Grant: Travel Awards - Institute Community Support

In preparation for fertilization and embryo development, the female egg grows within the ovarian follicle. During growth, the follicle-enclosed egg is surrounded by companion cells, which act as nursing cells, providing the egg with nutrients and ensuring its proper growth and development. The continuous presence and support of the surrounding cells is crucial for the production of a mature egg, capable of undergoing fertilization and developing into a healthy embryo. The egg however, is physically separated from its surrounding nursing cells by a protein coat termed the zona. The surrounding cells bypass the physical barrier imposed by the zona by means of narrow feet-like extensions, termed transzonal projections (TZPs), that traverse the zona and contact the egg. These projections constitute bridges linking the cells to the egg, allowing the transfer of essential nutrients to the egg, and enabling the two compartments of the ovarian follicle to communicate. TZPs have been identified in all mammalian species studied to date, including mouse and human. As the only means of communication with the follicle-enclosed egg, the TZPs play a fundamental and indispensable role in egg development. Since the growth of the egg affects the health of the embryo developed after fertilization, TZPs also have a crucial role in fertility. My current research aims at determining the mechanism and timing of the formation and extension of these TZPs. I aim to identify what proteins are necessary to maintain these structures and direct them from the companion cells towards the growing egg. My results thus far show that new TZPs are made as the egg grows within the follicle, and suggest that the egg itself might instruct the companion cells to extend the TZPs towards it. Understanding the mechanism governing the formation of these structures would shed the light on an important parameter to monitor in future work aimed at growing eggs in vitro to preserve human and animal fertility.