Clinical application of next-generation sequencing in preimplantation genetic diagnosis cycles for Robertsonian and reciprocal translocations

The purpose of this study was to apply next-generation sequencing (NGS) technology to identify chromosomally normal embryos for transfer in preimplantation genetic diagnosis (PGD) cycles for translocations. A total of 21 translocation couples with a history of infertility and repeated miscarriage presented at our PGD clinic for 24-chromosome embryo testing using copy number variation sequencing (CNV-Seq). Testing of 98 embryo samples identified 68 aneuploid (69.4 %) and 30 (30.6 %) euploid embryos. Among the aneuploid embryos, the most common abnormalities were segmental translocation imbalances, followed by whole autosomal trisomies and monosomies, segmental imbalances of non-translocation chromosomes, and mosaicism. In all unbalanced embryos resulting from reciprocal translocations, CNV-Seq precisely identified both segmental imbalances, extending from the predicted breakpoints to the chromosome termini. From the 21 PGD cycles, eight patients had all abnormal embryos and 13 patients had at least one normal/balanced and euploid embryo available for transfer. In nine intrauterine transfer cycles, seven healthy babies have been born. In four of the seven children tested at 18 weeks gestation, the karyotypes matched with the original PGD results. In clinical PGD translocation cycles, CNV-Seq displayed the hallmarks of a comprehensive diagnostic technology for high-resolution 24-chromosome testing of embryos, capable of identifying true euploid embryos for transfer.