1
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San Roman AK, Skaletsky H, Godfrey AK, Bokil NV, Teitz L, Singh I, Blanton LV, Bellott DW, Pyntikova T, Lange J, Koutseva N, Hughes JF, Brown L, Phou S, Buscetta A, Kruszka P, Banks N, Dutra A, Pak E, Lasutschinkow PC, Keen C, Davis SM, Lin AE, Tartaglia NR, Samango-Sprouse C, Muenke M, Page DC. The human Y and inactive X chromosomes similarly modulate autosomal gene expression. Cell Genom 2024; 4:100462. [PMID: 38190107 PMCID: PMC10794785 DOI: 10.1016/j.xgen.2023.100462] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 08/15/2023] [Accepted: 11/14/2023] [Indexed: 01/09/2024]
Abstract
Somatic cells of human males and females have 45 chromosomes in common, including the "active" X chromosome. In males the 46th chromosome is a Y; in females it is an "inactive" X (Xi). Through linear modeling of autosomal gene expression in cells from individuals with zero to three Xi and zero to four Y chromosomes, we found that Xi and Y impact autosomal expression broadly and with remarkably similar effects. Studying sex chromosome structural anomalies, promoters of Xi- and Y-responsive genes, and CRISPR inhibition, we traced part of this shared effect to homologous transcription factors-ZFX and ZFY-encoded by Chr X and Y. This demonstrates sex-shared mechanisms by which Xi and Y modulate autosomal expression. Combined with earlier analyses of sex-linked gene expression, our studies show that 21% of all genes expressed in lymphoblastoid cells or fibroblasts change expression significantly in response to Xi or Y chromosomes.
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Affiliation(s)
| | - Helen Skaletsky
- Whitehead Institute, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Whitehead Institute, Cambridge, MA 02142, USA
| | - Alexander K Godfrey
- Whitehead Institute, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Neha V Bokil
- Whitehead Institute, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Levi Teitz
- Whitehead Institute, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Isani Singh
- Whitehead Institute, Cambridge, MA 02142, USA; Harvard Medical School, Boston, MA 02115, USA
| | | | | | | | - Julian Lange
- Whitehead Institute, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | | | - Laura Brown
- Whitehead Institute, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Whitehead Institute, Cambridge, MA 02142, USA
| | - Sidaly Phou
- Whitehead Institute, Cambridge, MA 02142, USA; Howard Hughes Medical Institute, Whitehead Institute, Cambridge, MA 02142, USA
| | - Ashley Buscetta
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Paul Kruszka
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Nicole Banks
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA; Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Amalia Dutra
- Cytogenetics and Microscopy Core, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Evgenia Pak
- Cytogenetics and Microscopy Core, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | | | | | - Shanlee M Davis
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Angela E Lin
- Medical Genetics, Massachusetts General for Children, Boston, MA 02114, USA; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
| | - Nicole R Tartaglia
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, USA; Developmental Pediatrics, eXtraOrdinarY Kids Program, Children's Hospital Colorado, Aurora, CO 80011, USA
| | - Carole Samango-Sprouse
- Focus Foundation, Davidsonville, MD 21035, USA; Department of Pediatrics, George Washington University, Washington, DC 20052, USA; Department of Human and Molecular Genetics, Florida International University, Miami, FL 33199, USA
| | - Maximilian Muenke
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - David C Page
- Whitehead Institute, Cambridge, MA 02142, USA; Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, Whitehead Institute, Cambridge, MA 02142, USA.
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2
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San Roman AK, Skaletsky H, Godfrey AK, Bokil NV, Teitz L, Singh I, Blanton LV, Bellott DW, Pyntikova T, Lange J, Koutseva N, Hughes JF, Brown L, Phou S, Buscetta A, Kruszka P, Banks N, Dutra A, Pak E, Lasutschinkow PC, Keen C, Davis SM, Lin AE, Tartaglia NR, Samango-Sprouse C, Muenke M, Page DC. The human Y and inactive X chromosomes similarly modulate autosomal gene expression. bioRxiv 2023:2023.06.05.543763. [PMID: 37333288 PMCID: PMC10274745 DOI: 10.1101/2023.06.05.543763] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2023]
Abstract
Somatic cells of human males and females have 45 chromosomes in common, including the "active" X chromosome. In males the 46th chromosome is a Y; in females it is an "inactive" X (Xi). Through linear modeling of autosomal gene expression in cells from individuals with zero to three Xi and zero to four Y chromosomes, we found that Xi and Y impact autosomal expression broadly and with remarkably similar effects. Studying sex-chromosome structural anomalies, promoters of Xi- and Y-responsive genes, and CRISPR inhibition, we traced part of this shared effect to homologous transcription factors - ZFX and ZFY - encoded by Chr X and Y. This demonstrates sex-shared mechanisms by which Xi and Y modulate autosomal expression. Combined with earlier analyses of sex-linked gene expression, our studies show that 21% of all genes expressed in lymphoblastoid cells or fibroblasts change expression significantly in response to Xi or Y chromosomes.
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Affiliation(s)
| | - Helen Skaletsky
- Whitehead Institute; Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Whitehead Institute; Cambridge, MA 02142, USA
| | - Alexander K. Godfrey
- Whitehead Institute; Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology; Cambridge, MA 02139, USA
| | - Neha V. Bokil
- Whitehead Institute; Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology; Cambridge, MA 02139, USA
| | - Levi Teitz
- Whitehead Institute; Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology; Cambridge, MA 02139, USA
| | - Isani Singh
- Whitehead Institute; Cambridge, MA 02142, USA
- Harvard Medical School, Boston, MA 02115, USA
| | | | | | | | - Julian Lange
- Whitehead Institute; Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology; Cambridge, MA 02139, USA
| | | | | | - Laura Brown
- Whitehead Institute; Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Whitehead Institute; Cambridge, MA 02142, USA
| | - Sidaly Phou
- Whitehead Institute; Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Whitehead Institute; Cambridge, MA 02142, USA
| | - Ashley Buscetta
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda; MD 20892, USA
| | - Paul Kruszka
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda; MD 20892, USA
| | - Nicole Banks
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda; MD 20892, USA
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health; Bethesda, MD 20892 USA
| | - Amalia Dutra
- Cytogenetics and Microscopy Core, National Human Genome Research Institute, National Institutes of Health; Bethesda, MD 20892 USA
| | - Evgenia Pak
- Cytogenetics and Microscopy Core, National Human Genome Research Institute, National Institutes of Health; Bethesda, MD 20892 USA
| | | | | | - Shanlee M. Davis
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, USA
| | - Angela E. Lin
- Medical Genetics, Massachusetts General for Children, Boston, MA 02114, USA; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
| | - Nicole R. Tartaglia
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, USA
- Developmental Pediatrics, eXtraOrdinarY Kids Program, Children’s Hospital Colorado, Aurora, CO 80011, USA
| | - Carole Samango-Sprouse
- Focus Foundation, Davidsonville, MD 21035, USA
- Department of Pediatrics, George Washington University, Washington, DC 20052, USA; Department of Human and Molecular Genetics, Florida International University, Miami, FL 33199, USA
| | - Maximilian Muenke
- Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda; MD 20892, USA
| | - David C. Page
- Whitehead Institute; Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology; Cambridge, MA 02139, USA
- Howard Hughes Medical Institute, Whitehead Institute; Cambridge, MA 02142, USA
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3
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Bellott DW, Cho TJ, Jackson EK, Skaletsky H, Hughes JF, Page DC. SHIMS 3.0: Highly efficient single-haplotype iterative mapping and sequencing using ultra-long nanopore reads. PLoS One 2022; 17:e0269692. [PMID: 35700171 PMCID: PMC9197060 DOI: 10.1371/journal.pone.0269692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 05/25/2022] [Indexed: 11/18/2022] Open
Abstract
The reference sequence of structurally complex regions can only be obtained through a highly accurate clone-based approach that we call Single-Haplotype Iterative Mapping and Sequencing (SHIMS). In recent years, improvements to SHIMS have reduced the cost and time required by two orders of magnitude, but internally repetitive clones still require extensive manual effort to transform draft assemblies into reference-quality finished sequences. Here we describe SHIMS 3.0, using ultra-long nanopore reads to augment the Illumina data from SHIMS 2.0 assemblies and resolve internally repetitive structures. This greatly minimizes the need for manual finishing of Illumina-based draft assemblies, allowing a small team with no prior finishing experience to sequence challenging targets with high accuracy. This protocol proceeds from clone-picking to finished assemblies in 2 weeks for about $80 (USD) per clone. We recently used this protocol to produce reference sequence of structurally complex palindromes on chimpanzee and rhesus macaque X chromosomes. Our protocol provides access to structurally complex regions that would otherwise be inaccessible from whole-genome shotgun data or require an impractical amount of manual effort to generate an accurate assembly.
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Affiliation(s)
- Daniel W. Bellott
- Whitehead Institute, Cambridge, Massachusetts, United States of America
- * E-mail:
| | - Ting-Jan Cho
- Whitehead Institute, Cambridge, Massachusetts, United States of America
| | - Emily K. Jackson
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - Helen Skaletsky
- Whitehead Institute, Cambridge, Massachusetts, United States of America
- Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts, United States of America
| | | | - David C. Page
- Whitehead Institute, Cambridge, Massachusetts, United States of America
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
- Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts, United States of America
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4
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Hughes JF, Skaletsky H, Nicholls PK, Drake A, Pyntikova T, Cho TJ, Bellott DW, Page DC. A gene deriving from the ancestral sex chromosomes was lost from the X and retained on the Y chromosome in eutherian mammals. BMC Biol 2022; 20:133. [PMID: 35676717 PMCID: PMC9178871 DOI: 10.1186/s12915-022-01338-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 05/25/2022] [Indexed: 11/14/2022] Open
Abstract
Background The mammalian X and Y chromosomes originated from a pair of ordinary autosomes. Over the past ~180 million years, the X and Y have become highly differentiated and now only recombine with each other within a short pseudoautosomal region. While the X chromosome broadly preserved its gene content, the Y chromosome lost ~92% of the genes it once shared with the X chromosome. PRSSLY is a Y-linked gene identified in only a few mammalian species that was thought to be acquired, not ancestral. However, PRSSLY’s presence in widely divergent species—bull and mouse—led us to further investigate its evolutionary history. Results We discovered that PRSSLY is broadly conserved across eutherians and has ancient origins. PRSSLY homologs are found in syntenic regions on the X chromosome in marsupials and on autosomes in more distant animals, including lizards, indicating that PRSSLY was present on the ancestral autosomes but was lost from the X and retained on the Y in eutherian mammals. We found that across eutheria, PRSSLY’s expression is testis-specific, and, in mouse, it is most robustly expressed in post-meiotic germ cells. The closest paralog to PRSSLY is the autosomal gene PRSS55, which is expressed exclusively in testes, involved in sperm differentiation and migration, and essential for male fertility in mice. Outside of eutheria, in species where PRSSLY orthologs are not Y-linked, we find expression in a broader range of somatic tissues, suggesting that PRSSLY has adopted a germ-cell-specific function in eutherians. Finally, we generated Prssly mutant mice and found that they are fully fertile but produce offspring with a modest female-biased sex ratio compared to controls. Conclusions PRSSLY appears to be the first example of a gene that derives from the mammalian ancestral sex chromosomes that was lost from the X and retained on the Y. Although the function of PRSSLY remains to be determined, it may influence the sex ratio by promoting the survival or propagation of Y-bearing sperm. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-022-01338-8.
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Affiliation(s)
| | - Helen Skaletsky
- Whitehead Institute, Cambridge, MA, 02142, USA.,Howard Hughes Medical Institute, Whitehead Institute, Cambridge, MA, 02142, USA
| | - Peter K Nicholls
- Whitehead Institute, Cambridge, MA, 02142, USA.,Present Address: Faculty of Life Sciences, University of Bradford, BD71DP, Bradford, UK
| | | | | | | | | | - David C Page
- Whitehead Institute, Cambridge, MA, 02142, USA.,Howard Hughes Medical Institute, Whitehead Institute, Cambridge, MA, 02142, USA.,Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, 02142, USA
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5
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Jackson EK, Bellott DW, Skaletsky H, Page DC. GC-biased gene conversion in X-chromosome palindromes conserved in human, chimpanzee, and rhesus macaque. G3 Genes|Genomes|Genetics 2021; 11:6317831. [PMID: 34849781 PMCID: PMC8981503 DOI: 10.1093/g3journal/jkab224] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 06/28/2021] [Indexed: 12/03/2022]
Abstract
Gene conversion is GC-biased across a wide range of taxa. Large palindromes on mammalian
sex chromosomes undergo frequent gene conversion that maintains arm-to-arm sequence
identity greater than 99%, which may increase their susceptibility to the effects of
GC-biased gene conversion. Here, we demonstrate a striking history of GC-biased gene
conversion in 12 palindromes conserved on the X chromosomes of human, chimpanzee, and
rhesus macaque. Primate X-chromosome palindrome arms have significantly higher GC content
than flanking single-copy sequences. Nucleotide replacements that occurred in human and
chimpanzee palindrome arms over the past 7 million years are one-and-a-half times as
GC-rich as the ancestral bases they replaced. Using simulations, we show that our observed
pattern of nucleotide replacements is consistent with GC-biased gene conversion with a
magnitude of 70%, similar to previously reported values based on analyses of human
meioses. However, GC-biased gene conversion since the divergence of human and rhesus
macaque explains only a fraction of the observed difference in GC content between
palindrome arms and flanking sequence, suggesting that palindromes are older than 29
million years and/or had elevated GC content at the time of their formation. This work
supports a greater than 2:1 preference for GC bases over AT bases during gene conversion
and demonstrates that the evolution and composition of mammalian sex chromosome
palindromes is strongly influenced by GC-biased gene conversion.
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Affiliation(s)
- Emily K Jackson
- Whitehead Institute, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Whitehead Institute, Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | - Helen Skaletsky
- Whitehead Institute, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Whitehead Institute, Cambridge, MA 02142, USA
| | - David C Page
- Whitehead Institute, Cambridge, MA 02142, USA
- Howard Hughes Medical Institute, Whitehead Institute, Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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6
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Jackson EK, Bellott DW, Cho TJ, Skaletsky H, Hughes JF, Pyntikova T, Page DC. Large palindromes on the primate X Chromosome are preserved by natural selection. Genome Res 2021; 31:1337-1352. [PMID: 34290043 PMCID: PMC8327919 DOI: 10.1101/gr.275188.120] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Accepted: 05/17/2021] [Indexed: 12/27/2022]
Abstract
Mammalian sex chromosomes carry large palindromes that harbor protein-coding gene families with testis-biased expression. However, there are few known examples of sex-chromosome palindromes conserved between species. We identified 26 palindromes on the human X Chromosome, constituting more than 2% of its sequence, and characterized orthologous palindromes in the chimpanzee and the rhesus macaque using a clone-based sequencing approach that incorporates full-length nanopore reads. Many of these palindromes are missing or misassembled in the current reference assemblies of these species' genomes. We find that 12 human X palindromes have been conserved for at least 25 million years, with orthologs in both chimpanzee and rhesus macaque. Insertions and deletions between species are significantly depleted within the X palindromes' protein-coding genes compared to their noncoding sequence, demonstrating that natural selection has preserved these gene families. The spacers that separate the left and right arms of palindromes are a site of localized structural instability, with seven of 12 conserved palindromes showing no spacer orthology between human and rhesus macaque. Analysis of the 1000 Genomes Project data set revealed that human X-palindrome spacers are enriched for deletions relative to arms and flanking sequence, including a common spacer deletion that affects 13% of human X Chromosomes. This work reveals an abundance of conserved palindromes on primate X Chromosomes and suggests that protein-coding gene families in palindromes (most of which remain poorly characterized) promote X-palindrome survival in the face of ongoing structural instability.
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Affiliation(s)
- Emily K Jackson
- Whitehead Institute, Cambridge, Massachusetts 02142, USA
- Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts 02142, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | | | - Ting-Jan Cho
- Whitehead Institute, Cambridge, Massachusetts 02142, USA
| | - Helen Skaletsky
- Whitehead Institute, Cambridge, Massachusetts 02142, USA
- Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts 02142, USA
| | | | | | - David C Page
- Whitehead Institute, Cambridge, Massachusetts 02142, USA
- Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts 02142, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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7
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Bellott DW, Page DC. Dosage-sensitive functions in embryonic development drove the survival of genes on sex-specific chromosomes in snakes, birds, and mammals. Genome Res 2021; 31:198-210. [PMID: 33479023 PMCID: PMC7849413 DOI: 10.1101/gr.268516.120] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Accepted: 12/04/2020] [Indexed: 12/18/2022]
Abstract
Different ancestral autosomes independently evolved into sex chromosomes in snakes, birds, and mammals. In snakes and birds, females are ZW and males are ZZ; in mammals, females are XX and males are XY. Although X and Z Chromosomes retain nearly all ancestral genes, sex-specific W and Y Chromosomes suffered extensive genetic decay. In both birds and mammals, the genes that survived on sex-specific chromosomes are enriched for broadly expressed, dosage-sensitive regulators of gene expression, subject to strong purifying selection. To gain deeper insight into the processes that govern survival on sex-specific chromosomes, we carried out a meta-analysis of survival across 41 species-three snakes, 24 birds, and 14 mammals-doubling the number of ancestral genes under investigation and increasing our power to detect enrichments among survivors relative to nonsurvivors. Of 2564 ancestral genes, representing an eighth of the ancestral amniote genome, only 324 survive on present-day sex-specific chromosomes. Survivors are enriched for dosage-sensitive developmental processes, particularly development of neural crest-derived structures, such as the face. However, there was no enrichment for expression in sex-specific tissues, involvement in sex determination or gonadogenesis pathways, or conserved sex-biased expression. Broad expression and dosage sensitivity contributed independently to gene survival, suggesting that pleiotropy imposes additional constraints on the evolution of dosage compensation. We propose that maintaining the viability of the heterogametic sex drove gene survival on amniote sex-specific chromosomes, and that subtle modulation of the expression of survivor genes and their autosomal orthologs has disproportionately large effects on development and disease.
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Affiliation(s)
| | - David C Page
- Whitehead Institute, Cambridge, Massachusetts 02142, USA
- Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts 02142, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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8
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Hughes JF, Skaletsky H, Pyntikova T, Koutseva N, Raudsepp T, Brown LG, Bellott DW, Cho TJ, Dugan-Rocha S, Khan Z, Kremitzki C, Fronick C, Graves-Lindsay TA, Fulton L, Warren WC, Wilson RK, Owens E, Womack JE, Murphy WJ, Muzny DM, Worley KC, Chowdhary BP, Gibbs RA, Page DC. Sequence analysis in Bos taurus reveals pervasiveness of X-Y arms races in mammalian lineages. Genome Res 2020; 30:1716-1726. [PMID: 33208454 PMCID: PMC7706723 DOI: 10.1101/gr.269902.120] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 10/28/2020] [Indexed: 12/28/2022]
Abstract
Studies of Y Chromosome evolution have focused primarily on gene decay, a consequence of suppression of crossing-over with the X Chromosome. Here, we provide evidence that suppression of X-Y crossing-over unleashed a second dynamic: selfish X-Y arms races that reshaped the sex chromosomes in mammals as different as cattle, mice, and men. Using super-resolution sequencing, we explore the Y Chromosome of Bos taurus (bull) and find it to be dominated by massive, lineage-specific amplification of testis-expressed gene families, making it the most gene-dense Y Chromosome sequenced to date. As in mice, an X-linked homolog of a bull Y-amplified gene has become testis-specific and amplified. This evolutionary convergence implies that lineage-specific X-Y coevolution through gene amplification, and the selfish forces underlying this phenomenon, were dominatingly powerful among diverse mammalian lineages. Together with Y gene decay, X-Y arms races molded mammalian sex chromosomes and influenced the course of mammalian evolution.
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Affiliation(s)
| | - Helen Skaletsky
- Whitehead Institute, Cambridge, Massachusetts 02142, USA.,Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts 02142, USA
| | | | | | - Terje Raudsepp
- College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843, USA
| | - Laura G Brown
- Whitehead Institute, Cambridge, Massachusetts 02142, USA.,Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts 02142, USA
| | | | - Ting-Jan Cho
- Whitehead Institute, Cambridge, Massachusetts 02142, USA
| | - Shannon Dugan-Rocha
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Ziad Khan
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Colin Kremitzki
- The McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Catrina Fronick
- The McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Tina A Graves-Lindsay
- The McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Lucinda Fulton
- The McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Wesley C Warren
- The McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Richard K Wilson
- The McDonnell Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Elaine Owens
- College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843, USA
| | - James E Womack
- College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843, USA
| | - William J Murphy
- College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843, USA
| | - Donna M Muzny
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Kim C Worley
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Bhanu P Chowdhary
- College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843, USA
| | - Richard A Gibbs
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - David C Page
- Whitehead Institute, Cambridge, Massachusetts 02142, USA.,Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts 02142, USA.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
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9
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Janečka JE, Davis BW, Ghosh S, Paria N, Das PJ, Orlando L, Schubert M, Nielsen MK, Stout TAE, Brashear W, Li G, Johnson CD, Metz RP, Zadjali AMA, Love CC, Varner DD, Bellott DW, Murphy WJ, Chowdhary BP, Raudsepp T. Horse Y chromosome assembly displays unique evolutionary features and putative stallion fertility genes. Nat Commun 2018; 9:2945. [PMID: 30054462 PMCID: PMC6063916 DOI: 10.1038/s41467-018-05290-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Accepted: 05/23/2018] [Indexed: 01/08/2023] Open
Abstract
Dynamic evolutionary processes and complex structure make the Y chromosome among the most diverse and least understood regions in mammalian genomes. Here, we present an annotated assembly of the male specific region of the horse Y chromosome (eMSY), representing the first comprehensive Y assembly in odd-toed ungulates. The eMSY comprises single-copy, equine specific multi-copy, PAR transposed, and novel ampliconic sequence classes. The eMSY gene density approaches that of autosomes with the highest number of retained X-Y gametologs recorded in eutherians, in addition to novel Y-born and transposed genes. Horse, donkey and mule testis RNAseq reveals several candidate genes for stallion fertility. A novel testis-expressed XY ampliconic sequence class, ETSTY7, is shared with the parasite Parascaris genome, providing evidence for eukaryotic horizontal transfer and inter-chromosomal mobility. Our study highlights the dynamic nature of the Y and provides a reference sequence for improved understanding of equine male development and fertility.
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Affiliation(s)
| | - Brian W Davis
- Texas A&M University, College Station, TX, 77843, USA
| | | | - Nandina Paria
- Texas Scottish Rite Hospital for Children, Dallas, TX, 75219, USA
| | - Pranab J Das
- ICAR-National Research Centre on Pig, Guwahati, Assam, 781131, India
| | - Ludovic Orlando
- Natural History Museum of Denmark, 1350K, Copenhagen, Denmark.,Université de Toulouse, Université Paul Sabatier, 31000, Toulouse, France
| | - Mikkel Schubert
- Natural History Museum of Denmark, 1350K, Copenhagen, Denmark
| | | | | | | | - Gang Li
- Texas A&M University, College Station, TX, 77843, USA
| | | | - Richard P Metz
- Texas A&M AgriLife Research, College Station, TX, 77843, USA
| | | | | | | | | | | | - Bhanu P Chowdhary
- Texas A&M University, College Station, TX, 77843, USA. .,United Arab Emirates University, Al Ain, 15551, UAE.
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10
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Naqvi S, Bellott DW, Lin KS, Page DC. Conserved microRNA targeting reveals preexisting gene dosage sensitivities that shaped amniote sex chromosome evolution. Genome Res 2018; 28:474-483. [PMID: 29449410 PMCID: PMC5880238 DOI: 10.1101/gr.230433.117] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2017] [Accepted: 02/06/2018] [Indexed: 02/02/2023]
Abstract
Mammalian X and Y Chromosomes evolved from an ordinary autosomal pair. Genetic decay of the Y led to X Chromosome inactivation (XCI) in females, but some Y-linked genes were retained during the course of sex chromosome evolution, and many X-linked genes did not become subject to XCI. We reconstructed gene-by-gene dosage sensitivities on the ancestral autosomes through phylogenetic analysis of microRNA (miRNA) target sites and compared these preexisting characteristics to the current status of Y-linked and X-linked genes in mammals. Preexisting heterogeneities in dosage sensitivity, manifesting as differences in the extent of miRNA-mediated repression, predicted either the retention of a Y homolog or the acquisition of XCI following Y gene decay. Analogous heterogeneities among avian Z-linked genes predicted either the retention of a W homolog or gene-specific dosage compensation following W gene decay. Genome-wide analyses of human copy number variation indicate that these heterogeneities consisted of sensitivity to both increases and decreases in dosage. We propose a model of XY/ZW evolution incorporating such preexisting dosage sensitivities in determining the evolutionary fates of individual genes. Our findings thus provide a more complete view of the role of dosage sensitivity in shaping the mammalian and avian sex chromosomes and reveal an important role for post-transcriptional regulatory sequences (miRNA target sites) in sex chromosome evolution.
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Affiliation(s)
- Sahin Naqvi
- Whitehead Institute, Cambridge, Massachusetts 02142, USA.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | | | - Kathy S Lin
- Whitehead Institute, Cambridge, Massachusetts 02142, USA.,Program in Computational and Systems Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - David C Page
- Whitehead Institute, Cambridge, Massachusetts 02142, USA.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,Howard Hughes Medical Institute, Whitehead Institute, Cambridge, Massachusetts 02142, USA
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11
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Carmell MA, Dokshin GA, Skaletsky H, Hu YC, van Wolfswinkel JC, Igarashi KJ, Bellott DW, Nefedov M, Reddien PW, Enders GC, Uversky VN, Mello CC, Page DC. A widely employed germ cell marker is an ancient disordered protein with reproductive functions in diverse eukaryotes. eLife 2016; 5. [PMID: 27718356 PMCID: PMC5098910 DOI: 10.7554/elife.19993] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 10/05/2016] [Indexed: 12/17/2022] Open
Abstract
The advent of sexual reproduction and the evolution of a dedicated germline in multicellular organisms are critical landmarks in eukaryotic evolution. We report an ancient family of GCNA (germ cell nuclear antigen) proteins that arose in the earliest eukaryotes, and feature a rapidly evolving intrinsically disordered region (IDR). Phylogenetic analysis reveals that GCNA proteins emerged before the major eukaryotic lineages diverged; GCNA predates the origin of a dedicated germline by a billion years. Gcna gene expression is enriched in reproductive cells across eukarya - either just prior to or during meiosis in single-celled eukaryotes, and in stem cells and germ cells of diverse multicellular animals. Studies of Gcna-mutant C. elegans and mice indicate that GCNA has functioned in reproduction for at least 600 million years. Homology to IDR-containing proteins implicated in DNA damage repair suggests that GCNA proteins may protect the genomic integrity of cells carrying a heritable genome.
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Affiliation(s)
| | - Gregoriy A Dokshin
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, United States
| | - Helen Skaletsky
- Whitehead Institute, Cambridge, United States.,Howard Hughes Medical Institute, Chevy Chase, United States
| | | | | | | | | | - Michael Nefedov
- BACPAC Resources, Children's Hospital Oakland, Oakland, United States
| | - Peter W Reddien
- Whitehead Institute, Cambridge, United States.,Howard Hughes Medical Institute, Chevy Chase, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
| | - George C Enders
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, United States
| | - Vladimir N Uversky
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, United States
| | - Craig C Mello
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, United States.,Howard Hughes Medical Institute, Chevy Chase, United States
| | - David C Page
- Whitehead Institute, Cambridge, United States.,Howard Hughes Medical Institute, Chevy Chase, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, United States
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12
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Bellott DW, Hughes JF, Skaletsky H, Brown LG, Pyntikova T, Cho TJ, Koutseva N, Zaghlul S, Graves T, Rock S, Kremitzki C, Fulton RS, Dugan S, Ding Y, Morton D, Khan Z, Lewis L, Buhay C, Wang Q, Watt J, Holder M, Lee S, Nazareth L, Alföldi J, Rozen S, Muzny DM, Warren WC, Gibbs RA, Wilson RK, Page DC. Erratum: Corrigendum: Mammalian Y chromosomes retain widely expressed dosage-sensitive regulators. Nature 2014. [DOI: 10.1038/nature13719] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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13
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Bellott DW, Hughes JF, Skaletsky H, Brown LG, Pyntikova T, Cho TJ, Koutseva N, Zaghlul S, Graves T, Rock S, Kremitzki C, Fulton RS, Dugan S, Ding Y, Morton D, Khan Z, Lewis L, Buhay C, Wang Q, Watt J, Holder M, Lee S, Nazareth L, Alföldi J, Rozen S, Muzny DM, Warren WC, Gibbs RA, Wilson RK, Page DC. Mammalian Y chromosomes retain widely expressed dosage-sensitive regulators. Nature 2014; 508:494-9. [PMID: 24759411 PMCID: PMC4139287 DOI: 10.1038/nature13206] [Citation(s) in RCA: 432] [Impact Index Per Article: 43.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Accepted: 03/06/2014] [Indexed: 12/31/2022]
Abstract
The human X and Y chromosomes evolved from an ordinary pair of autosomes, but
millions of years ago genetic decay ravaged the Y chromosome, and only three percent of
its ancestral genes survived. We reconstructed the evolution of the Y chromosome across
eight mammals to identify biases in gene content and the selective pressures that
preserved the surviving ancestral genes. Our findings indicate that survival was
non-random, and in two cases, convergent across placental and marsupial mammals. We
conclude that the Y chromosome's gene content became specialized through selection
to maintain the ancestral dosage of homologous X-Y gene pairs that function as broadly
expressed regulators of transcription, translation and protein stability. We propose that
beyond its roles in testis determination and spermatogenesis, the Y chromosome is
essential for male viability, and plays unappreciated roles in Turner syndrome and in
phenotypic differences between the sexes in health and disease.
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Affiliation(s)
- Daniel W Bellott
- Whitehead Institute, Howard Hughes Medical Institute, & Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Jennifer F Hughes
- Whitehead Institute, Howard Hughes Medical Institute, & Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Helen Skaletsky
- Whitehead Institute, Howard Hughes Medical Institute, & Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Laura G Brown
- Whitehead Institute, Howard Hughes Medical Institute, & Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Tatyana Pyntikova
- Whitehead Institute, Howard Hughes Medical Institute, & Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Ting-Jan Cho
- Whitehead Institute, Howard Hughes Medical Institute, & Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Natalia Koutseva
- Whitehead Institute, Howard Hughes Medical Institute, & Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Sara Zaghlul
- Whitehead Institute, Howard Hughes Medical Institute, & Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Tina Graves
- The Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Susie Rock
- The Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Colin Kremitzki
- The Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Robert S Fulton
- The Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Shannon Dugan
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Yan Ding
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Donna Morton
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Ziad Khan
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Lora Lewis
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Christian Buhay
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Qiaoyan Wang
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Jennifer Watt
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Michael Holder
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Sandy Lee
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Lynne Nazareth
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Jessica Alföldi
- Whitehead Institute, Howard Hughes Medical Institute, & Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Steve Rozen
- Whitehead Institute, Howard Hughes Medical Institute, & Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
| | - Donna M Muzny
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Wesley C Warren
- The Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - Richard A Gibbs
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Richard K Wilson
- The Genome Institute, Washington University School of Medicine, St. Louis, Missouri 63108, USA
| | - David C Page
- Whitehead Institute, Howard Hughes Medical Institute, & Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142, USA
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14
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Chen N, Bellott DW, Page DC, Clark AG. Identification of avian W-linked contigs by short-read sequencing. BMC Genomics 2012; 13:183. [PMID: 22583744 PMCID: PMC3428670 DOI: 10.1186/1471-2164-13-183] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Accepted: 04/25/2012] [Indexed: 11/16/2022] Open
Abstract
Background The female-specific W chromosomes and male-specific Y chromosomes have proven difficult to assemble with whole-genome shotgun methods, creating a demand for new approaches to identify sequence contigs specific to these sex chromosomes. Here, we develop and apply a novel method for identifying sequences that are W-specific. Results Using the Illumina Genome Analyzer, we generated sequence reads from a male domestic chicken (ZZ) and mapped them to the existing female (ZW) genome sequence. This method allowed us to identify segments of the female genome that are underrepresented in the male genome and are therefore likely to be female specific. We developed a Bayesian classifier to automate the calling of W-linked contigs and successfully identified more than 60 novel W-specific sequences. Conclusions Our classifier can be applied to improve heterogametic whole-genome shotgun assemblies of the W or Y chromosome of any organism. This study greatly improves our knowledge of the W chromosome and will enhance future studies of avian sex determination and sex chromosome evolution.
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Affiliation(s)
- Nancy Chen
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, New York, USA.
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15
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Page DC, Hughes JF, Bellott DW, Mueller JL, Gill ME, Larracuente A, Graves T, Muzny D, Warren WC, Gibbs RA, Wilson RK, Skaletsky H. Reconstructing sex chromosome evolution. Genome Biol 2010. [PMCID: PMC3026214 DOI: 10.1186/gb-2010-11-s1-i21] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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16
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Bellott DW, Skaletsky H, Pyntikova T, Mardis ER, Graves T, Kremitzki C, Brown LG, Rozen S, Warren WC, Wilson RK, Page DC. Convergent evolution of chicken Z and human X chromosomes by expansion and gene acquisition. Nature 2010; 466:612-6. [PMID: 20622855 PMCID: PMC2943333 DOI: 10.1038/nature09172] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Accepted: 05/13/2010] [Indexed: 11/09/2022]
Abstract
In birds, as in mammals, one pair of chromosomes differs between the sexes. In birds, males are ZZ and females ZW. In mammals, males are XY and females XX. Like the mammalian XY pair, the avian ZW pair is believed to have evolved from autosomes, with most change occurring in the chromosomes found in only one sex--the W and Y chromosomes. By contrast, the sex chromosomes found in both sexes--the Z and X chromosomes--are assumed to have diverged little from their autosomal progenitors. Here we report findings that challenge this assumption for both the chicken Z chromosome and the human X chromosome. The chicken Z chromosome, which we sequenced essentially to completion, is less gene-dense than chicken autosomes but contains a massive tandem array containing hundreds of duplicated genes expressed in testes. A comprehensive comparison of the chicken Z chromosome with the finished sequence of the human X chromosome demonstrates that each evolved independently from different portions of the ancestral genome. Despite this independence, the chicken Z and human X chromosomes share features that distinguish them from autosomes: the acquisition and amplification of testis-expressed genes, and a low gene density resulting from an expansion of intergenic regions. These features were not present on the autosomes from which the Z and X chromosomes originated but were instead acquired during the evolution of Z and X as sex chromosomes. We conclude that the avian Z and mammalian X chromosomes followed convergent evolutionary trajectories, despite their evolving with opposite (female versus male) systems of heterogamety. More broadly, in birds and mammals, sex chromosome evolution involved not only gene loss in sex-specific chromosomes, but also marked expansion and gene acquisition in sex chromosomes common to males and females.
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Affiliation(s)
- Daniel W Bellott
- Department of Biology, Massachusetts Institute of Technology, 9 Cambridge Center, Cambridge, Massachusetts 02142, USA
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17
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Abstract
Sex chromosomes and their evolution have captivated researchers since their discovery. For more than 100 years, the dominant model of sex chromosome evolution has held that differentiated sex chromosomes, such as the X and Y chromosomes of mammals or the Z and W chromosomes of birds, evolved from ordinary autosomes, primarily through the degeneration of the sex-specific Y or W chromosome. At the same time, the sex chromosomes shared between sexes, the X and Z chromosomes, are expected to remain essentially untouched. This model was based on limited cytogenetic and genetic data. Only in the last decade, with the advent of genomics, has the complete sequence of any sex chromosome pair become available. High-quality finished sequences of the human and chimpanzee Y chromosomes, as well as the human X chromosome, have revealed sequence features unanticipated by the traditional model of sex chromosome evolution. Large, highly identical, tandem and inverted arrays of testis-expressed genes are major sources of innovation in gene content on sex-specific chromosomes as well as sex-shared chromosomes. Accounting for the emergence of these ampliconic structures presents a challenge for future studies of sex chromosome evolution.
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Affiliation(s)
- D W Bellott
- Howard Hughes Medical Institute, Whitehead Institute, and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02142, USA
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