Recurrent t(11;22) breakpoint mapping by chromosome flow sorting and spot-blot hybridization

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Abstract
The breakpoint of the recurrent t(11;22) translocation, one of the most frequent chromosome anomalies encountered in human population, always involves bands 11q23.2 and 22q11.2. The involvement of the Cλ locus of the immunoglobulin λ gene cluster on chromosome 22 has been suggested: however, in situ hybridization experiments have yielded conflicting results. In order to solve these discrepancies by another approach, we have used bivariate flow sorting to separate the chromosomes of interest and to map the specific breakpoints by direct spot-blot hybridization with the gene-specific radiolabelled DNA probes, Alu, Vλ, ets. The results showed unambiguously that in the t(11;22) patient analysed, a set of Cλ and Vλ genes was translocated to the der(11) chromosome. Since Vλ genes are situated proximally to Cλ genes, we demonstrate that, in the case studied here, the chromosome 22 breakpoint is not located within or even immediately close to the Cλ region.