Fig. 9: Activation of ERK/MAPK pathway by expression of BrafV600E results in increased expression of the cell cycle inhibitors p57Kip2 and of p27Kip1 in the Sox2+ve stem cells at E18.5.
a–l Coronal sections through the pituitary gland at E18.5 of Wt (a–c, g–i) and Prop1:Cre;BrafV600E/+ (d–f, j–l). Double immunofluorescence against cell cycle inhibitor p57Kip2 (green, a–f) and p27Kip1 (green, g–l) with the pituitary stem cell marker Sox2 (red, a–l). The cell cycle inhibitor p57Kip2 was found to be upregulated in the Prop1:Cre;BrafV600E/+ pituitaries (arrowheads in d) compared to the Wt (a). c′, f′ Merged enlarged images of squared areas in c and f reveal increased p57Kip2 immunoreactivity co-localising with Sox2 (arrowheads in f′) in the Prop1:Cre;BrafV600E mutant pituitaries compared to Wt (arrowheads in c′). Expression of p27Kip1 (arrowheads in j) is observed in the marginal zone (MZ) of the mutant pituitaries compared to Wt (g). Confocal merged images of the marginal zone revealed co-localisation of Sox2 with p27Kip1 in the mutant Prop1:Cre;BrafV600E/+ pituitaries (yellow nuclei, arrowheads in l′), while no co-localisation of p27Kip1 and Sox2 was seen in Wt pituitaries (arrows in i′). i′, l′ are enlarged images of the squared areas in i and l respectively. Images are representative of three embryos per genotype. AL anterior lobe, MZ marginal zone, PL posterior lobe. Scale bars in a and g represent 200 µm. Scale bars in c′ and i' represent 25 µm.
