Chromosomal Mosaicism Research Articles

Investigation of perinatal chromosomal mosaicism – using evidence to inform best practice

Investigation of perinatal chromosomal mosaicism – using evidence to inform best practice

Evaluating Chromosomal Mosaicism in Prenatal Diagnosis: The Complementary Roles of Chromosomal Microarray Analysis and Karyotyping.

To explore the impact of invitro cell subculture on prenatal diagnostic sample results and compare the efficacy of conventional karyotyping and chromosomal microarray analysis (CMA) in detecting chromosome mosaicism. We conducted a retrospective analysis of G-banding karyotyping and CMA data from 2007 amniocentesis cases to investigate chromosome mosaicism. Chromosome mosaicism was detected in 1.49% of cases (30/2007). Sex chromosome mosaicism was the most common form of mosaicism. Among the 30 mosaicisms, 18 results were consistent between the two methods. In four cases, CMA indicated mosaicism but the karyotypes were normal. In eight cases, CMA was normal while the karyotypes suggested mosaicism. CMA and karyotyping complement each other in prenatal genetic diagnosis. Combining both methods enhances detection accuracy, particularly in cases of chromosomal mosaicism, which may be missed after the subculture of adherent cells in karyotype analysis.

Time-lapse analysis of embryos classified as euploid, mosaic, and aneuploid after embryonic trophectoderm biopsy.

Analyze morphokinetic, morphology, and KIDscore™Day5 in different PGT-A classes, focusing on putative mosaicism level and type. The single-center retrospective study analyzed 832 embryoscope-cultured blastocysts from cycles with at least one putative mosaic, conducted from 2020 to 2022. A P-value < 0.05 was considered statistically significant. Putative mosaic embryos were significantly delayed compared to euploid in tPNF, t2, t4, t7, and t8 but significantly faster than aneuploid in tPNF, t2, t3, t4, t5, tSC, tM, tSB, and tB. Regarding the level, low-putative mosaic embryos (< 50%) showed significantly earlier tSC, tM, tSB, and tB compared to aneuploid, whereas high-putative mosaic embryos exhibited significantly earlier tSB and tB. Concerning the type of putative mosaicism, segmental aneuploidies reached significantly earlier t8, tM, and tB than complex aneuploidies. The study also investigated the usefulness of KIDscore™Day5 for embryo selection as an additional tool to PGT-A. A significant decrease in KIDscore™Day5 was observed from euploid to low-putative mosaic, from high-putative mosaic to aneuploid, and between segmental and complex-putative mosaic. The observed differences in KIDscore™Day5 were partially confirmed by transfer results: euploid blastocysts showed the most favorable clinical outcomes compared to low- and high-putative mosaics. Additionally, both euploid and segmental putative mosaic embryos exhibited the best clinical results compared to whole chromosome and complex putative mosaic. Moreover, within the same PGT-A class, embryos with the lowest KIDscore™Day5 values had significantly lower clinical results. The data highlight that morphology, morphokinetics, and chromosome content in trophectoderm biopsy are closely related, and the KIDscore™Day5 algorithm reflects this interplay.

Embryo Mosaicism Rate in National Referral Hospital of Indonesia Detected Using Next-Generation Sequencing: A Retrospective Study.

Chromosomal mosaicism, a phenomenon observed in a minority of embryos, showcases its prevalence and inherent unpredictability, leading to variations in embryo mosaic rates across different centers. This research endeavors to assess the prevalence of mosaicism and its characteristics within the scope of our preimplantation genetic testing-A (PGT-A) services in Indonesia. Specifically focusing on our center's experience since 2020, this study aims to elucidate mosaic rates among embryos in our care. In a retrospective approach, we collected secondary data sourced from our PGT-A outcomes dating back to 2020. A total of 196 embryos underwent analysis, their characteristics were documented and presented descriptively. Notably, the incidence of specific chromosome abnormalities was outlined. We assess a comparative analysis to investigate the relationship between mosaicism and its corresponding clinical characteristics. In the analysis of 196 embryos, 106 (54.1%) displayed chromosomal anomalies spanning from low-level mosaicism to whole chromosome aneuploidy. Low mosaicism was observed in 25 (12.8%) of the embryos, while high mosaicism was identified in 8 (4.1%) embryos. Notably, low-level mosaicism predominated in chromosome 9 (n=10, 5.1%), whereas abnormality prevalence was highest in chromosome 21 (n=20, 10.2%). Statistical analysis revealed no significant disparity in mean maternal age among embryos with low-level mosaicism, high mosaicism, and normal chromosomes (33.88 vs. 35 vs. 33.26 years old, respectively). However, a statistically significant difference in mean maternal age (35.84 vs. 33.26 years) was observed between embryos with aneuploidy (monosomy or trisomy) and those with normal chromosomes. Furthermore, a significant difference in high mosaicism rates was detected in patients with unexplained infertility (P<0.05). In contrast to the study conducted elsewhere, our center had a higher mosaicism rate. Chromosomes 9, 8, and 6 were the most frequently affected. There was a significant difference in the high mosaicism rate for PGT-Arelated unexplained infertility causes.

Chromosomal Mosaicism in the Placenta.

The clinical implications of placental chromosomal mosaicism can be challenging for patients and health care providers. Key considerations include the specific characteristics of the chromosomal abnormality (such as size, gene content, and copy number), the timing of the mosaicism's onset during embryogenesis or fetal development, the types of tissues involved, and the level of mosaicism (the ratio of normal to abnormal cells within those tissues). Genetic counseling can help inform patients about the chances of having a live-born child with a chromosomal abnormality. Each case requires individual assessment to provide accurate guidance. This chapter will explore the clinical implications of detecting mosaicism at 3 critical diagnostic stages: (1) chorionic villus sampling (CVS); (2) amniocentesis; and (3) cell-free DNA (cfDNA) testing.

Нарушение сперматогенеза и мейоза у пациентов с мозаицизмом и/или структурными аномалиями Y-хромосомы

Unbalanced structural Y chromosome abnormalities and pathogenic Y chromosome microdeletions are common genetic cause of severe male infertility due to spermatogenesis damage. Sex chromosomes (gonosomes) abnormalities are often associated with mosaicism the presence and percentage of gonosomal mosaicism may modify the damage of the negative effect of sex chromosome abnormalities and X- and Y-linked mutations. The combined effect of structural abnormalities and mosaicism of the Y chromosome on male fertility and semen parameters has not been sufficiently studied. The aim of the study was the analysis of the spermatological and genetic examination in mosaic patients with/or without structural abnormalities of the Y chromosome to evaluate the spermatogenesis and meiosis defects. Material and methods. A group of 40 men aged 31±7 (from 16 to 49) years was examined, mosaicism and/or structural abnormalities/variants of the Y chromosome were found in the karyotype of patients. The karyotype detected on the results of a standard cytogenetic study (on cultured peripheral blood lymphocytes), a FISH study with DNA probes for X and Y chromosomes was additionally performed. The presence/absence of Y-specific sequences (SRY and AZFa,b,c loci) was determined by multiplex polymerase chain reaction. A standard spermiological examination was performed according to the WHO Laboratory Manual, quantitative karyological analysis (QKA) of immature germ cells (IGCs) was performed in 12 patients. Results. Y chromosome mosaicism was found in 29 (72.5%) patients. Pathogenic AZF microdeletions (AZFa+b+c, n=3; AZFb+c, n=19; AZFc, n=3) were detected in 25 (62.5%) men, 17 of them had the Y chromosome mosaicism. Non-obstructive azoospermia and severe oligozoospermia were found in 88% and 12% of men with AZF deletions, and without AZF deletions in 47% and 20% of patients, respectively. Normozoospermia and mild forms of pathozoospermia were revealed in patients without AZF deletions. Only severe forms of spermatogenesis defects were found in all men with Yq11.2 deletions, ring and pseudodicentric Y chromosomes. QKA of IGCs revealed cryptozoospermia in 7 out of 10 azoospermic patients (according to semen analyses data) and signs of a partial meiotic arrest of spermatogenesis at pachytene and/or at the pre-pachytene stages of prophase I of meiosis. Conclusion. In patients with mosaicism and/or structural abnormalities of the Y chromosome, the spermatogenesis disorders vary from their absence to their severe forms. The severity of the spermatogenesis depletion depends on structural anomalies and Yq11.2(AZF) deletions, their type, and the breakpoints location, the additional pathogenic factors. Gonosomal mosaicism is an additional pathogenic factor affected fertility that can increase genetic and phenotypic changes.

Complex aneuploidy triggers autophagy and p53-mediated apoptosis and impairs the second lineage segregation in human preimplantation embryos

About 70% of human cleavage stage embryos show chromosomal mosaicism, falling to 20% in blastocysts. Chromosomally mosaic human blastocysts can implant and lead to healthy new-borns with normal karyotypes. Studies in mouse embryos and human gastruloids showed that aneuploid cells are eliminated from the epiblast by p53-mediated apoptosis while being tolerated in the trophectoderm. These observations suggest a selective loss of aneuploid cells from human embryos, but the underlying mechanisms are not yet fully understood. Here, we investigated the cellular consequences of aneuploidy in a total of 125 human blastocysts. RNA-sequencing of trophectoderm cells showed activated p53 pathway and apoptosis proportionate to the level of chromosomal imbalance. Immunostaining corroborated that aneuploidy triggers proteotoxic stress, autophagy, p53-signaling, and apoptosis independent from DNA damage. Total cell numbers were lower in aneuploid embryos, due to a decline both in trophectoderm and in epiblast/primitive endoderm cell numbers. While lower cell numbers in trophectoderm may be attributed to apoptosis, aneuploidy impaired the second lineage segregation, particularly primitive endoderm formation. This might be reinforced by retention of NANOG. Our findings might explain why fully aneuploid embryos fail to further develop and we hypothesize that the same mechanisms lead to the removal of aneuploid cells from mosaic embryos.

Complex aneuploidy triggers autophagy and p53-mediated apoptosis and impairs the second lineage segregation in human preimplantation embryos.

About 70% of human cleavage stage embryos show chromosomal mosaicism, falling to 20% in blastocysts. Chromosomally mosaic human blastocysts can implant and lead to healthy new-borns with normal karyotypes. Studies in mouse embryos and human gastruloids showed that aneuploid cells are eliminated from the epiblast by p53-mediated apoptosis while being tolerated in the trophectoderm. These observations suggest a selective loss of aneuploid cells from human embryos, but the underlying mechanisms are not yet fully understood. Here, we investigated the cellular consequences of aneuploidy in a total of 125 human blastocysts. RNA-sequencing of trophectoderm cells showed activated p53 pathway and apoptosis proportionate to the level of chromosomal imbalance. Immunostaining corroborated that aneuploidy triggers proteotoxic stress, autophagy, p53-signaling, and apoptosis independent from DNA damage. Total cell numbers were lower in aneuploid embryos, due to a decline both in trophectoderm and in epiblast/primitive endoderm cell numbers. While lower cell numbers in trophectoderm may be attributed to apoptosis, aneuploidy impaired the second lineage segregation, particularly primitive endoderm formation. This might be reinforced by retention of NANOG. Our findings might explain why fully aneuploid embryos fail to further develop and we hypothesize that the same mechanisms lead to the removal of aneuploid cells from mosaic embryos.

Approximate Bayesian computation supports a high incidence of chromosomal mosaicism in blastocyst-stage human embryos.

Chromosome mis-segregation is common in human meiosis and mitosis, and the resulting aneuploidies are the leading cause of pregnancy loss. Preimplantation genetic testing for aneuploidy (PGT-A) seeks to prioritize chromosomally normal embryos for transfer based on genetic analysis of a biopsy of approximately five trophectoderm cells from blastocyst-stage in vitro fertilized (IVF) embryos. While modern PGT-A platforms classify these biopsies as aneuploid, euploid, or mosaic (possessing a mixture of normal and aneuploid cells), the underlying incidences of aneuploid, euploid, and mosaic embryos and the rates of meiotic and mitotic error that produced them remain largely unknown. To address this knowledge gap, we paired a recent method for embryo simulation with approximate Bayesian computation (ABC) to infer rates of meiotic and mitotic error that best explain published PGT-A data. By simulating from these posterior distributions, we also evaluated the chromosomal status of entire embryos. For a published clinical sample, we estimated a 39-43% probability of meiotic error per meiosis, as well as a 1.0-3.0% probability of mitotic error per mitosis, depending on assumptions about spatial clustering of aneuploid cells within mosaic embryos. In addition, our analyses suggest that less than 1% of blastocysts are fully euploid, and that many embryos possess low-level mosaic clones that are not captured during biopsy. These broad conclusions were relatively insensitive to potential misclassification of mosaic biopsies. Together, our work helps overcome the limitations of embryo biopsies to estimate the fundamental rates of cell division errors that are the main causes of human pregnancy loss.

Analysis of non-targeted variants by invasive prenatal diagnosis for pregnant women undergoing preimplantation genetic testing

To compare the results of invasive prenatal diagnosis and preimplantation genetic testing (PGT) and explore the underlying mechanism. Clinical data of pregnant women undergoing PGT and invasive prenatal diagnosis at the Sixth Affiliated Hospital of Sun Yat-sen University from January 2019 to December 2022 were collected. The results of PGT and invasive prenatal diagnosis were compared, and the outcomes of pregnancies were followed up. This study has been approved by the Medical Ethics Committee of the Sixth Affiliated Hospital of Sun Yat-sen University (No. 2022ZSLYEC-491). A total of 172 couples were included in this study, and 26 non-targeted variants were discovered upon prenatal diagnosis, including 10 cases (38.5%) by chromosomal karyotyping, 15 (57.7%) by chromosomal microarray analysis (CMA), and 1 (3.8%) by whole exome sequencing. The 10 karyotypic anomalies had included 6 chromosomal polymorphisms, 2 chromosomal mosaicisms, 1 paternally derived translocation, and 1 missed maternal chromosomal inversion. CMA has identified 15 copy number variations (CNVs), which included 11 microdeletions and microduplications, 3 loss of heterozygosity, and 1 low-level mosaicism of paternal uniparental disomy. One CNV was classified as pathogenic, and another one was likely pathogenic, whilst the remaining 13 were classified as variants of uncertain significance. Therefore, 8.7% of CNVs was detected by invasive prenatal diagnosis after PGT. 92.3% (24/26) of the non-targeted variants have been due to technological limitations of next-generation sequencing (NGS). Invasive prenatal diagnosis after PGT can detect non-targeted variants, which may further reduce the incidence of birth defects.

Feasibility of preimplantation genetic testing for aneuploidy on frozen-thawed embryos following conventional IVF insemination.

Intracytoplasmic sperm injection (ICSI) is commonly employed in preimplantation genetic testing (PGT) to minimize the risk of foreign sperm DNA contamination. Cryopreserved embryos from patients with recurrent miscarriage or repeated implantation failure, who have undergone conventional in vitro fertilization (IVF), can be thawed and biopsied for PGT. Therefore, we aimed to assess the accuracy and effectiveness of preimplantation genetic testing for aneuploidy (PGT-A) on frozen embryos using conventional IVF (c-IVF) insemination methods. From January 2021 to November 2023, our center conducted 107 thawed cryopreserved embryo biopsy cycles to screen for PGT-A. Among them, 58 cycles used c-IVF insemination, and 49 used ICSI insemination. Basic patient clinical information, laboratory data, PGT test results, and clinical outcome data were collected. To minimize the confounding effects of patient characteristics and embryo quality on PGT-A outcomes, clinical outcomes, and contamination assessment, these variables were included in the analysis. We then evaluated the blastocyst euploidy rate, clinical outcomes, and accuracy of PGT-A results between the two groups and analyzed potential contamination in the c-IVF insemination group. A total of 320 blastocysts underwent PGT-A testing, with 179 blastocysts from c-IVF insemination and 141 from ICSI insemination. Considering participants' baseline characteristics and embryological outcomes, no significant differences were found between the two groups regarding infertility type, average age, body mass index, percentage of PGT-A indications, or quality of embryonic development. Regarding PGT-A results, all 320 biopsy samples were successfully analyzed, showing no statistical variance in chromosomal euploidy, abnormality, or mosaicism rates between the two insemination methods. No parental contamination was detected in the c-IVF insemination group. When assessing clinical outcomes, parameters such as biochemical pregnancy, clinical pregnancy, and miscarriage rates did not exhibit significant discrepancies between the two groups, and no misdiagnoses were reported during the study period. Embryo transfer and PGT-A results are not affected by potential parental contamination in frozen-thawed embryos conceived via c-IVF. PGT-A guided embryo transfer in thawed embryos conceived by c-IVF is a viable and clinically effective approach.

Chromosomal abnormalities in oocyte donor candidates: a French survey of over 8200 karyotypes

To study karyotypes of more than 8,200 oocyte donor candidates in nulliparous or multiparous women compared to a reference population. A retrospective observational multicentric study. The study included two cohorts of oocyte donor candidates recruited between January 2005 and October 2021: multiparous women with at least one child at the time of recruitment, and nulliparous women. Both were compared to a reference population composed of female newborns from literature. Not applicable. Blood lymphocyte karyotype. A total of 8229 oocyte donor candidates from 22 fertility centers were included in this study. Nulliparous women (n=1890) and multiparous ones (n=6339) were compared to 8102 female newborns. Overall, 65 candidates were carriers of chromosomal abnormalities and were therefore excluded from the donation process (0.79%, 95% CI: 0.60-0.98). The occurrence of balanced structural chromosomal rearrangements was globally increased in the study population (0.49%, 95% CI: 0.34-0.64) compared to female newborns (0.24%, 95% CI: 0.34-0.64, p=0.0086). The number of reciprocal translocations was increased 5-fold in nulliparous oocyte donor candidates (0.37%, 95% CI: 0.10-0.64, p=0.013). The incidence of sex chromosome mosaicism was notably increased in multiparous oocyte donor candidates, with 17 cases (0.27%, 95% CI: 0.14-0.40, p=0.0052). Among chromosomal aberration carriers only two nulliparous women (one reciprocal translocation and one sex chromosome mosaicism) had fertility issues with a diagnosis of premature ovarian failure. In this comprehensive 16-years French experience of karyotyping in oocyte donor candidates, we confirmed an increased incidence of balanced structural chromosomal rearrangements, especially among those without children at the time of recruitment. Karyotyping could be considered to identify any chromosomal abnormalities that may not be easily detectable through medical questioning. These abnormalities pose an inherent genetic risk for gamete recipients if left undetected.

Low-level chromosomal mosaicism does not explain the spontaneous menarche seen in some women with 45,X turner syndrome

Low-level chromosomal mosaicism does not explain the spontaneous menarche seen in some women with 45,X turner syndrome

Comprehensive diagnosis and genetic analysis of two children with ring chromosome 18

To clarify the genetic diagnosis of two children with ring chromosome 18 and explore their mechanisms and clinical phenotypes. Two patients treated at the Children's Hospital of Henan Province respectively in June 2022 and March 2023 were selected as the study subjects. Genetic testing and diagnosis were carried out through copy number variation sequencing (CNV-seq), G-banded chromosomal karyotyping, and whole exome sequencing (WES). Child 1 had mainly manifested developmental delay, white matter hypoplasia, type 1 diabetes mellitus, and micropenis. He was found to have a chromosomal karyotype of 46,XY,r(18)(p11.21q22.1)[40]/46,XY[7], and CNV-seq results showed that he has a 14.86 Mb deletion at 18p11.21p11.32 and a 14.02 Mb deletion at 18q22.1q23. Child 2 had peculiar facial features, delayed white matter myelination, developmental delay, atrial septal defect, severe sensorineural deafness, and congenital laryngeal stridor. He was found to have a chromosomal karyotype of 46,XY,r(18)(p11.2q23). CNV-seq result proved that he had a 14.86 Mb deletion at 18p11-21p11.32 and a 20.74 Mb deletion at 18q21.32q23. WES has failed to detect single nucleotide variants (SNVs) in either child, but revealed a large segmental deletion at chromosome 18 in both of them. Both children were diagnosed with ring chromosome 18 syndrome. The different size of the deletional fragments in the 18q region and mosaicism of ring chromosome 18 in child 1 may underlay the variation in their clinical phenotypes. The type 1 diabetes mellitus and micropenis noted in both children are novel features for ring chromosome 18 syndrome.

Developmental signals control chromosome segregation fidelity during pluripotency and neurogenesis by modulating replicative stress

Human development relies on the correct replication, maintenance and segregation of our genetic blueprints. How these processes are monitored across embryonic lineages, and why genomic mosaicism varies during development remain unknown. Using pluripotent stem cells, we identify that several patterning signals—including WNT, BMP, and FGF—converge into the modulation of DNA replication stress and damage during S-phase, which in turn controls chromosome segregation fidelity in mitosis. We show that the WNT and BMP signals protect from excessive origin firing, DNA damage and chromosome missegregation derived from stalled forks in pluripotency. Cell signalling control of chromosome segregation declines during lineage specification into the three germ layers, but re-emerges in neural progenitors. In particular, we find that the neurogenic factor FGF2 induces DNA replication stress-mediated chromosome missegregation during the onset of neurogenesis, which could provide a rationale for the elevated chromosomal mosaicism of the developing brain. Our results highlight roles for morphogens and cellular identity in genome maintenance that contribute to somatic mosaicism during mammalian development.

Innovative all-in-one exome sequencing strategy for diagnostic genetic testing in male infertility: Validation and 10-month experience.

Current guidelines indicate that patients with extreme oligozoospermia or azoospermia should be tested for chromosomal imbalances, azoospermia factor (AZF) deletions and/or CFTR variants. For other sperm abnormalities, no genetic diagnostics are recommended. To determine whether exome sequencing (ES) with combined copy number variant (CNV) and single nucleotide variant (SNV) analysis is a reliable first-tier method to replace current methods (validation study), and to evaluate the diagnostic yield after 10 months of implementation (evaluation study). In the validation study, ES was performed on DNA of patients already diagnosed with AZF deletions (n=17), (non-)mosaic sex chromosomal aneuploidies or structural chromosomal anomalies (n=37), CFTR variants (n=26), or variants in known infertility genes (n=4), and 90 controls. The data were analyzed using our standard diagnostic pipeline, with a bioinformatic filter for 130 male infertility genes. In the evaluation study, results of 292 clinical exomes were included. All previously reported variants in the validation cohort, including clinically relevant Y-chromosomal microdeletions, were correctly identified and reliably detected. In the evaluation study, we identified one or more clinically relevant genetic anomalies in 67 of 292 of all cases (22.9%): these included aberrations that could have been detected with current methods in 30 of 67 patients (10.2% of total), (possible) (mono)genetic causes in the male infertility gene panel in 28 of 67 patients (9.6%), and carriership of cystic fibrosis in nine of 67 patients (3.1%). ES is a reliable first-tier method to detect the most common genetic causes of male infertility and, as additional genetic causes can be detected, in our evaluation cohort the diagnostic yield almost doubled (10.2%-19.8%, excluding CF carriers). A genetic diagnosis provides answers on the cause of infertility and helps the professionals in the counseling for treatment, possible co-morbidities and risk for offspring and/or family members. Karyotyping will still remain necessary for detecting balanced translocations or low-grade chromosomal mosaicism.

The Impact of Chromosomal Mosaicisms on Prenatal Diagnosis and Genetic Counseling-A Narrative Review.

Genetic disorders represent a high-impact diagnosis for both patients and their families. Prenatal screening methods and, when recommended, genetic testing allow parents to make informed decisions about the course a pregnancy is going to take. Although offering certainty about the potential evolution and prognosis of the pregnancy, and then the newborn, is usually not possible, genetic counseling can offer valuable insights into genetic disorders. Chromosomal mosaicisms are genetic anomalies that affect only some cell lines in either the fetus or the placenta or both. They can affect autosomal or heterosomal chromosomes, and they can be either numerical or structural. The prognosis seems to be more severe if the genetic alterations are accompanied by malformations visible in ultrasounds. Several genetic techniques can be used to diagnose certain mosaicisms, depending on their nature. A novel approach in prenatal care is non-invasive prenatal screening (NIPS), also known as non-invasive prenatal testing (NIPT), which, although it does not always have diagnostic value, can provide valuable information about potential genetic anomalies, especially numerical, with high sensitivity (Se).

HIF1A contributes to the survival of aneuploid and mosaic pre-implantation embryos.

Human fertility is suboptimal, partly due to error-prone divisions in early cleavage-stages that result in aneuploidy. Most human pre-implantation are mosaics of euploid and aneuploid cells, however, mosaic embryos with a low proportion of aneuploid cells have a similar likelihood of developing to term as fully euploid embryos. How embryos manage aneuploidy during development is poorly understood. This knowledge is crucial for improving fertility treatments and reducing developmental defects. To explore these mechanisms, we established a new mouse model of chromosome mosaicism to study the fate of aneuploid cells during pre-implantation development. We previously used the Mps1 inhibitor reversine to generate aneuploidy in embryos. Here, we found that treatment with the more specific Mps1 inhibitor AZ3146 induced chromosome segregation defects in pre-implantation embryos, similar to reversine. However, AZ3146-treated embryos showed a higher developmental potential than reversine-treated embryos. Unlike reversine-treated embryos, AZ3146-treated embryos exhibited transient upregulation of Hypoxia Inducible-Factor-1A (HIF1A) and lacked p53 upregulation. Pre-implantation embryos develop in a hypoxic environment in vivo, and hypoxia exposure in vitro reduced DNA damage in response to Mps1 inhibition and increased the proportion of euploid cells in the mosaic epiblast. Inhibiting HIF1A in mosaic embryos also decreased the proportion of aneuploid cells in mosaic embryos. Our work illuminates potential strategies to improve the developmental potential of mosaic embryos.

The density of the inner cell mass is a new indicator of the quality of a human blastocyst: a valid supplement to the Gardner scoring system.

Can the density of the inner cell mass (ICM) be a new indicator of the quality of the human blastocyst? The densification index (DI) developed in this study can quantify ICM density and provide positive guidance for ploidy, pregnancy, and live birth. In evaluating the quality of ICM, reproductive care clinics still use size indicators without further evaluation. The main disadvantage of this current method is that the evaluation of blastocyst ICM is relatively rough and cannot meet the needs of clinical embryologists, especially when multiple blastocysts have the same ICM score, which makes them difficult to evaluate further. This observational study included data from 2272 blastocysts in 1991 frozen-thawed embryo transfer (FET) cycles between January 2018 to November 2021 and 1105 blastocysts in 430 preimplantation genetic testing cycles between January 2019 and February 2023. FET, ICSI, blastocyst culture, trophectoderm biopsy, time-lapse (TL) monitoring, and next-generation sequencing were performed. After preliminary sample size selection, the 11 focal plane images captured by the TL system were normalized and the spatial frequency was used to construct the DI of the ICM. This study successfully constructed a quantitative indicator DI that can reflect the degree of ICM density in terms of fusion and texture features. The higher the DI value, the better the density of the blastocyst ICM, and the higher the chances that the blastocyst was euploid (P < 0.001) and that pregnancy (P < 0.001) and live birth (P = 0.005) were reached. In blastocysts with ICM graded B and blastocysts graded 4BB, DI was also positively associated with ploidy, pregnancy, and live birth (P < 0.05). ROC analysis showed that combining the Gardner scoring system with DI can more effectively predict pregnancy and live births, when compared to using the Gardner scoring system alone. Accurate calculation of the DI value places high demands on image quality, requiring manual selection of the clearest focal plane and exposure control. Images with the ICM not completely within the field of view cannot be used. The association between the density of ICM and chromosomal mosaicism was not evaluated. The associations between the density of ICM and different assisted reproductive technologies and different culture conditions in embryo laboratories were also not evaluated. Prospective studies are needed to further investigate the impact of ICM density on clinical outcomes. ICM density assessment is a new direction in blastocyst assessment. This study explores new ways of assessing blastocyst ICM density and develops quantitative indicators and a corresponding qualitative evaluation scheme for ICM density. The DI of the blastocyst ICM developed in this study is easy to calculate and requires only TL equipment and image processing, providing positive guidance for clinical outcomes. The qualitative evaluation scheme of ICM density can assist embryologists without TL equipment to manually evaluate ICM density. ICM density is a simple indicator that can be used in practice and is a good complement to the blastocyst scoring systems currently used in most centers. This work was supported by the National Key Research & Development Program of China (2021YFC2700603). The authors report no financial or commercial conflicts of interest. N/A.

Clinicopathological and molecular genetic features of confined placental mosaicism

Objective: To investigate the clinicopathological and genetic features of confined placental mosaicism (CPM) and its effect on fetal intrauterine growth. Methods: Fourteen CPM cases of Haidian Maternal and Children Health Hospital were collected from May 2018 to March 2022. Clinicopathological examination on placental specimens and molecular genetic analysis were performed. Results: The age of the parturient women ranged from 27 to 34 years, with an average age of (30.0±3.54) years. The gestational weeks ranged from 35+1 to 41+2 weeks. There were 4 premature births and 10 term births, among which 6 were female and 8 were male fetuses. Nine cases (9/14) had adverse pregnancy outcomes, including 7 cases of fetal growth restriction. The weight of CPM placenta decreased, with 6 cases below the 10th percentile of weight standards and 5 cases between the 10th and 25th percentile. All 14 CPM placental specimens showed morphological changes of perfusion dysfunction to varying degrees, with mainly placental-maternal vascular malperfusion followed by placental-fetal vascular malperfusion. The mosaic chromosomes in different CPM cases varied, with 16-trisomy/monosomy mosaicism being the most common followed by 7-trisomy and 21-trisomy/monosomy mosaicism. The mosaic proportion was unequal in different parts of the same CPM placenta, with the mosaic proportion of umbilical cord, fetal membranes, fetal surface, maternal surface, and edge ranging from 1% to 70%. Conclusions: The mosaic chromosomes in different CPM cases vary, and the mosaic proportion is unequal in different parts of the same CPM placenta. The pathological morphology is mainly manifested as perfusion dysfunction, which can lead to adverse pregnancy outcomes such as fetal growth restriction and preterm birth.