Figure 1.

MGE progenitors and migrating cortical interneurons are located close to multiple cellular sources of Vegfa in the developing forebrain and express cognate receptors. (A) Vegfa mRNA expression in the MGE and in the dorsal VZ and meninges adjacent to deep and superficial Gad67-Gfp⁺ interneuron migratory streams in the E13.5 Gad67-Gfp⁺ mouse cortex. Insert shows high magnification of the cortex with strong localization of Vegfa in the meninges (Men) and at lower levels of expression in the forming CP. (B) Immunolocalization of Vegfa protein, the vascular endothelial marker IB4, and the pericyte-specific Pdgfrß/Cd140b protein in the E13.5 dorsal-lateral cortex. (C) In situ hybridization for Nrp1 in the E13.5 Gad67-Gfp⁺ mouse forebrain with colocalization of Nrp1 protein in Gad67-Gfp+ interneurons shown in bottom 2 inserts. (D) Imunostaining for VegfaR1 in the E13.5 Gad67-Gfp⁺ mouse forebrain with right panels comprising single optical confocal slices showing colocalization of VegfaR1 in Gad67-Gfp⁺ cells (denoted by stars). Histogram plots the distribution of pairs of voxel intensities for Gad67-Gfp (green channel) and VegfaR1 (red channel) (top right panel), with colocalised signal corresponding to false-colored magenta (right middle panel). Bottom panel shows high magnification of VegfaR1 (red) distributed around the cell soma of a Gad67-gfp⁺ interneuron (green) where these colocalise (yellow). (E) Quantifications of the percentage of Gad67-Gfp⁺ cortical interneurons which express VegfaR1 and Nrp1 receptors at different stages of development. (F) Immunostainings for VegfaR1, Nrp1 and Nrp2 receptors (red) in dissociated cultured E14.5 Gad67-Gfp+ interneurons. (G) RT-PCR analysis of VegfaR1, Nrp1, Nrp2 and Gapdh transcripts in FACS-isolated E13.5 Gad67-Gfp+ interneurons from the MGE and cortex (Cx). (Str, striatum; cpl, choroid plexus; MZ, marginal zone; CP, cortical plate; SP, subplate; IZ, intermediate zone; LIZ/SVZ, lower intermediate zone/subventricular zone; VZ, ventricular zone).