The Unc5h3 mutation acts intrinsic to intracerebellar granule cells for IGL boundary formation. Shown are parasagittal sections through lateral cerebella of anUnc5h3/Unc5h3 animal (A, B), chimera 5 (C, D), and chimera 2 (E, F). The posterior cerebellar region is shown. Thearrows in A, C, andE denote the region shown at higher magnification inB, D, and F, respectively. The white, double-sided arrows(B, D, and F) mark the boundary between the IGL and the white matter. Sections inA and B are stained with hematoxylin and eosin. In C–F, all cells are stained with neutral red, and wild-type (ROSA26) cells are labeled with the blue β-gal reaction product. As shown in D andF, the ectopic granule cells are virtually all ofUnc5h3/Unc5h3 origin. Scale bars:A, C, E, 400 μm;B, D, F, 50 μm.