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. 2007 Apr 4;27(14):3921–3932. doi: 10.1523/JNEUROSCI.4710-06.2007

Figure 2.

Figure 2.

Cerebellar defects in Plexin-B2-deficient mice. Adult cerebella from Plexin-B2+/− mice (A, C) and Plexin-B2−/− mice (B, D–J). A, B, Cerebella were stained in toto for β-gal histochemistry. Vermis lobes are indicated by Roman numerals. In Plexin-B2−/−, the foliation is altered, some folia are fused (VI–VII), some fissures are absent, and others are less pronounced. In addition, ectopic β-gal-expressing cell clusters are found at the cerebellar surface (arrowhead). C, D, Sagittal cerebellum sections immunostained with anti-α6. In Plexin-B2−/−, lobules I–III and VI–VII are fused and the cerebellar lamination is profoundly perturbed. The precentral fissure (ce) and intercrural fissure (i) are absent. Islands of α6-unlabeled cells (arrows) are intermingled with α6-expressing granule cells. Ectopic clusters of α6-positive granule cells are found at the cerebellar surface (arrowheads). E, Higher magnification of a section double stained for α6 and CaBP. α6-positive granule cells are intermingled with CaBP-positive Purkinje cells. The arrowheads point to the superficial clusters of granule cells. F, β-gal staining also revealed the profound disorganization of the cerebellum and the islands of β-gal-negative cells. G, A section immediately adjacent to F was stained for PLAP. PLAP is expressed by parallel fibers in the molecular layer and in the β-gal-negative islands (arrowhead, compare with F). H, I, The base of some cerebellar folia is completely disorganized, and some dispersed α6-positive granule cells (arrowheads) invade the deep nuclei (asterisk) containing the CaBP-positive Purkinje cells axons. Some ectopic Purkinje cells are also found in the white matter (arrow in I). J, In the molecular layer of the less disorganized lobules, a few ectopic α6-positive granule cells (arrows) with two emerging dendrites (arrowheads) can be observed. Scale bars: A, B, 1.2 mm; C, D, 445 μm; E, 200 μm; F, G, 650 μm; H, 240 μm; I, 120 μm; J, 40 μm. S, Simplex; c1, crus1; c2, crus2; cu, culmen; pml, paramedial lobe; 1, primary fissure; py, prepyramidal fissure; 2, secondary fissure; po, posterior fissure; p, paraflocculus.