Figure 3. EGFP-SMN granules exhibit rapid, bidirectional movements in processes that are dependent on either microtubules or microfilaments.

A, Small (S) granules frequently exhibited directed movements, both anterograde and retrograde (long white arrows denote trajectories of several small granules). Granules often moved beyond branch points into secondary neurites (see video 1). Large (L) granules often displayed either oscillatory or bidirectional movements over short distances (short black arrows).

B-E, Histograms showing frame by frame analysis of granule velocities. Anterograde movements are positive, and retrograde movements are negative.

B, Example of an anterograde trajectory of a small granule.

C, Example of small granule with a predominantly retrograde trajectory.

D, Example of granule showing bidirectional movements.

E, Example of a larger granule that showed predominantly nondirected, oscillatory movements.

F, Directed movements of small granules were dependent on microtubules and microfilaments.

G, Large granules showing nondirected movements, both oscillatory and bidirectional displacements over short distances, were dependent on actin filaments. *p < 0.01 when compared with untreated control.