Dynamics of GFP-I-BAR and mCherry- actin in co-expressing cells.

<p>(A,B) During protrusion (A) and retraction (B) dynamics of I-BAR (green) and actin (red) are indistinguishable. (C) Actin in a protruding filopodium transiently lags behind the I-BAR, but eventually catches up. (D) Withdrawal of actin produces stationary or retracting actin-free “filopodia”. (E) Actin undergoes polymerization (frames 1–3) and depolymerization (frames 4–6) within a stationary filopodium. (F) Random actin assembly in a stationary actin-free filopodium. The shown categories of filopodia dynamics represent following fractions of I-BAR-induced filopodia: A, 29.1%; B, 40.0%; C, 2.4%; D, 12.1%; E, 2.2%; F, 2.9%, and remaining 11.3% of filopodia showed no dynamics within the period of observation. N = 553 filopodia from 15 cells.