Interaction of acrocentric chromosome involved in translocation and sex of the carrier influences the proportion of alternate segregation in autosomal reciprocal translocations

Effects of Carrier's sex on the outcome of embryos and pregnancies in 412 couples undergoing preimplantation genetic testing for structural rearrangements

STUDY DESIGN

To ascertain whether the carrier's sex affects the outcome of embryos and pregnancies in couples undergoing preimplantation genetic testing for structural rearrangements (PGT-SR).

METHODS

This retrospective study comprised 412 couples with reciprocal translocations (RecT), Robertsonian translocations (RobT), or inversions (INV) between January 2017 and October 2022. We applied next-generation sequencing (NGS) on 2588 embryos after trophectoderm (TE) biopsy.

RESULTS

Genetically transferable blastocyst rate was higher in the male carrier group (34.0 % vs 31.7 %, P = 0.013) relative to the female carrier group whereas other embryo and pregnancy outcomes remained similar. Further analysis revealed that this result was primarily due to the alteration of segregation patterns in the RobT subgroup, in which the proportion of alternate segregation was higher (84.3 % vs 66.4 %, P < 0.001) in male carriers compared with female carriers. In the RecT subgroup, the genetically transferable blastocyst rate between male and female carriers was similar although the segregation models also changed, such that the frequency of the adjacent-1 segregation pattern was higher in male carriers than in female carriers (42.5 % vs 34.7 %, P = 0.002). In addition, interchromosomal effect (ICE) did not differ between male and female carriers although ICE was lower in male carriers of the RobT subgroup (pure ICE: 35.50 % vs 44.30 %, P = 0.14; total ICE: 35.50 % vs 40.30 %, P = 0.32) and higher in male carriers of the INV subgroup (pure ICE: 42.3 % vs 37.20 %, P = 0.33; total ICE: 40.90 % vs 36.00 %, P = 0.36).

CONCLUSIONS

The carrier's sex was closely associated with the genetically transferable embryo rate in couples undergoing PGT-SR, principally resulted from the change in segregation pattern in the RobT subgroup but not in the RecT and INV subgroups.

Preimplantation genetic testing for complex chromosomal rearrangements: clinical outcomes and potential risk factors

Objective

Complex chromosome rearrangements (CCR) are rare structural abnormalities involving at least three breakpoints, categorized into three types based on their structure: type A (three-way rearrangements), type B (double two-way translocations), and type C (exceptional CCR). However, thus far, limited data exists on preimplantation genetic testing for chromosomal structural rearrangements (PGT-SR) in CCR carriers. This study aims to evaluate the clinical outcomes and influencing factors of PGT-SR in couples with CCR.

Methods

Fifteen couples with unique CCR recruited from 793 couples following PGT-SR between January 2017 and May 2023. In addition, a total of 54 CCR cases, 39 previously reported as well as 15 newly added, were included in the analysis of factors associate with normal/balanced embryos.

Results

A total of 100 blastocysts were biopsied and analyzed in 15 CCR couples after 17 PGT-SR cycles, with 16.0% being euploid, 78.0% aneuploid and 6.0% mosaic. 11 normal/balanced embryos and one mosaic embryo were transferred, resulting in eight live births. Furthermore, based on the combined data from 54 CCR carriers, the proportion of normal/balanced embryos was 10.8%, with a significant decrease observed among female carriers compared to male heterozygotes (6.5% vs. 15.5%, p = 0.002). Type B exhibited the lowest rate of euploid embryos at only 6.7%, followed by type A at 11.6% and type C at 14.0%, although the differences were not significant (p = 0.182). After completing the multivariate generalized estimating equation (GEE) analysis, type B (p = 0.014) and female carrier (p = 0.002) were identified as independent risk factors for fewer euploid embryos.

Conclusion

The occurrence of balanced CCR in patients with reproductive abnormalities may be more frequent than we expected. Despite the proportion of normal/balanced embryos being significantly low, which can be influenced by CCR type and carrier's sex, PGT-SR may improve the reproductive outcomes among CCR cases. These findings can optimize the clinical management and genetic counseling of CCR carriers seeking assisted reproductive technology (ART).

Factors affecting the reproductive outcome in reciprocal translocation carriers undergoing preimplantation genetic testing for structural rearrangements (PGTSR)

OBJECTIVE

To investigate the reproductive outcomes of balanced reciprocal translocation carriers and evaluate the association between the number of metaphase-II oocytes retrieved and cumulative live birth rates (LBRs).

METHODS

This retrospective analysis included 344 preimplantation genetic testing (PGT) for structural rearrangement cycles of 281 couples with balanced reciprocal translocations between January 2018 and January 2021. All patients included in the analysis had either delivered a baby or had used all their embryos after one stimulation cycle. All women were followed up for at least 2 years.

RESULTS

After ovarian stimulation and oocyte fertilization, 44.2% of PGT for structural rearrangements cycles achieved a live birth. Carrier's sex and female age did not affect the cumulative LBR of reciprocal translocation carriers. Cumulative LBRs steadily increased with the number of oocytes, reaching 64% when >20 oocytes were retrieved. The cutoff values for achieving at least one live birth were 9.5 metaphase-II (MII) oocytes and 3.5 biopsied embryos.

CONCLUSION

Couples with reciprocal translocations have lower transferable embryo rates and cumulative LBRs. The MII oocytes retrieved may be a crucial factor for cumulative LBRs. A high ovarian response may further increase cumulative LBRs, but avoidance of ovarian hyperstimulation syndrome or other iatrogenic complications should be considered.

Chromosome balanced translocation in newborn fetus founded during prenatal diagnosis: Three cases reports

RATIONALE

Because of the normal phenotype, carriers of specific chromosomal translocations are often diagnosed only after their development of associated malignancies, recurrent miscarriages, and reproductive difficulties. In this paper, we report primary balanced fetal chromosomal translocations by performing the necessary invasive prenatal diagnosis in couples with previous malformations coupled with prenatal testing suggesting a high risk for trisomy 21.

PATIENT CONCERNS

Case 1 and Case 2 couples had malformed children, and Case 3 couples had a high risk of trisomy 21 on noninvasive preconception serological testing.

DIAGNOSIS AND INTERVENTION

A balanced chromosomal translocation diagnosis was confirmed by karyotyping of fetal cells obtained by amniocentesis.

OUTCOMES

All 3 couples decided to continue their pregnancies after learning about the consequences of the chromosomal abnormalities. Approximately a year after the children were born, the staff of the Prenatal Diagnostic Center followed up with a phone call and found that the children physical development and intelligence were normal.

LESSON

This case report reports healthy chromosomal balanced translocation newborns born to couples with poor maternal history and couples with abnormalities suggested by preconception testing, and followed up with the newborns to provide some experience in prenatal diagnosis and genetic counseling for chromosomal balanced translocations.

Effects of chromosomal translocation characteristics on fertilization and blastocyst development - a retrospective cohort study

OBJECTIVE

To determine the effect of different translocation characteristics on fertilization rate and blastocyst development in chromosomal translocation patients.

METHODS

This retrospective cohort study was conducted at the Third Affiliated Hospital of Zhengzhou University From January 2017 to December 2022.All couples were diagnosed as reciprocal translocation or Robertsonian translocation by karyotype of peripheral blood lymphocytes test. After adjusting for confounding factors, the effect of chromosomal rearrangement characteristics, such as carrier sex, translocation type, chromosome length and break sites, on fertilization rate and embryo development were analysed separately using multiple linear regression.

RESULTS

In cases of Robertsonian translocation (RobT), the carrier sex plays an independent role in fertilization rate, and the male carriers was lower than that of female carriers (76.16% vs.86.26%, P = 0.009). In reciprocal translocation (RecT), the carrier sex, chromosome types and break sites had no influence on fertilization rate, blastocyst formation rate (P > 0.05). However, patients with human longer chromosomal (chromosomes 1-5) translocation have a lower available blastocyst formation rate (Group AB vs. Group CD: 41.49%vs.46.01%, P = 0.027). For male carriers, the translocation types was an independent factor affecting the fertilization rate, and the RobT was the negative one (B = - 0.075, P = 0 0.009). In female carriers, we did not observe this difference (P = 0.227).

CONCLUSIONS

In patients with chromosomal translocation, the fertilization rate may be influenced by carrier sex and translocation type, chromosomes 1-5 translocation may adversely affect the formation of available blastocysts. Break sites have no role in fertilization and blastocyst development.

Does reciprocal translocation affect the meiotic segregation products of non-translocation chromosomes?

This retrospective cohort study aimed to assess the effect of chromosomal reciprocal translocation on meiotic segregation products of non-translocation chromosomes. A total of 744 reciprocal translocation carriers and 875 non-carriers were included in this study. A total of 6,832 blastocysts were biopsied and tested by next-generation sequencing. Blastocysts from the carrier group were classified into five subgroups according to the theoretical segregation pattern of quadrivalent structure. For carrier patients, normal meiotic segregation products of the non-translocation chromosome were classified after excluding the segregation modes of the quadrivalent structure. The proportion of normal non-translocation chromosome meiotic segregation products was similar between the carrier and noncarrier groups (p = 0.69). The generalized Estimation Equation revealed that there was no correlation between reciprocal translocation and meiotic segregation products of non-translocation chromosomes. Moreover, subgroup analyses showed that the segregation modes of quadrivalent structure (p = 0.00) and carrier's gender (p = 0.00) may affect the meiotic segregation products of non-translocation chromosomes. In conclusion, reciprocal translocation does not directly reduce the proportion of normal segregation products of non-translocation chromosomes. The difference among subgroups of different quadrivalent segregation patterns implied that interchromosomal effect may exist but the high incidence of chromosomal abnormalities for reciprocal translocation carriers should not be attributed to interchromosomal effect.

The effect of parental carrier of de novo mutated vs. inherited balanced reciprocal translocation on the chance of euploid embryos

OBJECTIVE

To evaluate whether the effect of de novo mutated balanced reciprocal translocation on the rate of euploid embryos varied from inherited balanced reciprocal translocation.

DESIGN

A retrospective cohort study compared the percentage of euploid embryo and proportion of patients with at least 1 euploid embryo between de novo mutated balanced reciprocal translocation (i.e., the group of de novo mutated carriers) and inherited balanced reciprocal translocation (i.e., the group of inherited carriers).

SETTING

An academic fertility center.

PATIENT(S)

A total of 413 couples with balanced reciprocal translocation (219 female carriers and 194 male carriers) who underwent their first cycle of preimplantation genetic testing for structural rearrangements were included.

INTERVENTION(S)

Carriers of balanced reciprocal translocation either de novo mutated or inherited.

MAIN OUTCOME MEASURE(S)

The percentage of euploid embryo and proportion of patients with at least 1 euploid embryo.

RESULT(S)

The carriers of the de novo mutated balanced reciprocal translocation had a lower percentage of euploid embryos (19.5% vs. 25.5%), and were less likely to have at least 1 euploid embryo (47.1% vs. 60.1%) compared with the carriers of the inherited balanced reciprocal translocation. In the male-carrier subgroup, the percentage of euploid embryos (16.7% vs. 26.7%) and proportion of patients with at least 1 euploid embryo (41.9% vs. 67.5%) were lower among the de novo mutated carriers than those among the inherited carriers. However, in the female-carrier subgroup, there was no statistically significant difference in the percentage of euploid embryos (22.4% vs. 24.4%) or the proportion of patients with at least 1 euploid embryo (52.3% vs. 53.7%) between the de novo mutated carriers and inherited carriers.

CONCLUSION(S)

The de novo mutated balanced reciprocal translocation was associated with a lower percentage of euploid embryos and lower chance of obtaining at least 1 euploid embryo than the inherited balanced reciprocal translocation.

Gene sequencing and result analysis of balanced translocation carriers by third-generation gene sequencing technology

Because the total gene copy number remains constant and all genes are normally expressed, carriers of balanced chromosomal translocations usually have a normal phenotype but are able to produce many different types of gametes during meiosis, and unbalanced gametes lead to increased risks of infertility, recurrent spontaneous abortion, stillbirth, neonatal death or malformations and intellectual abnormalities in offspring. The key to balanced translocations lies in finding the breakpoints, but current genetic testing techniques are all short-read sequencing, with the disadvantage of procedural complexity and imprecision for precisely identifying the breakpoints. The latest third-generation sequencing technology overcomes these drawbacks and uses robust long-read sequencing to accurately and rapidly detect genome-wide information and identify breakpoint locations. In this paper, we performed whole genome long-read sequencing using an Oxford Nanopore sequencer to detect the breakpoints of 4 balanced chromosomal translocation carriers. The results showed that employing about ~ 10× coverage confirmed 6 of the 8 breakpoints, of which, 2 had microdeletions/insertions identified near the breakpoints and 4 had breakpoints that disrupted the normal gene structure and were simultaneously tested for genome-wide structural variation (SV). The results show that whole genome long-read sequencing is an efficient method for pinpointing translocation breakpoints and providing genome-wide information, which is essential for medical genetics and preimplantation genetic testing.

Sperm Meiotic Segregation Analysis of Reciprocal Translocations Carriers: We Have Bigger FISH to Fry

Reciprocal translocation (RT) carriers produce a proportion of unbalanced gametes that expose them to a higher risk of infertility, recurrent miscarriage, and fetus or children with congenital anomalies and developmental delay. To reduce these risks, RT carriers can benefit from prenatal diagnosis (PND) or preimplantation genetic diagnosis (PGD). Sperm fluorescence in situ hybridization (spermFISH) has been used for decades to investigate the sperm meiotic segregation of RT carriers, but a recent report indicates a very low correlation between spermFISH and PGD outcomes, raising the question of the usefulness of spermFISH for these patients. To address this point, we report here the meiotic segregation of 41 RT carriers, the largest cohort reported to date, and conduct a review of the literature to investigate global segregation rates and look for factors that may or may not influence them. We confirm that the involvement of acrocentric chromosomes in the translocation leads to more unbalanced gamete proportions, in contrast to sperm parameters or patient age. In view of the dispersion of balanced sperm rates, we conclude that routine implementation of spermFISH is not beneficial for RT carriers.

Analysis of 2 men with t(8;22)(q13;q13) and t(8;14)(q13;q22) chromosomal translocation karyotypes

Male infertility is a multifactorial condition that is closely associated with chromosomal abnormalities. Reciprocal chromosomal translocation (RCT) is a significant structural genetic abnormality. The specific mechanisms of forms of RCT affecting male infertility include the product of chromosomally unbalanced gametes, thereby disrupting the structure and function of important genes responsible for spermatogenesis. RCT breakpoints have been found to disrupt gene structure and function in many medical fields However, the relationship between RCT breakpoints and male infertility remains to be determined. The purpose of this study is to describe 2 male carriers of RCTs 46,XY,t(8;22)(q13;q13) and 46,XY,t(8;14)(q13;q22). Both patients were collected from the second hospital of Jilin University. Semen parameters were detected using the computer-aided semen analysis system. Cytogenetic analysis was performed using standard operating procedure. Related genes on chromosomal breakpoints were searched using Online Mendelian Inheritance in Man. One man had semen parameters within the normal range, but the couple was infertile after 5 years of marriage. The other man showed normal semen parameters, and his wife had experienced 2 spontaneous miscarriages. Using a literature search, the association between chromosome 22q13 breakpoint and fertility were investigated. The results suggest that physicians should focus on the clinical phenotype of the patients and the breakpoints of RCT in genetic counseling. An important gene related to human male infertility is clearly located in chromosome region 22q13, and its function is worthy of further study.

Are ovarian responses and the number of transferable embryos different in females and partners of male balanced translocation carriers?

PURPOSE

To compare ovarian response and the number of transferable embryos between women with balanced autosomal translocations and women whose partners carry the translocation (control group). To investigate the predictive value of metaphase II (MII) oocyte number and biopsied embryo number for gaining at lowest one transferable embryo.

DESIGN

We retrospectively analyzed 1942 preimplantation genetic testing for structural rearrangements (PGT-SR) cycles of 1505 balanced autosomal translocation couples over 8 years. All cycles were divided into two subgroups: Robertsonian and reciprocal translocations (ROBT and ReBT). Receiver operator characteristic (ROC) curves were plotted to ascertain a cutoff of MII oocytes and biopsied embryos as predictors of gaining at lowest one transferable embryo.

RESULT

There were no statistical differences in baseline features or ovarian response indicators regarding the number of retrieved/MII oocytes, E2 level on the day of HCG, and ovarian sensitivity index (OSI) between women with balanced autosomal translocations and control group (P > 0.05). A decreased number of transferable embryos were found in women with balanced autosomal translocations regardless of the type of translocation. The cutoff values for gaining at lowest one transferable embryo are 12.5 MII oocytes and 4.5 biopsied embryos, respectively.

CONCLUSION

Women with balanced autosomal translocations have a normal ovarian response, but fewer transferable embryos, meaning that higher gonadotropin (Gn) doses may be required to increase transferable embryos. When fewer than 12.5 MII oocytes or 4.5 blastocysts are obtained in a PGT-SR cycle, couples should be notified that the likelihood of gaining a transferable embryo is low.

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.

Risk Factors Affecting Alternate Segregation in Blastocysts From Preimplantation Genetic Testing Cycles of Autosomal Reciprocal Translocations

Reciprocal translocations are the most common structural chromosome rearrangements and may be associated with reproductive problems. Therefore, the objective of this study was to analyze factors that can influence meiotic segregation patterns in blastocysts for reciprocal translocation carriers. Segregation patterns of quadrivalents in 10,846 blastocysts from 2,871 preimplantation genetic testing cycles of reciprocal translocation carriers were analyzed. The percentage of normal/balanced blastocysts was 34.3%, and 2:2 segregation was observed in 90.0% of the blastocysts. Increased TAR1 (ratio of translocated segment 1 over the chromosome arm) emerged as an independent protective factor associated with an increase in alternate segregation (p = 0.004). Female sex and involvement of an acrocentric chromosome (Acr-ch) were independent risk factors that reduced alternate segregation proportions (p < 0.001). Notably, a higher TAR1 reduced the proportion of adjacent-1 segregation (p < 0.001); a longer translocated segment and female sex increased the risk of adjacent-2 segregation (p = 0.009 and p < 0.001, respectively). Female sex and involvement of an Acr-ch enhanced the ratio of 3:1 segregation (p < 0.001 and p = 0.012, respectively). In conclusion, autosomal reciprocal translocation carriers have reduced proportions of alternate segregation in blastocysts upon the involvement of an Acr-ch, female sex, and lower TAR1. These results may facilitate more appropriate genetic counseling for couples with autosomal reciprocal translocation regarding their chances of producing normal/balanced blastocysts.

Analysis of clinical outcomes and meiotic segregation modes following preimplantation genetic testing for structural rearrangements using aCGH/NGS in couples with balanced chromosome rearrangement

Purpose

To retrospectively evaluate the effectiveness of PGT-SR by array comparative genomic hybridization (aCGH) or next-generation sequencing (NGS) in preventing recurrent miscarriages.

Methods

Thirty one couples with balanced translocation who underwent 68 PGT-SR cycles between 2012 and 2020 were evaluated. A total of 242 blastocysts were biopsied for aCGH or NGS. The genetically transferable blastocysts were transferred in the subsequent frozen-thawed single embryo transfer cycle.

Results

The genetically transferable blastocyst rate was 21.2% (51/241). Thirty five genetically transferable blastocysts were transferred into the uterine cavity. The clinical pregnancy rate was 57.1% (20/35), and the ongoing pregnancy rate was 100.0% (20/20). The incidence of interchromosomal effect (ICE) was influenced by ovarian stimulation protocol, female age, and carrier's gender, but dependent on the types of balanced translocation carriers. Furthermore, there was no significant difference in meiotic segregation modes in ovarian stimulation protocols and carrier's gender. Interestingly, the incidence of adjacent-1 segregation in ≧40 years group increased significantly compared with <35 years group.

Conclusions

For the first time in Japan, we show the effectiveness of PGT-SR using aCGH or NGS, which enables comprehensive analysis of chromosomes, in the prevention of recurrent miscarriages. Furthermore, our results may support better genetic counseling of balanced translocation carriers for PGT-SR cycles.

Effect of carriers' sex on meiotic segregation patterns and chromosome stability of reciprocal translocations

RESEARCH QUESTION

Does the sex of reciprocal translocation carriers affect meiotic segregation patterns and stability of non-translocated chromosomes during meiosis?

DESIGN

A total of 790 couples who underwent preimplantation genetic testing for reciprocal translocations by using the single nucleotide polymorphism (SNP) array platform between October 2016 and December 2019 were included. Among them, 294 couples had their euploid embryos distinguished between normal euploidies and balanced translocation carriers.

RESULTS

Female translocation carriers had a significantly lower incidence of alternate segregation pattern than male carriers (43.26% versus 47.98%, P = 0.001), but a higher incidence of 3:1 segregation pattern (6.70% versus 4.29%, P < 0.001). Stratified analysis showed only female translocation carriers with acrocentric chromosome (Acr-ch) involved had a lower incidence of alternate segregation pattern and a higher incidence of 3:1 segregation pattern compared with male carriers (41.63% versus 47.73%, P = 0.012; 9.32% versus 5.03%, P = 0.001). In 2233 embryos of 294 couples with identification of normal and balanced embryos, no significant differences were found in the paternal-origin aneuploidy rate (5.61% versus 5.82%, P = 0.861) and the maternal-origin aneuploidy rate (12.82% versus 12.08%, P = 0.673) in both male and female carriers. After excluding segmental aneuploidies, no differences were found between male and female carriers in both paternal-origin aneuploidy rate (2.14% versus 1.75%, P = 0.594) and maternal-origin aneuploidy rate (11.75% versus 11.06%, P = 0.683).

CONCLUSION

The sex of the translocation carriers affected meiotic segregation patterns with no effect on the stability of non-translocated chromosomes during meiosis.

Effects of Gender of Reciprocal Chromosomal Translocation on Blastocyst Formation and Pregnancy Outcome in Preimplantation Genetic Testing

Objective

To determine the effect of gender of reciprocal chromosomal translocation on blastocyst formation and pregnancy outcome in preimplantation genetic testing, including different parental ages.

Methods

This was a retrospective cohort study that enrolled 1034 couples undergoing preimplantation genetic testing-structural rearrangement on account of a carrier of reciprocal chromosomal translocation from the Reproductive Medicine Center of the First Affiliated Hospital of Zhengzhou University from January 2015 to December 2019. Group A represented 528 couples in which the man was the carrier of reciprocal translocation and group B represented 506 couples in which the woman was the carrier of reciprocal translocation. All patients were divided into two groups according to their age: female age<35 and female age≥35. Furthermore, the differences in blastocyst condition and pregnancy outcome between male and female carriers in each group were further explored according to their father's age.

Results

The blastocyst formation rate of group A (55.3%) is higher than that of group B (50%) and the results were statistically significant (P<0.05). The blastocyst formation rate of group A is higher than that of group B, no matter in young maternal age or in advanced maternal age (P<0.05). The blastocyst formation rate in maternal age<35y and paternal age<30y in group A(57.1%) is higher than that of Group B(50%); Similarly, the blastocyst formation rate in maternal age≥35 and paternal age≥38y(66.7%) is higher than that of Group B(33.3%)(all P<0.05). There was no difference in fertilization rate, aeuploidy rate, clinical pregnancy rate, miscarriage rate and live birth rate between Group A and Group B.

Conclusion

When the carrier of reciprocal translocation is male, the blastocyst formation rate is higher than that of female carrier. While there is no significant difference between the two in terms of fertilization rate, aeuploidy rate, clinical pregnancy rate, miscarriage rate and live birth rate.

Reproductive outcomes in individuals with chromosomal reciprocal translocations

PURPOSE

Patients with reciprocal balanced translocations (RBT) have a risk for recurrent pregnancy losses (RPL), affected child, and infertility. Currently, genetic counseling is based on karyotypes found among the products of conception (POC), although factors influencing the success of assisted reproductive technologies (ART) in RBT couples are not established.

METHODS

Cytogenetic results from 261 POC and offspring of the parents (113 women and 90 men) with RBT were evaluated. Chromosome segregation modes and number of euploid embryos were assessed in couples undergoing in vitro fertilization.

RESULTS

Patients with translocations involving an acrocentric chromosome have a higher risk of unbalanced gametes caused by a 3:1 segregation. Female RBT patients have a statistically higher risk of aneuploidy due to an interchromosomal effect. The rate of euploid embryos is low due to meiosis I malsegregation of RBT, meiosis II nondisjunction, additional whole chromosome or segmental aneusomies. RBT patients with RPL have a higher rate of miscarriage of euploid fetuses with RBT.

CONCLUSION

Chromosome-specific factors, female gender, age, and history of RPL are the risk elements influencing pregnancy and in vitro fertilization success in RBT patients. Chromosomal microarray analysis of POC is necessary to provide an accurate and timely diagnosis for patients with adverse reproductive outcomes.

A Rapid NGS-Based Preimplantation Genetic Testing for Chromosomal Abnormalities in Day-3 Blastomere Biopsy Allows Embryo Transfer Within the Same Treatment Cycle

Nowadays, most of the preimplantation genetic testing (PGT) is performed with a strategy of comprehensive chromosome screening and trophectoderm biopsy. Nevertheless, patients with ovarian insufficiency may not have competent blastocysts. In the present study, we aimed to establish the value of multiple annealing and looping-based amplification cycle (MALBAC)-based next-generation sequencing (NGS) for PGT in day-3 embryos. A total of 94.3% (1168/1239) of embryos yielded informative results, and the overall embryo euploid rate was 21.9% (256/1168). Overall, 225 embryos were transferred in 169 cycles with a clinical pregnancy rate of 49.1% (83/169). The live birth and implantation rates were 47.3% (80/169) and 44.4% (100/225), respectively. Double embryos transfer showed higher clinical pregnancy and live birth rates compared with single embryo transfer, but the implantation rates were similar (44.2% vs. 44.6%, P > 0.05). The euploid rate for reciprocal translocations (16.1%) was significantly lower than that for Robertsonian translocations (28.0%, P < 0.01) and inversions (28.0%, P < 0.01). However, higher percentages of embryos with de novo abnormalities were observed with Robertsonian translocations (23.3%, P < 0.01) and inversions (30.5%, P < 0.01) than with reciprocal translocations (11.6%). We demonstrated that NGS for PGT on day-3 embryos is an effective clinical application, particularly for patients with a diminished ovarian reserve and limited embryos.

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.

Partial trisomy 4q and monosomy 5p inherited from a maternal translocationt(4;5)(q33; p15) in three adverse pregnancies

Background

Carriers of balanced reciprocal chromosomal translocations are at known reproductive risk for offspring with unbalanced genotypes and resultantly abnormal phenotypes. Once fertilization of a balanced translocation gamete with a normal gamete, the partial monosomy or partial trisomy embryo will undergo abortion, fetal arrest or fetal malformations. We reported a woman with chromosomal balanced translocation who had two adverse pregnancies. Prenatal diagnosis was made for her third pregnancy to provide genetic counseling and guide her fertility.

Case presentation

We presented a woman with chromosomal balanced translocation who had three adverse pregnancies. Routine G banding and CNV-seq were used to analyze the chromosome karyotypes and copy number variants of amniotic fluid cells and peripheral blood. The karyotype of the woman was 46,XX,t(4;5)(q33;p15). During her first pregnancy, odinopoeia was performed due to fetal edema and abdominal fluid. The umbilical cord tissue of the fetus was examined by CNV-seq. The results showed a genomic gain of 24.18 Mb at 4q32.3-q35.2 and a genomic deletion of 10.84 Mb at 5p15.2-p15.33 and 2.36 Mb at 15q11.1-q11.2. During her second pregnancy, she did not receive a prenatal diagnosis because a routine prenatal ultrasound examination found no abnormalities. In 2016, she gave birth to a boy. The karyotype the of the boy was 46,XY,der(5)t(4;5)(q33;p15)mat. The results of CNV-seq showed a deletion of short arm of chromosome 5 capturing regions 5p15.2-p15.33, a copy gain of the distal region of chromosome 4 at segment 4q32.3q35.2, a duplication of chromosome 1 at segment 1q41q42.11 and a duplication of chromosome 17 at segment 17p12. During her third pregnancy, she underwent amniocentesis at 17 weeks of gestation. Chromosome karyotype hinted 46,XY,der(5)t(4;5)(q33;p15)mat. Results of CNV-seq showed a deletion of short arm (p) of chromosome 5 at the segment 5p15.2p15.33 and a duplication of the distal region of chromosome 4 at segment 4q32.3q35.2.

Conclusions

Chromosomal abnormalities in three pregnancies were inherited from the mother. Preimplantation genetic diagnosis is recommended to prevent the birth of children with chromosomal abnormalities.

Genome Sequencing Explores Complexity of Chromosomal Abnormalities in Recurrent Miscarriage

Recurrent miscarriage (RM) affects millions of couples globally, and half of them have no demonstrated etiology. Genome sequencing (GS) is an enhanced and novel cytogenetic tool to define the contribution of chromosomal abnormalities in human diseases. In this study we evaluated its utility in RM-affected couples. We performed low-pass GS retrospectively for 1,090 RM-affected couples, all of whom had routine chromosome analysis. A customized sequencing and interpretation pipeline was developed to identify chromosomal rearrangements and deletions/duplications with confirmation by fluorescence in situ hybridization, chromosomal microarray analysis, and PCR studies. Low-pass GS yielded results in 1,077 of 1,090 couples (98.8%) and detected 127 chromosomal abnormalities in 11.7% (126/1,077) of couples; both members of one couple were identified with inversions. Of the 126 couples, 39.7% (50/126) had received former diagnostic results by karyotyping characteristic of normal human male or female karyotypes. Low-pass GS revealed additional chromosomal abnormalities in 50 (4.0%) couples, including eight with balanced translocations and 42 inversions. Follow-up studies of these couples showed a higher miscarriage/fetal-anomaly rate of 5/10 (50%) compared to 21/93 (22.6%) in couples with normal GS, resulting in a relative risk of 2.2 (95% confidence interval, 1.1 to 4.6). In these couples, this protocol significantly increased the diagnostic yield of chromosomal abnormalities per couple (11.7%) in comparison to chromosome analysis (8.0%, chi-square test p = 0.000751). In summary, low-pass GS identified underlying chromosomal aberrations in 1 in 9 RM-affected couples, enabling identification of a subgroup of couples with increased risk of subsequent miscarriage who would benefit from a personalized intervention.

Effects of a carrier's sex and age on the segregation patterns of the trivalent of Robertsonian translocations

PURPOSE

To investigate the effects of a carrier's sex and age on the segregation patterns of the trivalent of Robertsonian translocations.

METHODS

This retrospective study was designed to analyze the segregation patterns of the trivalent and euploidy rates of blastocysts. Data were collected from 154 couples with Robertsonian translocation (77 with a female carrier and 77 with a male carrier). Embryos were diagnosed via array comparative genomic hybridization between January 2013 and July 2017. The segregation patterns of the trivalent of 604 blastocysts were analyzed according to the carrier's sex and age.

RESULTS

The proportion of alternate segregation was significantly higher (82.9% vs. 55.2%) in the male carriers than in the female carriers of Robertsonian translocation, and the proportion of adjacent segregation was significantly lower (16.8% vs. 42.6%), with no difference in 3:0 segregation. The segregation patterns were similar in same-sex carriers when analyzed according to the type of translocation. The carrier's age had no influence on the segregation patterns of the trivalent.

CONCLUSIONS

The proportions of the trivalent's meiotic segregation pattern differ significantly according to the carrier's sex in Robertsonian translocations and are independent of the carrier's age. A significantly higher proportion of alternate segregation for normal or balanced chromosome contents was observed in the blastocysts of the male carriers than in those of the female carriers.