scholarly journals PREIMPLANTATION GENETIC TESTING: Chromosome abnormalities in human embryos

Reproduction ◽  
2020 ◽  
Vol 160 (5) ◽  
pp. A33-A44
Author(s):  
Carmen Rubio ◽  
Lorena Rodrigo ◽  
Carlos Simón
Keyword(s):  
Genetic Testing ◽  
Culture Media ◽  
Sperm Concentration ◽  
Early Embryo ◽  
Chromosome Abnormalities ◽  
Critical Event ◽  
Human Embryos ◽  
Preimplantation Genetic Testing ◽  
Frequent Event

Aneuploidy is a frequent event in human embryos, and its incidence is higher in oocytes and embryos from women of advanced maternal age. Aneuploidy may also be a contributing factor in infertile populations, such as couples with recurrent miscarriages, repetitive implantation failure, or male infertility. For these reasons, preimplantation genetic testing for aneuploidy (PGT-A) has been proposed to prevent miscarriages and increase live birth rates in infertile couples undergoing in vitro fertilisation. Next-generation sequencing is currently being applied for the detection of aneuploidies in human embryos, including whole chromosome aneuploidies, segmental aneuploidies, uniform, and mosaic aneuploidies. More recently, this technology has been incorporated for the analysis of the cell-free DNA secreted by the embryo to the culture media. Chromosome abnormalities mostly originate in female meiosis. Recombination between homologous chromosomes is a critical event that occurs in the foetal ovary. The importance of altered recombination pertains to paternally as well as maternally derived trisomies, but as most aneuploidy arises during oogenesis, the female is at greater risk. For males, sperm concentration is associated with a higher risk of aneuploid sperm and thus aneuploid embryos. Mitosis errors can occur at all stages of early embryo development that result in chromosomally distinct cell populations. The clinical impact of mosaicism depends on the mosaicism type, location, and number of aneuploid cells. Transfer of mosaic embryos has been proposed when no euploid embryos are available in the PGT-A cycle.

scholarly journals Noninvasive preimplantation genetic testing for aneuploidy in spent medium may be more reliable than trophectoderm biopsy

2019 ◽  
Vol 116 (28) ◽  
pp. 14105-14112 ◽  
Author(s):  
Lei Huang ◽  
Berhan Bogale ◽  
Yaqiong Tang ◽  
Sijia Lu ◽  
Xiaoliang Sunney Xie ◽  
...  
Keyword(s):  
Genetic Testing ◽  
Inner Cell Mass ◽  
Culture Media ◽  
False Negative ◽  
Cell Mass ◽  
False Negative Rate ◽  
Critical Examination ◽  
Preimplantation Genetic Testing ◽  
Embryo Mosaicism

Preimplantation genetic testing for aneuploidy (PGT-A) with trophectoderm (TE) biopsy is widely applied in in vitro fertilization (IVF) to identify aneuploid embryos. However, potential safety concerns regarding biopsy and restrictions to only those embryos suitable for biopsy pose limitations. In addition, embryo mosaicism gives rise to false positives and false negatives in PGT-A because the inner cell mass (ICM) cells, which give rise to the fetus, are not tested. Here, we report a critical examination of the efficacy of noninvasive preimplantation genetic testing for aneuploidy (niPGT-A) in the spent culture media of human blastocysts by analyzing the cell-free DNA, which reflects ploidy of both the TE and ICM. Fifty-two frozen donated blastocysts with TE biopsy results were thawed; each of their spent culture medium was collected after 24-h culture and analyzed by next-generation sequencing (NGS). niPGT-A and TE-biopsy PGT-A results were compared with the sequencing results of the corresponding embryos, which were taken as true results for aneuploidy reporting. With removal of all corona-cumulus cells, the false-negative rate (FNR) for niPGT-A was found to be zero. By applying an appropriate threshold for mosaicism, both the positive predictive value (PPV) and specificity for niPGT-A were much higher than TE-biopsy PGT-A. Furthermore, the concordance rates for both embryo ploidy and chromosome copy numbers were higher for niPGT-A than TE-biopsy PGT-A. These results suggest that niPGT-A is less prone to errors associated with embryo mosaicism and is more reliable than TE-biopsy PGT-A.

scholarly journals Haplotype-aware inference of human chromosome abnormalities

2021 ◽  
Vol 118 (46) ◽  
pp. e2109307118
Author(s):  
Daniel Ariad ◽  
Stephanie M. Yan ◽  
Andrea R. Victor ◽  
Frank L. Barnes ◽  
Christo G. Zouves ◽  
...  
Keyword(s):  
Genetic Testing ◽  
Human Chromosome ◽  
Large Scale ◽  
Chromosome Abnormalities ◽  
Whole Genome Sequencing Data ◽  
Sequencing Data ◽  
Current Standard ◽  
Preimplantation Genetic Testing ◽  
Adverse Pregnancy

Extra or missing chromosomes—a phenomenon termed aneuploidy—frequently arise during human meiosis and embryonic mitosis and are the leading cause of pregnancy loss, including in the context of in vitro fertilization (IVF). While meiotic aneuploidies affect all cells and are deleterious, mitotic errors generate mosaicism, which may be compatible with healthy live birth. Large-scale abnormalities such as triploidy and haploidy also contribute to adverse pregnancy outcomes, but remain hidden from standard sequencing-based approaches to preimplantation genetic testing for aneuploidy (PGT-A). The ability to reliably distinguish meiotic and mitotic aneuploidies, as well as abnormalities in genome-wide ploidy, may thus prove valuable for enhancing IVF outcomes. Here, we describe a statistical method for distinguishing these forms of aneuploidy based on analysis of low-coverage whole-genome sequencing data, which is the current standard in the field. Our approach overcomes the sparse nature of the data by leveraging allele frequencies and linkage disequilibrium (LD) measured in a population reference panel. The method, which we term LD-informed PGT-A (LD-PGTA), retains high accuracy down to coverage as low as 0.05 × and at higher coverage can also distinguish between meiosis I and meiosis II errors based on signatures spanning the centromeres. LD-PGTA provides fundamental insight into the origins of human chromosome abnormalities, as well as a practical tool with the potential to improve genetic testing during IVF.

scholarly journals Preimplantation Genetic Testing Prevented Intergenerational Transmission of X-Linked Alport Syndrome

2021 ◽  
pp. 1-7
Author(s):  
Xiaoling Hu ◽  
Jiahui Zhang ◽  
Yuan Lv ◽  
Xijing Chen ◽  
Guofang Feng ◽  
...  
Keyword(s):  
Genetic Testing ◽  
Intergenerational Transmission ◽  
Alport Syndrome ◽  
Human Embryos ◽  
Radical Cure ◽  
Preimplantation Genetic Testing ◽  
Monogenic Disorders ◽  
Targeted Ngs ◽  
Stage Renal Disease

<b><i>Background:</i></b> Alport syndrome (AS) is a hereditary renal basement membrane disease that can lead to end-stage renal disease in young adults. It can be diagnosed by genetic analysis, being mostly caused by mutations in <i>COL4A3</i>, <i>COL­4A4</i>, and <i>COL4A5</i>. To date, there is no radical cure for this disease. <b><i>Objectives:</i></b> The aim of this study was to avoid the transmission of AS within an affected family by selecting healthy embryos for uterine transfer. The embryos were identified by preimplantation genetic testing for monogenic disorders (PGT-M). <b><i>Methods:</i></b> We used next-generation sequencing (NGS) to identify mutations in the proband and his parents. The results of NGS were confirmed by Sanger sequencing. Targeted NGS combined with targeted single-nucleotide polymorphism haplotyping was used for the in vitro identification of <i>COL4A5</i> mutations in human embryos to prevent their intergenerational transmission. <b><i>Results:</i></b> The c.349_359delGGACCTCAAGG and c.360_361insTGC mutations in <i>COL4A5</i> were identified in a family affected by X-linked AS. Whole-genome sequencing by NGS with targeted haplotyping was performed on biopsied trophectoderm cells. A healthy baby was born after transfer of a single freeze-thawed blastocyst. <b><i>Conclusions:</i></b> The use of targeted NGS for identifying diagnostic markers combined with targeted haplotyping is an easy and efficient PGT-M method for preventing intergenerational transmission of AS.

scholarly journals A Non-invasive Chromosome Screening Strategy for Prioritizing in vitro Fertilization Embryos for Implantation

2021 ◽  
Vol 9 ◽  
Author(s):  
Li Chen ◽  
Qin Sun ◽  
Juanjuan Xu ◽  
Haiyan Fu ◽  
Yuxiu Liu ◽  
...  
Keyword(s):  
Genetic Testing ◽  
Predictive Value ◽  
Large Scale ◽  
Human Embryos ◽  
Clinical Practices ◽  
Preimplantation Genetic Testing ◽  
Invasive Approach ◽  
Vitro Fertilization ◽  
Non Invasive

Preimplantation genetic testing for aneuploidy (PGT-A) is widely used to select embryos having normal ploidy for transfer, but they require an invasive embryo biopsy procedure that may cause harm to the embryos and offspring. Therefore, a non-invasive approach to select embryos with normal ploidy for implantation is highly demanded. Non-invasive chromosome screening (NICS) methods have been proposed and applied in clinical practices, but a large-scale validation versus invasive preimplantation genetic testing (PGT) and the whole embryo ploidy has not yet been reported. In this study, by using the whole embryo as a gold standard, we validated NICS assay in a total of 265 donated human embryos and compared its performance with conventional trophectoderm (TE) biopsy PGT. The NICS assay showed promising performance, which is comparable to PGT-TE [sensitivity: 87.36 versus 89.66%; specificity: 80.28 versus 82.39%; negative predictive value (NPV): 91.2 versus 92.86%; positive predictive value (PPV): 73.08 versus 75.73%]. Additionally, NICS provides a scoring system for prioritizing embryo: embryos can be categorized into three groups with euploid prediction probabilities of 90.0, 27.8, and 72.2% for group euploid (A), aneuploid (B), and multiple abnormal chromosomes (MAC) (C), respectively. When an addition of TE assay is provided as a secondary validation, the accuracy significantly increases from 72.2 to 84.3% for group B and from 27.8 to 83.3% for group C. Our results suggest that NICS is a good rule in assay for identifying chromosomal normal embryos for transfer and might serve as a non-invasive approach for prioritizing embryos instead of preventing transfer of aneuploid and MAC embryos. It will help to ensure the safety of offspring and efficient utilization of embryos.

scholarly journals Haplotype-aware inference of human chromosome abnormalities

2021 ◽  
Author(s):  
Daniel Ariad ◽  
Stephanie M. Yan ◽  
Andrea R. Victor ◽  
Frank L. Barnes ◽  
Christo G. Zouves ◽  
...  
Keyword(s):  
Genetic Testing ◽  
Human Chromosome ◽  
Large Scale ◽  
Chromosome Abnormalities ◽  
Whole Genome Sequencing Data ◽  
Sequencing Data ◽  
Current Standard ◽  
Preimplantation Genetic Testing ◽  
Adverse Pregnancy

Extra or missing chromosomes—a phenomenon termed aneuploidy—frequently arises during human meiosis and embryonic mitosis and is the leading cause of pregnancy loss, including in the context of in vitro fertilization (IVF). While meiotic aneuploidies affect all cells and are deleterious, mitotic errors generate mosaicism, which may be compatible with healthy live birth. Large-scale abnormalities such as triploidy and haploidy also contribute to adverse pregnancy outcomes, but remain hidden from standard sequencing-based approaches to preimplantation genetic testing (PGT-A). The ability to reliably distinguish meiotic and mitotic aneuploidies, as well as abnormalities in genome-wide ploidy may thus prove valuable for enhancing IVF outcomes. Here, we describe a statistical method for distinguishing these forms of aneuploidy based on analysis of low-coverage whole-genome sequencing data, which is the current standard in the field. Our approach overcomes the sparse nature of the data by leveraging allele frequencies and linkage disequilibrium (LD) measured in a population reference panel. The method, which we term LD-informed PGT-A (LD-PGTA), retains high accuracy down to coverage as low as 0.05x and at higher coverage can also distinguish between meiosis I and meiosis II errors based on signatures spanning the centromeres. LD-PGTA provides fundamental insight into the origins of human chromosome abnormalities, as well as a practical tool with the potential to improve genetic testing during IVF.

scholarly journals Preimplantation genetic testing for aneuploidy in uterus transplant patients

2021 ◽  
Vol 15 ◽  
pp. 263349412110098
Author(s):  
Rhea Chattopadhyay ◽  
Elliott Richards ◽  
Valerie Libby ◽  
Rebecca Flyckt
Keyword(s):  
Genetic Testing ◽  
In Vitro Fertilization ◽  
Immunosuppressive Agents ◽  
Live Birth Rate ◽  
Preimplantation Genetic Testing ◽  
Vitro Fertilization ◽  
Uterus Transplantation ◽  
Advantages And Disadvantages ◽  
Dilation And Curettage

Uterus transplantation is an emerging treatment for uterine factor infertility. In vitro fertilization with cryopreservation of embryos prior is required before a patient can be listed for transplant. Whether or not to perform universal preimplantation genetic testing for aneuploidy should be addressed by centers considering a uterus transplant program. The advantages and disadvantages of preimplantation genetic testing for aneuploidy in this unique population are presented. The available literature is reviewed to determine the utility of preimplantation genetic testing for aneuploidy in uterus transplantation protocols. Theoretical benefits of preimplantation genetic testing for aneuploidy include decreased time to pregnancy in a population that benefits from minimization of exposure to immunosuppressive agents and decreased chance of spontaneous abortion requiring a dilation and curettage. Drawbacks include increased cost per in vitro fertilization cycle, increased number of required in vitro fertilization cycles to achieve a suitable number of embryos prior to listing for transplant, and a questionable benefit to live birth rate in younger patients. Thoughtful consideration of whether or not to use preimplantation genetic testing for aneuploidy is necessary in uterus transplant trials. Age is likely a primary factor that can be useful in determining which uterus transplant recipients benefit from preimplantation genetic testing for aneuploidy.

Is there still a rationale for non-invasive PGT-A by analysis of cell-free DNA released by human embryos into culture medium?

2021 ◽  
Vol 36 (5) ◽  
pp. 1186-1190
Author(s):  
Raoul Orvieto ◽  
Adva Aizer ◽  
Norbert Gleicher
Keyword(s):  
Culture Media ◽  
Chromosomal Rearrangements ◽  
Primary Source ◽  
Normal Pregnancy ◽  
Early Embryo ◽  
Human Embryos ◽  
Cell Debris ◽  
Cell Free Dna ◽  
Non Invasive ◽  
Free Dna

Abstract Human embryos utilise an array of processes to eliminate the very high prevalence of aneuploid cells in early embryo stages. Human embryo self-correction was recently demonstrated by their ability to eliminate/expel abnormal blastomeres as cell debris/fragments. A whole genome amplification study has demonstrated that 63.6% of blastocysts expelled cell debris with abnormal chromosomal rearrangements. Moreover, 55.5% of euploid blastocysts expel aneuploid debris, strongly suggesting that the primary source of cell free DNA in culture media is expelled aneuploid blastomeres and/or their fragments. Such a substantial ability to self-correct downstream from the blastocyststage, therefore, renders any chromosomal diagnosis at the blastocyststage potentially useless, and this, unfortunately, also must particularly include non-invasive PGT-A based on cell-free DNA in spent medium. High rates of false-positive diagnoses of human embryos often lead to non-use and/or disposal of embryos with entirely normal pregnancy potential. Before adopting yet another round of unvalidated PGT-A as a routine adjunct to IVF, we here present facts that deserve to be considered.

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