Figure 1.

Experimental models to study the migratory behavior of MGE cells. A, To image MGE cells migrating in cortical slices, MGE explants dissected from GFP-expressing embryos were grafted homotopically in wild-type forebrain slices. The experimental model is schematized on the left. The green dot represents the GFP-expressing MGE explant. The dotted frame indicates the limits of the picture shown on the right. B and C illustrate the two coculture models used in the present study. B, GFP-expressing MGE explants were placed at the tip of cortical axons growing on a polylysine/laminin-coated substrate. In the scheme on the left, the MGE explant is a green dot; cortical explant and cortical axons are shown in red. MGE cells migrate on cortical axons. C, GFP-expressing MGE explants were placed on a monolayer of wild-type dissociated cortical cells (in pink in the scheme on the left). MGE cells migrate randomly on cortical cells. D, MGE cells migrating on cortical cells show bifurcated or branched leading processes. In some cases, a long thin neurite is observed at the trailing side (white arrowhead). GFP-positive MGE cells were immunostained using a green fluorescent secondary antibody (A-D). Cortical axons were immunostained with TUJ1 antibodies using a red fluorescent secondary antibody (B). CX, Cortex; GE, ganglionic eminence. Scale bars: A, C, 100 μm; D, 20 μm.