Cuman C, et al. - Experts evaluated if next generation sequencing (NGS) is capable of detecting smaller sub-chromosomal rearrangements in human embryos than the manufacturer’s quoted resolution suggests. Findings suggested the ability of NGS to detect unbalanced chromosome segments smaller than the manufacturer’s resolution.

Methods

• Authors conducted a retrospective assessment of stored DNA samples from embryos that had previously been diagnosed as unbalanced by array-CGH as part of routine PGD in two separate IVF clinics between November 2013 and April 2017.
• They subjected the surePlex whole genome amplification (WGA) products derived from DNA extracted from an embryo biopsy sample known to carry an unbalanced form of a chromosome rearrangement to a specific NGS workflow (VeriSeq PGS).
• They compared the results from the two technologies for each sample.
• Researchers sequenced and analysed the WGA products from 200 embryos known to carry unbalanced rearrangements.
• Seventy five patients known to carry a chromosome rearrangement created these embryos (68 reciprocal translocations, 3 pericentric inversions, 1 paracentric inversion, 2 insertions and 1 dual reciprocal and inversion).
• They evealuated each sample for the size of the segmental gain/loss (Mb), copy number for each segment and chromosome, segregation pattern, the number of bins in the analysis software used and concordance with array-CGH results.

Results

• Findings suggested that a total of 294 unbalanced chromosome segments were evaluated.
• Results demonstrated that NGS was capable of detecting 285/294 (97%) unbalanced segments previously identified using array-CGH.
• As per data, the final PGD diagnosis was concordant for 200/200 (100%) embryos.
• An unbalanced chromosome segment below the quoted 20 Mb manufacturer’s stated resolution was contained by total, 44/75 (59%) patients.
• Out of these, segments that were able to be detected using NGS, whilst maintaining clinical outcome concordance were seen in 35/44 (80%) patients.