title: The Drosophila gene Hairless encodes a novel basic protein that controls alternative cell fates in adult sensory organ development.
abstract: The mechanosensory bristles of adult Drosophila are composed of four cells that, in most cases, are progeny of a single sensory organ precursor (SOP) cell. Two sister cells in this lineage, the trichogen and tormogen, produce the external shaft and socket of the bristle, respectively. Loss-of-function mutations of Hairless (H) confer two distinct mutant phenotypes on adult bristles. The bristle loss phenotype results from the failure to specify and/or execute the SOP cell fate; the double socket phenotype results from the transformation of the trichogen (shaft) cell into a second tormogen (socket) cell. We have found that the H gene encodes a novel basic protein with a predicted molecular mass of 109 kD. Basal levels of expression of a transgene (P[Hs-H]) in which the H protein-coding region is under the control of the Hsp70 promoter are sufficient to provide full rescue of H mutant phenotypes. Heat shock treatment of P[Hs-H] transgenic animals as late larvae and early pupae produces a tormogen-to-trichogen (double shaft) cell fate transformation, as well as bristle multiplication and loss phenotypes very similar to those caused by loss-of-function mutations in the neurogenic gene Notch. Our results indicate that the SOP cell fate requires H to antagonize the activity of the neurogenic group of genes and that the expression of distinct cell fates by the trichogen/tormogen sister cell pair depends on an asymmetry in their levels of H+ activity or in their thresholds for response to H.
authors.affiliation: Department of Biology, University of California, San Diego, La Jolla 92093-0322.
authors.forename: A G
authors.initials: AG
authors.lastname: Bang
authors.forename: J W
authors.initials: JW
authors.lastname: Posakony
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation / Q000235:genetics*; D003001:Cloning, Molecular; D004330:Drosophila / Q000196:embryology / Q000235:genetics / Q000254:growth & development*; D029721:Drosophila Proteins; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics; D015183:Restriction Mapping; D012679:Sense Organs / Q000166:cytology / Q000254:growth & development; D014157:Transcription Factors
chemical_list: D029721:Drosophila Proteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C076560:H protein, Drosophila