FIGURE 9.

Comparison of activated caspase3 (AC3) immunoreactivity in the WT and Tbr2 cKO cerebella does not indicate that UBC precursors undergo apoptosis in the nodulus of the mutant cerebellum. (A,C) The WT cerebellum shows little AC3 activity at early stages of postnatal development and the Tbr2 cKO cerebellum shows similar levels and localizations of caspase3 activity (B,D). (E) At P10 there is increased immunoreactivity in the WT cerebellum particularly along pial surfaces. (F) In the Tbr2 cKO cerebellum there is increased immunoreactivity for caspase3 compared to earlier stages predominantly in the white matter and molecular layers of the cerebellum. The pattern of AC3 immunostaining in the mutant cerebellum does not suggest that putative UBC progenitors that failed to migrate out of the rhombic lip are undergoing apoptosis. During adulthood in the mouse there is no apparent AC3 in either the WT (G) or mutant (H) cerebellum.