Loss and recovery of protein productivity in genetically modified plant cell lines.

This paper addresses the problem of decreasing protein expression levels in genetically modified plant cells. A modeling approach was used to explain the loss of productivity over successive generations. Using this model, productivity losses were simulated for two cell lines. Although the lines were relatively stable, the protein production level could decrease by more than 80% after a large number of generations. Motivated by this problem, a dispersion method was developed to isolate productive cells from existing cell suspensions. Dilution of transgenic cells in a feeder layer of nonproducing cells at a ratio of 1:1000 facilitated the recovery of distinct, separate daughter colonies. Applying this method, it was possible to recover high producing cell lines.