Experimental attempts to extend the current preimplantation genetic diagnosis with individual karyotypization of human blastomeres.

The drug-induced chromosome condensation using okadaic acid, a potent protein phosphatase inhibitor, was studied in day 1 to day 4 (D1-D4) spare human preimplantation embryos. In order to obtain cells for genetic tests, we developed a modified displacement blastomere biopsy method. During the okadaic acid treatment, approximately 40% of biopsied cells were lost due to heavy changes of the plasma membrane; this detrimental effect of okadaic acid differed markedly with the respect to the age of embryos. In comparison with the natural embryonic mitotic index, day 1 and day 2 embryonic cells gave increased yields of chromosome spreads (up to 51% of the initial D1-D2 cell number); on days 3 and 4 we were not able to obtain from surviving cells more than 31% blastomeres with condensed chromosomes (9% of total D3-D4 cell number). All chromosome spreads were successfully used for recycling in G-banding and subsequent FISH analysis.