Reciprocal Translocation Carriers Research Articles

Assessment of quadrivalent characteristics influencing chromosome segregation by analyzing human preimplantation embryos from reciprocal translocation carriers.

Patterns of meiotic chromosome segregation were analyzed in cleavage stage and blastocyst stage human embryos from couples with autosomal reciprocal translocations (ART). The influence of quadrivalent asymmetry degree, the presence of terminal breakpoints, and the involvement of acrocentric chromosomes in the rearrangement were analyzed to evaluate their contribution to the formation of non-viable embryos with significant chromosomal imbalance due to pathological segregation patterns and to assess the selection of human embryos by the blastocyst stage. A selection of viable embryos resulting from alternate and adjacent-1 segregation and a significant reduction in the detection frequency of the 3 : 1 segregation pattern were observed in human embryos at the blastocyst stage. The presence of terminal breakpoints increased the frequency of 3 : 1 segregation and was also associated with better survival of human embryos resulting from adjacent-1 mode, reflecting the process of natural selection of viable embryos to the blastocyst stage. The demonstrated patterns of chromosome segregation and inheritance of a balanced karyotype in humans will contribute to optimizing the prediction of the outcomes of in vitro fertilization programs and assessing the risks of the formation of unbalanced embryos for ART carriers.

Robust evidence reveals the reliable rate of normal/balanced embryos for identifying reciprocal translocation and Robertsonian translocation carriers.

We aimed to evaluate the reliable rate of normal/balanced embryos for reciprocal translocation and Robertsonian translocation carriers and to provide convincing evidence for clinical staff to conduct genetic counselling regarding common structural rearrangements to alleviate patient anxiety. The characteristics of 39,459 embryos that were sourced from unpublished data and literature were analyzed. The samples consisted of 17,536 embryo karyotypes that were not published and 21,923 embryo karyotypes obtained from the literature. Using the PubMed, Cochrane Library, Web of Science, and Embase databases, specific keywords were used to screen the literature for reciprocal translocation and Robertsonian translocation. The ratio of normal/balanced embryos in the overall data was calculated and analyzed, and we grouped the results according to gender to confirm if there were gender differences. We also divided the data into the cleavage stage and blastocyst stage according to the biopsy period to verify if there was a difference in the ratio of normal/balanced embryos. By combining the unpublished data and data derived from the literature, the average rates of normal/balanced embryos for reciprocal translocation and Robertsonian translocation carriers were observed to be 26.96% (7953/29,495) and 41.59% (4144/9964), respectively. Reciprocal translocation and Robertson translocation exhibited higher rates in male carriers than they did in female carriers (49.60% vs. 37.44%; 29.84% vs. 27.67%). Additionally, the data for both translocations exhibited differences in the normal/balanced embryo ratios between the cleavage and blastocyst stages of carriers for both Robertsonian translocation and reciprocal translocation (36.07% vs 43.43%; 24.88% vs 27.67%). The differences between the two location types were statistically significant (P < 0.05). The normal/balanced ratio of embryos in carriers of reciprocal and RobT was higher than the theoretical ratio, and the values ranged from 26.96% to 41.59%. Moreover, the male carriers possessed a higher number of embryos that were normal or balanced. The ratio of normal/balanced embryos in the blastocyst stage was higher than that in the cleavage stage. The results of this study provide a reliable suggestion for future clinic genetic consulting regarding the rate of normal/balanced embryos of reciprocal translocation and Robertsonian translocation carriers.

Genetic analysis and prenatal diagnosis of a pedigree with developmental retardation due to paternal 8q/18q translocation

Key Clinical MessageBalanced reciprocal chromosomal translocation carriers will have greater risk to experience recurrent miscarriages, embryonic death, and infertility. We show the pedigree carrying a paternal karyotype which was reported first. This research helps to better understand the clinical manifestations and prognosis of patients with this rare chromosomal abnormality.

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.

P-721 Nanopore sequencing for detecting reciprocal translocation carrier status in preimplantation genetic testing

Abstract Study question Analyze the concordance between nanopore sequencing and MaReCs to validate the feasibility of nanopore sequencing in distinguishing normal embryos from carrier embryos in PGT-SR cycles. Summary answer Nanopore sequencing is a powerful strategy for accurately distinguishing nontranslocation embryos from translocation carrier embryos and precisely localizing translocation breakpoints. What is known already Balanced reciprocal translocation (BRT) is one of the most common chromosomal abnormalities that causes infertility, recurrent miscarriage, and birth defects. Preimplantation genetic testing (PGT) is widely used to select euploid embryos for BRT carriers to increase the chance of a healthy live birth. Several strategies can be used to distinguish reciprocal translocation carrier embryos from those with a normal karyotype; however, these techniques are time-consuming and difficult to implement in clinical laboratories. Study design, size, duration The Nanopore Sequencing was performed on two pregnant patients conducted on Mapping Allele with Resolved Carrier Status” (MaReCs) in PGT-SR cycles to identify translocation breakpoints for a year. Combined conventional MaReCs ’results, amniocentesis was performed to identify karyotypes at 18–20 weeks of gestation to verify the correctness of the Nanopore Sequencing. Participants/materials, setting, methods A total of 11 embryos from 2 couple1 and 12 embryos from couple 2 were tested simultaneously in PGT-SR cycles with a combination strategy of mate pair sequencing and PCR breakpoint analysis, SNP array-based comprehensive chromosome screening (CCS), NGS following micro-dissecting junction region (Micro-Seq) to distinguish between normal and carrier embryos. The Nanopore Sequencing based on TGS was performed on 2 couples. Lastly, amniocentesis was performed to test karyotypes. Main results and the role of chance The translocation breakpoints in both reciprocal translocation carriers were accurately identifed by nanopore sequencing and were in accordance with the results obtained using MaReCs. More than one euploid non-balanced translocation carrier embryo was identified in both patients. Amniocentesis results revealed normal karyotypes, consistent with the findings by MaReCs and nanopore sequencing. Limitations, reasons for caution One limitation is that it is not possible to identify the translocation breakpoints of Robertsonian translocation carriers or those located in the gap regions of the human genome. In addition, high-molecular-weight genomic DNA and large amounts of peripheral blood samples would be a challenge most PGT centers. Wider implications of the findings The nanopore sequencing accurately detects translocation breakpoints in BRT carriers and distinguishes translocation-free embryos from balanced diploid embryos in clinical PGT-SR cycles. It is superior to short reads (NGS) for the detection of translocation breakpoints, which shows broad prospects for clinical applications in blocking translocation propagation in the population. Trial registration number Not applicable

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

To evaluate whether the effect of de novo mutated balanced reciprocal translocation on the rate of euploid embryos varied from inherited balanced reciprocal translocation. 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). An academic fertility center. 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. Carriers of balanced reciprocal translocation either de novo mutated or inherited. The percentage of euploid embryo and proportion of patients with at least 1 euploid embryo. 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. 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.

“It becomes your whole life”—Exploring experiences of reciprocal translocation carriers and their partners

AbstractReciprocal translocation carriers are often diagnosed when they are experiencing difficulties conceiving or after a pregnancy affected by an unbalanced set of chromosomes inherited from the balanced carrier parent. Having a reciprocal translocation is not uncommon; carriers can benefit from reproductive options to achieve a healthy, chromosomally balanced, pregnancy. The aim of this study was to explore the lived experience of carriers and their partners. We conducted 13 semi‐structured telephone interviews. Participants were recruited through Victorian Clinical Genetics Services and interviews took place between May and September 2020. Interview transcripts were analyzed using thematic analysis. Reciprocal translocation carriers and their partners described long term emotional and reproductive impacts, with carrier status identified at the time of prenatal diagnosis having marked emotional consequences. Couples facing reproductive challenges found the diagnosis created uncertainty for their future. When considering a pregnancy, couples worried about experiencing a miscarriage; during pregnancy, there was a reluctance to have an invasive diagnostic procedure due to fearing the risk of losing an unaffected pregnancy. Adaptation to their new reality involved having access to accurate information, peer support and maintaining hope. Couples valued having the option to know the carrier status of their children. The complex impacts of carrying a reciprocal translocation highlight the importance of access to specialist genetic counseling services to ensure couples are supported in understanding the implications of their translocation

Nanopore sequencing for detecting reciprocal translocation carrier status in preimplantation genetic testing

BackgroundBalanced reciprocal translocation (BRT) is one of the most common chromosomal abnormalities that causes infertility, recurrent miscarriage, and birth defects. Preimplantation genetic testing (PGT) is widely used to select euploid embryos for BRT carriers to increase the chance of a healthy live birth. Several strategies can be used to distinguish reciprocal translocation carrier embryos from those with a normal karyotype; however, these techniques are time-consuming and difficult to implement in clinical laboratories. In this study, nanopore sequencing was performed in two reciprocal translocation carriers, and the results were validated using the next-generation sequencing-based method named, “Mapping Allele with Resolved Carrier Status” (MaReCs).ResultsThe translocation breakpoints in both reciprocal translocation carriers were accurately identified by nanopore sequencing and were in accordance with the results obtained using MaReCs. More than one euploid non-balanced translocation carrier embryo was identified in both patients. Amniocentesis results revealed normal karyotypes, consistent with the findings by MaReCs and nanopore sequencing.ConclusionOur results suggest that nanopore sequencing is a powerful strategy for accurately distinguishing non-translocation embryos from translocation carrier embryos and precisely localizing translocation breakpoints, which is essential for PGT and aids in reducing the propagation of reciprocal translocation in the population.

Анализ сегрегации хромосом у носителей реципрокных транслокаций в зависимости от характеристик профазного квадривалента

Введение. Преимущественное образование несбалансированных гамет вследствие нарушения мейотической сегрегации хромосом у носителей аутосомных реципрокных транслокаций (АРТ) может зависеть от степени асимметрии мейотического квадривалента и наличия терминальных точек разрывов. Комплексная оценка этих факторов на доимплантационном этапе позволит оценить весь спектр паттернов сегрегации для последующей оценки риска образования несбалансированных эмбрионов. Цель: оценить влияние степени асимметрии квадривалента и наличия терминальных точек разрывов на тип сегрегации хромосом у носителей АРТ. Методы. Кариотипирование супружеской пары, преимплантационное генетическое тестирование (ПГТ-СП) методом флуоресцентной in situ гибридизации (FISH) 271 бластомера эмбрионов, полученных в циклах вспомогательных репродуктивных технологий (ВРТ) у 26 пар-носителей АРТ. Определение паттернов сегрегации хромосом, степени асимметрии квадривалента и наличия терминальных точек разрывов. Результаты. Асимметрия квадривалента и терминальные точки разрыва не влияют на частоту образования эмбрионов со сбалансированным набором хромосом вследствие альтернативного типа сегрегации хромосом. Для носителей АРТ с сильной асимметрией квадривалента и терминальными точками разрывов более характерна сегрегация по типу 3:1 и 4:0, приводящая к хромосомному дисбалансу, в подавляющем большинстве случаев несовместимому с дальнейшим развитием эмбриона. Полученные данные могут быть использованы при медико-генетическом консультировании носителей АРТ. Background. Meiotic quadrivalent asymmetry degree or the presence of terminal breakpoints may affect the risk of unbalanced gametes’ formation due to pathological chromosome segregation in autosomal reciprocal translocations (ART) carriers during meiosis. A comprehensive analysis of these factors in preimplantation embryos allows evaluating the entire spectrum of segregation patterns in ART carriers for subsequent risk assessment. Aim: the purpose of the study was to assess the influence quadrivalent asymmetry degree and the presence of terminal breakpoints on the segregation type in ART carriers. Methods. Karyotyping for ART confirmation, preimplantation genetic testing (PGT-SP) using fluorescent in situ hybridization (FISH) on 271 embryos obtained in assisted reproductive technology (ART) cycles in 26 couples of ART carriers. The chromosome segregation patterns, the quadrivalents’ asymmetry degree, and the presence of terminal breakpoints were determined. Results. An alternative segregation type, leading to the formation of balanced gametes, was observed with the same frequency in ART carriers with and without terminal breakpoints, as well as in carriers with different quadrivalent asymmetry degrees. The 4:0 and 3:1 patterns were more common in ART carriers with severe quadrivalent asymmetry and terminal breakpoints and could result in large-scale chromosomal imbalance. The data obtained can be used in genetic counseling of ART carriers.

Influence of gender of reciprocal translocation carriers on the occurrence of embryonic chromosomal abnormalities

To explore the influence of gender of chromosomal translocation carriers on the occurrence of embryonic chromosomal aberrations. A retrospective study was carried out. Data were collected from 235 couples carrying reciprocal translocations (1163 blastocysts) and 70 couples carrying Robertsonian translocations (351 blastocysts). The preimplantation genetic testing for structural rearrangement (PGT-SR) analysis of 1514 blastocysts were completed through next generation sequencing (NGS). After adjusting the confounding factors such as female age, AMH, ovarian stimulation regimen, and Gn dosage, the results showed that the risk for blastocyst chromosomal abnormalities was 0.41 [OR(95%CI), 1.41(1.06, 1.87), P < 0.05] times higher in female reciprocal translocation carriers and 1.02 [OR(95%CI), 2.02 (1.20, 3.40), P < 0.01] times higher in female Robertsonian translocation carriers compared with male carriers, respectively. Compared with male carriers, the risk of blastocyst chromosomal abnormalities was increased by 0.67 times [OR(95%CI), 1.67 (1.10, 2.56), P < 0.05] in female reciprocal translocation carriers over 30 years old and 1.06 times [OR(95%CI), 2.06 (1.02, 4.15), P = 0.0434, P < 0.05] in female Robertsonian translocation carriers between 25 and 30 years old. Compared with male carriers, female carriers of reciprocal or Robertsonian translocations have a higher risk for producing embryos with chromosomal abnormalities, and their age may also be a risk factor.

P-549 Paraclinical and spermogram evaluation of infertile males with balanced chromosomal rearrangements referred to Royan institute from 2009-2021

Abstract Study question Whether balanced chromosomal rearrangements are associated with altered semen parameters/increased DNA Fragmentation Index (DFI), are the common breakpoints related to male infertility in patients ? Summary answer Balanced chromosomal rearrangements is associated with abnormal semen parameters and increased DFI in carriers. Chromosomes 9,1,3 showed the highest incidence of chromosomal rearrangement What is known already Among many factors, balanced chromosomal rearrangements are thought to be one of the major genetic factors influencing male infertility which can cause disorders related to spermogram, DNA fragmentation, increased risk of miscarriage and ART failure. Finding common chromosomal breakpoints in infertile men carrying balanced chromosomal translocations is significant since these patients usually possess normal clinical features. Numerous studies have been performed on the various chromosome translocations. However, there has not been any report on the common breakpoints in balanced chromosomal abnormalities related to male infertility in Iran. Study design, size, duration This cross-sectional study performed on 25000 patients’ files admitted to the Royan institute during the period 2009- 2021.Infertile men carrying balanced chromosomal rearrangements were included as case group. Sperm parameters, DFI and common chromosomal break points were evaluated Participants/materials, setting, methods 25000 files of patients were reviewed. 252 infertile men carrying balanced chromosomal rearrangements and 252 men with normal karyotype were included (case and control group, respectively). Sperm concentration, motility (CASA), sperm morphology (Papanicolaou Staining),DFI (SCSA) and cytogenetic analysis of peripheral blood lymphocytes (G-banding) were evaluated. Numerical chromosomal abnormalities, deletions, marker chromosomes, alcohol or drug addiction, smoking, chemotherapy and radiation, varicocele and exposure to environmental pollution were excluded. The common chromosomal breakpoints in translocations were investigated. Main results and the role of chance Sperm concentration, total motility and normal morphology were significantly lower in balanced chromosomal rearrangements carriers compared to control group(p &amp;lt; 0.05). DFI in patient was significantly higher in comparison to control group(p &amp;lt; 0.05). Among different kind of chromosomal rearrangement carriers’, sperm concentration and total motility were lower in Robertsonian translocation carriers comparing to the Reciprocal translocation and inversion ones. The reciprocal translocation and inversion carriers did not differ regarding to sperm concentration and total motility. Meanwhile, normal morphology was lower in the translocation compared to inversion carriers. No difference was observed in DFI among carriers of balanced chromosomal rearrangements. Among case group, inversion accounted for the largest share, followed by Reciprocal, Robertsonian translocation and insertion. Group C had the highest frequency in reciprocal translocation, inversion and insertion among the chromosomal groups. The highest balanced translocation prevalence was related to three chromosomes 9,3, and1. 9q12,1p36,3p11 were the most frequent breakpoints among them. Chromosome 9 had the largest contribution to inversions,22 to reciprocal translocations and14 to Robertsonian translocations. In the Robertsonian translocation, group D showed the highest frequency. Interestingly, patients carrying normal variations such as pericentric inversion of chromosome 9showed a significant alteration in sperm parameters, therefore normal variations showed a possible relationship to infertility. Limitations, reasons for caution In order to achieve stronger statistical results on DFI, a larger sample size would be more helpful. Wider implications of the findings The results may be useful to identify the most common breakpoints and consequently genes related to male infertility and can suggest appropriate molecular mechanism for their infertility. Trial registration number not applicable

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.

EP472: Deriving risk estimates for balanced rearrangement carriers utilizing PGT-SR data

Parental balanced rearrangements (PBRs) are identified in approximately 4% of couples with recurrent pregnancy loss compared to 0.2% in the general population. PBR carriers are typically healthy, as little or no chromosomal material is lost or gained; however, they are at increased risk of creating unbalanced embryos that can result either in miscarriage or in the birth of a child with health problems and/or birth defects. Currently, most couples carrying PBRs are counseled based on risk estimates from either gamete studies (sperm/ova) or rates of miscarriage and/or abnormal live births. Preimplantation genetic testing for structural rearrangements (PGT-SR) can be performed for many types of PBRs, with detection dependent on the specific chromosome breakpoints and the testing technology used. Using data from PGT-SR cycles can generate risk estimates that are more informative for the IVF community regarding success rates for PBR couples. Trophectoderm biopsies were analyzed using a modified FAST-SeqS NGS-based PGT method and bioinformatics pipeline, which detects whole chromosome and segmental aneuploidies (≥10Mb), most types of polyploidy, and many instances of single chromosome uniparental isodisomy. A retrospective analysis of all embryo biopsies from patients with an identified PBR from September 2015 to March 2021 was performed to analyze rates of abnormalities derived from the PBR [derivative chromosomes and whole-chromosome aneuploidy of the involved chromosome(s)]. A total of 238 patients, with 380 PGT-SR cycles, were analyzed. The largest cohort, carrying reciprocal translocations, included 172 patients with 280 cycles (50.6% maternal, 49.4% paternal). The observed rates of derivative abnormalities were similar between the two groups (58.51% maternal vs. 50.41% paternal). Robertsonian translocations were documented in 50 patients with 81 cycles (48.0% maternal, 52.0% paternal). Unlike reciprocal translocations, we observed a clear increase in derivative abnormalities from maternally-derived rearrangements (36.4% vs. 18.2%), with the most striking difference seen with rob(14;21) carriers (n=9; 36.4% maternal vs. 3.1% paternal). Finally, sixteen patients (19 cycles) carried inversions, with eleven pericentric and five paracentric inversions represented. Similar to Robertsonian translocations, we observed an increase in derivative abnormalities when the pericentric inversion was maternally-derived (34.4% vs. 17.7%). Unexpectedly, a single paternally-derived paracentric inversion, inv(3)(q26.1q29), produced 37.5% blastocyst-stage derivative-abnormal embryos. Overall, as expected from the literature, derivative-abnormal rates from PBRs are highest for reciprocal translocation carriers, followed by Robertsonian translocations and inversions. While gamete studies have shown a higher rate of abnormalities in maternally-derived translocations, our abnormal rates were similar between the two parent-of-origin groups. In contrast, there is a clear parent-of-origin effect for both Robertsonian translocations and inversions. In all PBR types, abnormal rates are lower than those observed in gametes, likely due to decreased viability of abnormal embryos even before the blastocyst stage. These rates, derived from the largest published cohort to date, can be a valuable tool in counseling patients with PBRs regarding the potential success of their IVF journey.

Identifying Balanced Chromosomal Translocations in Human Embryos by Oxford Nanopore Sequencing and Breakpoints Region Analysis.

Background: Balanced chromosomal aberrations, especially balanced translocations, can cause infertility, recurrent miscarriage or having chromosomally defective offspring. Preimplantation genetic testing for structural rearrangement (PGT-SR) has been widely implemented to improve the clinical outcomes by selecting euploid embryos for transfer, whereas embryos with balanced translocation karyotype were difficult to be distinguished by routine genetic techniques from those with a normal karyotype. Method: In this present study, we developed a clinically applicable method for reciprocal translocation carriers to reduce the risk of pregnancy loss. In the preclinical phase, we identified reciprocal translocation breakpoints in blood of translocation carriers by long-read Oxford Nanopore sequencing, followed by junction-spanning polymerase chain reaction (PCR) and Sanger sequencing. In the clinical phase of embryo diagnosis, aneuploidies and unbalanced translocations were screened by comprehensive chromosomal screening (CCS) with single nucleotide polymorphism (SNP) microarray, carrier embryos were diagnosed by junction-spanning PCR and family haplotype linkage analysis of the breakpoints region. Amniocentesis and cytogenetic analysis of fetuses in the second trimester were performed after embryo transfer to conform the results diagnosed by the presented method. Results: All the accurate reciprocal translocation breakpoints were effectively identified by Nanopore sequencing and confirmed by Sanger sequencing. Twelve embryos were biopsied and detected, the results of junction-spanning PCR and haplotype linkage analysis were consistent. In total, 12 biopsied blastocysts diagnosed to be euploid, in which 6 were aneuploid or unbalanced, three blastocysts were identified to be balanced translocation carriers and three to be normal karyotypes. Two euploid embryos were subsequently transferred back to patients and late prenatal karyotype analysis of amniotic fluid cells was performed. The outcomes diagnosed by the current approach were totally consistent with the fetal karyotypes. Conclusions: In summary, these investigations in our study illustrated that chromosomal reciprocal translocations in embryos can be accurately diagnosed. Long-read Nanopore sequencing and breakpoint analysis contributes to precisely evaluate the genetic risk of disrupted genes, and provides a way of selecting embryos with normal karyotype, especially for couples those without a reference.

Reciprocal translocation and Robertsonian translocation in relation to semen parameters: A retrospective study and systematic review

Reciprocal translocation and Robertsonian translocation are known to be causative factors of male infertility. However, the association between autosomal reciprocal translocation, Robertsonian translocation and semen parameters remains controversial. We performed a retrospective study and systematic review to investigate semen parameters in patients with autosomal reciprocal translocation or Robertsonian translocation. We recruited a total of 1,033 controls, 723 reciprocal translocation carriers and 326 Robertsonian translocation carriers. Men in the control, reciprocal translocation and Robertsonian translocation groups had a median age of 32.0 (95% CI, 32.0-33.0), 32.0 (95% CI, 32.0-33.0) and 33.0 (95% CI, 32.0-33.0) years respectively. Results showed that sperm concentration, total number per ejaculate, total motility, progressive motility of autosomal reciprocal translocation and Robertsonian translocation carriers were statistically lower than controls (p<.001). Eleven studies featuring 794 patients were enrolled in this systematic review. Compared with controls, autosomal reciprocal translocation and Robertsonian translocation carriers showed lower sperm concentration, total motility, progressive motility and normal morphology. Our results support the conclusion that sperm concentration, total number per ejaculate, total motility and progressive motility are significantly lower in autosomal reciprocal translocation and Robertsonian translocation carriers than in controls.

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

Research questionDoes the sex of reciprocal translocation carriers affect meiotic segregation patterns and stability of non-translocated chromosomes during meiosis? DesignA 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. ResultsFemale 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). ConclusionThe sex of the translocation carriers affected meiotic segregation patterns with no effect on the stability of non-translocated chromosomes during meiosis.

O-206 Meiotic segregation analysis for reciprocal translocation carriers: Assessment of factors influencing meiotic segregation patterns

Abstract Study question To analyze factors that could influence meiotic segregation patterns for reciprocal translocation carriers. Summary answer Involvement of an Acr-ch, female gender, and lower TAR1 (ratio of translocated segment 1 over the chromosome arm) were independent risk factors for alternate segregation. What is known already Reciprocal translocation is one of the more common structural rearrangements of chromosomes, which is associated with reproductive risks, such as infertility, spontaneous abortion and the delivery of babies with mental retardation or developmental delay. Extensive studies on meiotic segregation patterns of sperm, blastomere, and blastocysts have identified several factors that may influence the generation of unbalanced rearrangement of reciprocal translocations, including carrier’s gender and age, location of breakpoints, chromosome type, and the quadrivalent structure. However, some results are controversial. Study design, size, duration A retrospective study from October 2013 to December 2019, a total of 10846 blastocysts originating from 2871 oocyte retrieval cycles from 2253 couples with one of the partners carrying reciprocal were investigated. The mean maternal age was 29.97±4 years (20 –47years). Participants/materials, setting, methods Trophectoderm biopsy of blastocysts was performed on the 5th or 6th day of development. Whole genome amplification (WGA) was performed on all samples, and the WGA was analyzed with SNP array or NGS. Segregation patterns of quadrivalent in 10846 blastocysts were analyzed. Risk factors for segregation patterns were explored through analyzing carriers’ demographic and cytogenetic characteristics using multivariate generalized linear mixed models (GLMMs). Main results and the role of chance The percentage of normal/balanced blastocysts was 34.3%, and 2:2 segregation was observed in 90.0% of blastocysts. Increased TAR1 (the ratio of translocated segment 1 over the chromosome arm) was noted as an independent protective factor for the proportion of alternate segregation (P = 0.004). The female gender and involvement of an Acr-ch were found independent risk factors for alternate segregation (P &amp;lt; 0.001). A higher TAR1 reduced the risk of adjacent-1 segregation; longer translocated segment and female gender increased the risk of adjacent-2 segregation (P = 0.009 and P &amp;lt; 0.001, respectively). Female gender and involvement of an Acr-ch enhanced the risk of 3:1 segregation (P &amp;lt; 0.001 and P = 0.012, respectively). Limitations, reasons for caution About 1400 blastocysts were not diagnosed in the 2871 cycles, which might cause bias in the results. Secondly, the interchromosomal effect of reciprocal translocations was not analyzed in this study. Wider implications of the findings In conclusion, a carrier’s gender, involvement of an Acr-ch, and location of breakpoints may influence the segregation patterns. Besides, involvement of an Acr-ch, female gender, and lower TAR1 are independent risk factors for alternate segregation. These results may provide more appropriate genetic counseling for couples with balanced translocation. Trial registration number no

Meiotic Silencing in Pigs: A Case Study in a Translocated Azoospermic Boar.

Carriers of balanced constitutional reciprocal translocations usually present a normal phenotype, but often show reproductive disorders. For the first time in pigs, we analyzed the meiotic process of an autosome–autosome translocation associated with azoospermia. Meiotic process analysis revealed the presence of unpaired autosomal segments with histone γH2AX accumulation sometimes associated with the XY body. Additionally, γH2AX signals were observed on apparently synapsed autosomes other than the SSC1 or SSC15, as previously observed in Ataxia with oculomotor apraxia type 2 patients or knock-out mice for the Senataxin gene. Gene expression showed a downregulation of genes selected on chromosomes 1 and 15, but no upregulation of SSCX genes. We hypothesized that the total meiotic arrest observed in this boar might be due to the silencing of crucial autosomal genes by the mechanism referred to as meiotic silencing of unsynapsed chromatin (MSUC).

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

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

A mathematical model for predicting the number of transferable blastocysts in next-generation sequencing-based preimplantation genetic testing.

To investigate the clinical factors that could be used predict the number of transferable blastocysts in preimplantation genetic testing (PGT) cycles based on next-generation sequencing (NGS) and formed form a mathematical model to predict the chance likelihood of obtaining one transferable blastocyst, which is helpful for genetic counseling. This retrospective study enrolled couples undergoing PGT cycles for chromosomal structural rearrangement (PGT-SR, n = 363, 202 with reciprocal translocation carriers, 131 with Robertsonian translocation carriers, 30 with inversion carriers), monogenic diseases (PGT-M, n = 47), and for Aneuploidies (PGT-A, n = 132) from January 2015 to October 2018. Stepwise multiple linear regression analysis was used to identify the factors relevant for obtaining at least one transferable blastocyst. The factors that predict the number of biopsied blastocysts were further analyzed. The transferable blastocyst rates were 29.94, 41.99, 49.09, 41.42, and 44.37% in the reciprocal translocation carrier, Robertsonian translocation carrier, inversion carrier, PGT-M, and PGT-A cycles, respectively. The number of transferable blastocysts in these cycles were 0.3004 × the number of biopsied blastocysts (NBB) - 0.0031, 0.4063 × NBB + 0.0460, 0.5762 × NBB - 0.3128, 0.3611 × NBB + 0.1910, and 0.4831 × NBB - 0.0970, respectively. Furthermore, the number of MII oocytes and female age were clinical predictors of NBB in reciprocal translocation and PGT-A couples, while the number of MII oocytes was the only clinical predictor in Robertsonian translocation carriers, inversion carriers, and PGT-M couples. The number of biopsied blastocysts was the only clinical predictor of the ability to obtain a transferable blastocyst in PGT cycles; therefore, for clinical practice, theoretically the minimum numbers of biopsied blastocysts is 4 in reciprocal translocation carrier and 3 in couples undergoing PGT for other reasons. The number of MII oocytes and female age were clinical predictors of the number of biopsied blastocysts. With the mathematical models in our study as a reference, in clinical practice, clinicians will be able to conduct a more targeted genetic consultation for different kinds of PGT patients.