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 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 Sex chromosome evolution: historical insights and future perspectives

2017 ◽  
Vol 284 (1854) ◽  
pp. 20162806 ◽  
Author(s):  
Jessica K. Abbott ◽  
Anna K. Nordén ◽  
Bengt Hansson
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Empirical Studies ◽  
Analytical Models ◽  
Specific Gene ◽  
Sex Chromosome Evolution ◽  
Current Thinking

Many separate-sexed organisms have sex chromosomes controlling sex determination. Sex chromosomes often have reduced recombination, specialized (frequently sex-specific) gene content, dosage compensation and heteromorphic size. Research on sex determination and sex chromosome evolution has increased over the past decade and is today a very active field. However, some areas within the field have not received as much attention as others. We therefore believe that a historic overview of key findings and empirical discoveries will put current thinking into context and help us better understand where to go next. Here, we present a timeline of important conceptual and analytical models, as well as empirical studies that have advanced the field and changed our understanding of the evolution of sex chromosomes. Finally, we highlight gaps in our knowledge so far and propose some specific areas within the field that we recommend a greater focus on in the future, including the role of ecology in sex chromosome evolution and new multilocus models of sex chromosome divergence.

scholarly journals A bird’s white-eye view on avian sex chromosome evolution

2018 ◽  
Author(s):  
Thibault Leroy ◽  
Yoann Anselmetti ◽  
Marie-Ka Tilak ◽  
Sèverine Bérard ◽  
Laura Csukonyi ◽  
...  
Keyword(s):  
Molecular Evolution ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Chromosome Evolution ◽  
Weak Support ◽  
Unusual Event ◽  
Calibration Sets ◽  
Molecular Phylogenetic ◽  
Genomic Regions

ABSTRACTChromosomal organization is relatively stable among avian species, especially with regards to sex chromosomes. Members of the large Sylvioidea clade however have a pair of neo-sex chromosomes which is unique to this clade and originate from a parallel translocation of a region of the ancestral 4A chromosome on both W and Z chromosomes. Here, we took advantage of this unusual event to study the early stages of sex chromosome evolution. To do so, we sequenced a female (ZW) of two Sylvioidea species, a Zosterops borbonicus and a Z. pallidus. Then, we organized the Z. borbonicus scaffolds along chromosomes and annotated genes. Molecular phylogenetic dating under various methods and calibration sets confidently confirmed the recent diversification of the genus Zosterops (1-3.5 million years ago), thus representing one of the most exceptional rates of diversification among vertebrates. We then combined genomic coverage comparisons of five males and seven females, and homology with the zebra finch genome (Taeniopygia guttata) to identify sex chromosome scaffolds, as well as the candidate chromosome breakpoints for the two translocation events. We observed reduced levels of within-species diversity in both translocated regions and, as expected, even more so on the neoW chromosome. In order to compare the rates of molecular evolution in genomic regions of the autosomal-to-sex transitions, we then estimated the ratios of non-synonymous to synonymous polymorphisms (πN/πS) and substitutions (dN/dS). Based on both ratios, no or little contrast between autosomal and Z genes was observed, thus representing a very different outcome than the higher ratios observed at the neoW genes. In addition, we report significant changes in base composition content for translocated regions on the W and Z chromosomes and a large accumulation of transposable elements (TE) on the newly W region. Our results revealed contrasted signals of molecular evolution changes associated to these autosome-to-sex transitions, with congruent signals of a W chromosome degeneration yet a surprisingly weak support for a fast-Z effect.

scholarly journals Ecology and the Evolution of Sex Chromosomes

2021 ◽  
Author(s):  
Richard Meisel
Keyword(s):  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Ecological Factors ◽  
Sex Chromosome Evolution ◽  
Sexual Antagonism ◽  
Extrinsic Factors ◽  
Selection Pressures ◽  
Evolutionary Trajectories ◽  
Animal Genomes

This article reviews and discusses ecological factors that affect sex chromosome evolution. Sex chromosomes are common features of animal genomes, and are often the location where master sex determination genes are found. Many important aspects of sex chromosome evolution are thought to be driven by sex-specific selection pressures, such as sexual antagonism and sexual selection. Sex-specific selection affects both the formation of sex chromosomes from autosomes and differences in the evolutionary trajectories between sex chromosomes and autosomes. Most population genetic models are agnostic as to whether the sex-specific selection pressures arise from intrinsic features of organismal biology or extrinsic factors that depend on environment. Here, I review the evidence that extrinsic, or ecological, factors are important determinants of sex-specific selection pressures that shape sex chromosome evolution.

scholarly journals Sex chromosome evolution among amniotes: is the origin of sex chromosomes non-random?

2021 ◽  
Vol 376 (1833) ◽  
pp. 20200108 ◽  
Author(s):  
Lukáš Kratochvíl ◽  
Tony Gamble ◽  
Michail Rovatsos
Keyword(s):  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Current Knowledge ◽  
Current Data ◽  
Divergent Evolution ◽  
Random Pattern ◽  
Sex Chromosome Evolution ◽  
Great Opportunity

Sex chromosomes are a great example of a convergent evolution at the genomic level, having evolved dozens of times just within amniotes. An intriguing question is whether this repeated evolution was random, or whether some ancestral syntenic blocks have significantly higher chance to be co-opted for the role of sex chromosomes owing to their gene content related to gonad development. Here, we summarize current knowledge on the evolutionary history of sex determination and sex chromosomes in amniotes and evaluate the hypothesis of non-random emergence of sex chromosomes. The current data on the origin of sex chromosomes in amniotes suggest that their evolution is indeed non-random. However, this non-random pattern is not very strong, and many syntenic blocks representing putatively independently evolved sex chromosomes are unique. Still, repeatedly co-opted chromosomes are an excellent model system, as independent co-option of the same genomic region for the role of sex chromosome offers a great opportunity for testing evolutionary scenarios on the sex chromosome evolution under the explicit control for the genomic background and gene identity. Future studies should use these systems more to explore the convergent/divergent evolution of sex chromosomes. This article is part of the theme issue ‘Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part II)’.

scholarly journals Evolution of master sex determiners: TGF-β signalling pathways at regulatory crossroads

2021 ◽  
Vol 376 (1832) ◽  
pp. 20200091 ◽  
Author(s):  
Qiaowei Pan ◽  
Tomas Kay ◽  
Alexandra Depincé ◽  
Mateus Adolfi ◽  
Manfred Schartl ◽  
...  
Keyword(s):  
Transcription Factors ◽  
Sex Chromosomes ◽  
Regulatory Network ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Signalling Pathway ◽  
Signalling Pathways ◽  
Sex Chromosome Evolution ◽  
Theme Issue ◽  
Gene Regulatory

To date, more than 20 different vertebrate master sex-determining genes have been identified on different sex chromosomes of mammals, birds, frogs and fish. Interestingly, six of these genes are transcription factors ( Dmrt1 - or Sox3 - related) and 13 others belong to the TGF-β signalling pathway ( Amh , Amhr2 , Bmpr1b , Gsdf and Gdf6 ). This pattern suggests that only a limited group of factors/signalling pathways are prone to become top regulators again and again. Although being clearly a subordinate member of the sex-regulatory network in mammals, the TGF-β signalling pathway made it to the top recurrently and independently. Facing this rolling wave of TGF-β signalling pathways, this review will decipher how the TGF-β signalling pathways cope with the canonical sex gene regulatory network and challenge the current evolutionary concepts accounting for the diversity of sex-determining mechanisms. This article is part of the theme issue ‘Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part I)’.

scholarly journals DNA methylation is involved in sexual differentiation and sex chromosome evolution in the dioecious plant garden asparagus

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Shu-Fen Li ◽  
Can-Can Lv ◽  
Li-Na Lan ◽  
Kai-Lu Jiang ◽  
Yu-Lan Zhang ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Y Chromosome ◽  
Sexual Differentiation ◽  
Flower Development ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Chromosome Evolution ◽  
Male And Female ◽  
Garden Asparagus ◽  
Female Flowers

AbstractDNA methylation is a crucial regulatory mechanism in many biological processes. However, limited studies have dissected the contribution of DNA methylation to sexual differentiation in dioecious plants. In this study, we investigated the variances in methylation and transcriptional patterns of male and female flowers of garden asparagus. Compared with male flowers, female flowers at the same stages showed higher levels of DNA methylation. Both male and female flowers gained DNA methylation globally from the premeiotic to meiotic stages. Detailed analysis revealed that the increased DNA methylation was largely due to increased CHH methylation. Correlation analysis of differentially expressed genes and differentially methylated regions suggested that DNA methylation might not have contributed to the expression variation of the sex-determining genes SOFF and TDF1 but probably played important roles in sexual differentiation and flower development of garden asparagus. The upregulated genes AoMS1, AoLAP3, AoAMS, and AoLAP5 with varied methylated CHH regions might have been involved in sexual differentiation and flower development of garden asparagus. Plant hormone signaling genes and transcription factor genes also participated in sexual differentiation and flower development with potential epigenetic regulation. In addition, the CG and CHG methylation levels in the Y chromosome were notably higher than those in the X chromosome, implying that DNA methylation might have been involved in Y chromosome evolution. These data provide insights into the epigenetic modification of sexual differentiation and flower development and improve our understanding of sex chromosome evolution in garden asparagus.

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