Small lipophilic hormones, acting through their corresponding nuclear receptors, control a wide range of developmental and physiological responses in higher organisms. Although extensive studies have focused on the mechanisms by which nuclear receptors control target gene transcription, relatively little is known about how a hormonal signal is transduced into an appropriate biological response during development. We propose to define one such pathway in detail - steroid-triggered cell death - using Drosophila as a model system. It is well known that steroids play a central role in controlling cell death in higher organisms, including humans. Only in Drosophila, however, has a genetic cascade been identified that links the hormone to a death response - the destruction of the larval salivary glands in response to the steroid hormone ecdysone during metamorphosis. We propose to build off this foundation, using an open-ended genetic screen to identify key players in this pathway. By using GFP as a marker for salivary glands in living animals, we will identify mutants that show specific defects in the steroid-triggered death response. A pilot screen has demonstrated the feasibility of this approach. We identified known genes in the death pathway as well as several new players, including genes that encode the CBP transcriptional co-factor and the TBP-related factor, TRF2. We propose to characterize these two genes in detail, defining the mechanisms that link them to cell death. We also propose to expand our search for death regulators through saturation mutagenesis of approximately 40% of the genome. Mutations will be mapped to specific genes, and functions for these genes will be assigned. This work provides a basis for understanding the molecular mechanisms of hormone signal transduction - defining the players in a genetic cascade that link the hormone to a stage- and tissue-specific biological response during development. This work also represents the first attempt to use random mutagenesis to dissect an endogenous programmed cell death response in Drosophila, raising the possibility that we will uncover novel death regulators. Finally, our studies provide a foundation for determining how steroids control cell death in humans, with implications for understanding and treating human disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
3R01GM073670-04S1
Application #
7886051
Study Section
Molecular and Cellular Endocrinology Study Section (MCE)
Program Officer
Zatz, Marion M
Project Start
2009-08-13
Project End
2010-07-31
Budget Start
2009-08-13
Budget End
2010-07-31
Support Year
4
Fiscal Year
2009
Total Cost
$14,282
Indirect Cost
Name
University of Utah
Department
Genetics
Type
Schools of Medicine
DUNS #
009095365
City
Salt Lake City
State
UT
Country
United States
Zip Code
84112
Wang, Lei; Lam, Geanette; Thummel, Carl S (2010) Med24 and Mdh2 are required for Drosophila larval salivary gland cell death. Dev Dyn 239:954-64
Wang, Lei; Evans, Janelle; Andrews, Hillary K et al. (2008) A genetic screen identifies new regulators of steroid-triggered programmed cell death in Drosophila. Genetics 180:269-81
Bashirullah, Arash; Lam, Geanette; Yin, Viravuth P et al. (2007) dTrf2 is required for transcriptional and developmental responses to ecdysone during Drosophila metamorphosis. Dev Dyn 236:3173-9
Yin, Viravuth P; Thummel, Carl S; Bashirullah, Arash (2007) Down-regulation of inhibitor of apoptosis levels provides competence for steroid-triggered cell death. J Cell Biol 178:85-92
Thummel, Carl S (2007) To die or not to die--a role for Fork head. J Cell Biol 176:737-9
Lee, Cheng-Yu; Andersen, Ryan O; Cabernard, Clemens et al. (2006) Drosophila Aurora-A kinase inhibits neuroblast self-renewal by regulating aPKC/Numb cortical polarity and spindle orientation. Genes Dev 20:3464-74