The clinical application of affected-embryo-based SNP haplotype analysis for patients with de novo pathogenic mutations in PGT-M cycles.

Purpose: In preimplantation genetic testing for monogenic/single gene disorders (PGT-M) cycles, direct detection of the pathogenic mutation combined with indirect haplotype analysis are recommended to achieve accurate diagnosis. However, it poses a challenge to conduct haplotype analysis for patients carried de novo pathogenetic mutations or without no identified haplotype in families. Herein, the strategy of affected-embryo-based haplotype analysis was implemented in clinical practice to provide a convenient, economical and effective way for such patients.

Materials and methods: Eight cases with de novo mutations were recruited. Six cases found the embryo-proband from biopsied blastocysts, and two case (case5 and 6) found them from developmental arrested embryos. A total of thirty-seven biopsied blastocysts from eight PGT-M cycles were performed direct detection and affected-embryo-based single nucleotide polymorphism (SNP) haplotype analyses.

Results: Till now, five cases (case 1, 2, 3, 7, 8) had delivered healthy babies and one case (case6) achieved successful ongoing pregnancy. We reported for the first time to find proband from developmental arrested embryos to complete haplotype analyses when no carriers were found in biopsied ones in clinical practice.

Conclusion: Our study further proves and expands the application of the double-checking strategy based on affected-embryo proband and allows patients with de novo mutations or lack positive family members to benefit from the strategy.