title: Extracellular control of cell size.
abstract: Both cell growth (cell mass increase) and progression through the cell division cycle are required for sustained cell proliferation. Proliferating cells in culture tend to double in mass before each division, but it is not known how growth and division rates are co-ordinated to ensure that cell size is maintained. The prevailing view is that coordination is achieved because cell growth is rate-limiting for cell-cycle progression. Here, we challenge this view. We have investigated the relationship between cell growth and cell-cycle progression in purified rat Schwann cells, using two extracellular signal proteins that are known to influence these cells. We find that glial growth factor (GGF) can stimulate cell-cycle progression without promoting cell growth. We have used this restricted action of GGF to show that, for cultured Schwann cells, cell growth rate alone does not determine the rate of cell-cycle progression and that cell size at division is variable and depends on the concentrations of extracellular signal proteins that stimulate cell-cycle progression, cell growth, or both.
authors.affiliation: MRC Laboratory for Molecular Cell Biology and the Biology Department, University College London, London WC1E 6BT, UK. i.conlon@ucl.ac.uk
authors.forename: I J
authors.initials: IJ
authors.lastname: Conlon
authors.forename: G A
authors.initials: GA
authors.lastname: Dunn
authors.forename: A W
authors.initials: AW
authors.lastname: Mudge
authors.forename: M C
authors.initials: MC
authors.lastname: Raff
mesh_terms: D000818:Animals; D016590:Aphidicolin / Q000494:pharmacology; D002453:Cell Cycle / Q000502:physiology*; D048429:Cell Size / Q000502:physiology*; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D020890:Neuregulin-1 / Q000494:pharmacology*; D051381:Rats; D012583:Schwann Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D020890:Neuregulin-1; D016590:Aphidicolin; D007334:Insulin-Like Growth Factor I