title: Regional modulation of a stochastically expressed factor determines photoreceptor subtypes in the Drosophila retina.
abstract: Stochastic mechanisms are sometimes utilized to diversify cell fates, especially in nervous systems. In the Drosophila retina, stochastic expression of the PAS-bHLH transcription factor Spineless (Ss) controls photoreceptor subtype choice. In one randomly distributed subset of R7 photoreceptors, Ss activates Rhodopsin4 (Rh4) and represses Rhodopsin3 (Rh3); counterparts lacking Ss express Rh3 and repress Rh4. In the dorsal third region of the retina, the Iroquois Complex transcription factors induce Rh3 in Rh4-expressing R7s. Here, we show that Ss levels are controlled in a binary on/off manner throughout the retina yet are attenuated in the dorsal third region to allow Rh3 coexpression with Rh4. Whereas the sensitivity of rh3 repression to differences in Ss levels generates stochastic and regionalized patterns, the robustness of rh4 activation ensures its stochastic expression throughout the retina. Our findings show how stochastic and regional inputs are integrated to control photoreceptor subtype specification in the Drosophila retina.
authors.affiliation: Center for Developmental Genetics, Department of Biology, New York University, New York, NY 10003, USA.
authors.forename: Shivani U
authors.initials: SU
authors.lastname: Thanawala
authors.forename: Jens
authors.initials: J
authors.lastname: Rister
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Goldberg
authors.forename: Andrey
authors.initials: A
authors.lastname: Zuskov
authors.forename: Eugenia C
authors.initials: EC
authors.lastname: Olesnicky
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Flowers
authors.forename: David
authors.initials: D
authors.lastname: Jukam
authors.forename: Michael D
authors.initials: MD
authors.lastname: Purugganan
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Gavis
authors.forename: Claude
authors.initials: C
authors.lastname: Desplan
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Johnston
mesh_terms: D000483:Alleles; D000818:Animals; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D004330:Drosophila / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000378:metabolism / Q000502:physiology; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D020419:Photoreceptor Cells, Vertebrate / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D011401:Promoter Regions, Genetic; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism*; D012160:Retina / Q000378:metabolism / Q000502:physiology*; D012243:Rhodopsin / Q000235:genetics / Q000378:metabolism; D013045:Species Specificity; D014158:Transcription, Genetic
chemical_list: D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D018336:Receptors, Aryl Hydrocarbon; C523885:Rh5 protein, Drosophila; C105578:Rh6 protein, Drosophila; C114494:dve protein, Drosophila; C112211:ss protein, Drosophila; C109766:tgo protein, Drosophila; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D049452:Green Fluorescent Proteins; D012243:Rhodopsin