Subtelomeric rearrangements and 22q11.2 deletion syndrome in anomalous growth-restricted fetuses with normal or balanced G-banded karyotype.

OBJECTIVE: To determine the frequencies of cryptic subtelomeric rearrangements and 22q11.2 deletion in anomalous growth-restricted fetuses with normal or balanced G-banded karyotypes. METHODS: This was a study of 27 consecutive fetuses at a median gestational age of 26 (range, 19-33) weeks, that had intrauterine growth restriction (IUGR) as well as at least one major structural anomaly, and a normal or balanced G-banded karyotype. The median maternal age was 29 (range, 17-39) years. Fluorescence z in-situ hybridization (FISH) diagnosis of the cultured amniocytes with the probe TUPLE 1, and then the Chromoprobe Multiprobe-T system were used, respectively, to screen for the frequency of 22q11.2 deletion syndrome and subtelomeric rearrangements involving the 41 unique chromosome ends (i.e. excluding the five short arms of acrocentric autosomes (no. 13, 14, 15, 21 and 22)). Those that had suspected deleted subtelomeres were reanalyzed with a specific subtelomeric probe, TelVysion. RESULTS: Of the 27 fetuses, three (11%) were affected with 22q11.2 deletion syndrome and two (7.4%) had subtelomeric deletions (one monosomy 21q22.3, one monosomy 1p36.3). Of the 11 fetuses with congenital heart defects, three (27.3%) had 22q11.2 deletion syndrome and one (9.1%) had monosomy 1p36.3. In the remaining 16 fetuses without congenital heart defects, none had 22q11.2 deletion syndrome. However, one (6.3%) had cryptic rearrangement involving subtelomeres. CONCLUSION: Prenatal subtelomeric FISH screening is technically feasible using cultured amniocytes. We propose that 22q11.2 deletion syndrome and cryptic subtelomere rearrangements may be important etiologies of fetuses with IUGR and at least one structural anomaly, along with a normal karyotype or one that is balanced by traditional G-banding. Fetuses with congenital heart defects and IUGR should undergo FISH to exclude 22q11.2 deletion syndrome. In fetuses with IUGR and at least one major structural anomaly but without congenital heart defects, screening of subtelomeric rearrangements may contribute to further elucidation of the underlying etiology.     

Multiple fetal anomalies associated with subtle subtelomeric chromosomal rearrangements.

We report two cases of multiple fetal anomalies detected by prenatal ultrasound and associated with subtle subtelomeric chromosomal rearrangements. The first case presented at 25 weeks of gestation with an enlarged cisterna magna and ventriculomegaly. Karyotyping of amniocytes showed a subtle terminal abnormality of chromosome 6q. Thereafter, screening of all unique chromosomal subtelomeric regions using a panel of telomere-specific, fluorescence in situ hybridization (FISH) probes revealed an unbalanced reciprocal translocation between 6q and 17p [46,XX.ish der(6)t(6;17)(q25.3;p13)(TelVysion6q-;TelVysion17p+)]. The second case presented at 25 weeks of gestation with tetralogy of Fallot and at 34 weeks of gestation had additional ultrasound findings of an arachnoid cyst and intrauterine growth restriction. Postnatal karyotyping of peripheral blood was performed and appeared normal. However, a cryptic deletion of the subtelomeric region of the long arm of chromosome 14 was identified when the infant's blood sample was used as a control for an oncology FISH probe. Thereafter, screening of all unique chromosomal subtelomeric regions using a panel of telomere-specific FISH probes revealed an unbalanced reciprocal translocation of chromosomes 14q and 20p [46,XY.ish der(14)t(14;20)(q32.3;p13)(IGH-, D14S308-,TelVysion20p+)mat]. These two cases add to a growing number of reports of cryptic subtelomeric chromosomal rearrangements associated with congenital anomalies. This is the first report of multiple, simultaneous FISH screening of the subtelomeric regions in amniotic fluid and has demonstrated the technical feasibility of this technique in the prenatal period.     

Clinical importance of chromosomal translocations (author's transl)

5835 chromosomal analyses were performed between May 1, 1962 and December 31, 1978. We found 68 translocations (1.1%). 36 translocation carriers were identified as being chromosomally balanced, of whom 24 were healthy and 12 clinically abnormal (5 showed centric fusions - 3 x D/D, 2 x D/G - and 7 other chromosomal rearrangements). 32 translocation carriers were chromosomally non-balanced, among them 28 patients with centric fusions (12 x G/G, 2 x D/D, 14 x D/G) and 4 with other rearrangements combined with characteristic clinical features. A review of the chromosomal translocations found in our laboratory is presented. The relation between clinical appearance and chromosomal rearrangement is discussed.     

Large Clinically Consequential Imbalances Detected at the Breakpoints of Apparently Balanced and Inherited Chromosome Rearrangements

When a chromosome abnormality is identified in a child with a developmental delay and/or multiple congenital anomalies and the chromosome rearrangement appears balanced, follow-up studies often examine both parents for this rearrangement. If either clinically unaffected parent has a chromosome abnormality with a banding pattern identical to the affected child''s study, then it is assumed that the chromosome rearrangement is balanced and directly inherited from the normal carrier parent. It is therefore unlikely that the chromosome rearrangement is responsible for the child''s clinical presentation. We present two unrelated cases in which an identical and apparently balanced abnormal chromosome banding pattern was identified in both an affected child and an unaffected parent of that child. Despite the identical banding patterns, molecular characterization through genomic microarray and fluorescence in situ hybridization showed the parent to be balanced whereas the affected child was significantly unbalanced. These two cases emphasize the utility of genomic microarray for further characterization of apparently balanced inherited chromosome rearrangements and caution against the assumption that identical banding patterns between a child and parent represent identical genomic rearrangements.Numerous studies have shown that de novo apparently balanced translocations associated with an abnormal phenotype are often more complex than appreciated at the chromosome banding level. These translocations are therefore more likely to result in disruption of copy number sensitive loci, more likely to have a cryptic imbalance at or near one of the translocation breakpoints, or have cryptic imbalances elsewhere in the genome.^{1,2,3,4,5,6,7}However, most of these studies have focused on de novo apparently balanced rearrangements and have not examined inherited rearrangements. Because balanced translocations occur in approximately 1:500 individuals⁸ and the majority are inherited (1:2000 balanced rearrangements are de novo),⁹ it is easy to conclude that a phenotypic abnormality and a balanced translocation can occur coincidentally in an individual, especially when that same rearrangement is found in a normal related individual, such as a parent.It is also recognized that a de novo balanced rearrangement does increase the risk for a serious congenital anomaly to approximately 6.7%.⁹ This increased risk is usually thought to be due to a disruption of genes or regulatory elements. Many examples of this exist in the literature and have even led to the identification of the causative gene for numerous Mendelian conditions.¹⁰Therefore, when an apparently balanced rearrangement is identified in a child with phenotypic abnormalities, parental studies are often recommended as the next step as this is necessary for recurrence risk counseling and is useful for determining the clinical significance of the rearrangement. If the same balanced rearrangement is found in a normal parent, an alternative cause of the child''s phenotypic abnormalities is sought.We present two cases that challenge the algorithm of parental studies being the next step in follow-up as well as the assumption that an identical banding pattern in a normal parent can be interpreted as evidence that the rearrangement is coincidental to the child''s abnormal phenotype.     

多重荧光原位杂交检测骨髓增生异常综合征患者复杂核型异常

目的 探讨多重荧光原位杂交（M-FISH）技术存骨髓增牛异常综合征（MDS）患者复杂核型异常检测中的应用价值。方法 对10例常规R显带具有复杂染色体异常（CCA）的MDS患者应用M-FISH确定复杂染色体的重排及标记染色体的组成，识刖并确定微小易位。结果 M-FISH共检出37种结构重排，包括插入易位、缺夫、易值及衍生染色体，其中34种为不平衡重排；3种为平衡重排，包括：t（6；22）（q21；q12）、t（9；19）（q13；p13）和t（3；5）（？；？），有7种重排文献未见报道，涉及17号染色体的异常及-5／5q-最为常见（10例患者中两种异常各占7例）。结论 对伴有CCA的MDS患者M-FISH技术可以明确常规细胞遗传学（CC）分析中复杂染色体异常，并发现和纠正CC分析中漏检及误检的异常，为MDS患者染色体异常的分析提供了一种较理想的方法。     

First-trimester prenatal diagnosis of a familial subtelomeric translocation.

A new fluorescent in situ hybridization (FISH) technique utilizes a complete set of telomeric probes to screen for deletions or rearrangements within the subtelomeric regions of all chromosomes on a single slide. Such cryptic chromosome rearrangements would otherwise remain undetected by standard cytogenetic analysis. In this case report, we describe the first-trimester prenatal diagnosis of an unbalanced rearrangement in a family where such a cryptic subtelomeric rearrangement is segregating. Interestingly the fetus was also noted to have an increased nuchal translucency at the time first-trimester chorionic villus sampling was performed and a FISH diagnosis made. The result was subsequently confirmed on fetal material obtained after elective termination of the pregnancy. We believe this to be the first report in the literature (as by Medline, December 1999) of a first-trimester prenatal diagnosis using such subtelomeric probes where confirmation by conventional cytogenetic analysis was not possible.     

Chromosome analysis in couples with recurrent abortions

Chromosome analysis using a G-Banding technique was performed in 35 couples (70 individuals) with a history of two or more spontaneous abortions of unknown cause. Among these individuals, 5 (7%) showed balanced translocations, all of whom were female. The outcome of 31 pregnancies of 10 balanced translocation carriers was as follows: Ten of the offspring had normal phenotypes (32%), 5 (16%) were born with chromosomal abnormalities and 16 (52%) were spontaneously aborted.     

Detection of Gene Rearrangements in Targeted Clinical Next-Generation Sequencing

The identification of recurrent gene rearrangements in the clinical laboratory is the cornerstone for risk stratification and treatment decisions in many malignant tumors. Studies have reported that targeted next-generation sequencing assays have the potential to identify such rearrangements; however, their utility in the clinical laboratory is unknown. We examine the sensitivity and specificity of ALK and KMT2A (MLL) rearrangement detection by next-generation sequencing in the clinical laboratory. We analyzed a series of seven ALK rearranged cancers, six KMT2A rearranged leukemias, and 77 ALK/KMT2A rearrangement–negative cancers, previously tested by fluorescence in situ hybridization (FISH). Rearrangement detection was tested using publicly available software tools, including Breakdancer, ClusterFAST, CREST, and Hydra. Using Breakdancer and ClusterFAST, we detected ALK rearrangements in seven of seven FISH-positive cases and KMT2A rearrangements in six of six FISH-positive cases. Among the 77 ALK/KMT2A FISH-negative cases, no false-positive identifications were made by Breakdancer or ClusterFAST. Further, we identified one ALK rearranged case with a noncanonical intron 16 breakpoint, which is likely to affect its response to targeted inhibitors. We report that clinically relevant chromosomal rearrangements can be detected from targeted gene panel–based next-generation sequencing with sensitivity and specificity equivalent to that of FISH while providing finer-scale information and increased efficiency for molecular oncology testing.The detection of recurrent chromosomal rearrangements by cytogenetics was one of the earliest clinical molecular oncology assays and continues to play a major role in cancer diagnosis and prognosis.^1,2 Although translocations in the clinical laboratory are generally detected by cytogenetics, fluorescence in situ hybridization (FISH), or RT-PCR, studies have demonstrated that they may also be detected by next-generation sequencing (NGS) of DNA or RNA.^3–5 DNA-level translocations can be detected in particular areas of interest by first performing hybrid capture enrichment to target one or both partner genes in a translocation, followed by NGS.^4,6 NGS-based translocation detection has several advantages over conventional clinical laboratory methods, such as the ability to precisely define the breakpoint region, detect cryptic rearrangements and unknown partner genes, and run in parallel with gene mutation detection.Chromosomal rearrangements are detected in the clinical laboratory by routine cytogenetics, FISH, or RT-PCR; however, these methods have limitations. Cytogenetic studies, including chromosome analysis and metaphase FISH, require actively dividing cells, which can be especially difficult to obtain from solid tumors. In addition, chromosome analysis is of limited resolution, particularly in oncology specimens, and is therefore insensitive to cryptic and complex rearrangements.^5,7,8 Some rearrangements can be assayed via RNA-based RT-PCR methods, but this approach is less useful for translocations with a large number of partner genes or those with potentially diverse breakpoints.^9,10 FISH is among the most commonly used laboratory methods for the detection of chromosomal rearrangements and offers high sensitivity and the ability to test routine interphase, formalin-fixed, paraffin-embedded (FFPE) tissue sections. However, FISH relies on highly trained individuals to score rearrangements by fluorescent microcopy and is an inherently low-resolution method that may be confounded by complex, multiway rearrangements and may require numerous probes to fully elucidate translocation partners for promiscuous genes, such as KMT2A.^5,10 Finally, FISH results are generally difficult to validate by orthogonal methods, outside less sensitive cytogenetic assays.Two of the most commonly tested translocations in the clinical laboratory are for rearrangements of the anaplastic lymphoma kinase gene, ALK, in non–small cell lung cancer and of the mixed-lineage leukemia gene, KMT2A (formerly known as MLL), in acute leukemia. The EML4-ALK fusion results from an inversion event on chromosome 2p that generally causes an in-frame fusion of EML4 exons 1 to 13 to ALK exons 20 to 29, producing an aberrant fusion gene with constitutive kinase activity, sensitive to crizotinib.^11–14 The occurrence of ALK fusions and other common lung cancer gene mutations in KRAS and EGFR are generally considered to be mutually exclusive, arguing that these tumors represent a distinct subset of lung cancers.¹⁵ Although not pharmacologically targetable, KMT2A rearrangements are of diagnostic and prognostic significance in acute leukemias, including both acute myeloid leukemia (AML) and acute lymphocytic leukemia (ALL).^16,17 KMT2A rearrangements can be readily detected by FISH using break-apart probes; however, elucidation of the translocation partner gene may be difficult because >100 have been identified.^10,18NGS has had a tremendous effect on cancer discovery and is now becoming routine in the clinical molecular oncology laboratory.^3,19–21 NGS allows for the cost-effective, simultaneous evaluation of numerous sequence variants as part of focused clinical oncology panels or whole exomes. We and other groups have previously found that a range of DNA variants, including translocations, insertions or deletions, and copy number variants, can be detected from targeted NGS data and that it is possible to identify DNA-level breakpoints with single-nucleotide precision.^4,22,23 However, to be useful in the clinical setting, a thorough evaluation of the sensitivity and specificity of structural variation (SV) detection by NGS compared with standard methods is required. Given that numerous potential translocations can be evaluated by NGS simultaneously as part of a larger NGS cancer panel, for little to no additional cost, such methods could provide a significant savings for laboratories that perform multiple single-gene tests and multiple FISH assays on oncology specimens.We present a comprehensive evaluation of targeted translocation detection by NGS in the clinical laboratory by comparing four publicly available translocation detection tools (including the laboratory derived ClusterFAST) on targeted NGS data from 13 cases with ALK or KMT2A rearrangements (six lung carcinomas and one anaplastic large cell carcinoma with ALK rearrangements; six leukemias with KMT2A rearrangements) and 77 cancers negative for ALK and KMT2A rearrangements by FISH. We found that translocations can be reliably detected at the DNA level by targeted NGS panels and that such methods offer sensitivity and specificity similar to that of routine FISH with the advantage of single-nucleotide breakpoint resolution. Further, we examine approaches to designing capture probes for targeted NGS evaluation, evaluate the minimal coverage levels necessary to detect translocations, and explore methods to reduce false-positive translocation reports.     

Unbalanced translocation in an adult patient with premature ovarian failure and mental retardation detected by spectral karyotyping and array-comparative genomic hybridization

Background  There are only three cases of unbalanced translocation (X;1) reported in childhood in the literature, while no such phenotypic information is available in adults.
Materials and methods  To delineate the phenotype–genotype relationship of unbalanced translocation (X;1) in adulthood, we reported here a 20-year-old female with an unbalanced translocation (X;1) which was determined by spectral karyotyping, array-comparative genomic hybridization and subtelomeric fluorescence in situ hybridization (FISH).
Results  The phenotype of partial trisomy 1 and partial monosomy X of the present case was much attenuated, including premature ovarian failure, mental retardation, class I obesity, mild dysmorphism and delayed secondary sexual characteristics. The breakpoints of the unbalanced translocation were accurately located at Xq28 and 1q32·1. The large amplification on Chromosome 1 q arm was found to involve 312 genes and the deletion on Chromosome X q arm also involved 141 genes. Overall, genes associated with physiological process (47 genes), cellular process (33), development (23), response to stimulus (1) and reproduction (1) were observed in the amplification on Chromosome 1 q arm. In addition, genes related to physiological process (23 genes), cellular process (13), development (6) and response to stimulus (2) were observed in the large deletion on chromosome X q arm. Late-replication studies revealed the existence of skewed X inactivation in the derivative X chromosome.
Conclusions  The phenotype of partial monosomy X and partial trisomy 1q is much attenuated in case of unbalanced translocation (X;1) in adulthood probably owing to skewed X inactivation in derivative X chromosome.     

Rapid high-resolution mapping of balanced chromosomal rearrangements on tiling CGH arrays

The diagnosis and classification of many cancers depends in part on the identification of large-scale genomic aberrations such as chromosomal deletions, duplications, and balanced translocations. Array-based comparative genomic hybridization (array CGH) can detect chromosomal imbalances on a genome-wide scale but cannot reliably identify balanced chromosomal rearrangements. We describe a simple modification of array CGH that enables simultaneous identification of recurrent balanced rearrangements and genomic imbalances on the same microarray. Using custom tiling oligonucleotide arrays and gene-specific linear amplification primers, translocation CGH (tCGH) maps balanced rearrangements to ～100-base resolution and facilitates the rapid cloning and sequencing of novel rearrangement breakpoints. As proof of principle, we used tCGH to characterize nine of the most common gene fusions in mature B-cell neoplasms and myeloid leukemias. Because tCGH can be performed in any CGH-capable laboratory and can screen for multiple recurrent translocations and genome-wide imbalances, it should be of broad utility in the diagnosis and classification of various types of lymphomas, leukemias, and solid tumors.     

Low-grade B-Cell lymphomas with plasmacytic differentiation lack PAX5 gene rearrangements

The chromosomal translocation t(9;14)(p13;q32) has been reported in association with lymphoplasmacytic lymphoma (LPL). Although this translocation involving the paired homeobox-5 (PAX5) gene at chromosome band 9p13 and the immunoglobulin heavy chain (IgH) gene at 14q32 has been described in approximately 50% of LPL cases, the actual number of cases studied is quite small. Many of the initial cases associated with t(9;14)(p13;q32) were actually low-grade B-cell lymphomas with plasmacytic differentiation other than LPL. Thus, we analyzed a series of low-grade B-cell lymphomas for PAX5 gene rearrangements. We searched records from the Department of Pathology, Stanford University Medical Center for low-grade B-cell lymphomas, with an emphasis on plasmacytic differentiation, that had available paraffin blocks or frozen tissue. We identified 37 cases, including 13 LPL, 18 marginal zone lymphomas (nodal, extranodal, splenic, and alpha-heavy chain disease), and 6 small lymphocytic lymphomas. A novel dual-color break-apart bacterial artificial chromosome probe was designed to flank the PAX5 gene, spanning previously described PAX5 breakpoints, and samples were analyzed by interphase fluorescence in situ hybridization. All cases failed to demonstrate a PAX5 translocation, indicating that t(9;14)(p13;q32) and other PAX5 translocations are uncommon events in low-grade B-cell lymphomas with plasmacytic differentiation. This study also confirms recent reports that found an absence of PAX5 rearrangements in LPL, suggesting the reassessment of PAX5 rearrangements in LPL.     

Studying Early Lethality of 45,XO (Turner's Syndrome) Embryos Using Human Embryonic Stem Cells

Turner's syndrome (caused by monosomy of chromosome X) is one of the most common chromosomal abnormalities in females. Although 3% of all pregnancies start with XO embryos, 99% of these pregnancies terminate spontaneously during the first trimester. The common genetic explanation for the early lethality of monosomy X embryos, as well as the phenotype of surviving individuals is haploinsufficiency of pseudoautosomal genes on the X chromosome. Another possible mechanism is null expression of imprinted genes on the X chromosome due to the loss of the expressed allele. In contrast to humans, XO mice are viable, and fertile. Thus, neither cells from patients nor mouse models can be used in order to study the cause of early lethality in XO embryos. Human embryonic stem cells (HESCs) can differentiate in culture into cells from the three embryonic germ layers as well as into extraembryonic cells. These cells have been shown to have great value in modeling human developmental genetic disorders. In order to study the reasons for the early lethality of 45,XO embryos we have isolated HESCs that have spontaneously lost one of their sex chromosomes. To examine the possibility that imprinted genes on the X chromosome play a role in the phenotype of XO embryos, we have identified genes that were no longer expressed in the mutant cells. None of these genes showed a monoallelic expression in XX cells, implying that imprinting is not playing a major role in the phenotype of XO embryos. To suggest an explanation for the embryonic lethality caused by monosomy X, we have differentiated the XO HESCs in vitro an in vivo. DNA microarray analysis of the differentiated cells enabled us to compare the expression of tissue specific genes in XO and XX cells. The tissue that showed the most significant differences between the clones was the placenta. Many placental genes are expressed at much higher levels in XX cells in compare to XO cells. Thus, we suggest that abnormal placental differentiation as a result of haploinsufficiency of X-linked pseudoautosomal genes causes the early lethality in XO human embryos.     

Molecular analysis of chromosomal rearrangements in mammalian cells after phiC31-mediated integration

Reports on insertional mutagenesis due to integration of gene therapy vectors into the host genome have raised concerns about the genetic manipulation of somatic cells. Previously, it was demonstrated that integrase phiC31 derived from a Streptomyces phage mediates site-specific integration into the host genome of mammalian cells in vitro and in vivo by recombining the attB recognition site in an episomal plasmid and one or more pseudoattP sites in the host chromosomes. In the present study we investigated whether cryptic phiC31 recognition sites in the host genome may result in chromosomal rearrangements. Of 69 independent integration events analyzed in human cells, 6 (8.7%) integrated into human chromosome 19 (19q13.31) and 10 (14.49%) integrated into human chromosome 12 (12q22). Most importantly, of all integration sites analyzed, 15% were found to contain an integrated transgene that was flanked by DNA sequences originating from two different chromosomes. To confirm chromosomal translocations we performed a polymerase chain reaction analysis of chromosomal DNA flanking the transgene and also performed limited studies to determine the genotype of single-cell clones. Although the mechanism responsible for chromosomal translocations needs to be further characterized, we speculate that cryptic phiC31 attachment sites flanking the transgene and cryptic phiC31 attachment sites in the host genome recombine with each other.     

Haploinsufficiency of Activation-Induced Deaminase for Antibody Diversification and Chromosome Translocations both In Vitro and In Vivo

The humoral immune response critically relies on the secondary diversification of antibodies. This diversification takes places through somatic remodelling of the antibody genes by two molecular mechanisms, Class Switch Recombination (CSR) and Somatic Hypermutation (SHM). The enzyme Activation Induced Cytidine Deaminase (AID) initiates both SHM and CSR by deaminating cytosine residues on the DNA of immunoglobulin genes. While crucial for immunity, AID-catalysed deamination is also the triggering event for the generation of lymphomagenic chromosome translocations. To address whether restricting the levels of AID expression in vivo contributes to the regulation of its function, we analysed mice harbouring a single copy of the AID gene (AID^+/−). AID^+/− mice express roughly 50% of normal AID levels, and display a mild hyperplasia, reminiscent of AID deficient mice and humans. Moreover, we found that AID^+/− cells have an impaired competence for CSR and SHM, which indicates that AID gene dose is limiting for its physiologic function. We next evaluated the impact of AID reduction in AID^+/− mice on the generation of chromosome translocations. Our results show that the frequency of AID-promoted c-myc/IgH translocations is reduced in AID^+/− mice, both in vivo and in vitro. Therefore, AID is haploinsufficient for antibody diversification and chromosome translocations. These findings suggest that limiting the physiologic levels of AID expression can be a regulatory mechanism that ensures an optimal balance between immune proficiency and genome integrity.     

Six families with balanced chromosome translocation associated with reproductive risks in Hainan Province: Case reports and review of the literature

BACKGROUND Balanced translocation refers to the process where breakage and reconnection of chromosomes occur at abnormal positions.As the genetic substance with balanced translocation in individuals does not change,which is usually characterized by normal phenotype and intelligence,the individuals seek medical service after many miscarriages,resulting in considerable mental and physical burdens of the family members.In the current era with rapid advances in detection technology,cytogenetic examination,as a definitive approach,still plays an essential role.CASE SUMMARY We report six cases with balanced chromosome translocation:Case 1:46,XY,t(3;12)(q27;q24.1),infertility after 3 years of marriage;Case 2:46,XX,t(4;16)(q31;q12),small uterus and irregular menstruation;Case 3:46,XY,t(4;5)(q33;q13),9qh+,not pregnant after arrested fetal development;Case 4:46,XX,t(11;17)(q13;p11.2),not pregnant after two times of spontaneous abortion;Case 5:46,XX,t(10;13)(q24;q21.2),not pregnant after arrested fetal development for once;Case 6:46,XX,t(1;4)(p36.1;q31.1),not pregnant after arrested fetal development for two times.The first four cases had chromosomal aberration karyotypes.CONCLUSION These results suggested that balanced chromosomal translocation carriers are associated with reproductive risks and a very high probability of abnormal pregnancy.The discovery of the first four reported chromosomal aberration karyotypes provides an important basis for studying the occurrence of genetic diseases.     

Breakpoint of a balanced translocation (X:14) (q27.1;q32.3) in a girl with severe hemophilia B maps proximal to the factor IX gene

Summary.  Hemophilia B is an X-linked bleeding disorder caused by the deficiency of coagulation factor (F)IX, with an estimated prevalence of 1 in 30 000 male births. It is almost exclusively seen in males with rare exceptions. We report a girl who was diagnosed with severe (<1%) FIX deficiency at 4 months of age. Cytogenetic studies in the patient showed a balanced translocation between one of the X-chromosomes and chromosome 14, with breakpoints at bands Xq27.1 and 14q32.3. Both parents were found to have normal chromosomes. Late replication studies by incorporation of 5-bromodeoxyuridine showed non-random inactivation of the normal X-chromosome, a phenomenon frequently seen in balanced X/autosome translocations. To map the breakpoint, fluorescent in-situ hybridization was performed. A PAC DNA probe, RP6-88D7 (which contains the FIX gene) hybridized only on the normal chromosome X as well as onto the derivative 14. Using a PAC DNA probe, RP11-963P9 that is located proximal to the FIX gene, we obtained signals on the normal and derivative X and also on the derivative 14. We conclude that the breakpoint is located within the DNA sequence of this clone mapping proximal to the FIX gene. Since the FIX gene seems to be intact in the derivative 14, the breakpoint may affect an upstream regulatory sequence that subjects the gene to position effect variegation (PEV).     

骨髓增生异常综合征患者细胞遗传学特征分析

本研究探讨骨髓增生异常综合征（MDS）患者中染色体异常核型在MDS亚型中的分布及其数目异常和结构异常特点。常规培养骨髓细胞,采用G显带技术对染色体核型进行分析。结果表明,127例患者中异常核型比例为42．5％（54／127）,其中各亚型异常发生率MDS．RA为30％（3／10）,MDS．RCMD为35．9％（23／64）,MDS．RAS为22．2％（2／9）,MDS-RAEB-Ⅰ为45％（9／20）,MDS-RAEB-Ⅱ为66．7％（14／21）,5q-综合征100％（3／3）。54例异常核型中仅数目异常者21例,仅有结构异常者14例,同时有结构异常和数目异常者19例。常见染色体异常依次为复杂核型（11．02％,14／127）,单纯＋8（10．24％,13／127）,-7／7q-（3．9％,5／127）,1q＋（3．15％,4／127）,-X／-Y（3．15％,4／127）,20q-（2．36％,3／127）,5q-（2．36％,3／127）。MDS-RAEB（包括RAEB-Ⅰ和RAEB-Ⅱ）患者中复杂核型发生率为31．71％（13／41）,明显高于非RAEB（包括RA、RCMD、RAS、5q-综合征）患者中复杂核型发生率为1．16％（1／86）（P〈0．05）。平衡易位核型发生率为1．57％（2／127）,明显低于非平衡易位发生率为40．94％（52／127）（P〈0．05）,2例平衡易位患者均为MDS-RAEB。结论：MDS是一组高度异质性的克隆性疾病,染色体异常比较复杂,存在多种重现性异常;平衡易位较少见,仅存在于RAEB患者中;RAEB患者复杂异常核型发生率较高,本研究中伴dup（1）（q21q32）重现性异常核型所占比例较高。     

High resolution banding analysis of the involvement of strain BALB/c- and AKR-derived chromosomes No. 15 in plasmacytoma-specific translocations

Plasmacytomas were induced in (BALB/c X AKR 6;15) X BALB/c backcross mice where one of the BALB/c-derived chromosomes No. 15 was replaced by the AKR(6;15)-derived Robertsonian 6;15 chromosome. (BALB/c X AKR 6;15)F2 mice that were homozygous for Rb 6;15 were mated to BALB/c mice. Plasmacytomas were induced in the progeny by intraperitoneal injection of pristane. The cytogenetic marker permitted the distinctive identification of the two chromosome 15 homologues, including the distal segment involved in the plasmacytoma-specific translocations. 7 of the 10 plasmacytomas contained the typical t(12;15) translocation. The BALB/c-derived 15 chromosome served as the donor of the translocated segment in six of them. In the seventh, the Rb 6;15 chromosome of the AKR strain was the donor. The remaining three tumors contained the same type of intrachromosomal rearrangement. It arose by the pericentric inversion of the Rb 6;15 chromosome, leading to a variant plasmacytoma-associated rcpt (6;15) translocation. Unlike the usual 6;15 variant that arises by a reciprocal exchange between two separate chromosomes, it was generated by an exchange of the distal segments of a single chromosomal element. High resolution banding analysis of the tumors showed that all translocated breakpoints on chromosomes 15, 12, and 6 were identical with the previously described breakpoints characteristic for the typical 12;15 and the variant 6;15 translocation in murine plasmacytomas. It is known that the distal segment of chromosome 15 carries the c-myc oncogene (23). The PC- associated translocations cut across the 5'-exon of c-myc in the majority of the cases (24,26). The severed oncogene is transposed to the Ig-region on the recipient chromosome. Since the BALB/c strain is highly sensitive to PC-induction, we were interested to examine the question whether its chromosome 15 is preferred as the oncogene donor in AKR X BALB/c backcross mice that carry cytogenetically distinguishable 15 chromosomes. Our results show that this is not the case, since the same segment of the AKR-derived chromosome 15 could also serve in the same capacity. This is in contrast with T cell leukemogenesis where we have previously found that the trisomization- associated duplication of chromosome 15 occurred in a highly asymmetrical fashion, depending on the donor strain of No. 15 (9-11).     

Molecular cytogenetic studies of a male carrier with a unique (Y;14) translocation: Case report

BackgroundChromosome translocation is a genetic factor associated with male infertility. However, cases of Y chromosome/autosome translocation are rare. Individuals with translocation between the Y chromosome and an autosome have a variety of different clinical phenotypes. There is a need for further study of molecular cytogenetic feature of those with Y chromosome translocation.MethodsWe reported that an apparently healthy 31‐year‐old man, 168 cm tall and weighing 65 kg, had a 2‐year history of primary infertility after marriage. Clinical diagnostic techniques included semen analysis, hormone measurements, cytogenetic analysis, fluorescence in situ hybridization (FISH), and high‐throughput multiplex ligation‐dependent probe amplification semiconductor sequencing. Detailed genetic counseling was provided to the patient. Intracytoplasmic sperm injection treatment combined with preimplantation genetic diagnosis was chosen with the aim of achieving a successful pregnancy.ResultsSemen analysis revealed cryptozoospermia. Hormone levels were within the normal limits. Sequencing results indicated the presence of the sex‐determining region on Yp, and AZFa, AZFb, and AZFc regions on Yq. The patient''s karyotype was 45,X,psu,dic(Y;14)(p11.3;q11.2), which was confirmed by cytogenetic analysis and FISH.ConclusionThis study reports a case of cryptozoospermia in a male patient with a Y;14 chromosomal translocation. When clinical karyotyping has revealed potential Y chromosome abnormality, FISH or molecular detection should be further performed to facilitate identification of the chromosomal breakpoint.