The Japan Radiation Research Society Annual Meeting Abstracts
The 51st Annual Meeting of The Japan Radiation Research Society
Session ID : AP-25
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DNA damages / DNA Repair
Chromosome aberrations do not persist in the lymphocytes or bone marrow cells of mice irradiated in utero or soon after birth: Reevaluation of the findings by multi-color FISH
*Mimako NAKANOYoshiaki KODAMAKazuo OHTAKINori NAKAMURA
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CONFERENCE PROCEEDINGS FREE ACCESS

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Abstract
We have previously found that hematopoietic cells of mice irradiated in utero or soon after birth showed surprisingly low translocation frequencies when mice were examined at age of 20 weeks. The results were based on 2-color FISH for detection of translocations involving only chromosomes 1 and 3. To exclude a possibility that the bone marrow cell pool is derived from a very small number of fetal stem cells after irradiation, and hence such partial FISH painting of the genome might have overlooked the true figure including clonal translocations, we proceeded to multi-color FISH (M-FISH) to confirm that the finding also holds true for the entire genome. Mice were irradiated at fetal stage (15.5th day p.c.) or 4-days of age with 2 Gy of X-rays, and metaphases were obtained from spleen T lymphocytes at the age of 18 - 21 weeks. M-FISH was applied to paint all chromosomes (#1 – #19, X and Y) in the genome for detection of translocations. Mice irradiated at fetal or neonatal stage showed lower translocation frequencies than that of their mother (0 - 9% vs. 25%). Clonal translocations were observed in mice irradiated as fetuses or neonate, but not in their mother carrying even much more translocations. The correlation between the genomic translocation frequencies measured by the M-FISH and 2-color FISH for the same animals showed good concordance. M-FISH analysis validated our previous findings based on 2-color FISH. We speculated that fetuses or neonates were capable of quickly eliminating cells carrying radiation-induced chromosomal damage, but survived hematopoietic stem cells or their progenitor cells, which happened to hold translocations, could clonally propagate in vivo during rescue period after irradiation.
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© 2008 The Japan Radiation Research Society
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