Stem Cell Self-Renewal Specified by JAK-STAT Activation in Response to a Support Cell Cue

TLDR

Stem cells generate diverse differentiated cell types and maintain long‑term self‑renewal, yet few niche‑derived signals that specify self‑renewal have been identified. The study demonstrates that apical hub cells in the Drosophila testis serve as a niche supporting stem cell self‑renewal. Hub cells secrete Unpaired, activating JAK‑STAT signaling in neighboring germ cells to promote self‑renewal and maintain the germ line stem cell pool. These findings reveal that the Drosophila testis apical hub cells act as a niche by secreting Unpaired to activate JAK‑STAT signaling, thereby specifying self‑renewal and sustaining the germ line stem cell population.

Abstract

Stem cells generate many differentiated, short-lived cell types, such as blood, skin, and sperm, throughout adult life. Stem cells maintain a long-term capacity to divide, producing daughter cells that either self-renew or initiate differentiation. Although the surrounding microenvironment or “niche” influences stem cell fate decisions, few signals that emanate from the niche to specify stem cell self-renewal have been identified. Here we demonstrate that the apical hub cells in the Drosophila testis act as a cellular niche that supports stem cell self-renewal. Hub cells express the ligand Unpaired (Upd), which activates the Janus kinase–signal transducer and activator of transcription (JAK-STAT) pathway in adjacent germ cells to specify self-renewal and continual maintenance of the germ line stem cell population.