Jak-STAT regulation of cyst stem cell development in the Drosophila testis

► We examine the process of cyst stem cell (CySC) development in Drosophila testes. ► CySC establishment correlates with formation of the testis stem cell niche. ► Jak-STAT signaling is necessary and sufficient for CySC maintenance in larval testes. ► Zygotic Stat92E is not required for the initial establishment of CySCs at the embryo-larval transition. ► Signaling from CySCs promotes the maintenance of germline stem cells (GSCs) in larval testes.