Single intragenic microsatellite preimplantation genetic diagnosis for cystic fibrosis provides positive allele identification of all CFTR genotypes for informative couples

This study is part of a strategy aimed at using fluorescent polymerase chai n reaction (PCR) on informative genetic microsatellite markers as a diagnos tic tool in preimplantation genetic diagnosis (PGD) of severe monogenic dis ease. Two couples, both of whom had previously had children who were compou nd heterozygote for severe cystic fibrosis mutations, were offered PGD usin g fluorescent PCR of the highly polymorphic cystic fibrosis transmembrane c onductance regulator (CFTR) intragenic microsatellite marker IVS17bTA, Clea vage-stage embryo biopsy followed by PCR resulted in transfer of one unaffe cted carrier embryo for each couple. This approach eliminates the need for single cell multiplex PCR strategies to detect CF compound heterozygotes. I t also provides a control of chromosome 7 ploidy in the blastomeres and a s election against allele dropout by positive detection of each CFTR copy of all genotypes in preimplantation embryos from genetically informative famil ies.