Identification of cryptic breakpoints through single-tube long fragment read whole genome sequencing based on preimplantation genetic testing.

This study utilized single-tube long fragment read whole genome sequencing (stLFR WGS) to identify cryptic chromosomally balanced translocations in preimplantation genetic testing (PGT), aiming to improve outcomes for couples experiencing recurrent pregnancy loss (RPL). G-banded karyotyping initially revealed normal results for Family 1 and a reciprocal translocation for Family 2. However, PGT's low-coverage WGS uncovered recurrent copy number variations (CNVs) that contradicted the initial findings. Further analysis using stLFR WGS and Sanger sequencing precisely located the breakpoints, revealing a balanced translocation between chromosomes 7 and 13 in Family 1's male and a complex translocation involving chromosomes 9, 10, and 11 in Family 2's female. By selecting non-carrier embryos for transfer, the study resulted in successful births of healthy infants. These findings highlight the critical role of PGT in detecting concealed chromosomal rearrangements and demonstrate stLFR WGS as an effective diagnostic tool for breakpoint identification, significantly impacting reproductive decisions for couples with cryptic balanced translocations and RPL.