FIG. 2.

p19^ARF transcripts are induced in aberrantly proliferating CP epithelium. RNA in situ hybridization was performed with an antisense p19^ARF RNA probe. (A) Hematoxylin and eosin (H & E)-stained section from the same brain as in panel C shows the morphology of CP in the lateral ventricle and is in an orientation similar to that of dark-field panels B to D. The borders between brain parenchyma (br) and the ventricles (V) are depicted with white dashed lines in panels B to D. No p19^ARF expression above background is detected in the CP of nontransgenic mice (B). (Compare the signal in brain with that in CP.) p19^ARF transcripts are induced in TgT₁₂₁ CP (C). T₁₂₁-induced p19^ARF expression is p53 independent; the level of p19^ARF transcripts is similar in TgT₁₂₁;p53^−/− CP (D) and TgT₁₂₁ CP (C). (A) Bar, 200 μm (magnification is the same in all panels). Sense probe hybridization showed no signal above background (not shown).