Effect of DMSO on radiation-induced chromosome aberrations analysed by FISH

Abstract

The purpose of the present work was to determine if the described reduction in the frequency of radiation-induced chromosome aberrations by DMSO is homogeneous within different human chromosomes. Blood samples were irradiated with 4 Gy of X-rays in absence and presence of 0.5 M DMSO. FISH painting was carried out independently for human chromosomes 1, 2, 3, 4, 7, 11 and 12. The observed frequencies of apparently simple translocations and dicentrics for all these chromosomes, showed a homogeneous reduction when the irradiation was done in the presence of DMSO. Moreover, a better fit between the observed and expected frequencies was obtained when (DNA content)^2/3 was used to calculate the expected frequencies, instead of just the DNA content. This result supports the idea that for exchange type aberrations, a better adjustment is obtained when the surface area of spherical chromosome territories is considered.

Chromosome breakpoint distribution of damage induced in peripheral blood lymphocytes by densely ionizing radiation

“…A number of known fragile sites in human cells have been identified on both chromosome 2 and chromosome 11, but it is unclear whether these sites confer any more sensitivity for breakage than those identified on similarly sized chromosomes (e.g., chromosome 1 or chromosome 12). A search of the literature reveals no evidence for the over-involvement of chromosome 2 in radiation-induced breaks, only an underrepresentation of chromosome 2 has been reported (Knehr et al 1996, Braselmann et al 2003, Cigarran et al 2004. Further, there is no evidence for the over-involvement of either 11q or 13q in radiationinduced incomplete exchanges similar to those that were detected in this study.…”

“…Following from this, repetitive non-transcribed sequences such as centromeric DNA, are not thought to arrange on the periphery of chromosome territories, possibly accounting for the observation that inter-changes in these regions are not over-represented according to surface area predictions (Mahy et al 2002) (Table V). Overall, a statistical model that predicts break distribution based on the surface area of a chromosome territory is favoured (Wu et al 2001, Cigarran et al 2004. How 'convoluted' this surface area is and therefore what 'depth' or volume should also be considered for chromosome break distribution models (i.e., maximum migration distance for repair), remains to be established.…”

“…Further, there is no evidence for the over-involvement of either 11q or 13q in radiationinduced incomplete exchanges similar to those that were detected in this study. Interestingly though, chromosome 11 has recently been reported to be involved in more X-ray-induced breaks relative to its length (Cigarran et al 2004). Chromosome 11 is gene-rich and involved in a vast array of different translocations recurrent in various leukaemia's, including secondary (radiation) therapy-related leukaemia's, while deletions of 11q and 13q are common in lymphoid neoplasia's (Dessen & Huret 2002).…”