Person:
Gibson, Greg

Permanent Link
https://hdl.handle.net/1853/71291
Associated Organization(s)
Organizational Unit
ORCID
ArchiveSpace Name Record

Filters

3
3
3
3
Reset filters

Settings
Author: Gehring, Walter J. ×

Publication Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Identification of target genes of the homeotic gene Antennapedia by enhancer detection
    (Georgia Institute of Technology, 2003-08) Wagner-Bernholz, Juliane T. ; Wilson, Clive ; Gibson, Greg ; Schuh, Reinhard ; Gehring, Walter J.
    Localized expression of the homeotic gene Antennapedia (Antp) in Drosophila melanogaster is required for normal development of the thoracic segments. When the Antp gene is expressed ectopically in the larval primordium of the antenna, the antennal imaginal disc, the developmental fate of the disc is switched and the adult antenna is transformed to a mesothoracic leg. We screened approximately 550 different fly strains carrying single copies of an enhancer-detector transposon to identify regulatory elements and corresponding genes that are either activated or repressed in antennal discs in response to this transformation. Several regulatory elements that are either direct or indirect targets of Antp were found. One transposant that expresses the reporter gene (lacZ) in the antennal disc, but not in the leg disc, was studied in more detail. The enhancer detector in this strain is located near a similarly regulated gene at the spalt (sal) locus, which encodes a homeotic function involved in embryonic head and tail development. The expression of this newly discovered gene, spalt major (salm) is strongly repressed in gain-of-function mutants that express Antp in the antennal disc. Recessive loss-of-function mutations (Antp-) have the opposite developmental effect; they cause the differentiation of antennal structures in the second leg disc. Accordingly, salm is derepressed in clones of homozygous Antp- cells. Therefore, we conclude that Antp negatively regulates salm. The time course of the interaction and reporter gene fusion experiments suggests (but does not prove) a direct interaction between Antp and cis-regulatory elements of salm. Our analysis of several enhancer-detector strains suggests that the basic patterning information in the antennal and leg imaginal discs is very similar.
  • Thumbnail Image
    Item
    Effects of ectopic expression of caudal during Drosophila development
    (Georgia Institute of Technology, 1990-06-01) Mlodzik, Marek ; Gibson, Greg ; Gehring, Walter J.
    The effects of heat-shock-induced ectopic expression of the homeobox gene caudal (cad) at all stages of Drosophila development have been examined. Presence of cad protein (CAD) at the anterior end of cellular blastoderm embryos was found to disrupt head development and •segmentation, due to alteration of the expression of segmentation genes such asfushi tarazu and engrailed, as well as repression of head-determining genes such as Deformed. These results support the conclusion that, while CAD is probably required to activate transcription of fushi tarazu in the posterior half of the embryo, it should not be expressed in the anterior half prior to gastrulation, and thus suggest a role for the CAD gradient. Ectopic expression of CAD at later stages of development has no obvious effects on embryogenesis or imaginal disc development, suggesting that the homeotic genes of the Antennapedia and Bithorax Complexes are almost completely epistatic to caudal.
  • Thumbnail Image
    Item
    Head and thoracic transformations caused by ectopic expression ofAntennapedia during Drosophila development
    (Georgia Institute of Technology, 1988) Gibson, Greg ; Gehring, Walter J.
    Segmental identity in Drosophila is controlled by the activities of the homeotic genes. One such gene is Antennapedia, which is required for the proper development of the thoracic segments. Alteration of Antennapedia expression either in mutants, or artificially using an inducible promoter, can lead to alterations of segmental identity. In this report, we present the consequences of ectopic expression of the Antennapedia gene under the control of a heat-shock promoter, at distinct stages throughout Drosophila development. In young embryos, up to the stage of germ-band retraction, the ubiquitous expression of the Antennapedia protein causes a range of effects throughout the embryo, including failure of head involution, induction of extra denticles on the dorsal surface of the head and disruption of the prothoracic denticle belts. In older embryos, it results in larval lethality. Heat shocks during larval development can lead to defects in leg formation, but no alterations in leg identity have been observed. However, clear transformations of head towards second (meso-) thoracic segment can be induced in early third instar larvae. There is a distal-to-proximal temporal response to ectopic Antennapedia expression in the antennal disc, as evidenced by successive transformations of the arista, third antennal segment, second antennal segment and occiput towards their corresponding leg and dorsal thoracic structures. Overproduction of Antennapedia protein during the pupal stage is generally lethal. Comparison of the homeotic transformations in, and Western analysis of, different lines suggests that a relatively large amount of Antennapedia protein is required to cause antenna-to-leg transformations, and further argues that, in general, developmental programmes in the insect are well buffered against the effects of ectopic homeotic gene expression. Immunodetection of Scr and Antp protein also allows us to interpret the results in light of the hypothesis that the various selector genes compete with one another to control not only their own expression, but also that of downstream genes. The role of Antennapedia in imaginal disc determination is also discussed. rosophila development, segmentation.