Clustered Regularly Interspaced Palindromic Repeats (CRISPR) Applied to Gametes and Embryos

Preimplantation genetic testing (PGT) facilitates the identification of embryos affected by specific types of genetic abnormalities. However, PGT does not seek to treat the genetic abnormality, rather it is an embryo selection tool, employing a strategy of detection and exclusion. Until recently, the notion that mutations and aneuploidies could be corrected in gametes, or in embryos produced using in vitro fertilization (IVF), seemed improbable. However, rapid progress in the evolution of gene editing technologies may make this a realistic possibility in the near future. Not only would such an approach help to avoid the discard of human embryos, which some find challenging from ethical or religious perspectives, but it would also increase the number of embryos considered suitable for transfer, potentially leading to higher pregnancy rates than achieved in PGT cycles. This chapter considers the use of genome editing applied to human preimplantation embryos, describing a protocol that can be used to inactivate genes for research purposes, and which might, in the future, allow for the correction of pathogenic mutations.