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N Perrimon

Publications and source records attributed to N Perrimon.

At least 73 records · Page 4Linked to original sources
PubMed1998

Identifying loci required for follicular patterning using directed mosaics.

We have developed a 'directed mosaic' system in Drosophila by using the GAL4 system to control the expression of the yeast recombinase, FLP, in a spatial and temporal fashion. By directing FLP expression, we show that it is possible to efficiently and specifically target loss-of-function studies for vital loci to the developmental pathway of interest. A simple F1 adult phenotypic screen demonstrated that most adult tissues can be analyzed with this approach. Using GAL4 lines expressed during oogenesis, we have refined the system to examine the roles of vital loci in the development of the follicular epithelium. We have identified essential genes involved in egg chamber organization, cell migration and cell shape. Further, we have used this technique to gain insights into the role of the Drosophila EGF receptor pathway in establishing the egg axes. Finally, using different UAS-FLP, GAL4 and existing FRT lines, we have built stocks that permit the analysis of approximately 95% of the genome in follicular mosaics.

Animals↗
PubMed1998

Dual function of Ras in Raf activation.

The small guanine nucleotide binding protein p21(Ras) plays an important role in the activation of the Raf kinase. However, the precise mechanism by which Raf is activated remains unclear. It has been proposed that the sole function of p21(Ras )in Raf activation is to recruit Raf to the plasma membrane. We have used Drosophila embryos to examine the mechanism of Raf (Draf) activation in the complete absence of p21(Ras) (Ras1). We demonstrate that the role of Ras1 in Draf activation is not limited to the translocation of Draf to the membrane through a Ras1-Draf association. In addition, Ras1 is essential for the activation of an additional factor which in turn activates Draf.

Animals↗
PubMed1998

Creating mosaics in Drosophila.

The ability to create mosaic animals allows the phenotypic analysis of patches of groups of genetically different cells that develop in a wild type environment. In Drosophila, a variety of techniques have been developed over the years to generate mosaics, and in this chapter, I review the techniques that our laboratory has developed. These include the "Dominant Female Sterile" technique which allows the analysis of gene functions to oogenesis and embryogenesis; the "Gal4-UAS" technique which allows the control of where and when specific genes are expressed; and, the "Positive Marked Mutant Lineages" technique which allows clones of cells to express a specific reporter gene.

Animals↗
PubMed1997

A genetic screen for mutations that disrupt an auditory response in Drosophila melanogaster.

Hearing is one of the last sensory modalities to be subjected to genetic analysis in Drosophila melanogaster. We describe a behavioral assay for auditory function involving courtship among groups of males triggered by the pulse component of the courtship song. In a mutagenesis screen for mutations that disrupt the auditory response, we have recovered 15 mutations that either reduce or abolish this response. Mutant audiograms indicate that seven mutants reduced the amplitude of the response at all intensities. Another seven abolished the response altogether. The other mutant, 5L3, responded only at high sound intensities, indicating that the threshold was shifted in this mutant. Six mutants were characterized in greater detail. 5L3 had a general courtship defect; courtship of females by 5L3 males also was affected strongly. 5P1 males courted females normally but had reduced success at copulation. 5P1 and 5N18 showed a significant decrement in olfactory response, indicating that the defects in these mutations are not specific to the auditory pathway. Two other mutants, 5M8 and 5N30, produced amotile sperm although in 5N30 this phenotype was genetically separable from the auditory phenotype. Finally, a new adult circling behavior phenotype, the pirouette phenotype, associated with massive neurodegeneration in the brain, was discovered in two mutants, 5G10 and 5N18. This study provides the basis for a genetic and molecular dissection of auditory mechanosensation and auditory behavior.

Animals↗
PubMed1997

Inhibition of patterned cell shape change and cell invasion by Discs large during Drosophila oogenesis.

Drosophila Discs large (Dlg) is a tumor suppressor gene whose loss in epithelial tissues causes disrupted cell polarity and increased cell proliferation. A human Dlg homolog, hDlg, has been implicated in tumorigenic processes via its association with the product of the Adenomatous Polyposis Coli (APC) gene. We show for the first time that Drosophila Dlg is required to block cell invasion. Loss of dlg activity during oogenesis causes follicle cells to change shape and invade in a pattern similar to border cells, a small population of cells that break from the post-mitotic follicular epithelium during wild-type oogenesis, yet dlg mutant cells have not adopted a border cell fate. Both functional and morphological evidence indicates that cooperation between germ cell and follicle cell Dlg, probably mediated by Dlg PDZ domains, is crucial for regulating cell mixing, suggesting a novel developmental mechanism and mode of action for the Dlg family of molecules. These findings suggest that Dlg does not simply inhibit individual cell behaviors during oogenesis, but rather acts in a developmental pathway essential for blocking cell proliferation and migration in a spatio-temporally defined manner. A model for Dlg action in blocking cell invasion is presented.

Animals↗
PubMed1997

Drosophila Jun relays the Jun amino-terminal kinase signal transduction pathway to the Decapentaplegic signal transduction pathway in regulating epithelial cell sheet movement.

We have characterized mutations in the Drosophila homolog of the mammalian proto-oncogene c-Jun gene (Djun). We demonstrate that DJUN in the embryo is a downstream target of the JNK signal transduction pathway during dorsal closure formation, and that the function of the JNK/DJUN pathway is to control the localized expression of decapentalegic (dpp), a member of the TGF-beta growth factor family. In contrast to previous observations, we find that both in the embryo and during photoreceptor cell determination, DJUN is not regulated by a pathway that involves MAPK.

Animals↗
PubMed1997

The nuclear hormone receptor Ftz-F1 is a cofactor for the Drosophila homeodomain protein Ftz.

Homeobox genes specify cell fate and positional identity in embryos throughout the animal kingdom. Paradoxically, although each has a specific function in vivo, the in vitro DNA-binding specificities of homeodomain proteins are overlapping and relatively weak. A current model is that homeodomain proteins interact with cofactors that increase specificity in vivo. Here we use a native binding site for the homeodomain protein Fushi tarazu (Ftz) to isolate Ftz-F1, a protein of the nuclear hormone-receptor superfamily and a new Ftz cofactor. Ftz and Ftz-F1 are present in a complex in Drosophila embryos. Ftz-F1 facilitates the binding of Ftz to DNA, allowing interactions with weak-affinity sites at concentrations of Ftz that alone bind only high-affinity sites. Embryos lacking Ftz-F1 display ftz-like pair-rule cuticular defects. This phenotype is a result of abnormal ftz function because it is expressed but fails to activate downstream target genes. Cooperative interaction between homeodomain proteins and cofactors of different classes may serve as a general mechanism to increase HOX protein specificity and to broaden the range of target sites they regulate.

Animals↗
PubMed1997

The JAK-STAT pathway in Drosophila.

Recent studies in Drosophila have identified a single JAK and a single STAT protein. Genetic and biochemical analyses reveal that these two proteins operate in the same signal transduction pathway. Phenotypic analyses of JAK and STAT mutants implicate this pathway in a number of developmental decisions, in particular the regulation of pair-rule genes and fly hematopoiesis.

Animals↗
PubMed1997

A new enhancer of position-effect variegation in Drosophila melanogaster encodes a putative RNA helicase that binds chromosomes and is regulated by the cell cycle.

In Drosophila melanogaster, position-effect variegation of the white gene has been a useful phenomenon by which to study chromosome structure and the genes that modify it. We have identified a new enhancer of variegation locus, Dmrnahel (hel). Deletion of mutation of hel enhances white variegation, and this can be reversed by a transformed copy of hel+. In the presence of two endogenous copies, the transformed hel+ behaves as a suppressor of variegation. hel is an essential gene and functions both maternally and zygotically. The HEL protein is similar to known RNA helicases, but contains an unusual variant (DECD) of the DEAD motif common to these proteins. Potential HEL homologues have been found in mammals, yeast and worms. HEL protein associates with salivary gland chromosomes and locates to nuclei of embryos and ovaries, but disappears in mitotic domains of embryos as chromosomes condense. We propose that the HEL protein promotes an open chromatin structure that favors transcription during development by regulating the spread of heterochromatin, and that HEL is regulated by, and may have a role in, the mitotic cell cycle during embryogenesis.

Amino Acid Sequence↗
PubMed1997

The Drosophila sugarless gene modulates Wingless signaling and encodes an enzyme involved in polysaccharide biosynthesis.

We have identified and characterized a Drosophila gene, which we have named sugarless, that encodes a homologue of vertebrate UDP-glucose dehydrogenase. This enzyme is essential for the biosynthesis of various proteoglycans, and we find that in the absence of both maternal and zygotic activities of this gene, mutant embryos develop with segment polarity phenotypes reminiscent to loss of either Wingless or Hedgehog signaling. To analyze the function of Sugarless in cell-cell interaction processes, we have focused our analysis on its requirement for Wingless signaling in different tissues. We report that sugarless mutations impair signaling by Wingless, suggesting that proteoglycans contribute to the reception of Wingless. We demonstrate that overexpression of Wingless can bypass the requirement for sugarless, suggesting that proteoglycans modulate signaling by Wingless, possibly by limiting its diffusion and thereby facilitating the binding of Wingless to its receptor. We discuss the possibility that tissue-specific regulation of proteoglycans may be involved in regulating both Wingless short- or long-range effects.

Amino Acid Sequence↗
PubMed1997

The Drosophila 14-3-3 protein Leonardo enhances Torso signaling through D-Raf in a Ras 1-dependent manner.

14-3-3 proteins have been shown to interact with Raf-1 and cause its activation when overexpressed. However, their precise role in Raf-1 activation is still enigmatic, as they are ubiquitously present in cells and found to associate with Raf-1 in vivo regardless of its activation state. We have analyzed the function of the Drosophila 14-3-3 gene leonardo (leo) in the Torso (Tor) receptor tyrosine kinase (RTK) pathway. In the syncytial blastoderm embryo, activation of Tor triggers the Ras/Raf/MEK pathway that controls the transcription of tailless (tll). We find that, in the absence of Tor, overexpression of leo is sufficient to activate tll expression. The effect of leo requires D-Raf and Ras1 activities but not KSR or DOS, two recently identified essential components of Drosophila RTK signaling pathways. Tor signaling is impaired in embryos derived from females lacking maternal expression of leo. We propose that binding to 14-3-3 by Raf is necessary but not sufficient for the activation of Raf and that overexpressed Drosophila 14-3-3 requires Ras1 to activate D-Raf.

14-3-3 Proteins↗
PubMed1996

The segment polarity gene porcupine encodes a putative multitransmembrane protein involved in Wingless processing.

The Wnt protein Wingless (Wg) functions as a signal in patterning of both the Drosophila embryo and imaginal discs. Lack of porcupine (porc) activity is associated with mutant phenotypes similar to those of wg mutations. In porc mutant embryos, Wg protein is confined to the cells that produce it, suggesting that Porc plays a role in processing or secretion of Wg. porc encodes a novel transmembrane protein that appears to be concentrated at the endoplasmic reticulum. We present both genetic and in vitro evidence demonstrating that porc is involved specifically in the processing of Wg. We identified a human sequence related to Porc suggesting the existence of a family of proteins involved in processing of Wnts.

Amino Acid Sequence↗
PubMed1996

The nonreceptor protein tyrosine phosphatase corkscrew functions in multiple receptor tyrosine kinase pathways in Drosophila.

Corkscrew (csw) encodes a nonreceptor protein tyrosine phosphatase (PTPase) that has been implicated in signaling from the Torso receptor tyrosine kinase (RTK). csw mutations, unlike tor mutations, are associated with zygotic lethality, indicating that Csw plays additional roles during development. We have conducted a detailed phenotypic analysis of csw mutations to identify these additional functions of Csw. Our results indicate that Csw operates positively downstream of other Drosophila RTKs such as the Drosophila epidermal growth factor receptor (DER), the fibroblast growth factor receptor (Breathless), and likely other RTKs. This model is substantiated by specific dosage interactions between csw and DER. It is proposed that Csw is part of the evolutionarily conserved "signaling cassette" that operates downstream of all RTKs. In support of this hypothesis, we demonstrate that SHP-2, a vertebrate PTPase similar to Csw and previously implicated in RTK signaling, encodes the functional vertebrate homologue of Csw.

Alleles↗
PubMed1996

wingless refines its own expression domain on the Drosophila wing margin.

The imaginal discs of Drosophila, which give rise to the adult appendages, are patterned during a period of intense cell proliferation. The specification of differing regions occurs in some cases by subdividing the disc epithelium into lineage compartments. However, in most cases precise boundaries are formed between different cell types without early compartmentalization. One such boundary occurs between the wingless (wg)-expressing cells of the wing margin and the adjacent proneural cells, which give rise to margin sensory bristles. Here we show that this boundary arises in part by a mechanism of 'self-refinement', by which wingless protein (Wg) represses wg expression in adjacent cells. Cells unable to receive the Wg signal do not resolve the boundary between wg-expressing and proneural cells.

Adaptor Proteins, Signal Transducing↗