Unbalanced Reciprocal Translocation Research Articles

Chromosomal microarray analysis of 17 patients with unbalanced reciprocal translocations

To retrospectively analyze the results of chromosomal microarray analysis (CMA) and parental origins of unbalanced translocations among 17 patients, so as to provide reference for their genetic counseling. The results of CMA for 7 001 samples tested in Chengdu Women and Children's Central Hospital from January 2019 to January 2022 were retrospectively reviewed. Unbalanced reciprocal translocation was defined as two non-homologous chromosomes with lost and gained segments respectively or both with gained segments, and their parental origins were identified by parental chromosomal karyotyping and/or fluorescence in situ hybridization (FISH). In total 17 unbalanced translocations were identified. In three cases, two non-homologous chromosomes both had gained segments, which constituted a derivative chromosome, with the total number of chromosomes being 47. In the remaining 14 cases, there was a terminal deletion on one chromosome and a terminal duplication on the other, 10 of which were confirmed by karyotyping, with the total number of chromosomes being 46. In the derivative chromosome, the lost segment was replaced by a gained segment from another chromosome. Among 15 cases undergoing parental origin analysis, 12 had paternal or maternal chromosomal abnormalities, including 11 balanced translocations and 1 unbalanced translocation. The unbalanced gametes therefore may form through meiosis. In 3 cases, the parental chromosomes were normal, indicating a de novo origin. Discovery of terminal duplication and deletion or gained segments on two non-homologous chromosomes by CMA is suggestive of parental balanced translocation, which can facilitate genetic counseling and assessment the recurrence risk for subsequent pregnancies.

Inherited unbalanced reciprocal translocation with 3q duplication and 5p deletion in a foetus revealed by cell-free foetal DNA (cffDNA) testing: a case report

BackgroundSince 2011, screening maternal blood for cell-free foetal DNA (cffDNA) fragments has offered a robust clinical tool to classify pregnancy as low or high-risk for Down, Edwards, and Patau syndromes. With recent advances in molecular biology and improvements in data analysis algorithms, the screening’s scope of analysis continues to expand. Indeed, screening now encompassess additional conditions, including aneuploidies for sex chromosomes, microdeletions and microduplications, rare autosomal trisomies, and, more recently, segmental deletions and duplications called copy number variations (CNVs). Yet, the ability to detect CNVs creates a new challenge for cffDNA analysis in couples in which one member carries a structural rearrangement such as a translocation or inversion.Case presentationWe report a segmental duplication of the long arm of chromosome 3 and a segmental deletion of the short arm of chromosome 5 detected by cffDNA analysis in a 25-year-old pregnant woman. The blood sample was sequenced on a NextSeq 550 (Illumina) using the VeriSeq NIPT Solution v1 assay. G-band karyotyping in amniotic fluid only detected an abnormality in chromosome 5. Next-generation sequencing in amniocytes confirmed both abnormalities and identified breakpoints in 3q26.32q29 and 5p13.3p15. The foetus died at 21 weeks of gestation due to multiple abnormalities, and later G-band karyotyping in the parents revealed that the father was a carrier of a balanced reciprocal translocation [46,XY,t(3;5)(q26.2;p13)]. Maternal karyotype appeared normal.ConclusionThis case provides evidence that extended cffDNA can detect, in addition to aneuploidies for whole chromosomes, large segmental aneuploidies. In some cases, this may indicate the presence of chromosomal rearrangements in a parent. Such abnormalities are outside the scope of standard cffDNA analysis targeting chromosomes 13, 18, 21, X, and Y, potentially leading to undiagnosed congenital conditions.

Limited sensitivity of NGS-based detection of unbalanced products from reciprocal translocations inpolar bodies and blastocysts

Introduction Numerous publications have demonstrated that preimplantation genetic diagnosis (PGD) increases the implantation rate and percentage of healthy newborns or at least decreases themiscarriage rate for translocation carriers with recurrent pregnancy losses (Fisher et al. 2010, Ikumaet al. 2018). The aim of this study was to evaluate whether VeriSeq PGS, a next generation sequencingbasedmethod for aneuploidy screening, is also suitable for the detection of structural aberrations inpolar bodies and trophectoderm cells. Since the product provider didn´t validate the method forunbalanced structural changes, our goal was to determine its sensitivity. Material & methods Array-based preimplantation genetic diagnostic was performed on polar bodies obtained from 12 women as well as on trophectoderm samples from five couples being translocation carriers. Furthermore, polar bodies from four women carrying other structural aberrations (i.e.versions, insertions, duplications) were included in the study. Whole genome amplification (WGA)was performed using the SurePlex DNA Amplification System. Cy3-labelled sample DNA and Cy5-labelled male reference DNA were hybridized for 4-16 hours on 24sure+ arrays. The slides were washedand scanned according to the manufacturer´s protocol. NGS libraries (VeriSeq PGS, Illumina Inc.) wereprepared from the same WGA products and sequenced on a MiSeq as described by the manufacturer. Data obtained with both methods were analyzed using the BlueFuse Multi Software. Fisher's exact testwas applied for statistical analyses. Results Reciprocal translocations present on a total of 18 chromosomes were included in this study. The results obtained with next generation sequencing in general delivered an excellent signal-to- noiseratio and a high dynamic range. Although, no statistically significant differences in the detection ofstructural variants between aCGH and NGS were observed, the comparison of both methods revealedseveral discordant results. In three cases, only one out of two translocated segments was detectableby NGS, whereas the aCGH method identified both fragments. By contrast, in the cohort with otherstructural aberrations, a 17 Mb insertion of chromosome 3 was detected only by NGS. Conclusions Our data indicate that although it is possible to analyze structural aberrations in singlecells with VeriSeq PGS, this method has some limitations in the detection of small telomericimbalances. The detection of structural aberrations is not only determined by their size but moreimportantly, it is locus-dependent. Hence, unbalanced reciprocal translocations with both translocatedfragments smaller than 8 Mb containing repetitive or paralogous sequences, might not be detectablewith VeriSeq PGS resulting in false negative results. Therefore, PGD for such translocations requires aprevalidation by e.g. sequencing of single sperm cells or unbalanced products of conception in orderto determine the locus-specific detection sensitivity.

Prenatal diagnosis and molecular cytogenetic characterization of a de novo unbalanced reciprocal translocation of der(9)t(9;14)(p24.2;q32.11) associated with 9p terminal deletion and 14q distal duplication

ObjectiveWe present molecular cytogenetic characterization of a prenatally detected derivative chromosome 9 [der(9)] of unknown origin. Case ReportA 35-year-old woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age, which revealed a der(9) chromosome of unknown origin. The parental karyotypes were normal. Array comparative genomic hybridization (aCGH) analysis revealed a 2.593 Mb deletion of 9p24.3-p24.2 encompassing DOCK8, KANK1, DMRT1, and VLDLR and a 16.65 Mb duplication of 14q32.11-q32.33 encompassing DLK1, RTL1, MEG3, RTL1as, and MEG8. Quantitative fluorescent polymerase chain reaction (QF-PCR) analysis using D9S937 (9p24.2) and D14S605 (14q32.2) showed a paternal origin of 9p24.2 deletion and a paternal origin of 14q32.2 duplication consistent with a paternal origin of the de novo aberrant chromosome of der(9)t(9p;14q). The fetal karyotype was 46,XX,der(9)t(9;14) (p24.2;q32.11). Metaphase fluorescence in situ hybridization (FISH) analysis using RP11-57K23 (14q32.33), RP11-31F19 (9p24.3), RP11-30O14 (9p21.1), and RP11-1105I14 (14q11.2) confirmed an unbalanced reciprocal translocation of der(9)t(9p;14q). We discuss 9p deletion syndrome and 14q duplication syndrome in this case. ConclusionMolecular cytogenetic techniques such as aCGH, FISH, and QF-PCR are useful in the determination of the origin and nature of a prenatally detected de novo derivative chromosome of unknown origin.

Characterization of fibroblast-free CWR-R1ca castration-recurrent prostate cancer cell line.

The previously established CWR-R1 cell line has been used as an in vitro model representing castration-recurrent prostate cancer. Microscopic observation of subconfluent cells demonstrated two distinct cellular morphologies: polygonal closely aggregated epithelial cells surrounded by bipolar fibroblastic cells with long processes. This study sought to establish and characterize a fibroblast-free derivative of the CWR-R1 cell line. The CWR-R1ca cell line was established from CWR-R1 cells by removing fibroblasts using multiple cycles of short-term trypsinization, cloning, and pooling single-cell colonies. Authentication of fibroblast-free CWR-R1ca cells was demonstrated by analyzing the expression of cytodifferentiation and prostate-associated markers, DNA and cytogenetic profiling, and growth pattern in the absence or presence of androgen. CWR-R1ca is an androgen-sensitive cell line that expresses the androgen receptor (AR) and its splice variant 7 and the luminal epithelia markers, CK-8, CK-18, and c-Met. CWR-R1fb fibroblasts isolated from CWR-R1 cells express AR, hepatocyte growth factor-α, and mouse β-actin but not AR-V7 or epithelial markers. Cytogenetic analysis of CWR-R1ca cells revealed a hyperdiploid male with numerical gains in chromosomes 1, 7, 8, 10, 11, and 12, deletion of one chromosome 2 allele, structural abnormalities that include der(1)t(1:4), der(4)t(2:4), der(10)t(4:10), and an unbalanced reciprocal translocation between chromosome 6 and 14. DNA-profiling revealed that CWR-R1ca cells had significant short-tandem repeat marker homology with CWR22Pc and CWR22Rv1 cell lines, which indicated lineage derivation from CWR22 prostate cancer xenografts. CWR-R1ca cells were responsive to the growth stimulatory effects of dihydrotestosterone (DHT) in the femtomolar range. This study establishes CWR-R1ca cells as a fibroblast-free derivative of the castration-recurrent CWR-R1 cell line. Prostate 76:1067-1077, 2016. © 2016 Wiley Periodicals, Inc.

Prenatal diagnosis and molecular cytogenetic characterization of de novo partial monosomy 3p (3p26.3→pter) and partial trisomy 16q (16q23.1→qter)

ObjectiveTo present the prenatal diagnosis and molecular cytogenetic characterization of a de novo unbalanced reciprocal translocation. Case ReportA 37-year-old woman, G3P1, underwent amniocentesis at 17 weeks of gestation because of her advanced maternal age. Her husband was 38 years old. Amniocentesis revealed a derivative chromosome 3 with the deletion of terminal 3p and the addendum of an unknown extra chromosomal segment on the distal 3p. The parental karyotypes were normal. Prenatal ultrasound findings were unremarkable. Array comparative genomic hybridization (aCGH) analysis using cultured amniocytes revealed a 2.38-Mb deletion in 3p26.3 [arr 3p26.3 (1-2,380,760)×1] encompassing 15 genes, which included 3 OMIM genes CHL1, CNTN6, and CNTN4, and a 13.17-Mb duplication in 16q23.1-q24.3 [arr 16q23.1q24.3 (76,999,082-90,170,596)×3] encompassing 207 genes, which included 81 OMIM genes. The pregnancy was subsequently terminated, and a malformed fetus was delivered with facial dysmorphism. Postnatal cord blood analysis revealed a karyotype of 46,XY,der(3)t(3;16)(p26.3;q23.1)dn. Polymorphic DNA marker analysis by quantitative fluorescent polymerase chain reaction (QF-PCR) on the DNAs extracted from the placenta and parental blood showed a paternal origin of the aberrant chromosome. ConclusionThe aCGH and QF-PCR analyses helped in delineating the genomic imbalance and parental origin of prenatally detected de novo unbalanced reciprocal translocation.

Unbalanced Translocations Involving Chromosome Region 10q25.3q26.3 in Patients with Intellectual Disability and Complex Phenotypes

We describe 2 Ukrainian families with unbalanced reciprocal translocations (RTs) involving the distal part of chromosome 10q. In both families, the fathers were healthy carriers of the RT. Two affected patients from the first family had an ∼2.3-Mb loss at 10q26.3 and an ∼25-Mb gain at 2q35qter, and the patient from the other family had an ∼12.5-Mb loss at 5p15.2pter and an ∼18-Mb gain at 10q25.3q26.3. We assume that intellectual disability (ID) in association with congenital anomalies observed in our patients was the result of the cumulative effect of both gains and losses of the chromosomal regions involved in each translocation. Comparison of the sizes of the deleted and duplicated segments in our families as well as in other published families with translocations affecting the distal part of 10q showed that generally deletions seem to be ∼2 times more harmful than duplications of the same size. The data obtained here may contribute to improve the diagnosis and genetic counseling of families with similar chromosomal imbalances.

Robertsonian translocations: An overview of a 30-year experience in a single tertiary medical center in Taiwan

BackgroundAdvanced maternal age (AMA) is the most frequent indication for amniocentesis in predicting balanced reciprocal translocations, and abnormal ultrasound findings are indications in predicting unbalanced reciprocal translocations; however, to date, no studies have focused on Robertsonian translocations. MethodsA retrospective review was conducted on 16,749 pregnant women who underwent midtrimester amniocentesis between January 1981 and December 2010. Robertsonian translocations were identified in 39 cases. ResultsThe percentage of Robertsonian translocations in all amniocentesis cases was 0.23% (39/16,749); 31 were balanced and eight were unbalanced. De novo abnormality occurred in 17 cases, or in 43.6% of all Robertsonian translocations. The two major indications for amniocentesis with a diagnosis of Robertsonian translocations were AMA (41.0%, n = 16) and a parent with abnormal karyotypes (18.0%, n = 7). The highest percentage of Robertsonian translocations was found in parents with abnormal karyotypes (2.8%, 7/252), but neither of the indications were clearly superior for detecting de novo Robertsonian translocations. ConclusionAlthough AMA is an indication for amniocentesis in approximately two-fifths of cases with Robertsonian translocations, the indication of parent with abnormal karyotypes was more likely to lead to the detection of non-de novo Robertsonian translocations, suggesting that parents with abnormal karyotypes need careful prenatal consultation.

Balanced and unbalanced reciprocal translocation: An overview of a 30-year experience in a single tertiary medical center in Taiwan

BackgroundReciprocal translocation is the most common type of translocation; however, there are only a few studies that address the indications for reciprocal translocation in amniocentesis. Here we share our data, based on 30 years' experience in a single tertiary center, to investigate the rates and indications for amniocentesis in cases of reciprocal translocations. MethodsA retrospective review of 16,749 pregnant women, who underwent midtrimester amniocentesis between January 1981 and December 2010, was conducted. Seventy-four cases of reciprocal translocation were identified. ResultsThe percentage of reciprocal translocations in all amniocentesis cases was 0.44% (74/16,749); of these 74 cases, 56 were balanced and 18 unbalanced. De novo abnormality occurred in 23 cases, which constituted 31.1% of all reciprocal translocations. The three major indications for amniocentesis with a diagnosis of reciprocal translocation included advanced maternal age (AMA, 52.7%), a parent with an abnormal karyotype (17.6%), and abnormal biochemical markers in the maternal serum (12.2%). For individual types of reciprocal translocations (balanced and unbalanced), except for the presence of abnormal biochemical markers in maternal serum, both AMA and a parent with an abnormal karyotype were primary indications for amniocentesis. However, the highest percentage of reciprocal translocations in all amniocentesis cases was found in cases involving a parent with an abnormal karyotype (5.16%, 13/252). ConclusionPatients with a parent who carries an abnormal karyotype should be encouraged to undergo amniocentesis in prenatal consultation, since the risk of a diagnosis of reciprocal translocation can be particularly high.

Génétique et gliomes cérébraux

Chromosome arms 1p and 19q codeletion, corresponding to an unbalanced reciprocal translocation t(1;19)(q10;p10), is seen in oligodendroglial tumours and is associated with better prognosis and better chemosensitivity. BRAF abnormalities are observed in pilocytic astrocytomas (tandem duplication-rearrangement) and in pleomorphic xanthoastrocytomas (BRAF V600E mutation). The vast majority of primary or de novo glioblastomas exhibit genetic abnormalities disrupting the intracellular signaling pathways of: transmembrane tyrosine kinase receptors to growth factors and their downstream signaling pathways (i.e. NF1-RAS-RAF-MAPK and PTEN-PI3K-AKT-TSC-mTOR); RB and; TP53. IDH1 and IDH2 mutations are frequent in diffuse grade II and grade III gliomas and in secondary glioblastomas. They are diagnostic and favorable independent prognostic biomarkers. In contrast, they are rare in primary or de novo glioblastomas and not reported in pilocytic astrocytomas. Germlin mutations in MSH2/MLH1/PMS2/MSH6, CDKN2A, TSC1/TSC2, PTEN, TP53 and NF1/NF2 predispose to glial tumors in the setting of hereditary cancer predisposition syndromes. Single nucleotide polymorphisms in TERT,CCDC26, CDKN2A/CDKN2B, RTEL, EGFR and PHLDB1 confer an inherited susceptibility to glial tumors.

Rapid aneuploidy diagnosis of partial trisomy 7q (7q34→qter) and partial monosomy 10q (10q26.12→qter) by array comparative genomic hybridization using uncultured amniocytes

ObjectiveTo present rapid aneuploidy diagnosis (RAD) of partial trisomy 7q (7q34→qter) and partial monosomy 10q (10q26.12→qter) by array comparative genomic hybridization (aCGH) using uncultured amniocytes. Case ReportA 34-year-old, gravida 2, para 1, woman underwent amniocentesis at 20 weeks of gestation because of a previous mentally retarded child with an unbalanced reciprocal translocation inherited from the carrier father who had a karyotype of 46,XY,t(7;10) (q34;q26.12). Her first child was initially found to have a normal karyotype by routine cytogenetic analysis, but a cryptic chromosomal abnormality was subsequently diagnosed by aCGH. During this pregnancy, RAD by oligonucleotide-based aCGH using uncultured amniocytes revealed a 16.4-Mb duplication of 7q34–q36.3 and a 12.7-Mb deletion of 10q26.12–q26.3. Conventional cytogenetic analysis using cultured amniocytes revealed a karyotype of 46,XX,der(10)t(7;10)(q34;q26.12)pat. The parents elected to terminate the pregnancy. A malformed female fetus was delivered with a high prominent forehead, hypertelorism, epicanthic folds, a broad depressed nasal bridge, a prominent nose with anteverted nostrils, micrognathia, a short neck, large low-set ears, clinodactyly, small big toes, and normal female external genitalia. ConclusionaCGH is a useful tool for RAD of subtle chromosomal rearrangements in pregnancy, especially under the circumstance of a previous abnormal child with an unbalanced translocation derived from a parental subtle reciprocal translocation.

Validation of array comparative genome hybridization for diagnosis of translocations in preimplantation human embryos

Fluorescent in-situ hybridization (FISH) for preimplantation genetic diagnosis (PGD) of structural chromosome abnormalities has limitations, including carrier testing, inconclusive results and limited aneuploidy screening. Array comparative genome hybridization (CGH) was used in PGD cases for translocations. Unbalances could be identified if three fragments were detectable. Smallest detectable fragments were ∼6Mbp and ∼5Mbp for blastomeres and trophectoderm, respectively. Cases in which three or more fragments were detectable by array CGH underwent PGD by FISH and concordance was obtained in 53/54 (98.1%). The error rate for array CGH was 1.9% (1/54). Of 402 embryos analysed, 81 were normal or balanced, 92 unbalanced but euploid, 123 unbalanced and aneuploid and 106 balanced but aneuploid. FISH with additional probes to detect other aneuploidies would have missed 28 abnormal embryos in the reciprocal group and 10 in the Robertsonian group. PGD cases (926) were retrospectively reviewed for reciprocal translocations performed by FISH to identify which could have been analysed by array CGH. This study validates array CGH in PGD for translocations and shows that it can identify all embryos with unbalanced reciprocal and Robertsonian translocations. Array CGH is a better approach than FISH since it allows simultaneous screening of all chromosomes for aneuploidy.Fluorescent in-situ hybridization (FISH) has been used in preimplantation genetic diagnosis (PGD) for structural chromosome abnormalities. This approach has limitations such as the need for testing of carriers, poor fixation and no possibility for aneuploidy screening of all chromosomes. The use of array comparative genome hybridization (CGH) can solve these limitations. Array CGH was used in 47 PGD cases for Robertsonian or reciprocal translocations. The smallest detectable fragment size was ∼6Mbp for single blastomeres (day-3) and ∼5Mbp for trophectoderm (day-5) biopsies. Translocation cases in which three or more translocated fragments were detectable by array CGH underwent PGD. Of those, a total of 54 non-transferred embryos analysed by array CGH were reanalysed by FISH. The error rate for array CGH was 1.9% (1/54). Of the 402 embryos analysed by array CGH, 81 embryos were normal or balanced, 92 were unbalanced but euploid, 123 unbalanced and aneuploid and 106 balanced but aneuploid. We retrospectively reviewed 926 PGD cases for reciprocal translocations performed by FISH in order to identify those in which fewer than two fragments were less than ∼6Mbp. In conclusion, this study validates the use of array CGH in PGD for translocations showing a low error rate and shows that array CGH can identify all embryos with unbalanced reciprocal and Robertsonian translocations. Array CGH is a better approach than FISH or single-nucleotide polymorphism arrays because it allows simultaneous screening of all chromosomes for aneuploidy and does not require previous genetic testing of the parents.

Wolf-Hirschhorn (4p-) syndrome: Prenatal diagnosis, molecular cytogenetic characterization and association with a 1.2-Mb microduplication at 8p22-p21.3 and a 1.1-Mb microduplication at 10p15.3 in a fetus with an apparently pure 4p deletion

Objective To present prenatal diagnosis and molecular cytogenetic characterization of Wolf-Hirschhorn syndrome (WHS) associated with microduplications at 8p and 10p in a fetus with an apparently pure 4p deletion. Case Report A 35-year-old gravida 2, para 1 woman underwent amniocentesis at 18 weeks of gestation because of advanced maternal age. Her husband was 38 years of age. There was no family history of congenital malformations. Amniocentesis revealed a karyotype of 46,XY,del(4p16.1). The parental karyotypes were normal. Array comparative genomic hybridization (aCGH) analysis revealed a 6.5-Mb deletion at 4p16.3-p16.1, a 1.2-Mb microduplication at 8p22-p21.3, and a 1.1-Mb microduplication at 10p15.3, or arr cgh 4p16.3p16.1 (0–6,531,998 bp)×1, 8p22p21.3 (18,705,388–19,940,445 bp)×3, 10p15.3 (0–1,105,065 bp)×3. Polymorphic DNA marker analysis confirmed a paternal origin of 4p deletion. Prenatal ultrasound revealed facial dysmorphism and hypospadias. The aCGH analysis of the parents revealed no genomic imbalance. Fluorescence in situ hybridization study showed an unbalanced reciprocal translocation between chromosomes 4 and 10 at bands 4p16.1 and 10p15.3. The cytogenetic result, thus, was 46,XY,der(4)t(4;10)(p16.1;p15.3),dup(8)(p21.3p22). The parents elected to terminate the pregnancy, and a 470-g malformed fetus was delivered. Conclusion The present case provides evidence that an apparently pure 4p deletion can be associated with subtle chromosome imbalances in other chromosomes.

Unbalanced reciprocal translocations at amniocentesis

Objective To present perinatal findings, modes of ascertainments, and modes of segregation in unbalanced reciprocal translocations detected at amniocentesis. Materials and Methods Between January 1987 and July 2010, 40 cases with unbalanced reciprocal translocations were diagnosed by amniocentesis at Mackay Memorial Hospital, Taipei, Taiwan. The 40 cases originated from 29 families; 21 families with one case, 7 families with two cases, and 1 family with five cases. Results Of 40 cases, 33 (82.5%) presented fetal ultrasound abnormalities and 7 (17.5%) presented no ultrasound abnormalities. Of 40 cases, 36 (90%) had a segregation mode of adjacent-1 2:2 segregation, 3 (7.5%) had a segregation mode of 3:1 segregation with tertiary trisomy, and 1 (2.5%) had a segregation mode of 3:1 segregation with tertiary monosomy. Of 29 families, 7 (24.1%) had de novo translocations and 22 (75.9%) had inherited translocations. In seven de novo cases, the main modes of ascertainments included abnormal ultrasound findings ( n = 5) and advanced maternal age ( n = 2). In 22 inherited families, the main modes of first ascertainment included abnormal ultrasound findings ( n = 8), a previous aneuploid child ( n = 8), advanced maternal age ( n = 4), parental carrier status ( n = 1), and abnormal maternal serum screening results ( n = 1). Among 22 inherited families, 9 (40.9%) had a known parental carrier status, but 13 (59.1%) were unaware of parental carrier status at amniocentesis. Conclusion Unbalanced reciprocal translocations detected at amniocentesis are frequently associated with abnormal ultrasound findings. Prenatal diagnosis of an unbalanced translocation may incidentally detect a balanced translocation in the family. Prenatal diagnosis of fetal structural abnormalities should alert structural chromosome rearrangements and prompt cytogenetic analysis of the fetus and parents if necessary.

Balanced Reciprocal Translocations Detected at Amniocentesis

To present perinatal findings, modes of ascertainment and parental decision in balanced reciprocal translocations detected at amniocentesis. Between January 1987 and August 2010, 82 cases with a simple reciprocal translocation, two cases with two separate simple reciprocal translocations and three cases with a complex chromosome rearrangement (CCR) were diagnosed by amniocentesis at Mackay Memorial Hospital, Taipei, Taiwan. The 87 cases originated from 76 families; 65 families with one case and 11 families with two cases. In the 76 families, the main modes of ascertainment included advanced maternal age (n=38), a previous child with an unbalanced reciprocal translocation (n=11), recurrent miscarriage (n = 9), abnormal maternal serum screening results (n = 9), elective causes (n = 5), a previous child with congenital anomalies (n =2) and abnormal ultrasound findings (n = 2). In these families, there were 17 (22.4%) de novo cases including 14 simple translocations and three CCRs. Of 14 de novo cases with a simple translocation, one (7.1%) manifested a congenital malformation, which was related to an X-autosome translocation, and four (28.6%) were terminated. Of three de novo CCRs, two manifested congenital anomalies and one was terminated. In 87 cases, additional aneuploidy was noted in two cases including one inherited simple translocation with Turner syndrome, and one de novo CCR with concomitant deletions and duplication. Balanced reciprocal translocations detected at amniocentesis may be associated with fetal anomalies in cases of concomitant aneuploidy, de novo X-autosome translocation or de novo CCR. Genetic counseling of a de novo simple reciprocal translocation at amniocentesis remains difficult because approximately one-fourth of the parents opt for termination of the pregnancy, and detailed ultrasonography and array comparative genomic hybridization are helpful for parental counseling under such circumstances.

O11 Human embryonic stem cells harboring an unbalanced reciprocal translocation t(11;22) as a valuable model for studying single gene dosage effects

O11 Human embryonic stem cells harboring an unbalanced reciprocal translocation t(11;22) as a valuable model for studying single gene dosage effects

Molecular cytogenetic analysis by genomic hybridization to determine the cause of recurrent miscarriage

To characterize a t(2;6) by array-based comparative genomic hybridization (array-CGH) in a couple with recurrent miscarriage, to analyze the meiotic segregation of the t(2;6), and to discuss couple specific care-taking modality before intracytoplasmic sperm injection. Case report. INSERM U613 in Brest, France. Couple consulting for infertility. Array-CGH to characterize a t(2;6) and fluorescence in situ hybridization (FISH) to analyze the meiotic segregation were performed. Array-CGH, FISH with a panel of bacterial artificial chromosome clones and commercial probes. Analyses from peripheral blood lymphocytes identified a t(2;6)(q35;q24) unbalanced reciprocal translocation with microdeletions on the der(2) and the der(6). FISH on spermatozoa found that the frequency of normal (23,X or 23,Y) or "translocation-deletions" (23,X,der(2),der(6) or 23,Y,der(2),der(6)) spermatozoa was 41.10%. For our 46,XY,t(2;6)(q35;q24) carrier, more than 50% of the spermatozoa are chromosomally unbalanced. Moreover, FISH does not permit a distinction between normal and "translocation-deletion" phenotypes. So, in the possibility of preimplantation genetic diagnosis, is it necessary to select the normal embryos to the detriment of those translocation-deletions carriers? The pathogenicity of these microdeletions not been proved. Because the family history was oriented toward a variation of genetic equipment without phenotypic consequences, the couple decided not to make a selection between the normal embryos and the translocation-deletion carrier embryos.

Multiple primary tumors associated with chromosome 9p deletion

Multiple primary tumors associated with chromosome 9p deletion

The “Trans-Amplicon” in Myeloma; a Mechanism of Clonal Selection Favoring Retention of Derivative Chromosomes Involved in Translocations.

Background: Multiple mechanisms exist for the positive selection of genes involved in oncogenesis such as gene amplification and transcriptional deregulation associated with chromosome translocations. Here we describe the case of a myeloma cell line that over time acquired extra copies of a derivative chromosome 4 involved in the t(4;14). These changes occurred over time both in vitro (in the generated JMW myeloma cell lines) as well as in vivo from extramedullary myeloma samples collected from the patient at various time points. In the case of the t(4;14)(p16;q32) 30% can be unbalanced translocations, always with loss of the der(14) and consequent loss of the FGFR3 gene expression, suggesting an indispensable role for MMSET located in the der(4).Results: We performed serial analysis on patient samples obtained at 9, 10 and 12 mos from diagnosis, along with a time course analysis of the cell line. At diagnosis the patient tumor cells displayed a complex clinical karyotype subsequently characterized by hypodiploidy, a t(4;14)(p16;q32), 13 monosomy and 17p13.1-. The remaining chromosome 13 and 17 were involved in an unbalanced reciprocal translocation. Notably, over time the cell line duplicated the total chromosome number becoming near-tetraploid. At the time of diagnosis, FISH analysis was performed on the patient sample revealing the translocation t(4;14)(p16.3:q32) in nearly all cells. The t(4;14) was also present in the stable cell line. It was noted that the patient cells exhibited more than one fusion signal per cell for the t(4;14) by FISH. As the disease progresses both in vitro and in vivo, the number of t(4;14)(p16.3:q32) fusion signals detected per cell increased with time suggesting a positive selection of the derivative chromosomes of the translocation. We further analyzed the t(4;14) in the JMW cells by FISH using MMSET/VH, and FGFR3/CH probe combinations. The full-length (MMSET/FGFR3+VH/CH) probe was used to detect the total number of fusions in the JMW cells. At the time of analysis (cell line passage #23), the majority of the cells (69%) had 6 fusion signals per cell while 23% had 5 fusions and 8% of the cells had 4 fusions. We found that most of the cells (88%) displayed 4 fusion signals detected using the MMSET/VH probes. In parallel studies using the FGFR3/CH probes, 61% of the cells had 2 fusion signals and 39% with 1 fusion signal. It is evident that the tumor cells display positive selection of the derivative chromosome der(4) of the t(4;14)(p16.3;q32), accompanied by an increased dosage of the target gene (MMSET) upregulated by the translocation.Conclusion: We present evidence for the amplification of the translocated chromosome in multiple myeloma, which we have termed “trans-amplicons”. Trans-amplicons may provide a selective growth and survival advantage to the myeloma tumor cells in an analogous manner to amplicons of DNA segments, but with much more powerful transcriptional consequences. Importantly, the evolution of genomic instability exemplified by the “trans-amplicons” in the patient cells was paralleled in vitro in the JMW cells.

Cytogenetic Analysis of a Scapular Chondromyxoid Fibroma

Chondromyxoid fibroma (CMF) is a rare cartilaginous tumor of bone. It typically presents in the lower extremities of young males. Cytogenetic analysis of two chondromyxoid fibromas has been previously reported. We studied a scapular CMF from an 11-year-old female by cytogenetic and molecular cytogenetic methods and found an unbalanced reciprocal translocation between the short arm of chromosome 3 and the long arm of chromosome 6. In this translocation, several bands from chromosome 3 (3p12, 3p13, 3p14, 3p21) are lost and several bands on chromosome 6 (6q21, 6q22, 6q23) appear rearranged. Two known cartilage-related genes are located in the regions affected by this unbalanced rearrangement: the type X collagen gene (COL10A1) located at 6q21-q22 and the parathyroid hormone/parathyroid hormone-related peptide receptor gene (PTH/PTHrP) located at 3p21.1-p22. These genes function to control growth and maturation of endochondral bone, the site of origin of cartilaginous tumors.