Fig. 2. In vitro and in vivo migration assays show that granule cells migrate more slowly in mice lacking astrotactin. (A) In vitro migration assay. The majority of wild-type granule cells migrate faster than 10 µm/h (gray) whereas the majority of granule cells from astrotactin null mice migrate more slowly than 10 µm/h. (B-G) Midline sagittal sections of cerebella from mice after varying survival times after intraperitoneal injection of BrdU. Brown peroxidase product shows cells that have taken up BrdU, sections were counterstained with Hematoxylin. In all figures, the EGL is at the top and is marked yellow, the IGL is marked by a blue bar. Six hours after BrdU injection there are similar numbers of heavily labeled cells in wild type (B) and astrotactin null (C) EGL. After 24 hours survival there are more labeled cells in the molecular layer and IGL of wild-type (D) cerebella than in astrotactin null mice (E). Forty-eight hours after injection, there are many labeled cells in the IGL and heavily labeled cells in the EGL of wild-type mice (F), whereas there are still a substantial number in the EGL and fewer in the IGL of the mutant mice (G). Scale bars: 30 µm.