(A–H) Sagittal sections of the embryonic mouse cerebellum in WT (A, C, C′, E, G) and Foxc1 null mutants (B, D, D′, F, H) at e13.5 (A, B), e15.5 (C–D′), e17.5 (E, F) and 19.5 (G, H) stained for Nestin. While radial glial fibers extended from the ventricular zone to the pial surface in the WT cerebellum (C, C′, arrows), in the Foxc1 null mutant, fibers were discontinuous and did not extend all the way to the pial surface (D, D′, arrows). In the WT cerebellum, Bergmann glial fibers extended from the EGL to the PL at e17.5 (E) and e19.5 (G, L; arrows). The white straight line in (E) demarcates the anlage into two regions—an anterior (left) region where fibers extend from the VZ to the pia, and the other (right) where Bergmann glial fibers extend from the EGL to the IGL. In the Foxc1 null mutant, these two zones were not apparent and fiber morphology was severely disrupted (F, H; arrows). (I) Graph showing the number of TUNEL positive cells that span the length of the cerebellar ventricular zone. The number of TUNEL positive cells in the ventricular zone of the Foxc1−/− cerebellum was significantly higher than WT at e13.5 and e15.5. Data represented as average number of TUNEL positive cells per section analysed ± s.e.m. *** indicates significance with respect to corresponding WT Control (p < 0.05). (J–M) Sagittal sections of the WT (J, L) and Foxc1−/− cerebellum (K, M) stained for BLBP. In the e19.5 WT cerebellum (J, box; L, arrow), BG were present as a layer overlapping with the PL. However, in the Foxc1 null mutant, (K, box; M, arrow) BG were ectopically located in the EGL. Abbreviations used; NTZ—Nuclear Transitory Zone and VZ—Ventricular Zone. The white dashed line indicates the outer boundary of the EGL and the mesenchyme, while the yellow dotted line represents the cerebellar ventricular surface. The white straight line in Image E represents the boundary between two zones—one where fibers extend from the VZ to the pia, and the other where BG fibers extend from the EGL to the IGL. C′–D′ are high magnification images of C–D respectively. Scale bar = 100 µm.