The role of segment polarity genes during early oogenesis in Drosophila

Development ◽  
1996 ◽  
Vol 122 (10) ◽  
pp. 3283-3294 ◽  
Author(s):  
A.J. Forbes ◽  
A.C. Spradling ◽  
P.W. Ingham ◽  
H. Lin
Keyword(s):  
Germ Line ◽  
Somatic Cells ◽  
Ectopic Expression ◽  
Imaginal Discs ◽  
Negative Effects ◽  
Cubitus Interruptus ◽  
Segment Polarity ◽  
Egg Chambers ◽  
Hh Signaling ◽  
Drosophila Ovary

In the Drosophila ovary, hedgehog (hh) signaling from cells near the apical tip of the germarium stimulates the proliferation and specification of somatic cells in region 2 of the germarium, 2–5 cells away from the hh-expressing cells (A. J. Forbes, H. Lin, P. Ingham and A. Spradling (1996) Development 122, 1125–1135). This report examines the role during early oogenesis of several genes that are known to function in hh-mediated signaling during embryonic and larval development (P. Ingham (1995) Current Opin. Genetics Dev. 5, 528–534). As in imaginal discs, engrailed (en) is co-expressed with hh in the germarium, while patched (ptc) and cubitus interruptus (ci) are expressed in somatic cells throughout the germarium and in developing egg chambers, with ptc expression being elevated within 10 cell diameters of the source of the hh signal. Moreover, the somatic cell overproliferation caused by ectopic hh expression is accompanied by elevated levels of ptc and is phenocopied in ptc- somatic clones. These analyses suggest that ptc and ci are components of the hh signaling pathway in the germarium. However, unlike embryos and imaginal discs, neither wingless (wg) nor decapentaplegic (dpp) appear to mediate the ovarian hh signal. wg is expressed in ‘cap cells,’ a subset of hh-expressing cells located adjacent to germ-line stem cells, but is unaffected by ectopic hh expression. Nor does the ectopic expression of wg or dpp mimic the effect of ectopic hh expression. We propose that Hh diffuses from apical cells, including cap cells, and regulates the proliferation of nearby ovarian somatic cells by antagonizing the negative effects of ptc on ci activity in these cells, thereby allowing the transcription of ci-dependent genes, including ptc itself.

Ectopic expression of wingless in imaginal discs interferes with decapentaplegic expression and alters cell determination

Development ◽  
1996 ◽  
Vol 122 (11) ◽  
pp. 3519-3529 ◽  
Author(s):  
L.A. Johnston ◽  
G. Schubiger
Keyword(s):  
Ectopic Expression ◽  
Imaginal Discs ◽  
Dorsal Side ◽  
Homeotic Genes ◽  
Cell Determination ◽  
Segment Polarity ◽  
High Level ◽  
Dorsal Cells ◽  
Dose Dependent ◽  
Dorsal Pattern

We have expressed the segment polarity gene wingless (wg) ectopically in imaginal discs to examine its regulation of both ventral patterning and transdetermination. By experimentally manipulating the amount of Wg protein, we show that different thresholds of Wg activity elicit different outcomes, which are mediated by regulation of decapentaplegic (dpp) expression and result in alterations in the expression of homeotic genes. A high level of Wg activity leads to loss of all dorsal pattern elements and the formation of a complete complement of ventral pattern elements on the dorsal side of legs, and is correlated with repression of dpp expression. wg expression in dorsal cells of each disc also leads to dose-dependent transdetermination in those cells in homologous discs such as the labial, antennal and leg, but not in cells of dorsally located discs. When dpp expression is repressed by high levels of Wg, transdetermination does not occur, confirming that dpp participates with wg to induce transdetermination. These and other experiments suggest that dorsal expression of wg alters disc patterning and disc cell determination by modulating the expression of dpp. The dose-dependent effects of wg on dpp expression, ventralization of dorsal cells and transdetermination support a model in which wg functions as a morphogen in imaginal discs.

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.

A role for the Drosophila segment polarity gene armadillo in cell adhesion and cytoskeletal integrity during oogenesis

Development ◽  
1993 ◽  
Vol 118 (4) ◽  
pp. 1191-1207 ◽  
Author(s):  
M. Peifer ◽  
S. Orsulic ◽  
D. Sweeton ◽  
E. Wieschaus
Keyword(s):  
Cell Adhesion ◽  
Germ Line ◽  
Adherens Junctions ◽  
Beta Catenin ◽  
Cell Adhesive ◽  
Segment Polarity ◽  
Drosophila Ovary ◽  
Segment Polarity Gene ◽  
Polarity Gene ◽  
Cell Cell

The epithelial sheet is a structural unit common to many tissues. Its organization appears to depend on the function of the multi-protein complexes that form adherens junctions. Elegant cell biological experiments have provided support for hypotheses explaining the function of adherens junctions and of their components. These systems, however, lack the ability to test function within an entire organism during development. The realization that the product of the Drosophila segment polarity gene armadillo is related to the vertebrate adhesive junction components plakoglobin and beta-catenin led to the suggestion that armadillo might provide a genetic handle to study adhesive junction structure and function. An examination of the potential function of Armadillo in cell-cell adhesive junctions was initiated using the Drosophila ovary as the model system. We examined the distribution of Armadillo in the Drosophila ovary and demonstrated that this localization often parallels the location of cell-cell adhesive junctions. The consequences of removing armadillo function from the germ-line cells of the ovary were also examined. Germ-line armadillo mutations appear to disrupt processes requiring cell adhesion and integrity of the actin cytoskeleton, consistent with a role for Armadillo in cell-cell adhesive junctions. We have also used armadillo mutations to examine the effects on ovarian development of altering the stereotyped cell arrangements of the ovary. The implications of these results for the role of adhesive junctions during development are discussed.

scholarly journals Oligomerization and endocytosis of Hedgehog is necessary for its efficient exovesicular secretion

2015 ◽  
Vol 26 (25) ◽  
pp. 4700-4717 ◽  
Author(s):  
Anup Parchure ◽  
Neha Vyas ◽  
Charles Ferguson ◽  
Robert G. Parton ◽  
Satyajit Mayor
Keyword(s):  
Cell Surface ◽  
Long Range ◽  
Imaginal Discs ◽  
Multivesicular Bodies ◽  
Selective Effect ◽  
Endosomal Sorting ◽  
Drosophila Wing ◽  
Dependent Process ◽  
Wing Imaginal Discs ◽  
Hh Signaling

Hedgehog (Hh) is a secreted morphogen involved in both short- and long-range signaling necessary for tissue patterning during development. It is unclear how this dually lipidated protein is transported over a long range in the aqueous milieu of interstitial spaces. We previously showed that the long-range signaling of Hh requires its oligomerization. Here we show that Hh is secreted in the form of exovesicles. These are derived by the endocytic delivery of cell surface Hh to multivesicular bodies (MVBs) via an endosomal sorting complex required for transport (ECSRT)–dependent process. Perturbations of ESCRT proteins have a selective effect on long-range Hh signaling in Drosophila wing imaginal discs. Of importance, oligomerization-defective Hh is inefficiently incorporated into exovesicles due to its poor endocytic delivery to MVBs. These results provide evidence that nanoscale organization of Hh regulates the secretion of Hh on ESCRT-derived exovesicles, which in turn act as a vehicle for long-range signaling.

The ethics of genome editing in the clinic: A dose of realism for healthcare leaders

2017 ◽  
Vol 30 (3) ◽  
pp. 159-163
Author(s):  
Tania Bubela ◽  
Yael Mansour ◽  
Dianne Nicol
Keyword(s):  
Genome Editing ◽  
Germ Line ◽  
Genetic Diseases ◽  
Somatic Cells ◽  
Clinical Translation ◽  
Preclinical Research ◽  
Societal Issues ◽  
Realistic Assessment ◽  
Healthcare Leaders

Genome editing technologies promise therapeutic advances for genetic diseases. We discuss the ethical and societal issues raised by these technologies, including their use in preclinical research, their potential to address mutations in somatic cells, and their potential to make germ line alterations that may be passed to subsequent generations. We call for a proportionate response from health leaders based on a realistic assessment of benefits, risks, and timelines for clinical translation.

Insertion and excision of Caenorhabditis elegans transposable element Tc1

1988 ◽  
Vol 8 (2) ◽  
pp. 737-746
Author(s):  
D Eide ◽  
P Anderson
Keyword(s):  
Amino Acid ◽  
Caenorhabditis Elegans ◽  
Transposable Element ◽  
Dna Sequences ◽  
Germ Line ◽  
Consensus Sequence ◽  
Somatic Cells ◽  
Chain Gene ◽  
Imprecise Excision ◽  
Insertion Sites

The transposable element Tc1 is responsible for most spontaneous mutations that occur in Caenorhabditis elegans variety Bergerac. We investigated the genetic and molecular properties of Tc1 transposition and excision. We show that Tc1 insertion into the unc-54 myosin heavy-chain gene was strongly site specific. The DNA sequences of independent Tc1 insertion sites were similar to each other, and we present a consensus sequence for Tc1 insertion that describes these similarities. We show that Tc1 excision was usually imprecise. Tc1 excision was imprecise in both germ line and somatic cells. Imprecise excision generated novel unc-54 alleles that had amino acid substitutions, amino acid insertions, and, in certain cases, probably altered mRNA splicing. The DNA sequences remaining after Tc1 somatic excision were the same as those remaining after germ line excision, but the frequency of somatic excision was at least 1,000-fold higher than that of germ line excision. The genetic properties of Tc1 excision, combined with the DNA sequences of the resulting unc-54 alleles, demonstrated that excision was dependent on Tc1 transposition functions in both germ line and somatic cells. Somatic excision was not regulated in the same strain-specific manner as germ-line excision was. In a genetic background where Tc1 transposition and excision in the germ line was not detectable, Tc1 excision in the soma still occurred at high frequency.

Positional signaling by hedgehog in Drosophila imaginal disc development

Development ◽  
1995 ◽  
Vol 121 (1) ◽  
pp. 1-10 ◽  
Author(s):  
A.L. Felsenfeld ◽  
J.A. Kennison
Keyword(s):  
Hedgehog Signaling ◽  
Imaginal Disc ◽  
Ectopic Expression ◽  
Posterior Compartment ◽  
Anterior Compartment ◽  
Segment Polarity ◽  
Wing Structures ◽  
Wing Discs ◽  
Segment Polarity Gene ◽  
Polarity Gene

We describe a dominant gain-of-function allele of the segment polarity gene hedgehog. This mutation causes ectopic expression of hedgehog mRNA in the anterior compartment of wing discs, leading to overgrowth of tissue in the anterior of the wing and partial duplication of distal wing structures. The posterior compartment of the wing is unaffected. Other imaginal derivatives are affected, resulting in duplications of legs and antennae and malformations of eyes. In mutant imaginal wing discs, expression of the decapentaplegic gene, which is implicated in the hedgehog signaling pathway, is also perturbed. The results suggest that hedgehog protein acts in the wing as a signal to instruct neighboring cells to adopt fates appropriate to the region of the wing just anterior to the compartmental boundary.

fringeandNotchspecify polar cell fate duringDrosophilaoogenesis

Development ◽  
2001 ◽  
Vol 128 (12) ◽  
pp. 2243-2253 ◽  
Author(s):  
Muriel Grammont ◽  
Kenneth D. Irvine
Keyword(s):  
Cell Fate ◽  
Null Allele ◽  
Somatic Cells ◽  
Ectopic Expression ◽  
Notch Receptor ◽  
Drosophila Oogenesis ◽  
Early Stages ◽  
Polar Cell ◽  
Hypomorphic Alleles ◽  
Notch Activation

fringe encodes a glycosyltransferase that modulates the ability of the Notch receptor to be activated by its ligands. We describe studies of fringe function during early stages of Drosophila oogenesis. Animals mutant for hypomorphic alleles of fringe contain follicles with an incorrect number of germline cells, which are separated by abnormally long and disorganized stalks. Analysis of clones of somatic cells mutant for a null allele of fringe localizes the requirement for fringe in follicle formation to the polar cells, and demonstrates that fringe is required for polar cell fate. Clones of cells mutant for Notch also lack polar cells and the requirement for Notch in follicle formation appears to map to the polar cells. Ectopic expression of fringe or of an activated form of Notch can generate an extra polar cell. Our results indicate that fringe plays a key role in positioning Notch activation during early oogenesis, and establish a function for the polar cells in separating germline cysts into individual follicles.

scholarly journals Hypothesis of the conjunct expression gene: can random mutation explain the phenotypic variability?

2018 ◽  
Author(s):  
Víctor A Zapata Trejo
Keyword(s):  
Gene Expression ◽  
Germ Line ◽  
Phenotypic Variability ◽  
Somatic Cells ◽  
Random Mutation ◽  
Differentiated Cells ◽  
Undifferentiated Cells

The epigenome regulates the gene expression of all differentiated cells and indicates which specific genes must be transcribed. It is argued that the expression factors that act in specific genes of the somatic cells involved in a behavior also act in the partial transcription of the same genes in the most undifferentiated cells of the germ line. It is proposed how a probabilistic view of the random mutation can explain the evolution of the phenotypes and integrate all the evidence pointing to a conjunct evolution with the environment.

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