Figure 6

Less neurons and interneurons are present in the cortical primordium of perlecan-null embryos. (A-D) β-tubulin type III immunostaining at E13.5 (A, B) and at E16.5 (C, D). At E13.5, the telencephalic vesicles show immunoreactivity in the mantle of the cortical primordium and of the septal and ganglionic eminences. In the perlecan-null, the extension of β-tubulin immunoreactivity is reduced in the pallium and in the subpallium (arrows in B). At E16.5, neocortical β-tubulin expression is strong in the wild-type subplate (C) but clearly reduced in the perlecan mutants (D). (E, F) At E16.5, the transcription factor Tbr1 labels the nuclei of early-born neurons in MZ, CP and SP. In the perlecan-null embryos the number of Tbr1⁺ neurons decreases severely and the lower tier of the CP is indistinguishable from the SP (F). Note an ectopia at the right hand side of (F). (G, H) Cortical interneurons detected by calbindin immunohistochemistry at E17.5. Comparable rostro-caudal levels are shown. Note in the perlecan-null brain (H) a notorious descent of the packing density of calbindin-immunoreactive interneurons that have invaded the subplate and cortical plate, as well as the hippocampus. Scale bars: 100 μm (A-D), 40 μm (E, F), 200 μm (G, H). Abbreviations: CP, cortical plate; DTh, dorsal thalamus; Hp, hippocampus; IZ, intermediate zone; POC, primary olfactory cortex anlage; SP, subplate.