The cell adhesion molecule Echinoid defines a new pathway that antagonizes the Drosophila EGF receptor signaling pathway.
Photoreceptor and cone cells in the Drosophila eye are recruited following activation of the epidermal growth factor receptor (EGFR) pathway. We have identified echinoid (ed) as a novel putative cell adhesion molecule that negatively regulates EGFR signaling. The ed mutant phenotype is associated with extra photoreceptor and cone cells. Conversely, ectopic expression of ed in the eye leads to a reduction in the number of photoreceptor cells. ed expression is independent of EGFR signaling and ED is localized to the plasma membrane of every cells throughout the eye disc. We present evidence that ed acts nonautonomously to generate extra R7 cells by a mechanism that is sina-independent but upstream of Tramtrack (TTK88). Together, our results support a model whereby ED defines an independent pathway that antagonizes EGFR signaling by regulating the activity, but not the level, of the TTK88 transcriptional repressor.
Bai
J
J
Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan 30043, Republic of China.
Chiu
W
W
Wang
J
J
Tzeng
T
T
Perrimon
N
N
Hsu
J
J
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D015815:Cell Adhesion Molecules / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D004330:Drosophila / Q000166:cytology / Q000196:embryology / Q000235:genetics* / Q000378:metabolism*; D029721:Drosophila Proteins; D004843:Epistasis, Genetic; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D006651:Histocytochemistry; D007136:Immunoglobulins / Q000235:genetics; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology / Q000196:embryology / Q000378:metabolism / Q000648:ultrastructure; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases; D014921:Wings, Animal / Q000196:embryology / Q000378:metabolism; D000098563:Seven in Absentia Proteins
D015815:Cell Adhesion Molecules; D029721:Drosophila Proteins; C422623:ED protein, Drosophila; D007136:Immunoglobulins; D019476:Insect Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; C075878:ttk protein, Drosophila; D044767:Ubiquitin-Protein Ligases; D000098563:Seven in Absentia Proteins; D066246:ErbB Receptors