Clinical application of sequencing-based methods for parallel preimplantation genetic testing for mitochondrial DNA disease and aneuploidy

Objective: To validate and apply a strategy permitting parallel preimplantation genetic testing (PGT) for mitochondrial DNA (mtDNA) disease and aneuploidy (PGT-A). Design: Preclinical test validation and case reports. Setting: Fertility centers. Diagnostics laboratory. Patients: Four patients at risk of transmitting mtDNA disease caused by m.8993T>G (Patients A and B), m.10191T>G (Patient C), and m.3243A>G (Patient D). Patients A, B, and C had affected children. Patients A and D displayed somatic heteroplasmy for mtDNA mutations. Interventions: Embryo biopsy, genetic testing, and uterine transfer of embryos predicted to be euploid and mutation-free. Main Outcome Measures: Test accuracy, treatment outcomes, and mutation segregation. Results: Accuracy of mtDNA mutation quantification was confirmed. The test was compatible with PGT-A, and half of the embryos tested were shown to be aneuploid (16/33). Mutations were detected in approximately 40% of embryo biopsies from Patients A and D (10/24) but in none from Patients B and C (n 1/4 29). Patients B and C had healthy children following PGT and natural conception, respectively. The m.8993T>G mutation displayed skewed segregation, whereas m.3243A>G mutation levels were relatively low and potentially impacted embryo development. Conclusions: Considering the high aneuploidy rate, strategies providing a combination of PGT for mtDNA disease and aneuploidy may be advantageous compared with approaches that consider only mtDNA. Heteroplasmic women had a higher incidence of affected embryos than those with undetectable somatic mutant mtDNA but were still able to produce mutation-free embryos. While not conclusive, the results are consistent with the existence of mutation-specific segregation mechanisms occurring during oogenesis and possibly embryogenesis. ((C)2021 by American Society for Reproductive Medicine.)

Automated summary

This study validated and applied a new preimplantation genetic testing strategy for simultaneously detecting mitochondrial DNA disease and aneuploidy. The results showed that heteroplasmic women had more affected embryos compared to those with undetectable somatic mutant mtDNA, but were still able to produce mutation-free embryos.