1
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Wei C, Kesner B, Yin H, Lee JT. Imprinted X chromosome inactivation at the gamete-to-embryo transition. Mol Cell 2024; 84:1442-1459.e7. [PMID: 38458200 PMCID: PMC11031340 DOI: 10.1016/j.molcel.2024.02.013] [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: 07/22/2023] [Revised: 12/23/2023] [Accepted: 02/13/2024] [Indexed: 03/10/2024]
Abstract
In mammals, dosage compensation involves two parallel processes: (1) X inactivation, which equalizes X chromosome dosage between males and females, and (2) X hyperactivation, which upregulates the active X for X-autosome balance. The field currently favors models whereby dosage compensation initiates "de novo" during mouse development. Here, we develop "So-Smart-seq" to revisit the question and interrogate a comprehensive transcriptome including noncoding genes and repeats in mice. Intriguingly, de novo silencing pertains only to a subset of Xp genes. Evolutionarily older genes and repetitive elements demonstrate constitutive Xp silencing, adopt distinct signatures, and do not require Xist to initiate silencing. We trace Xp silencing backward in developmental time to meiotic sex chromosome inactivation in the male germ line and observe that Xm hyperactivation is timed to Xp silencing on a gene-by-gene basis. Thus, during the gamete-to-embryo transition, older Xp genes are transmitted in a "pre-inactivated" state. These findings have implications for the evolution of imprinting.
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Affiliation(s)
- Chunyao Wei
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA; Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Barry Kesner
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA; Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Hao Yin
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA; Department of Genetics, Harvard Medical School, Boston, MA, USA
| | - Jeannie T Lee
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA; Department of Genetics, Harvard Medical School, Boston, MA, USA.
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2
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Dementieva NV, Dysin AP, Shcherbakov YS, Nikitkina EV, Musidray AA, Petrova AV, Mitrofanova OV, Plemyashov KV, Azovtseva AI, Griffin DK, Romanov MN. Risk of Sperm Disorders and Impaired Fertility in Frozen-Thawed Bull Semen: A Genome-Wide Association Study. Animals (Basel) 2024; 14:251. [PMID: 38254422 PMCID: PMC10812825 DOI: 10.3390/ani14020251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2023] [Revised: 01/08/2024] [Accepted: 01/11/2024] [Indexed: 01/24/2024] Open
Abstract
Cryopreservation is a widely used method of semen conservation in animal breeding programs. This process, however, can have a detrimental effect on sperm quality, especially in terms of its morphology. The resultant sperm disorders raise the risk of reduced sperm fertilizing ability, which poses a serious threat to the long-term efficacy of livestock reproduction and breeding. Understanding the genetic factors underlying these effects is critical for maintaining sperm quality during cryopreservation, and for animal fertility in general. In this regard, we performed a genome-wide association study to identify genomic regions associated with various cryopreservation sperm abnormalities in Holstein cattle, using single nucleotide polymorphism (SNP) markers via a high-density genotyping assay. Our analysis revealed a significant association of specific SNPs and candidate genes with absence of acrosomes, damaged cell necks and tails, as well as wrinkled acrosomes and decreased motility of cryopreserved sperm. As a result, we identified candidate genes such as POU6F2, LPCAT4, DPYD, SLC39A12 and CACNB2, as well as microRNAs (bta-mir-137 and bta-mir-2420) that may play a critical role in sperm morphology and disorders. These findings provide crucial information on the molecular mechanisms underlying acrosome integrity, motility, head abnormalities and damaged cell necks and tails of sperm after cryopreservation. Further studies with larger sample sizes, genome-wide coverage and functional validation are needed to explore causal variants in more detail, thereby elucidating the mechanisms mediating these effects. Overall, our results contribute to the understanding of genetic architecture in cryopreserved semen quality and disorders in bulls, laying the foundation for improved animal reproduction and breeding.
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Affiliation(s)
- Natalia V. Dementieva
- Russian Research Institute of Farm Animal Genetics and Breeding—Branch of the L. K. Ernst Federal Research Centre for Animal Husbandry, Pushkin, 196601 St. Petersburg, Russia; (A.P.D.); (Y.S.S.); (E.V.N.); (A.A.M.); (A.V.P.); (O.V.M.); (A.I.A.)
| | - Artem P. Dysin
- Russian Research Institute of Farm Animal Genetics and Breeding—Branch of the L. K. Ernst Federal Research Centre for Animal Husbandry, Pushkin, 196601 St. Petersburg, Russia; (A.P.D.); (Y.S.S.); (E.V.N.); (A.A.M.); (A.V.P.); (O.V.M.); (A.I.A.)
| | - Yuri S. Shcherbakov
- Russian Research Institute of Farm Animal Genetics and Breeding—Branch of the L. K. Ernst Federal Research Centre for Animal Husbandry, Pushkin, 196601 St. Petersburg, Russia; (A.P.D.); (Y.S.S.); (E.V.N.); (A.A.M.); (A.V.P.); (O.V.M.); (A.I.A.)
| | - Elena V. Nikitkina
- Russian Research Institute of Farm Animal Genetics and Breeding—Branch of the L. K. Ernst Federal Research Centre for Animal Husbandry, Pushkin, 196601 St. Petersburg, Russia; (A.P.D.); (Y.S.S.); (E.V.N.); (A.A.M.); (A.V.P.); (O.V.M.); (A.I.A.)
| | - Artem A. Musidray
- Russian Research Institute of Farm Animal Genetics and Breeding—Branch of the L. K. Ernst Federal Research Centre for Animal Husbandry, Pushkin, 196601 St. Petersburg, Russia; (A.P.D.); (Y.S.S.); (E.V.N.); (A.A.M.); (A.V.P.); (O.V.M.); (A.I.A.)
| | - Anna V. Petrova
- Russian Research Institute of Farm Animal Genetics and Breeding—Branch of the L. K. Ernst Federal Research Centre for Animal Husbandry, Pushkin, 196601 St. Petersburg, Russia; (A.P.D.); (Y.S.S.); (E.V.N.); (A.A.M.); (A.V.P.); (O.V.M.); (A.I.A.)
| | - Olga V. Mitrofanova
- Russian Research Institute of Farm Animal Genetics and Breeding—Branch of the L. K. Ernst Federal Research Centre for Animal Husbandry, Pushkin, 196601 St. Petersburg, Russia; (A.P.D.); (Y.S.S.); (E.V.N.); (A.A.M.); (A.V.P.); (O.V.M.); (A.I.A.)
| | - Kirill V. Plemyashov
- Federal State Budgetary Educational Institution of Higher Education “St. Petersburg State University of Veterinary Medicine”, 196084 St. Petersburg, Russia;
| | - Anastasiia I. Azovtseva
- Russian Research Institute of Farm Animal Genetics and Breeding—Branch of the L. K. Ernst Federal Research Centre for Animal Husbandry, Pushkin, 196601 St. Petersburg, Russia; (A.P.D.); (Y.S.S.); (E.V.N.); (A.A.M.); (A.V.P.); (O.V.M.); (A.I.A.)
| | | | - Michael N. Romanov
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, UK;
- L. K. Ernst Federal Research Centre for Animal Husbandry, Dubrovitsy, 142132 Podolsk, Moscow Oblast, Russia
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3
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Valero-Regalón FJ, Solé M, López-Jiménez P, Valerio-de Arana M, Martín-Ruiz M, de la Fuente R, Marín-Gual L, Renfree MB, Shaw G, Berríos S, Fernández-Donoso R, Waters PD, Ruiz-Herrera A, Gómez R, Page J. Divergent patterns of meiotic double strand breaks and synapsis initiation dynamics suggest an evolutionary shift in the meiosis program between American and Australian marsupials. Front Cell Dev Biol 2023; 11:1147610. [PMID: 37181752 PMCID: PMC10166821 DOI: 10.3389/fcell.2023.1147610] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 04/06/2023] [Indexed: 05/16/2023] Open
Abstract
In eutherian mammals, hundreds of programmed DNA double-strand breaks (DSBs) are generated at the onset of meiosis. The DNA damage response is then triggered. Although the dynamics of this response is well studied in eutherian mammals, recent findings have revealed different patterns of DNA damage signaling and repair in marsupial mammals. To better characterize these differences, here we analyzed synapsis and the chromosomal distribution of meiotic DSBs markers in three different marsupial species (Thylamys elegans, Dromiciops gliorides, and Macropus eugenii) that represent South American and Australian Orders. Our results revealed inter-specific differences in the chromosomal distribution of DNA damage and repair proteins, which were associated with differing synapsis patterns. In the American species T. elegans and D. gliroides, chromosomal ends were conspicuously polarized in a bouquet configuration and synapsis progressed exclusively from the telomeres towards interstitial regions. This was accompanied by sparse H2AX phosphorylation, mainly accumulating at chromosomal ends. Accordingly, RAD51 and RPA were mainly localized at chromosomal ends throughout prophase I in both American marsupials, likely resulting in reduced recombination rates at interstitial positions. In sharp contrast, synapsis initiated at both interstitial and distal chromosomal regions in the Australian representative M. eugenii, the bouquet polarization was incomplete and ephemeral, γH2AX had a broad nuclear distribution, and RAD51 and RPA foci displayed an even chromosomal distribution. Given the basal evolutionary position of T. elegans, it is likely that the meiotic features reported in this species represent an ancestral pattern in marsupials and that a shift in the meiotic program occurred after the split of D. gliroides and the Australian marsupial clade. Our results open intriguing questions about the regulation and homeostasis of meiotic DSBs in marsupials. The low recombination rates observed at the interstitial chromosomal regions in American marsupials can result in the formation of large linkage groups, thus having an impact in the evolution of their genomes.
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Affiliation(s)
| | - Mireia Solé
- Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
- Genetics of Male Fertility Group, Unitat de Biologia Cel·lular, Universitat Autònoma de Barcelona, Spain
| | - Pablo López-Jiménez
- Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
| | - María Valerio-de Arana
- Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
| | - Marta Martín-Ruiz
- Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
| | - Roberto de la Fuente
- Department of Experimental Embryology, Institute of Genetics and Animal Biotechnology of The Polish Academy of Sciences, Jastrzębiec, Poland
| | - Laia Marín-Gual
- Departament de Biologia Cel·lular, Universitat Autònoma de Barcelona, Barcelona, Spain
- Genome Integrity and Instability Group, Institut de Biotecnologia i Biomedicina, Barcelona, Spain
| | - Marilyn B. Renfree
- School of BioSciences, The University of Melbourne, Melbourne, VIC, Australia
| | - Geoff Shaw
- School of BioSciences, The University of Melbourne, Melbourne, VIC, Australia
| | - Soledad Berríos
- Programa de Genética Humana, Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago, Chile
| | - Raúl Fernández-Donoso
- Programa de Genética Humana, Facultad de Medicina, Instituto de Ciencias Biomédicas, Universidad de Chile, Santiago, Chile
| | - Paul D. Waters
- School of Biotechnology and Biomolecular Science, Faculty of Science, University of New South Wales, Sydney, NSW, Australia
| | - Aurora Ruiz-Herrera
- Departament de Biologia Cel·lular, Universitat Autònoma de Barcelona, Barcelona, Spain
- Genome Integrity and Instability Group, Institut de Biotecnologia i Biomedicina, Barcelona, Spain
| | - Rocío Gómez
- Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
| | - Jesús Page
- Departamento de Biología, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain
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4
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Alavattam KG, Maezawa S, Andreassen PR, Namekawa SH. Meiotic sex chromosome inactivation and the XY body: a phase separation hypothesis. Cell Mol Life Sci 2021; 79:18. [PMID: 34971404 DOI: 10.1007/s00018-021-04075-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 09/08/2021] [Accepted: 10/14/2021] [Indexed: 10/19/2022]
Abstract
In mammalian male meiosis, the heterologous X and Y chromosomes remain unsynapsed and, as a result, are subject to meiotic sex chromosome inactivation (MSCI). MSCI is required for the successful completion of spermatogenesis. Following the initiation of MSCI, the X and Y chromosomes undergo various epigenetic modifications and are transformed into a nuclear body termed the XY body. Here, we review the mechanisms underlying the initiation of two essential, sequential processes in meiotic prophase I: MSCI and XY-body formation. The initiation of MSCI is directed by the action of DNA damage response (DDR) pathways; downstream of the DDR, unique epigenetic states are established, leading to the formation of the XY body. Accumulating evidence suggests that MSCI and subsequent XY-body formation may be driven by phase separation, a physical process that governs the formation of membraneless organelles and other biomolecular condensates. Thus, here we gather literature-based evidence to explore a phase separation hypothesis for the initiation of MSCI and the formation of the XY body.
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Affiliation(s)
- Kris G Alavattam
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA, 98195, USA.,Center for Cardiovascular Biology, University of Washington, Seattle, WA, 98109, USA.,Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA, 98109, USA.,Department of Genome Sciences, University of Washington, Seattle, WA, 98195, USA
| | - So Maezawa
- Faculty of Science and Technology, Department of Applied Biological Science, Tokyo University of Science, Chiba, 278-8510, Japan
| | - Paul R Andreassen
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, 45229, USA
| | - Satoshi H Namekawa
- Department of Microbiology and Molecular Genetics, University of California, Davis, CA, 95616, USA.
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5
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Xiong X, Samollow PB, Cao W, Metz R, Zhang C, Leandro AC, VandeBerg JL, Wang X. Genetic and genomic architecture in eight strains of the laboratory opossum Monodelphis domestica. G3-GENES GENOMES GENETICS 2021; 12:6423994. [PMID: 34751383 PMCID: PMC8728031 DOI: 10.1093/g3journal/jkab389] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 10/24/2021] [Indexed: 11/21/2022]
Abstract
The gray short-tailed opossum (Monodelphis domestica) is an established laboratory-bred marsupial model for biomedical research. It is a critical species for comparative genomics research, providing the pivotal phylogenetic outgroup for studies of derived vs ancestral states of genomic/epigenomic characteristics for eutherian mammal lineages. To characterize the current genetic profile of this laboratory marsupial, we examined 79 individuals from eight established laboratory strains. Double digest restriction site-associated DNA sequencing and whole-genome resequencing experiments were performed to investigate the genetic architecture in these strains. A total of 66,640 high-quality single nucleotide polymorphisms (SNPs) were identified. We analyzed SNP density, average heterozygosity, nucleotide diversity, and population differentiation parameter Fst within and between the eight strains. Principal component and population structure analysis clearly resolve the strains at the level of their ancestral founder populations, and the genetic architecture of these strains correctly reflects their breeding history. We confirmed the successful establishment of the first inbred laboratory opossum strain LSD (inbreeding coefficient F > 0.99) and a nearly inbred strain FD2M1 (0.98 < F < 0.99), each derived from a different ancestral background. These strains are suitable for various experimental protocols requiring controlled genetic backgrounds and for intercrosses and backcrosses that can generate offspring with informative SNPs for studying a variety of genetic and epigenetic processes. Together with recent advances in reproductive manipulation and CRISPR/Cas9 techniques for Monodelphis domestica, the existence of distinctive inbred strains will enable genome editing on different genetic backgrounds, greatly expanding the utility of this marsupial model for biomedical research.
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Affiliation(s)
- Xiao Xiong
- Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA.,School of Life Sciences and Technology, Tongji University, Shanghai 200092, China
| | - Paul B Samollow
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, USA
| | - Wenqi Cao
- Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA
| | - Richard Metz
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, USA
| | - Chao Zhang
- Department of Plastic and Reconstructive Surgery, Shanghai Ninth People's Hospital, Shanghai Institute of Precision Medicine, Shanghai JiaoTong University School of Medicine, Shanghai 200240, China
| | - Ana C Leandro
- South Texas Diabetes and Obesity Institute and Department of Human Genetics, School of Medicine, The University of Texas Rio Grande Valley, Brownsville, TX 78520, USA
| | - John L VandeBerg
- South Texas Diabetes and Obesity Institute and Department of Human Genetics, School of Medicine, The University of Texas Rio Grande Valley, Brownsville, TX 78520, USA
| | - Xu Wang
- Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA.,Alabama Agricultural Experiment Station, Auburn, AL 36849, USA.,HudsonAlpha Institute for Biotechnology, Huntsville, AL 35806, USA
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6
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Cook LE, Newton AH, Hipsley CA, Pask AJ. Postnatal development in a marsupial model, the fat-tailed dunnart (Sminthopsis crassicaudata; Dasyuromorphia: Dasyuridae). Commun Biol 2021; 4:1028. [PMID: 34475507 PMCID: PMC8413461 DOI: 10.1038/s42003-021-02506-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 07/29/2021] [Indexed: 02/07/2023] Open
Abstract
Marsupials exhibit unique biological features that provide fascinating insights into many aspects of mammalian development. These include their distinctive mode of reproduction, altricial stage at birth, and the associated heterochrony that is required for their crawl to the pouch and teat attachment. Marsupials are also an invaluable resource for mammalian comparative biology, forming a distinct lineage from the extant placental and egg-laying monotreme mammals. Despite their unique biology, marsupial resources are lagging behind those available for placentals. The fat-tailed dunnart (Sminthopsis crassicaudata) is a laboratory based marsupial model, with simple and robust husbandry requirements and a short reproductive cycle making it amenable to experimental manipulations. Here we present a detailed staging series for the fat-tailed dunnart, focusing on their accelerated development of the forelimbs and jaws. This study provides the first skeletal developmental series on S. crassicaudata and provides a fundamental resource for future studies exploring mammalian diversification, development and evolution.
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Affiliation(s)
- Laura E Cook
- School of Biosciences, University of Melbourne, Parkville, VIC, Australia
| | - Axel H Newton
- Department of Anatomy and Developmental Biology, Monash University, Clayton, VIC, Australia
| | - Christy A Hipsley
- School of Biosciences, University of Melbourne, Parkville, VIC, Australia
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
- Department of Sciences, Museums Victoria, Carlton, VIC, Australia
| | - Andrew J Pask
- School of Biosciences, University of Melbourne, Parkville, VIC, Australia.
- Department of Sciences, Museums Victoria, Carlton, VIC, Australia.
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7
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The Methylome of Vertebrate Sex Chromosomes. Genes (Basel) 2018; 9:genes9050230. [PMID: 29723955 PMCID: PMC5977170 DOI: 10.3390/genes9050230] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2018] [Revised: 04/17/2018] [Accepted: 04/26/2018] [Indexed: 01/08/2023] Open
Abstract
DNA methylation is a key epigenetic modification in vertebrate genomes known to be involved in the regulation of gene expression, X chromosome inactivation, genomic imprinting, chromatin structure, and control of transposable elements. DNA methylation is common to all eukaryote genomes, but we still lack a complete understanding of the variation in DNA methylation patterns on sex chromosomes and between the sexes in diverse species. To better understand sex chromosome DNA methylation patterns between different amniote vertebrates, we review literature that has analyzed the genome-wide distribution of DNA methylation in mammals and birds. In each system, we focus on DNA methylation patterns on the autosomes versus the sex chromosomes.
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8
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Waters SA, Livernois AM, Patel H, O’Meally D, Craig JM, Marshall Graves JA, Suter CM, Waters PD. Landscape of DNA Methylation on the Marsupial X. Mol Biol Evol 2017; 35:431-439. [DOI: 10.1093/molbev/msx297] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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Abstract
Meiosis is essential for reproduction in sexually reproducing organisms. A key stage in meiosis is the synapsis of maternal and paternal homologous chromosomes, accompanied by exchange of genetic material to generate crossovers. A decade ago, studies found that when chromosomes fail to synapse, the many hundreds of genes housed within them are transcriptionally inactivated. This process, meiotic silencing, is conserved in all mammals studied to date, but its purpose is not yet defined. Here, I review the molecular genetics of meiotic silencing and consider the many potential functions that it could serve in the mammalian germ line. In addition, I discuss how meiotic silencing influences sex differences in meiotic infertility and the profound impact that meiotic silencing has had on the evolution of mammalian sex chromosomes.
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10
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Hu YC, Namekawa SH. Functional significance of the sex chromosomes during spermatogenesis. Reproduction 2016; 149:R265-77. [PMID: 25948089 DOI: 10.1530/rep-14-0613] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Mammalian sex chromosomes arose from an ordinary pair of autosomes. Over hundreds of millions of years, they have evolved into highly divergent X and Y chromosomes and have become increasingly specialized for male reproduction. Both sex chromosomes have acquired and amplified testis-specific genes, suggestive of roles in spermatogenesis. To understand how the sex chromosome genes participate in the regulation of spermatogenesis, we review genes, including single-copy, multi-copy, and ampliconic genes, whose spermatogenic functions have been demonstrated in mouse genetic studies. Sex chromosomes are subject to chromosome-wide transcriptional silencing in meiotic and postmeiotic stages of spermatogenesis. We also discuss particular sex-linked genes that escape postmeiotic silencing and their evolutionary implications. The unique gene contents and genomic structures of the sex chromosomes reflect their strategies to express genes at various stages of spermatogenesis and reveal the driving forces that shape their evolution.Free Chinese abstract: A Chinese translation of this abstract is freely available at http://www.reproduction-online.org/content/149/6/R265/suppl/DC1.Free Japanese abstract: A Japanese translation of this abstract is freely available at http://www.reproduction-online.org/content/149/6/R265/suppl/DC2.
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Affiliation(s)
- Yueh-Chiang Hu
- Division of Developmental BiologyDivision of Reproductive SciencesCincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA
| | - Satoshi H Namekawa
- Division of Developmental BiologyDivision of Reproductive SciencesCincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA Division of Developmental BiologyDivision of Reproductive SciencesCincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA
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11
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Abstract
Differentiated sex chromosomes in mammals and other vertebrates evolved independently but in strikingly similar ways. Vertebrates with differentiated sex chromosomes share the problems of the unequal expression of the genes borne on sex chromosomes, both between the sexes and with respect to autosomes. Dosage compensation of genes on sex chromosomes is surprisingly variable - and can even be absent - in different vertebrate groups. Systems that compensate for different gene dosages include a wide range of global, regional and gene-by-gene processes that differ in their extent and their molecular mechanisms. However, many elements of these control systems are similar across distant phylogenetic divisions and show parallels to other gene silencing systems. These dosage systems cannot be identical by descent but were probably constructed from elements of ancient silencing mechanisms that are ubiquitous among vertebrates and shared throughout eukaryotes.
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12
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Global DNA Methylation patterns on marsupial and devil facial tumour chromosomes. Mol Cytogenet 2015; 8:74. [PMID: 26435750 PMCID: PMC4591559 DOI: 10.1186/s13039-015-0176-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Accepted: 09/19/2015] [Indexed: 12/19/2022] Open
Abstract
Background Despite DNA methylation being one of the most widely studied epigenetic modifications in eukaryotes, only a few studies have examined the global methylation status of marsupial chromosomes. The emergence of devil facial tumour disease (DFTD), a clonally transmissible cancer spreading through the Tasmanian devil population, makes it a particularly pertinent time to determine the methylation status of marsupial and devil facial tumour chromosomes. DNA methylation perturbations are known to play a role in genome instability in human tumours. One of the interesting features of the devil facial tumour is its remarkable karyotypic stability over time as only four strains with minor karyotypic differences having been reported. The cytogenetic monitoring of devil facial tumour (DFT) samples collected over an eight year period and detailed molecular cytogenetic analysis performed on the different DFT strains enables chromosome rearrangements to be correlated with methylation status as the tumour evolves. Results We used immunofluorescent staining with an antibody to 5-methylcytosine on metaphase chromosomes prepared from fibroblast cells of three distantly related marsupials, including the Tasmanian devil, as well as DFTD chromosomes prepared from samples collected from different years and representing different karyotypic strains. Staining of chromosomes from male and female marsupial cell lines indicate species-specific differences in global methylation patterns but with the most intense staining regions corresponding to telomeric and/or centromeric regions of autosomes. In males, the X chromosome was hypermethylated as was one X in females. Similarly, telomeric regions on DFTD chromosomes and regions corresponding to material from one of the two X chromosomes were hypermethylated. No difference in global methylation in samples of the same strain taken in different years was observed. Conclusions The methylation patterns on DFTD chromosomes suggests that the hypermethylated active X was shattered in the formation of the tumour chromosomes, with atypical areas of methylation on DFTD chromosomes corresponding to locations of X chromosome material from the shattered X. The incredibly stable broad methylation patterns observed between strains and over time may reflect the overall genomic stability of the devil facial tumour. Electronic supplementary material The online version of this article (doi:10.1186/s13039-015-0176-x) contains supplementary material, which is available to authorized users.
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13
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Abnormal meiotic recombination with complex chromosomal rearrangement in an azoospermic man. Reprod Biomed Online 2015; 30:651-8. [DOI: 10.1016/j.rbmo.2015.02.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Revised: 01/23/2015] [Accepted: 02/26/2015] [Indexed: 11/22/2022]
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Yu H, Pask AJ, Hu Y, Shaw G, Renfree MB. ARX/Arx is expressed in germ cells during spermatogenesis in both marsupial and mouse. Reproduction 2014; 147:279-89. [PMID: 24307230 DOI: 10.1530/rep-13-0361] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The X-linked aristaless gene, ARX, is essential for the development of the gonads, forebrain, olfactory bulb, pancreas, and skeletal muscle in mice and humans. Mutations cause neurological diseases, often accompanied by ambiguous genitalia. There are a disproportionately high number of testis and brain genes on the human and mouse X chromosomes. It is still unknown whether the X chromosome accrued these genes during its evolution or whether genes that find themselves on the X chromosome evolve such roles. ARX was originally autosomal in mammals and remains so in marsupials, whereas in eutherian mammals it translocated to the X chromosome. In this study, we examined autosomal ARX in tammars and compared it with the X-linked Arx in mice. We detected ARX mRNA in the neural cells of the forebrain, midbrain and hindbrain, and olfactory bulbs in developing tammars, consistent with the expression in mice. ARX was detected by RT-PCR and mRNA in situ hybridization in the developing tammar wallaby gonads of both sexes, suggestive of a role in sexual development as in mice. We also detected ARX/Arx mRNA in the adult testis in both tammars and mice, suggesting a potential novel role for ARX/Arx in spermiogenesis. ARX transcripts were predominantly observed in round spermatids. Arx mRNA localization distributions in the mouse adult testis suggest that it escaped meiotic sex chromosome inactivation during spermatogenesis. Our findings suggest that ARX in the therian mammal ancestor already played a role in male reproduction before it was recruited to the X chromosome in eutherians.
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Affiliation(s)
- Hongshi Yu
- ARC Centre of Excellence for Kangaroo Genomics
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15
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Wang X, Douglas KC, Vandeberg JL, Clark AG, Samollow PB. Chromosome-wide profiling of X-chromosome inactivation and epigenetic states in fetal brain and placenta of the opossum, Monodelphis domestica. Genome Res 2013; 24:70-83. [PMID: 24065774 PMCID: PMC3875863 DOI: 10.1101/gr.161919.113] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Evidence from a few genes in diverse species suggests that X-chromosome inactivation (XCI) in marsupials is characterized by exclusive, but leaky inactivation of the paternally derived X chromosome. To study the phenomenon of marsupial XCI more comprehensively, we profiled parent-of-origin allele-specific expression, DNA methylation, and histone modifications in fetal brain and extra-embryonic membranes in the gray, short-tailed opossum (Monodelphis domestica). The majority of X-linked genes (152 of 176 genes with trackable SNP variants) exhibited paternally imprinted expression, with nearly 100% of transcripts derived from the maternal allele; whereas 24 loci (14%) escaped inactivation, showing varying levels of biallelic expression. In addition to recently reported evidence of marsupial XCI regulation by the noncoding Rsx transcript, strong depletion of H3K27me3 at escaper gene loci in the present study suggests that histone state modifications also correlate strongly with opossum XCI. In contrast to mouse, the opossum did not show an association between X-linked gene expression and promoter DNA methylation, with one notable exception. Unlike all other X-linked genes examined, Rsx was differentially methylated on the maternal and paternal X chromosomes, and expression was exclusively from the inactive (paternal) X chromosome. Our study provides the first comprehensive catalog of parent-of-origin expression status for X-linked genes in a marsupial and sheds light on the regulation and evolution of imprinted XCI in mammals.
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Affiliation(s)
- Xu Wang
- Department of Molecular Biology & Genetics, Cornell University, Ithaca, New York 14853, USA
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16
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Sado T, Sakaguchi T. Species-specific differences in X chromosome inactivation in mammals. Reproduction 2013; 146:R131-9. [PMID: 23847260 DOI: 10.1530/rep-13-0173] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
In female mammals, the dosage difference in X-linked genes between XX females and XY males is compensated for by inactivating one of the two X chromosomes during early development. Since the discovery of the X inactive-specific transcript (XIST) gene in humans and its subsequent isolation of the mouse homolog, Xist, in the early 1990s, the molecular basis of X chromosome inactivation (X-inactivation) has been more fully elucidated using genetically manipulated mouse embryos and embryonic stem cells. Studies on X-inactivation in other mammals, although limited when compared with those in the mice, have revealed that, while their inactive X chromosome shares many features with those in the mice, there are marked differences in not only some epigenetic modifications of the inactive X chromosome but also when and how X-inactivation is initiated during early embryonic development. Such differences raise the issue about what extent of the molecular basis of X-inactivation in the mice is commonly shared among others. Recognizing similarities and differences in X-inactivation among mammals may provide further insight into our understanding of not only the evolutionary but also the molecular aspects for the mechanism of X-inactivation. Here, we reviewed species-specific differences in X-inactivation and discussed what these differences may reveal.
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Affiliation(s)
- Takashi Sado
- Division of Epigenomics and Development, Medical Institute of Bioregulation, Kyushu University, 3-1-1, Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
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Sin HS, Namekawa SH. The great escape: Active genes on inactive sex chromosomes and their evolutionary implications. Epigenetics 2013; 8:887-92. [PMID: 23880818 DOI: 10.4161/epi.25672] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Epigenetic mechanisms precisely regulate sex chromosome inactivation as well as genes that escape the silencing process. In male germ cells, DNA damage response factor RNF8 establishes active epigenetic modifications on the silent sex chromosomes during meiosis, and activates escape genes during a state of sex chromosome-wide silencing in postmeiotic spermatids. During the course of evolution, the gene content of escape genes in postmeiotic spermatids recently diverged on the sex chromosomes. This evolutionary feature mirrors the epigenetic processes of sex chromosomes in germ cells. In this article, we describe how epigenetic processes have helped to shape the evolution of sex chromosome-linked genes. Furthermore, we compare features of escape genes on sex chromosomes in male germ cells to escape genes located on the single X chromosome silenced during X-inactivation in females, clarifying the distinct evolutionary implications between male and female escape genes.
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Affiliation(s)
- Ho-Su Sin
- Division of Reproductive Sciences; Division of Developmental Biology; Perinatal Institute; Cincinnati Children's Hospital Medical Center; Cincinnati, OH USA; Department of Pediatrics; University of Cincinnati College of Medicine; Cincinnati, OH USA
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18
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Abstract
Marsupial and eutherian mammals inactivate one X chromosome in female somatic cells in what is thought to be a means of compensating for the unbalanced X chromosome dosage between XX females and XY males. The hypothesis of X chromosome inactivation (XCI) was first published by Mary Lyon just over 50 years ago, with the discovery of XCI in marsupials occurring a decade later. However, we are still piecing together the evolutionary origins of this fascinating epigenetic mechanism. From the very first studies on marsupial X inactivation, it was apparent that, although there were some similarities between marsupial and eutherian XCI, there were also some striking differences. For instance, the paternally derived X was found to be preferentially silenced in marsupials, although the silencing was often incomplete, which was in contrast to the random and more tightly controlled inactivation of the X chromosome in eutherians. Many of these earlier studies used isozymes to study the activity of just a few genes in marsupials. The sequencing of several marsupial genomes and the advent of molecular cytogenetic techniques have facilitated more in-depth studies into marsupial X chromosome inactivation and allowed more detailed comparisons of the features of XCI to be made. Several important findings have come from such comparisons, among which is the absence of the XIST gene in marsupials, a non-coding RNA gene with a critical role in eutherian XCI, and the discovery of the marsupial RSX gene, which appears to perform a similar role to XIST. Here I review the history of marsupial XCI studies, the latest advances that have been made and the impact they have had towards unravelling the evolution of XCI in mammals.
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Mechanisms and evolutionary patterns of mammalian and avian dosage compensation. PLoS Biol 2012; 10:e1001328. [PMID: 22615540 PMCID: PMC3352821 DOI: 10.1371/journal.pbio.1001328] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Accepted: 03/30/2012] [Indexed: 11/19/2022] Open
Abstract
As a result of sex chromosome differentiation from ancestral autosomes, male mammalian cells only contain one X chromosome. It has long been hypothesized that X-linked gene expression levels have become doubled in males to restore the original transcriptional output, and that the resulting X overexpression in females then drove the evolution of X inactivation (XCI). However, this model has never been directly tested and patterns and mechanisms of dosage compensation across different mammals and birds generally remain little understood. Here we trace the evolution of dosage compensation using extensive transcriptome data from males and females representing all major mammalian lineages and birds. Our analyses suggest that the X has become globally upregulated in marsupials, whereas we do not detect a global upregulation of this chromosome in placental mammals. However, we find that a subset of autosomal genes interacting with X-linked genes have become downregulated in placentals upon the emergence of sex chromosomes. Thus, different driving forces may underlie the evolution of XCI and the highly efficient equilibration of X expression levels between the sexes observed for both of these lineages. In the egg-laying monotremes and birds, which have partially homologous sex chromosome systems, partial upregulation of the X (Z in birds) evolved but is largely restricted to the heterogametic sex, which provides an explanation for the partially sex-biased X (Z) expression and lack of global inactivation mechanisms in these lineages. Our findings suggest that dosage reductions imposed by sex chromosome differentiation events in amniotes were resolved in strikingly different ways.
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20
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Deakin JE. Marsupial genome sequences: providing insight into evolution and disease. SCIENTIFICA 2012; 2012:543176. [PMID: 24278712 PMCID: PMC3820666 DOI: 10.6064/2012/543176] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 09/26/2012] [Indexed: 05/08/2023]
Abstract
Marsupials (metatherians), with their position in vertebrate phylogeny and their unique biological features, have been studied for many years by a dedicated group of researchers, but it has only been since the sequencing of the first marsupial genome that their value has been more widely recognised. We now have genome sequences for three distantly related marsupial species (the grey short-tailed opossum, the tammar wallaby, and Tasmanian devil), with the promise of many more genomes to be sequenced in the near future, making this a particularly exciting time in marsupial genomics. The emergence of a transmissible cancer, which is obliterating the Tasmanian devil population, has increased the importance of obtaining and analysing marsupial genome sequence for understanding such diseases as well as for conservation efforts. In addition, these genome sequences have facilitated studies aimed at answering questions regarding gene and genome evolution and provided insight into the evolution of epigenetic mechanisms. Here I highlight the major advances in our understanding of evolution and disease, facilitated by marsupial genome projects, and speculate on the future contributions to be made by such sequences.
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Affiliation(s)
- Janine E. Deakin
- Division of Evolution, Ecology and Genetics, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia
- *Janine E. Deakin:
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21
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Homolka D, Jansa P, Forejt J. Genetically enhanced asynapsis of autosomal chromatin promotes transcriptional dysregulation and meiotic failure. Chromosoma 2011; 121:91-104. [PMID: 22002499 PMCID: PMC3260437 DOI: 10.1007/s00412-011-0346-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 09/27/2011] [Accepted: 10/02/2011] [Indexed: 01/05/2023]
Abstract
During meiosis, pairing of homologous chromosomes and their synapsis are essential prerequisites for normal male gametogenesis. Even limited autosomal asynapsis often leads to spermatogenic impairment, the mechanism of which is not fully understood. The present study was aimed at deliberately increasing the size of partial autosomal asynapsis and analysis of its impact on male meiosis. For this purpose, we studied the effect of t(12) haplotype encompassing four inversions on chromosome 17 on mouse autosomal translocation T(16;17)43H (abbreviated T43H). The T43H/T43H homozygotes were fully fertile in both sexes, while +/T43H heterozygous males, but not females, were sterile with meiotic arrest at late pachynema. Inclusion of the t(12) haplotype in trans to the T43H translocation resulted in enhanced asynapsis of the translocated autosome, ectopic phosphorylation of histone H2AX, persistence of RAD51 foci, and increased gene silencing around the translocation break. Increase was also on colocalization of unsynapsed chromatin with sex body. Remarkably, we found that transcriptional silencing of the unsynapsed autosomal chromatin precedes silencing of sex chromosomes. Based on the present knowledge, we conclude that interference of meiotic silencing of unsynapsed autosomes with meiotic sex chromosome inactivation is the most likely cause of asynapsis-related male sterility.
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Affiliation(s)
- David Homolka
- Department of Mouse Molecular Genetics, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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22
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Gallach M, Domingues S, Betrán E. Gene duplication and the genome distribution of sex-biased genes. INTERNATIONAL JOURNAL OF EVOLUTIONARY BIOLOGY 2011; 2011:989438. [PMID: 21904687 PMCID: PMC3167187 DOI: 10.4061/2011/989438] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2010] [Revised: 03/26/2011] [Accepted: 06/05/2011] [Indexed: 12/04/2022]
Abstract
In species that have two sexes, a single genome encodes two morphs, as each sex can be thought of as a distinct morph. This means that the same set of genes are differentially expressed in the different sexes. Many questions emanate from this statement. What proportion of genes contributes to sexual dimorphism? How do they contribute to sexual dimorphism? How is sex-biased expression achieved? Which sex and what tissues contribute the most to sex-biased expression? Do sex-biased genes have the same evolutionary patterns as nonbiased genes? We review the current data on sex-biased expression in species with heteromorphic sex chromosomes and comment on the most important hypotheses suggested to explain the origin, evolution, and distribution patterns of sex-biased genes. In this perspective we emphasize how gene duplication serves as an important molecular mechanism to resolve genomic clashes and genetic conflicts by generating sex-biased genes, often sex-specific genes, and contributes greatly to the underlying genetic basis of sexual dimorphism.
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Affiliation(s)
- Miguel Gallach
- Department of Biology, University of Texas at Arlington, P.O. Box 19498, Arlington, TX 76019, USA
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23
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Payer B, Lee JT, Namekawa SH. X-inactivation and X-reactivation: epigenetic hallmarks of mammalian reproduction and pluripotent stem cells. Hum Genet 2011; 130:265-80. [PMID: 21667284 PMCID: PMC3744832 DOI: 10.1007/s00439-011-1024-7] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 05/27/2011] [Indexed: 01/07/2023]
Abstract
X-chromosome inactivation is an epigenetic hallmark of mammalian development. Chromosome-wide regulation of the X-chromosome is essential in embryonic and germ cell development. In the male germline, the X-chromosome goes through meiotic sex chromosome inactivation, and the chromosome-wide silencing is maintained from meiosis into spermatids before the transmission to female embryos. In early female mouse embryos, X-inactivation is imprinted to occur on the paternal X-chromosome, representing the epigenetic programs acquired in both parental germlines. Recent advances revealed that the inactive X-chromosome in both females and males can be dissected into two elements: repeat elements versus unique coding genes. The inactive paternal X in female preimplantation embryos is reactivated in the inner cell mass of blastocysts in order to subsequently allow the random form of X-inactivation in the female embryo, by which both Xs have an equal chance of being inactivated. X-chromosome reactivation is regulated by pluripotency factors and also occurs in early female germ cells and in pluripotent stem cells, where X-reactivation is a stringent marker of naive ground state pluripotency. Here we summarize recent progress in the study of X-inactivation and X-reactivation during mammalian reproduction and development as well as in pluripotent stem cells.
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Affiliation(s)
- Bernhard Payer
- Department of Genetics, Harvard Medical School, Boston, MA, USA. Howard Hughes Medical Institute, Boston, MA, USA. Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
| | - Jeannie T. Lee
- Department of Genetics, Harvard Medical School, Boston, MA, USA. Howard Hughes Medical Institute, Boston, MA, USA. Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
| | - Satoshi H. Namekawa
- Division of Reproductive Sciences, Perinatal Institute, Cincinnati Children’s Hospital Medical Center, Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, USA
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24
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Evolutionary diversity and developmental regulation of X-chromosome inactivation. Hum Genet 2011; 130:307-27. [PMID: 21687993 PMCID: PMC3132430 DOI: 10.1007/s00439-011-1029-2] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2011] [Accepted: 05/31/2011] [Indexed: 12/26/2022]
Abstract
X-chromosome inactivation (XCI) results in the transcriptional silencing of one X-chromosome in females to attain gene dosage parity between XX female and XY male mammals. Mammals appear to have developed rather diverse strategies to initiate XCI in early development. In placental mammals XCI depends on the regulatory noncoding RNA X-inactive specific transcript (Xist), which is absent in marsupials and monotremes. Surprisingly, even placental mammals show differences in the initiation of XCI in terms of Xist regulation and the timing to acquire dosage compensation. Despite this, all placental mammals achieve chromosome-wide gene silencing at some point in development, and this is maintained by epigenetic marks such as chromatin modifications and DNA methylation. In this review, we will summarise recent findings concerning the events that occur downstream of Xist RNA coating of the inactive X-chromosome (Xi) to ensure its heterochromatinization and the maintenance of the inactive state in the mouse and highlight similarities and differences between mammals.
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25
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Zhang A, Skaar DA, Li Y, Huang D, Price TM, Murphy SK, Jirtle RL. Novel retrotransposed imprinted locus identified at human 6p25. Nucleic Acids Res 2011; 39:5388-400. [PMID: 21421564 PMCID: PMC3141237 DOI: 10.1093/nar/gkr108] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Differentially methylated regions (DMRs) are stable epigenetic features within or in proximity to imprinted genes. We used this feature to identify candidate human imprinted loci by quantitative DNA methylation analysis. We discovered a unique DMR at the 5′-end of FAM50B at 6p25.2. We determined that sense transcripts originating from the FAM50B locus are expressed from the paternal allele in all human tissues investigated except for ovary, in which expression is biallelic. Furthermore, an antisense transcript, FAM50B-AS, was identified to be monoallelically expressed from the paternal allele in a variety of tissues. Comparative phylogenetic analysis showed that FAM50B orthologs are absent in chicken and platypus, but are present and biallelically expressed in opossum and mouse. These findings indicate that FAM50B originated in Therians after divergence from Prototherians via retrotransposition of a gene on the X chromosome. Moreover, our data are consistent with acquisition of imprinting during Eutherian evolution after divergence of Glires from the Euarchonta mammals. FAM50B expression is deregulated in testicular germ cell tumors, and loss of imprinting occurs frequently in testicular seminomas, suggesting an important role for FAM50B in spermatogenesis and tumorigenesis. These results also underscore the importance of accounting for parental origin in understanding the mechanism of 6p25-related diseases.
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Affiliation(s)
- Aiping Zhang
- Department of Radiation Oncology, Department of Community and Family Medicine and Department of Obstetrics and Gynecology, Duke University Medical Center, Durham, NC 27710, USA
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26
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Al Nadaf S, Waters PD, Koina E, Deakin JE, Jordan KS, Graves JA. Activity map of the tammar X chromosome shows that marsupial X inactivation is incomplete and escape is stochastic. Genome Biol 2010; 11:R122. [PMID: 21182760 PMCID: PMC3046482 DOI: 10.1186/gb-2010-11-12-r122] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Revised: 12/08/2010] [Accepted: 12/23/2010] [Indexed: 11/20/2022] Open
Abstract
Background X chromosome inactivation is a spectacular example of epigenetic silencing. In order to deduce how this complex system evolved, we examined X inactivation in a model marsupial, the tammar wallaby (Macropus eugenii). In marsupials, X inactivation is known to be paternal, incomplete and tissue-specific, and occurs in the absence of an XIST orthologue. Results We examined expression of X-borne genes using quantitative PCR, revealing a range of dosage compensation for different loci. To assess the frequency of 1X- or 2X-active fibroblasts, we investigated expression of 32 X-borne genes at the cellular level using RNA-FISH. In female fibroblasts, two-color RNA-FISH showed that genes were coordinately expressed from the same X (active X) in nuclei in which both loci were inactivated. However, loci on the other X escape inactivation independently, with each locus showing a characteristic frequency of 1X-active and 2X-active nuclei, equivalent to stochastic escape. We constructed an activity map of the tammar wallaby inactive X chromosome, which identified no relationship between gene location and extent of inactivation, nor any correlation with the presence or absence of a Y-borne paralog. Conclusions In the tammar wallaby, one X (presumed to be maternal) is expressed in all cells, but genes on the other (paternal) X escape inactivation independently and at characteristic frequencies. The paternal and incomplete X chromosome inactivation in marsupials, with stochastic escape, appears to be quite distinct from the X chromosome inactivation process in eutherians. We find no evidence for a polar spread of inactivation from an X inactivation center.
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Affiliation(s)
- Shafagh Al Nadaf
- Research School of Biology, The Australian National University, Biology Place, Canberra 0200, Australia.
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27
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Namekawa SH, Payer B, Huynh KD, Jaenisch R, Lee JT. Two-step imprinted X inactivation: repeat versus genic silencing in the mouse. Mol Cell Biol 2010; 30:3187-205. [PMID: 20404085 PMCID: PMC2897575 DOI: 10.1128/mcb.00227-10] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2010] [Revised: 03/24/2010] [Accepted: 04/13/2010] [Indexed: 12/12/2022] Open
Abstract
Mammals compensate for unequal X-linked gene dosages between the sexes by inactivating one X chromosome in the female. In marsupials and in the early mouse embryo, X chromosome inactivation (XCI) is imprinted to occur selectively on the paternal X chromosome (X(P)). The mechanisms and events underlying X(P) imprinting remain unclear. Here, we find that the imprinted X(P) can be functionally divided into two domains, one comprising traditional coding genes (genic) and the other comprising intergenic repetitive elements. X(P) repetitive element silencing occurs by the two-cell stage, does not require Xist, and occurs several divisions prior to genic silencing. In contrast, genic silencing initiates at the morula-to-blastocyst stage and absolutely requires Xist. Genes translocate into the presilenced repeat region as they are inactivated, whereas active genes remain outside. Thus, during the gamete-embryo transition, imprinted XCI occurs in two steps, with repeat silencing preceding genic inactivation. Nucleolar association may underlie the epigenetic asymmetry of X(P) and X(M). We hypothesize that transgenerational information (the imprint) is carried by repeats from the paternal germ line or that, alternatively, repetitive elements are silenced at the two-cell stage in a parent-of-origin-specific manner. Our model incorporates aspects of the so-called classical, de novo, and preinactivation hypotheses and suggests that Xist RNA functions relatively late during preimplantation mouse development.
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Affiliation(s)
- Satoshi H. Namekawa
- Howard Hughes Medical Institute, Department of Molecular Biology, Massachusetts General Hospital, Department of Genetics, Harvard Medical School, Boston, Massachusetts, Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Boston, Massachusetts
| | - Bernhard Payer
- Howard Hughes Medical Institute, Department of Molecular Biology, Massachusetts General Hospital, Department of Genetics, Harvard Medical School, Boston, Massachusetts, Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Boston, Massachusetts
| | - Khanh D. Huynh
- Howard Hughes Medical Institute, Department of Molecular Biology, Massachusetts General Hospital, Department of Genetics, Harvard Medical School, Boston, Massachusetts, Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Boston, Massachusetts
| | - Rudolf Jaenisch
- Howard Hughes Medical Institute, Department of Molecular Biology, Massachusetts General Hospital, Department of Genetics, Harvard Medical School, Boston, Massachusetts, Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Boston, Massachusetts
| | - Jeannie T. Lee
- Howard Hughes Medical Institute, Department of Molecular Biology, Massachusetts General Hospital, Department of Genetics, Harvard Medical School, Boston, Massachusetts, Whitehead Institute for Biomedical Research and Department of Biology, Massachusetts Institute of Technology, Boston, Massachusetts
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28
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Vaskova EA, Pavlova SV, Shevchenko AI, Zakian SM. Meiotic inactivation of sex chromosomes in mammals. RUSS J GENET+ 2010. [DOI: 10.1134/s1022795410040010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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29
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Ho KKK, Deakin JE, Wright ML, Graves JAM, Grützner F. Replication asynchrony and differential condensation of X chromosomes in female platypus (Ornithorhynchus anatinus). Reprod Fertil Dev 2010; 21:952-63. [PMID: 19874719 DOI: 10.1071/rd09099] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2009] [Accepted: 09/15/2009] [Indexed: 11/23/2022] Open
Abstract
A common theme in the evolution of sex chromosomes is the massive loss of genes on the sex-specific chromosome (Y or W), leading to a gene imbalance between males (XY) and females (XX) in a male heterogametic species, or between ZZ and ZW in a female heterogametic species. Different mechanisms have evolved to compensate for this difference in dosage of X-borne genes between sexes. In therian mammals, one of the X chromosomes is inactivated, whereas bird dosage compensation is partial and gene-specific. In therian mammals, hallmarks of the inactive X are monoallelic gene expression, late DNA replication and chromatin condensation. Platypuses have five pairs of X chromosomes in females and five X and five Y chromosomes in males. Gene expression analysis suggests a more bird-like partial and gene-specific dosage compensation mechanism. We investigated replication timing and chromosome condensation of three of the five X chromosomes in female platypus. Our data suggest asynchronous replication of X-specific regions on X(1), X(3) and X(5) but show significantly different condensation between homologues for X(3) only, and not for X(1) or X(5). We discuss these results in relation to recent gene expression analysis of X-linked genes, which together give us insights into possible mechanisms of dosage compensation in platypus.
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Affiliation(s)
- Kristen K K Ho
- School of Molecular and Biomedical Science, The University of Adelaide, Adelaide, SA 5005, Australia
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30
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Svartman M. American marsupials chromosomes: Why study them? Genet Mol Biol 2009; 32:675-87. [PMID: 21637437 PMCID: PMC3036883 DOI: 10.1590/s1415-47572009005000084] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2008] [Accepted: 06/17/2009] [Indexed: 11/22/2022] Open
Abstract
Marsupials, one of the three main groups of mammals, are only found in Australia and in the American continent. Studies performed in Australian marsupials have demonstrated the great potential provided by the group for the understanding of basic genetic mechanisms and chromosome evolution in mammals. Genetic studies in American marsupials are relatively scarce and cytogenetic data of most species are restricted to karyotype descriptions, usually without banding patterns. Nevertheless, the first marsupial genome sequenced was that of Monodelphis domestica, a South American species. The knowledge about mammalian genome evolution and function that resulted from studies on M. domestica is in sharp contrast with the lack of genetic data on most American marsupial species. Here, we present an overview of the chromosome studies performed in marsupials with emphasis on the South American species.
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Affiliation(s)
- Marta Svartman
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG Brazil
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31
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Abstract
Sex chromosomes have evolved multiple times in many taxa. The recent explosion in the availability of whole genome sequences from a variety of organisms makes it possible to investigate sex chromosome evolution within and across genomes. Comparative genomic studies have shown that quite distant species may share fundamental properties of sex chromosome evolution, while very similar species can evolve unique sex chromosome systems. Furthermore, within-species genomic analyses can illuminate chromosome-wide sequence and expression polymorphisms. Here, we explore recent advances in the study of vertebrate sex chromosomes achieved using genomic analyses.
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Affiliation(s)
- Melissa A Wilson
- Center for Comparative Genomics and Bioinformatics, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
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Deakin JE, Chaumeil J, Hore TA, Marshall Graves JA. Unravelling the evolutionary origins of X chromosome inactivation in mammals: insights from marsupials and monotremes. Chromosome Res 2009; 17:671-85. [DOI: 10.1007/s10577-009-9058-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Mahadevaiah SK, Royo H, VandeBerg JL, McCarrey JR, Mackay S, Turner JMA. Key features of the X inactivation process are conserved between marsupials and eutherians. Curr Biol 2009; 19:1478-84. [PMID: 19716301 DOI: 10.1016/j.cub.2009.07.041] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Revised: 07/06/2009] [Accepted: 07/07/2009] [Indexed: 10/20/2022]
Abstract
In female marsupials, X chromosome inactivation (XCI) is imprinted, affecting the paternal X chromosome. One model, supported by recent studies, proposes that XCI in marsupials is achieved through inheritance of an already silent X chromosome from the father, with XCI initiated by meiotic sex chromosome inactivation (MSCI). This model is appealing because marsupials have no Xist gene and the marsupial inactive X chromosome is epigenetically dissimilar to that of mice, apparently lacking repressive histone marks such as H3K27 trimethylation. A central prediction of the meiotic inactivation model of XCI is that silencing of genes on the X chromosome, initiated during male meiosis, is stably maintained during subsequent spermiogenesis. Here we characterize XCI in the male germline and female soma of the marsupial Monodelphis domestica. Contrary to the meiotic inactivation model, we find that X genes silenced by MSCI are reactivated after meiosis and are subsequently inactivated in the female. A reexamination of the female somatic inactive marsupial X chromosome reveals that it does share common properties with that of eutherians, including H3K27 trimethylation and targeting to the perinucleolar compartment. We conclude that aspects of the XCI process are more highly conserved in therian mammals than previously thought.
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Affiliation(s)
- Satoshi H. Namekawa
- Howard Hughes Medical Institute, Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jeannie T. Lee
- Howard Hughes Medical Institute, Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
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35
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Abstract
The development of genetic sex determination and cytologically distinct sex chromosomes leads to the potential problem of gene dosage imbalances between autosomes and sex chromosomes and also between males and females. To circumvent these imbalances, mammals have developed an elaborate system of dosage compensation that includes both upregulation and repression of the X chromosome. Recent advances have provided insights into the evolutionary history of how both the imprinted and random forms of X chromosome inactivation have come about. Furthermore, our understanding of the epigenetic switch at the X-inactivation center and the molecular aspects of chromosome-wide silencing has greatly improved recently. Here, we review various facets of the ever-expanding field of mammalian dosage compensation and discuss its evolutionary, developmental, and mechanistic components.
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Affiliation(s)
- Bernhard Payer
- Howard Hughes Medical Institute, Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
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36
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Abstract
The strategic importance of the genome sequence of the gray, short-tailed opossum, Monodelphis domestica, accrues from both the unique phylogenetic position of metatherian (marsupial) mammals and the fundamental biologic characteristics of metatherians that distinguish them from other mammalian species. Metatherian and eutherian (placental) mammals are more closely related to one another than to other vertebrate groups, and owing to this close relationship they share fundamentally similar genetic structures and molecular processes. However, during their long evolutionary separation these alternative mammals have developed distinctive anatomical, physiologic, and genetic features that hold tremendous potential for examining relationships between the molecular structures of mammalian genomes and the functional attributes of their components. Comparative analyses using the opossum genome have already provided a wealth of new evidence regarding the importance of noncoding elements in the evolution of mammalian genomes, the role of transposable elements in driving genomic innovation, and the relationships between recombination rate, nucleotide composition, and the genomic distributions of repetitive elements. The genome sequence is also beginning to enlarge our understanding of the evolution and function of the vertebrate immune system, and it provides an alternative model for investigating mechanisms of genomic imprinting. Equally important, availability of the genome sequence is fostering the development of new research tools for physical and functional genomic analyses of M. domestica that are expanding its versatility as an experimental system for a broad range of research applications in basic biology and biomedically oriented research.
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37
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Ideraabdullah FY, Vigneau S, Bartolomei MS. Genomic imprinting mechanisms in mammals. Mutat Res 2008; 647:77-85. [PMID: 18778719 DOI: 10.1016/j.mrfmmm.2008.08.008] [Citation(s) in RCA: 173] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2008] [Revised: 07/31/2008] [Accepted: 08/07/2008] [Indexed: 11/25/2022]
Abstract
Genomic imprinting is a form of epigenetic gene regulation that results in expression from a single allele in a parent-of-origin-dependent manner. This form of monoallelic expression affects a small but growing number of genes and is essential to normal mammalian development. Despite extensive studies and some major breakthroughs regarding this intriguing phenomenon, we have not yet fully characterized the underlying molecular mechanisms of genomic imprinting. This is in part due to the complexity of the system in that the epigenetic markings required for proper imprinting must be established in the germline, maintained throughout development, and then erased before being re-established in the next generation's germline. Furthermore, imprinted gene expression is often tissue or stage-specific. It has also become clear that while imprinted loci across the genome seem to rely consistently on epigenetic markings of DNA methylation and/or histone modifications to discern parental alleles, the regulatory activities underlying these markings vary among loci. Here, we discuss different modes of imprinting regulation in mammals and how perturbations of these systems result in human disease. We focus on the mechanism of genomic imprinting mediated by insulators as is present at the H19/Igf2 locus, and by non-coding RNA present at the Igf2r and Kcnq1 loci. In addition to imprinting mechanisms at autosomal loci, what is known about imprinted X-chromosome inactivation and how it compares to autosomal imprinting is also discussed. Overall, this review summarizes many years of imprinting research, while pointing out exciting new discoveries that further elucidate the mechanism of genomic imprinting, and speculating on areas that require further investigation.
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Affiliation(s)
- Folami Y Ideraabdullah
- Department of Cell and Developmental Biology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA
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Erwin JA, Lee JT. New twists in X-chromosome inactivation. Curr Opin Cell Biol 2008; 20:349-55. [PMID: 18508252 DOI: 10.1016/j.ceb.2008.04.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2008] [Accepted: 04/21/2008] [Indexed: 10/22/2022]
Abstract
Dosage compensation, the mechanism by which organisms equalize the relative gene expression of dimorphic sex chromosomes, requires action of a diverse range of epigenetic mechanisms. The mammalian form, 'named X-chromosome inactivation' (XCI), involves silencing of one X chromosome in the female cell and regulation by genes that make noncoding RNAs (ncRNA). With large-scale genomic and transcriptome studies pointing to a crucial role for noncoding elements in organizing the epigenome, XCI emerges as a major paradigm and a focus of active research worldwide. With more surprising twists, recent advances point to the significance of RNA-directed chromatin change, chromosomal trans-interactions, nuclear organization, and evolutionary change. These findings have impacted our understanding of general gene regulation and are discussed herein.
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Affiliation(s)
- Jennifer A Erwin
- Howard Hughes Medical Institute, Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA
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Angelopoulou R, Lavranos G, Manolakou P. Regulatory RNAs and chromatin modification in dosage compensation: a continuous path from flies to humans? Reprod Biol Endocrinol 2008; 6:12. [PMID: 18355403 PMCID: PMC2324084 DOI: 10.1186/1477-7827-6-12] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Accepted: 03/20/2008] [Indexed: 11/20/2022] Open
Abstract
Chromosomal sex determination is a widely distributed strategy in nature. In the most classic scenario, one sex is characterized by a homologue pair of sex chromosomes, while the other includes two morphologically and functionally distinct gonosomes. In mammalian diploid cells, the female is characterized by the presence of two identical X chromosomes, while the male features an XY pair, with the Y bearing the major genetic determinant of sex, i.e. the SRY gene. In other species, such as the fruitfly, sex is determined by the ratio of autosomes to X chromosomes. Regardless of the exact mechanism, however, all these animals would exhibit a sex-specific gene expression inequality, due to the different number of X chromosomes, a phenomenon inhibited by a series of genetic and epigenetic regulatory events described as "dosage compensation". Since adequate available data is currently restricted to worms, flies and mammals, while for other groups of animals, such as reptiles, fish and birds it is very limited, it is not yet clear whether this is an evolutionary conserved mechanism. However certain striking similarities have already been observed among evolutionary distant species, such as Drosophila melanogaster and Mus musculus. These mainly refer to a) the need for a counting mechanism, to determine the chromosomal content of the cell, i.e. the ratio of autosomes to gonosomes (a process well understood in flies, but still hypothesized in mammals), b) the implication of non-translated, sex-specific, regulatory RNAs (roX and Xist, respectively) as key elements in this process and the location of similar mediators in the Z chromosome of chicken c) the inclusion of a chromatin modification epigenetic final step, which ensures that gene expression remains stably regulated throughout the affected area of the gonosome. This review summarizes these points and proposes a possible role for comparative genetics, as they seem to constitute proof of maintained cell economy (by using the same basic regulatory elements in various different scenarios) throughout numerous centuries of evolutionary history.
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Affiliation(s)
- Roxani Angelopoulou
- Department of Histology-Embryology, Medical School, Athens University, Greece
| | - Giagkos Lavranos
- Department of Histology-Embryology, Medical School, Athens University, Greece
| | - Panagiota Manolakou
- Department of Histology-Embryology, Medical School, Athens University, Greece
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