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Regulation of gurken expression during Drosophila melanogaster oogenesis

Faculty Mentor: Amanda Norvell

Student: Letitia Thompson

During Drosophila oogenesis, the TGF-alpha protein Gurken (Grk) is responsible for pattering the dorsal-ventral (D-V) axis of the egg and future embryo.  Consequently, Grk distribution within the ovary is tightly controlled and the spatial and temporal regulation of Grk protein activity is, in part, achieved through post-transcriptional mechanisms. The goal of this project is to determine whether any aspects of Grk regulation are mediated through alterations in the polyadenylation of grk mRNA. Polyadenylation is the process of adding a poly(A) tail to the 3’ untranslated region (UTR) of the mRNA. Hex sites (AAUAAA) are required in order for polyadenylation to occur.  We have found that grk mRNA is polyadenylated throughout oogenesis, and moreover that there are two major polyadenylated grk transcripts that differ by approximately 15 nucleotides in size.   The grk 3’UTR does contain two Hex sites suggesting that alternative polyadenylation may occur. We have isolated and sequenced the two grk RNA transcripts in the ovary and found that these are indeed the result of alternative use of the two HEX sites.  In future work we will investigate the functional consequences of the alternative polyadenylation and attempt to identify proteins that could play a role in this alternative processing event. We are in the process of making transgenes that delete the individual HEX sites and these flies will be analyzed for oogenesis defects.  Finally, others have demonstrated that the Drosophila Sex-Lethal (Sxl) protein functions in the alternative polyadenylation of at least one transcript during oogenesis, so we will examine grk polyadenylation in these mutants.