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Parker RJ, Auld VJ. Signaling in glial development: differentiation migration and axon guidance. Biochem Cell Biol 2004; 82:694-707. [PMID: 15674437 DOI: 10.1139/o04-119] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Glial cells have diverse functions that are necessary for the proper development and function of complex nervous systems. During development, a variety of reciprocal signaling interactions between glia and neurons dictate all parts of nervous system development. Glia may provide attractive, repulsive, or contact-mediated cues to steer neuronal growth cones and ensure that neurons find their appropriate synaptic targets. In fact, both neurons and glia may act as migrational substrates for one another at different times during development. Also, the exchange of trophic signals between glia and neurons is essential for the proper bundling, fasciculation, and ensheathement of axons as well as the differentiation and survival of both cell types. The growing number of links between glial malfunction and human disease has generated great interest in glial biology. Because of its relative simplicity and the many molecular genetic tools available, Drosophila is an excellent model organism for studying glial development. This review will outline the roles of glia and their interactions with neurons in the embryonic nervous system of the fly.Key words: glia, axon guidance, migration, EGF receptor.
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Affiliation(s)
- Robert J Parker
- Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, BC V6T 1Z4, Canada
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102
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Sonnenfeld MJ, Barazesh N, Sedaghat Y, Fan C. The jing and ras1 pathways are functionally related during CNS midline and tracheal development. Mech Dev 2004; 121:1531-47. [PMID: 15511644 DOI: 10.1016/j.mod.2004.07.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2003] [Revised: 06/23/2004] [Accepted: 07/09/2004] [Indexed: 10/26/2022]
Abstract
The Drosophila jing gene encodes a zinc finger protein required for the differentiation and survival of embryonic CNS midline and tracheal cells. We show that there is a functional relationship between jing and the Egfr pathway in the developing CNS midline and trachea. jing function is required for Egfr pathway gene expression and MAPK activity in both the CNS midline and trachea. jing over-expression effects phenocopy those of the Egfr pathway and require Egfr pathway function. Activation of the Egfr pathway in loss-of-function jing mutants partially rescues midline cell loss. Egfr pathway genes and jing show dominant genetic interactions in the trachea and CNS midline. Together, these results show that jing regulates signal transduction in developing midline and tracheal cells.
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Affiliation(s)
- Margaret J Sonnenfeld
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Ont., Canada.
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103
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Pielage J, Kippert A, Zhu M, Klämbt C. The Drosophila transmembrane protein Fear-of-intimacy controls glial cell migration. Dev Biol 2004; 275:245-57. [PMID: 15464587 DOI: 10.1016/j.ydbio.2004.07.039] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2004] [Revised: 07/27/2004] [Accepted: 07/28/2004] [Indexed: 11/17/2022]
Abstract
Development of complex organs depends on intensive cell-cell interactions, which help coordinate movements of many cell types. In a genetic screen aimed to identify genes controlling midline glia migration in the Drosophila nervous system, we have identified mutations in the gene kastchen. Here we show that during embryogenesis kastchen is also required for the normal migration of longitudinal and peripheral glial cells. During larval development, kastchen non-cell autonomously affects the migration of the subretinal glia into the eye disc. During embryonic development, kastchen not only affects glial cell migration but also controls the migration of muscle cells toward their attachment sites. In all cases, kastchen apparently functions in terminating or restricting cell migration. We identified the molecular nature of the gene by performing transgenic rescue experiments and by sequence analysis of mutant alleles. Kastchen corresponds to the recently described gene fear-of-intimacy (foi) that was identified in screen for genes affecting germ cell migration, suggesting that Foi-Kastchen is more generally involved in regulating cell migration. It encodes a member of an eight-transmembrane domain protein family of putative Zinc transporters or proteases. We determined the topology of the Foi protein by using antisera against luminal and intracellular domains of the protein and provide evidence that it does not act as a Zinc transporter. Genetic evidence suggests that one of the functions of foi may be associated with hedgehog signaling.
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Affiliation(s)
- Jan Pielage
- Institut für Neurobiologie, Universität Münster, Münster D-48149, Germany
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104
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Tanaka H, Takasu E, Aigaki T, Kato K, Hayashi S, Nose A. Formin3 is required for assembly of the F-actin structure that mediates tracheal fusion in Drosophila. Dev Biol 2004; 274:413-25. [PMID: 15385168 DOI: 10.1016/j.ydbio.2004.07.035] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2003] [Revised: 07/08/2004] [Accepted: 07/19/2004] [Indexed: 01/19/2023]
Abstract
During tracheal development in Drosophila, some branches join to form a continuous luminal network. Specialized cells at the branch tip, called fusion cells, extend filopodia to make contact and become doughnut shaped to allow passage of the lumen. These morphogenetic processes accompany the highly regulated cytoskeletal reorganization of fusion cells. We identified the Drosophila formin3 (form3) gene that encodes a novel formin and plays a role in tracheal fusion. Formins are a family of proteins characterized by highly conserved formin homology (FH) domains. The formin family functions in various actin-based processes, including cytokinesis and cell polarity. During embryogenesis, form3 mRNA is expressed mainly in the tracheal system. In form3 mutant embryos, the tracheal fusion does not occur at some points. This phenotype is rescued by the forced expression of form3 in the trachea. We used live imaging of GFP-moesin during tracheal fusion to show that an F-actin structure that spans the adjoining fusion cells and mediates the luminal connection does not form at abnormal anastomosis sites in form3 mutants. These results suggested that Form3 plays a role in the F-actin assembly, which is essential for cellular rearrangement during tracheal fusion.
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Affiliation(s)
- Hiromasa Tanaka
- Department of Physics, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
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105
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McGovern VL, Pacak CA, Sewell ST, Turski ML, Seeger MA. A targeted gain of function screen in the embryonic CNS of Drosophila. Mech Dev 2004; 120:1193-207. [PMID: 14568107 DOI: 10.1016/s0925-4773(03)00159-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In order to identify genes involved in the development of the central nervous system (CNS) we have undertaken a gain of function screen in the embryonic CNS of Drosophila. Transposable P-elements and the UAS/GAL4 system were used to initiate transcription of genes in a pan-neural pattern using scaGAL4. Over 4100 individual P-element insertion lines were screened with monoclonal antibodies BP102 and 1D4 to visualize axon pathways. Twenty-five P-element insertions corresponding to 18 genes resulted in aberrant CNS axon pathfinding when misexpressed with scaGAL4. Genes involved in axon guidance, embryonic patterning, and cell cycle regulation were isolated. In addition, we identified several zinc finger transcription factors not previously implicated in axon guidance or CNS development. This group includes Squeeze, Kruppel homolog-1, Hepatocyte nuclear factor 4, and two uncharacterized genes, CG11966 and CG9650. Calnexin99A, a putative molecular chaperone, was isolated as well.
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Affiliation(s)
- Vicki L McGovern
- Department of Molecular Genetics and The Center for Molecular Neurobiology, 125 Rightmire Hall, The Ohio State University, 1060 Carmack Rd., Columbus, OH 43210, USA
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106
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Fradkin LG, van Schie M, Wouda RR, de Jong A, Kamphorst JT, Radjkoemar-Bansraj M, Noordermeer JN. The Drosophila Wnt5 protein mediates selective axon fasciculation in the embryonic central nervous system. Dev Biol 2004; 272:362-75. [PMID: 15282154 DOI: 10.1016/j.ydbio.2004.04.034] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2004] [Revised: 03/25/2004] [Accepted: 04/01/2004] [Indexed: 10/26/2022]
Abstract
The decision of whether and where to cross the midline, an evolutionarily conserved line of bilateral symmetry in the central nervous system, is the first task for many newly extending axons. We show that Wnt5, a member of the conserved Wnt secreted glycoprotein family, is required for the formation of the anterior of the two midline-crossing commissures present in each Drosophila hemisegment. Initial path finding of pioneering neurons across the midline in both commissures is normal in wnt5 mutant embryos; however, the subsequent separation of the early midline-crossing axons into two distinct commissures does not occur. The majority of the follower axons that normally cross the midline in the anterior commissure fail to do so, remaining tightly associated near their cell bodies, or projecting inappropriately across the midline in between the commissures. The lateral and intermediate longitudinal pathways also fail to form correctly, similarly reflecting earlier failures in pathway defasciculation. Panneural expression of Wnt5 in a wnt5 mutant background rescues both the commissural and longitudinal defects. We show that the Wnt5 protein is predominantly present on posterior commissural axons and at a low level on the anterior commissure and longitudinal projections. Finally, we demonstrate that transcriptional repression of wnt5 in AC neurons by the recently described Wnt5 receptor, Derailed, contributes to this largely posterior commissural localization of Wnt5 protein.
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Affiliation(s)
- Lee G Fradkin
- Department of Molecular and Cell Biology, Leiden University Medical Center, 2333 AL Leiden, The Netherlands.
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107
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Kadner D, Stollewerk A. Neurogenesis in the chilopod Lithobius forficatus suggests more similarities to chelicerates than to insects. Dev Genes Evol 2004; 214:367-79. [PMID: 15278451 DOI: 10.1007/s00427-004-0419-z] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2004] [Accepted: 05/12/2004] [Indexed: 10/26/2022]
Abstract
In a recent comparative study on neurogenesis in the diplopod Glomeris marginata we have shown that the millipede and the spider share several features that cannot be found in homologous form in insects and crustaceans. The most distinctive difference is that groups of neural precursors are singled out from the neuroectoderm of the spider and the diplopod, rather than individual cells (i.e. neuroblasts) as in insects or crustacean. This observation constitutes the first morphological indication for a close myriapod/chelicerate relationship that has otherwise only been suggested by molecular phylogenetic analysis. To see whether the pattern of neurogenesis described for the diplopod is representative for myriapods, we analysed neurogenesis in the basal chilopod Lithobius forficatus. We show here that groups of cells invaginate from the chilopod neuroectoderm at strikingly similar positions as the invaginating cell groups of the diplopod and the spider. Furthermore, the expression patterns of the proneural and neurogenic genes reveal more similarities to the chelicerate and the diplopod than to insects. Thus, chelicerates and myriapods share the developmental mechanism for neurogenesis, either because they are true sister groups, or because this reflects the ancestral state of neurogenesis in arthropods.
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Affiliation(s)
- Diana Kadner
- Institute for Genetics, University of Cologne, Weyertal 121, 50931 Cologne, Germany
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108
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Gallio M, Englund C, Kylsten P, Samakovlis C. Rhomboid 3 orchestrates Slit-independent repulsion of tracheal branches at the CNS midline. Development 2004; 131:3605-14. [PMID: 15229181 DOI: 10.1242/dev.01242] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
EGF-receptor ligands act as chemoattractants for migrating epithelial cells during organogenesis and wound healing. We present evidence that Rhomboid 3/EGF signalling, which originates from the midline of the Drosophila ventral nerve cord, repels tracheal ganglionic branches and prevents them from crossing it. rho3 acts independently from the main midline repellent Slit, and originates from a different sub-population of midline cells: the VUM neurons. Expression of dominant-negative Egfr or Ras induces midline crosses, whereas activation of the Egfr or Ras in the leading cell of the ganglionic branch can induce premature turns away from the midline. This suggests that the level of Egfr intracellular signalling, rather than the asymmetric activation of the receptor on the cell surface, is an important determinant in ganglionic branch repulsion. We propose that Egfr activation provides a necessary switch for the interpretation of a yet unknown repellent function of the midline.
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Affiliation(s)
- Marco Gallio
- Department of Developmental Biology, Wenner-Gren Institute, Stockholm University, S-106 96 Stockholm, Sweden
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109
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Abstract
The evolutionary origin of the tritocerebral neuromere, which is a brain segment located at the junction between the supra- and subesophageal ganglia in most mandibulates (arthropods such as crustaceans and insects), is a subject rich in contentious debate. Various models have argued that the tritocerebrum came from a segmental nerve cord ganglia that was recruited into the head during the course of arthropod evolution. However, despite much thought on the subject, the origin of the tritocerebrum remains obscure. Here I describe the development of the tritocerebral commissure in Drosophila and demonstrate that the tritocerebral and mandibular commissures actually form as one commissure and then separate in a manner very similar to how the anterior and posterior commissures of a ventral nerve cord neuromere form. I propose that the tritocerebral neuromere originated from the splitting of an ancestral neuromere located in the anterior subesophageal ganglion into distinct tritocerebral and mandibular neuromeres. Also, I discuss the problem of arthropod brain neuromere homology in reference to this hypothesis.
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Affiliation(s)
- Damon T Page
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
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110
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Dearborn R, Kunes S. An axon scaffold induced by retinal axons directs glia to destinations in the Drosophila optic lobe. Development 2004; 131:2291-303. [PMID: 15102705 DOI: 10.1242/dev.01111] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the developing Drosophila visual system, glia migrate into stereotyped positions within the photoreceptor axon target fields and provide positional information for photoreceptor axon guidance. Glial migration conversely depends on photoreceptor axons, as glia precursors stall in their progenitor zones when retinal innervation is eliminated. Our results support the view that this requirement for retinal innervation reflects a role of photoreceptor axons in the establishment of an axonal scaffold that guides glial cell migration. Optic lobe cortical axons extend from dorsal and ventral positions towards incoming photoreceptor axons and establish at least four separate pathways that direct glia to proper destinations in the optic lobe neuropiles. Photoreceptor axons induce the outgrowth of these scaffold axons. Most glia do not migrate when the scaffold axons are missing. Moreover, glia follow the aberrant pathways of scaffold axons that project aberrantly, as occurs in the mutant dachsous. The local absence of glia is accompanied by extensive apoptosis of optic lobe cortical neurons. These observations reveal a mechanism for coordinating photoreceptor axon arrival in the brain with the distribution of glia to multiple target destinations, where they are required for axon guidance and neuronal survival.
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Affiliation(s)
- Richard Dearborn
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
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111
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Schlurmann M, Hausen K. Mesothoracic ventral unpaired median (mesVUM) neurons in the blowfly Calliphora erythrocephala. J Comp Neurol 2004; 467:435-53. [PMID: 14608604 DOI: 10.1002/cne.10930] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The study describes five ventral unpaired median neurons in the mesothoracic neuromere of the fused thoracic ganglion of Calliphora identified by biocytin staining (mesVUM neurons). The group comprises four efferent neurons and one interneuron which are characterized by a common soma cluster in the ventral midline of the neuromere, bifurcating primary neurites and bilaterally symmetrical arborizations. Respective soma clusters of not-yet-identified VUM neurons were also found in the prothoracic, metathoracic, and abdominal neuromeres. The efferent mesVUM neurons are associated with the flight system. Their main arborizations are located in the mesothoracic wing neuropil and their bilateral axons terminate at the flight control muscles, the flight starter muscles, the flight power muscles, or at myocuticular junctions of the latter. In contrast, an association of the interneuron with a particular functional system is not apparent. The arborizations of the neuron are intersegmental and invade all thoracic neuromeres. A further difference between the two types of neurons regards their somatic action potentials, which are overshooting in the efferent neurons and strongly attenuated in the interneuron. Immunocytochemical stainings revealed four clusters of octopamine-immunoreactive (OA-IR) somata in the thoracic ganglion, which reside in the same positions as the VUM somata. We regard this as strong evidence that all groups of VUM neurons contain OA-IR cells and that, in particular, the identified efferent mesVUM neurons are OA-IR. Our results demonstrate that the mesVUM neurons of Calliphora have similar morphological, electrophysiological, and presumably also immunocytochemical characteristics as the unpaired median neurons of other insects.
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112
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Boyan GS, Bräunig P, Posser S, Williams JLD. Embryonic development of the sensory innervation of the clypeo-labral complex: further support for serially homologous appendages in the locust. ARTHROPOD STRUCTURE & DEVELOPMENT 2003; 32:289-302. [PMID: 18089013 DOI: 10.1016/j.asd.2003.07.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2003] [Accepted: 07/31/2003] [Indexed: 05/25/2023]
Abstract
The clypeo-labrum, or upper lip, of insects is intimately involved in feeding behavior and is accordingly endowed with a rich sensory apparatus. In the present study we map the temporal appearance of all major clusters of sensory cells on this structure in the locust during the first half of embryogenesis. The identities of these sensory cell clusters were defined according to the origin of the branching point of their axons from the labral sensory nerve as seen at mid-embryogenesis. The first sensory cells to differentiate from the labral epithelium do so at stereotypic sites beginning at around 32% of embryogenesis. Bilaterally symmetrical clusters of differentiated neurons rapidly appear and pioneering of the labral sensory nerve on each side is performed by a specific cell from each cluster. This cell directs its axon anteriorly towards a bilaterally symmetrical pair of cells, the frontal commissure pioneers, on either side of the developing frontal ganglion. The final trajectory of the sensory nerve within the labrum closely matches the pattern of Repo-expressing glial cells. The majority of the sensory cell clusters differentiate during embryogenesis, but the number of sensory cells in some clusters are modified significantly during postembryonic development. Comparing the innervation pattern of the clypeo-labrum with that of other mouthparts and the leg at mid-embryogenesis, we find a striking similarity in organization which we interpret as support for the homologous appendage hypothesis.
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Affiliation(s)
- G S Boyan
- Developmental Neurobiology Group, Department of Biology II, Zoologisches Institut der Ludwig-Maximilians-Universität, Luisenstrasse 14, 80333 Munich, Germany
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113
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Michaud S, Tanguay RM. Expression of the Hsp23 chaperone during Drosophila embryogenesis: association to distinct neural and glial lineages. BMC DEVELOPMENTAL BIOLOGY 2003; 3:9. [PMID: 14617383 PMCID: PMC293469 DOI: 10.1186/1471-213x-3-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/18/2003] [Accepted: 11/14/2003] [Indexed: 11/28/2022]
Abstract
Background In addition to their strong induction following stress, small heat shock proteins (Hsp) are also expressed during development in a wide variety of organisms. However, the precise identity of cell(s) expressing these proteins and the functional contribution of small heat shock proteins in such developmental context remain to be determined. The present study provides a detailed description of the Drosophila small heat shock protein Hsp23 expression pattern during embryogenesis and evaluates its functional contribution to central nervous system development. Results Throughout embryogenesis, Hsp23 is expressed in a stage-specific manner by a restricted number of neuronal and glial lineages of the central nervous system. Hsp23 is also detected in the amnioserosa and within a single lateral chordotonal organ. Its expression within the MP2 lineage does not require the presence of a functional midline nor the activity of the Notch signaling pathway. Transactivation assays demonstrate that transcription factors implicated in the differentiation of the midline also regulate hsp23 promoter activity. Phenotypic analysis of a transgenic line exhibiting loss of Hsp23 expression in the central nervous system suggests that Hsp23 is not required for development and function of this tissue. Likewise, its overexpression does not cause deleterious effects, as development remains unaffected. Conclusions Based on the presented data, we suggest that the tightly regulated developmental expression of Hsp23 is not actively involved in cell differentiation and central nervous system development per se but rather reflects a putative role in preventive "pre-stress" neuroprotection or in non-vital process(es) common to the identified cell lineages.
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Affiliation(s)
- Sébastien Michaud
- Laboratoire de Génétique Cellulaire et Développementale, Département de Médecine, Pavillon Marchand, Université Laval, Ste-Foy, Québec, Canada, G1K 7P4
- Current address: Brigham and Women's Hospital / Harvard Medical School, Department of Medicine, Division of Genetics, Harvard Medical School New Research Building, 77 Avenue Louis Pasteur, Boston, USA, 02115
| | - Robert M Tanguay
- Laboratoire de Génétique Cellulaire et Développementale, Département de Médecine, Pavillon Marchand, Université Laval, Ste-Foy, Québec, Canada, G1K 7P4
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114
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Shirai T, Maehara A, Kiritooshi N, Matsuzaki F, Handa H, Nakagoshi H. Differential requirement of EGFR signaling for the expression of defective proventriculus gene in the Drosophila endoderm and ectoderm. Biochem Biophys Res Commun 2003; 311:473-7. [PMID: 14592438 DOI: 10.1016/j.bbrc.2003.10.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
A homeobox gene, defective proventriculus (dve), is expressed in various tissues including the ventral ectoderm and midgut. Here, we show the expression pattern of dve in the ventral ectoderm, in which dve expression is induced by Spitz, a ligand for Drosophila epidermal growth factor receptor (EGFR). In spitz mutants, dve expression is only lost in the ventral ectoderm and overexpression of Spitz induces ectopic dve activation in the ventral ectoderm. Dve expression in the middle midgut depends on Decapentaplegic (Dpp) signaling, while expression of a dominant-negative form of Drosophila EGFR (DER(DN)) also causes a marked decrease in dve expression in the middle midgut. Furthermore, heterozygous mutation of thick veins (tkv), a Dpp receptor, strongly enhances the effect of DER(DN). These results indicate that EGFR signaling is crucial for dve expression in the ventral ectoderm and is required in the middle midgut where it cooperates with Dpp signaling.
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Affiliation(s)
- Tetsuya Shirai
- Graduate School of Natural and Science Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530, Japan
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115
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Araújo SJ, Tear G. Axon guidance mechanisms and molecules: lessons from invertebrates. Nat Rev Neurosci 2003; 4:910-22. [PMID: 14595402 DOI: 10.1038/nrn1243] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Sofia J Araújo
- Molecular Neurobiology Department, Medical Research Council Centre for Developmental Neurobiology, New Hunts House, Guy's Campus, King's College, London, SE1 1UL, UK
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116
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Georgiou M, Tear G. The N-terminal and transmembrane domains of Commissureless are necessary for its function and trafficking within neurons. Mech Dev 2003; 120:1009-19. [PMID: 14550530 DOI: 10.1016/s0925-4773(03)00179-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Commissureless (Comm) is a novel transmembrane molecule necessary both for commissural axons to cross the midline of the Drosophila central nervous system and normal synaptogenesis. Comm is able to reduce cell surface levels of Roundabout (Robo), a receptor for the midline repellent Slit, on commissural axons and unknown inhibitors of synaptogenesis expressed on muscle cells. Comm is expressed dynamically and is found at the cell surface and within intracellular vesicles. Comm can bind Robo and when the proteins are co-expressed Robo is found co-localised with Comm intracellularly. Here we show that the ability of Comm to localise intracellularly and hence regulate Robo surface levels requires sequences in both the N-terminal and transmembrane domains. We also show that Comm can dimerise via its N-terminal domain. Furthermore, absence of the Comm N-terminal and transmembrane regions results in the protein being restricted to the neuron soma.
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Affiliation(s)
- Marios Georgiou
- Molecular Neurobiology Group, MRC Centre for Developmental Neurobiology, New Hunt's House, Guy's Campus, King's College, London SE1 1UL, UK
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117
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Urbach R, Technau GM. Early steps in building the insect brain: neuroblast formation and segmental patterning in the developing brain of different insect species. ARTHROPOD STRUCTURE & DEVELOPMENT 2003; 32:103-123. [PMID: 18088998 DOI: 10.1016/s1467-8039(03)00042-2] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2003] [Accepted: 05/19/2003] [Indexed: 05/25/2023]
Abstract
In insects, morphological, molecular and genetic studies have provided a detailed insight into the ontogenetic processes that shape the ventral nerve cord. On the other hand, owing to its complexity and less obvious segmental composition, the knowledge about the development of the brain is still fragmentary. A promising approach towards gaining insight into fundamental processes underlying brain development is the comparison of embryonic brain development among different insect species. However, so far such comparative analyses are scarce. In this review, we summarize and compare data on the early steps in brain formation in different hemi- and holometabolous insects. We show that basic aspects of the spatial and temporal development of the embryonic brain neuroblast pattern are conserved among insects. Furthermore, we compare the number and proliferation patterns of neuroblasts related to major neuropil structures such as mushroom bodies, central complex, and antennal lobe. Finally, comparing the expression patterns of engrailed in different species, and considering new data from Drosophila melanogaster, we discuss the segmental organization of the insect brain.
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Affiliation(s)
- Rolf Urbach
- Institute for Genetics, University of Mainz, Saarstrasse 21, 55122 Mainz, Germany
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118
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Boyan G, Reichert H, Hirth F. Commissure formation in the embryonic insect brain. ARTHROPOD STRUCTURE & DEVELOPMENT 2003; 32:61-77. [PMID: 18088996 DOI: 10.1016/s1467-8039(03)00037-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2003] [Accepted: 03/28/2003] [Indexed: 05/25/2023]
Abstract
The primary axon scaffold of the insect brain is established early in embryogenesis and comprises a preoral protocerebral commissure, a postoral tritocerebral commissure and longitudinal fiber pathways linking the two. In both grasshopper and fly its form is approximately orthogonal and is centered around the stomodeum. We show how pioneer fibers from the protocerebrum and tritocerebrum cross the brain midline directly via their respective commissures. The deutocerebrum, however, lacks its own commissure and we describe how deutocerebral pioneers circumnavigate the gut to cross the midline either via the protocerebral commissure or the tritocerebral commissure. In contrast to all other commissures of the central nervous system, the protocerebral commissure persists, albeit in reduced form, in the commissureless mutation in the fly. Besides the com gene, a further, as yet unidentified, mechanism must regulate this commissure. The formation of the tritocerebral commissure involves labial, a member of the Hox gene group. Genetic rescue experiments in labial mutants reveal that the formation of this commissure can be rescued by all other Hox genes except Abdominal-B. However, only in the labial and Deformed null mutants are the commissures associated with the respective expression domains (tritocerebral, mandibular, respectively) absent. This suggests that the molecular mechanisms regulating postoral brain commissure formation are distinct from those in the neuromeres of the ventral nerve cord.
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Affiliation(s)
- George Boyan
- Department of Biology II, Ludwig-Maximilians-Universität, Luisenstrasse 14, 80333 Munich, Germany
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119
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Sears HC, Kennedy CJ, Garrity PA. Macrophage-mediated corpse engulfment is required for normal Drosophila CNS morphogenesis. Development 2003; 130:3557-65. [PMID: 12810602 DOI: 10.1242/dev.00586] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cell death plays an essential role in development, and the removal of cell corpses presents an important challenge for the developing organism. Macrophages are largely responsible for the clearance of cell corpses in Drosophila melanogaster and mammalian systems. We have examined the developmental requirement for macrophages in Drosophila and find that macrophage function is essential for central nervous system (CNS) morphogenesis. We generate and analyze mutations in the Pvr locus, which encodes a receptor tyrosine kinase of the PDGF/VEGF family that is required for hemocyte migration. We find that loss of Pvr function causes the mispositioning of glia within the CNS and the disruption of the CNS axon scaffold. We further find that inhibition of hemocyte development or of Croquemort, a receptor required for macrophage-mediated corpse engulfment, causes similar CNS defects. These data indicate that macrophage-mediated clearance of cell corpses is required for proper morphogenesis of the Drosophila CNS.
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Affiliation(s)
- Heather C Sears
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue 68-230B, Cambridge, MA 02139, USA
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120
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Yuasa Y, Okabe M, Yoshikawa S, Tabuchi K, Xiong WC, Hiromi Y, Okano H. Drosophila homeodomain protein REPO controls glial differentiation by cooperating with ETS and BTB transcription factors. Development 2003; 130:2419-28. [PMID: 12702656 DOI: 10.1242/dev.00468] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In Drosophila, cell-fate determination of all neuroectoderm-derived glial cells depends on the transcription factor Glial cells missing (GCM), which serves as a binary switch between the neuronal and glial cell fates. Because the expression of GCM is restricted to the early phase of glial development, other factors must be responsible for the terminal differentiation of glial cells. Expression of three transcription factors, Reversed Polarity (REPO), Tramtrack p69 (TTK69) and PointedP1 (PNTP1), is induced by GCM in glial cells. REPO is a paired-like homeodomain protein, expressed exclusively in glial cells, and is required for the migration and differentiation of embryonic glial cells. To understand how REPO functions in glial terminal differentiation, we have analyzed the mechanism of gene regulation by REPO. We show that REPO can act as a transcriptional activator through the CAATTA motif in glial cells, and define three genes whose expression in vivo depends on REPO function. In different types of glial cells, REPO can act alone, or cooperate with either TTK69 or PNTP1 to regulate different target genes. Coordination of target gene expression by these three transcription factors may contribute to the diversity of glial cell types. In addition to promoting glial differentiation, we found that REPO is also necessary to suppress neuronal development, cooperating with TTK69. We propose that REPO plays a key role in both glial development and diversification.
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Affiliation(s)
- Yoshihiro Yuasa
- Division of Neuroanatomy (D12), Department of Neuroscience, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
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121
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Settle M, Gordon MD, Nadella M, Dankort D, Muller W, Jacobs JR. Genetic identification of effectors downstream of Neu (ErbB-2) autophosphorylation sites in a Drosophila model. Oncogene 2003; 22:1916-26. [PMID: 12673197 DOI: 10.1038/sj.onc.1206240] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The ErbB-2/Neu receptor tyrosine kinase plays a causal role in tumorigenesis in mammals. Neu's carboxyl terminus contains five phosphorylated tyrosines that mediate transformation through interaction with cytoplasmic SH2 or PTB containing adaptor proteins. We show that Drosophila adaptors signal from individual phosphotyrosine sites of rat Neu. Activated Neu expression in the midline glia suppressed apoptosis, similar to that seen with activated Drosophila EGF-R expression. Expression in eye and wing tissues generated graded phenotypes suitable for dosage-sensitive modifier genetics. Suppression of ErbB-2/Neu-induced phenotypes in tissues haplosufficient for genes encoding adaptor protein or second messengers suggests that pTyr 1227(YD) signals require Shc, and that pTyr 1253 (YE) signalling does not employ Ras, but does require Raf function. Signalling from pTyr (YB) was affected by a haplosufficiency in drk (Grb-2), and in genes thought to function downstream of Grb-2: dab, sos, csw (Shp-2), and dos (Gab-1). These data demonstrate the power of Drosophila genetics to unmask the molecules that signal from oncogenic ErbB-2/Neu.
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MESH Headings
- Adaptor Proteins, Vesicular Transport
- Animals
- Animals, Genetically Modified
- Apoptosis/genetics
- Apoptosis/physiology
- Drosophila Proteins/genetics
- Drosophila Proteins/physiology
- Drosophila melanogaster/embryology
- Drosophila melanogaster/genetics
- Drosophila melanogaster/growth & development
- Drosophila melanogaster/metabolism
- ErbB Receptors/physiology
- Eye/growth & development
- Eye Proteins/genetics
- Eye Proteins/physiology
- Gene Dosage
- Gene Expression Regulation, Developmental
- Morphogenesis/genetics
- Morphogenesis/physiology
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/physiology
- Phenotype
- Phosphorylation
- Phosphotyrosine/chemistry
- Protein Kinases
- Protein Processing, Post-Translational
- Protein Structure, Tertiary
- Protein Tyrosine Phosphatases/genetics
- Protein Tyrosine Phosphatases/physiology
- Protein Tyrosine Phosphatases, Non-Receptor
- Proteins/genetics
- Proteins/physiology
- Proto-Oncogene Proteins c-raf/genetics
- Proto-Oncogene Proteins c-raf/physiology
- Rats
- Receptor, ErbB-2/chemistry
- Receptor, ErbB-2/physiology
- Receptors, Invertebrate Peptide/physiology
- Recombinant Fusion Proteins/physiology
- Shc Signaling Adaptor Proteins
- Signal Transduction/genetics
- Signal Transduction/physiology
- Son of Sevenless Protein, Drosophila/genetics
- Son of Sevenless Protein, Drosophila/physiology
- Structure-Activity Relationship
- Wings, Animal/growth & development
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Affiliation(s)
- Mark Settle
- Department of Biology, McMaster University, Hamilton, ON, Canada
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122
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Shandala T, Takizawa K, Saint R. The dead ringer/retained transcriptional regulatory gene is required for positioning of the longitudinal glia in the Drosophila embryonic CNS. Development 2003; 130:1505-13. [PMID: 12620977 DOI: 10.1242/dev.00377] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The Drosophila dead ringer (dri, also known as retained, retn) gene encodes a nuclear protein with a conserved DNA-binding domain termed the ARID (AT-rich interaction domain). We show here that dri is expressed in a subset of longitudinal glia in the Drosophila embryonic central nervous system and that dri forms part of the transcriptional regulatory cascade required for normal development of these cells. Analysis of mutant embryos revealed a role for dri in formation of the normal embryonic CNS. Longitudinal glia arise normally in dri mutant embryos, but they fail to migrate to their final destinations. Disruption of the spatial organization of the dri-expressing longitudinal glia accounts for the mild defects in axon fasciculation observed in the mutant embryos. Consistent with the late phenotypes observed, expression of the glial cells missing (gcm) and reversed polarity (repo) genes was found to be normal in dri mutant embryos. However, from stage 15 of embryogenesis, expression of locomotion defects (loco) and prospero (pros) was found to be missing in a subset of LG. This suggests that loco and pros are targets of DRI transcriptional activation in some LG. We conclude that dri is an important regulator of the late development of longitudinal glia.
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Affiliation(s)
- Tetyana Shandala
- Centre for the Molecular Genetics of Development, Adelaide University, Adelaide SA 5005, Australia
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123
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Seppo A, Matani P, Sharrow M, Tiemeyer M. Induction of neuron-specific glycosylation by Tollo/Toll-8, a Drosophila Toll-like receptor expressed in non-neural cells. Development 2003; 130:1439-48. [PMID: 12588858 DOI: 10.1242/dev.00347] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Specific glycan expression is an essential characteristic of developing tissues. Our molecular characterization of a mutation that abolishes neural-specific glycosylation in the Drosophila embryo demonstrates that cellular interactions influence glycan expression. The HRP epitope is an N-linked oligosaccharide expressed on a subset of neuronal glycoproteins. Embryos homozygous for the TM3 balancer chromosome lack neural HRP-epitope expression. Genetic and molecular mapping of the relevant locus reveals that Tollo/Toll-8, a member of the Toll-like receptor family, is altered on the TM3 chromosome. In wild-type embryos, Tollo/Toll-8 is expressed by ectodermal cells that surround differentiating neurons and precedes HRP-epitope appearance. Re-introduction of Tollo/Toll-8 into null embryos rescues neural-specific glycan expression. Thus, loss of an ectodermal cell surface protein alters glycosylation in juxtaposed differentiating neurons. The portfolio of expressed oligosaccharides in a cell reflects its identity and also influences its interactions with other cells and with pathogens. Therefore, the ability to induce specific glycan expression complements the previously identified developmental and innate immune functions of Toll-like receptors.
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Affiliation(s)
- Antti Seppo
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA
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124
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Giesen K, Lammel U, Langehans D, Krukkert K, Bunse I, Klämbt C. Regulation of glial cell number and differentiation by ecdysone and Fos signaling. Mech Dev 2003; 120:401-13. [PMID: 12676319 DOI: 10.1016/s0925-4773(03)00009-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the midline glia of the embryonic ventral nerve cord of Drosophila, differentiation as well as the subsequent regulation of cell number is under the control of EGF-receptor signaling. During pupal stages apoptosis of all midline glial cells is initiated by ecdysone signaling. In a genetic screen we have identified mutations in disembodied, rippchen, spook, shade, shadow, shroud and tramtrack that all share a number of phenotypic traits, including defects in cuticle differentiation and nervous system development. Some of these genes were previously placed in the so-called 'Halloween-group' and were shown to affect ecdysone synthesis during embryogenesis. Here we demonstrate that the Halloween mutations not only affect glial differentiation but also lead to an increase in the number of midline glial cells, suggesting that during embryogenesis ecdysone signaling is required to adjust glial cell number similar to pupal stages. Finally we isolated a P-element-induced mutation of shroud, which controls the expression of ecdysone inducible genes. The P-element insertion occurs in one of the promoters of the Drosophila fos gene for which we present a yet undescribed complex genomic organization. The recently described kayak alleles affect only one of the six different Fos isoforms. This work for the first time links ecydsone signaling to Fos function and shows that during embryonic and pupal stages similar developmental mechanisms control midline glia survival.
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Affiliation(s)
- Kay Giesen
- Institut für Neurobiologie, Badestrasse 9, Universität Münster, 48149 Münster, Germany
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125
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With S, Rice T, Salinas C, Auld V. Fire exit is a potential four transmembrane protein expressed in developing Drosophila glia. Genesis 2003; 35:143-52. [PMID: 12640618 DOI: 10.1002/gene.10177] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Glia from many diverse organisms play a number of important roles during the development of the nervous system. Therefore, knowing the molecules that control glial cell function will further our understanding of the mechanisms that control nervous system development. We have isolated a novel gene in Drosophila melanogaster that is expressed in a subset of the peripheral glia. We call this gene "Fire exit" (Fie), as the glia that express this gene do so during a time when they mark the entry and exit point of axons at the CNS/PNS boundary. This subset of peripheral glia act as intermediate targets during pathfinding and migration of the sensory axons in particular. Fire exit has been cloned and found to encode a novel transmembrane protein. Fire exit belongs to a group of proteins identified in the Drosophila melanogaster and Anopheles gambiae databases which contain four predicted transmembrane domains and a shared intracellular motif. Mutations that remove the fire exit protein have no obvious disruption to glial function. On the other hand, glia expressing the Fire exit gene bridge the transition zone between CNS and PNS and play a role in sensory axon guidance. Therefore, it appears that, while the glia that express this protein mediate axon guidance, Fire exit itself plays a nonessential part in this function. A role for Fire exit in glial development may be suggested by its evolutionary relationship to a family of lysosome-associated proteins called LAPTMs and suggests that Fire exit may function in intracellular transport during glial development.
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Affiliation(s)
- Sheila With
- Cell Biology Group, Department of Zoology, University of British Columbia, Vancouver, Canada
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126
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Jia XX, Siegler MVS. Midline lineages in grasshopper produce neuronal siblings with asymmetric expression of Engrailed. Development 2002; 129:5181-93. [PMID: 12399310 DOI: 10.1242/dev.129.22.5181] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The median neuroblast lineage of grasshopper has provided a model for the development of differing neuronal types within the insect central nervous system. According to the prevailing model, neurons of different types are produced in sequence. Contrary to this, we show that each ganglion mother cell from the median neuroblast produces two neurons of asymmetric type: one is Engrailed positive (of interneuronal fate); and one is Engrailed negative (of efferent fate). The mature neuronal population, however, results from differential neuronal death. This yields many interneurons and relatively few efferent neurons. Also contrary to previous reports, we find no evidence for glial production by the median neuroblast. We discuss evidence that neuronal lineages typically produce asymmetric progeny, an outcome that has important developmental and evolutionary implications.
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Affiliation(s)
- Xi Xi Jia
- Department of Biology and Graduate Program in Neuroscience, Emory University, Atlanta, GA 30322, USA
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127
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Abstract
The formation of an adult animal from a fertilized embryo involves the production and death of cells. Surprisingly, many cells are produced during development with an ultimate fate of death, and defects in programmed cell death can result in developmental abnormalities. Recent studies indicate that cells can die by many different mechanisms, and these differences have implications for proper animal development and disorders such as cancer and autoimmunity.
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Affiliation(s)
- Eric H Baehrecke
- Center for Biosystems Research, University of Maryland Biotechnology Institute, College Park, Maryland 20742, USA.
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128
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Pielage J, Steffes G, Lau DC, Parente BA, Crews ST, Strauss R, Klämbt C. Novel behavioral and developmental defects associated with Drosophila single-minded. Dev Biol 2002; 249:283-99. [PMID: 12221007 DOI: 10.1006/dbio.2002.0770] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In Drosophila, the development of the midline cells of the embryonic ventral nerve cord depends on the function of the bHLH-PAS transcription factor Single-minded (Sim). The expression domain of sim, however, is also found anterior and posterior to the developing ventral cord throughout the germ band. Indeed, mutations in sim were identified based on their characteristic cuticle phenotype. Eight abdominal segments (A1-A8) can be easily seen in the larval cuticle, while three more can be identified during embryogenesis. Cells located in A8-A10 give rise to the formation of the genital imaginal discs, and a highly modified A11 segment gives rise to the anal pads that flank the anus. sim is expressed in all these segments and is required for the formation of both the anal pads and the genital imaginal discs. A new temperature-sensitive sim allele allowed an assessment of possible postembryonic function(s) of sim. Reduction of sim function below a 50% threshold leads to sterile flies with marked behavioral deficits. Most mutant sim flies were only able to walk in circles. Further analyses indicated that this phenotype is likely due to defects in the brain central complex. This brain region, which has previously been implicated in the control of walking behavior, expresses high levels of nuclear Sim protein in three clusters of neurons in each central brain hemisphere. Additional Sim localization in the medullary and laminar neurons of the optic lobes may correlate with the presence of ectopic axon bundles observed in the optic lobes of sim mutant flies.
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Affiliation(s)
- Jan Pielage
- Institut für Neurobiologie, Universität Münster, Badestrasse 9, D-48149 Münster, Germany
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129
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Soustelle L, Besson MT, Rival T, Birman S. Terminal glial differentiation involves regulated expression of the excitatory amino acid transporters in the Drosophila embryonic CNS. Dev Biol 2002; 248:294-306. [PMID: 12167405 DOI: 10.1006/dbio.2002.0742] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Drosophila excitatory amino acid transporters dEAAT1 and dEAAT2 are nervous-specific transmembrane proteins that mediate the high affinity uptake of L-glutamate or aspartate into cells. Here, we demonstrate by colocalization studies that both genes are expressed in discrete and partially overlapping subsets of differentiated glia and not in neurons in the embryonic central nervous system (CNS). We show that expression of these transporters is disrupted in mutant embryos deficient for the glial fate genes glial cells missing (gcm) and reversed polarity (repo). Conversely, ectopic expression of gcm in neuroblasts, which forces all nerve cells to adopt a glial fate, induces an ubiquitous expression of both EAAT genes in the nervous system. We also detected the dEAAT transcripts in the midline glia in late embryos and dEAAT2 in a few peripheral neurons in head sensory organs. Our results show that glia play a major role in excitatory amino acid transport in the Drosophila CNS and that regulated expression of the dEAAT genes contributes to generate the functional diversity of glial cells during embryonic development.
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Affiliation(s)
- Laurent Soustelle
- Laboratoire de Génétique et Physiologie du Développement, CNRS-Université de la Méditerranée, Developmental Biology Institute of Marseille, Campus de Luminy case 907, 13288 Marseille Cedex 09, France
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130
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Myat A, Henry P, McCabe V, Flintoft L, Rotin D, Tear G. Drosophila Nedd4, a ubiquitin ligase, is recruited by Commissureless to control cell surface levels of the roundabout receptor. Neuron 2002; 35:447-59. [PMID: 12165468 DOI: 10.1016/s0896-6273(02)00795-x] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Crossing the midline produces changes in axons such that they are no longer attracted to the midline. In Drosophila, Roundabout reaches high levels on axons once they have crossed the midline, and this prohibits recrossing. Roundabout protein levels are regulated by Commissureless. We show that Commissureless binds to and is regulated by the ubiquitin ligase DNedd4. We further show that the ability of Commissureless to regulate Roundabout protein levels requires an intact DNedd4 binding site and ubiquitin acceptor sites within the Commissureless protein. The ability of Commissureless to regulate Robo in the embryo also requires a Commissureless/DNedd4 interaction. Our results show that changes in axonal sensitivity to external cues during pathfinding across the midline makes use of ubiquitin-dependent mechanisms to regulate transmembrane protein levels.
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Affiliation(s)
- Anna Myat
- Molecular Neurobiology Group, MRC Centre for Developmental Neurobiology, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL, United Kingdom
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131
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Uhler J, Garbern J, Yang L, Kamholz J, Mellerick DM. Nk6, a novel Drosophila homeobox gene regulated by vnd. Mech Dev 2002; 116:105-16. [PMID: 12128210 DOI: 10.1016/s0925-4773(02)00155-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Nk(x)-type homeobox genes are an evolutionarily conserved family that regulate diverse developmental processes. Here we describe a novel Drosophila gene, Nk6, which encodes an Nk-type transcription factor most homologous to vertebrate Nkx6.1 and Nkx6.2. The homeodomains and NK decapeptide domains of all three proteins are highly conserved. Nk6 is expressed in the embryonic brain, ventral nerve cord, hindgut, and internal head structures. Nerve cord expression is in midline precursors, several ventral and intermediate column neuroblasts, and later in neurons but not glia, similar to the known expression of Nkx6 genes in the neural tube. We show genetically that Nk6 is positively regulated, directly or indirectly, by vnd in brain precursors. In vnd mutants, head neuroectoderm Nk6 expression is abolished where it is normally co-expressed with vnd. Conversely, vnd-overexpression leads to ectopic Nk6 expression in the brain. These findings further highlight the importance of interactions between Nk(x)-type genes in regulating their expression.
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Affiliation(s)
- Jay Uhler
- Department of Pathology, University of Michigan, Ann Arbor 48109, USA
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132
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Abstract
A majority of neurons that form the ventral nerve cord send out long axons that cross the midline through anterior or posterior commissures. A smaller fraction extend longitudinally and never cross the midline. The decision to cross the midline is governed by a balance of attractive and repulsive signals. We have explored the role of a G-protein, Galphaq, in altering this balance in Drosophila. A splice variant of Galphaq, dgqalpha3, is expressed in early axonal growth cones, which go to form the commissures in the Drosophila embryonic CNS. Misexpression of a gain-of-function transgene of dgqalpha3 (AcGq3) leads to ectopic midline crossing. Analysis of the AcGq3 phenotype in roundabout and frazzled mutants shows that AcGq3 function is antagonistic to Robo signaling and requires Frazzled to promote ectopic midline crossing. Our results show for the first time that a heterotrimeric G-protein can affect the balance of attractive versus repulsive cues in the growth cone and that it can function as a component of signaling pathways that regulate axonal pathfinding.
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133
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Oland LA, Tolbert LP. Key interactions between neurons and glial cells during neural development in insects. ANNUAL REVIEW OF ENTOMOLOGY 2002; 48:89-110. [PMID: 12194908 DOI: 10.1146/annurev.ento.48.091801.112654] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Nervous system function is entirely dependent on the intricate and precise pattern of connections made by individual neurons. Much of the insightful research into mechanisms underlying the development of this pattern of connections has been done in insect nervous systems. Studies of developmental mechanisms have revealed critical interactions between neurons and glia, the non-neuronal cells of the nervous system. Glial cells provide trophic support for neurons, act as struts for migrating neurons and growing axons, form boundaries that restrict neuritic growth, and have reciprocal interactions with neurons that govern specification of cell fate and axonal pathfinding. The molecular mechanisms underlying these interactions are beginning to be understood. Because many of the cellular and molecular mechanisms underlying neural development appear to be common across disparate insect species, and even between insects and vertebrates, studies in developing insect nervous systems are elucidating mechanisms likely to be of broad significance.
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Affiliation(s)
- Lynne A Oland
- Arizona Research Laboratories Division of Neurobiology, University of Arizona, Tucson, Arizona 85721, USA.
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134
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Georgiou M, Tear G. Commissureless is required both in commissural neurones and midline cells for axon guidance across the midline. Development 2002; 129:2947-56. [PMID: 12050141 DOI: 10.1242/dev.129.12.2947] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the absence of Commissureless (Comm) function, axons are unable to extend across the central nervous system midline. Comm downregulates levels of Roundabout (Robo), a receptor for the midline repellent Slit, in order to allow axons to cross the midline. comm transcript is expressed at high levels in the midline glia and Comm protein accumulates on axons at the midline. This has led to the hypothesis that Comm moves from the midline glia to the axons, where it can reduce Robo levels. We have found that expression of Comm in the midline cells is unable to rescue the comm phenotype and that tagged versions of Comm are not transferred to axons. A re-examination of Comm protein expression and the use of targeted RNA interference reveal that correct midline crossing requires that Comm is expressed in the commissural axons and midline glia. We suggest that accumulation of Comm protein at the midline spatially limits Comm activity and prevents it from being active on the contralateral side of the central nervous system.
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Affiliation(s)
- Marios Georgiou
- Molecular Neurobiology Group, MRC Centre for Developmental Neurobiology, Guy's Hospital Campus, King's College, London SE1 1UL, UK
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135
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Shamloula HK, Mbogho MP, Pimentel AC, Chrzanowska-Lightowlers ZMA, Hyatt V, Okano H, Venkatesh TR. rugose (rg), a Drosophila A kinase anchor protein, is required for retinal pattern formation and interacts genetically with multiple signaling pathways. Genetics 2002; 161:693-710. [PMID: 12072466 PMCID: PMC1462145 DOI: 10.1093/genetics/161.2.693] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In the developing Drosophila eye, cell fate determination and pattern formation are directed by cell-cell interactions mediated by signal transduction cascades. Mutations at the rugose locus (rg) result in a rough eye phenotype due to a disorganized retina and aberrant cone cell differentiation, which leads to reduction or complete loss of cone cells. The cone cell phenotype is sensitive to the level of rugose gene function. Molecular analyses show that rugose encodes a Drosophila A kinase anchor protein (DAKAP 550). Genetic interaction studies show that rugose interacts with the components of the EGFR- and Notch-mediated signaling pathways. Our results suggest that rg is required for correct retinal pattern formation and may function in cell fate determination through its interactions with the EGFR and Notch signaling pathways.
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Affiliation(s)
- Hoda K Shamloula
- Department of Biology, City College and The Graduate Center, City University of New York, New York 10031, USA
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136
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Sedaghat Y, Miranda WF, Sonnenfeld MJ. ThejingZn-finger transcription factor is a mediator of cellular differentiation in theDrosophilaCNS midline and trachea. Development 2002; 129:2591-606. [PMID: 12015288 DOI: 10.1242/dev.129.11.2591] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We establish that the jing zinc-finger transcription factor plays an essential role in controlling CNS midline and tracheal cell differentiation. jing transcripts and protein accumulate from stage 9 in the CNS midline, trachea and in segmental ectodermal stripes. JING protein localizes to the nuclei of CNS midline and tracheal cells implying a regulatory role during their development. Loss of jing-lacZ expression in homozygous sim mutants and induction of jing-lacZ by ectopic sim expression establish that jing is part of the CNS midline lineage. We have isolated embryonic recessive lethal jing mutations that display genetic interactions in the embryonic CNS midline and trachea, with mutations in the bHLH-PAS genes single-minded and trachealess, and their downstream target genes (slit and breathless). Loss- and gain-of-function jing is associated with defects in CNS axon and tracheal tubule patterning. In jing homozygous mutant embryos, reductions in marker gene expression and inappropriate apoptosis in the CNS midline and trachea establish that jing is essential for the proper differentiation and survival of these lineages. These results establish that jing is a key component of CNS midline and tracheal cell development. Given the similarities between JING and the vertebrate CCAAT-binding protein AEBP2, we propose that jing regulates transcriptional mechanisms in Drosophila embryos and promotes cellular differentiation in ectodermal derivatives.
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Affiliation(s)
- Yalda Sedaghat
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ontario K1H 8M5, Canada
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137
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Fascetti N, Baumgartner S. Expression of Drosophila Ten-a, a dimeric receptor during embryonic development. Mech Dev 2002; 114:197-200. [PMID: 12175511 DOI: 10.1016/s0925-4773(02)00055-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Ten-a and Ten-m are the two Drosophila members of the newly discovered Ten-m family of dimeric type II transmembrane proteins. Here, we report complete cDNA cloning and protein expression patterns of Ten-a. The Ten-a protein, a dimeric receptor of about 500 kDa is mainly expressed on axons of the embryonic central nervous system and on muscle attachment sites.
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Affiliation(s)
- Nora Fascetti
- Section for Developmental Biology, Lund University, BMC B13, 22184 Lund, Sweden
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138
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Hortsch M, Paisley KL, Tian MZ, Qian M, Bouley M, Chandler R. The axonal localization of large Drosophila ankyrin2 protein isoforms is essential for neuronal functionality. Mol Cell Neurosci 2002; 20:43-55. [PMID: 12056839 DOI: 10.1006/mcne.2002.1113] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In polarized cells, such as neurons, ankyrin-type proteins are the major molecules that link the actin-spectrin-based membrane cytoskeleton to the plasma membrane. In Drosophila the second ankyrin gene, Dank2, is exclusively expressed in neuronal cells. Similar to ankyrin genes in other organisms, the Dank2 gene generates several ankyrin protein isoforms by differential splicing. Here we report that in Drosophila, the short Dank2 protein isoform is restricted to neuronal cell bodies and is excluded from axons, whereas the long Dank2 isoforms are localized specifically to axons. Thus the long and short Dank2 protein isoforms are localized to complementary neuronal subdomains, demonstrating that in vivo the composition of the neuronal cortical cytoskeleton is highly polarized. We show that once polarization is established, it persists during later stages of Drosophila development. We also present genetic evidence that the absence of axonal Dank2 protein is lethal.
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MESH Headings
- Animals
- Ankyrins/genetics
- Ankyrins/metabolism
- Axons/metabolism
- Axons/ultrastructure
- Cell Adhesion Molecules, Neuronal/genetics
- Cell Adhesion Molecules, Neuronal/metabolism
- Cell Differentiation/physiology
- Cell Polarity/physiology
- Cloning, Molecular
- Cytoskeleton/metabolism
- Drosophila Proteins
- Drosophila melanogaster/cytology
- Drosophila melanogaster/embryology
- Drosophila melanogaster/metabolism
- Embryo, Nonmammalian/cytology
- Embryo, Nonmammalian/embryology
- Embryo, Nonmammalian/metabolism
- Female
- Gene Expression Regulation, Developmental/physiology
- Genes, Lethal/genetics
- Male
- Molecular Sequence Data
- Mutation/genetics
- Nervous System/cytology
- Nervous System/embryology
- Nervous System/metabolism
- Protein Isoforms/genetics
- Protein Isoforms/metabolism
- Pupa/cytology
- Pupa/growth & development
- Pupa/metabolism
- Sequence Homology, Amino Acid
- Sequence Homology, Nucleic Acid
- Transcription, Genetic/genetics
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Affiliation(s)
- Michael Hortsch
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor 48109-0616, USA.
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139
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Sullivan KMC, Rubin GM. The Ca(2+)-calmodulin-activated protein phosphatase calcineurin negatively regulates EGF receptor signaling in Drosophila development. Genetics 2002; 161:183-93. [PMID: 12019233 PMCID: PMC1462097 DOI: 10.1093/genetics/161.1.183] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Calcineurin is a Ca(2+)-calmodulin-activated, Ser-Thr protein phosphatase that is essential for the translation of Ca(2+) signals into changes in cell function and development. We carried out a dominant modifier screen in the Drosophila eye using an activated form of the catalytic subunit to identify new targets, regulators, and functions of calcineurin. An examination of 70,000 mutagenized flies yielded nine specific complementation groups, four that enhanced and five that suppressed the activated calcineurin phenotype. The gene canB2, which encodes the essential regulatory subunit of calcineurin, was identified as a suppressor group, demonstrating that the screen was capable of identifying genes relevant to calcineurin function. We demonstrated that a second suppressor group was sprouty, a negative regulator of receptor tyrosine kinase signaling. Wing and eye phenotypes of ectopic activated calcineurin and genetic interactions with components of signaling pathways suggested a role for calcineurin in repressing Egf receptor/Ras signal transduction. On the basis of our results, we propose that calcineurin, upon activation by Ca(2+)-calmodulin, cooperates with other factors to negatively regulate Egf receptor signaling at the level of sprouty and the GTPase-activating protein Gap1.
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Affiliation(s)
- Kathleen M C Sullivan
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3200, USA.
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140
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Crowner D, Madden K, Goeke S, Giniger E. Lola regulates midline crossing of CNS axons in Drosophila. Development 2002; 129:1317-25. [PMID: 11880341 DOI: 10.1242/dev.129.6.1317] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The pattern and level of expression of axon guidance proteins must be choreographed with exquisite precision for the nervous system to develop its proper connectivity. Previous work has shown that the transcription factor Lola is required for central nervous system (CNS) axons of Drosophila to extend longitudinally. We show here that Lola is simultaneously required to repel these same longitudinal axons away from the midline, and that it acts, in part, by augmenting the expression both of the midline repellant, Slit, and of its axonal receptor, Robo. Lola is thus the examplar of a class of axon guidance molecules that control axon patterning by coordinating the regulation of multiple, independent guidance genes, ensuring that they are co-expressed at the correct time, place and relative level.
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Affiliation(s)
- Daniel Crowner
- Division of Basic Sciences, Program in Developmental Biology, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave, N., Seattle, WA 98109, USA
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141
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Beck G, Fainzilber M. Genetic models meet trophic mechanisms: EGF family members are gliatrophins in Drosophila. Neuron 2002; 33:673-5. [PMID: 11879645 DOI: 10.1016/s0896-6273(02)00619-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Trophic survival mechanisms are crucial for the determination of cell numbers in the developing vertebrate nervous system, but important neurotrophic factor families such as the neurotrophins have not yet been found in either Drosophila or C. elegans. Two independent studies on distinct glial populations in Drosophila have now shown that their survival is regulated by EGF family members secreted by adjacent neurons. Fly genetics thus promises new insights on trophic signaling mechanisms and confirms that trophic regulation of cell survival is an evolutionarily ancient mechanism for building the nervous system.
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Affiliation(s)
- Gad Beck
- Department of Biological Chemistry, Weizmann Institute of Science, 76100, Rehovot, Israel
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142
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Mellerick DM, Modica V. Regulated vnd expression is required for both neural and glial specification in Drosophila. JOURNAL OF NEUROBIOLOGY 2002; 50:118-36. [PMID: 11793359 DOI: 10.1002/neu.10022] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The Drosophila embryonic CNS arises from the neuroectoderm, which is divided along the dorsal-ventral axis into two halves by specialized mesectodermal cells at the ventral midline. The neuroectoderm is in turn divided into three longitudinal stripes--ventral, intermediate, and lateral. The ventral nervous system defective, or vnd, homeobox gene is expressed from cellularization throughout early neural development in ventral neuroectodermal cells, neuroblasts, and ganglion mother cells, and later in an unrelated pattern in neurons. Here, in the context of the dorsal-ventral location of precursor cells, we reassess the vnd loss- and gain-of-function CNS phenotypes using cell specific markers. We find that over expression of vnd causes significantly more profound effects on CNS cell specification than vnd loss. The CNS defects seen in vnd mutants are partly caused by loss of progeny of ventral neuroblasts-the commissures are fused and the longitudinal connectives are aberrantly positioned close to the ventral midline. The commissural vnd phenotype is associated with defects in cells that arise from the mesectoderm, where the VUM neurons have pathfinding defects, the MP1 neurons are mis-specified, and the midline glia are reduced in number. vnd over expression results in the mis-specification of progeny arising from all regions of the neuroectoderm, including the ventral neuroblasts that normally express the gene. The CNS of embryos that over express vnd is highly disrupted, with weak longitudinal connectives that are placed too far from the ventral midline and severely reduced commissural formation. The commissural defects seen in vnd gain-of-function mutants correlate with midline glial defects, whereas the mislocalization of interneurons coincides with longitudinal glial mis-specification. Thus, Drosophila neural and glial specification requires that vnd expression by tightly regulated.
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Affiliation(s)
- Dervla M Mellerick
- Department of Pathology, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA.
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143
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McGregor JR, Xi R, Harrison DA. JAK signaling is somatically required for follicle cell differentiation inDrosophila. Development 2002; 129:705-17. [PMID: 11830571 DOI: 10.1242/dev.129.3.705] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Janus kinase (JAK) pathway activity is an integral part of signaling through a variety of ligands and receptors in mammals. The extensive re-utilization and pleiotropy of this pathway in vertebrate development is conserved in other animals as well. In Drosophila melanogaster, JAK signaling has been implicated in embryonic pattern formation, sex determination, larval blood cell development, wing venation, planar polarity in the eye, and formation of other adult structures. Here we describe several roles for JAK signaling in Drosophila oogenesis. The gene for a JAK pathway ligand, unpaired, is expressed specifically in the polar follicle cells, two pairs of somatic cells at the anterior and posterior poles of the developing egg chamber. Consistent with unpaired expression, reduced JAK pathway activity results in the fusion of developing egg chambers. A primary defect of these chambers is the expansion of the polar cell population and concomitant loss of interfollicular stalk cells. These phenotypes are enhanced by reduction of unpaired activity, suggesting that Unpaired is a necessary ligand for the JAK pathway in oogenesis. Mosaic analysis of both JAK pathway transducers, hopscotch and Stat92E, reveals that JAK signaling is specifically required in the somatic follicle cells. Moreover, JAK activity is also necessary for the initial commitment of epithelial follicle cells. Many of these roles are in common with, but distinct from, the known functions of Notch signaling in oogenesis. Consistent with these data is a model in which Notch signaling determines a pool of cells to be competent to adopt stalk or polar fate, while JAK signaling assigns specific identity within that competent pool.
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Affiliation(s)
- Jennifer R McGregor
- University of Kentucky, T. H. Morgan School of Biological Sciences, 101 Morgan Building, Lexington, KY 40506, USA
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144
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Bergmann A, Tugentman M, Shilo BZ, Steller H. Regulation of cell number by MAPK-dependent control of apoptosis: a mechanism for trophic survival signaling. Dev Cell 2002; 2:159-70. [PMID: 11832242 DOI: 10.1016/s1534-5807(02)00116-8] [Citation(s) in RCA: 167] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Trophic mechanisms in which neighboring cells mutually control their survival by secreting extracellular factors play an important role in determining cell number. However, how trophic signaling suppresses cell death is still poorly understood. We now show that the survival of a subset of midline glia cells in Drosophila depends upon direct suppression of the proapoptotic protein HID via the EGF receptor/RAS/MAPK pathway. The TGFalpha-like ligand SPITZ is activated in the neurons, and glial cells compete for limited amounts of secreted SPITZ to survive. In midline glia that fail to activate the EGFR pathway, HID induces apoptosis by blocking a caspase inhibitor, Diap1. Therefore, a direct pathway linking a specific extracellular survival factor with a caspase-based death program has been established.
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Affiliation(s)
- Andreas Bergmann
- Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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145
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Hummel T, Attix S, Gunning D, Zipursky SL. Temporal control of glial cell migration in the Drosophila eye requires gilgamesh, hedgehog, and eye specification genes. Neuron 2002; 33:193-203. [PMID: 11804568 DOI: 10.1016/s0896-6273(01)00581-5] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In the Drosophila visual system, photoreceptor neurons (R cells) extend axons towards glial cells located at the posterior edge of the eye disc. In gilgamesh (gish) mutants, glial cells invade anterior regions of the eye disc prior to R cell differentiation and R cell axons extend anteriorly along these cells. gish encodes casein kinase Igamma. gish, sine oculis, eyeless, and hedgehog (hh) act in the posterior region of the eye disc to prevent precocious glial cell migration. Targeted expression of Hh in this region rescues the gish phenotype, though the glial cells do not require the canonical Hh signaling pathway to respond. We propose that the spatiotemporal control of glial cell migration plays a critical role in determining the directionality of R cell axon outgrowth.
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Affiliation(s)
- Thomas Hummel
- Department of Biological Chemistry, Howard Hughes Medical Institute, University of California, Los Angeles, School of Medicine, 5-748 MRL, 675 Charles Young Drive South, Los Angeles, CA 90095, USA
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146
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Montalta-He H, Leemans R, Loop T, Strahm M, Certa U, Primig M, Acampora D, Simeone A, Reichert H. Evolutionary conservation of otd/Otx2 transcription factor action: a genome-wide microarray analysis in Drosophila. Genome Biol 2002; 3:RESEARCH0015. [PMID: 11983056 PMCID: PMC115189 DOI: 10.1186/gb-2002-3-4-research0015] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2002] [Revised: 02/05/2002] [Accepted: 02/13/2002] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Homeobox genes of the orthodenticle (otd)/Otx family have conserved roles in the embryogenesis of head and brain. Gene replacement experiments show that the Drosophila otd gene and orthologous mammalian Otx genes are functionally equivalent, in that overexpression of either gene in null mutants of Drosophila or mouse can restore defects in cephalic and brain development. This suggests that otd and Otx genes control a comparable subset of downstream target genes in either organism. Here we use quantitative transcript imaging to analyze this equivalence of otd and Otx gene action at a genomic level. RESULTS Oligonucleotide arrays representing 13,400 annotated Drosophila genes were used to study differential gene expression in flies in which either the Drosophila otd gene or the human Otx2 gene was overexpressed. Two hundred and eighty-seven identified transcripts showed highly significant changes in expression levels in response to otd overexpression, and 682 identified transcripts showed highly significant changes in expression levels in response to Otx2 overexpression. Among these, 93 showed differential expression changes following overexpression of either otd or Otx2, and for 90 of these, comparable changes were observed under both experimental conditions. We postulate that these transcripts are common downstream targets of the fly otd gene and the human Otx2 gene in Drosophila. CONCLUSION Our experiments indicate that approximately one third of the otd-regulated transcripts also respond to overexpression of the human Otx2 gene in Drosophila. These common otd/Otx2 downstream genes are likely to represent the molecular basis of the functional equivalence of otd and Otx2 gene action in Drosophila.
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Affiliation(s)
- Haiqiong Montalta-He
- Institute of Zoology, Biozentrum/Pharmazentrum, Klingelbergstrasse 50, University of Basel, CH-4056 Basel, Switzerland.
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147
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Klapper R, Stute C, Schomaker O, Strasser T, Janning W, Renkawitz-Pohl R, Holz A. The formation of syncytia within the visceral musculature of the Drosophila midgut is dependent on duf, sns and mbc. Mech Dev 2002; 110:85-96. [PMID: 11744371 DOI: 10.1016/s0925-4773(01)00567-6] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The visceral musculature of the Drosophila midgut consists of an inner layer of circular and an outer layer of longitudinal muscles. Here, we show that the circular muscles are organised as binucleate syncytia that persist through metamorphosis. At stage 11, prior to the onset of the fusion processes, we detected two classes of myoblasts within the visceral trunk mesoderm. One class expresses the founder-cell marker rP298-LacZ in a one- to two-cells-wide strip along the ventralmost part of the visceral mesoderm, whereas the adjacent two to three cell rows are characterised by the expression of Sticks-and-stones (SNS). During the process of cell fusion at stage 12 SNS expression decreases within the newly formed syncytia that spread out dorsally over the midgut. At both margins of the visceral band several cells remain unfused and continue to express SNS. Additional rP298-LacZ-expressing cells arise from the posterior tip of the mesoderm, migrate anteriorly and eventually fuse with the remaining SNS-expressing cells, generating the longitudinal muscles. Thus, although previous studies proposed a separate primordium for the longitudinal musculature located at the posteriormost part of the mesoderm anlage, our cell lineage analyses as well as our morphological observations reveal that a second population of cells originates from the trunk mesoderm. Mutations of genes that are involved in somatic myoblast fusion, such as sns, dumbfounded (duf) or myoblast city (mbc), also cause severe defects within the visceral musculature. The circular muscles are highly unorganised while the longitudinal muscles are almost absent. Thus the fusion process seems to be essential for a proper visceral myogenesis. Our results provide strong evidence that the founder-cell hypothesis also applies to visceral myogenesis, employing the same genetic components as are used in the somatic myoblast fusion processes.
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Affiliation(s)
- Robert Klapper
- Institut für Allgemeine Zoologie und Genetik der Westfälischen Wilhelms-Universität, Schlossplatz 5, 48149 Münster, Germany.
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148
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Abstract
The pannier (pnr) gene of Drosophila encodes a zinc-finger transcription factor of the GATA family and is involved in several developmental processes during embryonic and imaginal development. We report some novel aspects of the regulation and function of pnr during embryogenesis. Previous work has shown that pnr is activated by decapentaplegic (dpp) in early development, but we find that after stage 10, the roles are reversed and pnr becomes an upstream regulator of dpp. This function of pnr is necessary for the activation of the Dpp pathway in the epidermal cells implicated in dorsal closure and is not mediated by the JNK pathway, which is also necessary for Dpp activity in these cells. In addition, we show that pnr behaves as a selector-like gene in generating morphological diversity in the dorsoventral body axis. It is responsible for maintaining a subdivision of the dorsal half of the embryo into two distinct, dorsomedial and dorsolateral, regions, and also specifies the identity of the dorsomedial region. These results, together with prior work on its function in adults, suggest that pnr is a major factor in the genetic subdivision of the body of Drosophila.
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Affiliation(s)
- H Herranz
- Centro de Biología Molecular, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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149
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Sharrow M, Tiemeyer M. Gliolectin-mediated carbohydrate binding at theDrosophilamidline ensures the fidelity of axon pathfinding. Development 2001; 128:4585-95. [PMID: 11714683 DOI: 10.1242/dev.128.22.4585] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Gliolectin is a carbohydrate-binding protein (lectin) that mediates cell adhesion in vitro and is expressed by midline glial cells in the Drosophila melanogaster embryo. Gliolectin expression is maximal during early pathfinding of commissural axons across the midline (stages 12-13), a process that requires extensive signaling and cell-cell interactions between the midline glia and extending axons. Deletion of the gliolectin locus disrupts the formation of commissural pathways and also delays the completion of longitudinal pathfinding. The disruption in commissure formation is accompanied by reduced axon-glial contact, such that extending axons grow on other axons and form a tightly fasciculated bundle that arches over the midline. By contrast, pioneering commissural axons normally cross the midline as a distributed array of fibers that interdigitate among the midline glia, maximizing contact and, therefor, communication between axon and glia. Restoration of Gliolectin protein expression in the midline glia rescues the observed pathfinding defects of null mutants in a dose-dependent manner. Hypomorphic alleles generated by ethylmethanesulfonate mutagenesis exhibit a similar phenotype in combination with a deletion and these defects are also rescued by transgenic expression of Gliolectin protein. The observed phenotypes indicate that carbohydrate-lectin interactions at the Drosophila midline provide the necessary surface contact to capture extending axons, thereby ensuring that combinatorial codes of positive and negative growth signals are interpreted appropriately.
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Affiliation(s)
- M Sharrow
- Department of Cell Biology, Yale University School of Medicine, 333 Cedar St, New Haven, CT 06510, USA
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150
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Dworak HA, Charles MA, Pellerano LB, Sink H. Characterization ofDrosophila hibris, a gene related to human nephrin. Development 2001; 128:4265-76. [PMID: 11684662 DOI: 10.1242/dev.128.21.4265] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hibris encodes a protein that is a newly identified member of the immunoglobulin superfamily and has homology to vertebrate Nephrins and Drosophila Sticks-and-Stones. The Hibris protein has eight Ig-like domains, a fibronectin domain and a 160 amino acid cytoplasmic tail. The hibris transcript is expressed in a broad range of tissues and across life stages. In the embryo, hibris transcript is present in the mesectoderm, then in a group of cells at the developing CNS midline and in a subset of glia. In the periphery, hibris is expressed by fusion competent myoblasts and the epidermal muscle attachment site cells. Deletion analyses show that loss of hibris does not visibly affect embryonic CNS or somatic muscle development. However overexpressing hibris in the somatic mesoderm disrupts myoblast fusion. Furthermore, when overexpressed in the epidermis, Hibris causes comprehensive derangement of muscle insertion locations. A similar myoblast fusion defect is observed when the Drosophila homologs of DM-GRASP/BEN/SC1 (irregular chiasm-roughest and dumbfounded) are deleted together. Our S2 cell aggregation assays have revealed a heterotypic interaction between Hibris and Dumbfounded, but not between Hibris and Irregular Chiasm-Roughest. We propose that Hibris is an extracellular partner for Dumbfounded and potentially mediates the response of myoblasts to this attractant.
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Affiliation(s)
- H A Dworak
- Skirball Institute of Biomolecular Medicine and Department of Pharmacology, New York University Medical School, 540 First Avenue, New York, NY 10016, USA
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