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Li L, Li P, Xue L. The RED domain of Paired is specifically required for Drosophila accessory gland maturation. Open Biol 2015; 5:140179. [PMID: 25694546 PMCID: PMC4345280 DOI: 10.1098/rsob.140179] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The evolutionarily conserved paired domain consists of the N-terminal PAI and the C-terminal RED domains, each containing a helix–turn–helix motif capable of binding DNA. Despite its conserved sequence, the physiological functions of the RED domain remain elusive. Here, we constructed a prd transgene expressing a truncated Paired (Prd) protein without the RED domain, and examined its rescue ability in prd mutants. We found that the RED domain is specifically required for the expression of Acp26Aa and sex peptide in male accessory glands, and the induction of female post-mating response. Our data thus identified an important physiological function for the evolutionarily conserved RED domain.
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Affiliation(s)
- Li Li
- Institute of Intervention Vessel, Shanghai 10th People's Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, 1239 Siping Road, Shanghai 200092, People's Republic of China
| | - Ping Li
- Institute of Intervention Vessel, Shanghai 10th People's Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, 1239 Siping Road, Shanghai 200092, People's Republic of China
| | - Lei Xue
- Institute of Intervention Vessel, Shanghai 10th People's Hospital, Shanghai Key Laboratory of Signaling and Disease Research, School of Life Science and Technology, Tongji University, 1239 Siping Road, Shanghai 200092, People's Republic of China
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2
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Parikh A, Wu J, Blanton RM, Tzanakakis ES. Signaling Pathways and Gene Regulatory Networks in Cardiomyocyte Differentiation. TISSUE ENGINEERING PART B-REVIEWS 2015; 21:377-92. [PMID: 25813860 DOI: 10.1089/ten.teb.2014.0662] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Strategies for harnessing stem cells as a source to treat cell loss in heart disease are the subject of intense research. Human pluripotent stem cells (hPSCs) can be expanded extensively in vitro and therefore can potentially provide sufficient quantities of patient-specific differentiated cardiomyocytes. Although multiple stimuli direct heart development, the differentiation process is driven in large part by signaling activity. The engineering of hPSCs to heart cell progeny has extensively relied on establishing proper combinations of soluble signals, which target genetic programs thereby inducing cardiomyocyte specification. Pertinent differentiation strategies have relied as a template on the development of embryonic heart in multiple model organisms. Here, information on the regulation of cardiomyocyte development from in vivo genetic and embryological studies is critically reviewed. A fresh interpretation is provided of in vivo and in vitro data on signaling pathways and gene regulatory networks (GRNs) underlying cardiopoiesis. The state-of-the-art understanding of signaling pathways and GRNs presented here can inform the design and optimization of methods for the engineering of tissues for heart therapies.
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Affiliation(s)
- Abhirath Parikh
- 1 Lonza Walkersville, Inc. , Lonza Group, Walkersville, Maryland
| | - Jincheng Wu
- 2 Department of Chemical and Biological Engineering, Tufts University , Medford, Massachusetts
| | - Robert M Blanton
- 3 Division of Cardiology, Molecular Cardiology Research Institute , Tufts Medical Center, Tufts School of Medicine, Boston, Massachusetts
| | - Emmanuel S Tzanakakis
- 2 Department of Chemical and Biological Engineering, Tufts University , Medford, Massachusetts.,4 Tufts Clinical and Translational Science Institute (CTSI) , Boston, Massachusetts
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Manavalan MA, Gaziova I, Bhat KM. The midline protein regulates axon guidance by blocking the reiteration of neuroblast rows within the Drosophila ventral nerve cord. PLoS Genet 2013; 9:e1004050. [PMID: 24385932 PMCID: PMC3873230 DOI: 10.1371/journal.pgen.1004050] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 11/05/2013] [Indexed: 01/30/2023] Open
Abstract
Guiding axon growth cones towards their targets is a fundamental process that occurs in a developing nervous system. Several major signaling systems are involved in axon-guidance, and disruption of these systems causes axon-guidance defects. However, the specific role of the environment in which axons navigate in regulating axon-guidance has not been examined in detail. In Drosophila, the ventral nerve cord is divided into segments, and half-segments and the precursor neuroblasts are formed in rows and columns in individual half-segments. The row-wise expression of segment-polarity genes within the neuroectoderm provides the initial row-wise identity to neuroblasts. Here, we show that in embryos mutant for the gene midline, which encodes a T-box DNA binding protein, row-2 neuroblasts and their neuroectoderm adopt a row-5 identity. This reiteration of row-5 ultimately creates a non-permissive zone or a barrier, which prevents the extension of interneuronal longitudinal tracts along their normal anterior-posterior path. While we do not know the nature of the barrier, the axon tracts either stall when they reach this region or project across the midline or towards the periphery along this zone. Previously, we had shown that midline ensures ancestry-dependent fate specification in a neuronal lineage. These results provide the molecular basis for the axon guidance defects in midline mutants and the significance of proper specification of the environment to axon-guidance. These results also reveal the importance of segmental polarity in guiding axons from one segment to the next, and a link between establishment of broad segmental identity and axon guidance. During nervous system development, once formed from neuroblasts, neurons grow axons in the direction of their synaptic partners. Genetic forces guide these axon growth cones towards the target. This is known as axon guidance or pathfinding. There are a number of proteins that regulate axon-pathfinding. The well-known examples are the Slit and its receptor Roundabout, and Netrin and its receptor Frazzled. The Drosophila embryo and the nervous system are divided into segments by segmentation genes. Mutations in segmentation genes affect axon guidance, although how they do so is not well understood. In our work described here, we show that the T-box protein Midline prevents mis-specification of neuroblast rows, in particular, it prevents row 2 from becoming row 5. Thus, in midline mutants, row 2 changes into row 5, ultimately creating a non-permissive barrier that prevents axons from following their defined path. Thus, axons stop and diverge when they reach this barrier. Our results show how mutations in segmentation genes can affect axon guidance and how significant the environment is for axon-pathfinding. Our work is also a cautionary reminder that guidance defects need to be interpreted with care and can arise due to a variety of other defects.
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Affiliation(s)
- Mary Ann Manavalan
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch School of Medicine, Galveston, Texas, United States of America
| | - Ivana Gaziova
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch School of Medicine, Galveston, Texas, United States of America
| | - Krishna Moorthi Bhat
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch School of Medicine, Galveston, Texas, United States of America
- * E-mail:
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4
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Frank CA. Homeostatic plasticity at the Drosophila neuromuscular junction. Neuropharmacology 2013; 78:63-74. [PMID: 23806804 DOI: 10.1016/j.neuropharm.2013.06.015] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2013] [Revised: 05/31/2013] [Accepted: 06/11/2013] [Indexed: 02/07/2023]
Abstract
In biology, homeostasis refers to how cells maintain appropriate levels of activity. This concept underlies a balancing act in the nervous system. Synapses require flexibility (i.e. plasticity) to adjust to environmental challenges. Yet there must also exist regulatory mechanisms that constrain activity within appropriate physiological ranges. An abundance of evidence suggests that homeostatic regulation is critical in this regard. In recent years, important progress has been made toward identifying molecules and signaling processes required for homeostatic forms of neuroplasticity. The Drosophila melanogaster third instar larval neuromuscular junction (NMJ) has been an important experimental system in this effort. Drosophila neuroscientists combine genetics, pharmacology, electrophysiology, imaging, and a variety of molecular techniques to understand how homeostatic signaling mechanisms take shape at the synapse. At the NMJ, homeostatic signaling mechanisms couple retrograde (muscle-to-nerve) signaling with changes in presynaptic calcium influx, changes in the dynamics of the readily releasable vesicle pool, and ultimately, changes in presynaptic neurotransmitter release. Roles in these processes have been demonstrated for several molecules and signaling systems discussed here. This review focuses primarily on electrophysiological studies or data. In particular, attention is devoted to understanding what happens when NMJ function is challenged (usually through glutamate receptor inhibition) and the resulting homeostatic responses. A significant area of study not covered in this review, for the sake of simplicity, is the homeostatic control of synapse growth, which naturally, could also impinge upon synapse function in myriad ways. This article is part of the Special Issue entitled 'Homeostatic Synaptic Plasticity'.
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Affiliation(s)
- C Andrew Frank
- Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA.
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5
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Watson JD, Crews ST. Formation and specification of a Drosophila dopaminergic precursor cell. Development 2012; 139:3316-25. [PMID: 22874915 DOI: 10.1242/dev.079525] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Dopaminergic neurons play important roles in animal behavior, including motivation, reward and locomotion. The Drosophila dopaminergic H-cell interneuron is an attractive system for studying the genetics of neural development because analysis is focused on a single neuronal cell type. Here we provide a mechanistic understanding of how MP3, the precursor to the H-cell, forms and acquires its identity. We show that the gooseberry/gooseberry-neuro (gsb/gsb-n) transcription factor genes act to specify MP3 cell fate. It is proposed that single-minded commits neuroectodermal cells to a midline fate, followed by a series of signaling events that result in the formation of a single gsb(+)/gsb-n(+) MP3 cell per segment. The wingless signaling pathway establishes a midline anterior domain by activating expression of the forkhead transcription factors sloppy paired 1 and sloppy paired 2. This is followed by hedgehog signaling that activates gsb/gsb-n expression in a subgroup of anterior cells. Finally, Notch signaling results in the selection of a single MP3, with the remaining cells becoming midline glia. In MP3, gsb/gsb-n direct H-cell development, in large part by activating expression of the lethal of scute and tailup H-cell regulatory genes. Thus, a series of signaling and transcriptional events result in the specification of a unique dopaminergic precursor cell. Additional genetic experiments indicate that the molecular mechanisms that govern MP3/H-cell development might also direct the development of non-midline dopaminergic neurons.
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Affiliation(s)
- Joseph D Watson
- Department of Biochemistry and Biophysics, Program in Molecular Biology and Biotechnology, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
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Fujioka M, Jaynes JB. Regulation of a duplicated locus: Drosophila sloppy paired is replete with functionally overlapping enhancers. Dev Biol 2011; 362:309-19. [PMID: 22178246 DOI: 10.1016/j.ydbio.2011.12.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Revised: 11/16/2011] [Accepted: 12/01/2011] [Indexed: 11/28/2022]
Abstract
In order to investigate regulation and redundancy within the sloppy paired (slp) locus, we analyzed 30 kilobases of DNA encompassing the tandem, coordinately regulated slp1 and slp2 transcription units. We found a remarkable array of stripe enhancers with overlapping activities surrounding the slp1 transcription unit, and, unexpectedly, glial cell enhancers surrounding slp2. The slp stripe regulatory region generates 7 stripes at blastoderm, and later 14 stripes that persist throughout embryogenesis. Phylogenetic analysis among drosophilids suggests that the multiplicity of stripe enhancers did not evolve through recent duplication. Most of the direct integration among cis-regulatory modules appears to be simply additive, with one notable exception. Despite the apparent redundancy among stripe enhancers, transgenic rescue suggests that most are required for full function, to maintain wingless expression and parasegment boundaries throughout embryogenesis. Transgenic rescue also reveals indirect positive autoregulation by the 7 early stripes, without which alternate stripes within the 14-stripe pattern are lost, leading to embryos with a pair-rule phenotype.
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Affiliation(s)
- Miki Fujioka
- Dept. of Biochemistry and Molecular Biology, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA
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Brancaccio M, Pivetta C, Granzotto M, Filippis C, Mallamaci A. Emx2 and Foxg1 inhibit gliogenesis and promote neuronogenesis. Stem Cells 2010; 28:1206-18. [PMID: 20506244 DOI: 10.1002/stem.443] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Neural stem cells (NSCs) give rise to all cell types forming the cortex: neurons, astrocytes, and oligodendrocytes. The transition from the former to the latter ones takes place via lineage-restricted progenitors in a highly regulated way. This process is mastered by large sets of genes, among which some implicated in central nervous system pattern formation. The aim of this study was to disentangle the kinetic and histogenetic roles exerted by two of these genes, Emx2 and Foxg1, in cortico-cerebral precursors. For this purpose, we set up a new integrated in vitro assay design. Embryonic cortical progenitors were transduced with lentiviral vectors driving overexpression of Emx2 and Foxg1 in NSCs and neuronal progenitors. Cells belonging to different neuronogenic and gliogenic compartments were labeled by spectrally distinguishable fluoroproteins driven by cell type-specific promoters and by cell type-specific antibodies and were scored via multiplex cytofluorometry and immunocytofluorescence. A detailed picture of Emx2 and Foxg1 activities in cortico-cerebral histogenesis resulted from this study. Unexpectedly, we found that both genes inhibit gliogenesis and promote neuronogenesis, through distinct mechanisms, and Foxg1 also dramatically stimulates neurite outgrowth. Remarkably, such activities, alone or combined, may be exploited to ameliorate the neuronal output obtainable from neural cultures, for purposes of cell-based brain repair.
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Affiliation(s)
- Marco Brancaccio
- SISSA, Neurobiology Sector, Laboratory of Cerebral Cortex Development, Trieste, Italy
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Erezyilmaz DF, Kelstrup HC, Riddiford LM. The nuclear receptor E75A has a novel pair-rule-like function in patterning the milkweed bug, Oncopeltus fasciatus. Dev Biol 2009; 334:300-10. [PMID: 19580803 DOI: 10.1016/j.ydbio.2009.06.038] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 06/17/2009] [Accepted: 06/27/2009] [Indexed: 12/16/2022]
Abstract
Genetic studies of the fruit fly Drosophila have revealed a hierarchy of segmentation genes (maternal, gap, pair-rule and HOX) that subdivide the syncytial blastoderm into sequentially finer-scale coordinates. Within this hierarchy, the pair-rule genes translate gradients of information into periodic stripes of expression. How pair-rule genes function during the progressive mode of segmentation seen in short and intermediate-germ insects is an ongoing question. Here we report that the nuclear receptor Of'E75A is expressed with double segment periodicity in the head and thorax. In the abdomen, Of'E75A is expressed in a unique pattern during posterior elongation, and briefly resembles a sequence that is typical of pair-rule genes. Depletion of Of'E75A mRNA caused loss of a subset of odd-numbered parasegments, as well as parasegment 6. Because these parasegments straddle segment boundaries, we observe fusions between adjacent segments. Finally, expression of Of'E75A in the blastoderm requires even-skipped, which is a gap gene in Oncopeltus. These data show that the function of Of'E75A during embryogenesis shares many properties with canonical pair-rule genes in other insects. They further suggest that parasegment specification may occur through irregular and episodic pair-rule-like activity.
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Affiliation(s)
- Deniz F Erezyilmaz
- Department of Biology, University of Washington, Seattle, WA 98195-1800, USA.
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9
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Chaves M, Albert R. Studying the effect of cell division on expression patterns of the segment polarity genes. J R Soc Interface 2008; 5 Suppl 1:S71-84. [PMID: 18434279 PMCID: PMC2706454 DOI: 10.1098/rsif.2007.1345.focus] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 04/02/2008] [Indexed: 11/12/2022] Open
Abstract
The segment polarity gene family, and its gene regulatory network, is at the basis of Drosophila embryonic development. The network's capacity for generating and robustly maintaining a specific gene expression pattern has been investigated through mathematical modelling. The models have provided several useful insights by suggesting essential network links, or uncovering the importance of the relative time scales of different biological processes in the formation of the segment polarity genes' expression patterns. But the developmental pattern formation process raises many other questions. Two of these questions are analysed here: the dependence of the signalling protein sloppy paired on the segment polarity genes and the effect of cell division on the segment polarity genes' expression patterns. This study suggests that cell division increases the robustness of the segment polarity network with respect to perturbations in biological processes.
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Affiliation(s)
- Madalena Chaves
- COMORE, INRIA2004 Route des Lucioles, BP 93, 06902 Sophia Antipolis, France
| | - Réka Albert
- Department of Physics and Huck Institutes for the Life Sciences, Pennsylvania State UniversityUniversity Park, PA 16802, USA
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10
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Lindner JR, Hillman PR, Barrett AL, Jackson MC, Perry TL, Park Y, Datta S. The Drosophila Perlecan gene trol regulates multiple signaling pathways in different developmental contexts. BMC DEVELOPMENTAL BIOLOGY 2007; 7:121. [PMID: 17980035 PMCID: PMC2174950 DOI: 10.1186/1471-213x-7-121] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2007] [Accepted: 11/02/2007] [Indexed: 11/30/2022]
Abstract
Background Heparan sulfate proteoglycans modulate signaling by a variety of growth factors. The mammalian proteoglycan Perlecan binds and regulates signaling by Sonic Hedgehog, Fibroblast Growth Factors (FGFs), Vascular Endothelial Growth Factor (VEGF) and Platelet Derived Growth Factor (PDGF), among others, in contexts ranging from angiogenesis and cardiovascular development to cancer progression. The Drosophila Perlecan homolog trol has been shown to regulate the activity of Hedgehog and Branchless (an FGF homolog) to control the onset of stem cell proliferation in the developing brain during first instar. Here we extend analysis of trol mutant phenotypes to show that trol is required for a variety of developmental events and modulates signaling by multiple growth factors in different situations. Results Different mutations in trol allow developmental progression to varying extents, suggesting that trol is involved in multiple cell-fate and patterning decisions. Analysis of the initiation of neuroblast proliferation at second instar demonstrated that trol regulates this event by modulating signaling by Hedgehog and Branchless, as it does during first instar. Trol protein is distributed over the surface of the larval brain, near the regulated neuroblasts that reside on the cortical surface. Mutations in trol also decrease the number of circulating plasmatocytes. This is likely to be due to decreased expression of pointed, the response gene for VEGF/PDGF signaling that is required for plasmatocyte proliferation. Trol is found on plasmatocytes, where it could regulate VEGF/PDGF signaling. Finally, we show that in second instar brains but not third instar brain lobes and eye discs, mutations in trol affect signaling by Decapentaplegic (a Transforming Growth Factor family member), Wingless (a Wnt growth factor) and Hedgehog. Conclusion These studies extend the known functions of the Drosophila Perlecan homolog trol in both developmental and signaling contexts. These studies also highlight the fact that Trol function is not dedicated to a single molecular mechanism, but is capable of regulating different growth factor pathways depending on the cell-type and event underway.
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Affiliation(s)
- Jonathan R Lindner
- Department of Biochemistry & Biophysics, Texas A&M University, College Station, Texas, 77843-2128, USA.
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11
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Bhat KM. Wingless activity in the precursor cells specifies neuronal migratory behavior in the Drosophila nerve cord. Dev Biol 2007; 311:613-22. [PMID: 17936746 DOI: 10.1016/j.ydbio.2007.09.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2007] [Revised: 08/29/2007] [Accepted: 09/06/2007] [Indexed: 01/18/2023]
Abstract
Neurons and their precursor cells are formed in different regions within the developing CNS, but they migrate and occupy very specific sites in the mature CNS. The ultimate position of neurons is crucial for establishing proper synaptic connectivity in the brain. In Drosophila, despite its extensive use as a model system to study neurogenesis, we know almost nothing about neuronal migration or its regulation. In this paper, I show that one of the most studied neuronal pairs in the Drosophila nerve cord, RP2/sib, has a complicated migratory route. Based on my studies on Wingless (Wg) signaling, I report that the neuronal migratory pattern is determined at the precursor cell stage level. The results show that Wg activity in the precursor neuroectodermal and neuroblast levels specify neuronal migratory pattern two divisions later, thus, well ahead of the actual migratory event. Moreover, at least two downstream genes, Cut and Zfh1, are involved in this process but their role is at the downstream neuronal level. The functional importance of normal neuronal migration and the requirement of Wg signaling for the process are indicated by the finding that mislocated RP2 neurons in embryos mutant for Wg-signaling fail to properly send out their axon projection.
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Affiliation(s)
- Krishna Moorthi Bhat
- Department of Neuroscience and Cell Biology, University of Texas Medical School, Galveston, TX 77555, USA
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12
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Mondal S, Ivanchuk SM, Rutka JT, Boulianne GL. Sloppy paired 1/2 regulate glial cell fates by inhibiting Gcm Function. Glia 2006; 55:282-93. [PMID: 17091489 DOI: 10.1002/glia.20456] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Organization of the central nervous system during embryonic development is an intricate process involving a host of molecular players. The Drosophila segmentation genes, sloppy paired (slp) 1/2 have been shown to be necessary for development of a neuronal precursor cell subtype, the NB4-2 cells. Here, we show that slp1/2 also have roles in regulating glial cell fates. Using slp1/2 loss-of-function mutants, we show an increase in glial cell markers, glial cells missing (gcm) and reversed polarity. In contrast, misexpression of either slp1 or slp2 causes downregulation of glial cell-specific genes and alters the fate of glial and neuronal cells. Furthermore, we demonstrate that Slp1 and its mammalian ortholog, Foxg1, inhibit Gcm transcriptional activity as well as bind Gcm. Taken together, these data show that Slp1/Foxg1 regulate glial cell fates by inhibiting Gcm function.
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Affiliation(s)
- Soma Mondal
- The Arthur and Sonia Labatt Brain Tumour Research Center, Hospital for Sick Children, Toronto, Ontario, Canada
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Bhat KM. Slit-roundabout signaling neutralizes netrin-Frazzled-mediated attractant cue to specify the lateral positioning of longitudinal axon pathways. Genetics 2005; 170:149-59. [PMID: 15716500 PMCID: PMC1449716 DOI: 10.1534/genetics.104.036863] [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] [Received: 09/24/2004] [Accepted: 01/26/2005] [Indexed: 11/18/2022] Open
Abstract
An extending axon growth cone is subjected to attractant and repellent cues. It is not clear how these growth cones discriminate the two opposing forces and select their projection paths. Here, we report that in the Drosophila nerve cord the growth cones of longitudinal tracts are subjected to attraction by the Netrin-Frazzled pathway. However, the midline Slit neutralizes this pathway in a Robo-dependent manner and prevents Netrin-Frazzled-mediated attraction of longitudinal tracts. Our results suggest that the loss of a neutralizing effect on the Netrin-mediated attraction is responsible for the longitudinal tracts entering the midline in slit mutants as opposed to a loss of repulsion as is currently believed. This effect is not via a direct inhibition of Frazzled by Robo; instead, it is at a level downstream of Frazzled. Thus, the growth cones of longitudinal tracts subjected to two opposing forces are able to block one with the other and specify their correct lateral positioning along the midline.
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Affiliation(s)
- Krishna Moorthi Bhat
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322
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14
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Lee HH, Frasch M. Survey of forkhead domain encoding genes in the Drosophila genome: Classification and embryonic expression patterns. Dev Dyn 2004; 229:357-66. [PMID: 14745961 DOI: 10.1002/dvdy.10443] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Genetic approaches in Drosophila led to the identification of Forkhead, the prototype of forkhead domain transcription factors that are now known to comprise an evolutionarily conserved family of proteins with essential roles in development and differentiation. Sequence analysis of the recently published genomic scaffold sequence from Drosophila melanogaster has allowed us to determine the presumably full complement of forkhead domain encoding genes in this species. We show herein that the Drosophila genome contains 17 forkhead domain encoding genes; 13 of these genes have orthologs in chordate species, and their products can be assigned to 10 of the 17 forkhead domain subclasses known from chordates. One Drosophila forkhead domain gene only has a Caenorhabditis elegans ortholog and may represent a subclass that is absent in chordates, while the remaining three cannot be classified. We present the mRNA expression patterns of seven previously uncharacterized members of this gene family and show that they are expressed in tissues from all three germ layers, including central and peripheral nervous system, epidermis, salivary gland primordia, endoderm, somatic mesoderm, and hemocyte progenitors. Furthermore, the expression patterns of two of these genes, fd19B and fd102C, suggest a role for them as gap genes during early embryonic head segmentation.
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Affiliation(s)
- Hsiu-Hsiang Lee
- Mount Sinai School of Medicine, Brookdale Department of Molecular, Cell and Developmental Biology, New York, New York, USA
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15
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Von Dassow G, Odell GM. Design and constraints of the Drosophila segment polarity module: robust spatial patterning emerges from intertwined cell state switches. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 2002; 294:179-215. [PMID: 12362429 DOI: 10.1002/jez.10144] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The Drosophila segment polarity genes constitute the last tier in the segmentation cascade; their job is to maintain the boundaries between parasegments and provide positional "read-outs" within each parasegment for the entire developmental history of the animal. These genes constitute a relatively well-defined network with a relatively well-understood patterning task. In a previous publication (von Dassow et al. 2000. Nature 406:188-192) we showed that a computer model predicts the segment polarity network to be a robust boundary-making device. Here we elaborate those findings. First, we explore the constraints among parameters that govern the network model. Second, we test architectural variants of the core network, and show that the network tolerates a wide variety of adjustments in design. Third, we evaluate several topologically identical models that incorporate more or less molecular detail, finding that more-complex models perform noticeably better than simplified ones. Fourth, we discuss two instances in which the failure of the network model to behave in a life-like fashion highlights mechanistic details that need further experimental investigation. We conclude with an explanation of how the segment polarity network can be understood as an interwoven conspiracy of simple dynamical elements, several bistable switches and a homeostat. The robustness with which the network as a whole maintains a spatial regime of stable cell state emerges from generic dynamical properties of these simple elements.
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Affiliation(s)
- George Von Dassow
- Department of Zoology, University of Washington, Seattle, Washington 98105, USA.
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Meir E, Munro EM, Odell GM, Von Dassow G. Ingeneue: a versatile tool for reconstituting genetic networks, with examples from the segment polarity network. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 2002; 294:216-51. [PMID: 12362430 DOI: 10.1002/jez.10187] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Here we describe a software tool for synthesizing molecular genetic data into models of genetic networks. Our software program Ingeneue, written in Java, lets the user quickly turn a map of a genetic network into a dynamical model consisting of a set of ordinary differential equations. We developed Ingeneue as part of an ongoing effort to explore the design and evolvability of genetic networks. Ingeneue has three principal advantages over other available mathematical software: it automates instantiation of the same network model in each cell in a 2-D sheet of cells; it constructs model equations from pre-made building blocks corresponding to common biochemical processes; and it automates searches through parameter space, sensitivity analyses, and other common tasks. Here we discuss the structure of the software and some of the issues we have dealt with. We conclude with some examples of results we have achieved with Ingeneue for the Drosophila segment polarity network.
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Affiliation(s)
- Eli Meir
- Department of Zoology, University of Washington, Seattle, Washington 98105, USA.
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17
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Abstract
The Drosophila compound eye is specified by the concerted action of seven nuclear factors that include Eyeless/Pax6. These factors have been called "master control" proteins because loss-of-function mutants lack eyes and ectopic expression can direct ectopic eye development. However, inactivation of these genes does not cause the presumptive eye to change identity. Surprisingly, we find that several of these eye specification genes are not coexpressed in the same embryonic cells-or even in the presumptive eye. We demonstrate that the EGF Receptor and Notch signaling pathways have homeotic functions that are genetically upstream of the eye specification genes, and show that specification occurs much later than previously thought-not during embryonic development but in the second larval stage.
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Affiliation(s)
- J P Kumar
- Department of Cell Biology, Emory University School of Medicine, 1648 Pierce Drive, Atlanta, GA 30322, USA
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18
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Lee HH, Frasch M. Wingless effects mesoderm patterning and ectoderm segmentation events via induction of its downstream target sloppy paired. Development 2000; 127:5497-508. [PMID: 11076769 DOI: 10.1242/dev.127.24.5497] [Citation(s) in RCA: 71] [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
Inactivation of either the secreted protein Wingless (Wg) or the forkhead domain transcription factor Sloppy Paired (Slp) has been shown to produce similar effects in the developing Drosophila embryo. In the ectoderm, both gene products are required for the formation of the segmental portions marked by naked cuticle. In the mesoderm, Wg and Slp activities are crucial for the suppression of bagpipe (bap), and hence visceral mesoderm formation, and the promotion of somatic muscle and heart formation within the anterior portion of each parasegment. In this report, we show that, during these developmental processes, wg and slp act in a common pathway in which slp serves as a direct target of Wg signals that mediates Wg effects in both germ layers. We present evidence that the induction of slp by Wg involves binding of the Wg effector Pangolin (Drosophila Lef-1/TCF) to multiple binding sites within a Wg-responsive enhancer that is located in 5′ flanking regions of the slp1 gene. Based upon our genetic and molecular analysis, we conclude that Wg signaling induces striped expression of Slp in the mesoderm. Mesodermal Slp is then sufficient to abrogate the induction of bagpipe by Dpp/Tinman, which explains the periodic arrangement of trunk visceral mesoderm primordia in wild type embryos. Conversely, mesodermal Slp is positively required, although not sufficient, for the specification of somatic muscle and heart progenitors. We propose that Wg-induced slp provides striped mesodermal domains with the competence to respond to subsequent slp-independent Wg signals that induce somatic muscle and heart progenitors. We also propose that in wg-expressing ectodermal cells, slp is an integral component in an autocrine feedback loop of Wg signaling.
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Affiliation(s)
- H H Lee
- Department of Biochemistry and Molecular Biology, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, NY 10029, USA
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19
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Song Y, Chung S, Kunes S. Combgap relays wingless signal reception to the determination of cortical cell fate in the Drosophila visual system. Mol Cell 2000; 6:1143-54. [PMID: 11106753 DOI: 10.1016/s1097-2765(00)00112-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The dorsoventral axis of the Drosophila visual cortex is patterned by nonautonomous signals expressed at its dorsal and ventral margins. wingless (wg) expression at the margins induces decapentaplegic (dpp), optomotor blind (omb), and aristaless in adjacent domains. We show that Combgap, a zinc finger protein, represses Wg target gene expression in the visual cortex. Wg signal reception downregulates combgap expression and derepresses target gene transcription. Combgap participates in a Hedgehog-controlled circuit in the developing wing and leg by regulating the expression of Cubitus interruptus. Combgap is thus a tissue-specific relay between Wingless and its target genes for the determination of cell fate in the visual cortex.
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Affiliation(s)
- Y Song
- Department of Molecular and Cellular Biology Harvard University, Cambridge, MA 02138, USA
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20
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Abstract
Many constituents of Wnt signaling pathways are expressed in the developing and mature nervous systems. Recent work has shown that Wnt signaling controls initial formation of the neural plate and many subsequent patterning decisions in the embryonic nervous system, including formation of the neural crest. Wnt signaling continues to be important at later stages of development. Wnts have been shown to regulate the anatomy of the neuronal cytoskeleton and the differentiation of synapses in the cerebellum. Wnt signaling has been demonstrated to regulate apoptosis and may participate in degenerative processes leading to cell death in the aging brain.
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Affiliation(s)
- Ardem Patapoutian
- Department of Cell Biology, MB6, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
| | - Louis F Reichardt
- Howard Hughes Medical Institute and Department of Physiology, University of California, 533 Parnassus Avenue, San Francisco, CA 94143-0724, USA
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