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At least 325 records · Page 18Linked to original sources
PubMed1998

Inhibitory action of BMPs on Pax1 expression and on shoulder girdle formation during limb development.

Pax1 expression in vertebrate limb buds is confined to cells in a discrete anterior proximal domain (Timmons et al. [1994] Development 120:2773-2785; Ebensperger et al. [1995] Anat. Embryol. 191:297-310). In dorsoventral patterning of Drosophila, expression of pox meso, an insect gene with high sequence similarity to Pax1, is repressed by decapentaplegic (dpp) in dorsal mesoderm and, thus, is restricted to a discrete ventral domain (Staehling-Hampton et al. [1994] Nature 372:783-786). In the chick wing, cells expressing a vertebrate homolog of dpp, bone morphogenetic protein 4 (Bmp4), abut the Pax1 domain, suggesting a similar relationship between homologous genes in both vertebrates and invertebrates. Here, we show that two BMPs (BMP4, and BMP2, also highly related to dpp) can repress Pax1 in the developing chick wing. Chick wing bud cells expressing Pax1 give rise to the shoulder girdle. Cells in an equivalent position in the mouse forelimb also express Pax1, and Pax1 mutant mice display shoulder girdle defects. Similarly in chick embryos, girdle defects are produced by treatments with signalling molecules that lead to expression of BMPs, which subsequently reduce Pax1 expression in the limb bud. Recently, BMP4 has been shown to inhibit Pax1 expression in the developing trunk (Monsoro-Burq et al. [1996] Development 122:3607-3616) and Pax9 expression in developing teeth (Neubüser et al. [1997] Cell 90:247-255). Thus, a property of BMPs appears to be to regulate pox meso homologs negatively and, thus, limit their expression domains.

Animals↗
PubMed1996

The Drosophila brain revisited by enhancer detection.

The patterns of gene expression in the Drosophila brain were studied by using the lacZ reporter gene carried on an enhancer detector element. From the analysis of serial sections of the heads of 6000 enhancer detector lines, reporter gene expression in some lines was found to generally follow boundaries established by cell type or anatomy, revealing distinct patterns of lacZ expression restricted to the lamina, the medulla, mushroom bodies, antennal lobes, or other anatomical subdivisions. About 15% of the lines showed ubiquitous expression in most or all head tissues and 25% of the lines showed expression throughout the CNS. Another quarter of the lines showed widespread expression in the CNS, with large regions of the brain showing expression. This suggests that the majority of detected genes are expressed with little spatial specificity. The expression patterns produced by 12 different insertions at the rutabaga locus were found to be extremely similar in the brain and offer strong evidence that the enhancer detector elements generally report the activity of an adjacent gene. Only 15% of the lines were judged to have relatively specific expression in one brain region, including those with preferential or specific expression in the mushroom bodies, antennal lobes, lamina, medulla, etc. The cytological insertion sites for elements showing preferential mushroom body expression were found to be dispersed in the genome at approximately 50 different chromosomal regions. In addition to providing a broad picture of the transcriptional activity in the Drosophila brain, these enhancer detector lines offer access to interesting new genes and form a novel collection of lines in which identifiable brain cells are marked in a reproducible way.

Animals↗
PubMed1999

Drosophila larval neuromuscular junction's responses to reduction of cAMP in the nervous system.

We investigated the effects of chronically lowered cyclic adenosine monophosphate (cAMP) on the morphology and physiology of the Drosophila larval neuromuscular junction, using two fly lines in which cAMP was significantly lower than normal in the nervous system: (a) transgenic flies in which the dunce (dnc) gene product was overexpressed in the nervous system, and (b) flies mutant for the rutabaga gene (rut1) which have reduced adenylyl cyclase activity. In comparison with controls, larvae with reduced cAMP exhibited a smaller number of synaptic varicosities. This effect was more pronounced in transgenic larvae, in which the reduction of neural cAMP was more pronounced. Synaptic transmission was also reduced in both cases, as evidenced by smaller excitatory junctional potentials (EJPs). Synaptic currents recorded from individual synaptic varicosities of the neuromuscular junction indicated almost normal transmitter release properties in transgenic larvae and a modest impairment in rut1 larvae. Thus, reduction in EJP amplitude in transgenic larvae is primarily due to reduced innervation, while in rut1 larvae it is attributable to the combined effects of reduced innervation and a mild impairment of transmitter release. We conclude that the major effect of chronically lowered cAMP is reduction of innervation rather than impairment of transmitter release properties.

Adenylyl Cyclases↗
PubMed1998

Multigeneration exposure test of Drosophila melanogaster to ELF magnetic fields.

Mutations, other than dominant lethals, were accumulated on wild type second chromosomes (+) of Drosophila melanogaster during exposure to 50 Hz sinusoidal alternating magnetic fields of 0.5 or 5 mT (rms) for 40 generations by the Curly/Plum(Cy/Pm) accumulation method. We maintained, for 40 generations under continuous exposure, each (+) chromosome as a heterozygote with (Cy) chromosome. Viability of the (+) chromosome was tested by sib-mating of (Cy/+) male and (Cy/+) female in a culture every 10th generation to obtain the homozygote. Viability indices, defined as twice the ratio of number of (+/+) flies to that of (Cy/+) flies plus 1 in the progeny of the test mating, also were calculated, which equaled 1.00 at the starting point. For the control and 0.5 and 5 mT exposed groups, percent frequencies of recessive lethal lines, defined as a line with (+/+) flies less than 0.3% in the test mating, were, respectively, 1.9, 0.9, and 2.9% (10th), 9.0, 4.9, and 9.5% (20th), 30.3, 22.9, and 30.4% (30th), and 39.9, 32.4, and 43.3% (40th generation). For the control and 0.5 and 5 mT groups, average viability indices, excluding lethals and markedly deleterious, were, respectively, 0.778, 0.796, and 0.752 (20th), 0.704, 0.698, and 0.694 (30th), and 0.669, 0.678, and 0.595 (40th generation). Their decreasing rates were 0.0054, 0.0059, and 0.0078 per generation. No significant difference was detected among the exposure levels in either the recessive lethal mutation frequency or the viability index.

Animals↗
PubMed2000

Spatial activation and repression of the drosophila vitelline membrane gene VM32E are switched by a complex cis-regulatory system.

The VM32E gene is differently expressed in the distinct cell domains composing the follicular epithelium. Our previous work on the VM32E gene defined the promoter regions required for the control of gene expression in the ventral and dorsal follicle domains. In this report, we present data from a finer dissection of each upstream regulatory region, allowing to draw the functional interactions among different regulatory elements. A 73-bp proximal region (-112/-39) contains regulatory element(s) to dictate the activation of the gene in the follicular epithelium. This region interacts with two other cis-regulatory elements and is absolutely required for their output. The first element (-206/ -113), individually unable to raise reporter expression, elicits gene activity in the ventral domain when joined to the proximal fragment; a second element (-348/-254) joined to the same proximal fragment sustains the full dorsal and ventral activity. Moreover, the ectopic expression driven by some promoter fragments in border or posterior cells uncovers the existence of specific negative regulatory elements. So, the follicular domain specificity of VM32E gene expression is achieved through the combined activities of cell-type specific positive and negative elements.

Animals↗
PubMed2000

Cell size and the morphogenesis of wing hairs in Drosophila.

Almost all epidermal cells on the Drosophila wing produce a single cuticular hair. This is formed in the pupae from a microvillus-like cell projection called the prehair. Previous experiments have shown the existence of two mechanisms that ensure that only a single hair is made. One is the restriction of prehair initiation to a small subregion of the cell by the action of the frizzled tissue polarity pathway. The second is a system that ensures the integrity of the prehair. Mutations and drugs that inhibit the actin cytoskeleton lead to the splitting of a single prehair into multiple smaller hairs. We report that large polyploid cells produce multiple hairs both because they form multiple independent prehair initiation centers and because the larger than normal hairs these cells produce have a tendency to split. We show that reducing cell size by starvation partially suppresses the phenotype seen in polyploid cells and that increasing apical cell surface area by mechanical stretching also results in the formation of multiple prehair initiation centers. We also show that the frizzled tissue polarity pathway is functional in large polyploid cells even if it is unable to restrict prehair initiation to a small region of the cell. We conclude that both of these cellular systems are limited in their ability to scale to accommodate larger cell size.

Animals↗
PubMed2004

Profiling catalase gene expression in Drosophila melanogaster during development and aging.

Catalase represents one of the key antioxidant enzymes (AOE) in the metabolism of oxygen free radicals. A comprehensive analysis was brought to bear on establishing catalase gene expression profiles during development and aging, with the underlying objective being to identify potential regulatory factors. Expression of the catalase gene exhibits substantial variations during development and aging in a stage- and tissue-specific manner. At the temporal level, previous observations of the coincidence of ecdysteroid pulses with peaks in catalase expression during developmental stages were largely corroborated. In adults, a small but significant decline in catalase expression was noted in adults as a function of age. Spatially, it was ascertained that catalase expression is mostly confined to tissues related to intermediary metabolism, digestive and adipose systems as well as oenocytes. By combining histochemical analysis of reporter gene expression with immunostaining of the endogenous product, it was possible to identify putative positive and negative regulatory elements that control catalase expression. Finally, when adult flies were subjected to various environmental insults, such as heat, paraquat, hyperoxia and H(2)O(2), no significant responses were observed, suggesting that catalase gene expression is largely governed by intrinsic genetic programs.

Aging↗
PubMed1993

Conditional cell ablation in Drosophila.

Targeting of cell ablation agents under the control of tissue-specific promoters promises to be an important tool for studies of development and function in higher organisms. Temperature-sensitive cell ablation agents, recently developed for Drosophila, extend control to temporal as well as spatial aspects of toxin expression. Here we discuss achievements to date, together with a novel form of enhancer trap technology with the potential for driving toxin expression in a large range of cell types.

Animals↗
PubMed1996

Dosage-dependent modification of position-effect variegation in Drosophila.

Many loci in Drosophila exhibit dosage effects on single phenotypes. In the case of modifiers of position-effect variegation, increases and decreases in dosage can have opposite effects on variegating phenotypes. This is seemingly paradoxical: if each locus encodes a limiting gene product sensitive to dosage decreases, then increasing the dosage of any one should have no effect, because the others should remain limiting. An earlier model put forward to resolve this paradox suggested that dosage-dependent modifiers encode protein subunits of a macromolecular complex that is sensitive to mass action equilibrium conditions. Because chemical equilibria are dynamic, however, such hypothetical complexes will be unstable to an extent that is inconsistent with the known properties of molecules that make up chromatin. An alternative model accounts for the dosage effects in terms of interactions between structural proteins that bind at multiple linked sites. These might include indirect interactions occurring between regulatory proteins and genes for structural proteins or their protein products. The large number of direct and inverse regulatory genes which are known to exist in Drosophila could account for the apparent genetic complexity that is seen for modifiers of position-effect variegation and for other systems of phenotypic modification.

Animals↗
PubMed1993

Attenuation of white gene expression in transgenic Drosophila melanogaster: possible role of a catalytic antisense RNA.

We have transformed Drosophila melanogaster with a DNA construct encoding a catalytic antisense RNA directed against the primary white gene RNA transcript. Total RNA isolated from transformed flies was shown to catalyze the specific cleavage of in vitro transcribed substrate RNA, indicating the expression of a functional ribozyme. Moreover, transgenic lines carrying homozygous copies of this construct depict a further clear-cut reduction in eye pigmentation when present in a genetic background that has a priori reduced levels of white gene expression.

Alleles↗
PubMed1994

Screen for enhancers of Polycomb and Polycomblike in Drosophila melanogaster.

There are 11 Polycomb group genes known in Drosophila. These genes are negative regulators of homeotic gene expression, and may act by modifying chromatin structure. It is not clear how many members of the Polycomb group of genes exist. Many were discovered because of their homeotic phenotypes, or because they enhance homeotic mutations. Systematic screens for enhancers of Polycomb have identified previously known members of the Polycomb group. In an attempt to discover cytological locations of new Polycomb group genes, we crossed deletions uncovering about 20% of the genome to Polycomb-like and Polycomb and scored for enhancement of the extra sex combs phenotype. Haploidy for four regions, 36F7-37A, 43E18; 44B5-9, 70C2-6, and 70C6-15; 70D enhanced the extra sex comb phenotype associated with strong Polycomb group mutations. These regions have homeotic phenotypes either as homozygous embryos or heterozygous adults, or both. We also show that spalt enhances Polycomb group mutations. These results are discussed with respect to previous estimates of Polycomb group gene number.

Animals↗
PubMed1995

Tumor suppression in Drosophila is causally related to the function of the lethal(2) tumorous imaginal discs gene, a dnaJ homolog.

The Drosophila melanogaster tumor suppressor gene lethal(2)tumorous imaginal discs (l(2)tid) causes in homozygotes malignant growth of cells of the imaginal discs and the death of the mutant larvae at the time of puparium formation. We describe the molecular cloning of the l(2)tid+ gene and its temporal expression pattern in the wild-type and mutant alleles. Germ line rescue of the tumor phenotype was achieved with a 7.0 kb Hindlll-fragment derived from the polytene chromosome band 59F5. The l(2)tid+ gene spans approximately 2.5 kb of genomic DNA. The protein coding region, 1,696 bps long, is divided by an intron into two exons. The predicted Tid56 protein contains 518 amino acids and possesses a theoretical molecular weight of 56 kDa. It shows significant homology to all known DnaJ related proteins from bacteria, yeast, and man. The possible function of the Tid56 protein in tumor suppression is delineated.

Alleles↗
PubMed1995

Genetic mosaic analysis of the equatorial-less mutation in Drosophila melanogaster.

eql (equatorial-less) is a recessive lethal mutation on the second chromosome of Drosophila melanogaster. J. Campos-Ortega found that eql clones in somatic mosaic flies have reduced numbers of photoreceptor cells, and he suggested that only the R1, R6, and R7 photoreceptor cells were missing in this mutant. These photoreceptor cells help to define the inverted orientation of ommatidial facets along the equatorial midline of the fly eye, hence the mutation was named "equatorial-less." We have conducted a detailed analysis of the eql mutation, by serial section reconstruction of eql clones marked with bw- or w- in somatic mosaic flies. We found that all photoreceptor cell types (R1-R8) could be deleted by the eql mutation, and in rare cases the number of photoreceptor cells was increased. The apparent lack of photoreceptor cell type specificity was confirmed by our analysis of genetically mosaic facets, which indicated that no single photoreceptor cell, or subset of photoreceptor cells, was uniquely required to express eql+. Rather, eql appears to function in all photoreceptor cells, and possibly in all eye precursor cells. The distribution of photoreceptor cell numbers in w eql facets was consistent with the hypothesis that each photoreceptor cell was deleted independently of the others. The eql gene is located on the right arm of chromosome 2 at map location 2-104.5 +/- 0.7 and lies between the polytene chromosome bands 59D8 and 60A7.

Animals↗
PubMed1995

Spatial expression of the hsr-omega (93D) gene in different tissues of Drosophila melanogaster and identification of promoter elements controlling its developmental expression.

Developmental expression of the heat shock inducible non-protein coding hsr-omega gene in several larval and adult tissues of Drosophila melanogaster was examined by in situ hybridization to transcripts in intact organs and by X-gal staining in the germline transformants and carrying the lacZ reporter gene under the control of hsr-omega promoter. This gene is expressed in a specific spatial pattern in all the larval and adult tissue types examined; however, its transcripts were specifically absent in certain gonadal cell types like the male as well as female gonial cells and in follicle cells and oocytes in ovary. All polytenised tissues like the prothoracic and salivary glands, certain regions of larval gut and the Malpighian tubules showed a greater abundance of hsr-omega transcripts with a strong hybridization in nuclei. Our results with promoter deletion variant germline transformants suggest that a region between -346bp to -844bp upstream contains major regulatory elements for developmental expression of this gene in most of the larval and adult tissues examined; however, this region is not sufficient for its normal expression in male and female reproductive systems. An analysis of the base sequence of the hsr-omega promoter (upto - 844 bp) reveals putative ecdysone receptor element half-sites and two GAGA factor binding sites which may be involved in its developmental expression and its ready inducibility. The widespread expression in most tissue types and the known lethality associated with its homozygous deletion, suggest that the variety of non-protein coding transcripts of the hsr-omega gene have vital "house-keeping" functions.

Animals↗
PubMed2004

Genotoxicity modulation by cadmium treatment: studies in the Drosophila wing spot test.

The genotoxic activity of cadmium chloride (CC) has been evaluated in the somatic mutation and recombination test (SMART) in Drosophila melanogaster. In addition, its possible modulating effect on the genotoxicity of two known mutagenic agents, potassium dichromate (PDC) and ethyl methanesulfonate (EMS), was investigated. Three different types of combined treatments of CC with the two genotoxins were performed: pretreatment, cotreatment, and posttreatment. The SMART assay is based on the principle that loss of heterozygosity for the recessive markers, multiple wing hairs (mwh) and flare-3 (flr(3)), leads to the formation of mutant clones in the imaginal disks of larvae, which are expressed as mutant spots on the wings of adult flies. Thus, after adult emergence, the wings of the adult flies were scored for the presence of single and/or twin spots. Our results show that CC alone was not effective in increasing the frequency of any of the three categories of spots (small, large, and twin). In the cotreatment experiments, CC increased the genotoxicity of PDC but it decreased the genotoxicity of EMS. No effects of CC were observed in the pretreatment or posttreatment experiments; however, only low concentrations of CC, PDC, and EMS were tested in the pretreatment assays due to the high toxicity of the treatment. Although our results with PDC are consistent with the hypothesis that cadmium can interfere with repair mechanisms, the EMS data suggest that other modulating mechanisms are also involved in the genotoxicity of this metal.

Animals↗
PubMed1993

A human homologue of Saccharomyces cerevisiae SNF2/SWI2 and Drosophila brm genes potentiates transcriptional activation by the glucocorticoid receptor.

Several of the SNF and SWI genes of Saccharomyces cerevisiae code for proteins believed to assist transcriptional activators by relieving nucleosome repression. One of these proteins, SNF2/SWI2, has a homologue in Drosophila, a regulator of homeotic genes known as brahma or brm. In this report, we show that a counterpart of SNF2/SWI2 also exists in mice and humans. The human protein, designated hbrm, is a 180 kDa nuclear factor that can function as a transcriptional activator when fused to a heterologous DNA binding domain. The mouse homologue of hbrm is expressed in all mouse organs tested while hbrm was detected in some but not all investigated human cell lines. In cells failing to express the endogenous gene, transfected hbrm cooperates with the glucocorticoid receptor (GR) in transcriptional activation. However, hbrm had no effect on the activity of several other transcription factors, including the homeoprotein HNF-1. The co-operation between hbrm and GR required the DNA binding domain of GR and two separated regions of the hbrm protein, including a domain with homology to known helicases.

Amino Acid Sequence↗
PubMed1993

Mutations in the segment polarity genes wingless and porcupine impair secretion of the wingless protein.

We have characterized the molecular nature of mutations in wingless (wg), a segment polarity gene acting during various stages of Drosophila development. Embryo-lethal alleles have undergone mutations in the protein-encoding domain of the gene, including deletions and point mutations of conserved residues. In a temperature sensitive mutation, a conserved cysteine residue is replaced by a serine. In embryo-viable alleles, the wg transcriptional unit is not affected. Immunostaining of mutant embryos shows that the embryo-lethal alleles produce either no wg antigen or a form of the protein that is retained within cells. Interestingly, embryos mutant for the segment polarity gene porcupine show a similar retention of the wg antigen. We have also transfected wild type wg alleles into Drosophila tissue culture cells, which then display wg protein on the cell surface and in the extracellular matrix. In similar experiments with mutant alleles, the proteins are retained in intracellular compartments and appear not to be secreted. These data provide further evidence that wg acts as a secreted factor and suggest that porcupine provides an accessory function for wg protein secretion or transport.

Alleles↗