Detection of dedifferentiated stem cells in the Drosophila testis

Dedifferentiation is the process by which partially or terminally differentiated cells revert to a stem cell state, a conserved mechanism that supports stem cell maintenance across various systems. In the <i>Drosophila</i> testis, dedifferentiated germline stem cells (GSCs) have been identified using a lineage-tracing method that relies on the lineage-specific promoter of the differentiation factor bam. However, the specificity and sensitivity of this method have never been thoroughly evaluated. Here, we estimate "false-positive" and "false-negative" marking rates of the bam-dependent lineage tracing system by combining live imaging with mathematical modeling. Our study not only provides a refined tool to facilitate the investigation of dedifferentiation in the <i>Drosophila</i> GSC system but also underscores the importance of quantitatively validating genetic marking systems to ensure the accuracy of lineage-tracing experiments.