BlastAssist: a deep learning pipeline to measure interpretable features of human embryos

STUDY QUESTION

Can the BlastAssist deep learning pipeline perform comparably to or outperform human experts and embryologists at measuring interpretable, clinically relevant features of human embryos in IVF?

SUMMARY ANSWER

The BlastAssist pipeline can measure a comprehensive set of interpretable features of human embryos and either outperform or perform comparably to embryologists and human experts in measuring these features.

WHAT IS KNOWN ALREADY

Some studies have applied deep learning and developed 'black-box' algorithms to predict embryo viability directly from microscope images and videos but these lack interpretability and generalizability. Other studies have developed deep learning networks to measure individual features of embryos but fail to conduct careful comparisons to embryologists' performance, which are fundamental to demonstrate the network's effectiveness.

STUDY DESIGN, SIZE, DURATION

We applied the BlastAssist pipeline to 67 043 973 images (32 939 embryos) recorded in the IVF lab from 2012 to 2017 in Tel Aviv Sourasky Medical Center. We first compared the pipeline measurements of individual images/embryos to manual measurements by human experts for sets of features, including: (i) fertilization status (n = 207 embryos), (ii) cell symmetry (n = 109 embryos), (iii) degree of fragmentation (n = 6664 images), and (iv) developmental timing (n = 21 036 images). We then conducted detailed comparisons between pipeline outputs and annotations made by embryologists during routine treatments for features, including: (i) fertilization status (n = 18 922 embryos), (ii) pronuclei (PN) fade time (n = 13 781 embryos), (iii) degree of fragmentation on Day 2 (n = 11 582 embryos), and (iv) time of blastulation (n = 3266 embryos). In addition, we compared the pipeline outputs to the implantation results of 723 single embryo transfer (SET) cycles, and to the live birth results of 3421 embryos transferred in 1801 cycles.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In addition to EmbryoScope™ image data, manual embryo grading and annotations, and electronic health record (EHR) data on treatment outcomes were also included. We integrated the deep learning networks we developed for individual features to construct the BlastAssist pipeline. Pearson's χ2 test was used to evaluate the statistical independence of individual features and implantation success. Bayesian statistics was used to evaluate the association of the probability of an embryo resulting in live birth to BlastAssist inputs.

MAIN RESULTS AND THE ROLE OF CHANCE

The BlastAssist pipeline integrates five deep learning networks and measures comprehensive, interpretable, and quantitative features in clinical IVF. The pipeline performs similarly or better than manual measurements. For fertilization status, the network performs with very good parameters of specificity and sensitivity (area under the receiver operating characteristics (AUROC) 0.84-0.94). For symmetry score, the pipeline performs comparably to the human expert at both 2-cell (r = 0.71 ± 0.06) and 4-cell stages (r = 0.77 ± 0.07). For degree of fragmentation, the pipeline (acc = 69.4%) slightly under-performs compared to human experts (acc = 73.8%). For developmental timing, the pipeline (acc = 90.0%) performs similarly to human experts (acc = 91.4%). There is also strong agreement between pipeline outputs and annotations made by embryologists during routine treatments. For fertilization status, the pipeline and embryologists strongly agree (acc = 79.6%), and there is strong correlation between the two measurements (r = 0.683). For degree of fragmentation, the pipeline and embryologists mostly agree (acc = 55.4%), and there is also strong correlation between the two measurements (r = 0.648). For both PN fade time (r = 0.787) and time of blastulation (r = 0.887), there's strong correlation between the pipeline and embryologists. For SET cycles, 2-cell time (P < 0.01) and 2-cell symmetry (P < 0.03) are significantly correlated with implantation success rate, while other features showed correlations with implantation success without statistical significance. In addition, 2-cell time (P < 5 × 10-11), PN fade time (P < 5 × 10-10), degree of fragmentation on Day 3 (P < 5 × 10-4), and 2-cell symmetry (P < 5 × 10-3) showed statistically significant correlation with the probability of the transferred embryo resulting in live birth.

LIMITATIONS, REASONS FOR CAUTION

We have not tested the BlastAssist pipeline on data from other clinics or other time-lapse microscopy (TLM) systems. The association study we conducted with live birth results do not take into account confounding variables, which will be necessary to construct an embryo selection algorithm. Randomized controlled trials (RCT) will be necessary to determine whether the pipeline can improve success rates in clinical IVF.

WIDER IMPLICATIONS OF THE FINDINGS

BlastAssist provides a comprehensive and holistic means of evaluating human embryos. Instead of using a black-box algorithm, BlastAssist outputs meaningful measurements of embryos that can be interpreted and corroborated by embryologists, which is crucial in clinical decision making. Furthermore, the unprecedentedly large dataset generated by BlastAssist measurements can be used as a powerful resource for further research in human embryology and IVF.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by Harvard Quantitative Biology Initiative, the NSF-Simons Center for Mathematical and Statistical Analysis of Biology at Harvard (award number 1764269), the National Institute of Heath (award number R01HD104969), the Perelson Fund, and the Sagol fund for embryos and stem cells as part of the Sagol Network. The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

Not applicable.

Isoform-resolved transcriptome of the human preimplantation embryo

Human preimplantation development involves extensive remodeling of RNA expression and splicing. However, its transcriptome has been compiled using short-read sequencing data, which fails to capture most full-length mRNAs. Here, we generate an isoform-resolved transcriptome of early human development by performing long- and short-read RNA sequencing on 73 embryos spanning the zygote to blastocyst stages. We identify 110,212 unannotated isoforms transcribed from known genes, including highly conserved protein-coding loci and key developmental regulators. We further identify 17,964 isoforms from 5,239 unannotated genes, which are largely non-coding, primate-specific, and highly associated with transposable elements. These isoforms are widely supported by the integration of published multi-omics datasets, including single-cell 8CLC and blastoid studies. Alternative splicing and gene co-expression network analyses further reveal that embryonic genome activation is associated with splicing disruption and transient upregulation of gene modules. Together, these findings show that the human embryo transcriptome is far more complex than currently known, and will act as a valuable resource to empower future studies exploring development.

Cleavage stage at compaction-a good predictor for IVF outcome

OBJECTIVE

To analyze whether cleavage stage at compaction, and not only kinetics, can serve as a reliable predictor for clinical outcome.

METHODS

A retrospective cohort study including 1194 embryos, classified by compaction initiation stage (Group 1: compaction at fewer than eight cells, Group 2: compaction at eight cells, Group 3: compaction at more than eight cells). Of these, 815 embryos were evaluated for morphokinetic preimplantation parameters, and 379 embryos were analyzed for clinical implantation following thawing and transfer of single blastocysts during the same period.

RESULTS

In total, 1194 embryos were analyzed. Embryos that underwent compaction from more than eight cells (Group 3) exhibited more synchronous cleavage compared with Groups 1 and 2 (at both S2 and S3; P < 0.001), and displayed a significantly lower fragmentation rate. The likelihood of obtaining top-quality blastocysts decreased by 73% and 44% when comparing Group 3 embryos with those of Groups 1 and 2, respectively, (P < 0.03). Clinical validation of the results shows that while compaction from fewer than eight cells barely produced blastocysts for transfer, compaction at eight or more cells is crucial for implantation and birth (birth rates 11.1% and 18.5% for Groups 2 and 3, respectively).

CONCLUSION

Cleavage stage at compaction has a direct effect on blastocyst quality and subsequent pregnancy, so can be included in newly developed deep learning models for embryo selection.

Transcriptomic Analysis of Human Fragile X Syndrome Neurons Reveals Neurite Outgrowth Modulation by the TGFβ/BMP Pathway

Fragile X Syndrome (FXS) is the main genetic reason for intellectual disability and is caused by the silencing of fragile X mental retardation protein (FMRP), an RNA-binding protein regulating the translation of many neuronal mRNAs. Neural differentiation of FX human embryonic stem cells (hESC) mimics the neurodevelopment of FXS fetuses and thus serves as a good model to explore the mechanisms underlining the development of FXS. Isogenic hESC clones with and without the FX mutation that share the same genetic background were in vitro differentiated into neurons, and their transcriptome was analyzed by RNA sequencing. FX neurons inactivating FMR1 expression presented delayed neuronal development and maturation, concomitant with dysregulation of the TGFβ/BMP signaling pathway, and genes related to the extracellular matrix. Migration assay showed decreased neurite outgrowth in FX neurons that was rescued by inhibition of the TGFβ/BMP signaling pathway. Our results provide new insights into the molecular pathway by which loss of FMRP affects neuronal network development. In FX neurons, the lack of FMRP dysregulates members of the BMP signaling pathway associated with ECM organization which, in a yet unknown mechanism, reduces the guidance of axonal growth cones, probably leading to the aberrant neuronal network function seen in FXS.

Developmental Stage Classification of Embryos Using Two-Stream Neural Network with Linear-Chain Conditional Random Field

The developmental process of embryos follows a monotonic order. An embryo can progressively cleave from one cell to multiple cells and finally transform to morula and blastocyst. For time-lapse videos of embryos, most existing developmental stage classification methods conduct per-frame predictions using an image frame at each time step. However, classification using only images suffers from overlapping between cells and imbalance between stages. Temporal information can be valuable in addressing this problem by capturing movements between neighboring frames. In this work, we propose a two-stream model for developmental stage classification. Unlike previous methods, our two-stream model accepts both temporal and image information. We develop a linear-chain conditional random field (CRF) on top of neural network features extracted from the temporal and image streams to make use of both modalities. The linear-chain CRF formulation enables tractable training of global sequential models over multiple frames while also making it possible to inject monotonic development order constraints into the learning process explicitly. We demonstrate our algorithm on two time-lapse embryo video datasets: i) mouse and ii) human embryo datasets. Our method achieves 98.1% and 80.6% for mouse and human embryo stage classification, respectively. Our approach will enable more pro-found clinical and biological studies and suggests a new direction for developmental stage classification by utilizing temporal information.

Pharmacological Manipulation of Wnt/β-Catenin Signaling Pathway in Human Neural Precursor Cells Alters Their Differentiation Potential and Neuronal Yield

The canonical Wnt/β-catenin pathway is a master-regulator of cell fate during embryonic and adult neurogenesis and is therefore a major pharmacological target in basic and clinical research. Chemical manipulation of Wnt signaling during in vitro neuronal differentiation of stem cells can alter both the quantity and the quality of the derived neurons. Accordingly, the use of Wnt activators and blockers has become an integral part of differentiation protocols applied to stem cells in recent years. Here, we investigated the effects of the glycogen synthase kinase-3β inhibitor CHIR99021, which upregulates β-catenin agonizing Wnt; and the tankyrase-1/2 inhibitor XAV939, which downregulates β-catenin antagonizing Wnt. Both drugs and their potential neurogenic and anti-neurogenic effects were studied using stable lines human neural precursor cells (hNPCs), derived from embryonic stem cells, which can be induced to generate mature neurons by chemically-defined conditions. We found that Wnt-agonism by CHIR99021 promotes induction of neural differentiation, while also reducing cell proliferation and survival. This effect was not synergistic with those of pro-neural growth factors during long-term neuronal differentiation. Conversely, antagonism of Wnt by XAV939 consistently prevented neuronal progression of hNPCs. We show here how these two drugs can be used to manipulate cell fate and how self-renewing hNPCs can be used as reliable human in vitro drug-screening platforms.

Skin exposure to UVB light induces a skin-brain-gonad axis and sexual behavior

Ultraviolet (UV) light affects endocrinological and behavioral aspects of sexuality via an unknown mechanism. Here we discover that ultraviolet B (UVB) exposure enhances the levels of sex-steroid hormones and sexual behavior, which are mediated by the skin. In female mice, UVB exposure increases hypothalamus-pituitary-gonadal axis hormone levels, resulting in larger ovaries; extends estrus days; and increases anti-Mullerian hormone (AMH) expression. UVB exposure also enhances the sexual responsiveness and attractiveness of females and male-female interactions. Conditional knockout of p53 specifically in skin keratinocytes abolishes the effects of UVB. Thus, UVB triggers a skin-brain-gonadal axis through skin p53 activation. In humans, solar exposure enhances romantic passion in both genders and aggressiveness in men, as seen in analysis of individual questionaries, and positively correlates with testosterone level. Our findings suggest opportunities for treatment of sex-steroid-related dysfunctions.

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UVB exposure increases circulating sex-steroid levels in mice and humans

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UVB exposure enhances female attractiveness and receptiveness toward males

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UVB exposure increases females’ estrus phase, HPG axis hormones, and follicle growth

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Skin p53 regulates UVB-induced sexual behavior and ovarian physiological changes

Principles of signaling pathway modulation for enhancing human naive pluripotency induction

Isolating human MEK/ERK signaling-independent pluripotent stem cells (PSCs) with naive pluripotency characteristics while maintaining differentiation competence and (epi)genetic integrity remains challenging. Here, we engineer reporter systems that allow the screening for defined conditions that induce molecular and functional features of human naive pluripotency. Synergistic inhibition of WNT/β-CATENIN, protein kinase C (PKC), and SRC signaling consolidates the induction of teratoma-competent naive human PSCs, with the capacity to differentiate into trophoblast stem cells (TSCs) and extraembryonic naive endodermal (nEND) cells in vitro. Divergent signaling and transcriptional requirements for boosting naive pluripotency were found between mouse and human. P53 depletion in naive hPSCs increased their contribution to mouse-human cross-species chimeric embryos upon priming and differentiation. Finally, MEK/ERK inhibition can be substituted with the inhibition of NOTCH/RBPj, which induces alternative naive-like hPSCs with a diminished risk for deleterious global DNA hypomethylation. Our findings set a framework for defining the signaling foundations of human naive pluripotency.

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Inhibition of SRC, PKC, and WNT consolidates human naive pluripotency induction

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Competitiveness of p53 depleted human PSCs in cross-species chimeric embryos

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Opposing net effect for ACTIVIN and WNT on mouse versus human naive pluripotency

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2i and ERKi independent alternative human naive-like PSC conditions

Heterozygous APC germline mutations impart predisposition to colorectal cancer

Familial adenomatous polyposis (FAP) is an inherited syndrome caused by a heterozygous adenomatous polyposis coli (APC) germline mutation, associated with a profound lifetime risk for colorectal cancer. While it is well accepted that tumorigenic transformation is initiated following acquisition of a second mutation and loss of function of the APC gene, the role of heterozygous APC mutation in this process is yet to be discovered. This work aimed to explore whether a heterozygous APC mutation induces molecular defects underlying tumorigenic transformation and how different APC germline mutations predict disease severity. Three FAP-human embryonic stem cell lines (FAP1/2/3-hESC lines) carrying germline mutations at different locations of the APC gene, and two control hESC lines free of the APC mutation, were differentiated into colon organoids and analyzed by immunohistochemistry and RNA sequencing. In addition, data regarding the genotype and clinical phenotype of the embryo donor parents were collected from medical records. FAP-hESCs carrying a complete loss-of-function of a single APC allele (FAP3) generated complex and molecularly mature colon organoids, which were similar to controls. In contrast, FAP-hESCs carrying APC truncation mutations (FAP1 and FAP2) generated only few cyst-like structures and cell aggregates of various shape, occasionally with luminal parts, which aligned with their failure to upregulate critical differentiation genes early in the process, as shown by RNA sequencing. Abnormal disease phenotype was shown also in non-pathological colon of FAP patients by the randomly distribution of proliferating cells throughout the crypts, compared to their focused localization in the lower part of the crypt in healthy/non-FAP patients. Genotype/phenotype analysis revealed correlations between the colon organoid maturation potential and FAP severity in the carrier parents. In conclusion, this study suggest that a single truncated APC allele is sufficient to initiate early molecular tumorigenic activity. In addition, the results hint that patient-specific hESC-derived colon organoids can probably predict disease severity among FAP patients.

Automated Measurements of Key Morphological Features of Human Embryos for IVF

A major challenge in clinical In-Vitro Fertilization (IVF) is selecting the highest quality embryo to transfer to the patient in the hopes of achieving a pregnancy. Time-lapse microscopy provides clinicians with a wealth of information for selecting embryos. However, the resulting movies of embryos are currently analyzed manually, which is time consuming and subjective. Here, we automate feature extraction of time-lapse microscopy of human embryos with a machine-learning pipeline of five convolutional neural networks (CNNs). Our pipeline consists of (1) semantic segmentation of the regions of the embryo, (2) regression predictions of fragment severity, (3) classification of the developmental stage, and object instance segmentation of (4) cells and (5) pronuclei. Our approach greatly speeds up the measurement of quantitative, biologically relevant features that may aid in embryo selection.

Adenomatous Polyposis Coli as a Major Regulator of Human Embryonic Stem Cells Self-Renewal

Human embryonic stem cells (hESCs) provide an essential tool to investigate early human development, study disease pathogenesis, and examine therapeutic interventions. Adenomatous polyposis coli (APC) is a negative regulator of Wnt/β-catenin signaling, implicated in the majority of sporadic colorectal cancers and in the autosomal dominant inherited syndrome familial adenomatous polyposis (FAP). Studies into the role of Wnt/β-catenin signaling in hESCs arrived at conflicting results, due at least in part to variations in culture conditions and the use of external inhibitors and agonists. Here, we directly targeted APC in hESCs carrying a germline APC mutation, derived from affected blastocysts following preimplantation genetic diagnosis (PGD) for FAP, in order to answer open questions regarding the role of APC in regulating pluripotency and differentiation potential of hESCs. Using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR associated protein 9 (Cas9), we generated second hit APC mutations in FAP-hESCs. Despite high CRISPR/Cas9 targeting efficiency and the successful isolation of many clones, none of the isolated clones carried a loss of function mutation in the wild-type (WT) APC allele. Using a fluorescent β-catenin reporter and analysis of mutated-allele frequencies in the APC locus, we show that APC double mutant hESCs robustly activate Wnt/β-catenin signaling that results in rapid differentiation to endodermal and mesodermal lineages. Here, we provide direct evidence for a strict requirement for constant β-catenin degradation through the APC destruction complex in order to maintain pluripotency, highlighting a fundamental role for APC in self-renewal of hESCs. Stem Cells 2019;37:1505-1515.

Optimal timing for blastomere biopsy of 8-cell embryos for preimplantation genetic diagnosis

STUDY QUESTION

What is the optimal timing for blastomere biopsy during the 8-cell stage, at which embryos will have the best implantation potential?

SUMMARY ANSWER

Fast-cleaving embryos that are biopsied during the last quarter (Q4) of the 8-cell stage and are less affected by the biopsy procedure, and their implantation potential is better than that of embryos biopsied earlier during the 8-cell stage (Q1-Q3).

WHAT IS KNOWN ALREADY

Blastomer biopsy from cleavage-stage embryos is usually performed on the morning of Day 3 when the embryos are at the 6- to 8-cell stage and is still the preferred biopsy method for preimplantation genetic diagnosis (PGD) for monogentic disorders or chromosomal translocations. Human embryos usually remain at the 8-cell stage for a relatively long 'arrest phase' in which cells grow, duplicate their DNA and synthesize various proteins in preparation for the subsequent division.

STUDY DESIGN, SIZE, DURATION

This is a retrospective cohort study. The study group (195 embryos) included all 8-cell stage embryos that underwent blastomere biopsy for PGD for monogenetic disorders and chromosomal translocations in our unit between 2012-2014 and cultured in the EmbryoScope until transfer. The control group (115 embryos) included all embryos that underwent intracytoplasmic sperm injection without a biopsy during the same period.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The 8-cell stage was divided into four quarters: the first 5 h post-t8 (Q1), 5-10 h post-t8 (Q2), 10-15 h post-t8 (Q3) and at 15-20 h post-t8 (Q4). Non-biopsied control embryos were divided into four equivalent quarters. Embryos were evaluated for timing of developmental events following biopsy including timing of first cleavge after biopsy, timing of comapction (tM) and start of blastulation (tSB). Timing of these events were compared between PGD and control embryos, as well as with 56 PGD implanted embryos with Known Implantation Data (PGD-KID-positive embryos).

MAIN RESULTS AND THE ROLE OF CHANCE

Embryos that were biopsied during Q3 (10-15 h from entry into 8-cell stage) were delayed in all three subsequent developmental events, including first cleavage after biopsy, compaction and start of blastulation. In contrast, these events occurred exactly at the same time as in the control group, in embryos that were biopsied during Q1, Q2 or Q4 of the 8-cell stage. The results show also that embryos that were biopsied during Q1, Q2 or Q3 of the 8-cell stage demonstrated a significant delay from the biopsied implanted embryos already in t8 as well as in tM and tSB. However, embryos that were biopsied during Q4 demonstrated dynamics similar to those of the biopsied implanted embryos in t8 and tM, and a delay was noticed only in the last stage of tSB.

LIMITATIONS, REASONS FOR CAUTION

This is a retrospective study that is limited to the timing of biopsy that is routinely performed in the IVF lab. A prospective study in which biopsy will be performed at a desired timing is needed in order to differ between the effect of biopsy itself and the cleavage rate of the embryo.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings showed that blastomere biopsy can be less harmful to further development if it is carried out during a critical period of embryonic growth, i.e during Q4 of the 8-cell stage. They also demonstrated the added value of time-lapse microscopy for determining the optimal timing for blastomere biopsy.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by the routine budget of our IVF unit.

TRIAL REGISTRATION NUMBER

N/A.

Modeling FXS: Human Pluripotent Stem Cells and In Vitro Neural Differentiation

In fragile X syndrome (FXS) embryos FMRP is widely expressed during early stages of embryogenesis however it is inactivated by the end of the first trimester. In the same manner, human embryonic stem cell (hESC) lines from FXS blastocysts, bearing the full CGG expansion mutation, express FMRP in their pluripotent stage and in neurons derived following in vitro differentiation, FMR1 is completely silenced. Therefore, in vitro neural differentiation of FX-hESC lines serves as a uniquely valuable model system to study the developmental mechanisms underlying FXS, together with the proper differentiation protocol to mimic the neurodevelopmental process occurs in vivo.

The Effect of Advanced Maternal Age on Embryo Morphokinetics

Purpose: To compare the morphokinetic parameters of pre-implantation development between embryos of women of advanced maternal age (AMA) and young women. Methods: Time-lapse microscopy was used to compare morphokinetic variables between 495 embryos of AMA women ≥ age 42 years and 653 embryos of young patients (<age 38 years) who underwent IVF in our unit. Developmental events annotated and analyzed include observed cell divisions in correlation to the timing of fertilization, synchrony of the second (s2) and third cell cycles (s3) and the duration to the second (cc2) and third cleavages (cc3). Results: No significant differences were observed in cleavage times between the embryos of AMA and the control embryos. Interestingly, the older embryos appear to be more prone to developmental arrest (a higher percentage of embryos of older women arrested at 4-7 cells resulting in less embryos reaching the 8-cell stage (66% vs. 72%, respectively), though this difference did not reach a significance at least during the first 3 days of development (p > 0.05). Conclusions: While early morphokinetic parameters do not reflect dynamics unique to embryos of older women, a tendency toward developmental arrest was observed, which would likely be even more pronounced at later stages of development.

Time-lapse imaging reveals delayed development of embryos carrying unbalanced chromosomal translocations

PURPOSE

The purpose of the study was to compare the morphokinetic parameters of embryos carrying balanced chromosomal translocations with those carrying unbalanced chromosomal translocations using time-lapse microscopy.

METHODS

The study group included 270 embryos that underwent biopsies on day 3 for preimplantation genetic diagnosis (PGD) for chromosomal translocations in our unit between 2013 and 2015. All embryos were incubated under time-lapse microscopy and evaluated for timing of developmental events up to day 5. The timing of these events was compared between balanced and unbalanced embryos, potentially viable and nonviable variants, and maternal versus paternal inheritance of the translocation.

RESULTS

The PGD analysis found that 209 (77%) of the 270 biopsied embryos carried an unbalanced translocation. Embryos carrying unbalanced translocations, which are expected to lead to implantation failure or miscarriage, cleaved less synchronously and were delayed in time of cleavage to the 4-cell stage (t4) and in time of start of blastulation (tSB) compared with balanced embryos (P < 0.05). Furthermore, embryos carrying nonviable translocations demonstrated a significant delay at the time of pronuclei fading (tPNf) compared with those carrying potentially viable translocations (P < 0.05). Embryos whose unbalanced translocations were of maternal origin were significantly delayed in most of the morphokinetic parameters (including tPNf, t2, t3, t4, t6, t7, t8, cc2, s2, and tSB) compared with embryos carrying balanced translocations (P < 0.05).

CONCLUSIONS

Embryos carrying unbalanced chromosomal translocations mainly of maternal origin undergo delayed development and asynchronous cleavage that may lead to implantation failure or miscarriage.

Improving preimplantation genetic diagnosis (PGD) reliability by selection of sperm donor with the most informative haplotype

BACKGROUND

The study is aimed to describe a novel strategy that increases the accuracy and reliability of PGD in patients using sperm donation by pre-selecting the donor whose haplotype does not overlap the carrier's one.

METHODS

A panel of 4-9 informative polymorphic markers, flanking the mutation in carriers of autosomal dominant/X-linked disorders, was tested in DNA of sperm donors before PGD. Whenever the lengths of donors' repeats overlapped those of the women, additional donors' DNA samples were analyzed. The donor that demonstrated the minimal overlapping with the patient was selected for IVF.

RESULTS

In 8 out of 17 carriers the markers of the initially chosen donors overlapped the patients' alleles and 2-8 additional sperm donors for each patient were haplotyped. The selection of additional sperm donors increased the number of informative markers and reduced misdiagnosis risk from 6.00% ± 7.48 to 0.48% ±0.68. The PGD results were confirmed and no misdiagnosis was detected.

CONCLUSIONS

Our study demonstrates that pre-selecting a sperm donor whose haplotype has minimal overlapping with the female's haplotype, is critical for reducing the misdiagnosis risk and ensuring a reliable PGD. This strategy may contribute to prevent the transmission of affected IVF-PGD embryos using a simple and economical procedure.

TRIAL REGISTRATION

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. DNA testing of donors was approved by the institutional Helsinki committee (registration number 319-08TLV, 2008). The present study was approved by the institutional Helsinki committee (registration number 0385-13TLV, 2013).

The effect of a germline mutation in the APC gene on β-catenin in human embryonic stem cells

Background

Most cases of colorectal cancer (CRC) are initiated by inactivation mutations in the APC gene, which is a negative regulator of the Wnt-β-catenin pathway. Patients with familial adenomatous polyposis (FAP) inherit a germline mutation in one APC allele, and loss of the second allele leads to the development of polyps that will turn malignant if not removed. It is not fully understood which molecular mechanisms are activated by APC loss and when the loss of the second APC allele occurs.

Methods

Two FAP human embryonic stem cell (hESCs) lines were derived from APC mutated embryos following pre-implantation genetic diagnosis (PGD) for FAP. These FAP-hESCs were cultured in vitro and following extended culture: 1) β-catenin expression was analyzed by Western blot analysis; 2) Wnt-β-catenin/TCF-mediated transcription luciferase assay was performed; 3) cellular localization of β-catenin was evaluated by immunoflorecence confocal microscopy; and 4) DNA sequencing of the APC gene was performed.

Results

We have established a novel human in-vitro model for studying malignant transformation, using hESCs that carry a germline mutation in the APC gene following PGD for FAP. Extended culturing of FAP1 hESCs led to activation of the Wnt signaling pathway, as demonstrated by enhanced β-catenin/TCF-mediated activity. Additionally, β-catenin showed a distinct perinuclear distribution in most (91 %) of the FAP1 hESCs high passage colonies. DNA sequencing of the whole gene detected several polymorphisms in FAP1 hESCs, however, no somatic mutations were discovered in the APC gene. On the other hand, no changes in β-catenin were detected in the FAP2 hESCs, demonstrating the natural diversity of the human FAP population.

Conclusions

Our results describe the establishment of novel hESC lines from FAP patients with a predisposition for cancer mutation. These cells can be maintained in culture for long periods of time and may serve as a platform for studying the initial molecular and cellular changes that occur during early stages of malignant transformation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2809-9) contains supplementary material, which is available to authorized users.

Blastomere biopsy for PGD delays embryo compaction and blastulation: a time-lapse microscopic analysis

PURPOSE

The purpose of the study was to explore the effect of blastomere biopsy for preimplantation genetic diagnosis (PGD) on the embryos' dynamics, further cleavage, development, and implantation.

METHODS

The study group included 366 embryos from all PGD treatments (September 2012 to June 2014) cultured in the EmbryoScope™ time-lapse monitoring system. The control group included all intracytoplasmic sperm injection (ICSI) embryos cultured in EmbryoScope™ until day 5 during the same time period (385 embryos). Time points of key embryonic events were analyzed with an EmbryoViewer™.

RESULTS

Most (88 %) of the embryos were biopsied at ≥8 cells. These results summarize the further dynamic development of the largest cohort of biopsied embryos and demonstrate that blastomere biopsy of cleavage-stage embryos significantly delayed compaction and blastulation compared to the control non-biopsied embryos. This delay in preimplanation developmental events also affected postimplantation development as observed when the dynamics of non-implanted embryos (known implantation data (KID) negative) were compared to those of implanted embryos (KID positive).

CONCLUSION

Analysis of morphokinetic parameters enabled us to explore how blastomere biopsy interferes with the dynamic sequence of developmental events. Our results show that biopsy delays the compaction and the blastulation of the embryos, leading to a decrease in implantation.

Molecular mechanisms regulating impaired neurogenesis of fragile X syndrome human embryonic stem cells

Fragile X syndrome (FXS) is the most common form of inherited cognitive impairment. It is caused by developmental inactivation of the FMR1 gene and the absence of its encoded protein FMRP, which plays pivotal roles in brain development and function. In FXS embryos with full FMR1 mutation, FMRP is expressed during early embryogenesis and is gradually downregulated at the third trimester of pregnancy. FX-human embryonic stem cells (FX-hESCs), derived from FX human blastocysts, demonstrate the same pattern of developmentally regulated FMR1 inactivation when subjected to in vitro neural differentiation (IVND). In this study, we used this in vitro human platform to explore the molecular mechanisms downstream to FMRP in the context of early human embryonic neurogenesis. Our results show a novel role for the SOX superfamily of transcription factors, specifically for SOX2 and SOX9, which could explain the reduced and delayed neurogenesis observed in FX cells. In addition, we assess in this study the "GSK3β theory of FXS" for the first time in a human-based model. We found no evidence for a pathological increase in GSK3β protein levels upon cellular loss of FMRP, in contrast to what was found in the brain of Fmr1 knockout mice. Our study adds novel data on potential downstream targets of FMRP and highlights the importance of the FX-hESC IVND system.

Impaired function of trophoblast cells derived from translocated hESCs may explain pregnancy loss in women with balanced translocation (11;22)

PURPOSE

The aim of the study was to study whether the trophoblasts carrying unbalanced translocation 11,22 [t(11;12)] display abnormal expression of trophoblastic genes and impaired functional properties that may explain implantation failure.

METHODS

t(11;22) hESCs and control hESCs were differentiated in vitro into trophoblast cells in the presence of BMP4, and trophoblast vesicles (TBVs) were created in suspension. The expression pattern of extravillous trophoblast (EVT) genes was compared between translocated and control TBVs. The functional properties of the TBVs were evaluated by their attachment to endometrium cells (ECC1) and invasion through trans-well inserts.

RESULTS

TBVs derived from control hESCs expressed EVT genes from functioning trophoblast cells. In contrast, TBVs differentiated from the translocated hESC line displayed impaired expression of EVT genes. Moreover, the number of TBVs that were attached to endometrium cells was significantly lower compared to the controls. Correspondingly, invasiveness of trophoblast-differentiated translocated cells was also significantly lower than that of the control cells.

CONCLUSIONS

These results may explain the reason for implantation failure in couple carriers of t(11;22). They also demonstrate that translocated hESCs comprise a valuable in vitro human model for studying the mechanisms underlying implantation failure.

Immature Responses to GABA in Fragile X Neurons Derived from Human Embryonic Stem Cells

Fragile X Syndrome (FXS) is the most common form of inherited cognitive disability. However, functional deficiencies in FX neurons have been described so far almost exclusively in animal models. In a recent study we found several functional deficits in FX neurons differentiated in-vitro from human embryonic stem cells (hESCs), including their inability to fire repetitive action potentials, and their lack of synaptic activity. Here, we investigated the responses of such neurons to pulse application of the neurotransmitter GABA. We found two distinct types of responses to GABA and sensitivity to the GABA-A receptor antagonist bicuculline; type 1 (mature) characterized by non-desensitized responses to GABA as well as a high sensitivity to bicuculline, and type 2 (immature) which are desensitized to GABA and insensitive to bicuculline. Type 1 responses were age-dependent and dominant in mature WT neurons. In contrast, FX neurons expressed primarily type 2 phenotype. Expression analysis of GABA-A receptor subunits demonstrated that this bias in human FX neurons was associated with a significant alteration in the expression pattern of the GABA-A receptor subunits α2 and β2. Our results indicate that FMRP may play a role in the development of the GABAergic synapse during neurogenesis. This is the first demonstration of the lack of a mature response to GABA in human FX neurons and may explain the inappropriate synaptic functions in FXS.

Modeling neurodevelopmental disorders using human pluripotent stem cells

Neurodevelopmental disorders (NDs) are impairments that affect the development and growth of the brain and the central nervous system during embryonic and early postnatal life. Genetically manipulated animals have contributed greatly to the advancement of ND research, but many of them differ considerably from the human phenotype. Cellular in vitro models are also valuable, but the availability of human neuronal cells is limited and their lifespan in culture is short. Human pluripotent stem cells (hPSCs), including embryonic stem cells and induced pluripotent stem cells, comprise a powerful tool for studying developmentally regulated diseases, including NDs. We reviewed all recent studies in which hPSCs were used as in vitro models for diseases and syndromes characterized by impairment of neurogenesis or synaptogenesis leading to intellectual disability and delayed neurodevelopment. We analyzed their methodology and results, focusing on the data obtained following in vitro neural differentiation and gene expression and profiling of the derived neurons. Electrophysiological recording of action potentials, synaptic currents and response to neurotransmitters is pivotal for validation of the neuronal fate as well as for assessing phenotypic dysfunctions linked to the disease in question. We therefore focused on the studies which included electrophysiological recordings on the in vitro-derived neurons. Finally, we addressed specific issues that are critical for the advancement of this area of research, specifically in providing a reliable human pre-clinical research model and drug screening platform.

Human embryonic stem cells carrying an unbalanced translocation demonstrate impaired differentiation into trophoblasts: an in vitro model of human implantation failure

Carriers of the balanced translocation t(11;22), the most common reciprocal translocation in humans, are at high risk of creating gametes with unbalanced translocation, leading to repeated miscarriages. Current research models for studying translocated embryos and the biological basis for their implantation failure are limited. The aim of this study was to elucidate whether human embryonic stem cells (hESCs) carrying the unbalanced chromosomal translocation t(11;22) can provide an explanation for repeated miscarriages of unbalanced translocated embryos. Fluorescent in situ hybridization and karyotype analysis were performed to analyze the t(11;22) in embryos during PGD and in the derived hESC line. The hESC line was characterized by RT-PCR and FACS analysis for pluripotent markers. Directed differentiation to trophoblasts was carried out by bone morphogenetic protein 4 (BMP4). Trophoblast development was analyzed by measuring β-hCG secretion, by β-hCG immunostaining and by gene expression of trophoblastic markers. We derived the first hESC line carrying unbalanced t(11;22), which showed the typical morphological and molecular characteristics of a hESC line. Control hESCs differentiated into trophoblasts secreted increasing levels of β-hCG and concomitantly expressed the trophoblast genes, CDX2, TP63, KRT7, ERVW1, CGA, GCM1, KLF4 and PPARG. In contrast, differentiated translocated hESCs displayed reduced and delayed secretion of β-hCG concomitant with impaired expression of the trophoblastic genes. The reduced activation of trophoblastic genes may be responsible for the impaired trophoblastic differentiation in t(11;22)-hESCs, associated with implantation failure in unbalanced t(11;22) embryos. Our t(11;22) hESCs are presented as a valuable human model for studying the mechanisms underlying implantation failure.

Electrical maturation of neurons derived from human embryonic stem cells

In-vitro neuronal differentiation of human pluripotent stem cells has become a widely used tool in disease modeling and prospective regenerative medicine. Most studies evaluate neurons molecularly and only a handful of them use electrophysiological tools to directly indicate that these are genuine neurons. Therefore, the specific timing of development of intrinsic electrophysiological properties and synaptic capabilities remains poorly understood. Here we describe a systematic analysis of developing neurons derived in-vitro from human embryonic stem cells (hESCs). We show that hESCs differentiated in-vitro into early embryonic neurons, displaying basically mature morphological and electrical features as early as day 37. This early onset of action potential discharges suggests that first stages of neurogenesis in humans are already associated with electrical maturation. Spike frequency, amplitude, duration, threshold and after hyperpolarization were found to be the most predictive parameters for electrical maturity. Furthermore, we were able to detect spontaneous synaptic activity already at these early time-points, demonstrating that neuronal connectivity can develop concomitantly with the gradual process of electrical maturation. These results highlight the functional properties of hESCs in the process of their development into neurons. Moreover, our results provide practical tools for the direct measurement of functional maturity, which can be reproduced and implemented for stem cell research of neurogenesis in general, and neurodevelopmental disorders in particular.

Derivation of novel human ground state naive pluripotent stem cells

Mouse embryonic stem (ES) cells are isolated from the inner cell mass of blastocysts, and can be preserved in vitro in a naive inner-cell-mass-like configuration by providing exogenous stimulation with leukaemia inhibitory factor (LIF) and small molecule inhibition of ERK1/ERK2 and GSK3β signalling (termed 2i/LIF conditions). Hallmarks of naive pluripotency include driving Oct4 (also known as Pou5f1) transcription by its distal enhancer, retaining a pre-inactivation X chromosome state, and global reduction in DNA methylation and in H3K27me3 repressive chromatin mark deposition on developmental regulatory gene promoters. Upon withdrawal of 2i/LIF, naive mouse ES cells can drift towards a primed pluripotent state resembling that of the post-implantation epiblast. Although human ES cells share several molecular features with naive mouse ES cells, they also share a variety of epigenetic properties with primed murine epiblast stem cells (EpiSCs). These include predominant use of the proximal enhancer element to maintain OCT4 expression, pronounced tendency for X chromosome inactivation in most female human ES cells, increase in DNA methylation and prominent deposition of H3K27me3 and bivalent domain acquisition on lineage regulatory genes. The feasibility of establishing human ground state naive pluripotency in vitro with equivalent molecular and functional features to those characterized in mouse ES cells remains to be defined. Here we establish defined conditions that facilitate the derivation of genetically unmodified human naive pluripotent stem cells from already established primed human ES cells, from somatic cells through induced pluripotent stem (iPS) cell reprogramming or directly from blastocysts. The novel naive pluripotent cells validated herein retain molecular characteristics and functional properties that are highly similar to mouse naive ES cells, and distinct from conventional primed human pluripotent cells. This includes competence in the generation of cross-species chimaeric mouse embryos that underwent organogenesis following microinjection of human naive iPS cells into mouse morulas. Collectively, our findings establish new avenues for regenerative medicine, patient-specific iPS cell disease modelling and the study of early human development in vitro and in vivo.

Genomic analysis of hESC pedigrees identifies de novo mutations and enables determination of the timing and origin of mutational events

Given the association between mutational load and cancer, the observation that genetic aberrations are frequently found in human pluripotent stem cells (hPSCs) is of concern. Prior studies in human induced pluripotent stem cells (hiPSCs) have shown that deletions and regions of loss of heterozygosity (LOH) tend to arise during reprogramming and early culture, whereas duplications more frequently occur during long-term culture. For the corresponding experiments in human embryonic stem cells (hESCs), we studied two sets of hESC lines: one including the corresponding parental DNA and the other generated from single blastomeres from four sibling embryos. Here, we show that genetic aberrations observed in hESCs can originate during preimplantation embryo development and/or early derivation. These early aberrations are mainly deletions and LOH, whereas aberrations arising during long-term culture of hESCs are more frequently duplications. Our results highlight the importance of close monitoring of genomic integrity and the development of improved methods for derivation and culture of hPSCs.

Neural differentiation of Fragile X human Embryonic Stem Cells reveals abnormal patterns of development despite successful neurogenesis

Fragile X Syndrome (FXS) is the most common form of inherited intellectual disability, caused by developmentally regulated inactivation of FMR1, leading to the absence of its encoded protein FMRP. We have previously shown that undifferentiated Fragile X human Embryonic Stem Cells (FX-hESCs) express FMRP, despite the presence of the full FMR1 mutation (>200 CGG repeats). We describe here, for the first time, in-vitro differentiation of FX-hESCs into neurons progressively inactivating FMR1. Abnormal neurogenesis and aberrant gene expression were found already during early stages of differentiation, leading to poor neuronal maturation and high gliogenic development. Human FX neurons fired action potentials but displayed poor spontaneous synaptic activity and lacked reactivity to glutamate. Our dynamic FX-hESCs model can contribute to the understanding of the sequence of developmental events taking place during neurogenesis and how they are altered in FXS individuals, leading to intellectual disability. Furthermore, it may shed light over the striking phenotypic features characterizing FXS in human.

Screening ethnically diverse human embryonic stem cells identifies a chromosome 20 minimal amplicon conferring growth advantage

The International Stem Cell Initiative analyzed 125 human embryonic stem (ES) cell lines and 11 induced pluripotent stem (iPS) cell lines, from 38 laboratories worldwide, for genetic changes occurring during culture. Most lines were analyzed at an early and late passage. Single-nucleotide polymorphism (SNP) analysis revealed that they included representatives of most major ethnic groups. Most lines remained karyotypically normal, but there was a progressive tendency to acquire changes on prolonged culture, commonly affecting chromosomes 1, 12, 17 and 20. DNA methylation patterns changed haphazardly with no link to time in culture. Structural variants, determined from the SNP arrays, also appeared sporadically. No common variants related to culture were observed on chromosomes 1, 12 and 17, but a minimal amplicon in chromosome 20q11.21, including three genes expressed in human ES cells, ID1, BCL2L1 and HM13, occurred in >20% of the lines. Of these genes, BCL2L1 is a strong candidate for driving culture adaptation of ES cells.

Female sex bias in human embryonic stem cell lines

The factors limiting the rather inefficient derivation of human embryonic stem cells (HESCs) are not fully understood. The aim of this study was to analyze the sex ratio in our 42 preimplantation genetic diagnosis (PGD)-HESC lines, in an attempt to verify its affect on the establishment of HESC lines. The ratio between male and female PGD-derived cell lines was compared. We found a significant increase in female cell lines (76%). This finding was further confirmed by a meta-analysis for combining the results of all PGD-derived HESC lines published to date (148) and all normal karyotyped HESC lines derived from spare in vitro fertilization embryos worldwide (397). Further, gender determination of embryos demonstrated that this difference originates from the actual derivation process rather than from unequal representation of male and female embryos. It can therefore be concluded that the clear-cut tendency for female preponderance is attributed to suboptimal culture conditions rather than from a true gender imbalance in embryos used for derivation of HESC lines. We propose a mechanism in which aberrant X chromosome inactivation and/or overexpression of critical metabolic X-linked genes might explain this sex dimorphism.

[Preimplantation genetic diagnosis (PGD) for cancer predisposition syndromes]

INTRODUCTION

Most cases of cancer are sporadic and only 5%-10% are inherited with variable penetrance. Whenever the causative mutation is known, prevention of affected offspring birth may be achieved by prenatal or preimplantation genetic diagnosis (PGD).

AIM

To devise a scoring system (SS) that appraises the justification of PGD for each patient and to evaluate the efficacy, reliability and accuracy of PGD for cancer predisposition syndromes in 48 cycles.

METHODS

A semi-quantitative SS was developed by evaluating disease characteristics (onset, severity, inheritance pattern and penetrance) and patient clinical variables (infertility, objection to abortion and a need for diagnosis of additional genetic syndrome). PGD cycles were performed by blastomere biopsy of cleavage stage embryos, followed by single cell multiplex nested PCR for the cancer predisposition mutation and flanking polymorphic markers.

RESULTS

Seventeen couples referred to PGD for cancer predisposition. According to the devised SS, fourteen were accepted and 3 were declined. Of the 14 accepted couples, 13 had at Least one affected member and 11 couples required IVF anyway. A total of 48 PGD cycles were performed resulting in 8 pregnancies.

CONCLUSION

PGD for cancer predisposition genes is a possible and reliable procedure, suitable especiaLly for infertile carrier couples.

DISCUSSION AND SUMMARY

The assessment of the characteristics of the cancer syndrome and consideration of the variables of each couple enable, the justified application of PGD procedure. The continuous discovery of cancer predisposition mutations will result in an ever-increasing demand for PGD to prevent the transmission of Lethal mutations to the next generations.

Virtual azoospermia and cryptozoospermia--fresh/frozen testicular or ejaculate sperm for better IVF outcome?

Men diagnosed as having azoospermia occasionally have a few mature sperm cells in other ejaculates. Other men may have constant, yet very low quality and quantity of sperm cells in their ejaculates, resulting in poor intracytoplasmic sperm injection (ICSI) outcome. It has not been conclusively established which source of sperm cells is preferable for ICSI when both ejaculate and testicular (fresh or frozen) sperm cells are available. It is also unclear whether there is any advantage of fresh over frozen sperm if testicular sperm is to be used. We used ejaculate, testicular (fresh or frozen) sperm cells, or both for ICSI in 13 couples. Five of these couples initially underwent ICSI by testicular sperm extraction, because the males had total azoospermia, and in later cycles with ejaculate sperm cells. Ejaculate sperm cells were initially used for ICSI in the other 8 patients, and later with testicular sperm cells. The fertilization rate was significantly higher when fresh or frozen-thawed testicular sperm cells were used than when ejaculated sperm cells were used. Likewise, the quality of the embryos from testicular (fresh and frozen) sperm was higher than from ejaculated sperm (65.3% vs 53.2%, respectively, P < .05). The use of fresh testicular sperm yielded better implantation rates than both frozen testicular sperm and ejaculate. Therefore, fresh testicular sperm should be considered first for ICSI in patients with virtual azoospermia or cryptozoospermia because of their superior fertility.

Resolving a genetic paradox throughout preimplantation genetic diagnosis for autosomal dominant severe congenital neutropenia

OBJECTIVE

Severe congenital neutropenia is an inherited disease characterized by low peripheral blood neutrophils, amenable to bone marrow transplantation. Genetic analysis in the family here described detected a ELA2 splice-site mutation in the affected child and also in his asymptomatic father. The parents requested preimplantation genetic diagnosis (PGD), coupled with HLA matching, to obtain a suitable bone marrow donor for the affected child.

METHODS

A PGD protocol was developed, based on multiplex nested PCR for direct analysis of the ELA2 mutation, flanking polymorphic markers and HLA typing.

RESULTS

The amplification efficiency of the mutation was > 90% in single leukocytes from the affected child but only 67% in the father. Analysis of single haploid sperm cells from the father demonstrated three different sperm-cell populations: (1) sperm cells harboring the ELA2 mutation on the 'affected' haplotype, (2) sperm cells without the ELA2 mutation on the 'normal' haplotype, and (3) sperm cells without the ELA2 mutation on the 'affected' haplotype.

CONCLUSION

These data demonstrate that the ELA2 mutation in the father occurred de novo during his embryonic development, resulting in somatic as well as germ-line mosaicism. This conclusion was also taken into consideration when PGD was performed.

Retrieval of immature oocytes after chemotherapy for Hodgkin's disease and prolonged ovarian down-regulation with gonadotropin-releasing hormone agonist

OBJECTIVE

To describe isolation and in vitro maturation of primary oocytes from the ovarian cortex in the presence of hypothalamic pituitary down-regulation.

DESIGN

Case report.

SETTING

Tertiary care university-affiliated hospital.

PATIENT(S)

An 18-year-old patient was given treatment with the ABVD (Adriamycin, bleomycin, vinblastine, and dacarbazine) protocol for Hodgkin's disease. She underwent ovarian tissue cryopreservation while being cotreated with GnRH agonist because of disease relapse.

INTERVENTION(S)

Laparoscopic oophorectomy, ovarian tissue cryopreservation, and in vitro maturation of primary oocytes.

MAIN OUTCOME MEASURE(S)

Maturation of primary oocytes isolated from the medium used for preparation of ovarian tissue.

RESULT(S)

Twenty-one immature germinal vesicle-stage oocytes were isolated from the medium of dissection. All were incubated in in vitro maturation medium, and five were maturated and frozen.

CONCLUSION(S)

The fact that germinal vesicle-stage oocytes were present in our patient's medium despite hormonal down-regulation demonstrates that GnRH agonist does not completely inhibit antral follicle development.

Preimplantation genetic diagnosis for fragile X syndrome: is there increased transmission of abnormal FMR1 alleles among female heterozygotes?

BACKGROUND

Fragile X syndrome is caused by a CGG triplet-repeat expansion mutation in the FMR1 gene. Previous studies have shown increased transmission of abnormal alleles in the 51-60 repeat range. This study was undertaken to evaluate the performance of preimplantation genetic diagnosis (PGD) for fragile X, and to assess the transmission rate of the abnormal FMR1 alleles in this setting.

METHOD

The study included 18 fragile X carriers who applied for PGD. FMR1 CGG repeats ranged from 70 to 300. PGD was performed using multiplex-nested PCR, with simultaneous amplification of the CGG repeat region and several polymorphic markers, and sex chromosome markers.

RESULTS

Four patients had a poor ovarian response, and could not undergo PGD. The remaining 14 patients underwent 47 PGD cycles. A total of 565 oocytes were aspirated. Of the 386 embryos that were successfully biopsied, 18 (6.4%) could not be analyzed due to amplification failure, and 12 (4.3%) had sex chromosomal abnormalities. Of the remaining 250 embryos, the abnormal allele was transmitted to 124 embryos (49.6%) compared to 126 (50.4%) for the normal allele. This difference was not statistically significant. Only embryos carrying the normal allele were transferred, resulting in 7 clinical pregnancies (18% per embryo transfer).

CONCLUSIONS

Our results demonstrate that PGD for fragile X is feasible, and that carriers transmit the abnormal allele at the same frequency as the normal allele.

Assessment of ovarian reserve following ovarian tissue banking and/or GnRH-a co-treatment prior to chemotherapy in patients with Hodgkin's disease

PURPOSE

To examine ovarian reserve following chemotherapy in women with Hodgkin's disease.

METHODS

The study included nine patients who underwent ovarian tissue cryopreservation (OTCP) prior to chemotherapy consisting of the ABVD regimen (Adriamycin, bleomycin, vinblastine, and dacarbazine) and co-treatment with gonadotropin-releasing hormone agonist (GnRH-a) (Group A), and 13 patients treated by the ABVD protocol only without GnRH-a (Group B). The average age was 25.2 +/- 2.7 years for the women in Group A and 31.8 +/- 6.8 years for those in Group B.

RESULTS

Six months following the end of chemotherapy, the menstrual cycle resumed in all Group A patients and in four Group B patients who had amenorrhea. Eight Group B patients had regular menses during and after chemotherapy. None of the patients suffered from ovarian failure. Two Group A patients conceived in the first year after completing chemotherapy.

CONCLUSIONS

Co-treatment with GnRH-a has little effect on ovarian protection in women with Hodgkin's disease.

Developmental study of fragile X syndrome using human embryonic stem cells derived from preimplantation genetically diagnosed embryos

We report on the establishment of a human embryonic stem cell (HESC) line from a preimplantation fragile X-affected embryo and demonstrate its value as an appropriate model to study developmentally regulated events that are involved in the pathogenesis of this disorder. Fragile X syndrome results from FMR1 gene inactivation due to a CGG expansion at the 5'UTR region of the gene. Early events in FMR1 silencing have not been fully characterized due to the lack of appropriate animal or cellular models. Here we show that, despite the presence of a full mutation, affected undifferentiated HESCs express FMR1 and are DNA unmethylated. However, epigenetic silencing by DNA methylation and histone modification occurs upon differentiation. Our unique cell system allows the dissection of the sequence by which these epigenetic changes are acquired and illustrates the importance of HESCs in unraveling developmentally regulated mechanisms associated with human genetic disorders.

Preimplantation aneuploid embryos undergo self-correction in correlation with their developmental potential

OBJECTIVE

To investigate the incidence of embryos' self-correction during preimplantation development in terms of mosaicism and in correlation with its developmental stage.

DESIGN

Prospective study to compare the chromosome status of embryos on day 3 with that of day 5, in correlation with their developmental stage.

SETTING

In vitro fertilization unit of a university-affiliated hospital.

PATIENT(S)

Eighty-three aneuploid embryos.

INTERVENTION(S)

Fluorescence in situ hybridization (FISH) reanalysis.

MAIN OUTCOME MEASURE(S)

Day 3 embryos classified as mosaic or chromosomally abnormal by preimplantation genetic screening (PGS) were reanalyzed on day 5. The results were evaluated in correlation with the embryos' developmental stage.

RESULT(S)

Out of 83 day 3 aneuploid embryos, 15 (18.1%) were diagnosed with mosaicism. The FISH reanalysis on day 5 demonstrated that 27 embryos (32.6%) were partly or entirely normal disomic. Of these 83 aneuploid embryos, 8 (9.7%) underwent complete self-correction. The PGS results demonstrated that 26.5% of the embryos were trisomic, of which 41.0% underwent trisomic rescue by day 5. Self-correction was in correlation with the embryo's developmental stage, i.e., 38.1% of aneuploid embryos that developed to the blastocyst stage underwent self-correction compared with only 12.5% of embryos that only cleaved after biopsy.

CONCLUSION(S)

Our results demonstrate that self-correction of aneuploid and mosaic embryos occurs probably more significantly during development toward the blastocyst stage than in delayed embryos. In addition, trisomic embryos correct themselves more than other aneuploidies. These findings suggest that PGS results must be interpreted with caution.

Does high serum progesterone level on the day of human chorionic gonadotropin administration affect pregnancy rate after intracytoplasmic sperm injection and embryo transfer?

OBJECTIVE

The present study was conducted to evaluate the effect of serum progesterone (P) levels on the day of human chorionic gonadotropin (hCG) administration on embryo quality and pregnancy rate in intracytoplasmic sperm injection (ICSI) cycles.

DESIGN AND SETTING

This was a retrospective analysis conducted in the in vitro fertilization (IVF) unit of a tertiary hospital.

PATIENTS

Two hundred and one patients who underwent a total of 280 IVF treatment cycles allocated to ICSI during routine IVF/embryo transfer treatment. Results. In cycles with elevated serum P, higher estradiol levels were noted (1915 pg/ml vs. 1256 pg/ml; p<0.05), more oocytes were retrieved and manipulated, and more embryos were available for transfer. Embryo grading was comparable between the two groups. The average age was lower in the group with elevated P; but the pregnancy rate was significantly lower (16.4% vs. 27.6%, p = 0.03).

CONCLUSIONS

Our data demonstrate no deleterious effect of elevated P on embryo quality. However, high serum P adversely affects implantation and pregnancy rates.