title: A modifier screen for Bazooka/PAR-3 interacting genes in the Drosophila embryo epithelium.
abstract: BACKGROUND
  The development and homeostasis of multicellular organisms depends on sheets of epithelial cells. Bazooka (Baz; PAR-3) localizes to the apical circumference of epithelial cells and is a key hub in the protein interaction network regulating epithelial structure. We sought to identify additional proteins that function with Baz to regulate epithelial structure in the Drosophila embryo.
  
  
  RESULTS
  The baz zygotic mutant cuticle phenotype could be dominantly enhanced by loss of known interaction partners. To identify additional enhancers, we screened molecularly defined chromosome 2 and 3 deficiencies. 37 deficiencies acted as strong dominant enhancers. Using deficiency mapping, bioinformatics, and available single gene mutations, we identified 17 interacting genes encoding known and predicted polarity, cytoskeletal, transmembrane, trafficking and signaling proteins. For each gene, their loss of function enhanced adherens junction defects in zygotic baz mutants during early embryogenesis. To further evaluate involvement in epithelial polarity, we generated GFP fusion proteins for 15 of the genes which had not been found to localize to the apical domain previously. We found that GFP fusion proteins for Drosophila ASAP, Arf79F, CG11210, Septin 5 and Sds22 could be recruited to the apical circumference of epithelial cells. Nine of the other proteins showed various intracellular distributions, and one was not detected.
  
  
  CONCLUSIONS
  Our enhancer screen identified 17 genes that function with Baz to regulate epithelial structure in the Drosophila embryo. Our secondary localization screen indicated that some of the proteins may affect epithelial cell polarity by acting at the apical cell cortex while others may act through intracellular processes. For 13 of the 17 genes, this is the first report of a link to baz or the regulation of epithelial structure.
authors.affiliation: Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Wei
authors.initials: W
authors.lastname: Shao
authors.forename: Johnny
authors.initials: J
authors.lastname: Wu
authors.forename: Jeyla
authors.initials: J
authors.lastname: Chen
authors.forename: Donghoon M
authors.initials: DM
authors.lastname: Lee
authors.forename: Alisa
authors.initials: A
authors.lastname: Tishkina
authors.forename: Tony J C
authors.initials: TJ
authors.lastname: Harris
mesh_terms: D022005:Adherens Junctions / Q000235:genetics; D000818:Animals; D016764:Cell Polarity / Q000235:genetics; D002869:Chromosome Aberrations; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics*; D004625:Embryo, Nonmammalian; D004843:Epistasis, Genetic; D004848:Epithelium / Q000196:embryology*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D011506:Proteins / Q000032:analysis / Q000235:genetics; D049490:Systems Biology
chemical_list: D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; C400774:baz protein, Drosophila