1
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Christensen CF, Laurichesse Q, Loudhaief R, Colombani J, Andersen DS. Drosophila activins adapt gut size to food intake and promote regenerative growth. Nat Commun 2024; 15:273. [PMID: 38177201 PMCID: PMC10767106 DOI: 10.1038/s41467-023-44553-9] [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: 03/14/2023] [Accepted: 12/19/2023] [Indexed: 01/06/2024] Open
Abstract
Rapidly renewable tissues adapt different strategies to cope with environmental insults. While tissue repair is associated with increased intestinal stem cell (ISC) proliferation and accelerated tissue turnover rates, reduced calorie intake triggers a homeostasis-breaking process causing adaptive resizing of the gut. Here we show that activins are key drivers of both adaptive and regenerative growth. Activin-β (Actβ) is produced by stem and progenitor cells in response to intestinal infections and stimulates ISC proliferation and turnover rates to promote tissue repair. Dawdle (Daw), a divergent Drosophila activin, signals through its receptor, Baboon, in progenitor cells to promote their maturation into enterocytes (ECs). Daw is dynamically regulated during starvation-refeeding cycles, where it couples nutrient intake with progenitor maturation and adaptive resizing of the gut. Our results highlight an activin-dependent mechanism coupling nutrient intake with progenitor-to-EC maturation to promote adaptive resizing of the gut and further establish activins as key regulators of adult tissue plasticity.
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Affiliation(s)
- Christian F Christensen
- Department of Biology, Faculty of Science, University of Copenhagen, Universitetsparken 15, Build. 3, 3rd floor, 2100 Copenhagen O, Copenhagen, Denmark
| | - Quentin Laurichesse
- Department of Biology, Faculty of Science, University of Copenhagen, Universitetsparken 15, Build. 3, 3rd floor, 2100 Copenhagen O, Copenhagen, Denmark
| | - Rihab Loudhaief
- Department of Biology, Faculty of Science, University of Copenhagen, Universitetsparken 15, Build. 3, 3rd floor, 2100 Copenhagen O, Copenhagen, Denmark
| | - Julien Colombani
- Department of Biology, Faculty of Science, University of Copenhagen, Universitetsparken 15, Build. 3, 3rd floor, 2100 Copenhagen O, Copenhagen, Denmark.
| | - Ditte S Andersen
- Department of Biology, Faculty of Science, University of Copenhagen, Universitetsparken 15, Build. 3, 3rd floor, 2100 Copenhagen O, Copenhagen, Denmark.
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2
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Lin S. The making of the Drosophila mushroom body. Front Physiol 2023; 14:1091248. [PMID: 36711013 PMCID: PMC9880076 DOI: 10.3389/fphys.2023.1091248] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2022] [Accepted: 01/02/2023] [Indexed: 01/14/2023] Open
Abstract
The mushroom body (MB) is a computational center in the Drosophila brain. The intricate neural circuits of the mushroom body enable it to store associative memories and process sensory and internal state information. The mushroom body is composed of diverse types of neurons that are precisely assembled during development. Tremendous efforts have been made to unravel the molecular and cellular mechanisms that build the mushroom body. However, we are still at the beginning of this challenging quest, with many key aspects of mushroom body assembly remaining unexplored. In this review, I provide an in-depth overview of our current understanding of mushroom body development and pertinent knowledge gaps.
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3
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Lipophorin receptors regulate mushroom body development and complex behaviors in Drosophila. BMC Biol 2022; 20:198. [PMID: 36071487 PMCID: PMC9454125 DOI: 10.1186/s12915-022-01393-1] [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: 12/07/2021] [Accepted: 08/17/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Drosophila melanogaster lipophorin receptors (LpRs), LpR1 and LpR2, are members of the LDLR family known to mediate lipid uptake in a range of organisms from Drosophila to humans. The vertebrate orthologs of LpRs, ApoER2 and VLDL-R, function as receptors of a glycoprotein involved in development of the central nervous system, Reelin, which is not present in flies. ApoER2 and VLDL-R are associated with the development and function of the hippocampus and cerebral cortex, important association areas in the mammalian brain, as well as with neurodevelopmental and neurodegenerative disorders linked to those regions. It is currently unknown whether LpRs play similar roles in the Drosophila brain. RESULTS We report that LpR-deficient flies exhibit impaired olfactory memory and sleep patterns, which seem to reflect anatomical defects found in a critical brain association area, the mushroom bodies (MB). Moreover, cultured MB neurons respond to mammalian Reelin by increasing the complexity of their neurite arborization. This effect depends on LpRs and Dab, the Drosophila ortholog of the Reelin signaling adaptor protein Dab1. In vitro, two of the long isoforms of LpRs allow the internalization of Reelin, suggesting that Drosophila LpRs interact with human Reelin to induce downstream cellular events. CONCLUSIONS These findings demonstrate that LpRs contribute to MB development and function, supporting the existence of a LpR-dependent signaling in Drosophila, and advance our understanding of the molecular factors functioning in neural systems to generate complex behaviors in this model. Our results further emphasize the importance of Drosophila as a model to investigate the alterations in specific genes contributing to neural disorders.
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4
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Russo K, Wharton KA. BMP/TGF-β signaling as a modulator of neurodegeneration in ALS. Dev Dyn 2021; 251:10-25. [PMID: 33745185 DOI: 10.1002/dvdy.333] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 03/12/2021] [Accepted: 03/12/2021] [Indexed: 12/19/2022] Open
Abstract
This commentary focuses on the emerging intersection between BMP/TGF-β signaling roles in nervous system function and the amyotrophic lateral sclerosis (ALS) disease state. Future research is critical to elucidate the molecular underpinnings of this intersection of the cellular processes disrupted in ALS and those influenced by BMP/TGF-β signaling, including synapse structure, neurotransmission, plasticity, and neuroinflammation. Such knowledge promises to inform us of ideal entry points for the targeted modulation of dysfunctional cellular processes in an effort to abrogate ALS pathologies. It is likely that different interventions are required, either at discrete points in disease progression, or across multiple dysfunctional processes which together lead to motor neuron degeneration and death. We discuss the challenging, but intriguing idea that modulation of the pleiotropic nature of BMP/TGF-β signaling could be advantageous, as a way to simultaneously treat defects in more than one cell process across different forms of ALS.
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Affiliation(s)
- Kathryn Russo
- Department of Neuroscience, Brown University, Providence, Rhode Island, USA.,Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, Rhode Island, USA
| | - Kristi A Wharton
- Robert J. and Nancy D. Carney Institute for Brain Science, Brown University, Providence, Rhode Island, USA.,Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island, USA
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5
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Birnbaum A, Sodders M, Bouska M, Chang K, Kang P, McNeill E, Bai H. FOXO Regulates Neuromuscular Junction Homeostasis During Drosophila Aging. Front Aging Neurosci 2021; 12:567861. [PMID: 33584240 PMCID: PMC7874159 DOI: 10.3389/fnagi.2020.567861] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Accepted: 12/04/2020] [Indexed: 12/17/2022] Open
Abstract
The transcription factor foxo is a known regulator of lifespan extension and tissue homeostasis. It has been linked to the maintenance of neuronal processes across many species and has been shown to promote youthful characteristics by regulating cytoskeletal flexibility and synaptic plasticity at the neuromuscular junction (NMJ). However, the role of foxo in aging neuromuscular junction function has yet to be determined. We profiled adult Drosophila foxo- null mutant abdominal ventral longitudinal muscles and found that young mutants exhibited morphological profiles similar to those of aged wild-type flies, such as larger bouton areas and shorter terminal branches. We also observed changes to the axonal cytoskeleton and an accumulation of late endosomes in foxo null mutants and motor neuron-specific foxo knockdown flies, similar to those of aged wild-types. Motor neuron-specific overexpression of foxo can delay age-dependent changes to NMJ morphology, suggesting foxo is responsible for maintaining NMJ integrity during aging. Through genetic screening, we identify several downstream factors mediated through foxo-regulated NMJ homeostasis, including genes involved in the MAPK pathway. Interestingly, the phosphorylation of p38 was increased in the motor neuron-specific foxo knockdown flies, suggesting foxo acts as a suppressor of p38/MAPK activation. Our work reveals that foxo is a key regulator for NMJ homeostasis, and it may maintain NMJ integrity by repressing MAPK signaling.
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Affiliation(s)
- Allison Birnbaum
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, United States.,Department of Cell, Developmental and Integrative Biology, University of Alabama Birmingham, Birmingham, AL, United States
| | - Maggie Sodders
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, United States
| | - Mark Bouska
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, United States
| | - Kai Chang
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, United States
| | - Ping Kang
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, United States
| | - Elizabeth McNeill
- Department of Food Science and Human Nutrition, Iowa State University, Ames, IA, United States
| | - Hua Bai
- Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, IA, United States
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6
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Wang Z, Lee G, Vuong R, Park JH. Two-factor specification of apoptosis: TGF-β signaling acts cooperatively with ecdysone signaling to induce cell- and stage-specific apoptosis of larval neurons during metamorphosis in Drosophila melanogaster. Apoptosis 2020; 24:972-989. [PMID: 31641960 DOI: 10.1007/s10495-019-01574-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Developmentally regulated programmed cell death (PCD) is one of the key cellular events for precise controlling of neuronal population during postembryonic development of the central nervous system. Previously we have shown that a group of corazonin-producing peptidergic neurons (vCrz) undergo apoptosis in response to ecdysone signaling via ecdysone receptor (EcR)-B isoforms and Ultraspiracle during early phase of metamorphosis. Further utilizing genetic, transgenic, and mosaic analyses, we have found that TGF-β signaling mediated by a glia-produced ligand, Myoglianin, type-I receptor Baboon (particularly Babo-A isoform) and dSmad2, is also required autonomously for PCD of the vCrz neurons. Our studies show that TGF-β signaling is not acting epistatically to EcR or vice versa. We also show that ectopic expression of a constitutively active phosphomimetic form of dSmad2 (dSmad2PM) is capable of inducing premature death of vCrz neurons in larva but not other larval neurons. Intriguingly, the dSmad2PM-mediated killing is completely suppressed by coexpression of a dominant-negative form of EcR (EcRDN), suggesting that EcR function is required for the proapoptotic dSmad2PM function. Based on these data, we suggest that TGF-β and ecdysone signaling pathways act cooperatively to induce vCrz neuronal PCD. We propose that this type of two-factor authentication is a key developmental strategy to ensure the timely PCD of specific larval neurons during metamorphosis.
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Affiliation(s)
- Zixing Wang
- UT-ORNL Graduate School of Genome Science and Technology Program, University of Tennessee, Knoxville, TN, 37996, USA
| | - Gyunghee Lee
- Department of Biochemistry and Cellular and Molecular Biology and NeuroNet Research Center, University of Tennessee, Knoxville, TN, 37996, USA
| | - Richard Vuong
- Undergraduate program in Neuroscience, University of Tennessee, Knoxville, TN, 37996, USA
| | - Jae H Park
- Department of Biochemistry and Cellular and Molecular Biology and NeuroNet Research Center, University of Tennessee, Knoxville, TN, 37996, USA. .,UT-ORNL Graduate School of Genome Science and Technology Program, University of Tennessee, Knoxville, TN, 37996, USA.
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7
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Visualization of Endogenous Type I TGF-β Receptor Baboon in the Drosophila Brain. Sci Rep 2020; 10:5132. [PMID: 32198477 PMCID: PMC7083856 DOI: 10.1038/s41598-020-61950-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 03/02/2020] [Indexed: 11/08/2022] Open
Abstract
The transforming growth factor β (TGF-β) signaling pathway is evolutionarily conserved and widely used in the animal kingdom to regulate diverse developmental processes. Prior studies have shown that Baboon (Babo), a Drosophila type I TGF-β receptor, plays essential roles in brain development and neural circuit formation. However, the expression pattern for Babo in the developing brain has not been previously reported. We generated a knock-in fly with a human influenza hemagglutinin (HA) tag at the C-terminus of Babo and assessed its localization. Babo::HA was primarily expressed in brain structures enriched with neurites, including the mushroom body lobe and neuropils of the optic lobe, where Babo has been shown to instruct neuronal morphogenesis. Since the babo 3' untranslated region contains a predicted microRNA-34 (miR-34) target sequence, we further tested whether Babo::HA expression was affected by modulating the level of miR-34. We found that Babo was upregulated by mir-34 deletion and downregulated by miR-34 overexpression, confirming that it is indeed a miR-34 target gene. Taken together, our results demonstrate that the baboHA fly permits accurate visualization of endogenous Babo expression during brain development and the construction of functional neural circuits.
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8
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The Ubiquitin System: a Regulatory Hub for Intellectual Disability and Autism Spectrum Disorder. Mol Neurobiol 2020; 57:2179-2193. [DOI: 10.1007/s12035-020-01881-x] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 01/15/2020] [Indexed: 12/15/2022]
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9
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Marmor-Kollet N, Gutman I, Issman-Zecharya N, Schuldiner O. Glial Derived TGF-β Instructs Axon Midline Stopping. Front Mol Neurosci 2019; 12:232. [PMID: 31611773 PMCID: PMC6776989 DOI: 10.3389/fnmol.2019.00232] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 09/11/2019] [Indexed: 11/13/2022] Open
Abstract
A fundamental question that underlies the proper wiring and function of the nervous system is how axon extension stops during development. However, our mechanistic understanding of axon stopping is currently poor. The stereotypic development of the Drosophila mushroom body (MB) provides a unique system in which three types of anatomically distinct neurons (γ, α’/β’, and α/β) develop and interact to form a complex neuronal structure. All three neuronal types innervate the ipsi-lateral side and do not cross the midline. Here we find that Plum, an immunoglobulin (Ig) superfamily protein that we have previously shown to function as a TGF-β accessory receptor, is required within MB α/β neurons for their midline stopping. Overexpression of Plum within MB neurons is sufficient to induce retraction of α/β axons. As expected, rescue experiments revealed that Plum likely functions in α/β neurons and mediates midline stopping via the downstream effector RhoGEF2. Finally, we have identified glial-derived Myoglianin (Myo) as the major TGF-β ligand that instructs midline stopping of MB neurons. Taken together, our study strongly suggests that TGF-β signals originating from the midline facilitate midline stopping of α/β neuron in a Plum dependent manner.
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Affiliation(s)
- Neta Marmor-Kollet
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, Israel
| | - Itai Gutman
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, Israel
| | - Noa Issman-Zecharya
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, Israel
| | - Oren Schuldiner
- Department of Molecular Cell Biology, Weizmann Institute of Sciences, Rehovot, Israel
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10
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Upadhyay A, Moss-Taylor L, Kim MJ, Ghosh AC, O'Connor MB. TGF-β Family Signaling in Drosophila. Cold Spring Harb Perspect Biol 2017; 9:cshperspect.a022152. [PMID: 28130362 DOI: 10.1101/cshperspect.a022152] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The transforming growth factor β (TGF-β) family signaling pathway is conserved and ubiquitous in animals. In Drosophila, fewer representatives of each signaling component are present compared with vertebrates, simplifying mechanistic study of the pathway. Although there are fewer family members, the TGF-β family pathway still regulates multiple and diverse functions in Drosophila. In this review, we focus our attention on several of the classic and best-studied functions for TGF-β family signaling in regulating Drosophila developmental processes such as embryonic and imaginal disc patterning, but we also describe several recently discovered roles in regulating hormonal, physiological, neuronal, innate immunity, and tissue homeostatic processes.
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Affiliation(s)
- Ambuj Upadhyay
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455
| | - Lindsay Moss-Taylor
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455
| | - Myung-Jun Kim
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455
| | - Arpan C Ghosh
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455
| | - Michael B O'Connor
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455
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11
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Wells BS, Pistillo D, Barnhart E, Desplan C. Parallel Activin and BMP signaling coordinates R7/R8 photoreceptor subtype pairing in the stochastic Drosophila retina. eLife 2017; 6:25301. [PMID: 28853393 PMCID: PMC5599232 DOI: 10.7554/elife.25301] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2017] [Accepted: 08/25/2017] [Indexed: 12/27/2022] Open
Abstract
Drosophila color vision is achieved by comparing outputs from two types of color-sensitive photoreceptors, R7 and R8. Ommatidia (unit eyes) are classified into two subtypes, known as 'pale' or 'yellow', depending on Rhodopsin expression in R7 and R8. Subtype specification is controlled by a stochastic decision in R7 and instructed to the underlying R8. We find that the Activin receptor Baboon is required in R8 to receive non-redundant signaling from the three Activin ligands, activating the transcription factor dSmad2. Concomitantly, two BMP ligands activate their receptor, Thickveins, and the transcriptional effector, Mad. The Amon TGFβ processing factor appears to regulate components of the TGFβ pathway specifically in pale R7. Mad and dSmad2 cooperate to modulate the Hippo pathway kinase Warts and the growth regulator Melted; two opposing factors of a bi-stable loop regulating R8 Rhodopsin expression. Therefore, TGFβ and growth pathways interact in postmitotic cells to precisely coordinate cell-specific output.
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Affiliation(s)
- Brent S Wells
- Center for Developmental Genetics, Department of Biology, New York University, New York, United States
| | - Daniela Pistillo
- Center for Developmental Genetics, Department of Biology, New York University, New York, United States
| | - Erin Barnhart
- Center for Developmental Genetics, Department of Biology, New York University, New York, United States
| | - Claude Desplan
- Center for Developmental Genetics, Department of Biology, New York University, New York, United States
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12
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Augustin H, McGourty K, Steinert JR, Cochemé HM, Adcott J, Cabecinha M, Vincent A, Halff EF, Kittler JT, Boucrot E, Partridge L. Myostatin-like proteins regulate synaptic function and neuronal morphology. Development 2017; 144:2445-2455. [PMID: 28533206 PMCID: PMC5536874 DOI: 10.1242/dev.152975] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 05/15/2017] [Indexed: 12/27/2022]
Abstract
Growth factors of the TGFβ superfamily play key roles in regulating neuronal and muscle function. Myostatin (or GDF8) and GDF11 are potent negative regulators of skeletal muscle mass. However, expression of myostatin and its cognate receptors in other tissues, including brain and peripheral nerves, suggests a potential wider biological role. Here, we show that Myoglianin (MYO), the Drosophila homolog of myostatin and GDF11, regulates not only body weight and muscle size, but also inhibits neuromuscular synapse strength and composition in a Smad2-dependent manner. Both myostatin and GDF11 affected synapse formation in isolated rat cortical neuron cultures, suggesting an effect on synaptogenesis beyond neuromuscular junctions. We also show that MYO acts in vivo to inhibit synaptic transmission between neurons in the escape response neural circuit of adult flies. Thus, these anti-myogenic proteins act as important inhibitors of synapse function and neuronal growth. Summary: Myostatin-like proteins can modulate neuromuscular synapse strength as well as synaptogenesis beyond neuromuscular junctions, highlighting a key role for these proteins in synapse function and neuronal growth.
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Affiliation(s)
- Hrvoje Augustin
- Institute of Healthy Ageing, and GEE, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK.,Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, Cologne D-50931, Germany
| | - Kieran McGourty
- Institute of Structural and Molecular Biology, University College London, Darwin Building Gower Street, London WC1E 6BT, UK
| | - Joern R Steinert
- MRC Toxicology Unit, Hodgkin Building, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK
| | - Helena M Cochemé
- Institute of Healthy Ageing, and GEE, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK.,Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, Cologne D-50931, Germany.,MRC Clinical Sciences Centre, Du Cane Road, London W12 0NN, UK.,Institute of Clinical Sciences, Imperial College London, ICTEM Building, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Jennifer Adcott
- Institute of Healthy Ageing, and GEE, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK.,Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, Cologne D-50931, Germany
| | - Melissa Cabecinha
- Institute of Healthy Ageing, and GEE, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Alec Vincent
- Institute of Healthy Ageing, and GEE, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK
| | - Els F Halff
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Josef T Kittler
- Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK
| | - Emmanuel Boucrot
- Institute of Structural and Molecular Biology, University College London, Darwin Building Gower Street, London WC1E 6BT, UK
| | - Linda Partridge
- Institute of Healthy Ageing, and GEE, University College London, Darwin Building, Gower Street, London WC1E 6BT, UK .,Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Str. 9b, Cologne D-50931, Germany
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13
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Le Berre‐Scoul C, Chevalier J, Oleynikova E, Cossais F, Talon S, Neunlist M, Boudin H. A novel enteric neuron-glia coculture system reveals the role of glia in neuronal development. J Physiol 2017; 595:583-598. [PMID: 27436013 PMCID: PMC5233665 DOI: 10.1113/jp271989] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 07/07/2016] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS Unlike astrocytes in the brain, the potential role of enteric glial cells (EGCs) in the formation of the enteric neuronal circuit is currently unknown. To examine the role of EGCs in the formation of the neuronal network, we developed a novel neuron-enriched culture model from embryonic rat intestine grown in indirect coculture with EGCs. We found that EGCs shape axonal complexity and synapse density in enteric neurons, through purinergic- and glial cell line-derived neurotrophic factor-dependent pathways. Using a novel and valuable culture model to study enteric neuron-glia interactions, our study identified EGCs as a key cellular actor regulating neuronal network maturation. ABSTRACT In the nervous system, the formation of neuronal circuitry results from a complex and coordinated action of intrinsic and extrinsic factors. In the CNS, extrinsic mediators derived from astrocytes have been shown to play a key role in neuronal maturation, including dendritic shaping, axon guidance and synaptogenesis. In the enteric nervous system (ENS), the potential role of enteric glial cells (EGCs) in the maturation of developing enteric neuronal circuit is currently unknown. A major obstacle in addressing this question is the difficulty in obtaining a valuable experimental model in which enteric neurons could be isolated and maintained without EGCs. We adapted a cell culture method previously developed for CNS neurons to establish a neuron-enriched primary culture from embryonic rat intestine which was cultured in indirect coculture with EGCs. We demonstrated that enteric neurons grown in such conditions showed several structural, phenotypic and functional hallmarks of proper development and maturation. However, when neurons were grown without EGCs, the complexity of the axonal arbour and the density of synapses were markedly reduced, suggesting that glial-derived factors contribute strongly to the formation of the neuronal circuitry. We found that these effects played by EGCs were mediated in part through purinergic P2Y1 receptor- and glial cell line-derived neurotrophic factor-dependent pathways. Using a novel and valuable culture model to study enteric neuron-glia interactions, our study identified EGCs as a key cellular actor required for neuronal network maturation.
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14
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Jiang Y, Sun L, Xuan X, Wang J. Impacts of N-Butylphthalide on expression of growth factors in rats with focal cerebral ischemia. Bosn J Basic Med Sci 2016; 16:102-7. [PMID: 26773175 PMCID: PMC4852990 DOI: 10.17305/bjbms.2016.560] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Revised: 01/01/2016] [Accepted: 08/01/2015] [Indexed: 12/15/2022] Open
Abstract
This study investigates the impacts of n-butylphthalide (NBP) on the expression of vascular endothelial growth factor (VEGF) and transforming growth factor-β1 (TGF-β1) in rats with focal cerebral ischemia. The thread embolization method was used to prepare the rat model of cerebral ischemia-reperfusion (CIR). The animals were divided into a sham operation group, a model control group and NBP treatment group. The NBP group was orally administered 25 mg/kg NBP twice a day after the surgery. The immunohistochemistry and reverse transcription-polymerase chain reaction were performed to observe the protein and mRNA expressions of VEGF and TGF-β 16 hours, 1 day and 2 days after inducing CIR. The mRNA and protein expressions of VEGF and TGF-β1 in the model control group and the NBP treatment group were all increased after CIR, and those of the NBP treatment group at each post-CIR time point were higher than the model control group (p < 0.01). After CIR, the expressions of VEGF and TGF-β1 increased, suggesting that VEGF and TGF-β1 exhibited protective effects towards the ischemic brain injuries, and that NBP could upregulate the expressions of VEGF and TGF-β1 in the peri-infarcted area, thus possibly protecting the ischemic brain tissues through this mechanism.
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Affiliation(s)
- Yan Jiang
- Department of Neurology, the Fifth Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, China.
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15
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Carrella S, Barbato S, D’Agostino Y, Salierno FG, Manfredi A, Banfi S, Conte I. TGF-β Controls miR-181/ERK Regulatory Network during Retinal Axon Specification and Growth. PLoS One 2015; 10:e0144129. [PMID: 26641497 PMCID: PMC4671616 DOI: 10.1371/journal.pone.0144129] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 11/14/2015] [Indexed: 12/03/2022] Open
Abstract
Retinal axon specification and growth are critically sensitive to the dosage of numerous signaling molecules and transcription factors. Subtle variations in the expression levels of key molecules may result in a variety of axonal growth anomalies. miR-181a and miR-181b are two eye-enriched microRNAs whose inactivation in medaka fish leads to alterations of the proper establishment of connectivity and function in the visual system. miR-181a/b are fundamental regulators of MAPK signaling and their role in retinal axon growth and specification is just beginning to be elucidated. Here we demonstrate that miR-181a/b are key nodes in the interplay between TGF-β and MAPK/ERK within the functional pathways that control retinal axon specification and growth. Using a variety of in vivo and in vitro approaches in medaka fish, we demonstrate that TGF-β signaling controls the miR-181/ERK regulatory network, which in turn strengthens the TGF-β-mediated regulation of RhoA degradation. Significantly, these data uncover the role of TGF-β signaling in vivo, for the first time, in defining the correct wiring and assembly of functional retina neural circuits and further highlight miR-181a/b as key factors in axon specification and growth.
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Affiliation(s)
- Sabrina Carrella
- Telethon Institute of Genetics and Medicine, Via Campi Flegrei 34, Pozzuoli (Naples), 80078, Italy
| | - Sara Barbato
- Telethon Institute of Genetics and Medicine, Via Campi Flegrei 34, Pozzuoli (Naples), 80078, Italy
| | - Ylenia D’Agostino
- Telethon Institute of Genetics and Medicine, Via Campi Flegrei 34, Pozzuoli (Naples), 80078, Italy
| | | | - Anna Manfredi
- Telethon Institute of Genetics and Medicine, Via Campi Flegrei 34, Pozzuoli (Naples), 80078, Italy
| | - Sandro Banfi
- Telethon Institute of Genetics and Medicine, Via Campi Flegrei 34, Pozzuoli (Naples), 80078, Italy
- Medical Genetics, Dipartimento di Biochimica, Biofisica e Patologia Generale, Second University of Naples, via Luigi De Crecchio 7, 80138, Naples, Italy
- * E-mail: (SB); (IC)
| | - Ivan Conte
- Telethon Institute of Genetics and Medicine, Via Campi Flegrei 34, Pozzuoli (Naples), 80078, Italy
- * E-mail: (SB); (IC)
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16
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Lengil T, Gancz D, Gilboa L. Activin signaling balances proliferation and differentiation of ovarian niche precursors and enables adjustment of niche numbers. Development 2015; 142:883-92. [PMID: 25633355 DOI: 10.1242/dev.113902] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
How the numbers of niches and resident stem cells within a particular organ are determined during development and how they may be modulated or corrected is a question with significant medical implications. In the larval ovary of Drosophila melanogaster, somatic precursors for niches, and germ cells that will become germline stem cells, co-develop. Somatic precursors proliferate during the first 3 days of larval development. By mid-third instar, adult terminal filament (TF) (part of the germline stem cell niche) cells first appear, and differentiation terminates 24 h later when 16-20 TFs fully form. The developmental sequence responsible for TF cell determination and final TF numbers is only partially understood. We show that TF formation proceeds through several, hitherto uncharacterized stages, which include an early exit from the cell cycle to form TF precursors and two steps of cell shape change to form the mature TF cells. The Activin receptor Baboon (Babo) is required for somatic precursor cell proliferation and therefore determines the pool of TF precursors available for TF differentiation. During the final differentiation stage, Babo facilitates TF and germ cell differentiation, and promotes the accumulation of Broad-Z1, which is also a target of the steroid hormone ecdysone. Epistasis analysis shows that Activin controls cell proliferation in an ecdysone-independent manner and TF differentiation by affecting ecdysone targets. We propose that this mode of function allows Activin to balance proliferation and differentiation, and to equilibrate niche numbers. These results suggest a novel model for how niche numbers are corrected during development.
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Affiliation(s)
- Tamar Lengil
- Department of Biological regulation, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Dana Gancz
- Department of Biological regulation, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Lilach Gilboa
- Department of Biological regulation, Weizmann Institute of Science, Rehovot 76100, Israel
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17
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Abe T, Yamazaki D, Murakami S, Hiroi M, Nitta Y, Maeyama Y, Tabata T. The NAV2 homolog Sickie regulates F-actin-mediated axonal growth in Drosophila mushroom body neurons via the non-canonical Rac-Cofilin pathway. Development 2014; 141:4716-28. [DOI: 10.1242/dev.113308] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Rac-Cofilin pathway is essential for cytoskeletal remodeling to control axonal development. Rac signals through the canonical Rac-Pak-LIMK pathway to suppress Cofilin-dependent axonal growth and through a Pak-independent non-canonical pathway to promote outgrowth. Whether this non-canonical pathway converges to promote Cofilin-dependent F-actin reorganization in axonal growth remains elusive. We demonstrate that Sickie, a homolog of the human microtubule-associated protein neuron navigator 2, cell-autonomously regulates axonal growth of Drosophila mushroom body (MB) neurons via the non-canonical pathway. Sickie was prominently expressed in the newborn F-actin-rich axons of MB neurons. A sickie mutant exhibited axonal growth defects, and its phenotypes were rescued by exogenous expression of Sickie. We observed phenotypic similarities and genetic interactions among sickie and Rac-Cofilin signaling components. Using the MARCM technique, distinct F-actin and phospho-Cofilin patterns were detected in developing axons mutant for sickie and Rac-Cofilin signaling regulators. The upregulation of Cofilin function alleviated the axonal defect of the sickie mutant. Epistasis analyses revealed that Sickie suppresses the LIMK overexpression phenotype and is required for Pak-independent Rac1 and Slingshot phosphatase to counteract LIMK. We propose that Sickie regulates F-actin-mediated axonal growth via the non-canonical Rac-Cofilin pathway in a Slingshot-dependent manner.
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Affiliation(s)
- Takashi Abe
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
- Graduate Program in Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
| | - Daisuke Yamazaki
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Satoshi Murakami
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Makoto Hiroi
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Yohei Nitta
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Yuko Maeyama
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
| | - Tetsuya Tabata
- Institute of Molecular and Cellular Biosciences, University of Tokyo, Tokyo 113-0032, Japan
- Graduate Program in Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan
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18
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Peterson AJ, O'Connor MB. Strategies for exploring TGF-β signaling in Drosophila. Methods 2014; 68:183-93. [PMID: 24680699 PMCID: PMC4057889 DOI: 10.1016/j.ymeth.2014.03.016] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 03/14/2014] [Accepted: 03/17/2014] [Indexed: 02/06/2023] Open
Abstract
The TGF-β pathway is an evolutionarily conserved signal transduction module that mediates diverse biological processes in animals. In Drosophila, both the BMP and Activin branches are required for viability. Studies rooted in classical and molecular genetic approaches continue to uncover new developmental roles for TGF-β signaling. We present an overview of the secreted ligands, transmembrane receptors and cellular Smad transducer proteins that compose the core pathway in Drosophila. An assortment of tools have been developed to conduct tissue-specific loss- and gain-of-function experiments for these pathway components. We discuss the deployment of these reagents, with an emphasis on appropriate usage and limitations of the available tools. Throughout, we note reagents that are in need of further improvement or development, and signaling features requiring further study. A general theme is that comparison of phenotypes for ligands, receptors, and Smads can be used to map tissue interactions, and to separate canonical and non-canonical signaling activities. Core TGF-β signaling components are subject to multiple layers of regulation, and are coupled to context-specific inputs and outputs. In addition to fleshing out how TGF-β signaling serves the fruit fly, we anticipate that future studies will uncover new regulatory nodes and modes and will continue to advance paradigms for how TGF-β signaling regulates general developmental processes.
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Affiliation(s)
- Aidan J Peterson
- Department of Genetics, Cell Biology & Development, 6-160 Jackson Hall, 321 Church St SE, University of Minnesota, Minneapolis, MN 55455, United States
| | - Michael B O'Connor
- Department of Genetics, Cell Biology & Development, 6-160 Jackson Hall, 321 Church St SE, University of Minnesota, Minneapolis, MN 55455, United States.
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19
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He Y, Zhang H, Yung A, Villeda SA, Jaeger PA, Olayiwola O, Fainberg N, Wyss-Coray T. ALK5-dependent TGF-β signaling is a major determinant of late-stage adult neurogenesis. Nat Neurosci 2014; 17:943-52. [PMID: 24859199 PMCID: PMC4096284 DOI: 10.1038/nn.3732] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Accepted: 04/30/2014] [Indexed: 01/19/2023]
Abstract
The transforming growth factor-β (TGF-β) signaling pathway serves critical functions in central nervous system (CNS) development, but apart from its proposed neuroprotective actions, its physiological role in the adult brain is unclear. We observed a prominent activation of TGF-β signaling in the adult dentate gyrus and expression of downstream Smad proteins in this neurogenic zone. Consistent with a function of TGF-β signaling in adult neurogenesis, genetic deletion of the TGF-β receptor ALK5 reduced the number, migration, and dendritic arborization of newborn neurons. Conversely, constitutive activation of neuronal ALK5 in forebrain caused a striking increase in these aspects of neurogenesis and was associated with higher expression of c-fos in newborn neurons and with stronger memory function. Our findings describe a new and unexpected role for ALK5-dependent TGF-β signaling as a regulator of the late stages of adult hippocampal neurogenesis which may have implications for changes in neurogenesis during aging and disease.
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Affiliation(s)
- Yingbo He
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, USA
| | - Hui Zhang
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, USA
| | - Andrea Yung
- Department of Biology, Stanford University, Stanford, California, USA
| | - Saul A Villeda
- Present address: The Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, University of California San Francisco, San Francisco, California, USA (S.A.V.), Department of Bioengineering, University of California San Diego, La Jolla, California, USA, and Department of Medicine, University of California San Diego, La Jolla, California, USA (P.A.J.)
| | - Philipp A Jaeger
- Present address: The Eli and Edythe Broad Center for Regeneration Medicine and Stem Cell Research, University of California San Francisco, San Francisco, California, USA (S.A.V.), Department of Bioengineering, University of California San Diego, La Jolla, California, USA, and Department of Medicine, University of California San Diego, La Jolla, California, USA (P.A.J.)
| | - Oluwatobi Olayiwola
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, USA
| | - Nina Fainberg
- Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, USA
| | - Tony Wyss-Coray
- 1] Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, California, USA. [2] Center for Tissue Regeneration, Repair and Rehabilitation, VA Palo Alto Health Care System, Palo Alto, California, USA
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20
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Ting CY, McQueen PG, Pandya N, Lin TY, Yang M, Reddy OV, O'Connor MB, McAuliffe M, Lee CH. Photoreceptor-derived activin promotes dendritic termination and restricts the receptive fields of first-order interneurons in Drosophila. Neuron 2014; 81:830-846. [PMID: 24462039 DOI: 10.1016/j.neuron.2013.12.012] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/02/2013] [Indexed: 01/10/2023]
Abstract
How neurons form appropriately sized dendritic fields to encounter their presynaptic partners is poorly understood. The Drosophila medulla is organized in layers and columns and innervated by medulla neuron dendrites and photoreceptor axons. Here, we show that three types of medulla projection (Tm) neurons extend their dendrites in stereotyped directions and to distinct layers within a single column for processing retinotopic information. In contrast, the Dm8 amacrine neurons form a wide dendritic field to receive ∼16 R7 photoreceptor inputs. R7- and R8-derived Activin selectively restricts the dendritic fields of their respective postsynaptic partners, Dm8 and Tm20, to the size appropriate for their functions. Canonical Activin signaling promotes dendritic termination without affecting dendritic routing direction or layer. Tm20 neurons lacking Activin signaling expanded their dendritic fields and aberrantly synapsed with neighboring photoreceptors. We suggest that afferent-derived Activin regulates the dendritic field size of their postsynaptic partners to ensure appropriate synaptic partnership.
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Affiliation(s)
- Chun-Yuan Ting
- Section on Neuronal Connectivity, Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Philip G McQueen
- Mathematical and Statistical Computing Laboratory, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, MD 20892, USA
| | - Nishith Pandya
- Biomedical Imaging Research Services Section, Center for Information Technology, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tzu-Yang Lin
- Section on Neuronal Connectivity, Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Meiluen Yang
- Section on Neuronal Connectivity, Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - O Venkateswara Reddy
- National Center for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bangalore 560065, India
| | - Michael B O'Connor
- Department of Genetics, Cell Biology and Development, University of Minnesota, MN 55455, USA
| | - Matthew McAuliffe
- Biomedical Imaging Research Services Section, Center for Information Technology, National Institutes of Health, Bethesda, MD 20892, USA
| | - Chi-Hon Lee
- Section on Neuronal Connectivity, Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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21
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p21-Activated kinase (PAK) is required for Bone Morphogenetic Protein (BMP)-induced dendritogenesis in cortical neurons. Mol Cell Neurosci 2013; 57:83-92. [PMID: 24141051 DOI: 10.1016/j.mcn.2013.10.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 10/01/2013] [Accepted: 10/08/2013] [Indexed: 01/21/2023] Open
Abstract
Bone Morphogenetic Proteins (BMPs) are crucial for many aspects of the development and differentiation of the nervous system and are important in controlling cytoskeletal remodeling during neuronal morphogenesis. BMPs are TGFβ superfamily members that signal through a heteromeric complex of type I and type II BMP receptors. The BMPRII receptor is particularly important in mediating remodeling of the neuronal cytoskeleton through the activation of BMPRII-bound cytoskeletal regulators, such as LIM Kinase (LIMK). Here, we show that PAK1, a key regulator of diverse neuronal processes and an upstream activator of LIMK, binds to the BMP type I receptor, ALK2. Although, PAK1 is dispensable for activation of the Smad transcriptional mediators, abrogation of PAK1 expression or inhibition of PAK1 activity prevents BMP-induced neurite outgrowth in cultured neuroblastoma cell lines. Moreover, in primary murine embryonic cortical neurons, inhibition of PAK activity blocks BMP7-induced cofilin phosphorylation, prevents remodeling of the actin cytoskeleton and thereby blocks BMP7-induced dendrite formation. Thus, we propose a model in which BMP7 signaling leads to the recruitment of ALK2-bound PAK1 to BMPRII, which binds a downstream regulator of the actin cytoskeleton, LIMK1, and that the BMP receptor complex thereby acts as a scaffold to localize and coordinate actin cytoskeletal remodeling. We propose that this scaffold plays a key role in mediating BMP7-dependent dendritogenesis in primary cortical neurons.
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22
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R7 photoreceptor axon growth is temporally controlled by the transcription factor Ttk69, which inhibits growth in part by promoting transforming growth factor-β/activin signaling. J Neurosci 2013; 33:1509-20. [PMID: 23345225 DOI: 10.1523/jneurosci.2023-12.2013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Work on axon growth has classically focused on understanding how extrinsic cues control growth cone dynamics independent of the cell body. However, more recently, neuron-intrinsic transcription factors have been shown to influence both normal and regenerative axon growth, suggesting that understanding their mechanism of action is of clinical importance. We are studying axon targeting in the Drosophila visual system and here show that the BTB/POZ zinc-finger transcription factor Tramtrack69 (Ttk69) plays an instructive role in inhibiting the growth of R7 photoreceptor axon terminals. Although ttk69 mutant R7 axons project to the correct medullar target layer, M6, their terminals fail to remain retinotopically restricted and instead grow laterally within M6. This overgrowth is not caused by an inability to be repelled by neighboring R7 axons or by an inability to recognize and initiate synapse formation with postsynaptic targets. The overgrowth is progressive and occurs even if contact between ttk69 mutant R7 axons and their normal target layer is disrupted. Ttk69 is first expressed in wild-type R7s after their axons have reached the medulla; ttk69 mutant R7 axon terminal overgrowth begins shortly after this time point. We find that expressing Ttk69 prematurely in R7s collapses their growth cones and disrupts axon extension, indicating that Ttk69 plays an instructive role in this process. A TGF-β/Activin pathway was shown previously to inhibit R7 axon terminal growth. We find that Ttk69 is required for normal activation of this pathway but that Ttk69 likely also inhibits R7 axon growth by a TGF-β/Activin-independent mechanism.
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23
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Peterson AJ, O'Connor MB. Activin receptor inhibition by Smad2 regulates Drosophila wing disc patterning through BMP-response elements. Development 2013; 140:649-59. [PMID: 23293296 DOI: 10.1242/dev.085605] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Imaginal disc development in Drosophila requires coordinated cellular proliferation and tissue patterning. In our studies of TGFβ superfamily signaling components, we found that a protein null mutation of Smad2, the only Activin subfamily R-Smad in the fruit fly, produces overgrown wing discs that resemble gain of function for BMP subfamily signaling. The wing discs are expanded specifically along the anterior-posterior axis, with increased proliferation in lateral regions. The morphological defect is not observed in mutants for the TGFβ receptor baboon, and epistasis tests showed that baboon is epistatic to Smad2 for disc overgrowth. Rescue experiments indicate that Baboon binding, but not canonical transcription factor activity, of Smad2 is required for normal disc growth. Smad2 mutant discs generate a P-Mad stripe that is narrower and sharper than the normal gradient, and activation targets are correspondingly expressed in narrowed domains. Repression targets of P-Mad are profoundly mis-regulated, with brinker and pentagone reporter expression eliminated in Smad2 mutants. Loss of expression requires a silencer element previously shown to be controlled by BMP signaling. Epistasis experiments show that Baboon, Mad and Schnurri are required to mediate the ectopic silencer output in the absence of Smad2. Taken together, our results show that loss of Smad2 permits promiscuous Baboon activity, which represses genes subject to control by Mad-dependent silencer elements. The absence of Brinker and Pentagone in Smad2 mutants explains the compound wing disc phenotype. Our results highlight the physiological relevance of substrate inhibition of a kinase, and reveal a novel interplay between the Activin and BMP pathways.
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Affiliation(s)
- Aidan J Peterson
- Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455, USA
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24
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Nikitina EA, Medvedeva AV, Dolgaya YF, Korochkin LI, Pavlova GV, Savvateeva-Popova EV. Involvement of GDNF and LIMK1 and heat shock proteins in drosophila learning and memory formation. J EVOL BIOCHEM PHYS+ 2013. [DOI: 10.1134/s0022093012050076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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25
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Takaesu NT, Stinchfield MJ, Shimizu K, Arase M, Quijano JC, Watabe T, Miyazono K, Newfeld SJ. Drosophila CORL is required for Smad2-mediated activation of Ecdysone Receptor expression in the mushroom body. Development 2012; 139:3392-401. [PMID: 22874913 DOI: 10.1242/dev.079442] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
CORL proteins (FUSSEL/SKOR proteins in humans) are related to Sno/Ski oncogenes but their developmental roles are unknown. We have cloned Drosophila CORL and show that its expression is restricted to distinct subsets of cells in the central nervous system. We generated a deletion of CORL and noted that homozygous individuals rarely survive to adulthood. Df(4)dCORL adult escapers display mushroom body (MB) defects and Df(4)dCORL larvae are lacking Ecdysone Receptor (EcR-B1) expression in MB neurons. This is phenocopied in CORL-RNAi and Smad2-RNAi clones in wild-type larvae. Furthermore, constitutively active Baboon (type I receptor upstream of Smad2) cannot stimulate EcR-B1 MB expression in Df(4)dCORL larvae, which demonstrates a formal requirement for CORL in Smad2 signaling. Studies of mouse Corl1 (Skor1) revealed that it binds specifically to Smad3. Overall, the data suggest that CORL facilitates Smad2 activity upstream of EcR-B1 in the MB. The conservation of neural expression and strong sequence homology of all CORL proteins suggests that this is a new family of Smad co-factors.
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Affiliation(s)
- Norma T Takaesu
- School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA
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26
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Peterson AJ, Jensen PA, Shimell M, Stefancsik R, Wijayatonge R, Herder R, Raftery LA, O'Connor MB. R-Smad competition controls activin receptor output in Drosophila. PLoS One 2012; 7:e36548. [PMID: 22563507 PMCID: PMC3341346 DOI: 10.1371/journal.pone.0036548] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Accepted: 04/10/2012] [Indexed: 02/07/2023] Open
Abstract
Animals use TGF-β superfamily signal transduction pathways during development and tissue maintenance. The superfamily has traditionally been divided into TGF-β/Activin and BMP branches based on relationships between ligands, receptors, and R-Smads. Several previous reports have shown that, in cell culture systems, "BMP-specific" Smads can be phosphorylated in response to TGF-β/Activin pathway activation. Using Drosophila cell culture as well as in vivo assays, we find that Baboon, the Drosophila TGF-β/Activin-specific Type I receptor, can phosphorylate Mad, the BMP-specific R-Smad, in addition to its normal substrate, dSmad2. The Baboon-Mad activation appears direct because it occurs in the absence of canonical BMP Type I receptors. Wing phenotypes generated by Baboon gain-of-function require Mad, and are partially suppressed by over-expression of dSmad2. In the larval wing disc, activated Baboon cell-autonomously causes C-terminal Mad phosphorylation, but only when endogenous dSmad2 protein is depleted. The Baboon-Mad relationship is thus controlled by dSmad2 levels. Elevated P-Mad is seen in several tissues of dSmad2 protein-null mutant larvae, and these levels are normalized in dSmad2; baboon double mutants, indicating that the cross-talk reaction and Smad competition occur with endogenous levels of signaling components in vivo. In addition, we find that high levels of Activin signaling cause substantial turnover in dSmad2 protein, providing a potential cross-pathway signal-switching mechanism. We propose that the dual activity of TGF-β/Activin receptors is an ancient feature, and we discuss several ways this activity can modulate TGF-β signaling output.
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Affiliation(s)
- Aidan J. Peterson
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Philip A. Jensen
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - MaryJane Shimell
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Ray Stefancsik
- Cutaneous Biology Research Center, Massachusetts General Hospital/Harvard Medical School, Charlestown, Massachusetts, United States of America
| | - Ranjula Wijayatonge
- Cutaneous Biology Research Center, Massachusetts General Hospital/Harvard Medical School, Charlestown, Massachusetts, United States of America
| | - Rachel Herder
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Laurel A. Raftery
- Cutaneous Biology Research Center, Massachusetts General Hospital/Harvard Medical School, Charlestown, Massachusetts, United States of America
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, Nevada, United States of America
| | - Michael B. O'Connor
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota, United States of America
- * E-mail:
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27
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Hwang HS, Hwang SG, Cho JH, Chae JS, Yoon KW, Cho SG, Choi EJ. CIIA functions as a molecular switch for the Rac1-specific GEF activity of SOS1. ACTA ACUST UNITED AC 2012; 195:377-86. [PMID: 22042618 PMCID: PMC3206349 DOI: 10.1083/jcb.201106138] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
CIIA mediates the TGF-β–induced activation of SOS1–Rac1 signaling and cell migration. Son of sevenless 1 (SOS1) is a dual guanine nucleotide exchange factor (GEF) that activates the guanosine triphosphatases Rac1 and Ras, which mediate signaling initiated by peptide growth factors. In this paper, we show that CIIA is a new binding partner of SOS1. CIIA promoted the SOS1–Rac1 interaction and inhibited the SOS1–Ras interaction. Furthermore, CIIA promoted the formation of an SOS1–EPS8 complex and SOS1-mediated Rac1 activation, whereas it inhibited SOS1-mediated activation of Ras. Transforming growth factor β (TGF-β) up-regulated the expression of CIIA and thereby promoted the association between CIIA and SOS1 in A549 human lung adenocarcinoma cells. Depletion of CIIA in these cells by ribonucleic acid interference inhibited the TGF-β–induced interaction between SOS1 and EPS8, activation of Rac1, and cell migration. Together, these results suggest that CIIA mediates the TGF-β–induced activation of SOS1–Rac1 signaling and cell migration in A549 cells. They further show that CIIA functions as a molecular switch for the GEF activity of SOS1, directing this activity toward Rac1.
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Affiliation(s)
- Hyun Sub Hwang
- Laboratory of Cell Death and Human Diseases, School of Life Sciences, Korea University, Seoul 136-701, South Korea
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28
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Kalinovsky A, Boukhtouche F, Blazeski R, Bornmann C, Suzuki N, Mason CA, Scheiffele P. Development of axon-target specificity of ponto-cerebellar afferents. PLoS Biol 2011; 9:e1001013. [PMID: 21346800 PMCID: PMC3035609 DOI: 10.1371/journal.pbio.1001013] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Accepted: 12/14/2010] [Indexed: 01/19/2023] Open
Abstract
The function of neuronal networks relies on selective assembly of synaptic connections during development. We examined how synaptic specificity emerges in the pontocerebellar projection. Analysis of axon-target interactions with correlated light-electron microscopy revealed that developing pontine mossy fibers elaborate extensive cell-cell contacts and synaptic connections with Purkinje cells, an inappropriate target. Subsequently, mossy fiber-Purkinje cell connections are eliminated resulting in granule cell-specific mossy fiber connectivity as observed in mature cerebellar circuits. Formation of mossy fiber-Purkinje cell contacts is negatively regulated by Purkinje cell-derived BMP4. BMP4 limits mossy fiber growth in vitro and Purkinje cell-specific ablation of BMP4 in mice results in exuberant mossy fiber-Purkinje cell interactions. These findings demonstrate that synaptic specificity in the pontocerebellar projection is achieved through a stepwise mechanism that entails transient innervation of Purkinje cells, followed by synapse elimination. Moreover, this work establishes BMP4 as a retrograde signal that regulates the axon-target interactions during development.
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Affiliation(s)
- Anna Kalinovsky
- Department of Physiology & Cellular Biophysics and Department of Neuroscience, Columbia University, New York, New York, United States of America
| | | | - Richard Blazeski
- Department of Pathology & Cell Biology and Department of Neuroscience and Ophthalmology, Columbia University, New York, New York, United States of America
| | | | - Noboru Suzuki
- Mie University Life Science Research Center of Animal Genomics, Functional Genomics Institute, Japan
| | - Carol A. Mason
- Department of Pathology & Cell Biology and Department of Neuroscience and Ophthalmology, Columbia University, New York, New York, United States of America
| | - Peter Scheiffele
- Department of Physiology & Cellular Biophysics and Department of Neuroscience, Columbia University, New York, New York, United States of America
- Biozentrum, University of Basel, Basel, Switzerland
- * E-mail:
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Ghatpande SK, Zhou HR, Cakstina I, Carlson C, Rondini EA, Romeih M, Zile MH. Transforming growth factor beta2 is negatively regulated by endogenous retinoic acid during early heart morphogenesis. Dev Growth Differ 2010; 52:433-55. [PMID: 20507358 DOI: 10.1111/j.1440-169x.2010.01183.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Vitamin A-deficient (VAD) quail embryos lack the vitamin A-active form, retinoic acid (RA) and are characterized by a phenotype that includes a grossly abnormal cardiovascular system that can be rescued by RA. Here we report that the transforming growth factor, TGFbeta2 is involved in RA-regulated cardiovascular development. In VAD embryos TGFbeta2 mRNA and protein expression are greatly elevated. The expression of TGFbeta receptor II is also elevated in VAD embryos but is normalized by treatment with TGFbeta2-specific antisense oligonucleotides (AS). Administration of this AS or an antibody specific for TGFbeta2 to VAD embryos normalizes posterior heart development and vascularization, while the administration of exogenous active TGFbeta2 protein to normal quail embryos mimics the excessive TGFbeta2 status of VAD embryos and induces VAD cardiovascular phenotype. In VAD embryos pSmad2/3 and pErk1 are not activated, while pErk2 and pcRaf are elevated and pSmad1/5/8 is diminished. We conclude that in the early avian embryo TGFbeta2 has a major role in the retinoic acid-regulated posterior heart morphogenesis for which it does not use Smad2/3 pathways, but may use other signaling pathways. Importantly, we conclude that retinoic acid is a critical negative physiological regulator of the magnitude of TGFbeta2 signals during vertebrate heart formation.
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Horbelt D, Guo G, Robinson PN, Knaus P. Quantitative analysis of TGFBR2 mutations in Marfan-syndrome-related disorders suggests a correlation between phenotypic severity and Smad signaling activity. J Cell Sci 2010; 123:4340-50. [PMID: 21098638 DOI: 10.1242/jcs.074773] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Mutations in the gene encoding transforming growth factor-beta receptor type II (TGFBR2) have been described in patients with Loeys-Dietz syndrome (LDS), Marfan syndrome type 2 (MFS2) and familial thoracic aortic aneurysms and dissections (TAAD). Here, we present a comprehensive and quantitative analysis of TGFBR2 expression, turnover and TGF-β-induced Smad and ERK signaling activity for nine mutations identified in patients with LDS, MFS2 and TAAD. The mutations had different effects on protein stability, internalization and signaling. A dominant-negative effect was demonstrated for mutations associated with LDS and MFS2. No mutation showed evidence of an immediate cell-autonomous paradoxical activation of TGF-β signaling. There were no cell biological differences between mutations described in patients with LDS and MFS2. By contrast, R460C, which has been found in familial TAAD but not in MFS2 or LDS, showed a less-severe dominant-negative effect and retained residual Smad phosphorylation and transcriptional activity. TAAD is characterized primarily by thoracic aortic aneurysms or dissections. By contrast, MFS2 is characterized by numerous skeletal abnormalities, and patients with LDS additionally can display craniofacial and other abnormalities. Therefore, our findings suggest that the balance between defects in Smad and ERK signaling might be an important determinant of phenotypic severity in disorders related to mutations in TGFBR2.
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Affiliation(s)
- Daniel Horbelt
- Institute for Chemistry-Biochemistry, Freie Universität Berlin, Berlin, 14195, Germany
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31
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Hemocyte-secreted type IV collagen enhances BMP signaling to guide renal tubule morphogenesis in Drosophila. Dev Cell 2010; 19:296-306. [PMID: 20708591 PMCID: PMC2941037 DOI: 10.1016/j.devcel.2010.07.019] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Revised: 07/09/2010] [Accepted: 07/28/2010] [Indexed: 12/17/2022]
Abstract
Details of the mechanisms that determine the shape and positioning of organs in the body cavity remain largely obscure. We show that stereotypic positioning of outgrowing Drosophila renal tubules depends on signaling in a subset of tubule cells and results from enhanced sensitivity to guidance signals by targeted matrix deposition. VEGF/PDGF ligands from the tubules attract hemocytes, which secrete components of the basement membrane to ensheath them. Collagen IV sensitizes tubule cells to localized BMP guidance cues. Signaling results in pathway activation in a subset of tubule cells that lead outgrowth through the body cavity. Failure of hemocyte migration, loss of collagen IV, or abrogation of BMP signaling results in tubule misrouting and defective organ shape and positioning. Such regulated interplay between cell-cell and cell-matrix interactions is likely to have wide relevance in organogenesis and congenital disease.
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Yi JJ, Barnes AP, Hand R, Polleux F, Ehlers MD. TGF-beta signaling specifies axons during brain development. Cell 2010; 142:144-57. [PMID: 20603020 DOI: 10.1016/j.cell.2010.06.010] [Citation(s) in RCA: 212] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Revised: 01/21/2010] [Accepted: 04/26/2010] [Indexed: 10/19/2022]
Abstract
In the mammalian brain, the specification of a single axon and multiple dendrites occurs early in the differentiation of most neuron types. Numerous intracellular signaling events for axon specification have been described in detail. However, the identity of the extracellular factor(s) that initiate neuronal polarity in vivo is unknown. Here, we report that transforming growth factor beta (TGF-beta) initiates signaling pathways both in vivo and in vitro to fate naive neurites into axons. Neocortical neurons lacking the type II TGF-beta receptor (TbetaR2) fail to initiate axons during development. Exogenous TGF-beta is sufficient to direct the rapid growth and differentiation of an axon, and genetic enhancement of receptor activity promotes the formation of multiple axons. Finally, we show that the bulk of these TGF-beta-dependent events are mediated by site-specific phosphorylation of Par6. These results define an extrinsic cue for neuronal polarity in vivo that patterns neural circuits in the developing brain.
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Affiliation(s)
- Jason J Yi
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
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Lee J, Moon HJ, Lee JM, Joo CK. Smad3 regulates Rho signaling via NET1 in the transforming growth factor-beta-induced epithelial-mesenchymal transition of human retinal pigment epithelial cells. J Biol Chem 2010; 285:26618-27. [PMID: 20547485 DOI: 10.1074/jbc.m109.073155] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We previously demonstrated that RhoA-dependent signaling regulates transforming growth factor-beta1 (TGF-beta1)-induced cytoskeletal reorganization in the human retinal pigment epithelial cell line ARPE-19. Smad pathways have also been shown to mediate TGF-beta1 activity. Here, we examined what regulates Rho GTPase activity and tested whether Smad signaling cross-talks with Rho pathways during TGF-beta1-induced actin rearrangement. Using small interfering RNAs, we found that NET1, the guanine nucleotide exchange factor of RhoA, is critical for TGF-beta1-induced cytoskeletal reorganization, N-cadherin expression, and RhoA activation. In ARPE-19 cells lacking NET1, TGF-beta1-induced stress fibers and N-cadherin expression were not observed. Interestingly, in dominant-negative Smad3-expressing or constitutively active Smad7 cells, TGF-beta1 failed to induce NET1 mRNA and protein expression. Consistent with these results, both dominant-negative Smad3 and constitutively active Smad7 blocked the cytoplasmic localization of NET1 and inhibited interactions between NET1 and RhoA. Finally, we found that NET1 is a direct gene target of TGF-beta1 via Smad3. Taken together, our results demonstrate that Smad3 regulates RhoA activation and cytoskeletal reorganization by controlling NET1 in TGF-beta1-induced ARPE-19 cells. These data define a new role for Smad3 as a modulator of RhoA activation in the regulation of TGF-beta1-induced epithelial-mesenchymal transitions.
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Affiliation(s)
- Jungeun Lee
- Laboratory of Ophthalmology and Visual Science, Catholic Research Institutes of Medical Sciences, Korean Eye Tissue and Gene Bank Related to Blindness, College of Medicine, The Catholic University of Korea, Seoul, Korea.
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Rallis A, Moore C, Ng J. Signal strength and signal duration define two distinct aspects of JNK-regulated axon stability. Dev Biol 2009; 339:65-77. [PMID: 20035736 PMCID: PMC2845820 DOI: 10.1016/j.ydbio.2009.12.016] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Revised: 12/10/2009] [Accepted: 12/11/2009] [Indexed: 11/29/2022]
Abstract
Signaling proteins often control multiple aspects of cell morphogenesis. Yet the mechanisms that govern their pleiotropic behavior are often unclear. Here we show activity levels and timing mechanisms determine distinct aspects of Jun N-terminal kinase (JNK) pathway dependent axonal morphogenesis in Drosophila mushroom body (MB) neurons. In the complete absence of Drosophila JNK (Basket), MB axons fail to stabilize, leading to their subsequent degeneration. However, with a partial loss of Basket (Bsk), or of one of the upstream JNK kinases, Hemipterous or Mkk4, these axons overextend. This suggests that Bsk activity prevents axons from destabilizing, resulting in degeneration and overextension beyond their terminal targets. These distinct phenotypes require different threshold activities involving the convergent action of two distinct JNK kinases. We show that sustained Bsk signals are essential throughout development and act additively but are dispensable at adulthood. We also suggest that graded Bsk inputs are translated into AP-1 transcriptional outputs consisting of Fos and Jun proteins.
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Affiliation(s)
- Andrew Rallis
- MRC Centre for Developmental Neurobiology, New Hunt's House, Guy's Campus, King's College, London SE1 1UL, UK
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Sánchez-Camacho C, Bovolenta P. Emerging mechanisms in morphogen-mediated axon guidance. Bioessays 2009; 31:1013-25. [PMID: 19705365 DOI: 10.1002/bies.200900063] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Early in animal development, gradients of secreted morphogenic molecules, such as Sonic hedgehog (Shh), Wnt and TGFbeta/Bmp family members, regulate cell proliferation and determine the fate and phenotype of the target cells by activating well-characterized signalling pathways, which ultimately control gene transcription. Shh, Wnt and TGFbeta/Bmp signalling also play an important and evolutionary conserved role in neural circuit assembly. They regulate neuronal polarization, axon and dendrite development and synaptogenesis, processes that require rapid and local changes in cytoskeletal organization and plasma membrane components. A key question then is whether morphogen signalling at the growth cone uses similar mechanisms and intracellular pathway components to those described for morphogen-mediated cell specification. This review discusses recent advances towards the understanding of this problem, showing how Shh, Wnt and TGFbeta/Bmp have adapted their 'classical' signalling pathways or adopted alternative and novel molecular mechanisms to influence different aspects of neuronal circuit formation.
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Affiliation(s)
- Cristina Sánchez-Camacho
- Departamento de Neurobiología Molecular, Celular y del Desarrollo, Instituto Cajal, CSIC and CIBER de Enfermedades Raras (CIBERER), Madrid, Spain
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