title: Control of compartment size by an EGF ligand from neighboring cells.
abstract: Insect bodies are subdivided into anterior (A) and posterior (P) compartments: cohesive fields of distinct cell lineage and cell affinity . Like organs in many animal species, compartments can develop to normal sizes despite considerable variation in cell division . This implies that overall compartment dimensions are subject to genetic control, but the mechanisms are unknown. Here, studying Drosophila's embryonic segments, I show that P compartment dimensions depend on epidermal growth factor receptor (EGFR) signaling. I suggest the primary activating ligand is Spitz, emanating from neighboring A compartment cells. Spi/EGFR activity stimulates P compartment cell enlargement and survival, but evidence is presented that Spitz is secreted in limited amounts, so that increasing the number of cells within the P compartment causes the per-cell Spitz level to drop. This leads to compensatory apoptosis and cell-size reductions that preserve compartment dimensions. Conversely, I propose that lowering P compartment cell numbers enhances per-cell Spitz availability; this increases cell survival and cell size, again safeguarding compartment size. The results argue that the gauging of P compartment size is due, at least in part, to cells surviving and growing according to Spi availability. These data offer mechanistic insight into how diffusible molecules control organ size.
authors.affiliation: Division of Cell Biology, Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom. jp2488@columbia.edu
authors.forename: Joseph
authors.initials: J
authors.lastname: Parker
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D019521:Body Patterning / Q000502:physiology*; D001837:Body Weights and Measures; D004330:Drosophila / Q000196:embryology*; D029721:Drosophila Proteins / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000502:physiology; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism*; D005434:Flow Cytometry; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008024:Ligands; D008565:Membrane Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D029721:Drosophila Proteins; D008024:Ligands; D008565:Membrane Proteins; C076026:spi protein, Drosophila; D004815:Epidermal Growth Factor; D066246:ErbB Receptors