Dosage compensation

About: Dosage compensation is a research topic. Over the lifetime, 1920 publications have been published within this topic receiving 124589 citations.

Little evidence for demasculinization of the Drosophila X chromosome among genes expressed in the male germline.

Abstract: Male-biased genes—those expressed at higher levels in males than in females—are underrepresented on the X chromosome of Drosophila melanogaster. Several evolutionary models have been posited to explain this so-called demasculinization of the X. Here, we show that the apparent paucity of male-biased genes on the X chromosome is attributable to global X-autosome differences in expression in Drosophila testes, owing to a lack of sex chromosome dosage compensation in the male germline, but not to any difference in the density of testis-specific or testis-biased genes on the X chromosome. First, using genome-wide gene expression data from 20 tissues, we find no evidence that genes with testis-specific expression are underrepresented on the X chromosome. Second, using contrasts in gene expression profiles among pairs of tissues, we recover a statistical underrepresentation of testis-biased genes on the X but find that the pattern largely disappears once we account for the lack of dosage compensation in the Drosophila male germline. Third, we find that computationally “demasculinizing” the autosomes is not sufficient to produce an expression profile similar to that of the X chromosome in the testes. Our findings thus show that the lack of sex chromosome dosage compensation in Drosophila testes can explain the apparent signal of demasculinization on the X, whereas evolutionary demasculinization of the X cannot explain its overall reduced expression in the testes.

The Evolution of Sex Chromosomes and Dosage Compensation in Plants.

Abstract: Plant sex chromosomes can be vastly different from those of the few historical animal model organisms from which most of our understanding of sex chromosome evolution is derived. Recently, we have seen several advancements from studies on green algae, brown algae, and land plants that are providing a broader understanding of the variable ways in which sex chromosomes can evolve in distant eukaryotic groups. Plant sex-determining genes are being identified and, as expected, are completely different from those in animals. Species with varying levels of differentiation between the X and Y have been found in plants, and these are hypothesized to be representing different stages of sex chromosome evolution. However, we are also finding that sex chromosomes can remain morphologically unchanged over extended periods of time. Where degeneration of the Y occurs, it appears to proceed similarly in plants and animals. Dosage compensation (a phenomenon that compensates for the consequent loss of expression from the Y) has now been documented in a plant system, its mechanism, however, remains unknown. Research has also begun on the role of sex chromosomes in sexual conflict resolution, and it appears that sex-biased genes evolve similarly in plants and animals, although the functions of these genes remain poorly studied. Because the difficulty in obtaining sex chromosome sequences is increasingly being overcome by methodological developments, there is great potential for further discovery within the field of plant sex chromosome evolution.

Drosophila Dosage Compensation Involves Enhanced Pol II Recruitment to Male X-Linked Promoters

Abstract: Through hyperacetylation of histone H4 lysine 16 (H4K16), the male-specific lethal (MSL) complex in Drosophila approximately doubles transcription from the single male X chromosome in order to match X-linked expression in females and expression from diploid autosomes. By obtaining accurate measurements of RNA polymerase II (Pol II) occupancies and short promoter-proximal RNA production, we detected a consistent, genome-scale increase in Pol II activity at the promoters of male X-linked genes. Moreover, we found that enhanced Pol II recruitment to male X-linked promoters is largely dependent on the MSL complex. These observations provide insights into how global modulation of chromatin structure by histone acetylation contributes to the precise control of Pol II function.