Preimplantation single-cell analysis of multiple genetic loci by whole-genome amplification.

Due to the limited amount of DNA in a single diploid cell, preimplantation genetic diagnosis has relied on single- or dual-locus analyses in biopsied blastomers. We have applied single-cell whole-genome preamplification to PCR-based analysis of multiple disease loci from the same diploid cell. This method allows diagnosis of multiple disease genes, analysis of multiple exons/introns within a gene, or corroborative embryo-sex assignment and specific mutation detection at sex-linked loci. A blinded study of six genetic loci was performed with whole-genome preamplification followed by nested PCR. Amplification was observed in 103 of 105 assays (98%) and a correct diagnosis was made in 98%. All human blastomeres were correctly diagnosed (100%) at loci where the genotype could be confirmed, attesting to the reliability of the technique. Preamplification has now been applied successfully to the analysis of the two major mutations responsible for Tay-Sachs disease and of a common restriction polymorphism in the gene responsible for hemophilia A. The fidelity and length of product derived from this preamplification step make it an appealing technique for preimplantation genetic diagnoses requiring analyses at more than one locus. IMAGES: