FIG. 8.
Embryonic day 12.5 Nf1−/− astroglial cells show a significant increase in growth in vitro but lack tumorigenic properties. (A) Western blotting of astroglial cell extracts with an antineurofibromin antibody demonstrated loss of neurofibromin in Nf1−/− astroglial cells. (B) Growth curves of Nf1−/−, Nf1+/−, and Nf1+/+ astrocytes showed a significant growth advantage for Nf1−/− astroglial cells at 3 and 6 days in culture. (C) When stimulated with fetal bovine serum, Nf1−/− astroglial cells showed increased [3H]thymidine incorporation in comparison with Nf1+/− astrocytes. (D) The growth advantage observed by cell counting and [3H]thymidine incorporation was also demonstrated by flow cytometry analysis of the cell cycle of Nf1−/− and Nf1+/− cells. (E) Nf1−/− and Nf1+/− astroglial cells do not form colonies in soft agar. C6 glioma cells were used as a positive control in the soft agar assay.