Detection of DNA sequences in nuclei in suspension by in situ hybridization and dual beam flow cytometry.

This report describes the fluorescence hybridization of DNA sequence probes to interphase nuclei in suspension and the quantification of bound probe by dual beam flow cytometry. Nuclear proteins were first cross-linked with dimethylsuberimidate to prevent disintegration of the nuclei during denaturation and hybridization. To demonstrate that in situ hybridization can be performed in suspension, stabilized mouse thymocyte nuclei were hybridized with a probe for mouse satellite DNA sequences. The DNA probes were labeled with 2-acetylaminofluorene. After hybridization, an indirect immunofluorescent labeling procedure was used to visualize the target sequences. With dual beam flow cytometry, both the amount of hybridized probe and the DNA content of individual nuclei were determined. Thus, the specificity of DNA hybridization can be combined with the speed and quantitative analysis provided by flow cytometry.