Preimplantation testing for chromosomal disorders improves reproductive outcome of poor-prognosis patients

PGT for structural chromosomal rearrangements in 300 couples reveals specific risk factors but an interchromosomal effect is unlikely

RESEARCH QUESTION

What factors affect the proportion of chromosomally balanced embryos in structural rearrangement carriers? Is there any evidence for an interchromosomal effect (ICE)?

DESIGN

Preimplantation genetic testing outcomes of 300 couples (198 reciprocal, 60 Robertsonian, 31 inversion and 11 complex structural rearrangement carriers) were assessed retrospectively. Blastocysts were analysed either by array-comparative genomic hybridization or next-generation sequencing techniques. ICE was investigated using a matched control group and sophisticated statistical measurement of effect size (φ).

RESULTS

300 couples underwent 443 cycles; 1835 embryos were analysed and 23.8% were diagnosed as both normal/balanced and euploid. The overall cumulative clinical pregnancy and live birth rates were 69.5% and 55.8%, respectively. Complex translocations and female age (≥35) were found to be risk factors associated with lower chance of having a transferable embryo (P < 0.001). Based on analysis of 5237 embryos, the cumulative de-novo aneuploidy rate was lower in carriers compared to controls (45.6% versus 53.4%, P < 0.001) but this was a 'negligible' association (φ < 0.1). A further assessment of 117,033 chromosomal pairs revealed a higher individual chromosome error rate in embryos of carriers compared to controls (5.3% versus 4.9%), which was also a 'negligible' association (φ < 0.1), despite a P-value of 0.007.

CONCLUSIONS

These findings suggest that rearrangement type, female age and sex of the carrier have significant impacts on the proportion of transferable embryos. Careful examination of structural rearrangement carriers and controls indicated little or no evidence for an ICE. This study helps to provide a statistical model for investigating ICE and an improved personalized reproductive genetics assessment for structural rearrangement carriers.

The Effectiveness of Next-Generation Sequencing-Based Preimplantation Genetic Testing for Balanced Translocation Couples

The purpose of this study was to evaluate the effectiveness of next-generation sequencing (NGS)-based preimplantation genetic testing (PGT) for balanced translocation carriers to identify normal/balanced blastocysts and to measure pregnancy outcomes following euploid embryo transfer. We enrolled 75 couples with a balanced translocation who underwent 83 PGT cycles (58 cycles for carriers with reciprocal translocations and 25 cycles for carriers with Robertsonian translocations) and 388 blastocysts were diagnosed. Moreover, we transferred single euploid blastocysts through frozen embryo transfer and calculated the biochemical pregnancy, clinical pregnancy, miscarriage, and ongoing pregnancy rates per embryo transfer cycle. Despite a mean maternal age of 29.8 years and mean of 4.34 embryos biopsied, there was a 32.8% chance of recording no chromosomally normal/balanced embryos for reciprocal translocation carriers. The proportion of normal/balanced embryos was significantly higher (44.1 vs. 27.8%) in Robertsonian translocation carriers than in reciprocal translocation carriers. Female carriers had a significantly lower (23.3 vs. 42.4%, 34.7 vs. 54.7%, respectively) percentage of normal/balanced embryos than male carriers, regardless of the translocation. After transfering single blastocysts, we obtained a 64.4% clinical pregnancy rate per transfer, and the clinical miscarriage rate was 5.7%. Amniocentesis results showed that all karyotypes of the fetuses were consistent with PGT results. The clinical outcomes are probably not influenced by the type of translocation, maternal age, and blastocyst morphology following the transfer of euploid blastocysts. Therefore, we conclude that NGS-based PGT is an efficient method for analyzing balanced translocation carriers, and aneuploidy screening had good clinical outcomes.

The impact of patient, embryo, and translocation characteristics on the ploidy status of young couples undergoing preimplantation genetic testing for structural rearrangements (PGT-SR) by next generation sequencing (NGS)

PURPOSE

To evaluate the factors that affect the incidence of euploid balanced embryos and interchromosomal effect (ICE) in carriers of different structural rearrangements.

METHODS

This retrospective study includes 95 couples with reciprocal translocations (RecT) and 36 couples with Robertsonian translocations (RobT) undergoing Preimplantation Genetic Testing for Structural Rearrangements (PGT-SR) between March 2016 and July 2019. Next-generation sequencing (NGS) was the technique used coupled with trophectoderm (TE) biopsy. Only cases with females under 38 years were included. A total of 532 blastocysts were evaluated.

RESULTS

The euploidy rate was similar in RobT when compared with RecT carriers [57/156 (36.5%) vs. 112/376 (29.8%), p = 0.127]. The pure ICE rate was significantly higher in RobT carriers [48/156 (30.8%) vs. 53/376 (14.1%), p < 0.001] than it was in RecT carriers. Female age was the independent factor for the probability of obtaining a euploid embryo in RecT and RobT carriers, and increasing female age decreases the probability of obtaining a euploid embryo. In RecT carriers, no significant differences were observed in euploidy rates, pure ICE, or combined ICE according to the length of the translocated fragment and the chromosome group. However, total ICE was significantly lower when there was a breakpoint in the short chromosome arm together with a breakpoint in the long arm [(44/158 (27.8%) for pq or qp, 51/155 (32.9%) for pp and 30/63 (47.6%) for qq; p = 0.02].

CONCLUSION

The incidence of euploid/balanced blastocysts was similar in both types of translocations. However, there was a significant increase in pure ICE in RobT compared to RecT carriers. In RecT carriers, the presence of the breakpoints in the long arm of the chromosomes involved in the rearrangement resulted in a higher total ICE.

In vitro fertilization outcomes after preimplantation genetic testing for chromosomal structural rearrangements comparing fluorescence in-situ hybridization, microarray comparative genomic hybridization, and next-generation sequencing

Objective

To compare in vitro fertilization (IVF) outcomes for preimplantation genetic testing for chromosomal structural rearrangements (PGT-SR) using various testing platforms.

Design

Retrospective cohort.

Setting

Large academic IVF center.

Patient(s)

Fifty-one balanced translocation carriers undergoing IVF with PGT-SR who completed a total of 91 cycles, including 31 fluorescence in-situ hybridization (FISH), 24 microarray comparative genomic hybridization (aCGH), and 36 next-generation sequencing (NGS) testing cycles.

Intervention(s)

PGT-SR.

Main Outcome Measure(s)

Primary outcome of live-birth rate and secondary outcomes including implantation rate, clinical loss rate, and percentages of normal or balanced, unbalanced, and aneuploid embryos detected.

Result(s)

There was no statistically significant difference in LBR, though there was a tendency toward a higher LBR for NGS testing (14 of 19, 73.7%) compared with FISH (8 of 18, 44.4%) and aCGH (10 of 20, 50.0%). The implantation rate was statistically significantly higher for NGS (16 of 20, 80.0%) compared with FISH (11 of 25, 44.0%) and aCGH (16 of 30, 53.3%). There was no statistically significant difference in clinical pregnancy losses. There was a lower percentage of normal or balanced embryos with FISH (12.5%) compared with aCGH (23.7%) and with NGS (20.7%).

Conclusion(s)

This is the first report of PGT-SR outcomes for translocation carriers directly comparing PGT-SR using FISH, aCGH, and NGS. Our findings suggest an improvement in pregnancy outcomes parallel to the advancement in technology and are reassuring for continued use of NGS for this population.

The Clinical Effectiveness of Preimplantation Genetic Diagnosis for Chromosomal Translocation Carriers: A Meta-analysis

Published data on the relationship between pregnancy outcomes of preimplantation genetic diagnosis (PGD) in translocation carriers have implicated inconclusive results. To identify potentially eligible reports, an electronic search was conducted in several databases, including PubMed, Scopus, Web of Knowledge, and Cochrane. Pooled odd ratios (ORs) and 95% confidence intervals (Cis) were estimated based on a random-effect model to evaluate the strength of association between PGD and successful pregnancy outcome in translocation carriers. A total of six cohort studies were included in the current study. The meta-analysis of these studies revealed that the PGD method was associated with an increased successful pregnancy outcome of translocation carriers (OR = 8.58; 95%CI: 1.40–52.76). In subgroup analysis, there was no significant association according to the chromosomal translocation carrier origin and the type of translocated chromosomes, as well as country. In developed countries, the pregnancy outcome of PGD was significantly improved in translocation carriers (OR = 21.79; 95%CI: 1.93–245.52). The current meta-analysis demonstrated that the PGD method is associated with successful pregnancy outcome in both types of reciprocal and Robertsonian translocation carriers, especially in developed countries.

Male Infertility in Robertsonian Translocation: A Case Report

Case series

Patients: Male, 34-year-old • Male, 35-year-old

Final Diagnosis: Primary infertility • Robertsonian translocation

Symptoms: Asymptomatic

Medication: —

Clinical Procedure: —

Specialty: Urology

Trophectoderm biopsy protocols can affect clinical outcomes: time to focus on the blastocyst biopsy technique

OBJECTIVE

To compare two different blastocyst biopsy protocols.

DESIGN

Retrospective single-center cohort study.

SETTINGS

Private in vitro fertilization center.

PATIENT(S)

The study included 1,670 frozen-thawed embryo transfers (FETs) with preimplantation genetic testing for aneuploidy (PGT-A).

INTERVENTION

None.

MAIN OUTCOME MEASURE(S)

Survival rate (SR) after thawing, clinical pregnancy rate (CPR), ongoing implantation rate (IR), and live birth rate (LBR).

RESULT(S)

Eight hundred thirty-five FETs with PGT-A cycles including only embryos biopsied in the sequential blastocyst hatching and biopsy protocol paired with the ablation of one-fourth of the zona pellucida (ZP) were matched with 835 FETs with PGT-A cycles including only embryos biopsied in the day 3 prehatching protocol by female age (±1 year), number of embryos transferred, use of gestational carrier or egg donor, and day of blastocyst transfer. Only FETs with euploid blastocysts graded no lower than 4BB were included, and cycles with fewer than five oocytes were excluded. SR after thawing, CPR, ongoing IR, and LBR were significantly higher in the FET cycles with the embryos biopsied in the sequential hatching and biopsy protocol. Four cases of monozygotic twin pregnancies were reported with the day 3 prehatching protocol and none with the sequential hatching and biopsy protocol.

CONCLUSION(S)

Our results show, for the first time, that using different blastocyst biopsy protocols can affect clinical outcomes. Because the study was retrospective, our findings should be validated in a prospective trial.

Interchromosomal effect in carriers of translocations and inversions assessed by preimplantation genetic testing for structural rearrangements (PGT-SR)

PURPOSE

Balanced carriers of structural rearrangements have an increased risk of unbalanced embryos mainly due to the production of unbalanced gametes during meiosis. Aneuploidy for other chromosomes not involved in the rearrangements has also been described. The purpose of this work is to know if the incidence of unbalanced embryos, interchromosomal effect (ICE) and clinical outcomes differ in carriers of different structural rearrangements.

METHODS

Cohort retrospective study including 359 preimplantation genetic testing cycles for structural rearrangements from 304 couples was performed. Comparative genomic hybridisation arrays were used for chromosomal analysis. The results were stratified and compared according to female age and carrier sex. The impact of different cytogenetic features of chromosomal rearrangements was evaluated.

RESULTS

In carriers of translocations, we observed a higher percentage of abnormal embryos from day 3 biopsies compared with day 5/6 biopsies and for reciprocal translocations compared with other rearrangements. We observed a high percentage of embryos with aneuploidies for chromosomes not involved in the rearrangement that could be attributed to total ICE (aneuploid balanced and unbalanced embryos). No significant differences were observed in these percentages between types of rearrangements. Pure ICE (aneuploid balanced embyos) was independent of female age only for Robertsonian translocations, and significantly increased in day 3 biopsies for all types of abnormalities. Furthermore, total ICE for carriers of Robertsonian translocations and biopsy on day 3 was independent of female age too. High ongoing pregnancy rates were observed for all studied groups, with higher pregnancy rate for male carriers.

CONCLUSION

We observed a higher percentage of abnormal embryos for reciprocal translocations. No significant differences for total ICE was found among the different types of rearrangements, with higher pure ICE only for Robertsonian translocations. There was a sex effect for clinical outcome for carriers of translocations, with higher pregnancy rate for male carriers. The higher incidence of unbalanced and aneuploid embryos should be considered for reproductive counselling in carriers of structural rearrangements.

Detection of a balanced translocation carrier through trophectoderm biopsy analysis: a case report

BACKGROUND

Balanced translocation carriers are burdened with fertility issues due to improper chromosome segregation in gametes, resulting in either implantation failure, miscarriage or birth of a child with chromosomal disorders. At the same time, these individuals are typically healthy with no signs of developmental problems, hence they often are unaware of their condition. Yet, because of difficulties in conceiving, balanced translocation carriers often turn to assisted reproduction, some of whom may also undergo preimplantation genetic testing for aneuploidy (PGT-A) to improve the likelihood of achieving a successful pregnancy.

CASE REPORT

We describe a female patient, who pursued in vitro fertilization (IVF) treatment coupled with PGT-A following two consecutive miscarriages, unaware of her genetic condition. PGT-A was performed on blastocyst-stage embryos and the results of comprehensive chromosome screening from a first IVF cycle demonstrated reciprocal segmental aberrations on chromosome 7 and chromosome 10 in two out of four embryos. Due to distinct embryo profiles, the couple was then referred for genetic counselling and subsequent parental karyotyping revealed the presence of a previously undetected balanced translocation in the mother.

CONCLUSIONS

These results confirm previous reports that genome-wide PGT-A can facilitate the identification of balanced translocation carriers in IVF patients, providing explanation for poor reproductive outcome and allowing adjustments in treatment strategies.

Overview of Preimplantation Genetic Diagnosis (PGD): Historical Perspective and Future Direction

Preimplantation genetic diagnosis (PGD) can be considered the earliest form of prenatal testing. It was first used in humans over 26 years ago. At its inception, PGD could only be performed for a limited number of genetic disorders. Technological advances in molecular biology and cytogenomics have been utilized in the field of PGD to greatly expand the spectrum of genetic disorders that can now be detected in early human embryos.

The number of biopsied trophectoderm cells may affect pregnancy outcomes

OBJECTIVE

To study if the number of trophectoderm (TE) biopsied cells has an impact on implantation rates.

DESIGN

A retrospective cohort study in a single-center study.

SETTING

In vitro fertilization center.

PATIENTS

Patients who underwent PGT-A from January 2013 to March 2016. In total, 482 vitrified/warmed single embryo transfers were included.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Clinical pregnancies rate, implantation rate.

RESULTS

Overall, clinical pregnancies per embryo transfer were higher when a regular TE were biopsied compared to larger size biopsy cells (66% (175/267) vs 53% (115/215) (p < 0.005) respectively). Pregnancy rates were also analyzed according to embryo morphology at the moment of embryo biopsy, when a good-quality embryo was transferred the clinical outcome was 75% (81/108) in group 1 and 61% (60/99) in group 2 (p < 0.05). Data was also stratified by age in patients ≤ 35 years and > 35 years. The clinical pregnancy was 67% (51/76) in women ≤ 35 years and 65% (124/191) in women > 35 years when a regular size biopsy was performed. These results significantly reduced when a larger size biopsy was performed 54% (49/91) and 53% (66/124), respectively (p < 0.05). Further investigation indicated that miscarriage rate was similar between these groups (4% (7/182) in group 1 and 5% (6/121) in group 2).

CONCLUSIONS

These findings underscore that when a large amount of TE cells are biopsied, it may negatively affect implantation rates, but once implanted, the embryos have the same chance to miscarry or reach term.

Preimplantation genetic testing for complex chromosomal rearrangement carriers by next-generation sequencing

RESEARCH QUESTION

Can preimplantation genetic testing (PGT) with next-generation sequencing (NGS) increase the chance of achieving a balanced euploid pregnancy in complex chromosome rearrangement (CCR) carriers?

DESIGN

Six couples underwent PGT at the Clinical Centre of Reproductive Medicine, First Affiliated Hospital, Nanjing Medical University. The CCR carriers in the six couples were: Case A: 46,XY,t(1;4;11)(p31;p16;q22); Case B: 46,XY,t(3;13;5)(p14;q21;p14); Case C: 46,XX,t(6;11;21)(q21;q21;q13); Case D: 46,XX,inv(9)(p12; q13),t(13;15)(q14;q24); Case E: 46,XX,inv(9)(p12;q13),t(7;9)(q22;p22); and Case F: 46,XX,t(2;7)(q21;q36),t(2;4)(p10;q10),t(2;4)(q15;q10). After ovarian stimulation followed by oocyte retrieval and embryo culture, PGT was performed on day 5 or 6 blastocyst biopsies using NGS to identify normal/balanced euploid embryos. Vitrified-warmed single embryo transfers were performed using normal/balanced euploid embryos.

RESULTS

After seven cycles, 84 oocytes were retrieved. Whole genome sequencing by NGS was performed on 25 trophectoderm biosies. Six (24%) embryos were identified as normal/balanced euploid, four were transferred resulting in four live births. Case A, C, D and E each gave birth to a healthy baby after their first cycle. There was no transferable embryo after two cycles for Case B and one cycle for Case F. The implantation rate per transfer was 4/4 and the live birth rate was 4/4.

CONCLUSION

These results strongly support the use of NGS for CCR carriers.

Combination of spindle and first polar body chromosome images for the enhanced prediction of developmental potency of mouse metaphase II oocytes

The objective of this study was to classify spindle and first polar body (PB1) chromosome images in ovulated mouse oocytes over time to predict the developmental competence of metaphase II (MII) oocytes. Oocytes were collected at 12, 15, 20, and 25 h after human chorionic gonadotropin (hCG) injection, and stained for spindle tubulin, chromosomes, and PB1 chromosomes. MII spindle morphology was classified as tapered type or barrel type and PB1 chromosomes were categorized as aggregated, separated, dot, or collapsed. To determine whether differences in spindle and PB1 images in MII oocytes are associated with fertilization success, we performed in vitro fertilization (IVF) at various times after hCG injection. Barrel-type spindles and aggregate-type PB1 were dominant at 12 h after hCG injection. Oocyte spindles collected 1 h after injection were tapered, and PB1 chromosomes were separated. At 20 and 25 h after treatment, spindle and PB1 images were classified as collapsed. The rate of development to 2-cell embryos after IVF did not differ between the 12 h and 15 h treatments; however, it was significantly lower for the 25 h treatment than for other treatments. The rates of development to blastocysts at 12, 15, 20, and 25 h after hCG injection were 61, 46, 42, and 9%, respectively. MII oocytes with barrel-type spindles and aggregate-type PB1 had high rates of fertilization and blastocyst development, and spindle and PB1 characteristics were correlated with the outcomes of IVF and embryo culture. These results suggested that images of spindles combined with those of PB1 chromosomes enable the prediction of oocytic and/or embryonic quality.

Causes and estimated incidences of sex-chromosome misdiagnosis in preimplantation genetic diagnosis of aneuploidy

Preimplantation genetic diagnosis of aneuploidy (PGD-A) with comprehensive chromosome analysis has been known to improve pregnancy outcomes. Accuracy in detecting sex chromosomes becomes important when selecting against embryos at risk for sex-linked disorders. A total of 21,356 PGD-A cycles consisting of day-3 (cleavage) or day-5 (blastocyst) biopsies were received at the same laboratory for PGD-A via fluorescence in situ hybridization (FISH) or array comparative genome hybridization (aCGH) from multiple fertility centres. The misdiagnosis rates were 0.12% (Wilson 95% CI 0.05 to 0.25%) in day-3 FISH cycles, 0.48% (Wilson 95% CI 0.19 to 1.22%) in day-3 aCGH cycles and 0.0% (Wilson 95% CI 0 to 0.26) in day-5 aCGH cycles. Although rare, the likely causative biological event for true misdiagnosis is embryonic XX/XY mosaicism. Reanalysis of 1219 abnormal cleavage-stage research embryos revealed a 73% incidence of minor and major mosaicism. Only four (0.3%) embryos were found to be diploid and contained XX and XY cells that could potentially account for the misdiagnosis of sex. Our investigation identified errors leading to misdiagnosis and their attribution to specific events during PGD-A testing. The reported misdiagnosis rates suggest that PGD-A for sex determination is highly accurate, particularly when using aCGH applied to blastocyst biopsies.

Outcomes of in vitro fertilization with preimplantation genetic diagnosis: an analysis of the United States Assisted Reproductive Technology Surveillance Data, 2011-2012

OBJECTIVE

To assess the characteristics of IVF cycles for which preimplantation genetic diagnosis (PGD) was used and to evaluate indications for PGD and treatment outcomes associated with this procedure as compared with cycles without PGD with the data from the U.S. National ART Surveillance System.

DESIGN

Retrospective cohort study.

SETTING

None.

PATIENT(S)

Fresh autologous cycles that involved transfer of at least one embryo at blastocyst when available.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

PGD indications and age-specific reproductive outcomes.

RESULT(S)

There were a total of 97,069 non-PGD cycles and 9,833 PGD cycles: 55.6% were performed for aneuploidy screening (PGD Aneuploidy), 29.1% for other reasons (PGD Other), and 15.3% for genetic testing (PGD Genetic). In comparison to non-PGD cycles, PGD Aneuploidy cycles showed a decreased odds of miscarriage among women 35-37 years (adjusted odds ratio [aOR] 0.62; 95% CI, 0.45-0.87) and women >37 years (aOR 0.55; 95% CI, 0.43-0.70); and an increased odds of clinical pregnancy (aOR 1.18; 95% CI, 1.05-1.34), live-birth delivery (aOR 1.43; 95% CI, 1.26-1.62), and multiple-birth delivery (aOR 1.98; 95% CI, 1.52-2.57) among women >37 years.

CONCLUSION(S)

Aneuploidy screening was the most common indication for PGD. Use of PGD was not observed to be associated with an increased odds of clinical pregnancy or live birth for women <35 years. PGD for aneuploidy was associated with a decreased odds of miscarriage for women >35 years, but an increased odds of a live-birth and a multiple live-birth delivery among women >37 years.

Reproductive outcomes in men with karyotype abnormalities: Case report and review of the literature

Reciprocal translocations of autosomal chromosomes are present in about 1/625 men, yet often there are no symptoms except primary infertility. Abnormal segregation during meiosis often produces sperm and subsequent embryos with unbalanced translocations that often ultimately result in spontaneous abortions. We report on a 37-year-old man and his 39-year-old wife who complained of primary infertility. Previous in vitro fertilization (IVF) had resulted in pregnancy, but two spontaneous abortions. Upon chromosomal testing, the man was diagnosed with a reciprocal translocation and his wife was diagnosed with mosaic Turner's syndrome. Through testicular sperm extraction (TESE) and IVF with preimplantation genetic screening (PGS), they succeeded in having two healthy children. Since men with different karyotype abnormalities can have male infertility, we reviewed the literature and summarized the reproductive outcomes for men with both autosome and sex chromosomal karyotype abnormalities.

Validation of a semiconductor next-generation sequencing-based protocol for preimplantation genetic diagnosis of reciprocal translocations

OBJECTIVE

We aim to validate a semiconductor next-generation sequencing (NGS)-based method to detect unbalanced chromosome translocation in preimplantation embryos.

METHODS

The study consisted of a blinded retrospective evaluation with NGS of 145 whole-genome amplification products obtained from biopsy of cleavage-stage embryos or blastocysts, derived from 33 couples carrying different balanced translocations. Consistency of NGS-based copy number assignments was evaluated and compared with the results obtained by array-comparative genomic hybridization.

RESULTS

Reliably identified with the NGS-based protocol were 162 segmental imbalances derived from 33 different chromosomal translocations, with the smallest detectable chromosomal segment being 5 Mb in size. Of the 145 embryos analysed, 20 (13.8%) were balanced, 43 (29.6%) were unbalanced, 53 (36.5%) were unbalanced and aneuploid, and 29 (20%) were balanced but aneuploid. NGS sensitivity for unbalanced/aneuploid chromosomal call (consistency of chromosome copy number assignment) was 99.75% (402/403), with a specificity of 100% (3077/3077). NGS specificity and sensitivity for unbalanced/aneuploid embryo call were 100%.

CONCLUSIONS

Next-generation sequencing can detect chromosome imbalances in embryos with the added benefit of simultaneous comprehensive aneuploidy screening. Given the high level of consistency with array-comparative genomic hybridization, NGS has been demonstrated to be a robust high-throughput technique ready for clinical application in preimplantation genetic diagnosis for chromosomal translocations, with potential advantages of automation, increased throughput and reduced cost.

Clinical outcome of preimplantation genetic diagnosis and screening using next generation sequencing

Background

Next generation sequencing (NGS) is now being used for detecting chromosomal abnormalities in blastocyst trophectoderm (TE) cells from in vitro fertilized embryos. However, few data are available regarding the clinical outcome, which provides vital reference for further application of the methodology. Here, we present a clinical evaluation of NGS-based preimplantation genetic diagnosis/screening (PGD/PGS) compared with single nucleotide polymorphism (SNP) array-based PGD/PGS as a control.

Results

A total of 395 couples participated. They were carriers of either translocation or inversion mutations, or were patients with recurrent miscarriage and/or advanced maternal age. A total of 1,512 blastocysts were biopsied on D5 after fertilization, with 1,058 blastocysts set aside for SNP array testing and 454 blastocysts for NGS testing. In the NGS cycles group, the implantation, clinical pregnancy and miscarriage rates were 52.6% (60/114), 61.3% (49/80) and 14.3% (7/49), respectively. In the SNP array cycles group, the implantation, clinical pregnancy and miscarriage rates were 47.6% (139/292), 56.7% (115/203) and 14.8% (17/115), respectively. The outcome measures of both the NGS and SNP array cycles were the same with insignificant differences. There were 150 blastocysts that underwent both NGS and SNP array analysis, of which seven blastocysts were found with inconsistent signals. All other signals obtained from NGS analysis were confirmed to be accurate by validation with qPCR. The relative copy number of mitochondrial DNA (mtDNA) for each blastocyst that underwent NGS testing was evaluated, and a significant difference was found between the copy number of mtDNA for the euploid and the chromosomally abnormal blastocysts. So far, out of 42 ongoing pregnancies, 24 babies were born in NGS cycles; all of these babies are healthy and free of any developmental problems.

Conclusions

This study provides the first evaluation of the clinical outcomes of NGS-based pre-implantation genetic diagnosis/screening, and shows the reliability of this method in a clinical and array-based laboratory setting. NGS provides an accurate approach to detect embryonic imbalanced segmental rearrangements, to avoid the potential risks of false signals from SNP array in this study.

Electronic supplementary material

The online version of this article (doi:10.1186/2047-217X-3-30) contains supplementary material, which is available to authorized users.

Is preimplantation genetic diagnosis the ideal embryo selection method in aneuploidy screening?

To select cytogenetically normal embryos, preimplantation genetic diagnosis (PGD) aneuploidy screening (AS) is used in numerous centers around the world. Chromosomal abnormalities lead to developmental problems, implantation failure, and early abortion of embryos. The usefulness of PGD in identifying single-gene diseases, human leukocyte antigen typing, X-linked diseases, and specific genetic diseases is well-known. In this review, preimplantation embryo genetics, PGD research studies, and the European Society of Human Reproduction and Embryology PGD Consortium studies and reports are examined. In addition, criteria for embryo selection, technical aspects of PGD-AS, and potential noninvasive embryo selection methods are described. Indications for PGD and possible causes of discordant PGD results between the centers are discussed. The limitations of fluorescence in situ hybridization, and the advantages of the array comparative genomic hybridization are included in this review. Although PGD-AS for patients of advanced maternal age has been shown to improve in vitro fertilization outcomes in some studies, to our knowledge, there is not sufficient evidence to use advanced maternal age as the sole indication for PGD-AS. PGD-AS might be harmful and may not increase the success rates of in vitro fertilization. At the same time PGD, is not recommended for recurrent implantation failure and unexplained recurrent pregnancy loss.

Knowledge and Educational Needs about Pre-Implantation Genetic Diagnosis (PGD) among Oncology Nurses

Preimplantation genetic diagnosis (PGD), a form of assisted reproductive technology, is a new technology with limited awareness among health care professionals and hereditary cancer families. Nurses play a key role in the care of patients and are often in an ideal position to discuss and refer patients on sensitive quality of life issues, such as PGD. Two hundred and one nurses at Moffitt Cancer Center (MCC) responded to an online survey assessing knowledge and educational needs regarding PGD and families with hereditary cancer. The majority of respondents were female (n = 188), white (n = 175), had an RN/BSN degree (n = 83), and provided outpatient care at the cancer center (n = 102). More than half of respondents (78%) were unfamiliar with PGD prior to the survey and respondents who had heard of PGD had limited knowledge. More than half of the participants reported PGD was an acceptable option for families with hereditary cancer syndromes and thought individuals with a strong family or personal history should be provided with information about PGD. This study indicates that oncology nurses may benefit from and desire education about PGD. With advances in reproductive technology and options, further PGD education is needed among healthcare professionals. An examination of current oncology nursing curriculum and competencies regarding genetic education may identify need for future revisions and updates.

Advances in huntington disease drug discovery: novel approaches to model disease phenotypes

Huntington disease is a monogenic, autosomal dominant, progressive neurodegenerative disorder caused by a trinucleotide CAG repeat expansion in exon 1 of the huntingtin (HTT) gene; age of onset of clinical symptoms inversely correlates with expanded CAG repeat length. HD leads to extensive degeneration of the basal ganglia, hypothalamic nuclei, and selected cortical areas, and a wide range of molecular mechanisms have been implicated in disease pathology in animal or cellular models expressing mutated HTT (mHTT) proteins, either full-length or amino-terminal fragments. However, HD cellular models that recapitulate the slow progression of the disease have not been available due to the toxicity of overexpressed exogenous mHTT or to limitations with using primary cells for long-term studies. Most investigations of the effects of mHTT relied on cytotoxicity or aggregation end points in heterologous systems or in primary embryonic neuroglial cultures derived from HD mouse models. More innovative approaches are currently under active investigation, including screening using electrophysiological endpoints, as well as the recent use of primary blood mononuclear cells and of human embryonic stem cells derived from a variety of HD research participants. Here we describe how these cellular systems are being used to investigate HD biology as well as to identify mechanisms with therapeutic potential.

A feasible strategy of preimplantation genetic diagnosis for carriers with chromosomal translocation: Using blastocyst biopsy and array comparative genomic hybridization

BACKGROUND/PURPOSE

Patients with chromosomal translocation are highly vulnerable to produce unbalanced gametes that result in recurrent miscarriages, affected offspring, or infertility. Preimplantation genetic diagnosis (PGD) with blastomere biopsy and fluorescent in-situ hybridization (FISH) has been used to select normal/balanced embryos for transfer. However, FISH is inherent with some technical difficulties such as cell fixation and signal reading. Here we introduce a strategy of PGD using blastocyst biopsy and array comparative genomic hybridization (aCGH) for reproductive problems of patients with chromosomal translocation.

METHODS

Twelve patients diagnosed as having chromosomal translocation who underwent PGD cycles were included in this single-center observational study. Blastocyst biopsy was performed and biopsied blastocysts were cryopreserved individually. Testing was performed with aCGH, and the euploid embryos were transferred in the following thawing cycles.

RESULTS

The overall diagnostic efficiency was 90.2% (55/61) and the euploidy rate was 32.7% (18/55). Ten cycles of thawed embryo transfer (ET) were carried out, resulting in three live births and another three ongoing pregnancies with an ongoing pregnancy rate of 60%/transfer cycle. The prenatal diagnosis with chorionic villi sampling confirmed the results of PGD/aCGH in all six pregnant women. No miscarriage happened in our case series.

CONCLUSION

Our study demonstrates an effective PGD strategy with promising outcomes. Blastocyst biopsy can retrieve more genetic material and may provide more reliable results, and aCGH offers not only detection of chromosomal translocation but also more comprehensive analysis of 24 chromosomes than traditional FISH. More cases are needed to verify our results and this strategy might be considered in general clinical practice.

Preimplantation genetic diagnosis for aneuploidy and translocations using array comparative genomic hybridization

At least 50% of human embryos are abnormal, and that increases to 80% in women 40 years or older. These abnormalities result in low implantation rates in embryos transferred during in vitro fertilization procedures, from 30% in women <35 years to 6% in women 40 years or older. Thus selecting normal embryos for transfer should improve pregnancy results. The genetic analysis of embryos is called Preimplantation Genetic Diagnosis (PGD) and for chromosome analysis it was first performed using FISH with up to 12 probes analyzed simultaneously on single cells. However, suboptimal utilization of the technique and the complexity of fixing single cells produced conflicting results. PGD has been invigorated by the introduction of microarray testing which allows for the analysis of all 24 chromosome types in one test, without the need of cell fixation, and with staggering redundancy, making the test much more robust and reliable. Recent data published and presented at scientific meetings has been suggestive of increased implantation rates and pregnancy rates following microarray testing, improvements in outcome that have been predicted for quite some time. By using markers that cover most of the genome, not only aneuploidy can be detected in single cells but also translocations. Our validation results indicate that array CGH has a 6Mb resolution in single cells, and thus the majority of translocations can be analyzed since this is also the limit of karyotyping. Even for translocations with smaller exchanged fragments, provided that three out of the four fragments are above 6Mb, the translocation can be detected.

Gender eugenics? The ethics of PGD for intersex conditions

This article discusses the ethics of the use of preimplantation genetic diagnosis (PGD) to prevent the birth of children with intersex conditions/disorders of sex development (DSDs), such as congenital adrenal hyperplasia (CAH) and androgen insensitivity syndrome (AIS). While pediatric surgeries performed on children with ambiguous genitalia have been the topic of intense bioethical controversy, there has been almost no discussion to date of the ethics of the use of PGD to reduce the prevalence of these conditions. I suggest that PGD for those conditions that involve serious medical risks for those born with them is morally permissible and that PGD for other "cosmetic" variations in sexual anatomy is more defensible than might first appear. However, importantly, the arguments that establish the latter claim have radical and disturbing implications for our attitude toward diversity more generally.

Chromosome-specific DNA repeats: rapid identification in silico and validation using fluorescence in situ hybridization

Chromosome enumeration in interphase and metaphase cells using fluorescence in situ hybridization (FISH) is an established procedure for the rapid and accurate cytogenetic analysis of cell nuclei and polar bodies, the unambiguous gender determination, as well as the definition of tumor-specific signatures. Present bottlenecks in the procedure are a limited number of commercial, non-isotopically labeled probes that can be combined in multiplex FISH assays and the relatively high price and effort to develop additional probes. We describe a streamlined approach for rapid probe definition, synthesis and validation, which is based on the analysis of publicly available DNA sequence information, also known as “database mining”. Examples of probe preparation for the human gonosomes and chromosome 16 as a selected autosome outline the probe selection strategy, define a timeline for expedited probe production and compare this novel selection strategy to more conventional probe cloning protocols.

Preimplantation genetic diagnosis to improve pregnancy outcomes in subfertility

Pre-implantation genetic diagnosis provides prenatal genetic diagnosis before implantation, thus allowing detection of chromosomal abnormalities and their exclusion from embryo transfer in assisted reproductive technologies. Polar body, blastomere or trophectoderm can each be used to obtain requisite genetic or embryonic DNA. Pre-implantation genetic diagnosis for excluding unbalanced translocations is well accepted, and pre-implantation genetic diagnosis aneuploidy testing to avoid repeated pregnancy losses in couples having recurrent aneuploidy is efficacious in reducing miscarriages. Controversy remains about whether pre-implantation genetic diagnosis aneuploidy testing improves take home pregnancy rates, for which reason adherence to specific indications is recommended while the issue is being adjudicated. Current recommendations are for obligatory 24 chromosome testing, most readily using array comparative genome hybridisation.

Chromosomal disorders and male infertility

Infertility in humans is surprisingly common occurring in approximately 15% of the population wishing to start a family. Despite this, the molecular and genetic factors underlying the cause of infertility remain largely undiscovered. Nevertheless, more and more genetic factors associated with infertility are being identified. This review will focus on our current understanding of the chromosomal basis of male infertility specifically: chromosomal aneuploidy, structural and numerical karyotype abnormalities and Y chromosomal microdeletions. Chromosomal aneuploidy is the leading cause of pregnancy loss and developmental disabilities in humans. Aneuploidy is predominantly maternal in origin, but concerns have been raised regarding the safety of intracytoplasmic sperm injection as infertile men have significantly higher levels of sperm aneuploidy compared to their fertile counterparts. Males with numerical or structural karyotype abnormalities are also at an increased risk of producing aneuploid sperm. Our current understanding of how sperm aneuploidy translates to embryo aneuploidy will be reviewed, as well as the application of preimplantation genetic diagnosis (PGD) in such cases. Clinical recommendations where possible will be made, as well as discussion of the use of emerging array technology in PGD and its potential applications in male infertility.

Origins and rates of aneuploidy in human blastomeres

OBJECTIVE

To characterize chromosomal error types and parental origin of aneuploidy in cleavage-stage embryos using an informatics-based technique that enables the elucidation of aneuploidy-causing mechanisms.

DESIGN

Analysis of blastomeres biopsied from cleavage-stage embryos for preimplantation genetic screening during IVF.

SETTING

Laboratory.

PATIENT(S)

Couples undergoing IVF treatment.

INTERVENTION(S)

Two hundred seventy-four blastomeres were subjected to array-based genotyping and informatics-based techniques to characterize chromosomal error types and parental origin of aneuploidy across all 24 chromosomes.

MAIN OUTCOME MEASURE(S)

Chromosomal error types (monosomy vs. trisomy; mitotic vs. meiotic) and parental origin (maternal vs. paternal).

RESULT(S)

The rate of maternal meiotic trisomy rose significantly with age, whereas other types of trisomy showed no correlation with age. Trisomies were mostly maternal in origin, whereas paternal and maternal monosomies were roughly equal in frequency. No examples of paternal meiotic trisomy were observed. Segmental error rates were found to be independent of maternal age.

CONCLUSION(S)

All types of aneuploidy that rose with increasing maternal age can be attributed to disjunction errors during meiosis of the oocyte. Chromosome gains were predominantly maternal in origin and occurred during meiosis, whereas chromosome losses were not biased in terms of parental origin of the chromosome. The ability to determine the parental origin for each chromosome, as well as being able to detect whether multiple homologs from a single parent were present, allowed greater insights into the origin of aneuploidy.

Preimplantation genetic diagnosis for couples with a Robertsonian translocation: practical information for genetic counseling

PURPOSE

To evaluate the proportions of abnormal and normal embryos detected by preimplantation genetic diagnosis (PGD) of infertile couples of whom one was a Robertsonian translocation (RT) carrier, and to provide practical information, including details of reproductive outcomes, to aid in genetic counseling of such couples.

METHODS

We retrospectively analyzed all PGD cycles conducted to deal with RT at our center between January 2000 and December 2009. Subject demographic and clinical data were compared with the results of PGD.

RESULTS

Employing PGD, we conducted a total of 66 cycles on 34 couples of whom one was an RT carrier, including 24 female and 10 male carriers. Of the 514 blastomeres tested, 161 (31.3%) were normal or balanced. Of the 57 cycles that included embryo transfer, 17 (29.8%) attained positivity for human chorionic gonadotropin (hCG). A total of 17 embryos were implanted and 16 babies, including two sets of twins, were born. The takehome baby rate was 41.2% per couple and the loss rate 6.6%. Receiver operating characteristic curve analysis showed that the proportion of alternate embryos associated with a sensitivity of 70.6% for prediction of clinical pregnancy following PGD was 0.31. Sex of the carrier and type of translocation were not significantly associated with pregnancy outcomes.

CONCLUSION

Couples with RT may benefit from PGD; pregnancy success rate is improved and embryo loss reduced. We found that about 30% of embryos were of normal or balanced chromosomal constitution and that the percentage of normal or balanced embryos was predictive of PGD outcome.

PGD for reciprocal and Robertsonian translocations using array comparative genomic hybridization

BACKGROUND

Fluorescence in situ hybridization (FISH) is the most widely used method for detecting unbalanced chromosome rearrangements in preimplantation embryos but it is known to have several technical limitations. We describe the clinical application of a molecular-based assay, array comparative genomic hybridization (array-CGH), to simultaneously screen for unbalanced translocation derivatives and aneuploidy of all 24 chromosomes.

METHODS

Cell biopsy was carried out on cleavage-stage embryos (Day 3). Single cells were first lysed and DNA amplified by whole-genome amplification (WGA). WGA products were then processed by array-CGH using 24sure + arrays, BlueGnome. Balanced/normal euploid embryos were then selected for transfer on Day 5 of the same cycle.

RESULTS

Twenty-eight consecutive cycles of preimplantation genetic diagnosis were carried out for 24 couples carrying 18 different balanced translocations. Overall, 187/200 (93.5%) embryos were successfully diagnosed. Embryos suitable for transfer were identified in 17 cycles (60.7%), with transfer of 22 embryos (mean 1.3 ± 0.5). Twelve couples achieved a clinical pregnancy (70.6% per embryo transfer), with a total of 14 embryos implanted (63.6% per transferred embryo). Three patients delivered three healthy babies, during writing, the other pregnancies (two twins and seven singletons) are ongoing beyond 20 weeks of gestation.

CONCLUSIONS

The data obtained demonstrate that array-CGH can detect chromosome imbalances in embryos, also providing the added benefit of simultaneous aneuploidy screening of all 24 chromosomes. Array-CGH has the potential to overcome several inherent limitations of FISH-based tests, providing improvements in terms of test performance, automation, sensitivity and reliability.

Preimplantation genetic diagnosis at 20 years

First reported in 1990, PGD has evolved into a complementary form of prenatal diagnosis offering novel indications. DNA for PGD can be recovered with equal safety and facility from polar bodies I and II, blastomere (8 cell embryo) and trophectoderm (5-6 day blastocyst). Diagnostic accuracy is very high (>99%) for both chromosomal abnormalities and single gene disorders. Traditional application of FISH with chromosome specific probes for detecting aneuploidy and translocations may be replaced or complemented by array comparative genome hybridization (array CGH); biopsied embryos can now be cryopreserved (vitrification) while analysis proceeds in orderly fashion. PGD has been accomplished for over 200 different single gene disorders. Novel indications for PGD not readily applicable by traditional prenatal genetic diagnosis include avoiding clinical pregnancy termination, performing preconceptional diagnosis (polar body I), obtaining prenatal diagnosis without disclosure of prenatal genotype (nondisclosure), diagnosing adult-onset disorders particularly cancer, and identifying HLA compatible embryos suitable for recovering umbilical cord blood stem cells.

Are zona pellucida laser drilling and polar body biopsy safe for in vitro matured oocytes?

INTRODUCTION

Preconception diagnosis requires first polar body biopsy. When the hole in the zona pellucida is made with a laser beam, heat propagation could, like the biopsy itself, be deleterious. Our aim was to evaluate the effect of this technique on human in vitro matured oocyte and embryo development.

METHODS

One hunded fifty five retrieved immature oocytes from 75 women, matured in vitro, were distributed in 3 groups: 50 oocytes in a control group, without laser drilling and first polar body biopsy, 52 oocytes in a group with only laser drilling, and 53 oocytes in a group with both laser drilling and first polar body biopsy. Safety was evaluated using four criteria: [1] oocyte lysis rate, [2] oocyte activation rate, [3] oocyte development after calcium ionophore treatment, [4] and embryo chromosome breakage incidence after Tarkowski preparation.

RESULTS

No difference in the four criteria was observed between the 3 oocyte groups.

CONCLUSIONS

We did not find evidence of deleterious effect of laser drilling and first polar body biopsy on in vitro matured oocytes, according to our criteria.

Conversion and non-conversion approach to preimplantation diagnosis for chromosomal rearrangements in 475 cycles

Due to the limitations of preimplantation genetic diagnosis (PGD) for chromosomal rearrangements by interphase fluorescent in-situ hybridization (FISH) analysis, a method for obtaining chromosomes from single blastomeres was introduced by their fusion with enucleated or intact mouse zygotes, followed by FISH analysis of the resulting heterokaryons. Although this allowed a significant improvement in the accuracy of testing of both maternally and paternally derived translocations, it is still labour intensive and requires the availability of fertilized mouse oocytes, also creating ethical issues related to the formation of interspecies heterokaryons. This method was modified with a chemical conversion procedure that has now been clinically applied for the first time on 877 embryos from PGD cycles for chromosomal rearrangements and has become the method of choice for performing PGD for structural rearrangements. This is presented within the context of overall experience of 475 PGD cycles for translocations with pre-selection and transfer of balanced or normal embryos in 342 (72%) of these cycles, which resulted in 131 clinical pregnancies (38%), with healthy deliveries of 113 unaffected children. The spontaneous abortion rate in these cycles was as low as 17%, which confirms an almost five-fold reduction of spontaneous abortion rate following PGD for chromosomal rearrangements.

Effect of karyotype on successful human embryonic stem cell derivation

The success rate of human embryonic stem cell (hESC) derivation depends on both culture conditions and embryo quality and is routinely determined by morphological criteria. However, high incidence of chromosomal abnormality even in high-grade cleavage embryos from in vitro fertilization (IVF) patients suggests that the morphological grade of supernumerary embryos obtained from IVF clinics may not be a good prediction factor for successful hESC derivation. We show here that from one donor under identical derivation conditions 12 karyotypically abnormal post-bioptic embryos did not yield hESC lines, whereas two out of four normal embryos did. This suggests that the capacity of embryos to give rise to hESC line is likely to be influenced by their genetic status.