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Guarracino A, Buonaiuto S, de Lima LG, Potapova T, Rhie A, Koren S, Rubinstein B, Fischer C, Gerton JL, Phillippy AM, Colonna V, Garrison E. Recombination between heterologous human acrocentric chromosomes. Nature 2023; 617:335-343. [PMID: 37165241 PMCID: PMC10172130 DOI: 10.1038/s41586-023-05976-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 03/17/2023] [Indexed: 05/12/2023]
Abstract
The short arms of the human acrocentric chromosomes 13, 14, 15, 21 and 22 (SAACs) share large homologous regions, including ribosomal DNA repeats and extended segmental duplications1,2. Although the resolution of these regions in the first complete assembly of a human genome-the Telomere-to-Telomere Consortium's CHM13 assembly (T2T-CHM13)-provided a model of their homology3, it remained unclear whether these patterns were ancestral or maintained by ongoing recombination exchange. Here we show that acrocentric chromosomes contain pseudo-homologous regions (PHRs) indicative of recombination between non-homologous sequences. Utilizing an all-to-all comparison of the human pangenome from the Human Pangenome Reference Consortium4 (HPRC), we find that contigs from all of the SAACs form a community. A variation graph5 constructed from centromere-spanning acrocentric contigs indicates the presence of regions in which most contigs appear nearly identical between heterologous acrocentric chromosomes in T2T-CHM13. Except on chromosome 15, we observe faster decay of linkage disequilibrium in the pseudo-homologous regions than in the corresponding short and long arms, indicating higher rates of recombination6,7. The pseudo-homologous regions include sequences that have previously been shown to lie at the breakpoint of Robertsonian translocations8, and their arrangement is compatible with crossover in inverted duplications on chromosomes 13, 14 and 21. The ubiquity of signals of recombination between heterologous acrocentric chromosomes seen in the HPRC draft pangenome suggests that these shared sequences form the basis for recurrent Robertsonian translocations, providing sequence and population-based confirmation of hypotheses first developed from cytogenetic studies 50 years ago9.
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Affiliation(s)
- Andrea Guarracino
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, USA
- Genomics Research Centre, Human Technopole, Milan, Italy
| | - Silvia Buonaiuto
- Institute of Genetics and Biophysics, National Research Council, Naples, Italy
| | | | - Tamara Potapova
- Stowers Institute for Medical Research, Kansas City, MO, USA
| | - Arang Rhie
- Genome Informatics Section, Computational and Statistical Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - Sergey Koren
- Genome Informatics Section, Computational and Statistical Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | | | - Christian Fischer
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, USA
| | | | - Adam M Phillippy
- Genome Informatics Section, Computational and Statistical Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA
| | - Vincenza Colonna
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, USA
- Institute of Genetics and Biophysics, National Research Council, Naples, Italy
| | - Erik Garrison
- Department of Genetics, Genomics and Informatics, University of Tennessee Health Science Center, Memphis, TN, USA.
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Ghosh S, Kjöllerström J, Metcalfe L, Reed S, Juras R, Raudsepp T. The Second Case of Non-Mosaic Trisomy of Chromosome 26 with Homologous Fusion 26q;26q in the Horse. Animals (Basel) 2022; 12:ani12070803. [PMID: 35405793 PMCID: PMC8996834 DOI: 10.3390/ani12070803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 03/16/2022] [Accepted: 03/18/2022] [Indexed: 12/16/2022] Open
Abstract
Simple Summary We present chromosome and DNA analysis of a normal Thoroughbred mare and her abnormal foal born with neurologic defects. We show that the foal has an abnormal karyotype with three copies of chromosome 26 (trisomy chr26), instead of the normal two. However, two of the three chr26 have fused, forming an unusual derivative chromosome. Chromosomes of the dam are normal, suggesting that the chromosome abnormality found in the foal happened during egg or sperm formation or after fertilization. Analysis of the foal and the dam with chr26 DNA markers indicates that the extra chr26 in the foal is likely of maternal origin and that the unusual derivative chromosome resulted from the fusion of two parental chr26. We demonstrate that although conventional karyotype analysis can accurately identify chromosome abnormalities, determining the mechanism and parental origin of these abnormalities requires DNA analysis. Most curiously, this is the second case of trisomy chr26 with unusual derivative chromosome in the horse, whereas all other equine trisomies have three separate copies of the chromosome involved. Because horse chr26 shares genetic similarity with human chr21, which trisomy causes Down syndrome, common features between trisomies of horse chr26 and human chr21 are discussed. Abstract We present cytogenetic and genotyping analysis of a Thoroughbred foal with congenital neurologic disorders and its phenotypically normal dam. We show that the foal has non-mosaic trisomy for chromosome 26 (ECA26) but normal 2n = 64 diploid number because two copies of ECA26 form a metacentric derivative chromosome der(26q;26q). The dam has normal 64,XX karyotype indicating that der(26q;26q) in the foal originates from errors in parental meiosis or post-fertilization events. Genotyping ECA26 microsatellites in the foal and its dam suggests that trisomy ECA26 is likely of maternal origin and that der(26q;26q) resulted from Robertsonian fusion. We demonstrate that conventional and molecular cytogenetic approaches can accurately identify aneuploidy with a derivative chromosome but determining the mechanism and parental origin of the rearrangement requires genotyping with chromosome-specific polymorphic markers. Most curiously, this is the second case of trisomy ECA26 with der(26q;26q) in the horse, whereas all other equine autosomal trisomies are ‘traditional’ with three separate chromosomes. We discuss possible ECA26 instability as a contributing factor for the aberration and likely ECA26-specific genetic effects on the clinical phenotype. Finally, because ECA26 shares evolutionary homology with human chromosome 21, which trisomy causes Down syndrome, cytogenetic, molecular, and phenotypic similarities between trisomies ECA26 and HSA21 are discussed.
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Affiliation(s)
- Sharmila Ghosh
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843, USA; (S.G.); (J.K.); (R.J.)
| | - Josefina Kjöllerström
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843, USA; (S.G.); (J.K.); (R.J.)
| | - Laurie Metcalfe
- Rood & Riddle Equine Hospital, Lexington, KY 40580, USA; (L.M.); (S.R.)
| | - Stephen Reed
- Rood & Riddle Equine Hospital, Lexington, KY 40580, USA; (L.M.); (S.R.)
| | - Rytis Juras
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843, USA; (S.G.); (J.K.); (R.J.)
| | - Terje Raudsepp
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843, USA; (S.G.); (J.K.); (R.J.)
- Correspondence:
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3
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Detection of paternal origin of fetal de novo rea(21q;21q) down syndrome in a pregnancy of a young woman associated with an abnormal first-trimester maternal serum screening result. Taiwan J Obstet Gynecol 2022; 61:356-358. [DOI: 10.1016/j.tjog.2022.02.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/21/2021] [Indexed: 11/17/2022] Open
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4
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Hervé B, Quibel T, Taieb S, Ruiz M, Molina-Gomes D, Vialard F. Are de novo rea(21;21) chromosomes really de novo? Clin Case Rep 2015; 3:786-9. [PMID: 26509006 PMCID: PMC4614639 DOI: 10.1002/ccr3.341] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 04/30/2015] [Accepted: 07/13/2015] [Indexed: 11/11/2022] Open
Abstract
We report a rare case of recurrent trisomy 21 caused by an isochromosome 21q and what is very likely to be maternal germ-line cell mosaicism. Over 90% of cases of rob(21;21) reported in the literature are due to an isochromosome 21q, with a risk of recurrence of more than 10%.
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Affiliation(s)
- Bérénice Hervé
- Service de Cytogénétique, Centre Hospitalier Intercommunal de Poissy Saint-Germain-en-Laye 10 rue du Champ Gaillard, F-78303, Poissy, France ; UPCG, UFR des Sciences de la Santé Simone Veil 2 avenue de la source de la Bièvre, F-78180, Montigny le Bretonneux, France
| | - Thibaud Quibel
- Service de Gynécologie-Obstétrique, Centre Hospitalier Intercommunal de Poissy Saint-Germain-en-Laye 10 rue du Champ Gaillard, F-78303, Poissy, France
| | - Stéphane Taieb
- Unité d'Empreintes Génétiques, Centre Hospitalier Intercommunal de Poissy-Saint Germain-en-Laye 20 rue Armagis, F-78100, Saint Germain-en-Laye, France
| | - Mireille Ruiz
- Service de Gynécologie-Obstétrique, Centre Hospitalier Intercommunal de Poissy Saint-Germain-en-Laye 10 rue du Champ Gaillard, F-78303, Poissy, France
| | - Denise Molina-Gomes
- Service de Cytogénétique, Centre Hospitalier Intercommunal de Poissy Saint-Germain-en-Laye 10 rue du Champ Gaillard, F-78303, Poissy, France
| | - François Vialard
- Service de Cytogénétique, Centre Hospitalier Intercommunal de Poissy Saint-Germain-en-Laye 10 rue du Champ Gaillard, F-78303, Poissy, France ; UPCG, UFR des Sciences de la Santé Simone Veil 2 avenue de la source de la Bièvre, F-78180, Montigny le Bretonneux, France
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5
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Flores-Ramírez F, Palacios-Guerrero C, García-Delgado C, Morales-Jiménez AB, Arias-Villegas CM, Cervantes A, Morán-Barroso VF. Cytogenetic Profile in 1,921 Cases of Trisomy 21 Syndrome. Arch Med Res 2015; 46:484-9. [DOI: 10.1016/j.arcmed.2015.08.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 08/17/2015] [Indexed: 10/23/2022]
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6
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Zhao WW, Wu M, Chen F, Jiang S, Su H, Liang J, Deng C, Hu C, Yu S. Robertsonian translocations: an overview of 872 Robertsonian translocations identified in a diagnostic laboratory in China. PLoS One 2015; 10:e0122647. [PMID: 25932913 PMCID: PMC4416705 DOI: 10.1371/journal.pone.0122647] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 02/11/2015] [Indexed: 11/18/2022] Open
Abstract
Robertsonian translocations (ROBs) have an estimated incidence rate of 1/1000 births, making this type of rearrangement the most common structural chromosomal abnormalities seen in the general population. In this study, we reports 872 cases of ROBs from 205,001 specimens karyotyped postnatally in a single accredited laboratory in China, including 583 balanced ROBs, 264 unbalanced ROBs, 9 mosaic ROBs, and 18 complex ROBs. Ninety-three percent of the balanced ROBs observed were adults with infertility, miscarriage, or offspring(s) with known chromosomal abnormalities. Significant excess of females were found to be carriers of balanced ROBs with an adjusted male/female ratio of 0.77. Ninety-eight percent of the unbalanced ROBs observed were children with variable referral reasons. Almost all of the unbalanced ROBs involved chromosome 21 except a single ROB with [46,XX,der(13;14),+13] identified in a newborn girl with multiple congenital anomalies. Multiple novel ROB karyotypes were reported in this report. This study represents the largest collections of ROBs in Chinese population.
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Affiliation(s)
- Wei-Wei Zhao
- KingMed Genome Diagnostic Laboratory, Guangzhou, China
| | - Menghua Wu
- KingMed Genome Diagnostic Laboratory, Guangzhou, China
| | - Fan Chen
- KingMed Genome Diagnostic Laboratory, Guangzhou, China
| | - Shuai Jiang
- KingMed Genome Diagnostic Laboratory, Guangzhou, China
| | - Hui Su
- KingMed Genome Diagnostic Laboratory, Guangzhou, China
| | - Jianfen Liang
- KingMed Genome Diagnostic Laboratory, Guangzhou, China
| | - Chunhua Deng
- KingMed Genome Diagnostic Laboratory, Guangzhou, China
| | - Chaohui Hu
- KingMed Genome Diagnostic Laboratory, Guangzhou, China
| | - Shihui Yu
- KingMed Genome Diagnostic Laboratory, Guangzhou, China
- Department of Laboratory Medicine, University of Washington School of Medicine and Seattle Children’s Hospital, Seattle, Washington, United States of America
- * E-mail:
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7
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Bint SM, Scriven PN, Ogilvie CM. Successful PGD cycles for mosaic Robertsonian translocation carriers provide insights into the mechanism of formation of the derivative chromosomes. Am J Med Genet A 2013; 161A:566-71. [PMID: 23401053 DOI: 10.1002/ajmg.a.35600] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 07/06/2012] [Indexed: 11/09/2022]
Abstract
Preimplantation genetic diagnosis (PGD) has been carried out for two couples with different mosaic Robertsonian translocations. Two PGD cycles for a mosaic 13;13 homologous Robertsonian translocation carrier resulted in the birth of a healthy child in each cycle, illustrating the importance of scanning G-banded preparations from homologous Robertsonian carriers for the presence of a normal cell line. One couple was referred for PGD because the male partner carried a mosaic 14;15 Robertsonian translocation with a normal cell line. A single PGD cycle resulted in the birth of a healthy child. Follow-up studies and extended FISH analysis of the carrier's lymphocytes detected three cell lines, two carrying different 14;15 Robertsonian chromosomes and one normal cell line. The two 14;15 Robertsonian chromosomes had different breakpoints in the proximal short arm regions. We suggest that the presence of the D15Z1 polymorphism on the short arm of one chromosome 14 mediated the post-zygotic formation of the two different Robertsonian chromosomes.
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Affiliation(s)
- Susan M Bint
- Cytogenetics Department, GSTS Pathology, Guy's Hospital, London, UK.
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8
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Dutta UR, Pidugu VK, Goud V, Dalal AB. Mosaic Down syndrome with a marker: Molecular cytogenetic characterization of the marker chromosome. Gene 2012; 495:199-204. [DOI: 10.1016/j.gene.2011.12.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2011] [Revised: 11/21/2011] [Accepted: 12/15/2011] [Indexed: 10/14/2022]
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9
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Hosseini S, Vahid Dastjerdi M, Asgari Z, Samiee H. Premature ovarian failure in a woman with a balanced 15;21 translocation: a case report. J Med Case Rep 2011; 5:250. [PMID: 21714880 PMCID: PMC3150317 DOI: 10.1186/1752-1947-5-250] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Accepted: 06/29/2011] [Indexed: 11/29/2022] Open
Abstract
Introduction A case of premature ovarian failure with concomitant findings of Robertsonian translocation between 15 and 21 chromosomes is reported here. The aforementioned karyotypic aberration has not been reported in the context of premature ovarian failure to date. Case presentation We present a case of premature ovarian failure in a 27-year-old infertile Kurdish Iranian woman with a Robertsonian 15;21 translocation. Conclusions The diagnosis of premature ovarian failure of unknown etiology, but with karyotypic evidence of a balanced autosomal translocation, suggests the possible role of autosomal genes in the pathogenesis of ovarian follicular attrition.
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Affiliation(s)
- Sayedehafagh Hosseini
- Arash University Hospital, Department of Obstetrics & Gynecology, Tehran University of Medical Sciences, Tehran, Iran.
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10
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Reddy KS. The conundrum of a jumping translocation (JT) in CVS from twins and review of JTs. Am J Med Genet A 2011; 152A:2924-36. [PMID: 20979197 DOI: 10.1002/ajmg.a.33710] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Jumping translocations (JTs) are rare constitutional or acquired rearrangements involving a donor and several receiver chromosomes. They may be inherited or de novo. JTs can be found as a cultural artifact, in normal individuals or in pathological conditions. The clinical consequences range from spontaneous abortion, loss of fetus, chromosome syndrome, congenital abnormalities, and infertility to malignancy. Considering the breakpoints of JTs, they are localized predominantly in repeat regions such as pericentromeric, centromeric, subtelomeric, telomeric, and occasionally interstitial regions that may be in a low copy repeats (LCR) or in a telomere like sequence. Differences between the constitutional and acquired JTs donor breakpoints suggest an independent mechanism in their formation. In this review, a new JT involving a donor chromosome 18p10qter and recipients 17q25qter or 1q25qter found by CVS of a twin pregnancy is described. This case illustrates the diagnostic challenges posed by JTs.In this study, our knowledge on JTs is consolidated to improve identification, management, and counseling.
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Affiliation(s)
- Kavita S Reddy
- Kaiser Permanente Southern California, 4580 ElectronicPlace, Los Angeles, CA 90039, USA.
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11
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Chen CP, Chern SR, Wu PC, Tsai FJ, Lee CC, Town DD, Chen WL, Chen LF, Lee MS, Pan CW, Wang W. Unbalanced and balanced heterologous acrocentric rearrangements involving chromosome 21 at amniocentesis. Taiwan J Obstet Gynecol 2010; 49:62-8. [PMID: 20466295 DOI: 10.1016/s1028-4559(10)60011-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/26/2009] [Indexed: 10/19/2022] Open
Abstract
OBJECTIVE To present unbalanced and balanced heterologous acrocentric rearrangements involving chromosome 21 at amniocentesis. MATERIALS AND METHODS Between January 1987 and September 2009, 31,194 amniocenteses were performed at Mackay Memorial Hospital, Taipei, Taiwan. Two cases with an unbalanced heterologous acrocentric rearrangements involving chromosome 21 from two families and seven cases with balanced heterologous acrocentric rearrangements involving chromosome 21 from five families were diagnosed and investigated. RESULTS We detected rob(14q21q),+21 (one case), rob(13q21q),+21 (one case), rob(14q21q) (four cases), rob(13q21q) (one case) and rob(15q21q) (two cases). Of the nine cases that underwent parental cytogenetic investigation, one was de novo and eight were inherited (five maternal and three paternal). The six families with an inherited acrocentric rearrangement included rob(14q21q) (three families), rob(13q21q) (two families) and rob(15q21q) (one family). Of these six families, three had a known parental carrier status before the first amniocentesis, while the other three were aware of their parental carrier status only after prenatal diagnosis of a fetus with a heterologous acrocentric rearrangement. The seven fetuses with a balanced heterologous acrocentric rearrangement were inherited from two paternal carriers of rob(14q21q), one maternal carrier of rob(14q21q), one maternal carrier of rob(13q21q), and one maternal carrier of rob(15q21q). No uniparental disomy 14 was detected in any of the three cases with rob(14q21q) tested for uniparental disomy. CONCLUSION Concerning heterologous acrocentric rearrangements involving chromosome 21, the frequency of unbalanced rearrangements was 0.0064% and that of balanced rearrangements was 0.0224% at amniocentesis. In this study, rob(14q21q) was the most common, and rob(13q21q) and rob(15q21q) were the second most common rearrangements. Of the six families with an inherited heterologous acrocentric rearrangement involving chromosome 21, 50% (3/6) were aware of their parental carrier status only after prenatal diagnosis of a fetus with a translocation by amniocentesis.
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Affiliation(s)
- Chih-Ping Chen
- Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, Taiwan.
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12
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Chen CP, Chern SR, Tsai FJ, Wu PC, Chiang SS, Lee CC, Wang W. Down syndrome due to unbalanced homologous acrocentric rearrangements and its recurrence in subsequent pregnancies: prenatal diagnosis by amniocentesis. Taiwan J Obstet Gynecol 2010; 48:403-7. [PMID: 20045763 DOI: 10.1016/s1028-4559(09)60331-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
OBJECTIVE To present our experience of amniocentesis for the prenatal diagnosis of Down syndrome due to unbalanced homologous acrocentric rearrangements and its recurrence in subsequent pregnancies. CASE REPORT From January 1987 to September 2009, six cases with rea(21q21q) Down syndrome were diagnosed among 31,194 patients who underwent amniocentesis at Mackay Memorial Hospital, Taipei, Taiwan. Cytogenetic analysis of parental blood lymphocytes was performed in each case, and polymorphic DNA markers were used to investigate the nature of the aberrant chromosome. Three of the six cases were associated with recurrence in subsequent pregnancies. The rea(21q21q) Down syndrome was associated with advanced maternal age in three cases, a previous child with rea(21q21q) Down syndrome in three cases, an abnormal maternal serum screening result in one case, and an abnormal ultrasound finding in one case. All six cases arose de novo. Among the six cases with molecular analysis results, all had isochromosome 21, five of which were determined to be of maternal origin. CONCLUSION We found a frequency of 0.019% for rea(21q21q) Down syndrome in patients undergoing amniocentesis. Down syndrome caused by the homologous rearrangement rea(21q21q) can be associated with recurrence. Prenatal diagnosis of rea(21q21q) Down syndrome should include extensive cytogenetic and molecular analyses of the parents and probands.
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Affiliation(s)
- Chih-Ping Chen
- Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, Taiwan.
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Iwarsson E, Sahlén S, Nordgren A. Jumping translocation in a phenotypically normal male: A study of mosaicism in spermatozoa, lymphocytes, and fibroblasts. Am J Med Genet A 2009; 149A:1706-11. [PMID: 19610103 DOI: 10.1002/ajmg.a.32984] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Both Robertsonian translocations, rob(13;13) and rob(13;15), (in the present case defined as dic(13;15)), are rare chromosomal rearrangements and there is scarce information regarding their behavior during meiosis. In this report we describe a man with mosaicism for two cell lines, each cell line containing a different de novo Robertsonian translocation with the common breakpoint in the centromeric region on chromosome 13. The karyotype was finally defined as: 45,XY,rob(13;13)(q10;q10)[29]/45,XY,dic(13;15)(p11.2;p12)[22], a phenomenon referred to as jumping translocation. The relative occurrence of the two clones in lymphocytes and fibroblasts as well as the meiotic segregation in spermatozoa and the mechanism of formation were studied using karyotype analysis, fluorescence in situ hybridization (FISH), and quantitative fluorescence-PCR. Karyotype analysis of cultured lymphocytes revealed 57% rob(13;13) cells and 43% dic(13;15) cells and for cultured skin fibroblasts the figures were almost identical (56% and 44%, respectively). FISH analysis showed 55% balanced nuclei for unselected spermatozoa and after swim-up selection the number of balanced spermatozoa decreased to 41%. In addition, 16% of the unselected spermatozoa and 27% of the spermatozoa after swim-up selection carried an additional chromosome 13, indicating a high risk for a trisomy 13 offspring. Swim-up selection did not increase the number of balanced spermatozoa.
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Affiliation(s)
- Erik Iwarsson
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
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Abstract
The predominance of females segregating chromosome aberrations to their offspring has been explained mostly by selection disadvantage of unbalanced products of spermatogenesis. However, analysis of data from the literature supports the idea that somatic cells of early female embryos are similar to female germ cells in that they are prone to malsegregation. The goal of this study was to compare the sex ratio (male to female ratio) of carriers of presumably mitotic-occurring chromosome abnormalities to identify any sex biases. In examining the literature, we found a female prevalence in cases of mosaicism associated with uniparental disomy (UPD) (26 male individuals/conceptions and 45 female individuals/conceptions, sex ratio is 0.58, significantly different from 1.06 in newborn population, P = 0.0292). This predominance was highest at gestational age <16 week (8 male and 22 female conceptuses, sex ratio is 0.36, significantly different from expected figure of 1.28, P = 0.0025), which diminished at later stages of fetal development indicating potential correction of trisomies predominantly in females. There is a threefold prevalence of 46,XX/45,X mosaics over 46,XY/45,X mosaics in prenatally diagnosed cases, which also suggests a gender-specific postzygotic chromosome loss. The male prevalence in Prader-Willi syndrome with maternal UPD of chromosome 15 also can be explained by sex-specific trisomy correction, with predominant loss of a maternal chromosome causing biparental inheritance and therefore, complete correction of trisomy in females (without UPD). Finally, there is a female predominance in carriers of chromosome rearrangement with pericentromere break (mosaicism for Robertsonian translocation/isochromosome, centric fission, nonacrocentric isochromosome, and whole arm rearrangement), in both prenatal (21 males and 36 females, sex ratio is 0.58, P < 0.0184) and postnatal ill-defined cases (14 males and 35 females, sex ratio is 0.40, P = 0.001). Thus, the findings presented in this paper suggest that, in addition to reduction in male fertility, and to probable selection against abnormal cell line(s), there are two mechanisms that contribute to female preponderance among carriers of mosaicism: sex-specific chromosome loss and sex-specific centromere instability. The data obtained suggest that females may have gonadal mosaicism for aneuploidies and structural rearrangements more often than males. This may lead to the maternal origin bias in offspring with trisomies or structural rearrangements.
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Affiliation(s)
- Natalia V Kovaleva
- St. Petersburg Centre for Medical Genetics, St. Petersburg, Russian Federation.
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