Drosophila puckered regulates Fos/Jun levels during follicle cell morphogenesis

Development ◽  
2001 ◽  
Vol 128 (10) ◽  
pp. 1845-1856 ◽  
Author(s):  
L.L. Dobens ◽  
E. Martin-Blanco ◽  
A. Martinez-Arias ◽  
F.C. Kafatos ◽  
L.A. Raftery
Keyword(s):  
Nurse Cell ◽  
Ectopic Expression ◽  
Follicle Cell ◽  
Small Gtpase ◽  
Dominant Negative ◽  
Drosophila Embryo ◽  
Follicle Cells ◽  
Cell Morphogenesis ◽  
Jnk Pathway ◽  
Egg Chambers

puckered (puc) encodes a VH1-like phosphatase that down-regulates Jun kinase (JNK) activity during dorsal closure of the Drosophila embryo. We report a role for puc in follicle cell morphogenesis during oogenesis. puc mRNA accumulates preferentially in the centripetally migrating follicle cells and cells of the elongating dorsal appendages. Proper levels of Puc activity in the follicle cells are critical for the production of a normal egg: either reduced or increased Puc activity result in incomplete nurse cell dumping and aberrant dorsal appendages. Phenotypes associated with puc mutant follicle cells include altered DE-cadherin expression in the follicle cells and a failure of nurse cell dumping to coordinate with dorsal appendage elongation, leading to the formation of cup-shaped egg chambers. The JNK pathway target A251-lacZ showed cell-type-specific differences in its regulation by puc and by the small GTPase DRac1. puc mutant cells displayed region-specific ectopic expression of the A251-lacZ enhancer trap whereas overexpression of a transgene encoding Puc was sufficient to suppress lacZ expression in a cell autonomous fashion. Strikingly, decreased or increased puc function leads to a corresponding increase or decrease, respectively, of Fos and Jun protein levels. Taken together, these data indicate that puc modulates gene expression responses by antagonizing a Ρ GTPase signal transduction pathway that stabilizes the AP-1 transcription factor. Consistent with this, overexpression of a dominant negative DRac1 resulted in lower levels of Fos/Jun.

scholarly journals Cell type-specific roles for Cdc42, Rac, and RhoL in Drosophila oogenesis.

1996 ◽  
Vol 133 (3) ◽  
pp. 617-630 ◽  
Author(s):  
A M Murphy ◽  
D J Montell
Keyword(s):  
Nurse Cell ◽  
Follicle Cell ◽  
Dominant Negative ◽  
Follicle Cells ◽  
Cell Type ◽  
Specific Effects ◽  
Rho Protein ◽  
Cell Type Specific ◽  
Mutant Forms ◽  
Drosophila Ovary

The Rho subfamily of GTPases has been shown to regulate cellular morphology. We report the discovery of a new member of the Rho family, named RhoL, which is equally similar to Rac, Rho, and Cdc42. Expression of a dominant-negative RhoL transgene in the Drosophila ovary caused nurse cells to collapse and fuse together. Mutant forms of Cdc42 mimicked this effect. Expression of constitutively active RhoL led to nurse cell subcortical actin breakdown and disruption of nurse cell-follicle cell contacts, followed by germ cell apoptosis. In contrast, Rac activity was specifically required for migration of a subset of follicle cells called border cells. All three activities were necessary for normal transfer of nurse cell cytoplasm to the oocyte. These results suggest that Rho protein activities have cell type-specific effects on morphogenesis.

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.

Drac1 and Crumbs participate in amnioserosa morphogenesis during dorsal closure in Drosophila

2002 ◽  
Vol 115 (10) ◽  
pp. 2119-2129 ◽  
Author(s):  
Nicholas Harden ◽  
Michael Ricos ◽  
Kelly Yee ◽  
Justina Sanny ◽  
Caillin Langmann ◽  
...  
Keyword(s):  
Morphological Changes ◽  
Shape Change ◽  
Apical Cell ◽  
Small Gtpase ◽  
Dominant Negative ◽  
Epithelial Morphogenesis ◽  
Drosophila Embryo ◽  
Dorsal Closure ◽  
Contractile Apparatus ◽  
Constitutively Active

Dorsal closure of the Drosophila embryo involves morphological changes in two epithelia, the epidermis and the amnioserosa, and is a popular system for studying the regulation of epithelial morphogenesis. We previously implicated the small GTPase Drac1 in the assembly of an actomyosin contractile apparatus, contributing to cell shape change in the epidermis during dorsal closure. We now present evidence that Drac1 and Crumbs, a determinant of epithelial polarity, are involved in setting up an actomyosin contractile apparatus that drives amnioserosa morphogenesis by inducing apical cell constriction. Expression of constitutively active Drac1 causes excessive constriction of amnioserosa cells and contraction of the tissue, whereas expression of dominant-negative Drac1 impairs amnioserosa morphogenesis. These Drac1 transgenes may be acting through their effects on the amnioserosa cytoskeleton, as constitutively active Drac1 causes increased staining for F-actin and myosin, whereas dominant-negative Drac1 reduces F-actin levels. Overexpression of Crumbs causes premature cell constriction in the amnioserosa, and dorsal closure defects are seen in embryos homozygous for hypomorphic crumbs alleles. The ability of constitutively active Drac1 to cause contraction of the amnioserosa is impaired in a crumbsmutant background. We propose that amnioserosa morphogenesis is a useful system for studying the regulation of epithelial morphogenesis by Drac1.

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.

scholarly journals fs (1) Yb is required for ovary follicle cell differentiation in Drosophila melanogaster and has genetic interactions with the Notch group of neurogenic genes.

Genetics ◽  
1995 ◽  
Vol 140 (1) ◽  
pp. 207-217 ◽  
Author(s):  
E Johnson ◽  
S Wayne ◽  
R Nagoshi
Keyword(s):  
Cell Fate ◽  
Ovarian Follicle ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Female Sterility ◽  
Specific Factor ◽  
Temperature Sensitive ◽  
Egg Maturation ◽  
Egg Chambers ◽  
Mutant Phenotypes

Abstract Phenotypic and genetic analyses demonstrate that fs (1) Yb activity is required in the soma for the development of a subset of ovarian follicle cells and to support later stages of egg maturation. Mutations in fs (1) Yb cause a range of ovarian phenotypes, from the improper segregation of egg chambers to abnormal dorsal appendage formation. The mutant phenotypes associated with fs (1) Yb are very similar to the ovarian aberrations produced by temperature-sensitive alleles of Notch and Delta. Possible functional or regulatory interactions between fs (1) Yb and Notch are suggested by genetic studies. A duplication of the Notch locus partially suppresses the female-sterility caused by fs (1) Yb mutations, while reducing Notch dosage makes the fs (1) Yb mutant phenotype more severe. In addition, fs (1) Yb alleles also interact with genes that are known to act with or regulate Notch activity, including Delta, daughterless, and mastermind. However, differences between the mutant ovarian phenotype of fs (1) Yb and that of Notch or Delta indicate that the genes do not have completely overlapping functions in the ovary. We propose that fs (1) Yb acts as an ovary-specific factor that determines follicle cell fate.

Regulation of cell proliferation and patterning in Drosophila oogenesis by Hedgehog signaling

Development ◽  
2000 ◽  
Vol 127 (10) ◽  
pp. 2165-2176 ◽  
Author(s):  
Y. Zhang ◽  
D. Kalderon
Keyword(s):  
Hedgehog Signaling ◽  
Developmental Stages ◽  
Somatic Cells ◽  
Follicle Cell ◽  
Follicle Cells ◽  
Cell Lineages ◽  
Egg Chambers ◽  
Hh Signaling ◽  
Egg Chamber ◽  
Activity Loss

The localized expression of Hedgehog (Hh) at the extreme anterior of Drosophila ovarioles suggests that it might provide an asymmetric cue that patterns developing egg chambers along the anteroposterior axis. Ectopic or excessive Hh signaling disrupts egg chamber patterning dramatically through primary effects at two developmental stages. First, excess Hh signaling in somatic stem cells stimulates somatic cell over-proliferation. This likely disrupts the earliest interactions between somatic and germline cells and may account for the frequent mis-positioning of oocytes within egg chambers. Second, the initiation of the developmental programs of follicle cell lineages appears to be delayed by ectopic Hh signaling. This may account for the formation of ectopic polar cells, the extended proliferation of follicle cells and the defective differentiation of posterior follicle cells, which, in turn, disrupts polarity within the oocyte. Somatic cells in the ovary cannot proliferate normally in the absence of Hh or Smoothened activity. Loss of protein kinase A activity restores the proliferation of somatic cells in the absence of Hh activity and allows the formation of normally patterned ovarioles. Hence, localized Hh is not essential to direct egg chamber patterning.

The neurogenic locus brainiac cooperates with the Drosophila EGF receptor to establish the ovarian follicle and to determine its dorsal-ventral polarity

Development ◽  
1992 ◽  
Vol 116 (1) ◽  
pp. 177-192 ◽  
Author(s):  
S. Goode ◽  
D. Wright ◽  
A.P. Mahowald
Keyword(s):  
Nurse Cell ◽  
Egf Receptor ◽  
Ovarian Follicle ◽  
Follicle Cell ◽  
Cell Complex ◽  
Follicle Cells ◽  
Sensitive Period ◽  
Cell Fates ◽  
Genetic Mosaic

We have characterized the function of a new neurogenic locus, brainiac (brn), during oogenesis. Homozygous brn females lay eggs with fused dorsal appendages, a phenotype associated with torpedo (top) alleles of the Drosophila EGF receptor (DER) locus. By constructing double mutant females for both brn and top, we have found that brn is required for determining the dorsal-ventral polarity of the ovarian follicle. However, embryos from mature brn eggs develop a neurogenic phenotype which can be zygotically rescued if a wild-type sperm fertilizes the egg. This is the first instance of a Drosophila gene required for determination of dorsal-ventral follicle cell fates that is not required for determination of embryonic dorsal-ventral cell fates. The temperature-sensitive period for brn dorsal-ventral patterning begins at the inception of vitellogenesis. The interaction between brn and DER is also required for at least two earlier follicle cell activities which are necessary to establish the ovarian follicle. Prefollicular cells fail to migrate between each oocyte/nurse cell complex, resulting in follicles with multiple sets of oocytes and nurse cells. brn and DER function is also required for establishing and/or maintaining a continuous follicular epithelium around each oocyte/nurse cell complex. These brn functions as well as the brn requirement for determination of dorsal-ventral polarity appear to be genetically separable functions of the brn locus. Genetic mosaic experiments show that brn is required in the germline during these processes whereas the DER is required in the follicle cells. We propose that brn may be part of a germline signaling pathway differentially regulating successive DER-dependent follicle cell activities of migration, division and/or adhesion and determination during oogenesis. These experiments indicate that brn is required in both tyrosine kinase and neurogenic intercellular signaling pathways. Moreover, the functions of brn in oogenesis are distinct from those of Notch and Delta, two other neurogenic loci that are known to be required for follicular development.

scholarly journals Intracellular Targeting of a Hordeiviral Membrane-Spanning Movement Protein: Sequence Requirements and Involvement of an Unconventional Mechanism

2007 ◽  
Vol 82 (3) ◽  
pp. 1284-1293 ◽  
Author(s):  
Mikhail V. Schepetilnikov ◽  
Andrey G. Solovyev ◽  
Elena N. Gorshkova ◽  
Joachim Schiemann ◽  
Alexey I. Prokhnevsky ◽  
...  
Keyword(s):  
Intracellular Transport ◽  
Fluorescent Protein ◽  
Ectopic Expression ◽  
Small Gtpase ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Detectable Effect ◽  
Movement Proteins ◽  
Membrane Spanning ◽  
Green Fluorescent

ABSTRACT The membrane-spanning protein TGBp3 is one of the three movement proteins (MPs) of Poa semilatent virus. TGBp3 is thought to direct other viral MPs and genomic RNA to peripheral bodies located in close proximity to plasmodesmata. We used the ectopic expression of green fluorescent protein-fused TGBp3 in epidermal cells of Nicotiana benthamiana leaves to study the TGBp3 intracellular trafficking pathway. Treatment with inhibitors was used to reveal that the targeting of TGBp3 to plasmodesmata does not require a functional cytoskeleton or secretory system. In addition, the suppression of endoplasmic reticulum-derived vesicle formation by a dominant negative mutant of small GTPase Sar1 had no detectable effect on TGBp3 trafficking to peripheral bodies. Collectively, these results suggested the involvement of an unconventional pathway in the intracellular transport of TGBp3. The determinants of targeting to plasmodesmata were localized to the C-terminal region of TGBp3, including the conserved hydrophilic and terminal membrane-spanning domains.

scholarly journals INTERCELLULAR MIGRATION OF CENTRIOLES IN THE GERMARIUM OF DROSOPHILA MELANOGASTER

1970 ◽  
Vol 45 (2) ◽  
pp. 306-320 ◽  
Author(s):  
Anthony P. Mahowald ◽  
Joan M. Strassheim
Keyword(s):  
Follicle Cell ◽  
Cell Cluster ◽  
Follicle Cells ◽  
Oocyte Nucleus ◽  
Nurse Cells ◽  
Serial Sections ◽  
Cell Border ◽  
Ring Canals ◽  
Egg Chambers ◽  
Stage 1

A cluster of centrioles has been found in the early Drosophila oocyte. Since the oocyte is connected to 15 nurse cells by a system of intercellular bridges or ring canals, the possibility that the cluster of centrioles arose in the germarium from an intercellular migration of centrioles from the nurse cells to the oocyte was analyzed in serial sections for the electron microscope. Initially, all of the 16 cells of the future egg chambers possess centrioles, which are located in a juxtanuclear position. At the time the 16 cell cluster becomes arranged in a lens-shaped layer laterally across the germarium, the centrioles lose their juxtanuclear position and move towards the oocyte. By the time the 16 cell cluster of cells is surrounded by follicle cells (Stage 1), between 14 and 17 centrioles are found in the oocyte. Later, these centrioles become located between the oocyte nucleus and the follicle cell border and become aggregated into a cluster less than 1.5 µ in its largest dimension. The fate of these centrioles in the oocyte is not known. The fine structure of the germarium and the early oocyte is also described.

scholarly journals Activation of a Ductal-to-Endocrine Transdifferentiation Transcriptional Program in the Pancreatic Cancer Cell Line PANC-1 Is Controlled by RAC1 and RAC1b through Antagonistic Regulation of Stemness Factors

Cancers ◽  
2021 ◽  
Vol 13 (21) ◽  
pp. 5541
Author(s):  
Paula Marie Schmidtlein ◽  
Clara Volz ◽  
Alexander Hackel ◽  
Isabel Thürling ◽  
Darko Castven ◽  
...  
Keyword(s):  
Tumor Cells ◽  
Epithelial Mesenchymal Transition ◽  
Ectopic Expression ◽  
Pancreatic Cancer Cell Line ◽  
Therapy Resistance ◽  
Small Gtpase ◽  
Dominant Negative ◽  
Transcriptional Program ◽  
Mesenchymal Transition ◽  
Insulin Producing Cells

Epithelial–mesenchymal transition (EMT) is a driving force for tumor growth, metastatic spread, therapy resistance, and the generation of cancer stem cells (CSCs). However, the regained stem cell character may also be exploited for therapeutic conversion of aggressive tumor cells to benign, highly differentiated cells. The PDAC-derived quasimesenchymal-type cell lines PANC-1 and MIA PaCa-2 have been successfully transdifferentiated to endocrine precursors or insulin-producing cells; however, the underlying mechanism of this increased plasticity remains elusive. Given its crucial role in normal pancreatic endocrine development and tumor progression, both of which involve EMT, we analyzed here the role of the small GTPase RAC1. Ectopic expression in PANC-1 cells of dominant negative or constitutively active mutants of RAC1 activation blocked or enhanced, respectively, the cytokine-induced activation of a ductal-to-endocrine transdifferentiation transcriptional program (deTDtP) as revealed by induction of the NEUROG3, INS, SLC2A2, and MAFA genes. Conversely, ectopic expression of RAC1b, a RAC1 splice isoform and functional antagonist of RAC1-driven EMT, decreased the deTDtP, while genetic knockout of RAC1b dramatically increased it. We further show that inhibition of RAC1 activation attenuated pluripotency marker expression and self-renewal ability, while depletion of RAC1b dramatically enhanced stemness features and clonogenic potential. Finally, rescue experiments involving pharmacological or RNA interference-mediated inhibition of RAC1 or RAC1b, respectively, confirmed that both RAC1 isoforms control the deTDtP in an opposite manner. We conclude that RAC1 and RAC1b antagonistically control growth factor-induced activation of an endocrine transcriptional program and the generation of CSCs in quasimesenchymal PDAC cells. Our results have clinical implications for PDAC patients, who in addition to eradication of tumor cells have a need for replacement of insulin-producing cells.

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