Detecting abnormal human chromosome constitutions by dual laser flow cytogenetics

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Abstract
Our custom dual laser chromosome sorter has been used to characterize and isolate metaphase human chromosomes rapidly for gene mapping purposes. Herein, we tested how well this system could detect unknown abnormal human chromosome constitutions. These results were compared to those of conventional cytogenetic analyses by banding and photomicrography. The sorter was used to analyze each cell line stained with two different stain pairs: DIPI‐chromomycin and Hoechst‐chromomycin. In 20 min, two histograms representing 2 × 105 chromosomes each were collected for each stain pair. A blind study of 11 samples by flow analysis demonstrated excellent concordance between the abnormal chromosomes detected and the diagnoses of Giemsa‐banded karyotypes. Aneuploidy was identified by changes in the number of chromosomes in each histogram peak, while rearrangements such as deletions and translocations caused shifts in the histogram peak positions. The direction and distance of histogram peak shifts are directly related to alterations in chromosome size and banding pattern. We conclude that dual‐laser flow analysis may provide a rapid approach to the screening and diagnosis of chromosome abnormalities.