title: Enhancer Turnover Is Associated with a Divergent Transcriptional Response to Glucocorticoid in Mouse and Human Macrophages.
abstract: Phenotypic differences between individuals and species are controlled in part through differences in expression of a relatively conserved set of genes. Genes expressed in the immune system are subject to especially powerful selection. We have investigated the evolution of both gene expression and candidate enhancers in human and mouse macrophages exposed to glucocorticoid (GC), a regulator of innate immunity and an important therapeutic agent. Our analyses revealed a very limited overlap in the repertoire of genes responsive to GC in human and mouse macrophages. Peaks of inducible binding of the GC receptor (GR) detected by chromatin immunoprecipitation-Seq correlated with induction, but not repression, of target genes in both species, occurred at distal regulatory sites not promoters, and were strongly enriched for the consensus GR-binding motif. Turnover of GR binding between mice and humans was associated with gain and loss of the motif. There was no detectable signal of positive selection at species-specific GR binding sites, but clear evidence of purifying selection at the small number of conserved sites. We conclude that enhancer divergence underlies the difference in transcriptional activation after GC treatment between mouse and human macrophages. Only the shared inducible loci show evidence of selection, and therefore these loci may be important for the subset of responses to GC that is shared between species.
authors.affiliation: MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Crewe Road, Edinburgh, EH4 2XU, Scotland, UK.|The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Easter Bush, Midlothian, EH25 9RG, Scotland, UK.
authors.forename: Alasdair W
authors.initials: AW
authors.lastname: Jubb
authors.affiliation: MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Crewe Road, Edinburgh, EH4 2XU, Scotland, UK.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Young
authors.affiliation: The Roslin Institute and Royal (Dick) School of Veterinary Studies, The University of Edinburgh, Easter Bush, Midlothian, EH25 9RG, Scotland, UK.
authors.forename: David A
authors.initials: DA
authors.lastname: Hume
authors.affiliation: MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, The University of Edinburgh, Crewe Road, Edinburgh, EH4 2XU, Scotland, UK.
authors.forename: Wendy A
authors.initials: WA
authors.lastname: Bickmore
mesh_terms: D000818:Animals; D047369:Chromatin Immunoprecipitation; D019143:Evolution, Molecular; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects* / Q000276:immunology; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D008264:Macrophages / Q000187:drug effects* / Q000276:immunology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D020411:Oligonucleotide Array Sequence Analysis; D011965:Receptors, Glucocorticoid / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013045:Species Specificity; D059467:Transcriptome / Q000187:drug effects*
chemical_list: D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid