Fig. 1. Morphology of normal (a) and mi-expressing (b) CNR cells. Dissociated CNR cells dissected from 8-day-old chicken embryos were plated in DMEM-F-12 medium supplemented with 10% FCS, 1% MEM/100x vitamins, and 10 µg/ml conalbumin. Dishes (60-mm diameter) containing 107 dissociated cells were transfected at 37°C with pSFCV-LE mi (LE-mi) and RAV-1 proviral DNA or with the empty retroviral vector pSFCV-LE (LE) and RAV-1. The transfected cells were selected in G418 containing complete medium for 10 days. Actin filaments were labeled with nitrobenzoxadiazole-labeled phallacidin, as described previously (22) .