View Program - 63rd Annual Drosophila Research Conference

Sexually reproducing species exhibit a wide variety of mechanisms to establish male and female identity at the cellular level. In D. melanogaster, sex lethal (sxl) is the master switch of sex determination in somatic cells; however, the process of sex determination in the germline remains poorly understood. Previous studies show that ovarian tumor (otu) acts genetically upstream of and promotes the expression of Sxl in the female germline, which ultimately leads to a female fate. How Otu protein controls Sxl expression is less clear. Through IP-mass spec analysis we find that Otu physically interacts with Bourbon (Bbn), a previously uncharacterized protein. bbn displays enriched expression in germ cells, and bbn null mutant females exhibit agametic ovarioles and cystic germline tumors. These germline tumors do not express Sxl protein and resemble sxl sterile mutants, displaying expanded and overlapping expression of Bam and Nanos. Transgenic expression of sxl can partially rescue this phenotype. We tagged bbn endogenously with an HA tag and found it is expressed in germline stem cells, cystoblasts and two cell cysts, similar to the expression pattern of cytoplasmic Sxl protein. In addition, Bbn is enriched in developing oocytes. Because the phenotypes and localization pattern of bbn are strikingly similar to those of otu and they physically interact, we are testing how Bbn impacts the ability of Otu to promote Sxl expression. We hypothesize that Otu, the founding member of a family of deubiquitinases, deubiquitinates Sxl to prevent its degradation by the proteasome. Future experiments will help us determine if Bbn regulates Otu expression levels, localization, substrate specificity or catalytic activity.

bourbon interacts with known germline sex determination regulator otu and promotes the expression of sxl in the Drosophila female germline