31 Multicolor FISH Techniques for the Detection of Inter- and Intrachromosomal Rearrangements
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and tumor cytogenetics for a quantification of radiation-induced chromosome aberrations and the detection of chromosomal rearrangements.
Proximity effects for the formation of chromosome aberrations are an
interesting topic in radiation cytogenetics. It has been shown for asymmetrical and, thus, unstable aberrations that the yield ratios for radiationinduced intra- and interchromosomal exchanges are linear energy transfer
(LET)-dependent. High LET radiation causes higher yields for intra-arm
intrachanges than low LET radiation possibly due to different proximity
mechanisms in the formation of aberration. To investigate potential bioindicators for high LET radiation also for stable aberration types, symmetrical translocations as well as paracentric inversions must be quantified
by FISH-painting approaches. A reliable and quick approach for scoring
inversions is the application of Rx-FISH, a multicolor technique using gibbon DNA that hybridizes to noncontiguous discrete sections on human
chromosomes and results in a distinct color banding pattern. Inversions
on human chromosomes are visible as irregular banding patterns.
For a more precise delineation of chromosomal alterations at the gene
level, the more sophisticated 'chromosomal rainbow (CR)' technique may
be used. This is of particular interest in the field of tumor cytogenetics
where small gene rearrangements might provide tumor-specific markers
enabling the rapid detection of tumor cells. The method of CR FISH, developed at the Lawrence Berkeley National Laboratory, is based on the
simultaneous hybridization of probes that bind on average every 8-10
megabase pairs (Mbp). Probe generation was facilitated by resources generated in the course of the International Human Genome Project such as
large insert DNA libraries and detailed physical maps. CR probes sets are
prepared and applied for one chromosome type at a time. Labeled with
distinct alternating reporter molecules, the probes are distributed more or
less evenly all along the target chromosome type to allow the detection of
intra- and interchromosomal rearrangements with a resolution of a few
Mbp. A rearrangement is indicated when the normal pattern of 'rainbow'
colors along the hybridized chromosome appears changed. CRs are also a
powerful tool to be used in combination with Comparative Genomic Hybridization (CGH) and Spectral Karyotyping (SKY). A single CR hybridization experiment can provide detailed information about the nature of a
copy number change detected by CGH or the approximate position of
chromosomal breakpoints.
409
and tumor cytogenetics for a quantification of radiation-induced chromosome aberrations and the detection of chromosomal rearrangements.
Proximity effects for the formation of chromosome aberrations are an
interesting topic in radiation cytogenetics. It has been shown for asymmetrical and, thus, unstable aberrations that the yield ratios for radiationinduced intra- and interchromosomal exchanges are linear energy transfer
(LET)-dependent. High LET radiation causes higher yields for intra-arm
intrachanges than low LET radiation possibly due to different proximity
mechanisms in the formation of aberration. To investigate potential bioindicators for high LET radiation also for stable aberration types, symmetrical translocations as well as paracentric inversions must be quantified
by FISH-painting approaches. A reliable and quick approach for scoring
inversions is the application of Rx-FISH, a multicolor technique using gibbon DNA that hybridizes to noncontiguous discrete sections on human
chromosomes and results in a distinct color banding pattern. Inversions
on human chromosomes are visible as irregular banding patterns.
For a more precise delineation of chromosomal alterations at the gene
level, the more sophisticated 'chromosomal rainbow (CR)' technique may
be used. This is of particular interest in the field of tumor cytogenetics
where small gene rearrangements might provide tumor-specific markers
enabling the rapid detection of tumor cells. The method of CR FISH, developed at the Lawrence Berkeley National Laboratory, is based on the
simultaneous hybridization of probes that bind on average every 8-10
megabase pairs (Mbp). Probe generation was facilitated by resources generated in the course of the International Human Genome Project such as
large insert DNA libraries and detailed physical maps. CR probes sets are
prepared and applied for one chromosome type at a time. Labeled with
distinct alternating reporter molecules, the probes are distributed more or
less evenly all along the target chromosome type to allow the detection of
intra- and interchromosomal rearrangements with a resolution of a few
Mbp. A rearrangement is indicated when the normal pattern of 'rainbow'
colors along the hybridized chromosome appears changed. CRs are also a
powerful tool to be used in combination with Comparative Genomic Hybridization (CGH) and Spectral Karyotyping (SKY). A single CR hybridization experiment can provide detailed information about the nature of a
copy number change detected by CGH or the approximate position of
chromosomal breakpoints.