Figure 2.

Interneurons in the SVZ/IZ migration stream decrease speed and increase branching as they migrate down the SDF1 expression gradient. A, SDF1 is expressed in two areas in the developing mouse brain: a narrow band near the surface of the brain and in a gradient within the cortex. These two areas are also the sites of interneuron stream migration seen in B. LGE, Lateral ganglionic eminence; V, lateral ventricle. B, Phase/confocal microscopy of GFP⁺ interneurons migrating in a mouse brain slice, showing areas defined for analysis. C, D, Near the cortical notch, an area of high endogenous SDF1, interneurons migrate at 53 ± 2 μm/h and branch infrequently (0.26 ± 0.02 branches/h). Once in the arch area, an area of lower SDF1 expression, interneurons slow down (47 ± 2 μm/h) and branch more frequently (0.6 ± 0.03 branches/h). E, F, Histograms of branch angle frequency show modest branch angles near the notch area, while in the arch area larger branch angles occur. Mean angles: 50 ± 2.2 (notch), 56 ± 2.2 (arch). Error bars are ± SEM (***p < 0.001, **p < 0.01, *p < 0.05, t test or χ² test in F); 90 cells for each condition; three independent experiments. Scale bar, 300 μm.