Extensive Gene Traffic on the Mammalian X Chromosome

  title={Extensive Gene Traffic on the Mammalian X Chromosome},
  author={J J Emerson and Henrik Kaessmann and Esther Betr{\'a}n and Manyuan Long},
  pages={537 - 540}
Mammalian sex chromosomes have undergone profound changes since evolving from ancestral autosomes. By examining retroposed genes in the human and mouse genomes, we demonstrate that, during evolution, the mammalian X chromosome has generated and recruited a disproportionately high number of functional retroposed genes, whereas the autosomes experienced lower gene turnover. Most autosomal copies originating from X-linked genes exhibited testis-biased expression. Such export is incompatible with… 
General gene movement off the X chromosome in the Drosophila genus.
Analysis of DNA-based and RNA-based gene relocations reveal that the out-of-the-X movement of testis-expressed genes is a general pattern in the Drosophila genus.
How the gene content of human sex chromosomes evolved.
Enhanced adaptive evolution of sperm-expressed genes on the mammalian X chromosome
It is suggested that hemizygous expression in males makes the X chromosome a preferred location for positively selected sperm genes that do not require postmeiotic transcription.
Evolution of gene function on the X chromosome versus the autosomes.
A synopsis of the current understanding of the origin of sex chromosomes, theoretical context for differences in rates and patterns of molecular evolution on the X chromosome versus the autosomes, as well as a summary of empirical molecular evolutionary data from Drosophila and mammalian genomes are presented.
A dynamic view of sex chromosome evolution.
  • D. Bachtrog
  • Biology
    Current opinion in genetics & development
  • 2006
Origins of new male germ-line functions from X-derived autosomal retrogenes in the mouse.
It is observed that positive selection is targeting these X-derived autosomal retrogenes with novel male-biased expression patterns, which suggests that such retrogens evolved new male germ-line functions that may be complementary to the functions of the parental paralogs, which themselves contribute little during spermatogenesis.
Sex, sex chromosomes and gene expression
The X chromosome has fewer testis-specific genes than autosomes in many species, and possible mechanisms underlying this bias, including sexual antagonism and dosage compensation are discussed.


Paucity of Genes on the Drosophila X Chromosome Showing Male-Biased Expression
Using comparative genomics, it is found that the X chromosome is a disfavored location for genes selectively expressed in males in Drosophila melanogaster and these same X-chromosome genes are exceptionally poorly conserved in the mosquito Anopheles gambiae.
The human Y chromosome, in the light of evolution
Far from being random and diverse, known human Y-chromosome genes show just a few distinct expression profiles, and their relative functional conformity reflects evolutionary factors inherent to sex-specific chromosomes.
Retroposed new genes out of the X in Drosophila.
The pattern of origin of the genes created by retroposition in Drosophila was investigated and it was found that most of these X-derived autosomal retrogenes had evolved a testis expression pattern.
Birth of Two Chimeric Genes in the Hominidae Lineage
Detailed structural, expression, and phylogenetic analysis showed that the PMCHL1 gene was created near 25 million years ago by a complex mechanism of exon shuffling through retrotransposition of an antisense MCH messenger RNA coupled to de novo creation of splice sites.
X inactivation in mammalian testis is correlated with inactive X–specific transcription
It is demonstrated here the existence of XIST transcripts in testes of man and mouse, and the silencing of X–linked genes is the price paid for the evolution of successful mechanisms of chromosomal sex determination.
Transposable elements and the evolution of genome organization in mammals
Four mechanisms are presented which may explain the nonrandom genomic distribution of mammalian transposons: i) sequence-specific insertion, ii) S-phase insertion, iii) ectopic excision, and iv) recombinational editing.
An abundance of X-linked genes expressed in spermatogonia
The findings indicate that the X chromosome has a predominant role in pre-meiotic stages of mammalian spermatogenesis, and hypothesize that theX chromosome acquired this prominent role in male germ-cell development as it evolved from an ordinary, unspecialized autosome.
The Relative Rates of Evolution of Sex Chromosomes and Autosomes
The frequently disproportionate effects of the sex chromosomes on interspecific inviability or sterility are consistent with the hypothesis that the gene differences concerned involve recessive or partially recessive alleles fixed by selection.
RNA-mediated gene duplication: the rat preproinsulin I gene is a functional retroposon.
DNA sequence comparisons of the gene-flanking regions in rats and mice indicated that the preproinsulin gene I has lost one of the two introns present in gene II, is flanked by a long (41-base) direct repeat, and has a remnant of a polydeoxyadenylate acid tract preceding the downstream direct repeat.