Dosage compensation

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

Evolution of sexual systems, sex chromosomes and sex-linked gene transcription in flatworms and roundworms

Abstract: Many species with separate male and female individuals (termed 'gonochorism' in animals) have sex-linked genome regions. Here, we investigate evolutionary changes when genome regions become completely sex-linked, by analyses of multiple species of flatworms (Platyhelminthes; among which schistosomes recently evolved gonochorism from ancestral hermaphroditism), and roundworms (Nematoda) which have undergone independent translocations of different autosomes. Although neither the evolution of gonochorism nor translocations fusing ancestrally autosomal regions to sex chromosomes causes inevitable loss of recombination, we document that formerly recombining regions show genomic signatures of recombination suppression in both taxa, and become strongly genetically degenerated, with a loss of most genes. Comparisons with hermaphroditic flatworm transcriptomes show masculinisation and some defeminisation in schistosome gonad gene expression. We also find evidence that evolution of sex-linkage in nematodes is accompanied by transcriptional changes and dosage compensation. Our analyses also identify sex-linked genes that could assist future research aimed at controlling some of these important parasites.

Identification and phylogeny of five male‐specific lethal genes in the silkworm Bombyx mori

Abstract: In the fruit fly (Drosophila melanogaster) dosage compensation equalization of X-linked genes between the sexes is achieved via a complex that is termed the compensasome, which is composed of at least five male-specific lethal (msl) genes and two non-coding RNAs. In the present study, we cloned all five homologs (termed the msls) from the silkworm, Bombyx mori, in which the issue of dosage compensation remains controversial. Data mining and robust phylogenetic analysis revealed that msls are ubiquitously present in genomes, from insects to mammals, with unknown biological functions. However, the five genes seem to have evolved at different times due to gene duplication. Real-time reverse transcriptase-polymerase chain reaction experiments demonstrated that in the silkworm, some Z-linked genes are expressed at higher levels in females than in males while others are expressed at lower levels in females than in males, which suggests that the msl genes in the silkworm and fruit fly may have different roles. We discussed the relationship of phylogeny between msl and sex-lethal.

Chd8 regulates X chromosome inactivation in mouse through fine-tuning control of Xist expression.

Abstract: Female mammals achieve dosage compensation by inactivating one of their two X chromosomes during development, a process entirely dependent on Xist, an X-linked long non-coding RNA (lncRNA). At the onset of X chromosome inactivation (XCI), Xist is up-regulated and spreads along the future inactive X chromosome. Contextually, it recruits repressive histone and DNA modifiers that transcriptionally silence the X chromosome. Xist regulation is tightly coupled to differentiation and its expression is under the control of both pluripotency and epigenetic factors. Recent evidence has suggested that chromatin remodelers accumulate at the X Inactivation Center (XIC) and here we demonstrate a new role for Chd8 in Xist regulation in differentiating ES cells, linked to its control and prevention of spurious transcription factor interactions occurring within Xist regulatory regions. Our findings have a broader relevance, in the context of complex, developmentally-regulated gene expression.

A De Novo Genome Assembly, Gene Annotation, And Expression Atlas For The Monarch Butterfly Danaus plexippus

Abstract: The monarch butterfly epitomizes insect biodiversity decline. Understanding the genetic basis of the adaptation of the monarch to a changing environment requires genomic and transcriptomic resources that better reflect its genetic diversity while being informative about gene functionality during life cycle. We report a reference-quality genome assembly from an individual resident at a nonmigratory colony in Mexico, and a new gene annotation and expression atlas for 14,865 genes, including 492 unreported long noncoding RNA (lncRNA) genes, based on RNA-seq data from 14 larval and pupal stages, plus adult morphological sections. Two thirds of the genes show significant expression changes associated with a life stage or section, with lncRNAs being more finely regulated during adulthood than protein-coding genes, and male-biased expression being four times more common than female-biased. The two portions of the heterochromosome Z display distinct patterns of differential expression between the sexes, reflecting that dosage compensation is either absent or incomplete –depending on the sample– in the ancestral but not in the novel portion of the Z. This study represents a major advance in the genomic and transcriptome resources available for D. plexippus while providing the first systematic analysis of its transcriptional program across most of its life cycle.

Le modèle de l’inactivation du chromosome X chez la souris

Abstract: X chromosome inactivation (XCI) is an excellent model for studying how epigenetic marks are initiated during early embryogenesis. XCI is an essential process that takes place in females, leading to dosage compensation between males and females. In mouse, it occurs in two waves: the first one is paternally imprinted, during the preimplantation period and the second one occurs in a random fashion. We provide here an update of the main molecular steps and hypothesis underlining this complex process.