Fig. 2. Migration of GFP⁺ neurons in cortical slices. (A) The time sequence of migrating neurons in a coronal slice taken over a time interval of 35 minutes in an E13.5 mouse embryo. (B,C) Similar to A but from an E15.5 mouse and taken at time intervals of 40 and 25 minutes, respectively. (D) A merged view of a time sequence taken at a 30 minutes interval from an E15.5 mouse. The image taken at an earlier time of observation was converted to green and later captured to red. Thus, cells colored yellow mostly represent cells that stayed in the same position during the intervals, although part of them could represent two different cells, one of which migrated to original position of the other. Those in red or green represent cells that had migrated during the interval. Note that most MZ neurons are yellow, suggesting no migration. (E,F) Enlarged view of an image generated by merging the two panels of A after color conversion described above. (E) Two tangentially migrating cells indicated by arrowheads in A are shown by a pair of arrows. The neuron labeled as `1' is deflected towards the MZ, whereas neuron `2' migrated tangentially. (F) Enlarged view of the area shown by a rectangle in A. Note that there are many yellow dots near the surface, suggesting that many cells in this region may be stationary. (G) A tangentially migrating neuron in the IZ. (H) A radially migrating neuron in the cortical plate towards the MZ. (G,H) Enlarged views of a merged image generated from B and C, respectively and the positions of these cells are indicated by arrowheads. (I) Radially migrating neuron away from the MZ. (J) A radially migrating neuron, with some angle, in the IZ over a 25 minutes interval. (K) A tangentially migrating neuron in the SVZ but in a reversed direction over a 30 minutes interval. (I-K) Merged view from an E15.5 mouse embryo. Medial is towards the left and dorsal is upwards. Scale bars: 100 µm in A–C; 50 µm in D; 25 µm in E-J. For animated versions of the complete time-lapse sequence, see Movies 1 and 2 at http://dev.biologists.org/supplemental/

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