1
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Tran TC, Mähl K, Kappel C, Dakhiya Y, Sampathkumar A, Sicard A, Lenhard M. Altered interactions between cis-regulatory elements partially resolve BLADE-ON-PETIOLE genetic redundancy in Capsella rubella. THE PLANT CELL 2024; 36:4637-4657. [PMID: 39158598 PMCID: PMC11448885 DOI: 10.1093/plcell/koae232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2023] [Revised: 07/12/2024] [Accepted: 07/16/2024] [Indexed: 08/20/2024]
Abstract
Duplicated genes are thought to follow one of three evolutionary trajectories that resolve their redundancy: neofunctionalization, subfunctionalization, or pseudogenization. Differences in expression patterns have been documented for many duplicated gene pairs and interpreted as evidence of subfunctionalization and a loss of redundancy. However, little is known about the functional impact of such differences and about their molecular basis. Here, we investigate the genetic and molecular basis for the partial loss of redundancy between the two BLADE-ON-PETIOLE genes BOP1 and BOP2 in red shepherd's purse (Capsella rubella) compared to Arabidopsis (Arabidopsis thaliana). While both genes remain almost fully redundant in A. thaliana, BOP1 in C. rubella can no longer ensure wild-type floral organ numbers and suppress bract formation, due to an altered expression pattern in the region of the cryptic bract primordium. We use two complementary approaches, transgenic rescue of A. thaliana atbop1 atbop2 double mutants and deletions in the endogenous AtBOP1 promoter, to demonstrate that several BOP1 promoter regions containing conserved noncoding sequences interact in a nonadditive manner to control BOP1 expression in the bract primordium and that changes in these interactions underlie the evolutionary divergence between C. rubella and A. thaliana BOP1 expression and activity. Similarly, altered interactions between cis-regulatory regions underlie the divergence in functional promoter architecture related to the control of floral organ abscission by BOP1. These findings highlight the complexity of promoter architecture in plants and suggest that changes in the interactions between cis-regulatory elements are key drivers for evolutionary divergence in gene expression and the loss of redundancy.
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Affiliation(s)
- Thi Chi Tran
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam-Golm D-14476, Germany
| | - Karoline Mähl
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam-Golm D-14476, Germany
| | - Christian Kappel
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam-Golm D-14476, Germany
| | - Yuri Dakhiya
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam-Golm D-14476, Germany
| | - Arun Sampathkumar
- Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm D-14476, Germany
| | - Adrien Sicard
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam-Golm D-14476, Germany
| | - Michael Lenhard
- Institute for Biochemistry and Biology, University of Potsdam, Potsdam-Golm D-14476, Germany
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2
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Kocher AA, Dutrow EV, Uebbing S, Yim KM, Rosales Larios MF, Baumgartner M, Nottoli T, Noonan JP. CpG island turnover events predict evolutionary changes in enhancer activity. Genome Biol 2024; 25:156. [PMID: 38872220 PMCID: PMC11170920 DOI: 10.1186/s13059-024-03300-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 06/04/2024] [Indexed: 06/15/2024] Open
Abstract
BACKGROUND Genetic changes that modify the function of transcriptional enhancers have been linked to the evolution of biological diversity across species. Multiple studies have focused on the role of nucleotide substitutions, transposition, and insertions and deletions in altering enhancer function. CpG islands (CGIs) have recently been shown to influence enhancer activity, and here we test how their turnover across species contributes to enhancer evolution. RESULTS We integrate maps of CGIs and enhancer activity-associated histone modifications obtained from multiple tissues in nine mammalian species and find that CGI content in enhancers is strongly associated with increased histone modification levels. CGIs show widespread turnover across species and species-specific CGIs are strongly enriched for enhancers exhibiting species-specific activity across all tissues and species. Genes associated with enhancers with species-specific CGIs show concordant biases in their expression, supporting that CGI turnover contributes to gene regulatory innovation. Our results also implicate CGI turnover in the evolution of Human Gain Enhancers (HGEs), which show increased activity in human embryonic development and may have contributed to the evolution of uniquely human traits. Using a humanized mouse model, we show that a highly conserved HGE with a large CGI absent from the mouse ortholog shows increased activity at the human CGI in the humanized mouse diencephalon. CONCLUSIONS Collectively, our results point to CGI turnover as a mechanism driving gene regulatory changes potentially underlying trait evolution in mammals.
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Affiliation(s)
- Acadia A Kocher
- Department of Genetics, Yale School of Medicine, New Haven, CT, 06510, USA
- Division of Molecular Genetics and Oncode Institute, Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - Emily V Dutrow
- Department of Genetics, Yale School of Medicine, New Haven, CT, 06510, USA
- Zoetis, Inc, 333 Portage St, Kalamazoo, MI, 49007, USA
| | - Severin Uebbing
- Department of Genetics, Yale School of Medicine, New Haven, CT, 06510, USA
- Genome Biology and Epigenetics, Institute of Biodynamics and Biocomplexity, Department of Biology, Utrecht University, Utrecht, The Netherlands
| | - Kristina M Yim
- Department of Genetics, Yale School of Medicine, New Haven, CT, 06510, USA
| | | | | | - Timothy Nottoli
- Department of Comparative Medicine, Yale School of Medicine, New Haven, CT, 06510, USA
- Yale Genome Editing Center, Yale School of Medicine, New Haven, CT, 06510, USA
| | - James P Noonan
- Department of Genetics, Yale School of Medicine, New Haven, CT, 06510, USA.
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, 06520, USA.
- Department of Neuroscience, Yale School of Medicine, New Haven, CT, 06510, USA.
- Wu Tsai Institute, Yale University, New Haven, CT, 06510, USA.
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3
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Li XC, Gandara L, Ekelöf M, Richter K, Alexandrov T, Crocker J. Rapid response of fly populations to gene dosage across development and generations. Nat Commun 2024; 15:4551. [PMID: 38811562 PMCID: PMC11137061 DOI: 10.1038/s41467-024-48960-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 05/17/2024] [Indexed: 05/31/2024] Open
Abstract
Although the effects of genetic and environmental perturbations on multicellular organisms are rarely restricted to single phenotypic layers, our current understanding of how developmental programs react to these challenges remains limited. Here, we have examined the phenotypic consequences of disturbing the bicoid regulatory network in early Drosophila embryos. We generated flies with two extra copies of bicoid, which causes a posterior shift of the network's regulatory outputs and a decrease in fitness. We subjected these flies to EMS mutagenesis, followed by experimental evolution. After only 8-15 generations, experimental populations have normalized patterns of gene expression and increased survival. Using a phenomics approach, we find that populations were normalized through rapid increases in embryo size driven by maternal changes in metabolism and ovariole development. We extend our results to additional populations of flies, demonstrating predictability. Together, our results necessitate a broader view of regulatory network evolution at the systems level.
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Affiliation(s)
- Xueying C Li
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.
- College of Life Sciences, Beijing Normal University, Beijing, China.
| | - Lautaro Gandara
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | - Måns Ekelöf
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | - Kerstin Richter
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
| | - Theodore Alexandrov
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany
- Molecular Medicine Partnership Unit between EMBL and Heidelberg University, Heidelberg, Germany
- BioInnovation Institute, Copenhagen, Denmark
| | - Justin Crocker
- European Molecular Biology Laboratory (EMBL), Heidelberg, Germany.
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4
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Ciren D, Zebell S, Lippman ZB. Extreme restructuring of cis-regulatory regions controlling a deeply conserved plant stem cell regulator. PLoS Genet 2024; 20:e1011174. [PMID: 38437180 PMCID: PMC10911594 DOI: 10.1371/journal.pgen.1011174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Accepted: 02/07/2024] [Indexed: 03/06/2024] Open
Abstract
A striking paradox is that genes with conserved protein sequence, function and expression pattern over deep time often exhibit extremely divergent cis-regulatory sequences. It remains unclear how such drastic cis-regulatory evolution across species allows preservation of gene function, and to what extent these differences influence how cis-regulatory variation arising within species impacts phenotypic change. Here, we investigated these questions using a plant stem cell regulator conserved in expression pattern and function over ~125 million years. Using in-vivo genome editing in two distantly related models, Arabidopsis thaliana (Arabidopsis) and Solanum lycopersicum (tomato), we generated over 70 deletion alleles in the upstream and downstream regions of the stem cell repressor gene CLAVATA3 (CLV3) and compared their individual and combined effects on a shared phenotype, the number of carpels that make fruits. We found that sequences upstream of tomato CLV3 are highly sensitive to even small perturbations compared to its downstream region. In contrast, Arabidopsis CLV3 function is tolerant to severe disruptions both upstream and downstream of the coding sequence. Combining upstream and downstream deletions also revealed a different regulatory outcome. Whereas phenotypic enhancement from adding downstream mutations was predominantly weak and additive in tomato, mutating both regions of Arabidopsis CLV3 caused substantial and synergistic effects, demonstrating distinct distribution and redundancy of functional cis-regulatory sequences. Our results demonstrate remarkable malleability in cis-regulatory structural organization of a deeply conserved plant stem cell regulator and suggest that major reconfiguration of cis-regulatory sequence space is a common yet cryptic evolutionary force altering genotype-to-phenotype relationships from regulatory variation in conserved genes. Finally, our findings underscore the need for lineage-specific dissection of the spatial architecture of cis-regulation to effectively engineer trait variation from conserved productivity genes in crops.
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Affiliation(s)
- Danielle Ciren
- Cold Spring Harbor Laboratory, School of Biological Sciences, Cold Spring Harbor, New York, United States of America
| | - Sophia Zebell
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
- Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
| | - Zachary B Lippman
- Cold Spring Harbor Laboratory, School of Biological Sciences, Cold Spring Harbor, New York, United States of America
- Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
- Howard Hughes Medical Institute, Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America
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5
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Sabarís G, Ortíz DM, Laiker I, Mayansky I, Naik S, Cavalli G, Stern DL, Preger-Ben Noon E, Frankel N. The Density of Regulatory Information Is a Major Determinant of Evolutionary Constraint on Noncoding DNA in Drosophila. Mol Biol Evol 2024; 41:msae004. [PMID: 38364113 PMCID: PMC10871701 DOI: 10.1093/molbev/msae004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 11/26/2023] [Accepted: 01/05/2024] [Indexed: 02/18/2024] Open
Abstract
Evolutionary analyses have estimated that ∼60% of nucleotides in intergenic regions of the Drosophila melanogaster genome are functionally relevant, suggesting that regulatory information may be encoded more densely in intergenic regions than has been revealed by most functional dissections of regulatory DNA. Here, we approached this issue through a functional dissection of the regulatory region of the gene shavenbaby (svb). Most of the ∼90 kb of this large regulatory region is highly conserved in the genus Drosophila, though characterized enhancers occupy a small fraction of this region. By analyzing the regulation of svb in different contexts of Drosophila development, we found that the regulatory information that drives svb expression in the abdominal pupal epidermis is organized in a different way than the elements that drive svb expression in the embryonic epidermis. While in the embryonic epidermis svb is activated by compact enhancers separated by large inactive DNA regions, svb expression in the pupal epidermis is driven by regulatory information distributed over broader regions of svb cis-regulatory DNA. In the same vein, we observed that other developmental genes also display a dense distribution of putative regulatory elements in their regulatory regions. Furthermore, we found that a large percentage of conserved noncoding DNA of the Drosophila genome is contained within regions of open chromatin. These results suggest that part of the evolutionary constraint on noncoding DNA of Drosophila is explained by the density of regulatory information, which may be greater than previously appreciated.
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Affiliation(s)
- Gonzalo Sabarís
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires (UBA), Buenos Aires 1428, Argentina
- Institute of Human Genetics, UMR 9002 CNRS-Université de Montpellier, Montpellier, France
| | - Daniela M Ortíz
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires (UBA), Buenos Aires 1428, Argentina
| | - Ian Laiker
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires (UBA), Buenos Aires 1428, Argentina
| | - Ignacio Mayansky
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires (UBA), Buenos Aires 1428, Argentina
| | - Sujay Naik
- Department of Genetics and Developmental Biology, The Rappaport Faculty of Medicine and Research Institute, Technion—Israel Institute of Technology, Haifa 3109601, Israel
| | - Giacomo Cavalli
- Institute of Human Genetics, UMR 9002 CNRS-Université de Montpellier, Montpellier, France
| | - David L Stern
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA 20147, USA
| | - Ella Preger-Ben Noon
- Department of Genetics and Developmental Biology, The Rappaport Faculty of Medicine and Research Institute, Technion—Israel Institute of Technology, Haifa 3109601, Israel
| | - Nicolás Frankel
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad de Buenos Aires (UBA), Buenos Aires 1428, Argentina
- Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales (FCEN), Universidad de Buenos Aires (UBA), Buenos Aires 1428, Argentina
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6
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Bachem K, Li X, Ceolin S, Mühling B, Hörl D, Harz H, Leonhardt H, Arnoult L, Weber S, Matarlo B, Prud’homme B, Gompel N. Regulatory evolution tuning pigmentation intensity quantitatively in Drosophila. SCIENCE ADVANCES 2024; 10:eadl2616. [PMID: 38266088 PMCID: PMC10807792 DOI: 10.1126/sciadv.adl2616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Accepted: 12/21/2023] [Indexed: 01/26/2024]
Abstract
Quantitative variation in attributes such as color, texture, or stiffness dominates morphological diversification. It results from combinations of alleles at many Mendelian loci. Here, we identify an additional source of quantitative variation among species, continuous evolution in a gene regulatory region. Specifically, we examined the modulation of wing pigmentation in a group of fly species and showed that inter-species variation correlated with the quantitative expression of the pigmentation gene yellow. This variation results from an enhancer of yellow determining darkness through species-specific activity. We mapped the divergent activities between two sister species and found the changes to be broadly distributed along the enhancer. Our results demonstrate that enhancers can act as dials fueling quantitative morphological diversification by modulating trait properties.
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Affiliation(s)
- Katharina Bachem
- Department of Evolutionary Ecology, Ludwig-Maximilians Universität München, München 82152, Germany
| | - Xinyi Li
- Department of Evolutionary Ecology, Ludwig-Maximilians Universität München, München 82152, Germany
| | - Stefano Ceolin
- Department of Evolutionary Ecology, Ludwig-Maximilians Universität München, München 82152, Germany
| | - Bettina Mühling
- Department of Evolutionary Ecology, Ludwig-Maximilians Universität München, München 82152, Germany
| | - David Hörl
- Human Biology and Bioimaging, Ludwig-Maximilians Universität München, München 82152, Germany
| | - Hartmann Harz
- Human Biology and Bioimaging, Ludwig-Maximilians Universität München, München 82152, Germany
| | - Heinrich Leonhardt
- Human Biology and Bioimaging, Ludwig-Maximilians Universität München, München 82152, Germany
| | - Laurent Arnoult
- Institut de Biologie du Développement de Marseille, Aix-Marseille Université, Marseille 13288, France
| | - Sabrina Weber
- Department of Evolutionary Ecology, Ludwig-Maximilians Universität München, München 82152, Germany
| | - Blair Matarlo
- Department of Evolutionary Ecology, Ludwig-Maximilians Universität München, München 82152, Germany
| | - Benjamin Prud’homme
- Institut de Biologie du Développement de Marseille, Aix-Marseille Université, Marseille 13288, France
| | - Nicolas Gompel
- Department of Evolutionary Ecology, Ludwig-Maximilians Universität München, München 82152, Germany
- Bonn Institute for Organismic Biology, University of Bonn, Bonn 53115, Germany
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7
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Ciren D, Zebell S, Lippman ZB. Extreme restructuring of cis -regulatory regions controlling a deeply conserved plant stem cell regulator. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.20.572550. [PMID: 38187729 PMCID: PMC10769289 DOI: 10.1101/2023.12.20.572550] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
A striking paradox is that genes with conserved protein sequence, function and expression pattern over deep time often exhibit extremely divergent cis -regulatory sequences. It remains unclear how such drastic cis -regulatory evolution across species allows preservation of gene function, and to what extent these differences influence how cis- regulatory variation arising within species impacts phenotypic change. Here, we investigated these questions using a plant stem cell regulator conserved in expression pattern and function over ∼125 million years. Using in-vivo genome editing in two distantly related models, Arabidopsis thaliana (Arabidopsis) and Solanum lycopersicum (tomato), we generated over 70 deletion alleles in the upstream and downstream regions of the stem cell repressor gene CLAVATA3 ( CLV3 ) and compared their individual and combined effects on a shared phenotype, the number of carpels that make fruits. We found that sequences upstream of tomato CLV3 are highly sensitive to even small perturbations compared to its downstream region. In contrast, Arabidopsis CLV3 function is tolerant to severe disruptions both upstream and downstream of the coding sequence. Combining upstream and downstream deletions also revealed a different regulatory outcome. Whereas phenotypic enhancement from adding downstream mutations was predominantly weak and additive in tomato, mutating both regions of Arabidopsis CLV3 caused substantial and synergistic effects, demonstrating distinct distribution and redundancy of functional cis -regulatory sequences. Our results demonstrate remarkable malleability in cis -regulatory structural organization of a deeply conserved plant stem cell regulator and suggest that major reconfiguration of cis -regulatory sequence space is a common yet cryptic evolutionary force altering genotype-to-phenotype relationships from regulatory variation in conserved genes. Finally, our findings underscore the need for lineage-specific dissection of the spatial architecture of cis -regulation to effectively engineer trait variation from conserved productivity genes in crops. Author summary We investigated the evolution of cis -regulatory elements (CREs) and their interactions in the regulation of a plant stem cell regulator gene, CLAVATA3 (CLV3) , in Arabidopsis and tomato. Despite diverging ∼125 million years ago, the function and expression of CLV3 is conserved in these species; however, cis -regulatory sequences upstream and downstream have drastically diverged, preventing identification of conserved non-coding sequences between them. We used CRISPR-Cas9 to engineer dozens of mutations within the cis -regulatory regions of Arabidopsis and tomato CLV3. In tomato, our results show that tomato CLV3 function primarily relies on interactions among CREs in the 5' non-coding region, unlike Arabidopsis CLV3 , which depends on a more balanced distribution of functional CREs between the 5' and 3' regions. Therefore, despite a high degree of functional conservation, our study demonstrates divergent regulatory strategies between two distantly related CLV3 orthologs, with substantial alterations in regulatory sequences, their spatial arrangement, and their relative effects on CLV3 regulation. These results suggest that regulatory regions are not only extremely robust to mutagenesis, but also that the sequences underlying this robustness can be lineage-specific for conserved genes, due to the complex and often redundant interactions among CREs that ensure proper gene function amidst large-scale sequence turnover.
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8
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Wang Z, Peng C, Wu W, Yan C, Lv Y, Li JT. Developmental regulation of conserved non-coding element evolution provides insights into limb loss in squamates. SCIENCE CHINA. LIFE SCIENCES 2023; 66:2399-2414. [PMID: 37256419 DOI: 10.1007/s11427-023-2362-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 05/09/2023] [Indexed: 06/01/2023]
Abstract
Limb loss shows recurrent phenotypic evolution across squamate lineages. Here, based on three de novo-assembled genomes of limbless lizards from different lineages, we showed that divergence of conserved non-coding elements (CNEs) played an important role in limb development. These CNEs were associated with genes required for limb initiation and outgrowth, and with regulatory signals in the early stage of limb development. Importantly, we identified the extensive existence of insertions and deletions (InDels) in the CNEs, with the numbers ranging from 111 to 756. Most of these CNEs with InDels were lineage-specific in the limbless squamates. Nearby genes of these InDel CNEs were important to early limb formation, such as Tbx4, Fgf10, and Gli3. Based on functional experiments, we found that nucleotide mutations and InDels both affected the regulatory function of the CNEs. Our study provides molecular evidence underlying limb loss in squamate reptiles from a developmental perspective and sheds light on the importance of regulatory element InDels in phenotypic evolution.
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Affiliation(s)
- Zeng Wang
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & h Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Changjun Peng
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & h Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Wei Wu
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & h Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chaochao Yan
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & h Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
| | - Yunyun Lv
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & h Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China
- College of Life Science, Neijiang Normal University, Neijiang, 641100, China
| | - Jia-Tang Li
- CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & h Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
- Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences, Yezin Nay Pyi Taw, 05282, Myanmar.
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9
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Li XC, Fuqua T, van Breugel ME, Crocker J. Mutational scans reveal differential evolvability of Drosophila promoters and enhancers. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220054. [PMID: 37004721 PMCID: PMC10067265 DOI: 10.1098/rstb.2022.0054] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2023] Open
Abstract
Rapid enhancer and slow promoter evolution have been demonstrated through comparative genomics. However, it is not clear how this information is encoded genetically and if this can be used to place evolution in a predictive context. Part of the challenge is that our understanding of the potential for regulatory evolution is biased primarily toward natural variation or limited experimental perturbations. Here, to explore the evolutionary capacity of promoter variation, we surveyed an unbiased mutation library for three promoters in Drosophila melanogaster. We found that mutations in promoters had limited to no effect on spatial patterns of gene expression. Compared to developmental enhancers, promoters are more robust to mutations and have more access to mutations that can increase gene expression, suggesting that their low activity might be a result of selection. Consistent with these observations, increasing the promoter activity at the endogenous locus of shavenbaby led to increased transcription yet limited phenotypic changes. Taken together, developmental promoters may encode robust transcriptional outputs allowing evolvability through the integration of diverse developmental enhancers. This article is part of the theme issue ‘Interdisciplinary approaches to predicting evolutionary biology’.
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Affiliation(s)
- Xueying C. Li
- European Molecular Biology Laboratory, Heidelberg, Baden-Württemberg 69117, Germany
| | - Timothy Fuqua
- European Molecular Biology Laboratory, Heidelberg, Baden-Württemberg 69117, Germany
| | | | - Justin Crocker
- European Molecular Biology Laboratory, Heidelberg, Baden-Württemberg 69117, Germany
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10
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Kocher AA, Dutrow EV, Uebbing S, Yim KM, Larios MFR, Baumgartner M, Nottoli T, Noonan JP. CpG island turnover events predict evolutionary changes in enhancer activity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.09.540063. [PMID: 37214934 PMCID: PMC10197647 DOI: 10.1101/2023.05.09.540063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Genetic changes that modify the function of transcriptional enhancers have been linked to the evolution of biological diversity across species. Multiple studies have focused on the role of nucleotide substitutions, transposition, and insertions and deletions in altering enhancer function. Here we show that turnover of CpG islands (CGIs), which contribute to enhancer activation, is broadly associated with changes in enhancer activity across mammals, including humans. We integrated maps of CGIs and enhancer activity-associated histone modifications obtained from multiple tissues in nine mammalian species and found that CGI content in enhancers was strongly associated with increased histone modification levels. CGIs showed widespread turnover across species and species-specific CGIs were strongly enriched for enhancers exhibiting species-specific activity across all tissues and species we examined. Genes associated with enhancers with species-specific CGIs showed concordant biases in their expression, supporting that CGI turnover contributes to gene regulatory innovation. Our results also implicate CGI turnover in the evolution of Human Gain Enhancers (HGEs), which show increased activity in human embryonic development and may have contributed to the evolution of uniquely human traits. Using a humanized mouse model, we show that a highly conserved HGE with a large CGI absent from the mouse ortholog shows increased activity at the human CGI in the humanized mouse diencephalon. Collectively, our results point to CGI turnover as a mechanism driving gene regulatory changes potentially underlying trait evolution in mammals.
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Affiliation(s)
- Acadia A. Kocher
- Department of Genetics, Yale School of Medicine, New Haven CT 06510, USA
| | - Emily V. Dutrow
- Department of Genetics, Yale School of Medicine, New Haven CT 06510, USA
- Present address: Cancer Genetics and Comparative Genomics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Severin Uebbing
- Department of Genetics, Yale School of Medicine, New Haven CT 06510, USA
| | - Kristina M. Yim
- Department of Genetics, Yale School of Medicine, New Haven CT 06510, USA
| | | | | | - Timothy Nottoli
- Department of Comparative Medicine, Yale School of Medicine, New Haven, CT 06510, USA
- Yale Genome Editing Center, Yale School of Medicine, New Haven, CT 06510, USA
| | - James P. Noonan
- Department of Genetics, Yale School of Medicine, New Haven CT 06510, USA
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520, USA
- Department of Neuroscience, Yale School of Medicine, New Haven, CT 06510, USA
- Wu Tsai Institute, Yale University, New Haven, CT 06510, USA
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11
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Murugesan SN, Monteiro A. Evolution of modular and pleiotropic enhancers. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART B, MOLECULAR AND DEVELOPMENTAL EVOLUTION 2023; 340:105-115. [PMID: 35334158 DOI: 10.1002/jez.b.23131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 01/14/2022] [Accepted: 02/28/2022] [Indexed: 11/05/2022]
Abstract
Cis-regulatory elements (CREs), or enhancers, are segments of noncoding DNA that regulate the spatial and temporal expression of nearby genes. Sometimes, genes are expressed in more than one tissue, and this can be driven by two main types of CREs: tissue-specific "modular" CREs, where different CREs drive expression of the gene in the different tissues, or by "pleiotropic" CREs, where the same CRE drives expression in the different tissues. In this perspective, we will discuss some of the ways (i) modular and pleiotropic CREs might originate; (ii) propose that modular CREs might derive from pleiotropic CREs via a process of duplication, degeneration, and complementation (the CRE-DDC model); and (iii) propose that hotspot loci of evolution are associated with the origin of modular CREs belonging to any gene in a regulatory network.
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Affiliation(s)
- Suriya N Murugesan
- Department of Biological Sciences, National University of Singapore, Singapore
| | - Antónia Monteiro
- Department of Biological Sciences, National University of Singapore, Singapore.,Division of Science, Yale-NUS College, Singapore
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12
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Ling L, Mühling B, Jaenichen R, Gompel N. Increased chromatin accessibility promotes the evolution of a transcriptional silencer in Drosophila. SCIENCE ADVANCES 2023; 9:eade6529. [PMID: 36800429 PMCID: PMC9937571 DOI: 10.1126/sciadv.ade6529] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Accepted: 01/17/2023] [Indexed: 06/18/2023]
Abstract
The loss of discrete morphological traits, the most common evolutionary transition, is typically driven by changes in developmental gene expression. Mutations accumulating in regulatory elements of these genes can disrupt DNA binding sites for transcription factors patterning their spatial expression, or delete entire enhancers. Regulatory elements, however, may be silenced through changes in chromatin accessibility or the emergence of repressive elements. Here, we show that increased chromatin accessibility at the gene yellow, combined with the gain of a repressor site, underlies the loss of a wing spot pigmentation pattern in a Drosophila species. The gain of accessibility of this repressive element is regulated by E93, a transcription factor governing the progress of metamorphosis. This convoluted evolutionary scenario contrasts with the parsimonious mutational paths generally envisioned and often documented for morphological losses. It illustrates how evolutionary changes in chromatin accessibility may directly contribute to morphological diversification.
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13
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Buffry AD, Kittelmann S, McGregor AP. Characterisation of the role and regulation of Ultrabithorax in sculpting fine-scale leg morphology. Front Cell Dev Biol 2023; 11:1119221. [PMID: 36861038 PMCID: PMC9968978 DOI: 10.3389/fcell.2023.1119221] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 01/20/2023] [Indexed: 02/16/2023] Open
Abstract
Hox genes are expressed during embryogenesis and determine the regional identity of animal bodies along the antero-posterior axis. However, they also function post-embryonically to sculpt fine-scale morphology. To better understand how Hox genes are integrated into post-embryonic gene regulatory networks, we further analysed the role and regulation of Ultrabithorax (Ubx) during leg development in Drosophila melanogaster. Ubx regulates several aspects of bristle and trichome patterning on the femurs of the second (T2) and third (T3) leg pairs. We found that repression of trichomes in the proximal posterior region of the T2 femur by Ubx is likely mediated by activation of the expression of microRNA-92a and microRNA-92b by this Hox protein. Furthermore, we identified a novel enhancer of Ubx that recapitulates the temporal and regional activity of this gene in T2 and T3 legs. We then used transcription factor (TF) binding motif analysis in regions of accessible chromatin in T2 leg cells to predict and functionally test TFs that may regulate the Ubx leg enhancer. We also tested the role of the Ubx co-factors Homothorax (Hth) and Extradenticle (Exd) in T2 and T3 femurs. We found several TFs that may act upstream or in concert with Ubx to modulate trichome patterning along the proximo-distal axis of developing femurs and that the repression of trichomes also requires Hth and Exd. Taken together our results provide insights into how Ubx is integrated into a post-embryonic gene regulatory network to determine fine-scale leg morphology.
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Affiliation(s)
- Alexandra D. Buffry
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford, United Kingdom
| | - Sebastian Kittelmann
- Centre for Functional Genomics, Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford, United Kingdom
| | - Alistair P. McGregor
- Department of Biosciences, Durham University, Durham, United Kingdom,*Correspondence: Alistair P. McGregor,
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14
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Galupa R, Alvarez-Canales G, Borst NO, Fuqua T, Gandara L, Misunou N, Richter K, Alves MRP, Karumbi E, Perkins ML, Kocijan T, Rushlow CA, Crocker J. Enhancer architecture and chromatin accessibility constrain phenotypic space during Drosophila development. Dev Cell 2023; 58:51-62.e4. [PMID: 36626871 PMCID: PMC9860173 DOI: 10.1016/j.devcel.2022.12.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 10/18/2022] [Accepted: 12/07/2022] [Indexed: 01/11/2023]
Abstract
Developmental enhancers bind transcription factors and dictate patterns of gene expression during development. Their molecular evolution can underlie phenotypical evolution, but the contributions of the evolutionary pathways involved remain little understood. Here, using mutation libraries in Drosophila melanogaster embryos, we observed that most point mutations in developmental enhancers led to changes in gene expression levels but rarely resulted in novel expression outside of the native pattern. In contrast, random sequences, often acting as developmental enhancers, drove expression across a range of cell types; random sequences including motifs for transcription factors with pioneer activity acted as enhancers even more frequently. Our findings suggest that the phenotypic landscapes of developmental enhancers are constrained by enhancer architecture and chromatin accessibility. We propose that the evolution of existing enhancers is limited in its capacity to generate novel phenotypes, whereas the activity of de novo elements is a primary source of phenotypic novelty.
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Affiliation(s)
- Rafael Galupa
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
| | | | | | - Timothy Fuqua
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Lautaro Gandara
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Natalia Misunou
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Kerstin Richter
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | | | - Esther Karumbi
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | | | - Tin Kocijan
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | | | - Justin Crocker
- European Molecular Biology Laboratory, 69117 Heidelberg, Germany.
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15
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Can changes in 3D genome architecture create new regulatory landscapes that contribute to phenotypic evolution? Essays Biochem 2022; 66:745-752. [PMID: 36250960 DOI: 10.1042/ebc20220057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 09/20/2022] [Accepted: 09/23/2022] [Indexed: 12/13/2022]
Abstract
Animal genomes are compartmentalized into insulated regulatory units named topology-associated domains (TADs). TADs insulate gene promoters from enhancers that occupy neighboring TADs. Chromosomal rearrangements that disrupt TAD structure can generate new regulatory interactions between enhancers and promoters that were once separated into different TADs, which might lead to new gene expression patterns. On the one hand, TAD rearrangements are known to cause deleterious phenotypes, but, on the other hand, rearrangements can also create novel expression patterns that may be selected during evolution because they generate advantageous phenotypes. Here, we review recent studies that explore the effects of chromosomal rearrangements and genetic perturbations on TAD structure and gene regulation in the context of development and evolution. We discuss the possible contribution of evolutionary breakpoints (EBRs) that affect TAD structure to the evolution of gene regulation and the phenotype.
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16
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Liang M, Foster CE, Yuan YW. Lost in translation: Molecular basis of reduced flower coloration in a self-pollinated monkeyflower ( Mimulus) species. SCIENCE ADVANCES 2022; 8:eabo1113. [PMID: 36103532 PMCID: PMC9473569 DOI: 10.1126/sciadv.abo1113] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Accepted: 05/27/2022] [Indexed: 06/15/2023]
Abstract
Phenotypic evolution is usually attributed to changes in protein function or gene transcription. In principle, mutations that affect protein abundance through enhancing or attenuating protein translation also could be an important source for phenotypic evolution. However, these types of mutations remain largely unexplored in the studies of phenotypic variation in nature. Through fine-scale genetic mapping and functional interrogation, we identify a single nucleotide substitution in an anthocyanin-activating R2R3-MYB gene causing flower color variation between a pair of closely related monkeyflower (Mimulus) species, the hummingbird-pollinated Mimulus cardinalis, and self-pollinated Mimulus parishii. This causal mutation is located in the 5' untranslated region and generates an upstream ATG start codon, leading to attenuated protein translation and reduced flower coloration in the self-pollinated species. Together, our results provide empirical support for the role of mutations affecting protein translation, as opposed to protein function or transcript level, in natural phenotypic variation.
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Affiliation(s)
- Mei Liang
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Caitlin E. Foster
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Yao-Wu Yuan
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT 06269, USA
- Institute for Systems Genomics, University of Connecticut, Storrs, CT 06269, USA
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17
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Ansai S, Kitano J. Speciation and adaptation research meets genome editing. Philos Trans R Soc Lond B Biol Sci 2022; 377:20200516. [PMID: 35634923 PMCID: PMC9149800 DOI: 10.1098/rstb.2020.0516] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 02/07/2022] [Indexed: 07/20/2023] Open
Abstract
Understanding the genetic basis of reproductive isolation and adaptive traits in natural populations is one of the fundamental goals in evolutionary biology. Genome editing technologies based on CRISPR-Cas systems and site-specific recombinases have enabled us to modify a targeted genomic region as desired and thus to conduct functional analyses of target loci, genes and mutations even in non-conventional model organisms. Here, we review the technical properties of genome editing techniques by classifying them into the following applications: targeted gene knock-out for investigating causative gene functions, targeted gene knock-in of marker genes for visualizing expression patterns and protein functions, precise gene replacement for identifying causative alleles and mutations, and targeted chromosomal rearrangement for investigating the functional roles of chromosomal structural variations. We describe examples of their application to demonstrate functional analysis of naturally occurring genetic variations and discuss how these technologies can be applied to speciation and adaptation research. This article is part of the theme issue 'Genetic basis of adaptation and speciation: from loci to causative mutations'.
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Affiliation(s)
- Satoshi Ansai
- Graduate School of Life Sciences, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai, Miyagi 980-8577, Japan
| | - Jun Kitano
- Ecological Genetics Laboratory, Department of Genomics and Evolutionary Biology, National Institute of Genetics, Yata 1111, Mishima, Shizuoka 411-8540, Japan
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18
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Perkins ML, Gandara L, Crocker J. A synthetic synthesis to explore animal evolution and development. Philos Trans R Soc Lond B Biol Sci 2022; 377:20200517. [PMID: 35634925 PMCID: PMC9149795 DOI: 10.1098/rstb.2020.0517] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Identifying the general principles by which genotypes are converted into phenotypes remains a challenge in the post-genomic era. We still lack a predictive understanding of how genes shape interactions among cells and tissues in response to signalling and environmental cues, and hence how regulatory networks generate the phenotypic variation required for adaptive evolution. Here, we discuss how techniques borrowed from synthetic biology may facilitate a systematic exploration of evolvability across biological scales. Synthetic approaches permit controlled manipulation of both endogenous and fully engineered systems, providing a flexible platform for investigating causal mechanisms in vivo. Combining synthetic approaches with multi-level phenotyping (phenomics) will supply a detailed, quantitative characterization of how internal and external stimuli shape the morphology and behaviour of living organisms. We advocate integrating high-throughput experimental data with mathematical and computational techniques from a variety of disciplines in order to pursue a comprehensive theory of evolution. This article is part of the theme issue ‘Genetic basis of adaptation and speciation: from loci to causative mutations’.
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Affiliation(s)
- Mindy Liu Perkins
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Lautaro Gandara
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Justin Crocker
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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19
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Alvarado AS. Developmental biology is poised to discover altogether new principles in biology in the 21st century. Dev Biol 2022; 488:47-53. [PMID: 35580728 PMCID: PMC9326816 DOI: 10.1016/j.ydbio.2022.05.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/04/2022] [Accepted: 05/06/2022] [Indexed: 01/05/2023]
Abstract
In the 20th century, developmental biology spearheaded a revolution in our understanding of complex biological problems. Its success rests in great part on a truly unique approach that has recruited a diversity of systems and research organisms rather than focusing on isolated cells or molecules, while also employing a wide variety of technological and intellectual approaches. But what will developmental biology contribute to this century? Advances in technology and instrumentation are presently moving at neck-breaking speed and herald the advent of an age of technological wonders in which previously inaccessible biology is now tangibly within our grasps. For instance, single-cell RNAseq has revealed novel, transient cell states in both stem and differentiated cells that are specified by defined changes in gene expression frequency during regeneration. Additionally, genome-wide epigenetic analyses combined with gene editing and transgenic methodologies have identified the existence of regeneration responsive enhancers in adult vertebrate tissues. These circumstances combined with our discipline’s diversity of experimental and intellectual approaches offer unimaginable opportunities for developmental biologists not only to discover new biology but also to reveal entirely new principles of biology.
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20
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McDonald JMC, Reed RD. Patterns of selection across gene regulatory networks. Semin Cell Dev Biol 2022; 145:60-67. [PMID: 35474149 DOI: 10.1016/j.semcdb.2022.03.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 01/31/2022] [Accepted: 03/23/2022] [Indexed: 12/29/2022]
Abstract
Gene regulatory networks (GRNs) are the core engine of organismal development. If we would like to understand the origin and diversification of phenotypes, it is necessary to consider the structure of GRNs in order to reconstruct the links between genetic mutations and phenotypic change. Much of the progress in evolutionary developmental biology, however, has occurred without a nuanced consideration of the evolution of functional relationships between genes, especially in the context of their broader network interactions. Characterizing and comparing GRNs across traits and species in a more detailed way will allow us to determine how network position influences what genes drive adaptive evolution. In this perspective paper, we consider the architecture of developmental GRNs and how positive selection strength may vary across a GRN. We then propose several testable models for these patterns of selection and experimental approaches to test these models.
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Affiliation(s)
- Jeanne M C McDonald
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, United States.
| | - Robert D Reed
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, United States.
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21
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Luecke D, Rice G, Kopp A. Sex-specific evolution of a Drosophila sensory system via interacting cis- and trans-regulatory changes. Evol Dev 2022; 24:37-60. [PMID: 35239254 PMCID: PMC9179014 DOI: 10.1111/ede.12398] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 01/20/2022] [Accepted: 01/25/2022] [Indexed: 12/13/2022]
Abstract
The evolution of gene expression via cis-regulatory changes is well established as a major driver of phenotypic evolution. However, relatively little is known about the influence of enhancer architecture and intergenic interactions on regulatory evolution. We address this question by examining chemosensory system evolution in Drosophila. Drosophila prolongata males show a massively increased number of chemosensory bristles compared to females and males of sibling species. This increase is driven by sex-specific transformation of ancestrally mechanosensory organs. Consistent with this phenotype, the Pox neuro transcription factor (Poxn), which specifies chemosensory bristle identity, shows expanded expression in D. prolongata males. Poxn expression is controlled by nonadditive interactions among widely dispersed enhancers. Although some D. prolongata Poxn enhancers show increased activity, the additive component of this increase is slight, suggesting that most changes in Poxn expression are due to epistatic interactions between Poxn enhancers and trans-regulatory factors. Indeed, the expansion of D. prolongata Poxn enhancer activity is only observed in cells that express doublesex (dsx), the gene that controls sexual differentiation in Drosophila and also shows increased expression in D. prolongata males due to cis-regulatory changes. Although expanded dsx expression may contribute to increased activity of D. prolongata Poxn enhancers, this interaction is not sufficient to explain the full expansion of Poxn expression, suggesting that cis-trans interactions between Poxn, dsx, and additional unknown genes are necessary to produce the derived D. prolongata phenotype. Overall, our results demonstrate the importance of epistatic gene interactions for evolution, particularly when pivotal genes have complex regulatory architecture.
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Affiliation(s)
- David Luecke
- Department of Evolution and Ecology, University of California – Davis,Current Address: Department of Integrative Biology, Michigan State University
| | - Gavin Rice
- Department of Evolution and Ecology, University of California – Davis,Current Address: Department of Biological Sciences, University of Pittsburgh
| | - Artyom Kopp
- Department of Evolution and Ecology, University of California – Davis
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22
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Murad R, Macias-Muñoz A, Wong A, Ma X, Mortazavi A. Coordinated Gene Expression and Chromatin Regulation during Hydra Head Regeneration. Genome Biol Evol 2021; 13:evab221. [PMID: 34877597 PMCID: PMC8651858 DOI: 10.1093/gbe/evab221] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/20/2021] [Indexed: 12/13/2022] Open
Abstract
The cnidarian model organism Hydra has long been studied for its remarkable ability to regenerate its head, which is controlled by a head organizer located near the hypostome. The canonical Wnt pathway plays a central role in head organizer function during regeneration and during bud formation, which is the asexual mode of reproduction in Hydra. However, it is unclear how shared the developmental programs of head organizer genesis are in budding and regeneration. Time-series analysis of gene expression changes during head regeneration and budding revealed a set of 298 differentially expressed genes during the 48-h head regeneration and 72-h budding time courses. In order to understand the regulatory elements controlling Hydra head regeneration, we first identified 27,137 open-chromatin elements that are open in one or more sections of the organism body or regenerating tissue. We used histone modification ChIP-seq to identify 9,998 candidate proximal promoter and 3,018 candidate enhancer-like regions respectively. We show that a subset of these regulatory elements is dynamically remodeled during head regeneration and identify a set of transcription factor motifs that are enriched in the enhancer regions activated during head regeneration. Our results show that Hydra displays complex gene regulatory structures of developmentally dynamic enhancers, which suggests that the evolution of complex developmental enhancers predates the split of cnidarians and bilaterians.
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Affiliation(s)
- Rabi Murad
- Department of Developmental and Cell Biology, University of California Irvine, USA
- Center for Complex Biological Systems, University of California Irvine, USA
| | - Aide Macias-Muñoz
- Department of Developmental and Cell Biology, University of California Irvine, USA
- Center for Complex Biological Systems, University of California Irvine, USA
| | - Ashley Wong
- Department of Developmental and Cell Biology, University of California Irvine, USA
- Center for Complex Biological Systems, University of California Irvine, USA
| | - Xinyi Ma
- Department of Developmental and Cell Biology, University of California Irvine, USA
- Center for Complex Biological Systems, University of California Irvine, USA
| | - Ali Mortazavi
- Department of Developmental and Cell Biology, University of California Irvine, USA
- Center for Complex Biological Systems, University of California Irvine, USA
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23
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Auer TO, Shahandeh MP, Benton R. Drosophila sechellia: A Genetic Model for Behavioral Evolution and Neuroecology. Annu Rev Genet 2021; 55:527-554. [PMID: 34530638 DOI: 10.1146/annurev-genet-071719-020719] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Defining the mechanisms by which animals adapt to their ecological niche is an important problem bridging evolution, genetics, and neurobiology. We review the establishment of a powerful genetic model for comparative behavioral analysis and neuroecology, Drosophila sechellia. This island-endemic fly species is closely related to several cosmopolitan generalists, including Drosophila melanogaster, but has evolved extreme specialism, feeding and reproducing exclusively on the noni fruit of the tropical shrub Morinda citrifolia. We first describe the development and use of genetic approaches to facilitate genotype/phenotype associations in these drosophilids. Next, we survey the behavioral, physiological, and morphological adaptations of D. sechellia throughout its life cycle and outline our current understanding of the genetic and cellular basis of these traits. Finally, we discuss the principles this knowledge begins to establish in the context of host specialization, speciation, and the neurobiology of behavioral evolution and consider open questions and challenges in the field.
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Affiliation(s)
- Thomas O Auer
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, CH-1015 Lausanne, Switzerland; , ,
| | - Michael P Shahandeh
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, CH-1015 Lausanne, Switzerland; , ,
| | - Richard Benton
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, CH-1015 Lausanne, Switzerland; , ,
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24
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Stöck M, Dedukh D, Reifová R, Lamatsch DK, Starostová Z, Janko K. Sex chromosomes in meiotic, hemiclonal, clonal and polyploid hybrid vertebrates: along the 'extended speciation continuum'. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200103. [PMID: 34304588 PMCID: PMC8310718 DOI: 10.1098/rstb.2020.0103] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/12/2021] [Indexed: 12/15/2022] Open
Abstract
We review knowledge about the roles of sex chromosomes in vertebrate hybridization and speciation, exploring a gradient of divergences with increasing reproductive isolation (speciation continuum). Under early divergence, well-differentiated sex chromosomes in meiotic hybrids may cause Haldane-effects and introgress less easily than autosomes. Undifferentiated sex chromosomes are more susceptible to introgression and form multiple (or new) sex chromosome systems with hardly predictable dominance hierarchies. Under increased divergence, most vertebrates reach complete intrinsic reproductive isolation. Slightly earlier, some hybrids (linked in 'the extended speciation continuum') exhibit aberrant gametogenesis, leading towards female clonality. This facilitates the evolution of various allodiploid and allopolyploid clonal ('asexual') hybrid vertebrates, where 'asexuality' might be a form of intrinsic reproductive isolation. A comprehensive list of 'asexual' hybrid vertebrates shows that they all evolved from parents with divergences that were greater than at the intraspecific level (K2P-distances of greater than 5-22% based on mtDNA). These 'asexual' taxa inherited genetic sex determination by mostly undifferentiated sex chromosomes. Among the few known sex-determining systems in hybrid 'asexuals', female heterogamety (ZW) occurred about twice as often as male heterogamety (XY). We hypothesize that pre-/meiotic aberrations in all-female ZW-hybrids present Haldane-effects promoting their evolution. Understanding the preconditions to produce various clonal or meiotic allopolyploids appears crucial for insights into the evolution of sex, 'asexuality' and polyploidy. This article is part of the theme issue 'Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part II)'.
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Affiliation(s)
- Matthias Stöck
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries - IGB (Forschungsverbund Berlin), Müggelseedamm 301, 12587 Berlin, Germany
- Amphibian Research Center, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
| | - Dmitrij Dedukh
- Institute of Animal Physiology and Genetics, Laboratory of Fish Genetics, The Czech Academy of Sciences, 277 21 Libechov, Czech Republic
| | - Radka Reifová
- Department of Zoology, Faculty of Science, Charles University, Viničná 7, Prague 2, 128 00, Czech Republic
| | - Dunja K. Lamatsch
- Research Department for Limnology, University of Innsbruck, Mondseestrasse 9, A-5310 Mondsee, Austria
| | - Zuzana Starostová
- Department of Zoology, Faculty of Science, Charles University, Viničná 7, Prague 2, 128 00, Czech Republic
| | - Karel Janko
- Institute of Animal Physiology and Genetics, Laboratory of Fish Genetics, The Czech Academy of Sciences, 277 21 Libechov, Czech Republic
- Department of Biology and Ecology, Faculty of Science, University of Ostrava, 701 03 Ostrava, Czech Republic
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25
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Shih CH, Fay J. Cis-regulatory variants affect gene expression dynamics in yeast. eLife 2021; 10:e68469. [PMID: 34369376 PMCID: PMC8367379 DOI: 10.7554/elife.68469] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 08/06/2021] [Indexed: 12/14/2022] Open
Abstract
Evolution of cis-regulatory sequences depends on how they affect gene expression and motivates both the identification and prediction of cis-regulatory variants responsible for expression differences within and between species. While much progress has been made in relating cis-regulatory variants to expression levels, the timing of gene activation and repression may also be important to the evolution of cis-regulatory sequences. We investigated allele-specific expression (ASE) dynamics within and between Saccharomyces species during the diauxic shift and found appreciable cis-acting variation in gene expression dynamics. Within-species ASE is associated with intergenic variants, and ASE dynamics are more strongly associated with insertions and deletions than ASE levels. To refine these associations, we used a high-throughput reporter assay to test promoter regions and individual variants. Within the subset of regions that recapitulated endogenous expression, we identified and characterized cis-regulatory variants that affect expression dynamics. Between species, chimeric promoter regions generate novel patterns and indicate constraints on the evolution of gene expression dynamics. We conclude that changes in cis-regulatory sequences can tune gene expression dynamics and that the interplay between expression dynamics and other aspects of expression is relevant to the evolution of cis-regulatory sequences.
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Affiliation(s)
- Ching-Hua Shih
- Department of Biology, University of RochesterRochesterUnited States
| | - Justin Fay
- Department of Biology, University of RochesterRochesterUnited States
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26
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Pillai A, Gungi A, Reddy PC, Galande S. Epigenetic Regulation in Hydra: Conserved and Divergent Roles. Front Cell Dev Biol 2021; 9:663208. [PMID: 34041242 PMCID: PMC8141815 DOI: 10.3389/fcell.2021.663208] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Accepted: 04/13/2021] [Indexed: 12/12/2022] Open
Abstract
Transitions in gene regulatory processes responsible for the emergence of specialized cell types and spatiotemporal regulation of developmental signaling prior to the divergence of Cnidaria and Bilateria are poorly understood. As a sister group of Bilateria, the phylum Cnidaria can provide significant insights into these processes. Among the cnidarians, hydrae have been studied for >250 years to comprehend the mechanisms underlying their unique immortality and robust regenerative capacity. Studies on Hydra spp. and other pre-bilaterians alike have advanced our understanding of the evolutionary underpinnings governing eumetazoan tissue development, homeostasis, and regeneration. In addition to its regenerative potential, Hydra exhibits continuously active axial patterning due to its peculiar tissue dynamics. These distinctive physiological processes necessitate large scale gene expression changes that are governed by the multitude of epigenetic mechanisms operating in cells. This review highlights the contemporary knowledge of epigenetic regulation in Hydra with contemporary studies from other members of Cnidaria, as well as the interplay between regulatory mechanisms wherever demonstrated. The studies covered in the scope of this review reveal both ancestral and divergent roles played by conserved epigenetic mechanisms with emphasis on transcriptional regulation. Additionally, single-cell transcriptomics data was mined to predict the physiological relevance of putative gene regulatory components, which is in agreement with published findings and yielded insights into the possible functions of the gene regulatory mechanisms that are yet to be deciphered in Hydra, such as DNA methylation. Finally, we delineate potentially rewarding epigenetics research avenues that can further leverage the unique biology of Hydra.
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Affiliation(s)
| | | | - Puli Chandramouli Reddy
- Centre of Excellence in Epigenetics, Department of Biology, Indian Institute of Science Education and Research, Pune, India
| | - Sanjeev Galande
- Centre of Excellence in Epigenetics, Department of Biology, Indian Institute of Science Education and Research, Pune, India
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Al Hayek S, Alsawadi A, Kambris Z, Boquete J, Bohère J, Immarigeon C, Ronsin B, Plaza S, Lemaitre B, Payre F, Osman D. Steroid-dependent switch of OvoL/Shavenbaby controls self-renewal versus differentiation of intestinal stem cells. EMBO J 2021; 40:e104347. [PMID: 33372708 PMCID: PMC7883054 DOI: 10.15252/embj.2019104347] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 11/23/2020] [Accepted: 11/24/2020] [Indexed: 12/27/2022] Open
Abstract
Adult stem cells must continuously fine-tune their behavior to regenerate damaged organs and avoid tumors. While several signaling pathways are well known to regulate somatic stem cells, the underlying mechanisms remain largely unexplored. Here, we demonstrate a cell-intrinsic role for the OvoL family transcription factor, Shavenbaby (Svb), in balancing self-renewal and differentiation of Drosophila intestinal stem cells. We find that svb is a downstream target of Wnt and EGFR pathways, mediating their activity for stem cell survival and proliferation. This requires post-translational processing of Svb into a transcriptional activator, whose upregulation induces tumor-like stem cell hyperproliferation. In contrast, the unprocessed form of Svb acts as a repressor that imposes differentiation into enterocytes, and suppresses tumors induced by altered signaling. We show that the switch between Svb repressor and activator is triggered in response to systemic steroid hormone, which is produced by ovaries. Therefore, the Svb axis allows intrinsic integration of local signaling cues and inter-organ communication to adjust stem cell proliferation versus differentiation, suggesting a broad role of OvoL/Svb in adult and cancer stem cells.
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Affiliation(s)
- Sandy Al Hayek
- Faculty of Sciences IIILebanese UniversityTripoliLebanon
- Azm Center for Research in Biotechnology and its ApplicationsLBA3B, EDST, Lebanese UniversityTripoliLebanon
- Centre de Biologie du Développement (CBD)Centre de Biologie Intégrative (CBI)Université de ToulouseCNRSToulouseFrance
| | - Ahmad Alsawadi
- Centre de Biologie du Développement (CBD)Centre de Biologie Intégrative (CBI)Université de ToulouseCNRSToulouseFrance
| | - Zakaria Kambris
- Biology DepartmentFaculty of Arts and SciencesAmerican University of BeirutBeirutLebanon
| | | | - Jérôme Bohère
- Centre de Biologie du Développement (CBD)Centre de Biologie Intégrative (CBI)Université de ToulouseCNRSToulouseFrance
| | - Clément Immarigeon
- Centre de Biologie du Développement (CBD)Centre de Biologie Intégrative (CBI)Université de ToulouseCNRSToulouseFrance
| | - Brice Ronsin
- Centre de Biologie du Développement (CBD)Centre de Biologie Intégrative (CBI)Université de ToulouseCNRSToulouseFrance
| | - Serge Plaza
- Centre de Biologie du Développement (CBD)Centre de Biologie Intégrative (CBI)Université de ToulouseCNRSToulouseFrance
- Present address:
Laboratoire de Recherche en Sciences Végétales (LSRV)CNRSUPSCastanet‐TolosanFrance
| | - Bruno Lemaitre
- Global Health Institute, School of Life SciencesLausanneSwitzerland
| | - François Payre
- Centre de Biologie du Développement (CBD)Centre de Biologie Intégrative (CBI)Université de ToulouseCNRSToulouseFrance
| | - Dani Osman
- Faculty of Sciences IIILebanese UniversityTripoliLebanon
- Azm Center for Research in Biotechnology and its ApplicationsLBA3B, EDST, Lebanese UniversityTripoliLebanon
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28
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Kittelmann S, Preger-Ben Noon E, McGregor AP, Frankel N. A complex gene regulatory architecture underlies the development and evolution of cuticle morphology in Drosophila. Curr Opin Genet Dev 2021; 69:21-27. [PMID: 33529925 DOI: 10.1016/j.gde.2021.01.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 12/18/2020] [Accepted: 01/05/2021] [Indexed: 10/22/2022]
Abstract
The cuticle of insects is decorated with non-sensory hairs called trichomes. A few Drosophila species independently lost most of the dorso-lateral trichomes on first instar larvae. Genetic experiments revealed that this naked cuticle phenotype was caused by the evolution of enhancer function at the ovo/shavenbaby (ovo/svb) locus. Here we explore how this discovery catalyzed major new insights into morphological evolution in different developmental contexts, enhancer pleiotropy in gene regulation and the functionality and evolution of the Svb gene regulatory network (GRN). Taken together this highlights the importance of understanding the architecture and evolution of gene regulatory networks in detail and the great potential for further study of the Svb GRN.
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Affiliation(s)
- Sebastian Kittelmann
- Centre for Functional Genomics, Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom
| | - Ella Preger-Ben Noon
- Department of Genetics and Developmental Biology, The Rappaport Faculty of Medicine and Research Institute, Technion - Israel Institute of Technology, Haifa 3109601, Israel
| | - Alistair P McGregor
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, United Kingdom
| | - Nicolás Frankel
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, CONICET-UBA), Buenos Aires 1428, Argentina; Departamento de Ecología, Genética y Evolución (FCEyN, UBA), Buenos Aires 1428, Argentina.
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29
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Soverna AF, Rodriguez NC, Korgaonkar A, Hasson E, Stern DL, Frankel N. Cis-regulatory variation in the shavenbaby gene underlies intraspecific phenotypic variation, mirroring interspecific divergence in the same trait. Evolution 2020; 75:427-436. [PMID: 33314059 DOI: 10.1111/evo.14142] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 11/20/2020] [Accepted: 11/24/2020] [Indexed: 12/14/2022]
Abstract
Despite considerable progress in recent decades in dissecting the genetic causes of natural morphological variation, there is limited understanding of how variation within species ultimately contributes to species differences. We have studied patterning of the non-sensory hairs, commonly known as "trichomes," on the dorsal cuticle of first-instar larvae of Drosophila. Most Drosophila species produce a dense lawn of dorsal trichomes, but a subset of these trichomes were lost in D. sechellia and D. ezoana due entirely to regulatory evolution of the shavenbaby (svb) gene. Here, we describe intraspecific variation in dorsal trichome patterns of first-instar larvae of D. virilis that is similar to the trichome pattern variation identified previously between species. We found that a single large effect QTL, which includes svb, explains most of the trichome number difference between two D. virilis strains and that svb expression correlates with the trichome difference between strains. This QTL does not explain the entire difference between strains, implying that additional loci contribute to variation in trichome numbers. Thus, the genetic architecture of intraspecific variation exhibits similarities and differences with interspecific variation that may reflect differences in long-term and short-term evolutionary processes.
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Affiliation(s)
- Ana Faigon Soverna
- Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA, CONICET-UBA), Buenos Aires, 1417, Argentina
| | - Nahuel Cabrera Rodriguez
- Departamento de Ecología, Genética y Evolución (FCEyN, UBA) and Instituto de Ecología, Genética y Evolución de Buenos Aires (IEGEBA, CONICET-UBA), Buenos Aires, 1428, Argentina
| | - Aishwarya Korgaonkar
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA, 20147, USA
| | - Esteban Hasson
- Departamento de Ecología, Genética y Evolución (FCEyN, UBA) and Instituto de Ecología, Genética y Evolución de Buenos Aires (IEGEBA, CONICET-UBA), Buenos Aires, 1428, Argentina
| | - David L Stern
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, VA, 20147, USA
| | - Nicolás Frankel
- Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE, CONICET-UBA) and Departamento de Ecología, Genética y Evolución (FCEyN, UBA), Buenos Aires, 1428, Argentina
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30
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Wang W, Hu CK, Zeng A, Alegre D, Hu D, Gotting K, Ortega Granillo A, Wang Y, Robb S, Schnittker R, Zhang S, Alegre D, Li H, Ross E, Zhang N, Brunet A, Sánchez Alvarado A. Changes in regeneration-responsive enhancers shape regenerative capacities in vertebrates. Science 2020; 369:369/6508/eaaz3090. [PMID: 32883834 DOI: 10.1126/science.aaz3090] [Citation(s) in RCA: 119] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 03/05/2020] [Accepted: 07/07/2020] [Indexed: 12/13/2022]
Abstract
Vertebrates vary in their ability to regenerate, and the genetic mechanisms underlying such disparity remain elusive. Comparative epigenomic profiling and single-cell sequencing of two related teleost fish uncovered species-specific and evolutionarily conserved genomic responses to regeneration. The conserved response revealed several regeneration-responsive enhancers (RREs), including an element upstream to inhibin beta A (inhba), a known effector of vertebrate regeneration. This element activated expression in regenerating transgenic fish, and its genomic deletion perturbed caudal fin regeneration and abrogated cardiac regeneration altogether. The enhancer is present in mammals, shares functionally essential activator protein 1 (AP-1)-binding motifs, and responds to injury, but it cannot rescue regeneration in fish. This work suggests that changes in AP-1-enriched RREs are likely a crucial source of loss of regenerative capacities in vertebrates.
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Affiliation(s)
- Wei Wang
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA.,Howard Hughes Medical Institute, Kansas City, MO 64110, USA
| | - Chi-Kuo Hu
- Department of Genetics, Stanford University, Stanford, CA 94305, USA
| | - An Zeng
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Dana Alegre
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Deqing Hu
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Kirsten Gotting
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | | | - Yongfu Wang
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Sofia Robb
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | | | - Shasha Zhang
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Dillon Alegre
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Hua Li
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Eric Ross
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA.,Howard Hughes Medical Institute, Kansas City, MO 64110, USA
| | - Ning Zhang
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Anne Brunet
- Department of Genetics, Stanford University, Stanford, CA 94305, USA.,Glenn Laboratories for the Biology of Aging. Stanford University, Stanford, CA 94305, USA
| | - Alejandro Sánchez Alvarado
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA. .,Howard Hughes Medical Institute, Kansas City, MO 64110, USA
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31
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Zhang Q, Xia T, Zhang C. Chronic Exposure to Titanium Dioxide Nanoparticles Induces Commensal-to-Pathogen Transition in Escherichia coli. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:13186-13196. [PMID: 32960578 DOI: 10.1021/acs.est.0c04968] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Due to daily exposure to nanostructured titanium dioxide (nTiO2) for various purposes, concerns have been raised regarding the potential health impact of this material. Few studies have researched the chronic effect of nTiO2 on commensal gut bacteria, and the exposure scenario is typified by long durations, low doses, and dark conditions. We repeatedly exposed Escherichia coli to 5 mg/L nTiO2 for 200 subcultures (400 days) in the dark. Adaptive morphogenesis (i.e., filamentation, thickening of the cell wall, and biofilm formation) was observed, which diminished the sensitivity of the cells to oxidative stress and multiple antibiotics. The bacterial mobility was enhanced by approximately 66%, which was ascribed to the significant increases in flagellar assembly and fimbria biosynthesis. These adaptive traits were associated with increased pathogenicity, as corroborated by a higher death rate of macrophages in vitro and more severe bacterial infection in mice in vivo. The adaptive evolution was attributed to hydroxyl radical production by 5 mg/L nTiO2 in the dark due to surface oxygen vacancies. Therefore, although nTiO2 is generally considered inert in the absence of light, additional precautions should be taken when it is applied in food and daily products considering its potential toxic effects on the commensal microbial community.
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Affiliation(s)
- Qiurong Zhang
- School of Environment, Beijing Normal University, Beijing 100857, China
- College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China
| | - Tian Xia
- Division of Nanomedicine, Department of Medicine, California NanoSystems Institute, University of California, Los Angeles, Los Angeles 90095, California, United States
| | - Chengdong Zhang
- School of Environment, Beijing Normal University, Beijing 100857, China
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32
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Cis-regulatory differences in isoform expression associate with life history strategy variation in Atlantic salmon. PLoS Genet 2020; 16:e1009055. [PMID: 32997662 PMCID: PMC7549781 DOI: 10.1371/journal.pgen.1009055] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 10/12/2020] [Accepted: 08/17/2020] [Indexed: 02/07/2023] Open
Abstract
A major goal in biology is to understand how evolution shapes variation in individual life histories. Genome-wide association studies have been successful in uncovering genome regions linked with traits underlying life history variation in a range of species. However, lack of functional studies of the discovered genotype-phenotype associations severely restrains our understanding how alternative life history traits evolved and are mediated at the molecular level. Here, we report a cis-regulatory mechanism whereby expression of alternative isoforms of the transcription co-factor vestigial-like 3 (vgll3) associate with variation in a key life history trait, age at maturity, in Atlantic salmon (Salmo salar). Using a common-garden experiment, we first show that vgll3 genotype associates with puberty timing in one-year-old salmon males. By way of temporal sampling of vgll3 expression in ten tissues across the first year of salmon development, we identify a pubertal transition in vgll3 expression where maturation coincided with a 66% reduction in testicular vgll3 expression. The late maturation allele was not only associated with a tendency to delay puberty, but also with expression of a rare transcript isoform of vgll3 pre-puberty. By comparing absolute vgll3 mRNA copies in heterozygotes we show that the expression difference between the early and late maturity alleles is largely cis-regulatory. We propose a model whereby expression of a rare isoform from the late allele shifts the liability of its carriers towards delaying puberty. These results exemplify the potential importance of regulatory differences as a mechanism for the evolution of life history traits. Alternative life history strategies are an important source of diversity within populations and promote the maintenance of adaptive capacity and population resilience. However, in many cases the molecular basis of different life history strategies remains elusive. Age at maturity is a key adaptive life history trait in Atlantic salmon and has a relatively simple genetic basis. Using salmon age at maturity as a model, we report a mechanism whereby different transcript isoforms of the key age at maturity gene, vestigial-like 3 (vgll3), associate with variation in the timing of male puberty. Our results show how gene regulatory differences in conjunction with variation in gene transcript structure can encode for complex alternative life histories.
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33
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Archambeault SL, Bärtschi LR, Merminod AD, Peichel CL. Adaptation via pleiotropy and linkage: Association mapping reveals a complex genetic architecture within the stickleback Eda locus. Evol Lett 2020; 4:282-301. [PMID: 32774879 PMCID: PMC7403726 DOI: 10.1002/evl3.175] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Revised: 04/04/2020] [Accepted: 04/29/2020] [Indexed: 11/26/2022] Open
Abstract
Genomic mapping of the loci associated with phenotypic evolution has revealed genomic "hotspots," or regions of the genome that control multiple phenotypic traits. This clustering of loci has important implications for the speed and maintenance of adaptation and could be due to pleiotropic effects of a single mutation or tight genetic linkage of multiple causative mutations affecting different traits. The threespine stickleback (Gasterosteus aculeatus) is a powerful model for the study of adaptive evolution because the marine ecotype has repeatedly adapted to freshwater environments across the northern hemisphere in the last 12,000 years. Freshwater ecotypes have repeatedly fixed a 16 kilobase haplotype on chromosome IV that contains Ectodysplasin (Eda), a gene known to affect multiple traits, including defensive armor plates, lateral line sensory hair cells, and schooling behavior. Many additional traits have previously been mapped to a larger region of chromosome IV that encompasses the Eda freshwater haplotype. To identify which of these traits specifically map to this adaptive haplotype, we made crosses of rare marine fish heterozygous for the freshwater haplotype in an otherwise marine genetic background. Further, we performed fine-scale association mapping in a fully interbreeding, polymorphic population of freshwater stickleback to disentangle the effects of pleiotropy and linkage on the phenotypes affected by this haplotype. Although we find evidence that linked mutations have small effects on a few phenotypes, a small 1.4-kb region within the first intron of Eda has large effects on three phenotypic traits: lateral plate count, and both the number and patterning of the posterior lateral line neuromasts. Thus, the Eda haplotype is a hotspot of adaptation in stickleback due to both a small, pleiotropic region affecting multiple traits as well as multiple linked mutations affecting additional traits.
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Affiliation(s)
- Sophie L. Archambeault
- Institute of Ecology and EvolutionUniversity of BernBern3012Switzerland
- Graduate Program in Molecular and Cellular BiologyUniversity of WashingtonSeattleWashington98195
- Divisions of Basic Sciences and Human BiologyFred Hutchinson Cancer Research CenterSeattleWashington98109
| | - Luis R. Bärtschi
- Institute of Ecology and EvolutionUniversity of BernBern3012Switzerland
| | | | - Catherine L. Peichel
- Institute of Ecology and EvolutionUniversity of BernBern3012Switzerland
- Graduate Program in Molecular and Cellular BiologyUniversity of WashingtonSeattleWashington98195
- Divisions of Basic Sciences and Human BiologyFred Hutchinson Cancer Research CenterSeattleWashington98109
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34
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Amano T. Gene regulatory landscape of the sonic hedgehog locus in embryonic development. Dev Growth Differ 2020; 62:334-342. [PMID: 32343848 DOI: 10.1111/dgd.12668] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2020] [Revised: 03/31/2020] [Accepted: 04/15/2020] [Indexed: 12/22/2022]
Abstract
The organs of vertebrate species display a wide variety of morphology. A remaining challenge in evolutionary developmental biology is to elucidate how vertebrate lineages acquire distinct morphological features. Developmental programs are driven by spatiotemporal regulation of gene expression controlled by hundreds of thousands of cis-regulatory elements. Changes in the regulatory elements caused by the introduction of genetic variants can confer regulatory innovation that may underlie morphological novelties. Recent advances in sequencing technology have revealed a number of potential regulatory variants that can alter gene expression patterns. However, a limited number of studies demonstrate causal dependence between genetic and morphological changes. Regulation of Shh expression is a good model to understand how multiple regulatory elements organize tissue-specific gene expression patterns. This model also provides insights into how evolution of molecular traits, such as gene regulatory networks, lead to phenotypic novelty.
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Affiliation(s)
- Takanori Amano
- Next Generation Human Disease Model Team, RIKEN BioResource Research Center, Tsukuba, Japan
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35
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The complex genetic architecture of male mate choice evolution between Drosophila species. Heredity (Edinb) 2020; 124:737-750. [PMID: 32203250 DOI: 10.1038/s41437-020-0309-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 03/06/2020] [Accepted: 03/06/2020] [Indexed: 12/14/2022] Open
Abstract
Mate choice behaviors are among the most important reproductive isolating barriers in many animals. Little is known about the genetic basis of reproductively isolating behaviors, but examples to date provide evidence that they can have a simple genetic basis. However, it is unclear if these results indicate that individual genes with large effects are common, or are instead due to ascertainment biases. Here, we present the results of a QTL mapping study for the most important behavioral isolating barrier between Drosophila simulans and D. sechellia: male mate choice. Our QTL results initially suggested that differences in male mate choice may be due to a couple loci with large effects. However, as we divided the largest-effect QTL using stable introgression strains, we found evidence of multiple interacting loci. We further find that separate regions of the genome control different aspects of male choice. Taken together, our results suggest that the genetic architecture of mate choice behavior, in this case, is more complex than QTL mapping suggested, highlighting potential challenges to future mapping studies. We discuss the implications of these results as they relate to signal-receiver coevolution, mate choice, and reproductive isolation.
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36
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Tomoyasu Y, Halfon MS. How to study enhancers in non-traditional insect models. ACTA ACUST UNITED AC 2020; 223:223/Suppl_1/jeb212241. [PMID: 32034049 DOI: 10.1242/jeb.212241] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Transcriptional enhancers are central to the function and evolution of genes and gene regulation. At the organismal level, enhancers play a crucial role in coordinating tissue- and context-dependent gene expression. At the population level, changes in enhancers are thought to be a major driving force that facilitates evolution of diverse traits. An amazing array of diverse traits seen in insect morphology, physiology and behavior has been the subject of research for centuries. Although enhancer studies in insects outside of Drosophila have been limited, recent advances in functional genomic approaches have begun to make such studies possible in an increasing selection of insect species. Here, instead of comprehensively reviewing currently available technologies for enhancer studies in established model organisms such as Drosophila, we focus on a subset of computational and experimental approaches that are likely applicable to non-Drosophila insects, and discuss the pros and cons of each approach. We discuss the importance of validating enhancer function and evaluate several possible validation methods, such as reporter assays and genome editing. Key points and potential pitfalls when establishing a reporter assay system in non-traditional insect models are also discussed. We close with a discussion of how to advance enhancer studies in insects, both by improving computational approaches and by expanding the genetic toolbox in various insects. Through these discussions, this Review provides a conceptual framework for studying the function and evolution of enhancers in non-traditional insect models.
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Affiliation(s)
| | - Marc S Halfon
- Department of Biochemistry, University at Buffalo-State University of New York, Buffalo, NY 14203, USA
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37
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Kirbis A, Waller M, Ricca M, Bont Z, Neubauer A, Goffinet B, Szövényi P. Transcriptional Landscapes of Divergent Sporophyte Development in Two Mosses, Physcomitrium (Physcomitrella) patens and Funaria hygrometrica. FRONTIERS IN PLANT SCIENCE 2020; 11:747. [PMID: 32587596 PMCID: PMC7299128 DOI: 10.3389/fpls.2020.00747] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 05/11/2020] [Indexed: 05/03/2023]
Abstract
Understanding the molecular basis of morphological shifts is a fundamental question of evolutionary biology. New morphologies may arise through the birth/death of genes (gene gain/loss) or by reutilizing existing gene sets. Yet, the relative contribution of these two processes to radical morphological shifts is still poorly understood. Here, we use the model system of two mosses, Funaria hygrometrica and Physcomitrium (Physcomitrella) patens, to investigate the molecular mechanisms underlying contrasting sporophyte architectures. We used comparative analysis of time-series expression data for four stages of sporophyte development in both species to address this question in detail. We found that large-scale differences in sporophytic architecture are mainly governed by orthologous (i.e., shared) genes frequently experiencing temporal gene expression shifts between the two species. While the absolute number of species-specific genes expressed during sporophyte development is somewhat smaller, we observed a significant increase of their proportion in preferentially sporophyte expressed genes, suggesting a fundamental role in the sporophyte phase. However, further functional studies are necessary to determine their contribution to diverging sporophyte morphologies. Our results add to the growing set of studies suggesting that radical changes in morphology may rely on the heterochronic expression of conserved regulators.
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Affiliation(s)
- Alexander Kirbis
- Department of Systematic and Evolutionary Botany, University of Zurich, Zurich and Zurich-Basel Plant Science Center, Zurich, Switzerland
| | - Manuel Waller
- Department of Systematic and Evolutionary Botany, University of Zurich, Zurich and Zurich-Basel Plant Science Center, Zurich, Switzerland
| | - Mariana Ricca
- Department for BioMedical Research (DBMR), University of Bern, Bern, Switzerland
| | - Zoe Bont
- Institute of Plant Sciences, University of Bern, Bern, Switzerland
| | - Anna Neubauer
- Department of Systematic and Evolutionary Botany, University of Zurich, Zurich and Zurich-Basel Plant Science Center, Zurich, Switzerland
| | - Bernard Goffinet
- Department of Ecology and Evolutionary Biology, University of Connecticut, Storrs, CT, United States
| | - Péter Szövényi
- Department of Systematic and Evolutionary Botany, University of Zurich, Zurich and Zurich-Basel Plant Science Center, Zurich, Switzerland
- *Correspondence: Péter Szövényi,
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38
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The Genetic Basis of Scale-Loss Phenotype in the Rapid Radiation of Takifugu Fishes. Genes (Basel) 2019; 10:genes10121027. [PMID: 31835491 PMCID: PMC6947334 DOI: 10.3390/genes10121027] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 12/01/2019] [Accepted: 12/03/2019] [Indexed: 12/27/2022] Open
Abstract
Rapid radiation associated with phenotypic divergence and convergence provides an opportunity to study the genetic mechanisms of evolution. Here we investigate the genus Takifugu that has undergone explosive radiation relatively recently and contains a subset of closely-related species with a scale-loss phenotype. By using observations during development and genetic mapping approaches, we show that the scale-loss phenotype of two Takifugu species, T. pardalis Temminck & Schlegel and T. snyderi Abe, is largely controlled by an overlapping genomic segment (QTL). A search for candidate genes underlying the scale-loss phenotype revealed that the QTL region contains no known genes responsible for the evolution of scale-loss phenotype in other fishes. These results suggest that the genes used for the scale-loss phenotypes in the two Takifugu are likely the same, but the genes used for the similar phenotype in Takifugu and distantly related fishes are not the same. Meanwhile, Fgfrl1, a gene predicted to function in a pathway known to regulate bone/scale development was identified in the QTL region. Since Fgfr1a1, another memebr of the Fgf signaling pathway, has been implicated in scale loss/scale shape in fish distantly related to Takifugu, our results suggest that the convergence of the scale-loss phenotype may be constrained by signaling modules with conserved roles in scale development.
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Hajheidari M, Wang Y, Bhatia N, Vuolo F, Franco-Zorrilla JM, Karady M, Mentink RA, Wu A, Oluwatobi BR, Müller B, Dello Ioio R, Laurent S, Ljung K, Huijser P, Gan X, Tsiantis M. Autoregulation of RCO by Low-Affinity Binding Modulates Cytokinin Action and Shapes Leaf Diversity. Curr Biol 2019; 29:4183-4192.e6. [PMID: 31761704 DOI: 10.1016/j.cub.2019.10.040] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 10/08/2019] [Accepted: 10/21/2019] [Indexed: 11/28/2022]
Abstract
Mechanisms through which the evolution of gene regulation causes morphological diversity are largely unclear. The tremendous shape variation among plant leaves offers attractive opportunities to address this question. In cruciferous plants, the REDUCED COMPLEXITY (RCO) homeodomain protein evolved via gene duplication and acquired a novel expression domain that contributed to leaf shape diversity. However, the molecular pathways through which RCO regulates leaf growth are unknown. A key question is to identify genome-wide transcriptional targets of RCO and the DNA sequences to which RCO binds. We investigate this question using Cardamine hirsuta, which has complex leaves, and its relative Arabidopsis thaliana, which evolved simple leaves through loss of RCO. We demonstrate that RCO directly regulates genes controlling homeostasis of the hormone cytokinin to repress growth at the leaf base. Elevating cytokinin signaling in the RCO expression domain is sufficient to both transform A. thaliana simple leaves into complex ones and partially bypass the requirement for RCO in C. hirsuta complex leaf development. We also identify RCO as its own target gene. RCO directly represses its own transcription via an array of low-affinity binding sites, which evolved after RCO duplicated from its progenitor sequence. This autorepression is required to limit RCO expression. Thus, evolution of low-affinity binding sites created a negative autoregulatory loop that facilitated leaf shape evolution by defining RCO expression and fine-tuning cytokinin activity. In summary, we identify a transcriptional mechanism through which conflicts between novelty and pleiotropy are resolved during evolution and lead to morphological differences between species.
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Affiliation(s)
- Mohsen Hajheidari
- Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - Yi Wang
- Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - Neha Bhatia
- Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - Francesco Vuolo
- Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - José Manuel Franco-Zorrilla
- Unidad de Genómica and Departamento de Genética Molecular de Plantas, Centro Nacional de Biotecnología-Consejo Superior de Investigaciones Científicas, Calle Darwin 3, 28049 Madrid, Spain
| | - Michal Karady
- Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden
| | - Remco A Mentink
- Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - Anhui Wu
- Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - Bello Rilwan Oluwatobi
- Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - Bruno Müller
- Leibniz Institute of Plant Genetics and Crop Plant Research, Correnstr. 3, 06466 Seeland, Gatersleben, Germany
| | - Raffaele Dello Ioio
- Department of Biology and Biotechnology, Laboratory of Functional Genomics and Proteomics of Model Systems, Sapienza University of Rome, Via dei Sardi 70, 00185 Rome, Italy
| | - Stefan Laurent
- Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - Karin Ljung
- Umeå Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden
| | - Peter Huijser
- Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - Xiangchao Gan
- Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany
| | - Miltos Tsiantis
- Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany.
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Kondo T, Hayashi S. Two-step regulation of trachealess ensures tight coupling of cell fate with morphogenesis in the Drosophila trachea. eLife 2019; 8:45145. [PMID: 31439126 PMCID: PMC6707767 DOI: 10.7554/elife.45145] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 07/03/2019] [Indexed: 12/19/2022] Open
Abstract
During organogenesis, inductive signals cause cell differentiation and morphogenesis. However, how these phenomena are coordinated to form functional organs is poorly understood. Here, we show that cell differentiation of the Drosophila trachea is sequentially determined in two steps and that the second step is synchronous with the invagination of the epithelial sheet. The master gene trachealess is dispensable for the initiation of invagination, while it is essential for maintaining the invaginated structure, suggesting that tracheal morphogenesis and differentiation are separately induced. trachealess expression starts in bipotential tracheal/epidermal placode cells. After invagination, its expression is maintained in the invaginated cells but is extinguished in the remaining sheet cells. A trachealess cis-regulatory module that shows both tracheal enhancer activity and silencer activity in the surface epidermal sheet was identified. We propose that the coupling of trachealess expression with the invaginated structure ensures that only invaginated cells canalize robustly into the tracheal fate. Cells in developing organs have two important decisions to make: where to be and what cell type to become. If cells end up in the wrong places, they can stop an organ from working, so it is vital that one decision depends upon the other. The so-called progenitor cells responsible for forming the trachea, for example, can either become part of a flat sheet or part of a tube. The cells on the sheet need to become epidermal cells, while the cells in the tube need to become tracheal cells. Work on fruit flies found that a gene called 'trachealess' plays an important role in this process. Without it, developing flies cannot make a trachea at all. At the start of trachea development, some of the cells form thickened structures called placodes. The progenitor cells in the placodes start to divide, and the structures buckle inwards to form pockets. These pockets then lengthen into tubes. The trachealess gene codes for a protein that works as a genetic switch. It turns other genes on or off, helping the progenitor cells inside the pockets to become tracheal cells. But, it is not clear whether trachealess drives the formation of the pockets: the progenitor cells first decide what to be; or whether pocket formation tells the cells to use trachealess: the progenitor cells first decide where to be. To find out, Kondo and Hayashi imaged developing fly embryos and saw that the trachealess gene does not start pocket formation, but that it is essential to maintain the pockets. Flies without the gene managed to form pockets, but they did not last long. Looking at embryos with defects in other genes involved in pocket formation revealed why. In these flies, some of the progenitor cells using trachealess got left behind when the pockets started to form. But rather than forming pockets of their own (as they might if trachealess were driving pocket formation), they turned their trachealess gene off. Progenitor cells in the fly trachea seem to decide where to be before they decide what cell type to become. This helps to make sure that trachea cells do not form in the wrong places. A question that still remains is how do the cells know when they are inside a pocket? It is possible that the cells are sensing different mechanical forces or different chemical signals. Further research could help scientists to understand how organs form in living animals, and how they might better recreate that process in the laboratory.
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Affiliation(s)
- Takefumi Kondo
- Graduate School of Biostudies, Kyoto University, Kyoto, Japan.,The Keihanshin Consortium for Fostering the Next Generation of Global Leaders in Research (K-CONNEX), Kyoto, Japan
| | - Shigeo Hayashi
- Laboratory for Morphogenetic Signaling, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan.,Department of Biology, Kobe University Graduate School of Science, Kobe, Japan
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Sabarís G, Laiker I, Preger-Ben Noon E, Frankel N. Actors with Multiple Roles: Pleiotropic Enhancers and the Paradigm of Enhancer Modularity. Trends Genet 2019; 35:423-433. [DOI: 10.1016/j.tig.2019.03.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 03/21/2019] [Indexed: 10/27/2022]
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Hajheidari M, Koncz C, Bucher M. Chromatin Evolution-Key Innovations Underpinning Morphological Complexity. FRONTIERS IN PLANT SCIENCE 2019; 10:454. [PMID: 31031789 PMCID: PMC6474313 DOI: 10.3389/fpls.2019.00454] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 03/26/2019] [Indexed: 05/20/2023]
Abstract
The history of life consists of a series of major evolutionary transitions, including emergence and radiation of complex multicellular eukaryotes from unicellular ancestors. The cells of multicellular organisms, with few exceptions, contain the same genome, however, their organs are composed of a variety of cell types that differ in both structure and function. This variation is largely due to the transcriptional activity of different sets of genes in different cell types. This indicates that complex transcriptional regulation played a key role in the evolution of complexity in eukaryotes. In this review, we summarize how gene duplication and subsequent evolutionary innovations, including the structural evolution of nucleosomes and chromatin-related factors, contributed to the complexity of the transcriptional system and provided a basis for morphological diversity.
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Affiliation(s)
- Mohsen Hajheidari
- Botanical Institute, Cologne Biocenter, Cluster of Excellence on Plant Sciences, University of Cologne, Cologne, Germany
| | - Csaba Koncz
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany
- Biological Research Center, Institute of Plant Biology, Hungarian Academy of Sciences, Szeged, Hungary
| | - Marcel Bucher
- Botanical Institute, Cologne Biocenter, Cluster of Excellence on Plant Sciences, University of Cologne, Cologne, Germany
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Ray S, Rosenberg MI, Chanut-Delalande H, Decaras A, Schwertner B, Toubiana W, Auman T, Schnellhammer I, Teuscher M, Valenti P, Khila A, Klingler M, Payre F. The mlpt/Ubr3/Svb module comprises an ancient developmental switch for embryonic patterning. eLife 2019; 8:e39748. [PMID: 30896406 PMCID: PMC6428570 DOI: 10.7554/elife.39748] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 03/07/2019] [Indexed: 12/30/2022] Open
Abstract
Small open reading frames (smORFs) encoding 'micropeptides' exhibit remarkable evolutionary complexity. Conserved peptides encoded by mille-pattes (mlpt)/polished rice (pri)/tarsal less (tal) are essential for embryo segmentation in Tribolium but, in Drosophila, function in terminal epidermal differentiation and patterning of adult legs. Here, we show that a molecular complex identified in Drosophila epidermal differentiation, comprising Mlpt peptides, ubiquitin-ligase Ubr3 and transcription factor Shavenbaby (Svb), represents an ancient developmental module required for early insect embryo patterning. We find that loss of segmentation function for this module in flies evolved concomitantly with restriction of Svb expression in early Drosophila embryos. Consistent with this observation, artificially restoring early Svb expression in flies causes segmentation defects that depend on mlpt function, demonstrating enduring potency of an ancestral developmental switch despite evolving embryonic patterning modes. These results highlight the evolutionary plasticity of conserved molecular complexes under the constraints of essential genetic networks. Editorial note This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).
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Affiliation(s)
- Suparna Ray
- Department of Biology, Developmental BiologyUniversity of Erlangen-NurembergErlangenGermany
| | - Miriam I Rosenberg
- Department of Ecology, Evolution and BehaviorHebrew University of JerusalemJerusalemIsrael
| | | | | | - Barbara Schwertner
- Department of Biology, Developmental BiologyUniversity of Erlangen-NurembergErlangenGermany
| | | | - Tzach Auman
- Department of Ecology, Evolution and BehaviorHebrew University of JerusalemJerusalemIsrael
| | - Irene Schnellhammer
- Department of Biology, Developmental BiologyUniversity of Erlangen-NurembergErlangenGermany
| | - Matthias Teuscher
- Department of Biology, Developmental BiologyUniversity of Erlangen-NurembergErlangenGermany
| | - Philippe Valenti
- Centre de Biologie du Développement, Université Paul Sabatier de ToulouseToulouseFrance
| | | | - Martin Klingler
- Department of Biology, Developmental BiologyUniversity of Erlangen-NurembergErlangenGermany
| | - François Payre
- Centre de Biologie du Développement, Université Paul Sabatier de ToulouseToulouseFrance
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Neural Evolution of Context-Dependent Fly Song. Curr Biol 2019; 29:1089-1099.e7. [PMID: 30880014 DOI: 10.1016/j.cub.2019.02.019] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 12/21/2018] [Accepted: 02/05/2019] [Indexed: 01/06/2023]
Abstract
It is unclear where in the nervous system evolutionary changes tend to occur. To localize the source of neural evolution that has generated divergent behaviors, we developed a new approach to label and functionally manipulate homologous neurons across Drosophila species. We examined homologous descending neurons that drive courtship song in two species that sing divergent song types and localized relevant evolutionary changes in circuit function downstream of the intrinsic physiology of these descending neurons. This evolutionary change causes different species to produce divergent motor patterns in similar social contexts. Artificial stimulation of these descending neurons drives multiple song types, suggesting that multifunctional properties of song circuits may facilitate rapid evolution of song types.
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45
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Redundant and Cryptic Enhancer Activities of the Drosophila yellow Gene. Genetics 2019; 212:343-360. [PMID: 30842209 DOI: 10.1534/genetics.119.301985] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 02/25/2019] [Indexed: 11/18/2022] Open
Abstract
Cis-regulatory sequences known as enhancers play a key role in regulating gene expression. Evolutionary changes in these DNA sequences contribute to phenotypic evolution. The Drosophila yellow gene, which is required for pigmentation, has emerged as a model system for understanding how cis-regulatory sequences evolve, providing some of the most detailed insights available into how activities of orthologous enhancers have diverged between species. Here, we examine the evolution of yellow cis-regulatory sequences on a broader scale, by comparing the distribution and function of yellow enhancer activities throughout the 5' intergenic and intronic sequences of Drosophila melanogaster, D. pseudoobscura, and D. willistoni We find that cis-regulatory sequences driving expression in a particular tissue are not as modular as previously described, but rather have many redundant and cryptic enhancer activities distributed throughout the regions surveyed. Interestingly, cryptic enhancer activities of sequences from one species often drove patterns of expression observed in other species, suggesting that the frequent evolutionary changes in yellow expression observed among Drosophila species may be facilitated by gaining and losing repression of preexisting cis-regulatory sequences.
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46
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Bohère J, Mancheno-Ferris A, Al Hayek S, Zanet J, Valenti P, Akino K, Yamabe Y, Inagaki S, Chanut-Delalande H, Plaza S, Kageyama Y, Osman D, Polesello C, Payre F. Shavenbaby and Yorkie mediate Hippo signaling to protect adult stem cells from apoptosis. Nat Commun 2018; 9:5123. [PMID: 30504772 PMCID: PMC6269459 DOI: 10.1038/s41467-018-07569-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 11/12/2018] [Indexed: 01/06/2023] Open
Abstract
To compensate for accumulating damages and cell death, adult homeostasis (e.g., body fluids and secretion) requires organ regeneration, operated by long-lived stem cells. How stem cells can survive throughout the animal life remains poorly understood. Here we show that the transcription factor Shavenbaby (Svb, OvoL in vertebrates) is expressed in renal/nephric stem cells (RNSCs) of Drosophila and required for their maintenance during adulthood. As recently shown in embryos, Svb function in adult RNSCs further needs a post-translational processing mediated by the Polished rice (Pri) smORF peptides and impairing Svb function leads to RNSC apoptosis. We show that Svb interacts both genetically and physically with Yorkie (YAP/TAZ in vertebrates), a nuclear effector of the Hippo pathway, to activate the expression of the inhibitor of apoptosis DIAP1. These data therefore identify Svb as a nuclear effector in the Hippo pathway, critical for the survival of adult somatic stem cells.
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Affiliation(s)
- Jérôme Bohère
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Bat 4R3, 118 route de Narbonne, F-31062, Toulouse, France
| | - Alexandra Mancheno-Ferris
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Bat 4R3, 118 route de Narbonne, F-31062, Toulouse, France
| | - Sandy Al Hayek
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Bat 4R3, 118 route de Narbonne, F-31062, Toulouse, France
- Faculty of Sciences III, Lebanese University, Tripoli, 1300, Lebanon
- Azm Center for Research in Biotechnology and its Applications, LBA3B, EDST, Lebanese University, Tripoli, 1300, Lebanon
| | - Jennifer Zanet
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Bat 4R3, 118 route de Narbonne, F-31062, Toulouse, France
| | - Philippe Valenti
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Bat 4R3, 118 route de Narbonne, F-31062, Toulouse, France
| | - Kohsuke Akino
- Department of Biology, Graduate School of Science, Kobe, 657-8501, Japan
| | - Yuya Yamabe
- Department of Biology, Graduate School of Science, Kobe, 657-8501, Japan
| | - Sachi Inagaki
- Biosignal Research Center, Kobe University, 1-1 Rokko-dai, Nada, Kobe, 657-8501, Japan
| | - Hélène Chanut-Delalande
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Bat 4R3, 118 route de Narbonne, F-31062, Toulouse, France
| | - Serge Plaza
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Bat 4R3, 118 route de Narbonne, F-31062, Toulouse, France
- Laboratoire de Recherche en Sciences Végétales (LSRV), CNRS, UPS, 24 chemin de Borde Rouge, Auzeville, 31326, Castanet-Tolosan, France
| | - Yuji Kageyama
- Department of Biology, Graduate School of Science, Kobe, 657-8501, Japan
- Biosignal Research Center, Kobe University, 1-1 Rokko-dai, Nada, Kobe, 657-8501, Japan
| | - Dani Osman
- Faculty of Sciences III, Lebanese University, Tripoli, 1300, Lebanon
- Azm Center for Research in Biotechnology and its Applications, LBA3B, EDST, Lebanese University, Tripoli, 1300, Lebanon
| | - Cédric Polesello
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Bat 4R3, 118 route de Narbonne, F-31062, Toulouse, France.
| | - François Payre
- Centre de Biologie du Développement (CBD), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Bat 4R3, 118 route de Narbonne, F-31062, Toulouse, France.
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Liu Q, Onal P, Datta RR, Rogers JM, Schmidt-Ott U, Bulyk ML, Small S, Thornton JW. Ancient mechanisms for the evolution of the bicoid homeodomain's function in fly development. eLife 2018; 7:e34594. [PMID: 30298815 PMCID: PMC6177261 DOI: 10.7554/elife.34594] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 07/28/2018] [Indexed: 12/14/2022] Open
Abstract
The ancient mechanisms that caused developmental gene regulatory networks to diversify among distantly related taxa are not well understood. Here we use ancestral protein reconstruction, biochemical experiments, and developmental assays of transgenic animals carrying reconstructed ancestral genes to investigate how the transcription factor Bicoid (Bcd) evolved its central role in anterior-posterior patterning in flies. We show that most of Bcd's derived functions are attributable to evolutionary changes within its homeodomain (HD) during a phylogenetic interval >140 million years ago. A single substitution from this period (Q50K) accounts almost entirely for the evolution of Bcd's derived DNA specificity in vitro. In transgenic embryos expressing the reconstructed ancestral HD, however, Q50K confers activation of only a few of Bcd's transcriptional targets and yields a very partial rescue of anterior development. Adding a second historical substitution (M54R) confers regulation of additional Bcd targets and further rescues anterior development. These results indicate that two epistatically interacting mutations played a major role in the evolution of Bcd's controlling regulatory role in early development. They also show how ancestral sequence reconstruction can be combined with in vivo characterization of transgenic animals to illuminate the historical mechanisms of developmental evolution.
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Affiliation(s)
- Qinwen Liu
- Department of Ecology and EvolutionUniversity of ChicagoChicagoUnited States
| | - Pinar Onal
- Department of BiologyNew York UniversityNew YorkUnited States
| | - Rhea R Datta
- Department of BiologyNew York UniversityNew YorkUnited States
| | - Julia M Rogers
- Committee on Higher Degrees in BiophysicsHarvard UniversityCambridgeUnited States
- Division of Genetics, Department of MedicineBrigham and Women’s Hospital and Harvard Medical SchoolBostonUnited States
| | - Urs Schmidt-Ott
- Department of Organismal Biology and AnatomyUniversity of ChicagoChicagoUnited States
| | - Martha L Bulyk
- Committee on Higher Degrees in BiophysicsHarvard UniversityCambridgeUnited States
- Division of Genetics, Department of MedicineBrigham and Women’s Hospital and Harvard Medical SchoolBostonUnited States
- Department of PathologyBrigham and Women’s Hospital and Harvard Medical SchoolBostonUnited States
| | - Stephen Small
- Department of BiologyNew York UniversityNew YorkUnited States
| | - Joseph W Thornton
- Department of Ecology and EvolutionUniversity of ChicagoChicagoUnited States
- Department of Human GeneticsUniversity of ChicagoChicagoUnited States
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48
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Baudouin-Gonzalez L, Santos MA, Tempesta C, Sucena É, Roch F, Tanaka K. Diverse Cis-Regulatory Mechanisms Contribute to Expression Evolution of Tandem Gene Duplicates. Mol Biol Evol 2018; 34:3132-3147. [PMID: 28961967 PMCID: PMC5850857 DOI: 10.1093/molbev/msx237] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Pairs of duplicated genes generally display a combination of conserved expression patterns inherited from their unduplicated ancestor and newly acquired domains. However, how the cis-regulatory architecture of duplicated loci evolves to produce these expression patterns is poorly understood. We have directly examined the gene-regulatory evolution of two tandem duplicates, the Drosophila Ly6 genes CG9336 and CG9338, which arose at the base of the drosophilids between 40 and 60 Ma. Comparing the expression patterns of the two paralogs in four Drosophila species with that of the unduplicated ortholog in the tephritid Ceratitis capitata, we show that they diverged from each other as well as from the unduplicated ortholog. Moreover, the expression divergence appears to have occurred close to the duplication event and also more recently in a lineage-specific manner. The comparison of the tissue-specific cis-regulatory modules (CRMs) controlling the paralog expression in the four Drosophila species indicates that diverse cis-regulatory mechanisms, including the novel tissue-specific enhancers, differential inactivation, and enhancer sharing, contributed to the expression evolution. Our analysis also reveals a surprisingly variable cis-regulatory architecture, in which the CRMs driving conserved expression domains change in number, location, and specificity. Altogether, this study provides a detailed historical account that uncovers a highly dynamic picture of how the paralog expression patterns and their underlying cis-regulatory landscape evolve. We argue that our findings will encourage studying cis-regulatory evolution at the whole-locus level to understand how interactions between enhancers and other regulatory levels shape the evolution of gene expression.
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Affiliation(s)
- Luís Baudouin-Gonzalez
- Instituto Gulbenkian de Ciência, Oeiras, Portugal.,Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, France
| | | | - Camille Tempesta
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, France
| | - Élio Sucena
- Instituto Gulbenkian de Ciência, Oeiras, Portugal.,Departamento de Biologia Animal, Faculdade de Ciências, Universidade de Lisboa, Lisbon, Portugal
| | - Fernando Roch
- Centre de Biologie du Développement, Centre de Biologie Intégrative, Université de Toulouse, CNRS, UPS, France
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49
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Motifome comparison between modern human, Neanderthal and Denisovan. BMC Genomics 2018; 19:472. [PMID: 29914355 PMCID: PMC6006668 DOI: 10.1186/s12864-018-4710-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 04/22/2018] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND The availability of the genomes of two archaic humans, Neanderthal and Denisovan, and that of modern humans provides researchers an opportunity to investigate genetic differences between these three subspecies on a genome-wide scale. Here we describe an algorithm that predicts statistically significant motifs based on the difference between a given motif's actual and expected distributions. The algorithm was previously applied to plants but was modified for this work. RESULTS The result of applying the algorithm to the human, Neanderthal, and Denisovan genomes is a catalog of potential regulatory motifs in these three human subspecies. We examined the distributions of these motifs in genetic elements including human retroviruses, human accelerated regions, and human accelerated conserved noncoding sequences regions. Differences in these distributions could be the origin of differences in phenotype between the three subspecies. Twenty significant motifs common to all three genomes were found; thirty-three were found in endogenous retroviruses in Neanderthal and Denisovan. Ten of these motifs mapped to the 22 bp core of MiR-1304. The core of this genetic element regulates the ENAM and AMTN genes, which take part in odontogenesis and whose 3' UTRs contained significant motifs. The introns of 20 genes were found to contain a large number of significant motifs, which were also overrepresented in 49 human accelerated regions. These genes include NAV2, SorCS2, TRAPPC9, GRID1, PRDM16, CAMTA1, and ASIC which are all involved in neuroregulation. Further analysis of these genes using the GO database indicates that many are associated with neurodevelopment. Also, varying numbers of significant motifs were found to occur in regions of the Neanderthal and Denisovan genomes that are missing from the human genome, suggesting further functional differences between modern and archaic humans. CONCLUSION Although Neanderthal and Denisovan are now extinct, detailed examination of elements from their genomes can shed light on possible phenotypic and cognitive differences between these two archaic human subspecies and modern humans. Genetic similarities and differences between these three subspecies and other fossil hominids would also be of interest.
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Gene regulatory network architecture in different developmental contexts influences the genetic basis of morphological evolution. PLoS Genet 2018; 14:e1007375. [PMID: 29723190 PMCID: PMC5953500 DOI: 10.1371/journal.pgen.1007375] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Revised: 05/15/2018] [Accepted: 04/23/2018] [Indexed: 01/09/2023] Open
Abstract
Convergent phenotypic evolution is often caused by recurrent changes at particular nodes in the underlying gene regulatory networks (GRNs). The genes at such evolutionary ‘hotspots’ are thought to maximally affect the phenotype with minimal pleiotropic consequences. This has led to the suggestion that if a GRN is understood in sufficient detail, the path of evolution may be predictable. The repeated evolutionary loss of larval trichomes among Drosophila species is caused by the loss of shavenbaby (svb) expression. svb is also required for development of leg trichomes, but the evolutionary gain of trichomes in the ‘naked valley’ on T2 femurs in Drosophila melanogaster is caused by reduced microRNA-92a (miR-92a) expression rather than changes in svb. We compared the expression and function of components between the larval and leg trichome GRNs to investigate why the genetic basis of trichome pattern evolution differs in these developmental contexts. We found key differences between the two networks in both the genes employed, and in the regulation and function of common genes. These differences in the GRNs reveal why mutations in svb are unlikely to contribute to leg trichome evolution and how instead miR-92a represents the key evolutionary switch in this context. Our work shows that variability in GRNs across different developmental contexts, as well as whether a morphological feature is lost versus gained, influence the nodes at which a GRN evolves to cause morphological change. Therefore, our findings have important implications for understanding the pathways and predictability of evolution. A major goal of biology is to identify the genetic causes of organismal diversity. Convergent evolution of traits is often caused by changes in the same genes–evolutionary ‘hotspots’. shavenbaby is a ‘hotspot’ for larval trichome loss in Drosophila, but microRNA-92a underlies the gain of leg trichomes. To understand this difference in the genetics of phenotypic evolution, we compared the expression and function of genes in the underlying regulatory networks. We found that the pathway of evolution is influenced by differences in gene regulatory network architecture in different developmental contexts, as well as by whether a trait is lost or gained. Therefore, hotspots in one context may not readily evolve in a different context. This has important implications for understanding the genetic basis of phenotypic change and the predictability of evolution.
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