Figure 3.
TCAs segregate normally in PMBSF but not in anterior snout regions in RIIβ KO mice. A, B, SERT immunohistochemical staining of tangential sections through layer IV at P7 reveals clear TCA patches in PMBSF in WT (A) and RIIβ KO (B) mice. In RIIβ KO mice, staining appears more uniform in the AS regions with only the largest, more dorsomedial, patches being visible. The demarcations between different subregions (arrows) of SI were clearly visible in both WT and RIIβ KO mice, indicating that the loss of segregation within AS is not a result of a general problem of TCA pathfinding in this region. LL, Lower lip; FL, forelimb; HL, hindlimb. The five main rows barrels representing the five rows of mystacial vibrissas on the facepad are labeled as A–E in B. To assess TCA segregation in PMBSF, area measurements of PMBSF and TCA patches of barrels B2, B3, C2, C3, D2, and D3 were performed blind to genotype (supplemental Fig. 4, available at www.jneurosci.org as supplemental material) on five WT and six RIIβ KO P7 mice. No significant differences in any of these measurements were observed (PMBSF, p = 0.66; B2, p = 0.30; B3, p = 0.43; C2, p = 0.36; C3, p = 0.39; D2, p = 0.55; D3, p = 0.47). RIIβ is expressed in developing SI and VpM, but barreloids form normally in RIIβ KO mice. RIIβ is expressed at low levels in VpM and barreloids appear normal in RIIβ KO mice. C, At P7, RIIβ immunostaining can be seen throughout VpM with highest levels in the inter-barreloid regions. D, E, Cytochrome oxidase staining of coronal sections through the VpM nucleus of P7 WT (D) and RIIβ KO (E) mice revealed clear barreloids even in the regions representing the anterior snout whiskers. Scale bar: (in B) A, B, 200 μm; (in E) C–E, 80 μm.