Rna Regulation During Gametogenesis And Triggers Of Egg Activation In Drosophila Melanogaster
One of the most critical transitory periods during development occurs when an oocyte prepares to undergo embryogenesis, in a process called "egg activation". In many organisms, the oocyte has been at rest in the ovary, stored in a dormant state for a period ranging from a number of days (as in flies) to several decades (as in humans). Upon egg activation, this dormant egg must suddenly undergo several major cellular and molecular changes that prepare it for embryogenesis, including restructuring of the vitelline membrane, completion of meiosis, and changes to mRNA and protein pools. Where most organisms require a fertilizing sperm to set off these events, fruitflies are unique in that egg activation occurs prior to requirement of fertilization. I have used Drosophila melanogaster as a model system to dissect apart some key events of egg activation that are driven solely by the maternal components of the oocyte. In most animals, the initial trigger from the sperm sparks a calcium wave that traverses through the oocyte, acting as a message to kick off previously silenced biochemical pathways. For many years, it was unknown whether calcium played a role in egg activation in Drosophila. I have discovered that although Drosophila oocytes do not require a fertilizing sperm, a calcium wave does occur during egg activation. I have characterized the dynamics of this calcium influx using live imaging of Drosophila oocytes undergoing in vitro egg activation. Furthermore, I found that the calcium flux is not dependent upon internal stores but depends on extracellular calcium concentrations. Additionally, I have determined that the extracellular calcium likely enters the oocyte through mechanosensory TRP channels. Downstream of the calcium signal, there is major turnover of the maternallystored mRNAs within the oocyte. I have examined the phenotype and transcriptome changes in eggs from mothers carrying the prage mutation, an allele previously uncharacterized in egg activation. I have also performed microarray analysis of the global set of transcripts that undergo cytoplasmic polyadenylation by WISPY at egg activation. These data taken together give us a big-picture view of the global changes occurring in the mRNA pool during egg activation.
Drosophila; egg activation; spermatogenesis
Wolfner, Mariana Federica
Goldberg, Michael Lewis; Liu, Jun
Ph. D., Genetics
Doctor of Philosophy
dissertation or thesis