The steroid hormone ecdysone controls Drosophila ovarian germline stem cell (GSC) maintenance and germ cell differentiation. Prior studies demonstrated that ecdysone regulates germ cell differentiation non-autonomously via the nuclear receptor Ecdysone Receptor (EcR) in ovarian somatic cells. Although EcR is also expressed in germ cells, potential direct roles for EcR in the germline independent of the soma have not been examined. Here, we demonstrate that EcR functions autonomously in GSCs and cystoblasts to control germline differentiation. While depletion of EcR from GSCs mildly reduces their maintenance, over-expression of EcR specifically in GSCs and cystoblasts impedes germ cell differentiation, phenotypically resembling bag of marbles loss-of-function and Bone Morphogenetic Protein signaling constitutive activation. We propose that EcR functions as a transcriptional repressor in GSCs and cystoblasts to suppress differentiation, but becomes derepressed as ecdysone titer increases and co-repressor expression decreases in dividing germ cell cysts, providing temporal control over germline differentiation. These data support the model that germ cells integrate signals from multiple cell sources that spatially and temporally control their differentiation in response to local and physiological cues.
Jung et al. (Thu,) studied this question.