MULTIPARAMETER IN-SITU ANALYSIS OF TROPHOBLAST CELLS IN MIXED CELL-POPULATIONS BY COMBINED DNA AND RNA IN-SITU HYBRIDIZATION

We developed a non-radioactive assay for simultaneous detection of cyt oplasmic mRNA and nuclear genomic DNA in fetal trophoblast cells by se quential in situ hybridization. Trophoblast-specific mRNA is detected with a digoxigenin-labeled RNA probe complementary to HLA-G, followed by visualization through the generation of stable contrast-rich DAB/Ni complexes. Genomic target DNA is subsequently visualized in labeled c ells by fluorescent in situ hybridization using biotin-labeled chromos ome-specific DNA probes. Simultaneous visualization of both targets is made possible using a fluorescence microscope with FITC filter and co nventional brightfield light, This method allows detection of trophobl ast cells within a mixed cell population and, at the same time, analys is of chromosome anomalies in the trophoblast cells identified. For pr enatal diagnosis of fetal cells enriched from maternal peripheral bloo d during pregnancy, this multiparameter in situ analysis of immobilize d fetal trophoblast cells will be very useful.