Fig. 6. The loss of Sp8 provoked overgrowth of the neuroepithelium. (A-M) Expression analysis of several markers of the ventral midbrain: Shh (A,B), Nkx6.1 (C,D), Nkx2.2 (E,F), Wnt5a (G,H), Wnt1 (J,K) and Foxa2 (L,M) on frontal vibratome sections (45 µm) selected at the level of the posterior midbrain. The expression pattern of all these markers presented here reflects the expansion of the neuroepithelium and does not reveal a patterning defect at this stage of development. The overgrowth of the neuroepithelium results in reduced aqueduct space.