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A candidate gene analysis and GWAS for genes associated with maternal nondisjunction of chromosome 21. PLoS Genet 2019; 15:e1008414. [PMID: 31830031 PMCID: PMC6932832 DOI: 10.1371/journal.pgen.1008414] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Revised: 12/26/2019] [Accepted: 09/11/2019] [Indexed: 01/21/2023] Open
Abstract
Human nondisjunction errors in oocytes are the leading cause of pregnancy loss, and for pregnancies that continue to term, the leading cause of intellectual disabilities and birth defects. For the first time, we have conducted a candidate gene and genome-wide association study to identify genes associated with maternal nondisjunction of chromosome 21 as a first step to understand predisposing factors. A total of 2,186 study participants were genotyped on the HumanOmniExpressExome-8v1-2 array. These participants included 749 live birth offspring with standard trisomy 21 and 1,437 parents. Genotypes from the parents and child were then used to identify mothers with nondisjunction errors derived in the oocyte and to establish the type of error (meiosis I or meiosis II). We performed a unique set of subgroup comparisons designed to leverage our previous work suggesting that the etiologies of meiosis I and meiosis II nondisjunction differ for trisomy 21. For the candidate gene analysis, we selected genes associated with chromosome dynamics early in meiosis and genes associated with human global recombination counts. Several candidate genes showed strong associations with maternal nondisjunction of chromosome 21, demonstrating that genetic variants associated with normal variation in meiotic processes can be risk factors for nondisjunction. The genome-wide analysis also suggested several new potentially associated loci, although follow-up studies using independent samples are required. Approximately one of every 700 babies is born with trisomy 21—an extra copy of chromosome 21. Trisomy 21 is caused by the failure of chromosomes to segregate properly during meiosis, generally in the mother. Past studies have defined altered patterns of recombination along nondisjoined chromosomes as risk factors for human nondisjunction and model systems have clearly shown that specific genes involved recombination and other early meiotic processes play a role in the fidelity of chromosome segregation. However, no genome-wide genetic study (GWAS) has ever been conducted using maternal human nondisjunction as the disease phenotype. This study takes the first step to understand predisposing factors. We used chromosome 21 genotypes from the parents and child to identify mothers with nondisjunction errors derived in the oocyte and to establish the type of error (meiosis I or meiosis II). We then conducted a unique set of subgroup comparisons designed to leverage our previous work that shows that the etiologies of meiosis I and meiosis II nondisjunction differ for trisomy 21. Both the candidate gene study and the GWAS provide evidence that meiotic-specific structures and processes are vulnerable to genetic variants that lead to increased risk of human chromosome nondisjunction.
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Delhanty JDA, SenGupta SB, Ghevaria H. How common is germinal mosaicism that leads to premeiotic aneuploidy in the female? J Assist Reprod Genet 2019; 36:2403-2418. [PMID: 31705227 PMCID: PMC6910893 DOI: 10.1007/s10815-019-01596-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 09/25/2019] [Indexed: 11/25/2022] Open
Abstract
Purpose Molecular cytogenetic analysis has confirmed that a proportion of apparently meiotic aneuploidy may be present in the germ cells prior to the onset of meiosis, but there is no clear perception of its frequency. The aim of this review is to assess the evidence for premeiotic aneuploidy from a variety of sources to arrive at an estimate of its overall contribution to oocyte aneuploidy in humans. Methods Relevant scientific literature was covered from 1985 to 2018 by searching PubMed databases with search terms: gonadal/germinal mosaicism, ovarian mosaicism, premeiotic aneuploidy, meiosis and trisomy 21. Additionally, a key reference from 1966 was included. Results Data from over 9000 cases of Down syndrome showed a bimodal maternal age distribution curve, indicating two overlapping distributions. One of these matched the pattern for the control population, with a peak at about 28 years and included all cases that had occurred independently of maternal age, including those due to germinal mosaicism, about 40% of the cohort. The first cytological proof of germinal mosaicism was obtained by fluorescence in situ hybridisation analysis. Comparative genomic hybridisation analysis of oocyte chromosomes suggests an incidence of up to 15% in premeiotic oocytes. Direct investigation of fetal ovarian cells led to variable results for chromosome 21 mosaicism. Conclusions Oocytes with premeiotic errors will significantly contribute to the high level of preimplantation and prenatal death. Data so far available suggests that, depending upon the maternal age, up to 40% of aneuploidy that is present in oocytes at the end of meiosis I may be due to germinal mosaicism.
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Affiliation(s)
- Joy DA Delhanty
- Preimplantation Genetics Group, Institute for Women's Health, University College London, 86-96 Chenies Mews, London, WC1E 6HX, U.K
| | - Sioban B SenGupta
- Preimplantation Genetics Group, Institute for Women's Health, University College London, 86-96 Chenies Mews, London, WC1E 6HX, U.K
| | - Harita Ghevaria
- Preimplantation Genetics Group, Institute for Women's Health, University College London, 86-96 Chenies Mews, London, WC1E 6HX, U.K..
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Lenormand T, Engelstädter J, Johnston SE, Wijnker E, Haag CR. Evolutionary mysteries in meiosis. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2016.0001. [PMID: 27619705 DOI: 10.1098/rstb.2016.0001] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/15/2016] [Indexed: 01/25/2023] Open
Abstract
Meiosis is a key event of sexual life cycles in eukaryotes. Its mechanistic details have been uncovered in several model organisms, and most of its essential features have received various and often contradictory evolutionary interpretations. In this perspective, we present an overview of these often 'weird' features. We discuss the origin of meiosis (origin of ploidy reduction and recombination, two-step meiosis), its secondary modifications (in polyploids or asexuals, inverted meiosis), its importance in punctuating life cycles (meiotic arrests, epigenetic resetting, meiotic asymmetry, meiotic fairness) and features associated with recombination (disjunction constraints, heterochiasmy, crossover interference and hotspots). We present the various evolutionary scenarios and selective pressures that have been proposed to account for these features, and we highlight that their evolutionary significance often remains largely mysterious. Resolving these mysteries will likely provide decisive steps towards understanding why sex and recombination are found in the majority of eukaryotes.This article is part of the themed issue 'Weird sex: the underappreciated diversity of sexual reproduction'.
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Affiliation(s)
- Thomas Lenormand
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE)-Unité Mixte de Recherche 5175, Centre National de la Recherche Scientifique (CNRS), Université de Montpellier-Université Paul-Valéry Montpellier-Ecole Pratique des Hautes Etudes (EPHE), 1919 Route de Mende, 34293 Montpellier Cedex 5, France
| | - Jan Engelstädter
- School of Biological Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Susan E Johnston
- Institute of Evolutionary Biology, University of Edinburgh, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK
| | - Erik Wijnker
- Laboratory of Genetics, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands
| | - Christoph R Haag
- Centre d'Ecologie Fonctionnelle et Evolutive (CEFE)-Unité Mixte de Recherche 5175, Centre National de la Recherche Scientifique (CNRS), Université de Montpellier-Université Paul-Valéry Montpellier-Ecole Pratique des Hautes Etudes (EPHE), 1919 Route de Mende, 34293 Montpellier Cedex 5, France
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Malini SS, Savitha MR, Krishnamurthy B, Ramachandra NB. Advanced Maternal Grandmother Age is a Risk Factor in Causing Sex Chromosomal Aneuploidy. INT J HUM GENET 2017. [DOI: 10.1080/09723757.2007.11886008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Suttur S Malini
- Human Genetics Laboratory, Department of Studies in Zoology, University of Mysore, Manasagangothri, Mysore 570 006, Karnataka, India
| | - Mysore R. Savitha
- Department of Pediatrics, Cheluvamba Hospital, Mysore Medical College, Mysore, Karnataka, India
| | | | - Nallur B Ramachandra
- Human Genetics Laboratory, Department of Studies in Zoology, University of Mysore, Manasagangothri, Mysore 570 006, Karnataka, India
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Reichman R, Alleva B, Smolikove S. Prophase I: Preparing Chromosomes for Segregation in the Developing Oocyte. Results Probl Cell Differ 2017; 59:125-173. [PMID: 28247048 DOI: 10.1007/978-3-319-44820-6_5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Formation of an oocyte involves a specialized cell division termed meiosis. In meiotic prophase I (the initial stage of meiosis), chromosomes undergo elaborate events to ensure the proper segregation of their chromosomes into gametes. These events include processes leading to the formation of a crossover that, along with sister chromatid cohesion, forms the physical link between homologous chromosomes. Crossovers are formed as an outcome of recombination. This process initiates with programmed double-strand breaks that are repaired through the use of homologous chromosomes as a repair template. The accurate repair to form crossovers takes place in the context of the synaptonemal complex, a protein complex that links homologous chromosomes in meiotic prophase I. To allow proper execution of meiotic prophase I events, signaling processes connect different steps in recombination and synapsis. The events occurring in meiotic prophase I are a prerequisite for proper chromosome segregation in the meiotic divisions. When these processes go awry, chromosomes missegregate. These meiotic errors are thought to increase with aging and may contribute to the increase in aneuploidy observed in advanced maternal age female oocytes.
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Affiliation(s)
- Rachel Reichman
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA
| | - Benjamin Alleva
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA
| | - Sarit Smolikove
- Department of Biology, University of Iowa, Iowa City, IA, 52242, USA.
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MacLennan M, Crichton JH, Playfoot CJ, Adams IR. Oocyte development, meiosis and aneuploidy. Semin Cell Dev Biol 2015; 45:68-76. [PMID: 26454098 PMCID: PMC4828587 DOI: 10.1016/j.semcdb.2015.10.005] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/14/2015] [Accepted: 10/05/2015] [Indexed: 01/15/2023]
Abstract
Meiosis is one of the defining events in gametogenesis. Male and female germ cells both undergo one round of meiotic cell division during their development in order to reduce the ploidy of the gametes, and thereby maintain the ploidy of the species after fertilisation. However, there are some aspects of meiosis in the female germline, such as the prolonged arrest in dictyate, that appear to predispose oocytes to missegregate their chromosomes and transmit aneuploidies to the next generation. These maternally-derived aneuploidies are particularly problematic in humans where they are major contributors to miscarriage, age-related infertility, and the high incidence of Down's syndrome in human conceptions. This review will discuss how events that occur in foetal oocyte development and during the oocytes' prolonged dictyate arrest can influence meiotic chromosome segregation and the incidence of aneuploidy in adult oocytes.
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Affiliation(s)
- Marie MacLennan
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK.
| | - James H Crichton
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK.
| | - Christopher J Playfoot
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK.
| | - Ian R Adams
- MRC Human Genetics Unit, MRC Institute of Genetics and Molecular Medicine, University of Edinburgh, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, UK.
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Middlebrooks CD, Mukhopadhyay N, Tinker SW, Allen EG, Bean LJH, Begum F, Chowdhury R, Cheung V, Doheny K, Adams M, Feingold E, Sherman SL. Evidence for dysregulation of genome-wide recombination in oocytes with nondisjoined chromosomes 21. Hum Mol Genet 2013; 23:408-17. [PMID: 24014426 DOI: 10.1093/hmg/ddt433] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In oocytes with nondisjoined chromosomes 21 due to a meiosis I (MI) error, recombination is significantly reduced along chromosome 21; several lines of evidence indicate that this contributes to the nondisjunction event. A pilot study found evidence that these oocytes also have reduced recombination genome-wide when compared with controls. This suggests that factors that act globally may be contributing to the reduced recombination on chromosome 21, and hence, the nondisjunction event. To identify the source of these factors, we examined two levels of recombination count regulation in oocytes: (i) regulation at the maternal level that leads to correlation in genome-wide recombination across her oocytes and (ii) regulation at the oocyte level that leads to correlation in recombination count among the chromosomes of an oocyte. We sought to determine whether either of these properties was altered in oocytes with an MI error. As it relates to maternal regulation, we found that both oocytes with an MI error (N = 94) and their siblings (N = 64) had reduced recombination when compared with controls (N = 2723). At the oocyte level, we found that the correlation in recombination count among the chromosomes of an oocyte is reduced in oocytes with MI errors compared with that of their siblings or controls. These results suggest that regulation at the maternal level predisposes MI error oocytes to reduced levels of recombination, but additional oocyte-specific dysregulation contributes to the nondisjunction event.
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Affiliation(s)
- Candace D Middlebrooks
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA
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Meola N, Gennarino VA, Banfi S. microRNAs and genetic diseases. PATHOGENETICS 2009; 2:7. [PMID: 19889204 PMCID: PMC2778645 DOI: 10.1186/1755-8417-2-7] [Citation(s) in RCA: 117] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Accepted: 11/04/2009] [Indexed: 12/19/2022]
Abstract
microRNAs (miRNAs) are a class of small RNAs (19-25 nucleotides in length) processed from double-stranded hairpin precursors. They negatively regulate gene expression in animals, by binding, with imperfect base pairing, to target sites in messenger RNAs (usually in 3' untranslated regions) thereby either reducing translational efficiency or determining transcript degradation. Considering that each miRNA can regulate, on average, the expression of approximately several hundred target genes, the miRNA apparatus can participate in the control of the gene expression of a large quota of mammalian transcriptomes and proteomes. As a consequence, miRNAs are expected to regulate various developmental and physiological processes, such as the development and function of many tissue and organs. Due to the strong impact of miRNAs on the biological processes, it is expected that mutations affecting miRNA function have a pathogenic role in human genetic diseases, similar to protein-coding genes. In this review, we provide an overview of the evidence available to date which support the pathogenic role of miRNAs in human genetic diseases. We will first describe the main types of mutation mechanisms affecting miRNA function that can result in human genetic disorders, namely: (1) mutations affecting miRNA sequences; (2) mutations in the recognition sites for miRNAs harboured in target mRNAs; and (3) mutations in genes that participate in the general processes of miRNA processing and function. Finally, we will also describe the results of recent studies, mostly based on animal models, indicating the phenotypic consequences of miRNA alterations on the function of several tissues and organs. These studies suggest that the spectrum of genetic diseases possibly caused by mutations in miRNAs is wide and is only starting to be unravelled.
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Affiliation(s)
- Nicola Meola
- Telethon Institute of Genetics and Medicine (TIGEM), 80131 Naples, Italy.
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Li W, Freudenberg J. Two-parameter characterization of chromosome-scale recombination rate. Genome Res 2009; 19:2300-7. [PMID: 19752285 DOI: 10.1101/gr.092676.109] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The genome-wide recombination rate (RR) of a species is often described by one parameter, the ratio between total genetic map length (G) and physical map length (P), measured in centimorgans per megabase (cM/Mb). The value of this parameter varies greatly between species, but the cause for these differences is not entirely clear. A constraining factor of overall RR in a species, which may cause increased RR for smaller chromosomes, is the requirement of at least one chiasma per chromosome (or chromosome arm) per meiosis. In the present study, we quantify the relative excess of recombination events on smaller chromosomes by a linear regression model, which relates the genetic length of chromosomes to their physical length. We find for several species that the two-parameter regression, G = G(0) + k x P , provides a better characterization of the relationship between genetic and physical map length than the one-parameter regression that runs through the origin. A nonzero intercept (G(0)) indicates a relative excess of recombination on smaller chromosomes in a genome. Given G(0), the parameter k predicts the increase of genetic map length over the increase of physical map length. The observed values of G(0) have a similar magnitude for diverse species, whereas k varies by two orders of magnitude. The implications of this strategy for the genetic maps of human, mouse, rat, chicken, honeybee, worm, and yeast are discussed.
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Affiliation(s)
- Wentian Li
- The Robert S. Boas Center for Genomics and Human Genetics, The Feinstein Institute for Medical Research, North Shore LIJ Health System, Manhasset, New York 11030, USA.
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ZHENG CG, QIN J, DU J, CHEN K, CHEN C, TIAN XX, XIANG L, SUN L, YANG Z. Cytogenetic study of Down syndrome cases in Nanning, China. YI CHUAN = HEREDITAS 2009; 31:261-4. [DOI: 10.3724/sp.j.1005.2009.00261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Fragouli E, Wells D, Whalley KM, Mills JA, Faed MJW, Delhanty JDA. Increased susceptibility to maternal aneuploidy demonstrated by comparative genomic hybridization analysis of human MII oocytes and first polar bodies. Cytogenet Genome Res 2006; 114:30-8. [PMID: 16717447 DOI: 10.1159/000091925] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2005] [Accepted: 11/15/2005] [Indexed: 01/02/2023] Open
Abstract
Single cell comparative genomic hybridization (CGH) was employed to extensively investigate 24 unfertilized or in vitromatured meiosis II oocytes and their corresponding first polar bodies (PBs), to determine how and whether all 23 chromosomes participate in female meiosis I errors and to accurately estimate the aneuploidy rate in the examined cells. Results were obtained for 15 oocytes and 16 PBs, representing 23 eggs (MII oocyte-PB complexes) donated from 15 patients (average age 32.2 years). Abnormalities were detected in ten eggs, giving an overall aneuploidy rate of 43.5%. In all, fourteen anomalies were scored, with the fertilized oocyte being at risk of monosomy in eight cases and at risk of trisomy in six; chromosomes of various sizes participated. CGH was able to give a comprehensive aneuploidy rate, as both absence of chromosomal material and the presence of extra copies were accurately scored. The aneuploidy mechanisms determined were: classical whole univalent non-disjunction; chromatid predivision prior to anaphase I, leading to metaphase II imbalance. There was also evidence of germinal mosaicism for a trisomic cell line. Three patients appeared to be predisposed to meiosis I errors, based on the presence of either multiple abnormalities in one or more of their examined cells, or of the same type of abnormality in all of their cells. Exclusion of these susceptible patients reduces the aneuploidy rate to 20%. Various hypotheses are put forward to explain these observations in order to stimulate research into the complex nature of female meiotic regulation.
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Affiliation(s)
- E Fragouli
- Department of Obstetrics and Gynaecology, University College London, London, UK.
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Delhanty JDA. Mechanisms of aneuploidy induction in human oogenesis and early embryogenesis. Cytogenet Genome Res 2006; 111:237-44. [PMID: 16192699 DOI: 10.1159/000086894] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2004] [Accepted: 02/25/2005] [Indexed: 11/19/2022] Open
Abstract
The mechanisms of aneuploidy induction in human oogenesis mainly involve nondisjunction arising during the first and second meiotic divisions. Nondisjunction equally affects both whole chromosomes and chromatids, in the latter case it is facilitated by "predivision" or precocious centromere division. Karyotyping and CGH studies show an excess of hypohaploidy, which is confirmed in studies of preimplantation embryos, providing evidence in favour of anaphase lag as a mechanism. Preferential involvement of the smaller autosomes has been clearly shown but the largest chromosomes are also abnormal in many cases. Overall, the rate of chromosomal imbalance in oocytes from women aged between 30 and 35 has been estimated at 11% from recent karyotyping data but accruing CGH results suggest that the true figure should be considerably higher. Clear evidence has been obtained in favour of germinal or gonadal mosaicism as a predisposing factor. Constitutional aneuploidy in embryos is most frequent for chromosomes 22, 16, 21 and 15; least frequently involved are chromosomes 14, X and Y, and 6. However, embryos of women under 37 are far more likely to be affected by mosaic aneuploidy, which is present in over 50% of 3-day-old embryos. There are two main types, diploid/aneuploid and chaotic mosaics. Chaotic mosaics arise independently of maternal age and may be related to centrosome anomalies and hence of male origin. Aneuploid mosaics most commonly arise by chromosome loss, followed by chromosome gain and least frequently by mitotic nondisjunction. All may be related to maternal age as well as to lack of specific gene products in the embryo. Partial aneuploidy as a result of chromosome breakage affects a minimum of 10% of embryos.
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Affiliation(s)
- J D A Delhanty
- UCL Centre for Preimplantation Diagnosis, Department of Obstetrics & Gynaecology, University College London, London, UK.
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Sherman SL, Freeman SB, Allen EG, Lamb NE. Risk factors for nondisjunction of trisomy 21. Cytogenet Genome Res 2006; 111:273-80. [PMID: 16192705 DOI: 10.1159/000086900] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2005] [Accepted: 03/15/2005] [Indexed: 11/19/2022] Open
Abstract
The leading cause of Down syndrome (DS) is nondisjunction of chromosome 21 occurring during the formation of gametes. In this review, we discuss the progress made to identify risk factors associated with this type of chromosome error occurring in oogenesis and spermatogenesis. For errors occurring in oocytes, the primary risk factors are maternal age and altered recombination. We review the current progress made with respect to these factors and briefly outline the potential environmental and genetic influences that may play a role. Although the studies of paternal nondisjunction are limited due to the relatively small proportion of errors of this type, we review the potential influence of paternal age, recombination and other environmental and genetic factors on susceptibility. Although progress has been made to understand the mechanisms and risk factors that underlie nondisjunction, considerably more research needs to be conducted to dissect this multifactorial trait, one that has a considerable impact on our species.
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Affiliation(s)
- S L Sherman
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA.
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Malini SS, Ramachandra NB. Influence of advanced age of maternal grandmothers on Down syndrome. BMC MEDICAL GENETICS 2006; 7:4. [PMID: 16412239 PMCID: PMC1360060 DOI: 10.1186/1471-2350-7-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2005] [Accepted: 01/14/2006] [Indexed: 11/10/2022]
Abstract
BACKGROUND Down syndrome (DS) is the most common chromosomal anomaly associated with mental retardation. This is due to the occurrence of free trisomy 21 (92-95%), mosaic trisomy 21 (2-4%) and translocation (3-4%). Advanced maternal age is a well documented risk factor for maternal meiotic nondisjunction. In India three children with DS are born every hour and more DS children are given birth to by young age mothers than by advanced age mothers. Therefore, detailed analysis of the families with DS is needed to find out other possible causative factors for nondisjunction. METHODS We investigated 69 families of cytogenetically confirmed DS children and constructed pedigrees of these families. We also studied 200 randomly selected families belonging to different religions as controls. Statistical analysis was carried out using logistic regression. RESULTS Out of the 69 DS cases studied, 67 were free trisomy 21, two cases were mosaic trisomy 21 and there were none with translocation. The number of DS births was greater for the young age mothers compared with the advanced age mothers. It has also been recorded that young age mothers (18 to 29 years) born to their mothers at the age 30 years and above produced as high as 91.3% of children with DS. The logistic regression of case- control study of DS children revealed that the odds ratio of age of grandmother was significant when all the four variables were used once at a time. However, the effect of age of mother and father was smaller than the effect of age of maternal grandmother. Therefore, for every year of advancement of age of the maternal grandmother, the risk (odds) of birth of DS baby increases by 30%. CONCLUSION Besides the known risk factors, mother's age, father's age, the age of the maternal grandmother at the time of birth of the mother is a risk factor for the occurrence of Down syndrome.
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Affiliation(s)
- Suttur S Malini
- Human Genetics Laboratory, Department of Studies in Zoology, University of Mysore, Manasagangotri, Mysore 570 006, India
| | - Nallur B Ramachandra
- Human Genetics Laboratory, Department of Studies in Zoology, University of Mysore, Manasagangotri, Mysore 570 006, India
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Lenzi ML, Smith J, Snowden T, Kim M, Fishel R, Poulos BK, Cohen PE. Extreme heterogeneity in the molecular events leading to the establishment of chiasmata during meiosis i in human oocytes. Am J Hum Genet 2005; 76:112-27. [PMID: 15558497 PMCID: PMC1196414 DOI: 10.1086/427268] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2004] [Accepted: 11/08/2004] [Indexed: 01/08/2023] Open
Abstract
In humans, ~50% of conceptuses are chromosomally aneuploid as a consequence of errors in meiosis, and most of these aneuploid conceptuses result in spontaneous miscarriage. Of these aneuploidy events, 70% originate during maternal meiosis, with the majority proposed to arise as a direct result of defective crossing over during meiotic recombination in prophase I. By contrast, <1%-2% of mouse germ cells exhibit prophase I-related nondisjunction events. This disparity among mammalian species is surprising, given the conservation of genes and events that regulate meiotic progression. To understand the mechanisms that might be responsible for the high error rates seen in human females, we sought to further elucidate the regulation of meiotic prophase I at the molecular cytogenetic level. Given that these events occur during embryonic development in females, samples were obtained during a defined period of gestation (17-24 weeks). Here, we demonstrate that human oocytes enter meiotic prophase I and progress through early recombination events in a similar temporal framework to mice. However, at pachynema, when chromosomes are fully paired, we find significant heterogeneity in the localization of the MutL homologs, MLH1 and MLH3, among human oocyte populations. MLH1 and MLH3 have been shown to mark late-meiotic nodules that correlate well with--and are thought to give rise to--the sites of reciprocal recombination between homologous chromosomes, which suggests a possible 10-fold variation in the processing of nascent recombination events. If such variability persists through development and into adulthood, these data would suggest that as many as 30% of human oocytes are predisposed to aneuploidy as a result of prophase I defects in MutL homolog-related events.
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Affiliation(s)
- Michelle L. Lenzi
- Departments of Molecular Genetics, Epidemiology and Population Health, and Pathology, Albert Einstein College of Medicine, Bronx, NY; and Kimmel Cancer Center, Philadelphia
| | - Jenetta Smith
- Departments of Molecular Genetics, Epidemiology and Population Health, and Pathology, Albert Einstein College of Medicine, Bronx, NY; and Kimmel Cancer Center, Philadelphia
| | - Timothy Snowden
- Departments of Molecular Genetics, Epidemiology and Population Health, and Pathology, Albert Einstein College of Medicine, Bronx, NY; and Kimmel Cancer Center, Philadelphia
| | - Mimi Kim
- Departments of Molecular Genetics, Epidemiology and Population Health, and Pathology, Albert Einstein College of Medicine, Bronx, NY; and Kimmel Cancer Center, Philadelphia
| | - Richard Fishel
- Departments of Molecular Genetics, Epidemiology and Population Health, and Pathology, Albert Einstein College of Medicine, Bronx, NY; and Kimmel Cancer Center, Philadelphia
| | - Bradford K. Poulos
- Departments of Molecular Genetics, Epidemiology and Population Health, and Pathology, Albert Einstein College of Medicine, Bronx, NY; and Kimmel Cancer Center, Philadelphia
| | - Paula E. Cohen
- Departments of Molecular Genetics, Epidemiology and Population Health, and Pathology, Albert Einstein College of Medicine, Bronx, NY; and Kimmel Cancer Center, Philadelphia
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Warburton D, Dallaire L, Thangavelu M, Ross L, Levin B, Kline J. Trisomy recurrence: a reconsideration based on North American data. Am J Hum Genet 2004; 75:376-85. [PMID: 15248154 PMCID: PMC1182017 DOI: 10.1086/423331] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2004] [Accepted: 06/15/2004] [Indexed: 01/14/2023] Open
Abstract
Few reliable data exist concerning the recurrence risk for individual trisomies or the risk for recurrence of trisomy for a different chromosome. We collected records from two sources: (1) prenatal diagnoses performed at the Hopital Sainte-Justine in Montreal and (2) karyotype analyses performed at Genzyme. Using the standardized morbidity ratio (SMR), we compared the observed number of trisomies at prenatal diagnosis with the expected numbers, given maternal age-specific rates (by single year). SMRs were calculated both for recurrence of the same trisomy (homotrisomy) and of a different trisomy (heterotrisomy). After all cases with an index trisomy 21 were combined, the SMR for homotrisomy was 2.4 (90% CI 1.6-3.4; P=.0005). For women with both the index trisomy and subsequent prenatal diagnosis at age <30 years, the SMR was 8.0; it was 2.1 for women with both pregnancies at age >/=30 years. For the other index viable trisomies (13, 18, XXX, and XXY) combined, the SMR for homotrisomy was 2.5 (90% CI 0.7-8.0). For heterotrisomy, the SMR after an index trisomy 21 was 2.3 (90% CI 1.5-3.8, P=.0007); the SMR did not vary with maternal age at the first trisomy. When all cases with index viable trisomies were combined, the SMR for heterotrisomy was 1.6 (90% CI 1.1-2.4; P=.04). For prenatal diagnoses following a nonviable trisomy diagnosed in a spontaneous abortion (from Genzyme data only), the SMR for a viable trisomy was 1.8 (90% CI 1.1-3.0; P=.04). The significantly increased risk for heterotrisomy supports the hypothesis that some women have a risk for nondisjunction higher than do others of the same age.
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Eichenlaub-Ritter U. Ageing and aneuploidy in oocytes. ERNST SCHERING RESEARCH FOUNDATION WORKSHOP 2003:111-36. [PMID: 12402543 DOI: 10.1007/978-3-662-04960-0_8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/27/2023]
Affiliation(s)
- U Eichenlaub-Ritter
- Faculty of Biology, University of Bielefeld, Universitätsstr. 26, 33615 Bielefeld, Germany.
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Abstract
Sperm from mice of the PL/J strain have a high frequency of sperm-head morphology abnormalities. Fluorescence in situ hybridization (FISH) methods revealed that PL/J sperm are also characterized by a high frequency of aneuploidy. The traits of abnormal sperm head morphology and aneuploidy are associated with numerous meiotic abnormalities. Spermatocytes of PL/J mice exhibit chromosome asynapsis during meiotic prophase as well as reduced crossing over, revealed by analysis of both MLH1 foci in pachytene spermatocytes and chiasmata seen at the first meiotic metaphase. During the first meiotic division, roughly one-third of the PL/J spermatocytes exhibit aberrant spindle morphology, with abnormalities including monopolar spindles, split spindle poles, and incomplete spindle formation and centrosomal abnormalities. F1 progeny of a cross between PL/J and C57BL/6J did not exhibit a high frequency of either sperm aneuploidy or sperm head morphology aberrations, as would be expected if the PL/J traits were dominant. Among progeny of a backcross of F1 mice to PL/J, none of 16 males assessed exhibited elevated frequencies of sperm head morphology abnormalities. Four of the individuals exhibited elevated sperm aneuploidy, but not at the levels of the PL/J parents. Thus, it is likely that the aberrant PL/J traits are due to several genes and/or modifiers affecting the generation of both sperm aneuploidy and abnormal sperm head morphology.
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Affiliation(s)
- April Pyle
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, TN 37996-0840, USA
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20
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Tease C, Hartshorne GM, Hultén MA. Patterns of meiotic recombination in human fetal oocytes. Am J Hum Genet 2002; 70:1469-79. [PMID: 11992253 PMCID: PMC379134 DOI: 10.1086/340734] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2001] [Accepted: 03/06/2001] [Indexed: 12/15/2022] Open
Abstract
Abnormal patterns of meiotic recombination (i.e., crossing-over) are believed to increase the risk of chromosome nondisjunction in human oocytes. To date, information on recombination has been obtained using indirect, genetic methods. Here we use an immunocytological approach, based on detection of foci of a DNA mismatch-repair protein, MLH1, on synaptonemal complexes at prophase I of meiosis, to provide the first direct estimate of the frequency of meiotic recombination in human oocytes. At pachytene, the stage of maximum homologous chromosome pairing, we found a mean of 70.3 foci (i.e., crossovers) per oocyte, with considerable intercell variability (range 48-102 foci). This mean equates to a genetic-map length of 3,515 cM. The numbers and positions of foci were determined for chromosomes 21, 18, 13, and X. These chromosomes yielded means of 1.23 foci (61.5 cM), 2.36 foci (118 cM), 2.5 foci (125 cM), and 3.22 foci (161 cM), respectively. The foci were almost invariably located interstitially and were only occasionally located close to chromosome ends. These data confirm the large difference, in recombination frequency, between human oocytes and spermatocytes and demonstrate a clear intersex variation in distribution of crossovers. In a few cells, chromosomes 21 and 18 did not have any foci (i.e., were presumptively noncrossover); however, configurations that lacked foci were not observed for chromosomes 13 and X. For the latter two chromosome pairs, the only instances of absence of foci were observed in abnormal cells that showed chromosome-pairing errors affecting these chromosomes. We speculate that these abnormal fetal oocytes may be the source of the nonrecombinant chromosomes 13 and X suggested, by genetic studies, to be associated with maternally derived chromosome nondisjunction.
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Affiliation(s)
- Charles Tease
- Department of Biological Sciences, University of Warwick, Coventry CV4 7AL, United Kingdom.
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