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At least 271 records · Page 15Linked to original sources
PubMed2006

MbIDGF, a novel member of the imaginal disc growth factor family in Mamestra brassicae, stimulates cell proliferation in two lepidopteran cell lines without insulin.

Imaginal disc growth factor (IDGF) is a soluble polypeptide growth factor that was first identified from the conditioned medium of Drosophilia imaginal disc C1.8+ cells. Working with insulin, IDGF stimulated the growth of cultured imaginal disk cells, which suggested that IDGF might function as a cofactor of Drosophila insulin or insulin like peptide. Here we report a new member of the IDGF family, named MbIDGF, from the cabbage armyworm, Mamestra brassicae. Using a cloned cDNA of MbIDGF, recombinant MbIDGF protein was expressed in baculovirus-infected Sf9 cells and purified. Without insulin, the recombinant MbIDGF protein stimulated cell growth of SES-MaBr-4 and NIAS-MaBr-93 cell lines that were derived from the fat bodies and hemocytes of M. brassicae, in a dose-dependent manner. The saturation of growth stimulation by MbIDGF was attained for the two types of cells at 80 ng/ml (0.8 nM) and 300 ng/ml (6 nM), respectively. The results suggest that MbIDGF may stimulate the growth of lepidopteran cells by a new mechanism without associating with the insulin pathway.

Amino Acid Sequence↗
PubMed2000

Control of growth and differentiation of the wing imaginal disk of Precis coenia (Lepidoptera: Nymphalidae).

During the last larval instar, the wing imaginal disks of Precis coenia grow continuously. The rate of disk growth is not disk-autonomous but closely matches the rate of somatic growth of the larva, so that the size of the disks is a function of the size of the body, irrespective of the growth rate of the larva. When larvae are starved, their wing disks cease growth within 4 h, which indicates the existence of an efficient coupling mechanism between the growth of the soma and growth of the imaginal disks. Disk growth is inhibited by juvenile hormone in a dose-dependent manner. In the presence of the hormone the wing disks stop growing even while the larva continues to grow normally. During the last larval instar the wing imaginal disks also undergo a complex differentiation, consisting of the development of the lacunae and tracheation that define the future adult wing venation system. In normally growing larvae, differentiation of the wing disk is tightly correlated with wing size. Differentiation and size can be dissociated by starvation. If larvae are starved at any time after differentiation has begun, differentiation continues at a normal rate, even though the wing disk does not grow. Differentiation does not begin spontaneously in larvae that are starved before differentiation has begun. These findings indicate that the initiation of differentiation and its continuation are controlled independently. Juvenile hormone inhibits differentiation in a dose-dependent manner. Upon treatment with juvenile hormone, the stage of differentiation becomes fixed. These findings indicate that continued differentiation of the wing disk can only occur in the absence of juvenile hormone. Although the circulating level of juvenile hormone may be elevated during starvation, it is unlikely that this elevation is responsible for the observed effect of starvation on growth and differentiation of the disk.

Journal Article↗
PubMed2002

Sex-specific deployment of FGF signaling in Drosophila recruits mesodermal cells into the male genital imaginal disc.

A central issue in developmental biology is how the deployment of generic signaling proteins produces diverse specific outcomes. We show that Drosophila FGF is used, only in males, to recruit mesodermal cells expressing its receptor to become part of the genital imaginal disc. Male-specific deployment of FGF signaling is controlled by the sex determination regulatory gene doublesex. The recruited mesodermal cells become epithelial and differentiate into parts of the internal genitalia. Our results provide exceptions to two basic tenets of imaginal disc biology-that imaginal disc cells are derived from the embryonic ectoderm and belong to either an anterior or posterior compartment. The recruited mesodermal cells migrate into the disc late in development and are neither anterior nor posterior.

Animals↗
PubMed1998

Modulation of Hedgehog target gene expression by the Fused serine-threonine kinase in wing imaginal discs.

The Fused (Fu) serine-threonine kinase and the Suppressor of fused (Su(fu)) product are part of the Hedgehog (Hh) signaling pathway both in embryos and in imaginal discs. In wing imaginal discs, the Hh signal induces Cubitus interruptus (Ci) accumulation and activates patched (ptc) and decapentaplegic (dpp) expression along the anterior/posterior (A/P) boundary. In this paper, we have examined the role of the Fu and Su(fu) proteins in the regulation of Hh target gene expression in wing imaginal discs, by using different classes of fu alleles and an amorphic Su(fu) mutation. We show that, at the A/P boundary, Fu kinase activity is involved in the maintenance of high ptc expression and in the induction of late anterior engrailed (en) expression. These combined effects can account for the modulation of Ci accumulation and for the precise localization of the Dpp morphogen stripe. In contrast, in more anterior cells which do not receive Hh signal, we show that Fu plays a role independent of its kinase function in the regulation of Ci accumulation. In these cells, Fu may be involved in the stabilization of a large protein complex which is probably responsible for the regulation of Ci cleavage and/or targeting to nucleus. We propose that the Fused function is necessary for the activation of full-length Ci and counteracts the negative Su(fu) effect on the pathway, leading to en, ptc and dpp expression.

Animals↗
PubMedDate not supplied

Preferential binding of imaginal disk cells to embryonic segments of Drosophila.

Cell recognition and selective adhesion may be important in pattern formation; such processes in Drosophila melanogaster could be responsible for the maintenance of segment boundaries, the morphogenesis of metamorphosing imaginal disks, and the paths of axon outgrowth during neurogenesis. As cells from different imaginal disks of Drosophila are able to recognize and sort out from one another, we decided to investigate whether these larval cells could recognize and bind to the epidermis of intact embryos. We report here that imaginal disk cells bind preferentially to the epidermis of the embryonic segments from which they are derived: thoracic disk cells to thoracic segments and genital disk cells to abdominal segments. Furthermore, thoracic disk cells recognize and bind, without preference, to all segments of the homoeotic mutant Df(3R)P9 (ref. 6). We conclude, therefore, that cells of the same segmental origin have similar recognition properties at different developmental stages.

Animals↗
PubMedDate not supplied

Patterns of dye coupling in the imaginal wing disk of Drosophila melanogaster.

Responses of developing tissues to experimental disruption demonstrate that cell interaction is important both in generating positional information and in controlling growth. However, the mechanism by which cells interact and the range over which the interactions are effective are not known. In the imaginal disks of Drosophila melanogaster, experiments on pattern regulation following surgical ablation suggest that the cell interactions are very local in nature; in fact, most of the data can be explained by assuming that cells interact only with their immediate neighbours. In contrast, studies of cell division patterns in the same tissue indicate that the "local' proliferative response to an ablation extends over a distance of up to about eight cell diameters. Still longer-range interactions have been proposed on the basis of theoretical considerations. It is possible that the interactions are mediated by the transfer of small molecules through gap junctions, as gap junctions are abundant in imaginal disks at the appropriate developmental stages. We have explored the range, timing and directionality of dye coupling between the cells of the wing disk as a test of the possible role of gap junctions in imaginal disk patterning. Our results indicate that interactions over different ranges are possible depending on the nature of the molecule being transferred.

Animals↗
PubMed2002

Crystal structure of imaginal disc growth factor-2. A member of a new family of growth-promoting glycoproteins from Drosophila melanogaster.

Imaginal disc growth factor-2 (IDGF-2) is a member of a recently described family of Drosophila melanogaster-soluble polypeptide growth factors that promote cell proliferation in imaginal discs. Although their precise mode of action has not been established, IDGFs cooperate with insulin in stimulating the growth of imaginal disc cells. We report the crystal structure of IDGF-2 at 1.3-A resolution. The structure shows the classical (betaalpha)(8) barrel-fold of family 18 glycosyl hydrolases, with an insertion of an alpha + beta domain similar to that of Serratia marcescens chitinases A and B. However, amino acid substitutions in the consensus catalytic sequence of chitinases give IDGF-2 a less negatively charged environment in its putative ligand-binding site and preclude the nucleophilic attack mechanism of chitin hydrolysis. Particularly important is the replacement of Glu by Gln at position 132, which has been shown to abolish enzymatic activity in chitinases. Nevertheless, a modest conservation of residues that participate in oligosaccharide recognition suggests that IDGF-2 could bind carbohydrates, assuming several conformational changes to open the partially occluded binding site. Thus, IDGFs may have evolved from chitinases to acquire new functions as growth factors, interacting with cell surface glycoproteins implicated in growth-promoting processes, such as the Drosophila insulin receptor.

Amino Acid Sequence↗
PubMed1988

Prepupal differentiation of Drosophila imaginal discs: identification of four genes whose transcripts accumulate in response to a pulse of 20-hydroxyecdysone.

We have isolated and initially characterized a novel set of four genes expressed during the prepupal differentiation of imaginal discs of Drosophila melanogaster. These four ecdysone-dependent genes are named EDG-42A, EDG-64CD, EDG-78E and EDG-84A-1 based on their respective chromosomal locations. Their expression is like that expected for genes encoding proteins that participate in the formation of the pupal cuticle. Transcripts complementary to these genes accumulate in imaginal discs during an 18-hr in vitro culture period that begins with a 6-hr pulse of 20-hydroxyecdysone (20-HE). Transcripts for three of these genes were not detected in imaginal discs following culture in the absence or the continuous presence of 20-HE (1 microgram/ml). Transcripts corresponding to EDG-64CD exhibit delayed accumulation in the continuous presence of 20-HE. Transcripts corresponding to three of the genes are only detected in the prepupal stage of development. Only EDG-64CD is complementary to transcripts present at other stages of development. One of the genes, EDG-78E, encodes a pupal cuticle protein. This is the first reported isolation of a set of steroid hormone-responsive genes that require first the presence, then removal of hormone for transcript accumulation.

Animals↗
PubMed1995

Drawing a stripe in Drosophila imaginal disks: negative regulation of decapentaplegic and patched expression by engrailed.

During development of the Drosophila adult appendage precursors, the larval imaginal disks, the decapentaplegic (dpp) gene is expressed in a stripe just anterior to the anterior/posterior (A/P) compartment boundary. Here, we investigate the genetic controls that lead to production of this stripe. We extend previous observations on leaky engrailed (en) mutations by showing that mutant clones completely lacking both en and invected (inv) activity ectopically express dpp-lacZ reporter genes in the posterior compartment, where dpp activity ordinarily is repressed. Similarly, patched (ptc) is also ectopically expressed in such posterior compartment en-inv- null clones. In contrast, these en-inv- clones exhibit loss of hedgehog (hh) expression. We suggest that the absence of dpp expression in the posterior compartment is due to direct repression by en. Ubiquitious expression of en in imaginal disks, produced by a hs-en construct, eliminates the expression of dpp-lacZ in its normal A/P boundary stripe. We identify three in vitro Engrailed binding sites in one of our dpp-lacZ reporter gene. Mutagenesis of these Engrailed binding sites results in ectopic expression of this reporter gene, but does not alter the normal stripe of expression at the A/P boundary. We propose that the en-hh-ptc regulatory loop that is responsible for segmental expression of wingless in the embryo is reutilized in imaginal disks to create a stripe of dpp expression along the A/P compartment boundary.

Animals↗
PubMed1995

Distinct parasegmental and imaginal enhancers and the establishment of the expression pattern of the Ubx gene.

The expression domain of the Ubx gene in Drosophila embryos is bounded by the product of the hb gene, acting as a repressor. We show that all Ubx fragments that bind Hb protein in vitro contain parasegmental enhancers active in the embryo in specific parasegmental patterns. We have found three new embryonic enhancer elements in the upstream region, in addition to the two previously identified. Each produces a pattern initially bounded at PS6 by Hb but sooner or later breaks down this boundary and begins to express in the anterior region. These enhancers do not respond to the long-term maintenance mediated by the Polycomb group of genes. They also cease functioning after germ band extension. Expression in imaginal tissues is due to a set of entirely separate and independent imaginal disc enhancers. These do not contain Hb binding sites and by themselves have no anterior/posterior positional information, although some distinguish between ventral and dorsal discs. A third kind of element, the Polycomb Response Element (PRE), has no enhancer activity but causes long-term maintenance of the expression domain of other enhancers present in the vicinity. The interaction of these elements results in the correct expression of Ubx in imaginal tissues.

Animals↗
PubMed1997

Enhancement of overgrowth by gene interactions in lethal(2)giant discs imaginal discs from Drosophila melanogaster.

Recessive lethal mutations of the lethal(2)giant discs (l(2)gd) and lethal(2)fat (l(2)ft) loci of Drosophila melanogaster cause imaginal disc hyperplasia during a prolonged larval stage. Imaginal discs from l(2)ft l(2)gd or Gl(2)gd double homozygotes show more extensive overgrowth than in either single homozygote, and double homozygous l(2)ft l(2)gd mitotic clones in adult flies show much more overgrowth than is seen in clones homozygous for either l(2)gd or l(2)ft alone. dachsous (ds) also acts as an enhancer of l(2)gd, producing dramatically overgrown discs and causing failure to pupariate in double homozygotes. The comb gap (cg) mutation, which also interacts with ds, greatly enhances the tendency of imaginal discs from l(2)gd larvae to duplicate as they overgrow. If l(2)gd homozygotes are made heterozygous for l(2)ft, then several discs duplicate, indicating that l(2)ft acts an a dominant enhancer of l(2)gd. l(2)ft also acts as a dominant enhancer of l(2)gd, and conversely l(2)gd acts as a dominant modifier of l(2)ft. The enhancement of overgrowth caused by various mutant combinations is accompanied by changes in expression of Decapentaplegic and Wingless. These results show that tumor suppressor genes act in combination to control cell proliferation, and that tissue hyperplasia can be associated with ectopic expression of genes involved in pattern formation.

Animals↗
PubMed1994

A prolyl endopeptidase of Sarcophaga peregrina (flesh fly): its purification and suggestion for its participation in the differentiation of the imaginal discs.

A prolyl endopeptidase that hydrolyses Suc-Gly-Pro-MCA (Suc, succinyl; MCA, methyl-coumaryl-7-amide) was purified to near homogeneity from NIH-Sape-4 cells derived from the flesh fly (Sarcophaga peregrina). The molecular mass of the purified enzyme was 84 kDa, and its activity was inhibited almost completely by 1 mM diisopropyl fluorophosphate (DFP). Immunoblotting and DFP-labeling experiments revealed that the leg imaginal discs of Sarcophaga contained this enzyme as a major serine proteinase. This prolyl endopeptidase is suggested to be involved in the differentiation of imaginal discs, because 2 mM DFP and 0.1 mM N-benzyloxycarbonyl-thioprolyl-thioprolynal-dimethylaceta l (ZTTA), a specific inhibitor for prolyl endopeptidase, inhibited differentiation of the imaginal discs from the eversion to the elongation stage.

Amino Acid Sequence↗
PubMed1993

A wingless-dependent polar coordinate system in Drosophila imaginal discs.

The patterning of the imaginal discs in Drosophila melanogaster is a progressive process that, like the patterning of the larval epidermis during embryogenesis, requires the activity of segment polarity genes. One segment polarity gene, wingless, encodes a homolog of the mouse proto-oncogene Wnt-1 and plays a prominent role in the patterning of the larval epidermis and the imaginal discs. However, whereas the function of wingless in the embryo is initially associated with a pattern of stripes along the anteroposterior axis that are part of a Cartesian coordinate system, it is shown here that during imaginal development wingless is associated with a pattern of sectors that provide references for a polar coordinate system homologous to that postulated in a well-known model for the regeneration of insect and vertebrate limbs.

Animals↗
PubMed1999

Down-regulation of RpS21, a putative translation initiation factor interacting with P40, produces viable minute imagos and larval lethality with overgrown hematopoietic organs and imaginal discs.

Down-regulation of the Drosophila ribosomal protein S21 gene (rpS21) causes a dominant weak Minute phenotype and recessively produces massive hyperplasia of the hematopoietic organs and moderate overgrowth of the imaginal discs during larval development. Here, we show that the S21 protein (RpS21) is bound to native 40S ribosomal subunits in a salt-labile association and is absent from polysomes, indicating that it acts as a translation initiation factor rather than as a core ribosomal protein. RpS21 can interact strongly with P40, a ribosomal peripheral protein encoded by the stubarista (sta) gene. Genetic studies reveal that P40 underexpression drastically enhances imaginal disc overgrowth in rpS21-deficient larvae, whereas viable combinations between rpS21 and sta affect the morphology of bristles, antennae, and aristae. These data demonstrate a strong interaction between components of the translation machinery and showed that their underexpression impairs the control of cell proliferation in both hematopoietic organs and imaginal discs.

Amino Acid Sequence↗
PubMed1995

Analysis of an enhancer trap expressed in regenerating Drosophila imaginal discs.

In Drosophila, imaginal discs are the undifferentiated larval precursors of the pattern of epidermal and sensory neural cells in each adult segment. Although cell fates are already specified by late third instar, disc fragments can either regenerate or duplicate after growth in culture. The outcome depends on signaling between cells across the healed wound and involves a redeployment of the expression patterns of selector genes and other disc pattern genes. We recently used the enhancer-trap method to screen for such genes that are expressed ectopically at the wound-heal site in imaginal discs undergoing regeneration. Here we report the cloning by plasmid rescue of transcribed sequences adjacent to one such enhancer-trap insertion. Using Northern analysis and in situ hybridization we show that one transcript is expressed in the embryo and in imaginal discs in a pattern similar to that of the enhancer trap. We also, by imprecise excision of the enhancer-trap insertion, generated a series of flanking deletions that were mapped using Southern analysis and complementation.

Animals↗
PubMed2001

Treatment of reactivated post-traumatic stress disorder. Imaginal exposure in an older adult with multiple traumas.

A single-case analysis was used to assess the effects of imaginal exposure in a 57-year-old woman suffering from current and reactivated post-traumatic stress disorder (PTSD) following a transient ischemic attack. The client's responses to self-reported depression, anxiety, and PTSD symptoms were repeatedly recorded during four phases: (a) initial psychotherapy, (b) imaginal exposure, (c) skill generalization, and (d) fading of treatment. In addition to dramatic reduction in levels of depression and anxiety, results showed a significant improvement in PTSD symptoms relating to recent and remote traumatic experiences. Improvements were maintained approximately 16 months after imaginal exposure ended, despite ongoing external stressors.

Adolescent↗
PubMed2003

The role of buttonhead and Sp1 in the development of the ventral imaginal discs of Drosophila.

The related genes buttonhead (btd) and Drosophila Sp1 (the Drosophila homologue of the human SP1 gene) encode zinc-finger transcription factors known to play a developmental role in the formation of the Drosophila head segments and the mechanosensory larval organs. We report a novel function of btd and Sp1: they induce the formation and are required for the growth of the ventral imaginal discs. They act as activators of the headcase (hdc) and Distal-less (Dll) genes, which allocate the cells of the disc primordia. The requirement for btd and Sp1 persists during the development of ventral discs: inactivation by RNA interference results in a strong reduction of the size of legs and antennae. Ectopic expression of btd in the dorsal imaginal discs (eyes, wings and halteres) results in the formation of the corresponding ventral structures (antennae and legs). However, these structures are not patterned by the morphogenetic signals present in the dorsal discs; the cells expressing btd generate their own signalling system, including the establishment of a sharp boundary of engrailed expression, and the local activation of the wingless and decapentaplegic genes. Thus, the Btd product has the capacity to induce the activity of the entire genetic network necessary for ventral imaginal discs development. We propose that this property is a reflection of the initial function of the btd/Sp1 genes that consists of establishing the fate of the ventral disc primordia and determining their pattern and growth.

Animals↗
PubMed1988

Transcription of the segment-polarity gene wingless in the imaginal discs of Drosophila, and the phenotype of a pupal-lethal wg mutation.

Wingless (wg) is a segment-polarity gene in Drosophila which is related to the murine proto-oncogene int1. In Drosophila embryos, wg transcription defines part of each parasegment. In situ hybridization shows that wg is also expressed in the imaginal discs which give rise to the adult during metamorphosis. Transcripts are localized in the apical cytoplasm of disc cells, and accumulate in different patterns in dorsal and ventral discs. The wgCX3 mutation produces morphological defect in the adult structures derived from these imaginal discs. The results show that wg is involved in the development of the adult, as well as the embryo, but that the imaginal discs do not express this segment-polarity gene in an identical pattern to the embryonic segments.

Animals↗