Figure 3. Timed thalamocortical WNT3 secretion regulates the R-protein composition of polysomes in the developing sensorimotor neocortex. A, Schematic of the spatiotemporal innervation of the neocortex beginning at midneurogenesis E15 by thalamic axons. B, Wnt3 qRT-PCR of the developing neocortex and thalamus (t test, p < 0.05). C, Immunohistochemistry and coronal imaging of Wnt3-Gfp mouse neocortical and subcortical structures at E15. GFP (green) in thalamus and thalamocortical axons reaching the neocortex (arrowheads; DAPI in blue). D, WNT3 immunohistochemistry (red) in coronal sections of the developing neocortex. LLs, ULs, intermediate zone (IZ) white matter, and VZ/SVZs (DAPI in blue). E, GFP immunohistochemistry (green) in coronal sections of Kcnc2-Cre/Gfp transgenic mice at E16. Thalamocortical axons reaching the neocortex are denoted by white arrowheads (DAPI in blue). Kcnc2 in situ hybridization in E14.5 neocortical sagittal sections (inset; from the Eurexpress Database, www.eurexpress.org), with thalamic expression denoted by black arrowhead. F, Western blot analysis of P0 Wnt3-cKO vs WT lysates confirming thalamic WNT3 depletion, and levels of RPL7 in total and nuclear-cytoplasmic fractionated neocortices (balanced to H3 and GAPDH). G, Western blot analysis of RPL7 in P0 Wnt3-cKO vs WT fractionated total neocortices (left). Quantification of RPL7 40S-60S-80S and polysome distribution (right; Mann–Whitney U test, p = 0.012). H, Western blot analysis of RPL7 levels in P0 Wnt3-cKO vs WT anterior sensorimotor and posterior auditory-visual fractionated neocortices. I, Western blot analysis of RPL7 levels in neuronal cell line (N2a) cultures exposed to mock, WNT3, or WNT3 plus SFRP1 inhibitor conditions; total levels (left); and nuclear-cytoplasmic fractionated levels (right) balanced to GAPDH and H3. J, Western blot analysis for RPL7 levels in polysome fractionations of N2a cultures exposed to mock, WNT3, or WNT3 plus SFRP1 inhibitor conditions.