1
|
Tjeerdema E, Lee Y, Metry R, Hamdoun A. Semi-automated, high-content imaging of drug transporter knockout sea urchin (Lytechinus pictus) embryos. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION 2024; 342:313-329. [PMID: 38087422 DOI: 10.1002/jez.b.23231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 11/08/2023] [Accepted: 11/19/2023] [Indexed: 05/01/2024]
Abstract
A defining feature of sea urchins is their extreme fecundity. Urchins produce millions of transparent, synchronously developing embryos, ideal for spatial and temporal analysis of development. This biological feature has been effectively utilized for ensemble measurement of biochemical changes. However, it has been underutilized in imaging studies, where single embryo measurements are used. Here we present an example of how stable genetics and high content imaging, along with machine learning-based image analysis, can be used to exploit the fecundity and synchrony of sea urchins in imaging-based drug screens. Building upon our recently created sea urchin ABCB1 knockout line, we developed a high-throughput assay to probe the role of this drug transporter in embryos. We used high content imaging to compare accumulation and toxicity of canonical substrates and inhibitors of the transporter, including fluorescent molecules and antimitotic cancer drugs, in homozygous knockout and wildtype embryos. To measure responses from the resulting image data, we used a nested convolutional neural network, which rapidly classified embryos according to fluorescence or cell division. This approach identified sea urchin embryos with 99.8% accuracy and determined two-cell and aberrant embryos with 96.3% and 89.1% accuracy, respectively. The results revealed that ABCB1 knockout embryos accumulated the transporter substrate calcein 3.09 times faster than wildtypes. Similarly, knockouts were 4.71 and 3.07 times more sensitive to the mitotic poisons vinblastine and taxol. This study paves the way for large scale pharmacological screens in the sea urchin embryo.
Collapse
Affiliation(s)
- Evan Tjeerdema
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
| | - Yoon Lee
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
| | - Rachel Metry
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
| | - Amro Hamdoun
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
| |
Collapse
|
2
|
Peng PC, Khoueiry P, Girardot C, Reddington JP, Garfield DA, Furlong EEM, Sinha S. The Role of Chromatin Accessibility in cis-Regulatory Evolution. Genome Biol Evol 2020; 11:1813-1828. [PMID: 31114856 PMCID: PMC6601868 DOI: 10.1093/gbe/evz103] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/13/2019] [Indexed: 02/07/2023] Open
Abstract
Transcription factor (TF) binding is determined by sequence as well as chromatin accessibility. Although the role of accessibility in shaping TF-binding landscapes is well recorded, its role in evolutionary divergence of TF binding, which in turn can alter cis-regulatory activities, is not well understood. In this work, we studied the evolution of genome-wide binding landscapes of five major TFs in the core network of mesoderm specification, between Drosophila melanogaster and Drosophila virilis, and examined its relationship to accessibility and sequence-level changes. We generated chromatin accessibility data from three important stages of embryogenesis in both Drosophila melanogaster and Drosophila virilis and recorded conservation and divergence patterns. We then used multivariable models to correlate accessibility and sequence changes to TF-binding divergence. We found that accessibility changes can in some cases, for example, for the master regulator Twist and for earlier developmental stages, more accurately predict binding change than is possible using TF-binding motif changes between orthologous enhancers. Accessibility changes also explain a significant portion of the codivergence of TF pairs. We noted that accessibility and motif changes offer complementary views of the evolution of TF binding and developed a combined model that captures the evolutionary data much more accurately than either view alone. Finally, we trained machine learning models to predict enhancer activity from TF binding and used these functional models to argue that motif and accessibility-based predictors of TF-binding change can substitute for experimentally measured binding change, for the purpose of predicting evolutionary changes in enhancer activity.
Collapse
Affiliation(s)
- Pei-Chen Peng
- Department of Computer Science, University of Illinois at Urbana-Champaign.,Center for Bioinformatics and Functional Genomics, Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, CA
| | - Pierre Khoueiry
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany.,American University of Beirut (AUB), Department of Biochemistry and Molecular Genetics, Beirut, Lebanon
| | - Charles Girardot
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - James P Reddington
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - David A Garfield
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany.,IRI-Life Sciences, Humboldt Universität zu Berlin, Berlin, Germany
| | - Eileen E M Furlong
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - Saurabh Sinha
- Department of Computer Science, University of Illinois at Urbana-Champaign.,Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign
| |
Collapse
|
3
|
Helmy M, Hatlen A, Marco A. The Impact of Population Variation in the Analysis of microRNA Target Sites. Noncoding RNA 2019; 5:E42. [PMID: 31234531 PMCID: PMC6630466 DOI: 10.3390/ncrna5020042] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 06/11/2019] [Accepted: 06/20/2019] [Indexed: 02/07/2023] Open
Abstract
The impact of population variation in the analysis of regulatory interactions is an underdeveloped area. MicroRNA target recognition occurs via pairwise complementarity. Consequently, a number of computational prediction tools have been developed to identify potential target sites that can be further validated experimentally. However, as microRNA target predictions are done mostly considering a reference genome sequence, target sites showing variation among populations are neglected. Here, we studied the variation at microRNA target sites in human populations and quantified their impact in microRNA target prediction. We found that African populations carry a significant number of potential microRNA target sites that are not detectable in the current human reference genome sequence. Some of these targets are conserved in primates and only lost in Out-of-Africa populations. Indeed, we identified experimentally validated microRNA/transcript interactions that are not detected in standard microRNA target prediction programs, yet they have segregating target alleles abundant in non-European populations. In conclusion, we show that ignoring population diversity may leave out regulatory elements essential to understand disease and gene expression, particularly neglecting populations of African origin.
Collapse
Affiliation(s)
- Mohab Helmy
- School of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK.
| | - Andrea Hatlen
- School of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK.
| | - Antonio Marco
- School of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK.
| |
Collapse
|
4
|
Hodin J, Ferner MC, Ng G, Gaylord B. Sand Dollar Larvae Show Within-Population Variation in Their Settlement Induction by Turbulence. THE BIOLOGICAL BULLETIN 2018; 235:152-166. [PMID: 30624118 DOI: 10.1086/699827] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Settlement-the generally irreversible transition from a planktonic phase to a benthic phase-is a critical stage in the life history of many shoreline organisms. It is reasonable to expect that larvae are under intense selection pressure to identify appropriate settlement habitat. Several decades of studies have focused mainly on local indicators that larvae use to identify suitable habitat, such as olfactory cues that indicate the presence of conspecifics or a favored food source. Our recent work has shown that the larvae of seashore-dwelling echinoids (sea urchins, sand dollars, and kin) can be primed to settle following a brief exposure to a broader-scale indicator of their approach to shore: an increase in fluid turbulence. Here we demonstrate that this priming shows within-population variation: the offspring of certain Pacific sand dollar (Dendraster excentricus) parents-both specific fathers and specific mothers, regardless of the other parent-are more responsive to turbulence than others. In particular, the observation of the effect correlating, in some cases, with specific fathers leads us to conclude that these behavioral differences are likely genetic and thus heritable. We also report that turbulence exposure causes larvae to temporarily sink to the bottom of a container of seawater and that larvae that respond in this way are also more likely to subsequently settle. We hypothesize a two-step scenario for the evolution of turbulence responsiveness at settlement and suggest that the evolutionary origin of these behaviors could be a driving force for population differentiation and speciation.
Collapse
|
5
|
Genome-wide use of high- and low-affinity Tbrain transcription factor binding sites during echinoderm development. Proc Natl Acad Sci U S A 2018; 114:5854-5861. [PMID: 28584099 DOI: 10.1073/pnas.1610611114] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sea stars and sea urchins are model systems for interrogating the types of deep evolutionary changes that have restructured developmental gene regulatory networks (GRNs). Although cis-regulatory DNA evolution is likely the predominant mechanism of change, it was recently shown that Tbrain, a Tbox transcription factor protein, has evolved a changed preference for a low-affinity, secondary binding motif. The primary, high-affinity motif is conserved. To date, however, no genome-wide comparisons have been performed to provide an unbiased assessment of the evolution of GRNs between these taxa, and no study has attempted to determine the interplay between transcription factor binding motif evolution and GRN topology. The study here measures genome-wide binding of Tbrain orthologs by using ChIP-sequencing and associates these orthologs with putative target genes to assess global function. Targets of both factors are enriched for other regulatory genes, although nonoverlapping sets of functional enrichments in the two datasets suggest a much diverged function. The number of low-affinity binding motifs is significantly depressed in sea urchins compared with sea star, but both motif types are associated with genes from a range of functional categories. Only a small fraction (∼10%) of genes are predicted to be orthologous targets. Collectively, these data indicate that Tbr has evolved significantly different developmental roles in these echinoderms and that the targets and the binding motifs in associated cis-regulatory sequences are dispersed throughout the hierarchy of the GRN, rather than being biased toward terminal process or discrete functional blocks, which suggests extensive evolutionary tinkering.
Collapse
|
6
|
Babbitt CC, Haygood R, Nielsen WJ, Wray GA. Gene expression and adaptive noncoding changes during human evolution. BMC Genomics 2017; 18:435. [PMID: 28583075 PMCID: PMC5460488 DOI: 10.1186/s12864-017-3831-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 05/31/2017] [Indexed: 01/14/2023] Open
Abstract
Background Despite evidence for adaptive changes in both gene expression and non-protein-coding, putatively regulatory regions of the genome during human evolution, the relationship between gene expression and adaptive changes in cis-regulatory regions remains unclear. Results Here we present new measurements of gene expression in five tissues of humans and chimpanzees, and use them to assess this relationship. We then compare our results with previous studies of adaptive noncoding changes, analyzing correlations at the level of gene ontology groups, in order to gain statistical power to detect correlations. Conclusions Consistent with previous studies, we find little correlation between gene expression and adaptive noncoding changes at the level of individual genes; however, we do find significant correlations at the level of biological function ontology groups. The types of function include processes regulated by specific transcription factors, responses to genetic or chemical perturbations, and differentiation of cell types within the immune system. Among functional categories co-enriched with both differential expression and noncoding adaptation, prominent themes include cancer, particularly epithelial cancers, and neural development and function. Electronic supplementary material The online version of this article (doi:10.1186/s12864-017-3831-2) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Courtney C Babbitt
- Department of Biology, Duke University, Durham, NC, 27708, USA. .,Institute for Genome Sciences & Policy, Duke University, Durham, NC, 27708, USA. .,Present Address: Department of Biology, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
| | | | | | - Gregory A Wray
- Department of Biology, Duke University, Durham, NC, 27708, USA.,Institute for Genome Sciences & Policy, Duke University, Durham, NC, 27708, USA.,Department of Evolutionary Anthropology, Duke University, Durham, NC, 27708, USA
| |
Collapse
|
7
|
Cary GA, Hinman VF. Echinoderm development and evolution in the post-genomic era. Dev Biol 2017; 427:203-211. [PMID: 28185788 DOI: 10.1016/j.ydbio.2017.02.003] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Revised: 02/04/2017] [Accepted: 02/06/2017] [Indexed: 01/01/2023]
Abstract
The highly recognizable animals within the phylum Echinodermata encompass an enormous disparity of adult and larval body plans. The extensive knowledge of sea urchin development has culminated in the description of the exquisitely detailed gene regulatory network (GRN) that governs the specification of various embryonic territories. This information provides a unique opportunity for comparative studies in other echinoderm taxa to understand the evolution and developmental mechanisms underlying body plan change. This review focuses on recent work that has utilized new genomic resources and systems-level experiments to address questions of evolutionary developmental biology. In particular, we synthesize the results of several recent studies from various echinoderm classes that have explored the development and evolution of the larval skeleton, which is a major feature that distinguishes the two predominant larval subtypes within the Phylum. We specifically examine the ways in which GRNs can evolve, either through cis regulatory and/or protein-level changes in transcription factors. We also examine recent work comparing evolution across shorter time scales that occur within and between species of sea urchin, and highlight the kinds of questions that can be addressed by these comparisons. The advent of new genomic and transcriptomic datasets in additional species from all classes of echinoderm will continue to empower the use of these taxa for evolutionary developmental studies.
Collapse
Affiliation(s)
- Gregory A Cary
- Department of Biological Sciences, Carnegie Mellon University, Mellon Institute, 4400 Fifth Ave, Pittsburgh, PA 15213, United States
| | - Veronica F Hinman
- Department of Biological Sciences, Carnegie Mellon University, Mellon Institute, 4400 Fifth Ave, Pittsburgh, PA 15213, United States.
| |
Collapse
|
8
|
Koga H, Fujitani H, Morino Y, Miyamoto N, Tsuchimoto J, Shibata TF, Nozawa M, Shigenobu S, Ogura A, Tachibana K, Kiyomoto M, Amemiya S, Wada H. Experimental Approach Reveals the Role of alx1 in the Evolution of the Echinoderm Larval Skeleton. PLoS One 2016; 11:e0149067. [PMID: 26866800 PMCID: PMC4750990 DOI: 10.1371/journal.pone.0149067] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 01/27/2016] [Indexed: 11/19/2022] Open
Abstract
Over the course of evolution, the acquisition of novel structures has ultimately led to wide variation in morphology among extant multicellular organisms. Thus, the origins of genetic systems for new morphological structures are a subject of great interest in evolutionary biology. The larval skeleton is a novel structure acquired in some echinoderm lineages via the activation of the adult skeletogenic machinery. Previously, VEGF signaling was suggested to have played an important role in the acquisition of the larval skeleton. In the present study, we compared expression patterns of Alx genes among echinoderm classes to further explore the factors involved in the acquisition of a larval skeleton. We found that the alx1 gene, originally described as crucial for sea urchin skeletogenesis, may have also played an essential role in the evolution of the larval skeleton. Unlike those echinoderms that have a larval skeleton, we found that alx1 of starfish was barely expressed in early larvae that have no skeleton. When alx1 overexpression was induced via injection of alx1 mRNA into starfish eggs, the expression patterns of certain genes, including those possibly involved in skeletogenesis, were altered. This suggested that a portion of the skeletogenic program was induced solely by alx1. However, we observed no obvious external phenotype or skeleton. We concluded that alx1 was necessary but not sufficient for the acquisition of the larval skeleton, which, in fact, requires several genetic events. Based on these results, we discuss how the larval expression of alx1 contributed to the acquisition of the larval skeleton in the putative ancestral lineage of echinoderms.
Collapse
Affiliation(s)
- Hiroyuki Koga
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Haruka Fujitani
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Yoshiaki Morino
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Norio Miyamoto
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
- Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan
| | - Jun Tsuchimoto
- Division of Life Science, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Japan
- Institute for Molecular Science of Medicine, Aichi Medical University, Nagakute, Japan
| | | | - Masafumi Nozawa
- Center for Information Biology, National Institute of Genetics, Mishima, Japan
- Department of Genetics, The Graduate University for Advanced Studies, Mishima, Japan
| | - Shuji Shigenobu
- National Institute for Basic Biology, Okazaki, Japan
- School of Life Science, The Graduate University for Advanced Studies, Okazaki, Japan
| | - Atsushi Ogura
- Nagahama Institute of Bio-Science and Technology, Nagahama, Japan
| | - Kazunori Tachibana
- Graduate School of Bioscience, Tokyo Institute of Technology, Yokohama, Japan
| | - Masato Kiyomoto
- Marine and Coastal Research Center, Ochanomizu University, Tateyama, Japan
| | - Shonan Amemiya
- Marine and Coastal Research Center, Ochanomizu University, Tateyama, Japan
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan
- Research and Education Center of Natural Sciences, Keio University, Yokohama, Japan
| | - Hiroshi Wada
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| |
Collapse
|
9
|
Payne JL, Wagner A. Mechanisms of mutational robustness in transcriptional regulation. Front Genet 2015; 6:322. [PMID: 26579194 PMCID: PMC4621482 DOI: 10.3389/fgene.2015.00322] [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] [Received: 09/11/2015] [Accepted: 10/10/2015] [Indexed: 12/17/2022] Open
Abstract
Robustness is the invariance of a phenotype in the face of environmental or genetic change. The phenotypes produced by transcriptional regulatory circuits are gene expression patterns that are to some extent robust to mutations. Here we review several causes of this robustness. They include robustness of individual transcription factor binding sites, homotypic clusters of such sites, redundant enhancers, transcription factors, redundant transcription factors, and the wiring of transcriptional regulatory circuits. Such robustness can either be an adaptation by itself, a byproduct of other adaptations, or the result of biophysical principles and non-adaptive forces of genome evolution. The potential consequences of such robustness include complex regulatory network topologies that arise through neutral evolution, as well as cryptic variation, i.e., genotypic divergence without phenotypic divergence. On the longest evolutionary timescales, the robustness of transcriptional regulation has helped shape life as we know it, by facilitating evolutionary innovations that helped organisms such as flowering plants and vertebrates diversify.
Collapse
Affiliation(s)
- Joshua L Payne
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich Zurich, Switzerland ; Swiss Institute of Bioinformatics Lausanne, Switzerland
| | - Andreas Wagner
- Institute of Evolutionary Biology and Environmental Studies, University of Zurich Zurich, Switzerland ; Swiss Institute of Bioinformatics Lausanne, Switzerland ; The Santa Fe Institute Santa Fe, NM, USA
| |
Collapse
|
10
|
A pipeline for the systematic identification of non-redundant full-ORF cDNAs for polymorphic and evolutionary divergent genomes: Application to the ascidian Ciona intestinalis. Dev Biol 2015; 404:149-63. [PMID: 26025923 PMCID: PMC4528069 DOI: 10.1016/j.ydbio.2015.05.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2014] [Revised: 05/11/2015] [Accepted: 05/12/2015] [Indexed: 12/17/2022]
Abstract
Genome-wide resources, such as collections of cDNA clones encoding for complete proteins (full-ORF clones), are crucial tools for studying the evolution of gene function and genetic interactions. Non-model organisms, in particular marine organisms, provide a rich source of functional diversity. Marine organism genomes are, however, frequently highly polymorphic and encode proteins that diverge significantly from those of well-annotated model genomes. The construction of full-ORF clone collections from non-model organisms is hindered by the difficulty of predicting accurately the N-terminal ends of proteins, and distinguishing recent paralogs from highly polymorphic alleles. We report a computational strategy that overcomes these difficulties, and allows for accurate gene level clustering of transcript data followed by the automated identification of full-ORFs with correct 5'- and 3'-ends. It is robust to polymorphism, includes paralog calling and does not require evolutionary proximity to well annotated model organisms. We developed this pipeline for the ascidian Ciona intestinalis, a highly polymorphic member of the divergent sister group of the vertebrates, emerging as a powerful model organism to study chordate gene function, Gene Regulatory Networks and molecular mechanisms underlying human pathologies. Using this pipeline we have generated the first full-ORF collection for a highly polymorphic marine invertebrate. It contains 19,163 full-ORF cDNA clones covering 60% of Ciona coding genes, and full-ORF orthologs for approximately half of curated human disease-associated genes.
Collapse
|
11
|
Evolutionary meandering of intermolecular interactions along the drift barrier. Proc Natl Acad Sci U S A 2014; 112:E30-8. [PMID: 25535374 DOI: 10.1073/pnas.1421641112] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many cellular functions depend on highly specific intermolecular interactions, for example transcription factors and their DNA binding sites, microRNAs and their RNA binding sites, the interfaces between heterodimeric protein molecules, the stems in RNA molecules, and kinases and their response regulators in signal-transduction systems. Despite the need for complementarity between interacting partners, such pairwise systems seem to be capable of high levels of evolutionary divergence, even when subject to strong selection. Such behavior is a consequence of the diminishing advantages of increasing binding affinity between partners, the multiplicity of evolutionary pathways between selectively equivalent alternatives, and the stochastic nature of evolutionary processes. Because mutation pressure toward reduced affinity conflicts with selective pressure for greater interaction, situations can arise in which the expected distribution of the degree of matching between interacting partners is bimodal, even in the face of constant selection. Although biomolecules with larger numbers of interacting partners are subject to increased levels of evolutionary conservation, their more numerous partners need not converge on a single sequence motif or be increasingly constrained in more complex systems. These results suggest that most phylogenetic differences in the sequences of binding interfaces are not the result of adaptive fine tuning but a simple consequence of random genetic drift.
Collapse
|
12
|
Horvath JE, Ramachandran GL, Fedrigo O, Nielsen WJ, Babbitt CC, St Clair EM, Pfefferle LW, Jernvall J, Wray GA, Wall CE. Genetic comparisons yield insight into the evolution of enamel thickness during human evolution. J Hum Evol 2014; 73:75-87. [PMID: 24810709 DOI: 10.1016/j.jhevol.2014.01.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 10/29/2013] [Accepted: 01/09/2014] [Indexed: 12/29/2022]
Abstract
Enamel thickness varies substantially among extant hominoids and is a key trait with significance for interpreting dietary adaptation, life history trajectory, and phylogenetic relationships. There is a strong link in humans between enamel formation and mutations in the exons of the four genes that code for the enamel matrix proteins and the associated protease. The evolution of thick enamel in humans may have included changes in the regulation of these genes during tooth development. The cis-regulatory region in the 5' flank (upstream non-coding region) of MMP20, which codes for enamelysin, the predominant protease active during enamel secretion, has previously been shown to be under strong positive selection in the lineages leading to both humans and chimpanzees. Here we examine evidence for positive selection in the 5' flank and 3' flank of AMELX, AMBN, ENAM, and MMP20. We contrast the human sequence changes with other hominoids (chimpanzees, gorillas, orangutans, gibbons) and rhesus macaques (outgroup), a sample comprising a range of enamel thickness. We find no evidence for positive selection in the protein-coding regions of any of these genes. In contrast, we find strong evidence for positive selection in the 5' flank region of MMP20 and ENAM along the lineage leading to humans, and in both the 5' flank and 3' flank regions of MMP20 along the lineage leading to chimpanzees. We also identify putative transcription factor binding sites overlapping some of the species-specific nucleotide sites and we refine which sections of the up- and downstream putative regulatory regions are most likely to harbor important changes. These non-coding changes and their potential for differential regulation by transcription factors known to regulate tooth development may offer insight into the mechanisms that allow for rapid evolutionary changes in enamel thickness across closely-related species, and contribute to our understanding of the enamel phenotype in hominoids.
Collapse
Affiliation(s)
- Julie E Horvath
- North Carolina Museum of Natural Sciences, Nature Research Center, Raleigh, NC 27601, USA; Department of Biology, North Carolina Central University, Durham, NC 27707, USA; Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA; Duke Institute for Genome Sciences and Policy, Duke University, Durham, NC 27708, USA
| | | | - Olivier Fedrigo
- Duke Institute for Genome Sciences and Policy, Duke University, Durham, NC 27708, USA
| | | | - Courtney C Babbitt
- Duke Institute for Genome Sciences and Policy, Duke University, Durham, NC 27708, USA; Department of Biology, Duke University, Durham, NC 27708, USA
| | | | | | - Jukka Jernvall
- Institute for Biotechnology, University of Helsinki, Helsinki, Finland
| | - Gregory A Wray
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA; Duke Institute for Genome Sciences and Policy, Duke University, Durham, NC 27708, USA; Department of Biology, Duke University, Durham, NC 27708, USA
| | - Christine E Wall
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA.
| |
Collapse
|
13
|
Naturally occurring deletions of hunchback binding sites in the even-skipped stripe 3+7 enhancer. PLoS One 2014; 9:e91924. [PMID: 24786295 PMCID: PMC4006794 DOI: 10.1371/journal.pone.0091924] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 02/18/2014] [Indexed: 11/23/2022] Open
Abstract
Changes in regulatory DNA contribute to phenotypic differences within and between taxa. Comparative studies show that many transcription factor binding sites (TFBS) are conserved between species whereas functional studies reveal that some mutations segregating within species alter TFBS function. Consistently, in this analysis of 13 regulatory elements in Drosophila melanogaster populations, single base and insertion/deletion polymorphism are rare in characterized regulatory elements. Experimentally defined TFBS are nearly devoid of segregating mutations and, as has been shown before, are quite conserved. For instance 8 of 11 Hunchback binding sites in the stripe 3+7 enhancer of even-skipped are conserved between D. melanogaster and Drosophila virilis. Oddly, we found a 72 bp deletion that removes one of these binding sites (Hb8), segregating within D. melanogaster. Furthermore, a 45 bp deletion polymorphism in the spacer between the stripe 3+7 and stripe 2 enhancers, removes another predicted Hunchback site. These two deletions are separated by ∼250 bp, sit on distinct haplotypes, and segregate at appreciable frequency. The Hb8Δ is at 5 to 35% frequency in the new world, but also shows cosmopolitan distribution. There is depletion of sequence variation on the Hb8Δ-carrying haplotype. Quantitative genetic tests indicate that Hb8Δ affects developmental time, but not viability of offspring. The Eve expression pattern differs between inbred lines, but the stripe 3 and 7 boundaries seem unaffected by Hb8Δ. The data reveal segregating variation in regulatory elements, which may reflect evolutionary turnover of characterized TFBS due to drift or co-evolution.
Collapse
|
14
|
Koga H, Morino Y, Wada H. The echinoderm larval skeleton as a possible model system for experimental evolutionary biology. Genesis 2014; 52:186-92. [PMID: 24549940 DOI: 10.1002/dvg.22758] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 02/12/2014] [Accepted: 02/14/2014] [Indexed: 01/29/2023]
Abstract
The evolution of various body plans results from the acquisition of novel structures as well as the loss of existing structures. Some novel structures necessitate multiple evolutionary steps, requiring organisms to overcome the intermediate steps, which might be less adaptive or neutral. To examine this issue, echinoderms might provide an ideal experimental system. A larval skeleton is acquired in some echinoderm lineages, such as sea urchins, probably via the co-option of the skeletogenic machinery that was already established to produce the adult skeleton. The acquisition of a larval skeleton was found to require multiple steps and so provides a model experimental system for reproducing intermediate evolutionary stages. The fact that echinoderm embryology has been studied with various natural populations also presents an advantage.
Collapse
Affiliation(s)
- Hiroyuki Koga
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennodai, Tsukuba, Japan
| | | | | |
Collapse
|
15
|
Garfield DA, Runcie DE, Babbitt CC, Haygood R, Nielsen WJ, Wray GA. The impact of gene expression variation on the robustness and evolvability of a developmental gene regulatory network. PLoS Biol 2013; 11:e1001696. [PMID: 24204211 PMCID: PMC3812118 DOI: 10.1371/journal.pbio.1001696] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 09/16/2013] [Indexed: 11/18/2022] Open
Abstract
Regulatory interactions buffer development against genetic and environmental perturbations, but adaptation requires phenotypes to change. We investigated the relationship between robustness and evolvability within the gene regulatory network underlying development of the larval skeleton in the sea urchin Strongylocentrotus purpuratus. We find extensive variation in gene expression in this network throughout development in a natural population, some of which has a heritable genetic basis. Switch-like regulatory interactions predominate during early development, buffer expression variation, and may promote the accumulation of cryptic genetic variation affecting early stages. Regulatory interactions during later development are typically more sensitive (linear), allowing variation in expression to affect downstream target genes. Variation in skeletal morphology is associated primarily with expression variation of a few, primarily structural, genes at terminal positions within the network. These results indicate that the position and properties of gene interactions within a network can have important evolutionary consequences independent of their immediate regulatory role.
Collapse
Affiliation(s)
- David A. Garfield
- Department of Biology, Duke University, Durham, North Carolina, United States of America
| | - Daniel E. Runcie
- Department of Biology, Duke University, Durham, North Carolina, United States of America
| | - Courtney C. Babbitt
- Department of Biology, Duke University, Durham, North Carolina, United States of America
- Institute for Genome Sciences & Policy, Duke University, Durham, North Carolina, United States of America
| | - Ralph Haygood
- Department of Biology, Duke University, Durham, North Carolina, United States of America
- Center for Systems Biology, Duke University, Durham, North Carolina, United States of America
| | - William J. Nielsen
- Department of Biology, Duke University, Durham, North Carolina, United States of America
- Institute for Genome Sciences & Policy, Duke University, Durham, North Carolina, United States of America
| | - Gregory A. Wray
- Department of Biology, Duke University, Durham, North Carolina, United States of America
- Institute for Genome Sciences & Policy, Duke University, Durham, North Carolina, United States of America
- Center for Systems Biology, Duke University, Durham, North Carolina, United States of America
- * E-mail:
| |
Collapse
|
16
|
Pespeni MH, Chan F, Menge BA, Palumbi SR. Signs of adaptation to local pH conditions across an environmental mosaic in the California Current Ecosystem. Integr Comp Biol 2013; 53:857-70. [PMID: 23980118 DOI: 10.1093/icb/ict094] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Little is known about the potential for rapid evolution in natural populations in response to the high rate of contemporary climatic change. Organisms that have evolved in environments that experience high variability across space and time are of particular interest as they may harbor genetic variation that can facilitate evolutionary response to changing conditions. Here we review what is known about genetic capacity for adaptation in the purple sea urchin, Strongylocentrotus purpuratus, a species that has evolved in the upwelling ecosystem of the Northeast Pacific Ocean. We also present new results testing for adaptation to local pH conditions in six populations from Oregon to southern California. We integrate data on 19,493 genetic polymorphisms with data on local pH conditions. We find correlations between allele frequency and rank average time spent at pH <7.8 in 318 single-nucleotide polymorphisms in 275 genes. Two of the genes most correlated with local pH are a protein associated with the cytoskeleton and a proton pump, with functional roles in maintenance of cell volume and with internal regulation of pH, respectively. Across all loci tested, high correlations with local pH were concentrated in genes related to transport of ions, biomineralization, lipid metabolism, and cell-cell adhesion, functional pathways important for maintaining homeostasis at low pH. We identify a set of seven genes as top candidates for rapid evolutionary response to acidification of the ocean. In these genes, the putative low-pH-adapted allele, based on allele frequencies in natural populations, rapidly increases in frequency in purple sea urchin larvae raised at low pH. We also found that populations from localities with high pH show a greater change in allele frequency toward putative low-pH-adapted alleles under experimental acidification, compared with low-pH populations, suggesting that both natural and artificial selection favor the same alleles for response to low pH. These results illustrate that purple sea urchins may be adapted to local pH and suggest that this species may possess the genetic capacity for rapid evolution in response to acidification. This adaptive capacity likely comes from standing genetic variation maintained in nature by balancing selection across the spatial and temporal environmental mosaic that characterizes the California Current Ecosystem.
Collapse
Affiliation(s)
- M H Pespeni
- *Department of Biology, Indiana University, Bloomington, IN 47405, USA; Department of Zoology, Oregon State University, Corvallis, OR 97331, USA; Department of Biology, Stanford University, Hopkins Marine Station, Pacific Grove, CA 93950, USA
| | | | | | | |
Collapse
|
17
|
Backström N, Shipilina D, Blom MPK, Edwards SV. Cis-regulatory sequence variation and association with Mycoplasma load in natural populations of the house finch (Carpodacus mexicanus). Ecol Evol 2013; 3:655-66. [PMID: 23532859 PMCID: PMC3605853 DOI: 10.1002/ece3.484] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 12/17/2012] [Accepted: 12/24/2012] [Indexed: 01/19/2023] Open
Abstract
Characterization of the genetic basis of fitness traits in natural populations is important for understanding how organisms adapt to the changing environment and to novel events, such as epizootics. However, candidate fitness-influencing loci, such as regulatory regions, are usually unavailable in nonmodel species. Here, we analyze sequence data from targeted resequencing of the cis-regulatory regions of three candidate genes for disease resistance (CD74, HSP90α, and LCP1) in populations of the house finch (Carpodacus mexicanus) historically exposed (Alabama) and naïve (Arizona) to Mycoplasma gallisepticum. Our study, the first to quantify variation in regulatory regions in wild birds, reveals that the upstream regions of CD74 and HSP90α are GC-rich, with the former exhibiting unusually low sequence variation for this species. We identified two SNPs, located in a GC-rich region immediately upstream of an inferred promoter site in the gene HSP90α, that were significantly associated with Mycoplasma pathogen load in the two populations. The SNPs are closely linked and situated in potential regulatory sequences: one in a binding site for the transcription factor nuclear NFYα and the other in a dinucleotide microsatellite ((GC)6). The genotype associated with pathogen load in the putative NFYα binding site was significantly overrepresented in the Alabama birds. However, we did not see strong effects of selection at this SNP, perhaps because selection has acted on standing genetic variation over an extremely short time in a highly recombining region. Our study is a useful starting point to explore functional relationships between sequence polymorphisms, gene expression, and phenotypic traits, such as pathogen resistance that affect fitness in the wild.
Collapse
Affiliation(s)
- Niclas Backström
- Department of Organismic and Evolutionary Biology (OEB), Museum of Comparative Zoology (MCZ), Harvard University26 Oxford Street, Cambridge, MA, 02138
| | - Daria Shipilina
- Department of Organismic and Evolutionary Biology (OEB), Museum of Comparative Zoology (MCZ), Harvard University26 Oxford Street, Cambridge, MA, 02138
| | - Mozes P K Blom
- Department of Organismic and Evolutionary Biology (OEB), Museum of Comparative Zoology (MCZ), Harvard University26 Oxford Street, Cambridge, MA, 02138
| | - Scott V Edwards
- Department of Organismic and Evolutionary Biology (OEB), Museum of Comparative Zoology (MCZ), Harvard University26 Oxford Street, Cambridge, MA, 02138
| |
Collapse
|
18
|
Spivakov M, Akhtar J, Kheradpour P, Beal K, Girardot C, Koscielny G, Herrero J, Kellis M, Furlong EEM, Birney E. Analysis of variation at transcription factor binding sites in Drosophila and humans. Genome Biol 2012; 13:R49. [PMID: 22950968 PMCID: PMC3491393 DOI: 10.1186/gb-2012-13-9-r49] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2012] [Revised: 05/23/2012] [Accepted: 06/08/2012] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Advances in sequencing technology have boosted population genomics and made it possible to map the positions of transcription factor binding sites (TFBSs) with high precision. Here we investigate TFBS variability by combining transcription factor binding maps generated by ENCODE, modENCODE, our previously published data and other sources with genomic variation data for human individuals and Drosophila isogenic lines. RESULTS We introduce a metric of TFBS variability that takes into account changes in motif match associated with mutation and makes it possible to investigate TFBS functional constraints instance-by-instance as well as in sets that share common biological properties. We also take advantage of the emerging per-individual transcription factor binding data to show evidence that TFBS mutations, particularly at evolutionarily conserved sites, can be efficiently buffered to ensure coherent levels of transcription factor binding. CONCLUSIONS Our analyses provide insights into the relationship between individual and interspecies variation and show evidence for the functional buffering of TFBS mutations in both humans and flies. In a broad perspective, these results demonstrate the potential of combining functional genomics and population genetics approaches for understanding gene regulation.
Collapse
Affiliation(s)
- Mikhail Spivakov
- European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridgeshire, CB10 1SD, UK.
| | | | | | | | | | | | | | | | | | | |
Collapse
|