A Strategy Potentially Suitable for Combined Preimplantation Genetic Testing of Aneuploidy and Monogenic Disease That Permits Direct Detection of Pathogenic Variants Including Repeat Expansions and Gene Deletions

Combined preimplantation genetic testing of aneuploidy (PGT-A) and monogenic disease (PGT-M) can be achieved through PCR-based whole genome amplification (WGA) and next-generation sequencing (NGS). However, pathogenic variant detection is usually achieved indirectly through single nucleotide polymorphism haplotyping, as direct detection of pathogenic variants is not always possible. We evaluated whether isothermal WGA was suitable for combined PGT-A and PGT-M that also permitted direct detection of repeat expansions and large deletions, in addition to indirect linkage analysis using microsatellite markers. Five-cell replicates from selected cell lines were subjected to isothermal or PCR-based WGA, followed by NGS-based PGT-A and direct and indirect PGT-M of Huntington's disease and spinal muscular atrophy. Both WGA methods accurately detected aneuploidy and large (10 Mb) segmental imbalances. However, isothermal WGA produced higher genotyping accuracy compared with PCR-based WGA for all analysed microsatellite markers (93.5% vs. 75.6%), as well as at the <i>HTT</i> CAG repeat locus (100% vs. 7.7%) and the <i>SMN1/2</i> locus (100% vs. 71.8%). These results demonstrate that isothermal WGA is potentially ideal for combined PGT-A and PGT-M that permits both direct and indirect detection of pathogenic variants including repeat expansions and gene deletions.