Fig. 2. Peripherin is present in growth cones. A living PC12 cell expressing GFP-peripherin during the early stages of neurite outgrowth. This cell was observed at 1-2 hours after plating in DM. Numerous GFP-peripherin particles and squiggles can be seen within the growth cone. A-C represents a single image from a time-lapse series. The image was captured by both phase-contrast and fluorescence microscopy to show the relationships between particles, squiggles, growth cones and filopodial extensions. The arrowheads indicate the positions of peripherin particles, some of which can also be detected with phase contrast. The particles and squiggles seen in the growth cone region are motile (see Movie 1 at jcs.biologists.org/supplemental). Bar, 5 µm in A-C. PC12 cells were plated in DM for 2 hours and then processed for platinum-replica immunogold TEM as described in Materials and Methods using rabbit anti-peripherin and gold-conjugated secondary antibodies. Ultrastructural observations (D-E) demonstrate that peripherin particles are present within the actin-rich growth cones and filopodia. In more proximal regions of growth cones, peripherin particles (indicated by clusters of 18 nm gold), as well as peripherin squiggles (most probably represented by linear arrays of gold; see arrows), are readily observed (F,G). E is a higher magnification view of area in the red box in D; F is a higher magnification view of the area in the green box in D; and G is a higher magnification view of the area in the blue box in F. Bar, 100 nm in D,E,G; Bar, 500 nm in F.