scholarly journals Conserved microRNA targeting reveals preexisting gene dosage sensitivities that shaped amniote sex chromosome evolution

2017 ◽  
Author(s):  
Sahin Naqvi ◽  
Daniel W. Bellott ◽  
Kathy S. Lin ◽  
David C. Page
Keyword(s):  
Mirna Target ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Gene Dosage ◽  
Current Status ◽  
Regulatory Sequences ◽  
Sex Chromosome Evolution ◽  
Target Sites ◽  
Gene Decay ◽  
Dosage Sensitivity

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.

scholarly journals Preexisting heterogeneities in gene dosage sensitivity shaped sex chromosome evolution in mammals and birds

2017 ◽  
Author(s):  
Sahin Naqvi ◽  
Daniel W. Bellott ◽  
David C. Page
Keyword(s):  
Experimental Data ◽  
Sex Chromosomes ◽  
Mirna Target ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Gene Dosage ◽  
Sex Chromosome Evolution ◽  
Y Chromosomes ◽  
Target Sites ◽  
Autosomal Pair

Mammalian X and Y chromosomes evolved from an ordinary autosomal pair; genetic decay decimated the Y, which in turn necessitated X chromosome inactivation (XCI). Genes of the ancestral autosomes are often assumed to have undertaken these transitions on uniform terms, but we hypothesized that they varied in their dosage constraints. We inferred such constraints from conservation of microRNA (miRNA)-mediated repression, validated by analysis of experimental data. X-linked genes with a surviving Y homolog have the most conserved miRNA target sites, followed by genes with no Y homolog and subject to XCI, and then genes with no Y homolog but escaping XCI; this heterogeneity existed on the ancestral autosomes. Similar results for avian Z-linked genes, with or without a W homolog, lead to a model of XY/ZW evolution incorporating preexisting dosage sensitivities of individual genes in determining their evolutionary fates, and ultimately shaping the mammalian and avian sex chromosomes.

scholarly journals Conserved microRNA targeting reveals preexisting gene dosage sensitivities that shaped amniote sex chromosome evolution

2018 ◽  
Vol 28 (4) ◽  
pp. 474-483 ◽  
Author(s):  
Sahin Naqvi ◽  
Daniel W. Bellott ◽  
Kathy S. Lin ◽  
David C. Page
Keyword(s):  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Gene Dosage ◽  
Sex Chromosome Evolution

scholarly journals Polyploidy in Amphibia

2015 ◽  
Vol 145 (3-4) ◽  
pp. 315-330 ◽  
Author(s):  
Michael Schmid ◽  
Ben J. Evans ◽  
James P. Bogart
Keyword(s):  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Current Status ◽  
Meiotic Pairing ◽  
Sex Chromosome Evolution ◽  
The Relationship

This review summarizes the current status of the known extant genuine polyploid anuran and urodelan species, as well as spontaneously originated and/or experimentally produced amphibian polyploids. The mechanisms by which polyploids can originate, the meiotic pairing configurations, the diploidization processes operating in polyploid genomes, the phenomenon of hybridogenesis, and the relationship between polyploidization and sex chromosome evolution are discussed. The polyploid systems in some important amphibian taxa are described in more detail.

scholarly journals Free-living human cells reconfigure their chromosomes in the evolution back to uni-cellularity

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Jin Xu ◽  
Xinxin Peng ◽  
Yuxin Chen ◽  
Yuezheng Zhang ◽  
Qin Ma ◽  
...  
Keyword(s):  
Cell Culture ◽  
Frequency Distribution ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Gene Dosage ◽  
Chromosomal Evolution ◽  
Sex Chromosome Evolution ◽  
Free Living ◽  
Male And Female

Cells of multi-cellular organisms evolve toward uni-cellularity in the form of cancer and, if humans intervene, continue to evolve in cell culture. During this process, gene dosage relationships may evolve in novel ways to cope with the new environment and may regress back to the ancestral uni-cellular state. In this context, the evolution of sex chromosomes vis-a-vis autosomes is of particular interest. Here, we report the chromosomal evolution in ~ 600 cancer cell lines. Many of them jettisoned either Y or the inactive X; thus, free-living male and female cells converge by becoming ‘de-sexualized’. Surprisingly, the active X often doubled, accompanied by the addition of one haploid complement of autosomes, leading to an X:A ratio of 2:3 from the extant ratio of 1:2. Theoretical modeling of the frequency distribution of X:A karyotypes suggests that the 2:3 ratio confers a higher fitness and may reflect aspects of sex chromosome evolution.

scholarly journals Free-living human cells reconfigure their chromosomes in the evolution back to uni-cellularity

2017 ◽  
Author(s):  
Jin Xu ◽  
Xinxin Peng ◽  
Yuxin Chen ◽  
Yuezheng Zhang ◽  
Qin Ma ◽  
...  
Keyword(s):  
Cell Culture ◽  
Frequency Distribution ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Gene Dosage ◽  
Chromosomal Evolution ◽  
Sex Chromosome Evolution ◽  
Free Living ◽  
Male And Female

AbstractCells of multi-cellular organisms evolve toward uni-cellularity in the form of cancer and, if humans intervene, continue to evolve in cell culture. During this process, gene dosage relationships may evolve in novel ways to cope with the new environment and may regress back to the ancestral unicellular state. In this context, the evolution of sex chromosomes vis-a-vis autosomes is of particular interest. Here, we report the chromosomal evolution in ~600 cancer cell lines. Many of them jettisoned either Y or the inactive X; thus, free-living male and female cells converge by becoming “de-sexualized”. Surprisingly, the active X often doubled, accompanied by the addition of one haploid complement of autosomes, leading to an X:A ratio of 2:3 from the extant ratio of 1:2. Theoretical modeling of the frequency distribution of X:A karyotypes suggests that the 2:3 ratio confers a higher fitness and may reflect aspects of sex chromosome evolution.

scholarly journals Sex and the flower – developmental aspects of sex chromosome evolution

2018 ◽  
Vol 122 (7) ◽  
pp. 1085-1101 ◽  
Author(s):  
Roman Hobza ◽  
Vojtech Hudzieczek ◽  
Zdenek Kubat ◽  
Radim Cegan ◽  
Boris Vyskot ◽  
...  
Keyword(s):  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Chromosome Evolution
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