scholarly journals mago nashi mediates the posterior follicle cell-to-oocyte signal to organize axis formation in Drosophila

Development ◽  
1997 ◽  
Vol 124 (16) ◽  
pp. 3197-3207 ◽  
Author(s):  
P.A. Newmark ◽  
S.E. Mohr ◽  
L. Gong ◽  
R.E. Boswell
Keyword(s):  
Germ Plasm ◽  
Egf Receptor ◽  
Germ Line ◽  
Follicle Cell ◽  
Posterior Pole ◽  
Follicle Cells ◽  
Oocyte Nucleus ◽  
Axis Formation ◽  
Pole Plasm ◽  
Mago Nashi

Establishment of the anteroposterior and dorsoventral axes in the Drosophila egg chamber requires reciprocal signaling between the germ line and soma. Upon activation of the Drosophila EGF receptor in the posterior follicle cells, these cells signal back to the oocyte, resulting in a reorganization of the oocyte cytoplasm and anterodorsal migration of the oocyte nucleus. We demonstrate that the gene mago nashi (mago) encodes an evolutionarily conserved protein that must be localized within the posterior pole plasm for germ-plasm assembly and Caenorhabditis elegans mago is a functional homologue of Drosophila mago. In the absence of mago+ function during oogenesis, the anteroposterior and dorsoventral coordinates of the oocyte are not specified and the germ plasm fails to assemble.

scholarly journals The Drosophila anterior-posterior axis is polarized by asymmetric myosin activation

2021 ◽  
Author(s):  
Helene Doerflinger ◽  
Vitaly Zimyanin ◽  
Daniel St Johnston
Keyword(s):  
Light Chain ◽  
Kinase Inhibitor ◽  
Germ Line ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Axis Formation ◽  
Posterior Cortex ◽  
Cortical Tension ◽  
Anterior Posterior ◽  
Anterior Posterior Axis

The Drosophila anterior-posterior (AP) axis is specified at mid-oogenesis when Par-1 kinase is recruited to the posterior cortex of the oocyte, where it polarises the microtubule cytoskeleton to define where the axis determinants, bicoid and oskar mRNAs localise. This polarity is established in response to an unknown signal from the follicle cells, but how this occurs is unclear. Here we show that the myosin chaperone, Unc-45 and Non-Muscle Myosin II (MyoII) are required in the germ line upstream of Par-1 in polarity establishment. Furthermore, the Myosin regulatory Light Chain (MRLC) is di-phosphorylated at the oocyte posterior in response to the follicle cell signal, inducing longer pulses of myosin contractility at the posterior and increased cortical tension. Over-expression of MRLC-T21A that cannot be di-phosphorylated or acute treatment with the Myosin light chain kinase inhibitor ML-7 abolish Par-1 localisation, indicating that posterior of MRLC di-phosphorylation is essential for polarity. Thus, asymmetric myosin activation polarizes the anterior-posterior axis by recruiting and maintaining Par-1 at the posterior cortex. This raises an intriguing parallel with AP axis formation in C. elegans where MyoII is also required to establish polarity, but functions to localize the anterior PAR proteins rather than PAR-1.

Mutations in the Drosophila gene bullwinkle cause the formation of abnormal eggshell structures and bicaudal embryos

Development ◽  
1995 ◽  
Vol 121 (9) ◽  
pp. 3023-3033 ◽  
Author(s):  
K.R. Rittenhouse ◽  
C.A. Berg
Keyword(s):  
Cell Migration ◽  
Cell Fate ◽  
Germ Line ◽  
Follicle Cell ◽  
Posterior Pole ◽  
Mirror Image ◽  
Follicle Cells ◽  
Anterior Pole ◽  
Posterior Group ◽  
General Transport

Subcellular localization of gene products and cell migration are both critical for pattern formation during development. The bullwinkle gene is required in Drosophila for disparate aspects of these processes. In females mutant at the bullwinkle locus, the follicle cells that synthesize the dorsal eggshell filaments do not migrate properly, creating short, broad structures. Mosaic analyses demonstrate that wild-type BULLWINKLE function is required in the germ line for these migrations. Since the mRNA for gurken, the putative ligand that signals dorsal follicle cell fate, is correctly localized in bullwinkle mutants, we conclude that our bullwinkle alleles do not affect the dorsoventral polarity of the oocyte and thus must be affecting the follicle cell migrations in some other way. In addition, the embryos that develop from bullwinkle mothers are bicaudal. A KINESIN:beta-GALACTOSIDASE fusion protein is correctly localized to the posterior pole of bullwinkle oocytes during stage 9. Thus, the microtubule structure of the oocyte and general transport along it do not appear to be disrupted prior to cytoplasmic streaming. Unlike other bicaudal mutants, oskar mRNA is localized correctly to the posterior pole of the oocyte at stage 10. By early embryogenesis, however, some oskar mRNA is mislocalized to the anterior pole. Consistent with the mislocalization of oskar mRNA, a fraction of the VASA protein and nanos mRNA are also mislocalized to the anterior pole of bullwinkle embryos. Mislocalization of nanos mRNA to the anterior is dependent on functional VASA protein. Although the mirror-image segmentation defects appear to result from the action of the posterior group genes, germ cells are not formed at the anterior pole. The bicaudal phenotype is also germ-line dependent for bullwinkle. We suspect that BULLWINKLE interacts with the cytoskeleton and extracellular matrix and is necessary for gene product localization and cell migration during oogenesis after stage 10a.

Combined activities of Gurken and decapentaplegic specify dorsal chorion structures of the Drosophila egg

Development ◽  
2000 ◽  
Vol 127 (4) ◽  
pp. 841-850 ◽  
Author(s):  
F. Peri ◽  
S. Roth
Keyword(s):  
Egf Receptor ◽  
Receptor Activation ◽  
Posterior Pole ◽  
Follicle Cells ◽  
Follicular Epithelium ◽  
Oocyte Nucleus ◽  
Main Body ◽  
Dorsal Appendage ◽  
Broad Complex ◽  
Anterior Posterior

During Drosophila oogenesis Gurken, associated with the oocyte nucleus, activates the Drosophila EGF receptor in the follicular epithelium. Gurken first specifies posterior follicle cells, which in turn signal back to the oocyte to induce the migration of the oocyte nucleus from a posterior to an anterior-dorsal position. Here, Gurken signals again to specify dorsal follicle cells, which give rise to dorsal chorion structures including the dorsal appendages. If Gurken signaling is delayed and starts after stage 6 of oogenesis the nucleus remains at the posterior pole of the oocyte. Eggs develop with a posterior ring of dorsal appendage material that is produced by main-body follicle cells expressing the gene Broad-Complex. They encircle terminal follicle cells expressing variable amounts of the TGFbeta homologue, decapentaplegic. By ectopically expressing decapentaplegic and clonal analysis with Mothers against dpp we show that Decapentaplegic signaling is required for Broad-Complex expression. Thus, the specification and positioning of dorsal appendages along the anterior-posterior axis depends on the intersection of both Gurken and Decapentaplegic signaling. This intersection also induces rhomboid expression and thereby initiates the positive feedback loop of EGF receptor activation, which positions the dorsal appendages along the dorsal-ventral egg axis.

Dorsoventral axis formation in Drosophila depends on the correct dosage of the gene gurken

Development ◽  
1994 ◽  
Vol 120 (9) ◽  
pp. 2457-2463 ◽  
Author(s):  
F.S. Neuman-Silberberg ◽  
T. Schupbach
Keyword(s):  
Germ Line ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Limiting Factor ◽  
Axis Formation ◽  
Dorsoventral Patterning ◽  
Wild Type ◽  
Cell Fates ◽  
Dorsoventral Axis ◽  
Signaling Process

The Drosophila gene gurken participates in a signaling process that occurs between the germ line and the somatic cells (follicle cells) of the ovary. This process is required for correct patterning of the dorsoventral axis of both the egg and the embryo. gurken produces a spatially localized transcript which encodes a TGF-alpha-like molecule (Neuman-Silberberg and Schupbach, Cell 75, 165–174, 1993). Mutations in gurken cause a ventralized phenotype in egg and embryo. To determine whether the gurken gene product plays an instructive role in dorsoventral patterning, we constructed females containing extra copies of a gurken transgene. Such females produce dorsalized eggs and embryos, which is expected if gurken acts as a limiting factor in the dorsoventral patterning process. In addition, the expression pattern of the gene rhomboid in the follicle cells is altered in ovaries of females containing extra copies of gurken. Our results indicate that changing gurken dosage in otherwise wild-type ovaries is sufficient to alter the number of somatic follicle cells directed to the dorsal fate. Therefore the gurken-torpedo signaling process plays an instructive role in oogenesis. It induces dorsal cell fates in the follicle cell epithelium and it controls the production of maternal components that will direct the embryonic dorsoventral pattern after fertilization.

Mechanisms of Gurken-dependentpiperegulation and the robustness of dorsoventral patterning inDrosophila

Development ◽  
2002 ◽  
Vol 129 (12) ◽  
pp. 2965-2975 ◽  
Author(s):  
Francesca Peri ◽  
Martin Technau ◽  
Siegfried Roth
Keyword(s):  
Egf Receptor ◽  
Follicle Cell ◽  
Dorsal Side ◽  
Drosophila Embryo ◽  
Follicle Cells ◽  
Follicular Epithelium ◽  
Axis Formation ◽  
Embryonic Patterning ◽  
Cell Fates ◽  
Egg Chamber

The restriction of Pipe, a potential glycosaminoglycan-modifying enzyme, to ventral follicle cells of the egg chamber is essential for dorsoventral axis formation in the Drosophila embryo. pipe repression depends on the TGFα-like ligand Gurken, which activates the Drosophila EGF receptor in dorsal follicle cells. An analysis of Raf mutant clones shows that EGF signalling is required cell-autonomously in all dorsal follicle cells along the anteroposterior axis of the egg chamber to repress pipe. However, the autoactivation of EGF signalling important for dorsal follicle cell patterning has no influence on pipe expression. Clonal analysis shows that also the mirror-fringe cassette suggested to establish a secondary signalling centre in the follicular epithelium is not involved in pipe regulation. These findings support the view that the pipe domain is directly delimited by a long-range Gurken gradient. Pipe induces ventral cell fates in the embryo via activation of the Spätzle/Toll pathway. However, large dorsal patches of ectopic pipe expression induced by Raf clones rarely affect embryonic patterning if they are separated from the endogenous pipe domain. This indicates that potent inhibitory processes prevent pipe dependent Toll activation at the dorsal side of the egg.

scholarly journals The RNA-binding protein Tsunagi interacts with Mago Nashi to establish polarity and localize oskar mRNA during Drosophila oogenesis

2001 ◽  
Vol 15 (21) ◽  
pp. 2886-2899 ◽  
Author(s):  
Stephanie E. Mohr ◽  
Simon T. Dillon ◽  
Robert E. Boswell
Keyword(s):  
Germ Cells ◽  
Rna Binding ◽  
Germ Line ◽  
Binding Protein ◽  
Primordial Germ Cells ◽  
Rna Binding Protein ◽  
Follicle Cell ◽  
Oocyte Nucleus ◽  
Egg Chambers ◽  
Mago Nashi

In Drosophila melanogaster, formation of the axes and the primordial germ cells is regulated by interactions between the germ line-derived oocyte and the surrounding somatic follicle cells. This reciprocal signaling results in the asymmetric localization of mRNAs and proteins critical for these oogenic processes. Mago Nashi protein interprets the posterior follicle cell-to-oocyte signal to establish the major axes and to determine the fate of the primordial germ cells. Using the yeast two-hybrid system we have identified an RNA-binding protein, Tsunagi, that interacts with Mago Nashi protein. The proteins coimmunoprecipitate and colocalize, indicating that they form a complex in vivo. Immunolocalization reveals that Tsunagi protein is localized within the posterior oocyte cytoplasm during stages 1–5 and 8–9, and that this localization is dependent on wild-type mago nashifunction. When tsunagi function is removed from the germ line, egg chambers develop in which the oocyte nucleus fails to migrate,oskar mRNA is not localized within the posterior pole, and dorsal–ventral pattern abnormalities are observed. These results show that a Mago Nashi–Tsunagi protein complex is required for interpreting the posterior follicle cell-to-oocyte signal to define the major body axes and to localize components necessary for determination of the primordial germ cells.

Sequential activation of the EGF receptor pathway during Drosophila oogenesis establishes the dorsoventral axis

Development ◽  
1998 ◽  
Vol 125 (2) ◽  
pp. 191-200 ◽  
Author(s):  
A. Sapir ◽  
R. Schweitzer ◽  
B.Z. Shilo
Keyword(s):  
Target Genes ◽  
Egf Receptor ◽  
Ectopic Expression ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Cell Fates ◽  
Dorsoventral Axis ◽  
Spatial Coordinates ◽  
Sequential Activation

Previous work has demonstrated a role for the Drosophila EGF receptor (Torpedo/DER) and its ligand, Gurken, in the determination of anterioposterior and dorsoventral axes of the follicle cells and oocyte. The roles of DER in establishing the polarity of the follicle cells were examined further, by following the expression of DER-target genes. One class of genes (e.g. kekon) is induced by the DER pathway at all stages. Broad expression of kekon at the stage in which the follicle cells migrate posteriorly over the oocyte, demonstrates the capacity of the pathway to pattern all follicle cells except the ventral-most rows. This may provide the spatial coordinates for the ventral-most follicle cell fates. A second group of target genes (e.g. rhomboid (rho)) is induced only at later stages of oogenesis, and may require additional inputs by signals emanating from the anterior, stretch follicle cells. The function of Rho was analyzed by ectopic expression in the stretch follicle cells, and shown to induce a non-autonomous dorsalizing activity that is independent of Gurken. Rho thus appears to be involved in processing a DER ligand in the follicle cells, to pattern the egg chamber and allow persistent activation of the DER pathway during formation of the dorsal appendages.

Patterning of the follicle cell epithelium along the anterior-posterior axis during Drosophila oogenesis

Development ◽  
1998 ◽  
Vol 125 (15) ◽  
pp. 2837-2846 ◽  
Author(s):  
A. Gonzalez-Reyes ◽  
D. St Johnston
Keyword(s):  
Follicle Cell ◽  
Cell Types ◽  
Follicle Cells ◽  
Follicular Epithelium ◽  
Axis Formation ◽  
Main Body ◽  
Drosophila Oogenesis ◽  
Egfr Mutant ◽  
Anterior Posterior ◽  
Anterior Posterior Axis

Gurken signals from the oocyte to the adjacent follicle cells twice during Drosophila oogenesis; first to induce posterior fate, thereby polarising the anterior-posterior axis of the future embryo and then to induce dorsal fate and polarise the dorsal-ventral axis. Here we show that Gurken induces two different follicle cell fates because the follicle cells at the termini of the egg chamber differ in their competence to respond to Gurken from the main-body follicle cells in between. By removing the putative Gurken receptor, Egfr, in clones of cells, we show that Gurken signals directly to induce posterior fate in about 200 cells, defining a terminal competence domain that extends 10–11 cell diameters from the pole. Furthermore, small clones of Egfr mutant cells at the posterior interpret their position with respect to the pole and differentiate as the appropriate anterior cell type. Thus, the two terminal follicle cell populations contain a symmetric prepattern that is independent of Gurken signalling. These results suggest a three-step model for the anterior-posterior patterning of the follicular epithelium that subdivides this axis into at least five distinct cell types. Finally, we show that Notch plays a role in both the specification and patterning of the terminal follicle cells, providing a possible explanation for the defect in anterior-posterior axis formation caused by Notch and Delta mutants.

scholarly journals Requirement for cell-proliferation control genes in Drosophila oogenesis.

Genetics ◽  
1991 ◽  
Vol 127 (3) ◽  
pp. 525-533
Author(s):  
J Szabad ◽  
V A Jursnich ◽  
P J Bryant
Keyword(s):  
Cell Proliferation ◽  
Germ Line ◽  
Follicle Cell ◽  
Mitotic Recombination ◽  
Follicle Cells ◽  
Egg Development ◽  
Proliferation Control ◽  
Dominant Female ◽  
Female Germ Line ◽  
Cell Proliferation Control

Abstract Genes that are required for cell proliferation control in Drosophila imaginal discs were tested for function in the female germ-line and follicle cells. Chimeras and mosaics were produced in which developing oocytes and nurse cells were mutant at one of five imaginal disc overgrowth loci (fat, lgd, lgl, c43 and dco) while the enveloping follicle cells were normal. The chimeras were produced by transplantation of pole cells and the mosaics were produced by X-ray-induced mitotic recombination using the dominant female-sterile technique. The results show that each of the genes tested plays an essential role in the development or function of the female germ line. The fat, lgl and c43 homozygous germ-line clones fail to produce eggs, indicating a germ-line requirement for the corresponding genes. Perdurance of the fat+ gene product in mitotic recombination clones allows the formation of a few infertile eggs from fat homozygous germ-line cells. The lgd homozygous germ-line clones give rise to a few eggs with abnormal chorionic appendages, a defect thought to result from defective cell communication between the mutant germ-line and the nonmutant follicle cells. One allele of dco (dcole88) prevents egg development when homozygous in the germ line, whereas the dco18 allele has no effect on germ-line development. Fs(2)Ugra, a recently described follicle cell-dependent dominant female-sterile mutation, allowed the analysis of egg primordia in which fat, lgd or lgl homozygous mutant follicle cells surrounded normal oocytes. The results show that the fat and lgd genes are not required for follicle cell functions, while absence of lgl function in follicles prevents egg development.(ABSTRACT TRUNCATED AT 250 WORDS)

Drosophila bunched integrates opposing DPP and EGF signals to set the operculum boundary

Development ◽  
2000 ◽  
Vol 127 (4) ◽  
pp. 745-754 ◽  
Author(s):  
L.L. Dobens ◽  
J.S. Peterson ◽  
J. Treisman ◽  
L.A. Raftery
Keyword(s):  
Cell Fate ◽  
Egf Receptor ◽  
Ovarian Follicle ◽  
Ectopic Expression ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Sharp Boundary ◽  
Smad Protein ◽  
Multiple Cell ◽  
Egf Signaling

The Drosophila BMP homolog DPP can function as a morphogen, inducing multiple cell fates across a developmental field. However, it is unknown how graded levels of extracellular DPP are interpreted to organize a sharp boundary between different fates. Here we show that opposing DPP and EGF signals set the boundary for an ovarian follicle cell fate. First, DPP regulates gene expression in the follicle cells that will create the operculum of the eggshell. DPP induces expression of the enhancer trap reporter A359 and represses expression of bunched, which encodes a protein similar to the mammalian transcription factor TSC-22. Second, DPP signaling indirectly regulates A359 expression in these cells by downregulating expression of bunched. Reduced bunched function restores A359 expression in cells that lack the Smad protein MAD; ectopic expression of BUNCHED suppresses A359 expression in this region. Importantly, reduction of bunched function leads to an expansion of the operculum and loss of the collar at its boundary. Third, EGF signaling upregulates expression of bunched. We previously demonstrated that the bunched expression pattern requires the EGF receptor ligand GURKEN. Here we show that activated EGF receptor is sufficient to induce ectopic bunched expression. Thus, the balance of DPP and EGF signals sets the boundary of bunched expression. We propose that the juxtaposition of cells with high and low BUNCHED activity organizes a sharp boundary for the operculum fate.

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