Carriers Of Chromosomal Rearrangements Research Articles

Characterization of cryptic complex chromosome rearrangements in balanced chromosomal rearrangement carriers and their PGT-SR clinical outcome assessments

Several reports have presented that balanced chromosomal rearrangements (BCRs) carriers with normal phenotypes may be carriers of complex rearrangements. However, the incidence and PGT clinical outcomes of cryptic complex chromosome rearrangements (CCCRs) in individuals with BCRs is remain unknown. We recruited a cohort of 1,264 individuals with BCR carriers from 2016 to 2021 at the Reproductive and Genetic Hospital of CITIC Xiangya. Peripheral blood was collected for karyotyping and genomic DNA extraction and the PGT-SR clinical outcomes of CCCRs carriers were analyzed and compared with those of BCR carriers. Our findings revealed that 3.6% (45/1,264) of BCR carriers had CCCRs, involving 3–25 breakpoints on 1–3 chromosomes. Furthermore, when mate-pair sequencing was employed, 63.3% (19/30) of CCCR carriers were found to have chromosome rearrangements that were different from those identified by the MicroSeq technique. And the transferable embryo rate of CCCR carriers with 3 chromosomes was significantly lower than that of CCCR carriers with only 1–2 chromosomes. In this research, we revealed that some of the BCR carriers were actually CCCR carriers, and the prognosis of PGT in CCCR carriers with one or two chromosomes is better than that of CCCR carriers with three chromosomes.

Evaluation of genetic risk of apparently balanced chromosomal rearrangement carriers by breakpoint characterization.

To report genetic characteristics and associatedrisk of chromosomal breaks due to chromosomal rearrangements in large samples. MicroSeq, a technique that combines chromosome microdissection and next-generation sequencing, was used to identify chromosomal breakpoints. Long-range PCR and Sanger sequencing were used to precisely characterize 100 breakpoints in 50 ABCR carriers. In addition to the recurrent regions of balanced rearrangement breaks in 8q24.13, 11q11.23, and 22q11.21 that had been documented, we have discovered a 10-Mb region of 12q24.13-q24.3 that could potentially be a sparse region of balanced rearrangement breaks. We found that 898 breakpoints caused gene disruption and a total of 188 breakpoints interrupted genes recorded in OMIM. The percentage of breakpoints that disrupted autosomal dominant genes recorded in OMIM was 25.53% (48/188). Fifty-four of the precisely characterized breakpoints had 1-8-bp microhomologous sequences. Our findings provide a reference for the evaluation of the pathogenicity of mutations in related genes that cause protein truncation in clinical practice. According to the characteristics of breakpoints, non-homologous end joining and microhomology-mediated break-induced replication may be the main mechanism for ABCRs formation.

P-736 Balanced cryptic chromosomal rearrangement carriers detection by optical genome mapping (OGM)

Abstract Study question To evaluate diagnosis value of optical genome mapping (OGM) for potential preimplantation genetic testing in chromosomal structural rearrangement (PGT-SR) patients with cryptic chromosomal rearrangement. Summary answer OGM is an efficient method for cryptic chromosomal rearrangement detection. However, SVs near telomere and centromere regions could hardly be reported with this method. What is known already About 5∼10% infertility or sterility people carry balanced chromosomal structural variations (SVs) with high risks of miscarriage and birth defects resulting from imbalanced gametes when producing fetus. However, some balanced cryptic SVs with specific location or small fragments cannot be detected by traditional cytogenetic techniques like G-banding testing or CNV-seq. Currently, several optimized techniques are able to detect typically cryptic structural abnormality. OGM, the molecular genetic detection technique relying on new principle in recent years, have overcome the shortcomings of former techniques and are potentially capable to detect both routine and cryptic SVs well. Study design, size, duration From 2019 to 2022, 12 couples in The First Affiliated Hospital of Sun Yat-sen University and The First People’s Hospital of Yunnan Province with history of offspring birth defect, recurrent unexplained recurrent miscarriage or unexpected copy number variation in embryos from previous PGT cycles were included for diagnosis or re-analysis. Participants/materials, setting, methods Peripheral blood lymphocytes from these patients were collected and detected by OGM or traditional karyotype analysis(G-400 banding), FISH, CNV-seq, third generation sequencing(Nanopore). The results of traditional genetic test and OGM were compared to evaluate the accuracy of OGM detection of chromosomal structure vatiation. Main results and the role of chance In the 11 couples bearing adverse pregnancy or childbirth defect with normal karyotype by G-banding, OGM discovered novel chromosome translocations or inversion in 9 couples (81.81%). In 1 couple with t(4:17)(q12;p13) diagnosed by G-banding, OGM detect an additional chromosomal translocation of t(17;19)(q12;p13), which produced the repeated CNVs in chromosome19 observed in embryos from two previous PGT cycles. For small fragment translocation, terminal translocation and inversion, OGM is able to detected balanced structure abnormal of 500kbs. The OGM diagnosis were confirmed by FISH or third generation sequencing (Nanopore) or embryo mutation. The breaking position reported by OGM and Nanopore were comparable. In sum, OGM reported further information of balanced SVs in 83.33% (10/12) potential patients with duplication and depletion in embryos or abortus. Limitations, reasons for caution Due to the limitation of principle, the structural abnormalities of some special locations (centromere, secondary constriction, etc.) cannot be detected. OGM has high sensitivity and many mutations, which requires examiners to have strong ability to analyze results and genetic counseling. The price of OGM also limits the promotion and application. Wider implications of the findings OGM can provide more precious result for SVs, and PGT-SR can definitely improve the outcome of certain population with cryptic chromosomal rearrangements. The shortcoming of OGM has not been overcame yet, so it is suggested as auxiliary method beside conventional G-binding in certain circumstances in ART population. Trial registration number Not applicable

P-719 Evaluation of genetic risk of apparently balanced chromosomal rearrangement carriers by breakpoint characterization

Abstract Study question What are breakpoint characteristics of ABCR carriers? What are the genetic risks of ABCR carriers caused by chromosome rearrangements? Summary answer We analyzed the characteristics of ABCR's breakpoints and found that heterogeneous deletion of some AD disease-related genes may not result in clinical phenotype. What is known already ABCRs are common chromosomal abnormalities. People with ABCRs generally lack any visible abnormal features; however, during childbirth, the abnormal pairing and missegregation of homologous chromosomes can lead to the production of unbalanced gametes, resulting in spontaneous abortion or the birth of children with chromosomal disorders. Prenatal diagnosis or preimplantation diagnosis can effectively prevent the birth of children with unbalanced chromosome rearrangements, but no substantial data has been collected to report on the characteristics and potential genetic risks of the chromosome breakage caused by the rearrangement. Study design, size, duration This is a retrospective study of 2441 breakpoints in 1219 ABCR carriers who underwent Preimplantation Genetic Testing (PGT) at the Reproductive and Genetic Hospital of Citic-Xiangya from August 1, 2016 to December 31, 2021. Participants/materials, setting, methods All patients in this study sought PGT treatment due to primary or secondary infertility caused by ABCRs. To characterize the chromosome breakpoints, the MicroSeq technique, which involves chromosome microdissection and next generation sequencing, was employed. Additionally, gap-junction PCR and Sanger sequencing were utilized to further validate some of the breakpoints. Main results and the role of chance In this study, we retrospectively analyzed 2441 chromosome rearrangement breakpoint MicroSeq localization data from 1219 ABCR carriers, including 2364 breakpoint regions in 1182 reciprocal translocations, 68 breakpoint regions in 34 inversions, and 9 breakpoint regions in 3 insertional translocations. We not only identified 8q24.13, 11q11.23, and 22q11.21 as previously reported hotspots of chromosomal balanced rearrangement breaks, but also identified the 10 Mb region of 12q24.13-q24.3 as a possible rare region of balanced rearrangement breaks. the average range of breakpoints identified by MicroSeq technology was only within 3.8 Kb, which clarified 95.82% (2339/2441) of balanced chromosomal rearrangements as to whether they broke genes or not. We identified 960 genes that were interrupted, of which 53 genes with autosomal dominant mode of inheritance (AD) were interrupted. Clinical phenotypic evaluation of these patients carrying interrupted AD genes identified that some of the AD genetic interruptions may not have a clinical phenotype. Limitations, reasons for caution MicroSeq cannot precisely pinpoint breakpoints to the gene or single base level. Moreover, carriers of ABCRs were not comprehensively assessed for other clinical characteristics, and the alteration in function of the known Haploinsufficiency gene could not be confirmed. Additionally, the position effect of the breakpoints has not been evaluated. Wider implications of the findings This investigation offers a reference for evaluating the pathogenicity and genetic risks of protein-truncation mutations in some AD genes. Trial registration number Not applicable

Preimplantation Genetic Testing for Couples with Balanced Chromosomal Rearrangements.

Chromosomal rearrangements play an important role in infertility. Carriers of chromosomal rearrangements have a lower chance of producing normal or balanced gametes due to abnormal segregation of chromosomes at meiosis, which leads to recurrent spontaneous abortions and infertility. Preimplantation genetic testing for structural chromosome rearrangements (PGT-SR) is offered to couples who have balanced chromosomal rearrangements in order to select embryos with a balanced karyotype prior to implantation, thereby increasing the chances of pregnancy. The purpose of the current study was to assess the outcomes of PGT-SR in patients carrying various balanced chromosomal rearrangements and to assess their clinical pregnancy outcome after in vitro fertilization (IVF). In this study, infertile couples with balanced chromosomal abnormalities undergoing PGT-SR were retrospectively analyzed at a single fertility center from January 2016 to December 2019. PGT-SR was performed on 87 embryos from 22 couples in whom one partner carried a balanced translocation or an inversion. Fifty-seven (65.5%) of these embryos had unbalanced or sporadic aneuploidies, 30 (34.5%) embryos were normal or chromosomally balanced, which were then transferred in 18 couples. A higher rate of unbalanced translocations in comparison to sporadic aneuploidies was observed in couples with reciprocal translocation. The live birth rate per embryo transfer was found to be 66.6% (12/18). PGT-SR is a useful tool in selecting normal or balanced embryos for transfer in IVF, which could lead to a pregnancy by reducing the chance of miscarriages due to chromosome aneuploidy in couples with balanced chromosomal rearrangements.

P-292 Laboratory performance in PGT-SR cases in carriers of chromosomal rearrangements

Abstract Study question Could laboratory outcomes, such as fertilisation and blastocyst formation rates be altered based on which partner carries a chromosomal rearrangement in PGT-SR cases? Summary answer Blastocyst formation is significantly reduced when both partners carry a mutation, compared to patients carrying paternally derived translocations What is known already Some research suggests that the presence of paternal translocations may significantly increase miscarriage rates in patients who conceive naturally, versus patients who conceive after PGT-SR. Additionally, there may be a trend towards a shorter time to livebirth when considering PGT-SR patients, versus those who conceive by natural conception. This could aid treatment choices for patients in this cohort. Research has evaluated laboratory and clinical outcomes for PGT-M patients and found that this cohort of patients have slightly higher success rates, when compared to PGT-SR patients. The commonality of these studies being multicentre warrants further investigation from a single centre ART. Study design, size, duration An observational single centre study performing retrospective analysis of data for patients having PGT-M or PGT-SR between 2015 and 2020. After exclusion criteria were considered, this study evaluated laboratory findings for 484 patients. This included PGT-SR patients affected by reciprocal and Robertsonian translocations as well as PGT-M patients, who were the control group. Patients with more complicated chromosomal rearrangements were excluded from analysis. Participants/materials, setting, methods IDEAS® (V6.0) software was used to capture all laboratory details relating to the patient cohort. This included number of cycles, number of oocytes collected, oocyte maturity, fertilisation rate and blastocyst formation rate. The official PGT-M or PGT-SR reports were consulted for information related to the embryos tested for each patient. Genetic testing was performed by Igenomix, CooperGenomics or Reprogenetics. All variables were evaluated using Chi-Square to establish whether there were any statistically significant differences noted. Main results and the role of chance A total of 5,149 oocytes were inseminated and 3,825 embryos were created from the 484 cycles included in this analysis. There were no significant differences in fertilisation rates for maternal or paternal mutations by direct comparison (p > 0.05). Of these, 2,354 embryos formed blastocysts suitable for PGT-M or PGT-SR. Blastocyst formation rates were marginally statistically lower when both partners carried a mutation when compared to maternal or paternal translocations or exclusively paternal translocations, respectively (p = 0.047; p = 0.033). We observed a slight trend towards decreased fertilisation and blastocyst formation rates when maternal and paternal mutations were present, but this was not statistically significant. Limitations, reasons for caution This study was limited by modest sample size; further research would include a larger cohort of patients. This study evaluated laboratory outcomes, but future research could assess clinical outcomes to establish any impact of the origin of chromosomal rearrangement on implantation, pregnancy, and live birth rates. Wider implications of the findings This study suggests reduced blastocyst formation rates when both partners carry a mutation; this information may be used to counsel patients. It may impact the treatment options and number of embryo batching cycles prior to blastocyst culture for PGT. This could help to improve and better inform the patient experience. Trial registration number IRB-001C02-01-22

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 < 0.05). DFI in patient was significantly higher in comparison to control group(p < 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

Complex Chromosomal Rearrangement Causes Male Azoospermia: A Case Report and Literature Review

Background: Male carriers of complex chromosomal rearrangements (CCRs) may have decreased fertility and usually present with azoospermia, oligospermia or teratospermia. Methods: High-resolution karyotype analysis using G-banding on peripheral blood lymphocytes was performed in an azoospermic male. Copy number variations (CNVs) were detected by chromosomal microarray analysis, and genetic variations were determined by long-read nanopore sequencing with Sanger sequencing for breakpoint confirmation. Results: The karyotype of the patient was 46,XY,t(4;21)(p11;p11),t(5;6;14)(p13q22;p22q22;q22), which did not involve CNVs with clinical significance. Twelve breakpoints in chromosomes 5, 6, and 14 were found by long-read nanopore sequencing. Reports on 17 males carrying CCRs with azoospermia were also reviewed. Conclusion: The extent of asynaptic regions in synaptonemal complexes during pachytene and the disruption of genes involved in male gametogenesis may cause azoospermia in CCR carriers.

Assisted reproductive technology outcomes of infertile men carrying balanced chromosomal rearrangements or Y-chromosome microdeletions - Retrospective study

The aim of this study was to evaluate the ART outcomes for infertile males carrying a balanced structural chromosomal rearrangement or a Y-chromosome microdeletion, and to compare the results with a control group. The primary outcome was the clinical pregnancy rate. A retrospective case-control study has been carried out in the ART departments of the university hospitals of Bordeaux and la Réunion. Results of karyotypes and Y-chromosome microdeletions analysis of infertile men with sperm concentration lower than 5millions/mL have been extracted from the softwares Jfiv® (Bordeaux) and MédiFirst® (la Réunion). The clinical pregnancy rate for carriers of balanced chromosomal rearrangements and Y-chromosome microdeletions was 28% and 43% respectively. The clinical pregnancy rate for the controls was 24% (non-significant difference). According to this study, balanced chromosomal rearrangements and Y-chromosome microdeletions are not found to affect the clinical pregnancy rate in conventional ART. Further larger scale studies are required to confirm these results.

A comprehensive and universal approach for embryo testing in patients with different genetic disorders.

Background In vitro fertilization (IVF) with preimplantation genetic testing (PGT) has markedly improved clinical pregnancy outcomes for carriers of gene mutations or chromosomal structural rearrangements by the selection of embryos free of disease‐causing genes and chromosome abnormalities. However, for detecting whole or segmental chromosome aneuploidies, gene variants or balanced chromosome rearrangements in the same embryo require separate procedures, and none of the existing detection platforms is universal for all patients with different genetic disorders.MethodsHere, we report a cost‐effective, family‐based haplotype phasing approach that can simultaneously evaluate multiple genetic variants, including monogenic disorders, aneuploidy, and balanced chromosome rearrangements in the same embryo with a single test. A total of 12 monogenic diseases carrier couples and either of them carried chromosomal rearrangements were enrolled simultaneously in this present study. Genome‐wide genotyping was performed with single‐nucleotide polymorphism (SNP)‐array, and aneuploidies were analyzed through SNP allele frequency and Log R ratio. Parental haplotypes were phased by an available genotype from a close relative, and the embryonic genome‐wide haplotypes were determined through family haplotype linkage analysis (FHLA). Disease‐causing genes and chromosomal rearrangements were detected by haplotypes located within the 2 Mb region covering the targeted genes or breakpoint regions.ResultsTwelve blastocysts were thawed, and then transferred into the uterus of female patients. Nine pregnancies had reached the second trimester and five healthy babies have been born. Fetus validation results, performed with the amniotic fluid or umbilical cord blood samples, were consistent with those at the blastocyst stage diagnosed by PGT.ConclusionsWe demonstrate that SNP‐based FHLA enables the accurate genetic detection of a wide spectrum of monogenic diseases and chromosome abnormalities in embryos, preventing the transfer of parental genetic abnormalities to the fetus. This method can be implemented as a universal platform for embryo testing in patients with different genetic disorders.

Chromosomal analysis for embryos from balanced chromosomal rearrangement carriers using next generation sequencing.

We aimed to use next generation sequencing (NGS) to investigate chromosomal abnormalities in blastocyst trophectoderm (TE) samples, and reproductive outcomes with the different types of chromosomal rearrangements (CR) and for each sex of CR carrier. A total of 1189 blastocyst TE samples were evaluated using NGS to detect chromosomal unbalanced translocations as well as aneuploidy, including blastocytes from 637 blastocysts from carriers of balanced CRand 552 blastocysts from carriers of normal chromosomes. The optimal embryos had lower chromosomal abnormality rates compared to the poor-quality embryos. The experimental group had significantly reduced rates of normal embryos and euploidy, and higher rates of total abnormalities, aneuploidy and unbalanced chromosomal aberrations. Carriers of reciprocal translocationshad a reduced rate of normal embryos and an increased percentage of embryos with total abnormalities and unbalanced chromosomal aberrations compared with carriers of Robertsonian translocations. Couples with female carriers of chromosomal abnormalities had significantly reduced rates of normal embryos and euploidy, and a higher percentage of embryos with total abnormalities, aneuploidy, and unbalanced chromosomal aberrations compared with couples of male carriers. Our preimplantation genetic testing (PGT) study identified higher rates of chromosomal abnormalities, including chromosomal unbalanced translocations and aneuploidy, in blastocysts from CR carriers, especially from the female carriers, in a Chinese population. The PGT cycles successfully improved clinical outcomes by increasing the fertilization rate and reducing the early spontaneous abortion rate compared with the in vitro fertilization and intracytoplasmic sperm injection cycles, especially for CR carriers.

Clinical outcomes following preimplantation genetic testing and microdissecting junction region in couples with balanced chromosome rearrangement

PurposeThe purpose of this study is to summarize the clinical outcomes of apparently balanced chromosome rearrangement (ABCR) carriers in preimplantation genetic testing (PGT) cycles by next-generation sequencing following microdissecting junction region (MicroSeq) to distinguish non-carrier embryos from balanced carriers.MethodsA retrospective study of 762 ABCR carrier couples who requested PGT for structural rearrangements combined with MicroSeq at the Reproductive and Genetic Hospital of CITIC-Xiangya was conducted between October 2014 and October 2019.ResultsTrophectoderm biopsy was performed in 4122 blastocysts derived from 917 PGT-SR cycles and 3781 blastocysts were detected. Among the 3781 blastocysts diagnosed, 1433 (37.9%, 1433/3781) were balanced, of which 739 blastocysts were carriers (51.57%, 739/1433) and 694 blastocysts were normal (48.43%, 694/1433). Approximately 26.39% of cycles had both carrier and normal embryo transfer, and the average number of biopsied blastocysts was 6.7. In the cumulative 223 biopsied cycles with normal embryo transfer, all couples chose to transfer the normal embryos. In the 225 cycles with only carrier embryos, the couples chose to transfer the carrier embryos in 169/225 (75.11%) cycles. A total of 732 frozen embryo transfer cycles were performed, resulting in 502 clinical pregnancies. Cumulatively, 326 babies were born; all of these babies were healthy and free of any developmental issues.ConclusionOur study provides the first evaluation of the clinical outcomes of a large sample with ABCR carrier couples undergoing the MicroSeq-PGT technique and reveals its powerful ability to distinguish between carrier and non-carrier balanced embryos.

Criteria to evaluate patterns of segmental and complete aneuploidies in preimplantation genetic testing for aneuploidy results suggestive of an inherited balanced translocation or inversion

ObjectiveTo define criteria for determining when preimplantation genetic testing for aneuploidy (PGT-A) results are suggestive of a potential balanced chromosomal rearrangement in the egg or sperm source and warrant karyotyping.DesignPerformance evaluation of criteria developed to assess PGT-A results for patterns of imbalances suggestive of a balanced chromosomal rearrangement in the egg or sperm source.SettingA single PGT-A laboratory and multiple in vitro fertilization centers.PatientsReproductive couples who underwent routine PGT-A testing.InterventionsKaryotyping of reproductive couples for whom patterns of imbalances observed in PGT-A results suggested a balanced chromosomal rearrangement in the egg or sperm source.Main Outcome MeasuresCorrect or incorrect flagging of predicted translocation in either the egg or sperm source based on chromosome analysis.ResultsProposed criteria correctly predicted a balanced reciprocal translocation in 97% of cases (n = 33), a (13;14) Robertsonian translocation in all cases (n = 3), and an inversion in all cases (n = 2). Other criteria evaluated were determined to be ineffective because of relatively low occurrences that met the criteria and/or low predictive value.ConclusionsOur results showed that the proposed criteria were effective for evaluating patterns of imbalances observed in PGT-A results suggestive of a potential chromosomal rearrangement in the egg or sperm source. Our proposed criteria can be employed by clinicians in the in vitro fertilization setting in combination with a patient’s reproductive history to identify PGT-A patients who are likely carriers of balanced chromosomal rearrangements.

Simple FISH-based evaluation of spermatic nuclear architecture shows an abnormal chromosomal organization in balanced chromosomal rearrangement carriers.

Interphasic DNA has a constant three-dimensional conformation, which is particularly striking for spermatic DNA, with distinct chromosomal territories and a constant chromosomal conformation. We hypothesized that this organization is fragile, and that an excess or a lack of chromosomal segments could hinder the genomic structure as a whole. Five human male chromosomal translocation carriers and five controls were included. Spermatic DNA spatial organization was studied, in both balanced and unbalanced spermatozoa, with two-dimensional fluorescent in situ hybridization (FISH) via analysis of chromosomes not implicated in the cases' translocations, compared to that of normal controls. Two parameters were studied: the distance between the two telomeric ends of chromosome 1, and the area of the chromosomal territories of chromosomes 1 and 17. Sperm FISH analysis of rearrangement carriers revealed changes in the nuclear architecture compared to that of controls. Inter-telomeric distance and chromosomal territories areas were both significantly increased. We show that an excess or lack of chromosomal segments can hinder the normal spatial nuclear architecture in sperm. These results show that nuclear architecture is a fragile assembly, and that local chromosomal abnormalities may impact the nucleus as a whole. This suggests a potential avenue for selection of spermatozoa prior to in vitro fertilization, not only in rearrangement carriers but also in the infertile population at large. Furthermore, we suggest that 2D-FISH could possibly be a useful tool in assessing spermatic nuclear organization in a way to evaluate male fertility.

57. ADDITIONAL DATA FOR CONTROVERSIAL INTER-CHROMOSOMAL EFFECT SUSCEPTIBILITY IN PGT-SR PATIENTS

Introduction NGS based translocation testing has been widely used as the possibility of detecting other chromosomal aneuploidies. Some studies claimed that balanced translocation carriers may have an increased risk for aneuploidies unrelated to translocation due to inter-chromosomal effect (ICE). Translocation causes unusual segregation of chromosomes involved in translocation. Furthermore this rearrangement may have an effect on the segregation of other structurally normal chromosomes during meiosis. Here we present a report of aneuploidy and complex aneuploidy rates among the embryos derived from patients carrying balanced chromosomal rearrangements (reciprocal or robertsonian translocations). Materials and Methods Whole Genome Amplification (WGA) was performed using SurePlex DNA Amplification System (Illumina, USA) and DOPlify (PerkinElmer Health Sciences - Australia). on biopsied cells. Veriseq PGS kit was used for further processing of WGA samples. BlueFuse Multi Software was used to analyse the data obtained from Miseq System. Results In this study, we collected 705 embryos from 168 patients with an average age of 31. At least one of the couples was previously reported to be a translocation carrier. According to our findings, 25.6% of these embryos was euploid and 69,4% was aneuploid/complex aneuploid (mosaic embryo results were excluded). 29.33% aneuploidy was detected in translocation of interest only. The rest (39.43%) was due to aneuploidy of other chromosomes . According to our in house PGT-A data (7200 embryos collected from 2177 patients) sum of aneuploidy and complex aneuploidy rates was 45.8. Overall these results fail to provide any support for the presence of an ICE. Conclusion In balanced chromosomal rearrangement carriers PGD by NGS array not only detects unbalanced chromosomal rearrangements due to chromosomes involved in translocation but also detects the possibility of other chromosomal aneuploidies. According to our findings, aneuploidy and complex aneuploidy rates do not increase in the embryos obtained from PGT-SR group of patients. Moreover, in addition to translocation chromosomes, we observed an additional aneuploidy risk related to other chromosomes in these embryos. Our data supports previous studies suggesting that ICE in embryos derived from balanced chromosomal rearrangement carriers is elusive. On the other hand average maternal age of PGT-A patients is significantly higher than PGT-SR group (35.1 vs 31.2 respectively). Although it is thought that increased maternal age may cause aneuploidy in some of the cases, some embryos have an increased aneuploidy rate regardless of maternal age. Nevertheless euploid embryo ratio in PGT-SR group is compared to PGT-A is relatively lower (25.6 vs 36.7) thus our results emphasize the importance of 24 chromosome scan in embryos derived from balanced translocation carriers NGS based translocation testing has been widely used as the possibility of detecting other chromosomal aneuploidies. Some studies claimed that balanced translocation carriers may have an increased risk for aneuploidies unrelated to translocation due to inter-chromosomal effect (ICE). Translocation causes unusual segregation of chromosomes involved in translocation. Furthermore this rearrangement may have an effect on the segregation of other structurally normal chromosomes during meiosis. Here we present a report of aneuploidy and complex aneuploidy rates among the embryos derived from patients carrying balanced chromosomal rearrangements (reciprocal or robertsonian translocations). Whole Genome Amplification (WGA) was performed using SurePlex DNA Amplification System (Illumina, USA) and DOPlify (PerkinElmer Health Sciences - Australia). on biopsied cells. Veriseq PGS kit was used for further processing of WGA samples. BlueFuse Multi Software was used to analyse the data obtained from Miseq System. In this study, we collected 705 embryos from 168 patients with an average age of 31. At least one of the couples was previously reported to be a translocation carrier. According to our findings, 25.6% of these embryos was euploid and 69,4% was aneuploid/complex aneuploid (mosaic embryo results were excluded). 29.33% aneuploidy was detected in translocation of interest only. The rest (39.43%) was due to aneuploidy of other chromosomes . According to our in house PGT-A data (7200 embryos collected from 2177 patients) sum of aneuploidy and complex aneuploidy rates was 45.8. Overall these results fail to provide any support for the presence of an ICE. In balanced chromosomal rearrangement carriers PGD by NGS array not only detects unbalanced chromosomal rearrangements due to chromosomes involved in translocation but also detects the possibility of other chromosomal aneuploidies.

The application of PGT-A for carriers of balanced structural chromosomal rearrangements

The aim of this study was to analyze differences in chromosomal aberrations and euploidy in embryos of each translocation type and gender of carrier in the case series of 10 couples with balanced translocations who underwent IVF with embryos trophectoderm (TE) biopsy and PGT-A to detect chromosomal aberrations. This is a Case Series (Retrospective study). In each case, controlled ovarian hyperstimulation, oocyte insemination with intracytoplasmic sperm injection (ICSI) and cultivation gave multiple blastocysts, that underwent trophectoderm (TE) biopsy with PGT-A analysis using aCGH and NGS. Number of total unbalanced translocations compared to the number of sporadic aneuploid embryos was 39.6% to 39.6% (50% to 50% of all 37 aneuploid embryos). The highest euploidy rate was in male carrier group – 26.7% and the lowest in the Robertsonian translocation carrier group – 18.2%. Sporadic aneuploidy – 68.2% was highest in Robertsonian translocation carrier group and lowest in female group – 11.1%. Chromosomal aberrations related to translocation were highest in female carrier group – 77.8% and lowest in Robertsonian translocation carrier group – 13.6%. Our study showed that expectancy of total embryo aneuploidy rates will be higher in carriers, than in people with normal karyotype. The prevalence of chromosomal aberrations related to translocation was 4.5 times higher in Reciprocal carrier group than in Robertsonian translocation carrier group. Among maternal and paternal carrier groups, the embryos from female carriers had the lowest euploidy rate, unbalanced translocation rate 4.7 times higher than in the male carrier group and higher total aneuploidy rates.

Results of preimplantation genetic testing for aneuploidies as a basis for parental karyotypes correction

Introduction Chromosomal abnormalities are the most common genetic cause of infertility. An information about karyotypes of patients undergoing in vitro fertilization (IVF) is not always known. Therefore, IVF patients can be potential carriers of structural chromosomal rearrangements. We report three cases, in which results of preimplantation genetic testing for aneuploidies (PGT-A) allowed us to suspect the presence of parental reciprocal translocations. In each case, the parental reciprocal translocation was confirmed. Material & Methods PGT-A was performed by microarray comparative genomic hybridization (aCGH) (24sure, Illumina) or by next generation sequencing (NGS) (VeriSeq, Illumina). Indications for preimplantation testing were advanced maternal age (case 1 and 2) and paternal pericentric inversion of chromosome 10 (case 3). Parental karyotypes were not known before PGT-A in cases 1 and 2. In case 3 patients’ karyotypes was known before PGT-A and were 46,XX and 46,XY,inv(10)(p11.2;q22). The trophectoderm biopsy was performed at 5-6 day of embryo development. Analysis of parental karyotypes after obtaining PGT results was performed by standard cytogenetic study or by fluorescence in situ hybridization (FISH) on peripheral blood lymphocyte culture. The choice of method of parental karyotypes analysis was determined by size of the embryo chromosomal imbalance. Results PGT-A results showed a nonrandom pattern of segmental loses and gains in each case (table 1). These facts were the basis for parental karyotypes analysis. It was confirmed, that in each case one of the couple was the carrier of reciprocal translocation. In case 1 a paternal reciprocal translocation between chromosomes 11 and 22 was found – 46,XY,t(11;22)(q23.3;q13). In case 2 a maternal reciprocal translocation between chromosomes 10 and 12 was found – ish t(10;12)(D10S2290-, D12S158+; D10S2290+, D12S158-). In case 3 a maternal reciprocal translocation between chromosomes 2 and 12 was found - ish t(2;12)(D2S2147-,D12S399+; D2S2147+, D12S399-). Table 1 Case № Number of embryos Number of embryos with nonrandom pattern of segmental abnormalities Chromosomes involved in nonrandom segmental abnormalities Case 1 5 3 Chromosomes 11 and 22 Case 2 4 4 Chromosomes 10 and 12 Case 3 4 3 Chromosomes 2 and 12 Conclusions It is very importantto draw attention to pattern of segmental chromosomal abnormalities of embryos. 24-chromosome aneuploidy testing is not only an actual method for detection of embryo chromosomal imbalance, but in some cases also can help to correct parental karyotypes.

Analysis of cytogenetic characteristics and fertility of carriers of complex chromosomal rearrangements from Henan region

To explore cytogenetic characteristics and fertility of carriers of complex chromosome rearrangements (CCR) from Henan region. G-banded karyotyping analysis was carried out on peripheral blood lymphocytes derived from 160 601 patients with reproductive abnormalities. Relevant literature was retrieved from domestic and overseas databases. Cytogenetic characteristics and clinical data of CCR carriers were analyzed. Twenty-seven CCR carriers were identified among the 160 601 patients. In addition, 6 cases were identified from the database research. Among the 33 CCR carriers, there were 17 three- and four-way exchange cases (51.5%), 10 double two-way exchange cases (30.3%), and 6 unusual CCRs (18.2%). Infertility was noted in 14 (42.4%) of the CCR carries. A total of 38 pregnancies were achieved in the remaining 19 cases (57.6%), among which spontaneous abortions or embryonic losses have occurred in 89.5% (34/38), multiple congenital abnormalities have occurred in 7.9% (3/38), while phenotypically normal offspring have occurred in 2.6% (1/38). Chromosomes 1, 11, 2, 4, 5 and 12 were more frequently involved, with their breakpoints occurred more than 3 times at 1p22, 11q23, 12p13 and 22q11. CCR carriers are at a higher risk for abnormal pregnancies. Even for those with normal pregnancy, prenatal diagnosis should be provided. Chromosomes and their breakpoints involved in CCR may affect the fertility of CCR carriers. Analyzing the types of CCR and involved chromosomes and breakpoints can facilitate genetic counseling for CCR carriers.

Clinical outcomes in carriers of complex chromosomal rearrangements: a retrospective analysis of comprehensive chromosome screening results in seven cases

To evaluate the clinical outcomes in carriers of complex chromosomal rearrangements (CCRs). Case series. An institute for reproductive and stem cell engineering. Seven couples with CCRs. Assisted reproduction with preimplantation genetic diagnosis (PGD). PGD results, embryo rating, pregnancy outcomes. In cases 1, 2, 3, 4, 5, and 6, each woman underwent one cycle of PGD. Case 7 underwent two PGD cycles. We obtained 51 blastocysts from seven couples with CCR, of which 47 were eligible for biopsy; only 3 (5.9%) were normal/balanced, and 2 (3.9%) conceptions resulted. One healthy baby girl was born (the other was not yet born at the time of publication). Karyotyping revealed that the healthy baby girl was 46,XX. Although the patient with both a balanced translocation and a CCR (case 7) had 12 embryos available for biopsy, all were chromosomally unbalanced. It is interesting that 22 (57.9%) of the total 38 blastocysts were of high quality for type A CCRs, and 2 (15.4%) of the total 13 blastocysts were of high quality for type B CCR at day 6 after fertilization. The chances of identifying normal/balanced blastocysts in patients with CCR are <6%; the chances of a pregnancy are <4%. Greater complexity CCRs result in fewer transplantable embryos. Moreover, CCRs of greater complexity have a lower rate of high quality blastocysts than CCRs of less complexity.

Reproductive Outcomes in 101 Couples with Balanced Chromosomal Rearrangements

Background: There are very few studies on reproductive outcomes in couples with balanced chromosomal translocations. Findings of such studies can shed light on the possible future outcomes and help in genetic counselling. Objectives: The overall objectives of this study were to report the various chromosomal balanced rearrangements in couples with history of bad reproductive history, to analyse the reproductive outcomes prior to the evaluation and to compare the chromosomal findings with the similar available data from literature. Methods: Reproductive history of couples identified with balanced chromosomal translocations at Genetic Health and Research Centre, Nashik was studied retrospectively, and the various pregnancy outcomes were tabulated and compared with the available literature data. Results: Out of 1580 couples investigated for chromosomal abnormalities for the various indications like recurrent miscarriages, infertility, intrauterine deaths, stillbirths, children with birth defects and neonatal deaths, 101 (6.39%) were found to be carriers of balanced chromosomal rearrangements. A total of 334 pregnancies (average 3.2) were documented in all these carriers. The mean maternal age at the time of evaluation was 29.4 years. Various reproductive outcomes documented were pregnancy losses in 290 couples (2.87 per couple), abnormal births in 25 couples, infertility in 9 couples and normal birth in 19 couples. Conclusion: Karyotyping of couples with bad reproductive outcomes is highly useful for further genetic counselling, appropriate management and close monitoring in subsequent pregnancies. Carriers of balanced chromosomal translocations have better chances of having a normal live birth, however the risk of having the birth of offspring with chromosomal abnormality need to be taken into consideration and prenatal diagnosis offered in all future viable pregnancies.