Keywords: e. primordial germ cells; b. germline stem cell
Transposable elements (TEs) are mobile genetic elements whose proliferation in the germline induce germ cell loss and sterility. Hosts reduce this fitness cost through resistance, which involves suppression of TE proliferation, or tolerance, where the germline withstands the damaging effects of transposition. While host resistance to TEs by piRNAs is studied extensively, little is known about host factors that confer tolerance. Our lab identified bruno as a source of natural variation in tolerance to P-element DNA transposon induced germ cell loss in Drosophila melanogaster. Bruno is an RNA binding protein and a translation repressor that plays important roles in the regulation of oocyte development in adults. However, the role of bruno in determining tolerance to transposition is unknown.
Recent studies have shown that P-element induced dysgenesis triggers loss of germ cells in the larval stage. While bruno previously had no known function in larvae, we have discovered that Bruno protein is expressed in larval primordial germ cells (PGCs) and that Bruno function impacts P-element induced germ cell loss specifically in the larval stage. We are currently testing two hypotheses to explain the relationship between Bruno function and PGC loss: 1) hybrid dysgenesis increases bruno expression in PGCs, resulting in activation of bruno-dependent differentiation pathways and 2) bruno increases transposition of P-element, leading to increased DNA damage and loss of PGCs.