Stage-specific differences in the requirements for germline stem cell maintenance in the Drosophila ovary

In this study, we uncover a role for microRNAs (miRNAs) in Drosophila germline stem cell (GSC) maintenance. Disruption of Dicer-1 function in GSCs during adult life results in GSC loss. Surprisingly, however, loss of Dicer-1 during development does not result in a GSC maintenance defect, although a defect is seen if both Dicer-1 and Dicer-2 function are disrupted. Loss of the bantam miRNA mimics the Dicer-1 maintenance defect when induced in adult GSCs, suggesting that bantam plays a key role in GSC self-renewal. Mad, a component of the TGF-beta pathway, behaves similarly to Dicer-1: adult GSC maintenance requires Mad if it is lost during adult life, but not if it is lost during pupal development. Overall, these results show stage-specific differential sensitivity of GSC maintenance to certain perturbations and suggest that there may be a Dicer-2-dependent GSC maintenance mechanism during development that is lost in later life.