Induction Of Chromosome Condensation Research Articles

Technical Report A simple method for simultaneous interphase-metaphase chromosome analysis in biodosimetry

Purpose: To find a simple protocol for measuring chromosome damage both in G1 and in G2/M chromosomes, to overcome problems related to low mitotic index and cell-cycle alterations in biodosimetric tests. Materials and methods: The protocol is based on the use of calyculin A to induce premature chromosome condensation in human peripheral blood lymphocytes in different phases of the cell cycle. Chromosome exchanges were measured by fluorescence in situ hybridization (chromosomes 2 and 4) in lymphocytes from four different donors. Cells were exposed to 4 Gy X-rays and the results were compared to aberrations in M phase (colcemid block) and G0 (premature chromosome condensation induced by fusion to mitotic hamster cells). Results: Treatment with calyculin A produced a high fraction of chromosome condensation in different phases of the cell cycle. Cells in G1 and G2/M could be scored simultaneously for biodosimetry by chromosome painting. The condensation index was 5-20 times higher than the mitotic index (colcemid alone). The calyculin A treatment did not produce a significant increase in the background of chromosomal aberrations or modify the yield ofchromosomal aberrations scored after exposure to X-rays. Conclusions: Induction of chromosome condensation by calyculin A is a powerful biodosimetric tool, which provides a high number of spreads for analysis and overcomes problems related to poor in vitro growth or cell-cycle alterations.

The induction of chromosome condensation in tsBN2, a temperature-sensitive mutant of BHK21, inhibited by the calmodulin antagonist, W-7

The induction of premature chromosome condensation (PCC) in tsBN2 cells, a temperature-sensitive ( ts) mutant of BHK21/13 which shows PCC at the non-permissive temperature, was almost completely inhibited by 40 μM W-7, an antagonist of calmodulin. The mitotic phosphorylation of histone H1 and H3 was also inhibited by W-7, W-5, a chlorine-deficient analogue of W-7 and which interacts weakly with calmodulin, did not inhibit the induction of PCC, even at a dose of 80 μM. The content of calmodulin in tsBN2 cells was increased by a temperature shift to 40.5°C. All these results suggested that calmodulin is required for the chromosome condensation.

Control of chromosome behavior in amphibian oocytes. II. The effect of inhibitors of RNA and protein synthesis on the induction of chromosome condensation in transplanted brain nuclei by oocyte cytoplasm.

We studied the effects of actinomycin D, alpha-amanitin, puromycin, and cycloheximide on the cytoplasmic activity of maturing Rana pipiens oocytes that induces chromosome condensation in transplanted brain nuclei. Treatment of oocytes with each inhibitor suppressed the chromosome condensation induced by metaphase oocytes to varying degrees depending upon the dose of inhibitor, despite the fact that untreated metaphase I oocytes already possessed chromosome condensation activity (CCA). Treatment of brain nuclei before injection completely suppressed condensation at all doses used. Chromosome condensation induced by metaphase II oocyte cytoplasm, however, was insensitive to all the inhibitors, even when the brain nuclei were pretreated. Oocytes treated with alpha-amanitin throughout maturation induced chromosome condensation when tested at metaphase II. Removal of the oocyte chromosomes after the germinal vesicle (GV) broke down did not prevent the development of CCA, whereas removal of the entire GV before initiation of maturation deprived oocytes of CCA. The results suggest that metaphase I oocyte cytoplasm stimulates synthesis of brain nuclear RNAs that are translated into proteins necessary for chromosome condensation, whereas metaphase II oocytes possess all the factors for chromosome condensation. In both cases, GV nucleoplasm appears indispensable for the development of CCA, whereas immediate activity of the oocyte genome is not required.