Development and Validation of Innovative Technologies for Highly Accurate and Cost-Effective Preimplantation Genetic Testing: Technical and Clinical Perspectives

Testing preimplantation embryos, obtained during in vitro fertilization treatments, using preimplantation genetic tests have been introduced into clinical practice in recent years. First applications involved the possibility of detecting embryos affected by monogenic disorders (PGT-M) inherited from parents. Subsequently, preimplantation genetic testing for aneuploidy (PGT-A) was introduced to improve IVF transfer outcomes. Indeed, identification of aneuploid and transfer of euploid embryos has demonstrated improved rates for implantation, pregnancy and live birth per transfer and reduced implantation failures. Developments in genomic technologies for PGT have revolutionized the ability to detect genetic abnormalities of various kinds, starting from a small number of cells biopsied from the embryo. The increased sensitivity and resolution of these methods has allowed to identify not only the gain or loss of entire chromosome but also partial or segmental aneuploidies and chromosomal mosaicism, introducing novel diagnostic categories with greater difficult management and interpretation. Of note the knowledge of the biology of these alterations and the outcomes is incomplete and still evolving. In recent years the demand for PGT has increased considerably. At the same time, the novel technologies adapted for preimplantation genetic diagnosis have allowed to increase the number of samples simultaneously analyzed, reducing the costs and time associated with analyses this allowed a greater diffusion and accessibility of PGT to a greater number of patients. Moreover, partial automation of procedures, increased analytical flexibility and simplified data analysis, provided by recent technologies, have significantly improved laboratory workflow and clinical management. The central theme of this thesis is the evolution of technologies and analytical methods employed in our laboratory for preimplantation genetic diagnosis. In this project the main application of PGT, chromosomal aneuploidies and monogenic disease, are presented separately. Since the beginning of my PhD training, I’ve been involved in the development and validation of new molecular genetics methodologies: the new Ion Reproseq protocol on Ion Torrent platform was validated and introduced into clinical practice for aneuploidy screening. Later Karyomapping approach was validated for monogenic disorders but didn’t replace the technology already in use. During the last year I focused my activity on the characterization of segmental aneuploidies: a considerable proportion was found to be mosaic in origin, reducing their diagnostic predictive value compared to whole chromosome aneuploidies.