Detection of dedifferentiated stem cells in Drosophila testis

Tissue homeostasis relies on the stable maintenance of the stem cell pool throughout an organism's lifespan. Dedifferentiation, a process in which partially or terminally differentiated cells revert to a stem cell state, has been observed in a wide range of stem cell systems, and it has been implicated in the mechanisms for stem cell maintenance. Dedifferentiated stem cells are morphologically indistinguishable from original stem cells, making them challenging to identify. Therefore, whether dedifferentiated stem cells have any distinguishable characteristics compared with original stem cells is poorly understood. The Drosophila testis provides a well-established model to study dedifferentiation. While our previous live imaging analyses have identified dedifferentiation events constantly occurring at steady state, existing genetic marking methods fail to detect most of the dedifferentiated stem cells and thus significantly underestimate the frequency of dedifferentiation events. Here, we established a genetic tool with improved sensitivity and used live imaging and mathematical modeling to evaluate the system. Our findings indicate that the specificity of lineage-specific promoters is critical for successfully identifying dedifferentiated stem cells.