DIRECT ASSESSMENT OF TRIPLOID CELLS IN MOSAIC HUMAN FETUSES BY FLUORESCENCE IN-SITU HYBRIDIZATION

Villous tissues from 30 spontaneous abortions and the same number of a rtificial abortions were obtained and analysed for the frequency of po lyploid cells. Single cell suspensions were made from these tissues wi thout culture and the ploidy of >100 cells was analysed. Trisomies of chromosomes 17 and 4 have rarely been reported in villous cells of spo ntaneous abortions, suggesting that the presence of more than three co pies of chromosomes 17 and 4 per cell indicates polyploidy. The number of chromosomes 17 and 4 was detected by fluorescence in-situ hybridiz ation analysis using centromeric probes D17Z1 and D4Z1. Most villous c ells from cases of spontaneous and artificial abortions had two D17Z1 or D4Z1 signals per cell, with very small percentages of cells (0.5 +/ - 0.4%) showing three signals per cell. However, in four cases of spon taneous abortions, 2-12% of cells had three D17Z1 or D4Z1 signals per cell, This indicates the presence of triploid cells in these cases of spontaneous abortion, al a significantly higher frequency compared to artificial or the remaining 26 cases of spontaneous abortion. In addit ion, three cases contained 0.2-0.4% of cells showing six signals, indi cating that these cells were dividing triploid cells, The low frequenc y of mosaicism reported here would not be detectable by conventional c hromosomal analysis.