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Chen Y, Li H, Yi TC, Shen J, Zhang J. Notch Signaling in Insect Development: A Simple Pathway with Diverse Functions. Int J Mol Sci 2023; 24:14028. [PMID: 37762331 PMCID: PMC10530718 DOI: 10.3390/ijms241814028] [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: 07/31/2023] [Revised: 09/05/2023] [Accepted: 09/06/2023] [Indexed: 09/29/2023] Open
Abstract
Notch signaling is an evolutionarily conserved pathway which functions between adjacent cells to establish their distinct identities. Despite operating in a simple mechanism, Notch signaling plays remarkably diverse roles in development to regulate cell fate determination, organ growth and tissue patterning. While initially discovered and characterized in the model insect Drosophila melanogaster, recent studies across various insect species have revealed the broad involvement of Notch signaling in shaping insect tissues. This review focuses on providing a comprehensive picture regarding the roles of the Notch pathway in insect development. The roles of Notch in the formation and patterning of the insect embryo, wing, leg, ovary and several specific structures, as well as in physiological responses, are summarized. These results are discussed within the developmental context, aiming to deepen our understanding of the diversified functions of the Notch signaling pathway in different insect species.
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Affiliation(s)
- Yao Chen
- Department of Plant Biosecurity and MOA Key Laboratory of Surveillance and Management for Plant Quarantine Pests, College of Plant Protection, China Agricultural University, Beijing 100193, China; (Y.C.)
| | - Haomiao Li
- Department of Plant Biosecurity and MOA Key Laboratory of Surveillance and Management for Plant Quarantine Pests, College of Plant Protection, China Agricultural University, Beijing 100193, China; (Y.C.)
| | - Tian-Ci Yi
- Guizhou Provincial Key Laboratory for Agricultural Pest Management of Mountainous Regions, Institute of Entomology, Guizhou University, Guiyang 550025, China
| | - Jie Shen
- Department of Plant Biosecurity and MOA Key Laboratory of Surveillance and Management for Plant Quarantine Pests, College of Plant Protection, China Agricultural University, Beijing 100193, China; (Y.C.)
| | - Junzheng Zhang
- Department of Plant Biosecurity and MOA Key Laboratory of Surveillance and Management for Plant Quarantine Pests, College of Plant Protection, China Agricultural University, Beijing 100193, China; (Y.C.)
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Majot AT, Bidwai AP. Analysis of transient hypermorphic activity of E(spl)D during R8 specification. PLoS One 2017; 12:e0186439. [PMID: 29036187 PMCID: PMC5643056 DOI: 10.1371/journal.pone.0186439] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 10/02/2017] [Indexed: 11/23/2022] Open
Abstract
Drosophila atonal (ato) is required for the specification of founding R8 photoreceptors during retinal development. ato is regulated via dual eye-specific enhancers; ato-3’ is subject to initial induction whereas 5’-ato facilitates Notch-mediated autoregulation. Notch is further utilized to induce bHLH repressors of the E(spl) locus to restrict Ato from its initial broad expression to individual cells. Although Notch operates in two, distinct phases, it has remained unclear how the two phases maintain independence from one another. The difference in these two phases has attributed to the hypothesized delayed expression of E(spl). However, immunofluorescence data indicate that E(spl) are expressed during early Ato patterning, suggesting a more sophisticated underlying mechanism. To probe this mechanism, we provide evidence that although E(spl) exert no influence on ato-3’, E(spl) repress 5’-ato and deletion of the E(spl) locus elicits precocious 5’-ato activity. Thus, E(spl) imposes a delay to the timing in which Ato initiates autoregulation. We next sought to understand this finding in the context of E(spl)D, which encodes a dysregulated variant of E(spl)M8 that perturbs R8 patterning, though, as previously reported, only in conjunction with the mutant receptor Nspl. We established a genetic interaction between E(spl)D and roughened eye (roe), a known modulator of Notch signaling in retinogenesis. This link further suggests a dosage-dependence between E(spl) and the proneural activators Ato and Sens, as indicated via interaction assays in which E(spl)D renders aberrant R8 patterning in conjunction with reduced proneural dosage. In total, the biphasicity of Notch signaling relies, to some degree, on the post-translational regulation of individual E(spl) members and, importantly, that post-translational regulation is likely necessary to modulate the level of E(spl) activity throughout the progression of Ato expression.
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Affiliation(s)
- Adam T. Majot
- Department of Biology, West Virginia University, Morgantown, West Virginia, United States of America
| | - Ashok P. Bidwai
- Department of Biology, West Virginia University, Morgantown, West Virginia, United States of America
- * E-mail:
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Ramat A, Audibert A, Louvet-Vallée S, Simon F, Fichelson P, Gho M. Escargot and Scratch regulate neural commitment by antagonizing Notch activity in Drosophila sensory organs. Development 2016; 143:3024-34. [PMID: 27471258 DOI: 10.1242/dev.134387] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 07/12/2016] [Indexed: 12/15/2022]
Abstract
During Notch (N)-mediated binary cell fate decisions, cells adopt two different fates according to the levels of N pathway activation: an Noff-dependent or an Non-dependent fate. How cells maintain these N activity levels over time remains largely unknown. We address this question in the cell lineage that gives rise to the Drosophila mechanosensory organs. In this lineage a primary precursor cell undergoes a stereotyped sequence of oriented asymmetric cell divisions and transits through two neural precursor states before acquiring a neuron identity. Using a combination of genetic and cell biology strategies, we show that Escargot and Scratch, two transcription factors belonging to the Snail superfamily, maintain Noff neural commitment by directly blocking the transcription of N target genes. We propose that Snail factors act by displacing proneural transcription activators from DNA binding sites. As such, Snail factors maintain the Noff state in neural precursor cells by buffering any ectopic variation in the level of N activity. Since Escargot and Scratch orthologs are present in other precursor cells, our findings are fundamental for understanding precursor cell fate acquisition in other systems.
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Affiliation(s)
- Anne Ramat
- CNRS, UMR 7622, Laboratoire de Biologie du Développement, IBPS, Paris F-75005, France
| | - Agnès Audibert
- Sorbonne Universités, UPMC Université Paris 06, UMR7622, Laboratoire de Biologie du Développement, Paris F-75005, France
| | - Sophie Louvet-Vallée
- Sorbonne Universités, UPMC Université Paris 06, UMR7622, Laboratoire de Biologie du Développement, Paris F-75005, France
| | - Françoise Simon
- CNRS, UMR 7622, Laboratoire de Biologie du Développement, IBPS, Paris F-75005, France
| | - Pierre Fichelson
- CNRS, UMR 7622, Laboratoire de Biologie du Développement, IBPS, Paris F-75005, France
| | - Michel Gho
- CNRS, UMR 7622, Laboratoire de Biologie du Développement, IBPS, Paris F-75005, France
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Dearden PK. Origin and evolution of the enhancer of split complex. BMC Genomics 2015; 16:712. [PMID: 26384649 PMCID: PMC4575448 DOI: 10.1186/s12864-015-1926-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 09/12/2015] [Indexed: 01/07/2023] Open
Abstract
BACKGROUND The Enhancer of split complex is an unusual gene complex found in Arthropod genomes. Where known this complex of genes is often regulated by Notch cell signalling and is critically important for neurogenesis. The Enhancer of split complex is made up of two different classes of genes, basic helix-loop-helix-orange domain transcription factors and bearded class genes. The association of these genes has been detected in the genomes of insects and crustaceans. RESULTS Tracing the evolution of the Enhancer of split complex in recently sequenced Arthropod genomes indicates that enhancer of split basic helix-loop-helix orange domain genes arose before the common ancestor of insects and Crustacea, and before the formation of the complex. Throughout insect and crustacean evolution, a four-gene cluster has been present with lineage specific gene losses and duplications. The complex can be found in the vast majority of genomes, but appears to be missing from the genomes of chalcid wasps, raising questions as to how they carry out neurogenesis in the absence of these crucial genes. CONCLUSIONS The enhancer of split complex arose in the common ancestor of Crustacea and insects, probably through the linkage of a basic helix-loop-helix orange domain gene and a bearded class gene. The complex has been maintained, with variations, throughout insect and crustacean evolution indicating some function of the complex, such as coordinate regulation, may maintain its structure through evolutionary time.
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Affiliation(s)
- Peter K Dearden
- Genetics Otago and Gravida (National Centre for Growth and Development), Biochemistry Department, University of Otago, Dunedin, Aotearoa, New Zealand.
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Liu M, Wang C, Li D, Liu Y, Sheng Q, Lv Z, Yu W, Wang D, Zhang Y, Nie Z. Cloning and expression characteristics of the notch-associated gene BmE(spl)mγ from silkworm, Bombyx mori. Appl Biochem Biotechnol 2014; 173:2065-75. [PMID: 24916802 DOI: 10.1007/s12010-014-1003-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 05/26/2014] [Indexed: 10/25/2022]
Abstract
The E(spl)mγ gene in Drosophila is a regulatory target gene downstream of the Notch pathway. BmE(spl)mγ (Bombyx mori, E(spl)mγ) is an ortholog of the Drosophila E(spl)mγ gene, and the gene encodes a protein with 248 amino acid residues. This gene was cloned and overexpressed in Escherichia coli BL21(DE3). The recombinant protein was purified and subsequently used to generate a rabbit polyclonal antibody. Western blotting analyses showed that BmE(spl)mγ expression is high in pupa and egg, and low in larva and moth. In the fifth instar larva, the protein levels are high in head, epidermis, sexual gland, trachea, and the fatbody and low in the Malpighian tubule, hemolymph, gut, and silk gland. The further immunohistochemical analyses also showed higher BmE(spl)mγ expression in the head of fifth instar larva and pupa. Of the four moth parts studied, the thorax had the highest expression level. Thus, BmE(spl)mγ might be associated with neurogenesis in silkworm. Furthermore, DAPT (a γ-secretase inhibitor and an indirect inhibitor of Notch) blocking experiments showed that higher concentrations of the blocking agent and a longer processing time reduce the transcription levels of the BmE(spl)mγ gene, demonstrating that the silkworm BmE(spl)mγ gene is associated with the Notch signal pathway. These findings suggest that the function of BmE(spl)mγ may be similar to that of its Drosophila homolog.
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Affiliation(s)
- Min Liu
- College of Life Sciences, Zhejiang Sci-Tech University, Hanghzou, 310018, China
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The Drosophila enhancer of split gene complex: architecture and coordinate regulation by notch, cohesin, and polycomb group proteins. G3-GENES GENOMES GENETICS 2013; 3:1785-94. [PMID: 23979932 PMCID: PMC3789803 DOI: 10.1534/g3.113.007534] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The cohesin protein complex functionally interacts with Polycomb group (PcG) silencing proteins to control expression of several key developmental genes, such as the Drosophila Enhancer of split gene complex [E(spl)-C]. The E(spl)-C contains 12 genes that inhibit neural development. In a cell line derived from the central nervous system, cohesin and the PRC1 PcG protein complex bind and repress E (spl)-C transcription, but the repression mechanisms are unknown. The genes in the E(spl)-C are directly activated by the Notch receptor. Here we show that depletion of cohesin or PRC1 increases binding of the Notch intracellular fragment to genes in the E(spl)-C, correlating with increased transcription. The increased transcription likely reflects both direct effects of cohesin and PRC1 on RNA polymerase activity at the E(spl)-C, and increased expression of Notch ligands. By chromosome conformation capture we find that the E(spl)-C is organized into a self-interactive architectural domain that is co-extensive with the region that binds cohesin and PcG complexes. The self-interactive architecture is formed independently of cohesin or PcG proteins. We posit that the E(spl)-C architecture dictates where cohesin and PcG complexes bind and act when they are recruited by as yet unidentified factors, thereby controlling the E(spl)-C as a coordinated domain.
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Kux K, Kiparaki M, Delidakis C. The two Tribolium E(spl) genes show evolutionarily conserved expression and function during embryonic neurogenesis. Mech Dev 2013; 130:207-25. [PMID: 23485410 DOI: 10.1016/j.mod.2013.02.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 02/13/2013] [Accepted: 02/14/2013] [Indexed: 01/05/2023]
Abstract
Tribolium castaneum is a well-characterised model insect, whose short germ-band mode of embryonic development is characteristic of many insect species and differs from the exhaustively studied Drosophila. Mechanisms of early neurogenesis, however, show significant conservation with Drosophila, as a characteristic pattern of neuroblasts arises from neuroectoderm proneural clusters in response to the bHLH activator Ash, a homologue of Achaete-Scute. Here we study the expression and function of two other bHLH proteins, the bHLH-O repressors E(spl)1 and E(spl)3. Their Drosophila homologues are expressed in response to Notch signalling and antagonize the activity of Achaete-Scute proteins, thus restricting the number of nascent neuroblasts. E(spl)1 and 3 are the only E(spl) homologues in Tribolium and both show expression in the cephalic and ventral neuroectoderm during embryonic neurogenesis, as well as a dynamic pattern of expression in other tissues. Their expression starts early, soon after Ash expression and is dependent on both Ash and Notch activities. They act redundantly, since a double E(spl) knockdown (but not single knockdowns) results in neurogenesis defects similar to those caused by Notch loss-of-function. A number of other activities have been evolutionarily conserved, most notably their ability to interact with proneural proteins Scute and Daughterless.
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Affiliation(s)
- Kristina Kux
- Institute of Molecular Biology & Biotechnology, Foundation for Research & Technology Hellas and Department of Biology, University of Crete, Heraklion, Crete, Greece
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Blanco E, Corominas M. CBS: an open platform that integrates predictive methods and epigenetics information to characterize conserved regulatory features in multiple Drosophila genomes. BMC Genomics 2012; 13:688. [PMID: 23228284 PMCID: PMC3564944 DOI: 10.1186/1471-2164-13-688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Accepted: 11/28/2012] [Indexed: 12/11/2022] Open
Abstract
Background Information about the composition of regulatory regions is of great value for designing experiments to functionally characterize gene expression. The multiplicity of available applications to predict transcription factor binding sites in a particular locus contrasts with the substantial computational expertise that is demanded to manipulate them, which may constitute a potential barrier for the experimental community. Results CBS (Conserved regulatory Binding Sites, http://compfly.bio.ub.es/CBS) is a public platform of evolutionarily conserved binding sites and enhancers predicted in multiple Drosophila genomes that is furnished with published chromatin signatures associated to transcriptionally active regions and other experimental sources of information. The rapid access to this novel body of knowledge through a user-friendly web interface enables non-expert users to identify the binding sequences available for any particular gene, transcription factor, or genome region. Conclusions The CBS platform is a powerful resource that provides tools for data mining individual sequences and groups of co-expressed genes with epigenomics information to conduct regulatory screenings in Drosophila.
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Affiliation(s)
- Enrique Blanco
- Departament de Genètica and Institut de Biomedicina (IBUB), Universitat de Barcelona, Av, Diagonal 643, 08028, Barcelona, Spain.
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Engel GL, Delwig A, Rand MD. The effects of methylmercury on Notch signaling during embryonic neural development in Drosophila melanogaster. Toxicol In Vitro 2011; 26:485-92. [PMID: 22230562 DOI: 10.1016/j.tiv.2011.12.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2011] [Revised: 12/19/2011] [Accepted: 12/20/2011] [Indexed: 10/14/2022]
Abstract
Methylmercury (MeHg) is a ubiquitous toxicant that targets the developing fetal nervous system. MeHg interacts with the Notch signaling pathway, a highly-conserved intercellular signaling mechanism required for normal development. Notch signaling is conveyed by activation of the genes in the enhancer of split (E(spl)) locus in Drosophila. We have previously shown that acute high doses of MeHg upregulate several E(spl) genes in Drosophila neural-derived C6 cells. Furthermore, MeHg induction of E(spl) can occur independent of the Notch receptor itself. We now show that MeHg, unlike inorganic mercury (HgCl2), preferentially upregulates E(spl)mδ and E(spl)mγ in Drosophila C6 cells. This is distinct from Delta ligand-induced Notch signaling in which no induction of E(spl)mδ is seen. MeHg is also seen to specifically upregulate E(spl)mδ in Drosophila embryos where HgCl2 showed no such effect. Additionally, treatment of embryos with MeHg caused a consistent failure in axonal outgrowth of the intersegmental nerve (ISN). This ISN phenotype was partially replicated by genetic activation of the Notch pathway, but was not replicated by increasing expression of E(spl)mδ. These data suggest a role for Notch signaling and the E(spl)mδ target gene in MeHg toxicity, however, the site of action for E(spl)mδ in this system remains to be elucidated.
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Affiliation(s)
- G L Engel
- Department of Anatomy and Neurobiology, College of Medicine, University of Vermont, USA
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Baker RH, Kuehl JV, Wilkinson GS. The Enhancer of split complex arose prior to the diversification of schizophoran flies and is strongly conserved between Drosophila and stalk-eyed flies (Diopsidae). BMC Evol Biol 2011; 11:354. [PMID: 22151427 PMCID: PMC3261227 DOI: 10.1186/1471-2148-11-354] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Accepted: 12/08/2011] [Indexed: 02/03/2023] Open
Abstract
Background In Drosophila, the Enhancer of split complex (E(spl)-C) comprises 11 bHLH and Bearded genes that function during Notch signaling to repress proneural identity in the developing peripheral nervous system. Comparison with other insects indicates that the basal state for Diptera is a single bHLH and Bearded homolog and that the expansion of the gene complex occurred in the lineage leading to Drosophila. However, comparative genomic data from other fly species that would elucidate the origin and sequence of gene duplication for the complex is lacking. Therefore, in order to examine the evolutionary history of the complex within Diptera, we reconstructed, using several fosmid clones, the entire E(spl)-complex in the stalk-eyed fly, Teleopsis dalmanni and collected additional homologs of E(spl)-C genes from searches of dipteran EST databases and the Glossina morsitans genome assembly. Results Comparison of the Teleopsis E(spl)-C gene organization with Drosophila indicates complete conservation in gene number and orientation between the species except that T. dalmanni contains a duplicated copy of E(spl)m5 that is not present in Drosophila. Phylogenetic analysis of E(spl)-complex bHLH and Bearded genes for several dipteran species clearly demonstrates that all members of the complex were present prior to the diversification of schizophoran flies. Comparison of upstream regulatory elements and 3' UTR domains between the species also reveals strong conservation for many of the genes and identifies several novel characteristics of E(spl)-C regulatory evolution including the discovery of a previously unidentified, highly conserved SPS+A domain between E(spl)mγ and E(spl)mβ. Conclusion Identifying the phylogenetic origin of E(spl)-C genes and their associated regulatory DNA is essential to understanding the functional significance of this well-studied gene complex. Results from this study provide numerous insights into the evolutionary history of the complex and will help refine the focus of studies examining the adaptive consequences of this gene expansion.
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Affiliation(s)
- Richard H Baker
- Sackler Institute for Comparative Genomics, American Museum of Natural History, New York, NY 10024, USA.
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Rybina OY, Pasyukova EG. A naturally occurring polymorphism at Drosophila melanogaster Lim3 Locus, a homolog of human LHX3/4, affects Lim3 transcription and fly lifespan. PLoS One 2010; 5:e12621. [PMID: 20838645 PMCID: PMC2935391 DOI: 10.1371/journal.pone.0012621] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2010] [Accepted: 08/05/2010] [Indexed: 11/18/2022] Open
Abstract
Lim3 encodes an RNA polymerase II transcription factor with a key role in neuron specification. It was also identified as a candidate gene that affects lifespan. These pleiotropic effects indicate the fundamental significance of the potential interplay between neural development and lifespan control. The goal of this study was to analyze the causal relationships between Lim3 structural variations, and gene expression and lifespan changes, and to provide insights into regulatory pathways controlling lifespan. Fifty substitution lines containing second chromosomes from a Drosophila natural population were used to analyze the association between lifespan and sequence variation in the 5'-regulatory region, and first exon and intron of Lim3A, in which we discovered multiple transcription start sites (TSS). The core and proximal promoter organization for Lim3A and a previously unknown mRNA named Lim3C were described. A haplotype of two markers in the Lim3A regulatory region was significantly associated with variation in lifespan. We propose that polymorphisms in the regulatory region affect gene transcription, and consequently lifespan. Indeed, five polymorphic markers located within 380 to 680 bp of the Lim3A major TSS, including two markers associated with lifespan variation, were significantly associated with the level of Lim3A transcript, as evaluated by real time RT-PCR in embryos, adult heads, and testes. A naturally occurring polymorphism caused a six-fold change in gene transcription and a 25% change in lifespan. Markers associated with long lifespan and intermediate Lim3A transcription were present in the population at high frequencies. We hypothesize that polymorphic markers associated with Lim3A expression are located within the binding sites for proteins that regulate gene function, and provide general rather than tissue-specific regulation of transcription, and that intermediate levels of Lim3A expression confer a selective advantage and longer lifespan.
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Duncan EJ, Dearden PK. Evolution of a genomic regulatory domain: the role of gene co-option and gene duplication in the Enhancer of split complex. Genome Res 2010; 20:917-28. [PMID: 20458100 DOI: 10.1101/gr.104794.109] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The Drosophila Enhancer of split complex [E(spl)-C] is a remarkable complex of genes many of which are effectors or modulators of Notch signaling. The complex contains different classes of genes including four bearded genes and seven basic helix-loop-helix (bHLH) genes. We examined the evolution of this unusual complex by identifying bearded and bHLH genes in the genome sequences of Arthropods. We find that a four-gene E(spl)-C, containing three bHLH genes and one bearded gene, is an ancient component of the genomes of Crustacea and Insects. The complex is well conserved in insects but is highly modified in Drosophila, where two of the ancestral genes of the complex are missing, and the remaining two have been duplicated multiple times. Through examining the expression of E(spl)-C genes in honeybees, aphids, and Drosophila, we determined that the complex ancestrally had a role in Notch signaling. The expression patterns of genes found inserted into the complex in some insects, or that of ancestral E(spl)-C genes that have moved out of the complex, imply that the E(spl)-C is a genomic domain regulated as a whole by Notch signaling. We hypothesize that the E(spl)-C is a Notch-regulated genomic domain conserved in Arthropod genomes for around 420 million years. We discuss the consequence of this conserved domain for the recruitment of novel genes into the Notch signaling cascade.
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Affiliation(s)
- Elizabeth J Duncan
- Laboratory for Evolution and Development, Genetics Otago and the National Research Centre for Growth and Development, Biochemistry Department, University of Otago, Dunedin 9054, New Zealand
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Schaaf CA, Misulovin Z, Sahota G, Siddiqui AM, Schwartz YB, Kahn TG, Pirrotta V, Gause M, Dorsett D. Regulation of the Drosophila Enhancer of split and invected-engrailed gene complexes by sister chromatid cohesion proteins. PLoS One 2009; 4:e6202. [PMID: 19587787 PMCID: PMC2703808 DOI: 10.1371/journal.pone.0006202] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Accepted: 06/16/2009] [Indexed: 01/14/2023] Open
Abstract
The cohesin protein complex was first recognized for holding sister chromatids together and ensuring proper chromosome segregation. Cohesin also regulates gene expression, but the mechanisms are unknown. Cohesin associates preferentially with active genes, and is generally absent from regions in which histone H3 is methylated by the Enhancer of zeste [E(z)] Polycomb group silencing protein. Here we show that transcription is hypersensitive to cohesin levels in two exceptional cases where cohesin and the E(z)-mediated histone methylation simultaneously coat the entire Enhancer of split and invected-engrailed gene complexes in cells derived from Drosophila central nervous system. These gene complexes are modestly transcribed, and produce seven of the twelve transcripts that increase the most with cohesin knockdown genome-wide. Cohesin mutations alter eye development in the same manner as increased Enhancer of split activity, suggesting that similar regulation occurs in vivo. We propose that cohesin helps restrain transcription of these gene complexes, and that deregulation of similarly cohesin-hypersensitive genes may underlie developmental deficits in Cornelia de Lange syndrome.
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Affiliation(s)
- Cheri A. Schaaf
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, Missouri, United States of America
| | - Ziva Misulovin
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, Missouri, United States of America
| | - Gurmukh Sahota
- Department of Genetics, Washington University School of Medicine, Saint Louis, Missouri, United States of America
| | - Akbar M. Siddiqui
- Microarray Core Facility, Molecular Microbiology and Immunology, Saint Louis University School of Medicine, Saint Louis, Missouri, United States of America
| | - Yuri B. Schwartz
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey, United States of America
| | - Tatyana G. Kahn
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey, United States of America
| | - Vincenzo Pirrotta
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey, United States of America
| | - Maria Gause
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, Missouri, United States of America
| | - Dale Dorsett
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, Missouri, United States of America
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Maeder ML, Megley C, Eastman DA. Differential expression of the Enhancer of split genes in the developing Drosophila midgut. Hereditas 2009; 146:11-8. [PMID: 19348652 DOI: 10.1111/j.1601-5223.2008.02094.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The Notch signaling pathway plays an important role during development in animals from worms to humans and pathway components are required for the differentiation of many different cell types. In Drosophila, Su(H) dependent Notch activation up-regulates transcription of the Enhancer of split-Complex (E(spl)-C). The E(spl) genes are known to function during neurogenesis, although expression and genetics studies suggest that they also play roles in the development of other tissues. The majority of the E(spl) genes contain upstream binding sites for Su(H), proneural proteins, and E(spl) bHLH proteins resulting in overlapping expression patterns during embryonic development. However, their expression patterns are quite distinct during later embryonic stages and in larval imaginal discs. In order to characterize expression patterns of the E(spl) genes during development and determine potential mechanisms through which expression is controlled, we examined the expression levels and patterns of the E(spl) genes in the midgut during metamorphosis. Quantitative Reverse Transcriptase-PCR and X-Gal staining results show that the genes have different levels and patterns of expression in the developing midgut. Two ancestral E(spl) genes, malpha and mbeta, are highly expressed and increase significantly at puparium formation, whereas another gene, mgamma, is expressed at low levels and decreases in expression at puparium formation. We also show that mbeta is expressed in cells throughout the midgut, while mgamma is expressed in two small regions. These results provide further evidence that the E(spl) genes function during midgut development and that they are regulated by different factors.
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Affiliation(s)
- Morgan L Maeder
- Department of Biology, Connecticut College, New London, Connecticut 06320, USA
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Abstract
Comparative developmental evidence indicates that reorganizations in developmental gene regulatory networks (GRNs) underlie evolutionary changes in animal morphology, including body plans. We argue here that the nature of the evolutionary alterations that arise from regulatory changes depends on the hierarchical position of the change within a GRN. This concept cannot be accomodated by microevolutionary nor macroevolutionary theory. It will soon be possible to investigate these ideas experimentally, by assessing the effects of GRN changes on morphological evolution.
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Affiliation(s)
- Douglas H Erwin
- Department of Paleobiology, MRC-121, National Museum of Natural History, PO BOX 37012, Washington, Washington DC 20013-7012, USA.
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Brody T, Rasband W, Baler K, Kuzin A, Kundu M, Odenwald WF. Sequence conservation and combinatorial complexity of Drosophila neural precursor cell enhancers. BMC Genomics 2008; 9:371. [PMID: 18673565 PMCID: PMC2529316 DOI: 10.1186/1471-2164-9-371] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Accepted: 08/01/2008] [Indexed: 11/10/2022] Open
Abstract
Background The presence of highly conserved sequences within cis-regulatory regions can serve as a valuable starting point for elucidating the basis of enhancer function. This study focuses on regulation of gene expression during the early events of Drosophila neural development. We describe the use of EvoPrinter and cis-Decoder, a suite of interrelated phylogenetic footprinting and alignment programs, to characterize highly conserved sequences that are shared among co-regulating enhancers. Results Analysis of in vivo characterized enhancers that drive neural precursor gene expression has revealed that they contain clusters of highly conserved sequence blocks (CSBs) made up of shorter shared sequence elements which are present in different combinations and orientations within the different co-regulating enhancers; these elements contain either known consensus transcription factor binding sites or consist of novel sequences that have not been functionally characterized. The CSBs of co-regulated enhancers share a large number of sequence elements, suggesting that a diverse repertoire of transcription factors may interact in a highly combinatorial fashion to coordinately regulate gene expression. We have used information gained from our comparative analysis to discover an enhancer that directs expression of the nervy gene in neural precursor cells of the CNS and PNS. Conclusion The combined use EvoPrinter and cis-Decoder has yielded important insights into the combinatorial appearance of fundamental sequence elements required for neural enhancer function. Each of the 30 enhancers examined conformed to a pattern of highly conserved blocks of sequences containing shared constituent elements. These data establish a basis for further analysis and understanding of neural enhancer function.
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Affiliation(s)
- Thomas Brody
- Neural Cell-Fate Determinants Section, NINDS, NIH, Bethesda, Maryland, USA.
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Maier D, Chen AX, Preiss A, Ketelhut M. The tiny Hairless protein from Apis mellifera: a potent antagonist of Notch signaling in Drosophila melanogaster. BMC Evol Biol 2008; 8:175. [PMID: 18559091 PMCID: PMC2440387 DOI: 10.1186/1471-2148-8-175] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Accepted: 06/17/2008] [Indexed: 01/24/2023] Open
Abstract
Background The Notch signaling pathway is fundamental to the regulation of many cell fate decisions in eumetazoans. Not surprisingly, members of this pathway are highly conserved even between vertebrates and invertebrates. There is one notable exception, Hairless, which acts as a general Notch antagonist in Drosophila. Hairless silences Notch target genes by assembling a repressor complex together with Suppressor of Hairless [Su(H)] and the co-repressors Groucho (Gro) and C-terminal binding protein (CtBP). Now with the availability of genomic databases, presumptive Hairless homologues are predicted, however only in insect species. To further our understanding of Hairless structure and function, we have cloned the Hairless gene from Apis mellifera (A.m.H) and characterized its functional conservation in Drosophila. Results The Apis Hairless protein is only one third of the size of the Drosophila orthologue. Interestingly, the defined Suppressor of Hairless binding domain is interrupted by a nonconserved spacer sequence and the N-terminal motif is sufficient for binding. In contrast to Apis Hairless, the Drosophila orthologue contains a large acidic domain and we provide experimental evidence that this acidic domain is necessary to silence Hairless activity in vivo. Despite the dramatic size differences, Apis Hairless binds to the Drosophila Hairless interactors Su(H), Gro, CtBP and Pros26.4. Hence, Apis Hairless assembles a repressor complex with Drosophila components that may have a different topology. Nevertheless, Apis Hairless is sufficient to repress the Notch target gene vestigial in Drosophila. Moreover, it is able to rescue Hairless mutant phenotypes, providing in vivo evidence for its function as a bona fide Notch antagonist. Conclusion This is the first interspecies-complementation analysis of the Hairless gene. Guided by evolutionary comparisons, we hope to eventually identify all the relevant structural domains and cofactors of Hairless, thereby opening an avenue for further insights into the repressor-complexes that down-regulate Notch signaling also in other, higher eukaryotes.
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Affiliation(s)
- Dieter Maier
- Universität Hohenheim, Institut für Genetik (240), Garbenstr, 30, 70599 Stuttgart, Germany.
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Rand MD, Bland CE, Bond J. Methylmercury activates enhancer-of-split and bearded complex genes independent of the notch receptor. Toxicol Sci 2008; 104:163-76. [PMID: 18367466 DOI: 10.1093/toxsci/kfn060] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Methylmercury (MeHg) is a persistent environmental toxin that has targeted effects on fetal neural development. Although a number of cytotoxic mechanisms of MeHg have been characterized in cultured cells, its mode of action in the developing nervous system in vivo is less clear. Studies of MeHg-affected rodent and human brains show disrupted cortical and cerebellar architecture suggestive of mechanisms that augment cell signaling pathways potentially affecting cell migration and proliferation. We previously identified the Notch receptor pathway, a highly conserved signaling mechanism fundamental for neural development, as a target for MeHg-induced signaling in Drosophila neural cell lines. Here we have expanded our use of the Drosophila model to resolve a broader spectrum of transcriptional changes resulting from MeHg exposure in vivo and in vitro. Several Notch target genes within the Enhancer-of-split (E(spl)C) and Bearded (BrdC) complexes are upregulated with MeHg exposure in the embryo and in cultured neural cells. However, the profile of MeHg-induced E(spl)C and BrdC gene expression differs significantly from that seen with activation of the Notch receptor. Targeted knockdown of Notch and of the downstream coactivator Suppressor of Hairless (Su(H)), shows no effect on MeHg-induced transcription, indicating a novel Notch-independent mechanism of action for MeHg. MeHg transcriptional activation is partially mimicked by iodoacetamide but not by N-ethylmaleimide, two thiol-specific electrophiles, revealing a degree of specificity of cellular thiol targets in MeHg-induced transcriptional events.
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Affiliation(s)
- Matthew D Rand
- Department of Anatomy and Neurobiology, College of Medicine, University of Vermont, Burlington, VT 05405, USA.
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Discovery of functional elements in 12 Drosophila genomes using evolutionary signatures. Nature 2008; 450:219-32. [PMID: 17994088 DOI: 10.1038/nature06340] [Citation(s) in RCA: 462] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2007] [Accepted: 10/04/2007] [Indexed: 12/25/2022]
Abstract
Sequencing of multiple related species followed by comparative genomics analysis constitutes a powerful approach for the systematic understanding of any genome. Here, we use the genomes of 12 Drosophila species for the de novo discovery of functional elements in the fly. Each type of functional element shows characteristic patterns of change, or 'evolutionary signatures', dictated by its precise selective constraints. Such signatures enable recognition of new protein-coding genes and exons, spurious and incorrect gene annotations, and numerous unusual gene structures, including abundant stop-codon readthrough. Similarly, we predict non-protein-coding RNA genes and structures, and new microRNA (miRNA) genes. We provide evidence of miRNA processing and functionality from both hairpin arms and both DNA strands. We identify several classes of pre- and post-transcriptional regulatory motifs, and predict individual motif instances with high confidence. We also study how discovery power scales with the divergence and number of species compared, and we provide general guidelines for comparative studies.
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