Feasibility study of repeated fluorescent in-situ hybridization in the same human blastomeres for preimplantation genetic diagnosis

In order to increase the number of chromosomes examined in each blastomere,we have developed a repeated fluorescent in-situ hybridization (FISH)procedure by which six or more chromosomes can be analysed per blastomereof a human embryo. Three consecutive FISH procedures with directly-labelledfluorescent Vysis DNA probes were carried out for examination ofchromosomes X, Y, 11, 13, 18 and 21 in the same blastomeres (n = 126) andlymphocytes (n = 164). Based on the initial number of nuclei, thepercentages of nuclear loss and presence of signals were 3 and 92%respectively in blastomeres; 6 and 91% respectively in lymphocytes afterthe first FISH; 7 and 87% respectively in blastomeres and 10 and 86%respectively in lymphocytes, after the second FISH. These percentages were13 and 78% respectively in blastomeres and 14 and 81% respectively inlymphocytes after the third FISH. The FISH procedure was repeatedsuccessfully in a couple for preimplantation genetic diagnosis ofchromosomal aneuploidies in biopsied blastomeres of their embryos in ourclinic. In conclusion, it is feasible to carry out repeated FISH proceduresin the same blastomeres. Six or more chromosomes of a single blastomere maybe examined using this procedure.