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Doe CQ, Thor S. 40 years of homeodomain transcription factors in the Drosophila nervous system. Development 2024; 151:dev202910. [PMID: 38819456 PMCID: PMC11190446 DOI: 10.1242/dev.202910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2024]
Abstract
Drosophila nervous system development progresses through a series of well-characterized steps in which homeodomain transcription factors (HDTFs) play key roles during most, if not all, phases. Strikingly, although some HDTFs have only one role, many others are involved in multiple steps of the developmental process. Most Drosophila HDTFs engaged in nervous system development are conserved in vertebrates and often play similar roles during vertebrate development. In this Spotlight, we focus on the role of HDTFs during embryogenesis, where they were first characterized.
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Affiliation(s)
- Chris Q. Doe
- Institute of Neuroscience, Howard Hughes Medical Institute, University of Oregon, Eugene, OR 97403, USA
| | - Stefan Thor
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD 4072, Australia
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2
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Mitchell KJ. Variability in Neural Circuit Formation. Cold Spring Harb Perspect Biol 2024; 16:a041504. [PMID: 38253418 PMCID: PMC10910361 DOI: 10.1101/cshperspect.a041504] [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: 01/24/2024]
Abstract
The study of neural development is usually concerned with the question of how nervous systems get put together. Variation in these processes is usually of interest as a means of revealing these normative mechanisms. However, variation itself can be an object of study and is of interest from multiple angles. First, the nature of variation in both the processes and the outcomes of neural development is relevant to our understanding of how these processes and outcomes are encoded in the genome. Second, variation in the wiring of the brain in humans may underlie variation in all kinds of psychological and behavioral traits, as well as neurodevelopmental disorders. And third, genetic variation that affects circuit development provides the raw material for evolutionary change. Here, I examine these different aspects of variation in circuit development and consider what they may tell us about these larger questions.
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Affiliation(s)
- Kevin J Mitchell
- Smurfit Institute of Genetics and Institute of Neuroscience, Trinity College Dublin, Dublin D02 PN40, Ireland
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3
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Velten J, Gao X, Van Nierop y Sanchez P, Domsch K, Agarwal R, Bognar L, Paulsen M, Velten L, Lohmann I. Single‐cell RNA sequencing of motoneurons identifies regulators of synaptic wiring in
Drosophila
embryos. Mol Syst Biol 2022; 18:e10255. [PMID: 35225419 PMCID: PMC8883443 DOI: 10.15252/msb.202110255] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 01/28/2022] [Accepted: 02/07/2022] [Indexed: 12/14/2022] Open
Abstract
The correct wiring of neuronal circuits is one of the most complex processes in development, since axons form highly specific connections out of a vast number of possibilities. Circuit structure is genetically determined in vertebrates and invertebrates, but the mechanisms guiding each axon to precisely innervate a unique pre‐specified target cell are poorly understood. We investigated Drosophila embryonic motoneurons using single‐cell genomics, imaging, and genetics. We show that a cell‐specific combination of homeodomain transcription factors and downstream immunoglobulin domain proteins is expressed in individual cells and plays an important role in determining cell‐specific connections between differentiated motoneurons and target muscles. We provide genetic evidence for a functional role of five homeodomain transcription factors and four immunoglobulins in the neuromuscular wiring. Knockdown and ectopic expression of these homeodomain transcription factors induces cell‐specific synaptic wiring defects that are partly phenocopied by genetic modulations of their immunoglobulin targets. Taken together, our data suggest that homeodomain transcription factor and immunoglobulin molecule expression could be directly linked and function as a crucial determinant of neuronal circuit structure.
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Affiliation(s)
- Jessica Velten
- Department of Developmental Biology Centre for Organismal Studies (COS) Heidelberg Heidelberg Germany
- The Barcelona Institute of Science and Technology Centre for Genomic Regulation (CRG) Barcelona Spain
- Flow Cytometry Core Facility European Molecular Biology Laboratory (EMBL) Heidelberg Germany
| | - Xuefan Gao
- Department of Developmental Biology Centre for Organismal Studies (COS) Heidelberg Heidelberg Germany
| | | | - Katrin Domsch
- Department of Developmental Biology Centre for Organismal Studies (COS) Heidelberg Heidelberg Germany
- Developmental Biology Erlangen‐Nürnberg University Erlangen Germany
| | - Rashi Agarwal
- Department of Developmental Biology Centre for Organismal Studies (COS) Heidelberg Heidelberg Germany
| | - Lena Bognar
- Department of Developmental Biology Centre for Organismal Studies (COS) Heidelberg Heidelberg Germany
| | - Malte Paulsen
- Flow Cytometry Core Facility European Molecular Biology Laboratory (EMBL) Heidelberg Germany
| | - Lars Velten
- The Barcelona Institute of Science and Technology Centre for Genomic Regulation (CRG) Barcelona Spain
- Universitat Pompeu Fabra (UPF) Barcelona Spain
| | - Ingrid Lohmann
- Department of Developmental Biology Centre for Organismal Studies (COS) Heidelberg Heidelberg Germany
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4
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Lhx2/9 and Etv1 Transcription Factors have Complementary roles in Regulating the Expression of Guidance Genes slit1 and sema3a. Neuroscience 2020; 434:66-82. [PMID: 32200077 DOI: 10.1016/j.neuroscience.2020.03.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 03/10/2020] [Accepted: 03/11/2020] [Indexed: 01/02/2023]
Abstract
During neural network development, growing axons read a map of guidance cues expressed in the surrounding tissue that lead the axons toward their targets. In particular, Xenopus retinal ganglion axons use the cues Slit1 and Semaphorin 3a (Sema3a) at a key guidance decision point in the mid-diencephalon in order to continue on to their midbrain target, the optic tectum. The mechanisms that control the expression of these cues, however, are poorly understood. Extrinsic Fibroblast Growth Factor (Fgf) signals are known to help coordinate the development of the brain by regulating gene expression. Here, we propose Lhx2/9 and Etv1 as potential downstream effectors of Fgf signalling to regulate slit1 and sema3a expression in the Xenopus forebrain. We find that lhx2/9 and etv1 mRNAs are expressed complementary to and within slit1/sema3a expression domains, respectively. Our data indicate that Lhx2 functions as an indirect repressor in that lhx2 overexpression within the forebrain downregulates the mRNA expression of both guidance genes, and in vitro lhx2/9 overexpression decreases the activity of slit1 and sema3a promoters. The Lhx2-VP16 constitutive activator fusion reduces sema3a promoter function, and the Lhx2-En constitutive repressor fusion increases slit1 induction. In contrast, etv1 gain of function transactivates both guidance genes in vitro and in the forebrain. Based on these data, together with our previous work, we hypothesize that Fgf signalling promotes both slit1 and sema3a expression in the forebrain through Etv1, while using Lhx2/9 to limit the extent of expression, thereby establishing the proper boundaries of guidance cue expression.
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5
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Wealing JC, Cholanian M, Flanigan EG, Levine RB, Fregosi RF. Diverse physiological properties of hypoglossal motoneurons innervating intrinsic and extrinsic tongue muscles. J Neurophysiol 2019; 122:2054-2060. [PMID: 31533009 PMCID: PMC6879950 DOI: 10.1152/jn.00478.2019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 09/05/2019] [Accepted: 09/13/2019] [Indexed: 12/16/2022] Open
Abstract
The mammalian tongue contains eight muscles that collaborate to ensure that suckling, swallowing, and other critical functions are robust and reliable. Seven of the eight tongue muscles are innervated by hypoglossal motoneurons (XIIMNs). A somatotopic organization of the XII motor nucleus, defined in part by the mechanical action of a neuron's target muscle, has been described, but whether or not XIIMNs within a compartment are functionally specialized is unsettled. We hypothesize that developing XIIMNs are assigned unique functional properties that reflect the challenges that their target muscle faces upon the transition from in utero to terrestrial life. To address this, we studied XIIMNs that innervate intrinsic and extrinsic tongue muscles, because intrinsic muscles play a more prominent role in suckling than the extrinsic muscles. We injected dextran-rhodamine into the intrinsic longitudinal muscles (IL) and the extrinsic genioglossus, and physiologically characterized the labeled XIIMNs. Consistent with earlier work, IL XIIMNs (n = 150) were located more dorsally within the nucleus, and GG XIIMNs (n = 55) more ventrally. Whole cell recordings showed that resting membrane potential was, on average, 9 mV more depolarized in IL than in GG XIIMNs (P = 0.0019), and the firing threshold in response to current injection was lower in IL (-31 ± 23 pA) than in GG XIIMNs (225 ± 39 pA; P < 0.0001). We also found that the appearance of net outward currents in GG XIIMNs occurred at more hyperpolarized membrane potentials than IL XIIMNs, consistent with lower excitability in GG XIIMNs. These observations document muscle-specific functional specializations among XIIMNs.NEW & NOTEWORTHY The hypoglossal motor nucleus contains motoneurons responsible for innervating one of seven different muscles with notably different biomechanics and patterns of use. Whether or not motoneurons innervating the different muscles also have unique functional properties (e.g., spiking behavior, synaptic physiology) is poorly understood. In this work we show that neonatal hypoglossal motoneurons innervating muscles that shape the tongue (intrinsic longitudinal muscles) have different electrical properties than those innervating the genioglossus, which controls tongue position.
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Affiliation(s)
- J. C. Wealing
- Department of Physiology, The University of Arizona, Tucson, Arizona
| | - M. Cholanian
- Department of Physiology, The University of Arizona, Tucson, Arizona
| | - E. G. Flanigan
- Department of Physiology, The University of Arizona, Tucson, Arizona
| | - R. B. Levine
- Department of Physiology, The University of Arizona, Tucson, Arizona
- Department of Neuroscience, The University of Arizona, Tucson, Arizona
| | - R. F. Fregosi
- Department of Physiology, The University of Arizona, Tucson, Arizona
- Department of Neuroscience, The University of Arizona, Tucson, Arizona
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6
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Transcriptional control of long-range cortical projections. Curr Opin Neurobiol 2018; 53:57-65. [DOI: 10.1016/j.conb.2018.05.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Accepted: 05/23/2018] [Indexed: 12/11/2022]
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7
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Yang JLJ, Bertolesi GE, Hehr CL, Johnston J, McFarlane S. Fibroblast growth factor receptor 1 signaling transcriptionally regulates the axon guidance cue slit1. Cell Mol Life Sci 2018; 75:3649-3661. [PMID: 29705951 PMCID: PMC11105281 DOI: 10.1007/s00018-018-2824-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 04/19/2018] [Accepted: 04/23/2018] [Indexed: 12/31/2022]
Abstract
Axons sense molecular cues in their environment to arrive at their post-synaptic targets. While many of the molecular cues have been identified, the mechanisms that regulate their spatiotemporal expression remain elusive. We examined here the transcriptional regulation of the guidance gene slit1 both in vitro and in vivo by specific fibroblast growth factor receptors (Fgfrs). We identified an Fgf-responsive 2.3 kb slit1 promoter sequence that recapitulates spatiotemporal endogenous expression in the neural tube and eye of Xenopus embryos. We found that signaling through Fgfr1 is the main regulator of slit1 expression both in vitro in A6 kidney epithelial cells, and in the Xenopus forebrain, even when other Fgfr subtypes are present in cells. These data argue that a specific signaling pathway downstream of Fgfr1 controls in a cell-autonomous manner slit1 forebrain expression and are novel in identifying a specific growth factor receptor for in vivo control of the expression of a key embryonic axon guidance cue.
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Affiliation(s)
- Jung-Lynn Jonathan Yang
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr., NW, Calgary, AB, T2N 4N1, Canada
| | - Gabriel E Bertolesi
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr., NW, Calgary, AB, T2N 4N1, Canada
| | - Carrie L Hehr
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr., NW, Calgary, AB, T2N 4N1, Canada
| | - Jillian Johnston
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr., NW, Calgary, AB, T2N 4N1, Canada
| | - Sarah McFarlane
- Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, 3330 Hospital Dr., NW, Calgary, AB, T2N 4N1, Canada.
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8
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Kinold JC, Pfarr C, Aberle H. Sidestep-induced neuromuscular miswiring causes severe locomotion defects in Drosophila larvae. Development 2018; 145:145/17/dev163279. [DOI: 10.1242/dev.163279] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Accepted: 07/17/2018] [Indexed: 01/12/2023]
Abstract
ABSTRACT
Mutations in motor axon guidance molecules cause aberrant projection patterns of motor nerves. As most studies in Drosophila have analysed these molecules in fixed embryos, the consequences for larval locomotion are entirely unexplored. Here, we took advantage of sidestep (side)-mutant larvae that display severe locomotion defects because of irreparable innervation errors. Mutations in side affected all motor nerve branches and all body wall regions. Innervation defects were non-stereotypical, showing unique innervation patterns in each hemisegment. Premature activation of Side in muscle precursors abrogated dorsal migration of motor nerves, resulting in larvae with a complete loss of neuromuscular junctions on dorsal-most muscles. High-speed videography showed that these larvae failed to maintain substrate contact and inappropriately raised both head and tail segments above the substrate, resulting in unique ‘arching’ and ‘lifting’ phenotypes. These results show that guidance errors in side mutants are maintained throughout larval life and are asymmetrical with respect to the bilateral body axis. Together with similar findings in mice, this study also suggests that miswiring could be an underlying cause of inherited movement disorders.
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Affiliation(s)
- Jaqueline C. Kinold
- Heinrich Heine University Düsseldorf, Functional Cell Morphology Lab, Building 26-12-00, Universitaetsstrasse 1, 40225 Düsseldorf, Germany
| | - Carsten Pfarr
- Heinrich Heine University Düsseldorf, Functional Cell Morphology Lab, Building 26-12-00, Universitaetsstrasse 1, 40225 Düsseldorf, Germany
| | - Hermann Aberle
- Heinrich Heine University Düsseldorf, Functional Cell Morphology Lab, Building 26-12-00, Universitaetsstrasse 1, 40225 Düsseldorf, Germany
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9
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Ulloa F, Cotrufo T, Ricolo D, Soriano E, Araújo SJ. SNARE complex in axonal guidance and neuroregeneration. Neural Regen Res 2018; 13:386-392. [PMID: 29623913 PMCID: PMC5900491 DOI: 10.4103/1673-5374.228710] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Through complex mechanisms that guide axons to the appropriate routes towards their targets, axonal growth and guidance lead to neuronal system formation. These mechanisms establish the synaptic circuitry necessary for the optimal performance of the nervous system in all organisms. Damage to these networks can be repaired by neuroregenerative processes which in turn can re-establish synapses between injured axons and postsynaptic terminals. Both axonal growth and guidance and the neuroregenerative response rely on correct axonal growth and growth cone responses to guidance cues as well as correct synapses with appropriate targets. With this in mind, parallels can be drawn between axonal regeneration and processes occurring during embryonic nervous system development. However, when studying parallels between axonal development and regeneration many questions still arise; mainly, how do axons grow and synapse with their targets and how do they repair their membranes, grow and orchestrate regenerative responses after injury. Major players in the cellular and molecular processes that lead to growth cone development and movement during embryonic development are the Soluble N-ethylamaleimide Sensitive Factor (NSF) Attachment Protein Receptor (SNARE) proteins, which have been shown to be involved in axonal growth and guidance. Their involvement in axonal growth, guidance and neuroregeneration is of foremost importance, due to their roles in vesicle and membrane trafficking events. Here, we review the recent literature on the involvement of SNARE proteins in axonal growth and guidance during embryonic development and neuroregeneration.
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Affiliation(s)
- Fausto Ulloa
- Department of Cell Biology, Physiology and Immunology, School of Biology, and Institute of Neurosciences, University of Barcelona, Barcelona; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III (ISCIII), Madrid, Spain
| | - Tiziana Cotrufo
- Department of Cell Biology, Physiology and Immunology, School of Biology, and Institute of Neurosciences, University of Barcelona, Barcelona; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III (ISCIII), Madrid, Spain
| | - Delia Ricolo
- Institut de Biologia Molecular de Barcelona (IBMB-CSIC), Parc Cientific de Barcelona; Department of Genetics, Microbiology and Statistics, School of Biology, University of Barcelona, Barcelona, Spain
| | - Eduardo Soriano
- Department of Cell Biology, Physiology and Immunology, School of Biology, and Institute of Neurosciences, University of Barcelona, Barcelona; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Instituto de Salud Carlos III (ISCIII), Madrid; Vall d´Hebron Institut de Recerca (VHIR), Barcelona, Spain
| | - Sofia J Araújo
- Institut de Biologia Molecular de Barcelona (IBMB-CSIC), Parc Cientific de Barcelona; Department of Genetics, Microbiology and Statistics, School of Biology, University of Barcelona, Barcelona, Spain
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10
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Hessinger C, Technau GM, Rogulja-Ortmann A. The Drosophila Hox gene Ultrabithorax acts in both muscles and motoneurons to orchestrate formation of specific neuromuscular connections. Development 2016; 144:139-150. [PMID: 27913640 PMCID: PMC5278631 DOI: 10.1242/dev.143875] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 11/17/2016] [Indexed: 12/29/2022]
Abstract
Hox genes are known to specify motoneuron pools in the developing vertebrate spinal cord and to control motoneuronal targeting in several species. However, the mechanisms controlling axial diversification of muscle innervation patterns are still largely unknown. We present data showing that the Drosophila Hox gene Ultrabithorax (Ubx) acts in the late embryo to establish target specificity of ventrally projecting RP motoneurons. In abdominal segments A2 to A7, RP motoneurons innervate the ventrolateral muscles VL1-4, with VL1 and VL2 being innervated in a Wnt4-dependent manner. In Ubx mutants, these motoneurons fail to make correct contacts with muscle VL1, a phenotype partially resembling that of the Wnt4 mutant. We show that Ubx regulates expression of Wnt4 in muscle VL2 and that it interacts with the Wnt4 response pathway in the respective motoneurons. Ubx thus orchestrates the interaction between two cell types, muscles and motoneurons, to regulate establishment of the ventrolateral neuromuscular network. Summary: Ultrabithorax controls correct innervation of ventrolateral muscles by coordinating Wnt4 ligand expression in muscles with the signalling pathway response in motoneurons.
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11
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cGMP-Dependent Protein Kinase Encoded by foraging Regulates Motor Axon Guidance in Drosophila by Suppressing Lola Function. J Neurosci 2016; 36:4635-46. [PMID: 27098704 DOI: 10.1523/jneurosci.3726-15.2016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2015] [Accepted: 03/21/2016] [Indexed: 12/18/2022] Open
Abstract
UNLABELLED Correct pathfinding and target recognition of a developing axon are exquisitely regulated processes that require multiple guidance factors. Among these factors, the second messengers, cAMP and cGMP, are known to be involved in establishing the guidance cues for axon growth through different intracellular signaling pathways. However, whether and how cGMP-dependent protein kinase (PKG) regulates axon guidance remains poorly understood. Here, we show that the motor axons of intersegmental nerve b (ISNb) in the Drosophila embryo display targeting defects during axon development in the absence of foraging(for), a gene encoding PKG.In vivo tag expression revealed PKG to be present in the ventral nerve code at late embryonic stages, supporting its function in embryonic axon guidance. Mechanistic studies showed that the transcription factor longitudinal lacking(lola) genetically interacts with for.PKG physically associates with the LolaT isoform via the C-terminal zinc-finger-containing domain. Overexpression of PKG leads to the cytoplasmic retention of LolaT in S2 cells, suggesting a role for PKG in mediating the nucleocytoplasmic trafficking of Lola. Together, these findings reveal a novel function of PKG in regulating the establishment of neuronal connectivity by sequestering Lola in the cytoplasm. SIGNIFICANCE STATEMENT Axon pathfinding and target recognition are important processes in the formation of specific neuronal connectivity, which rely upon precise coordinated deployment of multiple guidance factors. This paper reveals the role of cGMP-dependent protein kinase (PKG) in regulating the pathfinding and targeting of the developing axons in Drosophila Moreover, our study indicates that PKG regulates the cytoplasmic-nuclear trafficking of the transcription factor LolaT, suggesting a mechanism of PKG in directing motor axon guidance. These findings highlight a new function of PKG in axon guidance by suppressing a transcription factor.
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12
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Catela C, Shin MM, Lee DH, Liu JP, Dasen JS. Hox Proteins Coordinate Motor Neuron Differentiation and Connectivity Programs through Ret/Gfrα Genes. Cell Rep 2016; 14:1901-15. [PMID: 26904955 DOI: 10.1016/j.celrep.2016.01.067] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 12/07/2015] [Accepted: 01/21/2016] [Indexed: 11/25/2022] Open
Abstract
The accuracy of neural circuit assembly relies on the precise spatial and temporal control of synaptic specificity determinants during development. Hox transcription factors govern key aspects of motor neuron (MN) differentiation; however, the terminal effectors of their actions are largely unknown. We show that Hox/Hox cofactor interactions coordinate MN subtype diversification and connectivity through Ret/Gfrα receptor genes. Hox and Meis proteins determine the levels of Ret in MNs and define the intrasegmental profiles of Gfrα1 and Gfrα3 expression. Loss of Ret or Gfrα3 leads to MN specification and innervation defects similar to those observed in Hox mutants, while expression of Ret and Gfrα1 can bypass the requirement for Hox genes during MN pool differentiation. These studies indicate that Hox proteins contribute to neuronal fate and muscle connectivity through controlling the levels and pattern of cell surface receptor expression, consequently gating the ability of MNs to respond to limb-derived instructive cues.
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Affiliation(s)
- Catarina Catela
- Neuroscience Institute, Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - Maggie M Shin
- Neuroscience Institute, Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - David H Lee
- Neuroscience Institute, Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA
| | - Jeh-Ping Liu
- Department of Neuroscience, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Jeremy S Dasen
- Neuroscience Institute, Department of Neuroscience and Physiology, NYU School of Medicine, New York, NY 10016, USA.
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13
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Asadzadeh J, Neligan N, Kramer SG, Labrador JP. Tinman Regulates NetrinB in the Cardioblasts of the Drosophila Dorsal Vessel. PLoS One 2016; 11:e0148526. [PMID: 26840059 PMCID: PMC4740434 DOI: 10.1371/journal.pone.0148526] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 01/05/2016] [Indexed: 11/18/2022] Open
Abstract
Morphogenesis of the Drosophila dorsal vessel (DV) shares similarities with that of the vertebrate heart. Precursors line up at both sides of the embryo, migrate towards the midline and fuse to form a tubular structure. Guidance receptors and their ligands have been implicated in this process in vertebrates and invertebrates, as have been a series of evolutionarily conserved cardiogenic transcriptional regulators including Tinman, the Drosophila homolog of the transcription factor Nkx-2.5. NetrinB (NetB), a repulsive ligand for the Unc-5 receptor is required to preserve the dorsal vessel hollow. It localizes to the luminal space of the dorsal vessel but its source and its regulation is unknown. Here, using genetics together with in situ hybridization with single cell resolution, we show how tin is required for NetrinB expression in cardioblasts during DV tubulogenesis and sufficient to promote NetB transcription ectopically. We further identify a dorsal vessel-specific NetB enhancer and show that it is also regulated by tin in a similar fashion to NetB.
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Affiliation(s)
- Jamshid Asadzadeh
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin, Ireland
- Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
| | - Niamh Neligan
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin, Ireland
| | - Sunita G. Kramer
- Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Rutgers The State University of New Jersey, Piscataway, New Jersey, United States of America
| | - Juan-Pablo Labrador
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin, Ireland
- Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
- * E-mail:
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14
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Asadzadeh J, Neligan N, Canabal-Alvear JJ, Daly AC, Kramer SG, Labrador JP. The Unc-5 Receptor Is Directly Regulated by Tinman in the Developing Drosophila Dorsal Vessel. PLoS One 2015; 10:e0137688. [PMID: 26356221 PMCID: PMC4565662 DOI: 10.1371/journal.pone.0137688] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 08/19/2015] [Indexed: 01/05/2023] Open
Abstract
During early heart morphogenesis cardiac cells migrate in two bilateral opposing rows, meet at the dorsal midline and fuse to form a hollow tube known as the primary heart field in vertebrates or dorsal vessel (DV) in Drosophila. Guidance receptors are thought to mediate this evolutionarily conserved process. A core of transcription factors from the NK2, GATA and T-box families are also believed to orchestrate this process in both vertebrates and invertebrates. Nevertheless, whether they accomplish their function, at least in part, through direct or indirect transcriptional regulation of guidance receptors is currently unknown. In our work, we demonstrate how Tinman (Tin), the Drosophila homolog of the Nkx-2.5 transcription factor, regulates the Unc-5 receptor during DV tube morphogenesis. We use genetics, expression analysis with single cell mRNA resolution and enhancer-reporter assays in vitro or in vivo to demonstrate that Tin is required for Unc-5 receptor expression specifically in cardioblasts. We show that Tin can bind to evolutionary conserved sites within an Unc-5 DV enhancer and that these sites are required for Tin-dependent transactivation both in vitro and in vivo.
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Affiliation(s)
- Jamshid Asadzadeh
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin, Ireland
- Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
| | - Niamh Neligan
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin, Ireland
| | - Judith J. Canabal-Alvear
- Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
| | - Amanda C. Daly
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin, Ireland
- Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
| | - Sunita Gupta Kramer
- Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
| | - Juan-Pablo Labrador
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin, Ireland
- Institute of Neuroscience, Trinity College Dublin, Dublin, Ireland
- * E-mail:
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15
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Abstract
Evolutionary modifications in nervous systems enabled organisms to adapt to their specific environments and underlie the remarkable diversity of behaviors expressed by animals. Resolving the pathways that shaped and modified neural circuits during evolution remains a significant challenge. Comparative studies have revealed a surprising conservation in the intrinsic signaling systems involved in early patterning of bilaterian nervous systems but also raise the question of how neural circuit compositions and architectures evolved within specific animal lineages. In this review, we discuss the mechanisms that contributed to the emergence and diversity of animal nervous systems, focusing on the circuits governing vertebrate locomotion.
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Affiliation(s)
- Heekyung Jung
- Howard Hughes Medical Institute (HHMI), NYU Neuroscience Institute, Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY 10016, USA
| | - Jeremy S Dasen
- Howard Hughes Medical Institute (HHMI), NYU Neuroscience Institute, Department of Neuroscience and Physiology, New York University School of Medicine, New York, NY 10016, USA.
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16
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Allan DW, Thor S. Transcriptional selectors, masters, and combinatorial codes: regulatory principles of neural subtype specification. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2015; 4:505-28. [PMID: 25855098 PMCID: PMC4672696 DOI: 10.1002/wdev.191] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 03/04/2015] [Accepted: 03/04/2015] [Indexed: 01/08/2023]
Abstract
The broad range of tissue and cellular diversity of animals is generated to a large extent by the hierarchical deployment of sequence-specific transcription factors and co-factors (collectively referred to as TF's herein) during development. Our understanding of these developmental processes has been facilitated by the recognition that the activities of many TF's can be meaningfully described by a few functional categories that usefully convey a sense for how the TF's function, and also provides a sense for the regulatory organization of the developmental processes in which they participate. Here, we draw on examples from studies in Caenorhabditis elegans, Drosophila melanogaster, and vertebrates to discuss how the terms spatial selector, temporal selector, tissue/cell type selector, terminal selector and combinatorial code may be usefully applied to categorize the activities of TF's at critical steps of nervous system construction. While we believe that these functional categories are useful for understanding the organizational principles by which TF's direct nervous system construction, we however caution against the assumption that a TF's function can be solely or fully defined by any single functional category. Indeed, most TF's play diverse roles within different functional categories, and their roles can blur the lines we draw between these categories. Regardless, it is our belief that the concepts discussed here are helpful in clarifying the regulatory complexities of nervous system development, and hope they prove useful when interpreting mutant phenotypes, designing future experiments, and programming specific neuronal cell types for use in therapies. WIREs Dev Biol 2015, 4:505–528. doi: 10.1002/wdev.191 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
- Douglas W Allan
- Department of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, Canada
| | - Stefan Thor
- Department of Clinical and Experimental Medicine, Linkoping University, Linkoping, Sweden
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17
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Santiago C, Labrador JP, Bashaw GJ. The homeodomain transcription factor Hb9 controls axon guidance in Drosophila through the regulation of Robo receptors. Cell Rep 2014; 7:153-65. [PMID: 24685136 DOI: 10.1016/j.celrep.2014.02.037] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2013] [Revised: 02/06/2014] [Accepted: 02/25/2014] [Indexed: 02/05/2023] Open
Abstract
Transcription factors establish neural diversity and wiring specificity; however, how they orchestrate changes in cell morphology remains poorly understood. The Drosophila Roundabout (Robo) receptors regulate connectivity in the CNS, but how their precise expression domains are established is unknown. Here, we show that the homeodomain transcription factor Hb9 acts upstream of Robo2 and Robo3 to regulate axon guidance in the Drosophila embryo. In ventrally projecting motor neurons, hb9 is required for robo2 expression, and restoring Robo2 activity in hb9 mutants rescues motor axon defects. Hb9 requires its conserved repressor domain and functions in parallel with Nkx6 to regulate robo2. Moreover, hb9 can regulate the medio-lateral position of axons through robo2 and robo3, and restoring robo3 expression in hb9 mutants rescues the lateral position defects of a subset of neurons. Altogether, these data identify Robo2 and Robo3 as key effectors of Hb9 in regulating nervous system development.
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Affiliation(s)
- Celine Santiago
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | - Greg J Bashaw
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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18
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Zarin AA, Asadzadeh J, Hokamp K, McCartney D, Yang L, Bashaw GJ, Labrador JP. A transcription factor network coordinates attraction, repulsion, and adhesion combinatorially to control motor axon pathway selection. Neuron 2014; 81:1297-1311. [PMID: 24560702 DOI: 10.1016/j.neuron.2014.01.038] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/07/2014] [Indexed: 11/26/2022]
Abstract
Combinations of transcription factors (TFs) instruct precise wiring patterns in the developing nervous system; however, how these factors impinge on surface molecules that control guidance decisions is poorly understood. Using mRNA profiling, we identified the complement of membrane molecules regulated by the homeobox TF Even-skipped (Eve), the major determinant of dorsal motor neuron (dMN) identity in Drosophila. Combinatorial loss- and gain-of-function genetic analyses of Eve target genes indicate that the integrated actions of attractive, repulsive, and adhesive molecules direct eve-dependent dMN axon guidance. Furthermore, combined misexpression of Eve target genes is sufficient to partially restore CNS exit and can convert the guidance behavior of interneurons to that of dMNs. Finally, we show that a network of TFs, comprised of eve, zfh1, and grain, induces the expression of the Unc5 and Beaten-path guidance receptors and the Fasciclin 2 and Neuroglian adhesion molecules to guide individual dMN axons.
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Affiliation(s)
- Aref Arzan Zarin
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland; Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland
| | - Jamshid Asadzadeh
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland; Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland
| | - Karsten Hokamp
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland
| | - Daniel McCartney
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland
| | - Long Yang
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Greg J Bashaw
- Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Juan-Pablo Labrador
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland; Institute of Neuroscience, Trinity College Dublin, Dublin 2, Ireland.
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19
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Kaplan A, Kent CB, Charron F, Fournier AE. Switching responses: spatial and temporal regulators of axon guidance. Mol Neurobiol 2013; 49:1077-86. [PMID: 24271658 DOI: 10.1007/s12035-013-8582-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 10/31/2013] [Indexed: 11/29/2022]
Abstract
The ability of the axonal growth cone to switch between attraction and repulsion in response to guidance cues in the extracellular environment during nervous system development is fundamental to the precise wiring of complex neural circuits. Regulation of cell-surface receptors by means of transcriptional control, local translation, trafficking and proteolytic processing are powerful mechanisms to regulate the response of the growth cone. Important work has also revealed how intracellular signalling pathways, including calcium and cyclic nucleotide signalling, can alter the directional response elicited by a particular cue. Here, we describe how these multiple regulatory mechanisms influence growth cone turning behaviour. We focus on recent evidence that suggests a significant role for 14-3-3 adaptor proteins in modifying growth cone turning behaviour and mediating directional polarity switches during development. Characterizing how 14-3-3 s regulate growth cone signalling will provide invaluable insight into nervous system development and may facilitate the identification of novel targets for promoting nerve regeneration following injury.
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Affiliation(s)
- Andrew Kaplan
- Department of Neurology and Neurosurgery, Montreal Neurological Institute and Hospital, McGill University, Montreal, Quebec, H3A 2B4, Canada
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