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Genetic Testing Approach Explores Origins of Blastocyst Aneuploidy

Researchers at Rutgers University, Genomic Prediction, and elsewhere reporting in the American Journal of Human Genetics retrace aneuploidy origins in human blastocysts profiled by preimplantation genetic testing (PGT). By analyzing SNP genotypes in combination with copy number profiles, the team distinguished between aneuploid blastocysts stemming from missegregation of haploid sperm or egg chromosomes during meiosis, which leads to aneuploidy in all cells, and forms of aneuploidy linked to mitosis errors after zygote formation, which can produce mosaic blastocysts. In a set of almost 2,300 blastocysts with available parental DNA information, the authors saw meiotic aneuploidy in more than one-quarter of the blastocysts considered and mitotic aneuploidy in another 2 percent, suggesting that "bona fide mosaicism" is relatively uncommon. "The ability to accurately identify mitotic-origin aneuploidy in the blastocyst could benefit and better inform individuals whose IVF cycle results in all aneuploid embryos," they explain. "Clinical trials with this methodology might also help provide a definitive answer regarding the reproductive potential of bona fide mosaic embryos."