DNA Research, 2018, 25(4), 353–360 doi: 10.1093/dnares/dsy007 Advance Access Publication Date: 6 March 2018 Full Paper Full Paper Homologue-specific chromosome sequencing characterizes translocation junctions and permits allelic assignment Fumio Kasai1,2,*, Jorge C. Pereira2, Arihiro Kohara1, and Malcolm A. Ferguson-Smith2 1Japanese Collection of Research Bioresources (JCRB) Cell Bank, Laboratory of Cell Cultures, National Institutes of Biomedical Innovation, Health and Nutrition, Ibaraki 567-0085, Osaka, Japan, and 2Cambridge Resource Centre for Comparative Genomics, Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, UK *To whom correspondence should be addressed. Tel. þ81 72 641 9851. Fax. þ81 72 641 9859. Email:
[email protected] Edited by Dr. Yuji Kohara Received 13 August 2017; Editorial decision 11 February 2018; Accepted 12 February 2018 Abstract Chromosome translocations can be detected by cytogenetic analysis, but it is hard to character- ize the breakpoints at the sequence level. Chromosome sorting by flow cytometry produces flow karyotypes that enable the isolation of abnormal chromosomes and the generation of chromosome-specific DNA. In this study, a derivative chromosome t(9; 14) and its homologous normal chromosomes 9 and 14 from the Ishikawa 3-H-12 cell line were sorted to collect homologue-specific samples. Chromosome sequencing identified the breakpoint junction in the der(9) at 9p24.3 and 14q13.1 and uncovered the formation of a fusion gene, WASH1–NPAS3. Amplicon sequencing targeted for neighbouring genes at the fusion breakpoint revealed that the variant frequencies correlate with the allelic copy number. Sequencing of sorted chromo- somes permits the assignment of allelic variants and can lead to the characterization of abnor- mal chromosomes.