Abstract
Stem cell progeny undergoes a series of mitoses, called transit amplifying (TA) divisions, before terminal differentiation. To quantify the impact of the intrinsic and extrinsic factors regulating the rates of TA divisions, we developed a simplified mathematical model which could predict the periods of the germline divisions from the stage-wise distributions of spermatogonial cysts in Drosophila testis. Analysis of the wild-type data using this model suggested that the cell cycle periods speed up after the second TA division due to shortening of the G1 phases. Further, suppression of the cell cycle checkpoint control in germline and upregulation of the somatic EGFR signaling is estimated to slow-down the rates of both the germline stem cell and TA divisions, increasing the cellular life spans at each stage. Together, these results suggest that higher levels of EGFR activation could attenuate cell division rates in the neighborhood, controlling the extents of tissue growth.
