ABSTRACT
Drosophila nemo was first identified as a gene required for tissue polarity during ommatidial development. We have extended the analysis of nemo and found that it participates in multiple developmental processes. It is required during wing development for wing shape and vein patterning. We observe genetic interactions between nemo and mutations in the Notch, Wingless, Frizzled and Decapentaplegic pathways. Our data support the findings from other organisms that Nemo proteins act as negative regulators of Wingless signaling. nemo mutations cause polarity defects in the adult wing and overexpression of nemo leads to abdominal polarity defects. The expression of nemo during embryogenesis is dynamic and dsRNA inhibition and ectopic expression studies indicate that nemo is essential during embryogenesis.
Subject(s)
Body Patterning , Drosophila Proteins , Drosophila/embryology , Mitogen-Activated Protein Kinases/physiology , Alleles , Animals , Blotting, Northern , DNA, Complementary/metabolism , Frizzled Receptors , In Situ Hybridization , Insect Proteins/genetics , Membrane Proteins/genetics , Microscopy, Electron, Scanning , Models, Biological , Models, Genetic , Mutation , Phenotype , Photoreceptor Cells, Invertebrate/embryology , Photoreceptor Cells, Invertebrate/physiology , RNA/metabolism , RNA, Messenger/metabolism , Receptors, G-Protein-Coupled , Receptors, Notch , Signal Transduction , Wings, Animal/embryology , Wings, Animal/physiologyABSTRACT
The Notch receptor controls cell fate decisions throughout Drosophila development. Truncated, ligand-independent forms of this protein delay or block differentiation. We have previously shown that expression of the intracellular domain of the receptor under the control of the sevenless enhancer/promoter induces a rough eye phenotype in the adult fly. Analysis of the resultant cellular transformations suggested that this form of Notch acts as a constitutively activated receptor. To identify gene products that interact with Notch, a second-site mutagenesis screen was performed to isolate enhancers and suppressors of the eye phenotype caused by expression of these activated Notch molecules. We screened 137,000 mutagenized flies and recovered 290 dominant modifiers. Many new alleles of previously identified genes were isolated, as were mutations defining novel loci that may function in the Notch signaling pathway. We discuss the data with respect to known features of Notch receptor signaling and Drosophila eye development.
Subject(s)
Drosophila/genetics , Enhancer Elements, Genetic , Genes, Suppressor , Membrane Proteins/genetics , Receptors, Cell Surface/genetics , Animals , Drosophila Proteins , Eye/ultrastructure , Female , Genetic Complementation Test , Male , Mutagenesis, Site-Directed , Receptors, Notch , Signal Transduction/geneticsABSTRACT
The chickadee gene of Drosophila encodes profilin, a small actin binding protein. We present the first analysis of the effects of profilin deletion in a multicellular organism. Genomic deletions of the chickadee locus result in a late embryonic lethal phenotype indicating that profilin is essential in flies. In addition, viable alleles of chickadee with defects in oogenesis, spermatogenesis and bristle formation provide insight into profilin function in a variety of cell types. Defects in oogenesis include the previously described failure to assemble nurse cell actin filament bundles in addition to abnormal regulation of mitosis, binucleate cells and stalled cell migration. Malformed bristles are a result of aberrant actin assembly. Monoclonal antibodies against Drosophila profilin were generated to study profilin's cellular and subcellular localization.
Subject(s)
Contractile Proteins/physiology , Drosophila/embryology , Genes, Insect , Microfilament Proteins/physiology , Actins/pharmacology , Alleles , Animals , Blotting, Southern , Contractile Proteins/genetics , Drosophila/genetics , Drosophila/ultrastructure , Drosophila Proteins , Female , Gene Deletion , Microfilament Proteins/genetics , Microscopy, Electron, Scanning , Morphogenesis/genetics , Oogenesis/genetics , Phenotype , ProfilinsABSTRACT
Antibodies were used to quantify seven domain-specific integral proteins of the rat hepatocyte plasma membrane during rat liver regeneration in response to two-thirds hepatectomy. Quantitative immunoblotting revealed that a subset of the plasma membrane proteins exhibited transient 30-70% decreases in relative concentration during the period of hepatocyte proliferation. The list of affected proteins included at least one representative from each of the plasma membrane domains: the apical protein HA 4, the lateral protein HA 321, and the basolateral receptors for epidermal growth factor and asialoglycoproteins. In contrast, the relative concentrations of three other plasma membrane proteins, the basolateral protein CE 9 and the two apical proteins dipeptidylpeptidase IV and aminopeptidase N, remained unchanged throughout liver regeneration. The decreases in the relative concentrations of the plasma membrane proteins were observed even when the synthesis of hepatocyte DNA was blocked by hydroxyurea, suggesting that the signalling for these two delayed consequences of two-thirds hepatectomy occurred along parallel, dependent pathways. Pulse and pulse-chase metabolic radiolabeling studies revealed that the decreases in the concentrations of the PM proteins were accomplished through protein-selective decreases in the rates of synthesis of the high-mannose precursors of the affected proteins, but not through the accelerated degradation of the mature plasma membrane proteins.
