A genetic method to quantitate induced chromosome breaks using a mouse/human monochromosomal hybrid cell line: identification of potential clastogenic agents.
A genetic assay to detect the clastogenic potential of environmental agents is described. This assay is based on the cloning efficiency of cells in a medium that permits the growth of cells following loss of a specific chromosome segment resulting from a chromosome break. For this purpose a mouse/human hybrid cell line R12-2 containing a dominantly marked chromosome 5 as the only human component has been constructed. This chromosome 5 carries two dominant selectable markers, Ecogpt and the gene for sensitivity to diphtheria toxin (DTs). Ecogpt codes for the enzyme xanthine-guanine phosphoribosyltransferase which allows selection for cells containing chromosome 5 or the segment carrying Ecogpt as judged by growth in medium supplemented with mycophenolic acid and xanthine (MX medium). Human cells are sensitive to 10(-13) M DT, whereas mouse cells are resistant to 10(-7) M DT and DTs is expressed as a dominant phenotype. Cultivation of R12-2 cells in the medium containing 10(-13) M DT permit the selection of cells that have lost chromosome 5 or the segment carrying DTs. The presence of two selectable markers on the same chromosome permits the identification and quantitation of cells for the selective loss of a specific chromosome segment. Growth of R12-2 cells in MX medium containing 10(-13) M DT therefore, provides a convenient method to determine the frequency of clastogen induced breaks in chromosome 5. The utility of the proposed genetic assay is assessed using X-irradiation as a model clastogen. Our results clearly show a dose related response that is consistent with cytogenetic observations.
Gudi
R
R
Department of Microbiology and Molecular Genetics, New Jersey Medical School, Newark, NJ 07103.
Sandhu
S S
SS
Athwal
R S
RS
D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D002869:Chromosome Aberrations; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D006822:Hybrid Cells; D051379:Mice; D009152:Mutagenicity Tests / Q000379:methods*; D009153:Mutagens; D012641:Selection, Genetic; D014965:X-Rays
D009153:Mutagens