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Cheng D, Lu CF, Gong F, Du J, Yuan S, Luo KL, Tan YQ, Lu GX, Lin G. A case report of a normal fertile woman with 46,XX/46,XY somatic chimerism reveals a critical role for germ cells in sex determination. Hum Reprod 2024; 39:849-855. [PMID: 38420683 DOI: 10.1093/humrep/deae026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Revised: 01/16/2024] [Indexed: 03/02/2024] Open
Abstract
Individuals with 46,XX/XY chimerism can display a wide range of characteristics, varying from hermaphroditism to complete male or female, and can display sex chromosome chimerism in multiple tissues, including the gonads. The gonadal tissues of females contain both granulosa and germ cells. However, the specific sex chromosome composition of the granulosa and germ cells in 46,XX/XY chimeric female is currently unknown. Here, we reported a 30-year-old woman with secondary infertility who displayed a 46,XX/46,XY chimerism in the peripheral blood. FISH testing revealed varying degrees of XX/XY chimerism in multiple tissues of the female patient. Subsequently, the patient underwent preimplantation genetic testing (PGT) treatment, and 26 oocytes were retrieved. From the twenty-four biopsied mature oocytes, a total of 23 first polar bodies (PBs) and 10 second PBs were obtained. These PBs and two immature metaphase I (MI) oocytes only displayed X chromosome signals with no presence of the Y, suggesting that all oocytes in this chimeric female were of XX germ cell origin. On the other hand, granulosa cells obtained from individual follicles exhibited varied proportions of XX/XY cell types, and six follicles possessed 100% XX or XY granulosa cells. A total of 24 oocytes were successfully fertilized, and 12 developed into blastocysts, where 5 being XY and 5 were XX. Two blastocysts were transferred with one originating from an oocyte aspirated from a follicle containing 100% XY granulosa cells. This resulted in a twin pregnancy. Subsequent prenatal diagnosis confirmed normal male and female karyotypes. Ultimately, healthy boy-girl twins were delivered at full term. In summary, this 46,XX/XY chimerism with XX germ cells presented complete female, suggesting that germ cells may exert a significant influence on the sexual determination of an individual, which provide valuable insights into the intricate processes associated with sexual development and reproduction.
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Affiliation(s)
- Dehua Cheng
- Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-XIANGYA, Changsha, China
| | - Chang-Fu Lu
- Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-XIANGYA, Changsha, China
- Institute of Reproductive and Stem Cell Engineering, NHC Key Laboratory of Human Stem Cell and Reproductive Engineering, School of Basic Medical Science, Central South University, Changsha, China
- National Engineering and Research Center of Human Stem Cells, Changsha, China
- Hunan International Scientific and Technological Cooperation Base of Development and Carcinogenesis, Changsha, China
| | - Fei Gong
- Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-XIANGYA, Changsha, China
- Institute of Reproductive and Stem Cell Engineering, NHC Key Laboratory of Human Stem Cell and Reproductive Engineering, School of Basic Medical Science, Central South University, Changsha, China
- National Engineering and Research Center of Human Stem Cells, Changsha, China
- Hunan International Scientific and Technological Cooperation Base of Development and Carcinogenesis, Changsha, China
| | - Juan Du
- Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-XIANGYA, Changsha, China
- Institute of Reproductive and Stem Cell Engineering, NHC Key Laboratory of Human Stem Cell and Reproductive Engineering, School of Basic Medical Science, Central South University, Changsha, China
- National Engineering and Research Center of Human Stem Cells, Changsha, China
- Hunan International Scientific and Technological Cooperation Base of Development and Carcinogenesis, Changsha, China
| | - Shimin Yuan
- Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-XIANGYA, Changsha, China
| | - Ke-Li Luo
- Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-XIANGYA, Changsha, China
- Institute of Reproductive and Stem Cell Engineering, NHC Key Laboratory of Human Stem Cell and Reproductive Engineering, School of Basic Medical Science, Central South University, Changsha, China
| | - Yue-Qiu Tan
- Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-XIANGYA, Changsha, China
- Institute of Reproductive and Stem Cell Engineering, NHC Key Laboratory of Human Stem Cell and Reproductive Engineering, School of Basic Medical Science, Central South University, Changsha, China
- National Engineering and Research Center of Human Stem Cells, Changsha, China
- Hunan International Scientific and Technological Cooperation Base of Development and Carcinogenesis, Changsha, China
| | - Guang-Xiu Lu
- Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-XIANGYA, Changsha, China
- Institute of Reproductive and Stem Cell Engineering, NHC Key Laboratory of Human Stem Cell and Reproductive Engineering, School of Basic Medical Science, Central South University, Changsha, China
- National Engineering and Research Center of Human Stem Cells, Changsha, China
- Hunan International Scientific and Technological Cooperation Base of Development and Carcinogenesis, Changsha, China
| | - Ge Lin
- Clinical Research Center for Reproduction and Genetics in Hunan Province, Reproductive and Genetic Hospital of CITIC-XIANGYA, Changsha, China
- Institute of Reproductive and Stem Cell Engineering, NHC Key Laboratory of Human Stem Cell and Reproductive Engineering, School of Basic Medical Science, Central South University, Changsha, China
- National Engineering and Research Center of Human Stem Cells, Changsha, China
- Hunan International Scientific and Technological Cooperation Base of Development and Carcinogenesis, Changsha, China
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2
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Chen L, Wang L, Zeng Y, Yin D, Tang F, Xie D, Zhu H, Li L, Wang J. A prenatal case misunderstood as specimen confusion: 46,XY/46,XY chimerism. BMC Pregnancy Childbirth 2024; 24:126. [PMID: 38347456 PMCID: PMC10860253 DOI: 10.1186/s12884-024-06321-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2023] [Accepted: 02/05/2024] [Indexed: 02/15/2024] Open
Abstract
Chimerism results from the fusion of two zygotes in a single embryo, whereas mosaicism results from mitotic errors in a single zygote. True human chimerism is rare, with fewer than 100 cases reported in the literature. Here, we report a case in which the fetus was identified as having tetragametic chimerism based on short tandem repeat - polymerase chain reaction analysis of the family observed during amniocentesis for advanced maternal age. The chimerism occurred via the fertilization of two ova by two spermatozoa, followed by the fusion of early embryos. The genotypes of the two amniotic fluid samples obtained successively by one puncture were completely different, and the sex chromosomes were XY. Karyotyping and copy number variation sequencing showed no abnormalities. The fetus was delivered at term and the phenotype of the newborn was normal.
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Affiliation(s)
- Lin Chen
- Department of Medical Genetics / Prenatal Diagnostic Center, West China Second University Hospital, Sichuan University, Block 3 No. 20, Ren Min Nan Road, Wuhou District, Chengdu, 610041, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education, Chengdu, 610041, China
| | - Li Wang
- Department of Medical Genetics / Prenatal Diagnostic Center, West China Second University Hospital, Sichuan University, Block 3 No. 20, Ren Min Nan Road, Wuhou District, Chengdu, 610041, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education, Chengdu, 610041, China
| | - Yang Zeng
- Department of Medical Genetics / Prenatal Diagnostic Center, West China Second University Hospital, Sichuan University, Block 3 No. 20, Ren Min Nan Road, Wuhou District, Chengdu, 610041, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education, Chengdu, 610041, China
| | - Daishu Yin
- Department of Medical Genetics / Prenatal Diagnostic Center, West China Second University Hospital, Sichuan University, Block 3 No. 20, Ren Min Nan Road, Wuhou District, Chengdu, 610041, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education, Chengdu, 610041, China
| | - Feng Tang
- Department of Medical Genetics / Prenatal Diagnostic Center, West China Second University Hospital, Sichuan University, Block 3 No. 20, Ren Min Nan Road, Wuhou District, Chengdu, 610041, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education, Chengdu, 610041, China
| | - Dan Xie
- Department of Medical Genetics / Prenatal Diagnostic Center, West China Second University Hospital, Sichuan University, Block 3 No. 20, Ren Min Nan Road, Wuhou District, Chengdu, 610041, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education, Chengdu, 610041, China
| | - Hongmei Zhu
- Department of Medical Genetics / Prenatal Diagnostic Center, West China Second University Hospital, Sichuan University, Block 3 No. 20, Ren Min Nan Road, Wuhou District, Chengdu, 610041, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education, Chengdu, 610041, China
| | - Lingping Li
- Department of Medical Genetics / Prenatal Diagnostic Center, West China Second University Hospital, Sichuan University, Block 3 No. 20, Ren Min Nan Road, Wuhou District, Chengdu, 610041, China
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education, Chengdu, 610041, China
| | - Jing Wang
- Department of Medical Genetics / Prenatal Diagnostic Center, West China Second University Hospital, Sichuan University, Block 3 No. 20, Ren Min Nan Road, Wuhou District, Chengdu, 610041, China.
- Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education, Chengdu, 610041, China.
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Tan Y. Assisted Reproduction and Discussion of Rare Cases in Monozygotic Twinning. Twin Res Hum Genet 2023; 26:236-242. [PMID: 37288525 DOI: 10.1017/thg.2023.22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Assisted reproductive technology is a crucial factor that increases the incidence of monozygotic twinning in humans. This article discusses the impact of various indicators in assisted reproductive technology studies on pregnancy outcomes, especially studies with a large number of clinical cases. Furthermore, three rare cases in multiples pregnancy are discussed: fetus papyraceous of a pair of male monozygotic twins in a set of triplets, two pairs of sesquizygotic twins with sex-discordance, and rare conjoined triplets.
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Affiliation(s)
- Yuge Tan
- Independent Scholar, Langzhong City, Sichuan Province, China
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Charalsawadi C, Jaruratanasirikul S, Hnoonual A, Chantarapong A, Sangmanee P, Trongnit S, Jinawath N, Limprasert P. Case report: Molecular analysis of a 47,XY,+21/46,XX chimera using SNP microarray and review of literature. Front Genet 2022; 13:802362. [DOI: 10.3389/fgene.2022.802362] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 10/25/2022] [Indexed: 11/12/2022] Open
Abstract
Chimerism is a very rare genetic finding in human. Most reported cases have a chi 46,XX/46,XY karyotype. Only three non-twin cases carrying both trisomy 21 and a normal karyotype have been reported, including two cases with a chi 47,XY,+21/46,XX karyotype and a case with a chi 47,XX,+21/46,XY karyotype. Herein we describe an additional case with a chi 47,XY,+21/46,XX karyotype. For the case, a physical examination at the age of 1 year revealed ambiguous genitalia with no features of Down syndrome or other malformations. Growth and developmental milestones were within normal ranges. We performed short tandem repeat (STR) and single nucleotide polymorphism (SNP) microarray analyses to attempt to identify the mechanism underlying the chimerism in this patient and the origin of the extra chromosome 21. Cytogenetic analyses of the patient’s peripheral blood revealed approximately 17% of a 47,XY,+21 lineage by G-banding karyotype analysis, 13%–17% by FISH analyses of uncultured peripheral blood, and 10%–15% by SNP microarray analysis. Four years later, the percentage of trisomy 21 cells had decreased to approximately 6%. SNP microarray and STR analyses revealed a single maternal and double paternal genetic contribution to the patient for the majority of the markers, including the chromosome 21 markers. The extra chromosome 21 was paternally derived and meiosis I nondisjunction likely occurred during spermatogenesis. The mechanisms underlying chimera in our case was likely fertilization two spermatozoa, one with an ovum and the other with the second polar body.
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5
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De Coster T, Masset H, Tšuiko O, Catteeuw M, Zhao Y, Dierckxsens N, Aparicio AL, Dimitriadou E, Debrock S, Peeraer K, de Ruijter-Villani M, Smits K, Van Soom A, Vermeesch JR. Parental genomes segregate into distinct blastomeres during multipolar zygotic divisions leading to mixoploid and chimeric blastocysts. Genome Biol 2022; 23:201. [PMID: 36184650 PMCID: PMC9528162 DOI: 10.1186/s13059-022-02763-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 08/31/2022] [Indexed: 11/23/2022] Open
Abstract
Background During normal zygotic division, two haploid parental genomes replicate, unite and segregate into two biparental diploid blastomeres. Results Contrary to this fundamental biological tenet, we demonstrate here that parental genomes can segregate to distinct blastomeres during the zygotic division resulting in haploid or uniparental diploid and polyploid cells, a phenomenon coined heterogoneic division. By mapping the genomic landscape of 82 blastomeres from 25 bovine zygotes, we show that multipolar zygotic division is a tell-tale of whole-genome segregation errors. Based on the haplotypes and live-imaging of zygotic divisions, we demonstrate that various combinations of androgenetic, gynogenetic, diploid, and polyploid blastomeres arise via distinct parental genome segregation errors including the formation of additional paternal, private parental, or tripolar spindles, or by extrusion of paternal genomes. Hence, we provide evidence that private parental spindles, if failing to congress before anaphase, can lead to whole-genome segregation errors. In addition, anuclear blastomeres are common, indicating that cytokinesis can be uncoupled from karyokinesis. Dissociation of blastocyst-stage embryos further demonstrates that whole-genome segregation errors might lead to mixoploid or chimeric development in both human and cow. Yet, following multipolar zygotic division, fewer embryos reach the blastocyst stage and diploidization occurs frequently indicating that alternatively, blastomeres with genome-wide errors resulting from whole-genome segregation errors can be selected against or contribute to embryonic arrest. Conclusions Heterogoneic zygotic division provides an overarching paradigm for the development of mixoploid and chimeric individuals and moles and can be an important cause of embryonic and fetal arrest following natural conception or IVF. Supplementary Information The online version contains supplementary material available at 10.1186/s13059-022-02763-2.
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Affiliation(s)
- Tine De Coster
- Laboratory for Cytogenetics and Genome Research, Department of Human Genetics, KU Leuven, 3000, Leuven, Belgium.,Reproductive Biology Unit, Department of Internal Medicine, Reproduction and Population Medicine, Ghent University, 9820, Merelbeke, Belgium
| | - Heleen Masset
- Laboratory for Cytogenetics and Genome Research, Department of Human Genetics, KU Leuven, 3000, Leuven, Belgium
| | - Olga Tšuiko
- Laboratory for Cytogenetics and Genome Research, Department of Human Genetics, KU Leuven, 3000, Leuven, Belgium
| | - Maaike Catteeuw
- Reproductive Biology Unit, Department of Internal Medicine, Reproduction and Population Medicine, Ghent University, 9820, Merelbeke, Belgium
| | - Yan Zhao
- Laboratory for Cytogenetics and Genome Research, Department of Human Genetics, KU Leuven, 3000, Leuven, Belgium
| | - Nicolas Dierckxsens
- Laboratory for Cytogenetics and Genome Research, Department of Human Genetics, KU Leuven, 3000, Leuven, Belgium
| | - Ainhoa Larreategui Aparicio
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584CM, Utrecht, The Netherlands.,Hubrecht Institute, 3584CT, Utrecht, The Netherlands
| | - Eftychia Dimitriadou
- Laboratory for Cytogenetics and Genome Research, Department of Human Genetics, KU Leuven, 3000, Leuven, Belgium
| | - Sophie Debrock
- Leuven University Fertility Center, University Hospitals of Leuven, 3000, Leuven, Belgium
| | - Karen Peeraer
- Leuven University Fertility Center, University Hospitals of Leuven, 3000, Leuven, Belgium
| | - Marta de Ruijter-Villani
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Utrecht University, 3584CM, Utrecht, The Netherlands.,Hubrecht Institute, 3584CT, Utrecht, The Netherlands.,Division of Woman and Baby, Department Obstetrics and Gynaecology, University Medical Centre Utrecht, 3508, GA, Utrecht, The Netherlands
| | - Katrien Smits
- Reproductive Biology Unit, Department of Internal Medicine, Reproduction and Population Medicine, Ghent University, 9820, Merelbeke, Belgium
| | - Ann Van Soom
- Reproductive Biology Unit, Department of Internal Medicine, Reproduction and Population Medicine, Ghent University, 9820, Merelbeke, Belgium
| | - Joris Robert Vermeesch
- Laboratory for Cytogenetics and Genome Research, Department of Human Genetics, KU Leuven, 3000, Leuven, Belgium.
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Yu FNY, Li EYY, Kong MCW, Ma TWL, Chan KYK, Man E, Chung BHY, Kan ASY. Increasing prenatal diagnosis of chimeras with the use of noninvasive prenatal screening: Report of two cases. Prenat Diagn 2021; 41:697-700. [PMID: 33527400 DOI: 10.1002/pd.5911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2020] [Revised: 12/26/2020] [Accepted: 01/19/2021] [Indexed: 11/09/2022]
Affiliation(s)
- Florrie N Y Yu
- Department of Obstetrics and Gynaecology, Queen Elizabeth Hospital, Hong Kong, China
| | - Elizabeth Y Y Li
- Department of Obstetrics and Gynaecology, United Christian Hospital, Hong Kong, China
| | - Meliza C W Kong
- Department of Obstetrics and Gynaecology, United Christian Hospital, Hong Kong, China
| | - Teresa W L Ma
- Department of Obstetrics and Gynaecology, Queen Elizabeth Hospital, Hong Kong, China
| | - Kelvin Y K Chan
- Department of Obstetrics and Gynaecology, Prenatal Diagnostic Laboratory, Tsan Yuk Hospital, Hong Kong, China.,Department of Obstetrics and Gynaecology, Queen Mary Hospital, Hong Kong, China
| | - Elim Man
- Department of Paediatrics and Adolescent Medicine, Hong Kong Children's Hospital, Hong Kong, China
| | - Brian H Y Chung
- Department of Paediatrics and Adolescent Medicine, The University of Hong Kong, Hong Kong, China
| | - Anita S Y Kan
- Department of Obstetrics and Gynaecology, Prenatal Diagnostic Laboratory, Tsan Yuk Hospital, Hong Kong, China.,Department of Obstetrics and Gynaecology, Queen Mary Hospital, Hong Kong, China
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Ankathil R, Eva F, Bakar ZA, Yunus NM, Nawi NA, Annuar A, Ting CY, Sulong S. A Dual Gender Rare Case with 47,XY, + 18/46,XX Karyotype: Chimera or Mosaic? JOURNAL OF CHILD SCIENCE 2021. [DOI: 10.1055/s-0040-1722275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Our objective is to report one rare case of dual gender chimerism involving abnormal male trisomy 18 and normal female karyotype. The baby was born full term with birth weight of 1.8 kg, not vigorous with light meconium stained liquor and Apgar score of 51, 85 and 910. Parents are 40 years old and mother is G6P5 + 1. The baby had clinical features of Edwards syndrome, and a blood sample was sent to Human Genome Centre, Universiti Sains Malaysia, Malaysia for cytogenetic analysis. Conventional cytogenetic analysis results showed two distinct sex discordant genetic cell lines XY and XX in 90:10 ratio. The male genetic cell line XY also showed trisomy 18 (47,XY, + 18) consistent with clinical diagnosis of male Edwards syndrome, whereas the second genetic cell line showed normal 46,XX female. The present case was reported as dual gender chimera with chi 47,XY, + 18/46,XX karyotype pattern. To the best of available knowledge, dual gender chimerism with abnormal male trisomy 18 and normal female karyotype has not been reported so far, and this case is reported for its rarity and as the first report.
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Affiliation(s)
- Ravindran Ankathil
- Human Genome Centre, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
| | - Foong Eva
- Human Genome Centre, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
| | - Zulaikha Abu Bakar
- Human Genome Centre, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
| | - Nazihah Mohd Yunus
- Human Genome Centre, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
| | - Nurul Alia Nawi
- Human Genome Centre, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
| | - Aziati Annuar
- Human Genome Centre, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
| | - Cheng Yi Ting
- Human Genome Centre, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
| | - Sarina Sulong
- Human Genome Centre, School of Medical Sciences, Universiti Sains Malaysia, Kubang Kerian, Kelantan, Malaysia
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8
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Masset H, Tšuiko O, Vermeesch JR. Genome-wide abnormalities in embryos: Origins and clinical consequences. Prenat Diagn 2021; 41:554-563. [PMID: 33524193 DOI: 10.1002/pd.5895] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 12/03/2020] [Accepted: 12/30/2020] [Indexed: 12/25/2022]
Abstract
Ploidy or genome-wide chromosomal anomalies such as triploidy, diploid/triploid mixoploidy, chimerism, and genome-wide uniparental disomy are the cause of molar pregnancies, embryonic lethality, and developmental disorders. While triploidy and genome-wide uniparental disomy can be ascribed to fertilization or meiotic errors, the mechanisms causing mixoploidy and chimerism remain shrouded in mystery. Different models have been proposed, but all remain hypothetical and controversial, are deduced from the developmental persistent genomic constitutions present in the sample studied and lack direct evidence. New single-cell genomic methodologies, such as single-cell genome-wide haplotyping, provide an extended view of the constitution of normal and abnormal embryos and have further pinpointed the existence of mixoploidy in cleavage-stage embryos. Based on those recent findings, we suggest that genome-wide anomalies, which persist in fetuses and patients, can for a large majority be explained by a noncanonical first zygotic cleavage event, during which maternal and paternal genomes in a single zygote, segregate to different blastomeres. This process, termed heterogoneic division, provides an overarching theoretical basis for the different presentations of mixoploidy and chimerism.
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Affiliation(s)
- Heleen Masset
- Department of Human Genetics, Laboratory for Cytogenetics and Genome Research, KU Leuven, Leuven, Belgium
| | - Olga Tšuiko
- Department of Human Genetics, Laboratory for Cytogenetics and Genome Research, KU Leuven, Leuven, Belgium
| | - Joris R Vermeesch
- Department of Human Genetics, Laboratory for Cytogenetics and Genome Research, KU Leuven, Leuven, Belgium.,Center of Human Genetics, University Hospitals of Leuven, Leuven, Belgium
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9
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Natural human chimeras: A review. Eur J Med Genet 2020; 63:103971. [PMID: 32565253 DOI: 10.1016/j.ejmg.2020.103971] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 05/06/2020] [Accepted: 06/01/2020] [Indexed: 12/24/2022]
Abstract
The term chimera has been borrowed from Greek mythology and has a long history of use in biology and genetics. A chimera is an organism whose cells are derived from two or more zygotes. Recipients of tissue and organ transplants are artificial chimeras. This review concerns natural human chimeras. The first human chimera was reported in 1953. Natural chimeras can arise in various ways. Fetal and maternal cells can cross the placental barrier so that both mother and child may become microchimeras. Two zygotes can fuse together during an early embryonic stage to form a fusion chimera. Most chimeras remain undetected, especially if both zygotes are of the same genetic sex. Many are discovered accidently, for example, during a routine blood group test. Even sex-discordant chimeras can have a normal male or female phenotype. Only 28 of the 50 individuals with a 46,XX/46,XY karyotype were either true hermaphrodites or had ambiguous genitalia. Blood chimeras are formed by blood transfusion between dizygotic twins via the shared placenta and are more common than was once assumed. In marmoset monkey twins the exchange via the placenta is not limited to blood but can involve other tissues, including germ cells. To date there are no examples in humans of twin chimeras involving germ cells. If human chimeras are more common than hitherto thought there could be many medical, social, forensic, and legal implications. More multidisciplinary research is required for a better understanding of this fascinating subject.
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