Fig. 5. Pax6 GOF at early corticogenesis causes apoptosis. (A-B') TUNEL assay on sections from JoP6 (A,B) and JoP6;Emx1^IREScre (A',B') embryos at stages E11.5 (A,A' with higher magnification) and E14.5 (B,B') illustrates apoptosis of JoP6;Emx1^IREScre cortical progenitors, more severe at E11.5. (C,C') Immunolabeling against activated Casp3 confirms enhanced apoptosis in the JoP6;Emx1^IREScre cortex. (D-D'') Double immunostaining of E13.5 JoP6;Emx1^IREScre cortex against nestin (D) and activated Casp3 (D') illustrates that many of the apoptotic cells are nestin⁺ progenitors (D'' and magnifications counterstained with Hoechst). (E) At stage E18.5, apoptosis is no longer detected in JoP6;Emx1^IREScre. (F) In situ hybridization with ephrin A5 reveals that the apoptotic cell aggregates of the JoP6;Emx1^IREScre cortex are positive for ephrin A5 (arrows).