The role of the vimentin intermediate filaments in rat 3Y1 cells elucidated by immunoelectron microscopy and computer-graphic reconstruction.

The three-dimensional arrangement of vimentin intermediate filaments (IF) was studied in 3Y1, rat fibroblastic cell line, to elucidate its biological role in the cell. While actin filaments were observed exclusively in the superficial part of the cell, vimentin IF were found to be abundantly present in the inside of the cell where microtubules were occasionally discovered. By whole-mount immunoelectron microscopy and computer-graphic reconstruction of serial thin sections, it was observed in more detail that vimentin IF are located very close to the nucleus, endoplasmic reticulum, and mitochondria. Vimentin IF were observed to be attached to these organelles laterally or terminally. Thus, we can reasonably assume that vimentin IF are major cytoskeletal structures deep inside the cell and that they play an important role in supporting the location of the organelles. This is the first report which has visualized the three-dimensional relationship between vimentin IF and the organelles of the cell.