UCLA stem cell scientists have shown that two common tumor suppressor genes, TSC and PTEN, are vital to regulating the stem cell-like precursor cells that create the blood supply in Drosophila, the common fruit fly. The researchers examined a signaling pathway called TOR that the cells use to gauge nutrition levels and stress, said study senior author Dr. Julian A. Martinez-Agosto, an assistant professor of human genetics and pediatrics and a researcher with the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA.