Figure 1.

Plexin-B2 expression pattern in the developing cerebellum. All sections are sagittal. A, At E13, in situ hybridization with a DIG-labeled Plexin-B2 riboprobe showed that Plexin-B2 mRNA is highly expressed in the developing EGL (arrowheads) but is not expressed in the nuclear transitory zone (asterisk). B, E14 Plexin-B2^+/− cerebellum immunostained for β-gal and RORα. β-gal is highly expressed in the EGL (arrowheads) above RORα-positive migrating Purkinje cells (asterisks). The weak staining in the ventricular zone is not specific. C, At E17, Plexin-B2 mRNA is still detected in the EGL (arrowheads) above CaBP-labeled Purkinje cells (asterisks). Plexin-B2 signal has been artificially colored in red using Photoshop (Adobe Systems, San Jose, CA) and superimposed to the CaBP labeling. D, At P0, Plexin-B2 transcripts are highly expressed in the EGL (arrowhead). E, β-gal expression is also confined to the EGL (arrowhead) in the cerebellum of P1 Plexin-B2^+/−. F, In P7 Plexin-B2^+/− cerebellum, β-gal expression is observed in both the EGL (arrowhead) and IGL (arrow). G, At P10, CaBP-positive Purkinje cells (arrowheads) form a monolayer. Plexin-B2 mRNA is only detected in the upper EGL (u) and not in the lower EGL (l). Plexin-B2 signal has been artificially colored in red using Photoshop and superimposed to the CaBP and Hoechst labeling. H, J, Wild-type cerebellum sections immunostained with anti-Plexin-B2 antibodies. H, At E15, Plexin-B2 is only detected in the EGL and choroid plexus (Hoechst counterstaining). I, P0 section labeled for Plexin-B2, H3P, and Hoechst. In the EGL, mitotic cells labeled with H3P (arrowheads) also express Plexin-B2. J, P10 section immunostained for Plexin-B2, CaBP, and TAG-1. Plexin-B2 is expressed in the upper EGL, whereas TAG-1 is found in the lower EGL and top of the upper part of the molecular layer above CaBP-positive Purkinje cells. Scale bars: A, 130 μm; B, 160 μm; C, 220 μm; D, 200 μm; E, 300 μm; F, 550 μm; G, 18 μm; H, 120 μm; I, 35 μm (I).