Meeting Abstract

P2.62  Thursday, Jan. 5  Environmental and Genetic Control of Stem Cell divisions in the Drosophila Testis PARROTT, B.B.*; HUDSON, A.; BRADY, R.; SCHULZ, C.; Medical University of South Carolina, Dept. of Obstetrics and Gynecology; University of Georgia, Dept. of Cellular Biology; University of Georgia, Dept. of Cellular Biology; University of Georgia, Dept. of Cellular Biology

To realize the full therapeutic potential of stem cells, we must uncover the fundamental properties that govern their behavior in normal tissues as well as in those tissues affected by disease. In contrast to our understanding of the cell fate dynamics in tissues maintained by adult stem cells, we know relatively little regarding how organisms control the number of terminally differentiated cells they produce. Here, we report that in the Drosophila testis, the frequency of Germline Stem Cell (GSC) divisions depends on the levels of sexual activity that an animal experiences. These findings suggest that stem cells respond to the demand for the terminally differentiated cells they replenish by modulating their division frequency (positive or negative – does the frequency increase or decrease?). Furthermore, GSC division frequency depends on genetic factors. Mutations in an EGF encoding locus, spitz, result in the accumulation of early-stage, undifferentiated germ cells resembling a germ cell tumor. We observed that GSCs in animals, with attenuated EGF signaling, display a two-fold increase in their division frequency, suggesting a mechanism by which stem cells contribute to tumorigenesis. In addition, we show that two novel genetic suppressors of the spitz phenotype, seven-up and homothorax, specifically suppress the cell fate component of the phenotype without suppressing the hyper-proliferation of GSCs. These data provide evidence that EGF functions in two genetically distinct pathways to regulate cell fates and GSC divisions. Thus, this work provides a fundamental link between stem cell biology and the role they can play in various cancers.