Dosage compensation for the birds

Birchler, James A.

doi:10.1038/hdy.2008.134

Cited by 7 publications

(7 citation statements)

References 12 publications

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“…Dosage compensation in tongue sole has already proceeded to the level of complexity seen in birds but differs from mammals in terms of the mechanism by which the mammalian X chromosome is compensated. The question as to whether dosage compensation in birds represents a primordial form that is common to other types of sex chromosome has not been answered because avian sex chromosomes are not at an early stage of evolution 50 . Our finding of the same compensation mechanisms for the relatively young sex chromosomes of tongue sole provides support for this hypothesis.…”

Section: Discussionmentioning

confidence: 99%

Whole-genome sequence of a flatfish provides insights into ZW sex chromosome evolution and adaptation to a benthic lifestyle

et al. 2014

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The existence of males and females, which are often strikingly different in morphology, reproductive strategies and behavior, is one of the most widespread phenomena in biology. However, the genetic mechanisms that generate this ubiquitous pattern are surprisingly diverse and do not follow a phylogenetic pattern. Sex-determination mechanisms can differ between even closely related species and arise frequently and independently. Fish provide a paradigmatic example, as their sex-determination mechanisms range from environmental to different modes of genetic determination. The evolutionary meaning of this remarkable plasticity is unknown. For genetic sex determination, where the trigger for female or male development comes from the genetic constitution of the individual, the evolution of sex-determination mechanisms is connected to a very peculiar genomic process, namely the formation of sex chromosomes [1][2][3][4] .To improve understanding of the function and evolution of sex chromosomes, their genetic organization must be deciphered.However, owing to their degenerate nature and high repetitive DNA content, sex chromosomes pose almost insurmountable problems in deciphering their gene content and organization. So far, only the human 5 , chimpanzee 6 and rhesus macaque Y chromosomes 7 and the male-specific region on the Y chromosome of one fish, the medaka 8 , have been sequenced. These analyses have nevertheless provided important insights into the evolution of Y chromosomes, their genomic organization and their degeneration processes, as well as predictions as to their likely evolutionary fate 9-12 .Much less genomic information exists on W chromosomes because, as with Y chromosomes, they are predominantly highly repetitive in nature. The prevailing theory of the evolution of sex chromosomes predicts that degeneration of the heterogametic sex chromosome is a stepwise process that occurs over an extended period of time. We therefore reasoned that an evolutionarily young W chromosome Whole-genome sequence of a flatfish provides insights into ZW sex chromosome evolution and adaptation to a benthic lifestyle Genetic sex determination by W and Z chromosomes has developed independently in different groups of organisms. To better understand the evolution of sex chromosomes and the plasticity of sex-determination mechanisms, we sequenced the whole genomes of a male (ZZ) and a female (ZW) half-smooth tongue sole (Cynoglossus semilaevis). In addition to insights into adaptation to a benthic lifestyle, we find that the sex chromosomes of these fish are derived from the same ancestral vertebrate protochromosome as the avian W and Z chromosomes. Notably, the same gene on the Z chromosome, dmrt1, which is the male-determining gene in birds, showed convergent evolution of features that are compatible with a similar function in tongue sole. Comparison of the relatively young tongue sole sex chromosomes with those of mammals and birds identified events that occurred during the early phase of sex-chromosome evolution. Pertinent to...

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Section: Discussionmentioning

confidence: 99%

Whole-genome sequence of a flatfish provides insights into ZW sex chromosome evolution and adaptation to a benthic lifestyle

et al. 2014

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“…Animals adapt different dosage compensation mechanisms to balance the expression of sex chromosome genes between the two sexes and to balance the expression between sex chromosomal genes and autosomal genes [26,60]. In avian species, females are heterogametic with one Z and one W chromosome, and males are homogametic with two Z chromosomes.…”

Section: Discussionmentioning

confidence: 99%

Genome-wide annotation and analysis of zebra finch microRNA repertoire reveal sex-biased expression

et al. 2012

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BackgroundMicroRNAs (miRNAs) are small noncoding RNAs that regulate gene expression post-transcriptionally in a wide range of biological processes. The zebra finch (Taeniopygia guttata), an oscine songbird with characteristic learned vocal behavior, provides biologists a unique model system for studying vocal behavior, sexually dimorphic brain development and functions, and comparative genomics.ResultsWe deep sequenced small RNA libraries made from the brain, heart, liver, and muscle tissues of adult male and female zebra finches. By mapping the sequence reads to the zebra finch genome and to known miRNAs in miRBase, we annotated a total of 193 miRNAs. Among them, 29 (15%) are avian specific, including three novel zebra finch specific miRNAs. Many of the miRNAs exhibit sequence heterogeneity including length variations, untemplated terminal nucleotide additions, and internal substitution events occurring at the uridine nucleotide within a GGU motif. We also identified seven Z chromosome-encoded miRNAs. Among them, miR-2954, an avian specific miRNA, is expressed at significantly higher levels in males than in females in all tissues examined. Target prediction analysis reveals that miR-2954, but not other Z-linked miRNAs, preferentially targets Z chromosome-encoded genes, including several genes known to be expressed in a sexually dimorphic manner in the zebra finch brain.ConclusionsOur genome-wide systematic analysis of mature sequences, genomic locations, evolutionary sequence conservation, and tissue expression profiles of the zebra finch miRNA repertoire provides a valuable resource to the research community. Our analysis also reveals a miRNA-mediated mechanism that potentially regulates sex-biased gene expression in avian species.

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“…The proposal that the aggregation mechanism for self/not‐self discrimination initially evolved at the unicellular level and was subsequently adapted by multicellular organisms implies a fundamental process that should apply universally whenever an aneuploid threat to dosage balance arises 2 , 46 . Yet, sex chromosome dosage compensation in birds has long been in doubt 47 , 48 .…”

Section: Gene‐by‐gene Compensationmentioning

confidence: 99%

X chromosome reactivation perturbs intracellular self/not‐self discrimination

Forsdyke

2009

Immunol Cell Biol

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New reports indicate a chromosomal rather than hormonal basis for the susceptibility of females to autoimmune disease. It is held that if females reactivate an inactivated X chromosome, there will be overexpression of certain X-located genes affecting immune function. Hence, normal mechanisms of self/not-self discrimination might be impaired resulting in immune reaction to self antigens. However, the data are also consistent with the long-held view that the demands of intracellular self/not-self discrimination have driven the evolution of X-chromosome dosage compensation. It was proposed that, whether cells are in male or female bodies, concentrations of proteins are fine-tuned up to their aggregation thresholds. A disruption of this equilibrium, by agents originating either externally (for example, virus) or internally (for example, reactivated X chromosome), generates homoaggregates that trigger responses against the respective not-self or self antigens. Thus, female susceptibility to autoimmune disease may not be because certain immune system genes happen to be X-located, but because self/not-self discrimination was the raison d'eˆtre for X-chromosome dosage compensation in the first place.

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Dosage compensation for the birds

Cited by 7 publications

References 12 publications

Whole-genome sequence of a flatfish provides insights into ZW sex chromosome evolution and adaptation to a benthic lifestyle

Whole-genome sequence of a flatfish provides insights into ZW sex chromosome evolution and adaptation to a benthic lifestyle

Genome-wide annotation and analysis of zebra finch microRNA repertoire reveal sex-biased expression

X chromosome reactivation perturbs intracellular self/not‐self discrimination

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