Accurate detection of true incomplete exchanges in human lymphocytes exposed to neutron radiation using chromosome painting in combination with a telomeric PNA probe.
OBJECTIVE
To determine the frequency of true incomplete chromosome exchanges in human lymphocytes after exposure to high-LET neutrons using chromosome painting in combination with centromeric and telomeric probes in one FISH assay.


METHODS
Human lymphocytes were exposed in vitro to 1 MeV neutrons at a dose of 1 Gy (dose-rate 0.1Gy x min(-1)). Chromosome aberrations were analysed in the first mitosis after irradiation using a FISH technique that combined whole chromosome-specific DNA probes (for chromosomes 4 and 8), human pan-centromeric DNA and telomeric PNA probes.


RESULTS
The frequency of true incomplete exchanges induced by 1 MeV neutron irradiation was <5% in chromosomes 4 and 8. Comparison of the frequency of true incompleteness obtained in the present experiment with a previous study that used 4 Gy X-rays showed no striking differences between X-rays and neutrons in incomplete exchange patterns but differences in the spectrum of induced aberrations were detected. Simple exchanges were more frequent with X-rays, whereas complex types were significantly commoner following neutron irradiation (41 and 23% respectively). Differences were also found for complex rearrangements: both the number of these and their complexity increased after neutron-irradiation.


CONCLUSIONS
The combination of chromosome painting and the detection of centromeres and telomeres enable unequivocal discrimination between incomplete and complete exchanges. The application of telomeric probes to analyse chromosome aberrations has demonstrated that true incompleteness is a rare event (approximately 5%) following exposure to high-(neutron) as well as to low-(X-rays) LET radiation.
Fomina
J
J
MGC Department of Radiation Genetics and Chemical Mutagenesis, Leiden University Medical Centre, Wassenaareseweg 72, 2333 AL Leiden, The Netherlands.
Darroudi
F
F
Natarajan
A T
AT
D002478:Cells, Cultured; D002869:Chromosome Aberrations; D002872:Chromosome Deletion; D020223:Chromosome Painting / Q000379:methods*; D002875:Chromosomes / Q000528:radiation effects* / Q000648:ultrastructure; D002894:Chromosomes, Human, Pair 4 / Q000528:radiation effects; D002898:Chromosomes, Human, Pair 8 / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods; D008214:Lymphocytes / Q000528:radiation effects* / Q000648:ultrastructure*; D009502:Neutrons; D012854:Sister Chromatid Exchange; D014178:Translocation, Genetic; D014965:X-Rays