The impact of next-generation sequencing technology on preimplantation genetic diagnosis and screening.

Largely because of efforts required to complete the Human Genome Project, DNA sequencing has undergone a steady transformation with still-ongoing developments of high-throughput sequencing machines for which the cost per reaction is falling drastically. Similarly, the fast-changing landscape of reproductive technologies has been improved by genetic approaches. Preimplantation genetic diagnosis and screening were established more than two decades ago for selecting genetically normal embryos to avoid inherited diseases and to give the highest potential to achieve stable pregnancies. Most recent additions to the IVF practices (blastocyst/trophectoderm biopsy, embryo vitrification) and adoption of new genetics tools such as array comparative genome hybridization have allowed setting up more precise and efficient programs for clinical embryo diagnosis. Nevertheless, there is always room for improvements. Remarkably, a recent explosion in the release of advanced sequencing benchtop platforms, together with a certain maturity of bioinformatics tools, has set the target goal of sequencing individual cells for embryo diagnosis to be a realistically feasible scenario for the near future. Next-generation sequencing technology should provide the opportunity to simultaneously analyze single-gene disorders and perform an extensive comprehensive chromosome screening/diagnosis by concurrently sequencing, counting, and accurately assembling millions of DNA reads.