Project description:The difference in X chromosome copy number creates a potential difference in X chromosomal gene expression between males and females. In many animals, dosage compensation mechanisms equalize X chromosome expression between sexes. Yet, X chromosome is also enriched for sex-biased genes due to differences in the evolutionary history of the X and autosomes. The manner in which dosage compensation and sex-biased gene expression exist on the X chromosome remains an open question. Most studies compare gene expression between two sexes, which combines expression differences due to X chromosome number (dose) and sex. Here, we uncoupled the effects of sex and X dose in C. elegans and determined how each process affects expression of the X chromosome compared to autosomes. We found that in the soma, sex-biased expression on the X chromosome is almost entirely due to sex because the dosage compensation complex (DCC) effectively compensates for the X dose difference between sexes. In the germline where the DCC is not present, X chromosome copy number contributes to hermaphrodite-biased gene expression. These results suggest that X dose contributes to sex-biased gene expression based on the level of dosage compensation in different tissues and developmental stages.
Project description:The difference in X chromosome copy number creates a potential difference in X chromosomal gene expression between males and females. In many animals, dosage compensation mechanisms equalize X chromosome expression between sexes. Yet, X chromosome is also enriched for sex-biased genes due to differences in the evolutionary history of the X and autosomes. The manner in which dosage compensation and sex-biased gene expression exist on the X chromosome remains an open question. Most studies compare gene expression between two sexes, which combines expression differences due to X chromosome number (dose) and sex. Here, we uncoupled the effects of sex and X dose in C. elegans and determined how each process affects expression of the X chromosome compared to autosomes. We found that in the soma, sex-biased expression on the X chromosome is almost entirely due to sex because the dosage compensation complex (DCC) effectively compensates for the X dose difference between sexes. In the germline where the DCC is not present, X chromosome copy number contributes to hermaphrodite-biased gene expression. These results suggest that X dose contributes to sex-biased gene expression based on the level of dosage compensation in different tissues and developmental stages. RNA-Seq profiles of C. elegans XO hermaphrodite and XX male L3 larvae and adults
Project description:Uncoupling X chromosome number from sex determination separates contribution of sex and X dose to sex-biased gene expression in C. elegans
Project description:Gene dosage imbalance of heteromorphic sex chromosomes (XY or ZW) exists between the sexes, and with the autosomes. Mammalian X chromosome inactivation was long thought to imply a critical need for dosage compensation in vertebrates. However, mRNA abundance measurements that demonstrated sex chromosome transcripts are neither balanced between the sexes or with autosomes in monotreme mammals or birds brought sex chromosome dosage compensation into question. This study examines transcriptomic and proteomic levels of dosage compensation in platypus and chicken compared to mouse, a model eutherian species. We analyzed mRNA and protein levels in heart and liver tissues of chicken, mouse and platypus.
Project description:Among organisms with chromosome-based mechanisms of sex determination, failure to equalize expression of X-linked genes between the sexes is typically lethal. In C. elegans, XX hermaphrodites halve transcription from each X chromosome to match the output of XO males1. Here, we mapped the binding location of the condensin homolog DPY-27 and the zinc finger protein SDC-3, two components of the C. elegans dosage compensation complex (DCC)2,3. Strong foci of DCC binding were observed on X, around which broader regions of localization were centered. Binding foci, but not adjacent regions of localization, were distinguished by clusters of a stereotypic 10-bp DNA sequence, suggesting a recruitment-and-spreading mechanism for X recognition. In contrast to the Drosophila DCC, the C. elegans DCC was bound preferentially upstream of genes, suggesting modulation of transcriptional initiation and transcription-coupled spreading. A mechanism for tuning DCC activity at specific loci was indicated by stronger DCC binding upstream of genes with high transcriptional activity. These data provide a basis for understanding how proteins involved in higher-order chromosome dynamics can regulate transcription at individual loci. For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf Keywords: ChIP-chip dosage compensation complex