title: Induction in the developing compound eye of Drosophila: multiple mechanisms restrict R7 induction to a single retinal precursor cell.
abstract: The development of the Drosophila R7 photoreceptor cell is determined by a specific inductive interaction between the R8 photoreceptor cell and a single neighboring precursor cell. This process is mediated by bride of sevenless (boss), a cell-surface bound ligand, and the sevenless (sev) tyrosine kinase receptor. The boss ligand is expressed specifically on the surface of the R8 cell, whereas the sev receptor is expressed on 5 cells contacting the developing R8 cell and other cells not in contact with R8. By altering the spatial and temporal expression of boss, we demonstrate that sev-expressing cells that do not contact R8 can assume an R7 cell fate. By contrast, the sev-expressing precursor cells to the R1-R6 photoreceptor cells that do contact R8 are nonresponsive to the inductive cue. Using the rough and Nspl mutations, we demonstrate that an early commitment to an R1-R6 cell fate blocks the pathway of sev activation in these cells.
authors.affiliation: Howard Hughes Medical Institute, Department of Biological Chemistry, UCLA School of Medicine 90024-1737.
authors.forename: D L
authors.initials: DL
authors.lastname: Van Vactor
authors.forename: R L
authors.initials: RL
authors.lastname: Cagan
authors.forename: H
authors.initials: H
authors.lastname: Krämer
authors.forename: S L
authors.initials: SL
authors.lastname: Zipursky
mesh_terms: D000818:Animals; D003001:Cloning, Molecular; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000196:embryology*; D004627:Embryonic Induction; D005123:Eye / Q000196:embryology; D005136:Eye Proteins / Q000502:physiology*; D015870:Gene Expression; D008024:Ligands; D008562:Membrane Glycoproteins / Q000502:physiology*; D008565:Membrane Proteins / Q000502:physiology*; D009474:Neurons / Q000166:cytology; D010786:Photoreceptor Cells / Q000166:cytology / Q000196:embryology*; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D020794:Receptor Protein-Tyrosine Kinases; D018000:Receptors, Peptide
chemical_list: D029721:Drosophila Proteins; D005136:Eye Proteins; D008024:Ligands; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D018000:Receptors, Peptide; C072141:boss protein, Drosophila; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases; C056737:sev protein, Drosophila