Figure 3: Relationship between migrating neurons and radial glia.

(a) Normal migration behavior of clonal descendents. Left, schematic drawing of a wild-type neuronal clone. Right, normal clonal migration behavior in the posterior p35^−/− neocortex. Note the switch to glia-independent migration near the pia. (b) Possible relationships between p35^−/− neurons and radial glia during branched migration in the radial direction. (c) Branched neurons in the anterior p35^−/− neocortex do not associate with their mother glia. The distance of locomoting wild-type (WT) neurons and branched p35^−/− neurons from their mother glia is plotted against their distance from the ventricular surface. Whereas WT neurons maintain close contact with their mother glia (top), p35^−/− neurons detach early on and stay detached throughout their radial journey (bottom). (d) Representative examples of three migrating neurons in the anterior p35^−/− neocortex with branched leading processes (I–III). All three cell bodies are not associated with the mother glia (cell body in III is in a different z-plane than the radial glia, data not shown). Magnifications of I and III emphasize that individual branches are separated from the mother glia fiber. Magnification of II provides a better view of the branching. Large arrow, cell soma; small arrow, leading process branch; arrowhead, radial glia fiber; CP, cortical plate; IZ, intermediate zone; MZ, marginal zone; SP, subplate; VZ, ventricular zone; n = number of cells from eight different embryos.