Fig. 1

Proliferation of S2R+ cells at suboptimal temperatures. (A, B) For microscopic evaluation of cell proliferation, cells were plated in aliquots and shifted to the indicated suboptimal temperatures. Phase contrast images of the same regions were acquired at the indicated times after downshift. (B) High magnification views of cells grown to comparable cell density at the indicated temperatures illustrate increased cell aggregation and longer extensions (arrowheads) at low temperature. Scale bar = 50 μm (A) and 10 μm (B). (C) Cells were counted to assess cell proliferation at different temperatures (14, 18, 25 and 29 °C). Culture aliquots were shifted to the different target temperatures, followed by counting at the indicated times after the shift. Two replicates (R1 and R2) were analyzed for each temperature and time point. Counts of viable cells in the two replicates and their mean are displayed. (D) Temperature effects on the cell cycle profile. Additional culture aliquots beyond those used for the counting shown in panel (C) were analyzed by flow cytometry after DNA staining for identification of cells in the G1, S and G2/M phase. Mean and standard deviation (s.d.) are displayed (n = 2). (E) Immediate recovery of cell proliferation rate at 25 °C after prolonged incubation at 14 °C. Culture aliquots were shifted to either 14 or 25 °C. Moreover, after 10 days of incubation at 14 °C, some aliquots were transferred back to 25 °C. Mean and s.d. of the counts of viable cells are displayed (n = 3)