Stem cells resume asymmetric division upon niche re-entry through reactivating the centrosome orientation checkpoint

In Drosophila testis, germline stem cells (GSCs) typically divide asymmetrically, keeping one daughter cell within the niche for self-renewal and placing the other daughter cell outside the niche to undergo differentiation. This is the primary mechanism for maintaining a stable number of stem cells in the niche. However, it has been shown that small fraction of GSCs continuously leave the niche, necessitating an additional mechanism to compensate for this loss and maintain a constant number of GSCs. Dedifferentiation and symmetric renewal have been shown to replenish lost GSCs during regenerative and physiological conditions. However, it remains unknown whether dedifferentiated GSCs reacquire native GSC behaviors. Using long-term live imaging, we trace the cells following dedifferentiation and show that dedifferentiated GSCs appear to reacquire at least one aspect of native GSC behavior, the centrosome orientation checkpoint, a GSC-specific checkpoint mechanism that ensures oriented spindle to achieve asymmetric stem cell divisions. Our findings provide important insights into the robust mechanisms ensuring asymmetric division in the niche. Long-term live imaging in Drosophila testis shows that dedifferentiated germline stem cells re-acquire stem cell behaviours, including the centrosome orientation checkpoint, thereby ensuring asymmetric division after re-entering the niche.