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Berg C, Sieber M, Sun J. Finishing the egg. Genetics 2024; 226:iyad183. [PMID: 38000906 PMCID: PMC10763546 DOI: 10.1093/genetics/iyad183] [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: 07/05/2023] [Accepted: 09/27/2023] [Indexed: 11/26/2023] Open
Abstract
Gamete development is a fundamental process that is highly conserved from early eukaryotes to mammals. As germ cells develop, they must coordinate a dynamic series of cellular processes that support growth, cell specification, patterning, the loading of maternal factors (RNAs, proteins, and nutrients), differentiation of structures to enable fertilization and ensure embryonic survival, and other processes that make a functional oocyte. To achieve these goals, germ cells integrate a complex milieu of environmental and developmental signals to produce fertilizable eggs. Over the past 50 years, Drosophila oogenesis has risen to the forefront as a system to interrogate the sophisticated mechanisms that drive oocyte development. Studies in Drosophila have defined mechanisms in germ cells that control meiosis, protect genome integrity, facilitate mRNA trafficking, and support the maternal loading of nutrients. Work in this system has provided key insights into the mechanisms that establish egg chamber polarity and patterning as well as the mechanisms that drive ovulation and egg activation. Using the power of Drosophila genetics, the field has begun to define the molecular mechanisms that coordinate environmental stresses and nutrient availability with oocyte development. Importantly, the majority of these reproductive mechanisms are highly conserved throughout evolution, and many play critical roles in the development of somatic tissues as well. In this chapter, we summarize the recent progress in several key areas that impact egg chamber development and ovulation. First, we discuss the mechanisms that drive nutrient storage and trafficking during oocyte maturation and vitellogenesis. Second, we examine the processes that regulate follicle cell patterning and how that patterning impacts the construction of the egg shell and the establishment of embryonic polarity. Finally, we examine regulatory factors that control ovulation, egg activation, and successful fertilization.
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Affiliation(s)
- Celeste Berg
- Department of Genome Sciences, University of Washington, Seattle, WA 98195-5065USA
| | - Matthew Sieber
- Department of Physiology, UT Southwestern Medical Center, Dallas, TX 75390USA
| | - Jianjun Sun
- Department of Physiology and Neurobiology, University of Connecticut, Storrs, CT 06269USA
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Pechmann M, Kenny NJ, Pott L, Heger P, Chen YT, Buchta T, Özüak O, Lynch J, Roth S. Striking parallels between dorsoventral patterning in Drosophila and Gryllus reveal a complex evolutionary history behind a model gene regulatory network. eLife 2021; 10:e68287. [PMID: 33783353 PMCID: PMC8051952 DOI: 10.7554/elife.68287] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 03/24/2021] [Indexed: 12/18/2022] Open
Abstract
Dorsoventral pattering relies on Toll and BMP signalling in all insects studied so far, with variations in the relative contributions of both pathways. Drosophila and the beetle Tribolium share extensive dependence on Toll, while representatives of more distantly related lineages like the wasp Nasonia and bug Oncopeltus rely more strongly on BMP signalling. Here, we show that in the cricket Gryllus bimaculatus, an evolutionarily distant outgroup, Toll has, like in Drosophila, a direct patterning role for the ventral half of the embryo. In addition, Toll polarises BMP signalling, although this does not involve the conserved BMP inhibitor Sog/Chordin. Finally, Toll activation relies on ovarian patterning mechanisms with striking similarity to Drosophila. Our data suggest two surprising hypotheses: (1) that Toll's patterning function in Gryllus and Drosophila is the result of convergent evolution or (2) a Drosophila-like system arose early in insect evolution and was extensively altered in multiple independent lineages.
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Affiliation(s)
- Matthias Pechmann
- Institute for Zoology/Developmental Biology, Biocenter, University of CologneKölnGermany
| | | | - Laura Pott
- Institute for Zoology/Developmental Biology, Biocenter, University of CologneKölnGermany
| | - Peter Heger
- Regional Computing Centre (RRZK), University of CologneKölnGermany
| | - Yen-Ta Chen
- Institute for Zoology/Developmental Biology, Biocenter, University of CologneKölnGermany
| | - Thomas Buchta
- Institute for Zoology/Developmental Biology, Biocenter, University of CologneKölnGermany
| | - Orhan Özüak
- Institute for Zoology/Developmental Biology, Biocenter, University of CologneKölnGermany
| | - Jeremy Lynch
- Institute for Zoology/Developmental Biology, Biocenter, University of CologneKölnGermany
- Department of Biological Sciences, University of Illinois at ChicagoChicagoUnited States
| | - Siegfried Roth
- Institute for Zoology/Developmental Biology, Biocenter, University of CologneKölnGermany
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Ambrosi P, Chahda JS, Koslen HR, Chiel HJ, Mizutani CM. Modeling of the dorsal gradient across species reveals interaction between embryo morphology and Toll signaling pathway during evolution. PLoS Comput Biol 2014; 10:e1003807. [PMID: 25165818 PMCID: PMC4148200 DOI: 10.1371/journal.pcbi.1003807] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Accepted: 07/14/2014] [Indexed: 12/16/2022] Open
Abstract
Morphogenetic gradients are essential to allocate cell fates in embryos of varying sizes within and across closely related species. We previously showed that the maternal NF-κB/Dorsal (Dl) gradient has acquired different shapes in Drosophila species, which result in unequally scaled germ layers along the dorso-ventral axis and the repositioning of the neuroectodermal borders. Here we combined experimentation and mathematical modeling to investigate which factors might have contributed to the fast evolutionary changes of this gradient. To this end, we modified a previously developed model that employs differential equations of the main biochemical interactions of the Toll (Tl) signaling pathway, which regulates Dl nuclear transport. The original model simulations fit well the D. melanogaster wild type, but not mutant conditions. To broaden the applicability of this model and probe evolutionary changes in gradient distributions, we adjusted a set of 19 independent parameters to reproduce three quantified experimental conditions (i.e. Dl levels lowered, nuclear size and density increased or decreased). We next searched for the most relevant parameters that reproduce the species-specific Dl gradients. We show that adjusting parameters relative to morphological traits (i.e. embryo diameter, nuclear size and density) alone is not sufficient to reproduce the species Dl gradients. Since components of the Tl pathway simulated by the model are fast-evolving, we next asked which parameters related to Tl would most effectively reproduce these gradients and identified a particular subset. A sensitivity analysis reveals the existence of nonlinear interactions between the two fast-evolving traits tested above, namely the embryonic morphological changes and Tl pathway components. Our modeling further suggests that distinct Dl gradient shapes observed in closely related melanogaster sub-group lineages may be caused by similar sequence modifications in Tl pathway components, which are in agreement with their phylogenetic relationships. Embryo size can vary greatly among closely related species. How tissue specification either scales or is modified in the developing embryo in different species is an ongoing investigation in developmental biology. Here we asked how embryo morphology and specific molecular pathways influence tissue specification by altering the distribution of morphogens. Morphogens are molecules that form gradients that regulate gene expression patterns in a dosage-dependent fashion that result in tissue specification, and therefore are a prime target for evolution in order to adjust or maintain tissue proportions in relation to overall embryo size. We used a mathematical model to identify factors that influence the distribution of the Dorsal morphogen gradient that is responsible for patterning the dorsal-ventral axis of the Drosophila fruit fly embryo. We obtained experimental data from mutant conditions and different species of Drosophila to calibrate our model and found an interaction between embryo morphology and regulation of the Toll pathway, which regulates the Dorsal gradient. Furthermore, the model predicts that closely related species share similar modifications in Toll pathway components resulting in their species-specific gradient shapes, which are supported by interspecies amino acid comparison of the components Dorsal and Cactus.
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Affiliation(s)
- Priscilla Ambrosi
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Juan Sebastian Chahda
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Hannah R. Koslen
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Hillel J. Chiel
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail: (HJC); (CMM)
| | - Claudia Mieko Mizutani
- Department of Biology, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio, United States of America
- * E-mail: (HJC); (CMM)
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Stein DS, Stevens LM. Maternal control of the Drosophila dorsal-ventral body axis. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2014; 3:301-30. [PMID: 25124754 DOI: 10.1002/wdev.138] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2014] [Revised: 03/24/2014] [Accepted: 04/07/2014] [Indexed: 12/14/2022]
Abstract
UNLABELLED The pathway that generates the dorsal-ventral (DV) axis of the Drosophila embryo has been the subject of intense investigation over the previous three decades. The initial asymmetric signal originates during oogenesis by the movement of the oocyte nucleus to an anterior corner of the oocyte, which establishes DV polarity within the follicle through signaling between Gurken, the Drosophila Transforming Growth Factor (TGF)-α homologue secreted from the oocyte, and the Drosophila Epidermal Growth Factor Receptor (EGFR) that is expressed by the follicular epithelium cells that envelop the oocyte. Follicle cells that are not exposed to Gurken follow a ventral fate and express Pipe, a sulfotransferase that enzymatically modifies components of the inner vitelline membrane layer of the eggshell, thereby transferring DV spatial information from the follicle to the egg. These ventrally sulfated eggshell proteins comprise a localized cue that directs the ventrally restricted formation of the active Spätzle ligand within the perivitelline space between the eggshell and the embryonic membrane. Spätzle activates Toll, a transmembrane receptor in the embryonic membrane. Transmission of the Toll signal into the embryo leads to the formation of a ventral-to-dorsal gradient of the transcription factor Dorsal within the nuclei of the syncytial blastoderm stage embryo. Dorsal controls the spatially specific expression of a large constellation of zygotic target genes, the Dorsal gene regulatory network, along the embryonic DV circumference. This article reviews classic studies and integrates them with the details of more recent work that has advanced our understanding of the complex pathway that establishes Drosophila embryo DV polarity. For further resources related to this article, please visit the WIREs website. CONFLICT OF INTEREST The authors have declared no conflicts of interest for this article.
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Affiliation(s)
- David S Stein
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX, USA
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Carter JM, Baker SC, Pink R, Carter DRF, Collins A, Tomlin J, Gibbs M, Breuker CJ. Unscrambling butterfly oogenesis. BMC Genomics 2013; 14:283. [PMID: 23622113 PMCID: PMC3654919 DOI: 10.1186/1471-2164-14-283] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Accepted: 04/05/2013] [Indexed: 12/16/2022] Open
Abstract
Background Butterflies are popular model organisms to study physiological mechanisms
underlying variability in oogenesis and egg provisioning in response to
environmental conditions. Nothing is known, however, about; the
developmental mechanisms governing butterfly oogenesis, how polarity in the
oocyte is established, or which particular maternal effect genes regulate
early embryogenesis. To gain insights into these developmental mechanisms
and to identify the conserved and divergent aspects of butterfly oogenesis,
we analysed a de novo ovarian transcriptome of the Speckled Wood
butterfly Pararge aegeria (L.), and compared the results with known
model organisms such as Drosophila melanogaster and Bombyx
mori. Results A total of 17306 contigs were annotated, with 30% possibly novel or highly
divergent sequences observed. Pararge aegeria females expressed
74.5% of the genes that are known to be essential for D.
melanogaster oogenesis. We discuss the genes involved in all
aspects of oogenesis, including vitellogenesis and choriogenesis, plus those
implicated in hormonal control of oogenesis and transgenerational hormonal
effects in great detail. Compared to other insects, a number of significant
differences were observed in; the genes involved in stem cell maintenance
and differentiation in the germarium, establishment of oocyte polarity, and
in several aspects of maternal regulation of zygotic development. Conclusions This study provides valuable resources to investigate a number of divergent
aspects of butterfly oogenesis requiring further research. In order to fully
unscramble butterfly oogenesis, we also now also have the resources to
investigate expression patterns of oogenesis genes under a range of
environmental conditions, and to establish their function.
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Affiliation(s)
- Jean-Michel Carter
- Evolutionary Developmental Biology Research Group, Faculty of Health and Life Sciences, Department of Biological and Medical Sciences, Oxford Brookes University, Gipsy Lane, Headington, Oxford, OX3 0BP, UK
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Vreede BM, Lynch JA, Roth S, Sucena E. Co-option of a coordinate system defined by the EGFr and Dpp pathways in the evolution of a morphological novelty. EvoDevo 2013; 4:7. [PMID: 23448685 PMCID: PMC3621409 DOI: 10.1186/2041-9139-4-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2012] [Accepted: 12/06/2012] [Indexed: 12/01/2022] Open
Abstract
Background Morphological innovation is an elusive and fascinating concept in evolutionary biology. A novel structure may open up an array of possibilities for adaptation, and thus is fundamental to the evolution of complex multicellular life. We use the respiratory appendages on the dorsal-anterior side of the Drosophila eggshell as a model system for morphological novelty. To study the co-option of genetic pathways in the evolution of this novelty we have compared oogenesis and eggshell patterning in Drosophila melanogaster with Ceratitis capitata, a dipteran whose eggs do not bear dorsal appendages. Results During the final stages of oogenesis, the appendages are formed by specific groups of cells in the follicular epithelium of the egg chamber. These cells are defined via signaling activity of the Dpp and EGFr pathways, and we find that both pathways are active in C. capitata oogenesis. The transcription factor gene mirror is expressed downstream of EGFr activation in a dorsolateral domain in the D. melanogaster egg chamber, but could not be detected during C. capitata oogenesis. In D. melanogaster, mirror regulates the expression of two important genes: broad, which defines the appendage primordia, and pipe, involved in embryonic dorsoventral polarity. In C. capitata, broad remains expressed ubiquitously throughout the follicular epithelium, and is not restricted to the appendage primordia. Interestingly pipe expression did not differ between the two species. Conclusions Our analysis identifies both broad and mirror as important nodes that have been redeployed in the Drosophila egg chamber patterning network in the evolution of a morphologically novel feature. Further, our results show how pre-existing signals can provide an epithelium with a spatial coordinate system, which can be co-opted for novel patterns.
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Affiliation(s)
- Barbara Mi Vreede
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, Oeiras, Portugal.
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Technau M, Knispel M, Roth S. Molecular mechanisms of EGF signaling-dependent regulation of pipe, a gene crucial for dorsoventral axis formation in Drosophila. Dev Genes Evol 2011; 222:1-17. [PMID: 22198544 PMCID: PMC3291829 DOI: 10.1007/s00427-011-0384-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Accepted: 11/29/2011] [Indexed: 01/28/2023]
Abstract
During Drosophila oogenesis the expression of the sulfotransferase Pipe in ventral follicle cells is crucial for dorsoventral axis formation. Pipe modifies proteins that are incorporated in the ventral eggshell and activate Toll signaling which in turn initiates embryonic dorsoventral patterning. Ventral pipe expression is the result of an oocyte-derived EGF signal which down-regulates pipe in dorsal follicle cells. The analysis of mutant follicle cell clones reveals that none of the transcription factors known to act downstream of EGF signaling in Drosophila is required or sufficient for pipe regulation. However, the pipe cis-regulatory region harbors a 31-bp element which is essential for pipe repression, and ovarian extracts contain a protein that binds this element. Thus, EGF signaling does not act by down-regulating an activator of pipe as previously suggested but rather by activating a repressor. Surprisingly, this repressor acts independent of the common co-repressors Groucho or CtBP.
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Affiliation(s)
- Martin Technau
- Institute for Developmental Biology, Biocenter, University of Cologne, Zuelpicher Straße 47b, 50674, Cologne, Germany
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Abstract
The gene regulatory network (GRN) underpinning dorsal-ventral (DV) patterning of the Drosophila embryo is among the most thoroughly understood GRNs, making it an ideal system for comparative studies seeking to understand the evolution of development. With the emergence of widely applicable techniques for testing gene function, species with sequenced genomes, and multiple tractable species with diverse developmental modes, a phylogenetically broad and molecularly deep understanding of the evolution of DV axis formation in insects is feasible. Here, we review recent progress made in this field, compare our emerging molecular understanding to classical embryological experiments, and suggest future directions of inquiry.
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Affiliation(s)
- Jeremy A. Lynch
- Institute for Developmental Biology, University of Cologne, 50674 Cologne, Germany
| | - Siegfried Roth
- Institute for Developmental Biology, University of Cologne, 50674 Cologne, Germany
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Cho YS, Stevens LM, Stein D. Pipe-dependent ventral processing of Easter by Snake is the defining step in Drosophila embryo DV axis formation. Curr Biol 2010; 20:1133-7. [PMID: 20605458 DOI: 10.1016/j.cub.2010.04.056] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2010] [Revised: 04/25/2010] [Accepted: 04/27/2010] [Indexed: 11/28/2022]
Abstract
The establishment of Drosophila embryonic dorsal-ventral (DV) polarity relies on serine proteolytic activity in the perivitelline space between the embryonic membrane and the eggshell. Gastrulation Defective cleaves and activates Snake, which processes and activates Easter, which cleaves Spätzle to form the activating ligand for the Toll receptor. Ventral restriction of ligand formation depends on the Pipe sulfotransferase, which is expressed in ventral cells of the follicular epithelium surrounding the developing oocyte. Pipe modifies components of the developing eggshell to produce a ventral cue embedded in the vitelline membrane. This ventral cue is believed to promote one or more of the proteolysis steps in the perivitelline space. By examining the processing of transgenic, tagged versions of the perivitelline proteins during DV patterning, we find that the proteolysis of Easter by Snake is the first Pipe-dependent step and therefore the key ventrally restricted event in the protease cascade. We also find that Snake and Easter associate together in a complex in both wild-type and pipe mutant-derived embryos. This observation suggests a mechanism in which the sulfated target of Pipe promotes a productive interaction between Snake and Easter, perhaps by facilitating conformational changes in a complex containing the two proteins.
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Affiliation(s)
- Yong Suk Cho
- Section of Molecular Cell and Developmental Biology and Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA
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