Adult <i>Apoer2</i> null cerebella have Purkinje cell ectopia that is largely restricted to zebrin II-immunonegative cells.

<p>Sagittal sections are taken from either adult wild type (A–C) or <i>Apoer2</i> null (D–L) cerebella. Cerebella have been immunostained with antibodies against calbindin (CaBP-A, D, G, J), zebrin II (ZII-B, E, H), phospholipase Cß4 (PLCß4-C, F, I, L) or heat shock protein 25 (HSP25-K) to reveal immunopositive Purkinje cell bodies in the Purkinje cell layer (P) as well as their dendrites located within the molecular layer (M). Sections from the <i>Apoer2</i> null cerebellum are serial sections (zebrin II-calbindin-PLCß4) while wild type sections are not. Boxes in D–F indicate areas where higher-magnification pictures are presented below. High-magnification panels (G, H, I, J, L) illustrate the presence of discrete groups of ectopic Purkinje cells in the white matter of the <i>Apoer2</i> null cerebellum, as identified with CaBP-immunostaining (G, J).The absence of zebrin II immunoreactivity in these cells (H) indicates that the predominant phenotype of Purkinje cells in the white matter of these mutants is ZII-/PLC ß4+ (I, L). Black arrows in E point to areas in lobules IX and X where Purkinje cells are misaligned within the Purkinje cell monolayer. Arrowheads in H point to the rare occurrence of zebrin II immunopositive Purkinje cells in the ectopic clusters. K–HSP25 immunoreactivity is revealed in Purkinje cells throughout the NZ (dotted line). Roman numerals indicate lobules. Scale bar in L = 1 mm for A–F and 250 µm for E–L.