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Zhong H, Ren B, Lou C, Zhou Y, Luo Y, Xiao J. Nonadditive and allele-specific expression of ghrelin in hybrid tilapia. Front Endocrinol (Lausanne) 2023; 14:1292730. [PMID: 38152137 PMCID: PMC10751329 DOI: 10.3389/fendo.2023.1292730] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 11/07/2023] [Indexed: 12/29/2023] Open
Abstract
Background Interspecies hybridization is an important breeding method to generate fishes with heterosis in aquaculture. Using this method, hybrid Nile tilapia (Oreochromis niloticus, ♀) × blue tilapia (Oreochromis aureus, ♂) has been produced and widely farmed due to its growth and appetite superiorities. However, the genetic mechanism of these advanced traits is still not well understood. Ghrelin is a crucial gene that regulates growth and appetite in fishes. In the present study, we focused on the expression characteristics and its regulation of ghrelin in the hybrid. Results The tissue distribution analysis showed that ghrelin was predominantly expressed in the stomach in the hybrid. Ghrelin was more highly expressed in the stomach in the hybrid and Nile tilapia, compared to blue tilapia, showing a nonadditive pattern. Two single-nucleotide polymorphism (SNP) sites were identified including T/C and C/G from the second exon in the ghrelin gene from Nile tilapia and blue tilapia. By pyrosequencing based on the SNP sites, the allele-specific expression (ASE) of ghrelin in the hybrid was assayed. The result indicated that ghrelin in the hybrid showed higher maternal allelic transcript ratios. Fasting significantly increased ghrelin overall expression at 4, 8, 12, 24, and 48 h. In addition, higher maternal allelic transcript ratios were not changed in the fasting hybrids at 48 h. The cis and trans effects were determined by evaluating the overall expression and ASE values in the hybrid. The expression of ghrelin was mediated by compensating cis and trans effects in hybrid. Conclusion In summary, the present lines of evidence showed the nonadditive expression of ghrelin in the hybrid tilapia and its regulation by subgenomes, offering new insight into gene expression characteristics in hybrids.
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Affiliation(s)
- Huan Zhong
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Bingxin Ren
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Chenyi Lou
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Yi Zhou
- State Key Laboratory of Developmental Biology of Freshwater Fish, College of Life Sciences, Hunan Normal University, Changsha, China
| | - Yongju Luo
- Tilapia Genetics and Breeding Center, Guangxi Academy of Fishery Sciences, Nanning, China
| | - Jun Xiao
- Tilapia Genetics and Breeding Center, Guangxi Academy of Fishery Sciences, Nanning, China
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Lu Y, Bierbach D, Ormanns J, Warren WC, Walter RB, Schartl M. Fixation of allelic gene expression landscapes and expression bias pattern shape the transcriptome of the clonal Amazon molly. Genome Res 2021; 31:372-379. [PMID: 33547183 PMCID: PMC7919451 DOI: 10.1101/gr.268870.120] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2020] [Accepted: 01/12/2021] [Indexed: 02/07/2023]
Abstract
The Amazon molly is a unique clonal fish species that originated from an interspecies hybrid between Poecilia species P. mexicana and P. latipinna. It reproduces by gynogenesis, which eliminates paternal genomic contribution to offspring. An earlier study showed that Amazon molly shows biallelic expression for a large portion of the genome, leading to two main questions: (1) Are the allelic expression patterns from the initial hybridization event stabilized or changed during establishment of the asexual species and its further evolution? (2) Is allelic expression biased toward one parental allele a stochastic or adaptive process? To answer these questions, the allelic expression of P. formosa siblings was assessed to investigate intra- and inter-cohort allelic expression variability. For comparison, interspecies hybrids between P. mexicana and P. latipinna were produced in the laboratory to represent the P. formosa ancestor. We have identified inter-cohort and intra-cohort variation in parental allelic expression. The existence of inter-cohort divergence suggests functional P. formosa allelic expression patterns do not simply reflect the atavistic situation of the first interspecies hybrid but potentially result from long-term selection of transcriptional fitness. In addition, clonal fish show a transcriptional trend representing minimal intra-clonal variability in allelic expression patterns compared to the corresponding hybrids. The intra-clonal similarity in gene expression translates to sophisticated genetic functional regulation at the individuum level. These findings suggest the parental alleles inherited by P. formosa form tightly regulated genetic networks that lead to a stable transcriptomic landscape within clonal individuals.
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Affiliation(s)
- Yuan Lu
- Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas 78666, USA
| | - David Bierbach
- Department of Biology and Ecology of Fishes, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Humboldt Universität zu Berlin, 10099 Berlin, Germany
| | - Jenny Ormanns
- Biochemistry and Cell Biology, Biozentrum, University of Würzburg, 97074 Würzburg, Germany
| | - Wesley C Warren
- Bond Life Science Center, University of Missouri, Columbia, Missouri 65211, USA
| | - Ronald B Walter
- Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas 78666, USA.,Department of Life Sciences, Texas A&M University, Corpus Christi, Texas 78412, USA
| | - Manfred Schartl
- Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas 78666, USA.,Developmental Biochemistry, Biozentrum, University of Würzburg, 97074 Würzburg, Germany
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Lu Y, Olivas TJ, Boswell M, Boswell W, Warren WC, Schartl M, Walter RB. Intra-Strain Genetic Variation of Platyfish ( Xiphophorus maculatus) Strains Determines Tumorigenic Trajectory. Front Genet 2020; 11:562594. [PMID: 33133148 PMCID: PMC7573281 DOI: 10.3389/fgene.2020.562594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 09/09/2020] [Indexed: 11/16/2022] Open
Abstract
Xiphophorus interspecies hybrids represent a valuable model system to study heritable tumorigenesis, and the only model system that exhibits both spontaneous and inducible tumors. Types of tumorigenesis depend on the specific pedigree of the parental species, X. maculatus, utilized to produce interspecies hybrids. Although the ancestors of the two currently used X. maculatus parental lines, Jp163 A and Jp163 B, were originally siblings produced by the same mother, backcross interspecies hybrid progeny between X. hellerii and X. maculatus Jp163 A develop spontaneous melanoma initiating at the dorsal fin due to segregation of an oncogene and a regulator encoded by the X. maculatus genome, while the backcross hybrid progeny with X. hellerii or X. couchianus and Jp163 B exhibit melanoma on the flanks of their bodies, especially after treatment with ultraviolet light. Therefore, dissecting the genetic differences between these two closely related lines may lead to better understanding of functional molecular differences associated with tumorigenic mechanisms. For this purpose, comparative genomic analyses were undertaken to establish genetic variants between these two X. maculatus lines. Surprisingly, given the heritage of these two fish lines, we found genetic variants are clustered together in select chromosomal regions. Among these variants are non-synonymous mutations located in 381 genes. The non-random distribution of genetic variants between these two may highlight ancestral chromosomal recombination patterns that became fixed during subsequent inbreeding. Employing comparative transcriptomics, we also determined differences in the skin transcriptional landscape between the two lines. The genetic differences observed are associated with pathways highlighting fundamental cellular functions including inter-cellular and microenvironment-cellular interactions, and DNA repair. These results collectively lead to the conclusion that diverged functional genetic baselines are present between Jp163 A and B strains. Further, disruption of these fixed genetic baselines in the hybrids may give rise to spontaneous or inducible mechanisms of tumorigenesis.
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Affiliation(s)
- Yuan Lu
- Xiphophorus Genetic Stock Center, Texas State University, San Marcos, TX, United States
| | - Taryn J Olivas
- Xiphophorus Genetic Stock Center, Texas State University, San Marcos, TX, United States.,Department of Cell Biology, Yale University School of Medicine, New Haven, CT, United States
| | - Mikki Boswell
- Xiphophorus Genetic Stock Center, Texas State University, San Marcos, TX, United States
| | - William Boswell
- Xiphophorus Genetic Stock Center, Texas State University, San Marcos, TX, United States
| | - Wes C Warren
- Bond Life Sciences Center, University of Missouri, Columbia, MO, United States
| | - Manfred Schartl
- Xiphophorus Genetic Stock Center, Texas State University, San Marcos, TX, United States.,Developmental Biochemistry, Theodor-Boveri-Institute, Biozentrum, University of Würzburg, Würzburg, Germany
| | - Ronald B Walter
- Xiphophorus Genetic Stock Center, Texas State University, San Marcos, TX, United States
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Lu Y, Boswell M, Boswell W, Kneitz S, Hausmann M, Klotz B, Regneri J, Savage M, Amores A, Postlethwait J, Warren W, Schartl M, Walter R. Comparison of Xiphophorus and human melanoma transcriptomes reveals conserved pathway interactions. Pigment Cell Melanoma Res 2018; 31:496-508. [PMID: 29316274 PMCID: PMC6013346 DOI: 10.1111/pcmr.12686] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Accepted: 12/23/2017] [Indexed: 12/14/2022]
Abstract
Comparative analysis of human and animal model melanomas can uncover conserved pathways and genetic changes that are relevant for the biology of cancer cells. Spontaneous melanoma in Xiphophorus interspecies backcross hybrid progeny may be informative in identifying genes and functional pathways that are similarly related to melanoma development in all vertebrates, including humans. To assess functional pathways involved in the Xiphophorus melanoma, we performed gene expression profiling of the melanomas produced in interspecies BC1 and successive backcross generations (i.e., BC5 ) of the cross: X. hellerii × [X. maculatus Jp 163 A × X. hellerii]. Using RNA-Seq, we identified genes that are transcriptionally co-expressed with the driver oncogene, xmrk. We determined functional pathways in the fish melanoma that are also present in human melanoma cohorts that may be related to dedifferentiation based on the expression levels of pigmentation genes. Shared pathways between human and Xiphophorus melanomas are related to inflammation, cell migration, cell proliferation, pigmentation, cancer development, and metastasis. Our results suggest xmrk co-expressed genes are associated with dedifferentiation and highlight these signaling pathways as playing important roles in melanomagenesis.
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Affiliation(s)
- Yuan Lu
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas, USA
| | - Mikki Boswell
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas, USA
| | - William Boswell
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas, USA
| | - Susanne Kneitz
- Physiological Chemistry, Biozentrum, University of Würzburg, Würzburg, Germany
- Comprehensive Cancer Center Mainfranken, University Clinic Würzburg, D-97074 Würzburg, Germany
| | - Michael Hausmann
- Physiological Chemistry, Biozentrum, University of Würzburg, Würzburg, Germany
- Comprehensive Cancer Center Mainfranken, University Clinic Würzburg, D-97074 Würzburg, Germany
| | - Barbara Klotz
- Physiological Chemistry, Biozentrum, University of Würzburg, Würzburg, Germany
- Comprehensive Cancer Center Mainfranken, University Clinic Würzburg, D-97074 Würzburg, Germany
| | - Janine Regneri
- Physiological Chemistry, Biozentrum, University of Würzburg, Würzburg, Germany
- Comprehensive Cancer Center Mainfranken, University Clinic Würzburg, D-97074 Würzburg, Germany
| | - Markita Savage
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas, USA
| | - Angel Amores
- Institute of Neuroscience, University of Oregon, Eugene, Oregon, USA
| | - John Postlethwait
- Institute of Neuroscience, University of Oregon, Eugene, Oregon, USA
| | - Wesley Warren
- The Genome Institute, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Manfred Schartl
- Physiological Chemistry, Biozentrum, University of Würzburg, Würzburg, Germany
- Comprehensive Cancer Center Mainfranken, University Clinic Würzburg, D-97074 Würzburg, Germany
- Texas A&M Institute for Advanced Studies and Department of Biology, Texas A&M University, College Station, USA
| | - Ronald Walter
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, San Marcos, Texas, USA
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5
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Variant calling from RNA-seq data of the brain transcriptome of pigs and its application for allele-specific expression and imprinting analysis. Gene 2018; 641:367-375. [DOI: 10.1016/j.gene.2017.10.076] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 10/19/2017] [Accepted: 10/26/2017] [Indexed: 12/21/2022]
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Zhu F, Schlupp I, Tiedemann R. Allele-specific expression at the androgen receptor alpha gene in a hybrid unisexual fish, the Amazon molly (Poecilia formosa). PLoS One 2017; 12:e0186411. [PMID: 29023530 PMCID: PMC5638567 DOI: 10.1371/journal.pone.0186411] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 09/29/2017] [Indexed: 12/25/2022] Open
Abstract
The all-female Amazon molly (Poecilia formosa) is the result of a hybridization of the Atlantic molly (P. mexicana) and the sailfin molly (P. latipinna) approximately 120,000 years ago. As a gynogenetic species, P. formosa needs to copulate with heterospecific males including males from one of its bisexual ancestral species. However, the sperm only triggers embryogenesis of the diploid eggs. The genetic information of the sperm donor typically will not contribute to the next generation of P. formosa. Hence, P. formosa possesses generally one allele from each of its ancestral species at any genetic locus. This raises the question whether both ancestral alleles are equally expressed in P. formosa. Allele-specific expression (ASE) has been previously assessed in various organisms, e.g., human and fish, and ASE was found to be important in the context of phenotypic variability and disease. In this study, we utilized Real-Time PCR techniques to estimate ASE of the androgen receptor alpha (arα) gene in several distinct tissues of Amazon mollies. We found an allelic bias favoring the maternal ancestor (P. mexicana) allele in ovarian tissue. This allelic bias was not observed in the gill or the brain tissue. Sequencing of the promoter regions of both alleles revealed an association between an Indel in a known CpG island and differential expression. Future studies may reveal whether our observed cis-regulatory divergence is caused by an ovary-specific trans-regulatory element, preferentially activating the allele of the maternal ancestor.
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Affiliation(s)
- Fangjun Zhu
- University of Evolutionary Biology/Systematic Zoology, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
| | - Ingo Schlupp
- Department of Biology, University of Oklahoma, Norman, Oklahoma, United States of America
| | - Ralph Tiedemann
- University of Evolutionary Biology/Systematic Zoology, Institute of Biochemistry and Biology, University of Potsdam, Potsdam, Germany
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7
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Matos IMN, Coelho MM, Schartl M. Gene copy silencing and DNA methylation in natural and artificially produced allopolyploid fish. ACTA ACUST UNITED AC 2016; 219:3072-3081. [PMID: 27445349 DOI: 10.1242/jeb.140418] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2016] [Accepted: 07/19/2016] [Indexed: 12/28/2022]
Abstract
Allelic silencing is an important mechanism for coping with gene dosage changes in polyploid organisms that is well known in allopolyploid plants. Only recently, it was shown in the allotriploid fish Squalius alburnoides that this process also occurs in vertebrates. However, it is still unknown whether this silencing mechanism is common to other allopolyploid fish, and which mechanisms might be responsible for allelic silencing. We addressed these questions in a comparative study between Squalius alburnoides and another allopolyploid complex, the Amazon molly (Poecilia formosa). We examined the allelic expression patterns for three target genes in four somatic tissues of natural allo-anorthoploids and laboratory-produced tri-genomic hybrids of S. alburnoides and P. formosa. Also, for both complexes, we evaluated the correlation between total DNA methylation level and the ploidy status and genomic composition of the individuals. We found that allelic silencing also occurs in other allopolyploid organisms besides the single one that was previously known. We found and discuss disparities within and between the two considered complexes concerning the pattern of allele-specific expression and DNA methylation levels. Disparities might be due to intrinsic characteristics of each genome involved in the hybridization process. Our findings also support the idea that long-term evolutionary processes have an effect on the allele expression patterns and possibly also on DNA methylation levels.
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Affiliation(s)
- Isa M N Matos
- Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal Department of Physiological Chemistry, Biocenter, University of Würzburg, Würzburg 97078, Germany
| | - Maria M Coelho
- Centre for Ecology, Evolution and Environmental Changes, Faculdade de Ciências, Universidade de Lisboa, Lisboa 1749-016, Portugal
| | - Manfred Schartl
- Department of Physiological Chemistry, Biocenter, University of Würzburg, Würzburg 97078, Germany Comprehensive Cancer Center Mainfranken, University Clinic Würzburg, Würzburg 97078, Germany Texas Institute for Advanced Study and Department of Biology, Texas A&M University, College Station, TX 77843, USA
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Shen Y, Chalopin D, Garcia T, Boswell M, Boswell W, Shiryev SA, Agarwala R, Volff JN, Postlethwait JH, Schartl M, Minx P, Warren WC, Walter RB. X. couchianus and X. hellerii genome models provide genomic variation insight among Xiphophorus species. BMC Genomics 2016; 17:37. [PMID: 26742787 PMCID: PMC4705583 DOI: 10.1186/s12864-015-2361-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 12/30/2015] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Xiphophorus fishes are represented by 26 live-bearing species of tropical fish that express many attributes (e.g., viviparity, genetic and phenotypic variation, ecological adaptation, varied sexual developmental mechanisms, ability to produce fertile interspecies hybrids) that have made attractive research models for over 85 years. Use of various interspecies hybrids to investigate the genetics underlying spontaneous and induced tumorigenesis has resulted in the development and maintenance of pedigreed Xiphophorus lines specifically bred for research. The recent availability of the X. maculatus reference genome assembly now provides unprecedented opportunities for novel and exciting comparative research studies among Xiphophorus species. RESULTS We present sequencing, assembly and annotation of two new genomes representing Xiphophorus couchianus and Xiphophorus hellerii. The final X. couchianus and X. hellerii assemblies have total sizes of 708 Mb and 734 Mb and correspond to 98 % and 102 % of the X. maculatus Jp 163 A genome size, respectively. The rates of single nucleotide change range from 1 per 52 bp to 1 per 69 bp among the three genomes and the impact of putatively damaging variants are presented. In addition, a survey of transposable elements allowed us to deduce an ancestral TE landscape, uncovered potential active TEs and document a recent burst of TEs during evolution of this genus. CONCLUSIONS Two new Xiphophorus genomes and their corresponding transcriptomes were efficiently assembled, the former using a novel guided assembly approach. Three assembled genome sequences within this single vertebrate order of new world live-bearing fishes will accelerate our understanding of relationship between environmental adaptation and genome evolution. In addition, these genome resources provide capability to determine allele specific gene regulation among interspecies hybrids produced by crossing any of the three species that are known to produce progeny predisposed to tumor development.
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Affiliation(s)
- Yingjia Shen
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, 419 Centennial Hall, 601 University Drive, San Marcos, TX, 78666, USA.
- Key Laboratory of Coastal and Wetland Ecosystems, Ministry of Education, A316 Environment and Ecology Bldg., Xiamen, Fujian, 361102, China.
| | - Domitille Chalopin
- Institut de Génomique Fonctionnelle de Lyon, Unité Mixte de Recherche 5242, Centre National de la Recherche Scientifique, Université de Lyon I, Ecole Normale Supérieure de Lyon, Lyon, France.
| | - Tzintzuni Garcia
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, 419 Centennial Hall, 601 University Drive, San Marcos, TX, 78666, USA.
| | - Mikki Boswell
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, 419 Centennial Hall, 601 University Drive, San Marcos, TX, 78666, USA.
| | - William Boswell
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, 419 Centennial Hall, 601 University Drive, San Marcos, TX, 78666, USA.
| | - Sergey A Shiryev
- The National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD, 20894, USA.
| | - Richa Agarwala
- The National Center for Biotechnology Information, National Library of Medicine, Bethesda, MD, 20894, USA.
| | - Jean-Nicolas Volff
- Institut de Génomique Fonctionnelle de Lyon, Unité Mixte de Recherche 5242, Centre National de la Recherche Scientifique, Université de Lyon I, Ecole Normale Supérieure de Lyon, Lyon, France.
| | - John H Postlethwait
- Institute of Neuroscience, University of Oregon, 1425 E. 13th Avenue, Eugene, OR, 97403, USA.
| | - Manfred Schartl
- Universität Würzburg, Physiologische Chemie I, Biozentrum, Am Hubland, and Comprehensive Cancer Center Mainfranken, University Clinic Würzburg, D-97074, Würzburg, Germany.
| | - Patrick Minx
- Genome Sequencing Center, Washington University School of Medicine, 4444 Forest Park Blvd., St Louis, MO, 63108, USA.
| | - Wesley C Warren
- Genome Sequencing Center, Washington University School of Medicine, 4444 Forest Park Blvd., St Louis, MO, 63108, USA.
| | - Ronald B Walter
- The Xiphophorus Genetic Stock Center, Department of Chemistry and Biochemistry, Texas State University, 419 Centennial Hall, 601 University Drive, San Marcos, TX, 78666, USA.
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Lu Y, Bowswell M, Bowswell W, Yang K, Schartl M, Walter RB. Molecular genetic response of Xiphophorus maculatus-X. couchianus interspecies hybrid skin to UVB exposure. Comp Biochem Physiol C Toxicol Pharmacol 2015; 178:86-92. [PMID: 26254713 PMCID: PMC4662913 DOI: 10.1016/j.cbpc.2015.07.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Revised: 07/27/2015] [Accepted: 07/29/2015] [Indexed: 12/13/2022]
Abstract
The phenotypic and genetic similarities between Xiphophorus and human melanoma render Xiphophorus a useful animal model for studying the genetic basis of melanoma etiology. In the Xiphophorus model, melanoma has been shown to be inducible by ultraviolet light (UVB) exposure among interspecies hybrids, but not in parental line fish similarly treated. This leads to questions of what genes are responsive to UVB exposure in the skin of the interspecies hybrids, as well as how parental alleles in hybrids may be differentially regulated and the potential roles they may play in induced melanomagenesis. To address these questions, we produced X. maculatus Jp 163 B×X. couchianus (Sp-Couch) F1 hybrid fish, exposed both hybrid and parental fish to UVB, and performed gene expression profiling of the skin using RNA-Seq methodology. We characterized a group of unique UVB-responsive genes in Sp-Couch hybrid including dct, pmela, tyr, tyrp1a, slc2a11b, rab38a, rab27, tspan10, slc45a2, oca2, slc24a5, ptn and mitfa. These genes are associated with melanin production and melanocyte proliferation. They were also up-regulated in Sp-Couch hybrid, indicating that their UVB response is hybridization initiated. In the hybrid, several melanin production and pigmentation related genes, including slc45a2, tspan10, dct, slc2a11b and ptn showed either X. couchianus or X. maculatus allele specific expression. The finding that these genes exhibit allele specific expression regulatory mechanisms in Sp-Couch hybrids, but do not exhibit a corresponding UVB response in either one of the parental fishes, may suggest UVB targets and imply mechanisms regarding the susceptibility of Sp-Couch to induced melanomagenesis.
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Affiliation(s)
- Yuan Lu
- Molecular Bioscience Research Group, Department of Chemistry and Biochemistry Texas State University, San Marcos, TX, 78666
| | - Mikki Bowswell
- Molecular Bioscience Research Group, Department of Chemistry and Biochemistry Texas State University, San Marcos, TX, 78666
| | - William Bowswell
- Molecular Bioscience Research Group, Department of Chemistry and Biochemistry Texas State University, San Marcos, TX, 78666
| | - Kuan Yang
- Molecular Bioscience Research Group, Department of Chemistry and Biochemistry Texas State University, San Marcos, TX, 78666
| | - Manfred Schartl
- Physiologische Chemie, Universität Würzburg Biozentrum, Am Hubland, and Comprehensive Cancer Center Mainfranken, University Clinic Würzburg, D-97074 Würzburg, Germany
| | - Ronald B. Walter
- Molecular Bioscience Research Group, Department of Chemistry and Biochemistry Texas State University, San Marcos, TX, 78666
- Corresponding author:
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RNA-Seq alignment to individualized genomes improves transcript abundance estimates in multiparent populations. Genetics 2015; 198:59-73. [PMID: 25236449 PMCID: PMC4174954 DOI: 10.1534/genetics.114.165886] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Massively parallel RNA sequencing (RNA-seq) has yielded a wealth of new insights into transcriptional regulation. A first step in the analysis of RNA-seq data is the alignment of short sequence reads to a common reference genome or transcriptome. Genetic variants that distinguish individual genomes from the reference sequence can cause reads to be misaligned, resulting in biased estimates of transcript abundance. Fine-tuning of read alignment algorithms does not correct this problem. We have developed Seqnature software to construct individualized diploid genomes and transcriptomes for multiparent populations and have implemented a complete analysis pipeline that incorporates other existing software tools. We demonstrate in simulated and real data sets that alignment to individualized transcriptomes increases read mapping accuracy, improves estimation of transcript abundance, and enables the direct estimation of allele-specific expression. Moreover, when applied to expression QTL mapping we find that our individualized alignment strategy corrects false-positive linkage signals and unmasks hidden associations. We recommend the use of individualized diploid genomes over reference sequence alignment for all applications of high-throughput sequencing technology in genetically diverse populations.
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Braasch I, Peterson SM, Desvignes T, McCluskey BM, Batzel P, Postlethwait JH. A new model army: Emerging fish models to study the genomics of vertebrate Evo-Devo. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2014; 324:316-41. [PMID: 25111899 DOI: 10.1002/jez.b.22589] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Revised: 06/19/2014] [Accepted: 06/25/2014] [Indexed: 01/08/2023]
Abstract
Many fields of biology--including vertebrate Evo-Devo research--are facing an explosion of genomic and transcriptomic sequence information and a multitude of fish species are now swimming in this "genomic tsunami." Here, we first give an overview of recent developments in sequencing fish genomes and transcriptomes that identify properties of fish genomes requiring particular attention and propose strategies to overcome common challenges in fish genomics. We suggest that the generation of chromosome-level genome assemblies--for which we introduce the term "chromonome"--should be a key component of genomic investigations in fish because they enable large-scale conserved synteny analyses that inform orthology detection, a process critical for connectivity of genomes. Orthology calls in vertebrates, especially in teleost fish, are complicated by divergent evolution of gene repertoires and functions following two rounds of genome duplication in the ancestor of vertebrates and a third round at the base of teleost fish. Second, using examples of spotted gar, basal teleosts, zebrafish-related cyprinids, cavefish, livebearers, icefish, and lobefin fish, we illustrate how next generation sequencing technologies liberate emerging fish systems from genomic ignorance and transform them into a new model army to answer longstanding questions on the genomic and developmental basis of their biodiversity. Finally, we discuss recent progress in the genetic toolbox for the major fish models for functional analysis, zebrafish, and medaka, that can be transferred to many other fish species to study in vivo the functional effect of evolutionary genomic change as Evo-Devo research enters the postgenomic era.
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Affiliation(s)
- Ingo Braasch
- Institute of Neuroscience, University of Oregon, Eugene, Oregon
| | | | | | | | - Peter Batzel
- Institute of Neuroscience, University of Oregon, Eugene, Oregon
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Stevenson KR, Coolon JD, Wittkopp PJ. Sources of bias in measures of allele-specific expression derived from RNA-sequence data aligned to a single reference genome. BMC Genomics 2013; 14:536. [PMID: 23919664 PMCID: PMC3751238 DOI: 10.1186/1471-2164-14-536] [Citation(s) in RCA: 91] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 08/05/2013] [Indexed: 11/23/2022] Open
Abstract
Background RNA-seq can be used to measure allele-specific expression (ASE) by assigning sequence reads to individual alleles; however, relative ASE is systematically biased when sequence reads are aligned to a single reference genome. Aligning sequence reads to both parental genomes can eliminate this bias, but this approach is not always practical, especially for non-model organisms. To improve accuracy of ASE measured using a single reference genome, we identified properties of differentiating sites responsible for biased measures of relative ASE. Results We found that clusters of differentiating sites prevented sequence reads from an alternate allele from aligning to the reference genome, causing a bias in relative ASE favoring the reference allele. This bias increased with greater sequence divergence between alleles. Increasing the number of mismatches allowed when aligning sequence reads to the reference genome and restricting analysis to genomic regions with fewer differentiating sites than the number of mismatches allowed almost completely eliminated this systematic bias. Accuracy of allelic abundance was increased further by excluding differentiating sites within sequence reads that could not be aligned uniquely within the genome (imperfect mappability) and reads that overlapped one or more insertions or deletions (indels) between alleles. Conclusions After aligning sequence reads to a single reference genome, excluding differentiating sites with at least as many neighboring differentiating sites as the number of mismatches allowed, imperfect mappability, and/or an indel(s) nearby resulted in measures of allelic abundance comparable to those derived from aligning sequence reads to both parental genomes.
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Affiliation(s)
- Kraig R Stevenson
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI 48109, USA
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