Changed for Good: The Surprising Molecular Changes in Eggs, Sperm, and Females that Mediate Fertility
Mariana Wolfner, Ph.D.
Distinguished Professor of Molecular Biology and Genetics, Stephen H. Weiss Presidential Fellow
Cornell University
Mariana Federica Wolfner is the Distinguished Professor of Molecular Biology and Genetics, and a Stephen H. Weiss Presidential Fellow. Her research focuses on understanding, at the molecular/gene level, the important reproductive processes that occur around the time when a sperm fertilizes an egg. Using the Drosophila model, the Wolfner laboratory studies the molecular signals that "activate" an oocyte to begin embryo development and also studies how seminal proteins modulate the reproductive physiology and behavior of female insects. Mariana’s primary teaching areas are in Development & Evolution, and in Advanced Genetics. Mariana has a B.A. in Biology and Chemistry from Cornell, a Ph.D. in Biochemistry from Stanford, and she did postdoctoral work at UC San Diego. Mariana has been honored to receive awards and recognition for her research from the Genetics Society of America, the Entomological Society of America, the International Congress of Entomology Council, and awards from Cornell for her teaching and advising. Mariana is a Fellow of the American Association for the Advancement of Science, and a member of the National Academy of Sciences and of the American Academy of Arts and Sciences. She serves on several Editorial and Biology-organizations’ Boards, and on various grants panels.
Summary
We are taught that eggs and sperm combine to initiate the development of a new organism. While this statement is certainly true, it is less well known that changes that occur to gametes after they leave the gonads, and to female physiology after sexual maturity, are critical for fertility and the generation of high-quality offspring. Understanding these changes at the molecular level is important for identifying mechanisms of certain infertilities and optimizing conditions for assisted reproductive technologies.
This talk will present the post-gametogenesis changes to eggs and sperm that are required for efficient fertilization and initiation of embryonic development, and the physiological changes in mated females that promote optimal fertility and offspring quality. We will first discuss how a mature oocyte is “activated” to become capable of embryonic development if fertilized. The oocyte already contains all the proteins needed to initiate development, but these proteins are not yet in a state that would support embryogenesis. We will see that a rise in intracellular calcium in the oocyte triggers activation by modifying the phosphorylation states of the stored proteins, allowing them to drive the transition from differentiated oocyte to totipotent zygote. We will then turn to discussing sperm, exploring how they are modified once within the female, fostering their ability to survive and/or fertilize eggs. Proteomic and genetic data show that both seminal and female proteins associate with sperm within the female’s reproductive tract, improving sperms’ function, storage, and (possibly) longevity. Finally, we will explore how seminal proteins change the physiology of the female in ways that facilitate production of offspring of the highest quality.
Learning Objectives:
- Understand how eggs activate in order to initiate embryogenesis. Explore the high conservation of this process, as well as some species-specific aspects.
- Appreciate the modifications to sperm within the female and how such modifications can optimize fertility.
- Recognize that the mature female undergoes further “maturation”, triggered by molecules in seminal plasma, to support fertility.
- Consider the implications of these findings to human reproductive medicine, including for understanding the etiology of some infertilities and improving assisted reproductive technologies and contraceptives.
This page was last updated on Wednesday, August 26, 2026