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Verta JP, Landry CR, MacKay J. Dissection of expression-quantitative trait locus and allele specificity using a haploid/diploid plant system - insights into compensatory evolution of transcriptional regulation within populations. THE NEW PHYTOLOGIST 2016; 211:159-171. [PMID: 26891783 DOI: 10.1111/nph.13888] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 01/06/2016] [Indexed: 06/05/2023]
Abstract
Regulation of gene expression plays a central role in translating genotypic variation into phenotypic variation. Dissection of the genetic basis of expression variation is key to understanding how expression regulation evolves. Such analyses remain challenging in contexts where organisms are outbreeding, highly heterozygous and long-lived such as in the case of conifer trees. We developed an RNA sequencing (RNA-seq)-based approach for both expression-quantitative trait locus (eQTL) mapping and the detection of cis-acting (allele-specific) vs trans-acting (non-allele-specific) eQTLs. This method can be potentially applied to many conifers. We used haploid and diploid meiotic seed tissues of a single self-fertilized white spruce (Picea glauca) individual to dissect eQTLs according to linkage and allele specificity. The genetic architecture of local eQTLs linked to the expressed genes was particularly complex, consisting of cis-acting, trans-acting and, surprisingly, compensatory cis-trans effects. These compensatory effects influence expression in opposite directions and are neutral when combined in homozygotes. Nearly half of local eQTLs were under compensation, indicating that close linkage between compensatory cis-trans factors is common in spruce. Compensated genes were overrepresented in developmental and cell organization functions. Our haploid-diploid eQTL analysis in spruce revealed that compensatory cis-trans eQTLs segregate within populations and evolve in close genetic linkage.
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Affiliation(s)
- Jukka-Pekka Verta
- Centre d'étude de la forêt, Département des sciences du bois et de la forêt, Université Laval, Québec, QC, Canada G1V 0A6
- Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, QC, Canada G1V 0A6
| | - Christian R Landry
- Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, QC, Canada G1V 0A6
- Département de Biologie, Université Laval, Québec, QC, Canada G1V 0A6
| | - John MacKay
- Centre d'étude de la forêt, Département des sciences du bois et de la forêt, Université Laval, Québec, QC, Canada G1V 0A6
- Institut de Biologie Intégrative et des Systèmes, Université Laval, Québec, QC, Canada G1V 0A6
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB, UK
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102
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Contrasting Levels of Molecular Evolution on the Mouse X Chromosome. Genetics 2016; 203:1841-57. [PMID: 27317678 DOI: 10.1534/genetics.116.186825] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 06/08/2016] [Indexed: 11/18/2022] Open
Abstract
The mammalian X chromosome has unusual evolutionary dynamics compared to autosomes. Faster-X evolution of spermatogenic protein-coding genes is known to be most pronounced for genes expressed late in spermatogenesis, but it is unclear if these patterns extend to other forms of molecular divergence. We tested for faster-X evolution in mice spanning three different forms of molecular evolution-divergence in protein sequence, gene expression, and DNA methylation-across different developmental stages of spermatogenesis. We used FACS to isolate individual cell populations and then generated cell-specific transcriptome profiles across different stages of spermatogenesis in two subspecies of house mice (Mus musculus), thereby overcoming a fundamental limitation of previous studies on whole tissues. We found faster-X protein evolution at all stages of spermatogenesis and faster-late protein evolution for both X-linked and autosomal genes. In contrast, there was less expression divergence late in spermatogenesis (slower late) on the X chromosome and for autosomal genes expressed primarily in testis (testis-biased). We argue that slower-late expression divergence reflects strong regulatory constraints imposed during this critical stage of sperm development and that these constraints are particularly acute on the tightly regulated sex chromosomes. We also found slower-X DNA methylation divergence based on genome-wide bisulfite sequencing of sperm from two species of mice (M. musculus and M. spretus), although it is unclear whether slower-X DNA methylation reflects development constraints in sperm or other X-linked phenomena. Our study clarifies key differences in patterns of regulatory and protein evolution across spermatogenesis that are likely to have important consequences for mammalian sex chromosome evolution, male fertility, and speciation.
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103
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Torres-Oliva M, Almudi I, McGregor AP, Posnien N. A robust (re-)annotation approach to generate unbiased mapping references for RNA-seq-based analyses of differential expression across closely related species. BMC Genomics 2016; 17:392. [PMID: 27220689 PMCID: PMC4877740 DOI: 10.1186/s12864-016-2646-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 04/22/2016] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND RNA-seq based on short reads generated by next generation sequencing technologies has become the main approach to study differential gene expression. Until now, the main applications of this technique have been to study the variation of gene expression in a whole organism, tissue or cell type under different conditions or at different developmental stages. However, RNA-seq also has a great potential to be used in evolutionary studies to investigate gene expression divergence in closely related species. RESULTS We show that the published genomes and annotations of the three closely related Drosophila species D. melanogaster, D. simulans and D. mauritiana have limitations for inter-specific gene expression studies. This is due to missing gene models in at least one of the genome annotations, unclear orthology assignments and significant gene length differences in the different species. A comprehensive evaluation of four statistical frameworks (DESeq2, DESeq2 with length correction, RPKM-limma and RPKM-voom-limma) shows that none of these methods sufficiently accounts for inter-specific gene length differences, which inevitably results in false positive candidate genes. We propose that published reference genomes should be re-annotated before using them as references for RNA-seq experiments to include as many genes as possible and to account for a potential length bias. We present a straight-forward reciprocal re-annotation pipeline that allows to reliably compare the expression for nearly all genes annotated in D. melanogaster. CONCLUSIONS We conclude that our reciprocal re-annotation of previously published genomes facilitates the analysis of significantly more genes in an inter-specific differential gene expression study. We propose that the established pipeline can easily be applied to re-annotate other genomes of closely related animals and plants to improve comparative expression analyses.
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Affiliation(s)
- Montserrat Torres-Oliva
- />Georg-August-Universität Göttingen, Johann-Friedrich-Blumenbach-Institut für Zoologie und Anthropologie, Abteilung für Entwicklungsbiologie, GZMB Ernst-Caspari-Haus, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
- />Göttingen Center for Molecular Biosciences (GZMB), GZMB Ernst-Caspari-Haus, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
| | - Isabel Almudi
- />Department of Biological and Medical Sciences, Oxford Brookes University, Gipsy Lane, Oxford, OX3 0BP UK
- />Andalusian Centre of Developmental Biology, carretera de Utrera, km.1, 41013 Seville, Spain
| | - Alistair P. McGregor
- />Department of Biological and Medical Sciences, Oxford Brookes University, Gipsy Lane, Oxford, OX3 0BP UK
| | - Nico Posnien
- />Georg-August-Universität Göttingen, Johann-Friedrich-Blumenbach-Institut für Zoologie und Anthropologie, Abteilung für Entwicklungsbiologie, GZMB Ernst-Caspari-Haus, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
- />Göttingen Center for Molecular Biosciences (GZMB), GZMB Ernst-Caspari-Haus, Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany
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104
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Buffering of Genetic Regulatory Networks in Drosophila melanogaster. Genetics 2016; 203:1177-90. [PMID: 27194752 DOI: 10.1534/genetics.116.188797] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 05/17/2016] [Indexed: 01/01/2023] Open
Abstract
Regulatory variation in gene expression can be described by cis- and trans-genetic components. Here we used RNA-seq data from a population panel of Drosophila melanogaster test crosses to compare allelic imbalance (AI) in female head tissue between mated and virgin flies, an environmental change known to affect transcription. Indeed, 3048 exons (1610 genes) are differentially expressed in this study. A Bayesian model for AI, with an intersection test, controls type I error. There are ∼200 genes with AI exclusively in mated or virgin flies, indicating an environmental component of expression regulation. On average 34% of genes within a cross and 54% of all genes show evidence for genetic regulation of transcription. Nearly all differentially regulated genes are affected in cis, with an average of 63% of expression variation explained by the cis-effects. Trans-effects explain 8% of the variance in AI on average and the interaction between cis and trans explains an average of 11% of the total variance in AI. In both environments cis- and trans-effects are compensatory in their overall effect, with a negative association between cis- and trans-effects in 85% of the exons examined. We hypothesize that the gene expression level perturbed by cis-regulatory mutations is compensated through trans-regulatory mechanisms, e.g., trans and cis by trans-factors buffering cis-mutations. In addition, when AI is detected in both environments, cis-mated, cis-virgin, and trans-mated-trans-virgin estimates are highly concordant with 99% of all exons positively correlated with a median correlation of 0.83 for cis and 0.95 for trans We conclude that the gene regulatory networks (GRNs) are robust and that trans-buffering explains robustness.
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105
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He F, Arce AL, Schmitz G, Koornneef M, Novikova P, Beyer A, de Meaux J. The Footprint of Polygenic Adaptation on Stress-ResponsiveCis-Regulatory Divergence in theArabidopsis Genus. Mol Biol Evol 2016; 33:2088-101. [DOI: 10.1093/molbev/msw096] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
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106
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Abstract
Tandem gene duplication is an important mutational process in evolutionary adaptation and human disease. Hypothetically, two tandem gene copies should produce twice the output of a single gene, but this expectation has not been rigorously investigated. Here, we show that tandem duplication often results in more than double the gene activity. A naturally occurring tandem duplication of the Alcohol dehydrogenase (Adh) gene exhibits 2.6-fold greater expression than the single-copy gene in transgenic Drosophila This tandem duplication also exhibits greater activity than two copies of the gene in trans, demonstrating that it is the tandem arrangement and not copy number that is the cause of overactivity. We also show that tandem duplication of an unrelated synthetic reporter gene is overactive (2.3- to 5.1-fold) at all sites in the genome that we tested, suggesting that overactivity could be a general property of tandem gene duplicates. Overactivity occurs at the level of RNA transcription, and therefore tandem duplicate overactivity appears to be a previously unidentified form of position effect. The increment of surplus gene expression observed is comparable to many regulatory mutations fixed in nature and, if typical of other genomes, would shape the fate of tandem duplicates in evolution.
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107
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Abstract
Over the last decade, tremendous progress has been made toward a comparative understanding of gene regulatory evolution. However, we know little about how gene regulation evolves in birds, and how divergent genomes interact in their hybrids. Because of the unique features of birds – female heterogamety, a highly conserved karyotype, and the slow evolution of reproductive incompatibilities – an understanding of regulatory evolution in birds is critical to a comprehensive understanding of regulatory evolution and its implications for speciation. Using a novel complement of analyses of replicated RNA-seq libraries, we demonstrate abundant divergence in brain gene expression between zebra finch (Taeniopygia guttata) subspecies. By comparing parental populations and their F1 hybrids, we also show that gene misexpression is relatively rare among brain-expressed transcripts in male birds. If this pattern is consistent across tissues and sexes, it may partially explain the slow buildup of postzygotic reproductive isolation observed in birds relative to other taxa. Although we expected that the action of genetic drift on the island-dwelling zebra finch subspecies would be manifested in a higher rate of trans regulatory divergence, we found that most divergence was in cis regulation, following a pattern commonly observed in other taxa. Thus, our study highlights both unique and shared features of avian regulatory evolution.
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108
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Massey JH, Wittkopp PJ. The Genetic Basis of Pigmentation Differences Within and Between Drosophila Species. Curr Top Dev Biol 2016; 119:27-61. [PMID: 27282023 DOI: 10.1016/bs.ctdb.2016.03.004] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
In Drosophila, as well as in many other plants and animals, pigmentation is highly variable both within and between species. This variability, combined with powerful genetic and transgenic tools as well as knowledge of how pigment patterns are formed biochemically and developmentally, has made Drosophila pigmentation a premier system for investigating the genetic and molecular mechanisms responsible for phenotypic evolution. In this chapter, we review and synthesize findings from a rapidly growing body of case studies examining the genetic basis of pigmentation differences in the abdomen, thorax, wings, and pupal cases within and between Drosophila species. A core set of genes, including genes required for pigment synthesis (eg, yellow, ebony, tan, Dat) as well as developmental regulators of these genes (eg, bab1, bab2, omb, Dll, and wg), emerge as the primary sources of this variation, with most genes having been shown to contribute to pigmentation differences both within and between species. In cases where specific genetic changes contributing to pigmentation divergence were identified in these genes, the changes were always located in noncoding sequences and affected cis-regulatory activity. We conclude this chapter by discussing these and other lessons learned from evolutionary genetic studies of Drosophila pigmentation and identify topics we think should be the focus of future work with this model system.
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Affiliation(s)
- J H Massey
- University of Michigan, Ann Arbor, MI, United States
| | - P J Wittkopp
- University of Michigan, Ann Arbor, MI, United States.
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109
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Guerrero RF, Posto AL, Moyle LC, Hahn MW. Genome-wide patterns of regulatory divergence revealed by introgression lines. Evolution 2016; 70:696-706. [PMID: 26842879 DOI: 10.1111/evo.12875] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 01/24/2016] [Indexed: 01/03/2023]
Abstract
Understanding the genetic basis for changes in transcriptional regulation is an important aspect of understanding phenotypic evolution. Using interspecific introgression lines, we infer the mechanisms of divergence in genome-wide patterns of gene expression between the nightshades Solanum pennellii and S. lycopersicum (domesticated tomato). We find that cis- and trans-regulatory changes have had qualitatively similar contributions to divergence in this clade, unlike results from other systems. Additionally, expression data from four tissues (shoot apex, ripe fruit, pollen, and seed) suggest that introgressed regions in these hybrid lines tend to be downregulated, while background (nonintrogressed) genes tend to be upregulated. Finally, we find no evidence for an association between the magnitude of differential expression in NILs and previously determined sterility phenotypes. Our results contradict previous predictions of the predominant role of cis- over trans-regulatory divergence between species, and do not support a major role for gross genome-wide misregulation in reproductive isolation between these species.
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Affiliation(s)
- Rafael F Guerrero
- Department of Biology, Indiana University, Bloomington, Indiana, 47405.
| | - Amanda L Posto
- Department of Biology, Indiana University, Bloomington, Indiana, 47405
| | - Leonie C Moyle
- Department of Biology, Indiana University, Bloomington, Indiana, 47405
| | - Matthew W Hahn
- Department of Biology, Indiana University, Bloomington, Indiana, 47405.,School of Informatics and Computing, Indiana University, Bloomington, Indiana, 47405
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110
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Mack KL, Campbell P, Nachman MW. Gene regulation and speciation in house mice. Genome Res 2016; 26:451-61. [PMID: 26833790 PMCID: PMC4817769 DOI: 10.1101/gr.195743.115] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 01/28/2016] [Indexed: 01/15/2023]
Abstract
One approach to understanding the process of speciation is to characterize the genetic architecture of post-zygotic isolation. As gene regulation requires interactions between loci, negative epistatic interactions between divergent regulatory elements might underlie hybrid incompatibilities and contribute to reproductive isolation. Here, we take advantage of a cross between house mouse subspecies, where hybrid dysfunction is largely unidirectional, to test several key predictions about regulatory divergence and reproductive isolation. Regulatory divergence between Mus musculus musculus and M. m. domesticus was characterized by studying allele-specific expression in fertile hybrid males using mRNA-sequencing of whole testes. We found extensive regulatory divergence between M. m. musculus and M. m. domesticus, largely attributable to cis-regulatory changes. When both cis and trans changes occurred, they were observed in opposition much more often than expected under a neutral model, providing strong evidence of widespread compensatory evolution. We also found evidence for lineage-specific positive selection on a subset of genes related to transcriptional regulation. Comparisons of fertile and sterile hybrid males identified a set of genes that were uniquely misexpressed in sterile individuals. Lastly, we discovered a nonrandom association between these genes and genes showing evidence of compensatory evolution, consistent with the idea that regulatory interactions might contribute to Dobzhansky-Muller incompatibilities and be important in speciation.
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Affiliation(s)
- Katya L Mack
- Museum of Vertebrate Zoology and Department of Integrative Biology, University of California, Berkeley, California 94720-3160, USA
| | - Polly Campbell
- Department of Integrative Biology, Oklahoma State University, Stillwater, Oklahoma 74078, USA
| | - Michael W Nachman
- Museum of Vertebrate Zoology and Department of Integrative Biology, University of California, Berkeley, California 94720-3160, USA
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111
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Metzger BPH, Duveau F, Yuan DC, Tryban S, Yang B, Wittkopp PJ. Contrasting Frequencies and Effects of cis- and trans-Regulatory Mutations Affecting Gene Expression. Mol Biol Evol 2016; 33:1131-46. [PMID: 26782996 DOI: 10.1093/molbev/msw011] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Heritable differences in gene expression are caused by mutations in DNA sequences encoding cis-regulatory elements and trans-regulatory factors. These two classes of regulatory change differ in their relative contributions to expression differences in natural populations because of the combined effects of mutation and natural selection. Here, we investigate how new mutations create the regulatory variation upon which natural selection acts by quantifying the frequencies and effects of hundreds of new cis- and trans-acting mutations altering activity of the TDH3 promoter in the yeast Saccharomyces cerevisiae in the absence of natural selection. We find that cis-regulatory mutations have larger effects on expression than trans-regulatory mutations and that while trans-regulatory mutations are more common overall, cis- and trans-regulatory changes in expression are equally abundant when only the largest changes in expression are considered. In addition, we find that cis-regulatory mutations are skewed toward decreased expression while trans-regulatory mutations are skewed toward increased expression. We also measure the effects of cis- and trans-regulatory mutations on the variability in gene expression among genetically identical cells, a property of gene expression known as expression noise, finding that trans-regulatory mutations are much more likely to decrease expression noise than cis-regulatory mutations. Because new mutations are the raw material upon which natural selection acts, these differences in the frequencies and effects of cis- and trans-regulatory mutations should be considered in models of regulatory evolution.
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Affiliation(s)
- Brian P H Metzger
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor
| | - Fabien Duveau
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor
| | - David C Yuan
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor Department of Biology, Stanford University
| | - Stephen Tryban
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor
| | - Bing Yang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor
| | - Patricia J Wittkopp
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor
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112
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Carvunis AR, Wang T, Skola D, Yu A, Chen J, Kreisberg JF, Ideker T. Evidence for a common evolutionary rate in metazoan transcriptional networks. eLife 2015; 4. [PMID: 26682651 PMCID: PMC4764585 DOI: 10.7554/elife.11615] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Accepted: 12/17/2015] [Indexed: 12/13/2022] Open
Abstract
Genome sequences diverge more rapidly in mammals than in other animal lineages, such as birds or insects. However, the effect of this rapid divergence on transcriptional evolution remains unclear. Recent reports have indicated a faster divergence of transcription factor binding in mammals than in insects, but others found the reverse for mRNA expression. Here, we show that these conflicting interpretations resulted from differing methodologies. We performed an integrated analysis of transcriptional network evolution by examining mRNA expression, transcription factor binding and cis-regulatory motifs across >25 animal species, including mammals, birds and insects. Strikingly, we found that transcriptional networks evolve at a common rate across the three animal lineages. Furthermore, differences in rates of genome divergence were greatly reduced when restricting comparisons to chromatin-accessible sequences. The evolution of transcription is thus decoupled from the global rate of genome sequence evolution, suggesting that a small fraction of the genome regulates transcription. DOI:http://dx.doi.org/10.7554/eLife.11615.001 The genetic information that makes each individual unique is encoded in DNA molecules. Cells read this molecular instruction manual by a process called transcription, in which proteins called transcription factors bind to DNA in specific places and regulate which sections of the DNA will be expressed. These 'transcripts' are active molecules that determine the cell’s – and ultimately the individual’s – characteristics. However, it is not well understood how alterations in the DNA of different individuals or species can lead to changes in where the transcription factors bind, and in which transcripts are expressed. Carvunis, Wang, Skola et al. set out to determine if there is a relationship between how often DNA changes and how often transcription changes during the evolution of animals. The experiments examined the abundance of transcripts in the cells of a variety of animal species with close or distant evolutionary relationships. For example, the house mouse was compared to a close relative called the Algerian mouse, to another species of rodent (rat) and to humans. The experiments show that the changes in transcript abundances are happening at similar rates in mammals, birds and insects, even though DNA changes at very different rates in these groups of animals. This similarity was also observed for other aspects of transcription, such as in changes to where transcription factors bind to DNA. The next challenges are to find out what makes transcription evolve at such similar rates in these groups of animals, and whether these findings extend to other species and to other processes in cells. DOI:http://dx.doi.org/10.7554/eLife.11615.002
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Affiliation(s)
| | - Tina Wang
- Department of Medicine, University of California, San Diego, La Jolla, United States
| | - Dylan Skola
- Department of Medicine, University of California, San Diego, La Jolla, United States
| | - Alice Yu
- Department of Medicine, University of California, San Diego, La Jolla, United States
| | - Jonathan Chen
- Department of Medicine, University of California, San Diego, La Jolla, United States
| | - Jason F Kreisberg
- Department of Medicine, University of California, San Diego, La Jolla, United States
| | - Trey Ideker
- Department of Medicine, University of California, San Diego, La Jolla, United States
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113
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Hodgins-Davis A, Rice DP, Townsend JP. Gene Expression Evolves under a House-of-Cards Model of Stabilizing Selection. Mol Biol Evol 2015; 32:2130-40. [PMID: 25901014 PMCID: PMC4592357 DOI: 10.1093/molbev/msv094] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Divergence in gene regulation is hypothesized to underlie much of phenotypic evolution, but the role of natural selection in shaping the molecular phenotype of gene expression continues to be debated. To resolve the mode of gene expression, evolution requires accessible theoretical predictions for the effect of selection over long timescales. Evolutionary quantitative genetic models of phenotypic evolution can provide such predictions, yet those predictions depend on the underlying hypotheses about the distributions of mutational and selective effects that are notoriously difficult to disentangle. Here, we draw on diverse genomic data sets including expression profiles of natural genetic variation and mutation accumulation lines, empirical estimates of genomic mutation rates, and inferences of genetic architecture to differentiate contrasting hypotheses for the roles of stabilizing selection and mutation in shaping natural expression variation. Our analysis suggests that gene expression evolves in a domain of phenotype space well fit by the House-of-Cards (HC) model. Although the strength of selection inferred is sensitive to the number of loci controlling gene expression, the model is not. The consistency of these results across evolutionary time from budding yeast through fruit fly implies that this model is general and that mutational effects on gene expression are relatively large. Empirical estimates of the genetic architecture of gene expression traits imply that selection provides modest constraints on gene expression levels for most genes, but that the potential for regulatory evolution is high. Our prediction using data from laboratory environments should encourage the collection of additional data sets allowing for more nuanced parameterizations of HC models for gene expression.
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Affiliation(s)
- Andrea Hodgins-Davis
- Department of Ecology and Evolutionary Biology, Yale University Department of Biostatistics, School of Public Health, Yale University
| | - Daniel P Rice
- Department of Ecology and Evolutionary Biology, Yale University Department of Organismic and Evolutionary Biology, Harvard University
| | - Jeffrey P Townsend
- Department of Ecology and Evolutionary Biology, Yale University Department of Biostatistics, School of Public Health, Yale University Program in Computational Biology and Bioinformatics, Yale University
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114
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Gao Q, Sun W, Ballegeer M, Libert C, Chen W. Predominant contribution of cis-regulatory divergence in the evolution of mouse alternative splicing. Mol Syst Biol 2015; 11:816. [PMID: 26134616 PMCID: PMC4547845 DOI: 10.15252/msb.20145970] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Divergence of alternative splicing represents one of the major driving forces to shape phenotypic diversity during evolution. However, the extent to which these divergences could be explained by the evolving cis-regulatory versus trans-acting factors remains unresolved. To globally investigate the relative contributions of the two factors for the first time in mammals, we measured splicing difference between C57BL/6J and SPRET/EiJ mouse strains and allele-specific splicing pattern in their F1 hybrid. Out of 11,818 alternative splicing events expressed in the cultured fibroblast cells, we identified 796 with significant difference between the parental strains. After integrating allele-specific data from F1 hybrid, we demonstrated that these events could be predominately attributed to cis-regulatory variants, including those residing at and beyond canonical splicing sites. Contrary to previous observations in Drosophila, such predominant contribution was consistently observed across different types of alternative splicing. Further analysis of liver tissues from the same mouse strains and reanalysis of published datasets on other strains showed similar trends, implying in general the predominant contribution of cis-regulatory changes in the evolution of mouse alternative splicing.
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Affiliation(s)
- Qingsong Gao
- Laboratory for Systems Biology and Functional Genomics, Berlin Institute for Medical Systems Biology, Max-Delbrück-Centrum für Molekulare Medizin, Berlin, Germany
| | - Wei Sun
- Laboratory for Systems Biology and Functional Genomics, Berlin Institute for Medical Systems Biology, Max-Delbrück-Centrum für Molekulare Medizin, Berlin, Germany
| | - Marlies Ballegeer
- Inflammation Research Center, VIB, Ghent, Belgium Department of Biomedical Molecular Biology, University Ghent, Ghent, Belgium
| | - Claude Libert
- Inflammation Research Center, VIB, Ghent, Belgium Department of Biomedical Molecular Biology, University Ghent, Ghent, Belgium
| | - Wei Chen
- Laboratory for Systems Biology and Functional Genomics, Berlin Institute for Medical Systems Biology, Max-Delbrück-Centrum für Molekulare Medizin, Berlin, Germany
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115
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Abstract
Flies of the genus Drosophila, and particularly those of the species Drosophila melanogaster, are best known as laboratory organisms. As with all model organisms, they were domesticated for empirical studies, but they also continue to exist as wild populations. Decades of research on these flies in the laboratory have produced astounding and important insights into basic biological processes, but we have only scratched the surface of what they have to offer as research organisms. An outstanding challenge now is to build on this knowledge and explore how natural history has shaped D. melanogaster in order to advance our understanding of biology more generally. DOI:http://dx.doi.org/10.7554/eLife.06793.001
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Affiliation(s)
- Therese Ann Markow
- Division of Biological Sciences, Laboratorio Nacional para Genomica de la Biodiversidad, La Jolla, United States
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116
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Coolon JD, Stevenson KR, McManus CJ, Yang B, Graveley BR, Wittkopp PJ. Molecular Mechanisms and Evolutionary Processes Contributing to Accelerated Divergence of Gene Expression on the Drosophila X Chromosome. Mol Biol Evol 2015; 32:2605-15. [PMID: 26041937 DOI: 10.1093/molbev/msv135] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
In species with a heterogametic sex, population genetics theory predicts that DNA sequences on the X chromosome can evolve faster than comparable sequences on autosomes. Both neutral and nonneutral evolutionary processes can generate this pattern. Complex traits like gene expression are not predicted to have accelerated evolution by these theories, yet a "faster-X" pattern of gene expression divergence has recently been reported for both Drosophila and mammals. Here, we test the hypothesis that accelerated adaptive evolution of cis-regulatory sequences on the X chromosome is responsible for this pattern by comparing the relative contributions of cis- and trans-regulatory changes to patterns of faster-X expression divergence observed between strains and species of Drosophila with a range of divergence times. We find support for this hypothesis, especially among male-biased genes, when comparing different species. However, we also find evidence that trans-regulatory differences contribute to a faster-X pattern of expression divergence both within and between species. This contribution is surprising because trans-acting regulators of X-linked genes are generally assumed to be randomly distributed throughout the genome. We found, however, that X-linked transcription factors appear to preferentially regulate expression of X-linked genes, providing a potential mechanistic explanation for this result. The contribution of trans-regulatory variation to faster-X expression divergence was larger within than between species, suggesting that it is more likely to result from neutral processes than positive selection. These data show how accelerated evolution of both coding and noncoding sequences on the X chromosome can lead to accelerated expression divergence on the X chromosome relative to autosomes.
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Affiliation(s)
- Joseph D Coolon
- Department of Ecology and Evolutionary Biology, University of Michigan
| | - Kraig R Stevenson
- Department of Computational Medicine and Bioinformatics, University of Michigan
| | - C Joel McManus
- Department of Biological Sciences, Carnegie Mellon University Department of Genetics and Developmental Biology, Institute for Systems Genomics, University of Connecticut Health Center
| | - Bing Yang
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan
| | - Brenton R Graveley
- Department of Genetics and Developmental Biology, Institute for Systems Genomics, University of Connecticut Health Center
| | - Patricia J Wittkopp
- Department of Ecology and Evolutionary Biology, University of Michigan Department of Computational Medicine and Bioinformatics, University of Michigan Department of Molecular, Cellular, and Developmental Biology, University of Michigan
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Naval-Sánchez M, Potier D, Hulselmans G, Christiaens V, Aerts S. Identification of Lineage-Specific Cis-Regulatory Modules Associated with Variation in Transcription Factor Binding and Chromatin Activity Using Ornstein-Uhlenbeck Models. Mol Biol Evol 2015; 32:2441-55. [PMID: 25944915 PMCID: PMC4540964 DOI: 10.1093/molbev/msv107] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Scoring the impact of noncoding variation on the function of cis-regulatory regions, on their chromatin state, and on the qualitative and quantitative expression levels of target genes is a fundamental problem in evolutionary genomics. A particular challenge is how to model the divergence of quantitative traits and to identify relationships between the changes across the different levels of the genome, the chromatin activity landscape, and the transcriptome. Here, we examine the use of the Ornstein-Uhlenbeck (OU) model to infer selection at the level of predicted cis-regulatory modules (CRMs), and link these with changes in transcription factor binding and chromatin activity. Using publicly available cross-species ChIP-Seq and STARR-Seq data we show how OU can be applied genome-wide to identify candidate transcription factors for which binding site and CRM turnover is correlated with changes in regulatory activity. Next, we profile open chromatin in the developing eye across three Drosophila species. We identify the recognition motifs of the chromatin remodelers, Trithorax-like and Grainyhead as mostly correlating with species-specific changes in open chromatin. In conclusion, we show in this study that CRM scores can be used as quantitative traits and that motif discovery approaches can be extended towards more complex models of divergence.
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Affiliation(s)
- Marina Naval-Sánchez
- Laboratory of Computational Biology, Department of Human Genetics, University of Leuven, Leuven, Belgium
| | - Delphine Potier
- Laboratory of Computational Biology, Department of Human Genetics, University of Leuven, Leuven, Belgium
| | - Gert Hulselmans
- Laboratory of Computational Biology, Department of Human Genetics, University of Leuven, Leuven, Belgium
| | - Valerie Christiaens
- Laboratory of Computational Biology, Department of Human Genetics, University of Leuven, Leuven, Belgium
| | - Stein Aerts
- Laboratory of Computational Biology, Department of Human Genetics, University of Leuven, Leuven, Belgium
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118
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Combes MC, Hueber Y, Dereeper A, Rialle S, Herrera JC, Lashermes P. Regulatory divergence between parental alleles determines gene expression patterns in hybrids. Genome Biol Evol 2015; 7:1110-21. [PMID: 25819221 PMCID: PMC4419803 DOI: 10.1093/gbe/evv057] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Both hybridization and allopolyploidization generate novel phenotypes by conciliating divergent genomes and regulatory networks in the same cellular context. To understand the rewiring of gene expression in hybrids, the total expression of 21,025 genes and the allele-specific expression of over 11,000 genes were quantified in interspecific hybrids and their parental species, Coffea canephora and Coffea eugenioides using RNA-seq technology. Between parental species, cis- and trans-regulatory divergences affected around 32% and 35% of analyzed genes, respectively, with nearly 17% of them showing both. The relative importance of trans-regulatory divergences between both species could be related to their low genetic divergence and perennial habit. In hybrids, among divergently expressed genes between parental species and hybrids, 77% was expressed like one parent (expression level dominance), including 65% like C. eugenioides. Gene expression was shown to result from the expression of both alleles affected by intertwined parental trans-regulatory factors. A strong impact of C. eugenioides trans-regulatory factors on the upregulation of C. canephora alleles was revealed. The gene expression patterns appeared determined by complex combinations of cis- and trans-regulatory divergences. In particular, the observed biased expression level dominance seemed to be derived from the asymmetric effects of trans-regulatory parental factors on regulation of alleles. More generally, this study illustrates the effects of divergent trans-regulatory parental factors on the gene expression pattern in hybrids. The characteristics of the transcriptional response to hybridization appear to be determined by the compatibility of gene regulatory networks and therefore depend on genetic divergences between the parental species and their evolutionary history.
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Affiliation(s)
| | | | | | - Stéphanie Rialle
- MGX-Montpellier GenomiX, Institut de Génomique Fonctionnelle, Montpellier Cédex 5, France
| | - Juan-Carlos Herrera
- Centro Nacional de Investigaciones de Cafe, CENICAFE - FNC, Manizales, Colombia
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119
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Cheatle Jarvela AM, Hinman VF. Evolution of transcription factor function as a mechanism for changing metazoan developmental gene regulatory networks. EvoDevo 2015; 6:3. [PMID: 25685316 PMCID: PMC4327956 DOI: 10.1186/2041-9139-6-3] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 12/18/2014] [Indexed: 11/10/2022] Open
Abstract
The form that an animal takes during development is directed by gene regulatory networks (GRNs). Developmental GRNs interpret maternally deposited molecules and externally supplied signals to direct cell-fate decisions, which ultimately leads to the arrangements of organs and tissues in the organism. Genetically encoded modifications to these networks have generated the wide range of metazoan diversity that exists today. Most studies of GRN evolution focus on changes to cis-regulatory DNA, and it was historically theorized that changes to the transcription factors that bind to these cis-regulatory modules (CRMs) contribute to this process only rarely. A growing body of evidence suggests that changes to the coding regions of transcription factors play a much larger role in the evolution of developmental gene regulatory networks than originally imagined. Just as cis-regulatory changes make use of modular binding site composition and tissue-specific modules to avoid pleiotropy, transcription factor coding regions also predominantly evolve in ways that limit the context of functional effects. Here, we review the recent works that have led to this unexpected change in the field of Evolution and Development (Evo-Devo) and consider the implications these studies have had on our understanding of the evolution of developmental processes.
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Affiliation(s)
- Alys M Cheatle Jarvela
- Department of Biological Sciences, Carnegie Mellon University, 4400 5th Ave, Pittsburgh, PA 15213 USA
| | - Veronica F Hinman
- Department of Biological Sciences, Carnegie Mellon University, 4400 5th Ave, Pittsburgh, PA 15213 USA
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120
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Barreto FS, Pereira RJ, Burton RS. Hybrid Dysfunction and Physiological Compensation in Gene Expression. Mol Biol Evol 2014; 32:613-22. [DOI: 10.1093/molbev/msu321] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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121
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Abstract
Heritable differences in gene expression between individuals are an important source of phenotypic variation. The question of how closely the effects of genetic variation on protein levels mirror those on mRNA levels remains open. Here, we addressed this question by using ribosome profiling to examine how genetic differences between two strains of the yeast S. cerevisiae affect translation. Strain differences in translation were observed for hundreds of genes. Allele specific measurements in the diploid hybrid between the two strains revealed roughly half as many cis-acting effects on translation as were observed for mRNA levels. In both the parents and the hybrid, most effects on translation were of small magnitude, such that the direction of an mRNA difference was typically reflected in a concordant footprint difference. The relative importance of cis and trans acting variation on footprint levels was similar to that for mRNA levels. There was a tendency for translation to cause larger footprint differences than expected given the respective mRNA differences. This is in contrast to translational differences between yeast species that have been reported to more often oppose than reinforce mRNA differences. Finally, we catalogued instances of premature translation termination in the two yeast strains and also found several instances where erroneous reference gene annotations lead to apparent nonsense mutations that in fact reside outside of the translated gene body. Overall, genetic influences on translation subtly modulate gene expression differences, and translation does not create strong discrepancies between genetic influences on mRNA and protein levels. Individuals in a species differ from each other in many ways. For many traits, a fraction of this variation is genetic—it is caused by DNA sequence variants in the genome of each individual. Some of these variants influence traits by altering how much certain genes are expressed, i.e. how many mRNA and protein molecules are made in different individuals. Surprisingly, earlier work has found that the effects of genetic variants on mRNA and protein levels for the same genes appear to be very different. Many variants appeared to influence only mRNA (but not protein) levels, and vice versa. In this paper, we studied this question by using a technique called “ribosome profiling” to measure translation (the cellular process of reading mRNA molecules and synthesizing protein molecules) in two yeast strains. We found that the genetic differences between these two strains influence translation for hundreds of genes. Because most of these effects were small in magnitude, they explain at most a small fraction of the discrepancies between the effects of genetic variants on mRNA and protein levels.
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122
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Pai AA, Gilad Y. Comparative studies of gene regulatory mechanisms. Curr Opin Genet Dev 2014; 29:68-74. [PMID: 25215415 DOI: 10.1016/j.gde.2014.08.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 08/04/2014] [Accepted: 08/23/2014] [Indexed: 01/03/2023]
Abstract
It has become increasingly clear that changes in gene regulation have played an important role in adaptive evolution both between and within species. Over the past five years, comparative studies have moved beyond simple characterizations of differences in gene expression levels within and between species to studying variation in regulatory mechanisms. We still know relatively little about the precise chain of events that lead to most regulatory adaptations, but we have taken significant steps towards understanding the relative importance of changes in different mechanisms of gene regulatory evolution. In this review, we first discuss insights from comparative studies in model organisms, where the available experimental toolkit is extensive. We then focus on a few recent comparative studies in primates, where the limited feasibility of experimental manipulation dictates the approaches that can be used to study gene regulatory evolution.
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Affiliation(s)
- Athma A Pai
- Department of Biology, Massachusetts Institute of Technology, United States
| | - Yoav Gilad
- Department of Human Genetics, University of Chicago, United States.
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123
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McManus CJ, Coolon JD, Eipper-Mains J, Wittkopp PJ, Graveley BR. Evolution of splicing regulatory networks in Drosophila. Genome Res 2014; 24:786-96. [PMID: 24515119 PMCID: PMC4009608 DOI: 10.1101/gr.161521.113] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The proteome expanding effects of alternative pre-mRNA splicing have had a profound impact on eukaryotic evolution. The events that create this diversity can be placed into four major classes: exon skipping, intron retention, alternative 5′ splice sites, and alternative 3′ splice sites. Although the regulatory mechanisms and evolutionary pressures among alternative splicing classes clearly differ, how these differences affect the evolution of splicing regulation remains poorly characterized. We used RNA-seq to investigate splicing differences in D. simulans, D. sechellia, and three strains of D. melanogaster. Regulation of exon skipping and tandem alternative 3′ splice sites (NAGNAGs) were more divergent than other splicing classes. Splicing regulation was most divergent in frame-preserving events and events in noncoding regions. We further determined the contributions of cis- and trans-acting changes in splicing regulatory networks by comparing allele-specific splicing in F1 interspecific hybrids, because differences in allele-specific splicing reflect changes in cis-regulatory element activity. We find that species-specific differences in intron retention and alternative splice site usage are primarily attributable to changes in cis-regulatory elements (median ∼80% cis), whereas species-specific exon skipping differences are driven by both cis- and trans-regulatory divergence (median ∼50% cis). These results help define the mechanisms and constraints that influence splicing regulatory evolution and show that networks regulating the four major classes of alternative splicing diverge through different genetic mechanisms. We propose a model in which differences in regulatory network architecture among classes of alternative splicing affect the evolution of splicing regulation.
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Affiliation(s)
- C Joel McManus
- Department of Genetics and Developmental Biology, Institute for Systems Genomics, University of Connecticut Health Center, Farmington, Connecticut 06030, USA
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