Directional Analysis of Process Extension by Ras-Transformed Fibroblasts
Reynolds, Wm. Ryan
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Ras, a small G-protein, alters the activity of a cell's skeleton. Oncogenic, or cancer-causing, Ras proteins differ from non-oncogenic Ras proteins by a single amino acid substitution. The introduction of oncogenic Ras proteins into fibroblasts leads to changes in cell shape and orientation by stimulating membrane ruffling, and is thought to increase cell motility. Previous researchers have observed the formation of elongate processes by ras-transformed fibroblasts in two-dimensional (conventional) culture systems. The location of processes behind motile cells has suggested they were "tails." The purpose of this study was to determine the orientation of processes in relationship to the direction of cellular migration. Images captured via a monochromic CCD camera (Panasonic WV -BP31 0) were analyzed using NIH Image and Microsoft Excel. Results show ras-transformed fibroblasts tend to extend processes in the direction of cellular migration more than non-transformed fibroblasts. Thus, if Ras proteins increase cell motility and processes aid migration, then the ras-transformed fibroblasts have increased migration rates due to process orientation in the forward direction. Most studies of fibroblasts have been in two dimensions and thus have not been a true representation of the events in vivo. This study was conducted in three dimensions and therefore, process extension in the direction of cellular migration provides a mechanical model for events in vivo. It is possible that normal movement of fibroblasts during wound healing and tissue maintenance requires the establishment of a polarized cell shape resulting from process extension.