Award Date


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Biological Science

First Committee Member

Deborah K. Hoshizaki

Number of Pages



A universal problem in the development of complex organisms is programming totipotent cells into specialized cell types. I have focused on the Drosophila fat body and the characterization of the positional information required for the adoption of a fat cell identity by mesodermal cells. Central to this study is serpent, a transcription factor gene, both necessary and sufficient for fat-cell development; I characterized the patterns of activity for regulatory regions that control serpent expression within the fat body. The fat body is composed of three morphological domains (lateral fat body, ventral commissure, and dorsal fat cell projections) each of which requires serpent activity. Using these enhancer-regions in reporter-gene constructs, I traced the development of the dorsal fat-cell projections, the ventralmost lateral fat body, and a portion of the ventral commissure, and demonstrated that particular groups of fat-cell clusters give rise to these domains; In parallel, I determined, through mutant and misexpression genetic analysis, that the transcription factor genes, Abdominal B and tinman, are critical for serpent activation within the dorsal fat-cell cluster. Putative binding sites for these factors are present within the regulatory regions of serpent. Differing cues activate serpent in distinct embryonic regions, and I discuss the possibility that these factors are also important for the establishment of genetic differences among fat cells, and thus, functional differentiation of the fat body. Additionally, I genetically tested Ultrabithorax , another transcription factor gene with putative binding sites within one serpent-enhancer region, for its ability to regulate serpent expression. I determined that Ultabithorax is not involved in fat-cell specification, but is required for the proper morphological development of the fat body; I have also tested the proposal that within the lateral mesoderm, serpent is a cell-type switch between fat and somatic gonadal precursor cells. I find that serpent does not serve as a switch between these two cell choices. However, I provide evidence for a similar cell-fate switch, in the dorsal mesoderm, between dorsal fat cells and circular visceral muscle precursors. This switch relies on both serpent and the homeotic transcription factor, Abdominal B.


Analysis; Cell; Cell-fate Switch; Drosophila; Expression; Fat; Fat Cells; Fate; Gene; Melanogaster; Role; Serpent; Specific; Switch

Controlled Subject


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4034.56 KB

Degree Grantor

University of Nevada, Las Vegas




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