Abstract
By using two-dimensional DNA electrophoresis, we have been studying mutations in the F1 mice derived from X-irradiated spermatogonia cells in order to estimate the genetic risk of radiation. We previously reported the results of comparative genomic hybridization study with high-density microarray (HD-array CGH) on five deletion mutations identified in F1 mice derived from BALB/c male mice. Recently, we have determined the sizes and base-sequences of seven deletion mutations identified in F1 mice derived from B6C3 male mice. We have prepared custom arrays by selecting specific oligo-probes at every 1-5 kb intervals expanding approximately 10 Mb surrounding each NotI site involved in deletions. The array-CGH analyses revealed that among the six deletions in male alleles, the sizes of the five deletions in the exposed group were: 13 Mb, 10.7 Mb, 4.7 Mb, and 1.9 Mb. The sizes of the deletions in one control male allele and one control female allele were 2.3 Mb and 2.5 Mb respectively. The sequences around the break-points of five deletions in the exposed group and one deletion in the female allele contained no homologous sequences, this implies that these deletions were originated from non-homologous end joining. On the other hand, the spontaneous deletion in one control male allele contained highly homologous (96%) sequence spanning 2 kb at both ends of the break-points and this was thought to be derived from homologous recombination and subsequent deletion.
