EphA4 immunostaining in paraffin sections at various stages of early cerebellar development. A, Transverse section of a cerebellum at stage 27 (E5) with an adjacent nissl stain in B. Note EphA4 expression in the ventricular zone (vz), in the medial (M) and lateral (L) subdivisions of the mantle zone, and on a fiber tract (ft) separating the medial and lateral subdivisions. C, High magnification of the cerebellar anlage in A with an adjacent Tau staining inD showing the fibrous nature of the tract separating the medial and lateral subdivisions. E, Transverse section of stage 29 (E6) cerebellum with an adjacent nissl stain inF. The expression is similar to stage 27 except for downregulation in the vz and an area in the cerebellum that is devoid of EphA4 expression (E,egl). G, Transverse section through the caudal cerebellum at stage 29 (E6) with adjacent nissl stain in H. EphA4 expression appears more extensive in caudal sections as compared with rostral sections (E). egl, Future external granule cell layer as defined by Feirabend (1990); ft, fiber tract; hb, hindbrain; mz, mantle zone;M, medial subdivision; L, lateral subdivision; V, ventricle; vz, ventricular zone. Scale bars, 200 μm.