Date of Award

Spring 2020

Document Type

Open Access Thesis

First Advisor

Alissa Armstrong

Abstract

Adult Drosophila Melanogaster is a powerful model organism in genetic studies and has high tissue and gene homology to humans. Like humans, Drosophila tissues communicate in order to respond to physiological stimuli, such as diet, aging, and disease. The fat body, homologous to human adipocytes and hepatocytes, functions as both an endocrine and energy storage organ; and has been shown to play a critical role in many metabolic processes. The aim of this study is to characterize differences in fat body gene expression to ultimately identify if there are subpopulations of adipocytes with different functions related to fat body communication to other tissues. To do so, nine fly lines with a genetic insertion of Gal4, which encodes a transcription factor, under the influence of a tissue specific promoter, were mated with a fly line that encodes membrane bound green fluorescent protein under the control of UAS, the DNA sequence recognized by Gal4. Progeny containing both genetic elements will have cells that fluoresce green, GFP, at the cell membrane in tissues or cells where the promoter is active. This study reports that five of the nine Gal4 lines tested, with promoter sequences reported to be actively expressed in larval adipocytes, drive UAS-GFP expression in adult adipocytes, with distinct levels of gene expression. Three of the five lines were more carefully examined to uncover a link between level of gene expression and adipocyte size. These three lines, c754-Gal4, ppl-Gal4, and Lsp2(3.1)-Gal4, drove robust GFP expression in adult adipocytes. Lsp2(3.1)-Gal4 showed the strongest GFP expression, while expression levels for c754-Gal4 and ppl-Gal4 were comparable to each other. When correlating GFP intensity with adipocyte perimeter, a correlation was found with gene expression and adipocyte size for two of the three lines. In order to identify the causality between cell size on gene expression the data was further analyzed using a linear regression model. This information indicated that specific promoters and their corresponding genes are differentially expressed based on cell size. Altogether, I have identified at least one transgenic line, c754-Gal4, that was not previously known to promote gene expression in adult adipocytes and ruled out transgenic lines, Lsp2-Gal4.H, c591-Gal4, l(2)T 76T76 -Gal4, c855a-Gal4, C833-Gal4 that do not drive gene expression in the fat body of adult female flies. In the future, a full-body analysis in addition to an examination of other organelle characteristics will lead to a more comprehensive understanding of adipocyte functionality with respect to inter-tissue communication.

Rights

© 2020, Michael Edward Meyerink

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