title: abdominal A specifies one cell type in Drosophila by regulating one principal target gene.
abstract: The Hox/homeotic genes encode transcription factors that generate segmental diversity during Drosophila development. At the level of the whole animal, they are believed to carry out this role by regulating a large number of downstream genes. Here we address the unresolved issue of how many Hox target genes are sufficient to define the identity of a single cell. We focus on the larval oenocyte, which is restricted to the abdomen and induced in response to a non-cell autonomous, transient and highly selective input from abdominal A (abdA). We use Hox mutant rescue assays to demonstrate that this function of abdA can be reconstituted by providing Rhomboid (Rho), a processing factor for the EGF receptor ligand, secreted Spitz. Thus, in order to make an oenocyte, abdA regulates just one principal target, rho, that acts at the top of a complex hierarchy of cell-differentiation genes. These studies strongly suggest that, in at least some contexts, Hox genes directly control only a few functional targets within each nucleus. This raises the possibility that much of the overall Hox downstream complexity results from cascades of indirect regulation and cell-to-cell heterogeneity.
authors.affiliation: Medical Research Council, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.
authors.forename: Véronique
authors.initials: V
authors.lastname: Brodu
authors.forename: Philip R
authors.initials: PR
authors.lastname: Elstob
authors.forename: Alex P
authors.initials: AP
authors.lastname: Gould
mesh_terms: D000005:Abdomen / Q000196:embryology / Q000254:growth & development; D000818:Animals; D051943:Antennapedia Homeodomain Protein; D029681:Arabidopsis Proteins; D004330:Drosophila / Q000196:embryology / Q000235:genetics / Q000254:growth & development*; D029721:Drosophila Proteins; D004625:Embryo, Nonmammalian; D004815:Epidermal Growth Factor; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007814:Larva; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009687:Nuclear Proteins; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D051943:Antennapedia Homeodomain Protein; C497974:Antp protein, Drosophila; D029681:Arabidopsis Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D019476:Insect Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D010940:Plant Proteins; C081481:Rho protein, Drosophila; C100978:SCR protein, Arabidopsis; C472498:Stet protein, Drosophila; D014157:Transcription Factors; C083405:exd protein, Drosophila; C066591:abd-A protein, Drosophila; C076026:spi protein, Drosophila; D004815:Epidermal Growth Factor