Document Type

Honors Capstone Project

Date of Submission

Spring 5-1-2013

Capstone Advisor

Dr. Melissa E. Pepling

Honors Reader

Dr. Eleanor M. Maine

Capstone Major

Biology

Capstone College

Arts and Science

Audio/Visual Component

no

Capstone Prize Winner

no

Won Capstone Funding

yes

Honors Categories

Sciences and Engineering

Subject Categories

Biology

Abstract

The total number of oocytes that an individual will have available for reproduction is defined at birth. This established oocyte pool is essential to fertility, as a female loses oocytes throughout her life and never makes more. In the mouse, germ cells form in the fetus and migrate to the gonad, where they undergo mitosis and are referred to as oogonia. These cells are in germ line cysts, which are clusters of germ cells connected by intercellular bridges that form by incomplete cytokinesis. Germ cells in the human also develop in clusters with characteristics of cysts. The cells within the cysts soon begin to enter meiosis, and are now referred to as oocytes. Around post natal day (PND) 2, the cysts undergo a process called cyst breakdown, in which the oocytes break apart and become surrounded individually by granulosa cells. The mechanism of cyst breakdown is currently under investigation, as cysts that fail to properly break down often result in multiple oocyte follicles, which develop abnormally. The regulation of cell adhesion molecules (CAMs) likely plays a role in the process of cyst breakdown, and a hamster model has found two specific CAMs expressed in the ovary during egg cell development, E-Cadherin and N-Cadherin. The presence and location of these CAMs, as well as their role in cyst breakdown and follicle formation in the mouse, is being investigated in this study.

Three different experimental techniques were used in order to determine the role of E-Cadherin and N-Cadherin in cyst breakdown and follicle development in the mouse. First, immunicytochemistry was used in order to visualize the proteins in the mouse ovary. Then, organ culture experiments were performed in order to block these proteins during PND1-5 to determine their function. Finally, western blots were performed in order to determine protein expression levels of E-Cadherin and N-Cadherin during development.

From these experiments, it can be concluded that both E-Cadherin and N-Cadherin are expressed during development from 17.5 days post coitum (dpc) to PND5. E-Cadherin expression is higher in the cytoplasm of oocytes than in the granulosa cells. Starting at PND2, E-Cadherin is also expressed in the cell membrane of the oocytes, and is localized to certain spots within the membrane. The location of N-Cadherin expression within the ovary was unable to be determined from the immunocytochemistry experiments. Overall, N-Cadherin expression is higher in the neonatal ovary than E-Cadherin expression. Also, E-Cadherin expression increases from PND1 to PND3 and N-Cadherin expression increases from 17.5dpc to PND5.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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