Fig. 1. Expression of the Evi1, c-jun, and c-fos genes during RA or DMSO-induced differentiation of P19 EC cells. P19 cells were aggregated for 2 days and treated with 1 µM RA (A) or 1% DMSO (B) for an additional 2 days (days 1 and 2). The cells were then transferred into tissue culture dishes without additives. After incubation times of 2 and 4 days after replating (days 4 and 6), P19 cells were followed by mRNA extraction and Northern blot analysis. Five µg of mRNA were electrophoresed in each lane. The membrane was sequentially hybridized with Evi1, Mash1, MAP2 (or ActivinßA in B), c-jun, c-fos, and ß-actin probes, as described in "Materials and Methods.".