Molecular genetic approaches for the determination of embryo viability

Since its first application in the 1990s, genetic testing of preimplantation embryos has undergone a major transformation and its utilisation continues to grow. While in preimplantation genetic screening, euploid embryos are identified and prioritised for uterine transfer, preimplantation genetic diagnosis identifies embryos free of genetic disease to avoid transmission of hereditary genetic disorders from parents to offspring. This study aimed to deliver a novel preimplantation genetic screening protocol, which is capable of high accuracy aneuploidy detection utilising array-based, nano-scale quantitative real-time polymerase chain reaction. Furthermore, it focused on the development of a preimplantation genetic diagnosis protocol, which is capable of accurate detection of maternally inherited mitochondrial DNA mutations and which is fully compatible with comprehensive chromosome screening. After extensive validation, the novel preimplantation genetic screening technique was successfully implemented clinically for testing of blastocyst-stage embryos and now offers a valuable option for couples undergoing in vitro fertilisation combined with preimplantation genetic screening. It is a unique method in that it is streamlined, rapid, versatile and less labour intensive compared to other conventional methods for aneuploidy screening. Furthermore, it has the potential to become an in-house component of an in vitro fertilisation laboratory, thereby reducing the processing time and eliminating the need for embryo cryopreservation. This in turn will help reduce the cost of in vitro fertilisation cycles with preimplantation genetic screening. In addition, a new preimplantation genetic diagnosis protocol for detection of mitochondrial DNA diseases in conjunction with comprehensive chromosome screening using a next-generation sequencing technology was developed and delivered. The new method was successfully applied in four in vitro fertilisation patients transmitting different mutations causing mitochondrial DNA disease. In one patient, the transfer of an unaffected embryo resulted in the birth of a healthy child. In summary, two novel methods were successfully developed, validated and clinically implemented for preimplantation genetic screening and preimplantation genetic diagnosis of mitochondrial DNA diseases.