Cfi plan apo vc h 60x 1

Images were acquired using a confocal microscope (Nikon A1R) equipped with oil-immersion 40x and 60x objectives (CFI Plan Fluor 40x/1.3 and CFI Plan Apo VC H 60x/1.4, Nikon). At E14, Htr3a-GFP+ cells were counted in the PSB region located at the level of the LGE and in the CGE. In the PSB, the co-expression of SP8/COUPTFII was analysed on MEIS2+/Htr3a-GFP+ cells. At E18, co-expression of PROX1, ER81, SP8 and COUP-TFII was analysed on Htr3a-GFP+ in the PSB, in the subventricular zone (SVZ) tangential migratory stream and in the intermediate zone (IZ). Co-localization with MEIS2/PROX1 was analysed on all Htr3a-GFP+ cells whereas co-expression of ER81, SP8 and COUPTFII was analysed on MEIS2+/Htr3a-GFP+ cells. At P5 and P21, Htr3a-GFP+ cells were counted in the primary motor and somatosensory cortices and in the underlying white matter (WM) in coronal sections corresponding to the levels +0.2 to −0.1 mm from Bregma. The quantified region did not contain the rostral migratory stream or the SVZ. At P5 and P21, co-expression of PROX1, ER81, SP8 and COUPTFII was analysed on Htr3a-GFP+/MEIS2+ cells in the WM and cortex. At P5, BrdU+/ MEIS2+/Htr3a-GFP+ cells were counted in WM following BrdU injections ranging from E14 to E18. Detailed counts of cells and brains for each experimental condition are provided in Supplementary Table 14.

Images were acquired using confocal microscopes (Nikon A1R or Axio Imager.Z2 Basis LSM 800) equipped with oil-immersion 40x, 60x and 63x objectives (CFI Plan Fluor 40x/1.3 and CFI Plan Apo VC H 60x/1.4, Nikon or Plan-APO (UV) VIS-IR 40x/1.4 and Plan-Apochromat f/ELYRA 63x/1.4, LSM). For widefield illustrations (Figure 2—figure supplement 1), images were taken with Axioscan.Z1 slidescanner (Zeiss), equipped with Plan-Apochromat 10x/0.45 objective (Zeiss). Images were lightly treated (gamma, brightness and and despeckle filter only) for visual purpose with Photoshop CC and manual counts were achieved with Fiji. Data are presented as brain averages calculated from at least three slices at different rostro-caudal levels per brain (except for P5 Dbx1 brain 3). A detailed description of the counts, cells and brains in the different experiments is given in Supplementary file 1.