Cell-to-cell variation in store-operated calcium entry in HEK-293 cells and its impact on the interpretation of data from stable clones expressing exogenous calcium channels

To investigate the effect of cell-to-cell variation in store-operated calci um entry (SOCE) on the evaluation of data from stable cell clones selected following gene transfection, we measured SOCE in 2700 individual HEK-293 ce lls from the parent population and in 1900 individual cells from a clonal s ubpopulation of HEK-293 cells. We applied statistical resampling techniques to model conditions where one would compare the average SOCE in n control clones to the average SOCE in n experimental clones (n = 1-200). For an ove rexpression experiment with n = 1, there is a 27% chance of observing a 100 % or higher difference in SOCE between clones, with n = 10 there is a 34% p robability of observing a 20% or greater difference in SOCE, and with n = 1 00, there is less than a 10% chance of seeing a 10% or greater difference i n SOCE, based solely on random selection of clones from the parent HEK-293 cell population. To assure that the degree of cell-to-cell variation was pr edictive of the degree of clone-to-clone variation, we measured SOCE in 270 clones, each arising from a single cell, and found the variation to be ver y similar to that observed for individual cells. (C) 2000 Harcourt Publishe rs Ltd.