Stonewall and Brickwall: Two Partially Redundant Determinants Required for the Maintenance of Female Germline in

Proper specification of germline stem cells (GSCs) in ovaries depends on niche derived non-autonomous signaling and cell autonomous components of transcriptional machinery. Stonewall (Stwl), a MADF-BESS family protein, is one of the cell intrinsic transcriptional regulators involved in the establishment and/or maintenance of GSC fate in ovaries. Here we report identification and functional characterization of another member of the same protein family, CG3838/ Brickwall (Brwl) with analogous functions. Loss of function alleles of exhibit age dependent progressive degeneration of the developing ovarioles and loss of GSCs. Supporting the conclusion that the structural deterioration of mutant egg chambers is a result of apoptotic cell death, activated caspase levels are considerably elevated in ovaries. Moreover, as in the case of mutants, on several instances, loss of activity results in fusion of egg chambers and misspecification of the oocyte. Importantly, phenotypes can be partially rescued by germline specific over-expression of arguing for overlapping yet distinct functional capabilities of the two proteins. Taken together with our phylogenetic analysis, these data suggest that and likely share a common MADF-BESS ancestor and they are expressed in overlapping spatiotemporal domains to ensure robust development of the female germline.