Fig. 5: Effect of Otx2 ablation on Shh medulloblastoma formation and their maintenance.

Otx2^+/+ (WT), Otx2^CreERT2/+;R26^SmoM2/SmoM2 (allowing SmoM2 conditional expression) and Otx2^CreERT2/flox;R26^SmoM2/SmoM2 (allowing SmoM2 conditional expression and concomitant Otx2 ablation) mice were injected with tamoxifen at P2 and P5 and analysed at different stages. a Detection of proliferating cells in P11 cerebella. Mice were injected with EdU 1 h before euthanasia. Detection of Otx2 expression (red), EdU incorporation (yellow) and nuclei (blue) on lobule X (white boxes) shows massive hyperplasia, regardless of the presence of Otx2. b FACS quantification of EdU+ cells at P7, P11 and P15 in the GCP fraction of the three colour-coded genotypes. c Upper panels: Hematoxylin and eosin staining of posterior cerebella at P30 (coronal sections) showing the presence of classical medulloblastoma. Lower panels: Magnification of boxed areas in the above images. d Survival curves of Otx2^CreERT2/+;R26^SmoM2/SmoM2 and Otx2^CreERT2/flox;R26^SmoM2/SmoM2 mice showing divergence after 6 months. e Long-term follow-up of WT, Otx2^CreERT2/flox;R26^SmoM2/SmoM2 and Otx2^CreERT2/flox;R26^SmoM2/SmoM2 mice sampled after this divergence. M1: WT, 609 days; M2: Otx2^CreERT2/+;R26^SmoM2/SmoM2, 343 days; M3: Otx2^CreERT2/flox;R26^SmoM2/SmoM2; 605 days. Upper panels: Bright-field dorsal views of posterior brain (red lines delimit the cerebellum). Lower panels: Hoechst staining of mid-sagittal cerebellar sections showing dramatic tumour regression in Otx2^CreERT2/flox;R26^SmoM2/SmoM2 mice. Insets: Magnification of boxed areas at the level of lobules IX and X. Yellow arrowhead points to EGL-like persisting tumour remnants in external position in Otx2^CreERT2/flox;R26^SmoM2/SmoM2 cerebellum. P postnatal day. Scale bar: 300 μm (a) and 1000 μm (e). Data are displayed as mean ± sem. *p < 0.05, **p < 0.01