View Program - 63rd Annual Drosophila Research Conference

Limiting BMP signaling range in the stem cell niche of the ovary protects against germ cell tumors and supports germline homeostasis. In both the embryo and wing disc, the Brinker (Brk) transcription factor serves as the canonical repressor of Dpp, the main Drosophila BMP ligand, and its downstream targets. In the germline stem cell niche within the germarium of the ovary, Dpp provides a pivotal cue for maintaining stem cell identity. Despite this well-established role, Brk’s function in the germarium has not previously been described. Here we find that brk expression throughout the ovary requires a promoter-proximal element (PPE), a DNA region upstream of and distinct from the gene promoter. In the germarium, the PPE acts as an enhancer to regulate brk expression levels to support germline stem cell homeostasis and, surprisingly, to positively regulate Brk’s canonical antagonist, dpp. This PPE has been previously described in the embryo where it does not itself drive expression, but is required for the sequential action of two distal enhancers to support continuous brk expression. In the egg chambers of the ovariole, at least two enhancers perform a similar temporal handoff and their activities require the PPE, indicating that this element may serve a general function of managing gene regulation by multiple enhancers over time by coordinating shifts in local chromatin conformation.

brinker gene promoter-proximal element drives ovary expression and supports sequential action of distal enhancers