Fig. 9.

Regeneration and growth of murine fetal Purkinje cell axons on “mature cerebellar cultures” from CaBP knockout mice. Coculture of cerebellar slices of CaBP null mutant mice with a wild-type E16 cerebellar slice in E, and with dorsal regions of cut E17 in A, C, and D, and an E18 fetal cerebellar slice in B. A, Bundle of CaBP-immunoreactive embryonic Purkinje cell axons that give off single fibers near their end. B, Bundle of CaBP-immunoreactive fetal Purkinje cells that splits and forms small clusters of three or more thin fibers. C, D, Coculture double-labeled with anti-CaBP (C) and anti-parvalbumin (D) antibodies. In D, Purkinje as well as basket and stellate cells are parvalbumin-immunoreactive and therefore permit the identification of the three cortical layers and the underlying white matter. Although the majority of regenerating axons occupy a white matter location, some of the axons (arrows in C) grow in all directions, crossing and/or following the white matter as well as the three cortical layers (arrowheads in C andD point to approximately the same point). Note that fibers defasciculate in the area of deep nuclear neurons (curved arrow). In E, regenerating fetal Purkinje cell axons branch and form dense plexuses over the layer containing several rows of Purkinje cell bodies (arrows), establishing pericellular nests (arrows). In F, some CaBP-immunoreactive fetal Purkinje cell axons (arrow) cross the ventral region containing deep cerebellar neurons (curved arrow) and pursue their course into the mature cerebellar culture. Scale bar (shown in E):A, 60 μm; B, 35 μm; C, D, 100 μm; E, 40 μm; F, 25 μm.