Analysis of chromosome loss and chromosome segregation in cytokinesis-blocked human lymphocytes: non-disjunction is the prevalent mistake in chromosome segregation produced by low dose exposure to ionizing radiation

Abstract

The aim of the present work was to examine in human lymphocytes, firstly, whether in vitro gamma-rays as compared with X-rays also induce chromatid malsegregation and at higher frequencies than chromosome loss and, secondly, whether the cytokinesis-blocked micronucleus assay combined with fluorescence in situ hybridization might be useful for the biomonitoring of individuals exposed to ionizing radiation. After irradiation, the relative frequencies of centromere-positive micronuclei decreased from 39.2% at 0.1 Gy to 21. 63% at higher doses. There was no statistically significant increase in MNCen+ frequencies at doses below 1 Gy (0.1, 0.25 and 0.5 Gy), but a statistically significant increase at 1 (P < 0.05) and 2 Gy (P < 0.001) was observed for all the donors. No significant differences in baseline and gamma-ray-induced non-disjunction frequencies for chromosomes 1 (P = 0.9) and 17 (P = 0.8) between individuals were detected. For radiation-induced non-disjunction, lower doses (0.1, 0. 25 and 0.5 Gy) of gamma-rays did not induce a statistically significant increase in non-disjunction frequencies whereas 1 Gy and above clearly induced a statistically significant increase in the total non-disjunction frequencies for all the donors (P < 0.05 at 1 Gy and P < 0.0001 at 2 Gy). The aneugenic effect of radiation is less clearly dose dependent at the lower doses, suggesting an apparent threshold below which no change could be demonstrated. At high radiation doses the major mechanism for gamma-ray-induced aneuploidy is related to chromosome loss through non-disjunction, as has been demonstrated using X-rays, and not through the formation of micronuclei.

In vitro micronucleus assay scored by flow cytometry provides a comprehensive evaluation of cytogenetic damage and cytotoxicity

“…Finally, the cytotoxicants EtOH and STS did not cause dose-related increases in the frequency of hypodiploid nuclei, whereas each of the four genotoxic agents did. The ability of ETOPO, radiation, and VB to cause nondisjunction has been well documented [31][32][33]. While we had not anticipated MMS to exhibit aneuploid phenomena, there are reports of this and other alkylating agents having such effects [34][35].…”

Detection of Premature Segregation of Centromeres in Persons Exposed to Ionizing Radiation

“…Touil et al (2000) showed that the aneugenic effect of radiation is less clearly dose dependent at lower doses, suggesting an apparent threshold below which no change could be demonstrated. At high radiation doses the major mechanism for ␥-ray-induced aneuploidy is related to chromosome loss through non-disjunction, as has been demonstrated using x rays (Touil et al 2000).…”

“…IT IS well known that changes of genetic material in human lymphocytes can be induced by ionizing radiation (IR) and the development of unstable and stable structural chromosome aberrations (CAs) may be observed as the consequence of a major clastogenic effect (Rozgaj et al 1999(Rozgaj et al , 2002Kosuba et al 1995;Lamberti et al 1989;Milkovic-Kraus et al 1992;Schmid et al 1989;Lloyd et al 1988;Pincheira et al 1999;Bonassi et al 1997;Bauchinger 1995;Bigatti et al 1988;Maffei et al 2002;Garaj-Vrhovac et al 2006;Cardoso et al 2001;Touil et al 2000). Besides its clastogenic effect, IR can also induce aneuploidy (aneugenic activity) as demonstrated by using fluorescence in situ hybridization (FISH) in both mouse (Boei and Natarajan 1995) and human populations accidentally exposed to IR (Natarajan et al 1991(Natarajan et al , 1994(Natarajan et al , 1996.…”

Interphase cytogenetics in estimation of genomic mutations in somatic cells

“…This effect is oxygen-dependent and is inhibited in anaerobic conditions [32]. Apparently, a similar mechanism can induce AE at lower irradiation doses [33]. A significant role in the normal spindle functioning is played by centrioles, which can be damaged by some chemical compounds.…”