Irreversibility of Major Chromosome Changes in a Mycoplasma-Modified Line of FL Human Amnion Cells. ∗

Abstract

Summary

A line of mycoplasma-infected FL human amnion cells (F 138) has shown further chromosome changes from the first to the third year of cultivation, with mycoplasma present. Additional reduction in chromosome numbers to a present range between 61 and 66, with predominant numbers of 62 to 64 chromosomes per cell, an increase in some chromosome aberrations, in particular the frequency of dicentrics, and further increase in the number of metaphase plates with new chromosome varieties, most notably the large teleocentric chromosome, have occurred during this period. After elimination of mycoplasma from the cell line (F 138c1) with Aureomycin by a special method which is described, the chromosome numbers did not revert to higher numbers, and the large teleocentric chromosome persisted in practically all cells during one year of cultivation (present time). Many chromosome aberrations decreased in frequency to the level observed in uninfected (control) FL cells. The irreversible changes, which were correlated with alterations of in vitro and in vivo behavior of the cells, are referred to as reverse transformation or retransformation.