title: Loss of seven-up from Drosophila R1/R6 photoreceptors reveals a stochastic fate choice that is normally biased by Notch.
abstract: Recent evidence suggests that stochasticism is important for generating cell type diversity. We have identified a novel stochastic fate choice as part of the mechanism by which Delta/Notch (Dl/N) signaling specifies R7 fate in the Drosophila eye. The equivalence of R1/R6/R7 precursors is normally broken by the activation of N, which specifies the R7 fate. The orphan nuclear hormone receptor Seven-up (Svp) is necessary and sufficient to direct R1/R6/R7 precursors to adopt the R1/R6 fate. A simple model, therefore, is that N represses Svp, which otherwise prevents adoption of the R7 fate. However, we have found that R1/R6s lacking svp stochastically adopt either the R7 or the R8 fate with equal likelihood. We show that N specifies the R7 fate by a novel branched pathway: N represses Svp expression, thereby exposing an underlying stochastic choice between the R7 and R8 fates, and then tips this choice towards the R7 fate.
authors.affiliation: Institute of Molecular Biology, University of Oregon, 1370 Franklin Blvd, Eugene, OR 97403, USA.
authors.forename: Adam C
authors.initials: AC
authors.lastname: Miller
authors.forename: Heather
authors.initials: H
authors.lastname: Seymour
authors.forename: Christopher
authors.initials: C
authors.lastname: King
authors.forename: Tory G
authors.initials: TG
authors.lastname: Herman
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D019070:Cell Lineage; D004268:DNA-Binding Proteins / Q000172:deficiency* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology* / Q000378:metabolism; D007814:Larva / Q000166:cytology / Q000254:growth & development; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology*; D011679:Pupa / Q000166:cytology / Q000254:growth & development; D051880:Receptors, Notch / Q000378:metabolism*; D011987:Receptors, Steroid / Q000172:deficiency* / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism; D012243:Rhodopsin / Q000378:metabolism; D013269:Stochastic Processes
chemical_list: D015415:Biomarkers; D004268:DNA-Binding Proteins; D051880:Receptors, Notch; D011987:Receptors, Steroid; D012097:Repressor Proteins; C094295:svp protein, Drosophila; D012243:Rhodopsin