title: Chromosome-wide mechanisms to decouple gene expression from gene dose during sex-chromosome evolution.
abstract: Changes in chromosome number impair fitness by disrupting the balance of gene expression. Here we analyze mechanisms to compensate for changes in gene dose that accompanied the evolution of sex chromosomes from autosomes. Using single-copy transgenes integrated throughout theCaenorhabditis elegansgenome, we show that expression of all X-linked transgenes is balanced between XX hermaphrodites and XO males. However, proximity of a dosage compensation complex (DCC) binding site (rexsite) is neither necessary to repress X-linked transgenes nor sufficient to repress transgenes on autosomes. Thus, X is broadly permissive for dosage compensation, and the DCC acts via a chromosome-wide mechanism to balance transcription between sexes. In contrast, no analogous X-chromosome-wide mechanism balances transcription between X and autosomes: expression of compensated hermaphrodite X-linked transgenes is half that of autosomal transgenes. Furthermore, our results argue against an X-chromosome dosage compensation model contingent uponrex-directed positioning of X relative to the nuclear periphery.
authors: Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States.
authors: Bayly S
authors: BS
authors: Wheeler
authors: Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States.
authors: Erika
authors: E
authors: Anderson
authors: Department of Biology, Howard Hughes Medical Institute, University of Utah, Salt Lake City, United States.|Danish National Research Foundation Centre for Cardiac Arrhythmia, University of Copenhagen, Copenhagen, Denmark.
authors: Christian
authors: C
authors: Frøkjær-Jensen
authors: Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States.
authors: Qian
authors: Q
authors: Bian
authors: Department of Biology, Howard Hughes Medical Institute, University of Utah, Salt Lake City, United States.
authors: Erik
authors: E
authors: Jorgensen
authors: Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States.
authors: Barbara J
authors: 0000-0002-6530-4588
authors: BJ
authors: Meyer
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000235:genetics*; D005260:Female; D018628:Gene Dosage; D015870:Gene Expression; D020869:Gene Expression Profiling; D017930:Genes, Reporter; D008297:Male; D012730:Sex Chromosomes / Q000378:metabolism*
keywords: C. elegans; Ohno's Hypothesis; X-chromosome dosage compensation; X-chromosome evolution; aneuploidy; chromosomes; evolutionary biology; gene expression; genes; genomics