39. De La Cruz EM, Pollard TD (1996) Kinetics and thermodynamics of phalloidin binding to actin filaments from three divergent species. Biochemistry 35: 14054–14061. 40. Janson LW, Kolega J, Taylor DL (1991) Modulation of contraction by gelation/ solation in a reconstituted motile model. J Cell Biol 114: 1005–1015. 41. Kolega J, Janson LW, Taylor DL (1991) The role of solation-contraction coupling in regulating stress fiber dynamics in nonmuscle cells. J Cell Biol 114: 993–1003. 42. Mogilner A, Oster G (2003) Polymer motors: pushing out the front and pulling up the back. Curr Biol 13: R721–733. 43. Ishikawa R, Sakamoto T, Ando T, Higashi-Fujime S, Kohama K (2003) Polarized actin bundles formed by human fascin-1: their sliding and disassembly on myosin II and myosin V in vitro. J Neurochem 87: 676–685. 44. Murthy K, Wadsworth P (2005) Myosin-II-dependent localization and dynamics of F-actin during cytokinesis. Curr Biol 15: 724–731. 45. Guha M, Zhou M, Wang YL (2005) Cortical actin turnover during cytokinesis requires myosin II. Curr Biol 15: 732–736. 46. Zicha D, Dobbie IM, Holt MR, Monypenny J, Soong DY, et al. (2003) Rapid actin transport during cell protrusion. Science 300: 142–145. 47. Keren K, Yam PT, Kinkhabwala A, Mogilner A, Theriot JA (2009) Intracellular fluid flow in rapidly moving cells. Nat Cell Biol 11: 1219–1224. 48. Zebda N, Bernard O, Bailly M, Welti S, Lawrence DS, et al. (2000) Phosphorylation of ADF/cofilin abolishes EGF-induced actin nucleation at the leading edge and subsequent lamellipod extension. J Cell Biol 151: 1119–1128. 49. Lorenz M, DesMarais V, Macaluso F, Singer RH, Condeelis J (2004) Measurement of barbed ends, actin polymerization, and motility in live carcinoma cells after growth factor stimulation. Cell Motil Cytoskeleton 57: 207–217. Retrograde Flow Requires Actin Depolymerization 50. Endo M, Ohashi K, Mizuno K (2007) LIM kinase and slingshot are critical for neurite extension. J Biol Chem 282: 13692–13702. 51. Ahmed Z, Douglas MR, Read ML, Berry M, Logan A (2011) Citron kinase regulates axon growth through a pathway that converges on cofilin downstream of RhoA. Neurobiol Dis 41: 421–429. 52. Brown J, Bridgman PC (2003) Role of myosin II in axon outgrowth. J Histochem Cytochem 51: 421–428. 53. Vallee RB, Seale GE, Tsai JW (2009) Emerging roles for myosin II and cytoplasmic dynein in migrating neurons and growth cones. Trends Cell Biol 19: 347–355. 54. Heidemann SR, Lamoureux P, Buxbaum RE (1990) Growth cone behavior and production of traction force. J Cell Biol 111: 1949–1957. 55. Heidemann SR, Lamoureux P, Buxbaum RE (1995) Cytomechanics of axonal development. Cell Biochem Biophys 27: 135–155. 56. Svitkina TM, Verkhovsky AB, Borisy GG (1995) Improved procedures for electron microscopic visualization of the cytoskeleton of cultured cells. J Struct Biol 115: 290–303. 57. Thomann D, Dorn J, Sorger PK, Danuser G (2003) Automatic fluorescent tag localization II: Improvement in super-resolution by relative tracking. J Microsc 211: 230–248. 58. Thomann D, Rines DR, Sorger PK, Danuser G (2002) Automatic fluorescent tag detection in 3D with super-resolution: application to the analysis of chromosome movement. J Microsc 208: 49–64. 59. Vallotton P, Ponti A, Waterman-Storer CM, Salmon ED, Danuser G (2003) Recovery, visualization, and analysis of actin and tubulin polymer flow in live cells: a fluorescent speckle microscopy study. Biophys J 85: 1289–1306. PLoS ONE | www.plosone.org 15 February 2012 | Volume 7 | Issue 2 | e30959