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Zhang X, Sun D, Wong K, Salkini A, Najafi H, Kim WJ. The astrocyte-enriched gene deathstar plays a crucial role in the development, locomotion, and lifespan of D. melanogaster. Fly (Austin) 2024; 18:2368336. [PMID: 38884422 PMCID: PMC11185185 DOI: 10.1080/19336934.2024.2368336] [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: 10/22/2023] [Accepted: 06/11/2024] [Indexed: 06/18/2024] Open
Abstract
The Drosophila melanogaster brain is a complex organ with various cell types, orchestrating the development, physiology, and behaviors of the fly. While each cell type in Drosophila brain is known to express a unique gene set, their complete genetic profile is still unknown. Advances in the RNA sequencing techniques at single-cell resolution facilitate identifying novel cell type markers and/or re-examining the specificity of the available ones. In this study, exploiting a single-cell RNA sequencing data of Drosophila optic lobe, we categorized the cells based on their expression pattern for known markers, then the genes with enriched expression in astrocytes were identified. CG11000 was identified as a gene with a comparable expression profile to the Eaat1 gene, an astrocyte marker, in every individual cell inside the Drosophila optic lobe and midbrain, as well as in the entire Drosophila brain throughout its development. Consistent with our bioinformatics data, immunostaining of the brains dissected from transgenic adult flies showed co-expression of CG11000 with Eaat1 in a set of single cells corresponding to the astrocytes in the Drosophila brain. Physiologically, inhibiting CG11000 through RNA interference disrupted the normal development of male D. melanogaster, while having no impact on females. Expression suppression of CG11000 in adult flies led to decreased locomotion activity and also shortened lifespan specifically in astrocytes, indicating the gene's significance in astrocytes. We designated this gene as 'deathstar' due to its crucial role in maintaining the star-like shape of glial cells, astrocytes, throughout their development into adult stage.
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Affiliation(s)
- Xiaoli Zhang
- The HIT Center for Life Sciences, Harbin Institute of Technology, Harbin, China
| | - Dongyu Sun
- The HIT Center for Life Sciences, Harbin Institute of Technology, Harbin, China
| | - Kyle Wong
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Ammar Salkini
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
| | - Hadi Najafi
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
- Department of Molecular, Cell and Cancer Biology, University of Massachusetts Chan Medical School, Worcester, MA, USA
| | - Woo Jae Kim
- The HIT Center for Life Sciences, Harbin Institute of Technology, Harbin, China
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
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2
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Clayworth K, Gilbert M, Auld V. Cell Biology Techniques for Studying Drosophila Peripheral Glial Cells. Cold Spring Harb Protoc 2024; 2024:pdb.top108159. [PMID: 37399179 DOI: 10.1101/pdb.top108159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/05/2023]
Abstract
Glial cells are essential for the proper development and functioning of the peripheral nervous system (PNS). The ability to study the biology of glial cells is therefore critical for our ability to understand PNS biology and address PNS maladies. The genetic and proteomic pathways underlying vertebrate peripheral glial biology are understandably complex, with many layers of redundancy making it sometimes difficult to study certain facets of PNS biology. Fortunately, many aspects of vertebrate peripheral glial biology are conserved with those of the fruit fly, Drosophila melanogaster With simple and powerful genetic tools and fast generation times, Drosophila presents an accessible and versatile model for studying the biology of peripheral glia. We introduce here three techniques for studying the cell biology of peripheral glia of Drosophila third-instar larvae. With fine dissection tools and common laboratory reagents, third-instar larvae can be dissected, with extraneous tissues removed, revealing the central nervous system (CNS) and PNS to be processed using a standard immunolabeling protocol. To improve the resolution of peripheral nerves in the z-plane, we describe a cryosectioning method to achieve 10- to 20-µm thick coronal sections of whole larvae, which can then be immunolabeled using a modified version of standard immunolabeling techniques. Finally, we describe a proximity ligation assay (PLA) for detecting close proximity between two proteins-thus inferring protein interaction-in vivo in third-instar larvae. These methods, further described in our associated protocols, can be used to improve our understanding of Drosophila peripheral glia biology, and thus our understanding of PNS biology.
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Affiliation(s)
- Katherine Clayworth
- Department of Zoology, Cell and Developmental Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Mary Gilbert
- Department of Zoology, Cell and Developmental Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Vanessa Auld
- Department of Zoology, Cell and Developmental Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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3
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Contreras EG, Kautzmann S, Klämbt C. The Drosophila blood-brain barrier invades the nervous system in a GPCR-dependent manner. Front Cell Neurosci 2024; 18:1397627. [PMID: 38846639 PMCID: PMC11153769 DOI: 10.3389/fncel.2024.1397627] [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: 03/07/2024] [Accepted: 05/07/2024] [Indexed: 06/09/2024] Open
Abstract
The blood-brain barrier (BBB) represents a crucial interface between the circulatory system and the brain. In Drosophila melanogaster, the BBB is composed of perineurial and subperineurial glial cells. The perineurial glial cells are small mitotically active cells forming the outermost layer of the nervous system and are engaged in nutrient uptake. The subperineurial glial cells form occluding septate junctions to prevent paracellular diffusion of macromolecules into the nervous system. To address whether the subperineurial glia just form a simple barrier or whether they establish specific contacts with both the perineurial glial cells and inner central nervous system (CNS) cells, we undertook a detailed morphological analysis. Using genetically encoded markers alongside with high-resolution laser scanning confocal microscopy and transmission electron microscopy, we identified thin cell processes extending into the perineurial layer and into the CNS cortex. Interestingly, long cell processes were observed reaching the glia ensheathing the neuropil of the central brain. GFP reconstitution experiments highlighted multiple regions of membrane contacts between subperineurial and ensheathing glia. Furthermore, we identify the G-protein-coupled receptor (GPCR) Moody as negative regulator of the growth of subperineurial cell processes. Loss of moody triggered a massive overgrowth of subperineurial cell processes into the CNS cortex and, moreover, affected the polarized localization of the xenobiotic transporter Mdr65. Finally, we found that GPCR signaling, but not septate junction formation, is responsible for controlling membrane overgrowth. Our findings support the notion that the Drosophila BBB is able to bridge the communication gap between circulation and synaptic regions of the brain by long cell processes.
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Affiliation(s)
| | | | - Christian Klämbt
- Multiscale Imaging Center, Institute of Neuro- and Behavioral Biology, University of Münster, Münster, Germany
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4
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Luedke KP, Yoshino J, Yin C, Jiang N, Huang JM, Huynh K, Parrish JZ. Dendrite intercalation between epidermal cells tunes nociceptor sensitivity to mechanical stimuli in Drosophila larvae. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.14.557275. [PMID: 37745567 PMCID: PMC10515945 DOI: 10.1101/2023.09.14.557275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/26/2023]
Abstract
An animal's skin provides a first point of contact with the sensory environment, including noxious cues that elicit protective behavioral responses. Nociceptive somatosensory neurons densely innervate and intimately interact with epidermal cells to receive these cues, however the mechanisms by which epidermal interactions shape processing of noxious inputs is still poorly understood. Here, we identify a role for dendrite intercalation between epidermal cells in tuning sensitivity of Drosophila larvae to noxious mechanical stimuli. In wild-type larvae, dendrites of nociceptive class IV da neurons intercalate between epidermal cells at apodemes, which function as body wall muscle attachment sites, but not at other sites in the epidermis. From a genetic screen we identified miR-14 as a regulator of dendrite positioning in the epidermis: miR-14 is expressed broadly in the epidermis but not in apodemes, and miR-14 inactivation leads to excessive apical dendrite intercalation between epidermal cells. We found that miR-14 regulates expression and distribution of the epidermal Innexins ogre and Inx2 and that these epidermal gap junction proteins restrict epidermal dendrite intercalation. Finally, we found that altering the extent of epidermal dendrite intercalation had corresponding effects on nociception: increasing epidermal intercalation sensitized larvae to noxious mechanical inputs and increased mechanically evoked calcium responses in nociceptive neurons, whereas reducing epidermal dendrite intercalation had the opposite effects. Altogether, these studies identify epidermal dendrite intercalation as a mechanism for mechanical coupling of nociceptive neurons to the epidermis, with nociceptive sensitivity tuned by the extent of intercalation.
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Affiliation(s)
- Kory P. Luedke
- Department of Biology, University of Washington, Campus Box 351800, Seattle, WA 98195, USA
| | - Jiro Yoshino
- Department of Biology, University of Washington, Campus Box 351800, Seattle, WA 98195, USA
| | - Chang Yin
- Department of Biology, University of Washington, Campus Box 351800, Seattle, WA 98195, USA
| | - Nan Jiang
- Department of Biology, University of Washington, Campus Box 351800, Seattle, WA 98195, USA
| | - Jessica M. Huang
- Department of Biology, University of Washington, Campus Box 351800, Seattle, WA 98195, USA
| | - Kevin Huynh
- Department of Biology, University of Washington, Campus Box 351800, Seattle, WA 98195, USA
| | - Jay Z. Parrish
- Department of Biology, University of Washington, Campus Box 351800, Seattle, WA 98195, USA
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5
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Das M, Cheng D, Matzat T, Auld VJ. Innexin-Mediated Adhesion between Glia Is Required for Axon Ensheathment in the Peripheral Nervous System. J Neurosci 2023; 43:2260-2276. [PMID: 36801823 PMCID: PMC10072304 DOI: 10.1523/jneurosci.1323-22.2023] [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: 07/05/2022] [Revised: 01/03/2023] [Accepted: 02/09/2023] [Indexed: 02/19/2023] Open
Abstract
Glia are essential to protecting and enabling nervous system function and a key glial function is the formation of the glial sheath around peripheral axons. Each peripheral nerve in the Drosophila larva is ensheathed by three glial layers, which structurally support and insulate the peripheral axons. How peripheral glia communicate with each other and between layers is not well established and we investigated the role of Innexins in mediating glial function in the Drosophila periphery. Of the eight Drosophila Innexins, we found two (Inx1 and Inx2) are important for peripheral glia development. In particular loss of Inx1 and Inx2 resulted in defects in the wrapping glia leading to disruption of the glia wrap. Of interest loss of Inx2 in the subperineurial glia also resulted in defects in the neighboring wrapping glia. Inx plaques were observed between the subperineurial glia and the wrapping glia suggesting that gap junctions link these two glial cell types. We found Inx2 is key to Ca2+ pulses in the peripheral subperineurial glia but not in the wrapping glia, and we found no evidence of gap junction communication between subperineurial and wrapping glia. Rather we have clear evidence that Inx2 plays an adhesive and channel-independent role between the subperineurial and wrapping glia to ensure the integrity of the glial wrap.SIGNIFICANCE STATEMENT Gap junctions are critical for glia communication and formation of myelin in myelinating glia. However, the role of gap junctions in non-myelinating glia is not well studied, yet non-myelinating glia are critical for peripheral nerve function. We found the Innexin gap junction proteins are present between different classes of peripheral glia in Drosophila. Here Innexins form junctions to facilitate adhesion between the different glia but do so in a channel-independent manner. Loss of adhesion leads to disruption of the glial wrap around axons and leads to fragmentation of the wrapping glia membranes. Our work points to an important role for gap junction proteins in mediating insulation by non-myelinating glia.
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Affiliation(s)
- Mriga Das
- Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Duo Cheng
- Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Till Matzat
- Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Vanessa J Auld
- Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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6
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Neves JH, Rezende-Teixeira P, Palomino NB, Machado-Santelli GM. Molecular and morphological approach to study the innexin gap junctions in Rhynchosciara americana. Open Biol 2021; 11:210224. [PMID: 34753320 PMCID: PMC8580445 DOI: 10.1098/rsob.210224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Gap junctions mediate communication between adjacent cells and are fundamental to the development and homeostasis in multicellular organisms. In invertebrates, gap junctions are formed by transmembrane proteins called innexins. Gap junctions allow the passage of small molecules through an intercellular channel, between a cell and another adjacent cell. The dipteran Rhynchosciara americana has contributed to studying the biology of invertebrates and the study of the interaction and regulation of genes during biological development. Therefore, this paper aimed to study the R. americana innexin-2 by molecular characterization, analysis of the expression profile and cellular localization. The molecular characterization results confirm that the message is from a gap junction protein and analysis of the expression and cellular localization profile shows that innexin-2 can participate in many physiological processes during the development of R. americana.
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Affiliation(s)
- Jorge Henrique Neves
- Institute of Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes, 1524 – sala 307, São Paulo, SP, Brazil
| | - Paula Rezende-Teixeira
- Institute of Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes, 1524 – sala 307, São Paulo, SP, Brazil
| | - Natalia Bazan Palomino
- Institute of Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes, 1524 – sala 307, São Paulo, SP, Brazil
| | - Glaucia Maria Machado-Santelli
- Institute of Biomedical Sciences, University of São Paulo, Avenida Professor Lineu Prestes, 1524 – sala 307, São Paulo, SP, Brazil
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7
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Ramakrishnan A, Sheeba V. Gap junction protein Innexin2 modulates the period of free-running rhythms in Drosophila melanogaster. iScience 2021; 24:103011. [PMID: 34522854 PMCID: PMC8426565 DOI: 10.1016/j.isci.2021.103011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 07/13/2021] [Accepted: 08/17/2021] [Indexed: 10/25/2022] Open
Abstract
A neuronal circuit of ∼150 neurons modulates rhythmic activity-rest behavior of Drosophila melanogaster. While it is known that coherent ∼24-hr rhythms in locomotion are brought about when 7 distinct neuronal clusters function as a network due to chemical communication amongst them, there are no reports of communication via electrical synapses made up of gap junctions. Here, we report that gap junction proteins, Innexins play crucial roles in determining the intrinsic period of activity-rest rhythms in flies. We show the presence of Innexin2 in the ventral lateral neurons, wherein RNAi-based knockdown of its expression slows down the speed of activity-rest rhythm along with alterations in the oscillation of a core-clock protein PERIOD and the output molecule pigment dispersing factor. Specifically disrupting the channel-forming ability of Innexin2 causes period lengthening, suggesting that Innexin2 may function as hemichannels or gap junctions in the clock circuit.
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Affiliation(s)
- Aishwarya Ramakrishnan
- Chronobiology and Behavioural Neurogenetics Laboratory, Neuroscience Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore, Karnataka 560064, India
| | - Vasu Sheeba
- Chronobiology and Behavioural Neurogenetics Laboratory, Neuroscience Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bangalore, Karnataka 560064, India
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8
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Weiss S, Clamon LC, Manoim JE, Ormerod KG, Parnas M, Littleton JT. Glial ER and GAP junction mediated Ca 2+ waves are crucial to maintain normal brain excitability. Glia 2021; 70:123-144. [PMID: 34528727 DOI: 10.1002/glia.24092] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 08/29/2021] [Accepted: 08/30/2021] [Indexed: 11/08/2022]
Abstract
Astrocytes play key roles in regulating multiple aspects of neuronal function from invertebrates to humans and display Ca2+ fluctuations that are heterogeneously distributed throughout different cellular microdomains. Changes in Ca2+ dynamics represent a key mechanism for how astrocytes modulate neuronal activity. An unresolved issue is the origin and contribution of specific glial Ca2+ signaling components at distinct astrocytic domains to neuronal physiology and brain function. The Drosophila model system offers a simple nervous system that is highly amenable to cell-specific genetic manipulations to characterize the role of glial Ca2+ signaling. Here we identify a role for ER store-operated Ca2+ entry (SOCE) pathway in perineurial glia (PG), a glial population that contributes to the Drosophila blood-brain barrier. We show that PG cells display diverse Ca2+ activity that varies based on their locale within the brain. Ca2+ signaling in PG cells does not require extracellular Ca2+ and is blocked by inhibition of SOCE, Ryanodine receptors, or gap junctions. Disruption of these components triggers stimuli-induced seizure-like episodes. These findings indicate that Ca2+ release from internal stores and its propagation between neighboring glial cells via gap junctions are essential for maintaining normal nervous system function.
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Affiliation(s)
- Shirley Weiss
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.,Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Lauren C Clamon
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Julia E Manoim
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Kiel G Ormerod
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Moshe Parnas
- Department of Physiology and Pharmacology, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.,Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel
| | - J Troy Littleton
- The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.,Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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9
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Huang YC, Chen KH, Chen YY, Tsao LH, Yeh TH, Chen YC, Wu PY, Wang TW, Yu JY. βPS-Integrin acts downstream of Innexin 2 in modulating stretched cell morphogenesis in the Drosophila ovary. G3-GENES GENOMES GENETICS 2021; 11:6310741. [PMID: 34544125 PMCID: PMC8496311 DOI: 10.1093/g3journal/jkab215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Accepted: 06/14/2021] [Indexed: 11/25/2022]
Abstract
During oogenesis, a group of specialized follicle cells, known as stretched cells (StCs), flatten drastically from cuboidal to squamous shape. While morphogenesis of epithelia is critical for organogenesis, genes and signaling pathways involved in this process remain to be revealed. In addition to formation of gap junctions for intercellular exchange of small molecules, gap junction proteins form channels or act as adaptor proteins to regulate various cellular behaviors. In invertebrates, gap junction proteins are Innexins. Knockdown of Innexin 2 but not other Innexins expressed in follicle cells attenuates StC morphogenesis. Interestingly, blocking of gap junctions with an inhibitor carbenoxolone does not affect StC morphogenesis, suggesting that Innexin 2 might control StCs flattening in a gap-junction-independent manner. An excessive level of βPS-Integrin encoded by myospheroid is detected in Innexin 2 mutant cells specifically during StC morphogenesis. Simultaneous knockdown of Innexin 2 and myospheroid partially rescues the morphogenetic defect resulted from Innexin 2 knockdown. Furthermore, reduction of βPS-Integrin is sufficient to induce early StCs flattening. Taken together, our data suggest that βPS-Integrin acts downstream of Innexin 2 in modulating StCs morphogenesis.
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Affiliation(s)
- Yi-Chia Huang
- Department of Life Sciences and Institute of Genome Sciences, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
| | - Kuan-Han Chen
- Department of Life Sciences and Institute of Genome Sciences, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
| | - Yu-Yang Chen
- Department of Life Sciences and Institute of Genome Sciences, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
| | - Liang-Hsuan Tsao
- Department of Life Sciences and Institute of Genome Sciences, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
| | - Tsung-Han Yeh
- Department of Life Sciences and Institute of Genome Sciences, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
| | - Yu-Chia Chen
- Department of Life Sciences and Institute of Genome Sciences, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
| | - Ping-Yen Wu
- Department of Life Sciences and Institute of Genome Sciences, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
| | - Tsu-Wei Wang
- Department of Life Science, National Taiwan Normal University, Taipei 116, Taiwan
| | - Jenn-Yah Yu
- Department of Life Sciences and Institute of Genome Sciences, National Yang Ming Chiao Tung University, Taipei 112, Taiwan.,Brain Research Center, National Yang Ming Chiao Tung University, Taipei 112, Taiwan
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10
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Lee KM, Talikoti A, Shelton K, Grotewiel M. Tyramine synthesis, vesicular packaging, and the SNARE complex function coordinately in astrocytes to regulate Drosophila alcohol sedation. Addict Biol 2021; 26:e13019. [PMID: 33538092 PMCID: PMC8225576 DOI: 10.1111/adb.13019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 01/08/2021] [Accepted: 01/19/2021] [Indexed: 12/21/2022]
Abstract
Identifying mechanisms underlying alcohol-related behaviors could provide important insights regarding the etiology of alcohol use disorder. To date, most genetic studies on alcohol-related behavior in model organisms have focused on neurons, leaving the causal roles of glial mechanisms less comprehensively investigated. Here, we report our studies on the role of Tyrosine decarboxylase 2 (Tdc2), which converts tyrosine to the catecholamine tyramine, in glial cells in Drosophila alcohol sedation. Using genetic approaches that drove transgene expression constitutively in all glia, constitutively in astrocytes and conditionally in glia during adulthood, we found that knockdown and overexpression of Tdc2, respectively, increased and decreased the sensitivity to alcohol sedation in flies. Manipulation of the genes tyramine β-hydroxylase and tyrosine hydroxylase, which respectively synthesize octopamine and dopamine from tyramine and tyrosine, had no discernable effect on alcohol sedation, suggesting that Tdc2 affects alcohol sedation by regulating tyramine production. We also found that knockdown of the vesicular monoamine transporter (VMAT) and disruption of the SNARE complex in all glia or selectively in astrocytes increased sensitivity to alcohol sedation and that both VMAT and the SNARE complex functioned downstream of Tdc2. Our studies support a model in which the synthesis of tyramine and vesicle-mediated release of tyramine from adult astrocytes regulates alcohol sedation in Drosophila. Considering that tyramine is functionally orthologous to norepinephrine in mammals, our results raise the possibility that gliotransmitter synthesis release could be a conserved mechanism influencing behavioral responses to alcohol as well as alcohol use disorder.
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Affiliation(s)
- Kristen M. Lee
- Neuroscience Graduate Program, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Ananya Talikoti
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Keith Shelton
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, Virginia, USA
| | - Mike Grotewiel
- Neuroscience Graduate Program, Virginia Commonwealth University, Richmond, Virginia, USA
- Department of Human and Molecular Genetics, Virginia Commonwealth University, Richmond, Virginia, USA
- Virginia Commonwealth University Alcohol Research Center, Virginia Commonwealth University, Richmond, Virginia, USA
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11
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Baker BM, Mokashi SS, Shankar V, Hatfield JS, Hannah RC, Mackay TFC, Anholt RRH. The Drosophila brain on cocaine at single-cell resolution. Genome Res 2021; 31:1927-1937. [PMID: 34035044 DOI: 10.1101/gr.268037.120] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2020] [Accepted: 02/02/2021] [Indexed: 11/24/2022]
Abstract
Whereas the neurological effects of cocaine have been well documented, effects of acute cocaine consumption on genome-wide gene expression across the brain remain largely unexplored. This question cannot be readily addressed in humans but can be approached using the Drosophila melanogaster model, where gene expression in the entire brain can be surveyed at once. Flies exposed to cocaine show impaired locomotor activity, including climbing behavior and startle response (a measure of sensorimotor integration), and increased incidence of seizures and compulsive grooming. To identify specific cell populations that respond to acute cocaine exposure, we analyzed single-cell transcriptional responses in duplicate samples of flies that consumed fixed amounts of sucrose or sucrose supplemented with cocaine, in both sexes. Unsupervised clustering of the transcriptional profiles of a total of 86,224 cells yielded 36 distinct clusters. Annotation of clusters based on gene markers revealed that all major cell types (neuronal and glial) as well as neurotransmitter types from most brain regions were represented. The brain transcriptional responses to cocaine showed profound sexual dimorphism and were considerably more pronounced in males than females. Differential expression analysis within individual clusters indicated cluster-specific responses to cocaine. Clusters corresponding to Kenyon cells of the mushroom bodies and glia showed especially large transcriptional responses following cocaine exposure. Cluster specific coexpression networks and global interaction networks revealed a diverse array of cellular processes affected by acute cocaine exposure. These results provide an atlas of sexually dimorphic cocaine-modulated gene expression in a model brain.
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Affiliation(s)
- Brandon M Baker
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, South Carolina 29646, USA
| | - Sneha S Mokashi
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, South Carolina 29646, USA
| | - Vijay Shankar
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, South Carolina 29646, USA
| | - Jeffrey S Hatfield
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, South Carolina 29646, USA
| | - Rachel C Hannah
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, South Carolina 29646, USA
| | - Trudy F C Mackay
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, South Carolina 29646, USA
| | - Robert R H Anholt
- Center for Human Genetics, Department of Genetics and Biochemistry, Clemson University, Greenwood, South Carolina 29646, USA
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12
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Astrocyte-Endotheliocyte Axis in the Regulation of the Blood-Brain Barrier. Neurochem Res 2021; 46:2538-2550. [PMID: 33961207 DOI: 10.1007/s11064-021-03338-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 05/01/2021] [Accepted: 05/03/2021] [Indexed: 12/18/2022]
Abstract
The evolution of blood-brain barrier paralleled centralisation of the nervous system: emergence of neuronal masses required control over composition of the interstitial fluids. The barriers were initially created by glial cells, which employed septate junctions to restrict paracellular diffusion in the invertebrates and tight junctions in some early vertebrates. The endothelial barrier, secured by tight and adherent junctions emerged in vertebrates and is common in mammals. Astrocytes form the parenchymal part of the blood-brain barrier and commutate with endothelial cells through secretion of growth factors, morphogens and extracellular vesicles. These secreted factors control the integrity of the blood-brain barrier through regulation of expression of tight junction proteins. The astrocyte-endotheliocyte communications are particularly important in various neurological diseases associated with impairments to the blood-brain barrier. Molecular mechanisms supporting astrocyte-endotheliocyte axis in health and disease are in need of detailed characterisation.
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13
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Rigon L, De Filippis C, Napoli B, Tomanin R, Orso G. Exploiting the Potential of Drosophila Models in Lysosomal Storage Disorders: Pathological Mechanisms and Drug Discovery. Biomedicines 2021; 9:biomedicines9030268. [PMID: 33800050 PMCID: PMC8000850 DOI: 10.3390/biomedicines9030268] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 02/18/2021] [Accepted: 03/03/2021] [Indexed: 12/12/2022] Open
Abstract
Lysosomal storage disorders (LSDs) represent a complex and heterogeneous group of rare genetic diseases due to mutations in genes coding for lysosomal enzymes, membrane proteins or transporters. This leads to the accumulation of undegraded materials within lysosomes and a broad range of severe clinical features, often including the impairment of central nervous system (CNS). When available, enzyme replacement therapy slows the disease progression although it is not curative; also, most recombinant enzymes cannot cross the blood-brain barrier, leaving the CNS untreated. The inefficient degradative capability of the lysosomes has a negative impact on the flux through the endolysosomal and autophagic pathways; therefore, dysregulation of these pathways is increasingly emerging as a relevant disease mechanism in LSDs. In the last twenty years, different LSD Drosophila models have been generated, mainly for diseases presenting with neurological involvement. The fruit fly provides a large selection of tools to investigate lysosomes, autophagy and endocytic pathways in vivo, as well as to analyse neuronal and glial cells. The possibility to use Drosophila in drug repurposing and discovery makes it an attractive model for LSDs lacking effective therapies. Here, ee describe the major cellular pathways implicated in LSDs pathogenesis, the approaches available for their study and the Drosophila models developed for these diseases. Finally, we highlight a possible use of LSDs Drosophila models for drug screening studies.
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Affiliation(s)
- Laura Rigon
- Fondazione Istituto di Ricerca Pediatrica “Città della Speranza”, Corso Stati Uniti 4, 35127 Padova, Italy; (C.D.F.); (R.T.)
- Correspondence:
| | - Concetta De Filippis
- Fondazione Istituto di Ricerca Pediatrica “Città della Speranza”, Corso Stati Uniti 4, 35127 Padova, Italy; (C.D.F.); (R.T.)
- Laboratory of Diagnosis and Therapy of Lysosomal Disorders, Department of Women’s and Children’s Health, University of Padova, Via Giustiniani 3, 35128 Padova, Italy
| | - Barbara Napoli
- Laboratory of Molecular Biology, Scientific Institute, IRCCS Eugenio Medea, Via Don Luigi Monza 20, Bosisio Parini, 23842 Lecco, Italy;
| | - Rosella Tomanin
- Fondazione Istituto di Ricerca Pediatrica “Città della Speranza”, Corso Stati Uniti 4, 35127 Padova, Italy; (C.D.F.); (R.T.)
- Laboratory of Diagnosis and Therapy of Lysosomal Disorders, Department of Women’s and Children’s Health, University of Padova, Via Giustiniani 3, 35128 Padova, Italy
| | - Genny Orso
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via Marzolo 5, 35131 Padova, Italy;
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14
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Hasegawa DK, Zhang P, Turnbull MW. Intracellular dynamics of polydnavirus innexin homologues. INSECT MOLECULAR BIOLOGY 2020; 29:477-489. [PMID: 32683761 DOI: 10.1111/imb.12657] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Revised: 04/30/2020] [Accepted: 06/29/2020] [Indexed: 06/11/2023]
Abstract
Polydnaviruses associated with ichneumonid parasitoid wasps (Ichnoviruses) encode large numbers of genes, often in multigene families. The Ichnovirus Vinnexin gene family, which is expressed in parasitized lepidopteran larvae, encodes homologues of Innexins, the structural components of insect gap junctions. Here, we have examined intracellular behaviours of the Campoletis sonorensis Ichnovirus (CsIV) Vinnexins, alone and in combination with a host Innexin orthologue, Innexin2 (Inx2). QRT-PCR verified that transcription of CsIV vinnexins occurs contemporaneously with inx2, implying co-occurrence of Vinnexin and Inx2 proteins. Confocal microscopy demonstrated that epitope-tagged VinnexinG (VnxG) and VinnexinQ2 (VnxQ2) exhibit similar subcellular localization as Spodoptera frugiperda Inx2 (Sf-Inx2). Surface biotinylation assays verified that all three proteins localize to the cell surface, and cytochalasin B and nocodazole that they rely on actin and microtubule cytoskeletal networks for localization. Immunomicroscopy following co-transfection of constructs indicates extensive co-localization of Vinnexins with each other and Sf-Inx2, and live-cell imaging of mCherry-labelled Inx2 supports that Vinnexins may affect Sf-Inx2 distribution in a Vinnexin-specific fashion. Our findings support that the Vinnexins may disrupt host cell physiology in a protein-specific manner through altering gap junctional intercellular channel communication, as well as indirectly by affecting multicellular junction characteristics.
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Affiliation(s)
- D K Hasegawa
- Department of Biological Sciences, Clemson University, Clemson, SC, USA
- USDA-ARS, Crop Improvement and Protection Research Unit, Salinas, CA, USA
| | - P Zhang
- Department of Biological Sciences, Clemson University, Clemson, SC, USA
- Department of Plant and Environmental Sciences, Clemson University, Clemson, SC, USA
| | - M W Turnbull
- Department of Biological Sciences, Clemson University, Clemson, SC, USA
- Department of Plant and Environmental Sciences, Clemson University, Clemson, SC, USA
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15
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Wrapping glia regulates neuronal signaling speed and precision in the peripheral nervous system of Drosophila. Nat Commun 2020; 11:4491. [PMID: 32901033 PMCID: PMC7479103 DOI: 10.1038/s41467-020-18291-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 08/11/2020] [Indexed: 02/06/2023] Open
Abstract
The functionality of the nervous system requires transmission of information along axons with high speed and precision. Conductance velocity depends on axonal diameter whereas signaling precision requires a block of electrical crosstalk between axons, known as ephaptic coupling. Here, we use the peripheral nervous system of Drosophila larvae to determine how glia regulates axonal properties. We show that wrapping glial differentiation depends on gap junctions and FGF-signaling. Abnormal glial differentiation affects axonal diameter and conductance velocity and causes mild behavioral phenotypes that can be rescued by a sphingosine-rich diet. Ablation of wrapping glia does not further impair axonal diameter and conductance velocity but causes a prominent locomotion phenotype that cannot be rescued by sphingosine. Moreover, optogenetically evoked locomotor patterns do not depend on conductance speed but require the presence of wrapping glial processes. In conclusion, our data indicate that wrapping glia modulates both speed and precision of neuronal signaling.
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16
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Miao G, Godt D, Montell DJ. Integration of Migratory Cells into a New Site In Vivo Requires Channel-Independent Functions of Innexins on Microtubules. Dev Cell 2020; 54:501-515.e9. [PMID: 32668209 DOI: 10.1016/j.devcel.2020.06.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 05/03/2020] [Accepted: 06/19/2020] [Indexed: 12/31/2022]
Abstract
During embryonic development and cancer metastasis, migratory cells must establish stable connections with new partners at their destinations. Here, we establish the Drosophila border cells as a model for this multistep process. During oogenesis, border cells delaminate from the follicular epithelium and migrate. When they reach their target, the oocyte, they undergo a stereotypical series of steps to adhere to it, then connect with another migrating epithelium. We identify gap-junction-forming innexin proteins as critical. Surprisingly, the channel function is dispensable. Instead, Innexins 2 and 3 function within the border cells, and Innexin 4 functions within the germline, to regulate microtubules. The microtubule-dependent border cell-oocyte interaction is essential to brace the cells against external morphogenetic forces. Thus, we establish an experimental model and use genetic, thermogenetic, and live-imaging approaches to uncover the contributions of Innexins and microtubules to a cell-biological process important in development and cancer.
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Affiliation(s)
- Guangxia Miao
- Molecular, Cellular, and Developmental Biology Department, University of California, Santa Barbara, Santa Barbara, CA 93106, USA
| | - Dorothea Godt
- Department of Cell and Systems Biology, University of Toronto, 25 Harbord Street, Toronto, ON M5S 3G5, Canada
| | - Denise J Montell
- Molecular, Cellular, and Developmental Biology Department, University of California, Santa Barbara, Santa Barbara, CA 93106, USA.
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17
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Peterson NG, Stormo BM, Schoenfelder KP, King JS, Lee RRS, Fox DT. Cytoplasmic sharing through apical membrane remodeling. eLife 2020; 9:58107. [PMID: 33051002 PMCID: PMC7655102 DOI: 10.7554/elife.58107] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 10/13/2020] [Indexed: 12/12/2022] Open
Abstract
Multiple nuclei sharing a common cytoplasm are found in diverse tissues, organisms, and diseases. Yet, multinucleation remains a poorly understood biological property. Cytoplasm sharing invariably involves plasma membrane breaches. In contrast, we discovered cytoplasm sharing without membrane breaching in highly resorptive Drosophila rectal papillae. During a six-hour developmental window, 100 individual papillar cells assemble a multinucleate cytoplasm, allowing passage of proteins of at least 62 kDa throughout papillar tissue. Papillar cytoplasm sharing does not employ canonical mechanisms such as incomplete cytokinesis or muscle fusion pore regulators. Instead, sharing requires gap junction proteins (normally associated with transport of molecules < 1 kDa), which are positioned by membrane remodeling GTPases. Our work reveals a new role for apical membrane remodeling in converting a multicellular epithelium into a giant multinucleate cytoplasm.
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Affiliation(s)
- Nora G Peterson
- Department of Cell Biology, Duke University Medical CenterDurhamUnited States
| | - Benjamin M Stormo
- Department of Cell Biology, Duke University Medical CenterDurhamUnited States
| | | | - Juliet S King
- Department of Pharmacology & Cancer Biology, Duke University Medical CenterDurhamUnited States
| | | | - Donald T Fox
- Department of Cell Biology, Duke University Medical CenterDurhamUnited States,University Program in Genetics and Genomics, Duke UniversityDurhamUnited States,Department of Pharmacology & Cancer Biology, Duke University Medical CenterDurhamUnited States
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18
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Raad H, Robichon A. The pleiotropic effects of Innexin genes expressed in Drosophila glia encompass wing chemosensory sensilla. J Neurosci Res 2019; 97:1319-1330. [PMID: 31257643 DOI: 10.1002/jnr.24485] [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: 03/04/2019] [Revised: 06/05/2019] [Accepted: 06/07/2019] [Indexed: 11/07/2022]
Abstract
The neuroanatomy of Drosophila wing chemosensilla and the analysis of their sensory organ precursor cell lineage have demonstrated that they are surprisingly related to taste perception. The microarchitecture of wing bristles limits the use of electrophysiology methods to investigate wing chemosensory mechanisms. However, by monitoring the fluorescence of the complex calcium/GCaMP, calcium flux triggered upon tastant stimulation was observed within sensilla aligned along the wing anterior nerve. This string of fluorescent puncta was impaired in wings of Innexin 2 (Inx2) mutant flies; although it is unclear whether the Innexin proteins act at the level of the wing imaginal disc, adult wing and/or at both levels. Glial cells known to shelter Innexin(s) expression have no documented role in adult chemosensory sensilla. Our data suggest that Innexin(s) are likely required for the maturation of functional wing chemosensilla in adulthood. The unexpected presence of most Innexin transcripts in adult wing RNAseq data set argues for the expression of Innexin proteins in the larval imaginal wing disc that are continued in wing chemosensilla at adulthood. OPEN PRACTICES: This article has earned an Open Data badge for making publicly available the digitally-shareable data necessary to reproduce the reported results. The data is available as supporting materials and includes the electronic lab notebook. Learn more about the Open Practices badges from the Center for Open Science: https://osf.io/tvyxz/wiki.
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Affiliation(s)
- Hussein Raad
- INRA, CNRS, Université Côte d'Azur, Institut Sophia Agrobiotech, Sophia Antipolis, France.,Lebanese International University, Mazraa, Lebanon
| | - Alain Robichon
- INRA, CNRS, Université Côte d'Azur, Institut Sophia Agrobiotech, Sophia Antipolis, France
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19
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Read RD. Pvr receptor tyrosine kinase signaling promotes post-embryonic morphogenesis, and survival of glia and neural progenitor cells in Drosophila. Development 2018; 145:dev.164285. [PMID: 30327326 DOI: 10.1242/dev.164285] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Accepted: 10/10/2018] [Indexed: 12/30/2022]
Abstract
Stem cells reside in specialized microenvironments, called niches, that regulate their development and the development of their progeny. However, the development and maintenance of niches are poorly understood. In the Drosophila brain, cortex glial cells provide a niche that promotes self-renewal and proliferation of neural stem cell-like cells (neuroblasts). In the central brain, neuroblasts and their progeny control post-embryonic morphogenesis of cortex glia through PDGF-like ligands, and this PDGFR receptor tyrosine kinase (RTK) signaling in cortex glia is required for expression of DE-cadherin, which sustains neuroblasts. Thus, through an RTK-dependent feed-forward loop, neuroblasts and their glial niche actively maintain each other. When the EGFR RTK is constitutively activated in cortex glia, they overexpress PDGF orthologs to stimulate autocrine PDGFR signaling, which uncouples their growth and survival from neuroblasts, and drives neoplastic glial transformation and elimination of neuroblasts. These results provide fundamental insights into glial development and niche regulation, and show that niche-neural stem cell feed-forward signaling becomes hijacked to drive neural tumorigenesis.
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Affiliation(s)
- Renee D Read
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
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20
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Yildirim K, Petri J, Kottmeier R, Klämbt C. Drosophila glia: Few cell types and many conserved functions. Glia 2018; 67:5-26. [DOI: 10.1002/glia.23459] [Citation(s) in RCA: 75] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 04/25/2018] [Accepted: 05/04/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Kerem Yildirim
- Institute for Neuro and Behavioral Biology; University of Münster; Badestraße 9, 48149 Münster Germany
| | - Johanna Petri
- Institute for Neuro and Behavioral Biology; University of Münster; Badestraße 9, 48149 Münster Germany
| | - Rita Kottmeier
- Institute for Neuro and Behavioral Biology; University of Münster; Badestraße 9, 48149 Münster Germany
| | - Christian Klämbt
- Institute for Neuro and Behavioral Biology; University of Münster; Badestraße 9, 48149 Münster Germany
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21
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Güiza J, Barría I, Sáez JC, Vega JL. Innexins: Expression, Regulation, and Functions. Front Physiol 2018; 9:1414. [PMID: 30364195 PMCID: PMC6193117 DOI: 10.3389/fphys.2018.01414] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 09/18/2018] [Indexed: 01/02/2023] Open
Abstract
The innexin (Inx) proteins form gap junction channels and non-junctional channels (named hemichannels) in invertebrates. These channels participate in cellular communication playing a relevant role in several physiological processes. Pioneer studies conducted mainly in worms and flies have shown that innexins participate in embryo development and behavior. However, recent studies have elucidated new functions of innexins in Arthropoda, Nematoda, Annelida, and Cnidaria, such as immune response, and apoptosis. This review describes emerging data of possible new roles of innexins and summarizes the data available to date.
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Affiliation(s)
- Juan Güiza
- Laboratorio de Fisiología Experimental, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
| | - Iván Barría
- Laboratorio de Fisiología Experimental, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
| | - Juan C Sáez
- Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago, Chile.,Instituto de Neurociencias, Centro Interdisciplinario de Neurociencias de Valparaíso, Universidad de Valparaíso, Valparaíso, Chile
| | - José L Vega
- Laboratorio de Fisiología Experimental, Instituto Antofagasta, Universidad de Antofagasta, Antofagasta, Chile
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22
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Zhang W, Liu MW, Li M, Xiao W, Zhang XW, He HJ, Chen YB, Ding L, Luo KJ. Unexpected link between insect innexins and apoptosis of HeLa cells. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2018; 99:e21473. [PMID: 29862562 DOI: 10.1002/arch.21473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Little is known about how mammalian cells respond to the expression of innexins (Inxs), which are known to mediate cell-to-cell communication that causes apoptosis in the cells of the insect Spodoptera litura. The mammalian expression system, p3xFLAG tag protein, containing the CMV promoter, allowed us to construct two C-terminally elongated innexins (Cte-Inxs), SpliInx2 (Inx2-FLAG), and SpliInx3 (Inx3-FLAG), which were predicted to have the same secondary topological structures as the native SpliInx2 and SpliInx3. Here, we found that only the mRNAs of the two Cte-Inxs were expressed under the control of the CMV promoter in HeLa cells. Unexpectedly, mRNA expression of the two Cte-Inxs enhanced apoptosis of HeLa cells. The two Cte-Inx mRNAs were associated with a significant decrease in Akt phosphorylation in HeLa cells undergoing apoptosis. Furthermore, Inx3-FLAG mRNA expression in nonapoptotic HCT116 cells was also associated with a significant decrease in the levels of phosphorylated Akt. Intriguingly, expression of the mRNAs of the two Cte-Inxs did not activate caspase 3, but it markedly reduced Bid levels in HeLa cells undergoing apoptosis. These results suggest that mRNA expression of the two Cte-Inxs may activate a Bid-dependent apoptotic pathway in HeLa cells. Our study demonstrates that invertebrate gap junction mRNAs can function in vertebrate cancer cells as tumor suppressors.
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Affiliation(s)
- Wei Zhang
- School of Life Sciences, Yunnan University, Kunming, P.R. China
- Key Laboratory for Biochemistry and Molecular Biology of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
| | - Meng-Wei Liu
- School of Life Sciences, Yunnan University, Kunming, P.R. China
- Key Laboratory for Biochemistry and Molecular Biology of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
| | - Ming Li
- School of Life Sciences, Yunnan University, Kunming, P.R. China
- Key Laboratory for Biochemistry and Molecular Biology of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
| | - Wei Xiao
- School of Life Sciences, Yunnan University, Kunming, P.R. China
| | - Xue-Wen Zhang
- School of Life Sciences, Yunnan University, Kunming, P.R. China
- Key Laboratory for Biochemistry and Molecular Biology of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
| | - Hao-Juan He
- School of Life Sciences, Yunnan University, Kunming, P.R. China
- Key Laboratory for Biochemistry and Molecular Biology of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
| | - Ya-Bin Chen
- School of Life Sciences, Yunnan University, Kunming, P.R. China
- Key Laboratory for Biochemistry and Molecular Biology of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
| | - Lei Ding
- School of Life Sciences, Yunnan University, Kunming, P.R. China
- Key Laboratory for Biochemistry and Molecular Biology of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
| | - Kai-Jun Luo
- School of Life Sciences, Yunnan University, Kunming, P.R. China
- Key Laboratory for Biochemistry and Molecular Biology of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
- Key Laboratory for Animal Genetic Diversity and Evolution of High Education in Yunnan Province, Yunnan University, Kunming, P.R. China
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23
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Ueda A, Woods S, McElree I, O'Harrow TCDG, Inman C, Thenuwara S, Aftab M, Iyengar A. Two novel forms of ERG oscillation in Drosophila: age and activity dependence. J Neurogenet 2018; 32:118-126. [PMID: 29688104 DOI: 10.1080/01677063.2018.1461866] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Over an animal's lifespan, neuronal circuits and systems often decline in an inherently heterogeneous fashion. To compare the age-dependent progression of changes in visual behavior with alterations in retinal physiology, we examined phototaxis and electroretinograms (ERGs) in a wild-type D. melanogaster strain (Canton-S) across their lifespan. In aged flies (beyond 50% median lifespan), we found a marked decline in phototaxis, while motor coordination was less disrupted, as indicated by relatively stronger negative geotaxis. These aged flies displayed substantially reduced ERG transient amplitudes while the receptor potentials (RP) remained largely intact. Using a repetitive light flash protocol, we serendipitously discovered two forms of activity-dependent oscillation in the ERG waveforms of young flies: 'light-off' and 'light-on' oscillations. After repeated 500 ms light flashes, light-off oscillations appeared during the ERG off-transients (frequency: 50-120 Hz, amplitude: ∼1 mV). Light-on oscillations (100-200 Hz, ∼0.3 mV) were induced by a series of 50 ms flashes, and were evident during the ERG on-transients. Both forms of oscillation were observed in other strains of D. melanogaster (Oregon-R, Berlin), additional Drosophila species (D. funerbris, D. euronotus, D. hydei, D. americana), and were evoked by a variety of light sources. Both light-off and light-on oscillations were distinct from previously described ERG oscillations in the visual mutant rosA in terms of location within the waveform and frequency. However, within rosA mutants, light-off oscillations, but not light-on oscillations could be recruited by the repetitive light flash protocol. Importantly though, we found that both forms of oscillation were rarely observed in aged flies. Although the physiological bases of these oscillations remain to be elucidated, they may provide important clues to age-related changes in neuronal excitability and synaptic transmission.
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Affiliation(s)
- Atsushi Ueda
- a Department of Biology , University of Iowa , Iowa City , IA , USA
| | - Scott Woods
- a Department of Biology , University of Iowa , Iowa City , IA , USA
| | - Ian McElree
- a Department of Biology , University of Iowa , Iowa City , IA , USA
| | | | - Casey Inman
- a Department of Biology , University of Iowa , Iowa City , IA , USA
| | | | - Muhammad Aftab
- a Department of Biology , University of Iowa , Iowa City , IA , USA
| | - Atulya Iyengar
- a Department of Biology , University of Iowa , Iowa City , IA , USA
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24
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Volkenhoff A, Hirrlinger J, Kappel JM, Klämbt C, Schirmeier S. Live imaging using a FRET glucose sensor reveals glucose delivery to all cell types in the Drosophila brain. JOURNAL OF INSECT PHYSIOLOGY 2018; 106:55-64. [PMID: 28733241 DOI: 10.1016/j.jinsphys.2017.07.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 06/13/2017] [Accepted: 07/17/2017] [Indexed: 05/26/2023]
Abstract
All complex nervous systems are metabolically separated from circulation by a blood-brain barrier (BBB) that prevents uncontrolled leakage of solutes into the brain. Thus, all metabolites needed to sustain energy homeostasis must be transported across this BBB. In invertebrates, such as Drosophila, the major carbohydrate in circulation is the disaccharide trehalose and specific trehalose transporters are expressed by the glial BBB. Here we analyzed whether glucose is able to contribute to energy homeostasis in Drosophila. To study glucose influx into the brain we utilized a genetically encoded, FRET-based glucose sensor expressed in a cell type specific manner. When confronted with glucose all brain cells take up glucose within two minutes. In order to characterize the glucose transporter involved, we studied Drosophila Glut1, the homologue of which is primarily expressed by the BBB-forming endothelial cells and astrocytes in the mammalian nervous system. In Drosophila, however, Glut1 is expressed in neurons and is not found at the BBB. Thus, Glut1 cannot contribute to initial glucose uptake from the hemolymph. To test whether gap junctional coupling between the BBB forming cells and other neural cells contributes to glucose distribution we assayed these junctions using RNAi experiments and only found a minor contribution of gap junctions to glucose metabolism. Our results provide the entry point to further dissect the mechanisms underlying glucose distribution and offer new opportunities to understand brain metabolism.
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Affiliation(s)
- Anne Volkenhoff
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany
| | - Johannes Hirrlinger
- Carl-Ludwig-Institute for Physiology, Faculty of Medicine, University of Leipzig, Liebigstr. 27, D-04103 Leipzig, Germany; Department of Neurogenetics, Max-Planck-Institute for Experimental Medicine, Hermann-Rein-Str. 3, D-37075 Göttingen, Germany
| | - Johannes M Kappel
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany
| | - Christian Klämbt
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany
| | - Stefanie Schirmeier
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany.
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25
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Zhang SL, Yue Z, Arnold DM, Artiushin G, Sehgal A. A Circadian Clock in the Blood-Brain Barrier Regulates Xenobiotic Efflux. Cell 2018; 173:130-139.e10. [PMID: 29526461 PMCID: PMC5866247 DOI: 10.1016/j.cell.2018.02.017] [Citation(s) in RCA: 141] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2017] [Revised: 12/22/2017] [Accepted: 02/07/2018] [Indexed: 12/29/2022]
Abstract
Endogenous circadian rhythms are thought to modulate responses to external factors, but mechanisms that confer time-of-day differences in organismal responses to environmental insults/therapeutic treatments are poorly understood. Using a xenobiotic, we find that permeability of the Drosophila "blood"-brain barrier (BBB) is higher at night. The permeability rhythm is driven by circadian regulation of efflux and depends on a molecular clock in the perineurial glia of the BBB, although efflux transporters are restricted to subperineurial glia (SPG). We show that transmission of circadian signals across the layers requires cyclically expressed gap junctions. Specifically, during nighttime, gap junctions reduce intracellular magnesium ([Mg2+]i), a positive regulator of efflux, in SPG. Consistent with lower nighttime efflux, nighttime administration of the anti-epileptic phenytoin is more effective at treating a Drosophila seizure model. These findings identify a novel mechanism of circadian regulation and have therapeutic implications for drugs targeted to the central nervous system.
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Affiliation(s)
- Shirley L Zhang
- Center for Sleep and Circadian Neurobiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA; Chronobiology Program at Penn and Howard Hughes Medical Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Zhifeng Yue
- Chronobiology Program at Penn and Howard Hughes Medical Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Denice M Arnold
- Chronobiology Program at Penn and Howard Hughes Medical Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Gregory Artiushin
- Chronobiology Program at Penn and Howard Hughes Medical Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Amita Sehgal
- Center for Sleep and Circadian Neurobiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA; Chronobiology Program at Penn and Howard Hughes Medical Institute, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA 19104, USA.
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Calkins TL, Piermarini PM. A Blood Meal Enhances Innexin mRNA Expression in the Midgut, Malpighian Tubules, and Ovaries of the Yellow Fever Mosquito Aedes aegypti. INSECTS 2017; 8:insects8040122. [PMID: 29113099 PMCID: PMC5746805 DOI: 10.3390/insects8040122] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2017] [Revised: 10/30/2017] [Accepted: 10/31/2017] [Indexed: 11/16/2022]
Abstract
Mosquitoes are vectors of pathogens that cause diseases of medical and veterinary importance. Female mosquitoes transmit these pathogens while taking a blood meal, which most species require to produce eggs. The period after a blood meal is a time of extreme physiological change that requires rapid coordination of specific tissues. Gap junctions (GJ) are intercellular channels that aid in the coordination of cells within tissues via the direct transfer of certain small molecules and ions between cells. Evolutionarily distinct groups of proteins form the gap junctions of vertebrate and invertebrate animals (connexins and innexins, respectively). Aedes aegypti mosquitoes possess six genes encoding innexins: inx1, inx2, inx3, inx4, inx7, and inx8. The goal of this study was to identify potential roles of innexins in the physiology of mosquitoes after a blood meal by using qPCR to quantify their mRNA expression in adult females at 3 h and 24 h post-blood meal (PBM) relative to non-blood-fed controls. We found that at 24 h PBM, expression levels of inx2, inx3, and inx4 mRNAs increased; inx2 was the most highly upregulated innexin in key tissues associated with blood-meal digestion and egg production (i.e., the midgut and ovaries, respectively). However, knocking down inx2 mRNA levels by over 75% via RNA interference had no significant effect on fecundity. Altogether, our results suggest that a blood meal influences the molecular expression of innexins in mosquitoes, but their specific physiological roles remain to be elucidated.
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Affiliation(s)
- Travis L Calkins
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA.
| | - Peter M Piermarini
- Department of Entomology, Ohio Agricultural Research and Development Center, The Ohio State University, Wooster, OH 44691, USA.
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27
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Richard M, Bauer R, Tavosanis G, Hoch M. The gap junction protein Innexin3 is required for eye disc growth in Drosophila. Dev Biol 2017; 425:191-207. [PMID: 28390801 DOI: 10.1016/j.ydbio.2017.04.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 03/30/2017] [Accepted: 04/03/2017] [Indexed: 12/23/2022]
Abstract
The Drosophila compound eye develops from a bilayered epithelial sac composed of an upper peripodial epithelium layer and a lower disc proper, the latter giving rise to the eye itself. During larval stages, complex signalling events between the layers contribute to the control of cell proliferation and differentiation in the disc. Previous work in our lab established the gap junction protein Innexin2 (Inx2) as crucial for early larval eye disc growth. By analysing the contribution of other Innexins to eye size control, we have identified Innexin3 (Inx3) as an important growth regulator. Depleting inx3 during larval eye development reduces eye size, while elevating inx3 levels increases eye size, thus phenocopying the inx2 loss- and gain-of-function situation. As demonstrated previously for inx2, inx3 regulates disc cell proliferation and interacts genetically with the Dpp pathway, being required for the proper activation of the Dpp pathway transducer Mad at the furrow and the expression of Dpp receptor Punt in the eye disc. At the developmental timepoint corresponding to eye disc growth, Inx3 colocalises with Inx2 in disc proper and peripodial epithelium cell membranes. In addition, we show that Inx3 protein levels critically depend on inx2 throughout eye development and that inx3 modulates Inx2 protein levels in the larval eye disc. Rescue experiments demonstrate that Inx3 and Inx2 cooperate functionally to enable eye disc growth in Drosophila. Finally, we demonstrate that expression of Inx3 and Inx2 is not only needed in the disc proper but also in the peripodial epithelium to regulate growth of the eye disc. Our data provide a functional demonstration that putative Inx2/Inx3 heteromeric channels regulate organ size.
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Affiliation(s)
- Mélisande Richard
- Life & Medical Sciences Institute (LIMES) Development, Genetics & Molecular Physiology Unit University of Bonn, Carl-Troll-Straße, 31 53115 Bonn, Germany
| | - Reinhard Bauer
- Life & Medical Sciences Institute (LIMES) Development, Genetics & Molecular Physiology Unit University of Bonn, Carl-Troll-Straße, 31 53115 Bonn, Germany
| | - Gaia Tavosanis
- German Center for Neurodegenerative Diseases (DZNE), Dendrite Differentiation Unit, Sigmund-Freud-Str. 27, 53127 Bonn, Germany
| | - Michael Hoch
- Life & Medical Sciences Institute (LIMES) Development, Genetics & Molecular Physiology Unit University of Bonn, Carl-Troll-Straße, 31 53115 Bonn, Germany.
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28
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Hasegawa DK, Erickson SL, Hersh BM, Turnbull MW. Virus Innexins induce alterations in insect cell and tissue function. JOURNAL OF INSECT PHYSIOLOGY 2017; 98:173-181. [PMID: 28077262 DOI: 10.1016/j.jinsphys.2017.01.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Revised: 10/10/2016] [Accepted: 01/06/2017] [Indexed: 06/06/2023]
Abstract
Polydnaviruses are dsDNA viruses that induce immune and developmental alterations in their caterpillar hosts. Characterization of polydnavirus gene families and family members is necessary to understand mechanisms of pathology and evolution of these viruses, and may aid to elucidate the role of host homologues if present. For example, the polydnavirus vinnexin gene family encodes homologues of insect gap junction genes (innexins) that are expressed in host immune cells (hemocytes). While the roles of Innexin proteins and gap junctions in insect immunity are largely unclear, we previously demonstrated that Vinnexins form functional gap junctions and alter the junctional characteristics of a host Innexin when co-expressed in paired Xenopus oocytes. Here, we test the effect of ectopic vinnexin expression on host cell physiology using both a lepidopteran cell culture model and a dipteran whole organism model. Vinnexin expression in the cell culture system resulted in gene-specific alterations in cell morphology and a slight, but non-statistically significant, reduction in gap junction activity as measured by dye transfer, while ectopic expression of a lepidopteran innexin2 gene led to morphological alterations and increase in gap junction activity. Global ectopic expression in the model dipteran, Drosophila melanogaster, of one vinnexin (vinnexinG) or D. melanogaster innexin2 (Dm-inx2) resulted in embryonic lethality, while expression of the other vinnexin genes had no effect. Furthermore, ectopic expression of vinnexinG, but not other vinnexin genes or Dm-inx2, in D. melanogaster larval gut resulted in developmental arrest in the pupal stage. These data indicate the vinnexins likely have gene-specific roles in host manipulation. They also support the use of Drosophila in further analysis of the role of Vinnexins and other polydnavirus genes in modifying host physiological processes. Finally, our findings suggest the vinnexin genes may be useful to perturb and characterize the physiological functions of insect Innexins.
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Affiliation(s)
- Daniel K Hasegawa
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA.
| | | | - Bradley M Hersh
- Department of Biology, Allegheny College, Meadville, PA 16335, USA.
| | - Matthew W Turnbull
- Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA; Department of Plant and Environmental Sciences, Clemson University, Clemson, SC 29634, USA.
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29
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Amyloid Precursor Protein in Drosophila Glia Regulates Sleep and Genes Involved in Glutamate Recycling. J Neurosci 2017; 37:4289-4300. [PMID: 28314820 DOI: 10.1523/jneurosci.2826-16.2017] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 02/03/2017] [Accepted: 02/27/2017] [Indexed: 12/19/2022] Open
Abstract
Amyloid precursor protein (App) plays a crucial role in Alzheimer's disease via the production and deposition of toxic β-amyloid peptides. App is heavily expressed in neurons, the focus of the vast majority of studies investigating its function. Meanwhile, almost nothing is known about App's function in glia, where it is also expressed, and can potentially participate in the regulation of neuronal physiology. In this report, we investigated whether Appl, the Drosophila homolog of App, could influence sleep-wake regulation when its function is manipulated in glial cells. Appl inhibition in astrocyte-like and cortex glia resulted in higher sleep amounts and longer sleep bout duration during the night, while overexpression had the opposite effect. These sleep phenotypes were not the result of developmental defects, and were correlated with changes in expression in glutamine synthetase (GS) in astrocyte-like glia and in changes in the gap-junction component innexin2 in cortex glia. Downregulating both GS and innexin2, but not either one individually, resulted in higher sleep amounts, similarly to Appl inhibition. Consistent with these results, the expression of GS and innexin2 are increased following sleep deprivation, indicating that GS and innexin2 genes are dynamically linked to vigilance states. Interestingly, the reduction of GS expression and the sleep phenotype observed upon Appl inhibition could be rescued by increasing the expression of the glutamate transporter dEaat1. In contrast, reducing dEaat1 expression severely disrupted sleep. These results associate glutamate recycling, sleep, and a glial function for the App family proteins.SIGNIFICANCE STATEMENT The amyloid precursor protein (App) has been intensively studied for its implication in Alzheimer's disease (AD). The attributed functions of App are linked to the physiology and cellular biology of neurons where the protein is predominantly expressed. Consequences on glia in AD are generally thought to be secondary effects of the pathology in neurons. Researchers still do not know whether App plays a role in glia in nonpathological conditions. We report here that glial App plays a role in physiology and in the regulation of sleep/wake, which has been shown recently to be involved in AD pathology. These results also associate glutamate recycling and sleep regulation, adding further complexity to the physiological role of App and to its implication in AD.
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Exon-Enriched Libraries Reveal Large Genic Differences Between Aedes aegypti from Senegal, West Africa, and Populations Outside Africa. G3-GENES GENOMES GENETICS 2017; 7:571-582. [PMID: 28007834 PMCID: PMC5295602 DOI: 10.1534/g3.116.036053] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Aedes aegypti is one of the most studied mosquito species, and the principal vector of several arboviruses pathogenic to humans. Recently failure to oviposit, low fecundity, and poor egg-to-adult survival were observed when Ae. aegypti from Senegal (SenAae) West Africa were crossed with Ae. aegypti (Aaa) from outside of Africa, and in SenAae intercrosses. Fluorescent in situ hybridization analyses indicated rearrangements on chromosome 1, and pericentric inversions on chromosomes 2 and 3. Herein, high throughput sequencing (HTS) of exon-enriched libraries was used to compare chromosome-wide genetic diversity among Aaa collections from rural Thailand and Mexico, a sylvatic collection from southeastern Senegal (PK10), and an urban collection from western Senegal (Kaolack). Sex-specific polymorphisms were analyzed in Thailand and PK10 to assess genetic differences between sexes. Expected heterozygosity was greatest in SenAae FST distributions of 15,735 genes among all six pairwise comparisons of the four collections indicated that Mexican and Thailand collections are genetically similar, while FST distributions between PK10 and Kaolack were distinct. All four comparisons of SenAae with Aaa indicated extreme differentiation. FST was uniform between sexes across all chromosomes in Thailand, but were different, especially on the sex autosome 1, in PK10. These patterns correlate with the reproductive isolation noted earlier. We hypothesize that cryptic Ae. aegypti taxa may exist in West Africa, and the large genic differences between Aaa and SenAae detected in the present study have accumulated over a long period following the evolution of chromosome rearrangements in allopatric populations that subsequently cause reproductive isolation when these populations became sympatric.
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31
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Pézier AP, Jezzini SH, Bacon JP, Blagburn JM. Shaking B Mediates Synaptic Coupling between Auditory Sensory Neurons and the Giant Fiber of Drosophila melanogaster. PLoS One 2016; 11:e0152211. [PMID: 27043822 PMCID: PMC4833477 DOI: 10.1371/journal.pone.0152211] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 03/10/2016] [Indexed: 11/18/2022] Open
Abstract
The Johnston’s Organ neurons (JONs) form chemical and electrical synapses onto the giant fiber neuron (GF), as part of the neuronal circuit that mediates the GF escape response in Drosophila melanogaster. The purpose of this study was to identify which of the 8 Drosophila innexins (invertebrate gap junction proteins) mediates the electrical connection at this synapse. The GF is known to express Shaking B (ShakB), specifically the ShakB(N+16) isoform only, at its output synapses in the thorax. The shakB2 mutation disrupts these GF outputs and also abolishes JON-GF synaptic transmission. However, the identity of the innexin that forms the presynaptic hemichannels in the JONs remains unknown. We used electrophysiology, immunocytochemistry and dye injection, along with presynaptically-driven RNA interference, to investigate this question. The amplitude of the compound action potential recorded in response to sound from the base of the antenna (sound-evoked potential, or SEP) was reduced by RNAi of the innexins Ogre, Inx3, Inx6 and, to a lesser extent Inx2, suggesting that they could be required in JONs for proper development, excitability, or synchronization of action potentials. The strength of the JON-GF connection itself was reduced to background levels only by RNAi of shakB, not of the other seven innexins. ShakB knockdown prevented Neurobiotin coupling between GF and JONs and removed the plaques of ShakB protein immunoreactivity that are present at the region of contact. Specific shakB RNAi lines that are predicted to target the ShakB(L) or ShakB(N) isoforms alone did not reduce the synaptic strength, implying that it is ShakB(N+16) that is required in the presynaptic neurons. Overexpression of ShakB(N+16) in JONs caused the formation of ectopic dye coupling, whereas ShakB(N) prevented it altogether, supporting this conclusion and also suggesting that gap junction proteins may have an instructive role in synaptic target choice.
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Affiliation(s)
- Adeline P. Pézier
- Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico, United States of America
| | - Sami H. Jezzini
- Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico, United States of America
| | - Jonathan P. Bacon
- School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | - Jonathan M. Blagburn
- Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan, Puerto Rico, United States of America
- * E-mail:
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32
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Richard M, Hoch M. Drosophila eye size is determined by Innexin 2-dependent Decapentaplegic signalling. Dev Biol 2015; 408:26-40. [PMID: 26455410 DOI: 10.1016/j.ydbio.2015.10.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Revised: 08/23/2015] [Accepted: 10/06/2015] [Indexed: 12/21/2022]
Abstract
Organogenesis relies on specific genetic and molecular programmes, which orchestrate growth and cellular differentiation over developmental time. This is particularly important during Drosophila eye development in which cell-cell inductive events and long-range signalling have to be integrated to regulate proper cell proliferation, differentiation and morphogenesis. How these processes are coordinated is still not very well understood. Here we identify the gap junction protein Innexin2 (Inx2) as an important regulator of eye development. Depleting inx2 during eye development reduces eye size whereas elevating inx2 levels increases eye size. Loss- and gain-of-function experiments demonstrate that inx2 is required functionally in larval eye disc cells where it localises apico-laterally. inx2 regulates disc cell proliferation as well as morphogenetic furrow movement and as a result the amount of differentiated photoreceptors. inx2 interacts genetically with the Dpp pathway and we find that proper activation of the Dpp pathway transducer Mad at the furrow and expression of Dpp receptors Thickveins and Punt in the anterior disc compartment require inx2. We further show that inx2 is required for the transcriptional activation of dpp and punt in the eye disc. Our results highlight the crucial role of gap junction proteins in regulating morphogen-dependent organ size determination.
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Affiliation(s)
- Mélisande Richard
- Life & Medical Sciences Institute (LIMES) Development, Genetics & Molecular Physiology Unit, University of Bonn, Carl-Troll-Straße, 31, D-53115 Bonn, Germany.
| | - Michael Hoch
- Life & Medical Sciences Institute (LIMES) Development, Genetics & Molecular Physiology Unit, University of Bonn, Carl-Troll-Straße, 31, D-53115 Bonn, Germany.
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33
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Schirmeier S, Matzat T, Klämbt C. Axon ensheathment and metabolic supply by glial cells in Drosophila. Brain Res 2015; 1641:122-129. [PMID: 26367447 DOI: 10.1016/j.brainres.2015.09.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 09/02/2015] [Accepted: 09/03/2015] [Indexed: 02/06/2023]
Abstract
Neuronal function requires constant working conditions and a well-balanced supply of ions and metabolites. The metabolic homeostasis in the nervous system crucially depends on the presence of glial cells, which nurture and isolate neuronal cells. Here we review recent findings on how these tasks are performed by glial cells in the genetically amenable model organism Drosophila melanogaster. Despite the small size of its nervous system, which would allow diffusion of metabolites, a surprising division of labor between glial cells and neurons is evident. Glial cells are glycolytically active and transfer lactate and alanine to neurons. Neurons in turn do not require glycolysis but can use the glially provided compounds for their energy homeostasis. Besides feeding neurons, glial cells also insulate neuronal axons in a way similar to Remak fibers in the mammalian nervous system. The molecular mechanisms orchestrating this insulation require neuregulin signaling and resemble the mechanisms controlling glial differentiation in mammals surprisingly well. We hypothesize that metabolic cross talk and insulation of neurons by glial cells emerged early during evolution as two closely interlinked features in the nervous system. This article is part of a Special Issue entitled SI: Myelin Evolution.
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Affiliation(s)
- Stefanie Schirmeier
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany
| | - Till Matzat
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany
| | - Christian Klämbt
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany.
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34
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Volkenhoff A, Weiler A, Letzel M, Stehling M, Klämbt C, Schirmeier S. Glial Glycolysis Is Essential for Neuronal Survival in Drosophila. Cell Metab 2015; 22:437-47. [PMID: 26235423 DOI: 10.1016/j.cmet.2015.07.006] [Citation(s) in RCA: 196] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Revised: 05/19/2015] [Accepted: 06/02/2015] [Indexed: 12/14/2022]
Abstract
Neuronal information processing requires a large amount of energy, indicating that sugars and other metabolites must be efficiently delivered. However, reliable neuronal function also depends on the maintenance of a constant microenvironment in the brain. Therefore, neurons are efficiently separated from circulation by the blood-brain barrier, and their long axons are insulated by glial processes. At the example of the Drosophila brain, we addressed how sugar is shuttled across the barrier to nurture neurons. We show that glial cells of the blood-brain barrier specifically take up sugars and that their metabolism relies on glycolysis, which, surprisingly, is dispensable in neurons. Glial cells secrete alanine and lactate to fuel neuronal mitochondria, and lack of glial glycolysis specifically in the adult brain causes neurodegeneration. Our work implies that a global metabolic compartmentalization and coupling of neurons and glial cells is a conserved, fundamental feature of bilaterian nervous systems independent of their size.
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Affiliation(s)
- Anne Volkenhoff
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany
| | - Astrid Weiler
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany
| | - Matthias Letzel
- Organisch-Chemisches Institut der Universität Münster, Abt. Massenspektrometrie, Corrensstr. 40, 48149 Münster, Germany
| | - Martin Stehling
- MPI für molekulare Biomedizin, Röntgenstr. 20, 48149 Münster, Germany
| | - Christian Klämbt
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany
| | - Stefanie Schirmeier
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany.
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35
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Sasse S, Neuert H, Klämbt C. Differentiation ofDrosophilaglial cells. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2015; 4:623-36. [DOI: 10.1002/wdev.198] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 03/25/2015] [Accepted: 05/24/2015] [Indexed: 01/10/2023]
Affiliation(s)
- Sofia Sasse
- Institut für Neuro- und Verhaltensbiologie; Münster Germany
| | - Helen Neuert
- Institut für Neuro- und Verhaltensbiologie; Münster Germany
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36
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Schirmeier S, Klämbt C. The Drosophila blood-brain barrier as interface between neurons and hemolymph. Mech Dev 2015; 138 Pt 1:50-5. [PMID: 26103549 DOI: 10.1016/j.mod.2015.06.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 06/01/2015] [Accepted: 06/16/2015] [Indexed: 02/05/2023]
Abstract
The blood-brain barrier is an evolutionary ancient structure that provides direct support and protection of the nervous system. In all systems, it establishes a tight diffusion barrier that hinders uncontrolled paracellular diffusion into the nervous system. In invertebrates, the blood-brain barrier separates the nervous system from the hemolymph. Thus, the barrier-forming cells need to actively import ions and nutrients into the nervous system. In addition, metabolic or environmental signals from the external world have to be transmitted across the barrier into the nervous system. The first blood-brain barrier that formed during evolution was most likely based on glial cells. Invertebrates as well as primitive vertebrates still have a purely glial-based blood-brain barrier. Here we review the development and function of the barrier forming glial cells at the example of Drosophila.
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Affiliation(s)
- Stefanie Schirmeier
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany
| | - Christian Klämbt
- Institut für Neuro- und Verhaltensbiologie, Badestr. 9, 48149 Münster, Germany.
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37
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Limmer S, Weiler A, Volkenhoff A, Babatz F, Klämbt C. The Drosophila blood-brain barrier: development and function of a glial endothelium. Front Neurosci 2014; 8:365. [PMID: 25452710 PMCID: PMC4231875 DOI: 10.3389/fnins.2014.00365] [Citation(s) in RCA: 138] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 10/23/2014] [Indexed: 01/01/2023] Open
Abstract
The efficacy of neuronal function requires a well-balanced extracellular ion homeostasis and a steady supply with nutrients and metabolites. Therefore, all organisms equipped with a complex nervous system developed a so-called blood-brain barrier, protecting it from an uncontrolled entry of solutes, metabolites or pathogens. In higher vertebrates, this diffusion barrier is established by polarized endothelial cells that form extensive tight junctions, whereas in lower vertebrates and invertebrates the blood-brain barrier is exclusively formed by glial cells. Here, we review the development and function of the glial blood-brain barrier of Drosophila melanogaster. In the Drosophila nervous system, at least seven morphologically distinct glial cell classes can be distinguished. Two of these glial classes form the blood-brain barrier. Perineurial glial cells participate in nutrient uptake and establish a first diffusion barrier. The subperineurial glial (SPG) cells form septate junctions, which block paracellular diffusion and thus seal the nervous system from the hemolymph. We summarize the molecular basis of septate junction formation and address the different transport systems expressed by the blood-brain barrier forming glial cells.
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Affiliation(s)
- Stefanie Limmer
- Institut für Neuro- und Verhaltensbiologie, Universität Münster Münster, Germany
| | - Astrid Weiler
- Institut für Neuro- und Verhaltensbiologie, Universität Münster Münster, Germany
| | - Anne Volkenhoff
- Institut für Neuro- und Verhaltensbiologie, Universität Münster Münster, Germany
| | - Felix Babatz
- Institut für Neuro- und Verhaltensbiologie, Universität Münster Münster, Germany
| | - Christian Klämbt
- Institut für Neuro- und Verhaltensbiologie, Universität Münster Münster, Germany
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38
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Abstract
Reporting in this issue of Developmental Cell, Spéder and Brand (2014) show that gap junctions are required in blood-brain barrier glial cells to reactivate proliferation of quiescent neuroblasts. Gap junctions allow synchronous Ca(2+) waves and control insulin-like protein Dipl6 expression and secretion to trigger neuroblast division.
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Affiliation(s)
- Stefanie Limmer
- Institut für Neuro- und Verhaltensbiologie, Badestrasse 9, 48149 Münster, Germany
| | - Christian Klämbt
- Institut für Neuro- und Verhaltensbiologie, Badestrasse 9, 48149 Münster, Germany.
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39
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Spéder P, Brand AH. Gap junction proteins in the blood-brain barrier control nutrient-dependent reactivation of Drosophila neural stem cells. Dev Cell 2014; 30:309-21. [PMID: 25065772 PMCID: PMC4139190 DOI: 10.1016/j.devcel.2014.05.021] [Citation(s) in RCA: 96] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 04/15/2014] [Accepted: 05/24/2014] [Indexed: 01/27/2023]
Abstract
Neural stem cells in the adult brain exist primarily in a quiescent state but are reactivated in response to changing physiological conditions. How do stem cells sense and respond to metabolic changes? In the Drosophila CNS, quiescent neural stem cells are reactivated synchronously in response to a nutritional stimulus. Feeding triggers insulin production by blood-brain barrier glial cells, activating the insulin/insulin-like growth factor pathway in underlying neural stem cells and stimulating their growth and proliferation. Here we show that gap junctions in the blood-brain barrier glia mediate the influence of metabolic changes on stem cell behavior, enabling glia to respond to nutritional signals and reactivate quiescent stem cells. We propose that gap junctions in the blood-brain barrier are required to translate metabolic signals into synchronized calcium pulses and insulin secretion. Blood-brain barrier gap junctions are required for neural stem cell reactivation Gap junctions control both insulin transcription and secretion Calcium oscillations in the blood-brain barrier depend on gap junctions and nutrition Blood-brain barrier membrane polarization links calcium to insulin secretion
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Affiliation(s)
- Pauline Spéder
- The Gurdon Institute and Department of Physiology, Development and Neuroscience, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
| | - Andrea H Brand
- The Gurdon Institute and Department of Physiology, Development and Neuroscience, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK.
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40
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Kuuluvainen E, Hakala H, Havula E, Sahal Estimé M, Rämet M, Hietakangas V, Mäkelä TP. Cyclin-dependent kinase 8 module expression profiling reveals requirement of mediator subunits 12 and 13 for transcription of Serpent-dependent innate immunity genes in Drosophila. J Biol Chem 2014; 289:16252-61. [PMID: 24778181 DOI: 10.1074/jbc.m113.541904] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The Cdk8 (cyclin-dependent kinase 8) module of Mediator integrates regulatory cues from transcription factors to RNA polymerase II. It consists of four subunits where Med12 and Med13 link Cdk8 and cyclin C (CycC) to core Mediator. Here we have investigated the contributions of the Cdk8 module subunits to transcriptional regulation using RNA interference in Drosophila cells. Genome-wide expression profiling demonstrated separation of Cdk8-CycC and Med12-Med13 profiles. However, transcriptional regulation by Cdk8-CycC was dependent on Med12-Med13. This observation also revealed that Cdk8-CycC and Med12-Med13 often have opposite transcriptional effects. Interestingly, Med12 and Med13 profiles overlapped significantly with that of the GATA factor Serpent. Accordingly, mutational analyses indicated that GATA sites are required for Med12-Med13 regulation of Serpent-dependent genes. Med12 and Med13 were also found to be required for Serpent-activated innate immunity genes in defense to bacterial infection. The results reveal a novel role for the Cdk8 module in Serpent-dependent transcription and innate immunity.
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Affiliation(s)
- Emilia Kuuluvainen
- From the Institute of Biotechnology, University of Helsinki, P. O. Box 56, 00014 Helsinki
| | - Heini Hakala
- From the Institute of Biotechnology, University of Helsinki, P. O. Box 56, 00014 Helsinki
| | - Essi Havula
- From the Institute of Biotechnology, University of Helsinki, P. O. Box 56, 00014 Helsinki, the Department of Biosciences, University of Helsinki, P. O. Box 65, 00014 Helsinki
| | - Michelle Sahal Estimé
- From the Institute of Biotechnology, University of Helsinki, P. O. Box 56, 00014 Helsinki
| | - Mika Rämet
- the Institute of Biomedical Technology, and BioMediTech, University of Tampere, 33014 Tampere, the Department of Pediatrics, Tampere University Hospital, 22521 Tampere, the Department of Pediatrics, Institute of Clinical Medicine, and Medical Research Center Oulu, University of Oulu, 90014 Oulu, and the Department of Children and Adolescents, Oulu University Hospital, 90029 Oulu, Finland
| | - Ville Hietakangas
- From the Institute of Biotechnology, University of Helsinki, P. O. Box 56, 00014 Helsinki, the Department of Biosciences, University of Helsinki, P. O. Box 65, 00014 Helsinki
| | - Tomi P Mäkelä
- From the Institute of Biotechnology, University of Helsinki, P. O. Box 56, 00014 Helsinki,
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Hasegawa DK, Turnbull MW. Recent findings in evolution and function of insect innexins. FEBS Lett 2014; 588:1403-10. [DOI: 10.1016/j.febslet.2014.03.006] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 03/03/2014] [Accepted: 03/04/2014] [Indexed: 10/25/2022]
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Baker MW, Macagno ER. Control of neuronal morphology and connectivity: Emerging developmental roles for gap junctional proteins. FEBS Lett 2014; 588:1470-9. [DOI: 10.1016/j.febslet.2014.02.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 02/10/2014] [Accepted: 02/12/2014] [Indexed: 11/25/2022]
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Long-distance mechanism of neurotransmitter recycling mediated by glial network facilitates visual function in Drosophila. Proc Natl Acad Sci U S A 2014; 111:2812-7. [PMID: 24550312 DOI: 10.1073/pnas.1323714111] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Neurons rely on glia to recycle neurotransmitters such as glutamate and histamine for sustained signaling. Both mammalian and insect glia form intercellular gap-junction networks, but their functional significance underlying neurotransmitter recycling is unknown. Using the Drosophila visual system as a genetic model, here we show that a multicellular glial network transports neurotransmitter metabolites between perisynaptic glia and neuronal cell bodies to mediate long-distance recycling of neurotransmitter. In the first visual neuropil (lamina), which contains a multilayer glial network, photoreceptor axons release histamine to hyperpolarize secondary sensory neurons. Subsequently, the released histamine is taken up by perisynaptic epithelial glia and converted into inactive carcinine through conjugation with β-alanine for transport. In contrast to a previous assumption that epithelial glia deliver carcinine directly back to photoreceptor axons for histamine regeneration within the lamina, we detected both carcinine and β-alanine in the fly retina, where they are found in photoreceptor cell bodies and surrounding pigment glial cells. Downregulating Inx2 gap junctions within the laminar glial network causes β-alanine accumulation in retinal pigment cells and impairs carcinine synthesis, leading to reduced histamine levels and photoreceptor synaptic vesicles. Consequently, visual transmission is impaired and the fly is less responsive in a visual alert analysis compared with wild type. Our results suggest that a gap junction-dependent laminar and retinal glial network transports histamine metabolites between perisynaptic glia and photoreceptor cell bodies to mediate a novel, long-distance mechanism of neurotransmitter recycling, highlighting the importance of glial networks in the regulation of neuronal functions.
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