Date of Award

5-2022

Degree Type

Thesis

Degree Name

Honors Thesis

Department

Biology

First Advisor

Lindsay Lewellyn

Abstract

The relationship between the size of a cell and the size of its intracellular structures must be precisely regulated for proper development and functioning of the mature organism; however, the mechanisms that establish and maintain this relationship are not known. Much of the work on organelle size scaling has focused on individual cells or organelles, with some looking at how size scaling is maintained during development. However, it is not known whether the size of multiple organelles is coordinately regulated, and how cell size and organelle size are regulated within a syncytium or group of connected cells. Because many cell types exist within a syncytium, understanding size scaling in this context is important. We have used the developing fruit fly egg chamber as a model system to study the size relationship between multiple structures within the germline syncytium throughout oogenesis. The developing egg chamber contains a cluster of 16 germ cells connected by intercellular bridges, or ring canals. It has been observed that the size of the germline ring canals exhibits spatial variation with the smallest ring canals at the anterior of the egg chamber and the largest ring canals at the posterior near the oocyte. Recent work has also confirmed that nurse cells and their nuclei show a similar size distribution within the germline. Therefore, it is interesting to consider whether the size of these structures may be coordinately regulated, and whether altering the size of one structure (either throughout the germline or clonally) would impact the size of the other structure. We have used a combination of RNAi (Pendulin, Dacapo, or Ctf4), overexpression (Pendulin) and mosaic analysis (myc and arpC1) to try to alter either nuclear size or ring canal size in some or all cells within the germline. We used Fiji to measure the diameter of the ring canals, the size of the nurse cell nuclei (which has been used as a proxy for cell size), and the overall dimensions of the egg chamber. Preliminary data suggest that altering nuclear size within the entire germline does impact ring canal size, and that in mosaic tissue, there is typically a correlation between cell size, nuclear size, and ring canal size. In the future, we hope to further explore whether the size of these structures is coordinately regulated, and if so, to identify the underlying mechanisms that are involved.

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