Tudor5-like promotes post-transcriptional regulation of maternal RNAs
Authors: Caitlin Pozmanter; Sydney Kelly; Harrison Curnutte; Mark Van Doren
Affiliation: Johns Hopkins University
Keywords: j. RNA binding proteins; x. translational regulation
Tudor-domain containing proteins are conserved across the animal kingdom for their necessary functions in germline development including post-transcriptional gene regulation. Recent work in our lab identified Tudor5-like (Tdrd5l), which promotes male germline identity in germline stem cells (GSCs) in the testis, but is repressed by the RNA binding protein Sex lethal (SXL) in female GSCs. Interesting, Tdrd5l is also expressed in the differentiating germline in both sexes, indicating that it may also act to control germline differentiation in both sexes.
Previously we reported that Tdrd5l localizes to an RNA granule. To understand what RNA regulatory pathway Tdrd5l functions in, we conducted RNAi against the deadenylase twin in mutant gonads, which revealed a genetic interaction between Tdrd5l and the CCR4-NOT deadenylation complex. Recent investigation into the role Tdrd5l plays in the female germline showed a decreased hatch rate and dorsal appendage defects in eggs laid by Tdrd5l mutants. Since Grk regulates dorsal appendage development we stained for Gurken(Grk) in Tdrd5l mutant ovaries and wild type ovaries. In wild type flies we see normal Grk translation in the anterior dorsal corner of the oocyte, while in tdrd5l mutant ovaries we see translation of Grk in the nurse cells. A similar nurse cell expression phenotype is observed when immunostaining for Orb in Tdrd5l mutants which is a known activator of Grk translation. This suggests the loss of maternal RNA regulation by Tdrd5l could result in patterning defects.Additionally, both osk mRNA and protein are mislocalized in Tdrd5l mutant oocytes where we observed them localized to the center of the oocyte instead of the posterior. One possibility is Grk fails to specify the posterior before migrating to the dorsal anterior corner. To investigate if this was due to failure to specify the posterior pole we used kin-lacZ and found in Tdrd5l mutants, kinesin does not strictly localize to the posterior pole of the oocyte in stage 9 or later egg chambers. Together our results indicate that Tdrd5l functions in regulating maternal RNA repression. To determine the mechanism by which this occurs we are currently conducting proximal biotinylation to identify other proteins in the Tdrd5l granule.