Updated: August 2018
Eggs are remarkable cells that not only provide the maternal genetic contribution to a new organism but also supply the embryo with the raw materials it needs for development and survival. Oogenesis (egg development) occurs within the female ovary and requires close association and communication among all ovarian cells including the developing eggs. In addition to their direct role in egg development, the ovarian cells also mediate the hormonal signals that regulate egg growth and ovulation. How do the ovarian cells maintain contact/communication with the egg? How are the hormonal signals transduced from the ovarian cells to the egg? How do the ovarian cells "let go" of the egg at ovulation? How does the environment affect these processes? I am interested in exploring these questions and I am particularly interested in applying molecular biological techniques to investigate these cellular interactions during egg development.
Through our research, my students and I have focused on two systems to address ovarian cell interactions. First, we use zebrafish (Danio rerio) as a model system to study egg development. Although the hormonal signals involved in fish egg development and ovulation are known, the molecular mechanism(s) mediating these signals within the ovary, and the effects of environmental influences, are poorly understood. Two main areas my students and I have pursued are cell signaling and apoptosis (cell death). We are particularly interested in a family of cell-cell adhesion molecules called the cadherins and their role in vertebrate egg development. These proteins "stick" cells to one another and, together with a set of associated proteins called the catenins, may serve to relay signals into the egg. We have found that one of the catenins (beta-catenin) changes its location in the ovarian cells as the egg develops and is ovulated. This makes beta-catenin an exciting candidate for the hormonal signal pathway in ovarian cells and the egg. We have begun to test the hypothesis that beta-catenin serves to mediate intercellular contact and communication within the ovary and, upon hormonal stimulation, activates gene expression in ovarian cells during egg development and ovulation. We have also used the zebrafish model to investigate other cell signaling pathways during hormone-induced egg development, particularly the culling of non-viable eggs through apoptosis. We have focused on how the environmental contaminants BPA, BPS, and BPF affect expression of genes involved in apoptosis. We are investigating how these chemicals affect mRNA and protein expression in the zebrafish ovary.
The second system we study is livebearing fishes (Family Poeciliidae). These organisms offer the opportunity to study ovarian cell/"egg" interactions "post-ovulation." In all livebearing poeciliids, embryonic development takes place within the ovary. Although the embryos are nourished by egg yolk, some species exhibit maternal transfer of nutrients to the offspring. We are characterizing the cellular interactions within the ovary of livebearing fish at the molecular level and compare these interactions in species that provision the embryos during development with those species that rely on yolk as a nutrition source. These projects are of particular interest given that environmental conditions may play a role in nutrient transfer within these species.