Fig. 9. (A) Western blot of lysates from floxed ß1/wt (right lane) and floxed ß1/null (left two lanes) neurospheres after more than ten passages, showing that MAPK is phosphorylated equally in both groups. (B) Western blot of lysates from floxed ß1/wt (right) and floxed ß1/null (left) neurospheres (the same cultures as in A) exposed to AG1478 (20 µM), an inhibitor of the EGF receptor. This panel shows that MAPK phosphorylation is reduced to a greater extent in the null spheres (floxed ß1/null) than in the floxed ß1/wt in the presence of the inhibitor. AG, AG1478. WT represents floxed ß1/wt and Null represents floxed ß1/null spheres following exposure to cre recombinase.