Investigation of Global Gene Expression of Human Blastocysts Diagnosed as Mosaic using Next-generation Sequencing

Embryos are diagnosed as mosaic if their chromosomal copy number falls between euploid and aneuploid. The purpose of this study was to investigate the impact of mosaicism on global gene expression. This study included 42 blastocysts that underwent preimplantation genetic testing for aneuploidy (PGT-A) and were donated for IRB approved research. Fourteen blastocysts were diagnosed as mosaic with Next-generation Sequencing (NGS). Three NGS diagnosed euploid embryos, and 25 aneuploid embryos (9 NGS, 14 array Comparative Genomic Hybridization, 2 Single Nucleotide Polymorphism array) were used as comparisons. RNA-sequencing was performed on all of the blastocysts. Differentially expressed genes (DEGs) were calculated using DESeq2/3.5 (R Bioconductor Package) with p < 0.05 considered significantly differentially expressed. Pathway analysis was performed on mosaic embryos using EnrichR with p < 0.05 considered significant. With euploid embryo gene expression used as a control, 12 of 14 mosaic embryos had fewer DEGs compared to aneuploid embryos involving the same chromosome. On principal component analysis (PCA), mosaic embryos mapped separately from aneuploid embryos. Pathways involving cell proliferation, differentiation, and apoptosis were the most disrupted within mosaic embryos. Mosaic embryos have decreased disruption of global gene expression compared to aneuploid embryos. This study was limited by the small sample size, lack of replicate samples for each mosaic abnormality, and use of multiple different PGT-A platforms for the diagnosis of aneuploid embryos.