Balanced Translocation Carriers Research Articles

Comprehensive preimplantation genetic testing for balanced insertional translocation carriers

BackgroundBalanced insertional translocations (BITs) can increase the risk of infertility, recurrent miscarriages or neonatal birth defects due to chromosomal imbalances in gametes. However, studies on preimplantation genetic testing (PGT) for...

Analysis of Preimplantation and Clinical Outcomes of Two Cases by Oxford Nanopore Sequencing.

It is challenging to distinguish embryos with a balanced translocation karyotype from a normal karyotype by existing conventional genetic testing methods. However, in germ-cell gamete generation, chromosome exchange and separation through cell meiosis form a different proportion of unbalanced gametes. Adverse birth events may occur, such as repeated miscarriages and fetal birth defects. In this study, the exact breakpoints of structural variation (SV) from two balanced translocation carrier families by using Nanopore long reads sequencing technology were obtained, and haplotype analysis and Sanger verified the accuracy of the detection results, confirming the application value of the Nanopore sequencing technology in the detection of balanced translocation before embryo implantation. Nanopore long-read sequencing was performed to find the precise breakpoint of chromosome-balanced translocation carriers. The breakpoints were subsequently verified by designing primers across the breakpoints and Sanger sequencing. Haplotype linkage analysis of SNPs which can be linked by a read block of families around the breakpoint regions was followed. After frozen (-thawed) embryo transfer (FET), prenatal cytogenetic analysis of amniotic fluid cells confirmed the predicted karyotypes from the transferred embryos. The presence of breakpoints was detected in three embryos of patient 1. No breakpoints were detected in either embryo of patient 2. One balanced translocated embryo from patient 1 and one normal euploid embryo from patient 2 were transplanted back into the patients, and amniotic fluid cells were analyzed for the karyotype of fetuses. The results were entirely consistent with the fetal karyotype. And through late follow-up, both patients successfully had a live birth fetus. The breakpoint location of the balanced chromosome translocation can be accurately found by Nanopore sequencing. The haplotype of carriers can be successfully constructed by Nanopore and sanger sequencing confirmed that the results were accurate. This is very advantageous for preimplantation genetic testing for chromosomal structural rearrangements (PGT-SR) detection in the families without proband.

Identification of cryptic balanced translocations in couples with unexplained recurrent pregnancy loss based upon embryonic PGT-A results.

The goal of this study is to determine whether any balanced translocation (BT) had been missed by previous karyotyping in patients with unexplained recurrent pregnancy loss (uRPL). This case series included 48 uRPL-affected couples with normal karyotypes. The embryos from these couples have all undergone preimplantationtesting for aneuploidies (PGT-A). Based on the PGT-A's results, 48 couples could be categorized into two groups: 17 couples whose multiple embryos were detected with similar structural variations (SVs, segmental/complete) and 31 couples without such findings but who did not develop any euploid embryo despite at least three high-quality blastocysts being tested. The peripheral blood sample of each partner was then collected for mate-pair sequencing (MPseq) to determine whether any of them were BT carriers. MPseq analyses identified 13 BTs in the 17 couples whose multiple embryos had similar SVs detected (13/17, 76.47%) and three BTs in the 31 couples without euploid embryo obtained (3/31, 9.7%). Among the 16 MPseq-identified BTs, six were missed due to the limited resolution of G-bandingkaryotyping analysis, and the rest were mostly owing to thesimilar banding patterns and/or comparable sizes shared by the two segments exchanged. A normal karyotype does not eliminate the possibility of carrying BT for couples with uRPL. The use of PGT-A allows us to perceive the "carrier couples" missed by karyotyping analysis, providing an increased risk of finding cryptic BTs if similar SVs are always detected on two chromosomes among multiple embryos. Nonetheless, certain carriers with translocated segments of sub-resolution may still go unnoticed.

Preimplantation genetic testing using comprehensive genomic copy number analysis is beneficial for balanced translocation carriers.

Balanced chromosomal translocation is one of chromosomal variations. Carriers of balanced chromosomal translocations have an increased risk of spontaneous miscarriage. To avoid the risk, preimplantation genetic testing (PGT) using comprehensive genomic copy number analysis has been developed. This study aimed to verify whether and how embryos from couples in which one partner is a balanced translocation carrier have a higher ratio of chromosomal abnormalities. A total of 894 biopsied trophectoderms (TEs) were obtained from 130 couples in which one partner was a balanced translocation carrier (Robertsonian translocation, reciprocal translocation, or intrachromosomal inversion) and grouped as PGT-SR. Conversely, 3269 TEs from 697 couples who experienced recurrent implantation failure or recurrent pregnancy loss were included in the PGT-A group. The transferable blastocyst ratio was significantly lower in the PGT-SR group, even when bias related to the sample number and patient age was corrected. Subgroup analysis of the PGT-SR group revealed that the transferable blastocyst ratio was higher in the Robertsonian translocation group. Because the PGT-SR group had a higher proportion of untransferable embryos than the PGT-A group, PGT using comprehensive genomic copy number analysis was more beneficial for balanced translocation carriers than for infertility patients without chromosomal translocations. The frequencies of de novo aneuploidies were further analyzed, and the frequency in the PGT-SR group was lower than that in the PGT-A group. Therefore, we could not confirm the existence of interchromosomal effects in this study.

Prenatal cfDNA Screening for Emanuel Syndrome and Other Unbalanced Products of Conception in Carriers of the Recurrent Balanced Translocation t(11;22): One Laboratory's Retrospective Experience.

Prenatal cell-free DNA screening (cfDNA) can identify fetal chromosome abnormalities beyond common trisomies. Emanuel syndrome (ES), caused by an unbalanced translocation between chromosomes 11 and 22, has lacked a reliable prenatal screening option for families with a carrier parent. A cohort of cases (n = 46) sent for cfDNA screening with indications and/or results related to ES was queried; diagnostic testing and pregnancy outcomes were requested and analyzed. No discordant results were reported or suspected; there were ten true positives with diagnostic confirmation, six likely concordant positives based on known translocations and consistent cfDNA data, and twenty-six true negatives, by diagnostic testing or birth outcomes. For cases with parental testing, all affected ES cases had maternal translocation carriers. Expanded cfDNA may provide reassurance for t(11;22) carriers with screen negative results, and screen positive results appear to reflect a likely affected fetus, especially with a known maternal translocation. Current society guidelines support the use of expanded cfDNA screening in specific circumstances, such as for translocation carriers, with appropriate counseling. Diagnostic testing is recommended for prenatal diagnosis of ES and other chromosome abnormalities in pregnancy. To our knowledge, this cohort is the largest published group of cases with prenatal screening for carriers of t(11;22).

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.

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.

Outcomes of two different unbalanced segregations from a maternal t(4;10)(q33;p15.1) translocation

BackgroundUnbalanced translocations can cause developmental delay (DD), intellectual disability (ID), growth problems, dysmorphic features, and congenital anomalies. They may arise de novo or may be inherited from a parent carrying a balanced rearrangement. It is estimated that 1/500 people is a balanced translocation carrier. The outcomes of different chromosomal rearrangements have the potential to reveal the functional consequences of partial trisomy or partial monosomy and can help guide genetic counseling for balanced carriers, and other young patients diagnosed with similar imbalances.MethodsWe performed clinical phenotyping and cytogenetic analyses of two siblings with a history of developmental delay (DD), intellectual disability (ID) and dysmorphic features.ResultsThe proband, a 38-year-old female, has a history of short stature, dysmorphic features and aortic coarctation. She underwent chromosomal microarray analysis, which identified partial monosomy of 4q and partial trisomy of 10p. Her brother, a 37-year-old male, has a history of more severe DD, behavioral problems, dysmorphic features, and congenital anomalies. Subsequently, karyotype confirmed two different unbalanced translocations in the siblings: 46,XX,der(4)t(4;10)(q33;p15.1) and 46,XY,der(10)t(4;10)(q33;p15.1), respectively. These chromosomal rearrangements represent two possible outcomes from a parent who is a carrier for a balanced translocation 46,XX,t(4;10)(q33;p15.1).ConclusionTo our knowledge, this 4q and 10p translocation has not been described in literature. In this report we compare clinical features due to the composite effects of partial monosomy 4q with partial trisomy 10p and partial trisomy 4q with partial monosomy 10p. These findings speak to the relevance of old and new genomic testing, the viability of these segregation outcomes, and need for genetic counseling.

Cytogenetics evaluation of 261 couples with first-trimester recurrent pregnancy loss: A prevalent case–control study

Introduction: Recurrent pregnancy loss (RPL) is a common occurrence which affects approximately 15-20% of couples. Chromosomal abnormality is an important cause of recurrent abortions especially if either of the partner is a carrier of balanced translocation. The current study aimed to determine the prevalence of chromosomal abnormalities in couples suffering from first trimester RPL and compare with normal control. Materials and Methods: A prospective case-control study, in which 261 couples with history of two or more abortions were evaluated for various chromosomal abnormalities; and compared with 190 healthy couples with no history of abortion and at least one normal biological child. Peripheral blood T-lymphocytes were cultured using RPMI-1640 medium for obtaining metaphases and chromosomal analysis. SPSS software and Student's t test were used. p value < 0.05 was considered statistically significant. Results: Among 261 couples in RPL group, 240(91.95%) had normal karyotype, 17(6.51%) had major chromosomal abnormalities and 04(1.53%) had polymorphic variants. Most of the couples had two abortions (39.8%). Females were more commonly affected with M:F=0.214. Structural abnormalities (n=12,70.59%) were more frequent than numerical abnormalities (n=5,29.41%). There was no statistical correlation between age, number of abortions and major chromosomal abnormalities (p=0.06). Conclusion: Chromosomal aberrations in carrier parents, predispose them to RPL and can also be transmitted to the offspring which may results in imbalance in their genetic constitution, thus justifying the requirement of cytogenetic testing in these patients.

Citogenetička analiza odabranih genetski uvjetovanih bolesti u istočnoj Slovačkoj

This work presents the results of cytogenetic analysis performed during the period 1990-2021. The work focuses on cytogenetic analysis of selected diseases that represent a serious medical and social problem in the Prešov region of eastern Slovakia. The analysis also included the determination of cytogenetic and molecular-genetic marker frequency related to selected clinical genetic diseases in a specified population of Roma ethnicity. Chromosome analysis confirmed a wide spectrum of chromosomal aberrations in patients with Down’s syndrome and Turner syndrome, revealing a spectrum of aberrations from monosomy X, isochromosome Xq, and deletions Xp to marker chromosomes. Chromosomal aberrations cause 5.5% of fertility disorders in couples, with numerical and structural chromosomal aberrations found in 2.1 and 3.4% respectively, revealing a risk finding for offspring of carriers of balanced translocations. Microdeletions, combined microdeletions (AZFb,c) and complete deletion of the AZF region of the Y chromosome were found in men diagnosed with azoospermia. In addition, pathological karyotypes were detected in men and women (13 and 10%). Another set of analyses in patients with onco-haematological diseases revealed presence of Philadelphia chromosome (Ph1) in 94.4% of patients with chronic myeloid leukaemia, complex translocation of chromosomes 8, 9, 22; mosaic karyotype of Ph1. Chromosomal aberrations in patients with myelodysplastic syndrome also included also atypical and as yet unpublished cytogenetic markers. Myeloproliferative diseases were detected in 28.3% of patients with heterogenous chromosomal aberrations. Revelations from cytogenetic analysis enable improvement in the efficiency of health care, diagnostics, therapeutic significance and prognosis of affected people in the majority population and Roma minority in this region of Slovakia.

Reproductive Risk Estimation Calculator for Balanced Translocation Carriers.

Balanced translocation carriers experience elevated reproductive risks, including pregnancy loss and children with anomalies due to generating chromosomally unbalanced gametes. While understanding the likelihood of producing unbalanced conceptuses is critical for individuals to make reproductive decisions, risk estimates are difficult to obtain as most balanced translocations are unique. To improve reproductive risk estimates, Drs. Trunca and Mendell created models based on a logistic regression analysis of a dataset of over 6000 individuals from over 1000 translocation families. While risk assessments using these models have been offered as a free service for years, this protocol aims to create a sustainable model for genetics professionals to obtain risk estimates for their patients directly. This protocol guides the user through collecting clinical information, using a risk-generating Java program based on the models, and interpreting the program outputs. A practice tutorial is provided to ensure competency in interpretation prior to use. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Estimation of reproductive risks for balanced translocation carriers Basic Protocol 2: Practical examples of typical patient encounters with instructive interpretations.

Detection of a Cryptic 25bp Deletion and a 269Kb Microduplication by Nanopore Sequencing in a Seemingly Balanced Translocation Involving the LMLN and LOC105378102 Genes.

Preimplantation genetic testing plays a critical role in enabling a balanced translocation carrier to obtain the normal embryo. Identifying the precise breakpoints for the carriers with phenotypic abnormity, allows us to reveal disrupted genes. In this study, a seemingly balanced translocation 46, XX, t (3; 6) (q29; q26) was first detected using conventional karyotype analysis. To locate the precise breakpoints, whole genomes of DNA were sequenced based on the nanopore GridION platform, and bioinformatic analyses were further confirmed by polymerase-chain-reaction (PCR) and copy number variation (CNV). Nanopore sequencing results were consistent with the karyotype analysis. Meanwhile, two breakpoints were successfully validated using polymerase-chain-reaction and Sanger Sequencing. LOC105378102 and LMLN genes were disrupted at the breakpoint junctions. Notably, observations found that seemingly balanced translocation was unbalanced due to a cryptic 269 kilobases (Kb) microduplication and a 25 bp deletion at the breakpoints of chromosome (chr) 6 and chr 3, respectively. Furthermore, 269 Kb microduplication was also confirmed by copy number variation analyses. In summary, nanopore sequencing was a rapid and direct method for identifying the precise breakpoints of a balanced translocation despite low coverage (3.8×). In addition, cryptic deletion and duplication were able to be detected at the single-nucleotide level.

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

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. We retrospectively analyzed 1942 preimplantation genetic testing for structural rearrangements (PGT-SR) cycles of 1505 balanced autosomal translocation couples over 8years. 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. 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. 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.

Application of CNV-seq and chromosomal karyotyping in the prenatal diagnosis for carriers of balanced translocations

To assess the value of copy number variation sequencing (CNV-seq) and karyotyping in the prenatal diagnosis for carriers of balanced translocations. Clinical records of 135 amniocentesis samples of balanced translocation carriers undergoing simultaneous CNV-seq and karyotyping were analyzed. Chromosomal aberrations were defined as those can definitely lead to birth defects definitely, which included chromosomal numerical abnormality, large deletion/duplication and pathogenic copy number variations (pCNVs). The detection rates for karyotyping and CNV-seq were 4.44% (6/135) and 5.93% (8/135) respectively, and the latter had a detection rate of 1.48(2/135) higher than the former. A total of 68 fetal chromosomal translocations were detected by karyotying analysis. For couples carrying a balanced translocation, simultaneous CNV-seq and karyotyping is conducive to the detection of fetal chromosomal abnormalities and genetic counseling.

Genome wide noninvasive prenatal testing detects microduplication of the distal end of chromosome 15 in a fetus: a case report

BackgroundNoninvasive prenatal testing (NIPT) is the most recent modality widely used in prenatal diagnostics. Commercially available NIPT has high sensitivity and specificity for the common fetal chromosomal aneuploidies. As future advancements in NIPT sequencing technology are becoming promising and more reliable, the ability to detect beyond aneuploidies and to expand detection of submicroscopic genomic alterations, as well as single-gene disorders might become possible.Case presentationHere we present a case of a 34-year-old pregnant woman, G2P1, who had NIPT screening which detected a terminal microduplication of 10.34 Mb on the long arm of chromosome 15 (15q26.1q26.3). Subsequent prenatal diagnostic testing including karyotype, microarray and fluorescence in situ hybridization (FISH) analyses were performed. Microarray testing confirmed and particularized a copy number gain of 10.66 Mb of the distal end of the long arm of chromosome 15. The G-banding cytogenetic studies yielded results consistent with unbalanced translocation between chromosome 15 and 18. To further characterize the abnormality involving the long arm of chromosome 18 and to map the genomic location of the duplicated 15q more precisely, FISH analysis using specific sub-telomeric probes was performed. FISH analysis confirmed that the extra duplicated segment of chromosome 15 is translocated onto the distal end of the long arm of chromosome 18 at band 18q23. Parental karyotype and FISH studies were performed to see if this unbalanced rearrangement was inherited from a healthy balanced translocation carrier versus being a de novo finding. Parental chromosomal analysis provided no evidence of a rearrangement between chromosome 15 and chromosome 18. The final fetal karyotype was reported as 46,XX,der(18)t(15;18)(q26.2;q23)dn.ConclusionsIn this case study, the microduplication of fetal chromosome 15q26.1q26.3 was accurately detected using NIPT. Our results suggest that further refinements in NIPT have the potential to evolve to a powerful and efficient screening method, which might be used to detect a broad range of chromosomal imbalances. Since microduplications and microdeletions are a potential reportable result with NIPT, this must be included in pre-test counseling. Prenatal diagnostic testing of such findings is strongly recommended.

New insights regarding origin of monosomy occurrence in early developing embryos as demonstrated in preimplantation genetic testing

IntroductionAnalyses of miscarriage products indicate that the majority of aneuploidies in early developing embryos derive from errors occurring during maternal meiosis and the paternal contribution is less than 10%. Our aim was to assess the aneuploidy (mainly monosmies) frequencies at the earliest stages of embryo development, 3 days following fertilization during In vitro fertilization (IVF) treatments and to elucidate their parental origin. Later, we compared monosomies rates of day 3 to those of day 5 as demonstrated from Preimplantation Genetic Testing for Structural chromosomal Rearrangement (PGT-SR) results.MethodsFor a retrospective study, we collected data of 210 Preimplantation Genetic Testing for Monogenic Disorder (PGT-M) cycles performed between years 2008 and 2019.This study includes 2083 embryos, of 113 couples. It also included 432 embryos from 90 PGT-SR cycles of other 45 patients, carriers of balanced translocations. Defining the parental origin of aneuploidy in cleavage stage embryos was based on haplotypes analysis of at least six informative markers flanking the analyzed gene. For comprehensive chromosomal screening (CCS), chromosomal microarray (CMA) and next generation sequencing (NGS) was used.ResultsWe inspected haplotype data of 40 genomic regions, flanking analyzed genes located on 9 different chromosomes.151 (7.2%) embryos presented numerical alterations in the tested chromosomes. We found similar paternal and maternal contribution to monosomy at cleavage stage. We demonstrated paternal origin in 51.5% of the monosomy, and maternal origin in 48.5% of the monosomies cases.ConclusionIn our study, we found equal parental contribution to monosomies in cleavage-stage embryos. Comparison to CCS analyses of PGT-SR patients revealed a lower rate of monosomy per chromosome in embryos at day 5 of development. This is in contrast to the maternal dominancy described in studies of early miscarriage. Mitotic errors and paternal involvement in chemical pregnancies and IVF failure should be re-evaluated. Our results show monosomies are relatively common and may play a role in early development of ART embryos.

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.

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

PurposeTo retrospectively evaluate the effectiveness of PGT‐SR by array comparative genomic hybridization (aCGH) or next‐generation sequencing (NGS) in preventing recurrent miscarriages.MethodsThirty 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.ResultsThe 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.ConclusionsFor 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.

De novo balanced reciprocal translocation mosaic t(1;3)(q42;q25) detected by prenatal genetic diagnosis: a fetus conceived using preimplantation genetic testing due to a t(12;14)(q22;q13) balanced paternal reciprocal translocation

IntroductionDe novo balanced reciprocal translocations mosaicism in fetus conceived using preimplantation genetic testing from a different balanced translocation carrier parent has been rarely reported.MethodsChromosomal microarray analysis, karyotype analysis and fluorescent in situ hybridization were performed to verify the type and heredity of the rearrangement. STR analysis was conducted to identify potential contamination and verify kinship. In addition, a local BLAST engine was performed to locate potentially homologous segments which might contribute to the translocation in breakpoints of chromosome.ResultsA rare de novo balanced reciprocal translocations mosaicism mos 46,XY,t(1;3)(q42;q25)[40]/46,XY[39] was diagnosed in a fetus conceived using preimplantation genetic testing due to a 46,XY,t(12;14)(q22;q13) balanced translocation carrier father through multiplatform genetic techniques. Two of the largest continuous high homology segments were identified in chromosomal band 1q42.12 and 3q25.2. At the 21-months follow up, infant has achieved all psychomotor development milestones as well as growth within the normal reference range.ConclusionWe present a prenatal diagnosis of a rare de novo balanced reciprocal translocations mosaicism in a fetus who conceived by preimplantation genetic testing. The most reasonable driving mechanism was that a de novo mitotic error caused by nonallelic homologous recombination between 1q42.12 and 3q25.2 in a zygote within the first or early cell divisions, which results in a mosaic embryo with the variant present in a half proportion of cells.

A rare familial rearrangement of chromosomes 9 and 15 associated with intellectual disability: a clinical and molecular study

BackgroundThere are many reports on rearrangements occurring separately in the regions of chromosomes 9p and 15q affected in the case under study. 15q duplication syndrome is caused by the presence of at least one extra maternally derived copy of the Prader–Willi/Angelman critical region. Trisomy 9p is the fourth most frequent chromosome anomaly with a clinically recognizable syndrome often accompanied by intellectual disability. Here we report a new case of a patient with maternally derived unique complex sSMC resulting in partial trisomy of both chromosomes 9 and 15 associated with intellectual disability.Case presentationWe characterise a supernumerary derivative chromosome 15: 47,XY,+der(15)t(9;15)(p21.2;q13.2), likely resulting from 3:1 malsegregation during maternal gametogenesis. Chromosomal analysis showed that a phenotypically normal mother is a carrier of balanced translocation t(9;15)(p21.1;q13.2). Her 7-year-old son showed signs of intellectual disability and a number of physical abnormalities including bilateral cryptorchidism and congenital megaureter. The child’s magnetic resonance imaging showed changes in brain volume and in structural and functional connectivity revealing phenotypic changes caused by the presence of the extra chromosome material, whereas the mother’s brain MRI was normal. Sequence analyses of the microdissected der(15) chromosome detected two breakpoint regions: HSA9:25,928,021-26,157,441 (9p21.2 band) and HSA15:30,552,104-30,765,905 (15q13.2 band). The breakpoint region on chromosome HSA9 is poor in genetic features with several areas of high homology with the breakpoint region on chromosome 15. The breakpoint region on HSA15 is located in the area of a large segmental duplication.ConclusionsWe discuss the case of these phenotypic and brain MRI features in light of reported signatures for 9p partial trisomy and 15 duplication syndromes and analyze how the genomic characteristics of the found breakpoint regions have contributed to the origin of the derivative chromosome. We recommend MRI for all patients with a developmental delay, especially in cases with identified rearrangements, to accumulate more information on brain phenotypes related to chromosomal syndromes.