Figure 3.
EphrinA3-Fc induces filopodial outgrowth and elongation.
A
,
B
, Time-lapse image sequences of filopodia in two GFP-transfected astrocytes treated with the ephrinA3-Fc construct. Arrows indicate extensive elongation of filopodia (
A
) and extension of new filopodia at two sites in another cell (
B
). Time of image capture indicated in minutes relative to the addition of ephrinA3-Fc (7.6 μg/ml). Scale bar, 4 μm.
C
, Time-lapse image sequences of filopodia in a GFP-transfected astrocyte treated with the ephrinB1-Fc construct. Time of image capture is indicated in minutes relative to the addition of ephrinB1-Fc (7.6 μg/ml). Scale bar, 4 μm. No changes in filopodia were apparent.
D
, Plot of the time course of the change in total process length, normalized to the mean length during the baseline period, after addition of 7.6 μg/ml ephrinA3-Fc (black; n = 6 cells) or control saline as a vehicle control (gray; n = 6 cells). Each line represents the values for one cell, normalized to its own mean pre-ephrin value. Significant difference is indicated at times >15 min after application of ephrinA3-Fc (p < 0.05; Friedman's ANOVA).
E
, Summary of ephrinA3-Fc (n = 6 cells) and ephrinB1-Fc (n = 4 cells), and ephrinB2-Fc (n = 10 cells) effects on the number of filopodial per 30 μm of astrocytic process, the length of pre-existing filopodia, the total process length, and the average length of astrocytic filopodia. Each cell was normalized to its own mean value during the 30 min baseline period. **p < 0.01; *p < 0.05; ANOVA. Only ephrinA3-Fc promoted filopodial outgrowth and extension.