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Somatic cell mutations

As shown in the previous section, radiation effects on chromosomes remain in lymphocytes even many years after radiation exposure, and reflect effects on genetic material contained in the chromosomal DNA. Therefore, radiation effects on genes resulting in mutations in "somatic cells" (all the cells of the body other than the reproductive cells of the ovary or testes) were also expected to remain in the body. Following tests of several assay methods using blood cells, it was found that they did not record dose effects except for mutation in the glycophorin A (GPA) gene in red blood cells. The frequency of GPA mutant cells, however, varied extensively among ordinary people who were not exposed to radiation, which prevented us from evaluating individual radiation dose from the frequency. This observation is understandable if we assume that, while the mutation induction rate is generally on the order of 10-4 per Gy, the total number of longterm stem cells in bone marrow would not be sufficiently large, e.g., several 105. Thus, the GPA test is not considered useful for individual dose evaluation but collective dose of a group of people with similar exposures.
References about this subject
Kyoizumi S, Akiyama M, et al.: Somatic cell mutations at the glycophorin A locus in erythrocytes of atomic bomb survivors: Implications for radiation carcinogenesis. Radiation Research 1996; 146:43-52
Kyoizumi S, Kusunoki Y, et al.: Individual variation of somatic gene mutability in relation to cancer susceptibility: Prospective study on erythrocyte glycophorin A gene mutations of atomic bomb survivors. Cancer Research 2005; 65:5462-9
Hirai Y, Kusunoki Y, et al.: Mutant frequency at the HPRT locus in peripheral blood T-lymphocytes of atomic-bomb survivors. Mutation Research 1995; 329:183-6
Jensen RH, Langlois RG, Bigbee WL, et al.: Elevated frequency of glycophorin A mutations in erythrocytes from Chernobyl accident victims. Radiation Research 1995; 141:129-35