1
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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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2
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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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3
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El-Danaf RN, Rajesh R, Desplan C. Temporal regulation of neural diversity in Drosophila and vertebrates. Semin Cell Dev Biol 2023; 142:13-22. [PMID: 35623984 DOI: 10.1016/j.semcdb.2022.05.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Revised: 05/11/2022] [Accepted: 05/16/2022] [Indexed: 10/18/2022]
Abstract
The generation of neuronal diversity involves temporal patterning mechanisms by which a given progenitor sequentially produces multiple cell types. Several parallels are evident between the brain development programs of Drosophila and vertebrates, such as the successive emergence of specific cell types and the use of combinations of transcription factors to specify cell fates. Furthermore, cell-extrinsic cues such as hormones and signaling pathways have also been shown to be regulatory modules of temporal patterning. Recently, transcriptomic and epigenomic studies using large single-cell sequencing datasets have provided insights into the transcriptional dynamics of neurogenesis in the Drosophila and mammalian central nervous systems. We review these commonalities in the specification of neuronal identity and highlight the conserved or convergent strategies of brain development by discussing temporal patterning mechanisms found in flies and vertebrates.
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Affiliation(s)
- Rana N El-Danaf
- Center for Genomics and Systems Biology (CGSB), New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
| | - Raghuvanshi Rajesh
- Center for Genomics and Systems Biology (CGSB), New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Claude Desplan
- Center for Genomics and Systems Biology (CGSB), New York University Abu Dhabi, Abu Dhabi, United Arab Emirates; Department of Biology, New York University, New York, NY 10003, USA.
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4
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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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5
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Bu S, Lau SSY, Yong WL, Zhang H, Thiagarajan S, Bashirullah A, Yu F. Polycomb group genes are required for neuronal pruning in Drosophila. BMC Biol 2023; 21:33. [PMID: 36793038 PMCID: PMC9933400 DOI: 10.1186/s12915-023-01534-0] [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: 09/15/2022] [Accepted: 02/02/2023] [Indexed: 02/17/2023] Open
Abstract
BACKGROUND Pruning that selectively eliminates unnecessary or incorrect neurites is required for proper wiring of the mature nervous system. During Drosophila metamorphosis, dendritic arbourization sensory neurons (ddaCs) and mushroom body (MB) γ neurons can selectively prune their larval dendrites and/or axons in response to the steroid hormone ecdysone. An ecdysone-induced transcriptional cascade plays a key role in initiating neuronal pruning. However, how downstream components of ecdysone signalling are induced remains not entirely understood. RESULTS Here, we identify that Scm, a component of Polycomb group (PcG) complexes, is required for dendrite pruning of ddaC neurons. We show that two PcG complexes, PRC1 and PRC2, are important for dendrite pruning. Interestingly, depletion of PRC1 strongly enhances ectopic expression of Abdominal B (Abd-B) and Sex combs reduced, whereas loss of PRC2 causes mild upregulation of Ultrabithorax and Abdominal A in ddaC neurons. Among these Hox genes, overexpression of Abd-B causes the most severe pruning defects, suggesting its dominant effect. Knockdown of the core PRC1 component Polyhomeotic (Ph) or Abd-B overexpression selectively downregulates Mical expression, thereby inhibiting ecdysone signalling. Finally, Ph is also required for axon pruning and Abd-B silencing in MB γ neurons, indicating a conserved function of PRC1 in two types of pruning. CONCLUSIONS This study demonstrates important roles of PcG and Hox genes in regulating ecdysone signalling and neuronal pruning in Drosophila. Moreover, our findings suggest a non-canonical and PRC2-independent role of PRC1 in Hox gene silencing during neuronal pruning.
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Affiliation(s)
- Shufeng Bu
- grid.4280.e0000 0001 2180 6431Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore, 117604 Singapore ,grid.4280.e0000 0001 2180 6431Department of Biological Sciences, National University of Singapore, Singapore, 117543 Singapore
| | - Samuel Song Yuan Lau
- grid.4280.e0000 0001 2180 6431Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore, 117604 Singapore
| | - Wei Lin Yong
- grid.4280.e0000 0001 2180 6431Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore, 117604 Singapore
| | - Heng Zhang
- grid.4280.e0000 0001 2180 6431Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore, 117604 Singapore
| | - Sasinthiran Thiagarajan
- grid.4280.e0000 0001 2180 6431Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore, 117604 Singapore ,grid.4280.e0000 0001 2180 6431Department of Biological Sciences, National University of Singapore, Singapore, 117543 Singapore
| | - Arash Bashirullah
- grid.14003.360000 0001 2167 3675Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705-2222 USA
| | - Fengwei Yu
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore, 117604, Singapore. .,Department of Biological Sciences, National University of Singapore, Singapore, 117543, Singapore.
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6
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Nutrition influences nervous system development by regulating neural stem cell homeostasis. PROCEEDINGS OF THE INDIAN NATIONAL SCIENCE ACADEMY 2022. [DOI: 10.1007/s43538-022-00107-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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7
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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:iyac103. [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] [MESH Headings] [Grants] [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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8
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Yuh Chew L, He J, Wong JJL, Li S, Yu F. AMPK activates the Nrf2-Keap1 pathway to govern dendrite pruning via the insulin pathway in Drosophila. Development 2022; 149:275791. [DOI: 10.1242/dev.200536] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 06/16/2022] [Indexed: 11/20/2022]
Abstract
ABSTRACT
During Drosophila metamorphosis, the ddaC dendritic arborisation sensory neurons selectively prune their larval dendrites in response to steroid hormone ecdysone signalling. The Nrf2-Keap1 pathway acts downstream of ecdysone signalling to promote proteasomal degradation and thereby dendrite pruning. However, how the Nrf2-Keap1 pathway is activated remains largely unclear. Here, we demonstrate that the metabolic regulator AMP-activated protein kinase (AMPK) plays a cell-autonomous role in dendrite pruning. Importantly, AMPK is required for Mical and Headcase expression and for activation of the Nrf2-Keap1 pathway. We reveal that AMPK promotes the Nrf2-Keap1 pathway and dendrite pruning partly via inhibition of the insulin pathway. Moreover, the AMPK-insulin pathway is required for ecdysone signalling to activate the Nrf2-Keap1 pathway during dendrite pruning. Overall, this study reveals an important mechanism whereby ecdysone signalling activates the Nrf2-Keap1 pathway via the AMPK-insulin pathway to promote dendrite pruning, and further suggests that during the nonfeeding prepupal stage metabolic alterations lead to activation of the Nrf2-Keap1 pathway and dendrite pruning.
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Affiliation(s)
- Liang Yuh Chew
- 1 Research Link, National University of Singapore 1 Temasek Life Sciences Laboratory , , 117604 , Singapore
- National University of Singapore 2 Department of Biological Sciences , , 117543 , Singapore
| | - Jianzheng He
- 1 Research Link, National University of Singapore 1 Temasek Life Sciences Laboratory , , 117604 , Singapore
| | - Jack Jing Lin Wong
- 1 Research Link, National University of Singapore 1 Temasek Life Sciences Laboratory , , 117604 , Singapore
| | - Sheng Li
- Institute of Insect Science and Technology & School of Life Sciences, South China Normal University 3 Guangdong Provincial Key Laboratory of Insect Developmental Biology and Applied Technology , , Guangzhou 510631 , China
| | - Fengwei Yu
- 1 Research Link, National University of Singapore 1 Temasek Life Sciences Laboratory , , 117604 , Singapore
- National University of Singapore 2 Department of Biological Sciences , , 117543 , Singapore
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9
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Lai YW, Miyares RL, Liu LY, Chu SY, Lee T, Yu HH. Hormone-controlled changes in the differentiation state of post-mitotic neurons. Curr Biol 2022; 32:2341-2348.e3. [PMID: 35508173 DOI: 10.1016/j.cub.2022.04.027] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 03/22/2022] [Accepted: 04/12/2022] [Indexed: 11/16/2022]
Abstract
While we think of neurons as having a fixed identity, many show spectacular plasticity.1-10 Metamorphosis drives massive changes in the fly brain;11,12 neurons that persist into adulthood often change in response to the steroid hormone ecdysone.13,14 Besides driving remodeling,11-14 ecdysone signaling can also alter the differentiation status of neurons.7,15 The three sequentially born subtypes of mushroom body (MB) Kenyon cells (γ, followed by α'/β', and finally α/β)16 serve as a model of temporal fating.17-21 γ neurons are also used as a model of remodeling during metamorphosis. As γ neurons are the only functional Kenyon cells in the larval brain, they serve the function of all three adult subtypes. Correspondingly, larval γ neurons have a similar morphology to α'/β' and α/β neurons-their axons project dorsally and medially. During metamorphosis, γ neurons remodel to form a single medial projection. Both temporal fate changes and defects in remodeling therefore alter γ-neuron morphology in similar ways. Mamo, a broad-complex, tramtrack, and bric-à-brac/poxvirus and zinc finger (BTB/POZ) transcription factor critical for temporal specification of α'/β' neurons,18,19 was recently described as essential for γ remodeling.22 In a previous study, we noticed a change in the number of adult Kenyon cells expressing γ-specific markers when mamo was manipulated.18 These data implied a role for Mamo in γ-neuron fate specification, yet mamo is not expressed in γ neurons until pupariation,18,22 well past γ specification. This indicates that mamo has a later role in ensuring that γ neurons express the correct Kenyon cell subtype-specific genes in the adult brain.
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Affiliation(s)
- Yen-Wei Lai
- Institute of Cellular and Organismic Biology, Academia Sinica, Academia Road, Taipei 11529, Taiwan; Institute of Molecular and Cellular Biology, College of Life Science, National Taiwan University, Roosevelt Road, Taipei 10617, Taiwan
| | - Rosa L Miyares
- Howard Hughes Medical Institute, Janelia Research Campus, Helix Drive, Ashburn, VA 20147, USA
| | - Ling-Yu Liu
- Howard Hughes Medical Institute, Janelia Research Campus, Helix Drive, Ashburn, VA 20147, USA
| | - Sao-Yu Chu
- Institute of Cellular and Organismic Biology, Academia Sinica, Academia Road, Taipei 11529, Taiwan
| | - Tzumin Lee
- Howard Hughes Medical Institute, Janelia Research Campus, Helix Drive, Ashburn, VA 20147, USA.
| | - Hung-Hsiang Yu
- Institute of Cellular and Organismic Biology, Academia Sinica, Academia Road, Taipei 11529, Taiwan.
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10
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Karanja F, Sahu S, Weintraub S, Bhandari R, Jaszczak R, Sitt J, Halme A. Ecdysone exerts biphasic control of regenerative signaling, coordinating the completion of regeneration with developmental progression. Proc Natl Acad Sci U S A 2022; 119:e2115017119. [PMID: 35086929 PMCID: PMC8812538 DOI: 10.1073/pnas.2115017119] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 11/13/2021] [Indexed: 12/12/2022] Open
Abstract
In Drosophila melanogaster, loss of regenerative capacity in wing imaginal discs coincides with an increase in systemic levels of the steroid hormone ecdysone, a key coordinator of their developmental progression. Regenerating discs release the relaxin hormone Dilp8 (Drosophila insulin-like peptide 8) to limit ecdysone synthesis and extend the regenerative period. Here, we describe how regenerating tissues produce a biphasic response to ecdysone levels: lower concentrations of ecdysone promote local and systemic regenerative signaling, whereas higher concentrations suppress regeneration through the expression of broad splice isoforms. Ecdysone also promotes the expression of wingless during both regeneration and normal development through a distinct regulatory pathway. This dual role for ecdysone explains how regeneration can still be completed successfully in dilp8- mutant larvae: higher ecdysone levels increase the regenerative activity of tissues, allowing regeneration to reach completion in a shorter time. From these observations, we propose that ecdysone hormone signaling functions to coordinate regeneration with developmental progression.
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Affiliation(s)
- Faith Karanja
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22902
| | - Subhshri Sahu
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22902
| | - Sara Weintraub
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22902
| | - Rajan Bhandari
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22902
| | - Rebecca Jaszczak
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22902
| | - Jason Sitt
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22902
| | - Adrian Halme
- Department of Cell Biology, University of Virginia School of Medicine, Charlottesville, VA 22902
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11
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Chew LY, Zhang H, He J, Yu F. The Nrf2-Keap1 pathway is activated by steroid hormone signaling to govern neuronal remodeling. Cell Rep 2021; 36:109466. [PMID: 34348164 DOI: 10.1016/j.celrep.2021.109466] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 06/09/2021] [Accepted: 07/08/2021] [Indexed: 12/30/2022] Open
Abstract
The evolutionarily conserved Nrf2-Keap1 pathway is a key antioxidant response pathway that protects cells/organisms against detrimental effects of oxidative stress. Impaired Nrf2 function is associated with cancer and neurodegenerative diseases in humans. However, the function of the Nrf2-Keap1 pathway in the developing nervous systems has not been established. Here we demonstrate a cell-autonomous role of the Nrf2-Keap1 pathway, composed of CncC/Nrf2, Keap1, and MafS, in governing neuronal remodeling during Drosophila metamorphosis. Nrf2-Keap1 signaling is activated downstream of the steroid hormone ecdysone. Mechanistically, the Nrf2-Keap1 pathway is activated via cytoplasmic-to-nuclear translocation of CncC in an importin- and ecdysone-signaling-dependent manner. Moreover, Nrf2-Keap1 signaling regulates dendrite pruning independent of its canonical antioxidant response pathway, acting instead through proteasomal degradation. This study reveals an epistatic link between the Nrf2-Keap1 pathway and steroid hormone signaling and demonstrates an antioxidant-independent but proteasome-dependent role of the Nrf2-Keap1 pathway in neuronal remodeling.
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Affiliation(s)
- Liang Yuh Chew
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore; Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore
| | - Heng Zhang
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore
| | - Jianzheng He
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore
| | - Fengwei Yu
- Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore; Department of Biological Sciences, National University of Singapore, Singapore 117543, Singapore.
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12
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Leinwand SG, Scott K. Juvenile hormone drives the maturation of spontaneous mushroom body neural activity and learned behavior. Neuron 2021; 109:1836-1847.e5. [PMID: 33915110 DOI: 10.1016/j.neuron.2021.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Revised: 03/26/2021] [Accepted: 04/07/2021] [Indexed: 12/21/2022]
Abstract
Mature behaviors emerge from neural circuits sculpted by genetic programs and spontaneous and evoked neural activity. However, how neural activity is refined to drive maturation of learned behavior remains poorly understood. Here, we explore how transient hormonal signaling coordinates a neural activity state transition and maturation of associative learning. We identify spontaneous, asynchronous activity in a Drosophila learning and memory brain region, the mushroom body. This activity declines significantly over the first week of adulthood. Moreover, this activity is generated cell-autonomously via Cacophony voltage-gated calcium channels in a single cell type, α'/β' Kenyon cells. Juvenile hormone, a crucial developmental regulator, acts transiently in α'/β' Kenyon cells during a young adult sensitive period to downregulate spontaneous activity and enable subsequent enhanced learning. Hormone signaling in young animals therefore controls a neural activity state transition and is required for improved associative learning, providing insight into the maturation of circuits and behavior.
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Affiliation(s)
- Sarah G Leinwand
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA.
| | - Kristin Scott
- Department of Molecular and Cell Biology and Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA.
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13
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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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14
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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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15
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Chen HM, Marques JG, Sugino K, Wei D, Miyares RL, Lee T. CAMIO: a transgenic CRISPR pipeline to create diverse targeted genome deletions in Drosophila. Nucleic Acids Res 2020; 48:4344-4356. [PMID: 32187363 PMCID: PMC7192631 DOI: 10.1093/nar/gkaa177] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 02/06/2020] [Accepted: 03/10/2020] [Indexed: 02/07/2023] Open
Abstract
The genome is the blueprint for an organism. Interrogating the genome, especially locating critical cis-regulatory elements, requires deletion analysis. This is conventionally performed using synthetic constructs, making it cumbersome and non-physiological. Thus, we created Cas9-mediated Arrayed Mutagenesis of Individual Offspring (CAMIO) to achieve comprehensive analysis of a targeted region of native DNA. CAMIO utilizes CRISPR that is spatially restricted to generate independent deletions in the intact Drosophila genome. Controlled by recombination, a single guide RNA is stochastically chosen from a set targeting a specific DNA region. Combining two sets increases variability, leading to either indels at 1–2 target sites or inter-target deletions. Cas9 restriction to male germ cells elicits autonomous double-strand-break repair, consequently creating offspring with diverse mutations. Thus, from a single population cross, we can obtain a deletion matrix covering a large expanse of DNA at both coarse and fine resolution. We demonstrate the ease and power of CAMIO by mapping 5′UTR sequences crucial for chinmo's post-transcriptional regulation.
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Affiliation(s)
- Hui-Min Chen
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Jorge Garcia Marques
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Ken Sugino
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Dingjun Wei
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Rosa Linda Miyares
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Tzumin Lee
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
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16
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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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17
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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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18
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Marchetti G, Tavosanis G. Modulators of hormonal response regulate temporal fate specification in the Drosophila brain. PLoS Genet 2019; 15:e1008491. [PMID: 31809495 PMCID: PMC6919624 DOI: 10.1371/journal.pgen.1008491] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2019] [Revised: 12/18/2019] [Accepted: 10/24/2019] [Indexed: 12/03/2022] Open
Abstract
Neuronal diversity is at the core of the complex processing operated by the nervous system supporting fundamental functions such as sensory perception, motor control or memory formation. A small number of progenitors guarantee the production of this neuronal diversity, with each progenitor giving origin to different neuronal types over time. How a progenitor sequentially produces neurons of different fates and the impact of extrinsic signals conveying information about developmental progress or environmental conditions on this process represent key, but elusive questions. Each of the four progenitors of the Drosophila mushroom body (MB) sequentially gives rise to the MB neuron subtypes. The temporal fate determination pattern of MB neurons can be influenced by extrinsic cues, conveyed by the steroid hormone ecdysone. Here, we show that the activation of Transforming Growth Factor-β (TGF-β) signalling via glial-derived Myoglianin regulates the fate transition between the early-born α’β’ and the pioneer αβ MB neurons by promoting the expression of the ecdysone receptor B1 isoform (EcR-B1). While TGF-β signalling is required in MB neuronal progenitors to promote the expression of EcR-B1, ecdysone signalling acts postmitotically to consolidate theα’β’ MB fate. Indeed, we propose that if these signalling cascades are impaired α’β’ neurons lose their fate and convert to pioneer αβ. Conversely, an intrinsic signal conducted by the zinc finger transcription factor Krüppel-homolog 1 (Kr-h1) antagonises TGF-β signalling and acts as negative regulator of the response mediated by ecdysone in promoting α’β’ MB neuron fate consolidation. Taken together, the consolidation of α’β’ MB neuron fate requires the response of progenitors to local signalling to enable postmitotic neurons to sense a systemic signal. Throughout the development of the central nervous system (CNS), a vast number of neuronal types are produced with striking precision. The unique identity of each neuronal cell type and the great cellular complexity in the CNS are established by intricate gene regulatory networks. Disruption of these identity programs leads to neurodevelopmental disorders and defects in cognition. Here, we report an important regulatory mechanism involved in consolidating neuronal fate. We show that during brain development local signalling, derived from interactions between glial cells and neuronal progenitors, is required to promote the expression of a hormone receptor in immature neurons. The perception of a systemic hormonal cue in those postmitotic neurons is fundamental for the consolidation of their neuronal fate. In this context, we additionally uncover an intrinsic regulatory mechanism that coordinates the hormone response to maintain the final neuronal fate.
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Affiliation(s)
- Giovanni Marchetti
- Dynamics of neuronal circuits, German Center for Neurodegenerative Diseases (DZNE), Germany
- * E-mail: (GM); (GT)
| | - Gaia Tavosanis
- Dynamics of neuronal circuits, German Center for Neurodegenerative Diseases (DZNE), Germany
- LIMES-Institute, University of Bonn, Germany
- * E-mail: (GM); (GT)
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19
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Liu LY, Long X, Yang CP, Miyares RL, Sugino K, Singer RH, Lee T. Mamo decodes hierarchical temporal gradients into terminal neuronal fate. eLife 2019; 8:e48056. [PMID: 31545163 PMCID: PMC6764822 DOI: 10.7554/elife.48056] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 09/20/2019] [Indexed: 12/20/2022] Open
Abstract
Temporal patterning is a seminal method of expanding neuronal diversity. Here we unravel a mechanism decoding neural stem cell temporal gene expression and transforming it into discrete neuronal fates. This mechanism is characterized by hierarchical gene expression. First, Drosophila neuroblasts express opposing temporal gradients of RNA-binding proteins, Imp and Syp. These proteins promote or inhibit chinmo translation, yielding a descending neuronal gradient. Together, first and second-layer temporal factors define a temporal expression window of BTB-zinc finger nuclear protein, Mamo. The precise temporal induction of Mamo is achieved via both transcriptional and post-transcriptional regulation. Finally, Mamo is essential for the temporally defined, terminal identity of α'/β' mushroom body neurons and identity maintenance. We describe a straightforward paradigm of temporal fate specification where diverse neuronal fates are defined via integrating multiple layers of gene regulation. The neurodevelopmental roles of orthologous/related mammalian genes suggest a fundamental conservation of this mechanism in brain development.
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Affiliation(s)
- Ling-Yu Liu
- Howard Hughes Medical Institute, Janelia Research CampusAshburnUnited States
| | - Xi Long
- Howard Hughes Medical Institute, Janelia Research CampusAshburnUnited States
| | - Ching-Po Yang
- Howard Hughes Medical Institute, Janelia Research CampusAshburnUnited States
| | - Rosa L Miyares
- Howard Hughes Medical Institute, Janelia Research CampusAshburnUnited States
| | - Ken Sugino
- Howard Hughes Medical Institute, Janelia Research CampusAshburnUnited States
| | - Robert H Singer
- Howard Hughes Medical Institute, Janelia Research CampusAshburnUnited States
- Department of Anatomy and Structural Biology, Gruss Lipper Biophotonics CenterAlbert Einstein College of MedicineNew YorkUnited States
- Dominick P Purpura Department of Neuroscience, Gruss Lipper Biophotonics CenterAlbert Einstein College of MedicineNew YorkUnited States
| | - Tzumin Lee
- Howard Hughes Medical Institute, Janelia Research CampusAshburnUnited States
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20
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Lawson H, Vuong E, Miller RM, Kiontke K, Fitch DHA, Portman DS. The Makorin lep-2 and the lncRNA lep-5 regulate lin-28 to schedule sexual maturation of the C. elegans nervous system. eLife 2019; 8:e43660. [PMID: 31264582 PMCID: PMC6606027 DOI: 10.7554/elife.43660] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Accepted: 05/10/2019] [Indexed: 12/30/2022] Open
Abstract
Sexual maturation must occur on a controlled developmental schedule. In mammals, Makorin3 (MKRN3) and the miRNA regulators LIN28A/B are key regulators of this process, but how they act is unclear. In C. elegans, sexual maturation of the nervous system includes the functional remodeling of postmitotic neurons and the onset of adult-specific behaviors. Here, we find that the lin-28-let-7 axis (the 'heterochronic pathway') determines the timing of these events. Upstream of lin-28, the Makorin lep-2 and the lncRNA lep-5 regulate maturation cell-autonomously, indicating that distributed clocks, not a central timer, coordinate sexual differentiation of the C. elegans nervous system. Overexpression of human MKRN3 delays aspects of C. elegans sexual maturation, suggesting the conservation of Makorin function. These studies reveal roles for a Makorin and a lncRNA in timing of sexual differentiation; moreover, they demonstrate deep conservation of the lin-28-let-7 system in controlling the functional maturation of the nervous system.
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Affiliation(s)
- Hannah Lawson
- Department of BiologyUniversity of RochesterRochesterUnited States
| | - Edward Vuong
- Department of Biomedical GeneticsUniversity of RochesterRochesterUnited States
| | - Renee M Miller
- Department of Brain and Cognitive SciencesUniversity of RochesterRochesterUnited States
| | - Karin Kiontke
- Center for Developmental Genetics, Department of BiologyNew York UniversityNew YorkUnited States
| | - David HA Fitch
- Center for Developmental Genetics, Department of BiologyNew York UniversityNew YorkUnited States
| | - Douglas S Portman
- Department of BiologyUniversity of RochesterRochesterUnited States
- Department of Biomedical GeneticsUniversity of RochesterRochesterUnited States
- Department of NeuroscienceUniversity of RochesterRochesterUnited States
- DelMonte Institute for NeuroscienceUniversity of RochesterRochesterUnited States
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21
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Gegenhuber B, Tollkuhn J. Sex Differences in the Epigenome: A Cause or Consequence of Sexual Differentiation of the Brain? Genes (Basel) 2019; 10:genes10060432. [PMID: 31181654 PMCID: PMC6627918 DOI: 10.3390/genes10060432] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2019] [Revised: 05/29/2019] [Accepted: 06/03/2019] [Indexed: 12/19/2022] Open
Abstract
Females and males display differences in neural activity patterns, behavioral responses, and incidence of psychiatric and neurological diseases. Sex differences in the brain appear throughout the animal kingdom and are largely a consequence of the physiological requirements necessary for the distinct roles of the two sexes in reproduction. As with the rest of the body, gonadal steroid hormones act to specify and regulate many of these differences. It is thought that transient hormonal signaling during brain development gives rise to persistent sex differences in gene expression via an epigenetic mechanism, leading to divergent neurodevelopmental trajectories that may underlie sex differences in disease susceptibility. However, few genes with a persistent sex difference in expression have been identified, and only a handful of studies have employed genome-wide approaches to assess sex differences in epigenomic modifications. To date, there are no confirmed examples of gene regulatory elements that direct sex differences in gene expression in the brain. Here, we review foundational studies in this field, describe transcriptional mechanisms that could act downstream of hormone receptors in the brain, and suggest future approaches for identification and validation of sex-typical gene programs. We propose that sexual differentiation of the brain involves self-perpetuating transcriptional states that canalize sex-specific development.
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Affiliation(s)
- Bruno Gegenhuber
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
- Watson School of Biological Sciences, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
| | - Jessica Tollkuhn
- Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
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22
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Narbonne-Reveau K, Maurange C. Developmental regulation of regenerative potential in Drosophila by ecdysone through a bistable loop of ZBTB transcription factors. PLoS Biol 2019; 17:e3000149. [PMID: 30742616 PMCID: PMC6386533 DOI: 10.1371/journal.pbio.3000149] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 02/22/2019] [Accepted: 01/30/2019] [Indexed: 01/08/2023] Open
Abstract
In many organisms, the regenerative capacity of tissues progressively decreases as development progresses. However, the developmental mechanisms that restrict regenerative potential remain unclear. In Drosophila, wing imaginal discs become unable to regenerate upon damage during the third larval stage (L3). Here, we show that production of ecdysone after larvae reach their critical weight (CW) terminates the window of regenerative potential by acting on a bistable loop composed of two antagonistic Broad-complex/Tramtrack/Bric-à-brac Zinc-finger (ZBTB) genes: chinmo and broad (br). Around mid L3, ecdysone signaling silences chinmo and activates br to switch wing epithelial progenitors from a default self-renewing to a differentiation-prone state. Before mid L3, Chinmo promotes a strong regenerative response upon tissue damage. After mid L3, Br installs a nonpermissive state that represses regeneration. Transient down-regulation of ecdysone signaling or Br in late L3 larvae enhances chinmo expression in damaged cells that regain the capacity to regenerate. This work unveils a mechanism that ties the self-renewing and regenerative potential of epithelial progenitors to developmental progression. This study finds that the loss of regeneration potential in Drosophila wing imaginal discs is induced by the production of the steroid hormone ecdysone after the larva reaches its critical weight. Manipulating ecdysone signaling or the downstream transcription factors can uncouple regenerative properties from developmental progression. While some organisms exhibit remarkable regenerative abilities throughout their life, many animals, including mammals, present limited regenerative potential that progressively decreases during development. Understanding the mechanisms underlying this progressive loss is important to devise therapeutic approaches aiming at facilitating the regeneration of a damaged tissue throughout life. The fruitfly Drosophila is a powerful model organism to address such questions. Indeed, while tissues, such as imaginal discs, can fully regenerate if damaged during early development, they fail to do so upon damages during late development. We show here that restriction of regenerative potential occurring during midlarval stages is due to the production of a steroid hormone, named ecdysone. By genetically manipulating ecdysone signaling, we can uncouple regenerative abilities from developmental progression. In particular, we show that ecdysone signaling triggers a switch in the sequential expression of two transcription factors, Chinmo and Broad, that positively and negatively regulate the competence for imaginal disc regeneration, respectively. Our work therefore identifies a key developmental signal that restricts regenerative potential in insects and opens new perspectives on elucidating how regeneration-permissive transcriptional programs are locked as development progresses.
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Affiliation(s)
| | - Cédric Maurange
- Aix Marseille Université, CNRS, IBDM, UMR 7288, Marseille, France
- * E-mail:
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23
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Miyares RL, Lee T. Temporal control of Drosophila central nervous system development. Curr Opin Neurobiol 2018; 56:24-32. [PMID: 30500514 DOI: 10.1016/j.conb.2018.10.016] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 10/30/2018] [Indexed: 12/19/2022]
Abstract
A complex nervous system requires precise numbers of various neuronal types produced with exquisite spatiotemporal control. This striking diversity is generated by a limited number of neural stem cells (NSC), where spatial and temporal patterning intersect. Drosophila is a genetically tractable model system that has significant advantages for studying stem cell biology and neuronal fate specification. Here we review the latest findings in the rich literature of temporal patterning of neuronal identity in the Drosophila central nervous system. Rapidly changing consecutive transcription factors expressed in NSCs specify short series of neurons with considerable differences. More slowly progressing changes are orchestrated by NSC intrinsic temporal factor gradients which integrate extrinsic signals to coordinate nervous system and organismal development.
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Affiliation(s)
- Rosa Linda Miyares
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA
| | - Tzumin Lee
- Howard Hughes Medical Institute, Janelia Research Campus, 19700 Helix Drive, Ashburn, VA 20147, USA.
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24
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Sugie A, Marchetti G, Tavosanis G. Structural aspects of plasticity in the nervous system of Drosophila. Neural Dev 2018; 13:14. [PMID: 29960596 PMCID: PMC6026517 DOI: 10.1186/s13064-018-0111-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 06/12/2018] [Indexed: 12/15/2022] Open
Abstract
Neurons extend and retract dynamically their neurites during development to form complex morphologies and to reach out to their appropriate synaptic partners. Their capacity to undergo structural rearrangements is in part maintained during adult life when it supports the animal's ability to adapt to a changing environment or to form lasting memories. Nonetheless, the signals triggering structural plasticity and the mechanisms that support it are not yet fully understood at the molecular level. Here, we focus on the nervous system of the fruit fly to ask to which extent activity modulates neuronal morphology and connectivity during development. Further, we summarize the evidence indicating that the adult nervous system of flies retains some capacity for structural plasticity at the synaptic or circuit level. For simplicity, we selected examples mostly derived from studies on the visual system and on the mushroom body, two regions of the fly brain with extensively studied neuroanatomy.
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Affiliation(s)
- Atsushi Sugie
- Center for Transdisciplinary Research, Niigata University, Niigata, 951-8585 Japan
- Brain Research Institute, Niigata University, Niigata, 951-8585 Japan
| | | | - Gaia Tavosanis
- Center for Neurodegenerative Diseases (DZNE), 53127 Bonn, Germany
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