PREPARING FOR PREIMPLANTATION GENETIC DIAGNOSIS IN FRANCE

Preimplantation genetic diagnosis (PGD) allows the detection of geneti c defects before implantation, thus circumventing the possible need fo r abortion. France's current legislation allows the practice of PGD un der certain circumstances which include the prerequisite agreement of the French health authority. Unfortunately to enact the pending 'bioet hical law', voted in July 1994, a decree still needs to be published. So, for the moment, although we know that PGD should be authorized, it s practice is currently impossible in France. In order to prepare for licensing, me are setting up the relevant technologies, by performing biopsy on mouse embryos and fluorescent in-situ hybridization (FISH) e xperiments on human lymphoblast cells, We briefly describe the French legal situation with regard to PGD and the work we have performed in t his context to obtain the licensing to offer PGD to patients. After a period of preparation, 95.9% of biopsies were successful and up to 95. 4% of the biopsied blastomeres were properly spread onto slides. Biops ied and control mouse embryos were reimplanted into pseudopregnant fem ales and similar birth rates were obtained (33.4 and 30.9% respectivel y). In these experiments we noticed a birth delay of 12-24 h for the b iopsied embryos compared with the controls. Furthermore scanning elect ron microscopy of the biopsied embryos allowed assessment of the hole made by the Tyrode's acid. By intercrossing adults derived from biopsi ed embryos for two successive generations, it was shown that the biops y did not generate defects affecting their reproductive ability. FISH experiments were performed using specific probes for chromosomes X, Y and 1 on nuclei spread by a conventional protocol or a Tween/HCl blast omere spreading protocol; in the latter case, slides with 1-5 cells we re prepared, A similar percentage of correct X,Y,1,1 signal was obtain ed from all three types of spreading, varying from 85.5 to 89.9%.