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Mönch TC, Smylla TK, Brändle F, Preiss A, Nagel AC. Novel Genome-Engineered H Alleles Differentially Affect Lateral Inhibition and Cell Dichotomy Processes during Bristle Organ Development. Genes (Basel) 2024; 15:552. [PMID: 38790181 PMCID: PMC11121709 DOI: 10.3390/genes15050552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2024] [Revised: 04/22/2024] [Accepted: 04/25/2024] [Indexed: 05/26/2024] Open
Abstract
Hairless (H) encodes the major antagonist in the Notch signaling pathway, which governs cellular differentiation of various tissues in Drosophila. By binding to the Notch signal transducer Suppressor of Hairless (Su(H)), H assembles repressor complexes onto Notch target genes. Using genome engineering, three new H alleles, HFA, HLLAA and HWA were generated and a phenotypic series was established by several parameters, reflecting the residual H-Su(H) binding capacity. Occasionally, homozygous HWA flies develop to adulthood. They were compared with the likewise semi-viable HNN allele affecting H-Su(H) nuclear entry. The H homozygotes were short-lived, sterile and flightless, yet showed largely normal expression of several mitochondrial genes. Typical for H mutants, both HWA and HNN homozygous alleles displayed strong defects in wing venation and mechano-sensory bristle development. Strikingly, however, HWA displayed only a loss of bristles, whereas bristle organs of HNN flies showed a complete shaft-to-socket transformation. Apparently, the impact of HWA is restricted to lateral inhibition, whereas that of HNN also affects the respective cell type specification. Notably, reduction in Su(H) gene dosage only suppressed the HNN bristle phenotype, but amplified that of HWA. We interpret these differences as to the role of H regarding Su(H) stability and availability.
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Affiliation(s)
- Tanja C. Mönch
- Department of Molecular Genetics, Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany; (T.C.M.); (T.K.S.); (F.B.)
| | - Thomas K. Smylla
- Department of Molecular Genetics, Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany; (T.C.M.); (T.K.S.); (F.B.)
| | - Franziska Brändle
- Department of Molecular Genetics, Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany; (T.C.M.); (T.K.S.); (F.B.)
| | - Anette Preiss
- Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany;
| | - Anja C. Nagel
- Department of Molecular Genetics, Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany; (T.C.M.); (T.K.S.); (F.B.)
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2
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Maier D, Bauer M, Boger M, Sanchez Jimenez A, Yuan Z, Fechner J, Scharpf J, Kovall RA, Preiss A, Nagel AC. Genetic and Molecular Interactions between HΔCT, a Novel Allele of the Notch Antagonist Hairless, and the Histone Chaperone Asf1 in Drosophila melanogaster. Genes (Basel) 2023; 14:205. [PMID: 36672946 PMCID: PMC9858708 DOI: 10.3390/genes14010205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Revised: 01/03/2023] [Accepted: 01/09/2023] [Indexed: 01/15/2023] Open
Abstract
Cellular differentiation relies on the highly conserved Notch signaling pathway. Notch activity induces gene expression changes that are highly sensitive to chromatin landscape. We address Notch gene regulation using Drosophila as a model, focusing on the genetic and molecular interactions between the Notch antagonist Hairless and the histone chaperone Asf1. Earlier work implied that Asf1 promotes the silencing of Notch target genes via Hairless (H). Here, we generate a novel HΔCT allele by genome engineering. Phenotypically, HΔCT behaves as a Hairless gain of function allele in several developmental contexts, indicating that the conserved CT domain of H has an attenuator role under native biological contexts. Using several independent methods to assay protein-protein interactions, we define the sequences of the CT domain that are involved in Hairless-Asf1 binding. Based on previous models, where Asf1 promotes Notch repression via Hairless, a loss of Asf1 binding should reduce Hairless repressive activity. However, tissue-specific Asf1 overexpression phenotypes are increased, not rescued, in the HΔCT background. Counterintuitively, Hairless protein binding mitigates the repressive activity of Asf1 in the context of eye development. These findings highlight the complex connections of Notch repressors and chromatin modulators during Notch target-gene regulation and open the avenue for further investigations.
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Affiliation(s)
- Dieter Maier
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
| | - Milena Bauer
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
- Biozentrum, University of Basel, Spitalstrasse 41, CH-4056 Basel, Switzerland
| | - Mike Boger
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
- European Center for Angioscience, Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Straße 13–17, D-68167 Mannheim, Germany
| | - Anna Sanchez Jimenez
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
| | - Zhenyu Yuan
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Medical Sciences Building 2201, Albert Sabin Way, Cincinnati, OH 45267, USA
| | - Johannes Fechner
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
- Institute of Biomedical Genetics (IBMG), University of Stuttgart, Allmandring 31, D-70569 Stuttgart, Germany
| | - Janika Scharpf
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
| | - Rhett A. Kovall
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Medical Sciences Building 2201, Albert Sabin Way, Cincinnati, OH 45267, USA
| | - Anette Preiss
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
| | - Anja C. Nagel
- Institute of Biology, Genetics Department 190g, University of Hohenheim, Garbenstr. 30, D-70599 Stuttgart, Germany
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3
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Martins T, Meng Y, Korona B, Suckling R, Johnson S, Handford PA, Lea SM, Bray SJ. The conserved C2 phospholipid-binding domain in Delta contributes to robust Notch signalling. EMBO Rep 2021; 22:e52729. [PMID: 34347930 PMCID: PMC8490980 DOI: 10.15252/embr.202152729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 07/10/2021] [Accepted: 07/15/2021] [Indexed: 11/09/2022] Open
Abstract
Accurate Notch signalling is critical for development and homeostasis. Fine‐tuning of Notch–ligand interactions has substantial impact on signalling outputs. Recent structural studies have identified a conserved N‐terminal C2 domain in human Notch ligands which confers phospholipid binding in vitro. Here, we show that Drosophila ligands Delta and Serrate adopt the same C2 domain structure with analogous variations in the loop regions, including the so‐called β1‐2 loop that is involved in phospholipid binding. Mutations in the β1‐2 loop of the Delta C2 domain retain Notch binding but have impaired ability to interact with phospholipids in vitro. To investigate its role in vivo, we deleted five residues within the β1‐2 loop of endogenous Delta. Strikingly, this change compromises ligand function. The modified Delta enhances phenotypes produced by Delta loss‐of‐function alleles and suppresses that of Notch alleles. As the modified protein is present on the cell surface in normal amounts, these results argue that C2 domain phospholipid binding is necessary for robust signalling in vivo fine‐tuning the balance of trans and cis ligand–receptor interactions.
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Affiliation(s)
- Torcato Martins
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - Yao Meng
- Department of Biochemistry, University of Oxford, Oxford, UK
| | | | - Richard Suckling
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Steven Johnson
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | | | - Susan M Lea
- Sir William Dunn School of Pathology, University of Oxford, Oxford, UK
| | - Sarah J Bray
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, UK
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4
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Frankenreiter L, Gahr BM, Schmid H, Zimmermann M, Deichsel S, Hoffmeister P, Turkiewicz A, Borggrefe T, Oswald F, Nagel AC. Phospho-Site Mutations in Transcription Factor Suppressor of Hairless Impact Notch Signaling Activity During Hematopoiesis in Drosophila. Front Cell Dev Biol 2021; 9:658820. [PMID: 33937259 PMCID: PMC8079769 DOI: 10.3389/fcell.2021.658820] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 03/25/2021] [Indexed: 11/13/2022] Open
Abstract
The highly conserved Notch signaling pathway controls a multitude of developmental processes including hematopoiesis. Here, we provide evidence for a novel mechanism of tissue-specific Notch regulation involving phosphorylation of CSL transcription factors within the DNA-binding domain. Earlier we found that a phospho-mimetic mutation of the Drosophila CSL ortholog Suppressor of Hairless [Su(H)] at Ser269 impedes DNA-binding. By genome-engineering, we now introduced phospho-specific Su(H) mutants at the endogenous Su(H) locus, encoding either a phospho-deficient [Su(H) S269A ] or a phospho-mimetic [Su(H) S269D ] isoform. Su(H) S269D mutants were defective of Notch activity in all analyzed tissues, consistent with impaired DNA-binding. In contrast, the phospho-deficient Su(H) S269A mutant did not generally augment Notch activity, but rather specifically in several aspects of blood cell development. Unexpectedly, this process was independent of the corepressor Hairless acting otherwise as a general Notch antagonist in Drosophila. This finding is in agreement with a novel mode of Notch regulation by posttranslational modification of Su(H) in the context of hematopoiesis. Importantly, our studies of the mammalian CSL ortholog (RBPJ/CBF1) emphasize a potential conservation of this regulatory mechanism: phospho-mimetic RBPJ S221D was dysfunctional in both the fly as well as two human cell culture models, whereas phospho-deficient RBPJ S221A rather gained activity during fly hematopoiesis. Thus, dynamic phosphorylation of CSL-proteins within the DNA-binding domain provides a novel means to fine-tune Notch signal transduction in a context-dependent manner.
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Affiliation(s)
- Lisa Frankenreiter
- Department of General Genetics (190g), Institute of Biology (190), University of Hohenheim, Stuttgart, Germany
| | - Bernd M Gahr
- Department of General Genetics (190g), Institute of Biology (190), University of Hohenheim, Stuttgart, Germany
| | - Hannes Schmid
- Department of General Genetics (190g), Institute of Biology (190), University of Hohenheim, Stuttgart, Germany
| | - Mirjam Zimmermann
- Department of General Genetics (190g), Institute of Biology (190), University of Hohenheim, Stuttgart, Germany
| | - Sebastian Deichsel
- Department of General Genetics (190g), Institute of Biology (190), University of Hohenheim, Stuttgart, Germany
| | - Philipp Hoffmeister
- Department of Internal Medicine 1, Center for Internal Medicine, University Medical Center Ulm, Ulm, Germany
| | | | - Tilman Borggrefe
- Institute of Biochemistry, Justus-Liebig University of Giessen, Giessen, Germany
| | - Franz Oswald
- Department of Internal Medicine 1, Center for Internal Medicine, University Medical Center Ulm, Ulm, Germany
| | - Anja C Nagel
- Department of General Genetics (190g), Institute of Biology (190), University of Hohenheim, Stuttgart, Germany
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5
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Harrison NJ, Connolly E, Gascón Gubieda A, Yang Z, Altenhein B, Losada Perez M, Moreira M, Sun J, Hidalgo A. Regenerative neurogenic response from glia requires insulin-driven neuron-glia communication. eLife 2021; 10:58756. [PMID: 33527895 PMCID: PMC7880684 DOI: 10.7554/elife.58756] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Accepted: 02/01/2021] [Indexed: 12/21/2022] Open
Abstract
Understanding how injury to the central nervous system induces de novo neurogenesis in animals would help promote regeneration in humans. Regenerative neurogenesis could originate from glia and glial neuron-glia antigen-2 (NG2) may sense injury-induced neuronal signals, but these are unknown. Here, we used Drosophila to search for genes functionally related to the NG2 homologue kon-tiki (kon), and identified Islet Antigen-2 (Ia-2), required in neurons for insulin secretion. Both loss and over-expression of ia-2 induced neural stem cell gene expression, injury increased ia-2 expression and induced ectopic neural stem cells. Using genetic analysis and lineage tracing, we demonstrate that Ia-2 and Kon regulate Drosophila insulin-like peptide 6 (Dilp-6) to induce glial proliferation and neural stem cells from glia. Ectopic neural stem cells can divide, and limited de novo neurogenesis could be traced back to glial cells. Altogether, Ia-2 and Dilp-6 drive a neuron-glia relay that restores glia and reprogrammes glia into neural stem cells for regeneration.
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Affiliation(s)
- Neale J Harrison
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Elizabeth Connolly
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Alicia Gascón Gubieda
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Zidan Yang
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | | | - Maria Losada Perez
- Instituto Cajal, Consejo Superior de Investigaciones Cientificas (CSIC), Madrid, Spain
| | - Marta Moreira
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Jun Sun
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Alicia Hidalgo
- Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
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6
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Li Z, Guo X, Huang H, Wang C, Yang F, Zhang Y, Wang J, Han L, Jin Z, Cai T, Xi R. A Switch in Tissue Stem Cell Identity Causes Neuroendocrine Tumors in Drosophila Gut. Cell Rep 2020; 30:1724-1734.e4. [DOI: 10.1016/j.celrep.2020.01.041] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 11/15/2019] [Accepted: 01/13/2020] [Indexed: 12/12/2022] Open
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7
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Gahr BM, Brändle F, Zimmermann M, Nagel AC. An RBPJ- Drosophila Model Reveals Dependence of RBPJ Protein Stability on the Formation of Transcription-Regulator Complexes. Cells 2019; 8:cells8101252. [PMID: 31615108 PMCID: PMC6829621 DOI: 10.3390/cells8101252] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 10/07/2019] [Accepted: 10/10/2019] [Indexed: 01/07/2023] Open
Abstract
Notch signaling activity governs widespread cellular differentiation in higher animals, including humans, and is involved in several congenital diseases and different forms of cancer. Notch signals are mediated by the transcriptional regulator RBPJ in a complex with activated Notch (NICD). Analysis of Notch pathway regulation in humans is hampered by a partial redundancy of the four Notch receptor copies, yet RBPJ is solitary, allowing its study in model systems. In Drosophila melanogaster, the RBPJ orthologue is encoded by Suppressor of Hairless [Su(H)]. Using genome engineering, we replaced Su(H) by murine RBPJ in order to study its function in the fly. In fact, RBPJ largely substitutes for Su(H)’s function, yet subtle phenotypes reflect increased Notch signaling activity. Accordingly, the binding of RBPJ to Hairless (H) protein, the general Notch antagonist in Drosophila, was considerably reduced compared to that of Su(H). An H-binding defective RBPJLLL mutant matched the respective Su(H)LLL allele: homozygotes were lethal due to extensive Notch hyperactivity. Moreover, RBPJLLL protein accumulated at lower levels than wild type RBPJ, except in the presence of NICD. Apparently, RBPJ protein stability depends on protein complex formation with either H or NICD, similar to Su(H), demonstrating that the murine homologue underlies the same regulatory mechanisms as Su(H) in Drosophila. These results underscore the importance of regulating the availability of RBPJ protein to correctly mediate Notch signaling activity in the fly.
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Affiliation(s)
- Bernd M. Gahr
- Institute of Genetics (240), University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany; (B.M.G.); (F.B.); (M.Z.)
- Present address: Molecular Cardiology, Department of Internal Medicine II, University of Ulm, Albert-Einstein-Allee 23, 89081 Ulm, Germany
| | - Franziska Brändle
- Institute of Genetics (240), University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany; (B.M.G.); (F.B.); (M.Z.)
| | - Mirjam Zimmermann
- Institute of Genetics (240), University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany; (B.M.G.); (F.B.); (M.Z.)
| | - Anja C. Nagel
- Institute of Genetics (240), University of Hohenheim, Garbenstr. 30, 70599 Stuttgart, Germany; (B.M.G.); (F.B.); (M.Z.)
- Correspondence: ; Tel.: +49-711-45922210
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8
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Salazar JL, Yamamoto S. Integration of Drosophila and Human Genetics to Understand Notch Signaling Related Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1066:141-185. [PMID: 30030826 PMCID: PMC6233323 DOI: 10.1007/978-3-319-89512-3_8] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Notch signaling research dates back to more than one hundred years, beginning with the identification of the Notch mutant in the fruit fly Drosophila melanogaster. Since then, research on Notch and related genes in flies has laid the foundation of what we now know as the Notch signaling pathway. In the 1990s, basic biological and biochemical studies of Notch signaling components in mammalian systems, as well as identification of rare mutations in Notch signaling pathway genes in human patients with rare Mendelian diseases or cancer, increased the significance of this pathway in human biology and medicine. In the 21st century, Drosophila and other genetic model organisms continue to play a leading role in understanding basic Notch biology. Furthermore, these model organisms can be used in a translational manner to study underlying mechanisms of Notch-related human diseases and to investigate the function of novel disease associated genes and variants. In this chapter, we first briefly review the major contributions of Drosophila to Notch signaling research, discussing the similarities and differences between the fly and human pathways. Next, we introduce several biological contexts in Drosophila in which Notch signaling has been extensively characterized. Finally, we discuss a number of genetic diseases caused by mutations in genes in the Notch signaling pathway in humans and we expand on how Drosophila can be used to study rare genetic variants associated with these and novel disorders. By combining modern genomics and state-of-the art technologies, Drosophila research is continuing to reveal exciting biology that sheds light onto mechanisms of disease.
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Affiliation(s)
- Jose L Salazar
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, TX, USA
| | - Shinya Yamamoto
- Department of Molecular and Human Genetics, Baylor College of Medicine (BCM), Houston, TX, USA.
- Program in Developmental Biology, BCM, Houston, TX, USA.
- Department of Neuroscience, BCM, Houston, TX, USA.
- Jan and Dan Duncan Neurological Research Institute, Texas Children's Hospital, Houston, TX, USA.
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Chan SKK, Cerda-Moya G, Stojnic R, Millen K, Fischer B, Fexova S, Skalska L, Gomez-Lamarca M, Pillidge Z, Russell S, Bray SJ. Role of co-repressor genomic landscapes in shaping the Notch response. PLoS Genet 2017; 13:e1007096. [PMID: 29155828 PMCID: PMC5714389 DOI: 10.1371/journal.pgen.1007096] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 12/04/2017] [Accepted: 11/01/2017] [Indexed: 11/18/2022] Open
Abstract
Repressors are frequently deployed to limit the transcriptional response to signalling pathways. For example, several co-repressors interact directly with the DNA-binding protein CSL and are proposed to keep target genes silenced in the absence of Notch activity. However, the scope of their contributions remains unclear. To investigate co-repressor activity in the context of this well defined signalling pathway, we have analysed the genome-wide binding profile of the best-characterized CSL co-repressor in Drosophila, Hairless, and of a second CSL interacting repressor, SMRTER. As predicted there was significant overlap between Hairless and its CSL DNA-binding partner, both in Kc cells and in wing discs, where they were predominantly found in chromatin with active enhancer marks. However, while the Hairless complex was widely present at some Notch regulated enhancers in the wing disc, no binding was detected at others, indicating that it is not essential for silencing per se. Further analysis of target enhancers confirmed differential requirements for Hairless. SMRTER binding significantly overlapped with Hairless, rather than complementing it, and many enhancers were apparently co-bound by both factors. Our analysis indicates that the actions of Hairless and SMRTER gate enhancers to Notch activity and to Ecdysone signalling respectively, to ensure that the appropriate levels and timing of target gene expression are achieved. The communication between cells that occurs during development, as well as in disease contexts, involves a small number of signalling pathways of which the Notch pathway is one. One outstanding question is how these pathways can bring about different gene responses in different contexts. As gene expression is co-ordinated by a mixture of activators and repressors, we set out to investigate whether the distribution of repressors across the genome is important in shaping whether genes are able to respond to Notch activity. Our results from analyzing the binding profile of two repressors, Hairless and SMRTER, show that, in many cases, they are not essential for preventing a gene from responding. Instead they are deployed at a limited number of genetic loci where they gate the response, helping to set a threshold for gene activation. Perturbations to their function lead to enhanced gene expression in limited territories rather than to new programmes of gene expression. Their main role therefore is to restrict the time or levels of signal that a gene needs to receive before it will respond.
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Affiliation(s)
- Stephen K. K. Chan
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Gustavo Cerda-Moya
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Robert Stojnic
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
- Cambridge Systems Biology Centre, University of Cambridge, Cambridge, United Kingdom
| | - Kat Millen
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Bettina Fischer
- Cambridge Systems Biology Centre, University of Cambridge, Cambridge, United Kingdom
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Silvie Fexova
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Lenka Skalska
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Maria Gomez-Lamarca
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Zoe Pillidge
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Steven Russell
- Cambridge Systems Biology Centre, University of Cambridge, Cambridge, United Kingdom
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
| | - Sarah J. Bray
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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10
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Tay MLI, Pek JW. Maternally Inherited Stable Intronic Sequence RNA Triggers a Self-Reinforcing Feedback Loop during Development. Curr Biol 2017; 27:1062-1067. [DOI: 10.1016/j.cub.2017.02.040] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 01/15/2017] [Accepted: 02/16/2017] [Indexed: 12/01/2022]
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11
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Mavromatakis YE, Tomlinson A. R7 Photoreceptor Specification in the Developing Drosophila Eye: The Role of the Transcription Factor Deadpan. PLoS Genet 2016; 12:e1006159. [PMID: 27427987 PMCID: PMC4948816 DOI: 10.1371/journal.pgen.1006159] [Citation(s) in RCA: 4] [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: 04/11/2016] [Accepted: 06/10/2016] [Indexed: 02/02/2023] Open
Abstract
As cells proceed along their developmental pathways they make a series of sequential cell fate decisions. Each of those decisions needs to be made in a robust manner so there is no ambiguity in the state of the cell as it proceeds to the next stage. Here we examine the decision made by the Drosophila R7 precursor cell to become a photoreceptor and ask how the robustness of that decision is achieved. The transcription factor Tramtrack (Ttk) inhibits photoreceptor assignment, and previous studies found that the RTK-induced degradation of Ttk was critically required for R7 specification. Here we find that the transcription factor Deadpan (Dpn) is also required; it is needed to silence ttk transcription, and only when Ttk protein degradation and transcriptional silencing occur together is the photoreceptor fate robustly achieved. Dpn expression needs to be tightly restricted to R7 precursors, and we describe the role played by Ttk in repressing dpn transcription. Thus, Dpn and Ttk act as mutually repressive transcription factors, with Dpn acting to ensure that Ttk is effectively removed from R7, and Ttk acting to prevent Dpn expression in other cells. Furthermore, we find that N activity is required to promote dpn transcription, and only in R7 precursors does the removal of Ttk coincide with high N activity, and only in this cell does Dpn expression result. Animals are made from a vast diversity of different cell types, and understanding how they are specified is a major goal of developmental biology. In this study we use the Drosophila R7 photoreceptor as a model system for understanding how cell fate specification occurs. We examine the step when the R7 precursor cell adopts the photoreceptor fate, and ask how the signaling pathways active in the cell are integrated to provide an unambiguous directive to become a photoreceptor. The transcription factor Tramtrack (Ttk) represses the ability of the cell to become a photoreceptor, and how it is removed is the focus of this study. Previous work identified a protein degradation mechanism, and here we describe the role of the transcription factor Deadpan (Dpn) in repressing ttk transcription. We find that both the protein degradation mechanism and transcriptional silencing are required for efficient Ttk removal. Dpn expression needs to be restricted to the R7 precursor and we describe how the mutual antagonism between Ttk and Dpn and the action of the Notch signaling pathway are integrated to ensure that Dpn is selectively expressed in the cell.
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Affiliation(s)
- Yannis Emmanuel Mavromatakis
- Department of Genetics and Development, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - Andrew Tomlinson
- Department of Genetics and Development, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
- * E-mail:
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12
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Zacharioudaki E, Housden BE, Garinis G, Stojnic R, Delidakis C, Bray SJ. Genes implicated in stem cell identity and temporal programme are directly targeted by Notch in neuroblast tumours. Development 2015; 143:219-31. [PMID: 26657768 PMCID: PMC4725341 DOI: 10.1242/dev.126326] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Accepted: 12/02/2015] [Indexed: 01/03/2023]
Abstract
Notch signalling is involved in a multitude of developmental decisions and its aberrant activation is linked to many diseases, including cancers. One example is the neural stem cell tumours that arise from constitutive Notch activity in Drosophila neuroblasts. To investigate how hyperactivation of Notch in larval neuroblasts leads to tumours, we combined results from profiling the upregulated mRNAs and mapping the regions bound by the core Notch pathway transcription factor Su(H). This identified 246 putative direct Notch targets. These genes were highly enriched for transcription factors and overlapped significantly with a previously identified regulatory programme dependent on the proneural transcription factor Asense. Included were genes associated with the neuroblast maintenance and self-renewal programme that we validated as Notch regulated in vivo. Another group were the so-called temporal transcription factors, which have been implicated in neuroblast maturation. Normally expressed in specific time windows, several temporal transcription factors were ectopically expressed in the stem cell tumours, suggesting that Notch had reprogrammed their normal temporal regulation. Indeed, the Notch-induced hyperplasia was reduced by mutations affecting two of the temporal factors, which, conversely, were sufficient to induce mild hyperplasia on their own. Altogether, the results suggest that Notch induces neuroblast tumours by directly promoting the expression of genes that contribute to stem cell identity and by reprogramming the expression of factors that could regulate maturity.
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Affiliation(s)
- Evanthia Zacharioudaki
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK Institute of Molecular Biology and Biotechnology, FORTH-Hellas, Heraklion, Crete 70013, Greece Department of Biology, University of Crete, Heraklion, Greece GR71409
| | - Benjamin E Housden
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
| | - George Garinis
- Institute of Molecular Biology and Biotechnology, FORTH-Hellas, Heraklion, Crete 70013, Greece Department of Biology, University of Crete, Heraklion, Greece GR71409
| | - Robert Stojnic
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK Cambridge Systems Biology Centre, University of Cambridge, Cambridge CB2 1QR, UK
| | - Christos Delidakis
- Institute of Molecular Biology and Biotechnology, FORTH-Hellas, Heraklion, Crete 70013, Greece Department of Biology, University of Crete, Heraklion, Greece GR71409
| | - Sarah J Bray
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge CB2 3DY, UK
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Wurmbach E, Preiss A. Deletion mapping in the Enhancer of split complex. Hereditas 2015; 151:159-68. [PMID: 25588303 DOI: 10.1111/hrd2.00065] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 09/26/2014] [Indexed: 11/30/2022] Open
Abstract
The Enhancer of split complex [E(spl)-C] comprises twelve genes of different classes. Seven genes encode proteins of with a basic-helix-loop-helix-orange (bHLH-O) domain that function as transcriptional repressors and serve as effectors of the Notch signalling pathway. They have been named E(spl)m8-, m7-, m5-, m3-, mβ-, mγ- and mδ-HLH. Four genes, E(spl)m6-, m4-, m2- and mα-BFM are intermingled and encode Notch repressor proteins of the Bearded-family (BFM). The complex is split by a single gene of unrelated function, encoding a Kazal-type protease inhibitor (Kaz-m1). All members within a family, bHLH-O or BFM, are very similar in structure and in function. In an attempt to generate specific mutants, we have mobilised P-element constructs residing next to E(spl)m7-HLH and E(spl)mγ-HLH, respectively. The resulting deletions were mapped molecularly and by cytology. Two small deletions affected only E(spl)m7-HLH and E(spl)mδ. The deficient flies were viable without apparent phenotype. Larger deletions, generated also by X-ray mutagenesis, uncover most of the E(spl)-C. The phenotypes of homozygous deficient embryos were analysed to characterize the respective loss of Notch signalling activity.
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Affiliation(s)
- Elisa Wurmbach
- Office of Chief Medical Examiner, Department of Forensic Biology, New York, NY, USA
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Djiane A, Zaessinger S, Babaoğlan AB, Bray SJ. Notch inhibits Yorkie activity in Drosophila wing discs. PLoS One 2014; 9:e106211. [PMID: 25157415 PMCID: PMC4144958 DOI: 10.1371/journal.pone.0106211] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 08/04/2014] [Indexed: 01/03/2023] Open
Abstract
During development, tissues and organs must coordinate growth and patterning so they reach the right size and shape. During larval stages, a dramatic increase in size and cell number of Drosophila wing imaginal discs is controlled by the action of several signaling pathways. Complex cross-talk between these pathways also pattern these discs to specify different regions with different fates and growth potentials. We show that the Notch signaling pathway is both required and sufficient to inhibit the activity of Yorkie (Yki), the Salvador/Warts/Hippo (SWH) pathway terminal transcription activator, but only in the central regions of the wing disc, where the TEAD factor and Yki partner Scalloped (Sd) is expressed. We show that this cross-talk between the Notch and SWH pathways is mediated, at least in part, by the Notch target and Sd partner Vestigial (Vg). We propose that, by altering the ratios between Yki, Sd and Vg, Notch pathway activation restricts the effects of Yki mediated transcription, therefore contributing to define a zone of low proliferation in the central wing discs.
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Affiliation(s)
- Alexandre Djiane
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
- IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, France; INSERM, U896, Montpellier, France; Université Montpellier1, Montpellier, France; Institut régional du Cancer Montpellier, Montpellier, France
- * E-mail:
| | - Sophie Zaessinger
- IRCM, Institut de Recherche en Cancérologie de Montpellier, Montpellier, France; INSERM, U896, Montpellier, France; Université Montpellier1, Montpellier, France; Institut régional du Cancer Montpellier, Montpellier, France
| | - A. Burcu Babaoğlan
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Sarah J. Bray
- Department of Physiology Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
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