Double-factor preimplantation genetic diagnosis: monogenic and cytogenetic diagnoses analyzing a single blastomere

Novel Double Factor PGT strategy analyzing blastocyst stage embryos in a single NGS procedure

In families at risk from monogenic diseases affected offspring, it is fundamental the development of a suitable Double Factor Preimplantation Genetic Testing (DF-PGT) method for both single-gene analysis and chromosome complement screening. Aneuploidy is not only a major issue in advanced-maternal-age patients and balanced translocation carriers, but also the aneuploidy rate is extremely high in patients undergoing in vitro fertilization (IVF), even in young donors. To adequate NGS technology to the DF-PGT strategy four different whole genome amplification systems (Sureplex, MALBAC, and two multiple displacement amplification systems-MDA) were tested using TruSight One panel on cell lines and blastocyst trophectoderm biopsies-TE. Embryo cytogenetic status was analyzed by Nexus software. Sureplex and MALBAC DNA products were considered not suitable for PGT diagnosis due to inconsistent and poor results on Trusight one (TSO) panel. Results obtained with both MDA based methods (GEH-MDA and RG-MDA) were appropriate for direct mutation detection by TSO NGS platform. Nevertheless, RG-MDA amplification products showed better coverage and lower ADO rates than GEH-MDA. The present work also demonstrates that the same TSO sequencing data is suitable not only for the direct mutation detection, but also for the indirect mutation detection by linkage analysis of informative SNPs. The present work also demonstrates that Nexus software is competent for the detection of CNV by using with TSO sequencing data from RG-MDA products, allowing for the whole cytogenetic characterization of the embryos. In conclusion, successfully development of an innovative and promising DF-PGT strategy using TSO-NGS technology in TE biopsies, performed in-house in a single laboratory experience, has been done in the present work. Additional studies should be performed before it could be used as a diagnostic alternative in order to validate this approach for the detection of chromosomal aneuploidies.

Genetic and epigenetic risks of assisted reproduction

Assisted reproductive technology (ART) is used primarily for infertility treatments to achieve pregnancy and involves procedures such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), and cryopreservation. Moreover, preimplantation genetic diagnosis (PGD) of ART is used in couples for genetic reasons. In ART treatments, gametes and zygotes are exposed to a series of non-physiological processes and culture media. Although the majority of children born with this treatment are healthy, some concerns remain regarding the safety of this technology. Animal studies and follow-up studies of ART-borne children suggested that ART was associated with an increased incidence of genetic, physical, or developmental abnormalities, although there are also observations that contradict these findings. As IVF, ICSI, frozen-thawed embryo transfer, and PGD manipulate gametes and embryo at a time that is important for reprogramming, they may affect epigenetic stability, leading to gamete/embryo origins of adult diseases. In fact, ART offspring have been reported to have an increased risk of gamete/embryo origins of adult diseases, such as early-onset diabetes, cardiovascular disease, and so on. In this review, we will discuss evidence related to genetic, especially epigenetic, risks of assisted reproduction.