Preparing for preimplantation genetic diagnosis in France

Preimplantation genetic diagnosis (PGD) allows the detection of geneticdefects before implantation, thus circumventing the possible need forabortion. France's current legislation allows the practice of PGD undercertain circumstances which include the prerequisite agreement of theFrench health authority. Unfortunately, to enact the pending 'bioethicallaw', voted in July 1994, a decree still needs to be published. So, for themoment, although we know that PGD should be authorized, its practice iscurrently impossible in France. In order to prepare for licensing, we aresetting up the relevant technologies, by performing biopsy on mouse embryosand fluorescent in-situ hybridization (FISH) experiments on humanlymphoblast cells. We briefly describe the French legal situation withregard to PGD and the work we have performed in this context to obtain thelicensing to offer PGD to patients. After a period of preparation, 95.9% ofbiopsies were successful and up to 95.4% of the biopsied blastomeres wereproperly spread onto slides. Biopsied and control mouse embryos werereimplanted into pseudopregnant females and similar birth rates wereobtained (34.4 and 30.9% respectively). In these experiments we noticed abirth delay of 12-24 h for the biopsied embryos compared with the controls.Furthermore, scanning electron microscopy of the biopsied embryos allowedassessment of the hole made by the Tyrode's acid. By intercrossing adultsderived from biopsied embryos for two successive generations, it was shownthat the biopsy did not generate defects affecting their reproductiveability. FISH experiments were performed using specific probes forchromosomes X, Y and 1 on nuclei spread by a conventional protocol or aTween/HCl blastomere spreading protocol; in the latter case, slides with1-5 cells were prepared. A similar percentage of correct X,Y,1,1 signal wasobtained from all three types of spreading, varying from 85.5 to 89.9%.