title: Specific roles of Target of rapamycin in the control of stem cells and their progeny in the Drosophila ovary.
abstract: Stem cells depend on intrinsic and local factors to maintain their identity and activity, but they also sense and respond to changing external conditions. We previously showed that germline stem cells (GSCs) and follicle stem cells (FSCs) in the Drosophila ovary respond to diet via insulin signals. Insulin signals directly modulate the GSC cell cycle at the G2 phase, but additional unknown dietary mediators control both G1 and G2. Target of rapamycin, or TOR, is part of a highly conserved nutrient-sensing pathway affecting growth, proliferation, survival and fertility. Here, we show that optimal TOR activity maintains GSCs but does not play a major role in FSC maintenance, suggesting differential regulation of GSCs versus FSCs. TOR promotes GSC proliferation via G2 but independently of insulin signaling, and TOR is required for the proliferation, growth and survival of differentiating germ cells. We also report that TOR controls the proliferation of FSCs but not of their differentiating progeny. Instead, TOR controls follicle cell number by promoting survival, independently of either the apoptotic or autophagic pathways. These results uncover specific TOR functions in the control of stem cells versus their differentiating progeny, and reveal parallels between Drosophila and mammalian follicle growth.
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.
authors.forename: Leesa
authors.initials: L
authors.lastname: LaFever
authors.forename: Alexander
authors.initials: A
authors.lastname: Feoktistov
authors.forename: Hwei-Jan
authors.initials: HJ
authors.lastname: Hsu
authors.forename: Daniela
authors.initials: D
authors.lastname: Drummond-Barbosa
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000378:metabolism; D005260:Female; D007328:Insulin / Q000378:metabolism; D010053:Ovary / Q000166:cytology; D011494:Protein Kinases / Q000378:metabolism*; D015398:Signal Transduction; D013234:Stem Cells / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases
chemical_list: D029721:Drosophila Proteins; D007328:Insulin; D011494:Protein Kinases; C416303:target of rapamycin protein, Drosophila; D058570:TOR Serine-Threonine Kinases