on cell-intrinsic mechanisms and environmental influences. We then describe the various multi-omics approaches that have strongly contributed to our current understanding and discuss perspectives on the various -omics approaches that hold great potential for the future of temporal patterning research.
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Affiliation(s)
| | | | - Ludovic Telley
- Department of Basic Neuroscience, University of Lausanne, 1005 Lausanne, Switzerland; (A.L.); (E.M.)
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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: 14] [Impact Index Per Article: 3.5] [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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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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44
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Rossi AM, Desplan C. Extrinsic activin signaling cooperates with an intrinsic temporal program to increase mushroom body neuronal diversity. eLife 2020; 9:58880. [PMID: 32628110 PMCID: PMC7365662 DOI: 10.7554/elife.58880] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 07/03/2020] [Indexed: 12/16/2022] Open
Abstract
Temporal patterning of neural progenitors leads to the sequential production of diverse neurons. To understand how extrinsic cues influence intrinsic temporal programs, we studied Drosophila mushroom body progenitors (neuroblasts) that sequentially produce only three neuronal types: γ, then α’β’, followed by αβ. Opposing gradients of two RNA-binding proteins Imp and Syp comprise the intrinsic temporal program. Extrinsic activin signaling regulates the production of α’β’ neurons but whether it affects the intrinsic temporal program was not known. We show that the activin ligand Myoglianin from glia regulates the temporal factor Imp in mushroom body neuroblasts. Neuroblasts missing the activin receptor Baboon have a delayed intrinsic program as Imp is higher than normal during the α’β’ temporal window, causing the loss of α’β’ neurons, a decrease in αβ neurons, and a likely increase in γ neurons, without affecting the overall number of neurons produced. Our results illustrate that an extrinsic cue modifies an intrinsic temporal program to increase neuronal diversity.
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Affiliation(s)
- Anthony M Rossi
- Department of Biology, New York University, New York, United States
| | - Claude Desplan
- Department of Biology, New York University, New York, United States
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45
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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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46
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Hailstone M, Waithe D, Samuels TJ, Yang L, Costello I, Arava Y, Robertson E, Parton RM, Davis I. CytoCensus, mapping cell identity and division in tissues and organs using machine learning. eLife 2020; 9:e51085. [PMID: 32423529 PMCID: PMC7237217 DOI: 10.7554/elife.51085] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 03/17/2020] [Indexed: 01/16/2023] Open
Abstract
A major challenge in cell and developmental biology is the automated identification and quantitation of cells in complex multilayered tissues. We developed CytoCensus: an easily deployed implementation of supervised machine learning that extends convenient 2D 'point-and-click' user training to 3D detection of cells in challenging datasets with ill-defined cell boundaries. In tests on such datasets, CytoCensus outperforms other freely available image analysis software in accuracy and speed of cell detection. We used CytoCensus to count stem cells and their progeny, and to quantify individual cell divisions from time-lapse movies of explanted Drosophila larval brains, comparing wild-type and mutant phenotypes. We further illustrate the general utility and future potential of CytoCensus by analysing the 3D organisation of multiple cell classes in Zebrafish retinal organoids and cell distributions in mouse embryos. CytoCensus opens the possibility of straightforward and robust automated analysis of developmental phenotypes in complex tissues.
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Affiliation(s)
- Martin Hailstone
- Department of Biochemistry, University of OxfordOxfordUnited Kingdom
| | - Dominic Waithe
- Wolfson Imaging Center & MRC WIMM Centre for Computational Biology MRC Weather all Institute of Molecular Medicine University of OxfordOxfordUnited Kingdom
| | - Tamsin J Samuels
- Department of Biochemistry, University of OxfordOxfordUnited Kingdom
| | - Lu Yang
- Department of Biochemistry, University of OxfordOxfordUnited Kingdom
| | - Ita Costello
- The Dunn School of Pathology,University of OxfordOxfordUnited Kingdom
| | - Yoav Arava
- Department of Biology, Technion - Israel Institute of TechnologyHaifaIsrael
| | | | - Richard M Parton
- Department of Biochemistry, University of OxfordOxfordUnited Kingdom
- Micron Advanced Bioimaging Unit, Department of Biochemistry, University of OxfordOxfordUnited Kingdom
| | - Ilan Davis
- Department of Biochemistry, University of OxfordOxfordUnited Kingdom
- Micron Advanced Bioimaging Unit, Department of Biochemistry, University of OxfordOxfordUnited Kingdom
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Samuels TJ, Arava Y, Järvelin AI, Robertson F, Lee JY, Yang L, Yang CP, Lee T, Ish-Horowicz D, Davis I. Neuronal upregulation of Prospero protein is driven by alternative mRNA polyadenylation and Syncrip-mediated mRNA stabilisation. Biol Open 2020; 9:bio049684. [PMID: 32205310 PMCID: PMC7225087 DOI: 10.1242/bio.049684] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Accepted: 02/24/2020] [Indexed: 12/14/2022] Open
Abstract
During Drosophila and vertebrate brain development, the conserved transcription factor Prospero/Prox1 is an important regulator of the transition between proliferation and differentiation. Prospero level is low in neural stem cells and their immediate progeny, but is upregulated in larval neurons and it is unknown how this process is controlled. Here, we use single molecule fluorescent in situ hybridisation to show that larval neurons selectively transcribe a long prospero mRNA isoform containing a 15 kb 3' untranslated region, which is bound in the brain by the conserved RNA-binding protein Syncrip/hnRNPQ. Syncrip binding increases the stability of the long prospero mRNA isoform, which allows an upregulation of Prospero protein production. Adult flies selectively lacking the long prospero isoform show abnormal behaviour that could result from impaired locomotor or neurological activity. Our findings highlight a regulatory strategy involving alternative polyadenylation followed by differential post-transcriptional regulation.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Tamsin J Samuels
- Department of Biochemistry, The University of Oxford, Oxford, OX1 3QU, UK
| | - Yoav Arava
- Department of Biochemistry, The University of Oxford, Oxford, OX1 3QU, UK
- Department of Biology Technion, Haifa, 32000, Israel
| | - Aino I Järvelin
- Department of Biochemistry, The University of Oxford, Oxford, OX1 3QU, UK
| | | | - Jeffrey Y Lee
- Department of Biochemistry, The University of Oxford, Oxford, OX1 3QU, UK
| | - Lu Yang
- Department of Biochemistry, The University of Oxford, Oxford, OX1 3QU, UK
| | - Ching-Po Yang
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA, 20147 USA
| | - Tzumin Lee
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA, 20147 USA
| | - David Ish-Horowicz
- Department of Biochemistry, The University of Oxford, Oxford, OX1 3QU, UK
- MRC Laboratory for Molecular Cell Biology, University College, London, WC1E 6BT UK
| | - Ilan Davis
- Department of Biochemistry, The University of Oxford, Oxford, OX1 3QU, UK
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Maierbrugger KT, Sousa-Nunes R, Bateman JM. The mTOR pathway component Unkempt regulates neural stem cell and neural progenitor cell cycle in the Drosophila central nervous system. Dev Biol 2020; 461:55-65. [PMID: 31978396 DOI: 10.1016/j.ydbio.2020.01.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Revised: 01/06/2020] [Accepted: 01/08/2020] [Indexed: 11/21/2022]
Abstract
The formation of a complex nervous system requires the coordinated action of progenitor cell proliferation, differentiation and maturation. The Drosophila postembryonic central nervous system provides a powerful model for dissecting the cellular and molecular mechanisms underpinning neurogenesis. We previously identified the conserved zinc finger/RING protein Unkempt (Unk) as a key temporal regulator of neuronal differentiation in the Drosophila developing eye and showed that Unk acts downstream of the mechanistic target of rapamycin (mTOR) pathway together with its binding partner Headcase (Hdc). Here we investigate the role of Unk in Drosophila postembryonic thoracic neurogenesis. The Drosophila central nervous system contains neural stem cells, called neuroblasts, and neural progenitors, known as ganglion mother cells (GMCs). Unk is highly expressed in the central brain and ventral nerve cord but is not required to maintain neuroblast numbers or for the regulation of temporal series factor expression in neuroblasts. However, loss of Unk increases the number of neuroblasts and GMCs in S-phase of the cell cycle, resulting in the overproduction of neurons. We also show that Unk interacts with Hdc through its zinc finger domain. The zinc finger domain is required for the synergistic activity of Unk with Hdc during eye development but is not necessary for the activity of Unk in thoracic neurogenesis. Overall, this study shows that Unk and Hdc are novel negative regulators of neurogenesis in Drosophila and indicates a conserved role of mTOR signalling in nervous system development.
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Affiliation(s)
- Katja T Maierbrugger
- Maurice Wohl Clinical Neuroscience Institute, King's College London, 125 Coldharbour lane, London, SE5 9NU, UK
| | - Rita Sousa-Nunes
- Centre for Developmental Neurobiology, King's College London, New Hunts House, Newcomen Street, London, SE1 1UL, UK
| | - Joseph M Bateman
- Maurice Wohl Clinical Neuroscience Institute, King's College London, 125 Coldharbour lane, London, SE5 9NU, UK.
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let-7-Complex MicroRNAs Regulate Broad-Z3, Which Together with Chinmo Maintains Adult Lineage Neurons in an Immature State. G3-GENES GENOMES GENETICS 2020; 10:1393-1401. [PMID: 32071070 PMCID: PMC7144073 DOI: 10.1534/g3.120.401042] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
During Drosophila melanogaster metamorphosis, arrested immature neurons born during larval development differentiate into their functional adult form. This differentiation coincides with the downregulation of two zinc-finger transcription factors, Chronologically Inappropriate Morphogenesis (Chinmo) and the Z3 isoform of Broad (Br-Z3). Here, we show that br-Z3 is regulated by two microRNAs, let-7 and miR-125, that are activated at the larval-to-pupal transition and are known to also regulate chinmo. The br-Z3 3′UTR contains functional binding sites for both let-7 and miR-125 that confers sensitivity to both of these microRNAs, as determined by deletion analysis in reporter assays. Forced expression of let-7 and miR-125 miRNAs leads to early silencing of Br-Z3 and Chinmo and is associated with inappropriate neuronal sprouting and outgrowth. Similar phenotypes were observed by the combined but not separate depletion of br-Z3 and chinmo. Because persistent Br-Z3 was not detected in let-7-C mutants, this work suggests a model in which let-7 and miR-125 activation at the onset of metamorphosis may act as a failsafe mechanism that ensures the coordinated silencing of both br-Z3 and chinmo needed for the timely outgrowth of neurons arrested during larval development. The let-7 and miR-125 binding site sequences are conserved across Drosophila species and possibly other insects as well, suggesting that this functional relationship is evolutionarily conserved.
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50
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Hartenstein V, Omoto JJ, Lovick JK. The role of cell lineage in the development of neuronal circuitry and function. Dev Biol 2020; 475:165-180. [PMID: 32017903 DOI: 10.1016/j.ydbio.2020.01.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 01/23/2020] [Accepted: 01/23/2020] [Indexed: 12/13/2022]
Abstract
Complex nervous systems have a modular architecture, whereby reiterative groups of neurons ("modules") that share certain structural and functional properties are integrated into large neural circuits. Neurons develop from proliferating progenitor cells that, based on their location and time of appearance, are defined by certain genetic programs. Given that genes expressed by a given progenitor play a fundamental role in determining the properties of its lineage (i.e., the neurons descended from that progenitor), one efficient developmental strategy would be to have lineages give rise to the structural modules of the mature nervous system. It is clear that this strategy plays an important role in neural development of many invertebrate animals, notably insects, where the availability of genetic techniques has made it possible to analyze the precise relationship between neuronal origin and differentiation since several decades. Similar techniques, developed more recently in the vertebrate field, reveal that functional modules of the mammalian cerebral cortex are also likely products of developmentally defined lineages. We will review studies that relate cell lineage to circuitry and function from a comparative developmental perspective, aiming at enhancing our understanding of neural progenitors and their lineages, and translating findings acquired in different model systems into a common conceptual framework.
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Affiliation(s)
- Volker Hartenstein
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA, 90095, USA.
| | - Jaison J Omoto
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Jennifer K Lovick
- Department of Molecular Cell and Developmental Biology, University of California Los Angeles, Los Angeles, CA, 90095, USA
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