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.