Fig. 4. Altered dynamics of leading and trailing edges of migrating neurons in 3 integrin-deficient cortex. Time-lapse imaging of GFP-labeled neurons in the wild-type cortex indicates active extensions and retractions of the leading (arrow) and trailing processes (arrowhead) of migrating neurons (A). By contrast, 3 integrin mutant neurons displayed reduced protrusive activity in their leading and trailing processes (B). Quantification of extensions and retractions (activity index) indicates a 28% reduction in 3 integrin mutant cells. Cells shown are from the intermediate zone of E16 cortex. Time elapsed since the beginning of observations are indicated in minutes. Number of cells analyzed: n=24, wild type; n=28, mutant. Data shown are mean±s.e.m.; asterisk (C), significant when compared with controls at P<0.01 (Student's t-test). Scale bar: 25 µm. (Also see Movies 3, 4 in the supplementary material.)