Replication asynchrony and differential condensation of X chromosomes in female platypus (Ornithorhynchus anatinus)

Kristen Ho, Janine Deakin, Megan Wright, Jennifer Marshall Graves, Frank Grutzner

Research output: Contribution to journalArticle

7 Citations (Scopus)

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 fiveY chromosomes in males. Gene xpression 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 synchronous replication of X-specific regions on X1, X3 and X5 but show significantly different condensation between homologues for X3 only, and not for X1 or X5. 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.
Original languageEnglish
Pages (from-to)952-963
Number of pages12
JournalReproduction, Fertility and Development
Volume21
DOIs
Publication statusPublished - 2009
Externally publishedYes

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Platypus
X Chromosome
X chromosome
Sex Chromosomes
Genes
genes
Birds
Mammals
DNA Replication Timing
dosage
Gene Expression
X-Linked Genes
mammals
DNA Replication
W chromosome
chromosomes
Chromatin
gene expression
gender
birds

Cite this

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title = "Replication asynchrony and differential condensation of X chromosomes in female platypus (Ornithorhynchus anatinus)",
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 fiveY chromosomes in males. Gene xpression 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 synchronous replication of X-specific regions on X1, X3 and X5 but show significantly different condensation between homologues for X3 only, and not for X1 or X5. 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.",
author = "Kristen Ho and Janine Deakin and Megan Wright and {Marshall Graves}, Jennifer and Frank Grutzner",
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Replication asynchrony and differential condensation of X chromosomes in female platypus (Ornithorhynchus anatinus). / Ho, Kristen; Deakin, Janine; Wright, Megan; Marshall Graves, Jennifer; Grutzner, Frank.

In: Reproduction, Fertility and Development, Vol. 21, 2009, p. 952-963.

Research output: Contribution to journalArticle

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AB - 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 fiveY chromosomes in males. Gene xpression 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 synchronous replication of X-specific regions on X1, X3 and X5 but show significantly different condensation between homologues for X3 only, and not for X1 or X5. 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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