The Drosophila ovary is an important model system for studying oogenesis and has provided insight into broader, biological topics such as stem cell niche, differentiation, migration, morphogenesis, signaling, cell-size regulation, and tumorigenesis. The purpose of this dissertation was to build a comprehensive single-cell transcriptomic atlas of cells regulating oogenesis and ovulation and to use the ovarian follicle cells, as a model system to interrogate the role of ectopic Notch expression in development and during tumorigenesis. Single-cell RNA sequencing analysis revealed transcriptional signatures for each of the 28 expected ovarian cell types and developmental stages. Each stage of oogenesis was then separately analyzed with a special focus on the most diverse cell type, the follicle cells. This identified key cell-type specific expression patterns governing processes like differentiation, mitotic-to-endocycle switch, migration, morphogenesis, phagocytic removal of nurse cells, eggshell formation, and a newly identified shift of the pre-corpus lutuem cell expression from oogenesis-to-ovulation. Additional characterization of the interconnected tissues in the dataset identified novel cellular heterogeneity of the oviduct and a population of hemocytes associating closely with it. We further describe how this association occurs in a non-mating-dependent manner as early as the pupal stage (during oviduct development). Additional characterization of the hemocyte cluster reveals expression of many phagocytic genes including the newly identified enzymatic marker, Cp1. Additional validation of cell-type markers classifies these macrophage-like cells as plasmatocytes, one of the most common types of hemocytes in flies. Armed with a rich dataset describing proper signaling during development we turn to the follicle cells and switch focus to study dysregulated signaling of the Notch pathway and its involvement in tumor formation. First, we expressed ectopic Notch (NICD) in follicle cells and discovered an uneven pattern of nuclear NICD retention in a cell-cycle dependent manner. We find that the cell-cycle regulator, string (cdc25), can strongly impact the localization of NICD regardless of the cell-cycle status of the cell. We also identify that Vps proteins involved in forming the ESCRT complex can similarly regulate the nuclear NICD pattern. Next, we examined the role of ectopic Notch signaling in tumorigenesis and found that while not sufficient for tumor formation, Notch functions as a tumor promoter and leads to a more dysplastic tumor phenotype. Tumor cells with ectopic NICD gain a survival advantage which may be due to a bypass of the DNA damage sensing checkpoint. RNA sequencing revealed unique expression of these tumor cells with ectopic NICD in both pre- and post-tumor conditions. Specifically, we identified DNA stability related genes, RecQ4 and Xpd, which are upregulated in NICD-overexpressing pre-tumor cells. / A Dissertation submitted to the Department of Biological Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / 2019 / November 8, 2019. / Drosophila, hemocyte, Notch, oogenesis, ovulation, tumor / Includes bibliographical references. / Wu-Min Deng, Professor Co-Directing Dissertation; Kathryn Jones, Professor Co-Directing Dissertation; Timothy Megraw, University Representative; Kimberly Hughes, Committee Member; Steven Lenhert, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_752432 |
| Contributors | Jevitt, Allison M. (author), Deng, Wu-Min (professor co-directing dissertation), Jones, Kathryn M. (professor co-directing dissertation), Megraw, Timothy L. (university representative), Hughes, Kimberly A., 1960- (committee member), Lenhert, Steven John (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Biological Science (degree granting departmentdgg) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text, doctoral thesis |
| Format | 1 online resource (111 pages), computer, application/pdf |
Page generated in 0.0017 seconds