Yeast and animals cells control cell growth and division in different ways. In yeast, rates of cell growth are strictly controlled by nutrient availability. In nutrient-rich environments, growth rates are high and cells are large. In contrast, when nutrients are limiting, growth rates are slower and cells are smaller. Cell-size checkpoints function to ensure that yeast cells divide only at a critical size dictated by nutrient conditions; they therefore ensure that proliferation rates in yeast are appropriately tailored to environmental conditions. In animal development, cells are under the influence of a variety of extracellular stimuli such as nutrients, growth factors, mitogens and various patterning inputs, examples of which are shown. These signals mediate cell-to-cell communication and act to control both cell size and cell numbers, in order to ensure correct organ and organismal growth. Under these circumstances, strict cell-size checkpoints may not be necessary. Rather, overall proliferation is probably regulated by the independent but coordinated control of growth and division by diverse stimuli.
Grewal and Edgar Journal of Biology 2003 2:5 doi:10.1186/1475-4924-2-5