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Gene Review

gt  -  giant

Drosophila melanogaster

Synonyms: CG7952, Dmel\CG7952, EG:BACH7M4.5, GIAN_DROME, GT, ...
 
 
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Disease relevance of gt

 

High impact information on gt

  • CtBP-dependent activities of the short-range Giant repressor in the Drosophila embryo [2].
  • There are at least three short-range gap repressors in the precellular Drosophila embryo: Krüppel, Knirps, and Giant [2].
  • The misexpression of Giant in ventral regions of transgenic embryos results in the selective repression of eve stripe 5 [2].
  • A stripe5-lacZ transgene exhibits an abnormal staining pattern in dCtBP mutants that is consistent with attenuated repression by Giant [2].
  • The restricted activity of Knirps, in contrast to that of Giant, suggests that not all short-range repressors possess identical activities, consistent with recent findings showing that short-range repressors act through multiple pathways [3].
 

Biological context of gt

  • We describe the regulated expression of the segmentation gene giant (gt) during early embryogenesis [4].
  • Gene dosage studies indicate that different thresholds of the bcd gradient might trigger hb and gt expression, resulting in overlapping but noncoincident patterns of expression [4].
  • This comparative approach, coupled with the analysis of reporter gene expression in gap mutant embryos suggests that the Kr and gt proteins establish the anterior and posterior borders of h stripe 5, respectively, through spatial repression [5].
  • These interactions, typical of the cross-regulation previously observed among gap genes, confirm that gt is a member of the gap gene class whose function is necessary to establish the overall pattern of gap gene expression [6].
  • We tested the ability of endogenous Giant to repress when bound close to the transcriptional initiation site and found that Giant effectively represses a heterologous promoter when binding sites are located at -55 bp with respect to the start of transcription [7].
 

Anatomical context of gt

  • We also show that the gap repressor Giant (GT) initially establishes a posterior expression limit at PS9, which shifts posteriorly after the blastoderm stage [8].
  • To study short-range transcriptional repressors in cultured cells, we created chimeric tetracycline repressors based on Drosophila transcriptional repressors Giant, Drosophila C-terminal-binding protein (dCtBP), and Knirps [3].
  • To investigate any interactions between the Giant Fibre and the tergotroachanteral motorneuron, we arrested the growth of the motorneuron's medial neurite by targeted expression of a constitutively active form of Dcdc42 [1].
  • Hemolin from the Giant silkmoth, Hyalophora cecropia, identified as a bacteria-inducible molecule and a member of the immunoglobulin superfamily, is present as protein and transcripts in oocytes and embryos [9].
 

Physical interactions of gt

  • Here, we present evidence that Giant might also interact with dCtBP [2].
 

Regulatory relationships of gt

  • We demonstrate that posterior stripe boundaries are established by gap protein repressors unique to each stripe: h stripe 5 is repressed by the giant (gt) protein on its posterior border and h stripe 6 is repressed by the hunchback (hb) protein on its posterior border [10].
 

Other interactions of gt

  • Finally, gt is required for repression of zygotic hb expression in more anterior regions of the embryo [11].
  • The anterior border of Kr, which lies 4-5 nucleus diameters posterior to nuclei that express gt mRNA, is set by a threshold repression mechanism involving very low levels of gt protein [11].
  • In contrast, gt activity is required, but not sufficient for formation of the anterior border of eve stripe 2, which lies adjacent to nuclei that express gt mRNA [11].
  • Our previous work has described the development of the Giant Fibre in early metamorphosis and the involvement of the shaking-B locus in the formation of its electrical synapses [1].

References

  1. Synaptogenesis in the giant-fibre system of Drosophila: interaction of the giant fibre and its major motorneuronal target. Jacobs, K., Todman, M.G., Allen, M.J., Davies, J.A., Bacon, J.P. Development (2000) [Pubmed]
  2. CtBP-dependent activities of the short-range Giant repressor in the Drosophila embryo. Nibu, Y., Levine, M.S. Proc. Natl. Acad. Sci. U.S.A. (2001) [Pubmed]
  3. Cell-type specificity of short-range transcriptional repressors. Ryu, J.R., Olson, L.K., Arnosti, D.N. Proc. Natl. Acad. Sci. U.S.A. (2001) [Pubmed]
  4. Spatial regulation of the gap gene giant during Drosophila development. Kraut, R., Levine, M. Development (1991) [Pubmed]
  5. Conservation of regulatory elements controlling hairy pair-rule stripe formation. Langeland, J.A., Carroll, S.B. Development (1993) [Pubmed]
  6. Interactions of the Drosophila gap gene giant with maternal and zygotic pattern-forming genes. Eldon, E.D., Pirrotta, V. Development (1991) [Pubmed]
  7. Transcriptional repression by the Drosophila giant protein: cis element positioning provides an alternative means of interpreting an effector gradient. Hewitt, G.F., Strunk, B.S., Margulies, C., Priputin, T., Wang, X.D., Amey, R., Pabst, B.A., Kosman, D., Reinitz, J., Arnosti, D.N. Development (1999) [Pubmed]
  8. Functional analysis of repressor binding sites in the iab-2 regulatory region of the abdominal-A homeotic gene. Shimell, M.J., Peterson, A.J., Burr, J., Simon, J.A., O'Connor, M.B. Dev. Biol. (2000) [Pubmed]
  9. Hemolin gene silencing by ds-RNA injected into Cecropia pupae is lethal to next generation embryos. Bettencourt, R., Terenius, O., Faye, I. Insect Mol. Biol. (2002) [Pubmed]
  10. Positioning adjacent pair-rule stripes in the posterior Drosophila embryo. Langeland, J.A., Attai, S.F., Vorwerk, K., Carroll, S.B. Development (1994) [Pubmed]
  11. Two distinct mechanisms for differential positioning of gene expression borders involving the Drosophila gap protein giant. Wu, X., Vakani, R., Small, S. Development (1998) [Pubmed]
 
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