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Herrick J. Kimura's Theory of Non-Adaptive Radiation and Peto's Paradox: A Missing Link? BIOLOGY 2023; 12:1140. [PMID: 37627024 PMCID: PMC10452704 DOI: 10.3390/biology12081140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 08/07/2023] [Accepted: 08/15/2023] [Indexed: 08/27/2023]
Abstract
Karyotype diversity reflects genome integrity and stability. A strong correlation between karyotype diversity and species richness, meaning the number of species in a phylogenetic clade, was first reported in mammals over forty years ago: in mammalian phylogenetic clades, the standard deviation of karyotype diversity (KD) closely corresponded to species richness (SR) at the order level. These initial studies, however, did not control for phylogenetic signal, raising the possibility that the correlation was due to phylogenetic relatedness among species in a clade. Accordingly, karyotype diversity trivially reflects species richness simply as a passive consequence of adaptive radiation. A more recent study in mammals controlled for phylogenetic signals and established the correlation as phylogenetically independent, suggesting that species richness cannot, in itself, explain the observed corresponding karyotype diversity. The correlation is, therefore, remarkable because the molecular mechanisms contributing to karyotype diversity are evolutionarily independent of the ecological mechanisms contributing to species richness. Recently, it was shown in salamanders that the two processes generating genome size diversity and species richness were indeed independent and operate in parallel, suggesting a potential non-adaptive, non-causal but biologically meaningful relationship. KD depends on mutational input generating genetic diversity and reflects genome stability, whereas species richness depends on ecological factors and reflects natural selection acting on phenotypic diversity. As mutation and selection operate independently and involve separate and unrelated evolutionary mechanisms-there is no reason a priori to expect such a strong, let alone any, correlation between KD and SR. That such a correlation exists is more consistent with Kimura's theory of non-adaptive radiation than with ecologically based adaptive theories of macro-evolution, which are not excluded in Kimura's non-adaptive theory. The following reviews recent evidence in support of Kimura's proposal, and other findings that contribute to a wider understanding of the molecular mechanisms underlying the process of non-adaptive radiation.
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Affiliation(s)
- John Herrick
- Independent Researcher, 3, rue des Jeûneurs, 75002 Paris, France
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Zhao Q, Shao F, Li Y, Yi SV, Peng Z. Novel genome sequence of Chinese cavefish (Triplophysa rosa) reveals pervasive relaxation of natural selection in cavefish genomes. Mol Ecol 2022; 31:5831-5845. [PMID: 36125323 PMCID: PMC9828065 DOI: 10.1111/mec.16700] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 09/15/2022] [Indexed: 01/13/2023]
Abstract
All cavefishes, living exclusively in caves across the globe, exhibit similar phenotypic traits, including the characteristic loss of eyes. To understand whether such phenotypic convergence shares similar genomic bases, here we investigated genome-wide evolutionary signatures of cavefish phenotypes by comparing whole-genome sequences of three pairs of cavefishes and their surface fish relatives. Notably, we newly sequenced and generated a whole-genome assembly of the Chinese cavefish Triplophysa rosa. Our comparative analyses revealed several shared features of cavefish genome evolution. Cavefishes had lower mutation rates than their surface fish relatives. In contrast, the ratio of nonsynonymous to synonymous substitutions (ω) was significantly elevated in cavefishes compared to in surface fishes, consistent with the relaxation of purifying selection. In addition, cavefish genomes had an increased mutational load, including mutations that alter protein hydrophobicity profiles, which were considered harmful. Interestingly, however, we found no overlap in positively selected genes among different cavefish lineages, indicating that the phenotypic convergence in cavefishes was not caused by positive selection of the same sets of genes. Analyses of previously identified candidate genes associated with cave phenotypes supported this conclusion. Genes belonging to the lipid metabolism functional ontology were under relaxed purifying selection in all cavefish genomes, which may be associated with the nutrient-poor habitat of cavefishes. Our work reveals previously uncharacterized patterns of cavefish genome evolution and provides comparative insights into the evolution of cave-associated phenotypic traits.
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Affiliation(s)
- Qingyuan Zhao
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education)Southwest University School of Life SciencesChongqingChina,Department of Laboratory Animal Science, College of Basic Medical SciencesArmy Medical University (Third Military Medical University)ChongqingChina
| | - Feng Shao
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education)Southwest University School of Life SciencesChongqingChina
| | - Yanping Li
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education)Southwest University School of Life SciencesChongqingChina,Key Laboratory of Sichuan Province for Fish Conservation and Utilization in the Upper Reaches of the Yangtze RiverNeijiang Normal University College of Life SciencesNeijiangChina
| | - Soojin V. Yi
- Department of Ecology, Evolution and Marine BiologyUniversity of CaliforniaSanta BarbaraCaliforniaUSA
| | - Zuogang Peng
- Key Laboratory of Freshwater Fish Reproduction and Development (Ministry of Education)Southwest University School of Life SciencesChongqingChina,Academy of Plateau Science and SustainabilityQinghai Normal UniversityXiningChina
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Morgan T, Custódio FA, Tavares MP, Pereira OL, Guimarães VM, de Oliveira Mendes TA. Genome sequencing and evolutionary analysis of a new endophytic Trichoderma species isolated from orchid roots with reduced repertoire of protein-coding genes. Mycol Prog 2022. [DOI: 10.1007/s11557-022-01811-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Ezaz T, Edwards SV. Editorial: Evolutionary Feedbacks Between Population Biology and Genome Architecture. Front Genet 2018; 9:329. [PMID: 30186309 PMCID: PMC6112050 DOI: 10.3389/fgene.2018.00329] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2018] [Accepted: 07/31/2018] [Indexed: 01/11/2023] Open
Affiliation(s)
- Tariq Ezaz
- Institute for Applied Ecology, University of Canberra Canberra, ACT, Australia
| | - Scott V Edwards
- Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University Cambridge, MA, United States
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Evolutionary comparisons of miRNA regulation system in six model organisms. Genetica 2014; 142:109-18. [DOI: 10.1007/s10709-014-9758-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 02/01/2014] [Indexed: 01/05/2023]
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Ai B, Wang ZS, Ge S. GENOME SIZE IS NOT CORRELATED WITH EFFECTIVE POPULATION SIZE IN THEORYZASPECIES. Evolution 2012; 66:3302-10. [DOI: 10.1111/j.1558-5646.2012.01674.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Xu K, Bezakova I, Bunimovich L, Yi SV. Path lengths in protein-protein interaction networks and biological complexity. Proteomics 2011; 11:1857-67. [DOI: 10.1002/pmic.201000684] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Revised: 01/16/2011] [Accepted: 01/24/2011] [Indexed: 01/15/2023]
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Whitney KD, Garland T. Did genetic drift drive increases in genome complexity? PLoS Genet 2010; 6. [PMID: 20865118 PMCID: PMC2928810 DOI: 10.1371/journal.pgen.1001080] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Accepted: 07/22/2010] [Indexed: 11/18/2022] Open
Abstract
Mechanisms underlying the dramatic patterns of genome size variation across the tree of life remain mysterious. Effective population size (N(e)) has been proposed as a major driver of genome size: selection is expected to efficiently weed out deleterious mutations increasing genome size in lineages with large (but not small) N(e). Strong support for this model was claimed from a comparative analysis of N(e)u and genome size for ≈30 phylogenetically diverse species ranging from bacteria to vertebrates, but analyses at that scale have so far failed to account for phylogenetic nonindependence of species. In our reanalysis, accounting for phylogenetic history substantially altered the perceived strength of the relationship between N(e)u and genomic attributes: there were no statistically significant associations between N(e)u and gene number, intron size, intron number, the half-life of gene duplicates, transposon number, transposons as a fraction of the genome, or overall genome size. We conclude that current datasets do not support the hypothesis of a mechanistic connection between N(e) and these genomic attributes, and we suggest that further progress requires larger datasets, phylogenetic comparative methods, more robust estimators of genetic drift, and a multivariate approach that accounts for correlations between putative explanatory variables.
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Affiliation(s)
- Kenneth D Whitney
- Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas, United States of America.
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[The impact of microRNAs on the evolution of metazoan complexity]. YI CHUAN = HEREDITAS 2010; 32:105-14. [PMID: 20176553 DOI: 10.3724/sp.j.1005.2010.00105] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
MicroRNAs (miRNAs) are a novel class of ~22 nt non-coding small RNAs. As crucial post-transcriptional regulators, miRNAs are involved in comprehensive biological processes such as developmental timing, cell proliferation and differentiation, oncogenesis and viral defenses. In addition to the roles in ontogenic physiology, researches on the area of miRNA phylogenetic conservation and diversity suggested that miRNAs play important roles in animal evolution through driving phenotypic variations in development. It has been postulated that miRNAs have enormous impacts on phenotypic variation and developmental complexity. Here we reviewed recent advances in the studies on the roles of miRNA in animal evolution, from aspects of the rate of miRNA evolution, the spatio-temporal expression pattern, the variation of target sites, and miRNA gene dynamics. We gave evidence to support the hypothesis that innovations in miRNA-mediated regulations drive the increase of metazoan complexity.
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McCoy MW, Allen AP, Gillooly JF. The random nature of genome architecture: predicting open reading frame distributions. PLoS One 2009; 4:e6456. [PMID: 19649247 PMCID: PMC2714469 DOI: 10.1371/journal.pone.0006456] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2009] [Accepted: 06/23/2009] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND A better understanding of the size and abundance of open reading frames (ORFS) in whole genomes may shed light on the factors that control genome complexity. Here we examine the statistical distributions of open reading frames (i.e. distribution of start and stop codons) in the fully sequenced genomes of 297 prokaryotes, and 14 eukaryotes. METHODOLOGY/PRINCIPAL FINDINGS By fitting mixture models to data from whole genome sequences we show that the size-frequency distributions for ORFS are strikingly similar across prokaryotic and eukaryotic genomes. Moreover, we show that i) a large fraction (60-80%) of ORF size-frequency distributions can be predicted a priori with a stochastic assembly model based on GC content, and that (ii) size-frequency distributions of the remaining "non-random" ORFs are well-fitted by log-normal or gamma distributions, and similar to the size distributions of annotated proteins. CONCLUSIONS/SIGNIFICANCE Our findings suggest stochastic processes have played a primary role in the evolution of genome complexity, and that common processes govern the conservation and loss of functional genomics units in both prokaryotes and eukaryotes.
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Affiliation(s)
- Michael W McCoy
- Department of Biology, Boston University, Boston, Massachusetts, United States of America.
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Guo WJ, Ling J, Li P. Consensus features of microsatellite distribution: Microsatellite contents are universally correlated with recombination rates and are preferentially depressed by centromeres in multicellular eukaryotic genomes. Genomics 2009; 93:323-31. [DOI: 10.1016/j.ygeno.2008.12.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2008] [Revised: 12/14/2008] [Accepted: 12/16/2008] [Indexed: 10/21/2022]
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Assis R, Kondrashov AS, Koonin EV, Kondrashov FA. Nested genes and increasing organizational complexity of metazoan genomes. Trends Genet 2008; 24:475-8. [PMID: 18774620 PMCID: PMC3380635 DOI: 10.1016/j.tig.2008.08.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Revised: 07/24/2008] [Accepted: 08/01/2008] [Indexed: 10/21/2022]
Abstract
The most common form of protein-coding gene overlap in eukaryotes is a simple nested structure, whereby one gene is embedded in an intron of another. Analysis of nested protein-coding genes in vertebrates, fruit flies and nematodes revealed substantially higher rates of evolutionary gains than losses. The accumulation of nested gene structures could not be attributed to any obvious functional relationships between the genes involved and represents an increase of the organizational complexity of animal genomes via a neutral process.
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Affiliation(s)
- Raquel Assis
- Center for Computational Medicine and Biology and the Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
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Jackson HA, Accili EA. Evolutionary analyses of KCNQ1 and HERG voltage-gated potassium channel sequences reveal location-specific susceptibility and augmented chemical severities of arrhythmogenic mutations. BMC Evol Biol 2008; 8:188. [PMID: 18590565 PMCID: PMC2483723 DOI: 10.1186/1471-2148-8-188] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2008] [Accepted: 06/30/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Mutations in HERG and KCNQ1 potassium channels have been associated with Long QT syndrome and atrial fibrillation, and more recently with sudden infant death syndrome and sudden unexplained death. In other proteins, disease-associated amino acid mutations have been analyzed according to the chemical severity of the changes and the locations of the altered amino acids according to their conservation over metazoan evolution. Here, we present the first such analysis of arrhythmia-associated mutations (AAMs) in the HERG and KCNQ1 potassium channels. RESULTS Using evolutionary analyses, AAMs in HERG and KCNQ1 were preferentially found at evolutionarily conserved sites and unevenly distributed among functionally conserved domains. Non-synonymous single nucleotide polymorphisms (nsSNPs) are under-represented at evolutionarily conserved sites in HERG, but distribute randomly in KCNQ1. AAMs are chemically more severe, according to Grantham's Scale, than changes observed in evolution and their severity correlates with the expected chemical severity of the involved codon. Expected chemical severity of a given amino acid also correlates with its relative contribution to arrhythmias. At evolutionarily variable sites, the chemical severity of the changes is also correlated with the expected chemical severity of the involved codon. CONCLUSION Unlike nsSNPs, AAMs preferentially locate to evolutionarily conserved, and functionally important, sites and regions within HERG and KCNQ1, and are chemically more severe than changes which occur in evolution. Expected chemical severity may contribute to the overrepresentation of certain residues in AAMs, as well as to evolutionary change.
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Affiliation(s)
- Heather A Jackson
- Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.
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Abstract
The several thousand-fold range in genome size among animals has remained a subject of active research and debate for more than half a century, but no satisfactory explanation has yet been provided. Many one-dimensional models have been postulated, but so far none has been successful in accounting for observed patterns in genome size diversity. The recent model based on differences in effective population size appeared to gain empirical support with a study of genome size and inferred effective population size in fishes, but there were several questionable aspects of the analysis. First, it was based on an assumption that microsatellite heterozygosity indicates long-term effective population size, whereas in actuality these markers evolve quickly and are sensitive to demographic events. Second, it included both ancient polyploids and non-polyploids, the former of which did not gain their current genome sizes through the accumulation of slightly deleterious mutations as required in the model. Third, the analysis neglected the tremendous influence that Pleistocene glaciation bottlenecks had on heterozygosities in freshwater (and far less so, marine) fishes. In sum, it is apparent that genomes reached their current sizes in most fishes long before contemporary microsatellite heterozygosities were shaped, and that ancient polyploidy rather than the accumulation of mildly deleterious transposon insertions in small populations is the dominant factor that has influenced the large end of the range of genome sizes among fishes.
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Affiliation(s)
- T Ryan Gregory
- Department of Integrative Biology University of Guelph, Guelph, ON N1G 2W1, Canada.
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Garvin-Doxas K, Klymkowsky MW. Understanding randomness and its impact on student learning: lessons learned from building the Biology Concept Inventory (BCI). CBE LIFE SCIENCES EDUCATION 2008; 7:227-33. [PMID: 18519614 PMCID: PMC2424310 DOI: 10.1187/cbe.07-08-0063] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
While researching student assumptions for the development of the Biology Concept Inventory (BCI; http://bioliteracy.net), we found that a wide class of student difficulties in molecular and evolutionary biology appears to be based on deep-seated, and often unaddressed, misconceptions about random processes. Data were based on more than 500 open-ended (primarily) college student responses, submitted online and analyzed through our Ed's Tools system, together with 28 thematic and think-aloud interviews with students, and the responses of students in introductory and advanced courses to questions on the BCI. Students believe that random processes are inefficient, whereas biological systems are very efficient. They are therefore quick to propose their own rational explanations for various processes, from diffusion to evolution. These rational explanations almost always make recourse to a driver, e.g., natural selection in evolution or concentration gradients in molecular biology, with the process taking place only when the driver is present, and ceasing when the driver is absent. For example, most students believe that diffusion only takes place when there is a concentration gradient, and that the mutational processes that change organisms occur only in response to natural selection pressures. An understanding that random processes take place all the time and can give rise to complex and often counterintuitive behaviors is almost totally absent. Even students who have had advanced or college physics, and can discuss diffusion correctly in that context, cannot make the transfer to biological processes, and passing through multiple conventional biology courses appears to have little effect on their underlying beliefs.
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Affiliation(s)
| | - Michael W. Klymkowsky
- Molecular, Cellular, and Developmental Biology Department, University of Colorado, Boulder, CO 80309
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Lee CT, Risom T, Strauss WM. Evolutionary Conservation of MicroRNA Regulatory Circuits: An Examination of MicroRNA Gene Complexity and Conserved MicroRNA-Target Interactions through Metazoan Phylogeny. DNA Cell Biol 2007; 26:209-18. [PMID: 17465887 DOI: 10.1089/dna.2006.0545] [Citation(s) in RCA: 174] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
During the last decade, a variety of critical biological processes, including early embryo development, cell proliferation, differentiation, apoptosis, and metabolic regularity, have been shown to be genetically regulated by a large gene family encoding a class of tiny RNA molecules termed microRNAs (miRNAs). All miRNAs share a common biosynthetic pathway and reaction mechanisms. The sequence of many miRNAs is found to be conserved, in their mature form, among different organisms. In addition, the evolutionary appearance of multicellular organisms appears to correlate with the appearance of the miRNA pathway for regulating gene expression. The miRNA pathway has the potential to regulate vast networks of gene products in a coordinate manner. Recent evidence has not only implicated the miRNA pathway in regulating a vast array of basic cellular processes but also specialized processes that are required for cellular identity and tissue specificity. A survey of the literature shows that some miRNA pathways are conserved virtually intact throughout phylogeny while miRNA diversity also correlates with speciation. The number of miRNA genes, the expression of miRNAs, and target diversities of miRNAs tend to be positively correlated with morphological complexities observed in animals. Thus, organismal complexity can be estimated by the complexity of the miRNA circuitry. The complexity of the miRNA gene families establishes a link between genotypic complexity and phenotypic complexity in animal evolution. In this paper, we start with the discussion of miRNA conservation. Then we interpret the trends in miRNA conservation to deduce miRNA evolutionary trends in metazoans. Based on these conservation patterns observed in each component of the miRNA regulatory system, we attempt to propose a global insight on the probable consistency between morphological evolution in animals and the molecular evolution of miRNA gene activity in the cell.
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Affiliation(s)
- Chung-Tien Lee
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA
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