Fig. 4.
Severe morphological alterations at P3 and P7 after constitutive Wnt activation in cerebellar granule neuron precursors. From P3 on, consequences of activated Wnt signaling in the EGL were clearly visible on H&E stainings (sagittal sections [A and B]). While control animals exhibited a thick EGL consisting of proliferating granule neuron precursors, Math1-cre::ApcFl/Fl mice had only single granule neurons in the EGL. These changes were very clear in rostral parts but were still significant in caudal areas (C). Expression of β-catenin was membranous in control mice (D) but nuclear in almost 20% of granule neurons in rostral parts of Apc-deficient cerebella (E and F). At P7, cerebellar foliation was hardly visible on H&E sections of Math1-cre::ApcFl/Fl cerebella (H) compared to findings for control mice (G). The number of granule cells was significantly reduced (I), and nuclear β-catenin was still prominent in Apc-deficient granule cells (K and L). EGL, external granular layer; PC, Purkinje cells. Enlarged views of boxed areas in panels A, B, G, and H are presented in other panels, as indicated.