regulates niche ageing independently of the pathway in the ovary.

Proper stem cell activity in tissues ensures the correct balance between proliferation and differentiation, thus allowing tissue homeostasis and repair. The ovary develops well-defined niches that contain on average 2-4 germline stem cells (GSCs), whose maintenance depends on systemic signals and local factors. A known player in the decline of tissue homeostasis is ageing, which correlates with the waning of resident stem cell populations. In , ovaries from old females contain fewer GSCs than those from young flies. We isolated niche cells of aged ovaries, performed a transcriptomic analysis and identified as a factor for ovarian niche functionality during ageing. We show that is upregulated in aged niche cells and that we can induce premature GSC loss by overexpressing in otherwise young niche cells. High levels in niche cells induce reduced amounts, a decrease in cadherin levels and a likely increase in reactive oxygen species, three scenarios known to provoke GSC loss. Mam is a canonical co-activator of the Notch pathway in many tissues. However, we present evidence to support a Notch-independent role for in the ovarian germline niche.