Figure 4: Most Sox14⁺ neurons migrate into the dLGN in a dorsal to ventral direction.

Cellular morphology and migratory behaviour of Sox14⁺ neurons in the fixed and ex vivo Sox14^Gfp/+ dLGN. (a) Confocal imaging of Sox14⁺ neurons in the dLGN from P0 to P5, showing the progressive spread of GABAergic interneurons in the relay dLGN. Scale bar, 100 μm. (b) Methodology used for population-wide analysis of the migratory morphology of Gfp⁺ neurons in the Sox14^Gfp/+ dLGN: each green unit depicts the leading process orientation. Its angular components relative to the dorso-ventral and latero-medial axes of the dLGN can be determined. Scale bar, 10 μm. (c) Quantification of the orientation of leading processes at population level at P0, P1 and P2: respective histograms displaying their angular distribution in 20° bins, with a maximum along the downward dorso-ventral axis (red dotted line) and lack of any obvious upwardly oriented (blue dotted line) population. Black dots on the plots of angular components are population means, which are significantly different from 0 at each developmental time point (P0: P<0.025; P2–3 P<10⁻³; one-sample Wilcoxon signed rank test) and indicate a dominant dorso-ventral and latero-medial orientation (n=165 cells from 1 brain per developmental stage). (d) Frame shots of ex vivo time-lapse imaging of an acute coronal section containing the Sox14^Gfp/+ dLGN at P0.5 and imaged over the following 26 h. Neurons that cross the boundaries of the dLGN are colour coded post acquisition for clarity (Supplementary Movies 2 and 3). Scale bar, 100 μm; and 10 μm for close-up images.