The fluorescent dye DRAQ5 (Biostatus Ltd., UK) directly and stoichiometrically reports DNA content in cells, live or fixed. Stained cells can be gated and sorted into isolated populations with different DNA content relating to the cell cycle, such as elevated G2/M or aneuploidy. The DNA from the cell fractions can then be used directly for population-restricted PCR amplification. Because DRAQ5 is a far-red emitting fluorophore it can be easily multiplexed with other parameters, like cell surface phenotype. In a remarkable paper, (Douwes Dekker, et al. J Pathol 2004; 202:456) cells were extracted from paraffin-embedded sections, stained with a fluorescent antibody (S100) and with DRAQ5. Cells were sorted into antibody positive and aneuploid or G2/M positive fractions. The DNA was extracted and subjected to single exon PCR and restriction digest to detect the presence of a mutation in each of the sorted fractions.
