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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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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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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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Wolf D, Smylla TK, Reichmuth J, Hoffmeister P, Kober L, Zimmermann M, Turkiewicz A, Borggrefe T, Nagel AC, Oswald F, Preiss A, Maier D. Nucleo-cytoplasmic shuttling of Drosophila Hairless/Su(H) heterodimer as a means of regulating Notch dependent transcription. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:1520-1532. [PMID: 31326540 DOI: 10.1016/j.bbamcr.2019.07.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 07/02/2019] [Accepted: 07/16/2019] [Indexed: 12/21/2022]
Abstract
Activation and repression of Notch target genes is mediated by transcription factor CSL, known as Suppressor of Hairless (Su(H)) in Drosophila and CBF1 or RBPJ in human. CSL associates either with co-activator Notch or with co-repressors such as Drosophila Hairless. The nuclear translocation of transcription factor CSL relies on co-factor association, both in mammals and in Drosophila. The Drosophila CSL orthologue Su(H) requires Hairless for repressor complex formation. Based on its role in transcriptional silencing, H protein would be expected to be strictly nuclear. However, H protein is also cytosolic, which may relate to its role in the stabilization and nuclear translocation of Su(H) protein. Here, we investigate the function of the predicted nuclear localization signals (NLS 1-3) and single nuclear export signal (NES) of co-repressor Hairless using GFP-fusion proteins, reporter assays and in vivo analyses using Hairless wild type and shuttling-defective Hairless mutants. We identify NLS3 and NES to be critical for Hairless function. In fact, H⁎NLS3 mutant flies match H null mutants, whereas H⁎NLS3⁎NES double mutants display weaker phenotypes in agreement with a crucial role for NES in H export. As expected for a transcriptional repressor, Notch target genes are deregulated in H⁎NLS3 mutant cells, demonstrating nuclear requirement for its activity. Importantly, we reveal that Su(H) protein strictly follows Hairless protein localization. Together, we propose that shuttling between the nucleo-cytoplasmic compartments provides the possibility to fine tune the regulation of Notch target gene expression by balancing of Su(H) protein availability for Notch activation.
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Affiliation(s)
- Dorina Wolf
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Thomas K Smylla
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Jan Reichmuth
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Philipp Hoffmeister
- University Medical Center Ulm, Center for Internal Medicine, Department of Internal Medicine I, Albert-Einstein-Allee 23, 89081 Ulm, Germany
| | - Ludmilla Kober
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Mirjam Zimmermann
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Aleksandra Turkiewicz
- Justus-Liebig University of Giessen Institute of Biochemistry, Friedrichstrasse 24, 35392 Giessen, Germany
| | - Tilman Borggrefe
- Justus-Liebig University of Giessen Institute of Biochemistry, Friedrichstrasse 24, 35392 Giessen, Germany
| | - Anja C Nagel
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Franz Oswald
- University Medical Center Ulm, Center for Internal Medicine, Department of Internal Medicine I, Albert-Einstein-Allee 23, 89081 Ulm, Germany
| | - Anette Preiss
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany
| | - Dieter Maier
- University of Hohenheim, Institute of Genetics (240a), Garbenstr. 30, 70599 Stuttgart, Germany.
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