Preimplantation genetic diagnosis for ornithine transcarbamylase deficiency by simultaneous analysis of duplex-nested PCR and fluorescence in situ hybridization: a case report

Ornithine transcarbamylase (OTC) deficiency is an X-linked co-dominant disorder. A couple, with a previous history of a neonatal death and a therapeutical termination due to OTC deficiency, was referred to our center for preimplantation genetic diagnosis (PGD). The female partner has a nonsense mutation in the exon 9 of the OTC gene (R320X). We carried out nested polymerase chain reaction (PCR) for R320X mutation and fluorescence in situ hybridization (FISH) for aneuploidy screening. Among a total of 11 embryos, two blastomeres per embryo from 9 embryos were biopsied and analyzed by duplex-nested PCR and FISH, and one blastomere per embryo from 2 embryos by only duplex-nested PCR. As a result of PCR and restriction fragment length polymorphism analysis, four embryos were diagnosed as unaffected embryos having the normal OTC gene. Among these embryos, only one embryo was confirmed as euploidy for chromosome X, Y and 18 by FISH analysis. A single normal embryo was transferred to the mother, yielding an unaffected pregnancy and birth of a healthy boy. Based on our results, PCR for mutation loci and FISH for aneuploidy screening with two blastomeres from an embryo could provide higher accuracy for the selection of genetically and chromosomally normal embryos in the PGD for single gene defects.