Fig. 6.

Effects of cysteine deprivation on the growth of ES, MEF, and 3T3 cells. Cocultures of ES/MEF or ES/3T3 cells were subjected for 2 days to media containing varying amounts of supplemented cysteine. Cysteine deprivation severely impeded MEF cell growth at 10 and 3 μM and 3T3 growth at 3 μM (see also fig. S5). Although colony morphology was altered under the most severe conditions of cysteine deprivation, ES cell colonies were observed under all culture conditions tested.