%0 Journal Article %J Science (New York, N.Y.) %D 2001 %T Stem cell self-renewal specified by JAK-STAT activation in response to a support cell cue. %A Kiger, A A %A Jones, D L %A Schulz, C %A Rogers, M B %A Fuller, M T %K Animals %K Cell Differentiation %K Cell Division %K Cell Lineage %K Cues %K DNA-Binding Proteins %K Drosophila %K Drosophila Proteins %K Germ Cells %K Glycoproteins %K Janus Kinases %K Ligands %K Male %K Mutation %K Protein-Tyrosine Kinases %K Signal Transduction %K Spermatocytes %K Spermatogenesis %K STAT Transcription Factors %K Stem Cells %K Testis %K Trans-Activators %K Transcription Factors %N 5551 %P 2542-5 %R 10.1126/science.1066707 %V 294 %X Stem cells generate many differentiated, short-lived cell types, such as blood, skin, and sperm, throughout adult life. Stem cells maintain a long-term capacity to divide, producing daughter cells that either self-renew or initiate differentiation. Although the surrounding microenvironment or "niche" influences stem cell fate decisions, few signals that emanate from the niche to specify stem cell self-renewal have been identified. Here we demonstrate that the apical hub cells in the Drosophila testis act as a cellular niche that supports stem cell self-renewal. Hub cells express the ligand Unpaired (Upd), which activates the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway in adjacent germ cells to specify self-renewal and continual maintenance of the germ line stem cell population. %8 2001 Dec 21