Cytogenetic analysis of early and delayed chromosome aberrations

Cytogenetic analysis of early and delayed chromosome aberrations in Chinese hamster cells after 60 Co γ-irradiation D. V. Petrova 1, P. Bláha 1, 2, Y. V. Bogdanova 1, R. D. Govorun 1, N. A. Koshlan 1, I. V. Koshlan 1 1 Laboratory 2 of Radiation Biology, Joint Institute for Nuclear Research, Dubna, Russia Czech Technical University in Prague, Czech Republic

Genomic instability Genomic stability is one of the most significant evolutionary factors of normal cell functioning and the functioning of the organism in general. Various genetical, chromosomal and genomic mutations lead to its damages. It is known that ionizing radiation mutagenically affect living organisms, which can result in genomic instability: some of the cells that survived radiation exposure tend to form generations with an increased level of genomic damages. This effect is observed in all kinds of eukaryote exposed to ionizing radiation both in vitro and in vivo. At the moment, the mechanisms of genomic instability are remained study not enough.

Materials and methods Сell culture Unit Type of radiation Chinese hamster cells-V 79 “Rokus-M” γ-irradiation 60 Co Energy, Dose, Me. V Gy 1, 33 2 and 5 Cultivation time 3 hours to 42 days Scheme of the experiment 2 and 5 Gy Cell irradiation Cultivation Cytogenetic assay

Mitotic index, % Mitotic activity of γ-irradiated cells 12 11 10 9 8 7 6 5 4 3 2 1 0 2 Gy 5 Gy Control 0 3 6 9 12 15 18 21 24 27 Recultivation time, day 30 33 36 39 42

Aberrant cells, % Kinetics of aberrant cells and total number of chromosomal 70 aberration induced by γ-irradiation 60 2 Gy 5 Gy Control 50 40 30 20 10 Aberrations, per 100 cells 0 0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 120 110 100 90 80 70 60 50 40 30 20 10 0 Recultivation time, day

Ratio of chromosomal aberration types in different times after γ-irradiation 100 Type of aberrations, % 90 Chromatid aberations Chromosome aberrations Control 80 70 60 50 40 30 20 10 0 0, 1 0, 5 1 2 3 6 9 12 15 18 21 24 27 30 33 36 39 42 Recultivation time, days Chromatide aberration: сhromatide fragment (1) Chromosome aberration: chromosom fragments (2) and dicentric (3).

Ratio of acentric and centric aberration in different times after γ-irradiation 100 Type of aberrations, % 90 80 acentric aberrations centric aberration Control 70 60 50 40 30 20 10 0 0, 1 0, 5 1 2 3 6 9 12 15 18 21 24 27 30 33 36 39 42 Recultivation time, days Acentric aberrations: 2 -Chromosomebreak; 3 - Isodeletion; Сentric aberrations 1 -Dicentric 4 -Centric ring

Сonclusions � Mitotic activity of cells recovers on day 6 after 2 Gy 60 Co γ-irradiation � Mitotic activity of cells decreases for the whole cultivation period after 5 Gy 60 Co γ-irradiation � Emergence frequency of cells with chromosomal aberrations and the total number of chromosomal aberrations recovers on day 6 after γ-irradiation 60 Co. � Proportion of chromosomal aberrations in the total number of aberrations decreases on day 39 for all γ-irradiation 60 Co doses. � Proportion of dicentrics and rings in the total number of aberrations decreases on day 39 for all γ-irradiation 60 Co doses.

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