The inconsistency between two major aneuploidy-screening platforms-single-nucleotide polymorphism array and next-generation sequencing-in the detection of embryo mosaicism.

BACKGROUND: In preimplantation genetic testing for aneuploidy (PGT-A), appropriate evaluation of mosaic embryos is important because of the adverse implications of transferring embryos with high-level mosaicism or discarding those with low-level mosaicism. Despite the availability of multiple reliable techniques for PGT-A, data comparing the detection of mosaicism using these techniques are scarce. To address this gap in the literature, we compared the detection ability of the two most commonly used PGT-A platforms, next-generation sequencing (NGS) and the single-nucleotide polymorphism (SNP) array, for mosaic embryos. RESULTS: We retrospectively reviewed the data of PGT-A or preimplantation genetic testing for chromosomal structural rearrangements (PGT-SR) conducted at our center from January 2018 to October 2020, and selected blastocysts that underwent aneuploidy screening with both an SNP array and NGS. Trophectoderm biopsy, multiple displacement amplification (MDA), and aneuploidy screening with an SNP array were conducted on the enrolled blastocysts. When the SNP array indicated mosaicism, NGS was performed on the corresponding MDA product for verification. Among the 105 blastocysts diagnosed with mosaicism with the SNP array, 80 (76.19%) showed mosaicism in NGS, with complete and partial concordance rates of 47.62% (50/105) and 18.10% (19/105), respectively. The complete discordance rate of the two platforms was 34.29% (36/105). That is, 10.48% (11/105) of the blastocysts were diagnosed with completely different types of mosaicism with the two platforms, while 13.33% (14/105) and 10.48% (11/105) of the embryos diagnosed as showing mosaicism with SNP were detected as showing aneuploidy and euploidy with NGS, respectively. CONCLUSIONS: The consistency of NGS and the SNP array in the diagnosis of embryo mosaicism is extremely low, indicating the need for larger and well-designed studies to determine which platform is more accurate in detecting mosaic embryos.

Comparison of two mainstream endometrial preparation regimens in vitrified-warmed embryo transfers after PGT.

RESEARCH QUESTION: Which of the two mainstream endometrial preparation regimens, assisted natural cycle (NC) or hormone replacement treatment cycle (HRT), help frozen-thawed embryo transfer (FET) cycles after preimplantation genetic testing (PGT) achieve better clinical outcomes? DESIGN: This retrospective analysis included 3400 vitrified-warmed single blastocyst transfer cycles after PGT from January 2011 to November 2020, and involved 2332 patients with regular menstrual cycles. The decision to proceed with an assisted NC (n = 827) or HRT (n = 2573) before FET was reached based on a combination of patient preference and physician guidance. Clinical pregnancy rate, live birth rate, early miscarriage rate and obstetric outcomes were compared. RESULTS: No significant difference was observed between the assisted NC and HRT groups in terms of clinical pregnancy rate (51.6% versus 50.7%, P = 0.634), live birth rate (44.0% versus 43.4%, P = 0.746) or early miscarriage rate (12.6% versus 12.0%, P = 0.707). Multivariate analysis indicated that the endometrial preparation protocol was not an independent factor for a clinical pregnancy or live birth. In the HRT group, the Caesarean section rate (64.7% versus 51.9%, P < 0.001) and pregnancy complication rate (20.2% versus 13.8%, P = 0.003) were significantly higher. The two groups were not statistically different with respect to gestational age, early preterm birth rate, fetal weight or fetal birth defect rate. CONCLUSIONS: For patients undergoing a PGT-FET cycle involving a single blastocyst transfer, using assisted NC and HRT for the endometrial preparation could lead to comparable rates of clinical pregnancy and live birth. Additionally, NC is safer than HRT in terms of avoiding pregnancy complications and adverse obstetric outcomes.

Evaluating the application value of NGS-based PGT-A by screening cryopreserved MDA products of embryos from PGT-M cycles with known transfer outcomes.

PURPOSE: To determine the application value of next-generation sequencing (NGS)-based preimplantation genetic testing for aneuploidies (PGT-A). METHODS: We conducted a retrospective case-control study on a cohort of frozen-thawed embryo transfer (FET) cycles following preimplantation genetic testing for monogenic disorders (PGT-M) between 2014 and 2017. Cycles that produced live births or early miscarriages were divided into live birth group (n = 76) or miscarriage group (n = 19), respectively. The NGS-based aneuploidy screening was performed on the multiple displacement amplification (MDA) products of the embryonic trophectoderm biopsy samples that were cryopreserved following PGT-M. RESULTS: In the live birth group, 75% (57/76) embryos were euploid and 14.5% (11/76) were aneuploid. The remaining 10.5% (8/76) embryos were NGS-classified mosaic with the high- (≥ 50%) and low-level (< 50%) mosaicism rates at 7.9% (6/76) and 2.6% (2/76), respectively. In the miscarriage group, only 23.5% (4/17) embryos were aneuploid, while 58.8% (10/17) were euploid and 17.6% (3/17) were NGS-classified mosaic with the high- and low-level mosaicism rates at 11.8% (2/17) and 5.9% (1/17), respectively. For live birth and miscarriage groups, the transferable rate was 82.9% (63/76) and 70.6% (12/17), respectively, whereas the untransferable rate was 17.1% (13/76) and 29.4% (5/17), respectively. CONCLUSION: The application of NGS-based PGT-A remains questionable, as it may cause at least one in six embryos with reproductive potential to be discarded and prevent miscarriage in less than one in three embryos in single-gene disease carriers.

Feasibility study of using unbalanced embryos as a reference to distinguish euploid carrier from noncarrier embryos by single nucleotide polymorphism array for reciprocal translocations.

OBJECTIVES: To study the feasibility of using unbalanced embryos as a reference in distinguishing euploid carrier and noncarrier embryos by single nucleotide polymorphism (SNP) array-based preimplantation genetic testing (PGT) for reciprocal translocations. METHODS: After comprehensive chromosome screening (CCS), euploid embryos were identified as normal or carriers using a family member as a reference. Next, unbalanced embryos were used as a reference, and the results were compared with the previous ones. Karyotypes of transferred embryos were validated by prenatal diagnosis. RESULTS: Of 995 embryos from 110 couples, 288 were found to be euploid. Using a family member as a reference, 142 and 144 embryos were tested to be euploid noncarrier and carrier respectively, and the remaining 2 embryos were undetermined. When unbalanced embryos were selected as references, all the results were consistent with the previous ones. A total of 107 embryos were transferred, resulting in 66 clinical pregnancies. Karyotypes of prenatal diagnosis were all in accordance with the results of tested embryos. CONCLUSIONS: SNP array-based haplotyping is a rapid and effective way to distinguish between euploid carrier and noncarrier embryos. In case no family member is available as a reference, unbalanced embryos can be used for identification of euploid carrier and noncarrier embryos.

Karyomapping in preimplantation genetic testing for ß-thalassemia combined with HLA matching: a systematic summary.

PURPOSE: To investigate the validity, accuracy, and clinical outcomes of Karyomapping in preimplantation genetic testing (PGT) for ß-thalassemia combined with human leukocyte antigen (HLA) matching. METHODS: A total of 128 cycles from January 2014 to December 2017 were identified, and 1205 embryos were biopsied. The case group included 88 cycles using Karyomapping for PGT-HLA, compared with 40 cycles using polymerase chain reaction-short tandem repeat (PCR-STR) as the control group. RESULTS: There were significant differences in the HLA matching rate (21.34 vs. 14.37%), the matched transferable embryo rate (9.79 vs. 14.07%), the clinical pregnancy rate (65.08 vs. 41.86%), and the spontaneous miscarriage rate (2.44 vs. 22.22%) between the case and control groups. In the case group, nearly 1/3 (33.37%) of the embryos showed aneuploidy. According to the results of single nucleotide polymorphism (SNP) haplotype analysis, the recombination rates of HBB (hemoglobin subunit beta) and HLA were 11.46% and 5.61% respectively. HLA gene recombination was mostly distributed between HLA-A and HLA-B and the downstream region of HLA-DQB1. In addition, STR analysis could be considered in the case of copy-neutral loss of heterozygosity (LOH) in the region where the HLA gene is located. CONCLUSION: Karyomapping contributes to accurate selection of matched embryos, along with aneuploidy screening. However, STRs assist identification in cases of LOH in the target region.

Clinical application of next generation sequencing-based haplotype linkage analysis in the preimplantation genetic testing for germline mosaicisms.

BACKGROUND: Preimplantation genetic testing (PGT) for monogenic disorders (PGT-M) for germline mosaicism was previously highly dependent on polymerase chain reaction (PCR)-based directed mutation detection combined with linkage analysis of short tandem repeats (STRs). However, the number of STRs is usually limited. In addition, designing suitable probes and optimizing the reaction conditions for multiplex PCR are time-consuming and laborious. Here, we evaluated the effectiveness of next generation sequencing (NGS)-based haplotype linkage analysis in PGT of germline mosaicism. METHODS: PGT-M with NGS-based haplotype linkage analysis was performed for two families with maternal germline mosaicism for an X-linked Duchenne muscular dystrophy (DMD) mutation (del exon 45-50) or an autosomal TSC1 mutation (c.2074C > T). Trophectoderm biopsy and multiple displacement amplification (MDA) were performed for a total of nine blastocysts. NGS and Sanger sequencing were performed in genomic DNA of family members and embryonic MDA products to detect DMD deletion and TSC1 mutation, respectively. Single nucleotide polymorphism (SNP) sites closely linked to pathogenic mutations were detected with NGS and served in haplotype linkage analysis. NGS-based aneuploidy screening was performed for all embryos to reduce the risk of pregnancy loss. RESULTS: All nine blastocytes showed conclusive PGT results. Each family underwent one or two frozen-thawed embryo transfer cycles to obtain a clinical pregnancy, and the prenatal diagnosis showed that the fetus was genotypically normal and euploid for both families. CONCLUSIONS: NGS-SNP could effectively realize PGT for germline mosaicism. Compared with PCR-based methods, the NGS-SNP method with increased polymorphic informative markers can achieve a greater diagnostic accuracy. Further studies are warranted to verify the effectiveness of NGS-based PGT of germline mosaicism cases in the absence of surviving offsprings.

Comparison of chromosomal status in reserved multiple displacement amplification products of embryos that resulted in miscarriages or live births: a blinded, nonselection case-control study.

OBJECTIVE: To analyze chromosomal status in reserved multiple displacement amplification (MDA) products of embryos that result in miscarriages or live births. METHODS: Patients who underwent preimplantation genetic testing for monogenic disorders (PGT-Ms) without aneuploidy screening were included. The case group included 28 cycles that resulted in miscarriages. Controls included 56 cycles with live births. Comprehensive chromosomal screening (CCS) using next-generation sequencing (NGS) was performed on reserved MDA products from previous blastocyst trophectoderm biopsies. The incidence and type of chromosomal abnormalities in embryos resulting in miscarriages or live births were analyzed. RESULTS: Of 28 embryos resulting in miscarriages in the case group, the rate of chromosomal abnormalities was 53.6%, which was significantly greater than 14.3% for those resulting in live births in control group (P < 0.001). Whole-chromosome aneuploidy was not found in the control group but was noted in 25.0% of embryos in the case group. Although the rates of segmental abnormality and mosaicism were also greater in the case group, no significant differences were detected. One chaotic embryo in the control group progressed to live birth. CONCLUSION: Chromosomal abnormalities were the main reason leading to early pregnancy loss. However, abnormalities, such as segmental aneuploidy and mosaicism, should be managed cautiously, considering their undermined reproductive potential.

Simultaneous detection of genomic imbalance in patients receiving preimplantation genetic testing for monogenic diseases (PGT-M).

Background: Preimplantation genetic test for monogenic disorders (PGT-M) has been used to select genetic disease-free embryos for implantation during in vitro fertilization (IVF) treatment. However, embryos tested by PGT-M have risks of harboring chromosomal aneuploidy. Hence, a universal method to detect monogenic diseases and genomic imbalances is required. Methods: Here, we report a novel PGT-A/M procedure allowing simultaneous detection of monogenic diseases and genomic imbalances in one experiment. Library was prepared in a special way that multiplex polymerase chain reaction (PCR) was integrated into the process of whole genome amplification. The resulting library was used for one-step low-pass whole genome sequencing (WGS) and high-depth target enrichment sequencing (TES). Results: The TAGs-seq PGT-A/M was first validated with genomic DNA (gDNA) and the multiple displacement amplification (MDA) products of a cell line. Over 90% of sequencing reads covered the whole-genome region with around 0.3-0.4 × depth, while around 5.4%-7.3% of reads covered target genes with >10000 × depth. Then, for clinical validation, 54 embryos from 8 women receiving PGT-M of ß-thalassemia were tested by the TAGs-seq PGT-A/M. In each embryo, an average of 20.0 million reads with 0.3 × depth of the whole-genome region was analyzed for genomic imbalance, while an average of 0.9 million reads with 11260.0 × depth of the target gene HBB were analyzed for ß-thalassemia. Eventually, 18 embryos were identified with genomic imbalance with 81.1% consistency to karyomapping results. 10 embryos contained ß-thalassemia with 100% consistency to conventional PGT-M method. Conclusion: TAGs-seq PGT-A/M simultaneously detected genomic imbalance and monogenic disease in embryos without dramatic increase of sequencing data output.

Rapid characterization of sugar-binding specificity by in-solution proximity binding with photosensitizers.

Cell-surface carbohydrates are known to participate in many important physiological and pathological activities by interacting with their corresponding proteins or receptors. Although several methods have been developed for studying carbohydrate-protein interactions, one major problem originates from the weak bindings of carbohydrates/proteins that are often lost during repeating wash steps. Herein, we established a homogeneous solution carbohydrate array in which polyacrylamide-based glycans are used for offering a multivalent environment. The method requires no wash step and can be carried out in a high-throughput manner. We characterized the carbohydrate-binding specificities of 11 lectins and 7 antibodies, the majority of which displayed the binding patterns in consistence with previous reports. These results demonstrate that our developed solution carbohydrate array provides a useful alternative that is better than or comparable with the current available methods.

Role of aneuploidy screening in preimplantation genetic testing for monogenic diseases in young women.

OBJECTIVE: To investigate whether aneuploidy screening in preimplantation genetic testing (PGT) for monogenic diseases improves the ongoing pregnancy/live birth rate of single frozen/thawed embryo transfer (FET) cycles in young women. DESIGN: Retrospective cohort study. SETTING: Single university-based fertility center. PATIENT(S): From January 2016 to December 2017, 569 FET cycles were selected for analysis. The aneuploidy screening (AS) group included 131 FET cycles from 105 oocyte retrieval cycles in 98 patients who underwent PGT for monogenic diseases with aneuploidy screening, and the non-AS group included 438 FET cycles from 280 oocyte retrieval cycles in 266 patients who underwent PGT for monogenic diseases without aneuploidy screening. INTERVENTION(S): The patient population was all under the age of 35 years and underwent PGT for monogenic diseases with and without AS. MAIN OUTCOME MEASURE(S): Ongoing pregnancy/live birth rate, live birth rate, implantation rate, and miscarriage rate. RESULT(S): Aneuploidy screening significantly improved the ongoing pregnancy/live birth rate (61.22% vs. 43.98%), implantation rate (64.29% vs. 50.38%), and live birth rate (53.06% vs. 36.09%) of young women carrying monogenic diseases in the first FET cycles. When adjusted for the parity, number of previous miscarriages, and percentage of infertility, the likelihood of implantation was 1.874 times higher (95% confidence interval 1.126-3.119), and an ongoing pregnancy/live birth was 2.139 times more likely (95% confidence interval 1.295-3.534). In addition, the miscarriage rate was significantly decreased (3.17% vs. 11.94%). In the cumulative pregnancy outcomes, the cumulative ongoing pregnancy/live birth rate both per transfer and per patient were significantly higher in the AS group (62.24% vs. 50.38% and 79.59% vs. 68.80%), but no difference existed after adjusting for the parity, number of previous miscarriage, and percentage of infertility. Nevertheless, aneuploidy screening reduced the time interval from the first ET to the achievement a pregnancy. CONCLUSION(S): Aneuploidy screening in PGT significantly improved the ongoing pregnancy/live birth rate of young women carrying monogenic diseases in the first FET cycles.

Rapid synthesis of oligomannosides with orthogonally protected monosaccharides.

We developed a facile synthesis to yield orthogonally protected mannose building blocks with high overall yields. The protection/glycosylation steps can be carried out in a successive manner without purification of intermediate products. This developed synthesis led to formation of linear/branched tri-, penta- and heptasaccharides.

Structure and mechanism of Helicobacter pylori fucosyltransferase. A basis for lipopolysaccharide variation and inhibitor design.

Helicobacter pylori alpha1,3-fucosyltransferase (FucT) is involved in catalysis to produce the Lewis x trisaccharide, the major component of the bacteria's lipopolysaccharides, which has been suggested to mimic the surface sugars in gastric epithelium to escape host immune surveillance. We report here three x-ray crystal structures of FucT, including the FucT.GDP-fucose and FucT.GDP complexes. The protein structure is typical of the glycosyltransferase-B family despite little sequence homology. We identified a number of catalytically important residues, including Glu-95, which serves as the general base, and Glu-249, which stabilizes the developing oxonium ion during catalysis. The residues Arg-195, Tyr-246, Glu-249, and Lys-250 serve to interact with the donor substrate, GDP-fucose. Variations in the protein and ligand conformations, as well as a possible FucT dimer, were also observed. We propose a catalytic mechanism and a model of polysaccharide binding not only to explain the observed variations in H. pylori lipopolysaccharides, but also to facilitate the development of potent inhibitors.

Chiral Lewis acid-catalyzed asymmetric Baylis-Hillman reactions.

An effective chiral Lewis acid-catalyzed asymmetric Baylis-Hillman reaction is described. Good to high enantioselectivities were obtained using 3 mol % chiral catalyst. Novel camphor-derived dimerized ligands were prepared from the condensation of (+)-ketopinic acid with the corresponding diamines and hydrazine under acidic conditions. When alpha-naphthyl acrylate was used as a Michael acceptor, the reaction is complete within 20 min with high stereoselectivity and in reasonable chemical yields.