Fig. 1.

Chimeric cerebella exhibit a range of phenotypes. Hematoxylin and eosin-stained parasagittal sections through the superior cerebellar peduncle are shown from (A) an Unc5h3/+ control, (B) anUnc5h3/Unc5h3 animal, and (C–E) threeUnc5h3/Unc5h3↔ROSA26 chimeric animals (chimeras 1, 4, and 5, respectively). The primary fissure (pr) separates the anterior lobe (to theleft) from the posterior lobe (to theright). Ectopic cerebellar cells that have colonized the colliculus are to the left of thewhite arrows; black arrows indicate intracerebellar ectopias, and asterisks denote divots in the granule cell layer. Note that the phenotypes of chimeric cerebella are intermediate to wild-type andUnc5h3/Unc5h3 cerebella. Also note that the larger the extracerebellar ectopia, the more attenuated the cerebellum, particularly the anterior lobe. Scale bar, 700 μm.