Cytonemes: Cellular processes that project to the principal signaling center in Drosophila imaginal discs

Wing imaginal disc cells in Drosophila develop by using information receive d from a signaling center associated with the anterior/posterior compartmen t border. We show here that disc cells have thin, actin-based extensions (c ytonemes) that project to this signaling center. Cytonemes can be induced w hen cells from the lateral flanks of a wing disc are cultured next to cells from the A/P border or next to a source of fibroblast growth factor. Mouse limb bud cells also grow projections during a brief culture period, indica ting that cytonemes are an attribute of both vertebrate and invertebrate ce lls. We suggest that cytonemes may be responsible for some forms of long-ra nge cell-cell communication.