Preimplantation Genetic Testing

From biopsy to insight: a streamlined research kit for CNV analysis

Investigating the genomic integrity of precious, low-input samples like research biopsies presents significant technical challenges. Revvity’s PG_Seq Rapid v2 kit provides a complete and streamlined workflow, engineered to simplify the process from sample preparation to library generation for NGS. This kit is optimized for the reliable detection of copy number variations (CNVs), including whole-chromosome aneuploidies and sub-chromosomal changes, from just a few cells. By delivering high-quality, reproducible data, our kit empowers researchers to gain deeper insights into the fundamental biology of chromosomal variation.

Aneuploid embryos are embryos that possess an abnormal number of chromosomes, such as missing one or more chromosomes (monosomy) or having extra chromosomes (trisomy). This condition, known as aneuploidy, is associated with developmental disorders and is a known factor in implantation failure or miscarriages in the context of IVF research. Aneuploidy originates from meiotic and mitotic errors, increases with maternal age, and is a major contributor to reduced implantation potential. The characterization of aneuploid embryos is a key area of fertility research.

What is PGT-A?

Preimplantation Genetic Testing for Aneuploidies (PGT-A) is an advanced genetic screening technique used in fertility research to investigate embryos. PGT-A focuses on screening embryos to characterize their chromosomal composition. In research settings, PGT-A is typically performed on a trophectoderm (TE) biopsy from a day 5/6 blastocyst after whole-genome amplification (WGA), with results reported as euploid, aneuploid, or mosaic according to established research parameters.

PGT-A differs from Preimplantation Genetic Testing for Monogenic Disorders (PGT-M), which is a research method that targets a known variant in a specific gene. PGT-M is locus-specific and relies on parental phasing/haplotyping rather than genome-wide copy-number screening.

The use of NGS in PGT-A research

Next-Generation Sequencing (NGS) provides comprehensive genetic analysis of embryo biopsies for PGT-A research. NGS enables the detection of chromosomal abnormalities across all 24 chromosomes with high resolution (~7–10 Mb). The process involves analyzing the genetic material from a few cells using NGS to generate data for research into factors affecting embryo viability. In practice, PGT-A research with NGS is typically performed using low-pass whole-genome sequencing, which provides read-depth information across the genome.

Low-pass whole-genome read-depth profiling in a research setting can detect unbalanced changes, including:

• Whole-chromosome aneuploidies (trisomy/monosomy)
• Arm-level and segmental CNVs (microdeletions/microduplications)
• Unbalanced products of parental translocations
• Large isochromosomes/arm-level events
• Mosaic forms of the above

Future directions in preimplantation genetic research

The field of preimplantation testing is evolving to include the detection of triploidies and the identification of DNA contamination. Triploidy is a chromosomal anomaly where an embryo has an entire extra set of chromosomes. By incorporating triploidy detection into PGT research protocols, scientists can better investigate factors related to embryo viability. Additionally, the accuracy of PGT research results can be compromised by DNA contamination, which can lead to inaccurate data. Implementing rigorous detection methods for DNA contamination is essential for ensuring the integrity of genetic analysis and enhancing the reliability of data in fertility research.