Extensive axonal growth from grafted NPCs in the corpus callosum. Although grafted NPCs did not migrate from the transplant site at the corpus callosum, AP-positive axons from grafted NPCs showed extensive growth out of NPC-derived neurons along the corpus callosum. These axons not only reached to the midline of the corpus callosum but also entered the contralateral side of the corpus callosum (panels A and B). Panels A and B are images of the entire transplant. Unlike grafted NPCs in the spinal white matter, few NPCs migrated from the transplant. However, clear AP-positive fibers extended out of the transplant along the corpus callosum (panels d , e and f), reached to the midline (panel c), and crossed the midline toward the contralateral corpus callosum (panels a and b). Images in boxes a–f in panel B are shown at a high magnification. Scale bar = 2 mm in A; 1 mm in B; and 100 μm in a–f.