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Okamoto N, Yamanaka N. Steroid Hormone Entry into the Brain Requires a Membrane Transporter in Drosophila. Curr Biol 2020; 30:359-366.e3. [PMID: 31928869 DOI: 10.1016/j.cub.2019.11.085] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2019] [Revised: 11/14/2019] [Accepted: 11/28/2019] [Indexed: 02/08/2023]
Abstract
Steroid hormones control various aspects of brain development and behavior in metazoans, but how they enter the central nervous system (CNS) through the blood-brain barrier (BBB) remains poorly understood. It is generally believed that steroid hormones freely diffuse through the plasma membrane of the BBB cells to reach the brain [1], because of the predominant "simple diffusion" model of steroid hormone transport across cell membranes. Recently, however, we challenged the simple diffusion model by showing that a Drosophila organic anion-transporting polypeptide (OATP), which we named Ecdysone Importer (EcI), is required for cellular uptake of the primary insect steroid hormone ecdysone [2]. As ecdysone is first secreted into the hemolymph before reaching the CNS [3], our finding raised the question of how ecdysone enters the CNS through the BBB to exert its diverse role in Drosophila brain development. Here, we demonstrate in the Drosophila BBB that EcI is indispensable for ecdysone entry into the CNS to facilitate brain development. EcI is highly expressed in surface glial cells that form the BBB, and EcI knockdown in the BBB suppresses ecdysone signaling within the CNS and blocks ecdysone-mediated neuronal events during development. In an ex vivo culture system, the CNS requires EcI in the BBB to incorporate ecdysone from the culture medium. Our results suggest a transporter-mediated mechanism of steroid hormone entry into the CNS, which may provide important implications in controlling brain development and behavior by regulating steroid hormone permeability across the BBB.
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Affiliation(s)
- Naoki Okamoto
- Department of Entomology, Institute for Integrative Genome Biology, University of California, Riverside, 900 University Ave., Riverside, CA 92521, USA
| | - Naoki Yamanaka
- Department of Entomology, Institute for Integrative Genome Biology, University of California, Riverside, 900 University Ave., Riverside, CA 92521, USA.
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Regulatory Mechanisms of Metamorphic Neuronal Remodeling Revealed Through a Genome-Wide Modifier Screen in Drosophila melanogaster. Genetics 2017; 206:1429-1443. [PMID: 28476867 PMCID: PMC5500141 DOI: 10.1534/genetics.117.200378] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Accepted: 04/28/2017] [Indexed: 02/01/2023] Open
Abstract
During development, neuronal remodeling shapes neuronal connections to establish fully mature and functional nervous systems. Our previous studies have shown that the RNA-binding factor alan shepard (shep) is an important regulator of neuronal remodeling during metamorphosis in Drosophila melanogaster, and loss of shep leads to smaller soma size and fewer neurites in a stage-dependent manner. To shed light on the mechanisms by which shep regulates neuronal remodeling, we conducted a genetic modifier screen for suppressors of shep-dependent wing expansion defects and cellular morphological defects in a set of peptidergic neurons, the bursicon neurons, that promote posteclosion wing expansion. Out of 702 screened deficiencies that covered 86% of euchromatic genes, we isolated 24 deficiencies as candidate suppressors, and 12 of them at least partially suppressed morphological defects in shep mutant bursicon neurons. With RNA interference and mutant alleles of individual genes, we identified Daughters against dpp (Dad) and Olig family (Oli) as shep suppressor genes, and both of them restored the adult cellular morphology of shep-depleted bursicon neurons. Dad encodes an inhibitory Smad protein that inhibits bone morphogenetic protein (BMP) signaling, raising the possibility that shep interacted with BMP signaling through antagonism of Dad. By manipulating expression of the BMP receptor tkv, we found that activated BMP signaling was sufficient to rescue loss-of-shep phenotypes. These findings reveal mechanisms of shep regulation during neuronal development, and they highlight a novel genetic shep interaction with the BMP signaling pathway that controls morphogenesis in mature, terminally differentiated neurons during metamorphosis.
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Syed MH, Mark B, Doe CQ. Steroid hormone induction of temporal gene expression in Drosophila brain neuroblasts generates neuronal and glial diversity. eLife 2017; 6:26287. [PMID: 28394252 PMCID: PMC5403213 DOI: 10.7554/elife.26287] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 04/09/2017] [Indexed: 12/14/2022] Open
Abstract
An important question in neuroscience is how stem cells generate neuronal diversity. During Drosophila embryonic development, neural stem cells (neuroblasts) sequentially express transcription factors that generate neuronal diversity; regulation of the embryonic temporal transcription factor cascade is lineage-intrinsic. In contrast, larval neuroblasts generate longer ~50 division lineages, and currently only one mid-larval molecular transition is known: Chinmo/Imp/Lin-28+ neuroblasts transition to Syncrip+ neuroblasts. Here we show that the hormone ecdysone is required to down-regulate Chinmo/Imp and activate Syncrip, plus two late neuroblast factors, Broad and E93. We show that Seven-up triggers Chinmo/Imp to Syncrip/Broad/E93 transition by inducing expression of the Ecdysone receptor in mid-larval neuroblasts, rendering them competent to respond to the systemic hormone ecdysone. Importantly, late temporal gene expression is essential for proper neuronal and glial cell type specification. This is the first example of hormonal regulation of temporal factor expression in Drosophila embryonic or larval neural progenitors.
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Affiliation(s)
- Mubarak Hussain Syed
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Brandon Mark
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
| | - Chris Q Doe
- Institute of Neuroscience, Institute of Molecular Biology, Howard Hughes Medical Institute, University of Oregon, Eugene, United States
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Bodofsky S, Koitz F, Wightman B. CONSERVED AND EXAPTED FUNCTIONS OF NUCLEAR RECEPTORS IN ANIMAL DEVELOPMENT. NUCLEAR RECEPTOR RESEARCH 2017; 4:101305. [PMID: 29333434 PMCID: PMC5761748 DOI: 10.11131/2017/101305] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The nuclear receptor gene family includes 18 members that are broadly conserved among multiple disparate animal phyla, indicating that they trace their evolutionary origins to the time at which animal life arose. Typical nuclear receptors contain two major domains: a DNA-binding domain and a C-terminal domain that may bind a lipophilic hormone. Many of these nuclear receptors play varied roles in animal development, including coordination of life cycle events and cellular differentiation. The well-studied genetic model systems of Drosophila, C. elegans, and mouse permit an evaluation of the extent to which nuclear receptor function in development is conserved or exapted (repurposed) over animal evolution. While there are some specific examples of conserved functions and pathways, there are many clear examples of exaptation. Overall, the evolutionary theme of exaptation appears to be favored over strict functional conservation. Despite strong conservation of DNA-binding domain sequences and activity, the nuclear receptors prove to be highly-flexible regulators of animal development.
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Affiliation(s)
- Shari Bodofsky
- Biology Department, Muhlenberg College, 2400 Chew St., Allentown, PA 18104
| | - Francine Koitz
- Biology Department, Muhlenberg College, 2400 Chew St., Allentown, PA 18104
| | - Bruce Wightman
- Biology Department, Muhlenberg College, 2400 Chew St., Allentown, PA 18104
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Boulanger A, Dura JM. Nuclear receptors and Drosophila neuronal remodeling. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1849:187-95. [PMID: 24882358 DOI: 10.1016/j.bbagrm.2014.05.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 04/25/2014] [Accepted: 05/26/2014] [Indexed: 11/30/2022]
Abstract
During the development of both vertebrates and invertebrates, neurons undergo a crucial remodeling process that is necessary for their new function. Neuronal remodeling is composed of two stages: first, axons and dendrites are pruned without the loss of the cell body; later, this process is most commonly followed by a regrowth step. Holometabolous insects like the fruitfly Drosophila exhibit striking differences between their larval and adult stages. These neuronal remodeling processes occur during metamorphosis, the period of transformation from a larva to an adult. All axon and dendrite pruning events ultimately depend on the EcR nuclear receptor. Its ligand, the steroid molting hormone ecdysone, binds to heteromeric receptors comprising the nuclear receptor ECR and USP, and this complex regulates target genes involved in neuronal remodeling. Here we review the nuclear receptor-mediated genetic control of the main neuronal remodeling events described so far in Drosophila. These events consist of neurite degeneration in the mushroom bodies (MBs: the brain memory center) and in the dendritic arborizing sensory neurons, of neurite retraction or small scale elimination in the thoracic ventral neurosecretory cells, in the olfactory circuits and in the neuromuscular junction. MB axon regrowth after pruning and the role of MB neuron remodeling in memory formation are also reviewed. This article is part of a Special Issue entitled: Nuclear receptors in animal development.
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Affiliation(s)
- Ana Boulanger
- Institute of Human Genetics, UPR 1142, CNRS, 141, rue de la Cardonille, 34396 Montpellier, France.
| | - Jean-Maurice Dura
- Institute of Human Genetics, UPR 1142, CNRS, 141, rue de la Cardonille, 34396 Montpellier, France.
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Veverytsa L, Allan DW. Subtype-specific neuronal remodeling during Drosophila metamorphosis. Fly (Austin) 2013; 7:78-86. [PMID: 23579264 DOI: 10.4161/fly.23969] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
During metamorphosis in holometabolous insects, the nervous system undergoes dramatic remodeling as it transitions from its larval to its adult form. Many neurons are generated through post-embryonic neurogenesis to have adult-specific roles, but perhaps more striking is the dramatic remodeling that occurs to transition neurons from functioning in the larval to the adult nervous system. These neurons exhibit a remarkable degree of plasticity during this transition; many subsets undergo programmed cell death, others remodel their axonal and dendritic arbors extensively, whereas others undergo trans-differentiation to alter their terminal differentiation gene expression profiles. Yet other neurons appear to be developmentally frozen in an immature state throughout larval life, to be awakened at metamorphosis by a process we term temporally-tuned differentiation. These multiple forms of remodeling arise from subtype-specific responses to a single metamorphic trigger, ecdysone. Here, we discuss recent progress in Drosophila melanogaster that is shedding light on how subtype-specific programs of neuronal remodeling are generated during metamorphosis.
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Affiliation(s)
- Lyubov Veverytsa
- Department of Cellular and Physiological Sciences, Life Sciences Centre, Health Sciences Mall, University of British Columbia, Vancouver, BC Canada
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Boulanger A, Farge M, Ramanoudjame C, Wharton K, Dura JM. Drosophila motor neuron retraction during metamorphosis is mediated by inputs from TGF-β/BMP signaling and orphan nuclear receptors. PLoS One 2012; 7:e40255. [PMID: 22792255 PMCID: PMC3390346 DOI: 10.1371/journal.pone.0040255] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 06/04/2012] [Indexed: 11/19/2022] Open
Abstract
Larval motor neurons remodel during Drosophila neuro-muscular junction dismantling at metamorphosis. In this study, we describe the motor neuron retraction as opposed to degeneration based on the early disappearance of β-Spectrin and the continuing presence of Tubulin. By blocking cell dynamics with a dominant-negative form of Dynamin, we show that phagocytes have a key role in this process. Importantly, we show the presence of peripheral glial cells close to the neuro-muscular junction that retracts before the motor neuron. We show also that in muscle, expression of EcR-B1 encoding the steroid hormone receptor required for postsynaptic dismantling, is under the control of the ftz-f1/Hr39 orphan nuclear receptor pathway but not the TGF-β signaling pathway. In the motor neuron, activation of EcR-B1 expression by the two parallel pathways (TGF-β signaling and nuclear receptor) triggers axon retraction. We propose that a signal from a TGF-β family ligand is produced by the dismantling muscle (postsynapse compartment) and received by the motor neuron (presynaptic compartment) resulting in motor neuron retraction. The requirement of the two pathways in the motor neuron provides a molecular explanation for the instructive role of the postsynapse degradation on motor neuron retraction. This mechanism insures the temporality of the two processes and prevents motor neuron pruning before postsynaptic degradation.
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Affiliation(s)
- Ana Boulanger
- Neurogenetics and Memory, Department of Genetics and Development, Institute of Human Genetics, CNRS UPR1142, Montpellier, France
- * E-mail: (AB); (JMD)
| | - Morgane Farge
- Neurogenetics and Memory, Department of Genetics and Development, Institute of Human Genetics, CNRS UPR1142, Montpellier, France
| | - Christophe Ramanoudjame
- Neurogenetics and Memory, Department of Genetics and Development, Institute of Human Genetics, CNRS UPR1142, Montpellier, France
| | - Kristi Wharton
- Neurogenetics and Memory, Department of Genetics and Development, Institute of Human Genetics, CNRS UPR1142, Montpellier, France
- Division of Biology and Medicine, Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, Rhode Island, United States of America
| | - Jean-Maurice Dura
- Neurogenetics and Memory, Department of Genetics and Development, Institute of Human Genetics, CNRS UPR1142, Montpellier, France
- * E-mail: (AB); (JMD)
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Awasaki T, Huang Y, O'Connor MB, Lee T. Glia instruct developmental neuronal remodeling through TGF-β signaling. Nat Neurosci 2011; 14:821-3. [PMID: 21685919 PMCID: PMC3337551 DOI: 10.1038/nn.2833] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Accepted: 04/11/2011] [Indexed: 11/14/2022]
Abstract
Neural circuits are remodeled in response to developmental and environmental cues. Here we show that glia secrets Myoglianin, a TGF-β ligand, to instruct developmental neural remodeling in Drosophila. Glial Myoglianin up-regulates neuronal expression of an ecdysone nuclear receptor that triggers neurite remodeling following the late-larval ecdysone peak. This observation reveals that glia orchestrate developmental neural remodeling not only via engulfment of unwanted neurites but also through enabling neuron remodeling.
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Affiliation(s)
- Takeshi Awasaki
- Department of Neurobiology, University of Massachusetts, Worcester, Massachusetts, USA.
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