Identification of Chromosomal Errors in Human Preimplantation Embryos with Oligonucleotide DNA Microarray

Abstract

A previous study comparing the performance of different platforms for DNA microarray found that the oligonucleotide (oligo) microarray platform containing 385K isothermal probes had the best performance when evaluating dosage sensitivity, precision, specificity, sensitivity and copy number variations border definition. Although oligo microarray platform has been used in some research fields and clinics, it has not been used for aneuploidy screening in human embryos. The present study was designed to use this new microarray platform for preimplantation genetic screening in the human. A total of 383 blastocysts from 72 infertility patients with either advanced maternal age or with previous miscarriage were analyzed after biopsy and microarray. Euploid blastocysts were transferred to patients and clinical pregnancy and implantation rates were measured. Chromosomes in some aneuploid blastocysts were further analyzed by fluorescence in-situ hybridization (FISH) to evaluate accuracy of the results. We found that most (58.1%) of the blastocysts had chromosomal abnormalities that included single or multiple gains and/or losses of chromosome(s), partial chromosome deletions and/or duplications in both euploid and aneuploid embryos. Transfer of normal euploid blastocysts in 34 cycles resulted in 58.8% clinical pregnancy and 54.4% implantation rates. Examination of abnormal blastocysts by FISH showed that all embryos had matching results comparing microarray and FISH analysis. The present study indicates that oligo microarray conducted with a higher resolution and a greater number of probes is able to detect not only aneuploidy, but also minor chromosomal abnormalities, such as partial chromosome deletion and/or duplication in human embryos. Preimplantation genetic screening of the aneuploidy by DNA microarray is an advanced technology used to select embryos for transfer and improved embryo implantation can be obtained after transfer of the screened normal embryos.

Assessment of aneuploidy formation in human blastocysts resulting from donated eggs and the necessity of the embryos for aneuploidy screening

“…Recently, Yang et al investigated the aneuploidy formation in human embryos derived from young patients (less than 35 years old) and also found that approximately 40 % of blastocysts were aneuploid [7], a rate which was similar to our previous studies with the same age group [5,10]. In Yang's study, they found that transfer of PGS-selected embryos resulted in a higher implantation rate as compared with transfer of non-PGS embryos, suggesting that PGS is necessary not only for patients of advanced maternal ages, but also for young women [7].…”

“…An age-related reduced embryo implantation can also be improved by the transfer of selected euploid embryos with PGS [5]. Aneuploid embryos are present in infertile patients at various maternal ages with an increased tendency as maternal ages are increased [5,7,10,20,21]. Embryos from healthy egg donors should have low embryonic aneuploidy rates, but a previous study by Sills et al [18] and our present study indicate that high aneuploidy rates are present in human embryos from donor eggs.…”

“…In a previous study, it was reported that extra ovarian stimulation can increase aneuploidy formation in human IVF [25], but no further evidence to indicate that stimulation can increase the risk of aneuploidy. High aneuploidy rates observed in human IVF may be due to multiple factors, such as maternal age [5,7,10] and in vitro manipulation of eggs [22][23][24]. However, a comprehensible conclusion may need more basic and clinical investigations.…”

“…Preimplantation genetic screening (PGS) by all chromosome DNA microarray has become an advanced technology to screen chromosomal integrity in human embryos, which has provided the best approach to examine structural and numeral abnormalities in all chromosomes in the preimplantation embryos [5,7,9,10]. It has been found that PGS especially benefits patients of advanced maternal ages, recurrent miscarriage and previous spontaneous miscarriage, as aneuploidy is the main reason for unsuccessful embryo implantation in these populations of patients [5,[10][11][12].…”

“…It has been found that PGS especially benefits patients of advanced maternal ages, recurrent miscarriage and previous spontaneous miscarriage, as aneuploidy is the main reason for unsuccessful embryo implantation in these populations of patients [5,[10][11][12].…”