Screening of 24 chromosomes with NGS

This new technology, which has come as a New Generation Sequencing in the genetic science, became remarkable for reproductive genetics applications. In embryos, technology of screening the 24 chromosomes with NGS has taken place very quickly after array technology in PGT applications.

It has been a quarter century since the first Preimplantation Genetic Testing applied by Handyside (1990). Previously, this technique was used for screening single gene disorders and gender-related disorders, and then it was used for screening translocations and aneuploidies.

Advantages of NGS technology to array technologies:

(i) allows more samples (for 24 embryos) to be tested simultaneously, thanks to its high-scale sequencing capacity, and enables lower cost operation;

(ii) better captures partial or segmental aneuploidies (may decrease to a few megabase) due to the high resolution of chromosomal analysis;

(iii) reveals mosaicism more clearly in analysis where more than one cell is examined;

(iv) reduces human errors and operating time thanks to automation during library preparation;

(v) with NGS technology, translocation, aneuploidy screening and Single Gene Disorders can be identified from a single cell;

(vi) the entire procedure can be completed within 24 hours.

SCREENING OF 24 CHROMOSOMES (ARRAY CGH)

In Preimplantation Genetic Screening (PGT-A) 24 chromosome technology thanks to new developments in DNA microarray techniques it is now possible to screen 24 chromosomes in 24 hours and with the sureplex systems in a short time like 12 hours, and it is possible to select the competent embryo. Today, aneuploidy screenings with FISH, where 5-12 chromosomes can be examined, are replaced by array CGH technologies.

INDICATIONS:

Advanced maternal age

Recurrent miscarriages

Failed IVF trials

It has been shown that the rate of aneuploidy in embryos increases with the advanced maternal age, the selection of embryos with high potential for pregnancy for single embryo transfer is important (1).

It was reported that when using 24 chromosome technology in PGT-A, pregnancy rates increased by two compared to FISH (2) and implantation rates increased by 50% (3).

It is an important technique that can be used in the selection of a suitable embryo for single embryo transfer in IVF cycles.

It is aimed to prevent multiple pregnancies with single embryo transfer as a result of increasing implantation rates and more detailed elimination of embryos to be transferred with PGT-A applied by scanning 24 chromosomes.

As a result of increasing the implantation rates with PGT-A applied by screening 24 chromosomes and more detailed elimination of the embryos to be transferred, it is aimed to prevent multiple pregnancies with single embryo transfer.

1)Molecular Human Reproduction, Vol.16, No.8 pp. 583–589, 2010 Nathan R. Treff et al.
2) (Sher et al., 2009)
3) (Schoolcraft et al., 2009). Mol Hum Reprod. 2010 December; 16(12): 944–949.) D.S. Johnson,1et al