Semester of Graduation
Spring 2026
Degree Type
Thesis
Degree Name
Masters in Integrative Biology
Department
Department of Molecular and Cellular Biology
Committee Chair/First Advisor
Dr. Joanna Wardwell-Ozgo
Second Advisor
Dr. Martin L. Hudon
Third Advisor
Dr. Dongyu Jia
Abstract
Hormonal signaling is vital during metazoan development. In Drosophila melanogaster, the steroid hormone ecdysone (20E) coordinates development by activating the nuclear hormone receptor ecdysone receptor (EcR). EcR binds DNA and recruits coregulators to repress or activate gene expression. Existing tools lack the precision to determine how specific coregulators influence EcR’s transcriptional function at individual promoters or developmental stages. Thus, we created the transgene UAS-EcRLBD, enabling tissue- and time-specific expression of EcR's ligand-binding domain (LBD). EcRLBD functions as a molecular sponge, competing for cofactor binding, including 20E, without disrupting endogenous EcR/DNA binding. EcRLBD interferes with EcR-driven regulation of promoters, tissues, and developmental processes and serves as a platform to study the regulatory roles of individual coregulators in EcR-driven biology. As a proof-of-concept, we introduced the A483T mutation into our LBD tool, UAS-EcRLBD-A483T, disrupting its interaction with the corepressor Smrter. In salivary glands, EcRLBD expression blocks secretion and expectoration of glue protein without affecting production, whereas EcRLBD-A483T does not. EcRLBD also causes lumen diameter reduction in the salivary glands. Surprisingly, EcRLBD does not alter EcR transcriptional activity, suggesting these phenotypes are independent of coregulators bound to the LBD. Lumen reduction is partially rescued by expressing EcRLBD-A483T, indicating EcR Smrter-mediated repression is important for proper salivary gland function. Overall, this data highlights that 20E and Smrter are essential for maintaining tissue structure and lumen integrity, though regulation of EcR transcriptional activity in salivary glands may occur independently of the LBD.
Comments
This project is supported by Kennesaw State University Office of Research, Start-up funds from Kennesaw State University College of Science and Mathematics, and the National Institutes of Health (1R16GM158693-01). I would like to thank the National Institutes of Health Peach State Bridges to the Doctorate training program for funding my stipend and for professional development (5T32GM150548-03).