Chromosome aberrations in cultured cells deprived of single essential amino acids

Abstract

When cultured Chinese hamster cells (pseudodiploid line C14FAF28) were exposed to growth medium deficient for any single essential amino acid, the cell cycle was inhibited during S-phase; incorporation of 3H-thymidine into nuclear DNA declined markedly. After restoration of an adequate concentration of the omitted amino acid, the division cycle was completed. The metaphases of this division contained a high frequency of chromosome abnormalities, including chromosome breaks and exchanges, a major class of chromatid breaks and exchanges, and endoreduplication. A high frequency of breakage and exchange was associated with severe fragmentation, superficially resembling virus-induced pulverization, but distinguishable from the virus-induced phenomenon by non-labelling after terminal exposure to 3H-thymidine. The yield of aberrations increased progressively as a function of the time during which the cells were held in the inhibited state. When cells were cultured at a growth-limiting concentration of arginine, aberration-containing metaphases were revealed after addition of supplementary arginine. It is proposed that interruption of DNA replication, and consequent chromosome aberration, are the result of the inhibition of protein synthesis. Chromosome aberrations arising in this way may play a role in apparently spontaneous karyotypic remodeling in serially propagated cultured cell lines and progressing neoplasms. Cycling of cultured cells through amino acid deprivation is proposed as a technique for deliberately increasing the rate of chromosome alteration in genetic experiments.