Chromosomal Aberrations in Large Japanese Field Mice (Apodemus speciosus) Captured near Fukushima Dai-ichi Nuclear Power Plant

Abstract

Since the Fukushima Dai-ichi Nuclear Power Plant accident, radiation effects on nonhuman biota in the contaminated areas have been a major concern. Here, we analyzed the frequencies of chromosomal aberrations (translocations and dicentrics) in the splenic lymphocytes of large Japanese field mice (Apodemus speciosus) inhabiting Fukushima Prefecture. A. speciosus chromosomes 1, 2, and 5 were flow-sorted in order to develop A. speciosus chromosome-specific painting probes, and FISH (fluorescence in situ hybridization) was performed using these painting probes to detect the translocations and dicentrics. The average frequency of the translocations and dicentrics per cell in the heavily contaminated area was significantly higher than the frequencies in the case of the noncontaminated control area and the slightly and moderately contaminated areas, and this aberration frequency in individual mice tended to roughly increase with the estimated dose rates and accumulated doses. In all four sampling areas, the proportion of aberrations occurring in chromosome 2 was approximately >3 times higher than that in chromosomes 1 and 5, which suggests that A. speciosus chromosome 2 harbors a fragile site that is highly sensitive to chromosome breaks induced by cellular stress such as DNA replication. The elevated frequency of chromosomal aberrations in A. speciosus potentially resulting from the presence of a fragile site in chromosome 2 might make it challenging to observe the mild effect of chronic low-dose-rate irradiation on the induction of chromosomal aberrations in A. speciosus inhabiting the contaminated areas of Fukushima.

Estimation of Dose Rate for the Large Japanese Field Mouse (Apodemus speciosus) Distributed in the “Difficult-to-Return Zone” in Fukushima Prefecture

“…Thus, various indexes should be applied to evaluate the exposure effects on the species. In fact, chromosomal aberrations in the splenic lymphocytes of field mice captured near FNPP were reported [20]. Frequencies of translocations and dicentrics per cell (%) of the field mice distribution in "the heavily contaminated area (ambient dose equivalent rate = 80.0 μSv/h)" were significantly higher than that of the control area (ambient dose rate was 0.1 μSv/h), slightly contaminated area (ambient dose equivalent rate ranging from 0.3 to 0.4 μSv/h), and moderately contaminated area (ambient dose equivalent rate ranging from 7.5 to 30.7 μSv/h).…”

Developmental and hemocytological effects of ingesting Fukushima’s radiocesium on the cabbage white butterfly Pieris rapae

“…Fukumoto and colleagues have recently reported changes in gene expression in the small intestine of pigs 34 , DNA damage in bovine lymphocytes 35 , and enhanced spermatogenesis in large Japanese field mice 36 . Another independent group has also reported chromosomal aberrations in large Japanese field mice 37 . In contrast, some studies have reported no detectable effects.…”

Analysis of Radioactive Elements in Testes of Large Japanese Field Mice Using an Electron Probe Micro-Analyser after the Fukushima Accident

“…Okano et al [17] reported that, although the concentrations of 134 Cs and 137 Cs in wild mice from Fukushima exceeded 4000 Bq/kg, there were no significant differences in the frequencies of apoptotic cells or morphologically abnormal sperm when compared with wild mice from the non-contaminated control area. However, Kawagoshi et al [18] reported that the average frequencies of chromosomal aberrations in splenic lymphocytes of animals living in the heavily contaminated (approximately 3 mGy/day) area of Fukushima were higher than those of animals from the non-contaminated, slightly contaminated (approximately 0.03 mGy/day), and moderately contaminated (approximately 1 mGy/day) areas. Moreover, the aberration frequency in individual wild mice tended to increase with the estimated dose rates and accumulated doses.…”