University of Nevada – Las Vegas
Bond, Nichole Dinell.
The Role of ecdysone signaling in fat-body tissue remodeling and pupal metabolism.
Degree: PhD, Biological Science, 2010, University of Nevada – Las Vegas
Holometabolous insects undergo an astonishing transition during their development. During metamorphosis, the larva dramatically changes form and becomes an adult fly. During this process obsolete larval tissues must be eliminated, while tissues required for further development are retained and often remodeled to meet the needs of the adult fly. Tissue remodeling is characterized by morphological changes of the cells in a tissue mass. In many cases, remodeling is characterized by dissociation of the tissue mass, releasing cells to move freely around the body cavity. This process is also common in wound healing and is a key feature of human disease processes such as metastasis and airway destruction in asthmatics. The detachment of remodeled cells requires proteases that can break down the extracellular matrix, which is responsible for the integrity of the tissue.
The larval fat body of Drosophila is an indispensable tissue required to fuel animal development, thus this tissue is retained and remodeled during the transition from a larva to an adult. In this dissertation I identify the functions of two important proteins in the signaling cascade responsible for the remodeling of the fat body, and I propose a model for the role of this cascade in the fat body for animal survival during metamorphosis. I performed a detailed characterization of fat-body tissue remodeling and identified three distinct stages associated with remodeling (Nelliot et al., 2006). Using several genetic techniques, I show that the hemocytes (Drosophila blood cells) are not required for fat body remodeling and that the process of fat body remodeling is tissue autonomous. I then outline a role for the 20-hydroxyecdysone (20E) signaling cascade in fat body tissue remodeling. Through expression of dominant negative forms of the 20E receptor (EcR) and mosaic analysis I have determined that signaling through the EcR and expression of the competence factor βftz-f1 are both required for fat body remodeling. I have also identified the 20E signaling target gene Matrix Metalloproteinase 2 (MMP2) as the protease required for remodeling of fat cells during metamorphosis. In addition the role of MMP2 in fat body remodeling, I show that proper expression of MMP2 is required for animal survival. Also, through mutant analysis, I show that the other Drosophila Matrix Metalloproteinase, MMP1, is not involved in fat body remodeling. However, I do demonstrate a fat body specific role for MMP1 in the process of head eversion.
Overall, these results uncover another potential role for MMP2 in the fat body during metamorphosis. My experiments show that proper regulation of MMP2 expression in the fat body is required for animal survival. In an attempt to explain the importance of MMP2 in the fat body, I propose a model where 20E signaling in the fat body modulates insulin signaling via its induction of MMP2 expression. Matrix metalloproteinases are known to cleave Insulin-like Growth Factor Binding Proteins (IGF-BPs) and thus have a regulatory…
Advisors/Committee Members: Allen Gibbs, Chair, Deborah Hoshizaki, Andrew Andres, Jeffrey Shen, Craig Woodard.
Subjects/Keywords: Genetics; Molecular Genetics
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APA (6th Edition):
Bond, N. D. (2010). The Role of ecdysone signaling in fat-body tissue remodeling and pupal metabolism. (Doctoral Dissertation). University of Nevada – Las Vegas. Retrieved from https://digitalscholarship.unlv.edu/thesesdissertations/250
Chicago Manual of Style (16th Edition):
Bond, Nichole Dinell. “The Role of ecdysone signaling in fat-body tissue remodeling and pupal metabolism.” 2010. Doctoral Dissertation, University of Nevada – Las Vegas. Accessed August 14, 2020.
MLA Handbook (7th Edition):
Bond, Nichole Dinell. “The Role of ecdysone signaling in fat-body tissue remodeling and pupal metabolism.” 2010. Web. 14 Aug 2020.
Bond ND. The Role of ecdysone signaling in fat-body tissue remodeling and pupal metabolism. [Internet] [Doctoral dissertation]. University of Nevada – Las Vegas; 2010. [cited 2020 Aug 14].
Available from: https://digitalscholarship.unlv.edu/thesesdissertations/250.
Council of Science Editors:
Bond ND. The Role of ecdysone signaling in fat-body tissue remodeling and pupal metabolism. [Doctoral Dissertation]. University of Nevada – Las Vegas; 2010. Available from: https://digitalscholarship.unlv.edu/thesesdissertations/250